Sample records for oxygen deficient perovskite

  1. Enhancing perovskite electrocatalysis through strain tuning of oxygen deficiency

    DOE PAGES

    Barron, Sara C.; Lee, Ho Nyung; Petrie, Jonathan R.; ...

    2016-05-27

    Oxygen vacancies in transition-metal oxides facilitate catalysis critical for energy storage and generation. However, promoting vacancies at the lower temperatures required for operation in devices such as metal–air batteries and portable fuel cells has proven elusive. Here we used thin films of perovskite-based strontium cobaltite (SrCoO x) to show that epitaxial strain is a powerful tool for manipulating the oxygen content under conditions consistent with the oxygen evolution reaction, yielding increasingly oxygen-deficient states in an environment where the cobaltite would normally be fully oxidized. The additional oxygen vacancies created through tensile strain enhance the cobaltite’s catalytic activity toward this importantmore » reaction by over an order of magnitude, equaling that of precious-metal catalysts, including IrO2. Lastly, our findings demonstrate that strain in these oxides can dictate the oxygen stoichiometry independent of ambient conditions, allowing unprecedented control over oxygen vacancies essential in catalysis near room temperature.« less

  2. Structural and Magnetic Phase Coexistence in Oxygen Deficient Perovskites (Sr,Ca)FeO 2 . 5 + δ

    NASA Astrophysics Data System (ADS)

    Carlo, J. P.; Evans, M. E.; Anczarski, J. A.; Ock, J.; Boyd, K.; Pollichemi, J. R.; Leahy, I. A.; Vogel, W.; Viescas, A. J.; Papaefthymiou, G. C.

    A variety of compounds crystallize into perovskite and similar structures, making them versatile laboratories for many phenomena and applications, including multiferroicity, superconductivity, and photovoltaics. Oxygen-deficient perovskites ABOx have attracted interest for use in fuel cells and related applications due to high oxygen mobility and the possibility of charge disproportionation. Vast chemical flexibility is obtained through reductions in lattice symmetry and rotation/distortion of the BO6 octahedra, as well as ordering of oxygen vacancies. We have synthesized and studied the structural and magnetic properties of oxygen-deficient perovskites (Sr,Ca)FeO2 . 5 + δ using x-ray diffraction and Mossbauer spectroscopy. While the ideal perovskite has δ = 0.5, this requires Fe4+, and hence strongly oxidizing environments. When grown in air, Fe3+ is favored, yielding δ ~ 0. SrFeO2 . 5 + δ exhibits cubic symmetry and paramagnetism at 300K, but CaFeO2 . 5 + δ crystallizes into the orthorhombic brownmillerite structure, and is magnetically ordered at 300K. In the doped intermediaries we find coexistence of cubic/paramagnetic and orthorhombic/magnetic phases over a wide range of Ca content. Financial support from the Villanova Undergraduate Research Fellowship program and the Research Corporation for Science Advancement.

  3. (La1-xSrx)0.98MnO3 perovskite with A-site deficiencies toward oxygen reduction reaction in aluminum-air batteries

    NASA Astrophysics Data System (ADS)

    Xue, Yejian; Miao, He; Sun, Shanshan; Wang, Qin; Li, Shihua; Liu, Zhaoping

    2017-02-01

    The strontium doped Mn-based perovskites have been proposed as one of the best oxygen reduction reaction catalysts (ORRCs) to substitute the noble metal. However, few studies have investigated the catalytic activities of LSM with the A-site deficiencies. Here, the (La1-xSrx)0.98MnO3 (LSM) perovskites with A-site deficiencies are prepared by a modified solid-liquid method. The structure, morphology, valence state and oxygen adsorption behaviors of these LSM samples are characterized, and their catalytic activities toward ORR are studied by the rotating ring-disk electrode (RRDE) and aluminum-air battery technologies. The results show that the appropriate doping with Sr and introducing A-site stoichiometry can effectively tailor the Mn valence and increase the oxygen adsorption capacity of LSM. Among all the LSM samples in this work, the (La0.7Sr0.3)0.98MnO3 perovskite composited with 50% carbon (50%LSM30) exhibits the best ORR catalytic activity due to the excellent oxygen adsorption capacity. Also, this catalyst has much higher durability than that of commercial 20%Pt/C. Moreover, the maximum power density of the aluminum-air battery using 50%LSM30 as the ORRC can reach 191.3 mW cm-2. Our work indicates that the LSM/C composite catalysts with A-site deficiencies can be used as a promising ORRC in the metal-air batteries.

  4. Perovskite/Carbon Composites: Applications in Oxygen Electrocatalysis.

    PubMed

    Zhu, Yinlong; Zhou, Wei; Shao, Zongping

    2017-03-01

    Oxygen electrocatalysis, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), plays an extremely important role in oxygen-based renewable-energy technologies such as rechargeable metal-air batteries, regenerative fuel cells and water splitting. Perovskite oxides have recently attracted increasing interest and hold great promise as efficient ORR and OER catalysts to replace noble-metal-based catalysts, owing to their high intrinsic catalytic activity, abundant variety, low cost, and rich resources. The introduction of perovskite-carbon interfaces by forming perovskite/carbon composites may bring a synergistic effect between the two phases, thus benefiting the oxygen electrocatalysis. This review provides a comprehensive overview of recent advances in perovskite/carbon composites for oxygen electrocatalysis in alkaline media, aiming to provide insights into the key parameters that influence the ORR/OER performance of the composites, including the physical/chemical properties and morphologies of the perovskites, the multiple roles of carbon, the synthetic method and the synergistic effect. A special emphasis is placed on the origin of the synergistic effect associated with the interfacial interaction between the perovskite and the carbon phases for enhanced ORR/OER performance. Finally, the existing challenges and the future directions for the synthesis and development of more efficient oxygen catalysts based on perovskite/carbon composites are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

    DOE PAGES

    Yang, Tianrang; Mattick, Victoria F.; Chen, Yan; ...

    2018-01-29

    The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

  6. Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Tianrang; Mattick, Victoria F.; Chen, Yan

    The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

  7. Oxygen Vacancy Linear Clustering in a Perovskite Oxide

    DOE PAGES

    Eom, Kitae; Choi, Euiyoung; Choi, Minsu; ...

    2017-07-14

    Oxygen vacancies have been implicitly assumed isolated ones, and understanding oxide materials possibly containing oxygen vacancies remains elusive within the scheme of the isolated vacancies, although the oxygen vacancies have been playing a decisive role in oxide materials. We report the presence of oxygen vacancy linear clusters and their orientation along a specific crystallographic direction in SrTiO 3, a representative of a perovskite oxide. The presence of the linear clusters and associated electron localization was revealed by an electronic structure represented in the increase in the Ti 2+ valence state or corresponding Ti 3d 2 electronic configuration along with divacancymore » cluster model analysis and transport measurement. The orientation of the linear clusters along the [001] direction in perovskite SrTiO 3 was verified by further X-ray diffuse scattering analysis. And because SrTiO 3 is an archetypical perovskite oxide, the vacancy linear clustering with the specific aligned direction and electron localization can be extended to a wide variety of the perovskite oxides.« less

  8. Oxygen Vacancy Linear Clustering in a Perovskite Oxide

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eom, Kitae; Choi, Euiyoung; Choi, Minsu

    Oxygen vacancies have been implicitly assumed isolated ones, and understanding oxide materials possibly containing oxygen vacancies remains elusive within the scheme of the isolated vacancies, although the oxygen vacancies have been playing a decisive role in oxide materials. We report the presence of oxygen vacancy linear clusters and their orientation along a specific crystallographic direction in SrTiO 3, a representative of a perovskite oxide. The presence of the linear clusters and associated electron localization was revealed by an electronic structure represented in the increase in the Ti 2+ valence state or corresponding Ti 3d 2 electronic configuration along with divacancymore » cluster model analysis and transport measurement. The orientation of the linear clusters along the [001] direction in perovskite SrTiO 3 was verified by further X-ray diffuse scattering analysis. And because SrTiO 3 is an archetypical perovskite oxide, the vacancy linear clustering with the specific aligned direction and electron localization can be extended to a wide variety of the perovskite oxides.« less

  9. Strain coupling of oxygen non-stoichiometry in perovskite thin films

    NASA Astrophysics Data System (ADS)

    Herklotz, Andreas; Lee, Dongkyu; Guo, Er-Jia; Meyer, Tricia L.; Petrie, Jonathan R.; Lee, Ho Nyung

    2017-12-01

    The effects of strain and oxygen vacancies on perovskite thin films have been studied in great detail over the past decades and have been treated separately from each other. While epitaxial strain has been realized as a tuning knob to tailor the functional properties of correlated oxides, oxygen vacancies are usually regarded as undesirable and detrimental. In transition metal oxides, oxygen defects strongly modify the properties and functionalities via changes in oxidation states of the transition metals. However, such coupling is not well understood in epitaxial films, but rather deemed as cumbersome or experimental artifact. Only recently it has been recognized that lattice strain and oxygen non-stoichiometry are strongly correlated in a vast number of perovskite systems and that this coupling can be beneficial for information and energy technologies. Recent experimental and theoretical studies have focused on understanding the correlated phenomena between strain and oxygen vacancies for a wide range of perovskite systems. These correlations not only include the direct relationship between elastic strain and the formation energy of oxygen vacancies, but also comprise highly complex interactions such as strain-induced phase transitions due to oxygen vacancy ordering. Therefore, we aim in this review to give a comprehensive overview on the coupling between strain and oxygen vacancies in perovskite oxides and point out the potential applications of the emergent functionalities strongly coupled to oxygen vacancies.

  10. Effect of A-site deficiency in LaMn{sub 0.9}Co{sub 0.1}O{sub 3} perovskites on their catalytic performance for soot combustion

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dinamarca, Robinson; Garcia, Ximena; Jimenez, Romel

    Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La{sub 1-x}Ag{sub x}Mn{sub 0.9}Co{sub 0.1}O{sub 3}) and A-site deficient (La{sub 1-x}Mn{sub 0.9}Co{sub 0.1}O{sub 3-δ}) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O{sub 2}-TPD and TPR. The formationmore » of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag{sub 2}O segregated phases and the redox pair Mn{sup 4+}/Mn{sup 3+}. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn{sup 4+}/Mn{sup 3+}, which is attributed to the cubic crystalline structure.« less

  11. Effect of cation ordering on oxygen vacancy diffusion pathways in double perovskites

    DOE PAGES

    Uberuaga, Blas Pedro; Pilania, Ghanshyam

    2015-07-08

    Perovskite structured oxides (ABO 3) are attractive for a number of technological applications, including as superionics because of the high oxygen conductivities they exhibit. Double perovskites (AA’BB’O 6) provide even more flexibility for tailoring properties. Using accelerated molecular dynamics, we examine the role of cation ordering on oxygen vacancy mobility in one model double perovskite SrLaTiAlO 6. We find that the mobility of the vacancy is very sensitive to the cation ordering, with a migration energy that varies from 0.6 to 2.7 eV. In the extreme cases, the mobility is both higher and lower than either of the two endmore » member single perovskites. Further, the nature of oxygen vacancy diffusion, whether one-dimensional, two-dimensional, or three-dimensional, also varies with cation ordering. We correlate the dependence of oxygen mobility on cation structure to the distribution of Ti 4+ cations, which provide unfavorable environments for the positively charged oxygen vacancy. The results demonstrate the potential of using tailored double perovskite structures to precisely control the behavior of oxygen vacancies in these materials.« less

  12. Strong excitonic interactions in the oxygen K-edge of perovskite oxides.

    PubMed

    Tomita, Kota; Miyata, Tomohiro; Olovsson, Weine; Mizoguchi, Teruyasu

    2017-07-01

    Excitonic interactions of the oxygen K-edge electron energy-loss near-edge structure (ELNES) of perovskite oxides, CaTiO 3 , SrTiO 3 , and BaTiO 3 , together with reference oxides, MgO, CaO, SrO, BaO, and TiO 2 , were investigated using a first-principles Bethe-Salpeter equation calculation. Although the transition energy of oxygen K-edge is high, strong excitonic interactions were present in the oxygen K-edge ELNES of the perovskite oxides, whereas the excitonic interactions were negligible in the oxygen K-edge ELNES of the reference compounds. Detailed investigation of the electronic structure suggests that the strong excitonic interaction in the oxygen K-edge ELNES of the perovskite oxides is caused by the directionally confined, low-dimensional electronic structure at the Ti-O-Ti bonds. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Oxygen-induced defects at the lead halide perovskite/graphene oxide interfaces

    DOE PAGES

    Acik, Muge; Park, In Kee; Koritala, Rachel E.; ...

    2017-12-21

    Here, graphene oxide or its reduced derivative (GO/RGO) replace metal oxides in perovskite photovoltaics to achieve energy band alignment for minimization of the energy barriers at the film interfaces allowing efficient charge transport, and eliminate stability issues. However, the power conversion efficiencies fall in a wide range (~0.6–18%). Therefore, the perovskite growth and nucleation on GO/RGO require fundamental understanding to improve device function for controlled fabrication, which remain a major challenge. We analyze the surface morphology and crystallization of the lead halide perovskites (MAPbX 3) at 20–300 °C on GO using X-ray diffraction and photoelectron spectroscopy. To determine defect mechanismsmore » and their composition, we perform in situ transmission infrared and micro Raman spectroscopy, and the cross-sectional scanning microscopy that captures interfacial imperfections with the oxygen defects. We demonstrate the oxygen-induced defects at the MAPbX 3/GO interfaces that initiate at room temperature, and occur through the nucleophilic substitution reactions. Unexpectedly, structural defects nucleate in GO forming chemically reduced GO, and modify the surface morphology that yield a poor perovskite growth. Our theoretical studies also reveal that energetically favorable, exothermic reactions between the halides of the perovskite precursors and the oxygen groups of GO generate acidic reaction by-products ( i.e. HX), that confirm the formation of oxygen-induced defects.« less

  14. Oxygen-induced defects at the lead halide perovskite/graphene oxide interfaces

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Acik, Muge; Park, In Kee; Koritala, Rachel E.

    Here, graphene oxide or its reduced derivative (GO/RGO) replace metal oxides in perovskite photovoltaics to achieve energy band alignment for minimization of the energy barriers at the film interfaces allowing efficient charge transport, and eliminate stability issues. However, the power conversion efficiencies fall in a wide range (~0.6–18%). Therefore, the perovskite growth and nucleation on GO/RGO require fundamental understanding to improve device function for controlled fabrication, which remain a major challenge. We analyze the surface morphology and crystallization of the lead halide perovskites (MAPbX 3) at 20–300 °C on GO using X-ray diffraction and photoelectron spectroscopy. To determine defect mechanismsmore » and their composition, we perform in situ transmission infrared and micro Raman spectroscopy, and the cross-sectional scanning microscopy that captures interfacial imperfections with the oxygen defects. We demonstrate the oxygen-induced defects at the MAPbX 3/GO interfaces that initiate at room temperature, and occur through the nucleophilic substitution reactions. Unexpectedly, structural defects nucleate in GO forming chemically reduced GO, and modify the surface morphology that yield a poor perovskite growth. Our theoretical studies also reveal that energetically favorable, exothermic reactions between the halides of the perovskite precursors and the oxygen groups of GO generate acidic reaction by-products ( i.e. HX), that confirm the formation of oxygen-induced defects.« less

  15. Iron-based perovskite cathodes for solid oxide fuel cells

    DOEpatents

    Ralph, James M.; Rossignol, Cecile C.R.; Vaughey, John T.

    2007-01-02

    An A and/or A' site deficient perovskite of general formula of (A.sub.1-xA'.sub.x).sub.1-yFeO.sub.3-.delta. or of general formula A.sub.1-x-yA'.sub.xFeO.sub.3-67, wherein A is La alone or with one or more of the rare earth metals or a rare earth metal other than Ce alone or a combination of rare earth metals and X is in the range of from 0 to about 1; A' is Sr or Ca or mixtures thereof and Y is in the range of from about 0.01 to about 0.3; .delta. represents the amount of compensating oxygen loss. If either A or A' is zero the remaining A or A' is deficient. A fuel cell incorporating the inventive perovskite as a cathode is disclosed as well as an oxygen separation membrane. The inventive perovskite is preferably single phase.

  16. Enhanced Bifunctional Oxygen Catalysis in Strained LaNiO 3 Perovskites

    DOE PAGES

    Petrie, Jonathan R.; Cooper, Valentino R.; Freeland, John W.; ...

    2016-02-11

    Strain is known to greatly influence low-temperature oxygen electrocatalysis on noble metal films, leading to significant enhancements in bifunctional activity essential for fuel cells and metal-air batteries. Still, its catalytic impact on transition-metal oxide thin films, such as perovskites, is not widely understood. Here, we epitaxially strain the conducting perovskite LaNiO 3 to systematically determine its influence on both the oxygen reduction and oxygen evolution reaction. Uniquely, we found that compressive strain could significantly enhance both reactions, yielding a bifunctional catalyst that surpasses the performance of noble metals such as Pt. We attribute the improved bifunctionality to strain-induced splitting ofmore » the e g orbitals, which can customize orbital asymmetry at the surface. Lastly, analogous to strain-induced shifts in the d-band center of noble metals relative to the Fermi level, such splitting can dramatically affect catalytic activity in this perovskite and other potentially more active oxides.« less

  17. Compositional engineering of perovskite oxides for highly efficient oxygen reduction reactions.

    PubMed

    Chen, Dengjie; Chen, Chi; Zhang, Zhenbao; Baiyee, Zarah Medina; Ciucci, Francesco; Shao, Zongping

    2015-04-29

    Mixed conducting perovskite oxides are promising catalysts for high-temperature oxygen reduction reaction. Pristine SrCoO(3-δ) is a widely used parent oxide for the development of highly active mixed conductors. Doping a small amount of redox-inactive cation into the B site (Co site) of SrCoO(3-δ) has been applied as an effective way to improve physicochemical properties and electrochemical performance. Most findings however are obtained only from experimental observations, and no universal guidelines have been proposed. In this article, combined experimental and theoretical studies are conducted to obtain fundamental understanding of the effect of B-site doping concentration with redox-inactive cation (Sc) on the properties and performance of the perovskite oxides. The phase structure, electronic conductivity, defect chemistry, oxygen reduction kinetics, oxygen ion transport, and electrochemical reactivity are experimentally characterized. In-depth analysis of doping level effect is also undertaken by first-principles calculations. Among the compositions, SrCo0.95Sc0.05O(3-δ) shows the best oxygen kinetics and corresponds to the minimum fraction of Sc for stabilization of the oxygen-vacancy-disordered structure. The results strongly support that B-site doping of SrCoO(3-δ) with a small amount of redox-inactive cation is an effective strategy toward the development of highly active mixed conducting perovskites for efficient solid oxide fuel cells and oxygen transport membranes.

  18. The upper limit of thermoelectric power factors in the metal-band-insulator crossover of the perovskite-type oxygen deficient system SrTiO(₃- δ/₂).

    PubMed

    Onoda, Masashige; Tsukahara, Shuichi

    2011-02-02

    The electronic properties and the thermoelectric power factors in the metal-band-insulator crossover of the perovskite-type oxygen deficient system SrTiO(3 - δ/2) with 0.0046 ≤ δ < 0.06 are explored through measurements of x-ray diffraction, electrical resistivity, thermoelectric power, Hall coefficient and magnetic susceptibility. The metallic transport is confirmed to be basically explained through scattering by electron correlations, acoustic phonons and polar optical phonons, where each scattering coefficient is almost linear in the inverse of the effective carrier concentration estimated from the Hall coefficient. The upper limit of the thermoelectric power factor is 2 × 10( - 3) W m( - 1) K( - 2) with the carrier concentration of 2 × 10(20) cm( - 3) at around the Fermi energy comparable to the Debye temperature.

  19. The upper limit of thermoelectric power factors in the metal-band-insulator crossover of the perovskite-type oxygen deficient system SrTiO3 - δ/2

    NASA Astrophysics Data System (ADS)

    Onoda, Masashige; Tsukahara, Shuichi

    2011-02-01

    The electronic properties and the thermoelectric power factors in the metal-band-insulator crossover of the perovskite-type oxygen deficient system SrTiO3 - δ/2 with 0.0046 <= δ < 0.06 are explored through measurements of x-ray diffraction, electrical resistivity, thermoelectric power, Hall coefficient and magnetic susceptibility. The metallic transport is confirmed to be basically explained through scattering by electron correlations, acoustic phonons and polar optical phonons, where each scattering coefficient is almost linear in the inverse of the effective carrier concentration estimated from the Hall coefficient. The upper limit of the thermoelectric power factor is 2 × 10 - 3 W m - 1 K - 2 with the carrier concentration of 2 × 1020 cm - 3 at around the Fermi energy comparable to the Debye temperature.

  20. 30 CFR 57.8527 - Oxygen-deficiency testing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Oxygen-deficiency testing. 57.8527 Section 57... Underground Only § 57.8527 Oxygen-deficiency testing. Flame safety lamps or other suitable devices shall be used to test for acute oxygen deficiency. ...

  1. 30 CFR 57.8527 - Oxygen-deficiency testing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Oxygen-deficiency testing. 57.8527 Section 57... Underground Only § 57.8527 Oxygen-deficiency testing. Flame safety lamps or other suitable devices shall be used to test for acute oxygen deficiency. ...

  2. 30 CFR 57.8527 - Oxygen-deficiency testing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Oxygen-deficiency testing. 57.8527 Section 57... Underground Only § 57.8527 Oxygen-deficiency testing. Flame safety lamps or other suitable devices shall be used to test for acute oxygen deficiency. ...

  3. 30 CFR 57.8527 - Oxygen-deficiency testing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Oxygen-deficiency testing. 57.8527 Section 57... Underground Only § 57.8527 Oxygen-deficiency testing. Flame safety lamps or other suitable devices shall be used to test for acute oxygen deficiency. ...

  4. 30 CFR 57.8527 - Oxygen-deficiency testing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Oxygen-deficiency testing. 57.8527 Section 57... Underground Only § 57.8527 Oxygen-deficiency testing. Flame safety lamps or other suitable devices shall be used to test for acute oxygen deficiency. ...

  5. Strain effects on oxygen migration in perovskites.

    PubMed

    Mayeshiba, Tam; Morgan, Dane

    2015-01-28

    Fast oxygen transport materials are necessary for a range of technologies, including efficient and cost-effective solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Strain is often proposed as a method to enhance the performance of oxygen transport materials, but the magnitude of its effect and its underlying mechanisms are not well-understood, particularly in the widely-used perovskite-structured oxygen conductors. This work reports on an ab initio prediction of strain effects on migration energetics for nine perovskite systems of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. Biaxial strain, as might be easily produced in epitaxial systems, is predicted to lead to approximately linear changes in migration energy. We find that tensile biaxial strain reduces the oxygen vacancy migration barrier across the systems studied by an average of 66 meV per percent strain for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent strain across all systems. The estimated range for the change in migration barrier within each system is ±25 meV per percent strain when considering all hops. These results suggest that strain can significantly impact transport in these materials, e.g., a 2% tensile strain can increase the diffusion coefficient by about three orders of magnitude at 300 K (one order of magnitude at 500 °C or 773 K) for one of the most strain-responsive materials calculated here (LaCrO3). We show that a simple elasticity model, which assumes only dilative or compressive strain in a cubic environment and a fixed migration volume, can qualitatively but not quantitatively model the strain dependence of the migration energy, suggesting that factors not captured by continuum elasticity play a significant role in the strain response.

  6. Influence of transition metal electronegativity on the oxygen storage capacity of perovskite oxides.

    PubMed

    Liu, Lu; Taylor, Daniel D; Rodriguez, Efrain E; Zachariah, Michael R

    2016-08-16

    The selection of highly efficient oxygen carriers (OCs) is a key step necessary for the practical development of chemical looping combustion (CLC). In this study, a series of ABO3 perovskites, where A = La, Ba, Sr, Ca and B = Cr, Mn, Fe, Co, Ni, Cu, are synthesized and tested in a fixed bed reactor for reactivity and stability as OCs with CH4 as the fuel. We find that the electronegativity of the transition metal on the B-site (λB), is a convenient descriptor for oxygen storage capacity (OSC) of our perovskite samples. By plotting OSC for total methane oxidation against λB, we observe an inverted volcano plot relationship. These results could provide useful guidelines for perovskite OC design and their other energy related applications.

  7. Design Principles of Perovskites for Thermochemical Oxygen Separation

    PubMed Central

    Ezbiri, Miriam; Allen, Kyle M.; Gàlvez, Maria E.; Steinfeld, Aldo

    2015-01-01

    Abstract Separation and concentration of O2 from gas mixtures is central to several sustainable energy technologies, such as solar‐driven synthesis of liquid hydrocarbon fuels from CO2, H2O, and concentrated sunlight. We introduce a rationale for designing metal oxide redox materials for oxygen separation through “thermochemical pumping” of O2 against a pO2 gradient with low‐grade process heat. Electronic structure calculations show that the activity of O vacancies in metal oxides pinpoints the ideal oxygen exchange capacity of perovskites. Thermogravimetric analysis and high‐temperature X‐ray diffraction for SrCoO3−δ, BaCoO3−δ and BaMnO3−δ perovskites and Ag2O and Cu2O references confirm the predicted performance of SrCoO3−δ, which surpasses the performance of state‐of‐the‐art Cu2O at these conditions with an oxygen exchange capacity of 44 mmol O 2 mol SrCoO 3−δ −1 exchanged at 12.1 μmol O 2 min−1 g−1 at 600–900 K. The redox trends are understood due to lattice expansion and electronic charge transfer. PMID:25925955

  8. Design Principles of Perovskites for Thermochemical Oxygen Separation.

    PubMed

    Ezbiri, Miriam; Allen, Kyle M; Gàlvez, Maria E; Michalsky, Ronald; Steinfeld, Aldo

    2015-06-08

    Separation and concentration of O2 from gas mixtures is central to several sustainable energy technologies, such as solar-driven synthesis of liquid hydrocarbon fuels from CO2 , H2 O, and concentrated sunlight. We introduce a rationale for designing metal oxide redox materials for oxygen separation through "thermochemical pumping" of O2 against a pO2 gradient with low-grade process heat. Electronic structure calculations show that the activity of O vacancies in metal oxides pinpoints the ideal oxygen exchange capacity of perovskites. Thermogravimetric analysis and high-temperature X-ray diffraction for SrCoO3-δ , BaCoO3-δ and BaMnO3-δ perovskites and Ag2 O and Cu2 O references confirm the predicted performance of SrCoO3-δ , which surpasses the performance of state-of-the-art Cu2 O at these conditions with an oxygen exchange capacity of 44 mmol O 2 mol SrCoO 3-δ(-1) exchanged at 12.1 μmol O 2 min(-1)  g(-1) at 600-900 K. The redox trends are understood due to lattice expansion and electronic charge transfer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. 30 CFR 57.5015 - Oxygen deficiency.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen. Radiation—Underground...

  10. 30 CFR 57.5015 - Oxygen deficiency.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen. Radiation—Underground...

  11. 30 CFR 57.5015 - Oxygen deficiency.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen. Radiation—Underground...

  12. 30 CFR 57.5015 - Oxygen deficiency.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen. Radiation—Underground...

  13. 30 CFR 57.5015 - Oxygen deficiency.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Oxygen deficiency. 57.5015 Section 57.5015..., Physical Agents, and Diesel Particulate Matter Air Quality-Underground Only § 57.5015 Oxygen deficiency. Air in all active workings shall contain at least 19.5 volume percent oxygen. Radiation—Underground...

  14. The lanthanum gallate-based mixed conducting perovskite ceramics

    NASA Astrophysics Data System (ADS)

    Politova, E. D.; Stefanovich, S. Yu.; Aleksandrovskii, V. V.; Kaleva, G. M.; Mosunov, A. V.; Avetisov, A. K.; Sung, J. S.; Choo, K. Y.; Kim, T. H.

    2005-01-01

    The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O3- with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen.

  15. Effect of A-Site Cation Ordering on Chemical Stability, Oxygen Stoichiometry and Electrical Conductivity in Layered LaBaCo2O5+δ Double Perovskite

    PubMed Central

    Bernuy-Lopez, Carlos; Høydalsvik, Kristin; Einarsrud, Mari-Ann; Grande, Tor

    2016-01-01

    The effect of the A-site cation ordering on the chemical stability, oxygen stoichiometry and electrical conductivity in layered LaBaCo2O5+δ double perovskite was studied as a function of temperature and partial pressure of oxygen. Tetragonal A-site cation ordered layered LaBaCo2O5+δ double perovskite was obtained by annealing cubic A-site cation disordered La0.5Ba0.5CoO3-δ perovskite at 1100 °C in N2. High temperature X-ray diffraction between room temperature (RT) and 800 °C revealed that LaBaCo2O5+δ remains tetragonal during heating in oxidizing atmosphere, but goes through two phase transitions in N2 and between 450 °C and 675 °C from tetragonal P4/mmm to orthorhombic Pmmm and back to P4/mmm due to oxygen vacancy ordering followed by disordering of the oxygen vacancies. An anisotropic chemical and thermal expansion of LaBaCo2O5+δ was demonstrated. La0.5Ba0.5CoO3-δ remained cubic at the studied temperature irrespective of partial pressure of oxygen. LaBaCo2O5+δ is metastable with respect to La0.5Ba0.5CoO3-δ at oxidizing conditions inferred from the thermal evolution of the oxygen deficiency and oxidation state of Co in the two materials. The oxidation state of Co is higher in La0.5Ba0.5CoO3-δ resulting in a higher electrical conductivity relative to LaBaCo2O5+δ. The conductivity in both materials was reduced with decreasing partial pressure of oxygen pointing to a p-type semiconducting behavior. PMID:28773279

  16. Synthesis and Structure of A New Perovskite, SrCuO 2.5

    NASA Astrophysics Data System (ADS)

    Chen, Bai-Hao; Walker, Dave; Scott, Bruce A.; Mitzi, David B.

    1996-02-01

    A new oxygen-deficient perovskite, SrCuO2.5, was prepared at 950°C and 100 kbar pressure in a multianvil apparatus. Rietveld profile analysis, using X-ray powder diffraction data, was employed for the structural determination. SrCuO2.5is orthorhombic,Pbam(No. 55),Z= 4,a= 5.424(2) Â,b= 10.837(4) Â, andc= 3.731(1) Â, which is related to the perovskite subcell by root{2}ap× 2root{2}ap×ap, whereapis the simple cubic perovskite lattice parameter. It consists of corner-shared CuO5square pyramids with oxygen vacancy ordering in the CuO2layers. The ordered oxygen vacancies create parallel pseudo-hexagonal tunnels where the Sr atoms reside, forming SrO10polyhedra. Structural features with respect to oxygen vacancies, superstructures, and distortions are analogous to the type of ordering observed in Sr2CuO3+δ. Superconductivity was not observed in SrCuO2.5down to 5 K.

  17. Perovskite oxides: Oxygen electrocatalysis and bulk structure

    NASA Technical Reports Server (NTRS)

    Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, Ernest

    1987-01-01

    Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

  18. Oxygen Vacancy-Tuned Physical Properties in Perovskite Thin Films with Multiple B-site Valance States

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Enriquez, Erik; Chen, Aiping; Harrell, Zach

    Controlling oxygen content in perovskite oxides with ABO 3 structure is one of most critical steps for tuning their functionality. Notably, there have been tremendous efforts to understand the effect of changes in oxygen content on the properties of perovskite thin films that are not composed of cations with multiple valance states. Here, we study the effect of oxygen vacancies on structural and electrical properties in epitaxial thin films of SrFeO 3-δ (SFO), where SFO is a compound with multiple valance states at the B site. Various annealing treatments are used to produce different oxygen contents in the films, whichmore » has resulted in significant structural changes in the fully strained SFO films. The out-of-plane lattice parameter and tetragonality increase with decreasing oxygen concentration, indicating the crystal structure is closely related to the oxygen content. Importantly, variation of the oxygen content in the films significantly affects the dielectric properties, leakage conduction mechanisms, and the resistive hysteresis of the materials. These results establish the relationship between oxygen content and structural and functional properties for a range of multivalent transition metal oxides.« less

  19. Oxygen Vacancy-Tuned Physical Properties in Perovskite Thin Films with Multiple B-site Valance States

    DOE PAGES

    Enriquez, Erik; Chen, Aiping; Harrell, Zach; ...

    2017-04-18

    Controlling oxygen content in perovskite oxides with ABO 3 structure is one of most critical steps for tuning their functionality. Notably, there have been tremendous efforts to understand the effect of changes in oxygen content on the properties of perovskite thin films that are not composed of cations with multiple valance states. Here, we study the effect of oxygen vacancies on structural and electrical properties in epitaxial thin films of SrFeO 3-δ (SFO), where SFO is a compound with multiple valance states at the B site. Various annealing treatments are used to produce different oxygen contents in the films, whichmore » has resulted in significant structural changes in the fully strained SFO films. The out-of-plane lattice parameter and tetragonality increase with decreasing oxygen concentration, indicating the crystal structure is closely related to the oxygen content. Importantly, variation of the oxygen content in the films significantly affects the dielectric properties, leakage conduction mechanisms, and the resistive hysteresis of the materials. These results establish the relationship between oxygen content and structural and functional properties for a range of multivalent transition metal oxides.« less

  20. Cobalt-Doped Perovskite-Type Oxide LaMnO3 as Bifunctional Oxygen Catalysts for Hybrid Lithium-Oxygen Batteries.

    PubMed

    Liu, Xiao; Gong, Hao; Wang, Tao; Guo, Hu; Song, Li; Xia, Wei; Gao, Bin; Jiang, Zhongyi; Feng, Linfei; He, Jianping

    2018-03-02

    Perovskite-type oxides based on rare-earth metals containing lanthanum manganate are promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte. Perovskite-type LaMnO 3 shows excellent ORR performance, but poor OER activity. To improve the OER performance of LaMnO 3 , the element cobalt is doped into perovskite-type LaMnO 3 through a sol-gel method followed by a calcination process. To assess electrocatalytic activities for the ORR and OER, a series of LaMn 1-x Co x O 3 (x=0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) perovskite oxides were synthesized. The results indicate that the amount of doped cobalt has a significant effect on the catalytic performance of LaMn 1-x Co x O 3 . If x=0.3, LaMn 0.7 Co 0.3 O 3 not only shows a tolerable electrocatalytic activity for the ORR, but also exhibits a great improvement (>200 mV) on the catalytic activity for the OER; this indicates that the doping of cobalt is an effective approach to improve the OER performance of LaMnO 3 . Furthermore, the results demonstrate that LaMn 0.7 Co 0.3 O 3 is a promising cost-effective bifunctional catalyst with high performance in the ORR and OER for application in hybrid Li-O 2 batteries. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Perovskite-type oxides - Oxygen electrocatalysis and bulk structure

    NASA Technical Reports Server (NTRS)

    Carbonio, R. E.; Fierro, C.; Tryk, D.; Scherson, D.; Yeager, E.

    1988-01-01

    Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.

  2. Promotion on electrochemical performance of a cation deficient SrCo0.7Nb0.1Fe0.2O3-δ perovskite cathode for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Ding, Liming; Wang, Lixi; Ding, Dong; Zhang, Shihua; Ding, Xifeng; Yuan, Guoliang

    2017-06-01

    Solid oxide fuel cells (SOFCs) offer great promise for the most efficient and cost-effective conversion to electricity of a wide variety of fuels. The cathode materials with high electro-catalytic activity for oxygen reduction reaction is vital to the development of commercially-viable SOFCs to be operated at reduced temperatures. In present study, cobalt-based perovskite oxides SrxCo0.7Nb0.1Fe0.2O3-δ (SCNF, x = 0.95 and 1) were comparatively investigated as promising cathode materials for intermediate-temperature SOFCs. The SCNF compounds with a slight Sr deficiency (S0.95CNF) exhibited single phase of primitive cubic structure with Pm-3m symmetry. A small Sr deficiency is demonstrated to greatly enhance the electrochemical performance of stoichiometric SCNF cathode due to significantly increased oxygen vacancy. The polarization resistance of S0.95CNF at 700 °C was 0.11 Ω cm2, only about 61% of SCNF. The rate limiting step for oxygen reduction reaction (ORR) is demonstrated to be oxygen ion transfer within the bulk electrode and/or from electrode to electrolyte through the triple phase boundary. Full cells with the SCNF cathode present good performance and stable output at reduced temperatures, indicating the great potential for enhanced performance of Co-based cathodes with A-site deficiency.

  3. Toward Switchable Photovoltaic Effect via Tailoring Mobile Oxygen Vacancies in Perovskite Oxide Films.

    PubMed

    Ge, Chen; Jin, Kui-Juan; Zhang, Qing-Hua; Du, Jian-Yu; Gu, Lin; Guo, Hai-Zhong; Yang, Jing-Ting; Gu, Jun-Xing; He, Meng; Xing, Jie; Wang, Can; Lu, Hui-Bin; Yang, Guo-Zhen

    2016-12-21

    The defect chemistry of perovskite oxides involves the cause to most of their abundant functional properties, including interface magnetism, charge transport, ionic exchange, and catalytic activity. The possibility to achieve dynamic control over oxygen anion vacancies offers a unique opportunity for the development of appealing switchable devices, which at present are commonly based on ferroelectric materials. Herein, we report the discovery of a switchable photovoltaic effect, that the sign of the open voltage and the short circuit current can be reversed by inverting the polarity of the applied field, upon electrically tailoring the distribution of oxygen vacancies in perovskite oxide films. This phenomenon is demonstrated in lateral photovoltaic devices based on both ferroelectric BiFeO 3 and paraelectric SrTiO 3 films, under a reversed applied field whose magnitude is much smaller than the coercivity value of BiFeO 3 . The migration of oxygen vacancies was directly observed by employing an advanced annular bright-field scanning transmission electron microscopy technique with in situ biasing equipment. We conclude that the band bending induced by the motion of oxygen vacancies is the driving force for the reversible switching between two photovoltaic states. The present work can provide an active path for the design of novel switchable photovoltaic devices with a wide range of transition metal oxides in terms of the ionic degrees of freedom.

  4. Striped lanthanum cobaltite films: how strain orders oxygen defects

    NASA Astrophysics Data System (ADS)

    Birenbaum, Axiel Yael; Biegalski, Michael D.; Qiao, Liang; Cooper, Valentino R.; Borisevich, Albina

    Oxygen-deficient metal cobalt oxides have been widely studied for solid oxide fuel cell cathode applications. In order to predict atomic-scale transport pathways, a thorough understanding of its defect properties is crucial. Previous studies, including Scanning Transmission Electron Microscopy (STEM), demonstrate lanthanum cobaltite, grown as thin films on [100]pc oriented perovskites, spontaneously order its oxygen vacancies. In this work, we investigate the behavior of LaCoO3 - δ thin films grown on SrTiO3 [111] surface to determine if orientation can be used to shape the anisotropy of oxygen transport. For these films, STEM studies reveal ordered vacancy arrangements. We do so by establishing the structural and electronic properties of LaCoO3 - δ on SrTiO3, using ab initio electronic structure calculations. We then treat how epitaxial strain leads to oxygen vacancies forming these distinctive stripe patterns. The impact of different substrates is addressed. In addition, this leads to an opportunity to discuss the effect of reduced symmetry in oxygen deficient compounds on cobalt oxide behavior compared to the ideal perovskite environment. Research was sponsored by the US DoE, Office of Science, BES, MSED, and used resources at NERSC and OLCF.

  5. 30 CFR 77.1901-1 - Methane and oxygen deficiency tests; approved devices.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Methane and oxygen deficiency tests; approved... AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1901-1 Methane and oxygen deficiency tests; approved devices. Tests for oxygen deficiency shall be made with a permissible flame safety lamp or other...

  6. 30 CFR 77.1901-1 - Methane and oxygen deficiency tests; approved devices.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Methane and oxygen deficiency tests; approved... AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1901-1 Methane and oxygen deficiency tests; approved devices. Tests for oxygen deficiency shall be made with a permissible flame safety lamp or other...

  7. 30 CFR 77.1901-1 - Methane and oxygen deficiency tests; approved devices.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Methane and oxygen deficiency tests; approved... AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1901-1 Methane and oxygen deficiency tests; approved devices. Tests for oxygen deficiency shall be made with a permissible flame safety lamp or other...

  8. 30 CFR 77.1901-1 - Methane and oxygen deficiency tests; approved devices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Methane and oxygen deficiency tests; approved... AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1901-1 Methane and oxygen deficiency tests; approved devices. Tests for oxygen deficiency shall be made with a permissible flame safety lamp or other...

  9. Oxygen content tailored magnetic and electronic properties in cobaltite double perovskite thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harrell, Zach John; Enriquez, Erik M.; Chen, Aiping

    Oxygen content in transition metal oxides is one of the most important parameters to control for the desired physical properties. Recently, we have systematically studied the oxygen content and property relationship of the double perovskite PrBaCo 2O 5.5+δ (PBCO) thin films deposited on the LaAlO 3 substrates. The oxygen content in the films was varied by in-situ annealing in a nitrogen, oxygen, or ozone environment. Associated with the oxygen content, the out-of-plane lattice parameter progressively decreases with increasing oxygen content in the films. The saturated magnetization shows a drastic increase and resistivity is significantly reduced in the ozone annealed samples,more » indicating the strong coupling between physical properties and oxygen content. Furthermore, these results demonstrate that the magnetic properties of PBCO films are highly dependent on the oxygen contents, or the film with higher oxygen uptake has the largest magnetization.« less

  10. Oxygen content tailored magnetic and electronic properties in cobaltite double perovskite thin films

    DOE PAGES

    Harrell, Zach John; Enriquez, Erik M.; Chen, Aiping; ...

    2017-02-27

    Oxygen content in transition metal oxides is one of the most important parameters to control for the desired physical properties. Recently, we have systematically studied the oxygen content and property relationship of the double perovskite PrBaCo 2O 5.5+δ (PBCO) thin films deposited on the LaAlO 3 substrates. The oxygen content in the films was varied by in-situ annealing in a nitrogen, oxygen, or ozone environment. Associated with the oxygen content, the out-of-plane lattice parameter progressively decreases with increasing oxygen content in the films. The saturated magnetization shows a drastic increase and resistivity is significantly reduced in the ozone annealed samples,more » indicating the strong coupling between physical properties and oxygen content. Furthermore, these results demonstrate that the magnetic properties of PBCO films are highly dependent on the oxygen contents, or the film with higher oxygen uptake has the largest magnetization.« less

  11. 30 CFR 77.102 - Tests for methane; oxygen deficiency; qualified person, additional requirement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Tests for methane; oxygen deficiency; qualified... methane; oxygen deficiency; qualified person, additional requirement. Notwithstanding the provisions of... and oxygen deficiency unless he has demonstrated to the satisfaction of an authorized representative...

  12. 30 CFR 77.102 - Tests for methane; oxygen deficiency; qualified person, additional requirement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Tests for methane; oxygen deficiency; qualified... methane; oxygen deficiency; qualified person, additional requirement. Notwithstanding the provisions of... and oxygen deficiency unless he has demonstrated to the satisfaction of an authorized representative...

  13. 30 CFR 77.102 - Tests for methane; oxygen deficiency; qualified person, additional requirement.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Tests for methane; oxygen deficiency; qualified... methane; oxygen deficiency; qualified person, additional requirement. Notwithstanding the provisions of... and oxygen deficiency unless he has demonstrated to the satisfaction of an authorized representative...

  14. 30 CFR 77.102 - Tests for methane; oxygen deficiency; qualified person, additional requirement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Tests for methane; oxygen deficiency; qualified... methane; oxygen deficiency; qualified person, additional requirement. Notwithstanding the provisions of... and oxygen deficiency unless he has demonstrated to the satisfaction of an authorized representative...

  15. The effect of oxygen molecule adsorption on lead iodide perovskite surface by first-principles calculation

    NASA Astrophysics Data System (ADS)

    Ma, Xia-Xia; Li, Ze-Sheng

    2018-01-01

    Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O2 and perovskite based on the first-principles calculation. The results show that O2 is adsorbed on the (100) surface of MAPbI3 perovskite mainly by Van der Waals force. O2 adsorption makes the MAPbI3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO2). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O2 to form superoxide. The theoretical power conversion efficiency of the system with and without O2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O2 adsorption is slightly lower than that of the system without O2 adsorption. This result indicates that avoiding the introduction of O2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.

  16. 30 CFR 77.101 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Tests for methane and for oxygen deficiency... oxygen deficiency; qualified person. (a) The provisions of Subparts C, P, R, and T of this Part 77 require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a...

  17. 30 CFR 77.101 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Tests for methane and for oxygen deficiency... oxygen deficiency; qualified person. (a) The provisions of Subparts C, P, R, and T of this Part 77 require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a...

  18. 30 CFR 77.101 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Tests for methane and for oxygen deficiency... oxygen deficiency; qualified person. (a) The provisions of Subparts C, P, R, and T of this Part 77 require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a...

  19. 30 CFR 77.101 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Tests for methane and for oxygen deficiency... oxygen deficiency; qualified person. (a) The provisions of Subparts C, P, R, and T of this Part 77 require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a...

  20. Perovskites in catalysis and electrocatalysis

    NASA Astrophysics Data System (ADS)

    Hwang, Jonathan; Rao, Reshma R.; Giordano, Livia; Katayama, Yu; Yu, Yang; Shao-Horn, Yang

    2017-11-01

    Catalysts for chemical and electrochemical reactions underpin many aspects of modern technology and industry, from energy storage and conversion to toxic emissions abatement to chemical and materials synthesis. This role necessitates the design of highly active, stable, yet earth-abundant heterogeneous catalysts. In this Review, we present the perovskite oxide family as a basis for developing such catalysts for (electro)chemical conversions spanning carbon, nitrogen, and oxygen chemistries. A framework for rationalizing activity trends and guiding perovskite oxide catalyst design is described, followed by illustrations of how a robust understanding of perovskite electronic structure provides fundamental insights into activity, stability, and mechanism in oxygen electrocatalysis. We conclude by outlining how these insights open experimental and computational opportunities to expand the compositional and chemical reaction space for next-generation perovskite catalysts.

  1. Perovskites in catalysis and electrocatalysis.

    PubMed

    Hwang, Jonathan; Rao, Reshma R; Giordano, Livia; Katayama, Yu; Yu, Yang; Shao-Horn, Yang

    2017-11-10

    Catalysts for chemical and electrochemical reactions underpin many aspects of modern technology and industry, from energy storage and conversion to toxic emissions abatement to chemical and materials synthesis. This role necessitates the design of highly active, stable, yet earth-abundant heterogeneous catalysts. In this Review, we present the perovskite oxide family as a basis for developing such catalysts for (electro)chemical conversions spanning carbon, nitrogen, and oxygen chemistries. A framework for rationalizing activity trends and guiding perovskite oxide catalyst design is described, followed by illustrations of how a robust understanding of perovskite electronic structure provides fundamental insights into activity, stability, and mechanism in oxygen electrocatalysis. We conclude by outlining how these insights open experimental and computational opportunities to expand the compositional and chemical reaction space for next-generation perovskite catalysts. Copyright © 2017, American Association for the Advancement of Science.

  2. 30 CFR 75.150 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Tests for methane and for oxygen deficiency... Certified Persons § 75.150 Tests for methane and for oxygen deficiency; qualified person. (a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen...

  3. 30 CFR 75.150 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Tests for methane and for oxygen deficiency... Certified Persons § 75.150 Tests for methane and for oxygen deficiency; qualified person. (a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen...

  4. 30 CFR 75.150 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Tests for methane and for oxygen deficiency... Certified Persons § 75.150 Tests for methane and for oxygen deficiency; qualified person. (a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen...

  5. 30 CFR 75.150 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Tests for methane and for oxygen deficiency... Certified Persons § 75.150 Tests for methane and for oxygen deficiency; qualified person. (a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen...

  6. 30 CFR 75.150 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Tests for methane and for oxygen deficiency... Certified Persons § 75.150 Tests for methane and for oxygen deficiency; qualified person. (a) The provisions of Subpart D—Ventilation of this part and § 75.1106 require that tests for methane and for oxygen...

  7. Transition metal substituted SrTiO3 perovskite oxides as promising functional materials for oxygen sensor

    NASA Astrophysics Data System (ADS)

    Misra, Sunasira

    2012-07-01

    Modern industries employ several gases as process fluids. Leakage of these gases in the operating area could lead to undesirable consequences. Even in chemical industries, which use large quantities of inert gases in confined areas, accidental leakage of these process gases would result in the reduction of oxygen partial pressure in atmospheric air. For instance, large amounts of gaseous nitrogen and argon are used in pharmaceutical industries, gas filling/bottling plants, operating area of Fast Breeder reactors, etc. Fall of concentration of oxygen in air below 17% could lead to life risk (Asphyxiation) of the working personnel that has to be checked well in advance. Further, when the leaking gas is of explosive nature, its damage potential would be very high if its concentration level in air increases beyond its lower explosive limit. Surveillance of the ambient within these industries at the critical areas and also in the environment around them for oxygen therefore becomes highly essential. Sensitive and selective gas sensors made of advanced materials are required to meet this demand of monitoring environmental pollution. The perovskite class of oxides (ABO3) is chemically stable even at high temperatures and can tolerate large levels of dopants without phase transformations. The electronic properties of this parent functional material can be tailored by adding appropriate dopants that exhibit different valence states. Aliovalent transition metal substituted SrTiO3 perovskites are good mixed ionic and electronic conductors and potential candidates for sensing oxygen at percentage level exploiting their oxygen pressure dependent electrical conductivity. This paper presents the preparation, study of electrical conductivity and oxygen-sensing characteristics of iron and cobalt substituted SrTiO3.

  8. First-principles study of band gap engineering via oxygen vacancy doping in perovskite ABB'O₃ solid solutions

    DOE PAGES

    Qi, Tingting; Curnan, Matthew T.; Kim, Seungchul; ...

    2011-12-15

    Oxygen vacancies in perovskite oxide solid solutions are fundamentally interesting and technologically important. However, experimental characterization of the vacancy locations and their impact on electronic structure is challenging. We have carried out first-principles calculations on two Zr-modified solid solutions, Pb(Zn 1/3Nb 2/3)O₃ and Pb(Mg 1/3Nb 2/3)O₃, in which vacancies are present. We find that the vacancies are more likely to reside between low-valent cation-cation pairs than high-valent cation-cation pairs. Based on the analysis of our results, we formulate guidelines that can be used to predict the location of oxygen vacancies in perovskite solid solutions. Our results show that vacancies canmore » have a significant impact on both the conduction and valence band energies, in some cases lowering the band gap by ≈0.5 eV. The effects of vacancies on the electronic band structure can be understood within the framework of crystal field theory.« less

  9. 30 CFR 77.1901-1 - Methane and oxygen deficiency tests; approved devices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Methane and oxygen deficiency tests; approved... AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1901-1 Methane and oxygen deficiency tests... means approved by the Secretary, and tests for methane shall be made with a methane detector approved by...

  10. Mineralogy and Oxygen Isotope Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Snead, C.; Rahman, Z.; McKeegan, K. D.

    2012-01-01

    Hibonite-rich Ca- and Al-rich inclusions (CAIs) are among the earliest formed solids that condensed in the early nebula. We discovered an unusual refractory inclusion from the Allende CV3 chondrite (SHAL) containing an approx 500 micron long single crystal of hibonite and co-existing coarse-grained perovskite. The mineralogy and petrography of SHAL show strong similarities to some FUN inclusions, especially HAL. Here we report on the mineralogy, petrography, mineral chemistry and oxygen isotopic compositions in SHAL.

  11. 30 CFR 77.102 - Tests for methane; oxygen deficiency; qualified person, additional requirement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Tests for methane; oxygen deficiency; qualified... methane; oxygen deficiency; qualified person, additional requirement. Notwithstanding the provisions of § 77.101, on and after December 30, 1971, no person shall be a qualified person for testing for methane...

  12. 30 CFR 77.101 - Tests for methane and for oxygen deficiency; qualified person.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Tests for methane and for oxygen deficiency... AREAS OF UNDERGROUND COAL MINES Qualified and Certified Persons § 77.101 Tests for methane and for... require that tests for methane and for oxygen deficiency be made by a qualified person. A person is a...

  13. Strontium-free rare earth perovskite ferrites with fast oxygen exchange kinetics: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Berger, Christian; Bucher, Edith; Windischbacher, Andreas; Boese, A. Daniel; Sitte, Werner

    2018-03-01

    The Sr-free mixed ionic electronic conducting perovskites La0.8Ca0.2FeO3-δ (LCF82) and Pr0.8Ca0.2FeO3-δ (PCF82) were synthesized via a glycine-nitrate process. Crystal structure, phase purity, and lattice constants were determined by XRD and Rietveld analysis. The oxygen exchange kinetics and the electronic conductivity were obtained from in-situ dc-conductivity relaxation experiments at 600-800 °C and 1×10-3≤pO2/bar≤0.1. Both LCF82 and PCF82 show exceptionally fast chemical surface exchange coefficients and chemical diffusion coefficients of oxygen. The oxygen nonstochiometry of LCF82 and PCF82 was determined by precision thermogravimetry. A point defect model was used to calculate the thermodynamic factors of oxygen and to estimate self-diffusion coefficients and ionic conductivities. Density Functional Theory (DFT) calculations on the crystal structure, oxygen vacancy formation as well as oxygen migration energies are in excellent agreement with the experimental values. Due to their favourable properties both LCF82 and PCF82 are of interest for applications in solid oxide fuel cell cathodes, solid oxide electrolyser cell anodes, oxygen separation membranes, catalysts, or electrochemical sensors.

  14. Magnetism and Metal-Insulator Transition in Oxygen Deficient SrTiO 3

    DOE PAGES

    Lopez-Bezanilla, Alejandro; Ganesh, Panchapakesan; Littlewood, Peter B.

    2015-09-08

    First-principles calculations to study the electronic and magnetic properties of bulk, oxygen-deficient SrTiO 3 (STO) under different doping conditions and densities have been conducted. The appearance of magnetism in oxygen-deficient STO is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. We find that while an isolated vacancy behaves as a nonmagnetic double donor, manipulation of the doping conditions allows the stability of a single-donor state, with emergent local moments coupled ferromagnetically by carriers in the conduction band. Strong local lattice distortions enhancemore » the binding of this state. As a result, the energy of the in-gap local moment can be further tuned by orthorhombic strain. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient STO, which may have important implications in the design of optical devices.« less

  15. Effect of lone-electron-pair cations on the orientation of crystallographic shear planes in anion-deficient perovskites.

    PubMed

    Batuk, Dmitry; Batuk, Maria; Abakumov, Artem M; Tsirlin, Alexander A; McCammon, Catherine; Dubrovinsky, Leonid; Hadermann, Joke

    2013-09-03

    Factors affecting the structure and orientation of the crystallographic shear (CS) planes in anion-deficient perovskites were investigated using the (Pb(1-z)Sr(z))(1-x)Fe(1+x)O(3-y) perovskites as a model system. The isovalent substitution of Sr(2+) for Pb(2+) highlights the influence of the A cation electronic structure because these cations exhibit very close ionic radii. Two compositional ranges have been identified in the system: 0.05 ≤ z ≤ 0.2, where the CS plane orientation gradually varies but stays close to (203)p, and 0.3 ≤ z ≤ 0.45 with (101)p CS planes. The incommensurately modulated structure of Pb0.792Sr0.168Fe1.040O2.529 was refined from neutron powder diffraction data using the (3 + 1)D approach (space group X2/m(α0γ), X = (1/2, 1/2, 1/2, 1/2), a = 3.9512(1) Å, b = 3.9483(1) Å, c = 3.9165(1) Å, β = 93.268(2)°, q = 0.0879(1)a* + 0.1276(1)c*, RF = 0.023, RP = 0.029, and T = 900 K). A comparison of the compounds with different CS planes indicates that the orientation of the CS planes is governed mainly by the stereochemical activity of the lone-electron-pair cations inside the perovskite blocks.

  16. Density functional study on redox energetics of LaMO{sub 3−δ} (M=Sc–Cu) perovskite-type oxides

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pishahang, Mehdi, E-mail: Mehdi.Pishahang@sintef.no; Erik Mohn, Chris; Stølen, Svein

    2016-01-15

    This study evaluates the redox energetics of LaMO{sub 3−δ} (M=Sc–Cu) perovskite-type oxides via generalized gradient approximation (GGA) to DFT. Two different approaches to redox energetics of oxygen deficient perovskites of strongly non-stoichiometric (δ=0.5) and dilute defect limits (δ→0) are studied. In the first approach the enthalpies of oxidation are calculated using the stoichiometric end-compounds of LaMO{sub 3} and LaMO{sub 2.5}. The most common structures for the reduced lanthanides and strontides similar to the ones experimentally reported for SrMnO{sub 2.5}, SrFeO{sub 2.5}, and LaNiO{sub 2.5} are considered. The second approach to the oxidation enthalpies termed (δ→0) follow the trend observed experimentally.more » This approach represents the experimental conditions of the measured oxygen enthalpies, and is hampered less by the artificial features due to spurious self-interaction errors in GGA.« less

  17. Oxygen-vacancy-mediated dielectric property in perovskite Eu0.5Ba0.5TiO3-δ epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Li, Weiwei; Gu, Junxing; He, Qian; Zhang, Kelvin H. L.; Wang, Chunchang; Jin, Kuijuan; Wang, Yongqiang; Acosta, Matias; Wang, Haiyan; Borisevich, Albina Y.; MacManus-Driscoll, Judith L.; Yang, Hao

    2018-04-01

    Dielectric relaxation in ABO3 perovskite oxides can result from many different charge carrier-related phenomena. Despite a strong understanding of dielectric relaxations, a detailed investigation of the relationship between the content of oxygen vacancies (VO) and dielectric relaxation has not been performed in perovskite oxide films. In this work, we report a systematic investigation of the influence of the VO concentration on the dielectric relaxation of Eu0.5Ba0.5TiO3-δ epitaxial thin films. Nuclear resonance backscattering spectrometry was used to directly measure the oxygen concentration in Eu0.5Ba0.5TiO3-δ films. We found that dipolar defects created by VO interact with the off-centered Ti ions, which results in the dielectric relaxation in Eu0.5Ba0.5TiO3-δ films. Activation energy gradually increases with the increasing content of VO. The present work significantly extends our understanding of relaxation properties in oxide films.

