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Sample records for layered perovskite structure

  1. Layered structures of organic/inorganic hybrid halide perovskites

    NASA Astrophysics Data System (ADS)

    Huan, Tran Doan; Tuoc, Vu Ngoc; Minh, Nguyen Viet

    2016-03-01

    Organic-inorganic hybrid halide perovskites, in which the A cations of an ABX3 perovskite are replaced by organic cations, may be used for photovoltaic and solar thermoelectric applications. In this contribution, we systematically study three lead-free hybrid perovskites, i.e., methylammonium tin iodide CH3NH3SnI3 , ammonium tin iodide NH4SnI3 , and formamidnium tin iodide HC (NH2)2SnI3 by first-principles calculations. We find that in addition to the commonly known motif in which the corner-shared SnI6 octahedra form a three-dimensional network, these materials may also favor a two-dimensional (layered) motif formed by alternating layers of the SnI6 octahedra and the organic cations. These two motifs are nearly equal in free energy and are separated by low barriers. These layered structures features many flat electronic bands near the band edges, making their electronic structures significantly different from those of the structural phases composed of three-dimension networks of SnI6 octahedra. Furthermore, because the electronic structures of HC (NH2)2SnI3 are found to be rather similar to those of CH3NH3SnI3 , formamidnium tin iodide may also be promising for the applications of methylammonium tin iodide.

  2. Research Update: The electronic structure of hybrid perovskite layers and their energetic alignment in devices

    NASA Astrophysics Data System (ADS)

    Olthof, Selina

    2016-09-01

    In recent years, the interest in hybrid organic-inorganic perovskites has increased at a rapid pace due to their tremendous success in the field of thin film solar cells. This area closely ties together fundamental solid state research and device application, as it is necessary to understand the basic material properties to optimize the performances and open up new areas of application. In this regard, the energy levels and their respective alignment with adjacent charge transport layers play a crucial role. Currently, we are lacking a detailed understanding about the electronic structure and are struggling to understand what influences the alignment, how it varies, or how it can be intentionally modified. This research update aims at giving an overview over recent results regarding measurements of the electronic structure of hybrid perovskites using photoelectron spectroscopy to summarize the present status.

  3. New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure

    SciTech Connect

    Xiong, Kecai; Liu, Wei; Teat, Simon J.; An, Litao; Wang, Hao; Emge, Thomas J.; Li, Jing

    2015-10-15

    Two new hybrid lead halides (H{sub 2}BDA)[PbI{sub 4}] (1) (H{sub 2}BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI{sub 3}] (2) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively. - Graphical abstract: Two new hybrid lead halides built on one-dimensional edge-sharing double chains and two-dimensional corner-sharing perovskite layers are synthesized and their structural and electronic properties are analyzed. - Highlights: • Two new hybrid lead iodides are designed, synthesized, and characterized. • They are closely related to, but different from, perovskite structures. • The electronic properties of both compounds are analyzed by DFT calculations.

  4. Ion-exchangeable oxides with layered perovskite structures as photocatalysts for overall water splitting

    SciTech Connect

    Takata, T.; Hara, M.; Kondo, J.N.; Domen, K.; Shinohara, K.; Tanaka, A.

    1997-12-31

    A novel series of photocatalysts for an overall water splitting is reported. The catalysts have a layered perovskite type structure with a general formula of A{sub 2{minus}x}La{sub 2}Ti{sub 3{minus}x}Nb{sub x}O{sub 10} (A = K, Rb, Cs; x = 0, 0.5, 1.0). The catalysts, except for the one with x = 1.0, are spontaneously hydrated, and the band gap irradiation induced efficient evolution of H{sub 2} and O{sub 2} in a stoichiometric ratio from an aqueous alkaline solution when a proper amount of Ni loading was made. The reaction mechanism of water splitting on these catalysts is discussed on the bases of the structural study of the catalysts.

  5. A two-layer structured PbI2 thin film for efficient planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Ying, Chao; Shi, Chengwu; Wu, Ni; Zhang, Jincheng; Wang, Mao

    2015-07-01

    In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm-2 and a fill factor of 0.67.

  6. A two-layer structured PbI2 thin film for efficient planar perovskite solar cells.

    PubMed

    Ying, Chao; Shi, Chengwu; Wu, Ni; Zhang, Jincheng; Wang, Mao

    2015-07-28

    In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67. PMID:26118756

  7. New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure

    NASA Astrophysics Data System (ADS)

    Xiong, Kecai; Liu, Wei; Teat, Simon J.; An, Litao; Wang, Hao; Emge, Thomas J.; Li, Jing

    2015-10-01

    Two new hybrid lead halides (H2BDA)[PbI4] (1) (H2BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI3] (2) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively.

  8. Doped lanthanum nickelates with a layered perovskite structure as bifunctional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Jung, Jong-Hyuk; Im, Won Bin; Yoon, Sukeun; Shin, Kyung-Hee; Lee, Jong-Won

    2013-10-23

    Rechargeable metal-air batteries have attracted a great interest in recent years because of their high energy density. The critical challenges facing these technologies include the sluggish kinetics of the oxygen reduction-evolution reactions on a cathode (air electrode). Here, we report doped lanthanum nickelates (La2NiO4) with a layered perovskite structure that serve as efficient bifunctional electrocatalysts for oxygen reduction and evolution in an aqueous alkaline electrolyte. Rechargeable lithium-air and zinc-air batteries assembled with these catalysts exhibit remarkably reduced discharge-charge voltage gaps (improved round-trip efficiency) as well as high stability during cycling. PMID:24053465

  9. Ion exchange and structural aging in the layered perovskite phases H(1-x)Li(x)LaTiO4.

    PubMed

    Yip, T W S; Cussen, E J

    2013-06-17

    Grinding together the solid acid HLaTiO4 with stoichiometric quantities of lithium hydroxide monohydrate gives the solid solution H(1-x)Li(x)LaTiO4. The structures of these crystalline phases have been refined against neutron powder diffraction data to show that all of these compounds crystallize in the centrosymmetric space group P4/nmm. The protons and lithium cations occupy sites between the perovskite layers; the former in hydroxide groups that hydrogen-bond to adjacent layers while Li(+) is in four-coordinate sites that bridge the perovskite slabs with a geometry intermediate between square-planar and tetrahedral. The reaction proceeds rapidly, but the unit cell size continues to evolve over the course of days with a gradual compression along the interlayer direction that can be modeled using a power law dependence reminiscent of an Ostwald ripening process. On heating, these materials undergo a mass loss because of dehydration but retain the layered Ruddlesden-Popper structure up to 480 °C before a substantial loss of crystallinity on further heating to 600 °C. Impedance spectroscopy studies of the dehydrated materials shows that Li(+) mobility in these materials is lower than the LiLaTiO4 end member, possibly because of microstructural effects causing large intergrain resistance through the defective phases. PMID:23713950

  10. Hierarchically Structured Hole Transport Layers of Spiro-OMeTAD and Multiwalled Carbon Nanotubes for Perovskite Solar Cells.

    PubMed

    Lee, Jiyong; Menamparambath, Mini Mol; Hwang, Jae-Yeol; Baik, Seunghyun

    2015-07-20

    The low electrical conductivity of spiro-OMeTAD hole transport layers impedes further enhancements of the power conversion efficiency (PCE) of perovskite solar cells. We embedded multiwalled carbon nanotubes (MWNTs) in spiro-OMeTAD (spiro-OMeTAD/MWNTs) to increase carrier mobility and conductivity. However, direct electrical contact between CH3 NH3 PbI3 and the MWNTs created pathways for undesirable back-electron transfer, owing to the large work function of MWNTs, limiting enhancements of the PCE. A hierarchical structure of pure spiro-OMeTAD and spiro-OMeTAD/MWNTs was designed to block back-electron transfer and fully exploit the enhanced charge transport of spiro-OMeTAD/MWNTs. The enhanced fill factor, short-circuit current density, open-circuit voltage, and PCE (15.1 %) were achieved by using this hierarchical hole transport layer structure (MWNT concentration=2 wt %). The perovskite solar cells were fabricated by a low-temperature solution process, further decreasing their per-Watt cost. PMID:26013428

  11. Structure and dehydration of layered perovskite niobate with bilayer hydrates prepared by exfoliation/self-assembly process

    SciTech Connect

    Chen Yufeng; Zhao Xinhua; Ma Hui; Ma Shulan; Huang Gailing; Makita, Yoji; Bai Xuedong; Yang Xiaojing

    2008-07-15

    The crystals of an H-form niobate of HCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=0.5) being tetragonal symmetry (space group P4/mbm) with unit cell parameters a=5.4521(6) and c=14.414(2) A were exfoliated into nanosheets with the triple-layered perovskite structure. The colloid suspension of the nanosheets was put into dialysis membrane tubing and allowed self-assembly in a dilute KCl solution. By this method, a novel layered K-form niobate KCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=1.3, typically) with bilayer hydrates in the interlayer was produced. The Rieveld refinement and transmission electron microscope (TEM)/selected-area electron diffraction (SAED) observation indicated that the orientations of the a-/b-axis of each nanosheet as well as the c-axis are uniform, and the self-assembled compound had the same symmetry, tetragonal (P4/mbm) with a=5.453(2) and c=16.876(5) A, as the H-form precursor; the exfoliation/self-assembly process does not markedly affect the two-dimensional lattice of the layer. The large basal spacing resulted from the interlayer K{sup +} ions solvated by two layers of water molecules. The interlayer bilayers-water was gradually changed to monolayer when the temperatures higher than 100 deg. C, and all the water molecules lost when over 600 deg. C. Accompanying the dehydration, the crystal structure transformed from tetragonal to orthorhombic symmetry. Water molecules may take an important role for the layer layered compound to adjust the unit cell to tetragonal symmetry. - Graphical abstract: The structure of layered perovskite niobate KCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=1.3) having a bilayers-hydrates interlayer, obtained via the exfoliation of an H-form precursor and the self-assembly of Ca{sub 2}Nb{sub 3}O{sub 10}{sup -} nanosheets, was first discussed in detail and determined to be tetragonal symmetry (P4/mbm). The dehydration resulted in the structural transformation to orthorhombic structure.