  18. Non-hydrolytic metal oxide films for perovskite halide overcoating and stabilization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martinson, Alex B.; Kim, In Soo

    A method of protecting a perovskite halide film from moisture and temperature includes positioning the perovskite halide film in a chamber. The chamber is maintained at a temperature of less than 200 degrees Celsius. An organo-metal compound is inserted into the chamber. A non-hydrolytic oxygen source is subsequently inserted into the chamber. The inserting of the organo-metal compound and subsequent inserting of the non-hydrolytic oxygen source into the chamber is repeated for a predetermined number of cycles. The non-hydrolytic oxygen source and the organo-metal compound interact in the chamber to deposit a non-hydrolytic metal oxide film on perovskite halide film.more » The non-hydrolytic metal oxide film protects the perovskite halide film from relative humidity of greater than 35% and a temperature of greater than 150 degrees Celsius, respectively.« less

  19. Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells

    PubMed Central

    Zhao, Jingjing; Deng, Yehao; Wei, Haotong; Zheng, Xiaopeng; Yu, Zhenhua; Shao, Yuchuan; Shield, Jeffrey E.; Huang, Jinsong

    2017-01-01

    Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane direction and in-plane tensile strain. The strain accelerates degradation of perovskite films under illumination, which can be explained by increased ion migration in strained OIHP films. This study points out an avenue to enhance the intrinsic stability of perovskite films and solar cells by reducing residual strain in perovskite films. PMID:29159287

  20. Development of Perovskite-Type Materials for Thermoelectric Application.

    PubMed

    Wu, Tingjun; Gao, Peng

    2018-06-12

    Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

  1. Evolution of Structural and Electrical Properties of Oxygen-Deficient VO2 under Low Temperature Heating Process.

    PubMed

    Zhang, Jiasong; Zhao, Zhengjing; Li, Jingbo; Jin, Haibo; Rehman, Fida; Chen, Pengwan; Jiang, Yijie; Chen, Chunxu; Cao, Maosheng; Zhao, Yongjie

    2017-08-16

    Structural stability and functional performances of vanadium dioxide (VO 2 ) are strongly influenced by oxygen vacancies. However, the mechanism of metal-insulator transition (MIT) influenced by defects is still under debate. Here, we study the evolution of structure and electrical property of oxygen-deficient VO 2 by a low temperature annealing process (LTP) based on a truss-structured VO 2 nanonet. The oxygenation process of the oxygen-deficient VO 2 is greatly prolonged, which enables us to probe the gradual change of properties of the oxygen-deficient VO 2 . A continuous lattice reduction is observed during LTP. No recrystallization and structural collapse of the VO 2 nanonet can be found after LTP. The valence-band X-ray photoelectron spectroscopy (XPS) measurements indicate that the oxygen deficiency strongly affects the energy level of the valence band edge. Correspondingly, the resistance changes of the VO 2 films from 1 to 4.5 orders of magnitude are achieved by LTP. The effect of oxygen vacancy on the electric field driven MIT is investigated. The threshold value of voltage triggering the MIT decreases with increasing the oxygen vacancy concentration. This work demonstrates a novel and effective way to control the content of oxygen vacancies in VO 2 and the obvious impact of oxygen vacancy on MIT, facilitating further research on the role of oxygen vacancy in structure and MIT of VO 2 , which is important for the deep understanding of MIT and exploiting innovative functional application of VO 2 .

  2. Computational mineral physics and the physical properties of perovskite.

    PubMed

    Brodholt, John P; Oganov, A R; Price, G D

    2002-11-15

    The inherent uncertainties in modern first-principles calculations are reviewed using geophysically relevant examples. The elastic constants of perovskite at lower-mantle temperatures and pressures are calculated using ab initio molecular dynamics. These are used in conjunction with seismic tomographic models to estimate that the lateral temperature contrasts in the Earth's lower mantle are 800 K at a depth of 1000 km, and 1500 K at a depth of 2000 km. The effect of Al(3+) on the compressibility of MgSiO(3) perovskite is calculated using three different pseudopotentials. The results confirm earlier work and show that the compressibility of perovskites with Al(3+) substituted for both Si(4+) and Mg(2+) is very similar to the compressibility of Al(3+)-free perovskite. Even when 100% of the Si(4+) and Mg(2+) ions are replaced with Al(3+), the bulk modulus is only 7% less than that for Al(3+)-free perovskite. In contrast, perovskites where Al(3+) substitutes for Si(4+) only and that are charge balanced by oxygen vacancies do show higher compressibilities. When corrected to similar concentrations of Al(3+), the calculated compressibilities of the oxygen-vacancy-rich perovskites are in agreement with experimental results.

  3. Exsolution trends and co-segregation aspects of self-grown catalyst nanoparticles in perovskites.

    PubMed

    Kwon, Ohhun; Sengodan, Sivaprakash; Kim, Kyeounghak; Kim, Gihyeon; Jeong, Hu Young; Shin, Jeeyoung; Ju, Young-Wan; Han, Jeong Woo; Kim, Guntae

    2017-06-28

    In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn 2 O 5+δ layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution.

  4. Exsolution trends and co-segregation aspects of self-grown catalyst nanoparticles in perovskites

    PubMed Central

    Kwon, Ohhun; Sengodan, Sivaprakash; Kim, Kyeounghak; Kim, Gihyeon; Jeong, Hu Young; Shin, Jeeyoung; Ju, Young-Wan; Han, Jeong Woo; Kim, Guntae

    2017-01-01

    In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn2O5+δ layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution. PMID:28656965

  5. Synthesis and applications of nanoporous perovskite metal oxides

    PubMed Central

    Huang, Xiubing; Zhao, Guixia

    2018-01-01

    Perovskite-type metal oxides have been widely investigated and applied in various fields in the past several decades due to their extraordinary variability of compositions and structures with targeted physical and chemical properties (e.g., redox behaviour, oxygen mobility, electronic and ionic conductivity). Recently, nanoporous perovskite metal oxides have attracted extensive attention because of their special morphology and properties, as well as superior performance. This minireview aims at summarizing and reviewing the different synthesis methods of nanoporous perovskite metal oxides and their various applications comprehensively. The correlations between the nanoporous structures and the specific performance of perovskite oxides are summarized and highlighted. The future research directions of nanoporous perovskite metal oxides are also prospected. PMID:29862001

  6. Decreasing the Hydroxylation Affinity of La 1–x Sr x MnO 3 Perovskites To Promote Oxygen Reduction Electrocatalysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stoerzinger, Kelsey A.; Hong, Wesley T.; Wang, Xiao Renshaw

    Understanding the interaction between oxides and water is critical to design many of their functionalities, including the electrocatalysis of molecular oxygen reduction. In this study, we probed the hydroxylation of model (001)-oriented La(1-x)SrxMnO3 (LSMO) perovskite surfaces, where the electronic structure and manganese valence was controlled by five substitution levels of lanthanum with strontium, using ambient pressure X-ray photoelectron spectroscopy in a humid environment. The degree of hydroxyl formation on the oxide surface correlated with the proximity of the valence band center relative to the Fermi level. LSMO perovskites with a valence band center closer to the Fermi level were moremore » reactive toward water, forming more hydroxyl species at a given relative humidity. More hydroxyl species correlate with greater electron-donating character to the surface free energy in wetting, and reduce the activity to catalyze oxygen reduction reaction (ORR) kinetics in basic solution. New strategies to design more active catalysts should include design of electronically conducting oxides with lower valence band centers relative to the Fermi level at ORR-relevant potentials.« less

  7. Origin of Light Induced Photophysical Effects in Organic Metal Halide Perovskites in the Presence of Oxygen.

    PubMed

    Anaya, Miguel; Galisteo-López, Juan F; Calvo, Mauricio Ernesto; Espinos, Juan P; Miguez, Hernan

    2018-06-21

    Herein we present a combined study of the evolution of both the photoluminescence and the surface chemical structure of organic metal halide perovskites as environmental oxygen pressure rises from ultra-high vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photo-excitation under controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation. We find direct evidence of the formation of a superficial layer of negatively charged oxygen species capable of repelling the halide anions away from the surface and towards the bulk. The reported photoluminescence (PL) transient dynamics, the partial recovery of the initial state when photoexcitation stops and the eventual degradation after intense exposure times can thus be rationalized.

  8. Characterization of ordering in A-site deficient perovskite Ca 1–xLa 2x/3TiO 3 using STEM/EELS

    DOE PAGES

    Danaie, Mohsen; Kepaptsoglou, Demie; Ramasse, Quentin M.; ...

    2016-09-15

    The vacancy ordering behavior of an A-site deficient perovskite system, Ca 1–xLa 2x/3TiO 3, was studied using atomic resolution scanning transmission electron microscopy (STEM) in conjunction with electron energy-loss spectroscopy (EELS), with the aim of determining the role of A-site composition changes. At low La content (x = 0.2), adopting Pbnm symmetry, there was no indication of long-range ordering. Domains, with clear boundaries, were observed in bright-field (BF) imaging, but were not immediately visible in the corresponding high-angle annular dark-field (HAADF) image. These boundaries, with the aid of displacement maps from A-site cations in the HAADF signal, are shown tomore » be tilt boundaries. At the La-rich end of the composition (x = 0.9), adopting Cmmm symmetry, long-range ordering of vacancies and La 3+ ions was observed, with alternating La-rich and La-poor layers on (001)p planes, creating a double perovskite lattice along the c axis. These highly ordered domains can be found isolated within a random distribution of vacancies/La 3+, or within a large population, encompassing a large volume. In regions with a high number density of double perovskite domains, these highly ordered domains were separated by twin boundaries, with 90° or 180° lattice rotations across boundaries. In conclusion, the occurrence and characteristics of these ordered structures are discussed and compared with similar perovskite systems.« less

  9. Large isosymmetric reorientation of oxygen octahedra rotation axes in epitaxially strained perovskites.

    PubMed

    Rondinelli, James M; Coh, Sinisa

    2011-06-10

    Using first-principles density functional theory calculations, we discover an anomalously large biaxial strain-induced octahedral rotation axis reorientation in orthorhombic perovskites with tendency towards rhombohedral symmetry. The transition between crystallographically equivalent (isosymmetric) structures with different octahedral rotation magnitudes originates from strong strain-octahedral rotation coupling available to perovskites and the energetic hierarchy among competing octahedral tilt patterns. By elucidating these criteria, we suggest many functional perovskites would exhibit the transition in thin film form, thus offering a new landscape in which to tailor highly anisotropic electronic responses.

  10. Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

    DOEpatents

    Rieke, Peter C [Pasco, WA; Coffey, Gregory W [Richland, WA; Pederson, Larry R [Kennewick, WA; Marina, Olga A [Richland, WA; Hardy, John S [Richland, WA; Singh, Prabhaker [Richland, WA; Thomsen, Edwin C [Richland, WA

    2010-07-20

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

  11. Dinitrogen Fixation Within and Adjacent to Oxygen Deficient Waters of the Eastern Tropical South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Widner, B.; Mulholland, M. R.; Bernhardt, P. W.; Chang, B. X.; Jayakumar, A.

    2016-02-01

    Recent work suggests that planktonic diazotrophs are geographically more widely distributed than previously thought including relatively warm (14-23oC) aphotic oxygenated pelagic waters and in aphotic waters within oxygen deficient zones. Because the volume of aphotic water in the ocean is large and may increase in the future, if dinitrogen (N2) fixation is widely occurring at sub-euphotic depths, this could result in a dramatic upward revision of global nitrogen (N) inputs via this process. N2 fixation rates were measured during a cruise in the Eastern Tropical South Pacific using stable isotope tracer techniques that account for slow gas dissolution. Results are compared with light, nutrient, and oxygen gradients (and necessarily temperature gradients). In addition, rates of N2 fixation made in vertical profiles within and above oxygen deficient waters are compared with those measured in vertical profiles adjacent to oxygen deficient waters. Results suggest that while rates of N2 fixation were measurable in deeper anoxic waters, volumetric N2 fixation rates were higher in surface waters.

  12. Oxygen vacancy induced structural evolution of SrFeO3 -x epitaxial thin film from brownmillerite to perovskite

    NASA Astrophysics Data System (ADS)

    Roh, Seulki; Lee, Seokbae; Lee, Myounghoon; Seo, Yu-Seong; Khare, Amit; Yoo, Taesup; Woo, Sungmin; Choi, Woo Seok; Hwang, Jungseek; Glamazda, A.; Choi, K.-Y.

    2018-02-01

    We investigated SrFeO3 -x thin films on a SrTiO3 (001) substrate prepared via pulsed laser epitaxy using an optical spectroscopy technique. The oxygen vacancy level (x ) was controlled by post-annealing processes at different oxygen partial pressures. We achieved a brownmillerite (BM) structure at x =0.5 and observed the evolution of the crystal structure from BM into perovskite (PV) as the oxygen concentration increased. We observed the evolution of infrared-active phonons with respect to the oxygen concentration, which was closely related to the structural evolution observed via x-ray diffraction. We identified the phonons using the shell-model calculation. Furthermore, we studied temperature-dependent behaviors of the phonon modes of three representative samples: PV and two BMs (BMoop and BMip) with different orientations of the oxygen vacancy channel. In the BMoop sample, we observed a phonon mode, which exhibited an unusual redshift with decreasing temperature; this behavior may have been due to the apical oxygen instability in the FeO6 octahedron. Our results provide important information regarding the ionic conduction mechanism in SrFeO3 -x material systems.

  13. Energetics of magnesium, strontium, and barium doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Cheng, Jihong; Navrotsky, Alexandra

    2004-01-01

    LaGaO 3 perovskites doped with Sr or Ba at the La site and Mg at the Ga site were prepared by solid-state reaction or sol-gel method and characterized. Enthalpies of formation from constituent oxides at 298 K were determined by high-temperature oxide melt solution calorimetry. Energetic trends are discussed in terms of defect chemistry. As oxygen deficiency increases, formation enthalpies define three trends, LaGa 1- yMg yO 3- δ (LGM), La 1- xSr xGa 1- yMg yO 3- δ (LSGM), and La 1- xBa xGa 1- yMg yO 3- δ (LBGM). They become less exothermic with increasing doping, suggesting a dominant destabilization effect from oxygen vacancies. The endothermic enthalpy of vacancy formation is 275±37, 166±18 and 138±12 kJ/mol of VO·· for LGM, LBGM and LSGM, respectively. Tolerance factor and ion size mismatch also affect enthalpies. In terms of energetics, Sr is the best dopant for the La site and Mg for the Ga site, supporting earlier studies, including oxygen ion conductivity and computer modeling.

  14. Magnetism and metal-insulator transition in oxygen deficient SrTiO3

    NASA Astrophysics Data System (ADS)

    Lopez-Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter

    2015-03-01

    We report new findings in the electronic structure and magnetism of oxygen vacancies in SrTiO3. By means of first-principles calculations we show that the appearance of magnetism in oxygen-deficient SrTiO3 is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. While an isolated vacancy behaves as a non-magnetic double donor, manipulation of the doping conditions allows the stability of a single donor state with emergent local moments. Strong local lattice distortions enhance the binding of this state. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient SrTiO3, which may have important implications in the design of switchable magneto-optic devices. AL-B and PBL were supported by DOE-BES under Contract No. DE-AC02-06CH11357. PG was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT- Battelle, LLC, for the US Department of Energy.

  15. A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

    PubMed Central

    Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

    2015-01-01

    Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm−1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm−2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm−2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode. PMID:26648509

  16. A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

    2015-12-01

    Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm-1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm-2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm-2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

  17. A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells.

    PubMed

    Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

    2015-12-09

    Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm(-1) in 5% H2 and peak power densities of 1.72 and 0.54 W cm(-2) using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm(-2). To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

  18. Facile Aluminum Reduction Synthesis of Blue TiO2 with Oxygen Deficiency for Lithium-Ion Batteries.

    PubMed

    Zheng, Jing; Ji, Guangbin; Zhang, Peng; Cao, Xingzhong; Wang, Baoyi; Yu, Linghui; Xu, Zhichuan J

    2015-12-07

    An ultrafacile aluminum reduction method is reported herein for the preparation of blue TiO2 nanoparticles (donated as Al-TiO2 , anatase phase) with abundant oxygen deficiency for lithium-ion batteries. Under aluminum reduction, the morphology of the TiO2 nanosheets changes from well-defined rectangular into uniform round or oval nanoparticles and the particle size also decreases from 60 to 31 nm, which can aggressively accelerate the lithium-ion diffusion. Electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) results reveal that plentiful oxygen deficiencies relative to the Ti(3+) species were generated in blue Al-TiO2 ; this effectively enhances the electron conductivity of the TiO2 . X-ray photoelectron spectrometry (XPS) analysis indicates that a small peak is observed for the Al-O bond, which probably plays a very important role in the stabilization of the oxygen deficiencies/Ti(3+) species. As a result, the blue Al-TiO2 possesses significantly higher capacity, better rate performance, and a longer cycle life than the white pure TiO2 . Such improvements can be attributed to the decreased particle size, as well as the existence of the oxygen deficiencies/Ti(3+) species. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. High-resolution spectra of stars in globular clusters. VI - Oxygen-deficient red giant stars in M13

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brown, J.A.; Wallerstein, G.; Oke, J.B.

    From high-resolution, high signal-to-noise spectra, abundances of carbon, nitrogen, and oxygen and the C-12/C-13 ratio for five red giants in M13, including star II-67, which has previously been reported to be deficient in oxygen have been determined. Three of the five stars exhibit substantial oxygen deficiencies; O/Fe values range from +0.5 to less than about 0.3. The sum of the CNO nuclides is the same for all stars, which is interpreted as evidence that mixing of CNO-cycled material into the envelope is the cause of the variations in oxygen abundance. 41 refs.

  20. Oxygen-deficient hematite nanorods as high-performance and novel negative electrodes for flexible asymmetric supercapacitors.

    PubMed

    Lu, Xihong; Zeng, Yinxiang; Yu, Minghao; Zhai, Teng; Liang, Chaolun; Xie, Shilei; Balogun, Muhammad-Sadeeq; Tong, Yexiang

    2014-05-21

    Oxygen-deficient α-Fe2 O3 nanorods with outstanding capacitive performance are developed and demonstrated as novel negative electrodes for flexible asymmetric supercapacitors. The asymmetric-supercapacitor device based on the oxygen-deficient α-Fe2 O3 nanorod negative electrode and a MnO2 positive electrode achieves a maximum energy density of 0.41 mW·h/cm(3) ; it is also capable of charging a mobile phone and powering a light-emitting diode indicator. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Hierarchical Mesoporous/Macroporous Perovskite La0.5Sr0.5CoO3-x Nanotubes: A Bifunctional Catalyst with Enhanced Activity and Cycle Stability for Rechargeable Lithium Oxygen Batteries.

    PubMed

    Liu, Guoxue; Chen, Hongbin; Xia, Lu; Wang, Suqing; Ding, Liang-Xin; Li, Dongdong; Xiao, Kang; Dai, Sheng; Wang, Haihui

    2015-10-14

    Perovskites show excellent specific catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solutions; however, small surface areas of the perovskites synthesized by traditional sol-gel methods lead to low utilization of catalytic sites, which gives rise to poor Li-O2 batteries performance and restricts their application. Herein, a hierarchical mesporous/macroporous perovskite La0.5Sr0.5CoO3-x (HPN-LSC) nanotube is developed to promote its application in Li-O2 batteries. The HPN-LSC nanotubes were synthesized via electrospinning technique followed by postannealing. The as-prepared HPN-LSC catalyst exhibits outstanding intrinsic ORR and OER catalytic activity. The HPN-LSC/KB electrode displays excellent performance toward both discharge and charge processes for Li-O2 batteries, which enhances the reversibility, the round-trip efficiency, and the capacity of resultant batteries. The synergy of high catalytic activity and hierarchical mesoporous/macroporous nanotubular structure results in the Li-O2 batteries with good rate capability and excellent cycle stability of sustaining 50 cycles at a current density of 0.1 mA cm(-2) with an upper-limit capacity of 500 mAh g(-1). The results will benefit for the future development of high-performance Li-O2 batteries using hierarchical mesoporous/macroporous nanostructured perovskite-type catalysts.

  2. “Ba{sub 6}Nb{sub 4}RuO{sub 18}” and “LaBa{sub 4}Nb{sub 3}RuO{sub 15}” – The structural consequences of substituting paramagnetic cations into A{sub n}B{sub n−1}O{sub 3n} cation-deficient perovskite oxides

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kamil, Elynor L.; Morgan, Harry W.T.; Hayward, Michael A., E-mail: michael.hayward@chem.ox.ac.uk

    The B-cation deficient perovskite phases Ba{sub 6}Nb{sub 4}RuO{sub 18} and LaBa{sub 4}Nb{sub 3}RuO{sub 15} were prepared by ceramic synthesis. Neutron powder diffraction analysis indicates that rather than the 6-layer and 5-layer cation-deficient perovskite structures expected for these phases (by analogy to the known structures of Ba{sub 6}Nb{sub 4}TiO{sub 18} and LaBa{sub 4}Nb{sub 3}TiO{sub 15}) they adopt 5-layer and 4-layer B-cation deficient perovskite structures respectively, and are better described as Ba{sub 5}Nb{sub 3.33}Ru{sub 0.81}O{sub 15} and Ba{sub 3.16}La{sub 0.84}Nb{sub 2.36}Ru{sub 0.72}O{sub 12}. The factors that lead to the compositionally analogous Nb/Ru and Nb/Ti phases adopting different structures are discussed on themore » basis of the difference between d{sup 0} and non-d{sup 0} transition metal cations. - Graphical abstract: The ruthenium-containing B-cation deficient perovskite phases, Ba{sub 5}Nb{sub 3.33}Ru{sub 0.81}O{sub 15} and Ba{sub 3.16}La{sub 0.84}Nb{sub 2.36}Ru{sub 0.72}O{sub 12}, adopt 5-layer and 4-layer structures respectively, rather than the 6-layer and 5-layer cation-deficient structures adopted by the analogous titanium-containing phases Ba{sub 6}Nb{sub 4}TiO{sub 18} and LaBa{sub 4}Nb{sub 3}TiO{sub 15}. Display Omitted - Highlights: • B-cation deficient perovskite containing paramagnetic cations. • B-cation deficient structure determined by neutron powder diffraction. • Low ‘solubility’ of BaRuO{sub 3} in Ba{sub 5}Nb{sub 4}O{sub 15} leads to novel structure.« less

  3. Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Denny, Yus Rama; Firmansyah, Teguh; Oh, Suhk Kun

    2016-10-15

    Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS),more » and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.« less

  4. Recent advances of lanthanum-based perovskite oxides for catalysis

    DOE PAGES

    Zhu, Huiyuan; Zhang, Pengfei; Dai, Sheng

    2015-09-21

    There is a need to reduce the use of noble metal elements especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties e.g. redox behavior, oxygen mobility, and ion conductivity for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This review article summarizes the recent developmentmore » of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.« less

  5. Induced polarized state in intentionally grown oxygen deficient KTaO{sub 3} thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.

    2013-07-21

    Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO{sub 2}/Ti/Pt substrates. Once they were structurally characterized, the effect of oxygen vacancies on their electric properties was addressed by measuring leakage currents, dielectric constant, electric polarization, and thermally stimulated depolarization currents. By using K{sub 2}O rich KTaO{sub 3} targets and specific deposition conditions, KTaO{sub 3-{delta}} oxygen deficient thin films with a K/Ta = 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO{sub 3-{delta}} thin films are under a compressive strain of 2.3% relative to KTaO{sub 3} crystals. Leakage current results reveal themore » presence of a conductive mechanism, following the Poole-Frenkel formalism. Furthermore, dielectric, polarization, and depolarization current measurements yield the existence of a polarized state below T{sub pol} {approx} 367 Degree-Sign C. A Cole-Cole dipolar relaxation was also ascertained apparently due to oxygen vacancies induced dipoles. After thermal annealing the films in an oxygen atmosphere at a temperature above T{sub pol}, the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.« less

  6. Los Alamos Discovers Super Efficient Solar Using Perovskite Crystals

    ScienceCinema

    Mohite, Aditya; Nie, Wanyi

    2018-05-11

    State-of-the-art photovoltaics using high-purity, large-area, wafer-scale single-crystalline semiconductors grown by sophisticated, high temperature crystal-growth processes offer promising routes for developing low-cost, solar-based clean global energy solutions for the future. Solar cells composed of the recently discovered material organic-inorganic perovskites offer the efficiency of silicon, yet suffer from a variety of deficiencies limiting the commercial viability of perovskite photovoltaic technology. In research to appear in Science, Los Alamos National Laboratory researchers reveal a new solution-based hot-casting technique that eliminates these limitations, one that allows for the growth of high-quality, large-area, millimeter-scale perovskite crystals and demonstrates that highly efficient and reproducible solar cells with reduced trap assisted recombination can be realized.

  7. Perovskite-Perovskite Homojunctions via Compositional Doping.

    PubMed

    Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

    2018-05-11

    One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

  8. Novel catalytic properties of quadruple perovskites

    PubMed Central

    Yamada, Ikuya

    2017-01-01

    ABSTRACT Quadruple perovskite oxides AA′3 B 4O12 demonstrate a rich variety of structural and electronic properties. A large number of constituent elements for A/A′/B-site cations can be introduced using the ultra-high-pressure synthesis method. Development of novel functional materials consisting of earth-abundant elements plays a crucial role in current materials science. In this paper, functional properties, especially oxygen reaction catalysis, for quadruple perovskite oxides CaCu3Fe4O12 and AMn7O12 (A = Ca, La) composed of earth-abundant elements are reviewed. PMID:28970864

  9. Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Van Hest, Marinus F; Moore, David; Klein, Talysa

    Standard layer-by-layer solution processing methods constrain lead-halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet-visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer.more » Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance limitations from the substrate design. Overall, the developed lamination procedure curtails processing constraints, enables new device designs, and affords new opportunities for optimization.« less

  10. Ethanol flame synthesis of carbon nanotubes in deficient oxygen environments

    NASA Astrophysics Data System (ADS)

    Hu, Wei-Chieh; Lin, Ta-Hui

    2016-04-01

    In this study, carbon nanotubes (CNTs) were synthesized using ethanol diffusion flames in a stagnation-flow system composed of an upper oxidizer duct and a lower liquid pool. In the experiments, a gaseous mixture of oxygen and nitrogen flowed from the upper oxidizer duct, and then impinged onto the vertically aligned ethanol pool to generate a planar and steady diffusion flame in a deficient oxygen environment. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. The effect of low oxygen concentration on the formation of CNTs was explored. The oxygen concentration significantly influenced the flame environment and thus the synthesized carbon products. Lowering the oxygen concentration increased the yield, diameter, and uniformity of CNTs. The optimal operating conditions for CNT synthesis were an oxygen concentration in the range of 15%-19%, a flame temperature in the range of 460 °C-870 °C, and a sampling position of 0.5-1 mm below the upper edge of the blue flame front. It is noteworthy that the concentration gradient of C2 species and CO governed the CNT growth directly. CNTs were successfully fabricated in regions with uniform C2 species and CO distributions.

  11. Perovskite-type catalytic materials for environmental applications.

    PubMed

    Labhasetwar, Nitin; Saravanan, Govindachetty; Kumar Megarajan, Suresh; Manwar, Nilesh; Khobragade, Rohini; Doggali, Pradeep; Grasset, Fabien

    2015-06-01

    Perovskites are mixed-metal oxides that are attracting much scientific and application interest owing to their low price, adaptability, and thermal stability, which often depend on bulk and surface characteristics. These materials have been extensively explored for their catalytic, electrical, magnetic, and optical properties. They are promising candidates for the photocatalytic splitting of water and have also been extensively studied for environmental catalysis applications. Oxygen and cation non-stoichiometry can be tailored in a large number of perovskite compositions to achieve the desired catalytic activity, including multifunctional catalytic properties. Despite the extensive uses, the commercial success for this class of perovskite-based catalytic materials has not been achieved for vehicle exhaust emission control or for many other environmental applications. With recent advances in synthesis techniques, including the preparation of supported perovskites, and increasing understanding of promoted substitute perovskite-type materials, there is a growing interest in applied studies of perovskite-type catalytic materials. We have studied a number of perovskites based on Co, Mn, Ru, and Fe and their substituted compositions for their catalytic activity in terms of diesel soot oxidation, three-way catalysis, N 2 O decomposition, low-temperature CO oxidation, oxidation of volatile organic compounds, etc. The enhanced catalytic activity of these materials is attributed mainly to their altered redox properties, the promotional effect of co-ions, and the increased exposure of catalytically active transition metals in certain preparations. The recent lowering of sulfur content in fuel and concerns over the cost and availability of precious metals are responsible for renewed interest in perovskite-type catalysts for environmental applications.

  12. Perovskite-type catalytic materials for environmental applications

    PubMed Central

    Labhasetwar, Nitin; Saravanan, Govindachetty; Kumar Megarajan, Suresh; Manwar, Nilesh; Khobragade, Rohini; Doggali, Pradeep; Grasset, Fabien

    2015-01-01

    Perovskites are mixed-metal oxides that are attracting much scientific and application interest owing to their low price, adaptability, and thermal stability, which often depend on bulk and surface characteristics. These materials have been extensively explored for their catalytic, electrical, magnetic, and optical properties. They are promising candidates for the photocatalytic splitting of water and have also been extensively studied for environmental catalysis applications. Oxygen and cation non-stoichiometry can be tailored in a large number of perovskite compositions to achieve the desired catalytic activity, including multifunctional catalytic properties. Despite the extensive uses, the commercial success for this class of perovskite-based catalytic materials has not been achieved for vehicle exhaust emission control or for many other environmental applications. With recent advances in synthesis techniques, including the preparation of supported perovskites, and increasing understanding of promoted substitute perovskite-type materials, there is a growing interest in applied studies of perovskite-type catalytic materials. We have studied a number of perovskites based on Co, Mn, Ru, and Fe and their substituted compositions for their catalytic activity in terms of diesel soot oxidation, three-way catalysis, N2O decomposition, low-temperature CO oxidation, oxidation of volatile organic compounds, etc. The enhanced catalytic activity of these materials is attributed mainly to their altered redox properties, the promotional effect of co-ions, and the increased exposure of catalytically active transition metals in certain preparations. The recent lowering of sulfur content in fuel and concerns over the cost and availability of precious metals are responsible for renewed interest in perovskite-type catalysts for environmental applications. PMID:27877813

  13. High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-δ perovskites as prospective electrode materials for symmetrical SOFC

    NASA Astrophysics Data System (ADS)

    Istomin, S. Ya.; Morozov, A. V.; Abdullayev, M. M.; Batuk, M.; Hadermann, J.; Kazakov, S. M.; Sobolev, A. V.; Presniakov, I. A.; Antipov, E. V.

    2018-02-01

    La1-yCayFe0.5+x(Mg,Mo)0.5-xO3-δ oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mössbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-δ and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-δ) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-δ is oxygen deficient with δ ≈ 0.15. Oxides are stable in reducing atmosphere (Ar/H2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1-xGdxO2-x/2 electrolyte mixtures treated at 1173-1373K, while Fe-rich compositions (x≥0.1) react with Zr1-xYxO2-x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4-12.7 ppm K-1. In reducing atmosphere their TECs were found to increase up to 12.1-15.4 ppm K-1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell.

  14. Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

    PubMed

    Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

    2014-04-22

    Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800 °C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

  15. An NADPH Oxidase RBOH Functions in Rice Roots during Lysigenous Aerenchyma Formation under Oxygen-Deficient Conditions

    PubMed Central

    Yoshioka, Miki; Fukazawa, Aya; Nishizawa, Naoko K.

    2017-01-01

    Reactive oxygen species (ROS) produced by the NADPH oxidase, respiratory burst oxidase homolog (RBOH), trigger signal transduction in diverse biological processes in plants. However, the functions of RBOH homologs in rice (Oryza sativa) and other gramineous plants are poorly understood. Ethylene induces the formation of lysigenous aerenchyma, which consists of internal gas spaces created by programmed cell death of cortical cells, in roots of gramineous plants under oxygen-deficient conditions. Here, we report that, in rice, one RBOH isoform (RBOHH) has a role in ethylene-induced aerenchyma formation in roots. Induction of RBOHH expression under oxygen-deficient conditions was greater in cortical cells than in cells of other root tissues. In addition, genes encoding group I calcium-dependent protein kinases (CDPK5 and CDPK13) were strongly expressed in root cortical cells. Coexpression of RBOHH with CDPK5 or CDPK13 induced ROS production in Nicotiana benthamiana leaves. Inhibitors of RBOH activity or cytosolic calcium influx suppressed ethylene-induced aerenchyma formation. Moreover, knockout of RBOHH by CRISPR/Cas9 reduced ROS accumulation and inducible aerenchyma formation in rice roots. These results suggest that RBOHH-mediated ROS production, which is stimulated by CDPK5 and/or CDPK13, is essential for ethylene-induced aerenchyma formation in rice roots under oxygen-deficient conditions. PMID:28351990

  16. Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.

    2016-03-23

    Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1-xSr xCoO 3-δ. We attempt tomore » rationalize the high activities of La 1-xSr xCoO 3-δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

  17. Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

    DOE PAGES

    Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.; ...

    2016-03-23

    Here, perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1–xSr xCoO 3–δ. We attemptmore » to rationalize the high activities of La 1–xSr xCoO 3–δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

  18. Undocumented water column sink for cadmium in open ocean oxygen-deficient zones

    PubMed Central

    Janssen, David J.; Conway, Tim M.; John, Seth G.; Christian, James R.; Kramer, Dennis I.; Pedersen, Tom F.; Cullen, Jay T.

    2014-01-01

    Cadmium (Cd) is a micronutrient and a tracer of biological productivity and circulation in the ocean. The correlation between dissolved Cd and the major algal nutrients in seawater has led to the use of Cd preserved in microfossils to constrain past ocean nutrient distributions. However, linking Cd to marine biological processes requires constraints on marine sources and sinks of Cd. Here, we show a decoupling between Cd and major nutrients within oxygen-deficient zones (ODZs) in both the Northeast Pacific and North Atlantic Oceans, which we attribute to Cd sulfide (CdS) precipitation in euxinic microenvironments around sinking biological particles. We find that dissolved Cd correlates well with dissolved phosphate in oxygenated waters, but is depleted compared with phosphate in ODZs. Additionally, suspended particles from the North Atlantic show high Cd content and light Cd stable isotope ratios within the ODZ, indicative of CdS precipitation. Globally, we calculate that CdS precipitation in ODZs is an important, and to our knowledge a previously undocumented marine sink of Cd. Our results suggest that water column oxygen depletion has a substantial impact on Cd biogeochemical cycling, impacting the global relationship between Cd and major nutrients and suggesting that Cd may be a previously unidentified tracer for water column oxygen deficiency on geological timescales. Similar depletions of copper and zinc in the Northeast Pacific indicate that sulfide precipitation in ODZs may also have an influence on the global distribution of other trace metals. PMID:24778239

  19. Undocumented water column sink for cadmium in open ocean oxygen-deficient zones.

    PubMed

    Janssen, David J; Conway, Tim M; John, Seth G; Christian, James R; Kramer, Dennis I; Pedersen, Tom F; Cullen, Jay T

    2014-05-13

    Cadmium (Cd) is a micronutrient and a tracer of biological productivity and circulation in the ocean. The correlation between dissolved Cd and the major algal nutrients in seawater has led to the use of Cd preserved in microfossils to constrain past ocean nutrient distributions. However, linking Cd to marine biological processes requires constraints on marine sources and sinks of Cd. Here, we show a decoupling between Cd and major nutrients within oxygen-deficient zones (ODZs) in both the Northeast Pacific and North Atlantic Oceans, which we attribute to Cd sulfide (CdS) precipitation in euxinic microenvironments around sinking biological particles. We find that dissolved Cd correlates well with dissolved phosphate in oxygenated waters, but is depleted compared with phosphate in ODZs. Additionally, suspended particles from the North Atlantic show high Cd content and light Cd stable isotope ratios within the ODZ, indicative of CdS precipitation. Globally, we calculate that CdS precipitation in ODZs is an important, and to our knowledge a previously undocumented marine sink of Cd. Our results suggest that water column oxygen depletion has a substantial impact on Cd biogeochemical cycling, impacting the global relationship between Cd and major nutrients and suggesting that Cd may be a previously unidentified tracer for water column oxygen deficiency on geological timescales. Similar depletions of copper and zinc in the Northeast Pacific indicate that sulfide precipitation in ODZs may also have an influence on the global distribution of other trace metals.

  20. High diversity of ammonia-oxidizing archaea in permanent and seasonal oxygen-deficient waters of the eastern South Pacific.

    PubMed

    Molina, Verónica; Belmar, Lucy; Ulloa, Osvaldo

    2010-09-01

    The community structure of putative aerobic ammonia-oxidizing archaea (AOA) was explored in two oxygen-deficient ecosystems of the eastern South Pacific: the oxygen minimum zone off Peru and northern Chile (11°S-20°S), where permanent suboxic and low-ammonium conditions are found at intermediate depths, and the continental shelf off central Chile (36°S), where seasonal oxygen-deficient and relatively high-ammonium conditions develop in the water column, particularly during the upwelling season. The AOA community composition based on the ammonia monooxygenase subunit A (amoA) genes changed according to the oxygen concentration in the water column and the ecosystem studied, showing a higher diversity in the seasonal low-oxygen waters. The majority of the archaeal amoA genotypes was affiliated to the uncultured clusters A (64%) and B (35%), with Cluster A AOA being mainly associated with higher oxygen and ammonium concentrations and Cluster B AOA with permanent oxygen- and ammonium-poor waters. Q-PCR assays revealed that AOA are an abundant community (up to 10(5) amoA copies ml(-1) ), while bacterial amoA genes from β proteobacteria were undetected. Our results thus suggest that a diverse uncultured AOA community, for which, therefore, we do not have any physiological information, to date, is an important component of the nitrifying community in oxygen-deficient marine ecosystems, and particularly in rich coastal upwelling ones. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

  1. Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

    PubMed

    Hu, Yinghong; Schlipf, Johannes; Wussler, Michael; Petrus, Michiel L; Jaegermann, Wolfram; Bein, Thomas; Müller-Buschbaum, Peter; Docampo, Pablo

    2016-06-28

    Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

  2. Oxygen-deficient metabolism and corneal edema

    PubMed Central

    Leung, B.K.; Bonanno, J.A.; Radke, C.J.

    2014-01-01

    Wear of low-oxygen-transmissible soft contact lenses swells the cornea significantly, even during open eye. Although oxygen-deficient corneal edema is well-documented, a self-consistent quantitative prediction based on the underlying metabolic reactions is not available. We present a biochemical description of the human cornea that quantifies hypoxic swelling through the coupled transport of water, salt, and respiratory metabolites. Aerobic and anaerobic consumption of glucose, as well as acidosis and pH buffering, are incorporated in a seven-layer corneal model (anterior chamber, endothelium, stroma, epithelium, postlens tear film, contact lens, and prelens tear film). Corneal swelling is predicted from coupled transport of water, dissolved salts, and especially metabolites, along with membrane-transport resistances at the endothelium and epithelium. At the endothelium, the Na+/K+ - ATPase electrogenic channel actively transports bicarbonate ion from the stroma into the anterior chamber. As captured by the Kedem–Katchalsky membrane-transport formalism, the active bicarbonate-ion flux provides the driving force for corneal fluid pump-out needed to match the leak-in tendency of the stroma. Increased lactate-ion production during hypoxia osmotically lowers the pump-out rate requiring the stroma to swell to higher water content. Concentration profiles are predicted for glucose, water, oxygen, carbon dioxide, and hydronium, lactate, bicarbonate, sodium, and chloride ions, along with electrostatic potential and pressure profiles. Although the active bicarbonate-ion pump at the endothelium drives bicarbonate into the aqueous humor, we find a net flux of bicarbonate ion into the cornea that safeguards against acidosis. For the first time, we predict corneal swelling upon soft-contact-lens wear from fundamental biophysico-chemical principles. We also successfully predict that hypertonic tear alleviates contact-lens-induced edema. PMID:21820076

  3. Oxygen-deficient metabolism and corneal edema.

    PubMed

    Leung, B K; Bonanno, J A; Radke, C J

    2011-11-01

    Wear of low-oxygen-transmissible soft contact lenses swells the cornea significantly, even during open eye. Although oxygen-deficient corneal edema is well-documented, a self-consistent quantitative prediction based on the underlying metabolic reactions is not available. We present a biochemical description of the human cornea that quantifies hypoxic swelling through the coupled transport of water, salt, and respiratory metabolites. Aerobic and anaerobic consumption of glucose, as well as acidosis and pH buffering, are incorporated in a seven-layer corneal model (anterior chamber, endothelium, stroma, epithelium, postlens tear film, contact lens, and prelens tear film). Corneal swelling is predicted from coupled transport of water, dissolved salts, and especially metabolites, along with membrane-transport resistances at the endothelium and epithelium. At the endothelium, the Na+/K+ - ATPase electrogenic channel actively transports bicarbonate ion from the stroma into the anterior chamber. As captured by the Kedem-Katchalsky membrane-transport formalism, the active bicarbonate-ion flux provides the driving force for corneal fluid pump-out needed to match the leak-in tendency of the stroma. Increased lactate-ion production during hypoxia osmotically lowers the pump-out rate requiring the stroma to swell to higher water content. Concentration profiles are predicted for glucose, water, oxygen, carbon dioxide, and hydronium, lactate, bicarbonate, sodium, and chloride ions, along with electrostatic potential and pressure profiles. Although the active bicarbonate-ion pump at the endothelium drives bicarbonate into the aqueous humor, we find a net flux of bicarbonate ion into the cornea that safeguards against acidosis. For the first time, we predict corneal swelling upon soft-contact-lens wear from fundamental biophysico-chemical principles. We also successfully predict that hypertonic tear alleviates contact-lens-induced edema. Copyright © 2011 Elsevier Ltd. All rights

  4. Nature of potential barrier in (Ca 1/4,Cu 3/4)TiO 3 polycrystalline perovskite

    NASA Astrophysics Data System (ADS)

    Marques, V. P. B.; Bueno, P. R.; Simões, A. Z.; Cilense, M.; Varela, J. A.; Longo, E.; Leite, E. R.

    2006-04-01

    The nonohmic electrical features of (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics, which have very strong gigantic dielectric is believed originate from potential barriers at the grain boundaries. In the present study, we used the admittance and impedance spectroscopy technique to investigate (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics with low nonohmic electrical properties. The study was conducted under two different conditions: on as-sintered ceramics and on ceramics thermally treated in an oxygen-rich atmosphere. The results confirm that thermal treatment in oxygen-rich atmospheres influence the nonohmic properties. Annealing at oxygen-rich atmospheres improve the nonohmic behavior and annealing at oxygen-poor atmospheres decrease the nonohmic properties, a behavior already reported for common metal oxide nonohmic devices and here firstly evidenced for the (Ca 1/4,Cu 3/4)TiO 3 perovskite related materials. The results show that oxygen also influences the capacitance values at low frequencies, a behavior that is indicative of the Schottky-type nature of the potential barrier.

  5. Promotion of Oxygen Reduction by Exsolved Silver Nanoparticles on a Perovskite Scaffold for Low-Temperature Solid Oxide Fuel Cells.

    PubMed

    Zhu, Yinlong; Zhou, Wei; Ran, Ran; Chen, Yubo; Shao, Zongping; Liu, Meilin

    2016-01-13

    Solid oxide fuel cells (SOFCs) have potential to be the cleanest and most efficient electrochemical energy conversion devices with excellent fuel flexibility. To make SOFC systems more durable and economically competitive, however, the operation temperature must be significantly reduced, which depends sensitively on the development of highly active electrocatalysts for oxygen reduction reaction (ORR) at low temperatures. Here we report a novel silver nanoparticle-decorated perovskite oxide, prepared via a facile exsolution process from a Sr0.95Ag0.05Nb0.1Co0.9O3-δ (SANC) perovskite precursor, as a highly active and robust ORR electrocatalyst for low-temperature SOFCs. The exsolved Sr0.95Ag0.05Nb0.1Co0.9O3-δ (denoted as e-SANC) electrode is very active for ORR, achieving a very low area specific resistance (∼0.214 Ω cm(2) at 500 °C). An anode-supported cell with the new heterostructured cathode demonstrates very high peak power density (1116 mW cm(-2) at 500 °C) and stable operation for 140 h at a current density of 625 mA cm(-2). The superior ORR activity and stability are attributed to the fast oxygen surface exchange kinetics and the firm adhesion of the Ag nanoparticles to the Sr0.95Nb0.1Co0.9O3-δ (SNC0.95) support. Moreover, the e-SANC cathode displays improved tolerance to CO2. These unique features make the new heterostructured material a highly promising cathode for low-temperature SOFCs.

  6. Water electrolysis on La1−xSrxCoO3−δ perovskite electrocatalysts

    PubMed Central

    Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.; Hardin, William G.; Dai, Sheng; Kolpak, Alexie M.; Johnston, Keith P.; Stevenson, Keith J.

    2016-01-01

    Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr2+ substitution into La1−xSrxCoO3−δ. We attempt to rationalize the high activities of La1−xSrxCoO3−δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis. PMID:27006166

  7. Plentiful magnetic moments in oxygen deficient SrTiO 3

    DOE PAGES

    Ganesh, Panchapakesan; Lopez-Bezanilla, Alejandro; Littlewood, Peter B.

    2015-10-06

    In this research, correlated band theory is employed to investigate the magnetic and electronic properties of different arrangements of oxygen di- and tri-vacancy clusters in SrTiO 3. Hole and electron doping of oxygen deficient SrTiO 3 yields various degrees of magnetization as a result of the interaction between localized magnetic moments at the defect sites. Different kinds of Ti atomic orbital hybridization are described as a function of the doping level and defect geometry. We find that magnetism in SrTiO 3–δ is sensitive to the arrangement of neighbouring vacancy sites, charge carrier density, and vacancy-vacancy interaction. Permanent magnetic moments inmore » the absence of vacancy doping electrons are observed. Our description of the charged clusters of oxygen vacancies widens the previous descriptions of mono- and multi-vacancies and points out the importance of the controlled formation at the atomic level of defects for the realization of transition metal oxide based devices with a desirable magnetic performance.« less

  8. Oxygen vacancy formation characteristics in the bulk and across different surface terminations of La (1₋x)Sr xFe (1₋y)Co yO (3₋δ) perovskite oxides for CO 2 conversion

    DOE PAGES

    Maiti, Debtanu; Daza, Yolanda A.; Yung, Matthew M.; ...

    2016-03-07

    Density functional theory (DFT) based investigation of two parameters of prime interest -- oxygen vacancy and surface terminations along (100) and (110) planes -- has been conducted for La (1-x)Sr xFe(1-y)Co yO (3-more » $$\\delta$$) perovskite oxides in view of their application towards thermochemical carbon dioxide conversion reactions. The bulk oxygen vacancy formation energies for these mixed perovskite oxides are found to increase with increasing lanthanum and iron contents in the 'A' site and 'B' site, respectively. Surface terminations along (100) and (110) crystal planes are studied to probe their stability and their capabilities to accommodate surface oxygen vacancies. Amongst the various terminations, the oxygen-rich (110) surface and strontium-rich (100) surface are the most stable, while transition metal-rich terminations along (100) revealed preference towards the production of oxygen vacancies. The carbon dioxide adsorption strength, a key descriptor for CO 2 conversion reactions, is found to increase on oxygen vacant surfaces thus establishing the importance of oxygen vacancies in CO 2 conversion reactions. Amongst all the surface terminations, the lanthanum-oxygen terminated surface exhibited the strongest CO 2 adsorption strength. Finally, the theoretical prediction of the oxygen vacancy trends and the stability of the samples were corroborated by the temperature-programmed reduction and oxidation reactions and in situ XRD crystallography.« less

  9. Optimal levels of oxygen deficiency in the visible light photocatalyst TiO2-x and long-term stability of catalytic performance

    NASA Astrophysics Data System (ADS)

    Nakano, Takuma; Ito, Ryosuke; Kogoshi, Sumio; Katayama, Noboru

    2016-11-01

    The dependence of the visible light-responsive photocatalytic activity of oxygen deficient TiO2 (TiO2-x) prepared by Ar/H2 plasma surface treatment on the degree of oxygen deficiency (x) was assessed to determine the deficiency region associated with highest performance. The highest activity was obtained at x=0.06 (TiO1.94). The maximum visible light activity for this material, estimated from the formaldehyde (HCHO) removal rate, was three times higher than that exhibited by nitrogen-doped TiO2 (TiO2-xNx). The catalytic ability was found to decrease over the first week after fabrication of the material, after which it became stable, and the performance of TiO2-x at this point was found to be nearly equal to that of TiO2-xNx. The results of ab initio calculations of density of states for TiO2-x suggest that new oxygen deficiency states emerge at almost the exact center between the valence and conduction bands when x>0.06, which increases the recombination rate between electrons and holes. Therefore the declining performance of TiO2-x at larger x values is attributed to the emergence of new oxygen deficient states.

  10. Solid state oxygen sensor

    DOEpatents

    Garzon, Fernando H.; Chung, Brandon W.; Raistrick, Ian D.; Brosha, Eric L.

    1996-01-01

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer.

  11. Solid state oxygen sensor

    DOEpatents

    Garzon, F.H.; Chung, B.W.; Raistrick, I.D.; Brosha, E.L.

    1996-08-06

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer. 4 figs.

  12. Thermal engineering of lead-free nanostructured CH3NH3SnCl3 perovskite material for thin-film solar cell

    NASA Astrophysics Data System (ADS)

    Moyez, Sk Abdul; Roy, Subhasis

    2018-01-01

    Perovskite solar cell is a kind of revolutionary investigation in the field of renewable energy which is capable of mitigates the deficiencies of silicon solar cell and its uprising efficiency can bring blessing to society. The presence of lead (Pb) in perovskite solar cell can make worst and negative impact on environment and is not desirable for our society. In this paper, general plans are anticipated by replacement of Pb with tin (Sn) in open atmosphere to fabricate the CH3NH3SnCl3 photovoltaic cells in chlorine (Cl)-rich environment. Excess uses of Cl has positive influences on morphological growth of the film and it also suppresses the oxidation tendency of tin (Sn) with existing oxygen in atmosphere and maintains same chemical atmosphere as bulk. Various characterization tools like X-ray diffraction, scanning electron microscope (SEM) have been used to study the effect of annealing temperature on crystal stricture, phase formation, impurities, and morphologies of the film. Finally, photovoltaic performance was reported using the solar simulator under 1.5 sun illumination.

  13. Lewis Acid-Base Adduct Approach for High Efficiency Perovskite Solar Cells.

    PubMed

    Lee, Jin-Wook; Kim, Hui-Seon; Park, Nam-Gyu

    2016-02-16

    Since the first report on the long-term durable 9.7% solid-state perovskite solar cell employing methylammonium lead iodide (CH3NH3PbI3), mesoporous TiO2, and 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-MeOTAD) in 2012, following the seed technologies on perovskite-sensitized liquid junction solar cells in 2009 and 2011, a surge of interest has been focused on perovskite solar cells due to superb photovoltaic performance and extremely facile fabrication processes. The power conversion efficiency (PCE) of perovskite solar cells reached 21% in a very short period of time. Such an unprecedentedly high photovoltaic performance is due to the intrinsic optoelectronic property of organolead iodide perovskite material. Moreover, a high dielectric constant, sub-millimeter scale carrier diffusion length, an underlying ferroelectric property, and ion migration behavior can make organolead halide perovskites suitable for multifunctionality. Thus, besides solar cell applications, perovskite material has recently been applied to a variety fields of materials science such as photodetectors, light emitting diodes, lasing, X-ray imaging, resistive memory, and water splitting. Regardless of application areas, the growth of a well-defined perovskite layer with high crystallinity is essential for effective utilization of its excellent physicochemical properties. Therefore, an effective methodology for preparation of high quality perovskite layers is required. In this Account, an effective methodology for production of high quality perovskite layers is described, which is the Lewis acid-base adduct approach. In the solution process to form the perovskite layer, the key chemicals of CH3NH3I (or HC(NH2)2I) and PbI2 are used by dissolving them in polar aprotic solvents. Since polar aprotic solvents bear oxygen, sulfur, or nitrogen, they can act as a Lewis base. In addition, the main group compound PbI2 is known to be a Lewis acid. Thus, PbI2 has a chance

  14. Clear microstructure-performance relationships in Mn-containing perovskite and hexaaluminate compounds prepared by activated reactive synthesis.

    PubMed

    Laassiri, Said; Bion, Nicolas; Duprez, Daniel; Royer, Sébastien; Alamdari, Houshang

    2014-03-07

    Microstructural properties of mixed oxides play essential roles in their oxygen mobility and consequently in their catalytic performances. Two families of mixed oxides (perovskite and hexaaluminate) with different microstructural features, such as crystal size and specific surface area, were prepared using the activated reactive synthesis (ARS) method. It was shown that ARS is a flexible route to synthesize both mixed oxides with nano-scale crystal size and high specific surface area. Redox properties and oxygen mobility were found to be strongly affected by the material microstructure. Catalytic activities of hexaaluminate and perovskite materials for methane oxidation were discussed in the light of structural, redox and oxygen mobility properties.

  15. Photoluminescence characterisations of a dynamic aging process of organic-inorganic CH3NH3PbBr3 perovskite

    NASA Astrophysics Data System (ADS)

    Sheng, R.; Wen, X.; Huang, S.; Hao, X.; Chen, S.; Jiang, Y.; Deng, X.; Green, M. A.; Ho-Baillie, A. W. Y.

    2016-01-01

    After unprecedented development of organic-inorganic lead halide perovskite solar cells over the past few years, one of the biggest barriers towards their commercialization is the stability of the perovskite material. It is thus important to understand the interaction between the perovskite material and oxygen and/or humidity and the associated degradation process in order to improve device and encapsulation design for better durability. Here we characterize the dynamic aging process in vapour-assisted deposited (VASP) CH3NH3PbBr3 perovskite thin films using advanced optical techniques, such as time-resolved photoluminescence and fluorescence lifetime imaging microscopy (FLIM). Our investigation reveals that the perovskite grains grow spontaneously and the larger grains are formed at room temperature in the presence of moisture and oxygen. This crystallization process leads to a higher density of defects and a shorter carrier lifetime, specifically in the larger grains. Excitation-intensity-dependent steady-state photoluminescence shows both N2 stored and aged perovskite exhibit a super-linear increase of photoluminescence intensity with increasing excitation intensity; and the larger slope in aged sample suggests a larger density of defects is generated, consistent with time-resolved PL measurements.

  16. Observation of Nanoscale Morphological and Structural Degradation in Perovskite Solar Cells by In-Situ TEM

    DOE PAGES

    Yang, Bin; Dyck, Ondrej K.; Univ. of Tennessee, Knoxville, TN; ...

    2016-11-04

    The chemical stability of organometallic halide perovskites is a major barrier facing their application in the fast rising field of next generation photovoltaics. These materials were shown to undergo degradation due to the influence of heat or moisture, significantly limiting the lifetime of associated devices. To overcome this stability issue, a fundamental understanding of degradation mechanisms is of foremost importance. Here, high resolution in situ transmission electron microscopy and electron energy loss spectroscopy elemental mapping were applied to probe morphological and structural changes in perovskite films during controlled environmental exposure treatments. Both moisture and oxygen in ambient air are revealedmore » to facilitate degradation in CH 3NH 3PbI 3 perovskites through decomposition and oxidation pathways, respectively. In addition, even in moisture- and oxygen-free environment evident degradation could be induced by heating at the solar cell s real-field operating temperature and the degradation was found to originate from defect sites. These findings provide fundamental insight to prevent degradation of perovskite materials and associated devices for realistic applications.« less

  17. Observation of Nanoscale Morphological and Structural Degradation in Perovskite Solar Cells by In-Situ TEM

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Bin; Dyck, Ondrej K.; Univ. of Tennessee, Knoxville, TN

    The chemical stability of organometallic halide perovskites is a major barrier facing their application in the fast rising field of next generation photovoltaics. These materials were shown to undergo degradation due to the influence of heat or moisture, significantly limiting the lifetime of associated devices. To overcome this stability issue, a fundamental understanding of degradation mechanisms is of foremost importance. Here, high resolution in situ transmission electron microscopy and electron energy loss spectroscopy elemental mapping were applied to probe morphological and structural changes in perovskite films during controlled environmental exposure treatments. Both moisture and oxygen in ambient air are revealedmore » to facilitate degradation in CH 3NH 3PbI 3 perovskites through decomposition and oxidation pathways, respectively. In addition, even in moisture- and oxygen-free environment evident degradation could be induced by heating at the solar cell s real-field operating temperature and the degradation was found to originate from defect sites. These findings provide fundamental insight to prevent degradation of perovskite materials and associated devices for realistic applications.« less

  18. Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability

    NASA Astrophysics Data System (ADS)

    Christians, Jeffrey A.; Schulz, Philip; Tinkham, Jonathan S.; Schloemer, Tracy H.; Harvey, Steven P.; Tremolet de Villers, Bertrand J.; Sellinger, Alan; Berry, Joseph J.; Luther, Joseph M.

    2018-01-01

    Long-term device stability is the most pressing issue that impedes perovskite solar cell commercialization, given the achieved 22.7% efficiency. The perovskite absorber material itself has been heavily scrutinized for being prone to degradation by water, oxygen and ultraviolet light. To date, most reports characterize device stability in the absence of these extrinsic factors. Here we show that, even under the combined stresses of light (including ultraviolet light), oxygen and moisture, perovskite solar cells can retain 94% of peak efficiency despite 1,000 hours of continuous unencapsulated operation in ambient air conditions (relative humidity of 10-20%). Each interface and contact layer throughout the device stack plays an important role in the overall stability which, when appropriately modified, yields devices in which both the initial rapid decay (often termed burn-in) and the gradual slower decay are suppressed. This extensively modified device architecture and the understanding developed will lead towards durable long-term device performance.

  19. Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability

    DOE PAGES

    Christians, Jeffrey A.; Schulz, Philip; Tinkham, Jonathan S.; ...

    2017-11-28

    Long-term device stability is the most pressing issue that impedes perovskite solar cell commercialization, given the achieved 22.7% efficiency. The perovskite absorber material itself has been heavily scrutinized for being prone to degradation by water, oxygen and ultraviolet light. To date, most reports characterize device stability in the absence of these extrinsic factors. Here we show that, even under the combined stresses of light (including ultraviolet light), oxygen and moisture, perovskite solar cells can retain 94% of peak efficiency despite 1,000 hours of continuous unencapsulated operation in ambient air conditions (relative humidity of 10-20%). Each interface and contact layer throughoutmore » the device stack plays an important role in the overall stability which, when appropriately modified, yields devices in which both the initial rapid decay (often termed burn-in) and the gradual slower decay are suppressed. This extensively modified device architecture and the understanding developed will lead towards durable long-term device performance.« less

  20. Creation and Ordering of Oxygen Vacancies at WO 3-δ and Perovskite Interfaces

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Kelvin H. L.; Li, Guoqiang; Spurgeon, Steven R.