  12. Purple photochromism in Sr2SnO4:Eu3+ with layered perovskite-related structure

    NASA Astrophysics Data System (ADS)

    Kamimura, Sunao; Yamada, Hiroshi; Xu, Chao-Nan

    2013-01-01

    We report photochromism (PC) in Sr2SnO4:Eu3+ with layered perovskite-related structure. The Sr2SnO4:Eu3+ turned purple upon irradiation with UV light (λ < 350 nm), and the colored Sr2SnO4:Eu3+ returned to its initial colorless state when visible light (λ = 400-700 nm) was irradiated. Furthermore, the PC was strongly dependent on the firing temperature; purple color upon UV irradiation can be enhanced by increasing the firing temperature, which was attributed to an increase of the Sr vacancies in the host lattice from the results of crystal structure analysis. This suggests that controlling the lattice defect plays an important role for enhancing the PC performance.

  13. A nano-grid structure made of perovskite SrTiO3 nanowires for efficient electron transport layers in inverted polymer solar cells.

    PubMed

    Kim, Jeong Won; Suh, Yo-han; Lee, Chang-Lyoul; Kim, Yong Seok; Kim, Won Bae

    2015-03-14

    A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ∼32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film. PMID:25684116

  14. Atomic layer growth of oxide thin films with perovskite-type structure by reactive evaporation

    NASA Astrophysics Data System (ADS)

    Iijima, K.; Terashima, T.; Bando, Y.; Kamigaki, K.; Terauchi, H.

    1992-10-01

    Epitaxial growth of BaTiO3 and SrTiO3 films by the reactive evaporation method was investigated using reflection high-energy electron diffraction (RHEED). The investigations were carried out using two growth methods: coevaporation and alternate evaporation of the metal elements in an oxygen atmosphere. Atomic layer growth was achieved by the alternate supply of Ba or Sr and Ti on the growing surface. In the case of coevaporation, epitaxial growth occurred in a two-dimensional unit-cell-by-unit-cell mode. The surface of each unit cell is terminated by a (TiO2) layer. Artificial superlattices of BaTiO3/SrTiO3 were fabricated by monitoring the film thickness with the RHEED oscillations.

  15. New variant of highly symmetric layered perovskite with coordinated NO3(-) ligand: hydrothermal synthesis, structure, and characterization of Cs2PbCl2(NO3)2.

    PubMed

    Kim, Min Kyung; Jo, Vinna; Ok, Kang Min

    2009-08-01

    A new highly symmetric layered lead chloride material, Cs(2)PbCl(2)(NO(3))(2) has been synthesized by a hydrothermal reaction method using Pb(NO(3))(2), CsCl, and water at 240 degrees C. The structure has been determined by single-crystal X-ray diffraction. Cs(2)PbCl(2)(NO(3))(2) has a novel two-dimensional layered structure containing PbO(4)Cl(4) polyhedra and NO(3) trigonal planes. Cs(2)PbCl(2)(NO(3))(2) is a novel variant on the layered perovskite theme, of which the structure is closely related to the n = 1 layered perovskite families. Detailed structural analysis, Infrared and UV-vis diffuse reflectance spectra, thermogravimetric analysis, and ion-exchange reactions of Cs(2)PbCl(2)(NO(3))(2) are reported. Crystal data: Cs(2)PbCl(2)(NO(3))(2), tetragonal, space group I4(1)/amd (No. 141), a = b = 5.6905(6) A, c = 32.946(5) A, V = 1066.9(2) A(3), and Z = 4. PMID:19588958

  16. A nano-grid structure made of perovskite SrTiO3 nanowires for efficient electron transport layers in inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Won; Suh, Yo-Han; Lee, Chang-Lyoul; Kim, Yong Seok; Kim, Won Bae

    2015-02-01

    A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ~32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film.A nano-grid structure of perovskite SrTiO3 NWs is developed for a novel electron transport layer in inverted polymer solar cells. Due to the excellent charge transporting properties of the SrTiO3 nano-grid structure, the device employing this nanostructure showed ~32% enhanced photovoltaic performance, compared to the solar cell using a TiO2 thin film. Electronic supplementary information (ESI) available: Experimental details, HR-TEM images with EDX atomic ratio analysis, FE-SEM images, transmittance spectra and light absorbance spectra. See DOI: 10.1039/c4nr06720g

  17. Synthesis, structure, and electrochemical properties of nano-layered organic-inorganic perovskites containing Fe(CN)6 3- layers and its application for detection of DNA hybridization

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Liu, Hanxing; Lin, Zhidong; Cao, Minghe; Yu, Zhiyong; Hao, Hua; Guo, Linlin

    2009-07-01

    Steady organic-inorganic perovskite hybrids with [H22-AMP]3/2Fe(CN)6, [H23-AMP]3/2Fe(CN)6 and [H24- AMP]3/2Fe(CN)6 (AMP = aminomethylpyridine) were formed in the air. Each structure shows an unusual layered organic-inorganic structural type. The hybrids enveloped in paraffin, respectively, to prepare hybrid paste electrode (HPE) (HPE-2 with [H22-AMP]3/2Fe(CN)6, HPE-3 with [H23-AMP]3/2Fe(CN)6, HPE-4 with [H24-AMP]3/2Fe(CN)6). Three hybrids in HPEs showed good electrochemical characteristics. The sequence of redox activity is [H24- AMP]3/2Fe(CN)6 > [H22-AMP]3/2Fe(CN)6 > [H23-AMP]3/2Fe(CN)6 and that of electrocatalytical characteristics is [H23- AMP]3/2Fe(CN)6 > [H22-AMP]3/2Fe(CN)6 > [H24-AMP]3/2 Fe(CN)6. Three hybrids have been employed to investigate the interaction between DNA and three hybrids. The results indicate that between [H23-AMP]3/2Fe(CN)6 and DNA is useful and [H23-AMP]3/2Fe(CN)6 can detect the hybridization of DNA. And the interaction between [H22-AMP]3/2Fe(CN)6 and DNA and between [H24-AMP]3/2Fe(CN)6 and DNA is slender. Three HPEs display remarkable electrochemical sensitivity and stability. The variation coefficients (RSD) of repeatedly successive and interval assays are less than 2.5%. The chemical and physical stability of three hybrids is satisfactory.

  18. p-i-n/n-i-p type planar hybrid structure of highly efficient perovskite solar cells towards improved air stability: synthetic strategies and the role of p-type hole transport layer (HTL) and n-type electron transport layer (ETL) metal oxides.

    PubMed

    Mali, Sawanta S; Hong, Chang Kook

    2016-05-19

    There has been fast recent progress in perovskite solar cells (PSCs) towards low cost photovoltaic technology. Organometal mixed halide (MAPbX or FAPbX) perovskites are the most promising light absorbing material sandwiched between the electron transport layer (ETL) and hole transport layer (HTL). These two layers play a critical role in boosting the power conversion efficiency (PCE) and maintaining air stability. However, the device stability is a serious issue in regular as well as p-i-n inverted type perovskite solar cells. This mini-review briefly outlines the state-of-art of p-i-n/n-i-p type planar hybrid perovskite solar cells using MAPbX/FAPbX perovskite absorbing layers. Later, we will focus on recent trends, progress and further opportunities in exploring the air stable hybrid planar structure PSCs. PMID:27161123

  19. p-i-n/n-i-p type planar hybrid structure of highly efficient perovskite solar cells towards improved air stability: synthetic strategies and the role of p-type hole transport layer (HTL) and n-type electron transport layer (ETL) metal oxides

    NASA Astrophysics Data System (ADS)

    Mali, Sawanta S.; Hong, Chang Kook

    2016-05-01

    There has been fast recent progress in perovskite solar cells (PSCs) towards low cost photovoltaic technology. Organometal mixed halide (MAPbX or FAPbX) perovskites are the most promising light absorbing material sandwiched between the electron transport layer (ETL) and hole transport layer (HTL). These two layers play a critical role in boosting the power conversion efficiency (PCE) and maintaining air stability. However, the device stability is a serious issue in regular as well as p-i-n inverted type perovskite solar cells. This mini-review briefly outlines the state-of-art of p-i-n/n-i-p type planar hybrid perovskite solar cells using MAPbX/FAPbX perovskite absorbing layers. Later, we will focus on recent trends, progress and further opportunities in exploring the air stable hybrid planar structure PSCs.

  20. Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells.

    PubMed

    Lee, Yong Hui; Luo, Jingshan; Son, Min-Kyu; Gao, Peng; Cho, Kyung Taek; Seo, Jiyoun; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

    2016-05-01

    The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing. PMID:26928481

  1. Nano-structured electron transporting materials for perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang

    2016-03-01

    Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.

  2. Nano-structured electron transporting materials for perovskite solar cells.

    PubMed

    Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang

    2016-03-17

    Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells. PMID:26457406

  3. Aluminum-Doped Zinc Oxide as Highly Stable Electron Collection Layer for Perovskite Solar Cells.

    PubMed

    Zhao, Xingyue; Shen, Heping; Zhang, Ye; Li, Xin; Zhao, Xiaochong; Tai, Meiqian; Li, Jingfeng; Li, Jianbao; Li, Xin; Lin, Hong

    2016-03-01

    Although low-temperature, solution-processed zinc oxide (ZnO) has been widely adopted as the electron collection layer (ECL) in perovskite solar cells (PSCs) because of its simple synthesis and excellent electrical properties such as high charge mobility, the thermal stability of the perovskite films deposited atop ZnO layer remains as a major issue. Herein, we addressed this problem by employing aluminum-doped zinc oxide (AZO) as the ECL and obtained extraordinarily thermally stable perovskite layers. The improvement of the thermal stability was ascribed to diminish of the Lewis acid-base chemical reaction between perovskite and ECL. Notably, the outstanding transmittance and conductivity also render AZO layer as an ideal candidate for transparent conductive electrodes, which enables a simplified cell structure featuring glass/AZO/perovskite/Spiro-OMeTAD/Au. Optimization of the perovskite layer leads to an excellent and repeatable photovoltaic performance, with the champion cell exhibiting an open-circuit voltage (Voc) of 0.94 V, a short-circuit current (Jsc) of 20.2 mA cm(-2), a fill factor (FF) of 0.67, and an overall power conversion efficiency (PCE) of 12.6% under standard 1 sun illumination. It was also revealed by steady-state and time-resolved photoluminescence that the AZO/perovskite interface resulted in less quenching than that between perovskite and hole transport material. PMID:26960451

  4. Lead-nano-dopings effects on the structural, microstructural, vibrational and thermal properties of Bi 2- xPb xSrV 2O 9 layered perovskite

    NASA Astrophysics Data System (ADS)

    Elsabawy, Khaled M.; Abou Sekkina, Morsy M.; Asker, Mohamed A.; El-Newehy, Mohamed H.

    2010-07-01

    The sample with in the general formula Bi 2-xPb xSrV 2O 9, where x = 0.0, 0.05, 0.1, 0.2, 0.3, and 0.6 mol were synthesized by the high temperature solid state reaction and firing method. The X-ray diffractograms confirmed the formation of single phased layered perovskite in all samples. TGA and DTA thermal analyses on the green samples included steps of thermal analysis of strontium carbonate, bismuth carbonate, ammonium vanadate, lead oxide and finally on the high temperature solid state formation. The effect of lead dopings on the sintering, structural and micro-structure, properties of 212BiSrV-ceramics were investigated. The infrared absorption spectra show a series of vibrational modes within the range of 400-1600 cm -1.

  5. {110}-Layered B-cation ordering in the anion-deficient perovskite Pb2.4Ba2.6Fe2Sc2TiO13 with the crystallographic shear structure.

    PubMed

    Tyablikov, O A; Batuk, D; Tsirlin, A A; Batuk, M; Verchenko, V Yu; Filimonov, D S; Pokholok, K V; Sheptyakov, D V; Rozova, M G; Hadermann, J; Antipov, E V; Abakumov, A M

    2015-06-21

    A novel anion-deficient perovskite-based compound, Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13), was synthesized via the citrate-based route. This compound is an n = 5 member of the AnBnO(3n-2) homologous series with unit-cell parameters related to the perovskite subcell a(p)≈ 4.0 Å as a(p)√2 ×a(p)× 5a(p)√2. The crystal structure of Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) consists of quasi-2D perovskite blocks with a thickness of three octahedral layers separated by the 1/2[110](1[combining macron]01)(p) crystallographic shear (CS) planes, which are parallel to the {110} plane of the perovskite subcell. The CS planes transform the corner-sharing octahedra into chains of edge-sharing distorted tetragonal pyramids. Using a combination of neutron powder diffraction, (57)Fe Mössbauer spectroscopy and atomic resolution electron energy-loss spectroscopy we demonstrate that the B-cations in Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) are ordered along the {110} perovskite layers with Fe(3+) in distorted tetragonal pyramids along the CS planes, Ti(4+) preferentially in the central octahedra of the perovskite blocks and Sc(3+) in the outer octahedra of the perovskite blocks. Magnetic susceptibility and Mössbauer spectroscopy indicate a broadened magnetic transition around T(N)∼ 45 K and the onset of local magnetic fields at low temperatures. The magnetic order is probably reminiscent of that in other AnBnO(3n-2) homologues, where G-type AFM order within the perovskite blocks has been observed. PMID:25695142

  6. New Physical Deposition Approach for Low Cost Inorganic Hole Transport Layer in Normal Architecture of Durable Perovskite Solar Cells.

    PubMed

    Nejand, Bahram Abdollahi; Ahmadi, Vahid; Shahverdi, Hamid Reza

    2015-10-01

    In this work we reported sputter deposited NiOx/Ni double layer as an HTM/contact couple in normal architecture of perovskite solar cell. A perovskite solar cell that is durable for more than 60 days was achieved, with increasing efficiency from 1.3% to 7.28% within 6 days. Moreover, low temperature direct deposition of NiOx layer on perovskite layer was introduced as a potential hole transport material for an efficient cost-effective solar cell applicable for various morphologies of perovskite layers, even for perovskite layers containing pinholes, which is a notable challenge in perovskite solar cells. The angular deposition of NiOx layers by dc reactive magnetron sputtering showed uniform and crack-free coverage of the perovskite layer with no negative impact on perovskite structure that is suitable for nickel back contact layer, surface shielding against moisture, and mechanical damages. Replacing the expensive complex materials in previous perovskite solar cells with low cost available materials introduces cost-effective scalable perovskite solar cells. PMID:26402149

  7. Reduced thermal conductivity by nanoscale intergrowths in perovskite like layered structure La{sub 2}Ti{sub 2}O{sub 7}

    SciTech Connect

    Khaliq, Jibran; Chen, Kan; Li, Chunchun; Shi, Baogui; Ye, Haitao; Grande, Antonio M.; Yan, Haixue; Reece, Michael J.

    2015-02-21

    The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La{sub 2}Ti{sub 2}O{sub 7}. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La{sub 2}Ti{sub 2}O{sub 7} produced nanoscale intergrowths of n = 5 layered phase, while donor substitution produced nanoscale intergrowths of n = 3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as ∼20%. Pure La{sub 2}Ti{sub 2}O{sub 7} has a thermal conductivity value of ∼1.3 W/m K which dropped to a value of ∼1.12 W/m K for Sr doped La{sub 2}Ti{sub 2}O{sub 7} and ∼0.93 W/m K for Ta doped La{sub 2}Ti{sub 2}O{sub 7} at 573 K.

  8. Lead-Halide Perovskite Solar Cells by CH3NH3I Dripping on PbI2-CH3NH3I-DMSO Precursor Layer for Planar and Porous Structures Using CuSCN Hole-Transporting Material.

    PubMed

    Ito, Seigo; Tanaka, Soichiro; Nishino, Hitoshi

    2015-03-01

    The sequential fabrication scheme of the CH3NH3PbI3 layer has been improved to fabricate planar-structure CH3NH3PbI3 perovskite solar cells using CuSCN hole-transporting material (HTM). In the PbI2 layer fabricated by the spin-coating method, at first, small amounts of CH3NH3I (MAI) and DMSO were incorporated as the first-drip precursor layer on a flat TiO2 layer. On the first-drip precursor layers, an MAI solution was applied by either soaking (MAI-soaking method) or dripping using successive spin coating (MAI-dripping). The morphology and crystal transformations were observed by SEM and XRD, respectively. Using the normal sequential MAI-soaking method, we were unable to fabricate planar CH3NH3PbI3 perovskite solar cells with CuSCN HTM. Using the MAI-dripping method, however, a significant photovoltaic effect has been observed to be planar perovskite/CuSCN> solar cells. PMID:26262667

  9. Ferroelastic switching in a layered-perovskite thin film

    NASA Astrophysics Data System (ADS)

    Wang, Chuanshou; Ke, Xiaoxing; Wang, Jianjun; Liang, Renrong; Luo, Zhenlin; Tian, Yu; Yi, Di; Zhang, Qintong; Wang, Jing; Han, Xiu-Feng; van Tendeloo, Gustaaf; Chen, Long-Qing; Nan, Ce-Wen; Ramesh, Ramamoorthy; Zhang, Jinxing

    2016-02-01

    A controllable ferroelastic switching in ferroelectric/multiferroic oxides is highly desirable due to the non-volatile strain and possible coupling between lattice and other order parameter in heterostructures. However, a substrate clamping usually inhibits their elastic deformation in thin films without micro/nano-patterned structure so that the integration of the non-volatile strain with thin film devices is challenging. Here, we report that reversible in-plane elastic switching with a non-volatile strain of approximately 0.4% can be achieved in layered-perovskite Bi2WO6 thin films, where the ferroelectric polarization rotates by 90° within four in-plane preferred orientations. Phase-field simulation indicates that the energy barrier of ferroelastic switching in orthorhombic Bi2WO6 film is ten times lower than the one in PbTiO3 films, revealing the origin of the switching with negligible substrate constraint. The reversible control of the in-plane strain in this layered-perovskite thin film demonstrates a new pathway to integrate mechanical deformation with nanoscale electronic and/or magnetoelectronic applications.