    Changes in structure and composition resulting from oxygen deficiency can strongly impact the physical and chemical properties of transition metal oxides, which may lead to new functionalities for novel electronic devices. Oxygen vacancies (V o) can be readily formed to accomodate the lattice mismatch during epitixial thin film growth. In this paper, the effects of substrate strain and oxidizing power on the creation and distribution of V o in WO 3-δ thin films are investigated in detail. An 18O 2 isotope labeled time-of-flight secondary ion mass spectrometry study reveals that WO 3-δ films grown on SrTiO 3 substrates display amore » significantly larger oxygen vacancy gradient along the growth direction compared to those grown on LaAlO 3 substrates. This result is corroborated by scanning transmission electron microscopy imaging which reveals a large number of defects close to the interface to accommodate interfacial tensile strain, leading to the ordering of V o and the formation of semi-aligned Magnéli phases. The strain is gradually released and tetragonal phase with much better crystallinity is observed at the film/vacuum interface. The changes in structure resulting from oxygen defect creation are shown to have a direct impact on the electronic and optical properties of the films.« less

  1. Ab initio study of perovskite type oxide materials for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Lee, Yueh-Lin

    2011-12-01

    Perovskite type oxides form a family of materials of significant interest for cathodes and electrolytes of solid oxide fuel cells (SOFCs). These perovskites not only are active catalysts for surface oxygen reduction (OR) reactions but also allow incorporating the spilt oxygen monomers into their bulk, an unusual and poorly understood catalytic mechanism that couples surface and bulk properties. The OR mechanisms can be influenced strongly by defects in perovskite oxides, composition, and surface defect structures. This thesis work initiates a first step in developing a general strategy based on first-principles calculations for detailed control of oxygen vacancy content, transport rates of surface and bulk oxygen species, and surface/interfacial reaction kinetics. Ab initio density functional theory methods are used to model properties relevant for the OR reactions on SOFC cathodes. Three main research thrusts, which focus on bulk defect chemistry, surface defect structures and surface energetics, and surface catalytic properties, are carried to investigate different level of material chemistry for improved understanding of key physics/factors that govern SOFC cathode OR activity. In the study of bulk defect chemistry, an ab initio based defect model is developed for modeling defect chemistry of LaMnO 3 under SOFC conditions. The model suggests an important role for defect interactions, which are typically excluded in previous defect models. In the study of surface defect structures and surface energetics, it is shown that defect energies change dramatically (1˜2 eV lower) from bulk values near surfaces. Based on the existing bulk defect model with the calculated ab initio surface defect energetics, we predict the (001) MnO 2 surface oxygen vacancy concentration of (La0.9Sr0.1 )MnO3 is about 5˜6 order magnitude higher than that of the bulk under typical SOFC conditions. Finally, for surface catalytic properties, we show that area specific resistance, oxygen

  2. Localized Control of Curie Temperature in Perovskite Oxide Film by Capping-Layer-Induced Octahedral Distortion.

    PubMed

    Thomas, S; Kuiper, B; Hu, J; Smit, J; Liao, Z; Zhong, Z; Rijnders, G; Vailionis, A; Wu, R; Koster, G; Xia, J

    2017-10-27

    With reduced dimensionality, it is often easier to modify the properties of ultrathin films than their bulk counterparts. Strain engineering, usually achieved by choosing appropriate substrates, has been proven effective in controlling the properties of perovskite oxide films. An emerging alternative route for developing new multifunctional perovskite is by modification of the oxygen octahedral structure. Here we report the control of structural oxygen octahedral rotation in ultrathin perovskite SrRuO_{3} films by the deposition of a SrTiO_{3} capping layer, which can be lithographically patterned to achieve local control. Using a scanning Sagnac magnetic microscope, we show an increase in the Curie temperature of SrRuO_{3} due to the suppression octahedral rotations revealed by the synchrotron x-ray diffraction. This capping-layer-based technique may open new possibilities for developing functional oxide materials.

  3. Effects of sintering temperature on the pyrochlore phase in PZT nanotubes and their transformation to the perovskite phase by coating with PbO multilayers.

    PubMed

    Han, Jin Kyu; Choi, Yong Chan; Jeon, Do Hyen; Lee, Min Ku; Bu, Sang Don

    2014-11-01

    We report the phase evolution of Pb(Zr0.52Ti0.48)O3 nanotubes (PZT-NTs), from the pyrochlore to perovskite phase, with an outer diameter of about 420 nm and a wall thickness of about 10 nm. The PZT-NTs were fabricated in pores of porous anodic alumina membrane (PAM) using a spin coating of PZT sol-gel solution and subsequent annealing at 500-700 degrees C in oxygen gas. The pyrochlore phase was found to be formed at 500 degrees C, and also found not to be transformed into the perovskite phase, even though annealing was performed at higher temperatures to 700 degrees C. Elementary distribution analysis of PZT-NTs embedded in PAM reveal that Pb diffusion from nanotubes into pore walls of PAM is one of the main reasons. By employing firstly an additional PbO coating on the pyrochlore nanotubes and then subsequent annealing at 700 degrees C, we have successfully achieved an almost pure perovskite phase in nanotubes. These results suggest that PbO acts as a Pb-compensation agent in the Pb- deficient PZT-NTs. Moreover, our method can be used in the synthesis of all metal-oxide materials, including volatile elements.

  4. Environmental Effects on the Photophysics of Organic-Inorganic Halide Perovskites.

    PubMed

    Galisteo-López, Juan F; Anaya, M; Calvo, M E; Míguez, H

    2015-06-18

    The photophysical properties of films of organic-inorganic lead halide perovskites under different ambient conditions are herein reported. We demonstrate that their luminescent properties are determined by the interplay between photoinduced activation and darkening processes, which strongly depend on the atmosphere surrounding the samples. We have isolated oxygen and moisture as the key elements in each process, activation and darkening, both of which involve the interaction with photogenerated carriers. These findings show that environmental factors play a key role in the performance of lead halide perovskites as efficient luminescent materials.

  5. Environmental Effects on the Photophysics of Organic–Inorganic Halide Perovskites

    PubMed Central

    2015-01-01

    The photophysical properties of films of organic–inorganic lead halide perovskites under different ambient conditions are herein reported. We demonstrate that their luminescent properties are determined by the interplay between photoinduced activation and darkening processes, which strongly depend on the atmosphere surrounding the samples. We have isolated oxygen and moisture as the key elements in each process, activation and darkening, both of which involve the interaction with photogenerated carriers. These findings show that environmental factors play a key role in the performance of lead halide perovskites as efficient luminescent materials. PMID:26266592

  6. The origin of uniaxial negative thermal expansion in layered perovskites

    NASA Astrophysics Data System (ADS)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark S.; Mostofi, Arash A.; Bristowe, Nicholas C.

    2017-10-01

    Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It is generally accepted that there are two key ingredients that determine the extent of NTE: the presence of soft phonon modes that drive contraction (have negative Grüneisen parameters); and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific axis. This difference in thermal expansion properties is surprising since both ABO3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry phases. Using first principles calculations and symmetry analysis, we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen octahedra. This feature, unique to layered perovskites of certain symmetry, is what allows uniaxial NTE to persist over a large temperature range. This fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

  7. Nb K-edge x-ray absorption investigation of the pressure induced amorphization in A-site deficient double perovskite La1/3NbO3.

    PubMed

    Marini, C; Noked, O; Kantor, I; Joseph, B; Mathon, O; Shuker, R; Kennedy, B J; Pascarelli, S; Sterer, E

    2016-02-03

    Nb K-edge x-ray absorption spectroscopy is utilized to investigate the changes in the local structure of the A-site deficient double perovskite La1/3NbO3 which undergoes a pressure induced irreversible amorphization. EXAFS results show that with increasing pressure up to 7.5 GPa, the average Nb-O bond distance decreases in agreement with the expected compression and tilting of the NbO6 octahedra. On the contrary, above 7.5 GPa, the average Nb-O bond distance show a tendency to increase. Significant changes in the Nb K-edge XANES spectrum with evident low energy shift of the pre-peak and the absorption edge is found to happen in La1/3NbO3 above 6.3 GPa. These changes evidence a gradual reduction of the Nb cations from Nb(5+) towards Nb(4+) above 6.3 GPa. Such a valence change accompanied by the elongation of the average Nb-O bond distances in the octahedra, introduces repulsion forces between non-bonding adjacent oxygen anions in the unoccupied A-sites. Above a critical pressure, the Nb reduction mechanism can no longer be sustained by the changing local structure and amorphization occurs, apparently due to the build-up of local strain. EXAFS and XANES results indicate two distinct pressure regimes having different local and electronic response in the La1/3NbO3 system before the occurence of the pressure induced amorphization at  ∼14.5 GPa.

  8. Localized Control of Curie Temperature in Perovskite Oxide Film by Capping-Layer-Induced Octahedral Distortion

    DOE PAGES

    Thomas, S.; Kuiper, B.; Hu, J.; ...

    2017-10-27

    With reduced dimensionality, it is often easier to modify the properties of ultrathin films than their bulk counterparts. Strain engineering, usually achieved by choosing appropriate substrates, has been proven effective in controlling the properties of perovskite oxide films. An emerging alternative route for developing new multifunctional perovskite is by modification of the oxygen octahedral structure. Here we report the control of structural oxygen octahedral rotation in ultrathin perovskite SrRuO 3 films by the deposition of a SrTiO 3 capping layer, which can be lithographically patterned to achieve local control. Here, using a scanning Sagnac magnetic microscope, we show an increasemore » in the Curie temperature of SrRuO 3 due to the suppression octahedral rotations revealed by the synchrotron x-ray diffraction. Lastly, this capping-layer-based technique may open new possibilities for developing functional oxide materials.« less

  9. Charge doping and large lattice expansion in oxygen-deficient heteroepitaxial WO3

    NASA Astrophysics Data System (ADS)

    Mattoni, Giordano; Filippetti, Alessio; Manca, Nicola; Zubko, Pavlo; Caviglia, Andrea D.

    2018-05-01

    Tungsten trioxide (WO3) is a versatile material with widespread applications ranging from electrochromics and optoelectronics to water splitting and catalysis of chemical reactions. For technological applications, thin films of WO3 are particularly appealing, taking advantage from a high surface-to-volume ratio and tunable physical properties. However, the growth of stoichiometric crystalline thin films is challenging because the deposition conditions are very sensitive to the formation of oxygen vacancies. In this paper, we show how background oxygen pressure during pulsed laser deposition can be used to tune the structural and electronic properties of WO3 thin films. By performing x-ray diffraction and low-temperature electrical transport measurements, we find changes in the WO3 lattice volume of up to 10% concomitantly with a resistivity drop of more than five orders of magnitude at room temperature as a function of increased oxygen deficiency. We use advanced ab initio calculations to describe in detail the properties of the oxygen vacancy defect states and their evolution in terms of excess charge concentration. Our results depict an intriguing scenario where structural, electronic, optical, and transport properties of WO3 single-crystal thin films can all be purposely tuned by controlling the oxygen vacancy formation during growth.

  10. Reactive Oxygen Species Function to Mediate the Fe Deficiency Response in an Fe-Efficient Apple Genotype: An Early Response Mechanism for Enhancing Reactive Oxygen Production

    PubMed Central

    Sun, Chaohua; Wu, Ting; Zhai, Longmei; Li, Duyue; Zhang, Xinzhong; Xu, Xuefeng; Ma, Huiqin; Wang, Yi; Han, Zhenhai

    2016-01-01

    Reactive oxygen species (ROS) are important signaling molecules in plants that contribute to stress acclimation. This study demonstrated that ROS play a critical role in Fe deficiency-induced signaling at an early stage in Malus xiaojinensis. Once ROS production has been initiated, prolonged Fe starvation leads to activation of ROS scavenging mechanisms. Further, we demonstrated that ROS scavengers are involved in maintaining the cellular redox homeostasis during prolonged Fe deficiency treatment. Taken together, our results describe a feedback repression loop for ROS to preserve redox homeostasis and maintain a continuous Fe deficiency response in the Fe-efficient woody plant M. xiaojinensis. More broadly, this study reveals a new mechanism in which ROS mediate both positive and negative regulation of plant responses to Fe deficiency stress. PMID:27899933

  11. Reactive Oxygen Species Function to Mediate the Fe Deficiency Response in an Fe-Efficient Apple Genotype: An Early Response Mechanism for Enhancing Reactive Oxygen Production.

    PubMed

    Sun, Chaohua; Wu, Ting; Zhai, Longmei; Li, Duyue; Zhang, Xinzhong; Xu, Xuefeng; Ma, Huiqin; Wang, Yi; Han, Zhenhai

    2016-01-01

    Reactive oxygen species (ROS) are important signaling molecules in plants that contribute to stress acclimation. This study demonstrated that ROS play a critical role in Fe deficiency-induced signaling at an early stage in Malus xiaojinensis . Once ROS production has been initiated, prolonged Fe starvation leads to activation of ROS scavenging mechanisms. Further, we demonstrated that ROS scavengers are involved in maintaining the cellular redox homeostasis during prolonged Fe deficiency treatment. Taken together, our results describe a feedback repression loop for ROS to preserve redox homeostasis and maintain a continuous Fe deficiency response in the Fe-efficient woody plant M. xiaojinensis . More broadly, this study reveals a new mechanism in which ROS mediate both positive and negative regulation of plant responses to Fe deficiency stress.

  12. Dynamic Optoelectronic Properties in Perovskite Oxide Thin Films Measured with Ultrafast Transient Absorption & Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Smolin, Sergey Y.

    change in the near-infrared region in LSFO is indicative of carrier bandfilling of newly created electronic states by photoexcited carriers. Moreover, we find that similar transient spectral trends can be induced with A-site substitution or through oxygen vacancies, which is a surprising result. Probing the near-infrared region reveals similar nanosecond (1-3 ns) photoexcited carrier lifetimes for oxygen deficient and stoichiometric films. These results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in long lived recombination kinetics. Although this thesis represents one of the first comprehensive studies using broad band transient absorption and reflectance spectroscopy to study dynamic optoelectronic phenomena in perovskite oxides, it can also serve as a guide for the implementation and interpretation of ultrafast spectroscopy in other material systems. Moreover, the ultrafast work on perovskite oxides indicates that these materials have long nanosecond lifetimes required for light harvesting devices and should be investigated further.

  13. Single Crystal Elasticity of Iron Bearing Perovskite and Post Perovskite Analog

    NASA Astrophysics Data System (ADS)

    Yoneda, A.; Fukui, H.; Baron, A. Q. R.

    2014-12-01

    We measured single crystal elasticity of (1) pure and iron bearing MgSiO3 perovskite, and (2) Pbnm-CaIrO3 and Cmcm-CaIrO3, a representative analog of MgSiO3 perovskite and post perovskite, respectively, by means of inelastic X ray scattering at BL35XU, SPring-8. The present results for MgSiO3 perovskite demonstrate that elastic anisotropy of magnesium perovskite is highly enhanced by iron incorporation. Furthermore anti-correlation between bulk sound velocity and shear wave velocity was confirmed with iron content, which is against the theoretical prediction. The anti-correlation found in this study is important, because it enables us to interpret the recent seismological observation of the anti-correlation in the deep lower mantle by means of iron content difference in perovskite. On the other hand, we can learn difference of elasticity between perovskite and post perovskite thorough measurement on CaIrO3, as analog of MgSiO3 perovskite and post perovskite. From a characteristics of the single crystal elasticity of CaIrO3 compounds, we interpreted the texture pattern in the D" layer consistent with recent seismic observation.

  14. Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

    DOE PAGES

    Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; ...

    2017-05-19

    Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here in this work, we have measured themore » redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). Lastly, we present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.« less

  15. Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.

    Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here in this work, we have measured themore » redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). Lastly, we present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.« less

  16. Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

    NASA Astrophysics Data System (ADS)

    Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-Mi; Toner, Brandy M.; Marcus, Matthew A.

    2017-08-01

    Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). We present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.

  17. A new generation of high temperature oxygen sensors

    NASA Astrophysics Data System (ADS)

    Spirig, John V.

    -doped manganate perovskite and stabilized zirconia, served as a model system for joining electron carriers to an electrolyte without the creation of undesirable interlayers. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joining planes obtained with 2-D Raman microscopy demonstrated the absence of any new phases at the interface. A conducting perovskite with a lower Al:Mn ratio, but compensating A-site deficiency, La0.69Sr0.18Al0.45Mn0.55 O3, was joined to YTZP at 1250°C. X-ray diffraction was used to gain structural information on this A-site deficient perovskite. Room temperature resistivity measurements of the electroceramics were performed on joined and unjoined samples to determine the extent to which joining altered electron conduction within the LSAM. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joined samples demonstrated that joining temperature determines the extent to which interlayers begin to form in the joining plane. X-ray microdiffraction of the joining planes confirmed a threshold temperature for operation of a device created from these materials at 1350°C. A new material with diminished reactivity and high conductivity is presented to serve as a replacement for metal electrodes. In this manner, the model for a new generation of high-temperature oxygen sensors with internal references and ceramic wires is elucidated.

  18. Oxygen Transport Membranes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    S. Bandopadhyay

    2008-08-30

    the small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and

  19. Perovskite-related LaTiO3.41.

    PubMed

    Daniels, Peter; Lichtenberg, Frank; van Smaalen, Sander

    2003-02-01

    Crystals of pentalanthanum pentatitanium heptadecaoxide (La(5)Ti(5)O(17) with 0.3% oxygen excess, or LaTiO(3.41)) have been synthesized by floating-zone melting, and the structure has been solved using single-crystal X-ray diffraction intensities. The monoclinic (P2(1)/c) structure consists of perovskite-like slabs of vertex-sharing TiO(6) octahedra, which are separated by additional oxygen layers. The slabs are five octahedra wide. Due to the adjustment of the TiO(6) octahedra to meet the coordination requirements of the La(3+) cations, a superstructure develops along the a axis.

  20. Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface

    DOE PAGES

    Tsvetkov, Nikolai; Lu, Qiyang; Sun, Lixin; ...

    2016-06-13

    Segregation and phase separation of aliovalent dopants on perovskite oxide (ABO 3 ) surfaces are detrimental to the performance of energy conversion systems such as solid oxide fuel/electrolysis cells and catalysts for thermochemical H 2 O and CO 2 splitting. One key reason behind the instability of perovskite oxide surfaces is the electrostatic attraction of the negatively charged A-site dopants (for example, Sr La ') by the positively charged oxygen vacancies (Vmore » $$••\\atop{o}$$) enriched at the surface. Here we show that reducing the surface V $$••\\atop{o}$$ concentration improves the oxygen surface exchange kinetics and stability significantly, albeit contrary to the well-established understanding that surface oxygen vacancies facilitate reactions with O 2 molecules. We take La 0.8 Sr 0.2 CoO 3 (LSC) as a model perovskite oxide, and modify its surface with additive cations that are more and less reducible than Co on the B-site of LSC. By using ambient-pressure X-ray absorption and photoelectron spectroscopy, we proved that the dominant role of the less reducible cations is to suppress the enrichment and phase separation of Sr while reducing the concentration of V $$••\\atop{o}$$ and making the LSC more oxidized at its surface. Consequently, we found that these less reducible cations significantly improve stability, with up to 30 times faster oxygen exchange kinetics after 54 h in air at 530 °C achieved by Hf addition onto LSC. Finally, the results revealed a 'volcano' relation between the oxygen exchange kinetics and the oxygen vacancy formation enthalpy of the binary oxides of the additive cations. This volcano relation highlights the existence of an optimum surface oxygen vacancy concentration that balances the gain in oxygen exchange kinetics and the chemical stability loss.« less

  1. Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tsvetkov, Nikolai; Lu, Qiyang; Sun, Lixin

    Segregation and phase separation of aliovalent dopants on perovskite oxide (ABO 3 ) surfaces are detrimental to the performance of energy conversion systems such as solid oxide fuel/electrolysis cells and catalysts for thermochemical H 2 O and CO 2 splitting. One key reason behind the instability of perovskite oxide surfaces is the electrostatic attraction of the negatively charged A-site dopants (for example, Sr La ') by the positively charged oxygen vacancies (Vmore » $$••\\atop{o}$$) enriched at the surface. Here we show that reducing the surface V $$••\\atop{o}$$ concentration improves the oxygen surface exchange kinetics and stability significantly, albeit contrary to the well-established understanding that surface oxygen vacancies facilitate reactions with O 2 molecules. We take La 0.8 Sr 0.2 CoO 3 (LSC) as a model perovskite oxide, and modify its surface with additive cations that are more and less reducible than Co on the B-site of LSC. By using ambient-pressure X-ray absorption and photoelectron spectroscopy, we proved that the dominant role of the less reducible cations is to suppress the enrichment and phase separation of Sr while reducing the concentration of V $$••\\atop{o}$$ and making the LSC more oxidized at its surface. Consequently, we found that these less reducible cations significantly improve stability, with up to 30 times faster oxygen exchange kinetics after 54 h in air at 530 °C achieved by Hf addition onto LSC. Finally, the results revealed a 'volcano' relation between the oxygen exchange kinetics and the oxygen vacancy formation enthalpy of the binary oxides of the additive cations. This volcano relation highlights the existence of an optimum surface oxygen vacancy concentration that balances the gain in oxygen exchange kinetics and the chemical stability loss.« less

  2. Garden-like perovskite superstructures with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Ye, Meidan; Wang, Mengye; Zheng, Dajiang; Zhang, Nan; Lin, Changjian; Lin, Zhiqun

    2014-03-01

    By subjecting amorphous flower-like TiO2 to a facile hydrothermal synthesis in the presence of Sr2+, garden-like perovskite SrTiO3 superstructures were achieved. The amorphous TiO2 was preformed using ZnO flowers as templates. Different three-dimensional SrTiO3 architectures were coexisted in the garden, including SrTiO3 flowers composed of several hollow sword-shaped petals, many sheet-shaped petals or numerous flake-shaped petals, and SrTiO3 grass consisting of a number of long blades. These SrTiO3 superstructures were simultaneously grown on fluorine-doped tin oxide (FTO) substrates. On the basis of a comprehensive study on the effects of growth time, temperature, initial concentrations of precursor, and pH, the formation of these various hierarchical architectures was attributed primarily to the dissolution of amorphous TiO2 and precipitation of perovskite crystals, followed by the Ostwald ripening process of perovskite nanocrystals and self-organization of perovskite building blocks. Interestingly, this approach can be readily extended to create other perovskite structures, including dendritic BaTiO3 and nest-like CaTiO3, as well as PbTiO3 transformed from plate-like pyrochlore Pb2Ti2O6 after post-thermal treatment. Garden-like SrTiO3 superstructures showed a superior photocatalytic performance when compared to other as-prepared semiconductors and perovskite materials (i.e., ZnO, TiO2, BaTiO3, CaTiO3 and PbTiO3), probably due to their intrinsic photocatalytic activity and special garden-like features with a coexistence of various structures that significantly facilitated the adsorption and diffusion of methyl blue (MB) molecules and oxygen species in the photochemical reaction of MB degradation.By subjecting amorphous flower-like TiO2 to a facile hydrothermal synthesis in the presence of Sr2+, garden-like perovskite SrTiO3 superstructures were achieved. The amorphous TiO2 was preformed using ZnO flowers as templates. Different three-dimensional SrTiO3

  3. Passivation of interstitial and vacancy mediated trap-states for efficient and stable triple-cation perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mahmud, Md Arafat; Elumalai, Naveen Kumar; Upama, Mushfika Baishakhi; Wang, Dian; Gonçales, Vinicius R.; Wright, Matthew; Xu, Cheng; Haque, Faiazul; Uddin, Ashraf

    2018-04-01

    The current work reports the concurrent passivation of interstitial and oxygen vacancy mediated defect states in low temperature processed ZnO electron transport layer (ETL) via Ultraviolet-Ozone (UVO) treatment for fabricating highly efficient (maximum efficiency: 16.70%), triple cation based MA0.57FA0.38Rb0.05PbI3 (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cell (PSC). Under UV exposure, ozone decomposes to free atomic oxygen and intercalates into the interstitial and oxygen vacancy induced defect sites in the ZnO lattice matrix, which contributes to suppressed trap-assisted recombination phenomena in perovskite device. UVO treatment also reduces the content of functional hydroxyl group on ZnO surface, that increases the inter-particle connectivity and grain size of perovskite film on UVO treated ZnO ETL. Owing to this, the perovskite film atop UVO treated ZnO film exhibits reduced micro-strain and dislocation density values, which contribute to the enhanced photovoltaic performance of PSC with modified ZnO ETL. The modified PSCs exhibit higher recombination resistance (RRec) ∼40% compared to pristine ZnO ETL based control devices. Adding to the merit, the UVO treated ZnO PSC also demonstrates superior device stability, retaining about 88% of its initial PCE in the course of a month-long, systematic degradation study.

  4. Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites

    DOE PAGES

    Yoon, Seog Joon; Kuno, Masaru; Kamat, Prashant V.

    2017-06-01

    Minimizing photoinduced segregation in mixed halide lead perovskites is important for achieving stable photovoltaic performance. The shift in the absorption and the rate of formation of iodide- and bromide-rich regions following visible excitation of mixed halide lead perovskites is found to strongly depend on the halide ion concentration. Slower formation and recovery rates observed in halide-deficient films indicate the involvement of defect sites in influencing halide phase segregation. At higher halide concentrations (in stoichiometric excess), segregation effects become less prominent, as evidenced by faster recovery kinetics. These results suggest that light-induced compositional segregation can be minimized in mixed halide perovskitemore » films by using excess halide ions. In conclusion, the findings from this study further reflect the importance of halide ion post-treatment of perovskite films to improve their solar cell performance.« less

  5. Hierarchically porous LaFeO3 perovskite prepared from the pomelo peel bio-template for catalytic oxidation of NO

    NASA Astrophysics Data System (ADS)

    Zhao, Shaojun; Wang, Li; Wang, Ying; Li, Xing

    2018-05-01

    In this paper, pomelo peel was used as biological template to obtain hierarchically porous LaFeO3 perovskite for the catalytic oxidation of NO to NO2. In addition, X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption analyses, X-ray photoelectron spectra (XPS), NO temperature-programmed desorption (NO-TPD), oxygen temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) were used to investigate the micro-structure and the redox properties of the hierarchically porous LaFeO3 perovskite prepared from pomelo peel biological template and the LaFeO3 perovskite without the biological template. The results indicated that the hierarchically porous LaFeO3 perovskite successfully replicated the porous structure of pomelo peel with high specific surface area. Compared to the LaFeO3 perovskite prepared without the pomelo peel template, the hierarchically porous LaFeO3 perovskite showed better catalytic oxidization of NO to NO2 under the same conditions. The maximum NO conversions for LaFeO3 prepared with and without template were 90% at 305 °C and 76% at 313 °C, respectively. This is mainly attributed to the higher ratio of Fe4+/Fe3+, the hierarchically porous structure with more adsorbed oxygen species and higher surface area for the hierarchically porous LaFeO3 perovskite compared with the sample prepared without the pomelo peel template.

  6. Dynamic Octahedral Breathing in Oxygen-Deficient Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) Perovskite Performing as a Cathode in Intermediate-Temperature SOFC.

    PubMed

    Gong, Yudong; Sun, Chunwen; Huang, Qiu-an; Alonso, Jose Antonio; Fernández-Díaz, Maria Teresa; Chen, Liquan

    2016-03-21

    Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) outperforms as a cathode in solid-oxide fuel cells (SOFC), at temperatures as low as 700-750 °C. The microscopical reason for this performance was investigated by temperature-dependent neutron powder diffraction (NPD) experiments. In the temperature range of 25-800 °C, Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) shows a perfectly cubic structure (a = a0), with a significant oxygen deficiency in a single oxygen site, that substantially increases at the working temperatures of a SOFC. The anisotropic thermal motion of oxygen atoms considerably rises with T, reaching B(eq) ≈ 5 Å(2) at 800 °C, with prolate cigar-shaped, anisotropic vibration ellipsoids that suggest a dynamic breathing of the octahedra as oxygen ions diffuse across the structure by a vacancies mechanism, thus implying a significant ionic mobility that could be described as a molten oxygen sublattice. The test cell with a La(0.8)Sr(0.2)Ga(0.83)Mg(0.17)O(3-δ) electrolyte (∼300 μm in thickness)-supported configuration yields a peak power density of 0.20 and 0.40 W cm(-2) at temperatures of 700 and 750 °C, respectively, with pure H2 as fuel and ambient air as oxidant. The electrochemical impedance spectra (EIS) evolution with time of the symmetric cathode fuel cell measured at 750 °C shows that the Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) cathode possesses a superior ORR catalytic activity and long-term stability. The mixed electronic-ionic conduction properties of Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) account for its good performance as an oxygen-reduction catalyst.

  7. Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

    PubMed

    Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

    2017-10-11

    A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

  8. Perovskite-perovskite tandem photovoltaics with optimized band gaps

    NASA Astrophysics Data System (ADS)

    Eperon, Giles E.; Leijtens, Tomas; Bush, Kevin A.; Prasanna, Rohit; Green, Thomas; Wang, Jacob Tse-Wei; McMeekin, David P.; Volonakis, George; Milot, Rebecca L.; May, Richard; Palmstrom, Axel; Slotcavage, Daniel J.; Belisle, Rebecca A.; Patel, Jay B.; Parrott, Elizabeth S.; Sutton, Rebecca J.; Ma, Wen; Moghadam, Farhad; Conings, Bert; Babayigit, Aslihan; Boyen, Hans-Gerd; Bent, Stacey; Giustino, Feliciano; Herz, Laura M.; Johnston, Michael B.; McGehee, Michael D.; Snaith, Henry J.

    2016-11-01

    We demonstrate four- and two-terminal perovskite-perovskite tandem solar cells with ideally matched band gaps. We develop an infrared-absorbing 1.2-electron volt band-gap perovskite, FA0.75Cs0.25Sn0.5Pb0.5I3, that can deliver 14.8% efficiency. By combining this material with a wider-band gap FA0.83Cs0.17Pb(I0.5Br0.5)3 material, we achieve monolithic two-terminal tandem efficiencies of 17.0% with >1.65-volt open-circuit voltage. We also make mechanically stacked four-terminal tandem cells and obtain 20.3% efficiency. Notably, we find that our infrared-absorbing perovskite cells exhibit excellent thermal and atmospheric stability, not previously achieved for Sn-based perovskites. This device architecture and materials set will enable “all-perovskite” thin-film solar cells to reach the highest efficiencies in the long term at the lowest costs.

  9. Controlling octahedral rotations in a perovskite via strain doping

    DOE PAGES

    Herklotz, Andreas; Biegalski, Michael D.; Lee, Ho Nyung; ...

    2016-05-24

    The perovskite unit cell is the fundamental building block of many functional materials. The manipulation of this crystal structure is known to be of central importance to controlling many technologically promising phenomena related to superconductivity, multiferroicity, mangetoresistivity, and photovoltaics. The broad range of properties that this structure can exhibit is in part due to the centrally coordinated octahedra bond flexibility, which allows for a multitude of distortions from the ideal highly symmetric structure. However, continuous and fine manipulation of these distortions has never been possible. Here, we show that controlled insertion of He atoms into an epitaxial perovskite film canmore » be used to finely tune the lattice symmetry by modifying the local distortions, i.e., octahedral bonding angle and length. Orthorhombic SrRuO 3 films coherently grown on SrTiO 3 substrates are used as a model system. Implanted He atoms are confirmed to induce out-of-plane strain, which provides the ability to controllably shift the bulk-like orthorhombically distorted phase to a tetragonal structure by shifting the oxygen octahedra rotation pattern. Lastly, these results demonstrate that He implantation offers an entirely new pathway to strain engineering of perovskite-based complex oxide thin films, useful for creating new functionalities or properties in perovskite materials.« less

  10. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2003-01-01

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  11. Oxygen ion conducting materials

    DOEpatents

    Carter, J. David; Wang, Xiaoping; Vaughey, John; Krumpelt, Michael

    2004-11-23

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  12. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2005-07-12

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  13. The Impact of Atmosphere on the Local Luminescence Properties of Metal Halide Perovskite Grains.

    PubMed

    Brenes, Roberto; Eames, Christopher; Bulović, Vladimir; Islam, M Saiful; Stranks, Samuel D

    2018-04-01

    Metal halide perovskites are exceptional candidates for inexpensive yet high-performing optoelectronic devices. Nevertheless, polycrystalline perovskite films are still limited by nonradiative losses due to charge carrier trap states that can be affected by illumination. Here, in situ microphotoluminescence measurements are used to elucidate the impact of light-soaking individual methylammonium lead iodide grains in high-quality polycrystalline films while immersing them with different atmospheric environments. It is shown that emission from each grain depends sensitively on both the environment and the nature of the specific grain, i.e., whether it shows good (bright grain) or poor (dark grain) luminescence properties. It is found that the dark grains show substantial rises in emission, while the bright grain emission is steady when illuminated in the presence of oxygen and/or water molecules. The results are explained using density functional theory calculations, which reveal strong adsorption energies of the molecules to the perovskite surfaces. It is also found that oxygen molecules bind particularly strongly to surface iodide vacancies which, in the presence of photoexcited electrons, lead to efficient passivation of the carrier trap states that arise from these vacancies. The work reveals a unique insight into the nature of nonradiative decay and the impact of atmospheric passivation on the microscale properties of perovskite films. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Correlation between Geometrically Induced Oxygen Octahedral Tilts and Multiferroic Behaviors in BiFeO 3 Films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Sung Su; Kim, Young-Min; Lee, Hyun-Jae

    The equilibrium position of atoms in a unit cell is directly connected to crystal functionalities, e.g., ferroelectricity, ferromagnetism, and piezoelectricity. The artificial tuning of the energy landscape can involve repositioning atoms as well as manipulating the functionalities of perovskites (ABO 3), which are good model systems to test this legacy. Mechanical energy from external sources accommodating various clamping substrates is utilized to perturb the energy state of perovskite materials fabricated on the substrates and consequently change their functionalities; however, this approach yields undesired complex behaviors of perovskite crystals, such as lattice distortion, displacement of B atoms, and/or tilting of oxygenmore » octahedra. Owing to complimentary collaborations between experimental and theoretical studies, the effects of both lattice distortion and displacement of B atoms are well understood so far, which leaves us a simple question: Can we exclusively control the positions of oxygen atoms in perovskites for functionality manipulation? Here the artificial manipulation of oxygen octahedral tilt angles within multiferroic BiFeO 3 thin films using strong oxygen octahedral coupling with bottom SrRuO 3 layers is reported, which opens up new possibilities of oxygen octahedral engineering.« less

  15. Correlation between Geometrically Induced Oxygen Octahedral Tilts and Multiferroic Behaviors in BiFeO 3 Films

    DOE PAGES

    Lee, Sung Su; Kim, Young-Min; Lee, Hyun-Jae; ...

    2018-03-26

    The equilibrium position of atoms in a unit cell is directly connected to crystal functionalities, e.g., ferroelectricity, ferromagnetism, and piezoelectricity. The artificial tuning of the energy landscape can involve repositioning atoms as well as manipulating the functionalities of perovskites (ABO 3), which are good model systems to test this legacy. Mechanical energy from external sources accommodating various clamping substrates is utilized to perturb the energy state of perovskite materials fabricated on the substrates and consequently change their functionalities; however, this approach yields undesired complex behaviors of perovskite crystals, such as lattice distortion, displacement of B atoms, and/or tilting of oxygenmore » octahedra. Owing to complimentary collaborations between experimental and theoretical studies, the effects of both lattice distortion and displacement of B atoms are well understood so far, which leaves us a simple question: Can we exclusively control the positions of oxygen atoms in perovskites for functionality manipulation? Here the artificial manipulation of oxygen octahedral tilt angles within multiferroic BiFeO 3 thin films using strong oxygen octahedral coupling with bottom SrRuO 3 layers is reported, which opens up new possibilities of oxygen octahedral engineering.« less

  16. Nitrogen metabolism and translocation in soybean plants subjected to root oxygen deficiency.

    PubMed

    Oliveira, Halley C; Freschi, Luciano; Sodek, Ladaslav

    2013-05-01

    Although nitrate (NO3(-)) but not ammonium (NH4(+)) improves plant tolerance to oxygen deficiency, the mechanisms involved in this phenomenon are just beginning to be understood. By using gas chromatography-mass spectrometry, we investigated the metabolic fate of (15)NO3(-) and (15)NH4(+) in soybean plants (Glycine max L. Merril cv. IAC-23) subjected to root hypoxia. This stress reduced the uptake of (15)NO3(-) and (15)NH4(+) from the medium and decreased the overall assimilation of these nitrogen sources into amino acids in roots and leaves. Root (15)NO3(-) assimilation was more affected by hypoxia than that of (15)NH4(+), resulting in enhanced nitrite and nitric oxide release in the solution. However, (15)NO3(-) was translocated in substantial amounts by xylem sap and considerable (15)NO3(-) assimilation into amino acids also occurred in the leaves, both under hypoxia and normoxia. By contrast, (15)NH4(+) assimilation occurred predominantly in roots, resulting in accumulation of mainly (15)N-alanine in this tissue during hypoxia. Analysis of lactate levels suggested higher fermentation in roots from NH4(+)-treated plants compared to the NO3(-) treatment. Thus, foliar NO3(-) assimilation may be relevant to plant tolerance to oxygen deficiency, since it would economize energy expenditure by hypoxic roots. Additionally, the involvement of nitric oxide synthesis from nitrite in the beneficial effect of NO3(-) is discussed. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  17. Synthesis, stability range and characterization of Pr2Cu2O5

    NASA Astrophysics Data System (ADS)

    Fernández-Sanjulián, Javier; Morán, Emilio; Ángel Alario-Franco, Miguel

    2010-03-01

    A novel Pr2Cu2O5 phase has been prepared under high-pressure and high-temperature conditions (P ∼6 GPa and T ∼1673 K) in a Belt-type apparatus and characterized by X-ray diffraction and electron microscopy. The crystal structure appears to be an orthorhombic "oxygen-deficient perovskite" (M.T. Anderson, J.T. Vaughey, and K.R. Poeppelmeier, Structural similarities among oxygen-deficient perovskites, Chem. Mater. 5 (1993), pp. 151-165) isostructural with La2Cu2O5 (J.F. Bringley, B.A. Scott, S.J. La Placa, R.F. Boheme, T.M. Shaw, M.W. McElfresh, S.S. Trail, and D.E. Cox, Synthesis of the defect perovskite series LaCuO 3-δ with copper valence varying from 2+to 3+, Nature 347 (1990), pp. 263-265) and Nd2Cu2O5 (B.-H. Chen, D. Walker, E. Suard, B.A. Scott, B. Mercey, M. Hervieu, and B. Raveau, High pressure synthesis of NdCuO3-δ perovskites (0≤δ≤0.5). Inorg. Chem. 34 (1995), pp. 2077-2083).

  18. Recent progress in stabilizing hybrid perovskites for solar cell applications

    NASA Astrophysics Data System (ADS)

    Chen, Jianqing; Cai, Xin; Yang, Donghui; Song, Dan; Wang, Jiajia; Jiang, Jinghua; Ma, Aibin; Lv, Shiquan; Hu, Michael Z.; Ni, Chaoying

    2017-07-01

    Hybrid inorganic-organic perovskites have quickly evolved as a promising group of materials for solar cells and optoelectronic applications mainly owing to the inexpensive materials, relatively simple and versatile fabrication and high power conversion efficiency (PCE). The certified energy conversion efficiency for perovskite solar cell (PSC) has reached above 20%, which is compatible to the current best for commercial applications. However, long-term stabilities of the materials and devices remain to be the biggest challenging issue for realistic implementation of the PSCs. This article discusses the key issues related to the stability of perovskite absorbing layer including crystal structural stability, chemical stability under moisture, oxygen, illumination and interface reaction, effects of electron-transporting materials (ETM), hole-transporting materials (HTM), contact electrodes, ion migration and preparation conditions. Towards the end, prospective strategies for improving the stability of PSCs are also briefly discussed and summarized. We focus on recent understanding of the stability of materials and devices and our perspectives about the strategies for the stability improvement.

  19. First-principles study of Cs/Rb co-doped FAPbI3 stability and degradation in the presence of water and oxygen

    NASA Astrophysics Data System (ADS)

    Guo, Yao; Li, Chengbo; Xue, Yuanbin; Geng, Cuihuan; Tian, Dayong

    2018-02-01

    The poor stability of organometallic halide perovskite in humid environments is one of the biggest challenges for its commercialization in light harvesting and electroluminescent displays. Understanding the atomic detail of the perovskite/water (oxygen) interface is a critical way to explore the practicability of perovskite. In this work, we report a density functional study of water and oxygen adsorption on the Cs/Rb incorporated FAPbI3 (001) surface. The role played by water and oxygen molecules has been extensively studied in the initial degradation processes, where the strong interactions between adsorbates and perovskite surfaces are confirmed. Our results show that the dopant-terminated surface was relatively more stable than PbI2-termination one. The effects of doping on the optoelectronic properties were slight at low concentrations. The calculations showed that the molecule tend to adsorb on the I-top site of the Cs-terminated surface and the Pb-top site of the PbI2 (Cs)-terminated surface. The vdW contribution on the bonding between bare surface and molecule can be observed. The degradation-induced optical absorption decrease in the visible region could be found. Water and oxygen molecule destroy the perovskite surface structures and subsequently reduce its conversion efficiency. These findings contribute molecular-level insight into the initial stage of perovskite degradation, which should be helpful to inspire new interfacial modifications to improve the stability of corresponding perovskite materials under wet conditions.

  20. Electronic structure of stoichiometric and oxygen-deficient ferroelectric Hf0.5Zr0.5O2.

    PubMed

    Perevalov, T V; Islamov, D R; Gritsenko, V A; Prosvirin, I P

    2018-05-11

    The electronic structure of oxygen-deficient Hf 0.5 Zr 0.5 O 2 in the non-centrosymmetric orthorhombic (ferroelectric) phase was investigated by means of x-ray photoelectron spectroscopy and first-principle density functional theory calculations. It was established that a peak in the photoelectron spectra observed at an energy above the valence band top of ferroelectric Hf 0.5 Zr 0.5 O 2 in ion-etched samples was due to oxygen vacancies. A method for evaluating the oxygen vacancies concentration in the material from the comparison of experimental and theoretical photoelectron spectra of the valence band is proposed. It is found that oxygen polyvacancies are not formed in ferroelectric Hf 0.5 Zr 0.5 O 2 : an energy-favorable spatial arrangement of several oxygen vacancies in the crystal corresponds to the configuration formed by noninteracting vacancies distant from each other. The oxygen vacancies in five charged states were simulated. The electron levels in the bandgap caused by charged oxygen vacancies indicate that any type of oxygen vacancies in ferroelectric Hf 0.5 Zr 0.5 O 2 can capture both electrons and holes, i.e. can act as an amphoteric localization center for charge carriers.

  1. Electronic structure of stoichiometric and oxygen-deficient ferroelectric Hf0.5Zr0.5O2

    NASA Astrophysics Data System (ADS)

    Perevalov, T. V.; Islamov, D. R.; Gritsenko, V. A.; Prosvirin, I. P.

    2018-05-01

    The electronic structure of oxygen-deficient Hf0.5Zr0.5O2 in the non-centrosymmetric orthorhombic (ferroelectric) phase was investigated by means of x-ray photoelectron spectroscopy and first-principle density functional theory calculations. It was established that a peak in the photoelectron spectra observed at an energy above the valence band top of ferroelectric Hf0.5Zr0.5O2 in ion-etched samples was due to oxygen vacancies. A method for evaluating the oxygen vacancies concentration in the material from the comparison of experimental and theoretical photoelectron spectra of the valence band is proposed. It is found that oxygen polyvacancies are not formed in ferroelectric Hf0.5Zr0.5O2: an energy-favorable spatial arrangement of several oxygen vacancies in the crystal corresponds to the configuration formed by noninteracting vacancies distant from each other. The oxygen vacancies in five charged states were simulated. The electron levels in the bandgap caused by charged oxygen vacancies indicate that any type of oxygen vacancies in ferroelectric Hf0.5Zr0.5O2 can capture both electrons and holes, i.e. can act as an amphoteric localization center for charge carriers.

  2. Magnesium and Titanium Isotopic Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende: It Is Fun

    NASA Technical Reports Server (NTRS)

    Liu, M.-C.; Keller, L. P.; McKeegan, K. D.

    2016-01-01

    Introduction: Hibonite-rich refractory inclusions are among the first solids that formed in the solar nebula, and thus provide constraints on the earliest environment in the Solar System. An unusual hibonite-perovskite inclusion from Allende, SHAL, consists of a large (approximately 500 by 200 microns) single hibonite crystal and coexisting blocky perovskite (approximately 200 microns in size). The hibonite is characterized by chemical and oxygen isotopic compositions similar to those in the FUN (Fractionated and Unknown Nuclear anomalies) inclusion HAL. However, the rare earth element (REE) patterns measured at different spots of SHAL hibonite are highly variable, ranging from Group II-like (light REEs enriched relative to heavy REEs) to Group III-like (relatively flat with slight Eu depletions), but overall contrast largely with that of HAL, especially in the Ce and Yb abundances. This implies that SHAL hibonite formed and underwent distillation processes under more reducing conditions. Interestingly, the accompanying perovskite has uniform, unfractionated oxygen isotopic compositions (averaging delta (sup 17) O equals delta (sup 18) O equals -7 per mille) and REE abundances that are completely different from those of SHAL hibonite. This has been interpreted that perovskite and hibonite may not be co-genetic. Here we performed Al-Mg and Ti isotopic measurements of SHAL hibonite and perovskite to determine if the FUN characteristics are observed in these two isotope systems, and to further constrain the origin and evolution of SHAL. Results: Isotopic measurements of Al-Mg and Ti in SHAL were performed on the UCLA CAMECA ims-1290 ion microprobe by following the analytical protocols described in [1]. The Al-Mg and Ti data obtained in both terrestrial standards and SHAL hibonite and perovskite are shown below. Both SHAL hibonite and perovskite, despite very high (sup 27) Al to (sup 24) Mg ratios, are devoid of (sup 26) Mg excesses that can be attributed to the decay

  3. The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site

    PubMed Central

    Evans, Christopher D.; Smith, Paul J.; Manning, Troy D.; Miedziak, Peter J.; Brett, Gemma L.; Armstrong, Robert D.; Bartley, Jonathan K.; Taylor, Stuart H.; Rosseinsky, Matthew J.; Hutchings, Graham J.

    2016-01-01

    Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology. PMID:27074316

  4. The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site.

    PubMed

    Evans, Christopher D; Kondrat, Simon A; Smith, Paul J; Manning, Troy D; Miedziak, Peter J; Brett, Gemma L; Armstrong, Robert D; Bartley, Jonathan K; Taylor, Stuart H; Rosseinsky, Matthew J; Hutchings, Graham J

    2016-07-04

    Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology.

  5. The excellent performance of nest-like oxygen-deficient Cu1.5Mn1.5O4 applied in activated carbon air-cathode microbial fuel cell.

    PubMed

    Wang, Junjie; Tian, Pei; Li, Kexun; Ge, Baochao; Liu, Di; Liu, Yi; Yang, Tingting; Ren, Rong

    2016-12-01

    This study investigated the performance of nano spinel nest-like oxygen-deficient Cu 1.5 Mn 1.5 O 4 doping activated carbon (AC) as air cathode in microbial fuel cell (MFC). The Cu 1.5 Mn 1.5 O 4 was synthesized via hydrothermal method and subsequent annealed. The maximum power density (MPD) of MFC with oxygen-deficient Cu 1.5 Mn 1.5 O 4 modified cathode was 1928±18mWm -2 , which was 1.53 times higher than the bare cathode. The electrochemical studies showed that Cu 1.5 Mn 1.5 O 4 doping AC exhibited higher kinetic activity and lower resistance. The mechanism of oxygen reduction for the catalyst was a four electron pathway. The oxygen deficient of Cu 1.5 Mn 1.5 O 4 played an important role in catalytic activity. So Cu 1.5 Mn 1.5 O 4 would be an excellent promising catalyst for ORR in MFC. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3.

    PubMed

    Li, Ming; Pietrowski, Martha J; De Souza, Roger A; Zhang, Huairuo; Reaney, Ian M; Cook, Stuart N; Kilner, John A; Sinclair, Derek C

    2014-01-01

    Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.

  7. Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.

    PubMed

    Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro

    2017-08-25

    We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.

  8. Integration of perovskite oxide dielectrics into complementary metal-oxide-semiconductor capacitor structures using amorphous TaSiN as oxygen diffusion barrier

    NASA Astrophysics Data System (ADS)

    Mešić, Biljana; Schroeder, Herbert

    2011-09-01

    The high permittivity perovskite oxides have been intensively investigated for their possible application as dielectric materials for stacked capacitors in dynamic random access memory circuits. For the integration of such oxide materials into the CMOS world, a conductive diffusion barrier is indispensable. An optimized stack p++-Si/Pt/Ta21Si57N21/Ir was developed and used as the bottom electrode for the oxide dielectric. The amorphous TaSiN film as oxygen diffusion barrier showed excellent conductive properties and a good thermal stability up to 700 °C in oxygen ambient. The additional protective iridium layer improved the surface roughness after annealing. A 100-nm-thick (Ba,Sr)TiO3 film was deposited using pulsed laser deposition at 550 °C, showing very promising properties for application; the maximum relative dielectric constant at zero field is κ ≈ 470, and the leakage current density is below 10-6 A/cm2 for fields lower then ± 200 kV/cm, corresponding to an applied voltage of ± 2 V.

  9. Efficient ambient-air-stable solar cells with 2D-3D heterostructured butylammonium-caesium-formamidinium lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Wang, Zhiping; Lin, Qianqian; Chmiel, Francis P.; Sakai, Nobuya; Herz, Laura M.; Snaith, Henry J.

    2017-09-01

    Perovskite solar cells are remarkably efficient; however, they are prone to degradation in water, oxygen and ultraviolet light. Cation engineering in 3D perovskite absorbers has led to reduced degradation. Alternatively, 2D Ruddlesden-Popper layered perovskites exhibit improved stability, but have not delivered efficient solar cells so far. Here, we introduce n-butylammonium cations into a mixed-cation lead mixed-halide FA0.83Cs0.17Pb(IyBr1-y)3 3D perovskite. We observe the formation of 2D perovskite platelets, interspersed between highly orientated 3D perovskite grains, which suppress non-radiative charge recombination. We investigate the relationship between thin-film composition, crystal alignment and device performance. Solar cells with an optimal butylammonium content exhibit average stabilized power conversion efficiency of 17.5 ± 1.3% with a 1.61-eV-bandgap perovskite and 15.8 ± 0.8% with a 1.72-eV-bandgap perovskite. The stability under simulated sunlight is also enhanced. Cells sustain 80% of their 'post burn-in' efficiency after 1,000 h in air, and close to 4,000 h when encapsulated.

  10. Synthesis of a polar ordered oxynitride perovskite

    NASA Astrophysics Data System (ADS)

    Vadapoo, Rajasekarakumar; Ahart, Muhtar; Somayazulu, Maddury; Holtgrewe, Nicholas; Meng, Yue; Konopkova, Zuzana; Hemley, Russell J.; Cohen, R. E.

    2017-06-01

    For decades, numerous attempts have been made to produce polar oxynitride perovskites, where some of the oxygen is replaced by nitrogen, but a polar ordered oxynitride has never been demonstrated. Caracas and Cohen [Appl. Phys. Lett. 91, 092902 (2007), 10.1063/1.2776370] studied possible ordered polar oxynitrides within density-functional theory (DFT) and found a few candidates that were predicted to be insulating and at least metastable. YSi O2N stood out with huge predicted polarization and nonlinear optic coefficients. In this study, we demonstrate the synthesis of perovskite-structured YSi O2N by using a combination of a diamond-anvil cell and in situ laser-heating techniques. Subsequent in situ x-ray diffraction, second-harmonic generation, and Raman-scattering measurements confirm that it is polar and a strong nonlinear optical material, with structure and properties similar to those predicted by DFT.

  11. Synthesis of a polar ordered oxynitride perovskite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vadapoo, Rajasekarakumar; Ahart, Muhtar; Somayazulu, Maddury

    For decades, numerous attempts have been made to produce polar oxynitride perovskites, where some of the oxygen is replaced by nitrogen, but a polar ordered oxynitride has never been demonstrated. Caracas and Cohen [Appl. Phys. Lett. 91, 092902 (2007)] studied possible ordered polar oxynitrides within density-functional theory (DFT) and found a few candidates that were predicted to be insulating and at least metastable. YSi O 2 N stood out with huge predicted polarization and nonlinear optic coefficients. In this study, we demonstrate the synthesis of perovskite-structured YSi O 2 N by using a combination of a diamond-anvil cell and inmore » situ laser-heating techniques. Subsequent in situ x-ray diffraction, second-harmonic generation, and Raman-scattering measurements confirm that it is polar and a strong nonlinear optical material, with structure and properties similar to those predicted by DFT.« less

  12. Sorbent-based Oxygen Production for Energy Systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sethi, Vijay

    Project DE-FE0024075 deals with the development of a moderate-temperature sorbent-based oxygen production technology. Sorbent-based oxygen production process utilizes oxygen-storage properties of Perovskites to (1) adsorb oxygen from air in a solid sorbent, and (2) release the adsorbed oxygen into a sweep gas such as CO 2 and/or steam for gasification systems or recycled flue gas for oxy-combustion systems. Pure oxygen can be produced by the use of vacuum instead of a sweep gas to affect the pressure swing. By developing more efficient and stable, higher sorption capacity, newer class of materials operating at moderate temperatures this process represents a majormore » advancement in air separation technology. Newly developed perovskite ceramic sorbent materials with order-disorder transition have a higher O 2 adsorption capacity, potentially 200 °C lower operating temperatures, and up to two orders of magnitude faster desorption rates than those used in earlier development efforts. The performance advancements afforded by the new materials lead to substantial savings in capital investment and operational costs. Cost of producing oxygen using sorbents could be as much as 26% lower than VPSA and about 13% lower than a large cryogenic air separation unit. Cost advantage against large cryogenic separation is limited because sorbent-based separation numbers up sorbent modules for achieving the larger capacity.« less

  13. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    PubMed Central

    Perry, Nicola H.; Ishihara, Tatsumi

    2016-01-01

    Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic), and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS) with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance. PMID:28773978

  14. Gene expression profiling reveals decreased expression of two hemoglobin genes associated with increased consumption of oxygen in Chironomus tentans exposed to atrazine: a possible mechanism for adapting to oxygen deficiency.

    PubMed

    Anderson, Troy D; Jin-Clark, Ying; Begum, Khurshida; Starkey, Sharon R; Zhu, Kun Yan

    2008-01-31

    Atrazine is an extensively used triazine herbicide in agricultural and residential areas and has been routinely detected in many surface and ground waters. This study reveals various up- and down-regulated genes associated with hypoxic stress in atrazine-treated fourth-instar Chironomus tentans larvae (midges) by using restriction fragment differential display-PCR. Two down-regulated hemoglobin cDNAs were isolated from the midges. Northern blot analysis indicated CteHb-IIbeta and CteHb-III mRNA expressions decreased by 36 and 21%, respectively, in midges exposed to atrazine at 1 microg/L for 96h. Decreased hemoglobin gene expression was associated with elevated oxygen consumption in atrazine-treated midges. Midges exposed to atrazine at 1 microg/L increased their oxygen consumption by 47%, whereas midges exposed to atrazine at 1000 microg/L for 48h increased their oxygen consumption by 66%. Our study demonstrates for the first time that atrazine, at environmentally relevant concentrations, can elevate respiration, possibly eliciting counteractive measures at the transcriptional level to adapt to oxygen deficiency in an ecologically important aquatic insect. Our results further suggest that the ability to modulate both the quantity and quality of Hb serves as an adaptive response to counteract the initial onset of oxygen deficiency induced by atrazine in midges.

  15. Hybrid Organic-Inorganic Perovskite Photodetectors.

    PubMed

    Tian, Wei; Zhou, Huanping; Li, Liang

    2017-11-01

    Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Structural evolution across the insulator-metal transition in oxygen-deficient BaTiO 3-δ studied using neutron total scattering and Rietveld analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jeong, I.-K.; Lee, Seunghun; Jeong, Se-Young

    2011-08-29

    Oxygen-deficient BaTiO 3-δ exhibits an insulator-metal transition with increasing δ. We performed neutron total scattering measurements to study structural evolution across an insulator-metal transition in BaTiO 3-δ. Despite its significant impact on resistivity, slight oxygen reduction (δ=0.09) caused only a small disturbance on the local doublet splitting of Ti-O bond. This finding implies that local polarization is well preserved under marginal electric conduction. In the highly oxygen-deficient metallic state (δ=0.25), however, doublet splitting of the Ti-O bond became smeared. The smearing of the local Ti-O doublet is complemented with long-range structural analysis and demonstrates that the metallic conduction in themore » highly oxygen-reduced BaTiO 3-δ is due to the appearance of nonferroelectric cubic lattice.« less

  17. Multiscale modeling and experimental interpretation of perovskite oxide materials in thermochemical energy storage and conversion for application in concentrating solar power

    NASA Astrophysics Data System (ADS)

    Albrecht, Kevin J.

    Decarbonization of the electric grid is fundamentally limited by the intermittency of renewable resources such as wind and solar. Therefore, energy storage will play a significant role in the future of grid-scale energy generation to overcome the intermittency issues. For this reason, concentrating solar power (CSP) plants have been a renewable energy generation technology of interest due to their ability to participate in cost effective and efficient thermal energy storage. However, the ability to dynamically dispatch a CSP plant to meet energy demands is currently limited by the large quantities of sensible thermal energy storage material needed in a molten salt plant. Perovskite oxides have been suggested as a thermochemical energy storage material to enhance the energy storage capabilities of particle-based CSP plants, which combine sensible and chemical modes of energy storage. In this dissertation, computational models are used to establish the thermochemical energy storage potential of select perovskite compositions, identify system configurations that promote high values of energy storage and solar-to-electric efficiency, assess the kinetic and transport limitation of the chemical mode of energy storage, and create receiver and reoxidation reactor models capable of aiding in component design. A methodology for determining perovskite thermochemical energy storage potential is developed based on point defect models to represent perovskite non-stoichiometry as a function of temperature and gas phase oxygen partial pressure. The thermodynamic parameters necessary for the model are extracted from non-stoichiometry measurements by fitting the model using an optimization routine. The procedure is demonstrated for Ca0.9Sr0.1MnO 3-d which displayed combined energy storage values of 705.7 kJ/kg -1 by cycling between 773 K and 0.21 bar oxygen to 1173 K and 10 -4 bar oxygen. Thermodynamic system-level models capable of exploiting perovskite redox chemistry for energy

  18. LaFe 0.9Ni 0.1O 3 perovskite catalyst with enhanced activity and coke-resistance for dry reforming of ethane

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, Baohuai; Yan, Binhang; Yao, Siyu

    In this work, a LaFe 0.9Ni 0.1O 3 perovskite catalyst was evaluated for dry reforming of ethane (DRE), with two conventional oxide supported Ni catalysts (Ni/La 2O 3 and NiFe/La 2O 3) being used as references. LaFe 0.9Ni 0.1O 3 showed the best activity and high coke-/sintering-resistance. TEM, TGA, and Raman characterizations confirmed that the deactivation of Ni/La 2O 3 was owing to the growth of Ni particles and the accumulation of coke, although the formation of La 2O 2CO 3 was able to remove part of the coke during the reaction. The introduction of Fe-related species inhibited the cokemore » formation while decreased the activity due to the loss of active sites. A portion of Ni ions in the perovskite lattice could be reduced to form highly dispersed and stable Ni nanoparticles on the surface during the reaction and oxygen vacancies were left in the perovskite lattice. Pulse reactor studies revealed that the oxygen vacancies in the perovskite could facilitate the activation and dissociation of CO 2 to form CO and reactive oxygen species. Additionally, C 2H 6 was activated with the assistance of oxygen from the surface or subsurface of LaFe 0.9Ni 0.1O 3 to form CO, rather than directly dissociated to surface carbon species as observed over Ni/La 2O 3.« less

  19. LaFe 0.9Ni 0.1O 3 perovskite catalyst with enhanced activity and coke-resistance for dry reforming of ethane

    DOE PAGES

    Zhao, Baohuai; Yan, Binhang; Yao, Siyu; ...