  10. Ferroelastic switching in a layered-perovskite thin film.

    PubMed

    Wang, Chuanshou; Ke, Xiaoxing; Wang, Jianjun; Liang, Renrong; Luo, Zhenlin; Tian, Yu; Yi, Di; Zhang, Qintong; Wang, Jing; Han, Xiu-Feng; Van Tendeloo, Gustaaf; Chen, Long-Qing; Nan, Ce-Wen; Ramesh, Ramamoorthy; Zhang, Jinxing

    2016-01-01

    A controllable ferroelastic switching in ferroelectric/multiferroic oxides is highly desirable due to the non-volatile strain and possible coupling between lattice and other order parameter in heterostructures. However, a substrate clamping usually inhibits their elastic deformation in thin films without micro/nano-patterned structure so that the integration of the non-volatile strain with thin film devices is challenging. Here, we report that reversible in-plane elastic switching with a non-volatile strain of approximately 0.4% can be achieved in layered-perovskite Bi2WO6 thin films, where the ferroelectric polarization rotates by 90° within four in-plane preferred orientations. Phase-field simulation indicates that the energy barrier of ferroelastic switching in orthorhombic Bi2WO6 film is ten times lower than the one in PbTiO3 films, revealing the origin of the switching with negligible substrate constraint. The reversible control of the in-plane strain in this layered-perovskite thin film demonstrates a new pathway to integrate mechanical deformation with nanoscale electronic and/or magnetoelectronic applications. PMID:26838483

  11. Ferroelastic switching in a layered-perovskite thin film

    PubMed Central

    Wang, Chuanshou; Ke, Xiaoxing; Wang, Jianjun; Liang, Renrong; Luo, Zhenlin; Tian, Yu; Yi, Di; Zhang, Qintong; Wang, Jing; Han, Xiu-Feng; Van Tendeloo, Gustaaf; Chen, Long-Qing; Nan, Ce-Wen; Ramesh, Ramamoorthy; Zhang, Jinxing

    2016-01-01

    A controllable ferroelastic switching in ferroelectric/multiferroic oxides is highly desirable due to the non-volatile strain and possible coupling between lattice and other order parameter in heterostructures. However, a substrate clamping usually inhibits their elastic deformation in thin films without micro/nano-patterned structure so that the integration of the non-volatile strain with thin film devices is challenging. Here, we report that reversible in-plane elastic switching with a non-volatile strain of approximately 0.4% can be achieved in layered-perovskite Bi2WO6 thin films, where the ferroelectric polarization rotates by 90° within four in-plane preferred orientations. Phase-field simulation indicates that the energy barrier of ferroelastic switching in orthorhombic Bi2WO6 film is ten times lower than the one in PbTiO3 films, revealing the origin of the switching with negligible substrate constraint. The reversible control of the in-plane strain in this layered-perovskite thin film demonstrates a new pathway to integrate mechanical deformation with nanoscale electronic and/or magnetoelectronic applications. PMID:26838483

  12. Toward Revealing the Critical Role of Perovskite Coverage in Highly Efficient Electron-Transport Layer-Free Perovskite Solar Cells: An Energy Band and Equivalent Circuit Model Perspective.

    PubMed

    Huang, Like; Xu, Jie; Sun, Xiaoxiang; Du, Yangyang; Cai, Hongkun; Ni, Jian; Li, Juan; Hu, Ziyang; Zhang, Jianjun

    2016-04-20

    Currently, most efficient perovskite solar cells (PVKSCs) with a p-i-n structure require simultaneously electron transport layers (ETLs) and hole transport layers (HTLs) to help collecting photogenerated electrons and holes for obtaining high performance. ETL free planar PVKSC is a relatively new and simple structured solar cell that gets rid of the complex and high temperature required ETL (such as compact and mesoporous TiO2). Here, we demonstrate the critical role of high coverage of perovskite in efficient ETL free PVKSCs from an energy band and equivalent circuit model perspective. From an electrical point of view, we confirmed that the low coverage of perovskite does cause localized short circuit of the device. With coverage optimization, a planar p-i-n(++) device with a power conversion efficiency of over 11% was achieved, implying that the ETL layer may not be necessary for an efficient device as long as the perovskite coverage is approaching 100%. PMID:27020395

  13. [Luminescent properties of Eu3+ doped layered perovskite structure M2TiO4 (M = Ca, Sr, Ba) red-emitting phosphors].

    PubMed

    Lu, Zhou; Le, Zhang; Xu, Nai-Cen; Wang, Li-Xi; Zhang, Qi-Tu

    2012-10-01

    Series of Eu3+ doped layered perovskite structure M2TiO4: Eu3+ (M = Ca, Sr, Ba) red phosphors were prepared by the high-temperature solid state reaction method. Their phase compositions and photoluminescence properties were investigated by XRD, UV-Vis DRS and fluorescence spectra The results indicated that pure Sr2 TiO4 and Ba2 TiO4 powers could be prepared under 1 100 degrees C for 2 hours, but Ca2 TiO4 powers could not be synthesized even raising the calcination temperature and lengthening the calcination time. Ba2TiO4: Eu3+ phosphor emitted 594 nm (5D0 --> 7F1) and 615 nm (5D0 --> 7F2) orange-red light under the excitation of 395 nm. Sr2TiO4 : Eu3+ phosphor gave a unusual and strong orange-red emission of 578 nm (5D0 --> 7F0) and 626 nm (5 D0 --> 7F2) under the excitation of near ultraviolet or blue light, resulting in the better color purity and higher luminescent intensity. In addition, this phosphor had the highest luminous efficiency when excited by the charge migration excitation at 363 nm and it had the great potential to be a red phosphor for N-UV LED and blue light chip. PMID:23285854

  14. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers

    NASA Astrophysics Data System (ADS)

    You, Jingbi; Meng, Lei; Song, Tze-Bin; Guo, Tzung-Fang; Yang, Yang (Michael); Chang, Wei-Hsuan; Hong, Ziruo; Chen, Huajun; Zhou, Huanping; Chen, Qi; Liu, Yongsheng; De Marco, Nicholas; Yang, Yang

    2016-01-01

    Lead halide perovskite solar cells have recently attracted tremendous attention because of their excellent photovoltaic efficiencies. However, the poor stability of both the perovskite material and the charge transport layers has so far prevented the fabrication of devices that can withstand sustained operation under normal conditions. Here, we report a solution-processed lead halide perovskite solar cell that has p-type NiOx and n-type ZnO nanoparticles as hole and electron transport layers, respectively, and shows improved stability against water and oxygen degradation when compared with devices with organic charge transport layers. Our cells have a p-i-n structure (glass/indium tin oxide/NiOx/perovskite/ZnO/Al), in which the ZnO layer isolates the perovskite and Al layers, thus preventing degradation. After 60 days storage in air at room temperature, our all-metal-oxide devices retain about 90% of their original efficiency, unlike control devices made with organic transport layers, which undergo a complete degradation after just 5 days. The initial power conversion efficiency of our devices is 14.6 ± 1.5%, with an uncertified maximum value of 16.1%.

  15. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers.

    PubMed

    You, Jingbi; Meng, Lei; Song, Tze-Bin; Guo, Tzung-Fang; Yang, Yang Michael; Chang, Wei-Hsuan; Hong, Ziruo; Chen, Huajun; Zhou, Huanping; Chen, Qi; Liu, Yongsheng; De Marco, Nicholas; Yang, Yang

    2016-01-01

    Lead halide perovskite solar cells have recently attracted tremendous attention because of their excellent photovoltaic efficiencies. However, the poor stability of both the perovskite material and the charge transport layers has so far prevented the fabrication of devices that can withstand sustained operation under normal conditions. Here, we report a solution-processed lead halide perovskite solar cell that has p-type NiO(x) and n-type ZnO nanoparticles as hole and electron transport layers, respectively, and shows improved stability against water and oxygen degradation when compared with devices with organic charge transport layers. Our cells have a p-i-n structure (glass/indium tin oxide/NiO(x)/perovskite/ZnO/Al), in which the ZnO layer isolates the perovskite and Al layers, thus preventing degradation. After 60 days storage in air at room temperature, our all-metal-oxide devices retain about 90% of their original efficiency, unlike control devices made with organic transport layers, which undergo a complete degradation after just 5 days. The initial power conversion efficiency of our devices is 14.6 ± 1.5%, with an uncertified maximum value of 16.1%. PMID:26457966

  16. Ion-exchangeable, electronically conducting layered perovskite oxyfluorides.

    PubMed

    Kobayashi, Yoji; Tian, Mingliang; Eguchi, Miharu; Mallouk, Thomas E

    2009-07-22

    Cation-exchangeable d(0) layered perovskites are amenable to intercalation, exfoliation, and a variety of topochemical reactions, but they lack the interesting electronic and magnetic functionalities of mixed-valent perovskites. Conversely, electronically and magnetically interesting layered perovskites lack scope in terms of interlayer chemistry. To bridge this gap, the insulating, cation-exchangeable layered perovskites RbLaNb(2)O(7), KCa(2)Nb(3)O(10), and NaYTiO(4) were reacted with poly(tetrafluoroethylene) under inert atmosphere conditions to yield layer perovskites in which some of the oxygen is substituted by fluorine. In the fluorinated materials, the B-site cations are reduced to a mixed-valent state without introducing oxygen vacancies into the anion sublattice. The resulting electronically conducting solids can be exposed to air and water and even ion-exchanged in acid without oxidation of the B-site cations. Electronic transport measurements on the air-stable RbLaNb(2)O(6)F reveal room-temperature conductivity (2-7 x 10(2) ohms x cm) via a variable-range hopping mechanism, which is not substantially changed after aqueous proton exchange to H(1-x)Rb(x)LaNb(2)O(6)F (x approximately = 0.2). PMID:19548670

  17. Effects of hole-transporting layers of perovskite-based solar cells

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsushi; Kida, Tomoyasu; Takagi, Tatsuru; Oku, Takeo

    2016-02-01

    Fabrication and characterization of the photovoltaic and optical properties, and microstructure of perovskite-based solar cells with lead phthalocyanine (PbPc), zinc phthalocyanine, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and copper(I) thiocyanate as hole-transporting layers were investigated. X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to identify surface morphologies of the crystal structure and the elemental composition. Introducing PbPc into perovskite solar cells extended the retaining period of photovoltaic activity and performance. The effects of the hole-transporting layer on incident photon-to-current efficiency were investigated. The energy diagram and photovoltaic mechanism of the perovskite solar cells with the hole-transporting layer are discussed.