    2017-12-29

    In this work, a LaFe 0.9Ni 0.1O 3 perovskite catalyst was evaluated for dry reforming of ethane (DRE), with two conventional oxide supported Ni catalysts (Ni/La 2O 3 and NiFe/La 2O 3) being used as references. LaFe 0.9Ni 0.1O 3 showed the best activity and high coke-/sintering-resistance. TEM, TGA, and Raman characterizations confirmed that the deactivation of Ni/La 2O 3 was owing to the growth of Ni particles and the accumulation of coke, although the formation of La 2O 2CO 3 was able to remove part of the coke during the reaction. The introduction of Fe-related species inhibited the cokemore » formation while decreased the activity due to the loss of active sites. A portion of Ni ions in the perovskite lattice could be reduced to form highly dispersed and stable Ni nanoparticles on the surface during the reaction and oxygen vacancies were left in the perovskite lattice. Pulse reactor studies revealed that the oxygen vacancies in the perovskite could facilitate the activation and dissociation of CO 2 to form CO and reactive oxygen species. Additionally, C 2H 6 was activated with the assistance of oxygen from the surface or subsurface of LaFe 0.9Ni 0.1O 3 to form CO, rather than directly dissociated to surface carbon species as observed over Ni/La 2O 3.« less

  20. Effects of Oxygen Deficiency and Dopping of pr in Gd1-x Prx Ba2Cu3O7-y

    NASA Astrophysics Data System (ADS)

    Zolfagharkhani, G.; Daadmehr, V.; Farzaneh, M.; Sedighiani, A.; Akhavan, M.

    2000-09-01

    Single phase crystalline samples of Gd1-x Prx Ba2Cu3O7-y with 0.0 ≤ x ≤ 0.2 have been prepared by standard solid state reaction technique and characterized by SEM and XRD. The electrical measurements show two plateaus in Tc versus y curve for GdBa2Cu3O7-y (0oxygen deficiency. In deoxygenation process of Pr dopant samples, the plateaus come down to lower temperatures and the first plateau becomes smaller than undoped samples. Simultaneous doping of Pr and oxygen deficiency are superimposed on increasing of ρ before transition and suppression of Tc by decreasing of hole concentration in CuO2 planes. The experiments indicate that in GdPr-123 samples, presence of Pr causes the oxygen bond to become stronger than in undoped samples.

  1. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

    PubMed Central

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-01-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ∼80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg∼1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity. PMID:27187067

  2. Investigation of trimethylacetic acid adsorption on stoichiometric and oxygen-deficient CeO 2 (111) surfaces

    DOE PAGES

    Sanghavi, Shail; Wang, Weina; Nandasiri, Manjula I.; ...

    2016-05-12

    We studied the interactions between the carboxylate anchoring group from trimethylacetic acid (TMAA) and CeO 2(111) surfaces as a function of oxygen stoichiometry using in situ X-ray photoelectron spectroscopy (XPS). The stoichiometric CeO 2(111) surface was obtained by annealing the thin film under 2.0 × 10 –5 Torr of oxygen at ~550 °C for 30 min. In order to reduce the CeO 2(111) surface, the thin film was annealed under ~5.0 × 10 –10 Torr vacuum conditions at 550 °C, 650 °C, 750 °C and 850 °C for 30 min to progressively increase the oxygen defect concentration on the surface.more » The saturated TMAA coverage on the CeO 2(111) surface determined from XPS elemental composition is found to increase with increasing oxygen defect concentration. This is attributed to the increase of under-coordinated cerium sites on the surface with the increase in the oxygen defect concentrations. Furthermore, XPS results were in agreement with periodic density functional theory (DFT) calculations and indicate a stronger binding between the carboxylate group from TMAA and the oxygen deficient CeO 2–δ(111) surface through dissociative adsorption.« less

  3. What makes the difference in perovskite titanates?

    NASA Astrophysics Data System (ADS)

    Bussmann-Holder, Annette; Roleder, Krystian; Ko, Jae-Hyeon

    2018-06-01

    We have investigated in detail the lattice dynamics of five different perovskite titanates ATiO3 (A = Ca, Sr, Ba, Pb, Eu) where the A sites are occupied by +2 ions. In spite of the largely ionic character of these ions, the properties of these compounds differ substantially. They range from order/disorder like, to displacive ferroelectric, quantum paraelectric, and antiferromagnetic. All compounds crystallize in the cubic structure at high temperature and undergo structural phase transitions to tetragonal symmetry, partly followed by further transitions to lower symmetries. Since the TiO6 moiety is the essential electronic and structural unit, the question arises, what makes the significant difference between them. It is shown that the lattice dynamics of these compounds are very different, and that mode-mode coupling effects give rise to many distinct properties. In addition, the oxygen ion nonlinear polarizability plays a key role since it dominates the anharmonicity of these perovskites and determines the structural instability.

  4. Solution processed deposition of electron transport layers on perovskite crystal surface-A modeling based study

    NASA Astrophysics Data System (ADS)

    Mortuza, S. M.; Taufique, M. F. N.; Banerjee, Soumik

    2017-02-01

    The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.

  5. Perovskite electrodes and method of making the same

    DOEpatents

    Seabaugh, Matthew M [Columbus, OH; Swartz, Scott L [Columbus, OH

    2009-09-22

    The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

  6. Perovskite electrodes and method of making the same

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.

    2005-09-20

    The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

  7. Cardiomyocyte hypertrophy induced by Endonuclease G deficiency requires reactive oxygen radicals accumulation and is inhibitable by the micropeptide humanin.

    PubMed

    Blasco, Natividad; Cámara, Yolanda; Núñez, Estefanía; Beà, Aida; Barés, Gisel; Forné, Carles; Ruíz-Meana, Marisol; Girón, Cristina; Barba, Ignasi; García-Arumí, Elena; García-Dorado, David; Vázquez, Jesús; Martí, Ramon; Llovera, Marta; Sanchis, Daniel

    2018-06-01

    The endonuclease G gene (Endog), which codes for a mitochondrial nuclease, was identified as a determinant of cardiac hypertrophy. How ENDOG controls cardiomyocyte growth is still unknown. Thus, we aimed at finding the link between ENDOG activity and cardiomyocyte growth. Endog deficiency induced reactive oxygen species (ROS) accumulation and abnormal growth in neonatal rodent cardiomyocytes, altering the AKT-GSK3β and Class-II histone deacethylases (HDAC) signal transduction pathways. These effects were blocked by ROS scavengers. Lack of ENDOG reduced mitochondrial DNA (mtDNA) replication independently of ROS accumulation. Because mtDNA encodes several subunits of the mitochondrial electron transport chain, whose activity is an important source of cellular ROS, we investigated whether Endog deficiency compromised the expression and activity of the respiratory chain complexes but found no changes in these parameters nor in ATP content. MtDNA also codes for humanin, a micropeptide with possible metabolic functions. Nanomolar concentrations of synthetic humanin restored normal ROS levels and cell size in Endog-deficient cardiomyocytes. These results support the involvement of redox signaling in the control of cardiomyocyte growth by ENDOG and suggest a pathway relating mtDNA content to the regulation of cell growth probably involving humanin, which prevents reactive oxygen radicals accumulation and hypertrophy induced by Endog deficiency. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  8. Resonant halide perovskite nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

    2017-09-01

    The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

  9. Defective TiO 2 with high photoconductive gain for efficient and stable planar heterojunction perovskite solar cells

    DOE PAGES

    Li, Yanbo; Cooper, Jason K.; Liu, Wenjun; ...

    2016-08-18

    Formation of planar heterojunction perovskite solar cells exhibiting both high efficiency and stability under continuous operation remains a challenge. Here, we show this can be achieved by using a defective TiO 2 thin film as the electron transport layer. TiO 2 layers with native defects are deposited by electron beam evaporation in an oxygen-deficient environment. Deep-level hole traps are introduced in the TiO 2 layers and contribute to a high photoconductive gain and reduced photocatalytic activity. The high photoconductivity of the TiO 2 electron transport layer leads to improved efficiency for the fabricated planar devices. A maximum power conversion efficiencymore » of 19.0% and an average PCE of 17.5% are achieved. In addition, the reduced photocatalytic activity of the TiO 2 layer leads to enhanced long-Term stability for the planar devices. Under continuous operation near the maximum power point, an efficiency of over 15.4% is demonstrated for 100 h.« less

  10. Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites.

    PubMed

    Howard, John M; Tennyson, Elizabeth M; Barik, Sabyasachi; Szostak, Rodrigo; Waks, Edo; Toney, Michael F; Nogueira, Ana F; Neves, Bernardo R A; Leite, Marina S

    2018-06-21

    Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs x FA 1- x Pb(I y Br 1- y ) 3 perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

  11. Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells

    PubMed Central

    Nejand, Bahram Abdollahi; Gharibzadeh, Saba; Ahmadi, Vahid; Shahverdi, H. Reza

    2016-01-01

    We introduced a new approach to deposit perovskite layer with no need for dissolving perovskite precursors. Deposition of Solution-free perovskite (SFP) layer is a key method for deposition of perovskite layer on the hole or electron transport layers that are strongly sensitive to perovskite precursors. Using deposition of SFP layer in the perovskite solar cells would extend possibility of using many electron and hole transport materials in both normal and invert architectures of perovskite solar cells. In the present work, we synthesized crystalline perovskite powder followed by successful deposition on TiO2 and cuprous iodide as the non-sensitve and sensitive charge transport layers to PbI2 and CH3NH3I solution in DMF. The post compressing step enhanced the efficiency of the devices by increasing the interface area between perovskite and charge transport layers. The 9.07% and 7.71% cell efficiencies of the device prepared by SFP layer was achieved in respective normal (using TiO2 as a deposition substrate) and inverted structure (using CuI as deposition substrate) of perovskite solar cell. This method can be efficient in large-scale and low cost fabrication of new generation perovskite solar cells. PMID:27640991

  12. Pressure Induced Iron Spin Crossover in MgGeO3 Perovskite and Post-perovskite

    NASA Astrophysics Data System (ADS)

    Wentzcovitch, R. M.; Shukla, G.; Topsakal, M.

    2014-12-01

    MgGeO3-perovskite is known to be a low-pressure analog of MgSiO3-perovskite in many respects, but especially in regard to the post-perovskite transition. As such, investigation of spin state changes in Fe-bearing MgGeO3 might help to clarify some aspects of this type of state change in Fe-bearing MgSiO3. Using DFT+U calculations, we have investigated pressure induced state changes in Fe-bearing MgGeO3 perovskite and post-perovskite. Owing to the relatively larger atomic size of germanium compared to silicon, germanate phases have larger unit cell volume and interatomic distances than equivalent silicate phases at same pressures. As a result, all pressure induced state changes in iron occur at higher pressures in germanate phases than in the silicate ones, be it a spin state change or position change of (ferrous) iron in the perovskite cage. The effect of iron in the post-perovskite transition is also investigated.

  13. An experimental study of perovskite-structured mixed ionic- electronic conducting oxides and membranes

    NASA Astrophysics Data System (ADS)

    Zeng, Pingying

    In recent decades, ceramic membranes based on mixed ionic and electronic conducting (MIEC) perovskite-structured oxides have received many attentions for their applications for air separation, or as a membrane reactor for methane oxidation. While numerous perovskite oxide materials have been explored over the past two decades; there are hardly any materials with sufficient practical economic value and performance for large scale applications, which justifies continuing the search for new materials. The main purposes of this thesis study are: (1) develop several novel SrCoO3-delta based MIEC oxides, SrCoCo1-xMxO3-delta, based on which membranes exhibit excellent oxygen permeability; (2) investigate the significant effects of the species and concentration of the dopants M (metal ions with fixed valences) on the various properties of these membranes; (3) investigate the significant effects of sintering temperature on the microstructures and performance of oxygen permeation membranes; and (4) study the performance of oxygen permeation membranes as a membrane reactor for methane combustion. To stabilize the cubic phase structure of the SrCoO3-delta oxide, various amounts of scandium was doped into the B-site of SrCoO 3-delta to form a series of new perovskite oxides, SrScxCoCo 1-xO3-delta (SSCx, x = 0-0.7). The significant effects of scandium-doping concentration on the phase structure, electrical conductivity, sintering performance, thermal and structural stability, cathode performance, and oxygen permeation performance of the SSCx membranes, were systematically studied. Also for a more in-depth understanding, the rate determination steps for the oxygen transport process through the membranes were clarified by theoretical and experimental investigation. It was found that only a minor amount of scandium (5 mol%) doping into the B-site of SrCoO3-delta can effectively stabilize the cubic phase structure, and thus significantly improve the electrical conductivity and

  14. Cerebral glucose deficiency versus oxygen deficiency in neonatal encephalopathy.

    PubMed

    Rudolph, A M

    2018-04-24

    Hypoxic-ischemic encephalopathy (HIE) in newborn infants is generally considered to result from decreased arterial oxygen content or cerebral blood flow. Cerebral injury similar to that of HIE has been noted with hypoglycemia. Studies in fetal lambs have shown that ventilation with 3% oxygen did not change cerebral blood flow, but ventilation with 100% oxygen resulted in marked reduction in cerebral blood flow, glucose delivery and glucose consumption. Blood glucose concentration falls markedly after birth; this, associated with the fall in cerebral blood flow, greatly reduces glucose supply to the brain. In preterm infants, blood glucose levels tend to be very low. Also persistent patency of the ductus arteriosus may reduce cerebral flow in diastole, thus exaggerating the decrease in glucose supply. I propose that glycopenic-ischemic encephalopathy is a more appropriate term for the cerebral insult. We should consider more aggressive management of the low blood glucose concentrations in the neonate, and particularly in preterm infants. Administration of high levels of oxygen in inspired air should be avoided to reduce the enhancement of cerebral vasoconstriction and decreased flow that normally occurs after birth.

  15. Molecular tools for investigating microbial community structure and function in oxygen-deficient marine waters.

    PubMed

    Hawley, Alyse K; Kheirandish, Sam; Mueller, Andreas; Leung, Hilary T C; Norbeck, Angela D; Brewer, Heather M; Pasa-Tolic, Ljiljana; Hallam, Steven J

    2013-01-01

    Water column oxygen (O2)-deficiency shapes food-web structure by progressively directing nutrients and energy away from higher trophic levels into microbial community metabolism resulting in fixed nitrogen loss and greenhouse gas production. Although respiratory O2 consumption during organic matter degradation is a natural outcome of a productive surface ocean, global-warming-induced stratification intensifies this process leading to oxygen minimum zone (OMZ) expansion. Here, we describe useful tools for detection and quantification of potential key microbial players and processes in OMZ community metabolism including quantitative polymerase chain reaction primers targeting Marine Group I Thaumarchaeota, SUP05, Arctic96BD-19, and SAR324 small-subunit ribosomal RNA genes and protein extraction methods from OMZ waters compatible with high-resolution mass spectrometry for profiling microbial community structure and functional dynamics. © 2013 Elsevier Inc. All rights reserved.

  16. Highly Efficient Perovskite-Perovskite Tandem Solar Cells Reaching 80% of the Theoretical Limit in Photovoltage.

    PubMed

    Rajagopal, Adharsh; Yang, Zhibin; Jo, Sae Byeok; Braly, Ian L; Liang, Po-Wei; Hillhouse, Hugh W; Jen, Alex K-Y

    2017-09-01

    Organic-inorganic hybrid perovskite multijunction solar cells have immense potential to realize power conversion efficiencies (PCEs) beyond the Shockley-Queisser limit of single-junction solar cells; however, they are limited by large nonideal photovoltage loss (V oc,loss ) in small- and large-bandgap subcells. Here, an integrated approach is utilized to improve the V oc of subcells with optimized bandgaps and fabricate perovskite-perovskite tandem solar cells with small V oc,loss . A fullerene variant, Indene-C 60 bis-adduct, is used to achieve optimized interfacial contact in a small-bandgap (≈1.2 eV) subcell, which facilitates higher quasi-Fermi level splitting, reduces nonradiative recombination, alleviates hysteresis instabilities, and improves V oc to 0.84 V. Compositional engineering of large-bandgap (≈1.8 eV) perovskite is employed to realize a subcell with a transparent top electrode and photostabilized V oc of 1.22 V. The resultant monolithic perovskite-perovskite tandem solar cell shows a high V oc of 1.98 V (approaching 80% of the theoretical limit) and a stabilized PCE of 18.5%. The significantly minimized nonideal V oc,loss is better than state-of-the-art silicon-perovskite tandem solar cells, which highlights the prospects of using perovskite-perovskite tandems for solar-energy generation. It also unlocks opportunities for solar water splitting using hybrid perovskites with solar-to-hydrogen efficiencies beyond 15%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Carbon solids in oxygen-deficient explosives (LA-UR-13-21151)

    NASA Astrophysics Data System (ADS)

    Peery, Travis

    2013-06-01

    The phase behavior of excess carbon in oxygen-deficient explosives has a significant effect on detonation properties and product equations of state. Mixtures of fuel oil in ammonium nitrate (ANFO) above a stoichiometric ratio demonstrate that even small amounts of graphite, on the order of 5% by mole fraction, can substantially alter the Chapman-Jouget (CJ) state properties, a central ingredient in modeling the products equation of state. Similar effects can be seen for Composition B, which borders the carbon phase boundary between graphite and diamond. Nano-diamond formation adds complexity to the product modeling because of surface adsorption effects. I will discuss these carbon phase issues in our equation of state modeling of detonation products, including our statistical mechanics description of carbon clustering and surface chemistry to properly treat solid carbon formation. This work is supported by the Advanced Simulation and Computing Program, under the NNSA.

  18. TrxR2 deficiencies promote chondrogenic differentiation and induce apoptosis of chondrocytes through mitochondrial reactive oxygen species

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yan, Jidong; Xu, Jing; Fei, Yao

    Thioredoxin reductase 2 (TrxR2) is a selenium (Se) containing protein. Se deficiency is associated with an endemic osteoarthropathy characterized by impaired cartilage formation. It is unclear whether TrxR2 have roles in cartilage function. We examined the effects of TrxR2 on chondrogenic ATDC5 cells through shRNA-mediated gene silencing of TrxR2. We demonstrated TrxR2 deficiencies could enhance chondrogenic differentiation and apoptosis of ATDC5 cells. TrxR2 deficiencies increased accumulation of cartilage glycosaminoglycans (GAGs) and mineralization. TrxR2 deficiencies also stimulated expression of extracellular (ECM) gene including Collagen II and Aggrecan. The enhanced chondrogenic properties were further confirmed by activation of Akt signaling which aremore » required for chondrogenesis. In addition, TrxR2 deficiencies promoted chondrocyte proliferation through acceleration of cell cycle progression by increase in both S and G2/M phase cell distribution accompanied with induction of parathyroid hormone-related protein (PTHrP). Moreover, TrxR2 deficiencies induced chondrocyte death via apoptosis and increased cell sensitivity to exogenous oxidative stress. Furthermore, TrxR2 deficiencies induced emission of mitochondrial reactive oxygen species (ROS) without alteration of mitochondrial membrane potential and intracellular ATP content. Finally, treatment of TrxR2 deficiency cells with N-acetylcysteine (NAC) inhibited mitochondrial ROS production and chondrocyte apoptosis. NAC also prevented chondrogenic differentiation of TrxR2 deficiency cells by suppression of ECM gene expression, GAGs accumulation and mineralization, as well as attenuation of Akt signaling. Thus, TrxR2-mediated mitochondrial integrity is indispensable for chondrogenic differentiation of ATDC5 cells. TrxR2 deficiency-induced impaired proliferation and death of chondrocytes may be the pathological mechanism of the osteoarthropathy due to Se deficiency. Notably, this study also uncover the

  19. Efficient Suppression of Electron–Hole Recombination in Oxygen-Deficient Hydrogen-Treated TiO2 Nanowires for Photoelectrochemical Water Splitting

    PubMed Central

    2013-01-01

    There is an increasing level of interest in the use of black TiO2 prepared by thermal hydrogen treatments (H:TiO2) due to the potential to enhance both the photocatalytic and the light-harvesting properties of TiO2. Here, we examine oxygen-deficient H:TiO2 nanotube arrays that have previously achieved very high solar-to-hydrogen (STH) efficiencies due to incident photon-to-current efficiency (IPCE) values of >90% for photoelectrochemical water splitting at only 0.4 V vs RHE under UV illumination. Our transient absorption (TA) mechanistic study provides strong evidence that the improved electrical properties of oxygen-deficient TiO2 enables remarkably efficient spatial separation of electron–hole pairs on the submicrosecond time scale at moderate applied bias, and this coupled to effective suppression of microsecond to seconds charge carrier recombination is the primary factor behind the dramatically improved photoelectrochemical activity. PMID:24376902

  20. Mixed Sn-Ge Perovskite for Enhanced Perovskite Solar Cell Performance in Air.

    PubMed

    Ito, Nozomi; Kamarudin, Muhammad Akmal; Hirotani, Daisuke; Zhang, Yaohong; Shen, Qing; Ogomi, Yuhei; Iikubo, Satoshi; Minemoto, Takashi; Yoshino, Kenji; Hayase, Shuzi

    2018-04-05

    Lead-based perovskite solar cells have gained ground in recent years, showing efficiency as high as 20%, which is on par with that of silicon solar cells. However, the toxicity of lead makes it a nonideal candidate for use in solar cells. Alternatively, tin-based perovskites have been proposed because of their nontoxic nature and abundance. Unfortunately, these solar cells suffer from low efficiency and stability. Here, we propose a new type of perovskite material based on mixed tin and germanium. The material showed a band gap around 1.4-1.5 eV as measured from photoacoustic spectroscopy, which is ideal from the perspective of solar cells. In a solar cell device with inverted planar structure, pure tin perovskite solar cell showed a moderate efficiency of 3.31%. With 5% doping of germanium into the perovskite, the efficiency improved up to 4.48% (6.90% after 72 h) when measured in air without encapsulation.

  1. Chalcogenide Perovskites for Solar Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Perera, Samanthe

    Methylammonium Lead halide perovskites have recently emerged as a promising candidate for realizing high efficient low cost photovoltaic modules. Charge transport properties of the solution processed halide perovskites are comparable to some of the existing absorbers used in the current PV industry which require sophisticated processing techniques. Due to this simple processing required to achieve high efficiencies, halide perovskites have become an active field of research. As a result, perovskite solar cells are rapidly reaching towards theoretical efficiency limit of close to 30%. It's believed that ionicity inherent to perovskite materials is one of the contributing factors for the excellent charge transport properties of perovskites. Despite the growing interest for solar energy harvesting purposes, these halide perovskites have serious limitations such as toxicity and instability that need to be addressed in order to commercialize the solar cells incorporating them. This dissertation focuses on a new class of ionic semiconductors, chalcogenide perovskites for solar energy harvesting purposes. Coming from the family perovskites they are expected to have same excellent charge transport properties inherent to perovskites due to the ionicity. Inspired by few theoretical studies on chalcogenide perovskites, BaZrS3 and its Ti alloys were synthesized by sulfurizing the oxide counterpart. Structural characterizations have confirmed the predicted distorted perovskite phase. Optical characterizations have verified the direct band gap suitable for thin film single junction solar cells. Anion alloying was demonstrated by synthesizing oxysulfides with widely tunable band gap suitable for applications such as solid state lighting and sensing.

  2. Perovskite-like fluorides and oxyfluorides: Phase transitions and caloric effects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Flerov, I. N., E-mail: flerov@iph.krasn.ru; Gorev, M. V., E-mail: gorev@iph.krasn.ru; Tressaud, A.

    2011-01-15

    An analysis of the effect that chemical and hydrostatic pressures have on the thermodynamic properties of perovskite-like fluorine-oxygen compounds A{sub 2}A Prime MeO{sub x}F{sub 6-x} has revealed that materials under-going order-disorder transitions and having significant external-pressure compliance have the highest caloric efficiency. Some of the fluorides and oxyfluorides under study can be considered promising solid coolants.

  3. Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

    NASA Astrophysics Data System (ADS)

    Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

    2018-05-01

    The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

  4. Enhanced planar perovskite solar cell efficiency and stability using a perovskite/PCBM heterojunction formed in one step.

    PubMed

    Zhou, Long; Chang, Jingjing; Liu, Ziye; Sun, Xu; Lin, Zhenhua; Chen, Dazheng; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

    2018-02-08

    Perovskite/PCBM heterojunctions are efficient for fabricating perovskite solar cells with high performance and long-term stability. In this study, an efficient perovskite/PCBM heterojunction was formed via conventional sequential deposition and one-step formation processes. Compared with conventional deposition, the one-step process was more facile, and produced a perovskite thin film of substantially improved quality due to fullerene passivation. Moreover, the resulting perovskite/PCBM heterojunction exhibited more efficient carrier transfer and extraction, and reduced carrier recombination. The perovskite solar cell device based on one-step perovskite/PCBM heterojunction formation exhibited a higher maximum PCE of 17.8% compared with that from the conventional method (13.7%). The device also showed exceptional stability, retaining 83% of initial PCE after 60 days of storage under ambient conditions.

  5. Formation of reactive oxygen species in lung alveolar cells: effect of vitamin E deficiency.

    PubMed

    Sabat, Robert; Guthmann, Florian; Rüstow, Bernd

    2008-01-01

    Reactive oxygen species (ROS) play an important role in the pathogenesis of numerous pulmonary diseases. Various mainly membrane-bound ROS-generating processes exist in alveolar cells. Vitamin E (vit. E) is the most important lipophilic antioxidant. However, the significance of vit. E levels in alveolar cells for the regulation of ROS generation has not been investigated so far. We demonstrated here that feeding rats with vit. E-depleted nourishment for 5 weeks reduced the concentration of vit. E in alveolar type II cell preparations to one-fifth the amount of control animals. This reduction of vit. E levels was associated with an approximately threefold increase in ROS generation in type II pneumocytes, lymphocytes, and macrophages. The contribution of individual processes of ROS formation in control animals differed strongly among these three cell types. However, vit. E deficiency induced predominantly nonmitochondrial ROS formation in alveolar cells. Expression and NAD(P)H-oxidase activity in alveolar type II cell preparations was not affected by vit. E deficiency. Moreover, protein kinase C (PKC) also did not seem to be responsible for vit. E deficiency-induced ROS generation in alveolar cells. Alimentary vit. E supplementation for 2 days corrected the cellular vit. E concentration but failed to normalize ROS generation in alveolar cells. These data let us assume that alimentary vit. E deficiency caused a preferentially nonmitochondria-mediated increase of ROS formation in type II pneumocytes, macrophages, and lymphocytes. However, the short-term supplementation of vit. E does not reverse these effects.

  6. High Performance Perovskite Solar Cells

    PubMed Central

    Tong, Xin; Lin, Feng; Wu, Jiang

    2015-01-01

    Perovskite solar cells fabricated from organometal halide light harvesters have captured significant attention due to their tremendously low device costs as well as unprecedented rapid progress on power conversion efficiency (PCE). A certified PCE of 20.1% was achieved in late 2014 following the first study of long‐term stable all‐solid‐state perovskite solar cell with a PCE of 9.7% in 2012, showing their promising potential towards future cost‐effective and high performance solar cells. Here, notable achievements of primary device configuration involving perovskite layer, hole‐transporting materials (HTMs) and electron‐transporting materials (ETMs) are reviewed. Numerous strategies for enhancing photovoltaic parameters of perovskite solar cells, including morphology and crystallization control of perovskite layer, HTMs design and ETMs modifications are discussed in detail. In addition, perovskite solar cells outside of HTMs and ETMs are mentioned as well, providing guidelines for further simplification of device processing and hence cost reduction. PMID:27774402

  7. Oxygen deficiency and Sn doping of amorphous Ga{sub 2}O{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Heinemann, M. D.; Unold, T.; Berry, J.

    2016-01-11

    The potential of effectively n-type doping Ga{sub 2}O{sub 3} considering its large band gap has made it an attractive target for integration into transistors and solar cells. As a result amorphous GaO{sub x} is now attracting interest as an electron transport layer in solar cells despite little information on its opto-electrical properties. Here we present the opto-electronic properties, including optical band gap, electron affinity, and charge carrier density, for amorphous GaO{sub x} thin films deposited by pulsed laser deposition. These properties are strongly dependent on the deposition temperature during the deposition process. The deposition temperature has no significant influence onmore » the general structural properties but produces significant changes in the oxygen stoichiometry of the films. The density of the oxygen vacancies is found to be related to the optical band gap of the GaO{sub x} layer. It is proposed that the oxygen deficiency leads to defect band below the conduction band minimum that increases the electron affinity. These properties facilitate the use of amorphous GaO{sub x} as an electron transport layer in Cu(In,Ga)Se{sub 2} and in Cu{sub 2}O solar cells. Further it is shown that at low deposition temperatures, extrinsic doping with Sn is effective at low Sn concentrations.« less

  8. Electrocatalytic performances of LaNi1-xMgxO3 perovskite oxides as bi-functional catalysts for lithium air batteries

    NASA Astrophysics Data System (ADS)

    Du, Zhenzhen; Yang, Peng; Wang, Long; Lu, Yuhao; Goodenough, J. B.; Zhang, Jian; Zhang, Dawei

    2014-11-01

    Mg-doped perovskite oxides LaNi1-xMgxO3 (x = 0, 0.08, 0.15) electrocatalysts are synthesized by a sol-gel method using citric acid as complex agent and ethylene glycol as thickening agent. The intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity of as-prepared perovskite oxides in aqueous electrolyte are examined on a rotating disk electrode (RDE) set up. Li-air primary batteries on the basis of Mg-doped perovskite oxides LaNi1-xMgxO3 (x = 0, 0.08, 0.15) and nonaqueous electrolyte are also fabricated and tested. In terms of the ORR current densities and OER current densities, the performance is enhanced in the order of LaNiO3, LaNi0.92Mg0.08O3 and LaNi0.85Mg0.15O3. Most notably, partially substituting nickel with magnesium suppresses formation of Ni2+ and ensures high concentration of both OER and ORR reaction energy favorable Ni3+ (eg = 1) on the surface of perovskite catalysts. Nonaqueous Li-air primary battery using LaNi0.92Mg0.08O3 and LaNi0.85Mg0.15O3 as the cathode catalysts exhibit improved performances compared with LaNiO3 catalyst, which are consistent with the ORR current densities.

  9. Artificial oxygen transport protein

    DOEpatents

    Dutton, P. Leslie

    2014-09-30

    This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

  10. A facile photoassisted route to synthesis N, F-codoped oxygen-deficient TiO2 with enhanced photocatalytic performance under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kang, Xiaolan; Han, Ying; Song, Xuezhi; Tan, Zhenquan

    2018-03-01

    Herein, we report a facile and economical photoassisted strategy for synthesizing the highly active N, F-codoped oxygen-deficient TiO2 with coexposed {001} and {101} facets. NH4TiOF3 mesocrystals were used to act as the resource of dopants and the intermediate to fabricate TiO2 with highly active {001} facets. Comprehensive analysis based on X-ray photoelectron spectroscopy, transmission electron microscopy and electron spin resonances manifested that F, N and oxygen vacancies were simultaneously introduced to TiO2 through the photoassisted process. The test of phenol and Rhodamine B (RhB) degradation under visible light demonstrates that the as-prepared N, F codoped oxygen-deficient TiO2 exhibits higher photocatalytic activity than its references. The increased photocatalytic performances results from the synergetic effect of the induced Vo's and N, F codoping in TiO2 with co-exposed {001} and {101} facets, favoring the visible light utilization as well as the separation of photogenerated carriers. This strategy is expected to provide a new insight into the design of high performance photocatalysts.

  11. Perovskite in Earth’s deep interior

    NASA Astrophysics Data System (ADS)

    Hirose, Kei; Sinmyo, Ryosuke; Hernlund, John

    2017-11-01

    Silicate perovskite-type phases are the most abundant constituent inside our planet and are the predominant minerals in Earth’s lower mantle more than 660 kilometers below the surface. Magnesium-rich perovskite is a major lower mantle phase and undergoes a phase transition to post-perovskite near the bottom of the mantle. Calcium-rich perovskite is proportionally minor but may host numerous trace elements that record chemical differentiation events. The properties of mantle perovskites are the key to understanding the dynamic evolution of Earth, as they strongly influence the transport properties of lower mantle rocks. Perovskites are expected to be an important constituent of rocky planets larger than Mars and thus play a major role in modulating the evolution of terrestrial planets throughout the universe.

  12. Electric transport coefficients in highly epitaxial LaBaCo{sub 2}O{sub 5 + δ} films with “p-to-n” transition induced by oxygen deficiency

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shaibo, J.; Zhang, Q. Y., E-mail: qyzhang@dlut.edu.cn; Hu, H. C.

    2016-08-14

    Electric transport coefficients such as carrier type, density, and mobility are the important physical parameters in designing functional devices. In this work, we report the study on the electric transport coefficients of the highly epitaxial LaBaCo{sub 2}O{sub 5 + δ} (LBCO) films, which were discussed as a function of electric conductivity for the first time and compared with the results calculated by the theory for mixed conduction. The mobility in the LBCO films was determined to be ∼0.85 and ∼40 cm{sup 2}/V s for holes and electrons, respectively, and the density of p-type carriers strongly depends on the oxygen deficiency. Solid evidence ismore » presented to demonstrate that the oxygen deficiency cannot make LBCO materials changed from p- to n-type. The n-type conduction observed in experiment is a counterfeit phenomenon caused by the deficiency in Hall measurement, rather than a realistic transition induced by oxygen deficiency. In addition, the temperature-dependent conductivity was discussed using the differential coefficients, which might be useful in the study of the samples with magnetic transition.« less

  13. Oxygen ion-conducting dense ceramic

    DOEpatents

    Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

    1996-01-01

    Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

  14. Oxygen ion-conducting dense ceramic

    DOEpatents

    Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

    1997-01-01

    Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

  15. Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3- δ.

    PubMed

    Jeen, H; Choi, W S; Freeland, J W; Ohta, H; Jung, C U; Lee, H N

    2013-07-19

    Pulsed laser epitaxy of brownmillerite SrCoO2.5 thin films and their phase transformation to the perovskite SrCoO3-δ are investigated. While the direct growth of the fully oxidized perovskite films is found to be an arduous task, filling some of oxygen vacancies into SrCoO2.5 by topotactic oxidation accompanies systematic evolution of electronic, magnetic, and thermoelectric properties, useful for many information and energy technologies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Optically-Induced Persistent Magnetization in Oxygen Deficient Strontium Titanate

    NASA Astrophysics Data System (ADS)

    Crooker, Scott

    2015-03-01

    Interest in electronics and spintronics based on complex oxide materials has exploded in recent years, fueled by the ability to grow atomically-precise heterostructures of various oxides 1. A foundational material in this burgeoning field is strontium titanate, a (nominally) non-magnetic wide-bandgap semiconductor. Owing to its ubiquity in oxide materials science, studies of SrTiO3's interesting dielectric, lattice, and optical properties represent mature research areas. However, renewed interest in SrTiO3 was recently sparked by observations of unexpected spin and magnetization phenomena at interfaces between SrTiO3 and other nonmagnetic oxides 1. The formation and distribution of oxygen vacancies (VO) in SrTiO3 are widely thought to play an essential but as-yet-incompletely understood role in these emergent phenomena. Here we demonstrate a surprising new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically-induced and persistent magnetization in slightly oxygen-deficient SrTiO3-δ bulk crystals, using magnetic circular dichroism spectroscopy and optically-coupled SQUID studies 2. This magnetization appears below 18K, persists for hours below 10K, and is tunable via the polarization and wavelength of sub-bandgap (400-500 nm) light. As such, magnetic patterns can be ``written'' into SrTiO3-δ, and subsequently read out, using light alone. This magnetism occurs only in crystals containing VO, and is consistent with a metastable spin polarization of VO-related defect complexes. These data reveal a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material, which may yield new insights into the recent exciting spin physics observed at oxide interfaces.

  17. Efficient Sky-Blue Perovskite Light-Emitting Devices Based on Ethylammonium Bromide Induced Layered Perovskites.

    PubMed

    Wang, Qi; Ren, Jie; Peng, Xue-Feng; Ji, Xia-Xia; Yang, Xiao-Hui

    2017-09-06

    Low-dimensional organometallic halide perovskites are actively studied for the light-emitting applications due to their properties such as solution processability, high luminescence quantum yield, large exciton binding energy, and tunable band gap. Introduction of large-group ammonium halides not only serves as a convenient and versatile method to obtain layered perovskites but also allows the exploitation of the energy-funneling process to achieve a high-efficiency light emission. Herein, we investigate the influence of the addition of ethylammonium bromide on the morphology, crystallite structure, and optical properties of the resultant perovskite materials and report that the phase transition from bulk to layered perovskite occurs in the presence of excess ethylammonium bromide. On the basis of this strategy, we report green perovskite light-emitting devices with the maximum external quantum efficiency of ca. 3% and power efficiency of 9.3 lm/W. Notably, blue layered perovskite light-emitting devices with the Commission Internationale de I'Eclairage coordinates of (0.16, 0.23) exhibit the maximum external quantum efficiency of 2.6% and power efficiency of 1 lm/W at 100 cd/m 2 , representing a large improvement over the previously reported analogous devices.

  18. Nanostructured Perovskite LaCo1-xMnxO3 as Bifunctional Catalysts for Rechargeable Metal-Air Batteries

    NASA Astrophysics Data System (ADS)

    Ge, Xiaoming; Li, Bing; Wuu, Delvin; Sumboja, Afriyanti; An, Tao; Hor, T. S. Andy; Zong, Yun; Liu, Zhaolin

    2015-09-01

    Bifunctional catalyst that is active for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the most important components of rechargeable metal-air batteries. Nanostructured perovskite bifunctional catalysts comprising La, Co and Mn(LaCo1-xMnxO3, LCMO) are synthesized by hydrothermal methods. The morphology, structure and electrochemical activity of the perovskite bifunctional catalysts are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and rotating disk electrode (RDE) techniques. Nanorod, nanodisc and nanoparticle are typical morphologies of LCMO. The electrocatalytic activity of LCMO is significantly improved by the addition of conductive materials such as carbon nanotube. To demonstrate the practical utilization, LCMO in the composition of LaCo0.8Mn0.2O3(LCMO82) is used as air cathode catalysts for rechargeable zinc-air batteries. The battery prototype can sustain 470 h or 40 discharge-charge cycles equivalent.

  19. Synthesis and oxygen content dependent properties of hexagonal DyMnO[subscript 3+delta

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Remsen, S.; Dabrowski, B.; Chmaissem, O.

    2011-10-28

    Oxygen deficient polycrystalline samples of hexagonal P6{sub 3}cm (space group No.185) DyMnO{sub 3+{delta}} ({delta} < 0) were synthesized in Ar by intentional decomposition of its perovskite phase obtained in air. The relative stability of these phases is in accord with our previous studies of the temperature and oxygen vacancy dependent tolerance factor. Thermogravimetric measurements have shown that hexagonal samples of DyMnO{sub 3+{delta}} (0 {le} {delta} {le} 0.4) exhibit unusually large excess oxygen content, which readily incorporates on heating near 300 C in various partial-pressures of oxygen atmospheres. Neutron and synchrotron diffraction data show the presence of two new structural phasesmore » at {delta} {approx} 0.25 (Hex{sub 2}) and {delta} {approx} 0.40 (Hex{sub 3}). Rietveld refinements of the Hex{sub 2} phase strongly suggest it is well modeled by the R3 space group (No.146). These phases were observed to transform back to P6{sub 3}cm above {approx} 350 C when material becomes stoichiometric in oxygen content ({delta} = 0). Chemical expansion of the crystal lattice corresponding to these large changes of oxygen was found to be 3.48 x 10{sup -2} mol{sup -1}. Thermal expansion of stoichiometric phases were determined to be 11.6 x 10{sup -6} and 2.1 x 10{sup -6} K{sup -1} for the P6{sub 3}cm and Hex{sub 2} phases, respectively. Our measurements also indicate that the oxygen non-stoichiometry of hexagonal RMnO{sub 3+{delta}} materials may have important influence on their multiferroic properties.« less

  20. Recent advances of flexible hybrid perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Shin, Dong Hee; Heo, Jin Hyuck; Im, Sang Hyuk

    2017-11-01

    Recently, hybrid perovskite solar cells have attracted great interest because they can be fabricated to low cost, flexible, and highly efficient solar cells. Here, we introduced recent advances of flexible hybrid perovskite solar cells. We introduced research background of flexible perovskite solar cells in introduction part. Then we composed the main body to i) structure and properties of hybrid perovskite solar cells, ii) why flexible hybrid perovskite solar cells are important?, iii) transparent conducting oxide (TCO) based flexible hybrid perovskite solar cells, and iv) TCO-free transparent conducting electrode (TCE) based flexible hybrid perovskite solar cells. Finally, we summarized research outlook of flexible hybrid perovskite solar cells.

  1. Perovskite classification: An Excel spreadsheet to determine and depict end-member proportions for the perovskite- and vapnikite-subgroups of the perovskite supergroup

    NASA Astrophysics Data System (ADS)

    Locock, Andrew J.; Mitchell, Roger H.

    2018-04-01

    Perovskite mineral oxides commonly exhibit extensive solid-solution, and are therefore classified on the basis of the proportions of their ideal end-members. A uniform sequence of calculation of the end-members is required if comparisons are to be made between different sets of analytical data. A Microsoft Excel spreadsheet has been programmed to assist with the classification and depiction of the minerals of the perovskite- and vapnikite-subgroups following the 2017 nomenclature of the perovskite supergroup recommended by the International Mineralogical Association (IMA). Compositional data for up to 36 elements are input into the spreadsheet as oxides in weight percent. For each analysis, the output includes the formula, the normalized proportions of 15 end-members, and the percentage of cations which cannot be assigned to those end-members. The data are automatically plotted onto the ternary and quaternary diagrams recommended by the IMA for depiction of perovskite compositions. Up to 200 analyses can be entered into the spreadsheet, which is accompanied by data calculated for 140 perovskite compositions compiled from the literature.

  2. Bacterial transformations of inorganic nitrogen in the oxygen-deficient waters of the Eastern Tropical South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Lipschultz, F.; Wofsy, S. C.; Ward, B. B.; Codispoti, L. A.; Friedrich, G.; Elkins, J. W.

    1990-10-01

    Rates of transformations of inorganic nitrogen were measured in the low oxygen, subsurface waters (50-450 m) of the Eastern Tropical South Pacific during February 1985, using 15N tracer techniques. Oxygen concentrations over the entire region were in a range (O 2 < 2.5 μM) that allowed both oxidation and reduction of nitrogen to occur. A wide range of rates was observed for the lowest oxygen levels, indicating that observed oxygen concentration was not a primary factor regulating nitrogen metabolism. High values for subsurface metabolic rates correspond with high levels for surface primary production, both apparently associated with mesoscale features observed in satellite imagery and with mesoscale features of the current field. Measured rates of nitrate reduction and estimated rates of denitrification were sufficient to respire nearly all of the surface primary production that might be transported into the oxygen deficient zone. These results imply that the supply of labile organic material, especially from the surface, was more important than oxygen concentration in modulating the rates of nitrogen transformations within the low oxygen water mass of the Eastern Tropical South Pacific. The pattern of nitrite oxidation and nitrite reduction activities in the oxygen minimum zone supports the hypothesis ( ANDERSONet al., 1982, Deep-Sea Research, 29, 1113-1140) that nitrite, produced from nitrate reduction, can be recycled by oxidation at the interface between low and high oxygen waters. Rates for denitrification, estimated from nitrate reduction rates, were in harmony with previous estimates based on electron transport system (ETS) measurements and analysis of the nitrate deficit and water residence times. Assimilation rates of NH 4+ were substantial, providing evidence for heterotrophic bacterial growth in low oxygen waters. Ambient concentrations of ammonium were maintained at low values primarily by assimilation; ammonium oxidation was an important mechanism at

  3. Interface architecture between TiO2/perovskite, perovskite/hole transport layer, and perovskite grain boundary(Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hayase, Shuzi; Hirotani, Daisuke; Moriya, Masahiro; Ogomi, Yuhei; Shen, Qing; Yoshino, Kenji; Toyoda, Taro

    2016-09-01

    In order to examine the interface structure of TiO2/perovskite layer, quartz crystal microbalance sensor (QCM) was used. On the QCM sensor, TiO2 layer was fabricated and the PbI2 solution in Dimethylformamide (DMF) was passed on the QCM sensor to estimate the adsorption density of the PbI2 on the titania2. The amount of PbI2 adsorption on TiO2 surface increased as the adsorption time and leveled off at a certain time. PbI2 still remained even after the solvent only (DMF) was passed on the TiO2 layer on QCM (namely rinsing with DMF), suggesting that the PbI2 was tightly bonded on the TiO2 surface. The bonding structure was found to be Ti-O-Pb linkage by XPS analysis. We concluded that the Ti-OH on the surface of TiO2 reacts with I-Pb-I to form Ti-O-Pb-I and HI (Fig.1 B). The surface trap density was measured by thermally stimulated current (TSC) method. Before the PbI2 passivation, the trap density of TiO2 was 1019 cm3. The trap density decreased to 1016/cm3 after the PbI2 passivation, suggesting that the TiO2 surface trap was passivated with I-Pb-I. The passivation density was tuned by the concentration of PbI2 in DMF, by which TiO2 layer was passivated. Perovskite solar cells were fabricated on the passivated TiO2 layer with various PbI2 passivation densities by one step process (mixture of PbI2 + MAI in DMF). It was found that Jsc increased with an increase in the Ti-O-Pb density. We concluded that the interface between TiO2 and perovskite layer has passivation structure consisting of Ti-O-Pb-I which decreases the trap density of the interfaces and supresses charge recombination. The effect of Cl anion on high efficiency is still controversial when perovskite layer is prepared by one step method from the mixture of MAI and PbCl2. It was found that adsorption density of PbCl2 on TiO2 surface was much higher than that of PbI2 from the experiment using QCM sensor. After the surface was washed with DMF, Cl and Pb were detected. These results suggest that the TiO2

  4. Light-Independent Ionic Transport in Inorganic Perovskite and Ultrastable Cs-Based Perovskite Solar Cells.

    PubMed

    Zhou, Wenke; Zhao, Yicheng; Zhou, Xu; Fu, Rui; Li, Qi; Zhao, Yao; Liu, Kaihui; Yu, Dapeng; Zhao, Qing

    2017-09-07

    Due to light-induced effects in CH 3 NH 3 -based perovskites, such as ion migration, defects formation, and halide segregation, the degradation of CH 3 NH 3 -based perovskite solar cells under maximum power point is generally implicated. Here we demonstrated that the effect of light-enhanced ion migration in CH 3 NH 3 PbI 3 can be eliminated by inorganic Cs substitution, leading to an ultrastable perovskite solar cell. Quantitatively, the ion migration barrier for CH 3 NH 3 PbI 3 is 0.62 eV under dark conditions, larger than that of CsPbI 2 Br (0.45 eV); however, it reduces to 0.07 eV for CH 3 NH 3 PbI 3 under illumination, smaller than that for CsPbI 2 Br (0.43 eV). Meanwhile, photoinduced halide segregation is also suppressed in Cs-based perovskites. Cs-based perovskite solar cells retained >99% of the initial efficiency (10.3%) after 1500 h of maximum power point tracking under AM1.5G illumination, while CH 3 NH 3 PbI 3 solar cells degraded severely after 50 h of operation. Our work reveals an uncovered mechanism for stability improvement by inorganic cation substitution in perovskite-based optoelectronic devices.

  5. Tailoring perovskite compounds for broadband light absorption

    NASA Astrophysics Data System (ADS)

    Lu, Hengchang; Guo, Xiaowei; Yang, Cheng; Li, Shaorong

    2018-01-01

    Perovskite solar cells have experienced an outstanding advance in power conversion efficiency (PCE) by optimizing the perovskite layer morphology, composition, interfaces, and charge collection efficiency. To enhance PCE, the mixed perovskites were proposed in recent years. In this study, optoelectronic performance of pure perovskites and mixed ones were investigated. It was demonstrated that the mixed perovskites exhibit superior to the pure ones. The mixed material can absorb broadband light absorption and result in increased short circuit current density and power conversion efficiency.

  6. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

    PubMed

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-01-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

  7. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    NASA Astrophysics Data System (ADS)

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-10-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

  8. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    PubMed Central

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-01-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

  9. Inhomogeneous degradation in metal halide perovskites

    NASA Astrophysics Data System (ADS)

    Yang, Rong; Zhang, Li; Cao, Yu; Miao, Yanfeng; Ke, You; Wei, Yingqiang; Guo, Qiang; Wang, Ying; Rong, Zhaohua; Wang, Nana; Li, Renzhi; Wang, Jianpu; Huang, Wei; Gao, Feng

    2017-08-01

    Although the rapid development of organic-inorganic metal halide perovskite solar cells has led to certified power conversion efficiencies of above 20%, their poor stability remains a major challenge, preventing their practical commercialization. In this paper, we investigate the intrinsic origin of the poor stability in perovskite solar cells by using a confocal fluorescence microscope. We find that the degradation of perovskite films starts from grain boundaries and gradually extend to the center of the grains. Firmly based on our findings, we further demonstrate that the device stability can be significantly enhanced by increasing the grain size of perovskite crystals. Our results have important implications to further enhance the stability of optoelectronic devices based on metal halide perovskites.

  10. Magnetic Modes in Rare Earth Perovskites: A Magnetic-Field-Dependent Inelastic Light Scattering study.

    PubMed

    Saha, Surajit; Cao, Bing-Chen; Motapothula, M; Cong, Chun-Xiao; Sarkar, Tarapada; Srivastava, Amar; Sarkar, Soumya; Patra, Abhijeet; Ghosh, Siddhartha; Ariando; Coey, J M D; Yu, Ting; Venkatesan, T

    2016-11-15

    Here, we report the presence of defect-related states with magnetic degrees of freedom in crystals of LaAlO 3 and several other rare-earth based perovskite oxides using inelastic light scattering (Raman spectroscopy) at low temperatures in applied magnetic fields of up to 9 T. Some of these states are at about 140 meV above the valence band maximum while others are mid-gap states at about 2.3 eV. No magnetic impurity could be detected in LaAlO 3 by Proton-Induced X-ray Emission Spectroscopy. We, therefore, attribute the angular momentum-like states in LaAlO 3 to cationic/anionic vacancies or anti-site defects. Comparison with the other rare earth perovskites leads to the empirical rule that the magnetic-field-sensitive transitions require planes of heavy elements (e.g. lanthanum) and oxygen without any other light cations in the same plane. These magnetic degrees of freedom in rare earth perovskites with useful dielectric properties may be tunable by appropriate defect engineering for magneto-optic applications.

  11. Stabilization of highly polar BiFeO 3-like structure: a new interface design route for enhanced ferroelectricity in artificial perovskite superlattices

    DOE PAGES

    Wang, Hongwei; Wen, Jianguo; Miller, Dean; ...

    2016-03-14

    In ABO 3 perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in BiFeO 3 with an R3c structure [1] but suppress ferroelectricity in CaTiO 3 with a Pbnm symmetry [2]. For many CaTiO3-like perovskites, the BiFeO 3 structure is a metastable phase. Here, we report the stabilization of the highly polar BiFeO 3-like phase of CaTiO 3 in a BaTiO 3/CaTiO 3 superlattice grown on a SrTiO 3 substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk CaTiO 3 to a different patternmore » that is characteristic of a BiFeO 3 phase. The reconstruction is interpreted through a combination of amplitude-contrast sub-0.1-nm high-resolution transmission electron microscopy and first-principles theories of the structure, energetics, and polarization of the superlattice and its constituents. We further predict a number of new artificial ferroelectric materials demonstrating that nonpolar perovskites can be turned into ferroelectrics via this interface mechanism. Therefore, a large number of perovskites with the CaTiO 3 structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].« less

  12. Graded bandgap perovskite solar cells.

    PubMed

    Ergen, Onur; Gilbert, S Matt; Pham, Thang; Turner, Sally J; Tan, Mark Tian Zhi; Worsley, Marcus A; Zettl, Alex

    2017-05-01

    Organic-inorganic halide perovskite materials have emerged as attractive alternatives to conventional solar cell building blocks. Their high light absorption coefficients and long diffusion lengths suggest high power conversion efficiencies, and indeed perovskite-based single bandgap and tandem solar cell designs have yielded impressive performances. One approach to further enhance solar spectrum utilization is the graded bandgap, but this has not been previously achieved for perovskites. In this study, we demonstrate graded bandgap perovskite solar cells with steady-state conversion efficiencies averaging 18.4%, with a best of 21.7%, all without reflective coatings. An analysis of the experimental data yields high fill factors of ∼75% and high short-circuit current densities up to 42.1 mA cm -2 . The cells are based on an architecture of two perovskite layers (CH 3 NH 3 SnI 3 and CH 3 NH 3 PbI 3-x Br x ), incorporating GaN, monolayer hexagonal boron nitride, and graphene aerogel.

  13. Hybrid Lead Halide Layered Perovskites with Silsesquioxane Interlayers.

    PubMed

    Kataoka, Sho; Kaburagi, Wako; Mochizuki, Hiroyuki; Kamimura, Yoshihiro; Sato, Kazuhiko; Endo, Akira

    2018-01-01

    Hybrid organic-lead halide perovskites exhibit remarkable properties as semiconductors and light absorbers. Here, we report the formation of silsesquioxane-lead halide hybrid layered perovskites. We prepared silsesquioxane with a cubic cage-like structure and fabricated hybrid silsesquioxane-lead halide layered perovskites in a self-assembled manner. It is demonstrated that the silsesquioxane maintain their cage-like structure between lead halide perovskite layers. The silsesquioxane-lead halide perovskites also show excitonic absorption and emission in the visible light region similar to typical lead halide layered perovskites.

  14. Perovskite Solar Cells | Photovoltaic Research | NREL

    Science.gov Websites

    & Devices pages: High-Efficiency Crystalline PV Polycrystalline Thin-Film PV Perovskite and Organic -Defect Hybrid Organic/Inorganic Perovskite Films as PV Absorbers. (FY 2015FY 2016). In collaboration with organic metal halide perovskite (see article). Ultrahigh-Efficiency and Low-Cost Polycrystalline Halide

  15. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO 3)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Jie; Morrow, Darien J.; Fu, Yongping

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcomingmore » the limitation of island-forming Volmer–Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s –1), and low defect density of 10 12 cm –3, which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. Furthermore, the high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.« less

  16. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO 3)

    DOE PAGES

    Chen, Jie; Morrow, Darien J.; Fu, Yongping; ...

    2017-09-05

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcomingmore » the limitation of island-forming Volmer–Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s –1), and low defect density of 10 12 cm –3, which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. Furthermore, the high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.« less

  17. Electrochemical Doping of Halide Perovskites with Ion Intercalation.

    PubMed

    Jiang, Qinglong; Chen, Mingming; Li, Junqiang; Wang, Mingchao; Zeng, Xiaoqiao; Besara, Tiglet; Lu, Jun; Xin, Yan; Shan, Xin; Pan, Bicai; Wang, Changchun; Lin, Shangchao; Siegrist, Theo; Xiao, Qiangfeng; Yu, Zhibin

    2017-01-24

    Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

  18. Achieving High Performance Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Yang, Yang

    2015-03-01

    Recently, metal halide perovskite based solar cell with the characteristics of rather low raw materials cost, great potential for simple process and scalable production, and extreme high power conversion efficiency (PCE), have been highlighted as one of the most competitive technologies for next generation thin film photovoltaic (PV). In UCLA, we have realized an efficient pathway to achieve high performance pervoskite solar cells, where the findings are beneficial to this unique materials/devices system. Our recent progress lies in perovskite film formation, defect passivation, transport materials design, interface engineering with respect to high performance solar cell, as well as the exploration of its applications beyond photovoltaics. These achievements include: 1) development of vapor assisted solution process (VASP) and moisture assisted solution process, which produces perovskite film with improved conformity, high crystallinity, reduced recombination rate, and the resulting high performance; 2) examination of the defects property of perovskite materials, and demonstration of a self-induced passivation approach to reduce carrier recombination; 3) interface engineering based on design of the carrier transport materials and the electrodes, in combination with high quality perovskite film, which delivers 15 ~ 20% PCEs; 4) a novel integration of bulk heterojunction to perovskite solar cell to achieve better light harvest; 5) fabrication of inverted solar cell device with high efficiency and flexibility and 6) exploration the application of perovskite materials to photodetector. Further development in film, device architecture, and interfaces will lead to continuous improved perovskite solar cells and other organic-inorganic hybrid optoelectronics.

  19. Low-bandgap mixed tin–lead iodide perovskite absorbers with long carrier lifetimes for all-perovskite tandem solar cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, Dewei; Yu, Yue; Wang, Changlei

    Tandem solar cells using only metal-halide perovskite sub-cells are an attractive choice for next-generation solar cells. However, the progress in developing efficient all-perovskite tandem solar cells has been hindered by the lack of high-performance low-bandgap perovskite solar cells. Here in this paper, we report efficient mixed tin-lead iodide low-bandgap (~1.25 eV) perovskite solar cells with open-circuit voltages up to 0.85 V and over 70% external quantum efficiencies in the infrared wavelength range of 700-900 nm, delivering a short-circuit current density of over 29 mA cm -2 and demonstrating suitability for bottom-cell applications in all-perovskite tandem solar cells. Our low-bandgap perovskitemore » solar cells achieve a maximum power conversion efficiency of 17.6% and a certified efficiency of 17.01% with a negligible current-voltage hysteresis. Finally, when mechanically stacked with a ~1.58 eV bandgap perovskite top cell, our best all-perovskite 4-terminal tandem solar cell shows a steady-state efficiency of 21.0%.« less

  20. Low-bandgap mixed tin–lead iodide perovskite absorbers with long carrier lifetimes for all-perovskite tandem solar cells

    DOE PAGES

    Zhao, Dewei; Yu, Yue; Wang, Changlei; ...

    2017-03-01

    Tandem solar cells using only metal-halide perovskite sub-cells are an attractive choice for next-generation solar cells. However, the progress in developing efficient all-perovskite tandem solar cells has been hindered by the lack of high-performance low-bandgap perovskite solar cells. Here in this paper, we report efficient mixed tin-lead iodide low-bandgap (~1.25 eV) perovskite solar cells with open-circuit voltages up to 0.85 V and over 70% external quantum efficiencies in the infrared wavelength range of 700-900 nm, delivering a short-circuit current density of over 29 mA cm -2 and demonstrating suitability for bottom-cell applications in all-perovskite tandem solar cells. Our low-bandgap perovskitemore » solar cells achieve a maximum power conversion efficiency of 17.6% and a certified efficiency of 17.01% with a negligible current-voltage hysteresis. Finally, when mechanically stacked with a ~1.58 eV bandgap perovskite top cell, our best all-perovskite 4-terminal tandem solar cell shows a steady-state efficiency of 21.0%.« less

  1. Spin texture induced by oxygen vacancies in strontium perovskite (001) surfaces: A theoretical comparison between SrTiO3 and SrHfO3

    NASA Astrophysics Data System (ADS)

    Garcia-Castro, A. C.; Vergniory, M. G.; Bousquet, E.; Romero, A. H.

    2016-01-01

    The electronic structure of SrTiO3 and SrHfO3 (001) surfaces with oxygen vacancies is studied by means of first-principles calculations. We reveal how oxygen vacancies within the first atomic layer of the SrTiO3 surface (i) induce a large antiferrodistortive motion of the oxygen octahedra at the surface, (ii) drive localized magnetic moments on the Ti 3 d orbitals close to the vacancies, and (iii) form a two-dimensional electron gas localized within the first layers. The analysis of the spin texture of this system exhibits a splitting of the energy bands according to the Zeeman interaction, lowering of the Ti 3 dx y level in comparison with dx z and dy z, and also an in-plane precession of the spins. No Rashba-like splitting for the ground state or for the ab initio molecular dynamics trajectory at 400 K is recognized as suggested recently by A. F. Santander-Syro et al. [Nat. Mater. 13, 1085 (2014), 10.1038/nmat4107]. Instead, a sizable Rashba-like splitting is observed when the Ti atom is replaced by a heavier Hf atom with a much larger spin-orbit interaction. However, we observe the disappearance of the magnetism and the surface two-dimensional electron gas when full structural optimization of the SrHfO3 surface is performed. Our results uncover the sensitive interplay of spin-orbit coupling, atomic relaxations, and magnetism when tuning these Sr-based perovskites.