  18. Effect of Mesostructured Layer upon Crystalline Properties and Device Performance on Perovskite Solar Cells.

    PubMed

    Listorti, Andrea; Juarez-Perez, Emilio J; Frontera, Carlos; Roiati, Vittoria; Garcia-Andrade, Laura; Colella, Silvia; Rizzo, Aurora; Ortiz, Pablo; Mora-Sero, Ivan

    2015-05-01

    One of the most fascinating characteristics of perovskite solar cells (PSCs) is the retrieved obtainment of outstanding photovoltaic (PV) performances withstanding important device configuration variations. Here we have analyzed CH3NH3PbI3-xClx in planar or in mesostructured (MS) configurations, employing both titania and alumina scaffolds, fully infiltrated with perovskite material or presenting an overstanding layer. The use of the MS scaffold induces to the perovskite different structural properties, in terms of grain size, preferential orientation, and unit cell volume, in comparison to the ones of the material grown with no constraints, as we have found out by X-ray diffraction analyses. We have studied the effect of the PSC configuration on photoinduced absorption and time-resolved photoluminescence, complementary techniques that allow studying charge photogeneration and recombination. We have estimated electron diffusion length in the considered configurations observing a decrease when the material is confined in the MS scaffold with respect to a planar architecture. However, the presence of perovskite overlayer allows an overall recovering of long diffusion lengths explaining the record PV performances obtained with a device configuration bearing both the mesostructure and a perovskite overlayer. Our results suggest that performance in devices with perovskite overlayer is mainly ruled by the overlayer, whereas the mesoporous layer influences the contact properties. PMID:26263326

  19. Anisotropy of Earth's D'' layer and stacking faults in the MgSiO3 post-perovskite phase.

    PubMed

    Oganov, Artem R; Martonák, Roman; Laio, Alessandro; Raiteri, Paolo; Parrinello, Michele

    2005-12-22

    The post-perovskite phase of (Mg,Fe)SiO3 is believed to be the main mineral phase of the Earth's lowermost mantle (the D'' layer). Its properties explain numerous geophysical observations associated with this layer-for example, the D'' discontinuity, its topography and seismic anisotropy within the layer. Here we use a novel simulation technique, first-principles metadynamics, to identify a family of low-energy polytypic stacking-fault structures intermediate between the perovskite and post-perovskite phases. Metadynamics trajectories identify plane sliding involving the formation of stacking faults as the most favourable pathway for the phase transition, and as a likely mechanism for plastic deformation of perovskite and post-perovskite. In particular, the predicted slip planes are {010} for perovskite (consistent with experiment) and {110} for post-perovskite (in contrast to the previously expected {010} slip planes). Dominant slip planes define the lattice preferred orientation and elastic anisotropy of the texture. The {110} slip planes in post-perovskite require a much smaller degree of lattice preferred orientation to explain geophysical observations of shear-wave anisotropy in the D'' layer. PMID:16372006

  20. Magnetic coupling at perovskite and rock-salt structured interfaces

    SciTech Connect

    Matvejeff, M.; Ahvenniemi, E.; Takahashi, R.; Lippmaa, M.

    2015-10-05

    We study magnetic coupling between hole-doped manganite layers separated by either a perovskite or a rock-salt barrier of variable thickness. Both the type and the quality of the interface have a strong impact on the minimum critical barrier thickness where the manganite layers become magnetically decoupled. A rock-salt barrier layer only 1 unit cell (0.5 nm) thick remains insulating and is able to magnetically de-couple the electrode layers. The technique can therefore be used for developing high-performance planar oxide electronic devices such as magnetic tunnel junctions and quantum well structures that depend on magnetically and electronically sharp heterointerfaces.

  1. Autothermal reforming catalyst having perovskite structure

    DOEpatents

    Krumpel, Michael; Liu, Di-Jia

    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.

  2. A new layered nano hybrid perovskite film with enhanced resistance to moisture-induced degradation

    NASA Astrophysics Data System (ADS)

    Jiang, Wenlong; Ying, Jifei; Zhou, Wei; Shen, Kongchao; Liu, Xing; Gao, Xingyu; Guo, Fuqiang; Gao, Yanmin; Yang, Tieying

    2016-08-01

    In this paper, a new layered hybrid perovskite film ((EDA)(MA)2[Pb3I10]) was synthesized through one-step method. Ethylenediamine (EDA) cation was introduced into the perovskite lattice to synthesize a layered structure with improved resistance to degradation by humidity. The effects of humidity and time on crystal structure, composition, morphology and absorption spectra of (EDA)(MA)2[Pb3I10] were analyzed by in situ grazing incidence X-ray diffraction (GIXRD), scanning electron microscope (SEM), and UV-Vis spectroscope. The results reveal that a (EDA)(MA)2[Pb3I10] film is more moisture resistant than a CH3NH3PbI3 film which is widely used in the perovskite solar cell now. UV-Vis spectroscopy result also shows that the layered structure film is a suitable solar absorber with a bandgap (1.67 eV), which is close to the optimum value for solar photoelectric conversion. Compared to CH3NH3PbI3, the low-cost perovskite structure offers greater tunability on a molecular level for further material optimization and possibility for widely used in the future.

  3. Multifunctional MgO Layer in Perovskite Solar Cells.

    PubMed

    Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

    2015-06-01

    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. PMID:25851999

  4. Ab initio modeling of 2D layered organohalide lead perovskites.

    PubMed

    Fraccarollo, Alberto; Cantatore, Valentina; Boschetto, Gabriele; Marchese, Leonardo; Cossi, Maurizio

    2016-04-28

    A number of 2D layered perovskites A2PbI4 and BPbI4, with A and B mono- and divalent ammonium and imidazolium cations, have been modeled with different theoretical methods. The periodic structures have been optimized (both in monoclinic and in triclinic systems, corresponding to eclipsed and staggered arrangements of the inorganic layers) at the DFT level, with hybrid functionals, Gaussian-type orbitals and dispersion energy corrections. With the same methods, the various contributions to the solid stabilization energy have been discussed, separating electrostatic and dispersion energies, organic-organic intralayer interactions and H-bonding effects, when applicable. Then the electronic band gaps have been computed with plane waves, at the DFT level with scalar and full relativistic potentials, and including the correlation energy through the GW approximation. Spin orbit coupling and GW effects have been combined in an additive scheme, validated by comparing the computed gap with well known experimental and theoretical results for a model system. Finally, various contributions to the computed band gaps have been discussed on some of the studied systems, by varying some geometrical parameters and by substituting one cation in another's place. PMID:27131557

  5. Ab initio modeling of 2D layered organohalide lead perovskites

    NASA Astrophysics Data System (ADS)

    Fraccarollo, Alberto; Cantatore, Valentina; Boschetto, Gabriele; Marchese, Leonardo; Cossi, Maurizio

    2016-04-01

    A number of 2D layered perovskites A2PbI4 and BPbI4, with A and B mono- and divalent ammonium and imidazolium cations, have been modeled with different theoretical methods. The periodic structures have been optimized (both in monoclinic and in triclinic systems, corresponding to eclipsed and staggered arrangements of the inorganic layers) at the DFT level, with hybrid functionals, Gaussian-type orbitals and dispersion energy corrections. With the same methods, the various contributions to the solid stabilization energy have been discussed, separating electrostatic and dispersion energies, organic-organic intralayer interactions and H-bonding effects, when applicable. Then the electronic band gaps have been computed with plane waves, at the DFT level with scalar and full relativistic potentials, and including the correlation energy through the GW approximation. Spin orbit coupling and GW effects have been combined in an additive scheme, validated by comparing the computed gap with well known experimental and theoretical results for a model system. Finally, various contributions to the computed band gaps have been discussed on some of the studied systems, by varying some geometrical parameters and by substituting one cation in another's place.

  6. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    PubMed

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature. PMID:27451628

  7. Compact layer free perovskite solar cells with 13.5% efficiency.

    PubMed

    Liu, Dianyi; Yang, Jinli; Kelly, Timothy L

    2014-12-10

    The recent breakthrough of organometal halide perovskites as the light harvesting layer in photovoltaic devices has led to power conversion efficiencies of over 16%. To date, most perovskite solar cells have adopted a structure in which the perovskite light absorber is placed between carrier-selective electron- and hole-transport layers (ETLs and HTLs). Here we report a new type of compact layer free bilayer perovskite solar cell and conclusively demonstrate that the ETL is not a prerequisite for obtaining excellent device efficiencies. We obtained power conversion efficiencies of up to 11.6% and 13.5% when using poly(3-hexylthiophene) and 2,2',7,7'-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9'-spirobifluorene, respectively, as the hole-transport material. This performance is very comparable to that obtained with the use of a ZnO ETL. Impedance spectroscopy suggests that while eliminating the ZnO leads to an increase in contact resistance, this is offset by a substantial decrease in surface recombination. PMID:25405271

  8. Layering fabrication, structure, and electromagnetic properties of perovskite phases by hybrid process: self-propagated high-temperature synthesis and selective laser sintering

    NASA Astrophysics Data System (ADS)

    Shishkovsky, I.; Morozov, Yu.; Kuznetsov, M.