  2. Phase transition of a cobalt-free perovskite as a high-performance cathode for intermediate-temperature solid oxide fuel cells.

    PubMed

    Jiang, Shanshan; Zhou, Wei; Niu, Yingjie; Zhu, Zhonghua; Shao, Zongping

    2012-10-01

    It is generally recognized that the phase transition of a perovskite may be detrimental to the connection between cathode and electrolyte. Moreover, certain phase transitions may induce the formation of poor electronic and ionic conducting phase(s), thereby lowering the electrochemical performance of the cathode. Here, we present a study on the phase transition of a cobalt-free perovskite (SrNb(0.1)Fe(0.9)O(3-δ), SNF) and evaluate its effect on the electrochemical performance of the fuel cell. SNF exists as a primitive perovskite structure with space group P4mm (99) at room temperature. As evidenced by in situ high-temperature X-ray diffraction measurements over the temperature range of 600 to 1000 °C, SNF undergoes a transformation to a tetragonal structure with a space group I4/m (87). This phase transition is accompanied by a moderate change in the volume, allowing a good cathode/electrolyte interface on thermal cycling. According to the electrochemical impedance spectroscopy evaluation, the I4/m phase exhibits positive effects on the cathode's performance, showing the highest oxygen reduction reaction activity of cobalt-free cathodes reported so far. This activity improvement is attributed to enhanced oxygen surface processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 2D Ruddlesden-Popper Perovskites for Optoelectronics.

    PubMed

    Chen, Yani; Sun, Yong; Peng, Jiajun; Tang, Junhui; Zheng, Kaibo; Liang, Ziqi

    2018-01-01

    Conventional 3D organic-inorganic halide perovskites have recently undergone unprecedented rapid development. Yet, their inherent instabilities over moisture, light, and heat remain a crucial challenge prior to the realization of commercialization. By contrast, the emerging 2D Ruddlesden-Popper-type perovskites have recently attracted increasing attention owing to their great environmental stability. However, the research of 2D perovskites is just in their infancy. In comparison to 3D analogues, they are natural quantum wells with a much larger exciton binding energy. Moreover, their inner structural, dielectric, optical, and excitonic properties remain to be largely explored, limiting further applications. This review begins with an introduction to 2D perovskites, along with a detailed comparison to 3D counterparts. Then, a discussion of the organic spacer cation engineering of 2D perovskites is presented. Next, quasi-2D perovskites that fall between 3D and 2D perovskites are reviewed and compared. The unique excitonic properties, electron-phonon coupling, and polarons of 2D perovskites are then be revealed. A range of their (opto)electronic applications is highlighted in each section. Finally, a summary is given, and the strategies toward structural design, growth control, and photophysics studies of 2D perovskites for high-performance electronic devices are rationalized. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Achieving High Efficiency and Eliminating Degradation in Solid Oxide Electrochemical Cells Using High Oxygen-Capacity Perovskite.

    PubMed

    Jun, Areum; Kim, Junyoung; Shin, Jeeyoung; Kim, Guntae

    2016-09-26

    Recently, there have been efforts to use clean and renewable energy because of finite fossil fuels and environmental problems. Owing to the site-specific and weather-dependent characteristics of the renewable energy supply, solid oxide electrolysis cells (SOECs) have received considerable attention to store energy as hydrogen. Conventional SOECs use Ni-YSZ (yttria-stabilized zirconia) and LSM (strontium-doped lanthanum manganites)-YSZ as electrodes. These electrodes, however, suffer from redox-instability and coarsening of the Ni electrode along with delamination of the LSM electrode during steam electrolysis. In this study, we successfully design and fabricate highly efficient SOECs using layered perovskites, PrBaMn2 O5+δ (PBM) and PrBa0.5 Sr0.5 Co1.5 Fe0.5 O5+δ (PBSCF50), as both electrodes for the first time. The SOEC with layered perovskites as both-side electrodes shows outstanding performance, reversible cycling, and remarkable stability over 600 hours. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Recent patents on perovskite ferroelectric nanostructures.

    PubMed

    Zhu, Xinhua

    2009-01-01

    Ferroelectric oxide materials with a perovskite structure have promising applications in electronic devices such as random access memories, sensors, actuators, infrared detectors, and so on. Recent advances in science and technology of ferroelectrics have resulted in the feature sizes of ferroelectric-based electronic devices entering into nanoscale dimensions. At nanoscale perovskite ferroelectric materials exhibit a pronounced size effect manifesting itself in a significant deviation of the properties of low-dimensional structures from the bulk and film counterparts. One-dimensional perovskite ferroelectric nanotube/nanowire systems, offer fundamental scientific opportunities for investigating the intrinsic size effects in ferroelectrics. In the past several years, much progress has been made both in fabrication and physical property testing of perovskite ferroelectric nanostructures. In the first part of this paper, the recent patents and literatures for fabricating ferroelectric nanowires, nanorods, nanotubes, and nanorings with promising features, are reviewed. The second part deals with the recent advances on the physical property testing of perovskite ferroelectric nanostructures. The third part summarizes the recently patents and literatures about the microstructural characterizations of perovskite ferroelectric nanostructures, to improve their crystalline quality, morphology and uniformity. Finally, we conclude this review with personal perspectives towards the potential future developments of perovskite ferroelectric nanostructures.

  6. Perovskite photonic sources

    NASA Astrophysics Data System (ADS)

    Sutherland, Brandon R.; Sargent, Edward H.

    2016-05-01

    The field of solution-processed semiconductors has made great strides; however, it has yet to enable electrically driven lasers. To achieve this goal, improved materials are required that combine efficient (>50% quantum yield) radiative recombination under high injection, large and balanced charge-carrier mobilities in excess of 10 cm2 V-1 s-1, free-carrier densities greater than 1017 cm-3 and gain coefficients exceeding 104 cm-1. Solid-state perovskites are -- in addition to galvanizing the field of solar electricity -- showing great promise in photonic sources, and may be the answer to realizing solution-cast laser diodes. Here, we discuss the properties of perovskites that benefit light emission, review recent progress in perovskite electroluminescent diodes and optically pumped lasers, and examine the remaining challenges in achieving continuous-wave and electrically driven lasing.

  7. Acid–base catalysis over perovskites: a review

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Polo-Garzon, Felipe; Wu, Zili

    We present that perovskite catalysts have been extensively studied for reduction–oxidation (redox) reactions; however, their acid–base catalytic properties are still under-explored. This review collects work aiming to study the acid–base catalytic properties of perovskites. Reports regarding combined acid–base/redox catalysis over perovskites lie beyond the scope of the present review. For the characterization of acid–base properties, researchers have studied the interaction of probe molecules with perovskite surfaces by means of multiple techniques that provide information about the density, strength and type of adsorption sites. The top-surface composition of perovskites, which relates to the abundance of the acid–base sites, has been studiedmore » by means of low energy ion scattering (LEIS), and, the less surface sensitive, conventional X-ray photoelectron spectroscopy (XPS). Probe reactions, with the conversion of 2-propanol as the common choice, have also been employed for characterizing the acid–base catalytic properties of perovskites. The complex nature of perovskite surfaces, which explains the still absent fundamental relations between the structure of the catalyst and reaction rates/selectivity, encounters a great challenge due to the surface reconstruction of these materials. In this review, we devote a special section to highlight recent publications that report the impact of surface reconstruction and particle shape on acid–base catalysis over perovskites. In addition, we review promising catalytic performances of perovskite catalysts for other reactions of interest. Challenges in acid–base catalysis over perovskites focus on the development of time-resolved monolayer-sensitive characterization of surfaces under operando conditions and the discernment of combined acid–base/redox reaction mechanisms. Finally, opportunities lay on tuning the acid–base characteristics of perovskites with computation-based catalytic descriptors to

  8. Acid–base catalysis over perovskites: a review

    DOE PAGES

    Polo-Garzon, Felipe; Wu, Zili

    2018-01-15

    We present that perovskite catalysts have been extensively studied for reduction–oxidation (redox) reactions; however, their acid–base catalytic properties are still under-explored. This review collects work aiming to study the acid–base catalytic properties of perovskites. Reports regarding combined acid–base/redox catalysis over perovskites lie beyond the scope of the present review. For the characterization of acid–base properties, researchers have studied the interaction of probe molecules with perovskite surfaces by means of multiple techniques that provide information about the density, strength and type of adsorption sites. The top-surface composition of perovskites, which relates to the abundance of the acid–base sites, has been studiedmore » by means of low energy ion scattering (LEIS), and, the less surface sensitive, conventional X-ray photoelectron spectroscopy (XPS). Probe reactions, with the conversion of 2-propanol as the common choice, have also been employed for characterizing the acid–base catalytic properties of perovskites. The complex nature of perovskite surfaces, which explains the still absent fundamental relations between the structure of the catalyst and reaction rates/selectivity, encounters a great challenge due to the surface reconstruction of these materials. In this review, we devote a special section to highlight recent publications that report the impact of surface reconstruction and particle shape on acid–base catalysis over perovskites. In addition, we review promising catalytic performances of perovskite catalysts for other reactions of interest. Challenges in acid–base catalysis over perovskites focus on the development of time-resolved monolayer-sensitive characterization of surfaces under operando conditions and the discernment of combined acid–base/redox reaction mechanisms. Finally, opportunities lay on tuning the acid–base characteristics of perovskites with computation-based catalytic descriptors to

  9. Kinetics of oxygen surface exchange on epitaxial Ruddlesden–Popper phases and correlations to first-principles descriptors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Yueh -Lin; Wang, Xiao Renshaw; Lee, Ho Nyung

    2015-12-17

    Through alignment of theoretical modeling with experimental measurements of oxygen surface-exchange kinetics on (001)-oriented La 2–xSr xMO 4+δ (M = Co, Ni, Cu) thin films, we demonstrate here the capability of the theoretical bulk O 2p-band centers to correlate with oxygen surface-exchange kinetics of the Ruddlesden–Popper oxide (RP 214) (001)-oriented thin films. In addition, we demonstrate that the bulk O 2p-band centers can also correlate with the experimental activation energies for bulk oxygen transport and oxygen surface exchange of both the RP 214 and the perovskite polycrystalline materials reported in the literature, indicating the effectiveness of the bulk O 2p-bandmore » centers in describing the associated energetics and kinetics. Here, we propose that the opposite slopes of the bulk O 2p-band center correlations between the RP 214 and the perovskite materials are due to the intrinsic mechanistic differences of their oxygen surface-exchange kinetics bulk anionic transport.« less

  10. CD73 and AMPD3 deficiency enhance metabolic performance via erythrocyte ATP that decreases hemoglobin oxygen affinity.

    PubMed

    O'Brien, William G; Berka, Vladimir; Tsai, Ah-Lim; Zhao, Zhaoyang; Lee, Cheng Chi

    2015-08-07

    Erythrocytes are the key target in 5'-AMP induced hypometabolism. To understand how regulation of endogenous erythrocyte AMP levels modulates systemic metabolism, we generated mice deficient in both CD73 and AMPD3, the key catabolic enzymes for extracellular and intra-erythrocyte AMP, respectively. Under physiological conditions, these mice displayed enhanced capacity for physical activity accompanied by significantly higher food and oxygen consumption, compared to wild type mice. Erythrocytes from Ampd3(-/-) mice exhibited higher half-saturation pressure of oxygen (p50) and about 3-fold higher levels of ATP and ADP, while they maintained normal 2,3-bisphosphoglycerate (2,3-BPG), methemoglobin levels and intracellular pH. The affinity of mammalian hemoglobin for oxygen is thought to be regulated primarily by 2,3-BPG levels and pH (the Bohr effect). However, our results show that increased endogenous levels of ATP and ADP, but not AMP, directly increase the p50 value of hemoglobin. Additionally, the rise in erythrocyte p50 directly correlates with an enhanced capability of systemic metabolism.

  11. Large grained perovskite solar cells derived from single-crystal perovskite powders with enhanced ambient stability

    DOE PAGES

    Yen, Hung -Ju; Liang, Po -Wei; Chueh, Chu -Chen; ...

    2016-05-25

    In this study, we demonstrate the large grained perovskite solar cells prepared from precursor solution comprising single-crystal perovskite powders for the first time. Here, the resultant large grained perovskite thin film possesses negligible physical (structural) gap between each large grain and are highly crystalline as evidenced by its fan-shaped birefringence observed under polarized light, which is very different to the thin film prepared from the typical precursor route (MAI + PbI 2).

  12. Stable and Efficient Organo-Metal Halide Hybrid Perovskite Solar Cells via π-Conjugated Lewis Base Polymer Induced Trap Passivation and Charge Extraction.

    PubMed

    Qin, Ping-Li; Yang, Guang; Ren, Zhi-Wei; Cheung, Sin Hang; So, Shu Kong; Chen, Li; Hao, Jianhua; Hou, Jianhui; Li, Gang

    2018-03-01

    High-quality pinhole-free perovskite film with optimal crystalline morphology is critical for achieving high-efficiency and high-stability perovskite solar cells (PSCs). In this study, a p-type π-conjugated polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)-benzo[1,2-b:4,5-b'] dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl) benzo[1',2'-c:4',5'-c'] dithiophene-4,8-dione))] (PBDB-T) is introduced into chlorobenzene to form a facile and effective template-agent during the anti-solvent process of perovskite film formation. The π-conjugated polymer PBDB-T is found to trigger a heterogeneous nucleation over the perovskite precursor film and passivate the trap states of the mixed perovskite film through the formation of Lewis adducts between lead and oxygen atom in PBDB-T. The p-type semiconducting and hydrophobic PBDB-T polymer fills in the perovskite grain boundaries to improve charge transfer for better conductivity and prevent moisture invasion into the perovskite active layers. Consequently, the PSCs with PBDB-T modified anti-solvent processing leads to a high-efficiency close to 20%, and the devices show excellent stability, retaining about 90% of the initial power conversion efficiency after 150 d storage in dry air. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Fabrication and processing of next-generation oxygen carrier materials for chemical looping combustion

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nadarajah, Arunan

    Among numerous methods of controlling the global warming effect, Chemical Looping Combustion is known to be the most viable option currently. A key factor to a successful chemical looping process is the presence of highly effective oxygen carriers that enable fuel combustion by going through oxidation and reduction in the presence of air and fuel respectively. In this study, CaMnO 3-δ was used as the base material and doped on the A-site (Sr or La) and B-site (Fe, Ti, Zn and Al) by 10 mol % of dopants. Solid state reaction followed by mechanical extrusion (optimized paste formula) was usedmore » as the preparation method A series of novel doped perovskite-type oxygen carrier particles (Ca xLa (Or Sa) 1-x Mn 1-yByO 3-δ (B-site = Fe, Ti, Al, or Zr)) were synthesized by the proposed extrusion formula. The produced samples were characterized with XRD, SEM, BET and TGA techniques. According to the results obtained from TGA analysis, the oxygen capacity of the samples ranged between 1.2 for CLMZ and 1.75 for CSMF. Reactivity and oxygen uncoupling behaviors of the prepared samples were also evaluated using a fluidized bed chemical looping reactor using methane as the fuel at four different temperatures (800, 850, 900, 950 °C). All of the oxygen carriers showed oxygen uncoupling behavior and they were able to capture and release oxygen. Mass-based conversion of the perovskites was calculated and temperature increase proved to increase the mass-based conversion rate in all of the samples under study. Gas yield was calculated at 950 °C as well, and results showed that CLMZ, CM and CSMF showed 100% gas yields and CLMF and CSMZ showed approximately 85% yield in fluidized bed reactor, which is a high and acceptable quantity. Based on extended reactor tests the modified calcium manganese perovskite structures (CSMF) can be a good candidate for future pilot tests.« less

  14. Amine treatment induced perovskite nanowire network in perovskite solar cells: efficient surface passivation and carrier transport

    NASA Astrophysics Data System (ADS)

    Xiao, Ke; Cui, Can; Wang, Peng; Lin, Ping; Qiang, Yaping; Xu, Lingbo; Xie, Jiangsheng; Yang, Zhengrui; Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

    2018-02-01

    In the fabrication of high efficiency organic-inorganic metal halide perovskite solar cells (PSCs), an additional interface modifier is usually applied for enhancing the interface passivation and carrier transport. In this paper, we develop an innovative method with in-situ growth of one-dimensional perovskite nanowire (1D PNW) network triggered by Lewis amine over the perovskite films. To our knowledge, this is the first time to fabricate PSCs with shape-controlled perovskite surface morphology, which improved power conversion efficiency (PCE) from 14.32% to 16.66% with negligible hysteresis. The amine molecule can passivate the trap states on the polycrystalline perovskite surface to reduce trap-state density. Meanwhile, as a fast channel, the 1D PNWs would promote carrier transport from the bulk perovskite film to the electron transport layer. The PSCs with 1D PNW modification not only exhibit excellent photovoltaic performances, but also show good stability with only 4% PCE loss within 30 days in the ambient air without encapsulation. Our results strongly suggest that in-situ grown 1D PNW network provides a feasible and effective strategy for nanostructured optoelectronic devices such as PSCs to achieve superior performances.

  15. Water-Gas Shift and Methane Reactivity on Reducible Perovskite-Type Oxides

    PubMed Central

    2015-01-01

    Comparative (electro)catalytic, structural, and spectroscopic studies in hydrogen electro-oxidation, the (inverse) water-gas shift reaction, and methane conversion on two representative mixed ionic–electronic conducting perovskite-type materials La0.6Sr0.4FeO3−δ (LSF) and SrTi0.7Fe0.3O3−δ (STF) were performed with the aim of eventually correlating (electro)catalytic activity and associated structural changes and to highlight intrinsic reactivity characteristics as a function of the reduction state. Starting from a strongly prereduced (vacancy-rich) initial state, only (inverse) water-gas shift activity has been observed on both materials beyond ca. 450 °C but no catalytic methane reforming or methane decomposition reactivity up to 600 °C. In contrast, when starting from the fully oxidized state, total methane oxidation to CO2 was observed on both materials. The catalytic performance of both perovskite-type oxides is thus strongly dependent on the degree/depth of reduction, on the associated reactivity of the remaining lattice oxygen, and on the reduction-induced oxygen vacancies. The latter are clearly more reactive toward water on LSF, and this higher reactivity is linked to the superior electrocatalytic performance of LSF in hydrogen oxidation. Combined electron microscopy, X-ray diffraction, and Raman measurements in turn also revealed altered surface and bulk structures and reactivities. PMID:26045733

  16. A Study on Organic-Metal Halide Perovskite Film Morphology, Interfacial Layers, Tandem Applications, and Encapsulation

    NASA Astrophysics Data System (ADS)

    Fisher, Dallas A.

    decreased drastically due to poor band alignment. Fe2O3 appears to be better suited to a narrower band gap material than methylammonium lead iodide perovskite. Finally, encapsulation of perovskite devices with epoxy coatings is explored as a method to improve long-term stability. Perovskites are sensitive to a variety of conditions, but most importantly water and polar molecules. Encapsulants act as a moisture/oxygen barrier, but also prevent outgassing of the organic components. Three epoxies were tested in high heat and high humidity conditions. Important factors in the curing process were uncovered such as the sensitivity of UV-epoxies to amine functional groups found in common p-type dopants and perovskite layers. Moisture ingress was the failure point for high-humidity/heat devices which was confirmed through conversion to yellow lead iodide. A revised device fabrication method is proposed to reduce moisture ingress for future experiments.

  17. Investigation on the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ manganites

    NASA Astrophysics Data System (ADS)

    Arun, B.; Athira, M.; Akshay, V. R.; Sudakshina, B.; Mutta, Geeta R.; Vasundhara, M.

    2018-02-01

    We have investigated the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ Perovskite manganites. Rietveld refinement of the X-ray powder diffraction patterns confirms that all the studied compounds have crystallized into an orthorhombic structure with Pbnm space group. Transmission electron microscopy analysis reveals nanocrystalline compounds with crystallite size less than 50 nm. The selected area electron diffraction patterns reveal the highly crystalline nature of the compounds and energy dispersive X-ray spectroscopic analysis shows that the obtained compositions are nearly identical with the nominal one. The oxygen stoichiometry is estimated by iodometric titration method and stoichiometric compositions are confirmed by X-ray Fluorescence Spectrometry analysis. A large bifurcation is observed in the ZFC/FC curves and Arrott plots not show a linear relation but have a convex curvature nature. The temperature dependence of inverse magnetic susceptibility at higher temperature confirms the existence of ferromagnetic clusters. The experimental results reveal that the reduction of crystallite size to nano metric scale in Pr-deficient manganites adversely influences structural, magnetic and magnetocaloric properties as compared to its bulk counterparts reported earlier.

  18. Inorganic perovskite photocatalysts for solar energy utilization.

    PubMed

    Zhang, Guan; Liu, Gang; Wang, Lianzhou; Irvine, John T S

    2016-10-24

    The development and utilization of solar energy in environmental remediation and water splitting is being intensively studied worldwide. During the past few decades, tremendous efforts have been devoted to developing non-toxic, low-cost, efficient and stable photocatalysts for water splitting and environmental remediation. To date, several hundreds of photocatalysts mainly based on metal oxides, sulfides and (oxy)nitrides with different structures and compositions have been reported. Among them, perovskite oxides and their derivatives (layered perovskite oxides) comprise a large family of semiconductor photocatalysts because of their structural simplicity and flexibility. This review specifically focuses on the general background of perovskite and its related materials, summarizes the recent development of perovskite photocatalysts and their applications in water splitting and environmental remediation, discusses the theoretical modelling and calculation of perovskite photocatalysts and presents the key challenges and perspectives on the research of perovskite photocatalysts.

  19. Efficient semitransparent perovskite solar cells for 23.0%-efficiency perovskite/silicon four-terminal tandem cells

    DOE PAGES

    Chen, Bo; Bai, Yang; Yu, Zhengshan; ...

    2016-07-19

    Here, we have investigated semi-transparent perovskite solar cells and infrared enhanced silicon heterojunction cells for high-efficiency tandem devices. A semi-transparent metal electrode with good electrical conductivity and optical transparency has been fabricated by thermal evaporation of 7 nm of Au onto a 1-nm-thick Cu seed layer. For this electrode to reach its full potential, MAPbI3 thin films were formed by a modified one-step spin-coating method, resulting in a smooth layer that allowed the subsequent metal thin film to remain continuous. The fabricated semi-transparent perovskite solar cells demonstrated 16.5% efficiency under one-sun illumination, and were coupled with infrared-enhanced silicon heterojunction cellsmore » tuned specifically for perovskite/Si tandem devices. A double-layer antireflection coating at the front side and MgF2 reflector at rear side of the silicon heterojunction cells reduced parasitic absorption of near-infrared light, leading to 6.5% efficiency after filtering with a perovskite device and 23.0% summed efficiency for the perovskite/Si tandem device.« less

  20. Efficient semitransparent perovskite solar cells for 23.0%-efficiency perovskite/silicon four-terminal tandem cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Bo; Bai, Yang; Yu, Zhengshan

    Here, we have investigated semi-transparent perovskite solar cells and infrared enhanced silicon heterojunction cells for high-efficiency tandem devices. A semi-transparent metal electrode with good electrical conductivity and optical transparency has been fabricated by thermal evaporation of 7 nm of Au onto a 1-nm-thick Cu seed layer. For this electrode to reach its full potential, MAPbI3 thin films were formed by a modified one-step spin-coating method, resulting in a smooth layer that allowed the subsequent metal thin film to remain continuous. The fabricated semi-transparent perovskite solar cells demonstrated 16.5% efficiency under one-sun illumination, and were coupled with infrared-enhanced silicon heterojunction cellsmore » tuned specifically for perovskite/Si tandem devices. A double-layer antireflection coating at the front side and MgF2 reflector at rear side of the silicon heterojunction cells reduced parasitic absorption of near-infrared light, leading to 6.5% efficiency after filtering with a perovskite device and 23.0% summed efficiency for the perovskite/Si tandem device.« less

  1. Cooperative Couplings between Octahedral Rotations and Ferroelectricity in Perovskites and Related Materials

    NASA Astrophysics Data System (ADS)

    Gu, Teng; Scarbrough, Timothy; Yang, Yurong; Íñiguez, Jorge; Bellaiche, L.; Xiang, H. J.

    2018-05-01

    The structure of AB O 3 perovskites is dominated by two types of unstable modes, namely, the oxygen octahedral rotation (AFD) and ferroelectric (FE) mode. It is generally believed that such AFD and FE modes tend to compete and suppress each other. Here we use first-principles methods to show that a dual nature of the FE-AFD coupling, which turns from competitive to cooperative as the AFD mode strengthens, occurs in numerous perovskite oxides. We provide a unified model of such a dual interaction by introducing novel high-order coupling terms and explain the atomistic origin of the resulting new form of ferroelectricity in terms of universal steric mechanisms. We also predict that such a novel form of ferroelectricity leads to atypical behaviors, such as an enhancement of all the three Cartesian components of the electric polarization under hydrostatic pressure and compressive epitaxial strain.

  2. Tailoring Electronic Properties in Semiconducting Perovskite Materials through Octahedral Control

    NASA Astrophysics Data System (ADS)

    Choquette, Amber K.

    Perovskite oxides, which take the chemical formula ABO 3, are a very versatile and interesting materials family, exhibiting properties that include ferroelectricity, ferromagnetism, mixed ionic/electronic conductivity, metal-insulator behavior and multiferroicity. Key to these functionalities is the network of BO6 corner-connected octahedra, which are known to distort and rotate, directly altering electronic and ferroic properties. By controlling the BO6 octahedral distortions and rotations through cationic substitutions, the use of strain engineering, or through the formation of superlattice structures, the functional properties of perovskites can be tuned. Motivating the use of structure-driven design in oxide heterostructures is the prediction of hybrid improper ferroelectricity in A'BO3/ABO3 superlattices. Two key design rules to realizing hybrid improper ferroelectricity are the growth of high quality superlattice structures with odd periodicities of the A / A' layers, and the control of the octahedral rotation pattern. My work explores the rotational response in perovskite oxides to strain and interface effects in thin films of RFeO3 ( R = La, Eu). I demonstrate a synchrotron x-ray diffraction technique to identify the rotation pattern that is present in the films. I then establish substrate imprinting as a key tool for controlling the rotation patterns in heterostructures, providing a means to realize the necessary structural variants of the predicted hybrid improper ferroelectricity in superlattices. In addition, by pairing measured diffraction data with a structure factor calculation, I demonstrate how one can extract both A-site and oxygen atomic positions in single crystal perovskite oxide films. Finally, I show results from (LaFeO 3)n/(EuFeO3)n superlattices (n = 1-5), synthesized to test the motivating predictions of hybrid improper ferroelectricity in oxide superlattices.

  3. A new route of synthesizing perovskite nanotubes by templating approach

    NASA Astrophysics Data System (ADS)

    Habiballah, Anisah Shafiqah; Osman, Nafisah; Jani, Abdul Mutalib Md

    2017-09-01

    A perovskite oxide for example Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) has attracted growing attention due to its high catalytic activity and mixed ionic/electronic conductivity. Recent research of BSCF is more comprehensively based on a remarkable trajectory of innovation, in particular with regards to the synthesis of perovskite structures in one-dimensional (1-D) nanometric scales as they promote not only to increase an active electrode area for the oxygen reduction reaction, but also allow the tailoring of electrode's architecture. Nevertheless, achieving the desired 1-D structure by a conventional method such as hydrothermal, solvothermal, or sonochemical are far from satisfactory. Herein, the aim of this work is to synthesize the BSCF perovskite nanotubes via soft templating approach, particularly using anodic aluminium oxide (AAO) as a template, focusing on the morphology, composition and structural properties were demonstrated. After the AAO template was anodized at 80 V, the fabricated template was clamped between apair of spectroscopic cells containing BSCF sol and deionized water (with a hole of both sides) for 24 hours. After that, the sample was removed from the cells followed by heat treatment process. The FESEM images showed that BSCF nanotubes were successfully achieved, with the diameter of the nanotubes' approximately 80 nm. The EDX result also confirmed the nominal stoichiometry of Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Meanwhile, the XRD pattern confirmed a single crystalline phase of BSCF nanotubes was successfully obtained and congruent to a cubic perovskite structure of BSCF. Possible formation mechanism,as well as the schematic illustration of BSCF nanotubes inside the template was also discussed in this paper.

  4. Is Cu a stable electrode material in hybrid perovskite solar cells for a 30-year lifetime?

    DOE PAGES

    Zhao, Jingjing; Zheng, Xiaopeng; Deng, Yehao; ...

    2016-10-28

    One grand challenge for long-lived perovskite solar cells is that the common electrode materials in solar cells, such as silver and aluminum or even gold, strongly react with hybrid perovskites. Here we report the evaluation of the potential of copper (Cu) as the electrode material in perovskite solar cells for long-term stability. In encapsulated devices which limit exposure to oxygen and moisture, Cu in direct contact with CH 3NH 3PbI 3 showed no reaction at laboratory time scales, and is predicted to be stable for almost 170 years at room temperature and over 22 years at the nominal operating cellmore » temperature of 40 °C. No diffusion of Cu into CH 3NH 3PbI 3 has been observed after thermal annealing for over 100 hours at 80 °C, nor does Cu cause charge trap states in direct contact with CH 3NH 3PbI 3 after long-term thermal annealing or illumination. High performance devices with efficiency above 20% with Cu electrode retains 98% of the initial efficiency after 816 hours storage in ambient environment without encapsulation. Finally, the results indicate Cu is a promising low-cost electrode material for perovskite solar cells for long-term operation.« less

  5. Paintable Carbon-Based Perovskite Solar Cells with Engineered Perovskite/Carbon Interface Using Carbon Nanotubes Dripping Method.

    PubMed

    Ryu, Jaehoon; Lee, Kisu; Yun, Juyoung; Yu, Haejun; Lee, Jungsup; Jang, Jyongsik

    2017-10-01

    Paintable carbon electrode-based perovskite solar cells (PSCs) are of particular interest due to their material and fabrication process costs, as well as their moisture stability. However, printing the carbon paste on the perovskite layer limits the quality of the interface between the perovskite layer and carbon electrode. Herein, an attempt to enhance the performance of the paintable carbon-based PSCs is made using a modified solvent dripping method that involves dripping of the carbon nanotubes (CNTs), which is dispersed in chlorobenzene solution. This method allows CNTs to penetrate into both the perovskite film and carbon electrode, facilitating fast hole transport between the two layers. Furthermore, this method is results in increased open circuit voltage (V oc ) and fill factor (FF), providing better contact at the perovskite/carbon interfaces. The best devices made with CNT dripping show 13.57% power conversion efficiency and hysteresis-free performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Material and Device Stability in Perovskite Solar Cells.

    PubMed

    Kim, Hui-Seon; Seo, Ja-Young; Park, Nam-Gyu

    2016-09-22

    Organic-inorganic halide perovskite solar cells have attracted great attention because of their superb efficiency reaching 22 % and low-cost, facile fabrication processing. Nevertheless, stability issues in perovskite solar cells seem to block further advancements toward commercialization. Thus, device stability is one of the important topics in perovskite solar cell research. In the beginning, the poor moisture resistivity of the perovskite layer was considered as a main problem that hindered further development of perovskite solar cells, which encouraged engineering of the perovskite or protection of the perovskite by a buffer layer. Soon after, other parameters affecting long-term stability were sequentially found and various attempts have been made to enhance intrinsic and extrinsic stability. Here we review the recent progresses addressing stability issues in perovskite solar cells. In this report, we investigated factors affecting stability from material and device points of view. To gain a better understanding of the stability of the bulk perovskite material, decomposition mechanisms were investigated in relation to moisture, photons, and heat. Stability of full device should also be carefully examined because its stability is dependent not only on bulk perovskite but also on the interfaces and selective contacts. In addition, ion migration and current-voltage hysteresis were found to be closely related to stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Organic-inorganic perovskites containing trivalent metal halide layers: the templating influence of the organic cation layer.

    PubMed

    Mitzi, D B

    2000-12-25

    Thin sheetlike crystals of the metal-deficient perovskites (H2AEQT)M2/3I4 [M = Bi or Sb; AEQT = 5,5"'-bis-(aminoethyl)-2,2':5',2'':5'',2'''-quaterthiophene] were formed from slowly cooled ethylene glycol/2-butanol solutions containing the bismuth(III) or antimony(III) iodide and AEQT.2HI salts. Each structure was refined in a monoclinic (C2/m) subcell, with the lattice parameters a = 39.712(13) A, b = 5.976(2) A, c = 6.043(2) A, beta = 92.238(5) degrees, and Z = 2 for M = Bi and a = 39.439(7) A, b = 5.952(1) A, c = 6.031(1) A, beta = 92.245(3) degrees, and Z = 2 for M = Sb. The trivalent metal cations locally adopt a distorted octahedral coordination, with M-I bond lengths ranging from 3.046(1) to 3.218(3) A (3.114 A average) for M = Bi and 3.012(1) to 3.153(2) A (3.073 A average) for M = Sb. The new organic-inorganic hybrids are the first members of a metal-deficient perovskite family consisting of (Mn+)2/nV(n-2)/nX4(2-) sheets, where V represents a vacancy (generally left out of the formula) and the metal cation valence, n, is greater than 2. The organic layers in the AEQT-based organic-inorganic hybrids feature edge-to-face aromatic interactions among the rigid, rodlike quaterthiophene moieties, which may help to stabilize the unusual metal-deficient layered structures.

  8. Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

    DOE PAGES

    Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; ...

    2015-09-21

    Ruddlesden-Popper structured oxides, general form A n+1B nO 3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo 0.5Fe 0.5O 4-δ (n = 1), La 0.3Sr 2.7CoFeO 7-δ (n = 2), and LaSr 3Co 1.5Fe 1.5O 10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO 2 of 10 -1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, andmore » were found to have increased total oxygen vacancy concentration in the order La 0.3Sr 2.7CoFeO 7-δ > LaSr 3Co 1.5Fe 1.5O 10-δ > LaSrCo 0.5Fe 0.5O 4-δ, following the trend predicted for charge compensation upon increasing Sr 2+/La 3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.« less

  9. Perovskite Superlattices as Tunable Microwave Devices

    NASA Technical Reports Server (NTRS)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  10. Neutral- and Multi-Colored Semitransparent Perovskite Solar Cells.

    PubMed

    Lee, Kyu-Tae; Guo, L Jay; Park, Hui Joon

    2016-04-11

    In this review, we summarize recent works on perovskite solar cells with neutral- and multi-colored semitransparency for building-integrated photovoltaics and tandem solar cells. The perovskite solar cells exploiting microstructured arrays of perovskite "islands" and transparent electrodes-the latter of which include thin metallic films, metal nanowires, carbon nanotubes, graphenes, and transparent conductive oxides for achieving optical transparency-are investigated. Moreover, the perovskite solar cells with distinctive color generation, which are enabled by engineering the band gap of the perovskite light-harvesting semiconductors with chemical management and integrating with photonic nanostructures, including microcavity, are discussed. We conclude by providing future research directions toward further performance improvements of the semitransparent perovskite solar cells.

  11. Development of High Efficiency Four-Terminal Perovskite-Silicon Tandems

    NASA Astrophysics Data System (ADS)

    Duong, The Duc

    This thesis is concerned with the development of high efficiency four-terminal perovskite-silicon tandem solar cells with the potential to reduce the cost of solar energy. The work focuses on perovskite top cells and can be divided into three main parts: developing low parasitic absorption and efficient semi-transparent perovskite cells, doping perovskite materials with rubidium, and optimizing perovskite material's bandgap with quadruple-cation and mixed-halide. A further section investigates the light stability of optimized bandgap perovskite cells. In a four-terminal mechanically stacked tandem, the perovskite top cell requires two transparent contacts at both the front and rear sides. Through detailed optical and electrical power loss analysis of the tandem efficiency due to non-ideal properties of the two transparent contacts, optimal contact parameters in term of sheet resistance and transparency are identified. Indium doped tin oxide by sputtering is used for both two transparent contacts and their deposition parameters are optimized separately. The semi-transparent perovskite cell using MAPbI3 has an efficiency of more than 12% with less than 12% parasitic absorption and up to 80% transparency in the long wavelength region. Using a textured foil as anti-reflection coating, an outstanding average transparency of 84% in the long wavelength is obtained. The low parasitic absorption allows an opaque version of the semi-transparent perovskite cell to operate efficiently in a filterless spectrum splitting perovskite-silicon tandem configuration. To further enhance the performance of perovskite cells, it is essential to improve the quality of perovskite films. This can be achieved with mixed-perovskite FAPbI3/MAPbBr3. However, mixed-perovskite films normally contain small a small amount of a non-perovskite phase, which is detrimental for the cell performance. Rb-doping is found to eliminate the formation of the non-perovskite phase and enhance the crystallinity of

  12. White perovskite based lighting devices.

    PubMed

    Bidikoudi, M; Fresta, E; Costa, R D

    2018-06-28

    Hybrid organic-inorganic and all-inorganic metal halide perovskites have been one of the most intensively studied materials during the last few years. In particular, research focusing on understanding how to tune the photoluminescence features and to apply perovskites to optoelectronic applications has led to a myriad of new materials featuring high photoluminescence quantum yields covering the whole visible range, as well as devices with remarkable performances. Having already established their successful incorporation in highly efficient solar cells, the next step is to tackle the challenges in solid-state lighting (SSL) devices. Here, the most prominent is the preparation of white-emitting devices. Herein, we have provided a comprehensive view of the route towards perovskite white lighting devices, including thin film light-emitting diodes (PeLEDs) and hybrid LEDs (HLEDs), using perovskite based color down-converting coatings. While synthesis and photoluminescence features are briefly discussed, we focus on highlighting the major achievements and limitations in white devices. Overall, we expect that this review will provide the reader a general overview of the current state of perovskite white SSL, paving the way towards new breakthroughs in the near future.

  13. An efficient copper phthalocyanine additive of perovskite precursor for improving the photovoltaic performance of planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Wu, Shufang; Liu, Qingwei; Zheng, Ya; Li, Renjie; Peng, Tianyou

    2017-08-01

    Solution processable planar heterojunction perovskite solar cell has drawn much attention as a promising low-cost photovoltaic device, and much effort has been made to improve its power conversion efficiency by choosing appropriate additives for the perovskite precursor solution. Different to those additives reported, a soluble and thermal stable tert-butyl substituted copper phthalocyanine (CuPc(tBu)4) as additive is first introduced into the perovskite precursor solution of a planar perovskite solar cell that is fabricated via the one-step solution process. It is found that the pristine device without CuPc(tBu)4 additive exhibits a power conversion efficiency of 15.3%, while an extremely low concentration (4.4 × 10-3 mM) of CuPc(tBu)4 in the precursor solution leads to the corresponding device achieving an enhanced power conversion efficiency of 17.3%. CuPc(tBu)4 as an additive can improve the quality of perovskite layer with higher crystallinity and surface coverage, then resulting in enhanced light absorption and reduced charge recombination, and thus the better power conversion efficiency. The finding presented here provides a new choice for improving the quality of perovskite layer and the photovoltaic performance of the planar heterojunction perovskite solar cells.

  14. Advances in Perovskite Solar Cells

    PubMed Central

    Zuo, Chuantian; Bolink, Henk J.; Han, Hongwei; Huang, Jinsong

    2016-01-01

    Organolead halide perovskite materials possess a combination of remarkable optoelectronic properties, such as steep optical absorption edge and high absorption coefficients, long charge carrier diffusion lengths and lifetimes. Taken together with the ability for low temperature preparation, also from solution, perovskite‐based devices, especially photovoltaic (PV) cells have been studied intensively, with remarkable progress in performance, over the past few years. The combination of high efficiency, low cost and additional (non‐PV) applications provides great potential for commercialization. Performance and applications of perovskite solar cells often correlate with their device structures. Many innovative device structures were developed, aiming at large‐scale fabrication, reducing fabrication cost, enhancing the power conversion efficiency and thus broadening potential future applications. This review summarizes typical structures of perovskite solar cells and comments on novel device structures. The applications of perovskite solar cells are discussed. PMID:27812475

  15. Investigation of Thermally Induced Degradation in CH3NH3PbI3 Perovskite Solar Cells using In-situ Synchrotron Radiation Analysis.

    PubMed

    Kim, Nam-Koo; Min, Young Hwan; Noh, Seokhwan; Cho, Eunkyung; Jeong, Gitaeg; Joo, Minho; Ahn, Seh-Won; Lee, Jeong Soo; Kim, Seongtak; Ihm, Kyuwook; Ahn, Hyungju; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

    2017-07-05

    In this study, we employ a combination of various in-situ surface analysis techniques to investigate the thermally induced degradation processes in MAPbI 3 perovskite solar cells (PeSCs) as a function of temperature under air-free conditions (no moisture and oxygen). Through a comprehensive approach that combines in-situ grazing-incidence wide-angle X-ray diffraction (GIWAXD) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) measurements, we confirm that the surface structure of MAPbI 3 perovskite film changes to an intermediate phase and decomposes to CH 3 I, NH 3 , and PbI 2 after both a short (20 min) exposure to heat stress at 100 °C and a long exposure (>1 hour) at 80 °C. Moreover, we observe clearly the changes in the orientation of CH 3 NH 3 + organic cations with respect to the substrate in the intermediate phase, which might be linked directly to the thermal degradation processes in MAPbI 3 perovskites. These results provide important progress towards improved understanding of the thermal degradation mechanisms in perovskite materials and will facilitate improvements in the design and fabrication of perovskite solar cells with better thermal stability.

  16. La and Al co-doped CaMnO 3 perovskite oxides: From interplay of surface properties to anion exchange membrane fuel cell performance

    DOE PAGES

    Dzara, Michael J.; Christ, Jason M.; Joghee, Prabhuram; ...

    2017-09-01

    This work reports the first account of perovskite oxide and carbon composite oxygen reduction reaction (ORR) catalysts integrated into anion exchange membrane fuel cells (AEMFCs). Perovskite oxides with a theoretical stoichiometry of Ca 0.9La 0.1Al 0.1Mn 0.9O 3-δ are synthesized by an aerogel method and calcined at various temperatures, resulting in a set of materials with varied surface chemistry and surface area. Material composition is evaluated by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The perovskite oxide calcined at 800 degrees C shows the importance of balance between surface area, purity of the perovskite phase, and surfacemore » composition, resulting in the highest ORR mass activity when evaluated in rotating disk electrodes. Integration of this catalyst into AEMFCs reveals that the best AEMFC performance is obtained when using composites with 30:70 perovskite oxide:carbon composition. Doubling the loading leads to an increase in the power density from 30 to 76 mW cm -2. The AEMFC prepared with a composite based on perovskite oxide and N-carbon achieves a power density of 44 mW cm -2, demonstrating an ~50% increase when compared to the highest performing composite with undoped carbon at the same loading.« less

  17. La and Al co-doped CaMnO3 perovskite oxides: From interplay of surface properties to anion exchange membrane fuel cell performance

    NASA Astrophysics Data System (ADS)

    Dzara, Michael J.; Christ, Jason M.; Joghee, Prabhuram; Ngo, Chilan; Cadigan, Christopher A.; Bender, Guido; Richards, Ryan M.; O'Hayre, Ryan; Pylypenko, Svitlana

    2018-01-01

    This work reports the first account of perovskite oxide and carbon composite oxygen reduction reaction (ORR) catalysts integrated into anion exchange membrane fuel cells (AEMFCs). Perovskite oxides with a theoretical stoichiometry of Ca0.9La0.1Al0.1Mn0.9O3-δ are synthesized by an aerogel method and calcined at various temperatures, resulting in a set of materials with varied surface chemistry and surface area. Material composition is evaluated by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The perovskite oxide calcined at 800 °C shows the importance of balance between surface area, purity of the perovskite phase, and surface composition, resulting in the highest ORR mass activity when evaluated in rotating disk electrodes. Integration of this catalyst into AEMFCs reveals that the best AEMFC performance is obtained when using composites with 30:70 perovskite oxide:carbon composition. Doubling the loading leads to an increase in the power density from 30 to 76 mW cm-2. The AEMFC prepared with a composite based on perovskite oxide and N-carbon achieves a power density of 44 mW cm-2, demonstrating an ∼50% increase when compared to the highest performing composite with undoped carbon at the same loading.

  18. Environmentally Friendly Plasma-Treated PEDOT:PSS as Electrodes for ITO-Free Perovskite Solar Cells.

    PubMed

    Vaagensmith, Bjorn; Reza, Khan Mamun; Hasan, Md Nazmul; Elbohy, Hytham; Adhikari, Nirmal; Dubey, Ashish; Kantack, Nick; Gaml, Eman; Qiao, Qiquan

    2017-10-18

    Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent electrodes (TEs) offer great potential as a low cost alternative to expensive indium tin oxide (ITO). However, strong acids are typically used for enhancing the conductivity of PEDOT:PSS TEs, which produce processing complexity and environmental issues. This work presents an environmentally friendly acid free approach to enhance the conductivity of PEDOT:PSS using a light oxygen plasma treatment, in addition to solvent blend additives and post treatments. The plasma treatment was found to significantly reduce the sheet resistance of PEDOT:PSS TEs from 85 to as low as 15 Ω sq -1 , which translates to the highest reported conductivity of 5012 S/cm for PEDOT:PSS TEs. The plasma treated PEDOT:PSS TE resulted in an ITO-free perovskite solar cell efficiency of 10.5%, which is the highest reported efficiency for ITO-free perovskite solar cells with a PEDOT:PSS electrode that excludes the use of acid treatments. This research presents the first demonstration of this technology. Moreover, the PEDOT:PSS TEs enabled better charge extraction from the perovskite solar cells and reduced hysteresis in the current density-voltage (J-V) curves.

  19. High Performance Tandem Perovskite/Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Bag, Monojit; Page, Zachariah; Renna, Lawrence; Kim, Paul; Choi, Jaewon; Emrick, Todd; Venkataraman, D.; Russell, Thomas

    Combining perovskites with other inorganic materials, such as copper indium gallium diselenide (CIGS) or silicon, is enabling significant improvement in solar cell device performance. Here, we demonstrate a highly efficient hybrid tandem solar cell fabricated through a facile solution deposition approach to give a perovskite front sub-cell and a polymer:fullerene blend back sub-cell. This methodology eliminates the adverse effects of thermal annealing during perovskite fabrication on polymer solar cells. The record tandem solar cell efficiency of 15.96% is 40% greater than the corresponding perovskite-based single junction device and 65% greater than the polymer-based single junction device, while mitigating deleterious hysteresis effects often associated with perovskite solar cells. The hybrid tandem devices demonstrate the synergistic effects arising from the combination of perovskite and polymer-based materials for solar cells. This work was supported by the Department of Energy-supported Energy Frontier Research Center at the University of Massachusetts (DE-SC0001087). The authors acknowledge the W.M. Keck Electron Microscopy.

  20. Microbial functional diversity alters the structure and sensitivity of oxygen deficient zones

    NASA Astrophysics Data System (ADS)

    Penn, Justin; Weber, Thomas; Deutsch, Curtis

    2016-09-01

    Oxygen deficient zones (ODZs) below the ocean surface regulate marine productivity by removing bioavailable nitrogen (N). A complex microbial community mediates N loss, but the interplay of its diverse metabolisms is poorly understood. We present an ecosystem model of the North Pacific ODZ that reproduces observed chemical distributions yet predicts different ODZ structure, rates, and climatic sensitivity compared to traditional geochemical models. An emergent lower O2 limit for aerobic nitrification lies below the upper O2 threshold for anaerobic denitrification, creating a zone of microbial coexistence that causes a larger ODZ but slower total rates of N loss. The O2-dependent competition for the intermediate nitrite produces gradients in its oxidation versus reduction, anammox versus heterotrophic denitrification, and the net ecological stoichiometry of N loss. The latter effect implies that an externally driven ODZ expansion should favor communities that more efficiently remove N, increasing the sensitivity of the N cycle to climate change.

  1. Planar-integrated single-crystalline perovskite photodetectors

    PubMed Central

    Saidaminov, Makhsud I.; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L.; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H.; Bakr, Osman M.

    2015-01-01

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 104 electrons per photon) and high gain-bandwidth product (above 108 Hz) relative to other perovskite-based optical sensors. PMID:26548941

  2. Making and Breaking of Lead Halide Perovskites.

    PubMed

    Manser, Joseph S; Saidaminov, Makhsud I; Christians, Jeffrey A; Bakr, Osman M; Kamat, Prashant V

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  3. Making and Breaking of Lead Halide Perovskites

    DOE PAGES

    Manser, Joseph S.; Saidaminov, Makhsud I.; Christians, Jeffrey A.; ...

    2016-01-20

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80-150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapidmore » degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic-inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution

  4. Tunable thermodynamic activity of LaxSr1–xMnyAl1–yO3–δ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) perovskites for solar thermochemical fuel synthesis† †Electronic supplementary information (ESI) available: Computational details, comprehensive XRD analyses, oxygen nonstoichiometry measurements and thermodynamic characterization of the perovskites. See DOI: 10.1039/c6ta06644e Click here for additional data file.

    PubMed Central

    Ezbiri, M.; Takacs, M.; Theiler, D.; Steinfeld, A.

    2017-01-01

    Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO2 and/or H2O to produce CO and/or H2 (syngas), we investigate the equilibrium thermodynamics of the LaxSr1–xMnyAl1–yO3–δ perovskite family (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and La0.6Ca0.4Mn0.8Al0.2O3–δ, and compare them to those of CeO2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La0.2Sr0.8Mn0.8Al0.2O3–δ at 1773 K and 2.37 mbar O2. As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La0.6Sr0.4Mn0.4Al0.6O3–δ, rendering it attractive for CO2 and H2O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence. PMID:28580143

  5. Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

    PubMed

    Meng, Weiwei; Wang, Xiaoming; Xiao, Zewen; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

    2017-07-06

    Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB 2+ X 3 ) and double perovskites (A 2 B + B 3+ X 6 ) (A = Cs or monovalent organic ion, B 2+ = non-Pb divalent metal, B + = monovalent metal, B 3+ = trivalent metal, X = halogen). We show that if B 2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B + = In, Tl and B 3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoelectronic applications.

  6. Bifacial Modified Charge Transport Materials for Highly Efficient and Stable Inverted Perovskite Solar Cells.

    PubMed

    Li, Xin; Zhao, Xingyue; Hao, Feng; Yin, Xuewen; Yao, Zhibo; Zhou, Yu; Shen, Heping; Lin, Hong

    2018-05-30

    Significant efforts have been devoted to enhancing both the performance and long-term stability of lead halide perovskite solar cells (PSCs) to promote their practical application. In this context, a self-assembled monolayer composed of a dye molecule is demonstrated for the first time to be efficient in passivating the surface of the hole transport layer, NiO x , in the p-i-n PSCs through multiple functions, including the minimization of energy-level offset, reducing surface trap states, and enhancing wetting between NiO x and perovskite layers coupled with increasing perovskite crystallinity. Consequently, the dye monolayer has sufficiently improved the hole extraction efficiency and suppressed the charge recombination, validated by steady and transient photoluminescence measurements and the electrochemical impedance analysis. Concurrently, a mixed layer of BaSnO 3 nanoparticles and [6,6]-phenyl-C 61 -butyric acid methyl (PCBM) (barium stannate (BSO)/PCBM) was exploited as an efficient electron transport layer, resulting in superior electron transport properties and correspondingly excellent device stability. By incorporating these bifacial modifications, the device performance of the inverted PSC was propelled to 16.2%, compared with 14.0% for that without any interfacial and compositional engineering. Benefiting from the excellent crystallinity of the perovskite through dye passivation and the blocking of moisture, oxygen, and ion migration by using the hybrid BSO/PCBM layer, over 90% of the initial power conversion efficiency has been preserved for the device after exposure to ambient air for 650 h.

  7. Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

    PubMed

    Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

    2018-05-15

    Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

  8. A multiproxy approach to understanding the "enhanced" flux of organic matter through the oxygen deficient waters of the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Keil, R. G.; Neibauer, J.; Biladeau, C.; van der Elst, K.; Devol, A. H.

    2015-10-01

    Free-drifting sediment net traps were deployed 14 times at depths between 80 and 500 m for 1-3 days each during the late monsoon/intermonsoon transition in the central Arabian Sea. Two locations (19.5 and 15.5° N) were within the permanently oxygen deficient zone, and a third (11° N) had a shallow and thin oxygen minimum. The secondary nitrite maximum, which serves as a tracer of the oxygen deficient zone (ODZ) zone, thinned from ∼ 250 m thick at stations 19.5 and 15.5° N to ∼ 50 m thick at station 11° N. Overall, organic carbon fluxes ranged from 13.2 g m2 yr-1 at 80 m to a minimum of 1.1 g m2 yr-1 at 500 m. Fluxes at the more oxygenated 11° N station attenuate faster than within the permanent ODZ. Martin curve attenuation coefficients for 19.5 and 15.5° N are 0.59 and 0.63 and for 11° N it is 0.98. At least six potential mechanisms might explain why sinking particles sinking through the ODZ are more effectively transferred to depth; (M1) oxygen effects, (M2) microbial loop efficiencies and chemoautotrophy, (M3) changes in zooplankton dynamics, (M4) additions of ballast that might sorb and protect organic matter from decay, (M5) inputs of refractory organic matter, and (M6) changes in sinking speeds. These mechanisms are intertwined, and were explored using a combination of mineral (XPS) and organic matter characterizations of the sinking material and ship-board incubation experiments. Evidence was found supporting an oxygen effect and/or changes in the efficiency of the microbial loop including the addition of chemoautotrophic carbon to the sinking flux in the upper 500 m. Less evidence was found for the other potential mechanisms. A simple conceptual model consistent with our and other recent data suggests that the upper ODZ microbial community determines the initial flux attenuation, and that deeper in the water column zooplankton and sinking speed become more important. The exact interplay between the various mechanisms remains to be further

  9. Dimensional control of defect dynamics in perovskite oxide superlattices

    NASA Astrophysics Data System (ADS)

    Bredeson, Isaac; Zhang, Lipeng; Kent, P. R. C.; Cooper, Valentino R.; Xu, Haixuan

    2018-03-01

    Point defects play a critical role in the structural, physical, and interfacial properties of perovskite oxide superlattices. However, understanding of the fundamental properties of point defects in superlattices, especially their transport properties, is rather limited. Here, we report predictions of the stability and dynamics of oxygen vacancies in SrTi O3/PbTi O3 oxide superlattices using first-principles calculations in combination with the kinetic Monte Carlo method. By varying the stacking period, i.e., changing of n in n STO /n PTO , we discover a crossover from three-dimensional diffusion to primarily two-dimensional planar diffusion. Such planar diffusion may lead to novel designs of ionic conductors. We show that the dominant vacancy position may vary in the superlattices, depending on the superlattice structure and stacking period, contradicting the common assumption that point defects reside at interfaces. Moreover, we predict a significant increase in room-temperature ionic conductivity for 3STO/3PTO relative to the bulk phases. Considering the variety of cations that can be accommodated in perovskite superlattices and the potential mismatch of spin, charge, and orbitals at the interfaces, this paper identifies a pathway to control defect dynamics for technological applications.

  10. Octahedral tilting instabilities in inorganic halide perovskites

    NASA Astrophysics Data System (ADS)

    Bechtel, Jonathon S.; Van der Ven, Anton

    2018-02-01

    Dynamic instabilities, stabilized by anharmonic interactions in cubic and tetragonal halide perovskites at high temperature, play a role in the electronic structure and optoelectronic properties of halide perovskites. In particular, inorganic and hybrid perovskite materials undergo structural phase transitions associated with octahedral tilts of the metal-halide octahedra. We investigate the structural instabilities present in inorganic Cs M X3 perovskites with Pb or Sn on the metal site and Br or I on the X site. Defining primary order parameters in terms of symmetry-adapted collective displacement modes and secondary order parameters in terms of symmetrized Hencky strain components, we unravel the coupling between octahedral tilt modes and macroscopic strains as well as the role of A -site displacements in perovskite phase stability. Symmetry-allowed secondary strain order parameters are enumerated for the 14 unique perovskite tilt systems. Using first-principles calculations to explore the Born-Oppenheimer energy surface in terms of symmetrized order parameters, we find coupling between octahedral tilting and A -site displacements is necessary to stabilize P n m a ground states. Additionally, we show that the relative stability of an inorganic halide perovskite tilt system correlates with the volume decrease from the high-symmetry cubic phase to the low-symmetry distorted phase.

  11. Extrinsic ion migration in perovskite solar cells

    DOE PAGES

    Li, Zhen; Xiao, Chuanxiao; Yang, Ye; ...

    2017-04-10

    In this study, the migration of intrinsic ions (e.g., MA +, Pb 2+, I –) in organic–inorganic hybrid perovskites has received significant attention with respect to the critical roles of these ions in the hysteresis and degradation in perovskite solar cells (PSCs). Here, we demonstrate that extrinsic ions (e.g., Li +, H +, Na +), when used in the contact layers in PSCs, can migrate across the perovskite layer and strongly impact PSC operation. In a TiO 2/perovskite/spiro-OMeTAD-based PSC, Li +-ion migration from spiro-OMeTAD to the perovskite and TiO 2 layer is illustrated by time-of-flight secondary-ion mass spectrometry. The movementmore » of Li + ions in PSCs plays an important role in modulating the solar cell performance, tuning TiO 2 carrier-extraction properties, and affecting hysteresis in PSCs. The influence of Li +-ion migration was investigated using time-resolved photoluminescence, Kelvin probe force microscopy, and external quantum efficiency spectra. Other extrinsic ions such as H + and Na + also show a clear impact on the performance and hysteresis in PSCs. Understanding the impacts of extrinsic ions in perovskite-based devices could lead to new material and device designs to further advance perovskite technology for various applications.« less

  12. Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

    PubMed

    Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

    2018-05-01

    Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Stability issues pertaining large area perovskite and dye-sensitized solar cells and modules

    NASA Astrophysics Data System (ADS)

    Castro-Hermosa, S.; Yadav, S. K.; Vesce, L.; Guidobaldi, A.; Reale, A.; Di Carlo, A.; Brown, T. M.

    2017-01-01

    Perovskite and dye-sensitized solar cells are PV technologies which hold promise for PV application. Arguably, the biggest issue facing these technologies is stability. The vast majority of studies have been limited to small area laboratory cells. Moisture, oxygen, UV light, thermal and electrical stresses are leading the degradation causes. There remains a shortage of stability investigations on large area devices, in particular modules. At the module level there exist particular challenges which can be different from those at the small cell level such as encapsulation (not only of the unit cells but of interconnections and contacts), non-uniformity of the layer stacks and unit cells, reverse bias stresses, which are important to investigate for technologies that aim for industrial acceptance. Herein we present a review of stability investigations published in the literature pertaining large area perovskite and dye-sensitized solar devices fabricated both on rigid (glass) and flexible substrates.

  14. Oxygen vacancy diffusion in bulk SrTiO3 from density functional theory calculations

    DOE PAGES

    Zhang, Lipeng; Liu, Bin; Zhuang, Houlong; ...

    2016-04-01

    Point defects and point defect diffusion contribute significantly to the properties of perovskite materials. However, even for the prototypical case of oxygen vacancies in SrTiO 3 (STO), predictions vary widely. Here we present a comprehensive and systematic study of the diffusion barriers for this material. We use density functional theory (DFT) and assess the role of different cell sizes, density functionals, and charge states. Our results show that vacancy-induced octahedral rotations, which are limited by the boundary conditions of the supercell, can significantly affect the computed oxygen vacancy diffusion energy barrier. The diffusion energy barrier of a charged oxygen vacancymore » is lower than that of a neutral one. Unexpectedly, we find that with increasing supercell size, the effects of the oxygen vacancy charge state, the type of DFT exchange and correlation functional on the energy barrier diminish, and the different DFT predictions asymptote to a value in the range of 0.39-0.49 eV. This work provides important insight and guidance that should be considered for investigations of point defect diffusion in other perovskite materials and in oxide superlattices.« less

  15. BMI-1 Mediates Estrogen-Deficiency-Induced Bone Loss by Inhibiting Reactive Oxygen Species Accumulation and T Cell Activation.

    PubMed

    Li, Jinbo; Wang, Qian; Yang, Renlei; Zhang, Jiaqi; Li, Xing; Zhou, Xichao; Miao, Dengshun

    2017-05-01

    Previous studies have shown that estrogen regulates bone homeostasis through regulatory effects on oxidative stress. However, it is unclear how estrogen deficiency triggers reactive oxygen species (ROS) accumulation. Recent studies provide evidence that the B lymphoma Mo-MLV insertion region 1 (BMI-1) plays a critical role in protection against oxidative stress and that this gene is directly regulated by estrogen via estrogen receptor (ER) at the transcriptional level. In this study, ovariectomized mice were given drinking water with/without antioxidant N-acetyl-cysteine (NAC, 1 mg/mL) supplementation, and compared with each other and with sham mice. Results showed that ovariectomy resulted in bone loss with increased osteoclast surface, increased ROS levels, T cell activation, and increased TNF and RANKL levels in serum and in CD4 T cells; NAC supplementation largely prevented these alterations. BMI-1 expression levels were dramatically downregulated in CD4 T cells from ovariectomized mice. We supplemented drinking water to BMI-1-deficient mice with/without NAC and compared them with each other and with wild-type (WT) mice. We found that BMI-1 deficiency mimicked alterations observed in ovariectomy whereas NAC supplementation reversed all alterations induced by BMI-1 deficiency. Because T cells are critical in mediating ovariectomy-induced bone loss, we further assessed whether BMI-1 overexpression in lymphocytes can protect against estrogen deficiency-induced osteoclastogenesis and bone loss by inhibiting oxidative stress, T cell activation, and RANKL production. When WT and Eμ-BMI-1 transgenic mice with BMI-1 specifically overexpressed in lymphocytes were ovariectomized and compared with each other and with WT sham mice, we found that BMI-1 overexpression in lymphocytes clearly reversed all alterations induced by ovariectomy. Results from this study indicate that estrogen deficiency downregulates BMI-1 and subsequently increases ROS, T cell activation, and

  16. Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology

    NASA Astrophysics Data System (ADS)

    Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

    2018-01-01

    In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

  17. Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology.

    PubMed

    Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

    2018-01-10

    In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.

  18. Flake-like oxygen-deficient lithium vanadium oxides as a high ionic and electronic conductive cathode material for high-power Li-ion battery

    NASA Astrophysics Data System (ADS)

    Li, Jing-quan; Han, Chong; Jing, Mao-xiang; Yang, Hua; Shen, Xiang-qian; Qin, Shi-biao

    2018-06-01

    Low electronic and ionic conductivity for LiV3O8 cathode material could lead to poor cycling stability and rate capability, which are considered as the main restraint for its application in Li-ion battery. A novel flake-like LiV3O7.9 material modified by high ionic and electronic conductive Li0.3V2O5/C was fabricated via electrospinning and controlled thermal sintering processes. This oxygen-deficient LiV3O7.9/Li0.3V2O5-C composite electrode sintered at 500 °C exhibits improved rate and cycle stability. The electrode possesses a retention capacity of 151.9mAh/g after 500 cycles at 5C and 84.8mAh/g after 1000 cycles at 10C, respectively. The improvement of the electrochemical performance could be attributed to the synergistic effects of flake-like morphology, oxygen-deficiency and surface modification of Li0.3V2O5/C, which increase the ionic and electronic conductivity of LiV3O8.

  19. Trace Element Abundances in an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

    NASA Technical Reports Server (NTRS)

    Mane, Prajkta; Wadhwa, M.; Keller, L. P.

    2013-01-01

    Calcium-aluminum-rich refractory inclusions (CAIs) are thought to be the first-formed solids in the Solar protoplanetary disk and can provide information about the earliest Solar System processes (e.g., [1]). A hibonite-perovskitebearing CAI from the Allende CV3 chondrite (SHAL, [2]) contains a single of 500 micrometers hibonite grain and coarse-grained perovskite. The mineralogy and oxygen isotopic composition of this CAI shows similarities with FUN inclusions, especially HAL [2]. Here we present trace element abundances in SHAL.

  20. Perovskite and Organic Photovoltaics | Photovoltaic Research | NREL

    Science.gov Websites

    Perovskite and Organic Photovoltaics Perovskite and Organic Photovoltaics Scientist holds several solar cells; 2) electronic energy level alignment at the carbon nanotube/organic metal halide perovskite Hest in the PDIL in the S and TF at NREL. Organic Photovoltaics (OPV) We develop and apply new absorber

  1. Two-Photon Absorption in Organometallic Bromide Perovskites.

    PubMed

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  2. Thermochromic halide perovskite solar cells.

    PubMed

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A; Xie, Chenlu; Cui, Fan; Alivisatos, A Paul; Limmer, David T; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  3. Thermochromic halide perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Lin, Jia; Lai, Minliang; Dou, Letian; Kley, Christopher S.; Chen, Hong; Peng, Fei; Sun, Junliang; Lu, Dylan; Hawks, Steven A.; Xie, Chenlu; Cui, Fan; Alivisatos, A. Paul; Limmer, David T.; Yang, Peidong

    2018-03-01

    Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies.

  4. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    DOE PAGES

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou; ...

    2016-03-01

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ionsmore » prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.« less

  5. Deciphering Halogen Competition in Organometallic Halide Perovskite Growth

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Keum, Jong Kahk; Ovchinnikova, Olga S.; Chen, Shiyou

    Organometallic halide perovskites (OHPs) hold great promise for next-generation, low-cost optoelectronic devices. During the chemical synthesis and crystallization of OHP thin films a major unresolved question is the competition between multiple halide species (e.g. I-, Cl-, Br-) in the formation of the mixed halide perovskite crystals. Whether Cl- ions are successfully incorporated into the perovskite crystal structure or alternatively, where they are located, is not yet fully understood. Here, in situ X-ray diffraction measurements of crystallization dynamics are combined with ex situ TOF-SIMS chemical analysis to reveal that Br- or Cl- ions can promote crystal growth, yet reactive I- ionsmore » prevent them from incorporating into the lattice of the final perovskite crystal structure. The Cl- ions are located in the grain boundaries of the perovskite films. These findings significantly advance our understanding of the role of halogens during synthesis of hybrid perovskites, and provide an insightful guidance to the engineering of high-quality perovskite films, essential for exploring superior-performance and cost-effective optoelectronic devices.« less

  6. Growth of MAPbBr3 perovskite crystals and its interfacial properties with Al and Ag contacts for perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Najeeb, Mansoor Ani; Ahmad, Zubair; Shakoor, R. A.; Alashraf, Abdulla; Bhadra, Jolly; Al-Thani, N. J.; Al-Muhtaseb, Shaheen A.; Mohamed, A. M. A.

    2017-11-01

    In this work, the MAPbBr3 perovskite crystals were grown and the interfacial properties of the poly-crystalline MAPbBr3 with Aluminum (Al) and Silver (Ag) contacts has been investigated. MAPbBr3 crystals are turned into the poly-crystalline pellets (PCP) using compaction technique and the Al/PCP, Al/interface layer/PCP, Ag/PCP, and Ag/interface layer/PCP contacts were investigated. Scanning Electron Microscopic (SEM), Energy-dispersive X-ray spectroscopy (EDX) and current-voltage (I-V) characteristic technique were used to have an insight of the degradation mechanism happening at the Metal/perovskite interface. The Ag/PCP contact appears to be stable, whereas Al is found to be highly reactive with the MAPbBr3 perovskite crystals due to the infiltration setback of Al in to the perovskite crystals. The interface layer showed a slight effect on the penetration of Al in to the perovskite crystals however it does not seem to be an appropriate solution. It is noteworthy that the stability of the underlying metal/perovskite contact is very crucial towards the perovskite solar cells with extended device lifetime.

  7. Improved perovskite phototransistor prepared using multi-step annealing method

    NASA Astrophysics Data System (ADS)

    Cao, Mingxuan; Zhang, Yating; Yu, Yu; Yao, Jianquan

    2018-02-01

    Organic-inorganic hybrid perovskites with good intrinsic physical properties have received substantial interest for solar cell and optoelectronic applications. However, perovskite film always suffers from a low carrier mobility due to its structural imperfection including sharp grain boundaries and pinholes, restricting their device performance and application potential. Here we demonstrate a straightforward strategy based on multi-step annealing process to improve the performance of perovskite photodetector. Annealing temperature and duration greatly affects the surface morphology and optoelectrical properties of perovskites which determines the device property of phototransistor. The perovskite films treated with multi-step annealing method tend to form highly uniform, well-crystallized and high surface coverage perovskite film, which exhibit stronger ultraviolet-visible absorption and photoluminescence spectrum compare to the perovskites prepared by conventional one-step annealing process. The field-effect mobilities of perovskite photodetector treated by one-step direct annealing method shows mobility as 0.121 (0.062) cm2V-1s-1 for holes (electrons), which increases to 1.01 (0.54) cm2V-1s-1 for that treated with muti-step slow annealing method. Moreover, the perovskite phototransistors exhibit a fast photoresponse speed of 78 μs. In general, this work focuses on the influence of annealing methods on perovskite phototransistor, instead of obtains best parameters of it. These findings prove that Multi-step annealing methods is feasible to prepared high performance based photodetector.

  8. Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

    PubMed

    Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

    2017-06-21

    Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

  9. Effects of Fe-Enrichment on the Equation of State and Stability of (Mg,Fe)SiO3 Perovskite and Post-Perovskite

    NASA Astrophysics Data System (ADS)

    Dorfman, S. M.; Holl, C. M.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

    2010-12-01

    Fe-enrichment in the deep lower mantle has been proposed as an explanation for seismic anomalies such as large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs). In order to resolve the effect of Fe on the stability and equation of state of the lower mantle’s dominant constituent, (Mg,Fe)SiO3 perovskite, we have studied Fe-rich natural orthopyroxenes, (Mg0.61Fe0.37Ca0.02)SiO3 and (Mg0.25Fe0.70Ca0.05)SiO3 (compositions determined by microprobe analysis), at lower mantle P-T conditions. Pyroxene starting materials were mixed with Au (pressure calibrant and laser absorber) and loaded with NaCl or Ne (pressure medium and thermal insulator) in a symmetric diamond anvil cell. X-ray diffraction experiments at pressures up to 122 GPa with in-situ laser heating were performed at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating samples to 2000 K produced single-phase orthorhombic GdFeO3-type perovskite at 63 GPa for the Mg# 61 composition and at 72 GPa for the Mg# 25 composition. At lower pressures (56 GPa for Mg# 61, 67 GPa for Mg# 25), heating both compositions resulted in a mixture of perovskite, SiO2 and (Mg,Fe)O. These measurements provide new constraints on the dependence of (Mg,Fe)SiO3 perovskite stability on pressure and composition. Upon further compression to 93 GPa and higher pressures with laser heating, Mg# 25 perovskite transformed to a two-phase mixture of perovskite and post-perovskite. This is consistent with previous findings that Fe substitution destabilizes (Mg,Fe)SiO3 perovskite relative to (Mg,Fe)SiO3 post-perovskite (Mao et al. 2004, Caracas and Cohen 2005). The bulk modulus at 80 GPa (K80) is ~550 GPa for both Fe-rich perovskites, comparable to values measured for MgSiO3 perovskite (Lundin et al. 2008). However, the volume of Fe-rich perovskites increases linearly with Fe-content. The (Mg0.25Fe0.70Ca0.05)SiO3 perovskite is 3% greater at 80 GPa than V80 for the Mg end

  10. Impact of Ultrathin C60 on Perovskite Photovoltaic Devices.

    PubMed

    Liu, Dianyi; Wang, Qiong; Traverse, Christopher J; Yang, Chenchen; Young, Margaret; Kuttipillai, Padmanaban S; Lunt, Sophia Y; Hamann, Thomas W; Lunt, Richard R

    2018-01-23

    Halide perovskite solar cells have seen dramatic progress in performance over the past several years. Certified efficiencies of inverted structure (p-i-n) devices have now exceeded 20%. In these p-i-n devices, fullerene compounds are the most popular electron-transfer materials. However, the full function of fullerenes in perovskite solar cells is still under investigation, and the mechanism of photocurrent hysteresis suppression by fullerene remains unclear. In previous reports, thick fullerene layers (>20 nm) were necessary to fully cover the perovskite film surface to make good contact with perovskite film and avoid large leakage currents. In addition, the solution-processed fullerene layer has been broadly thought to infiltrate into the perovskite film to passivate traps on grain boundary surfaces, causing suppressed photocurrent hysteresis. In this work, we demonstrate an efficient perovskite photovoltaic device with only 1 nm C 60 deposited by vapor deposition as the electron-selective material. Utilizing a combination of fluorescence microscopy and impedance spectroscopy, we show that the ultrathin C 60 predominately acts to extract electrons from the perovskite film while concomitantly suppressing the photocurrent hysteresis by reducing space charge accumulation at the interface. This work ultimately helps to clarify the dominant role of fullerenes in perovskite solar cells while simplifying perovskite solar cell design to reduce manufacturing costs.

  11. Two-Dimensional Perovskite Activation with an Organic Luminophore.

    PubMed

    Jemli, Khaoula; Audebert, Pierre; Galmiche, Laurent; Trippé-Allard, Gaelle; Garrot, Damien; Lauret, Jean-Sébastien; Deleporte, Emmanuelle

    2015-10-07

    A great advantage of the hybrid organic-inorganic perovskites is the chemical flexibility and the possibility of a molecular engineering of each part of the material (the inorganic part and the organic part respectively) in order to improve or add some functionalities. An adequately chosen organic luminophore has been introduced inside a lead bromide type organic-inorganic perovskite, while respecting the two-dimensional perovskite structure. A substantial increase of the brilliance of the perovskite is obtained. This activation of the perovskite luminescence by the adequate engineering of the organic part is an original approach, and is particularly interesting in the framework of the light-emitting devices such as organic light-emitting diodes (OLEDs) or lasers.

  12. Quantum-dot-in-perovskite solids.

    PubMed

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H

    2015-07-16

    Heteroepitaxy-atomically aligned growth of a crystalline film atop a different crystalline substrate-is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  13. Impact of Interfacial Layers in Perovskite Solar Cells.

    PubMed

    Cho, An-Na; Park, Nam-Gyu

    2017-10-09

    Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Perovskite solar cells: from materials to devices.

    PubMed

    Jung, Hyun Suk; Park, Nam-Gyu

    2015-01-07

    Perovskite solar cells based on organometal halide light absorbers have been considered a promising photovoltaic technology due to their superb power conversion efficiency (PCE) along with very low material costs. Since the first report on a long-term durable solid-state perovskite solar cell with a PCE of 9.7% in 2012, a PCE as high as 19.3% was demonstrated in 2014, and a certified PCE of 17.9% was shown in 2014. Such a high photovoltaic performance is attributed to optically high absorption characteristics and balanced charge transport properties with long diffusion lengths. Nevertheless, there are lots of puzzles to unravel the basis for such high photovoltaic performances. The working principle of perovskite solar cells has not been well established by far, which is the most important thing for understanding perovksite solar cells. In this review, basic fundamentals of perovskite materials including opto-electronic and dielectric properties are described to give a better understanding and insight into high-performing perovskite solar cells. In addition, various fabrication techniques and device structures are described toward the further improvement of perovskite solar cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Static and dynamic optical properties of La 1-xSr xFeO 3-δ: The effects of A-site and oxygen stoichiometry

    DOE PAGES

    Sergey Y. Smolin; Sfeir, Matthew Y.; Scafetta, Mark D.; ...

    2015-12-09

    Perovskite oxides are a promising material class for photovoltaic and photocatalytic applications due to their visible band gaps, nanosecond recombination lifetimes, and great chemical diversity. However, there is limited understanding of the link between composition and static and dynamic optical properties, despite the critical role these properties play in the design of light-harvesting devices. To clarify these relationships, we systemically studied the optoelectronic properties in La 1-xSr xFeO 3-δ epitaxial films, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25more » eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy, revealing similar nanosecond photoexcited carrier lifetimes for oxygen deficient and stoichiometric films with the same nominal Fe valence. Furthermore, these results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in the recombination kinetics.« less

  16. Ion-Migration Inhibition by the Cation-π Interaction in Perovskite Materials for Efficient and Stable Perovskite Solar Cells.

    PubMed

    Wei, Dong; Ma, Fusheng; Wang, Rui; Dou, Shangyi; Cui, Peng; Huang, Hao; Ji, Jun; Jia, Endong; Jia, Xiaojie; Sajid, Sajid; Elseman, Ahmed Mourtada; Chu, Lihua; Li, Yingfeng; Jiang, Bing; Qiao, Juan; Yuan, Yongbo; Li, Meicheng

    2018-06-25

    Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Perovskite Materials for Light-Emitting Diodes and Lasers.

    PubMed

    Veldhuis, Sjoerd A; Boix, Pablo P; Yantara, Natalia; Li, Mingjie; Sum, Tze Chien; Mathews, Nripan; Mhaisalkar, Subodh G

    2016-08-01

    Organic-inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and perovskite light-emitting diodes with external quantum efficiencies of 8% and current efficiencies of 43 cd A(-1) have been achieved. Although perovskite light-emitting devices are yet to become industrially relevant, in merely two years these devices have achieved the brightness and efficiencies that organic light-emitting diodes accomplished in two decades. Further advances will rely decisively on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional perovskites, nanostructures, charge-transport materials, and device processing with architectural innovations. Here, the rapid advancements in perovskite light-emitting devices and lasers are reviewed. The key challenges in materials development, device fabrication, operational stability are addressed, and an outlook is presented that will address market viability of perovskite light-emitting devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Origins of n -type doping difficulties in perovskite stannates

    NASA Astrophysics Data System (ADS)

    Weston, L.; Bjaalie, L.; Krishnaswamy, K.; Van de Walle, C. G.

    2018-02-01

    The perovskite stannates (A SnO3 ; A = Ba, Sr, Ca) are promising for oxide electronics, but control of n -type doping has proved challenging. Using first-principles hybrid density functional calculations, we investigate La dopants and explore the formation of compensating acceptor defects. We find that La on the A site always behaves as a shallow donor, but incorporation of La on the Sn site can lead to self-compensation. At low La concentrations and in O-poor conditions, oxygen vacancies form in BaSnO3. A -site cation vacancies are found to be dominant among the native compensating centers. Compared to BaSnO3, charge compensation is a larger problem for the wider-band-gap stannates, SrSnO3 and CaSnO3, a trend we can explain based on conduction-band alignments. The formation of compensating acceptor defects can be inhibited by choosing oxygen-poor (cation-rich) growth or annealing conditions, thus providing a pathway for improved n -type doping.

  19. Perovskite Solar Cells for High-Efficiency Tandems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McGehee, Michael; Buonassisi, Tonio

    The first monolithic perovskite/silicon tandem was made with a diffused silicon p-n junction, a tunnel junction made of n ++ hydrogenated amorphous silicon, a titania electron transport layer, a methylammonium lead iodide absorber, and a Spiro-OMeTAD hole transport layer (HTL). The power conversion efficiency (PCE) was only 13.7% due to excessive parasitic absorption of light in the HTL, limiting the matched current density to 11.5 mA/cm 2. Werner et al. 15 raised the PCE to a record 21.2% by switching to a silicon heterojunction bottom cell and carefully tuning layer thicknesses to achieve lower optical loss and a higher currentmore » density of 15.9 mA/cm 2. It is clear from these reports that minimizing parasitic absorption in the window layers is crucial to achieving higher current densities and efficiencies in monolithic tandems. To this end, the window layers through which light first passes before entering the perovskite and silicon absorber materials must be highly transparent. The front electrode must also be conductive to carry current laterally across the top of the device. Indium tin oxide (ITO) is widely utilized as a transparent electrode in optoelectronic devices such as flat-panel displays, smart windows, organic light-emitting diodes, and solar cells due to its high conductivity and broadband transparency. ITO is typically deposited through magnetron sputtering; however, the high kinetic energy of sputtered particles can damage underlying layers. In perovskite solar cells, a sputter buffer layer is required to protect the perovskite and organic carrier extraction layers from damage during sputter deposition. The ideal buffer layer should also be energetically well aligned so as to act as a carrier-selective contact, have a wide bandgap to enable high optical transmission, and have no reaction with the halides in the perovskite. Additionally, this buffer layer should act as a diffusion barrier layer to prevent both organic cation evolution and

  20. A Long-Term View on Perovskite Optoelectronics.

    PubMed

    Docampo, Pablo; Bein, Thomas

    2016-02-16

    Recently, metal halide perovskite materials have become an exciting topic of research for scientists of a wide variety of backgrounds. Perovskites have found application in many fields, starting from photovoltaics and now also making an impact in light-emitting applications. This new class of materials has proven so interesting since it can be easily solution processed while exhibiting materials properties approaching the best inorganic optoelectronic materials such as GaAs and Si. In photovoltaics, in only 3 years, efficiencies have rapidly increased from an initial value of 3.8% to over 20% in recent reports for the commonly employed methylammonium lead iodide (MAPI) perovskite. The first light emitting diodes and light-emitting electrochemical cells have been developed already exhibiting internal quantum efficiencies exceeding 15% for the former and tunable light emission spectra. Despite their processing advantages, perovskite optoelectronic materials suffer from several drawbacks that need to be overcome before the technology becomes industrially relevant and hence achieve long-term application. Chief among these are the sensitivity of the structure toward moisture and crystal phase transitions in the device operation regime, unreliable device performance dictated by the operation history of the device, that is, hysteresis, the inherent toxicity of the structure, and the high cost of the employed charge selective contacts. In this Account, we highlight recent advances toward the long-term viability of perovskite photovoltaics. We identify material decomposition routes and suggest strategies to prevent damage to the structure. In particular, we focus on the effect of moisture upon the structure and stabilization of the material to avoid phase transitions in the solar cell operating range. Furthermore, we show strategies to achieve low-cost chemistries for the development of hole transporters for perovskite solar cells, necessary to be able to compete with other

  1. Molecular behavior of zero-dimensional perovskites

    PubMed Central

    Yin, Jun; Maity, Partha; De Bastiani, Michele; Dursun, Ibrahim; Bakr, Osman M.; Brédas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6 perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them. PMID:29250600

  2. Aqueous-Containing Precursor Solutions for Efficient Perovskite Solar Cells.

    PubMed

    Liu, Dianyi; Traverse, Christopher J; Chen, Pei; Elinski, Mark; Yang, Chenchen; Wang, Lili; Young, Margaret; Lunt, Richard R

    2018-01-01

    Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous-containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water-perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.

  3. Mixed-Halide Perovskites with Stabilized Bandgaps.

    PubMed

    Xiao, Zhengguo; Zhao, Lianfeng; Tran, Nhu L; Lin, Yunhui Lisa; Silver, Scott H; Kerner, Ross A; Yao, Nan; Kahn, Antoine; Scholes, Gregory D; Rand, Barry P

    2017-11-08

    One merit of organic-inorganic hybrid perovskites is their tunable bandgap by adjusting the halide stoichiometry, an aspect critical to their application in tandem solar cells, wavelength-tunable light emitting diodes (LEDs), and lasers. However, the phase separation of mixed-halide perovskites caused by light or applied bias results in undesirable recombination at iodide-rich domains, meaning open-circuit voltage (V OC ) pinning in solar cells and infrared emission in LEDs. Here, we report an approach to suppress halide redistribution by self-assembled long-chain organic ammonium capping layers at nanometer-sized grain surfaces. Using the stable mixed-halide perovskite films, we are able to fabricate efficient and wavelength-tunable perovskite LEDs from infrared to green with high external quantum efficiencies of up to 5%, as well as linearly tuned V OC from 1.05 to 1.45 V in solar cells.

  4. Monolithic Perovskite Silicon Tandem Solar Cells with Advanced Optics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goldschmidt, Jan C.; Bett, Alexander J.; Bivour, Martin

    2016-11-14

    For high efficiency monolithic perovskite silicon tandem solar cells, we develop low-temperature processes for the perovskite top cell, rear-side light trapping, optimized perovskite growth, transparent contacts and adapted characterization methods.

  5. Perovskites: transforming photovoltaics, a mini-review

    DOE PAGES

    Chilvery, Ashwith Kumar; Batra, Ashok K.; Yang, Bin; ...

    2015-01-06

    The recent power-packed advent of perovskite solar cells is transforming photovoltaics (PV) with their superior efficiencies, ease of fabrication, and cost. This perovskite solar cell further boasts of many unexplored features that can further enhance its PV properties and lead to it being branded as a successful commercial product. This paper provides a detailed insight of the organometal halide based perovskite structure, its unique stoichiometric design, and its underlying principles for PV applications. Finally, the compatibility of various PV layers and its fabrication methods is also discussed.

  6. On Characterization of Barium Rare-Earth Antimonates: Ordered Perovskites Suitable as Substrates for Superconducting Films

    NASA Astrophysics Data System (ADS)

    Alonso, J. A.; Cascales, C.; García Casado, P.; Rasines, I.

    1997-02-01

    The crystal structure of the ordered perovskites Ba2(RSb)O6(R=Y, Ho) is refined from neutron powder diffraction data in the space groupFmoverline3m(No. 225),Z=4, with Ba at 8(c),Rat 4(b), Sb at 4(a), oxygen at 24(e), oxygen positional parameterx=0.2636(2) forR=Y and Ho, and unit cell dimensions ofa/Å=8.4240(3) and 8.4170(2) forR=Y and Ho, respectively. Bond-valence analysis explains how the highly covalent Sb-O bonds determine the overall structure of these perovskites in whichR-O and Ba-O bonds are under compressive and tensile stresses, respectively. The magnetic susceptibility of Ba2(HoSb)O6has been measured in the temperature range 2-350 K. From ana prioriestimation of the crystal-field parameters corresponding to the point site symmetry of the rare-earth,Oh, and using the wave functions associated with the energy levels obtained, the paramagnetic susceptibility and its evolution vs temperature is simulated according to the van Vleck formalism. The observed deviation from the Curie-Weiss behavior at low temperature, very well reproduced, reflects the splitting of the ground state of this cation under the influence of the crystal field.

  7. Deficiency of the oxygen sensor prolyl hydroxylase 1 attenuates hypercholesterolaemia, atherosclerosis, and hyperglycaemia.

    PubMed

    Marsch, Elke; Demandt, Jasper A F; Theelen, Thomas L; Tullemans, Bibian M E; Wouters, Kristiaan; Boon, Mariëtte R; van Dijk, Theo H; Gijbels, Marion J; Dubois, Ludwig J; Meex, Steven J R; Mazzone, Massimiliano; Hung, Gene; Fisher, Edward A; Biessen, Erik A L; Daemen, Mat J A P; Rensen, Patrick C N; Carmeliet, Peter; Groen, Albert K; Sluimer, Judith C

    2016-10-14

    Normalization of hypercholesterolaemia, inflammation, hyperglycaemia, and obesity are main desired targets to prevent cardiovascular clinical events. Here we present a novel regulator of cholesterol metabolism, which simultaneously impacts on glucose intolerance and inflammation. Mice deficient for oxygen sensor HIF-prolyl hydroxylase 1 (PHD1) were backcrossed onto an atherogenic low-density lipoprotein receptor (LDLR) knockout background and atherosclerosis was studied upon 8 weeks of western-type diet. PHD1 -/- LDLR -/- mice presented a sharp reduction in VLDL and LDL plasma cholesterol levels. In line, atherosclerotic plaque development, as measured by plaque area, necrotic core expansion and plaque stage was hampered in PHD1 -/- LDLR -/- mice. Mechanistically, cholesterol-lowering in PHD1 deficient mice was a result of enhanced cholesterol excretion from blood to intestines and ultimately faeces. Additionally, flow cytometry of whole blood of these mice revealed significantly reduced counts of leucocytes and particularly of Ly6C high pro-inflammatory monocytes. In addition, when studying PHD1 -/- in diet-induced obesity (14 weeks high-fat diet) mice were less glucose intolerant when compared with WT littermate controls. Overall, PHD1 knockout mice display a metabolic phenotype that generally is deemed protective for cardiovascular disease. Future studies should focus on the efficacy, safety, and gender-specific effects of PHD1 inhibition in humans, and unravel the molecular actors responsible for PHD1-driven, likely intestinal, and regulation of cholesterol metabolism. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  8. ZnO/perovskite core–shell nanorod array based monolithic catalysts with enhanced propane oxidation and material utilization efficiency at low temperature

    DOE PAGES

    Wang, Sibo; Ren, Zheng; Song, Wenqiao; ...

    2015-04-24

    Here, a hydrothermal strategy combined with colloidal deposition synthesis was successfully used to grow ZnO/perovskite (LaBO 3, B=Mn, Co, Ni) core-shell nanorod arrays within three dimensional (3-D) honeycomb cordierite substrates. A facile sonication assisted colloidal wash coating process is able to coat a uniformly dispersed perovskite nanoparticles onto the large scale ZnO nanorod arrays rooted on the channel surfaces of the 3D cordierite substrate achieved by hydrothermal synthesis. Compared to traditional wash-coated perovskite catalysts, an enhanced catalytic performance was observed for propane oxidation with 25°C lower light-off temperature than wash-coated perovskite catalyst of similar LaMnO 3 loading (4.3mg). Temperature programmedmore » reduction and desorption under H 2 and O 2 atmosphere, respectively, were used to study the reducibility and oxygen activity of these core-shell nanorod arrays based monolithic catalysts, revealing a catalytic activity sequence of LaCoO 3>LaMnO 3>La 2NiO 4 at the initial stage of catalytic reaction. The good dispersion and size control in La-based perovskite nanoparticles and their interfaces to ZnO nanorod arrays support may contribute to the enhancement of catalytic performance. Lastly, this work may provide a new type of Pt-group metals (PGM) free catalysts with improved catalytic performance for hydrocarbon oxidations at low temperatures.« less

  9. Random lasing actions in self-assembled perovskite nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Sun, Wenzhao; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2016-05-01

    Solution-based perovskite nanoparticles have been intensively studied in the past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After synthesis from a solution, discrete lasing peaks have been observed from optically pumped perovskites without any well-defined cavity boundaries. We have demonstrated that the origin of the random lasing emissions is the scattering between the nanostructures in the perovskite microplates. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 μJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon-shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of perovskites, two-photon pumped random lasers have also been demonstrated for the first time. We believe this research will find its potential applications in low-cost coherent light sources and biomedical detection.

  10. Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells.

    PubMed

    Yin, Wei; Pan, Lijia; Yang, Tingbin; Liang, Yongye

    2016-06-25

    Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE) and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ) perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed.

  11. Confining metal-halide perovskites in nanoporous thin films

    PubMed Central

    Demchyshyn, Stepan; Roemer, Janina Melanie; Groiß, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Böhm, Anton; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus Clark; Sariciftci, Niyazi Serdar; Nickel, Bert; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

    2017-01-01

    Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability because the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy x-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next-generation photonic devices. PMID:28798959

  12. Low-Dimensional Organic-Inorganic Halide Perovskite: Structure, Properties, and Applications.

    PubMed

    Misra, Ravi K; Cohen, Bat-El; Iagher, Lior; Etgar, Lioz

    2017-10-09

    Three-dimensional (3 D) perovskite has attracted a lot of attention owing to its success in photovoltaic (PV) solar cells. However, one of its major crucial issues lies in its stability, which has limited its commercialization. An important property of organic-inorganic perovskite is the possibility of forming a layered material by using long organic cations that do not fit into the octahedral cage. These long organic cations act as a "barrier" that "caps" 3 D perovskite to form the layered material. Controlling the number of perovskite layers could provide a confined structure with chemical and physical properties that are different from those of 3 D perovskite. This opens up a whole new batch of interesting materials with huge potential for optoelectronic applications. This Minireview presents the synthesis, properties, and structural orientation of low-dimensional perovskite. It also discusses the progress of low-dimensional perovskite in PV solar cells, which, to date, have performance comparable to that of 3 D perovskite but with enhanced stability. Finally, the use of low-dimensional perovskite in light-emitting diodes (LEDs) and photodetectors is discussed. The low-dimensional perovskites are promising candidates for LED devices, mainly because of their high radiative recombination as a result of the confined low-dimensional quantum well. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Morphology-Controlled Synthesis of Organometal Halide Perovskite Inverse Opals.

    PubMed

    Chen, Kun; Tüysüz, Harun

    2015-11-09

    The booming development of organometal halide perovskites in recent years has prompted the exploration of morphology-control strategies to improve their performance in photovoltaic, photonic, and optoelectronic applications. However, the preparation of organometal halide perovskites with high hierarchical architecture is still highly challenging and a general morphology-control method for various organometal halide perovskites has not been achieved. A mild and scalable method to prepare organometal halide perovskites in inverse opal morphology is presented that uses a polystyrene-based artificial opal as hard template. Our method is flexible and compatible with different halides and organic ammonium compositions. Thus, the perovskite inverse opal maintains the advantage of straightforward structure and band gap engineering. Furthermore, optoelectronic investigations reveal that morphology exerted influence on the conducting nature of organometal halide perovskites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Ab-Initio Calculation of Electronic Structure of Lead Halide Perovskites with Formamidinium Cation as an Active Material for Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Indari, E. D.; Wungu, T. D. K.; Hidayat, R.

    2017-07-01

    Organic lead halide perovskite material based solar cells show impressive power conversion efficiencies, which can reach above 19 percent for perovskite solar cell with methyl-ammonium cations. These efficiencies are originated from efficient photoexcitation and charge carrier transport and not observed in conventional perovskite crystals. In this preliminary research work, we therefore performed Density Functional Theory (DFT) calculation of formamidinium lead iodide (FAPI), an alternative to methyl-ammonium lead iodide (MAPI), to predict their electronic structure and density of state (DOS). The calculation result at the most stable lattice parameters show a good agreement with the experiment results. The obtained band gap energy is 1.307 eV. The valence band is dominantly formed by the 5p orbitals of I- anions, while the conduction band is dominantly formed by the 6p orbitals of Pb2+ cations. The DOS of valence band of this perovskite seems smaller compared to the case of methyl-ammonium lead iodide perovskite, which then may explain the observation of smaller power conversion efficiencies in perovskite solar cells with this formamidinium cations.

  15. Bication lead iodide 2D perovskite component to stabilize inorganic α-CsPbI3 perovskite phase for high-efficiency solar cells

    PubMed Central

    Zhang, Taiyang; Dar, M. Ibrahim; Li, Ge; Xu, Feng; Guo, Nanjie; Grätzel, Michael; Zhao, Yixin

    2017-01-01

    Among various all-inorganic halide perovskites exhibiting better stability than organic-inorganic halide perovskites, α-CsPbI3 with the most suitable band gap for tandem solar cell application faces an issue of phase instability under ambient conditions. We discovered that a small amount of two-dimensional (2D) EDAPbI4 perovskite containing the ethylenediamine (EDA) cation stabilizes the α-CsPbI3 to avoid the undesirable formation of the nonperovskite δ phase. Moreover, not only the 2D perovskite of EDAPbI4 facilitate the formation of α-CsPbI3 perovskite films exhibiting high phase stability at room temperature for months and at 100°C for >150 hours but also the α-CsPbI3 perovskite solar cells (PSCs) display highly reproducible efficiency of 11.8%, a record for all-inorganic lead halide PSCs. Therefore, using the bication EDA presents a novel and promising strategy to design all-inorganic lead halide PSCs with high performance and reliability. PMID:28975149

  16. Oxygen influencing the photocarriers lifetime of CH3NH3PbI3-xClx film grown by two-step interdiffusion method and its photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Yuan, Shuai; Qiu, Zhiwen; Zhang, Hailiang; Gong, Haibo; Hao, Yufeng; Cao, Bingqiang

    2016-01-01

    During the growth of CH3NH3PbI3-xClx (MAPbI3-xClx) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI3-xClx grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.

  17. Influence of oxygen partial pressure on the composition and orientation of strontium-doped lead zirconate titanate thin films.

    PubMed

    Sriram, S; Bhaskaran, M; du Plessis, J; Short, K T; Sivan, V P; Holland, A S

    2009-01-01

    The influence of oxygen partial pressure during the deposition of piezoelectric strontium-doped lead zirconate titanate thin films is reported. The thin films have been deposited by RF magnetron sputtering in an atmosphere of high purity argon and oxygen (in the ratio of 9:1), on platinum-coated silicon substrates (heated to 650 degrees C). The influence of oxygen partial pressure is studied to understand the manner in which the stoichiometry of the thin films is modified, and to understand the influence of stoichiometry on the perovskite orientation. This article reports on the results obtained from films deposited at oxygen partial pressures of 1-5 mTorr. The thin films have been studied using a combination of X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GA-XRD), and atomic force microscopy (AFM). XPS analysis highlights the marked influence of variations in oxygen pressure during sputtering, observed by variations in oxygen concentration in the thin films, and in some cases by the undesirable decrease in lead concentration in the thin films. GA-XRD is used to study the relative variations in perovskite peak intensities, and has been used to determine the deposition conditions to attain the optimal combination of stoichiometry and orientation. AFM scans show the marked influence of the oxygen partial pressure on the film morphology.

  18. Scalable fabrication of perovskite solar cells

    DOE PAGES

    Li, Zhen; Klein, Talysa R.; Kim, Dong Hoe; ...

    2018-03-27

    Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discussmore » common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules.« less

  19. Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.

    PubMed

    Cao, Shi-Gu; Li, Yunsong; Wu, Hong-Hui; Wang, Jie; Huang, Baoling; Zhang, Tong-Yi

    2017-08-09

    The strong coupling between crystal structure and mechanical deformation can stabilize low-symmetry phases from high-symmetry phases or induce novel phase transformation in oxide thin films. Stress-induced structural phase transformation in oxide thin films has drawn more and more attention due to its significant influence on the functionalities of the materials. Here, we discovered experimentally a novel stress-induced cubic-to-hexagonal phase transformation in the perovskite nanothin films of barium titanate (BaTiO 3 ) with a special thermomechanical treatment (TMT), where BaTiO 3 nanothin films under various stresses are annealed at temperature of 575 °C. Both high-resolution transmission electron microscopy and Raman spectroscopy show a higher density of hexagonal phase in the perovskite thin film under higher tensile stress. Both X-ray photoelectron spectroscopy and electron energy loss spectroscopy does not detect any change in the valence state of Ti atoms, thereby excluding the mechanism of oxygen vacancy induced cubic-to-hexagonal (c-to-h) phase transformation. First-principles calculations show that the c-to-h phase transformation can be completed by lattice shear at elevated temperature, which is consistent with the experimental observation. The applied bending plus the residual tensile stress produces shear stress in the nanothin film. The thermal energy at the elevated temperature assists the shear stress to overcome the energy barriers during the c-to-h phase transformation. The stress-induced phase transformation in perovskite nanothin films with TMT provides materials scientists and engineers a novel approach to tailor nano/microstructures and properties of ferroelectric materials.

  20. The Dawn of Lead‐Free Perovskite Solar Cell: Highly Stable Double Perovskite Cs2AgBiBr6 Film

    PubMed Central

    Wu, Cuncun; Zhang, Qiaohui; Liu, Yang; Luo, Wei; Guo, Xuan; Huang, Ziru; Ting, Hungkit; Sun, Weihai; Zhong, Xinrui; Wei, Shiyuan

    2017-01-01

    Abstract Recently, lead‐free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently no solar cell based on these double perovskites has been reported, due to the challenge in film processing. Herein, a first lead‐free double perovskite planar heterojunction solar cell with a high quality Cs2AgBiBr6 film, fabricated by low‐pressure assisted solution processing under ambient conditions, is reported. The device presents a best power conversion efficiency of 1.44%. The preliminary efficiency and the high stability under ambient condition without encapsulation, together with the high film quality with simple processing, demonstrate promise for lead‐free perovskite solar cells. PMID:29593974

  1. The Dawn of Lead-Free Perovskite Solar Cell: Highly Stable Double Perovskite Cs2AgBiBr6 Film.

    PubMed

    Wu, Cuncun; Zhang, Qiaohui; Liu, Yang; Luo, Wei; Guo, Xuan; Huang, Ziru; Ting, Hungkit; Sun, Weihai; Zhong, Xinrui; Wei, Shiyuan; Wang, Shufeng; Chen, Zhijian; Xiao, Lixin

    2018-03-01

    Recently, lead-free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently no solar cell based on these double perovskites has been reported, due to the challenge in film processing. Herein, a first lead-free double perovskite planar heterojunction solar cell with a high quality Cs 2 AgBiBr 6 film, fabricated by low-pressure assisted solution processing under ambient conditions, is reported. The device presents a best power conversion efficiency of 1.44%. The preliminary efficiency and the high stability under ambient condition without encapsulation, together with the high film quality with simple processing, demonstrate promise for lead-free perovskite solar cells.

  2. Generalized trends in the formation energies of perovskite oxides.

    PubMed

    Zeng, ZhenHua; Calle-Vallejo, Federico; Mogensen, Mogens B; Rossmeisl, Jan

    2013-05-28

    Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site usually have quite different but ordered formation energies. On the other hand, for a given A-site cation, (III) the formation energies of perovskites vary linearly with respect to the atomic number of the elements at the B site within the same period of the periodic table, and the slopes depend systematically on the oxidation state of the A-site cation; and (IV) the trends in formation energies of perovskites with elements from different periods at the B site depend on the oxidation state of A-site cations. Since the energetics of perovskites is shown to be the superposition of the individual contributions of their constituent oxides, the trends can be rationalized in terms of A-O and B-O interactions in the ionic crystal. These findings reveal the existence of general systematic trends in the formation energies of perovskites and provide further insight into the role of ion-ion interactions in the properties of ternary compounds.

  3. A Family of A-Site Cation-Deficient Double-Perovskite-Related Iridates: Ln9Sr2Ir4O24 (Ln = La, Pr, Nd, Sm).

    PubMed

    Ferreira, Timothy; Smith, Mark D; Zur Loye, Hans-Conrad

    2018-06-21

    The compositions of the general formula Ln 11- x Sr x Ir 4 O 24 (Ln = La, Pr, Nd, Sm; 1.37 ≥ x ≥ 2) belonging to a family of A-site cation-deficient double-perovskite-related oxide iridates were grown as highly faceted single crystals from a molten strontium chloride flux. Their structures were determined by single-crystal X-ray diffraction. On the basis of the single-crystal results, additional compositions, Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm), were prepared as polycrystalline powders via solid-state reactions and structurally characterized by Rietveld refinement. The compositions Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm) contain Ir(V) and Ir(IV) in a 1:3 ratio with an average iridium oxidation state of 4.25. The single-crystal compositions La 9.15 Sr 1.85 Ir 4 O 24 and Pr 9.63 Sr 1.37 Ir 4 O 24 contain relatively less Ir(V), with the average iridium oxidation states being 4.21 and 4.09, respectively. The magnetic properties of Ln 9 Sr 2 Ir 4 O 24 (Ln = La, Pr, Nd, Sm) were measured, and complex magnetic behavior was observed in all cases at temperatures below 30 K.

  4. Charge storage in oxygen deficient phases of TiO2: defect Physics without defects.

    PubMed

    Padilha, A C M; Raebiger, H; Rocha, A R; Dalpian, G M

    2016-07-01

    Defects in semiconductors can exhibit multiple charge states, which can be used for charge storage applications. Here we consider such charge storage in a series of oxygen deficient phases of TiO2, known as Magnéli phases. These Magnéli phases (TinO2n-1) present well-defined crystalline structures, i.e., their deviation from stoichiometry is accommodated by changes in space group as opposed to point defects. We show that these phases exhibit intermediate bands with an electronic quadruple donor transitions akin to interstitial Ti defect levels in rutile TiO2. Thus, the Magnéli phases behave as if they contained a very large pseudo-defect density: ½ per formula unit TinO2n-1. Depending on the Fermi Energy the whole material will become charged. These crystals are natural charge storage materials with a storage capacity that rivals the best known supercapacitors.

  5. Crystal Engineering for Low Defect Density and High Efficiency Hybrid Chemical Vapor Deposition Grown Perovskite Solar Cells.

    PubMed

    Ng, Annie; Ren, Zhiwei; Shen, Qian; Cheung, Sin Hang; Gokkaya, Huseyin Cem; So, Shu Kong; Djurišić, Aleksandra B; Wan, Yangyang; Wu, Xiaojun; Surya, Charles

    2016-12-07

    Synthesis of high quality perovskite absorber is a key factor in determining the performance of the solar cells. We demonstrate that hybrid chemical vapor deposition (HCVD) growth technique can provide high level of versatility and repeatability to ensure the optimal conditions for the growth of the perovskite films as well as potential for batch processing. It is found that the growth ambient and degree of crystallization of CH 3 NH 3 PbI 3 (MAPI) have strong impact on the defect density of MAPI. We demonstrate that HCVD process with slow postdeposition cooling rate can significantly reduce the density of shallow and deep traps in the MAPI due to enhanced material crystallization, while a mixed O 2 /N 2 carrier gas is effective in passivating both shallow and deep traps. By careful control of the perovskite growth process, a champion device with power conversion efficiency of 17.6% is achieved. Our work complements the existing theoretical studies on different types of trap states in MAPI and fills the gap on the theoretical analysis of the interaction between deep levels and oxygen. The experimental results are consistent with the theoretical predictions.

  6. An isopropanol-assisted fabrication strategy of pinhole-free perovskite films in air for efficient and stable planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Ren, Ziqiu; Zhu, Menghua; Li, Xin; Dong, Cunku

    2017-09-01

    As a promising photovoltaic device, perovskite solar cells have attracted numerous attention in recent years, where forming a compact and pinhole-free perovskite film in air is of great importance. Herein, we evaluate highly efficient and air stable planar perovskite solar cells in air (relative humidity over 50%) with the modified two-step sequential deposition method by adjusting the CH3NH3I (MAI) concentrations and regulating the crystallization process of the perovskite film. The optimum MAI concentration is 60 mg mL-1 in isopropanol. With a planar structure of FTO/TiO2/MAPbI3/spiro-OMeTAD/Au, the efficient devices composed of compact and pinhole-free perovskite films are constructed in air, achieving a high efficiency of up to 15.10% and maintaining over 80% after 20 days storing without any encapsulation in air. With a facile fabrication process and high photovoltaic performance, this work represents a promising method for fabricating low-cost, highly efficient and stable photovoltaic device.

  7. Universal two-dimensional characteristics in perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Sato, Nobuya; Akashi, Ryosuke; Tsuneyuki, Shinji

    2017-07-01

    A series of unsynthesized perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs) are investigated by the density functional calculations. These oxyhydrides are stable in the sense of the formation energies for some possible synthesis reactions. They are crystallized into quite similar crystal structures with the long c-axis, and the corner-sharing TiO4H2 octahedra of the ideal perovskite-type structure are deformed into the 5-fold coordinated titanium atoms with the OH plane and the apical oxygen atoms. All of these oxyhydrides exhibit two-dimensional electronic states at the valence band maximum characterized by the in-plane oxygen 2p and the hydrogen 1s orbitals. While the c-axis becomes short as the ionic radius of the A atom becomes small and the two-dimensional characteristics are weakened, the electronic state at the valence band maximum is still characterized as the O-H in-plane state. Additionally, the Born effective charge tensors, spontaneous electric polarizations, dielectric tensors, and piezoelectric tensors are evaluated. It is found that the spontaneous electric polarizations of these oxyhydrides are much larger than that of tetragonal BaTiO3.

  8. Semitransparent Fully Air Processed Perovskite Solar Cells.

    PubMed

    Bu, Lingling; Liu, Zonghao; Zhang, Meng; Li, Wenhui; Zhu, Aili; Cai, Fensha; Zhao, Zhixin; Zhou, Yinhua

    2015-08-19

    Semitransparent solar cells are highly attractive for application as power-generating windows. In this work, we present semitransparent perovskite solar cells that employ conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) film as the transparent counter electrode. The PSS electrode is prepared by transfer lamination technique using plastic wrap as the transfer medium. The use of the transfer lamination technique avoids the damage of the CH3NH3PbI3 perovskite film by direct contact of PSS aqueous solution. The semitransparent perovskite solar cells yield a power conversion efficiency of 10.1% at an area of about 0.06 cm(2) and 2.9% at an area of 1 cm(2). The device structure and the fabrication technique provide a facile way to produce semitransparent perovskite solar cells.

  9. Highly efficient light management for perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells.

  10. Highly efficient light management for perovskite solar cells.

    PubMed

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-06

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells.

  11. Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites

    NASA Astrophysics Data System (ADS)

    Xiao, Zhengguo; Kerner, Ross A.; Zhao, Lianfeng; Tran, Nhu L.; Lee, Kyung Min; Koh, Tae-Wook; Scholes, Gregory D.; Rand, Barry P.

    2017-01-01

    Organic-inorganic hybrid perovskite materials are emerging as highly attractive semiconductors for use in optoelectronics. In addition to their use in photovoltaics, perovskites are promising for realizing light-emitting diodes (LEDs) due to their high colour purity, low non-radiative recombination rates and tunable bandgap. Here, we report highly efficient perovskite LEDs enabled through the formation of self-assembled, nanometre-sized crystallites. Large-group ammonium halides added to the perovskite precursor solution act as a surfactant that dramatically constrains the growth of 3D perovskite grains during film forming, producing crystallites with dimensions as small as 10 nm and film roughness of less than 1 nm. Coating these nanometre-sized perovskite grains with longer-chain organic cations yields highly efficient emitters, resulting in LEDs that operate with external quantum efficiencies of 10.4% for the methylammonium lead iodide system and 9.3% for the methylammonium lead bromide system, with significantly improved shelf and operational stability.

  12. Perovskite Solar Cell Stability Workshop: Quick Look Report

    DTIC Science & Technology

    2016-08-12

    Commercialization of Perovskite PV – Markets, Concerns, Opportunities” by Dirk Weiss, First Solar , USA j. “Expectations for PV Product Testing Today” by Sarah...Perovskite Solar Cell Stability Workshop Quick-Look Report Held by the Office of Naval Research at University...Workshop Summary, 11-12 Aug 2016 4. TITLE AND SUBTITLE Perovskite Solar Cell Stability Workshop: Quick-Look Report 5. FUNDING NUMBERS 6. AUTHOR(S

  13. Benzoyl Peroxide as an Efficient Dopant for Spiro-OMeTAD in Perovskite Solar Cells.

    PubMed

    Liu, Qiuju; Fan, Lisheng; Zhang, Qin'e; Zhou, An'an; Wang, Baozeng; Bai, Hua; Tian, Qingyong; Fan, Bin; Zhang, Tongyi

    2017-08-10

    Although organic small molecule spiro-OMeTAD is widely used as a hole-transport material in perovskite solar cells, its limited electric conductivity poses a bottleneck in the efficiency improvement of perovskite solar cells. Here, a low-cost and easy-fabrication technique is developed to enhance the conductivity and hole-extraction ability of spiro-OMeTAD by doping it with commercially available benzoyl peroxide (BPO). The experimental results show that the conductivity increases several orders of magnitude, from 6.2×10 -6  S cm -1 for the pristine spiro-OMeTAD to 1.1×10 -3  S cm -1 at 5 % BPO doping and to 2.4×10 -2  S cm -1 at 15 % BPO doping, which considerably outperform the conductivity of 4.62×10 -4  S cm -1 for the currently used oxygen-doped spiro-OMeTAD. The fluorescence spectra suggest that the BPO-doped spiro-OMeTAD-OMeTAD layer is able to efficiently extract holes from CH 3 NH 3 PbI 3 and thus greatly enhances the charge transfer. The BPO-doped spiro-OMeTAD is used in the fabrication of perovskite solar cells, which exhibit enhancement in the power conversion efficiency. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Spatially Resolved Imaging on Photocarrier Generations and Band Alignments at Perovskite/PbI2 Heterointerfaces of Perovskite Solar Cells by Light-Modulated Scanning Tunneling Microscopy.

    PubMed

    Shih, Min-Chuan; Li, Shao-Sian; Hsieh, Cheng-Hua; Wang, Ying-Chiao; Yang, Hung-Duen; Chiu, Ya-Ping; Chang, Chia-Seng; Chen, Chun-Wei

    2017-02-08

    The presence of the PbI 2 passivation layers at perovskite crystal grains has been found to considerably affect the charge carrier transport behaviors and device performance of perovskite solar cells. This work demonstrates the application of a novel light-modulated scanning tunneling microscopy (LM-STM) technique to reveal the interfacial electronic structures at the heterointerfaces between CH 3 NH 3 PbI 3 perovskite crystals and PbI 2 passivation layers of individual perovskite grains under light illumination. Most importantly, this technique enabled the first observation of spatially resolved mapping images of photoinduced interfacial band bending of valence bands and conduction bands and the photogenerated electron and hole carriers at the heterointerfaces of perovskite crystal grains. By systematically exploring the interfacial electronic structures of individual perovskite grains, enhanced charge separation and reduced back recombination were observed when an optimal design of interfacial PbI 2 passivation layers consisting of a thickness less than 20 nm at perovskite crystal grains was applied.

  15. Hybrid Perovskites: Prospects for Concentrator Solar Cells.

    PubMed

    Lin, Qianqian; Wang, Zhiping; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

    2018-04-01

    Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley-Queisser limit stipulated for a single-junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge-carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy-conversion efficiencies under solar concentration, where they are able to exceed the Shockley-Queisser limit and exhibit strongly elevated open-circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications.

  16. Highly efficient light management for perovskite solar cells

    PubMed Central

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells. PMID:26733112

  17. Vapor Grown Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Abdussamad Abbas, Hisham

    Perovskite solar cells has been the fastest growing solar cell material till date with verified efficiencies of over 22%. Most groups in the world focuses their research on solution based devices that has residual solvent in the material bulk. This work focuses extensively on the fabrication and properties of vapor based perovskite devices that is devoid of solvents. The initial part of my work focuses on the detailed fabrication of high efficiency consistent sequential vapor NIP devices made using P3HT as P-type Type II heterojunction. The sequential vapor devices experiences device anomalies like voltage evolution and IV hysteresis owing to charge trapping in TiO2. Hence, sequential PIN devices were fabricated using doped Type-II heterojunctions that had no device anomalies. The sequential PIN devices has processing restriction, as organic Type-II heterojunction materials cannot withstand high processing temperature, hence limiting device efficiency. Thereby bringing the need of co-evaporation for fabricating high efficiency consistent PIN devices, the approach has no-restriction on substrates and offers stoichiometric control. A comprehensive description of the fabrication, Co-evaporator setup and how to build it is described. The results of Co-evaporated devices clearly show that grain size, stoichiometry and doped transport layers are all critical for eliminating device anomalies and in fabricating high efficiency devices. Finally, Formamidinium based perovskite were fabricated using sequential approach. A thermal degradation study was conducted on Methyl Ammonium Vs. Formamidinium based perovskite films, Formamidinium based perovskites were found to be more stable. Lastly, inorganic films such as CdS and Nickel oxide were developed in this work.

  18. Hole-Transport Materials for Perovskite Solar Cells.

    PubMed

    Calió, Laura; Kazim, Samrana; Grätzel, Michael; Ahmad, Shahzada

    2016-11-14

    The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lu, Fengqi; Kuang, Xiaojun, E-mail: kuangxj@glut.edu.cn

    The structure of 18-layer shifted B-site deficient hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} compound has been re-examined by neutron powder diffraction. Structural analysis reveals that La{sub 6}MgTi{sub 4}O{sub 18} compound adopts a 18R octahedral-tilted structure with LaO{sub 3} layer stacking sequence of (hhcccc){sub 3} in space group R{sup {sup -}}3, in contrast with the previously proposed R3m. La{sub 6}MgTi{sub 4}O{sub 18} demonstrates partially ordered Mg cation distribution with a preference on the central octahedral sites over the outer octahedral sites in the cubic perovskite blocks isolated by the single vacant octahedral layers between the two consecutive hexagonal layers. The instabilitymore » of the La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic substrate at high temperature and its dependencies of cell parameters and permittivity were characterized as well. - Graphical abstract: 18-layer shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} adopts octahedral-tilted structure in R{sup {sup -}}3 and demonstrates partially ordered Mg distribution in the cubic perovskite blocks isolated by the vacant octahedral layers. - Highlights: • Neutron diffraction reveals an octahedra-tilted structure in R{sup {sup -}}3 for La{sub 6}MgTi{sub 4}O{sub 18}. • Mg/Ti distribution in La{sub 6}MgTi{sub 4}O{sub 18} is partially ordered in the perovskite blocks. • Instability of La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic at high temperature is demonstrated.« less

  20. Oxygen stoichiometry: A key parameter to tune structural phase diagram of La{sub 0.2}Sr{sub 0.8}MnO{sub 3-δ}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shahee, Aga, E-mail: agashahee@gmail.com; Lalla, N. P.

    2015-06-24

    Low temperature x-ray powder diffraction studies, in conjunction with transmission electron microscopy on stoichiometric (δ = 0.01) and oxygen deficient (δ =0.12) samples of La{sub 0.2}Sr{sub 0.8}MnO{sub 3-δ} manganites have been carried out. These studies revealed that oxygen stoichiometry plays a key role in controlling ground state of electron doped manganites. It is observed that the La{sub 0.2}Sr{sub 0.8}MnO{sub 2.99} undergoes a first order phase transition from cubic (Pm-3m) to JT-distorted twin tetragonal (I4/mcm) phase associated with C-type antiferromagnetic ordering at ∼260K. This JT-distortion induced cubic to tetragonal phase transition get totally suppressed in La{sub 0.2}Sr{sub 0.8}MnO{sub 2.88}. The basicmore » perovskite lattice of the off-stoichiometric La{sub 0.2}Sr{sub 0.8}MnO{sub 2.88} remains cubic down to 80K but undergoes a well-developed charge-ordering transition with 9x9 modulations at ∼260K.« less

  1. Dynamic surface self-reconstruction is the key of highly active perovskite nano-electrocatalysts for water splitting

    NASA Astrophysics Data System (ADS)

    Fabbri, Emiliana; Nachtegaal, Maarten; Binninger, Tobias; Cheng, Xi; Kim, Bae-Jung; Durst, Julien; Bozza, Francesco; Graule, Thomas; Schäublin, Robin; Wiles, Luke; Pertoso, Morgan; Danilovic, Nemanja; Ayers, Katherine E.; Schmidt, Thomas J.