    2013-11-01

    The paper discusses the fundamentals and the requirements for layer-by-layer manufacturing of three-dimensional porous parts from complex metal oxide systems (piezoceramics PbTi1-xZrxO3; hexaferrites - BaFe12-xCrxO19 and SrFe12O19; spinels - Li0.5Fe2.5-xCrxO4 and high-temperature superconducting ceramics (HTSC) - YBa2Cu3O7-y) and examines the main aspects of the overlapped processes associated with the self-propagated high-temperature synthesis (SHS) and selective laser sintering (SLS). These two techniques presently offered are joined as the original solutions in this external magnetic field. The perovskite phase compositions, morphology, and element distribution of the fabricated samples were analyzed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped the EDX analysis. Optimal regimes for the three-dimensional (3D) parts laser synthesis and some of their electro physical properties were estimated for conducting the concurrent SHS-SLS reactions, both for the case with the applied dc magnetic field and without it.

  9. Ferroelastic switching in a layered-perovskite thin film

    DOE PAGESBeta

    Wang, Chuanshou; Ke, Xiaoxing; Wang, Jianjun; Liang, Renrong; Luo, Zhenlin; Tian, Yu; Yi, Di; Zhang, Qintong; Wang, Jing; Han, Xiu -Feng; et al

    2016-02-03

    Here, a controllable ferroelastic switching in ferroelectric/multiferroic oxides is highly desirable due to the non-volatile strain and possible coupling between lattice and other order parameter in heterostructures. However, a substrate clamping usually inhibits their elastic deformation in thin films without micro/nano-patterned structure so that the integration of the non-volatile strain with thin film devices is challenging. Here, we report that reversible in-plane elastic switching with a non-volatile strain of approximately 0.4% can be achieved in layeredperovskite Bi2WO6 thin films, where the ferroelectric polarization rotates by 90 within four in-plane preferred orientations. Phase-field simulation indicates that the energy barrier of ferroelasticmore » switching in orthorhombic Bi2WO6 film is ten times lower than the one in PbTiO3 films, revealing the origin of the switching with negligible substrate constraint. The reversible control of the in-plane strain in this layered-perovskite thin film demonstrates a new pathway to integrate mechanical deformation with nanoscale electronic and/or magnetoelectronic applications.« less

  10. Efficient methylammonium lead iodide perovskite solar cells with active layers from 300 to 900 nm

    SciTech Connect

    Momblona, C.; Malinkiewicz, O.; Soriano, A.; Gil-Escrig, L.; Bandiello, E.; Scheepers, M.; Bolink, H. J.; Edri, E.

    2014-08-01

    Efficient methylammonium lead iodide perovskite-based solar cells have been prepared in which the perovskite layer is sandwiched in between two organic charge transporting layers that block holes and electrons, respectively. This configuration leads to stable and reproducible devices that do not suffer from strong hysteresis effects and when optimized lead to efficiencies close to 15%. The perovskite layer is formed by using a dual-source thermal evaporation method, whereas the organic layers are processed from solution. The dual-source thermal evaporation method leads to smooth films and allows for high precision thickness variations. Devices were prepared with perovskite layer thicknesses ranging from 160 to 900 nm. The short-circuit current observed for these devices increased with increasing perovskite layer thickness. The main parameter that decreases with increasing perovskite layer thickness is the fill factor and as a result optimum device performance is obtained for perovskite layer thickness around 300 nm. However, here we demonstrate that with a slightly oxidized electron blocking layer the fill factor for the solar cells with a perovskite layer thickness of 900 nm increases to the same values as for the devices with thin perovskite layers. As a result the power conversion efficiencies for the cells with 300 and 900 nm are very similar, 12.7% and 12%, respectively.

  11. Dominant factors limiting the optical gain in layered two-dimensional halide perovskite thin films.

    PubMed

    Chong, Wee Kiang; Thirumal, Krishnamoorthy; Giovanni, David; Goh, Teck Wee; Liu, Xinfeng; Mathews, Nripan; Mhaisalkar, Subodh; Sum, Tze Chien

    2016-05-25

    Semiconductors are ubiquitous gain media for coherent light sources. Solution-processed three-dimensional (3D) halide perovskites (e.g., CH3NH3PbI3) with their outstanding room temperature optical gain properties are the latest members of this family. Their two-dimensional (2D) layered perovskite counterparts with natural multiple quantum well structures exhibit strong light-matter interactions and intense excitonic luminescence. However, despite such promising traits, there have been no reports on room temperature optical gain in 2D layered perovskites. Herein, we reveal the challenges towards achieving amplified spontaneous emission (ASE) in the archetypal (C6H5C2H4NH3)2PbI4 (or PEPI) system. Temperature-dependent transient spectroscopy uncovers the dominant free exciton trapping and bound biexciton formation pathways that compete effectively with biexcitonic gain. Phenomenological rate equation modeling predicts a large biexciton ASE threshold of ∼1.4 mJ cm(-2), which is beyond the damage threshold of these materials. Importantly, these findings would rationalize the difficulties in achieving optical gain in 2D perovskites and provide new insights and suggestions for overcoming these challenges. PMID:27184073

  12. Fine control of perovskite-layered morphology and composition via sequential deposition crystallization process towards improved perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Luo, Yi; Meng, Fanli; Zhao, Erfei; Zheng, Yan-Zhen; Zhou, Yali; Tao, Xia

    2016-04-01

    The ability to prepare high coverage and compact perovskite films via solution-based crystallization manipulation processes still represents a vital issue towards improving the ultimate photoelectric conversion efficiency of devices. In this work, we prepare the active perovskite layer by means of sequential deposition crystallization process i.e. dipping PbI2-infiltrated TiO2 film within CH3NH3I solution from 20s to 60s. The morphology and thickness of the as-prepared perovskite layer, and its overall performance superiority are investigated. X-ray diffraction (XRD) reveals that a maximum conversion of PbI2 to perovskite is completed upon applying a sequential deposition crystallization process of 40s. Field emission scanning electron microscope (FESEM) demonstrates that the coverage of the perovskite capping layer exhibits a trend from rise to decline in the whole dipping time from 20s to 60s. By fine control of the dipping time, a 620 nm-thickness compact perovskite active layer is obtained at the optimized dipping time of 40s and is verified to possess strong light absorption and high electron extraction efficiency, leading to a higher photocurrent. By further optimizing the mesoporous TiO2 film thickness, a high photocurrent of 23.98 mA cm-2 and an efficiency of 13.47% are achieved.

  13. Atomically thin two-dimensional materials as hole extraction layers in organolead halide perovskite photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Kim, Yu Geun; Kwon, Ki Chang; Le, Quyet Van; Hong, Kootak; Jang, Ho Won; Kim, Soo Young

    2016-07-01

    Atomically thin two-dimensional materials such as MoS2, WS2, and graphene oxide (GO) are used as hole extraction layers (HEL) in organolead halide perovskites solar cells (PSCs) instead of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HEL. MoS2 and WS2 layers with a polycrystalline structure were synthesized by a chemical deposition method using a uniformly spin-coated (NH4)MoS4 and (NH4)WS4 precursor solution. GO was synthesized by the oxidation of natural graphite powder using Hummers' method. The work functions of MoS2, WS2, and GO are measured to be 5.0, 4.95, and 5.1 eV, respectively. The X-ray diffraction spectrum indicated that the synthesized perovskite material is CH3NH3PbI3-xClx. The PSCs with the p-n junction structure were fabricated based on the CH3NH3PbI3-xClx perovskite layer. The power conversion efficiencies of the MoS2, WS2, and GO-based PSCs were 9.53%, 8.02%, and 9.62%, respectively, which are comparable to those obtained from PEDOT:PSS-based devices (9.93%). These results suggest that two-dimensional materials such as MoS2, WS2, and GO can be promising candidates for the formation of HELs in the PSCs.

  14. Structural, electrochemical and magnetic characterization of the layered-type PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} perovskite

    SciTech Connect

    Azad, Abul K.; Kim, Jung H.; Irvine, John T.S.

    2014-05-01

    Structural, electrical and magnetic properties of the layered cobaltite PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrO{sub δ}] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2a{sub p} and c≈2a{sub p} (a{sub p} is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573 K in air, structural rearrangement takes place and the structure can be defined as a≈a{sub p} and c≈2a{sub p} in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373 K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973 K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573 K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153 Ωcm{sup 2} and 0.286 Ωcm{sup 2} at 973 K and 923 K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order. - Graphical abstract: Structural phase changes in PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at elevated temperatures determined by neutron powder diffraction. Depending on oxygen occupancy it form different phases at different temperatures. This pictures show the schematic 3D diagram of PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at 295 K (a), 373 K (b) and 573 K (c). Co atoms are inside the