    2017-09-01

    The growing need to store increasing amounts of renewable energy has recently triggered substantial R&D efforts towards efficient and stable water electrolysis technologies. The oxygen evolution reaction (OER) occurring at the electrolyser anode is central to the development of a clean, reliable and emission-free hydrogen economy. The development of robust and highly active anode materials for OER is therefore a great challenge and has been the main focus of research. Among potential candidates, perovskites have emerged as promising OER electrocatalysts. In this study, by combining a scalable cutting-edge synthesis method with time-resolved X-ray absorption spectroscopy measurements, we were able to capture the dynamic local electronic and geometric structure during realistic operando conditions for highly active OER perovskite nanocatalysts. Ba0.5Sr0.5Co0.8Fe0.2O3-δ as nano-powder displays unique features that allow a dynamic self-reconstruction of the material’s surface during OER, that is, the growth of a self-assembled metal oxy(hydroxide) active layer. Therefore, besides showing outstanding performance at both the laboratory and industrial scale, we provide a fundamental understanding of the operando OER mechanism for highly active perovskite catalysts. This understanding significantly differs from design principles based on ex situ characterization techniques.

  2. Perovskites-Based Solar Cells: A Review of Recent Progress, Materials and Processing Methods

    PubMed Central

    Shi, Zhengqi; Jayatissa, Ahalapitiya H.

    2018-01-01

    With the rapid increase of efficiency up to 22.1% during the past few years, hybrid organic-inorganic metal halide perovskite solar cells (PSCs) have become a research “hot spot” for many solar cell researchers. The perovskite materials show various advantages such as long carrier diffusion lengths, widely-tunable band gap with great light absorption potential. The low-cost fabrication techniques together with the high efficiency makes PSCs comparable with Si-based solar cells. But the drawbacks such as device instability, J-V hysteresis and lead toxicity reduce the further improvement and the future commercialization of PSCs. This review begins with the discussion of crystal and electronic structures of perovskite based on recent research findings. An evolution of PSCs is also analyzed with a greater detail of each component, device structures, major device fabrication methods and the performance of PSCs acquired by each method. The following part of this review is the discussion of major barriers on the pathway for the commercialization of PSCs. The effects of crystal structure, fabrication temperature, moisture, oxygen and UV towards the stability of PSCs are discussed. The stability of other components in the PSCs are also discussed. The lead toxicity and updated research progress on lead replacement are reviewed to understand the sustainability issues of PSCs. The origin of J-V hysteresis is also briefly discussed. Finally, this review provides a roadmap on the current needs and future research directions to address the main issues of PSCs. PMID:29734667

  3. Oxygen sensing and signaling.

    PubMed

    van Dongen, Joost T; Licausi, Francesco

    2015-01-01

    Oxygen is an indispensable substrate for many biochemical reactions in plants, including energy metabolism (respiration). Despite its importance, plants lack an active transport mechanism to distribute oxygen to all cells. Therefore, steep oxygen gradients occur within most plant tissues, which can be exacerbated by environmental perturbations that further reduce oxygen availability. Plants possess various responses to cope with spatial and temporal variations in oxygen availability, many of which involve metabolic adaptations to deal with energy crises induced by low oxygen. Responses are induced gradually when oxygen concentrations decrease and are rapidly reversed upon reoxygenation. A direct effect of the oxygen level can be observed in the stability, and thus activity, of various transcription factors that control the expression of hypoxia-induced genes. Additional signaling pathways are activated by the impact of oxygen deficiency on mitochondrial and chloroplast functioning. Here, we describe the molecular components of the oxygen-sensing pathway.

  4. Metal-halide perovskites for photovoltaic and light-emitting devices.

    PubMed

    Stranks, Samuel D; Snaith, Henry J

    2015-05-01

    Metal-halide perovskites are crystalline materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technology to commercialization.

  5. Structure-property relationships: Synthesis and characterization of Perovskite-related transition metal oxides

    NASA Astrophysics Data System (ADS)

    Whaley, Louis

    The fundamental structural component of perovskite-related phases is the octahedrally coordinated transition metal ion, symbolized as BO6 . Corner-sharing networks of BO6 octahedra are present in perovskites and related Ruddlesden-Popper Phases, ABO3 and AO(ABO 3)n, respectively. Face-sharing octahedra arranged into columns are characteristic of hexagonal, perovskite-related phases, and the relationship will be described in detail in Chapter 1. Edge sharing octahedra are characteristic of Keggin- and Lindquist-type polyoxometallates, which at first glance, seem unconnected from perovskites. However, Chapter 1 will show the deep connections among all of the phases mentioned above, by starting with perovskite phases. Temperature- and field-dependent, magnetic and electronic transitions are linked to the structure by overlap of metal d-orbitals with oxygen 2p orbitals, and (in special cases) direct d-d overlap. A mixed-transition metal oxide with two or more type of B ions provides an environment in which dissimilar B-ion orbitals can interact via exchange of charge carriers (hole or electron transport). The general goal in choosing two B ions is to provide an opportunity for the large combined magnetic moment and a low barrier to hopping of charge carriers, achieved by pairing a 3d-ion having 3 to 5 unpaired d-electrons, with a 4d or 5d transition metal ion, having 1 or 2 unpaired electrons, such as Fe(III) and Mo(V), which have compatible reduction potentials (i.e., they can co-exist in the same oxide, and exchange takes place with a low barrier). This research includes the following systems: an n = 2 Ruddlesden-Popper (RP) phase, Sr3Fe5/4Mo3/4O6.9, containing 3-7% Sr2FeMoO6, as intergrowths (not separate crystal grains, by high-resolution transmission electron microscopy), and G-type antiferromagnetism below 150°K and a "partial spin-reorientation transition" by powder neutron diffraction (PND), not previously reported for n = 2 RP phases in the Sr-Fe-Mo-O system

  6. Fast Postmoisture Treatment of Luminescent Perovskite Films for Efficient Light-Emitting Diodes.

    PubMed

    Wang, Haoran; Li, Xiaomin; Yuan, Mingjian; Yang, Xuyong

    2018-04-01

    Despite the recent advances in the performance of perovskite light-emitting diodes (PeLEDs), the effects of water on the perovskite emissive layer and its electroluminescence are still unclear, even though it has been previously demonstrated that moisture has a significant impact on the quality of perovskite films in the fabrication process of perovskite solar cells and is a prerequisite for obtaining high-performance PeLEDs. Here, the effects of postmoisture on the luminescent CH 3 NH 3 PbBr 3 (MAPbBr 3 ) perovskite films are systematically investigated. It is found that postmoisture treatment can efficiently control the morphology and growth of perovskite films and only a fast moisture exposure at a 60% high relative humidity results in significantly improved crystallinity, carrier lifetime, and photoluminescence quantum yield of perovskite films. With the optimized moisture-treated perovskite films, a high-performance PeLED is fabricated, exhibiting a maximum current efficiency of 20.4 cd A -1 , which is an almost 20-fold enhancement when compared with perovskite films without moisture treatment. The results provide valuable insights into the moisture-assisted growth of luminescent perovskite films and will aid in the development of high-performance perovskite light-emitting devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic-Inorganic Perovskites.

    PubMed

    Sutter-Fella, Carolin M; Ngo, Quynh P; Cefarin, Nicola; Gardner, Kira L; Tamura, Nobumichi; Stan, Camelia V; Drisdell, Walter S; Javey, Ali; Toma, Francesca M; Sharp, Ian D

    2018-06-13

    Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long-term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. Here, we shed light on photoinduced halide demixing using in situ photoluminescence spectroscopy and in situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2 ) 2 CsPb-halide (FACsPb-) and CH 3 NH 3 Pb-halide (MAPb-) perovskites upon illumination, thereby providing insights into why FACs-perovskites are less prone to halide demixing than MA-perovskites. We find that halide demixing occurs in both materials. However, the I-rich domains formed during demixing accumulate strain in FACsPb-perovskites but readily relax in MA-perovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPb-halides. In addition, we find that while halide demixing leads to a quenching of the high-energy photoluminescence emission from MA-perovskites, the emission is enhanced from FACs-perovskites. This behavior points to a reduction of nonradiative recombination centers in FACs-perovskites arising from the demixing process and buildup of strain. FACsPb-halide perovskites exhibit excellent intrinsic material properties with photoluminescence quantum yields that are comparable to MA-perovskites. Because improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells.

  8. Electrodeposition of organic-inorganic tri-halide perovskites solar cell

    NASA Astrophysics Data System (ADS)

    Charles, U. A.; Ibrahim, M. A.; Teridi, M. A. M.

    2018-02-01

    Perovskite (CH3NH3PbI3) semiconductor materials are promising high-performance light energy absorber for solar cell application. However, the power conversion efficiency of perovskite solar cell is severely affected by the surface quality of the deposited thin film. Spin coating is a low-cost and widely used deposition technique for perovskite solar cell. Notably, film deposited by spin coating evolves surface hydroxide and defeats from uncontrolled precipitation and inter-diffusion reaction. Alternatively, vapor deposition (VD) method produces uniform thin film but requires precise control of complex thermodynamic parameters which makes the technique unsuitable for large scale production. Most deposition techniques for perovskite require tedious surface optimization to improve the surface quality of deposits. Optimization of perovskite surface is necessary to significantly improve device structure and electrical output. In this review, electrodeposition of perovskite solar cell is demonstrated as a scalable and reproducible technique to fabricate uniform and smooth thin film surface that circumvents the need for high vacuum environment. Electrodeposition is achieved at low temperatures, supports precise control and optimization of deposits for efficient charge transfer.

  9. Chitosan-Assisted Crystallization and Film Forming of Perovskite Crystals through Biomineralization.

    PubMed

    Yang, Yang; Sun, Chen; Yip, Hin-Lap; Sun, Runcang; Wang, Xiaohui

    2016-03-18

    Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Oxygen Transport Membrane Reactors for Oxy-Fuel Combustion and Carbon Capture Purposes

    NASA Astrophysics Data System (ADS)

    Falkenstein-Smith, Ryan L.

    This thesis investigates oxygen transport membrane reactors (OTMs) for the application of oxy-fuel combustion. This is done by evaluating the material properties and oxygen permeability of different OTM compositions subjected to a variety of operating conditions. The scope of this work consists of three components: (1) evaluate the oxygen permeation capabilities of perovskite-type materials for the application of oxy-fuel combustion; (2) determine the effects of dual-phase membrane compositions on the oxygen permeation performance and membrane characteristics; and (3) develop a new method for estimating the oxygen permeation performance of OTMs utilized for the application of oxy-fuel combustion. SrSc0.1Co0.9O3-delta (SSC) is selected as the primary perovskite-type material used in this research due to its reported high ionic and electronic conductive properties and chemical stability. SSC's oxygen ion diffusivity is investigated using a conductivity relaxation technique and thermogravimetric analysis. Material properties such as chemical structure, morphology, and ionic and electronic conductivity are examined by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and conductivity testing using a four-probe method, respectively. Oxygen permeation tests study the oxygen permeability OTMs under modified membrane temperatures, sweeping gas flow rates, sweeping gas compositions, membrane configurations, and membrane compositions. When utilizing a pure CO2 sweeping gas, the membrane composition was modified with the addition of Sm0.2Ce0.8O1.9-delta (SDC) at varying wt.% to improve the membranes mechanical stability. A newly developed method to evaluate the oxygen permeation performance of OTMs is also presented by fitting OTM's oxygen permeability to the methane fraction in the sweeping gas composition. The fitted data is used to estimate the overall performance and size of OTMs utilized for the application of oxy-fuel combustion. The findings from this

  11. Spin-polarized two-dimensional t2 g electron gas: Ab initio study of EuO interface with oxygen-deficient SrTi O3

    NASA Astrophysics Data System (ADS)

    Gao, Lingyuan; Demkov, Alexander A.

    2018-03-01

    Using first-principles calculations we predict the existence of a spin-polarized two-dimensional electron gas (2DEG) at the interface of a ferromagnetic insulator EuO and oxygen-deficient SrTi O3 . The carriers are generated by oxygen vacancies in SrTi O3 near the interface and have predominantly Ti-t2 g orbital character. At the interface, the split-off dx y-derived conduction band of SrTi O3 is fully spin-polarized and the in-gap vacancy-induced state, found below the conduction-band edge, is aligned ferromagnetically with EuO. The calculations suggest a possible mechanism for generating spin-polarized 2DEG for spintronic applications.

  12. Universal Approach toward Hysteresis-Free Perovskite Solar Cell via Defect Engineering.

    PubMed

    Son, Dae-Yong; Kim, Seul-Gi; Seo, Ja-Young; Lee, Seon-Hee; Shin, Hyunjung; Lee, Donghwa; Park, Nam-Gyu

    2018-01-31

    Organic-inorganic halide perovskite is believed to be a potential candidate for high efficiency solar cells because power conversion efficiency (PCE) was certified to be more than 22%. Nevertheless, mismatch of PCE due to current density (J)-voltage (V) hysteresis in perovskite solar cells is an obstacle to overcome. There has been much lively debate on the origin of J-V hysteresis; however, effective methodology to solve the hysteric problem has not been developed. Here we report a universal approach for hysteresis-free perovskite solar cells via defect engineering. A severe hysteresis observed from the normal mesoscopic structure employing TiO 2 and spiro-MeOTAD is almost removed or does not exist upon doping the pure perovskites, CH 3 NH 3 PbI 3 and HC(NH 2 ) 2 PbI 3 , and the mixed cation/anion perovskites, FA 0.85 MA 0.15 PbI 2.55 Br 0.45 and FA 0.85 MA 0.1 Cs 0.05 PbI 2.7 Br 0.3 , with potassium iodide. Substantial reductions in low-frequency capacitance and bulk trap density are measured from the KI-doped perovskite, which is indicative of trap-hysteresis correlation. A series of experiments with alkali metal iodides of LiI, NaI, KI, RbI and CsI reveals that potassium ion is the right element for hysteresis-free perovskite. Theoretical studies suggest that the atomistic origin of the hysteresis of perovskite solar cells is not the migration of iodide vacancy but results from the formation of iodide Frenkel defect. Potassium ion is able to prevent the formation of Frenkel defect since K + energetically prefers the interstitial site. A complete removal of hysteresis is more pronounced at mixed perovskite system as compared to pure perovskites, which is explained by lower formation energy of K interstitial (-0.65 V for CH 3 NH 3 PbI 3 vs -1.17 V for mixed perovskite). The developed KI doping methodology is universally adapted for hysteresis-free perovskite regardless of perovskite composition and device structure.

  13. A DFT+U study of A-site and B-site substitution in BaFeO3-δ.

    PubMed

    Baiyee, Zarah Medina; Chen, Chi; Ciucci, Francesco

    2015-09-28

    BaFeO3-δ (BFO)-based perovskites have emerged as cheap and effective oxygen electrocatalysts for oxygen reduction reaction at high temperatures. The BFO cubic phase facilitates a high oxygen deficiency and is commonly stabilised by partial substitution. Understanding the electronic mechanisms of substitution and oxygen deficiency is key to rational material design, and can be realised through DFT analysis. In this work an in-depth first principle DFT+U study is undertaken to determine site distinctive characteristics for 12.5%, Y, La and Ce substitutions in BFO. In particular, it is shown that B-site doped structures exhibit a lower energy cost for oxygen vacancy formation relative to A site doping and pristine BFO. This is attributed to the stabilisation of holes in the oxygen sub-lattice and increased covalency of the Fe-O bonds of the FeO6 octahedra in B-site-substituted BFO. Charge analysis shows that A-site substitution amounts to donor doping and consequently impedes the accommodation of other donors (i.e. oxygen vacancies). However, A-site substitution may also exhibit a higher electronic conductivity due to less lattice distortion for oxygen deficiency compared to B-site doped structures. Furthermore, analysis of the local structural effects provides physical insight into stoichiometric expansions observed for this material.

  14. Mass-specific respiration of mesozooplankton and its role in the maintenance of an oxygen-deficient ecological barrier (BEDOX) in the upwelling zone off Chile upon presence of a shallow oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Donoso, Katty; Escribano, Ruben

    2014-01-01

    A shallow oxygen minimum zone (OMZ) in the coastal upwelling zone off Chile may vertically confine most zooplankton to a narrow (< 50 m) upper layer. From laboratory experiments, we estimated oxygen consumption of the mesozooplankton community obtained in Bay of Mejillones, northern Chile (23°S) in May 2010, December 2010 and August 2011. Mass-specific respiration rates were in the range of 8.2-24.5 μmol O2 mg dry mass- 1 day- 1, at an average temperature of 12 °C. Estimates of the mesozooplankton biomass in the water column indicated that its aerobic respiration may remove daily a maximum of about 20% of oxygen available at the base of the oxycline. Since previous work indicates that zooplankton aggregate near the base of the oxycline, the impact of aerobic respiration on oxygen content might be even stronger at this depth. Mesozooplankton respiration, along with community respiration by microorganisms near the base of the oxycline and a strongly stratified condition (limiting vertical flux of O2), are suggested as being critical factors causing and maintaining a persistent subsurface oxygen-deficient ecological barrier (BEDOX) in the upwelling zone. This BEDOX layer can have a major role in affecting and regulating zooplankton distribution and their dynamics in the highly productive coastal upwelling zone of the Humboldt Current System.

  15. Ultrasmooth Perovskite Film via Mixed Anti-Solvent Strategy with Improved Efficiency.

    PubMed

    Yu, Yu; Yang, Songwang; Lei, Lei; Cao, Qipeng; Shao, Jun; Zhang, Sheng; Liu, Yan

    2017-02-01

    Most antisolvents employed in previous research were miscible with perovskite precursor solution. They always led to fast formation of perovskite even if the intermediate stage existed, which was not beneficial to obtain high quality perovskite films and made the formation process less controllable. In this work, a novel ethyl ether/n-hexane mixed antisolvent (MAS) was used to achieve high nucleation density and slow down the formation process of perovskite, producing films with improved orientation of grains and ultrasmooth surfaces. These high quality films exhibited efficient charge transport at the interface of perovskite/hole transport material and perovskite solar cells based on these films showed greatly improved performance with the best power conversion efficiency of 17.08%. This work also proposed a selection principle of MAS and showed that solvent engineering by designing the mixed antisolvent system can lead to the fabrication of high-performance perovskite solar cells.

  16. Planar Heterojunction Perovskite Solar Cells Incorporating Metal-Organic Framework Nanocrystals.

    PubMed

    Chang, Ting-Hsiang; Kung, Chung-Wei; Chen, Hsin-Wei; Huang, Tzu-Yen; Kao, Sheng-Yuan; Lu, Hsin-Che; Lee, Min-Han; Boopathi, Karunakara Moorthy; Chu, Chih-Wei; Ho, Kuo-Chuan

    2015-11-25

    Zr-based porphyrin metal-organic framework (MOF-525) nanocrystals with a crystal size of about 140 nm are synthesized and incorporated into perovskite solar cells. The morphology and crystallinity of the perovskite thin film are enhanced since the micropores of MOF-525 allow the crystallization of perovskite to occur inside; this observation results in a higher cell efficiency of the obtained MOF/perovskite solar cell. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Influence of oxygen vacancies on the magnetic and electrical properties of La1-xSrxMnO3-x/2 manganites

    NASA Astrophysics Data System (ADS)

    Trukhanov, S. V.; Lobanovski, L. S.; Bushinsky, M. V.; Khomchenko, V. A.; Pushkarev, N. V.; Troyanchuk, I. O.; Maignan, A.; Flahaut, D.; Szymczak, H.; Szymczak, R.

    2004-11-01

    The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} as well as anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} (0le x le 0.30) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the 0 le x le 0.125 are an O'-orthorhombic perovskites whereas in the 0.175 le x le 0.30 - a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses (0.175 < x le 0.30) and temperature of the magnetic moment freezing is 40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} system have been established by the magnetic measurements and compared with those for the stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.

  18. Hybrid Perovskites: Prospects for Concentrator Solar Cells

    PubMed Central

    Lin, Qianqian; Wang, Zhiping; Snaith, Henry J.; Johnston, Michael B.

    2018-01-01

    Abstract Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley–Queisser limit stipulated for a single‐junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge‐carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy‐conversion efficiencies under solar concentration, where they are able to exceed the Shockley–Queisser limit and exhibit strongly elevated open‐circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications. PMID:29721426

  19. Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

    DOE PAGES

    Sutter-Fella, Carolin M.; Ngo, Quynh P.; Cefarin, Nicola; ...

    2018-04-30

    Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long-term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. In this paper, we shed light on photoinduced halide demixing using in situ photoluminescence spectroscopy and in situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2) 2CsPb-halide (FACsPb-) and CH 3NH 3Pb-halide (MAPb-) perovskites upon illumination, thereby providing insights into why FACs-perovskites are less prone to halide demixing than MA-perovskites. We find that halide demixing occurs in both materials.more » However, the I-rich domains formed during demixing accumulate strain in FACsPb-perovskites but readily relax in MA-perovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPb-halides. In addition, we find that while halide demixing leads to a quenching of the high-energy photoluminescence emission from MA-perovskites, the emission is enhanced from FACs-perovskites. This behavior points to a reduction of nonradiative recombination centers in FACs-perovskites arising from the demixing process and buildup of strain. FACsPb-halide perovskites exhibit excellent intrinsic material properties with photoluminescence quantum yields that are comparable to MA-perovskites. Finally, because improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells.« less

  20. Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sutter-Fella, Carolin M.; Ngo, Quynh P.; Cefarin, Nicola

    Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long-term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. In this paper, we shed light on photoinduced halide demixing using in situ photoluminescence spectroscopy and in situ synchrotron X-ray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2) 2CsPb-halide (FACsPb-) and CH 3NH 3Pb-halide (MAPb-) perovskites upon illumination, thereby providing insights into why FACs-perovskites are less prone to halide demixing than MA-perovskites. We find that halide demixing occurs in both materials.more » However, the I-rich domains formed during demixing accumulate strain in FACsPb-perovskites but readily relax in MA-perovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPb-halides. In addition, we find that while halide demixing leads to a quenching of the high-energy photoluminescence emission from MA-perovskites, the emission is enhanced from FACs-perovskites. This behavior points to a reduction of nonradiative recombination centers in FACs-perovskites arising from the demixing process and buildup of strain. FACsPb-halide perovskites exhibit excellent intrinsic material properties with photoluminescence quantum yields that are comparable to MA-perovskites. Finally, because improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells.« less

  1. Rational Strategies for Efficient Perovskite Solar Cells.

    PubMed

    Seo, Jangwon; Noh, Jun Hong; Seok, Sang Il

    2016-03-15

    A long-standing dream in the large scale application of solar energy conversion is the fabrication of solar cells with high-efficiency and long-term stability at low cost. The realization of such practical goals depends on the architecture, process and key materials because solar cells are typically constructed from multilayer heterostructures of light harvesters, with electron and hole transporting layers as a major component. Recently, inorganic-organic hybrid lead halide perovskites have attracted significant attention as light absorbers for the fabrication of low-cost and high-efficiency solar cells via a solution process. This mainly stems from long-range ambipolar charge transport properties, low exciton binding energies, and suitable band gap tuning by managing the chemical composition. In our pioneering work, a new photovoltaic platform for efficient perovskite solar cells (PSCs) was proposed, which yielded a high power conversion efficiency (PCE) of 12%. The platform consisted of a pillared architecture of a three-dimensional nanocomposite of perovskites fully infiltrating mesoporous TiO2, resulting in the formation of continuous phases and perovskite domains overlaid with a polymeric hole conductor. Since then, the PCE of our PSCs has been rapidly increased from 3% to over 20% certified efficiency. The unprecedented increase in the PCE can be attributed to the effective integration of the advantageous attributes of the refined bicontinuous architecture, deposition process, and composition of perovskite materials. Specifically, the bicontinuous architectures used in the high efficiency comprise a layer of perovskite sandwiched between mesoporous metal-oxide layer, which is a very thinner than that of used in conventional dye-sensitized solar cells, and hole-conducting contact materials with a metal back contact. The mesoporous scaffold can affect the hysteresis under different scan direction in measurements of PSCs. The hysteresis also greatly depends on

  2. Phase transformation of Ca-perovskite in MORB at D" region

    NASA Astrophysics Data System (ADS)

    Nishitani, N.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.

    2012-12-01

    Seismological studies indicate the presence of seismic anomalies in the Earth's deep interior. To investigate the anomaly, the physical property of the major minerals in lower mantle such as MgSiO3-perovskite, MgSiO3 post-perovskite and MgO periclase were studied well. Other candidate, CaSiO3 perovskite (Ca-perovskite) exists in peridotitic mantle and basaltic oceanic crust (mid-ocean ridge basalt; MORB). Previous studies indicate the abundance of Ca-perovskite is up to ~9 vol.% in the pyrolite mantle and ~24 vol.% in the MORB oceanic crust. However, the pressure range of previous works are still not enough to understand the D" region. In this study, natural MORB was compressed in double sided laser heated DAC. Au was used as a pressure maker and a laser absorber. NaCl was used as the thermal insulator and pressure medium. The phase relation of Ca-perovskite in MORB was investigated from 36 to 156 GPa and 300 to 2600 K by the in situ X-ray diffraction measurements at SPring-8 (BL10XU). The transition of Ca-perovskite from a tetragonal structure to a cubic structure occurred at about 1800 K up to about 100 GPa and below 1500 K at pressures above 100 GPa. This suggests that the tetragonal-cubic transition of Ca-perovskite could occur in MORB, associating with Al2O3 contents. The present results suggest that the seismic anomaly at D" layer could be caused by the transition in Ca-perovskite.

  3. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapormore » results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 degrees C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 degrees C in +/-25 degrees C steps (150-200 degrees C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.« less

  4. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapormore » results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 °C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 °C in ±25 °C steps (150-200 °C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.« less

  5. Reconditioning perovskite films in vapor environments through repeated cation doping

    NASA Astrophysics Data System (ADS)

    Boonthum, Chirapa; Pinsuwan, Kusuma; Ponchai, Jitprabhat; Srikhirin, Toemsak; Kanjanaboos, Pongsakorn

    2018-06-01

    Perovskites have attracted considerable attention for application as high-efficiency photovoltaic devices owing to their low-cost and low-temperature fabrication. A good surface and high crystallinity are necessary for high-performance devices. We examine the negative effects of chemical ambiences on the perovskite crystal formation and morphology. The repeated cation doping (RCD) technique was developed to remedy these issues by gradually dropping methylammonium ions on top of about-to-form perovskite surfaces to cause recrystallization. RCD promotes pinhole-free, compact, and polygonal-like surfaces under various vapor conditions. Furthermore, it enhances the electronic properties and crystallization. The benefits of RCD extend beyond perovskites under vapor ambiences, as it can improve regular and wasted perovskites.

  6. High annealing temperature induced rapid grain coarsening for efficient perovskite solar cells.

    PubMed

    Cao, Xiaobing; Zhi, Lili; Jia, Yi; Li, Yahui; Cui, Xian; Zhao, Ke; Ci, Lijie; Ding, Kongxian; Wei, Jinquan

    2018-08-15

    Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 °C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 °C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 °C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells. Copyright © 2018. Published by Elsevier Inc.

  7. Polarized emission from CsPbX3 perovskite quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Wu, Dan; Dong, Di; Chen, Wei; Hao, Junjie; Qin, Jing; Xu, Bing; Wang, Kai; Sun, Xiaowei

    2016-06-01

    Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption.Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01915c

  8. Novel growth techniques for the deposition of high-quality perovskite thin films

    NASA Astrophysics Data System (ADS)

    Ng, Annie; Ren, Zhiwei; Li, Gang; Djurišić, Aleksandra B.; Surya, Charles

    2018-02-01

    We present investigations on the growth of high quality CH3NH3PbI3 (MAPI) thin films using both vapor and solution techniques. Recent work on perovskite film growth indicates critical dependencies of the film quality on the nucleation and crystallization steps requiring: i.) uniform distribution of nucleation sites; and ii.) optimal crystallization rate that facilitates the growth of a compact, continuous film with low density of pinholes. Our work shows that the hybrid chemical vapor deposition technique (HCVD) technique is well suited for the deposition of evenly distributed nucleation sites and the optimization of the crystallization rate of the film through detailed monitoring of the thermal profile of the growth process. Signficant reduction in the defect states is recorded by annealing the perovskite films in O2. The results are consistent with theoretical studies by Yin et al. 1 on O and Cl passivation of the shallow states at the grain boundary of MAPI. Their work provides the theoretical basis for our experimental observations on the passivation of shallow states by oxygen annealing. High quality films were achieved through detailed management of the carrier gas composition and the thermal profile of the nucleation and crystallization steps.

  9. Improving the photovoltaic performance of perovskite solar cells with acetate

    PubMed Central

    Zhao, Qian; Li, G. R.; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X. P.

    2016-01-01

    In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells. PMID:27934924

  10. Improving the photovoltaic performance of perovskite solar cells with acetate.

    PubMed

    Zhao, Qian; Li, G R; Song, Jian; Zhao, Yulong; Qiang, Yinghuai; Gao, X P

    2016-12-09

    In an all-solid-state perovskite solar cell, methylammonium lead halide film is in charge of generating photo-excited electrons, thus its quality can directly influence the final photovoltaic performance of the solar cell. This paper accentuates a very simple chemical approach to improving the quality of a perovskite film with a suitable amount of acetic acid. With introduction of acetate ions, a homogeneous, continual and hole-free perovskite film comprised of high-crystallinity grains is obtained. UV-visible spectra, steady-state and time-resolved photoluminescence (PL) spectra reveal that the obtained perovskite film under the optimized conditions shows a higher light absorption, more efficient electron transport, and faster electron extraction to the adjoining electron transport layer. The features result in the optimized perovskite film can provide an improved short-circuit current. The corresponding solar cells with a planar configuration achieves an improved power conversion efficiency of 13.80%, and the highest power conversion efficiency in the photovoltaic measurements is up to 14.71%. The results not only provide a simple approach to optimizing perovskite films but also present a novel angle of view on fabricating high-performance perovskite solar cells.

  11. Ultrafast frequency-agile terahertz devices using methylammonium lead halide perovskites.

    PubMed

    Chanana, Ashish; Liu, Xiaojie; Zhang, Chuang; Vardeny, Zeev Valy; Nahata, Ajay

    2018-05-01

    The ability to control the response of metamaterial structures can facilitate the development of new terahertz devices, with applications in spectroscopy and communications. We demonstrate ultrafast frequency-agile terahertz metamaterial devices that enable such a capability, in which multiple perovskites can be patterned in each unit cell with micrometer-scale precision. To accomplish this, we developed a fabrication technique that shields already deposited perovskites from organic solvents, allowing for multiple perovskites to be patterned in close proximity. By doing so, we demonstrate tuning of the terahertz resonant response that is based not only on the optical pump fluence but also on the optical wavelength. Because polycrystalline perovskites have subnanosecond photocarrier recombination lifetimes, switching between resonances can occur on an ultrafast time scale. The use of multiple perovskites allows for new functionalities that are not possible using a single semiconducting material. For example, by patterning one perovskite in the gaps of split-ring resonators and bringing a uniform thin film of a second perovskite in close proximity, we demonstrate tuning of the resonant response using one optical wavelength and suppression of the resonance using a different optical wavelength. This general approach offers new capabilities for creating tunable terahertz devices.

  12. Adrenal-derived 11-oxygenated 19-carbon steroids are the dominant androgens in classic 21-hydroxylase deficiency.

    PubMed

    Turcu, Adina F; Nanba, Aya T; Chomic, Robert; Upadhyay, Sunil K; Giordano, Thomas J; Shields, James J; Merke, Deborah P; Rainey, William E; Auchus, Richard J

    2016-05-01

    To comprehensively characterize androgens and androgen precursors in classic 21-hydroxylase deficiency (21OHD) and to gain insights into the mechanisms of their formation. Serum samples were obtained from 38 patients (19 men) with classic 21OHD, aged 3-59, and 38 sex- and age-matched controls; 3 patients with 11β-hydroxylase deficiency; 4 patients with adrenal insufficiency; and 16 patients (8 men) undergoing adrenal vein sampling. Paraffin-embedded normal (n = 5) and 21OHD adrenal tissues (n = 3) were used for immunohistochemical studies. We measured 11 steroids in all sera by liquid chromatography-tandem mass spectrometry. Immunofluroescence localized 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2) and cytochrome b5 (CYB5A) within the normal and 21OHD adrenals. Four 11-oxygenated 19-carbon (11oxC19) steroids were significantly higher in male and female 21OHD patients than in controls: 11β-hydroxyandrostenedione, 11-ketoandrostenedione 11β-hydroxytestosterone, and 11-ketotestosterone (3-4-fold, P < 0.0001). For 21OHD patients, testosterone and 11-ketotestosterone were positively correlated in females, but inversely correlated in males. All 11oxC19 steroids were higher in the adrenal vein than in the inferior vena cava samples from men and women and rose with cosyntropin stimulation. Only trace amounts of 11oxC19 steroids were found in the sera of patients with 11β-hydroxylase deficiency and adrenal insufficiency, confirming their adrenal origin. HSD3B2 and CYB5A immunoreactivities were sharply segregated in the normal adrenal glands, whereas areas of overlapping expression were identified in the 21OHD adrenals. All four 11oxC19 steroids are elevated in both men and women with classic 21OHD. Our data suggest that 11oxC19 steroids are specific biomarkers of adrenal-derived androgen excess. © 2016 European Society of Endocrinology.

  13. Research progress on organic-inorganic halide perovskite materials and solar cells

    NASA Astrophysics Data System (ADS)

    Ono, Luis K.; Qi, Yabing

    2018-03-01

    Owing to the intensive research efforts across the world since 2009, perovskite solar cell power conversion efficiencies (PCEs) are now comparable or even better than several other photovoltaic (PV) technologies. In this topical review article, we review recent progress in the field of organic-inorganic halide perovskite materials and solar cells. We associate these achievements with the fundamental knowledge gained in the perovskite research. The major recent advances in the fundamental perovskite material and solar cell research are highlighted, including the current efforts in visualizing the dynamical processes (in operando) taking place within a perovskite solar cell under operating conditions. We also discuss the existing technological challenges. Based on a survey of recently published works, we point out that to move the perovskite PV technology forward towards the next step of commercialization, what perovskite PV technology need the most in the coming next few years is not only further PCE enhancements, but also up-scaling, stability, and lead-toxicity.

  14. Toward Increasing Micropore Volume between Hybrid Layered Perovskites with Silsesquioxane Interlayers.

    PubMed

    Kataoka, Sho; Kamimura, Yoshihiro; Endo, Akira

    2018-04-10

    Hybrid organic-inorganic layered perovskites are typically nonporous solids. However, the incorporation of silsesquioxanes with a cubic cage structure as interlayer materials creates micropores between the perovskite layers. In this study, we increase in the micropore volume in layered perovskites by replacing a portion of the silsesquioxane interlayers with organic amines. In the proposed method, approximately 20% of the silsesquioxane interlayers can be replaced without changing the layer distance owing to the size of the silsesquioxane. When small amines (e.g., ethylamine) are used in this manner, the micropore volume of the obtained hybrid layered perovskites increases by as much as 44%; when large amines (e.g., phenethylamine) are used, their micropore volume decreases by as much as 43%. Through the variation of amine fraction, the micropore volume can be adjusted in the range. Finally, the magnetic moment measurements reveal that the layered perovskites with mixed interlayers exhibit ferromagnetic ordering at temperature below 20 K, thus indicating that the obtained perovskites maintain their functions as layered perovskites.

  15. Fabrication of single phase 2D homologous perovskite microplates by mechanical exfoliation

    NASA Astrophysics Data System (ADS)

    Li, Junze; Wang, Jun; Zhang, Yingjun; Wang, Haizhen; Lin, Gaoming; Xiong, Xuan; Zhou, Weihang; Luo, Hongmei; Li, Dehui

    2018-04-01

    The two-dimensional (2D) Ruddlesden-Popper type perovskites have attracted intensive interest for their great environmental stability and various potential optoelectronic applications. Fundamental understanding of the photophysical and electronic properties of the 2D perovskites with pure single phase is essential for improving the performance of the optoelectronic devices and designing devices with new architectures. Investigating the optical and electronic properties of these materials with pure single phase is required to obtain pure single phase 2D perovskites. Here, we report on an alternative approach to fabricate (C4H9NH3)2(CH3NH3) n-1Pb n I3n+1 microplates with pure single n-number perovskite phase for n  >  2 by mechanical exfoliation. Micro-photoluminescence and absorption spectroscopy studies reveal that the as-synthesized 2D perovskite plates for n  >  2 are comprised by dominant n-number phase and small inclusions of hybrid perovskite phases with different n values, which is supported by excitation power dependent photoluminescence. By mechanical exfoliation method, 2D perovskite microplates with the thickness of around 20 nm are obtained, which surprisingly have single n-number perovskite phase for n  =  2-5. In addition, we have demonstrated that the exfoliated 2D perovskite microplates can be integrated with other 2D layered materials such as boron nitride, and are able to be transferred to prefabricated electrodes for photodetections. Our studies not only provide a strategy to prepare 2D perovskites with a single n-number perovskite phase allowing us to extract the basic optical and electronic parameters of pure phase perovskites, but also demonstrate the possibility to integrate the 2D perovskites with other 2D layered materials to extend the device’s functionalities.

  16. Full coverage of perovskite layer onto ZnO nanorods via a modified sequential two-step deposition method for efficiency enhancement in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Ruankham, Pipat; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Choopun, Supab; Sagawa, Takashi

    2017-07-01

    Full coverage of perovskite layer onto ZnO nanorod substrates with less pinholes is crucial for achieving high-efficiency perovskite solar cells. In this work, a two-step sequential deposition method is modified to achieve an appropriate property of perovskite (MAPbI3) film. Surface treatment of perovskite layer and its precursor have been systematically performed and their morphologies have been investigated. By pre-wetting of lead iodide (PbI2) and letting it dry before reacting with methylammonium iodide (MAI) provide better coverage of perovskite film onto ZnO nanorod substrate than one without any treatment. An additional MAI deposition followed with toluene drop-casting technique on the perovskite film is also found to increase the coverage and enhance the transformation of PbI2 to MAPbI3. These lead to longer charge carrier lifetime, resulting in an enhanced power conversion efficiency (PCE) from 1.21% to 3.05%. The modified method could been applied to a complex ZnO nanorods/TiO2 nanoparticles substrate. The enhancement in PCE to 3.41% is observed. These imply that our introduced method provides a simple way to obtain the full coverage and better transformation to MAPbI3 phase for enhancement in performances of perovskite solar cells.

  17. Conducting Layered Organic-inorganic Halides Containing <110>-Oriented Perovskite Sheets.

    PubMed

    Mitzi, D B; Wang, S; Feild, C A; Chess, C A; Guloy, A M

    1995-03-10

    Single crystals of the layered organic-inorganic perovskites, [NH(2)C(I=NH(2)](2)(CH(3)NH(3))m SnmI3m+2, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C(4)H(9)NH(3))(2)(CH(3)NH(3))n-1SnnI3n+1, which consists of (100)-terminated perovskite layers, structure determination reveals an unusual structural class with sets of m <110>-oriented CH(3)NH(3)SnI(3) perovskite sheets separated by iodoformamidinium cations. Whereas the m = 2 compound is semiconducting with a band gap of 0.33 +/- 0.05 electron volt, increasing m leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.

  18. Understanding perovskite formation through the intramolecular exchange method in ambient conditions

    NASA Astrophysics Data System (ADS)

    Szostak, Rodrigo; Castro, Jhon A. P.; Marques, Adriano S.; Nogueira, Ana F.

    2017-04-01

    Among the methods to prepare hybrid organic-inorganic perovskite films, the intramolecular exchange method was the first one that made possible to prepare perovskite solar cells with efficiencies higher than 20%. However, perovskite formation by this method is not completely understood, especially in ambient conditions. In this work, perovskite films were prepared by the intramolecular exchange method in ambient conditions. The spin coating speed and the frequency of the MAI solution dripping onto PbI2(DMSO) were varied during the deposition steps. With the combination of these two parameters, a rigid control of the solvent drying was possible. Thus, depending on the chosen conditions, the intermediate MAPb3I8·2DMSO was formed with residual PbI2. Otherwise, direct formation of perovskite film was attained. A mechanism for the direct formation of bulk perovskite was proposed. We also investigated how the posterior thermal annealing affects the crystallinity and defects in perovskite films. With prolonged thermal annealing, the excess of MAI can be avoided, increasing the efficiency and decreasing the hysteresis of the solar cells. The best perovskite solar cell achieved a stabilized power output of 12.9%. The findings of this work pave the way for realizing the fabrication of efficient perovskite solar cells in ambient atmosphere, a very desirable condition for cost-efficient large scale manufacturing of this technology.

  19. Selective dissolution of halide perovskites as a step towards recycling solar cells

    PubMed Central

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-01-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells. PMID:27211006

  20. Selective dissolution of halide perovskites as a step towards recycling solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-01

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb2+ cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  1. Selective dissolution of halide perovskites as a step towards recycling solar cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Here, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO 2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easilymore » decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb 2+ cations. After 10 cycles of recycling, a mesoporous TiO 2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.« less

  2. Selective dissolution of halide perovskites as a step towards recycling solar cells.

    PubMed

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; Park, So Yeon; Li, Zhen; Zhu, Kai; Jung, Hyun Suk

    2016-05-23

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb(2+) cations. After 10 cycles of recycling, a mesoporous TiO2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.

  3. Selective dissolution of halide perovskites as a step towards recycling solar cells

    DOE PAGES

    Kim, Byeong Jo; Kim, Dong Hoe; Kwon, Seung Lee; ...

    2016-05-23

    Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Here, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO 2-coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easilymore » decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb 2+ cations. After 10 cycles of recycling, a mesoporous TiO 2-coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.« less

  4. Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates

    NASA Astrophysics Data System (ADS)

    Baca, Alfred J.; Roberts, M. Joseph; Stenger-Smith, John; Baldwin, Lawrence

    2018-06-01

    Soft nanoimprinted titanium dioxide (TiO2) substrates decorated with methylammonium lead halide perovskite (MAPbI3) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI3 growth methods (1-step and 2-step processing). Both types of MAPbI3 crystals were fabricated on hydrophobic TiO2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

  5. Laser Direct Write Synthesis of Lead Halide Perovskites

    DOE PAGES

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.; ...

    2016-09-05

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH 3NH 3PbBr 3 on a range of substrates and fabricate and characterize a microscale photodetectormore » using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.« less

  6. Laser Direct Write Synthesis of Lead Halide Perovskites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chou, Stanley S.; Swartzentruber, Brian S.; Janish, Matthew T.

    Lead halide perovskites are increasingly considered for applications beyond photovoltaics, for example, light emission and detection, where an ability to pattern and prototype microscale geometries can facilitate the incorporation of this class of materials into devices. In this study, we demonstrate laser direct write of lead halide perovskites, a remarkably simple procedure that takes advantage of the inverse dependence between perovskite solubility and temperature by using a laser to induce localized heating of an absorbing substrate. We also demonstrate arbitrary pattern formation of crystalline CH 3NH 3PbBr 3 on a range of substrates and fabricate and characterize a microscale photodetectormore » using this approach. This direct write methodology provides a path forward for the prototyping and production of perovskite-based devices.« less

  7. Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  8. Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells.

    PubMed

    Sewvandi, Galhenage A; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-29

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  9. Paired N and O isotopic analysis of nitrate and nitrite in the Arabian Sea oxygen deficient zone

    NASA Astrophysics Data System (ADS)

    Martin, T. S.; Casciotti, K. L.

    2017-03-01

    The Arabian Sea is home to one of the three main oceanic oxygen deficient zones (ODZs). We present paired nitrogen (N) and oxygen (O) isotope measurements of nitrate (NO3-) and nitrite (NO2-) from the central Arabian Sea in order to understand the effects of N biogeochemistry on the distribution of these species in the low oxygen waters. Within the ODZ, NO2- accumulated in a secondary NO2- maximum (SNM), though the shape and magnitude of the SNM, along with the isotopic composition of NO3- and NO2-, were highly dependent on the location within the ODZ. We also explored water mass mixing within the Arabian Sea as an explanatory factor in the distribution of NO2- in the SNM. The intrusion of Persian Gulf Water at depth may influence the shape of the NO2- peak by introducing small amounts of dissolved oxygen (O2), favoring NO2- oxidation. There was also evidence that vertical mixing may play a role in shaping the top of the SNM peak. Finally, we present evidence for NO2- oxidation and NO2- reduction co-occurring within the ODZ, as has been previously suggested in the Arabian Sea, as well as in other ODZs. The decoupling of the N and O isotopes of NO3-, deviating from the expected 1:1 ratio for dissimilatory NO3- reduction, indicates that NO2- oxidation has a significant influence on the isotopic composition of NO3-. Additionally, the N isotopes of NO2- were generally fit well by Rayleigh curves for NO2- oxidation. However, the removal of dissolved inorganic nitrogen (DIN) within the domain reflects the importance of NO2- reduction to N2.

  10. Extended x-ray absorption fine structure study of phase transitions in the piezoelectric perovskite K0.5Na0.5NbO3

    NASA Astrophysics Data System (ADS)

    Kodre, A.; Tellier, J.; Arčon, I.; Malič, B.; Kosec, M.

    2009-06-01

    Following an x-ray diffraction study of phase transitions of the piezoelectric perovskite K0.5Na0.5NbO3 the structural changes of the material are studied using extended x-ray absorption fine structure analysis, whereby the neighborhood of Nb atom is determined in the temperature range of monoclinic, tetragonal, and cubic phases. Within the entire range Nb atom is displaced from the center of the octahedron of its immediate oxygen neighbors, as witnessed by the splitting of Nb-O distance. The model shows high prevalence of the displacement in the (111) crystallographic direction of the simple perovskite cell. The corresponding splitting of the Nb-Nb distance is negligible. There is no observable disalignment of the linear Nb-O-Nb bonds from the ideal cubic arrangement, judging from the intensity of the focusing of the photoelectron wave on the Nb-Nb scattering path by the interposed oxygen atom. As a general result, the phase transitions are found as an effect of the long-range order, while the placement of the atoms in the immediate vicinity remains largely unaffected.

  11. Novel Mg-Doped SrMoO3 Perovskites Designed as Anode Materials for Solid Oxide Fuel Cells

    PubMed Central

    Cascos, Vanessa; Alonso, José Antonio; Fernández-Díaz, María Teresa

    2016-01-01

    SrMo1−xMxO3−δ (M = Fe and Cr, x = 0.1 and 0.2) oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC) with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO3 perovskite. SrMo1−xMgxO3−δ (x = 0.1, 0.2) oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm−2 at 850 °C using pure H2 as fuel. We have studied its crystal structure with an “in situ” neutron power diffraction (NPD) experiment at temperatures as high as 800 °C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features. PMID:28773708

  12. Excited State Properties of Hybrid Perovskites.

    PubMed

    Saba, Michele; Quochi, Francesco; Mura, Andrea; Bongiovanni, Giovanni

    2016-01-19

    Metal halide perovskites have come to the attention of the scientific community for the progress achieved in solar light conversion. Energy sustainability is one of the priorities of our society, and materials advancements resulting in low-cost but efficient solar cells and large-area lighting devices represent a major goal for applied research. From a basic point of view, perovskites are an exotic class of hybrid materials combining some merits of organic and inorganic semiconductors: large optical absorption, large mobilities, and tunable band gap together with the possibility to be processed in solution. When a novel class of promising semiconductors comes into the limelight, lively discussions ensue on the photophysics of band-edge excitations, because just the states close to the band edge are entailed in energy/charge transport and light emission. This was the case several decades ago for III-V semiconductors, it has been up to 10 years ago for organics, and it is currently the case for perovskites. Our aim in this Account is to rationalize the body of experimental evidence on perovskite photophysics in a coherent theoretical framework, borrowing from the knowledge acquired over the years in materials optoelectronics. A crucial question is whether photon absorption leads to a population of unbound, conductive free charges or instead excitons, neutral and insulating bound states created by Coulomb interaction just below the energy of the band gap. We first focus on the experimental estimates of the exciton binding energy (Eb): at room temperature, Eb is comparable to the thermal energy kBT in MAPbI3 and increases up to values 2-3kBT in wide band gap MAPbBr3 and MAPbCl3. Statistical considerations predict that these values, even though comparable to or larger than thermal energy, let free carriers prevail over bound excitons for all levels of excitation densities relevant for devices. The analysis of photophysics evidence confirms that all hybrid halide

  13. Understanding and Tailoring Grain Growth of Lead-Halide Perovskite for Solar Cell Application.

    PubMed

    Ma, Yongchao; Liu, Yanliang; Shin, Insoo; Hwang, In-Wook; Jung, Yun Kyung; Jeong, Jung Hyun; Park, Sung Heum; Kim, Kwang Ho

    2017-10-04

    The fundamental mechanism of grain growth evolution in the fabrication process from the precursor phase to the perovskite phase is not fully understood despite its importance in achieving high-quality grains in organic-inorganic hybrid perovskites, which are strongly affected by processing parameters. In this work, we investigate the fundamental conversion mechanism from the precursor phase of perovskite to the complete perovskite phase and how the intermediate phase promotes growth of the perovskite grains during the fabrication process. By monitoring the morphological evolution of the perovskite during the film fabrication process, we observed a clear rod-shaped intermediate phase in the highly crystalline perovskite and investigated the role of the nanorod intermediate phase on the growth of the grains of the perovskite film. Furthermore, on the basis of these findings, we developed a simple and effective method to tailor grain properties including the crystallinity, size, and number of grain boundaries, and then utilized the film with the tailored grains to develop perovskite solar cells.

  14. Characteristics of Alpha-1 Antitrypsin-Deficient Individuals in the Long-term Oxygen Treatment Trial and Comparison with Other Subjects with Chronic Obstructive Pulmonary Disease.

    PubMed

    Stoller, James K; Aboussouan, Loutfi S; Kanner, Richard E; Wilson, Laura A; Diaz, Phil; Wise, Robert

    2015-12-01

    Alpha-1 antitrypsin deficiency (AATD) predisposes to chronic obstructive pulmonary disease, but is underrecognized. Oxygenation and exercise desaturation in individuals with AATD-associated chronic obstructive pulmonary disease has been sparsely studied. The Long-term Oxygen Treatment Trial (LOTT) permits comparing these features of individuals with AATD with alpha-1 antitrypsin-replete (called "usual chronic obstructive pulmonary disease") LOTT participants. Compare demographic, clinical, baseline oxygenation, and exercise desaturation features in participating AATD subjects with those of other LOTT subjects. LOTT is a multicenter randomized controlled trial comparing use of supplemental oxygen versus not in subjects with chronic obstructive pulmonary disease and moderate hypoxemia (resting oxygen saturation as measured by pulse oximetry, 89-93%) or normal oxygen saturation at rest and significant exercise desaturation. Among the 597 LOTT participants with nonmissing alpha-1 antitrypsin levels, 11 (1.8%) had severe AATD and 44 (7.4%) had mild/moderate AATD. Comparison of the 11 severely AAT-deficient individuals with the 542 LOTT participants with usual chronic obstructive pulmonary disease showed that the AATD subjects were younger and despite less smoking, had lower FEV1/FVC (mean post-bronchodilator FEV1/FVC, 0.38 ± 0.06 vs. 0.46 ± 0.13; P = 0.002). Comparison with 27 age-, sex-, and FEV1-matched alpha-1 antitrypsin-normal LOTT participants showed no baseline difference in resting room air pulse oximetry saturation (AATD, 93.6% ± 2.3% vs. 92.7% ± 2.2%; P = 0.64). Exercise-related desaturation was more severe in the individuals with AATD based on desaturation to 88% or less sooner during a 6-minute-walk test, having a higher percentage of desaturation points (e.g., <90%) during exercise, and having a higher distance-saturation product (defined as the distance walked in 6 min multiplied by the nadir saturation achieved during the 6-minute-walk test). These

  15. A Direct Bandgap Copper-Antimony Halide Perovskite.

    PubMed

    Vargas, Brenda; Ramos, Estrella; Pérez-Gutiérrez, Enrique; Alonso, Juan Carlos; Solis-Ibarra, Diego

    2017-07-12

    Since the establishment of perovskite solar cells (PSCs), there has been an intense search for alternative materials to replace lead and improve their stability toward moisture and light. As single-metal perovskite structures have yielded unsatisfactory performances, an alternative is the use of double perovskites that incorporate a combination of metals. To this day, only a handful of these compounds have been synthesized, but most of them have indirect bandgaps and/or do not have bandgaps energies well-suited for photovoltaic applications. Here we report the synthesis and characterization of a unique mixed metal ⟨111⟩-oriented layered perovskite, Cs 4 CuSb 2 Cl 12 (1), that incorporates Cu 2+ and Sb 3+ into layers that are three octahedra thick (n = 3). In addition to being made of abundant and nontoxic elements, we show that this material behaves as a semiconductor with a direct bandgap of 1.0 eV and its conductivity is 1 order of magnitude greater than that of MAPbI 3 (MA = methylammonium). Furthermore, 1 has high photo- and thermal-stability and is tolerant to humidity. We conclude that 1 is a promising material for photovoltaic applications and represents a new type of layered perovskite structure that incorporates metals in 2+ and 3+ oxidation states, thus significantly widening the possible combinations of metals to replace lead in PSCs.

  16. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes

    NASA Astrophysics Data System (ADS)

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

    2015-05-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3- antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

  17. Ultrafast frequency-agile terahertz devices using methylammonium lead halide perovskites

    PubMed Central

    Chanana, Ashish; Liu, Xiaojie; Vardeny, Zeev Valy

    2018-01-01

    The ability to control the response of metamaterial structures can facilitate the development of new terahertz devices, with applications in spectroscopy and communications. We demonstrate ultrafast frequency-agile terahertz metamaterial devices that enable such a capability, in which multiple perovskites can be patterned in each unit cell with micrometer-scale precision. To accomplish this, we developed a fabrication technique that shields already deposited perovskites from organic solvents, allowing for multiple perovskites to be patterned in close proximity. By doing so, we demonstrate tuning of the terahertz resonant response that is based not only on the optical pump fluence but also on the optical wavelength. Because polycrystalline perovskites have subnanosecond photocarrier recombination lifetimes, switching between resonances can occur on an ultrafast time scale. The use of multiple perovskites allows for new functionalities that are not possible using a single semiconducting material. For example, by patterning one perovskite in the gaps of split-ring resonators and bringing a uniform thin film of a second perovskite in close proximity, we demonstrate tuning of the resonant response using one optical wavelength and suppression of the resonance using a different optical wavelength. This general approach offers new capabilities for creating tunable terahertz devices. PMID:29736416

  18. Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

    DOE PAGES

    Aidhy, Dilpuneet S.; Liu, Bin; Zhang, Yanwen; ...

    2015-01-21

    We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO 2|ZrO 2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. Furthermore, these results couldmore » serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.« less

  19. Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates.

    PubMed

    Baca, Alfred J; Roberts, M Joseph; Stenger-Smith, John; Baldwin, Lawrence

    2018-06-22

    Soft nanoimprinted titanium dioxide (TiO 2 ) substrates decorated with methylammonium lead halide perovskite (MAPbI 3 ) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO 2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI 3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI 3 growth methods (1-step and 2-step processing). Both types of MAPbI 3 crystals were fabricated on hydrophobic TiO 2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI 3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

  20. Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ong, Alison

    2015-08-20

    Perovskite photovoltaics have recently come to prominence as a viable alternative to crystalline silicon based solar cells. In an effort to create consistent and high-quality films, we studied the effect of various annealing conditions as well as the effect of pyridine vapor treatment on mixed halide methylammonium lead perovskite films. Of six conditions tested, we found that annealing at 100°C for 90 minutes followed by 120°C for 15 minutes resulted in the purest perovskite. Perovskite films made using that condition were treated with pyridine for various amounts of time, and the effects on perovskite microstructure were studied using x-ray diffraction,more » UV-Vis spectroscopy, and time-resolved photoluminescence lifetime analysis (TRPL). A previous study found that pyridine vapor caused perovskite films to have higher photoluminescence intensity and become more homogenous. In this study we found that the effects of pyridine are more complex: while films appeared to become more homogenous, a decrease in bulk photoluminescence lifetime was observed. In addition, the perovskite bandgap appeared to decrease with increased pyridine treatment time. Finally, X-ray diffraction showed that pyridine vapor treatment increased the perovskite (110) peak intensity but also often gave rise to new unidentified peaks, suggesting the formation of a foreign species. It was observed that the intensity of this unknown species had an inverse correlation with the increase in perovskite peak intensity, and also seemed to be correlated with the decrease in TRPL lifetime.« less

  1. Exciton Dynamics of 2D Hybrid Perovskite Nanocrystal

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Zhu, Zhuan; Boulesbaa, Abdelaziz; Venkatesan, Swaminathan; Xiao, Kai; Bao, Jiming; Yao, Yan; Li, Wenzhi

    Organic-inorganic hybrid perovskites have emerged as promising materials for applications in photovoltaic and optoelectronic devices. Among the perovskites, two dimensional (2D) perovskites are of great interests due to their remarkable optical and electrical properties as well as the flexibility of material selection for the organic and inorganic moieties. In this study, we demonstrate the solution-phase growth of large square-shaped single-crystalline 2D hybrid perovskites of (C6H5C2H4 NH3) 2 PbBr4 with a few unit cells thickness. Compared to the bulk crystal, a band gap shift and new photoluminescence (PL) peak are observed from the hybrid perovskite sheets. Color of the 2D crystals can be tuned by adjusting the sheet thickness. Pump-probe spectroscopy is used to investigate the exciton dynamics and exhibits a biexponential decay with an amplitude-weighted lifetime of 16.7 ps. Such high-quality (C6H5C2H4 NH3) 2 PbBr4 sheets are expected to have high PL quantum efficiency which can be adopted for light-emitting devices. National Science Foundation (Grant No. CMMI-1334417 and DMR-1506640).

  2. Electron–phonon coupling in hybrid lead halide perovskites

    PubMed Central

    Wright, Adam D.; Verdi, Carla; Milot, Rebecca L.; Eperon, Giles E.; Pérez-Osorio, Miguel A.; Snaith, Henry J.; Giustino, Feliciano; Johnston, Michael B.; Herz, Laura M.

    2016-01-01

    Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron–phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites. PMID:27225329

  3. Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence

    PubMed Central

    Xing, Guichuan; Wu, Bo; Wu, Xiangyang; Li, Mingjie; Du, Bin; Wei, Qi; Guo, Jia; Yeow, Edwin K. L.; Sum, Tze Chien; Huang, Wei

    2017-01-01

    The slow bimolecular recombination that drives three-dimensional lead-halide perovskites' outstanding photovoltaic performance is conversely a fundamental limitation for electroluminescence. Under electroluminescence working conditions with typical charge densities lower than 1015 cm−3, defect-states trapping in three-dimensional perovskites competes effectively with the bimolecular radiative recombination. Herein, we overcome this limitation using van-der-Waals-coupled Ruddlesden-Popper perovskite multi-quantum-wells. Injected charge carriers are rapidly localized from adjacent thin few layer (n≤4) multi-quantum-wells to the thick (n≥5) multi-quantum-wells with extremely high efficiency (over 85%) through quantum coupling. Light emission originates from excitonic recombination in the thick multi-quantum-wells at much higher decay rate and efficiency than bimolecular recombination in three-dimensional perovskites. These multi-quantum-wells retain the simple solution processability and high charge carrier mobility of two-dimensional lead-halide perovskites. Importantly, these Ruddlesden-Popper perovskites offer new functionalities unavailable in single phase constituents, permitting the transcendence of the slow bimolecular recombination bottleneck in lead-halide perovskites for efficient electroluminescence. PMID:28239146

  4. Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence.