  15. Recent Advances in the Inverted Planar Structure of Perovskite Solar Cells.

    PubMed

    Meng, Lei; You, Jingbi; Guo, Tzung-Fang; Yang, Yang

    2016-01-19

    Inorganic-organic hybrid perovskite solar cells research could be traced back to 2009, and initially showed 3.8% efficiency. After 6 years of efforts, the efficiency has been pushed to 20.1%. The pace of development was much faster than that of any type of solar cell technology. In addition to high efficiency, the device fabrication is a low-cost solution process. Due to these advantages, a large number of scientists have been immersed into this promising area. In the past 6 years, much of the research on perovskite solar cells has been focused on planar and mesoporous device structures employing an n-type TiO2 layer as the bottom electron transport layer. These architectures have achieved champion device efficiencies. However, they still possess unwanted features. Mesoporous structures require a high temperature (>450 °C) sintering process for the TiO2 scaffold, which will increase the cost and also not be compatible with flexible substrates. While the planar structures based on TiO2 (regular structure) usually suffer from a large degree of J-V hysteresis. Recently, another emerging structure, referred to as an "inverted" planar device structure (i.e., p-i-n), uses p-type and n-type materials as bottom and top charge transport layers, respectively. This structure derived from organic solar cells, and the charge transport layers used in organic photovoltaics were successfully transferred into perovskite solar cells. The p-i-n structure of perovskite solar cells has shown efficiencies as high as 18%, lower temperature processing, flexibility, and, furthermore, negligible J-V hysteresis effects. In this Account, we will provide a comprehensive comparison of the mesoporous and planar structures, and also the regular and inverted of planar structures. Later, we will focus the discussion on the development of the inverted planar structure of perovskite solar cells, including film growth, band alignment, stability, and hysteresis. In the film growth part, several

  16. Perovskite solar cell based on network nanoporous layer consisted of TiO2 nanowires and its interface optimization

    NASA Astrophysics Data System (ADS)

    Tao, Hong; Ke, Weijun; Wang, Jing; Liu, Qin; Wan, Jiawei; Yang, Guang; Fang, Guojia

    2015-09-01

    Anatase TiO2 film with 3D network nanoporous structure consisted of 1D nanowires is obtained on SnO2:F (FTO) glass substrate by in-situ hydrothermal synthesis and applied in mesoporous perovskite (CH3NH3PbI3) solar cell. A thin Ti film is deposited on FTO substrate by magnetron sputtering before the hydrothermal treatment with sodium hydroxide solution. Then, a layer of network nanoporous TiO2 (NT) film is formed. The efficiency of perovskite solar cell based on this 3D structure with one-step sintering can be optimized to 9.19%. The NT film consisted of 1D TiO2 nanowires is beneficial to the transmission of charge carriers and the infiltration of hole transport material. And this one-step sintering process can reduce the interface defects and enhance the fill factor of the device. Then, we further optimize the surface of NT layer through TiCl4 post-treatment. The post-treatment can optimize the carrier separation and the deposition of perovskite layer, thus improving the open-circuit voltage (Voc) and short-circuit current density (Jsc) of perovskite solar cell. As a result, the value of Jsc gets an enhancement of 45.63% and the efficiency of perovskite solar cell reaches up to 12.78%.

  17. PbBr-Based Layered Perovskite Organic-Inorganic Superlattice Having Carbazole Chromophore; Hole-Mobility and Quantum Mechanical Calculation.

    PubMed

    Era, Masanao; Yasuda, Takeshi; Mori, Kento; Tomotsu, Norio; Kawano, Naoki; Koshimizu, Masanori; Asai, Keisuke

    2016-04-01

    We have successfully evaluated hole mobility in a spin-coated film of a lead-bromide based layered perovskite having carbazole chromophore-linked ammonium molecules as organic layer by using FET measurement. The values of hole mobility, threshold voltage and on/off ratio at room temperature were evaluated.to.be 1.7 x 10(-6) cm2 V-1 s-1, 27 V and 28 V, respectively. However, the spin-coated films on Si substrates were not so uniform compared with those on fused quartz substrates. To improve the film uniformity, we examined the relationship between substrate temperature during spin-coating and film morphology in the layered perovskite spin-coated films. The mean roughness of the spin-coated films on Si substrates was dependent on the substrate temperature. At 353 K, the mean roughness was minimized and the carrier mobility was enhanced by one order of magnitude; the values of hole mobility and threshold voltage were .estimated to be 3.4 x 10(-5) cm2 V-1 s-1, and 22 V at room temperature in a preliminary FET evaluation, respectively. In addition, we determined a crystal structure of the layered perovskite by X-ray diffraction analysis. To gain a better understanding of the observed hole transports, we conducted quantum mechanical calculations using the obtained crystal structure information. The calculated band structure of the layered organic perovskite showed that the valence band is composed of the organic carbazole layer, which confirms that.the measured hole mobility is mainly derived from the organic part of the layered perovskite. Band and hopping transport mechanisms were discussed by calculating the effective masses and transfer integrals for the 2D periodic system of the organic layer in isolation. PMID:27451598

  18. 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.

  19. Efficient Planar Perovskite Solar Cells with Reduced Hysteresis and Enhanced Open Circuit Voltage by Using PW12-TiO2 as Electron Transport Layer.

    PubMed

    Huang, Chun; Liu, Canjun; Di, Yunxiang; Li, Wenzhang; Liu, Fangyang; Jiang, Liangxing; Li, Jie; Hao, Xiaojing; Huang, Haitao

    2016-04-01

    An electron transport layer is essential for effective operation of planar perovskite solar cells. In this Article, PW12-TiO2 composite was used as the electron transport layer for the planar perovskite solar cell in the device structure of fluorine-doped tin oxide (FTO)-glass/PW12-TiO2/perovskite/spiro-OMeTAD/Au. A proper downward shift of the conduction band minimum (CBM) enhanced electron extraction from the perovskite layer to the PW12-TiO2 composite layer. Consequently, the common hysteresis effect in TiO2-based planar perovskite solar cells was significantly reduced and the open circuit voltage was greatly increased to about 1.1 V. Perovskite solar cells using the PW12-TiO2 compact layer showed an efficiency of 15.45%. This work can contribute to the studies on the electron transport layer and interface engineering for the further development of perovskite solar cells. PMID:26954448

  20. Influence of void-free perovskite capping layer on the charge recombination process in high performance CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Fu, Kunwu; Nelson, Christopher T.; Scott, Mary Cooper; Minor, Andrew; Mathews, Nripan; Wong, Lydia Helena

    2016-02-01

    The stunning rise of methylammonium lead iodide perovskite material as a light harvesting material in recent years has drawn much attention in the photovoltaic community. Here, we investigated in detail the uniform and void-free perovskite capping layer in the mesoscopic perovskite devices and found it to play a critical role in determining device performance and charge recombination process. Compared to the rough surface with voids of the perovskite layer, surface of the perovskite capping layer obtained from sequential deposition process is much more uniform with less void formation and distribution within the TiO2 mesoscopic scaffold is more homogeneous, leading to much improved photovoltaic parameters of the devices. The impact of void free perovskite capping layer surface on the charge recombination processes within the mesoscopic perovskite solar cells is further scrutinized via charge extraction measurement. Modulation of precursor solution concentrations in order to further improve the perovskite layer surface morphology leads to higher efficiency and lower charge recombination rates. Inhibited charge recombination in these solar cells also matches with the higher charge density and slower photovoltage decay profiles measured.The stunning rise of methylammonium lead iodide perovskite material as a light harvesting material in recent years has drawn much attention in the photovoltaic community. Here, we investigated in detail the uniform and void-free perovskite capping layer in the mesoscopic perovskite devices and found it to play a critical role in determining device performance and charge recombination process. Compared to the rough surface with voids of the perovskite layer, surface of the perovskite capping layer obtained from sequential deposition process is much more uniform with less void formation and distribution within the TiO2 mesoscopic scaffold is more homogeneous, leading to much improved photovoltaic parameters of the devices. The impact of

  1. Magnetic and electrical properties of quadruple perovskites with 12 layer structures Ba{sub 4}LnM{sub 3}O{sub 12} (Ln=rare earths; M=Ru, Ir): The role of metal-metal bonding in perovskite-related oxides

    SciTech Connect

    Shimoda, Yuki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio

    2010-09-15

    Structures and magnetic and electrical properties of quadruple perovskites containing rare earths Ba{sub 4}LnM{sub 3}O{sub 12} (Ln=rare earths; M=Ru, Ir) were investigated. They crystallize in the 12L-perovskite-type structure. Three MO{sub 6} octahedra are connected to each other by face-sharing and form a M{sub 3}O{sub 12} trimer. The M{sub 3}O{sub 12} trimers and LnO{sub 6} octahedra are alternately linked by corner-sharing, forming the perovskite-type structure with 12 layers. For Ln=Ce, Pr, and Tb, both the Ln and M ions are in the tetravalent state (Ba{sub 4}Ln{sup 4+}M{sup 4+}{sub 3}O{sub 12}), and for other Ln ions, Ln ions are in the trivalent state and the mean oxidation state of M ions is +4.33 (Ba{sub 4}Ln{sup 3+}M{sup 4.33+}{sub 3}O{sub 12}). All the Ba{sub 4}Ln{sup 3+}Ru{sup 4.33+}{sub 3}O{sub 12} compounds show magnetic ordering at low temperatures, while any of the corresponding iridium-containing compounds Ba{sub 4}Ln{sup 3+}Ir{sup 4.33+}{sub 3}O{sub 12} is paramagnetic down to 1.8 K. Ba{sub 4}Ce{sup 4+}Ir{sup 4+}{sub 3}O{sub 12} orders antiferromagnetically at 10.5 K, while the corresponding ruthenium-containing compound Ba{sub 4}Ce{sup 4+}Ru{sup 4+}{sub 3}O{sub 12} is paramagnetic. These magnetic results were well understood by the magnetic behavior of M{sub 3}O{sub 12}. The effective magnetic moments and the entropy change for the magnetic ordering show that the trimers Ru{sup 4.33+}{sub 3}O{sub 12} and Ir{sup 4+}{sub 3}O{sub 12} have the S=1/2 ground state, and in other cases there is no magnetic contribution from the trimers Ru{sup 4+}{sub 3}O{sub 12} or Ir{sup 4.33+}{sub 3}O{sub 12}. Measurements of the electrical resistivity of Ba{sub 4}LnM{sub 3}O{sub 12} and its analysis show that these compounds demonstrate two-dimensional Mott-variable range hopping behavior. - Graphical abstract: Structures and magnetic and electrical properties of quadruple perovskites containing rare earths Ba{sub 4}LnM{sub 3}O{sub 12} (Ln=rare earths; M = Ru, Ir