    PubMed

    Xing, Guichuan; Wu, Bo; Wu, Xiangyang; Li, Mingjie; Du, Bin; Wei, Qi; Guo, Jia; Yeow, Edwin K L; Sum, Tze Chien; Huang, Wei

    2017-02-27

    The slow bimolecular recombination that drives three-dimensional lead-halide perovskites' outstanding photovoltaic performance is conversely a fundamental limitation for electroluminescence. Under electroluminescence working conditions with typical charge densities lower than 10 15  cm -3 , defect-states trapping in three-dimensional perovskites competes effectively with the bimolecular radiative recombination. Herein, we overcome this limitation using van-der-Waals-coupled Ruddlesden-Popper perovskite multi-quantum-wells. Injected charge carriers are rapidly localized from adjacent thin few layer (n≤4) multi-quantum-wells to the thick (n≥5) multi-quantum-wells with extremely high efficiency (over 85%) through quantum coupling. Light emission originates from excitonic recombination in the thick multi-quantum-wells at much higher decay rate and efficiency than bimolecular recombination in three-dimensional perovskites. These multi-quantum-wells retain the simple solution processability and high charge carrier mobility of two-dimensional lead-halide perovskites. Importantly, these Ruddlesden-Popper perovskites offer new functionalities unavailable in single phase constituents, permitting the transcendence of the slow bimolecular recombination bottleneck in lead-halide perovskites for efficient electroluminescence.

  5. Tailoring the Interfacial Chemical Interaction for High-Efficiency Perovskite Solar Cells.

    PubMed

    Zuo, Lijian; Chen, Qi; De Marco, Nicholas; Hsieh, Yao-Tsung; Chen, Huajun; Sun, Pengyu; Chang, Sheng-Yung; Zhao, Hongxiang; Dong, Shiqi; Yang, Yang

    2017-01-11

    The ionic nature of perovskite photovoltaic materials makes it easy to form various chemical interactions with different functional groups. Here, we demonstrate that interfacial chemical interactions are a critical factor in determining the optoelectronic properties of perovskite solar cells. By depositing different self-assembled monolayers (SAMs), we introduce different functional groups onto the SnO 2 surface to form various chemical interactions with the perovskite layer. It is observed that the perovskite solar cell device performance shows an opposite trend to that of the energy level alignment theory, which shows that chemical interactions are the predominant factor governing the interfacial optoelectronic properties. Further analysis verifies that proper interfacial interactions can significantly reduce trap state density and facilitate the interfacial charge transfer. Through use of the 4-pyridinecarboxylic acid SAM, the resulting perovskite solar cell exhibits striking improvements to the reach the highest efficiency of 18.8%, which constitutes an ∼10% enhancement compared to those without SAMs. Our work highlights the importance of chemical interactions at perovskite/electrode interfaces and paves the way for further optimizing performances of perovskite solar cells.

  6. Junction Propagation in Organometal Halide Perovskite-Polymer Composite Thin Films.

    PubMed

    Shan, Xin; Li, Junqiang; Chen, Mingming; Geske, Thomas; Bade, Sri Ganesh R; Yu, Zhibin

    2017-06-01

    With the emergence of organometal halide perovskite semiconductors, it has been discovered that a p-i-n junction can be formed in situ due to the migration of ionic species in the perovskite when a bias is applied. In this work, we investigated the junction formation dynamics in methylammonium lead tribromide (MAPbBr 3 )/polymer composite thin films. It was concluded that the p- and n- doped regions propagated into the intrinsic region with an increasing bias, leading to a reduced intrinsic perovskite layer thickness and the formation of an effective light-emitting junction regardless of perovskite layer thicknesses (300 nm to 30 μm). The junction propagation also played a major role in deteriorating the LED operation lifetime. Stable perovskite LEDs can be achieved by restricting the junction propagation after its formation.

  7. Two-Dimensional Materials for Halide Perovskite-Based Optoelectronic Devices.

    PubMed

    Chen, Shan; Shi, Gaoquan

    2017-06-01

    Halide perovskites have high light absorption coefficients, long charge carrier diffusion lengths, intense photoluminescence, and slow rates of non-radiative charge recombination. Thus, they are attractive photoactive materials for developing high-performance optoelectronic devices. These devices are also cheap and easy to be fabricated. To realize the optimal performances of halide perovskite-based optoelectronic devices (HPODs), perovskite photoactive layers should work effectively with other functional materials such as electrodes, interfacial layers and encapsulating films. Conventional two-dimensional (2D) materials are promising candidates for this purpose because of their unique structures and/or interesting optoelectronic properties. Here, we comprehensively summarize the recent advancements in the applications of conventional 2D materials for halide perovskite-based photodetectors, solar cells and light-emitting diodes. The examples of these 2D materials are graphene and its derivatives, mono- and few-layer transition metal dichalcogenides (TMDs), graphdiyne and metal nanosheets, etc. The research related to 2D nanostructured perovskites and 2D Ruddlesden-Popper perovskites as efficient and stable photoactive layers is also outlined. The syntheses, functions and working mechanisms of relevant 2D materials are introduced, and the challenges to achieving practical applications of HPODs using 2D materials are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Conducting tin halides with a layered organic-based perovskite structure

    NASA Astrophysics Data System (ADS)

    Mitzi, D. B.; Feild, C. A.; Harrison, W. T. A.; Guloy, A. M.

    1994-06-01

    THE discovery1 of high-temperature superconductivity in layered copper oxide perovskites has generated considerable fundamental and technological interest in this class of materials. Only a few other examples of conducting layered perovskites are known; these are also oxides such as (La1-xSrx)n+1 MnnO3n+1 (ref. 2), Lan+1NinO3n+1 (ref. 3) and Ban+1PbnO3n+1 (ref. 4), all of which exhibit a trend from semiconducting to metallic behaviour with increasing number of perovskite layers (n). We report here the synthesis of a family of organic-based layered halide perovskites, (C4H9NH3)2(CH3NH3)n-1Snnl3n+1 which show a similar transition from semiconducting to metallic behaviour with increasing n. The incorporation of an organic modulation layer between the conducting tin iodide sheets potentially provides greater flexibility for tuning the electrical properties of the perovskite sheets, and we suggest that such an approach will prove valuable for exploring the range of transport properties possible with layered perovskites.

  9. Controllable lasing performance in solution-processed organic-inorganic hybrid perovskites.

    PubMed

    Kao, Tsung Sheng; Chou, Yu-Hsun; Hong, Kuo-Bin; Huang, Jiong-Fu; Chou, Chun-Hsien; Kuo, Hao-Chung; Chen, Fang-Chung; Lu, Tien-Chang

    2016-11-03

    Solution-processed organic-inorganic perovskites are fascinating due to their remarkable photo-conversion efficiency and great potential in the cost-effective, versatile and large-scale manufacturing of optoelectronic devices. In this paper, we demonstrate that the perovskite nanocrystal sizes can be simply controlled by manipulating the precursor solution concentrations in a two-step sequential deposition process, thus achieving the feasible tunability of excitonic properties and lasing performance in hybrid metal-halide perovskites. The lasing threshold is at around 230 μJ cm -2 in this solution-processed organic-inorganic lead-halide material, which is comparable to the colloidal quantum dot lasers. The efficient stimulated emission originates from the multiple random scattering provided by the micro-meter scale rugged morphology and polycrystalline grain boundaries. Thus the excitonic properties in perovskites exhibit high correlation with the formed morphology of the perovskite nanocrystals. Compared to the conventional lasers normally serving as a coherent light source, the perovskite random lasers are promising in making low-cost thin-film lasing devices for flexible and speckle-free imaging applications.

  10. Hybrid solar cells composed of perovskite and polymer photovoltaic structures

    NASA Astrophysics Data System (ADS)

    Phaometvarithorn, Apatsanan; Chuangchote, Surawut; Kumnorkaew, Pisist; Wootthikanokkhan, Jatuphorn

    2018-06-01

    Organic/inorganic lead halide perovskite solar cells have recently attracted much attention in photovoltaic research, due to the devices show promising ways to achieve high efficiencies. The perovskite devices with high efficiencies, however, are typically fabricated in tandem solar cell which is complicated. In this research work, we introduce a solar cell device with the combination of CH3NH3PbI3-xClx perovskite and bulk heterojunction PCDTBT:PC70BM polymer without any tandem structure. The new integrated perovskite/polymer hybrid structure of ITO/PEDOT:PSS/perovskite/PCDTBT:PC70BM/PC70BM/TiOx/Al provides higher power conversion efficiency (PCE) of devices compared with conventional perovskite cell structure. With the optimized PCDTBT:PC70BM thickness of ∼70 nm, the highest PCE of 11.67% is achieved. Variation of conducting donor polymers in this new structure is also preliminary demonstrated. This study provides an attractively innovative structure and a promising design for further development of the new-generation solar cells.

  11. Crystallization of perovskite film using ambient moisture and water as co-solvent for efficient planar perovskite solar cell (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Dubey, Ashish; Reza, Khan M.; Gaml, Eman; Adhikari, Nirmal; Qiao, Qiquan

    2016-09-01

    Smooth, compact and defect free morphology of perovskite is highly desired for enhanced device performance. Several routes such as thermal annealing, use of solvent mixtures, growth under controlled humidity has been adopted to obtain crystalline, smooth and defect free perovskite film. Herein we showed direct use of water (H2O) as co-solvent in precursor solution and have optimized the water content required to obtain smooth and dense film. Varying concentration of water was used in precursor solution of CH3NH3I and PbI2 mixed in γ-butyrolactone (GBL) and dimethylsulfoxide (DMSO). Perovskite films were crystallized using toluene assisted solvent engineering method using GBL:DMSO:H2O as solvent mixture. The amount of water was varied from 1% to 25%, which resulted in change in film morphology and perovskite crystallinity. It was concluded that an appropriate amount of water is required to assist the crystallization process to obtain smooth pin-hole free morphology. The change in morphology led to improved fill factor in the device, with highest efficiency 14%, which was significantly higher than devices made from perovskite film without adding water. We also showed that addition of up to 25% by volume of water does not significantly change the device performance.

  12. Distribution and Magnitude of Dinitrogen Fixation in the Eastern Tropical North Pacific Oxygen Deficient Zone.

    NASA Astrophysics Data System (ADS)

    Selden, C.; Mulholland, M. R.; Widner, B.; Bernhardt, P. W.; Macías Tapia, A.; Jayakumar, A.

    2016-12-01

    The Eastern Tropical North Pacific Ocean (ETNP) hosts one of the world's three major open ocean oxygen deficient zones (ODZs). Hotspots for fixed nitrogen (N) loss processes, ODZs have classically been discounted as areas of significant dinitrogen (N2) fixation, the microbe-mediated reduction of N2 to ammonium (NH4+), which has historically been ascribed primarily to euphotic, nutrient-deplete tropical waters. Challenging this paradigm, active expression of nifH (the dinitrogen reductase structural gene) has recently been documented in the ETNP, Eastern Tropical South Pacific, and Arabian Sea ODZs, implying a closer coupling of fixed nitrogen input and loss processes than previously thought. Here, we report rates of N­2 fixation measured in the ETNP ODZ along vertical gradients of oxygen, light, and dissolved N concentrations. Detailed vertical profiles of N2 fixation rates and dissolved N concentrations made within the ODZ were compared with similar profiles from oxic waters outside the ODZ. In addition, different organic carbon sources were investigated as potential rate-limiting factors for N2 fixation in sub-euphotic waters. By establishing the magnitude and distribution of N­2 fixation in the ETNP ODZ, this study contributes to current understanding of N cycling in anoxic and aphotic waters, and serves to elucidate nuances in the global N budget, enabling more accurate biogeochemical modeling. Understanding these processes in present day ODZs is crucial for predicting how ongoing anthropogenic intensification of coastal ODZs will alter biogeochemical cycles in the future.

  13. Application of carbon nanotubes in perovskite solar cells: A review

    NASA Astrophysics Data System (ADS)

    Oo, Thet Tin; Debnath, Sujan

    2017-11-01

    Solar power, as alternative renewable energy source, has gained momentum in global energy generation in recent time. Solar photovoltaics (PV) systems now fulfill a significant portion of electricity demand and the capacity of solar PV capacity is growing every year. PV cells efficiency has improved significantly following decades of research, evolving into third generations of PV cells. These third generation PV cells are set out to provide low-cost and efficient PV systems, further improving the commercial competitiveness of solar energy generation. Among these latest generations of PV cells, perovskite solar cells have gained attraction due to the simple manufacturing process and the immense growth in PV efficiency in a short period of research and development. Despite these advantages, perovskite solar cells are known for the weak stability and decomposition in exposure to humidity and high temperature, hindering the possibility of commercialization. This paper will discuss the role of carbon nanotubes (CNTs) in improving the efficiency and stability of perovskite solar cells, in various components such as perovskite layer and hole transport layer, as well as the application of CNTs in unique aspects. These includes the use of CNTs fiber in making the perovskite solar cells flexible, as well as simplification of perovskite PV production by using CNT flash evaporation printing process. Despite these advances, challenges remain in incorporation CNTs into perovskite such as lower conversion efficiency compared to rare earth metals and improvements need to be made. Thus, the paper will be also highlighting the CNTs materials suggested for further research and improvement of perovskite solar cells.

  14. Antiferroelectric Nature of CH3NH3PbI3−xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    PubMed Central

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-01-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3−xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3−xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation. PMID:27468802

  15. Autothermal reforming catalyst having perovskite structure

    DOEpatents

    Krumpel, Michael [Naperville, IL; Liu, Di-Jia [Naperville, IL

    2009-03-24

    The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

  16. High-surface-area, dual-function oxygen electrocatalysts for space power applications

    NASA Technical Reports Server (NTRS)

    Ham, David O.; Moniz, Gary; Taylor, E. Jennings

    1987-01-01

    The processes of hydration/dehydration and carbonation/decarbonation are investigated as an approach to provide higher surface area mixed metal oxides that are more active electrochemically. These materials are candidates for use as electrocatalysts and electrocatalyst supports for alkaline electrolyzers and fuel cells. For the case of the perovskite, LaCoO3 , higher surface areas were achieved with no change in structure and a more active oxygen electrocatalyst.

  17. Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires

    NASA Astrophysics Data System (ADS)

    Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

    2016-03-01

    Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

  18. Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires.

    PubMed

    Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

    2016-03-28

    Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

  19. Synthesis, crystal structure and magnetic properties of a new B-site ordered double perovskite Sr{sub 2}CuIrO{sub 6}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vasala, Sami; Yamauchi, Hisao; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi

    2014-12-15

    Here we synthesize and characterize a new double-perovskite oxide Sr{sub 2}CuIrO{sub 6}. The synthesis requires the use of high oxygen pressure to stabilize the VI oxidation state of iridium. The compound has a tetragonally-distorted crystal structure due to the Jahn–Teller active Cu{sup II} ion, and a high degree of B-site cation order. Magnetic transition is apparent at 15 K, but the zero-field-cooled and field-cooled susceptibilities diverge below this temperature. The high degree of cation order would exclude the possibility of a typical spin-glass, indicating that the divergence is probably due to a frustration of the magnetic interactions between Cu andmore » Ir, with a high frustration factor of f≈25. - Graphical abstract: A new member of the A{sub 2}B′B″O{sub 6} double-perovskite family with JT-active Cu{sup II} at the B′ site and Ir{sup VI} at the B″ site is synthesized through high pressure synthesis and characterized for the structural and magnetic properties. - Highlights: • New member of the A{sub 2}CuB″O{sub 6} double-perovskite family is synthesized with B″=Ir. • Stabilization of Ir{sup VI} requires the use of high oxygen pressure synthesis. • Crystal structure is tetragonally distorted due to JT-active Cu{sup II}. • Divergence of ZFC and FC curves is seen below the T{sub N} of 15 K. • This is presumably due to a frustration effect.« less

  20. Observation of decreasing resistivity of amorphous indium gallium zinc oxide thin films with an increasing oxygen partial pressure

    NASA Astrophysics Data System (ADS)

    Singh, Anup K.; Adhikari, Sonachand; Gupta, Rajeev; Deepak

    2017-01-01

    We have investigated the electrical resistivity behavior in amorphous indium gallium zinc oxide (a-IGZO) thin films. It is well known that resistivity increases as the film is deposited at a higher and higher oxygen partial pressure; we also record the same. However, in process we have discovered a remarkable region, in the oxygen deficient condition, that the resistivity shows an inverse behavior. This leads to the possibility that resistive films, suitable for thin film transistors, can also be obtained in oxygen deficient deposition conditions. Optical spectroscopic investigation could discern between a-IGZO films grown in oxygen deficient and oxygen rich conditions. The related resistivity behavior could be correlated to the presence of sub-bandgap states in films deposited in oxygen deficiency. These subgap states appear to be due to defects arising from local variations around the cations or oxygen atoms. The likely cause is an increase in Ga relative to In around O atom and the nature of cation-cation interaction when an oxygen atom is missing.

  1. CO2 Plasma-Treated TiO2 Film as an Effective Electron Transport Layer for High-Performance Planar Perovskite Solar Cells.

    PubMed

    Wang, Kang; Zhao, Wenjing; Liu, Jia; Niu, Jinzhi; Liu, Yucheng; Ren, Xiaodong; Feng, Jiangshan; Liu, Zhike; Sun, Jie; Wang, Dapeng; Liu, Shengzhong Frank

    2017-10-04

    Perovskite solar cells (PSCs) have received great attention because of their excellent photovoltaic properties especially for the comparable efficiency to silicon solar cells. The electron transport layer (ETL) is regarded as a crucial medium in transporting electrons and blocking holes for PSCs. In this study, CO 2 plasma generated by plasma-enhanced chemical vapor deposition (PECVD) was introduced to modify the TiO 2 ETL. The results indicated that the CO 2 plasma-treated compact TiO 2 layer exhibited better surface hydrophilicity, higher conductivity, and lower bulk defect state density in comparison with the pristine TiO 2 film. The quality of the stoichiometric TiO 2 structure was improved, and the concentration of oxygen-deficiency-induced defect sites was reduced significantly after CO 2 plasma treatment for 90 s. The PSCs with the TiO 2 film treated by CO 2 plasma for 90 s exhibited simultaneously improved short-circuit current (J SC ) and fill factor. As a result, the PSC-based TiO 2 ETL with CO 2 plasma treatment affords a power conversion efficiency of 15.39%, outperforming that based on pristine TiO 2 (13.54%). These results indicate that the plasma treatment by the PECVD method is an effective approach to modify the ETL for high-performance planar PSCs.

  2. The modulation of oxygen vacancies by the combined current effect and temperature cycling in La0.7Sr0.3CoO3 film

    NASA Astrophysics Data System (ADS)

    Li, J.; Wang, J.; Kuang, H.; Zhao, Y. Y.; Qiao, K. M.; Liu, Y.; Hu, F. X.; Sun, J. R.; Shen, B. G.

    2018-05-01

    Modulating the oxygen defect concentration has been accepted as an effective method to obtain high catalytic activity in perovskite cobaltites. However, controllably modifying the oxygen vacancy is still a challenge in this type of materials, which strongly obstructs their application. Here, we report a successful oxygen vacancies modulation in the La0.7Sr0.3CoO3 (LSCO) film by using combined current effect and temperature cycling. The temperature dependent transport properties of the LSCO/LAO film were investigated. The results revealed that the resistance of the film keeps increasing under the repeated measurements. It was found that the accumulation of the oxygen vacancy by current effect transforms the Co4+ ion into Co3+ ion, which results in the enhancement of the resistance and thus the transport switching behavior. Moreover, the resistance in the cooling process was found to be much higher than that in previous cooling and heating processes, which indicates that the oxygen escapes more quickly in the high temperature region. On the other hand, our analysis indicates that the CoO6 distortion may contribute to the switching of transport behaviors in the low temperature region. Our work provides an effective and controllable way to modulate oxygen defect in the perovskite-type oxides.

  3. Room temperature, air crystallized perovskite film for high performance solar cells

    DOE PAGES

    Dubey, Ashish; Kantack, Nicholas; Adhikari, Nirmal; ...

    2016-05-31

    For the first time, room temperature heating free growth and crystallization of perovskite films in ambient air without the use of thermal annealing is reported. Highly efficient perovskite nanorod-based solar cells were made using ITO/PEDOT:PSS/CH 3NH 3PbI 3 nanorods/PC 60BM/rhodamine/Ag. All the layers except PEDOT:PSS were processed at room temperature thereby eliminating the need for thermal treatment. Perovskite films were spin coated inside a N-2 filled glovebox and immediately were taken outside in air having 40% relative humidity (RH). Exposure to humid air was observed to promote the crystallization process in perovskite films even at room temperature. Perovskite films keptmore » for 5 hours in ambient air showed nanorod-like morphology having high crystallinity, with devices exhibiting the highest PCE of 16.83%, which is much higher than the PCE of 11.94% for traditional thermally annealed perovskite film based devices. Finally, it was concluded that moisture plays an important role in room temperature crystallization of pure perovskite nanorods, showing improved optical and charge transport properties, which resulted in high performance solar cells.« less

  4. Advancement on Lead-Free Organic-Inorganic Halide Perovskite Solar Cells: A Review.

    PubMed

    Sani, Faruk; Shafie, Suhaidi; Lim, Hong Ngee; Musa, Abubakar Ohinoyi

    2018-06-14

    Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing candidate to compete with conventional lead-based perovskite solar cells. The major challenge associated with the conventional perovskite solar cells is the toxic nature of lead (Pb) used in the active layer of perovskite material. If lead continues to be used in fabricating solar cells, negative health impacts will result in the environment due to the toxicity of lead. Alternatively, lead free perovskite solar cells could give a safe way by substituting low-cost, abundant and non toxic material. This review focuses on formability of lead-free organic-inorganic halide perovskite, alternative metal cations candidates to replace lead (Pb), and possible substitutions of organic cations, as well as halide anions in the lead-free organic-inorganic halide perovskite architecture. Furthermore, the review gives highlights on the impact of organic cations, metal cations and inorganic anions on stability and the overall performance of lead free perovskite solar cells.

  5. Unraveling the Role of Monovalent Halides in Mixed-Halide Organic-Inorganic Perovskites.

    PubMed

    Deepa, Melepurath; Ramos, F Javier; Shivaprasad, S M; Ahmad, Shahzada

    2016-03-16

    The performance of perovskite solar cells is strongly influenced by the composition and microstructure of the perovskite. A recent approach to improve the power conversion efficiencies utilized mixed-halide perovskites, but the halide ions and their roles were not directly studied. Unraveling their precise location in the perovskite layer is of paramount importance. Here, we investigated four different perovskites by using X-ray photoelectron spectroscopy, and found that among the three studied mixed-halide perovskites, CH3 NH3 Pb(I0.74 Br0.26 )3 and CH3 NH3 PbBr3-x Clx show peaks that unambiguously demonstrate the presence of iodide and bromide in the former, and bromide and chloride in the latter. The CH3 NH3 PbI3-x Clx perovskite shows anomalous behavior, the iodide content far outweighs that of the chloride; a small proportion of chloride, in all likelihood, resides deep within the TiO2 /absorber layer. Our study reveals that there are many distinguishable structural differences between these perovskites, and that these directly impact the photovoltaic performances. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Oxygen Diode Formed in Nickelate Heterostructures by Chemical Potential Mismatch

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guo, Erjia; Liu, Yaohua; Sohn, Changhee

    Deliberate control of oxygen vacancy formation and migration in perovskite oxide thin films is important for developing novel electronic and iontronic devices. Here in this paper, it is found that the concentration of oxygen vacancies (V O) formed in LaNiO 3 (LNO) during pulsed laser deposition is strongly affected by the chemical potential mismatch between the LNO film and its proximal layers. Increasing the V O concentration in LNO significantly modifies the degree of orbital polarization and drives the metal–insulator transition. Changes in the nickel oxidization state and carrier concentration in the films are confirmed by soft X-ray absorption spectroscopymore » and optical spectroscopy. The ability to unidirectional-control the oxygen flow across the heterointerface, e.g., a so-called “oxygen diode”, by exploiting chemical potential mismatch at interfaces provides a new avenue to tune the physical and electrochemical properties of complex oxides.« less

  7. Oxygen Diode Formed in Nickelate Heterostructures by Chemical Potential Mismatch

    DOE PAGES

    Guo, Erjia; Liu, Yaohua; Sohn, Changhee; ...

    2018-03-07

    Deliberate control of oxygen vacancy formation and migration in perovskite oxide thin films is important for developing novel electronic and iontronic devices. Here in this paper, it is found that the concentration of oxygen vacancies (V O) formed in LaNiO 3 (LNO) during pulsed laser deposition is strongly affected by the chemical potential mismatch between the LNO film and its proximal layers. Increasing the V O concentration in LNO significantly modifies the degree of orbital polarization and drives the metal–insulator transition. Changes in the nickel oxidization state and carrier concentration in the films are confirmed by soft X-ray absorption spectroscopymore » and optical spectroscopy. The ability to unidirectional-control the oxygen flow across the heterointerface, e.g., a so-called “oxygen diode”, by exploiting chemical potential mismatch at interfaces provides a new avenue to tune the physical and electrochemical properties of complex oxides.« less

  8. Temperature Gradient-Induced Instability of Perovskite via Ion Transport.

    PubMed

    Wang, Xinwei; Liu, Hong; Zhou, Feng; Dahan, Jeremy; Wang, Xin; Li, Zhengping; Shen, Wenzhong

    2018-01-10

    Perovskite has been known as a promising novel material for photovoltaics and other fields because of its excellent opto-electric properties and convenient fabrication. However, its stability has been a widely known haunting factor that has severely deteriorated its application in reality. In this work, it has been discovered for the first time that perovskite can become significantly chemically unstable with the existence of a temperature gradient in the system, even at temperature far below its thermal decomposition condition. A study of the detailed mechanism has revealed that the existence of a temperature gradient could induce a mass transport process of extrinsic ionic species into the perovskite layer, which enhances its decomposition process. Moreover, this instability could be effectively suppressed with a reduced temperature gradient by simple structural modification of the device. Further experiments have proved the existence of this phenomenon in different perovskites with various mainstream substrates, indicating the universality of this phenomenon in many previous studies and future research. Hopefully, this work may bring deeper understanding of its formation mechanisms and facilitate the general development of perovskite toward its real application.

  9. X-ray Scintillation in Lead Halide Perovskite Crystals

    PubMed Central

    Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.

    2016-01-01

    Current technologies for X-ray detection rely on scintillation from expensive inorganic crystals grown at high-temperature, which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, solution-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small density of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temperature. Although thermal quenching is significant at room temperature, the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temperature. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications. PMID:27849019

  10. Stable Formamidinium-Based Perovskite Solar Cells via In Situ Grain Encapsulation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Kai; Li, Zhen; Yang, Ye

    Formamidinium (FA)-based lead iodide perovskites have emerged as the most promising light-absorber materials in the prevailing perovskite solar cells (PSCs). However, they suffer from the phase-instability issue in the ambient atmosphere, which is holding back the realization of the full potential of FA-based PSCs in the context of high efficiency and stability. Herein, the tetraethylorthosilicate hydrolysis process is integrated with the solution crystallization of FA-based perovskites, forming a new film structure with individual perovskite grains encapsulated by amorphous silica layers that are in situ formed at the nanoscale. The silica not only protects perovskite grains from the degradation but alsomore » enhances the charge-carrier dynamics of perovskite films. The underlying mechanism is discussed using a joint experiment-theory approach. Through this in situ grain encapsulation method, PSCs show an efficiency close to 20% with an impressive 97% retention after 1000-h storage under ambient conditions.« less

  11. Sn2+-Stabilization in MASnI3 perovskites by superhalide incorporation.

    PubMed

    Xiang, Junxiang; Wang, Kan; Xiang, Bin; Cui, Xudong

    2018-03-28

    Sn-based hybrid halide perovskites are a potential solution to replace Pb and thereby reduce Pb toxicity in MAPbI 3 perovskite-based solar cells. However, the instability of Sn 2+ in air atmosphere causes a poor reproducibility of MASnI 3 , hindering steps towards this goal. In this paper, we propose a new type of organic metal-superhalide perovskite of MASnI 2 BH 4 and MASnI 2 AlH 4 . Through first-principles calculations, our results reveal that the incorporation of BH 4 and AlH 4 superhalides can realize an impressive enhancement of oxidation resistance of Sn 2+ in MASnI 3 perovskites because of the large electron transfer between Sn 2+ and [BH 4 ] - /[AlH 4 ] - . Meanwhile, the high carrier mobility is preserved in these superhalide perovskites and only a slight decrease is observed in the optical absorption strength. Our studies provide a new path to attain highly stable performance and reproducibility of Sn-based perovskite solar cells.

  12. Doping Lanthanide into Perovskite Nanocrystals: Highly Improved and Expanded Optical Properties.

    PubMed

    Pan, Gencai; Bai, Xue; Yang, Dongwen; Chen, Xu; Jing, Pengtao; Qu, Songnan; Zhang, Lijun; Zhou, Donglei; Zhu, Jinyang; Xu, Wen; Dong, Biao; Song, Hongwei

    2017-12-13

    Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Er 3+ , and Yb 3+ ) into the lattices of CsPbCl 3 perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

  13. Influence of coating steps of perovskite on low-temperature amorphous compact TiO x upon the morphology, crystallinity, and photovoltaic property correlation in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Shahiduzzaman, Md.; Furumoto, Yoshikazu; Yamamoto, Kohei; Yonezawa, Kyosuke; Azuma, Yosuke; Kitamura, Michinori; Matsuzaki, Hiroyuki; Karakawa, Makoto; Kuwabara, Takayuki; Takahashi, Kohshin; Taima, Tetsuya

    2018-03-01

    The fabrication of high-efficiency solution-processable perovskite solar cells has been achieved using mesostructured films and compact titanium dioxide (TiO2) layers in a process that involves high temperatures and cost. Here, we present an efficient approach for fabricating chemical-bath-deposited, low-temperature, and low-cost amorphous compact TiO x -based planar heterojunction perovskite solar cells by one-step and two-step coatings of the perovskite layer. We also investigate the effect of the number of perovskite coating steps on the compact TiO x layer. The grazing incidence wide-angle X-ray scattering technique is used to clarify the relationship between morphology, crystallinity, and photovoltaic properties of the resulting devices. Analysis of the films revealed that one-step spin-coating of perovskite exhibited an enhancement of film quality and crystallization that correlates to photovoltaic performance 1.5 times higher than that of a two-step-coated device. Our findings show that the resulting morphology, crystallinity, and device performances are strongly dependent on the number of coating steps of the perovskite thin layer on the compact TiO x layer. This result is useful knowledge for the low-cost production of planar perovskite solar cells.

  14. Cu-In Halide Perovskite Solar Absorbers.

    PubMed

    Zhao, Xin-Gang; Yang, Dongwen; Sun, Yuanhui; Li, Tianshu; Zhang, Lijun; Yu, Liping; Zunger, Alex

    2017-05-17

    The long-term chemical instability and the presence of toxic Pb in otherwise stellar solar absorber APbX 3 made of organic molecules on the A site and halogens for X have hindered their large-scale commercialization. Previously explored ways to achieve Pb-free halide perovskites involved replacing Pb 2+ with other similar M 2+ cations in ns 2 electron configuration, e.g., Sn 2+ or by Bi 3+ (plus Ag + ), but unfortunately this showed either poor stability (M = Sn) or weakly absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps stability and good optoelectronic properties might be contraindicated. Herein, we exploit the electronic structure underpinning of classic Cu[In,Ga]Se 2 (CIGS) chalcopyrite solar absorbers to design Pb-free halide perovskites by transmuting 2Pb to the pair [B IB + C III ] such as [Cu + Ga] or [Ag + In] and combinations thereof. The resulting group of double perovskites with formula A 2 BCX 6 (A = K, Rb, Cs; B = Cu, Ag; C = Ga, In; X = Cl, Br, I) benefits from the ionic, yet narrow-gap character of halide perovskites, and at the same time borrows the advantage of the strong Cu(d)/Se(p) → Ga/In(s/p) valence-to-conduction-band absorption spectra known from CIGS. This constitutes a new group of CuIn-based Halide Perovskite (CIHP). Our first-principles calculations guided by such design principles indicate that the CIHPs class has members with clear thermodynamic stability, showing direct band gaps, and manifesting a wide-range of tunable gap values (from zero to about 2.5 eV) and combination of light electron and heavy-light hole effective masses. Materials screening of candidate CIHPs then identifies the best-of-class Rb 2 [CuIn]Cl 6 , Rb 2 [AgIn]Br 6 , and Cs 2 [AgIn]Br 6 , having direct band gaps of 1.36, 1.46, and 1.50 eV, and theoretical spectroscopic limited maximal efficiency comparable to chalcopyrites and CH 3 NH 3 PbI 3 . Our finding offers a new routine for designing new-type Pb-free halide perovskite solar

  15. Organohalide Perovskites for Solar Energy Conversion.

    PubMed

    Lin, Qianqian; Armin, Ardalan; Burn, Paul L; Meredith, Paul

    2016-03-15

    Lead-based organohalide perovskites have recently emerged as arguably the most promising of all next generation thin film solar cell technologies. Power conversion efficiencies have reached 20% in less than 5 years, and their application to other optoelectronic device platforms such as photodetectors and light emitting diodes is being increasingly reported. Organohalide perovskites can be solution processed or evaporated at low temperatures to form simple thin film photojunctions, thus delivering the potential for the holy grail of high efficiency, low embedded energy, and low cost photovoltaics. The initial device-driven "perovskite fever" has more recently given way to efforts to better understand how these materials work in solar cells, and deeper elucidation of their structure-property relationships. In this Account, we focus on this element of organohalide perovskite chemistry and physics in particular examining critical electro-optical, morphological, and architectural phenomena. We first examine basic crystal and chemical structure, and how this impacts important solar-cell related properties such as the optical gap. We then turn to deeper electronic phenomena such as carrier mobilities, trap densities, and recombination dynamics, as well as examining ionic and dielectric properties and how these two types of physics impact each other. The issue of whether organohalide perovskites are predominantly nonexcitonic at room temperature is currently a matter of some debate, and we summarize the evidence for what appears to be the emerging field consensus: an exciton binding energy of order 10 meV. Having discussed the important basic chemistry and physics we turn to more device-related considerations including processing, morphology, architecture, thin film electro-optics and interfacial energetics. These phenomena directly impact solar cell performance parameters such as open circuit voltage, short circuit current density, internal and external quantum efficiency

  16. Unraveling the Chemical Nature of the 3D "Hollow" Hybrid Halide Perovskites.

    PubMed

    Spanopoulos, Ioannis; Ke, Weijun; Stoumpos, Constantinos C; Schueller, Emily C; Kontsevoi, Oleg Y; Seshadri, Ram; Kanatzidis, Mercouri G

    2018-05-02

    The newly introduced class of 3D halide perovskites, termed "hollow" perovskites, has been recently demonstrated as light absorbing semiconductor materials for fabricating lead-free perovskite solar cells with enhanced efficiency and superior stability. Hollow perovskites derive from three-dimensional (3D) AMX 3 perovskites ( A = methylammonium (MA), formamidinium (FA); M = Sn, Pb; X = Cl, Br, I), where small molecules such as ethylenediammonium cations ( en) can be incorporated as the dication without altering the structure dimensionality. We present in this work the inherent structural properties of the hollow perovskites and expand this class of materials to the Pb-based analogues. Through a combination of physical and spectroscopic methods (XRD, gas pycnometry, 1 H NMR, TGA, SEM/EDX), we have assigned the general formula (A) 1- x ( en) x (M) 1-0.7 x (X) 3-0.4 x to the hollow perovskites. The incorporation of en in the 3D perovskite structure leads to massive M and X vacancies in the 3D [ MX 3 ] framework, thus the term hollow. The resulting materials are semiconductors with significantly blue-shifted direct band gaps from 1.25 to 1.51 eV for Sn-based perovskites and from 1.53 to 2.1 eV for the Pb-based analogues. The increased structural disorder and hollow nature were validated by single crystal X-ray diffraction analysis as well as pair distribution function (PDF) analysis. Density functional theory (DFT) calculations support the experimental trends and suggest that the observed widening of the band gap is attributed to the massive M and X vacancies, which create a less connected 3D hollow structure. The resulting materials have superior air stability, where in the case of Sn-based hollow perovskites it exceeds two orders of temporal magnitude compared to the conventional full perovskites of MASnI 3 and FASnI 3 . The hollow perovskite compounds pose as a new platform of promising light absorbers that can be utilized in single junction or tandem solar cells.

  17. The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

    2018-01-01

    Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

  18. Matching Charge Extraction Contact for Wide-Bandgap Perovskite Solar Cells.

    PubMed

    Lin, Yuze; Chen, Bo; Zhao, Fuwen; Zheng, Xiaopeng; Deng, Yehao; Shao, Yuchuan; Fang, Yanjun; Bai, Yang; Wang, Chunru; Huang, Jinsong

    2017-07-01

    Efficient wide-bandgap (WBG) perovskite solar cells are needed to boost the efficiency of silicon solar cells to beyond Schottky-Queisser limit, but they suffer from a larger open circuit voltage (V OC ) deficit than narrower bandgap ones. Here, it is shown that one major limitation of V OC in WBG perovskite solar cells comes from the nonmatched energy levels of charge transport layers. Indene-C60 bisadduct (ICBA) with higher-lying lowest-unoccupied-molecular-orbital is needed for WBG perovskite solar cells, while its energy-disorder needs to be minimized before a larger V OC can be observed. A simple method is applied to reduce the energy disorder by isolating isomer ICBA-tran3 from the as-synthesized ICBA-mixture. WBG perovskite solar cells with ICBA-tran3 show enhanced V OC by 60 mV, reduced V OC deficit of 0.5 V, and then a record stabilized power conversion efficiency of 18.5%. This work points out the importance of matching the charge transport layers in perovskite solar cells when the perovskites have a different composition and energy levels. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Reversible Structural Swell-Shrink and Recoverable Optical Properties in Hybrid Inorganic-Organic Perovskite.

    PubMed

    Zhang, Yupeng; Wang, Yusheng; Xu, Zai-Quan; Liu, Jingying; Song, Jingchao; Xue, Yunzhou; Wang, Ziyu; Zheng, Jialu; Jiang, Liangcong; Zheng, Changxi; Huang, Fuzhi; Sun, Baoquan; Cheng, Yi-Bing; Bao, Qiaoliang

    2016-07-26

    Ion migration in hybrid organic-inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current-voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light-matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA(+) ions, will induce a reversible structural swell-shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell-shrink process. Knowledge regarding reversible structural swell-shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.

  20. Method for single crystal growth of photovoltaic perovskite material and devices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Jinsong; Dong, Qingfeng

    Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

  1. High-Efficiency Flexible Solar Cells Based on Organometal Halide Perovskites.

    PubMed

    Wang, Yuming; Bai, Sai; Cheng, Lu; Wang, Nana; Wang, Jianpu; Gao, Feng; Huang, Wei

    2016-06-01

    Flexible and light-weight solar cells are important because they not only supply power to wearable and portable devices, but also reduce the transportation and installation cost of solar panels. High-efficiency organometal halide perovskite solar cells can be fabricated by a low-temperature solution process, and hence are promising for flexible-solar-cell applications. Here, the development of perovskite solar cells is briefly discussed, followed by the merits of organometal halide perovskites as promising candidates as high-efficiency, flexible, and light-weight photovoltaic materials. Afterward, recent developments of flexible solar cells based on perovskites are reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Field-emission from quantum-dot-in-perovskite solids

    PubMed Central

    García de Arquer, F. Pelayo; Gong, Xiwen; Sabatini, Randy P.; Liu, Min; Kim, Gi-Hwan; Sutherland, Brandon R.; Voznyy, Oleksandr; Xu, Jixian; Pang, Yuangjie; Hoogland, Sjoerd; Sinton, David; Sargent, Edward

    2017-01-01

    Quantum dot and well architectures are attractive for infrared optoelectronics, and have led to the realization of compelling light sensors. However, they require well-defined passivated interfaces and rapid charge transport, and this has restricted their efficient implementation to costly vacuum-epitaxially grown semiconductors. Here we report solution-processed, sensitive infrared field-emission photodetectors. Using quantum-dots-in-perovskite, we demonstrate the extraction of photocarriers via field emission, followed by the recirculation of photogenerated carriers. We use in operando ultrafast transient spectroscopy to sense bias-dependent photoemission and recapture in field-emission devices. The resultant photodiodes exploit the superior electronic transport properties of organometal halide perovskites, the quantum-size-tuned absorption of the colloidal quantum dots and their matched interface. These field-emission quantum-dot-in-perovskite photodiodes extend the perovskite response into the short-wavelength infrared and achieve measured specific detectivities that exceed 1012 Jones. The results pave the way towards novel functional photonic devices with applications in photovoltaics and light emission. PMID:28337981

  3. Multifunctional MgO Layer in Perovskite Solar Cells.

    PubMed

    Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

    2015-06-08

    A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Perovskite Solar Cells—Towards Commercialization

    DOE PAGES

    Ono, Luis K.; Park, Nam-Gyu; Zhu, Kai; ...

    2017-07-13

    The Symposium ES1, Perovskite Solar Cells - Towards Commercialization, held at the 2017 Materials Research Society (MRS) Spring Meeting in Phoenix, Arizona (April 17-21, 2017) received ~200 abstracts. The 23 invited talks and 72 contributed oral presentations as well as 3 poster presentation sessions were organized into 13 principal themes according to the contents of the received abstracts. This Energy Focus article provides a concise summary of the opinions from the scientists and engineers who participated in this symposium regarding the recent progresses, challenges, and future directions for perovskite solar cells as well as other optoelectronic devices.

  5. Cu/Cu2O nanocomposite films as a p-type modified layer for efficient perovskite solar cells.

    PubMed

    Chen, You-Jyun; Li, Ming-Hsien; Huang, Jung-Chun-Andrew; Chen, Peter

    2018-05-16

    Cu/Cu 2 O films grown by ion beam sputtering were used as p-type modified layers to improve the efficiency and stability of perovskite solar cells (PSCs) with an n-i-p heterojunction structure. The ratio of Cu to Cu 2 O in the films can be tuned by the oxygen flow ratio (O 2 /(O 2  + Ar)) during the sputtering of copper. Auger electron spectroscopy was performed to determine the elemental composition and chemical state of Cu in the films. Ultraviolet photoelectron spectroscopy and photoluminescence spectroscopy revealed that the valence band maximum of the p-type Cu/Cu 2 O matches well with the perovskite. The Cu/Cu 2 O film not only acts as a p-type modified layer but also plays the role of an electron blocking buffer layer. By introducing the p-type Cu/Cu 2 O films between the low-mobility hole transport material, spiro-OMeTAD, and the Ag electrode in the PSCs, the device durability and power conversion efficiency (PCE) were effectively improved as compared to the reference devices without the Cu/Cu 2 O interlayer. The enhanced PCE is mainly attributed to the high hole mobility of the p-type Cu/Cu 2 O film. Additionally, the Cu/Cu 2 O film serves as a protective layer against the penetration of humidity and Ag into the perovskite active layer.

  6. Structural evolution of the double perovskites Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) upon reduction: Magnetic behavior of the uranium cations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pinacca, R.M., E-mail: rmp@unsl.edu.ar; Viola, M.C.; Pedregosa, J.C.

    2011-11-15

    Highlights: {yields} Evolution of the double perovskites Sr{sub 2}B'UO{sub 6} upon reduction were studied by XRPD. {yields} Orthorhombic (Pnma) disordered perovskites SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} were obtained at 900 {sup o}C. {yields} U{sup 5+/4+} and Zn{sup 2+} cations are distributed at random over the octahedral positions. {yields} AFM ordering for the perovskite with B' = Zn appears below 30 K. -- Abstract: We describe the preparation of five perovskite oxides obtained upon reduction of Sr{sub 2}B'UO{sub 6} (B' = Mn, Fe, Co, Ni, Zn) with H{sub 2}/N{sub 2} (5%/95%) at 900 {sup o}C during 8 h, and their structural characterizationmore » by X-ray powder diffraction (XRPD). During the reduction process there is a partial segregation of the elemental metal when B' = Co, Ni, Fe, and the corresponding B'O oxide when B' = Mn, Zn. Whereas the parent, oxygen stoichiometric double perovskites Sr{sub 2}B'UO{sub 6} are long-range ordered concerning B' and U cations. The crystal structures of the reduced phases, SrB'{sub 0.5-x}U{sub 0.5+x}O{sub 3} with 0.37 < x < 0.27, correspond to simple, disordered perovskites; they are orthorhombic, space group Pnma (No. 62), with a full cationic disorder at the B site. Magnetic measurements performed on the phase with B' = Zn, indicate uncompensated antiferromagnetic ordering of the U{sup 5+}/U{sup 4+} sublattice below 30 K.« less

  7. Efficient Planar Structured Perovskite Solar Cells with Enhanced Open-Circuit Voltage and Suppressed Charge Recombination Based on a Slow Grown Perovskite Layer from Lead Acetate Precursor.

    PubMed

    Li, Cong; Guo, Qiang; Wang, Zhibin; Bai, Yiming; Liu, Lin; Wang, Fuzhi; Zhou, Erjun; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

    2017-12-06

    For planar structured organic-inorganic hybrid perovskite solar cells (PerSCs) with the poly(3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) hole transport layer, the open-circuit voltage (V oc ) of the device is limited to be about 1.0 V, resulting in inferior performance in comparison with TiO 2 -based planar counterparts. Therefore, increasing V oc of the PEDOT:PSS-based planar device is an important way to enhance the efficiency of the PerSCs. Herein, we demonstrate a novel approach for perovskite film formation and the film is formed by slow growth from lead acetate precursor via a one-step spin-coating process without the thermal annealing (TA) process. Because the perovskite layer grows slowly and naturally, high-quality perovskite film can be achieved with larger crystalline particles, less defects, and smoother surface morphology. Ultraviolet absorption, X-ray diffraction, scanning electron microscopy, steady-state fluorescence spectroscopy (photoluminescence), and time-resolved fluorescence spectroscopy are used to clarify the crystallinity, morphology, and internal defects of perovskite thin films. The power conversion efficiency of p-i-n PerSCs based on slow-grown film (16.33%) shows greatly enhanced performance compared to that of the control device based on traditional thermally annealed perovskite film (14.33%). Furthermore, the V oc of the slow-growing device reaches 1.12 V, which is 0.1 V higher than that of the TA device. These findings indicate that slow growth of the perovskite layer from lead acetate precursor is a promising approach to achieve high-quality perovskite film for high-performance PerSCs.

  8. Stable Graphene-Two-Dimensional Multiphase Perovskite Heterostructure Phototransistors with High Gain.

    PubMed

    Shao, Yuchuan; Liu, Ye; Chen, Xiaolong; Chen, Chen; Sarpkaya, Ibrahim; Chen, Zhaolai; Fang, Yanjun; Kong, Jaemin; Watanabe, Kenji; Taniguchi, Takashi; Taylor, André; Huang, Jinsong; Xia, Fengnian

    2017-12-13

    Recently, two-dimensional (2D) organic-inorganic perovskites emerged as an alternative material for their three-dimensional (3D) counterparts in photovoltaic applications with improved moisture resistance. Here, we report a stable, high-gain phototransistor consisting of a monolayer graphene on hexagonal boron nitride (hBN) covered by a 2D multiphase perovskite heterostructure, which was realized using a newly developed two-step ligand exchange method. In this phototransistor, the multiple phases with varying bandgap in 2D perovskite thin films are aligned for the efficient electron-hole pair separation, leading to a high responsivity of ∼10 5 A W -1 at 532 nm. Moreover, the designed phase alignment method aggregates more hydrophobic butylammonium cations close to the upper surface of the 2D perovskite thin film, preventing the permeation of moisture and enhancing the device stability dramatically. In addition, faster photoresponse and smaller 1/f noise observed in the 2D perovskite phototransistors indicate a smaller density of deep hole traps in the 2D perovskite thin film compared with their 3D counterparts. These desirable properties not only improve the performance of the phototransistor, but also provide a new direction for the future enhancement of the efficiency of 2D perovskite photovoltaics.

  9. Electrical Conducting and Mechanism of Oxygen-Deficient Tin Oxide Films Deposited by RF Magnetron Sputtering at Various O2/Ar Ratios

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Chengbiao; Lv, Changchun; Wang, Yang; Peng, Zhijian; Fu, Xiuli

    Oxygen-deficient tin oxide thin films were prepared by radiofrequency magnetron sputtering with a sintered non-stoichiometric tin oxide ceramic target under an atmosphere of various ratios of O2/Ar from pure Ar to 1:1. X-ray diffraction analysis showed that the thin films were polycrystalline with relatively strong (1 1 0), (1 0 1) and (2 1 1) diffraction peaks. Scanning electron microscopy observation revealed that the thin films prepared at different O2/Ar ratios were all of relatively dense and homogeneous structure. With increasing O2/Ar ratio, the grain size of the films decreased slightly, and their chemical composition became close to the stoichiometric SnO2; but the deposition rate as well as film thickness increased first and then decreased sharply. It was revealed that the main defect in obtained films was oxygen vacancy (VO), and as the O2/Ar ratio increased, the concentration of VO fell down monotonously, which would lead to an increased electrical resistivity.

  10. Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

    NASA Astrophysics Data System (ADS)

    Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

    2018-03-01

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can

  11. Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

    PubMed

    Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M; Alsari, Mejd; Booker, Edward P; Hutter, Eline M; Pearson, Andrew J; Lilliu, Samuele; Savenije, Tom J; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H; Stranks, Samuel D

    2018-03-21

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach

  12. Topochemical synthesis of cation ordered double perovskite oxynitrides.

    PubMed

    Ceravola, Roberta; Oró-Solé, Judith; Black, Ashley P; Ritter, Clemens; Puente Orench, Inés; Mata, Ignasi; Molins, Elies; Frontera, Carlos; Fuertes, Amparo

    2017-04-19

    Topochemical nitridation in ammonia at moderate temperatures of cation ordered Sr 2 FeWO 6 produces new antiferromagnetic double perovskite oxynitrides Sr 2 FeWO 6-x N x with 0 < x ≤ 1. Nitrogen introduction induces the oxidation of Fe 2+ to Fe 3+ and decreases T N from 38 K (x = 0) to 13 K for Sr 2 FeWO 5 N which represents the first example of a double perovskite oxynitride with both high cationic order and nitrogen content. This synthetic approach can be extended to other cation combinations expanding the possibility of new materials in the large group of double perovskites.

  13. Perovskites keep on giving

    NASA Astrophysics Data System (ADS)

    2018-05-01

    Whether you like exploring the mysteries of light-matter interactions, playing with a versatile chemical platform, or developing the most efficient devices, metal halide perovskites could be the materials for you.

  14. Laser deposition of resonant silicon nanoparticles on perovskite for photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Tiguntseva, E. Y.; Zalogina, A. S.; Milichko, V. A.; Zuev, D. A.; Omelyanovich, M. M.; Ishteev, A.; Cerdan Pasaran, A.; Haroldson, R.; Makarov, S. V.; Zakhidov, A. A.

    2017-11-01

    Hybrid lead halide perovskite based optoelectronics is a promising area of modern technologies yielding excellent characteristics of light emitting diodes and lasers as well as high efficiencies of photovoltaic devices. However, the efficiency of perovskite based devices hold a potential of further improvement. Here we demonstrate high photoluminescence efficiency of perovskites thin films via deposition of resonant silicon nanoparticles on their surface. The deposited nanoparticles have a number of advances over their plasmonic counterparts, which were applied in previous studies. We show experimentally the increase of photoluminescence of perovskite film with the silicon nanoparticles by 150 % as compared to the film without the nanoparticles. The results are supported by numerical calculations. Our results pave the way to high throughput implementation of low loss resonant nanoparticles in order to create highly effective perovskite based optoelectronic devices.

  15. Enhanced photocurrent density of HTM-free perovskite solar cells by carbon quantum dots

    NASA Astrophysics Data System (ADS)

    Zou, Haiyuan; Guo, Daipeng; He, Bowen; Yu, Jiaguo; Fan, Ke

    2018-02-01

    Full-printable and hole transport material (HTM)-free perovskite solar cells (PSCs) with carbon counter electrodes feature high stability and low cost. However, the perovskite film prepared by conventional one-step solution-coating method always shows a relatively poor coverage on the substrate, leading to the limit of the photocurrent density. In this study, we incorporated carbon quantum dots (CQDs) in the perovskite films, and investigated their effects on the performance of TiO2 nanosheet-based and HTM-free PSCs. It was found that the addition of CQDs to the perovskite film can enhance the photocurrent density of PSCs, and the optimal PSC with 0.1% CQDs evolved 60% higher photocurrent density than the pristine one. The improved photocurrent density was attributed to the heterogeneous nuclei derived from CQDs during perovskite crystallization, which would increase amount of perovskite nuclei and form a fine perovskite grain, leading to a better coverage on the substrate. Moreover, due to the excellent conductivity, CQDs in perovskite films could efficiently transport the photo-excited electrons, accelerating the separation and mobilization of charge carriers. This study presents the incorporation of CQDs in perovskite as an efficient approach to promote the performance of HTM-free PSCs.

  16. Interplay of Cation Ordering and Ferroelectricity in Perovskite Tin Iodides: Designing a Polar Halide Perovskite for Photovoltaic Applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gou, Gaoyang; Young, Joshua; Liu, Xian

    2016-09-28

    Owing to its ideal semiconducting band gap and good carrier transport properties, the fully inorganic perovskite CsSnI 3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic inorganic lead halide perovskite CH 3NH 3PbI 3, CsSnI 3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI 3. Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI 3, including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to createmore » the double perovskite (CsRb)Sn 2I 6. We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI 6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI 3. More importantly, unlike nonpolar CsSnI 3, the electric polarization present in ferroelectric (CsRb)Sn 2I 6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with,potentially enhanced energy conversion efficiency.« less

  17. Trace fossils from storm-influenced, oxygen-deficient outer shelf: lower Mississippian Price Formation of southern West Virginia

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bjerstedt, T.W.

    The Price Formation in southern West Virginia was deposited dominantly in an oxygen-deficient, outer shelf environment along a siliciclastic profile from the basin plain to the alluvial plain. An overturned section at Bluefield, West Virginia, exposes the following lithofacies and environments in ascending order: laminated black silt-shales from the basin plain; a sand-rich submarine fan; outer shelf tempestites of hummocky, cross-stratified fine sandstone and completely bioturbated grayish-black, silt-shales; and shoreline sands in transition to thin, dirty coals of the coastal plain and Maccrady red beds of the alluvial plain. Trace fossils are abundant and are best preserved on the solesmore » of hummocky, cross-stratified sandstones. The Zoophycos ichnofacies occurs throughout 80 m of outer shelf deposits, which accumulated above storm wave base. The Zoophycos ichnofacies grades into the nearshore Skolithus ichnofacies with no apparent intervening Cruziana ichnofacies. Most ichnotaxa identified from the outer shelf are fodinichnia or pascichnia. Planar and helical Zoophycos, Helminthopsis, Helminthoida, Sclarituba (neonereites form), and Chondrites are characteristics. In most schemes, the Zoophycos ichnofacies occurs below storm wave base. At Bluefield, it has displaced the Cruziana ichnofacies above storm wave base due to the maintenance of a dysaerobic environment. The abundant organic matter preserved in a density-stratified water column was continually replenished during periods of upwelling. Conditions were extremely favorable for deposit feeders, but inhibiting to suspension feeders that were less tolerant of oxygen stress. The absence of distributary channel sands in the vertical sequence also indicates that offshore environments received no influx of oxygenated waters from the Price delta.« less

  18. Recent progress in efficient hybrid lead halide perovskite solar cells

    PubMed Central

    Cui, Jin; Yuan, Huailiang; Li, Junpeng; Xu, Xiaobao; Shen, Yan; Lin, Hong; Wang, Mingkui

    2015-01-01

    The efficiency of perovskite solar cells (PSCs) has been improved from 9.7 to 19.3%, with the highest value of 20.1% achieved in 2014. Such a high photovoltaic performance can be attributed to optically high absorption characteristics and balanced charge transport properties with long diffusion lengths of the hybrid lead halide perovskite materials. In this review, some fundamental details of hybrid lead iodide perovskite materials, various fabrication techniques and device structures are described, aiming for a better understanding of these materials and thus highly efficient PSC devices. In addition, some advantages and open issues are discussed here to outline the prospects and challenges of using perovskites in commercial photovoltaic devices. PMID:27877815

  19. Overcoming the Photovoltage Plateau in Large Bandgap Perovskite Photovoltaics.

    PubMed

    Rajagopal, Adharsh; Stoddard, Ryan J; Jo, Sae Byeok; Hillhouse, Hugh W; Jen, Alex K-Y

    2018-05-09

    Development of large bandgap (1.80-1.85 eV E g ) perovskite is crucial for perovskite-perovskite tandem solar cells. However, the performance of 1.80-1.85 eV E g perovskite solar cells (PVKSCs) are significantly lagging their counterparts in the 1.60-1.75 eV E g range. This is because the photovoltage ( V oc ) does not proportionally increase with E g due to lower optoelectronic quality of conventional (MA,FA,Cs)Pb(I,Br) 3 and results in a photovoltage plateau ( V oc limited to 80% of the theoretical limit for ∼1.8 eV E g ). Here, we incorporate phenylethylammonium (PEA) in a mixed-halide perovskite composition to solve the inherent material-level challenges in 1.80-1.85 eV E g perovskites. The amount of PEA incorporation governs the topography and optoelectronic properties of resultant films. Detailed structural and spectroscopic characterization reveal the characteristic trends in crystalline size, orientation, and charge carrier recombination dynamics and rationalize the origin of improved material quality with higher luminescence. With careful interface optimization, the improved material characteristics were translated to devices and V oc values of 1.30-1.35 V were achieved, which correspond to 85-87% of the theoretical limit. Using an optimal amount of PEA incorporation to balance the increase in V oc and the decrease in charge collection, a highest power conversion efficiency of 12.2% was realized. Our results clearly overcome the photovoltage plateau in the 1.80-1.85 eV E g range and represent the highest V oc achieved for mixed-halide PVKSCs. This study provides widely translatable insights, an important breakthrough, and a promising platform for next-generation perovskite tandems.

  20. Atmospheric Processing of Perovskite Solar Cells Using Intense Pulsed Light Sintering

    NASA Astrophysics Data System (ADS)

    Ankireddy, Krishnamraju; Lavery, Brandon W.; Druffel, Thad

    2018-02-01

    Atmospheric processing of metal-organic halide perovskite materials is highly desirable for large-scale manufacturing of solar cells. Atmospheric deposition and thermal processing of perovskite thin films for photovoltaic applications facilitated via rapid intense pulsed light (IPL) processing have been carried out. The interplay between the deposition chemistry, process, and IPL parameters to produce a functional photoactive thin film is discussed. Further addition of polyvinylpyrrolidone (PVP) as functional surfactant is explored to influence grain growth during the IPL process. Structural analysis by x-ray diffraction revealed formation of mixed-phase perovskite crystals from methylammonium chloride and lead iodide precursors. Ultraviolet-visible (UV-Vis) spectroscopy indicated that the light absorption by the perovskite films lay within a narrow band of the visible spectrum with bandgap of 2.9 eV. Scanning electron microscopy characterization of the surface morphology of the perovskite films revealed that addition of PVP to the ink chemistry assisted the IPL process in forming a fully covered surface with clearly defined grains. Functional devices with perovskite thin film processed by IPL under fully atmospheric conditions were demonstrated.