  2. Substantial improvement of perovskite solar cells stability by pinhole-free hole transport layer with doping engineering

    PubMed Central

    Jung, Min-Cherl; Raga, Sonia R.; Ono, Luis K.; Qi, Yabing

    2015-01-01

    We fabricated perovskite solar cells using a triple-layer of n-type doped, intrinsic, and p-type doped 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) (n-i-p) as hole transport layer (HTL) by vacuum evaporation. The doping concentration for n-type doped spiro-OMeTAD was optimized to adjust the highest occupied molecular orbital of spiro-OMeTAD to match the valence band maximum of perovskite for efficient hole extraction while maintaining a high open circuit voltage. Time-dependent solar cell performance measurements revealed significantly improved air stability for perovskite solar cells with the n-i-p structured spiro-OMeTAD HTL showing sustained efficiencies even after 840 h of air exposure. PMID:25985417

  3. Epitaxial Structure of (001)- and (111)-Oriented Perovskite Ferrate Films Grown by Pulsed-Laser Deposition.

    PubMed

    Chakraverty, Suvankar; Ohtomo, Akira; Okude, Masaki; Ueno, Kazunori; Kawasaki, Masashi

    2010-04-01

    The epitaxial structures of SrFeO(2.5) films grown on SrTiO(3) (001) and (111) substrates by PLD are reported. A layer-by-layer growth mode was achieved in the initial stage on both substrates. The films were stabilized with a monoclinic structure, where we identified the in-plane domain structures and orientation relationship. Our study presents a guide to control the heteroepitaxy of (111)-oriented noncubic perovskites. PMID:20383295

  4. Toward tailorable surfaces: A combined theoretical and experimental study of lanthanum niobate layered perovskites

    SciTech Connect

    Di Tommaso, Stefania E-mail: frederic.labat@chimie-paristech.fr; Giannici, Francesco; Mossuto Marculescu, Adriana; Martorana, Antonino; Adamo, Carlo; Labat, Frédèric E-mail: frederic.labat@chimie-paristech.fr

    2014-07-14

    A comprehensive theoretical investigation of the MLaNb{sub 2}O{sub 7} (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals. A general very good agreement with the available experimental (XRD, NPD, and EXAFS) data has been found. The structure of the protonated HLaNb{sub 2}O{sub 7} form has also been further clarified and a new tetragonal space group is proposed for this compound, better reproducing the experimental cell parameters and yielding to a more realistic picture of the system. The electronic investigation highlighted that all the compounds considered are very similar to each other and that the interaction between interlayer cations and perovskite slabs is purely ionic, except for the proton that is, instead, covalently bound.

  5. Laser-induced microstructuring of two-dimensional layered inorganic-organic perovskites.

    PubMed

    Kanaujia, Pawan K; Vijaya Prakash, G

    2016-04-14

    Non-contact bi-directional micropatterning of two-dimensional (2D) layered inorganic-organic (IO) perovskite [(R-NH3)2PbI4, R = organic moiety] thin films by direct laser writing (DLW) has been reported. These 2D materials are in the form of natural multiple quantum well (MQW) structures and show excitonic luminescence at room temperature because of quantum and dielectric confinement effects. Systematic optical and structural analyses of these laser processed hybrid systems provide an insight into laser-matter interaction and a pathway to develop technology to define complex 2D material based devices with new functionalities. These laser-matter interaction studies reveal several concurrent processes: single photon absorption, material ablation, melting and agglomeration of nanostructures and chemical/physical modifications. This study also provides an insight into chemical and optical changes in laser processed 2D perovskites which subsequently can be recovered by chemical processing. Apart from controllable feature sizes, the prolonged laser exposure results in material agglomeration in the form of nano-pillars at the laser track boundaries. Low-cost micro/nano-scaffolding of IO perovskites may have several important advantages in scalable optoelectronic devices, the realisation of luminescent photonic architectures (photonic crystals and waveguides), and light harvesting elements for IO LEDs and solar cells. PMID:26996747

  6. Toward tailorable surfaces: A combined theoretical and experimental study of lanthanum niobate layered perovskites

    NASA Astrophysics Data System (ADS)

    Di Tommaso, Stefania; Giannici, Francesco; Mossuto Marculescu, Adriana; Martorana, Antonino; Adamo, Carlo; Labat, Frédèric

    2014-07-01

    A comprehensive theoretical investigation of the MLaNb2O7 (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals. A general very good agreement with the available experimental (XRD, NPD, and EXAFS) data has been found. The structure of the protonated HLaNb2O7 form has also been further clarified and a new tetragonal space group is proposed for this compound, better reproducing the experimental cell parameters and yielding to a more realistic picture of the system. The electronic investigation highlighted that all the compounds considered are very similar to each other and that the interaction between interlayer cations and perovskite slabs is purely ionic, except for the proton that is, instead, covalently bound.

  7. Kinetics of Ion Transport in Perovskite Active Layers and Its Implications for Active Layer Stability.

    PubMed

    Bag, Monojit; Renna, Lawrence A; Adhikari, Ramesh Y; Karak, Supravat; Liu, Feng; Lahti, Paul M; Russell, Thomas P; Tuominen, Mark T; Venkataraman, D

    2015-10-14

    Solar cells fabricated using alkyl ammonium metal halides as light absorbers have the right combination of high power conversion efficiency and ease of fabrication to realize inexpensive but efficient thin film solar cells. However, they degrade under prolonged exposure to sunlight. Herein, we show that this degradation is quasi-reversible, and that it can be greatly lessened by simple modifications of the solar cell operating conditions. We studied perovskite devices using electrochemical impedance spectroscopy (EIS) with methylammonium (MA)-, formamidinium (FA)-, and MA(x)FA(1-x) lead triiodide as active layers. From variable temperature EIS studies, we found that the diffusion coefficient using MA ions was greater than when using FA ions. Structural studies using powder X-ray diffraction (PXRD) show that for MAPbI3 a structural change and lattice expansion occurs at device operating temperatures. On the basis of EIS and PXRD studies, we postulate that in MAPbI3 the predominant mechanism of accelerated device degradation under sunlight involves thermally activated fast ion transport coupled with a lattice-expanding phase transition, both of which are facilitated by absorption of the infrared component of the solar spectrum. Using these findings, we show that the devices show greatly improved operation lifetimes and stability under white-light emitting diodes, or under a solar simulator with an infrared cutoff filter or with cooling. PMID:26414066

  8. Structure and local structure of perovskite based materials

    NASA Astrophysics Data System (ADS)

    Rossell Abrodos, Marta Dacil

    Perovskites, with general formula ABX3, where A and B are cations and X is an anion, form a very important class of inorganic crystals whose physical properties are extensively used in many technological applications. The basic, so-called aristotype structure, consists of an infinite array of corner-linked anion octahedra, with the A cations in the spaces between the octahedra and a B cation at the center of each octahedron. Interesting physical properties are often related to the flexibility of the perovskite structure to deform or to form non-stoichiometric compositions. In this thesis, four perovskite-related systems are studied. Transmission electron microscopy (TEM) is of prime interest to analyze the influence of the structure and microstructure on the physical properties of these systems. (1) The anion-deficient Sr4Fe6O12+delta (delta < 1) derivatives. These materials are mixed conducting oxides with high oxygen and electronic conductivity. A complete characterization of the structure of these anion-deficient compounds is deduced from electron diffraction and high-resolution TEM. The presence of anion vacancies in the Sr4Fe6O12+delta (delta < 1) structure is suggested to have an influence on the transport properties. (2) The CaRMnSnO6 (R = La, Pr, Nd, Sm-Dy) double perovskites. A random distribution of the Ca and R cations over the A positions and Mn and Sn cations over the B positions is found. Due to a random distribution of the Mn 3+ and Sn4+ cations, a spin glass behavior was found for CaLaMnSnO6. (3) The K3AlF6 elpasolite-type (or ordered double perovskite) structure. This compound is of high technological importance since it is a basic component of the melts for low temperature electrolysis in aluminum smelting. A sequence of phase transitions at different temperatures in K3AlF6 along with the data on unit cell dimensions and space symmetry of three major polymorphs is reported. (4) Ca 2Fe2O5 brownmillerite-type thin films deposited on three different

  9. Performance enhancement of planar heterojunction perovskite solar cells by n-doping of the electron transporting layer.

    PubMed

    Kim, Shin Sung; Bae, Seunghwan; Jo, Won Ho

    2015-12-21

    Herein we report a simple n-doping method to enhance the performance of perovskite solar cells with a planar heterojunction structure. Devices with an n-doped PCBM electron transporting layer exhibit a power conversion efficiency of 13.8% with a remarkably enhanced short-circuit current of 22.0 mA cm(-2) as compared to the devices with an un-doped PCBM layer. PMID:26466302

  10. In situ intercalation dynamics in inorganic-organic layered perovskite thin films.

    PubMed

    Ahmad, Shahab; Kanaujia, Pawan K; Niu, Wendy; Baumberg, Jeremy J; Vijaya Prakash, G

    2014-07-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson-Mehl-Avrami-Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  11. In Situ Intercalation Dynamics in Inorganic–Organic Layered Perovskite Thin Films

    PubMed Central

    2014-01-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic–organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson–Mehl–Avrami–Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  12. Highly Efficient Perovskite Solar Cells with Tunable Structural Color

    PubMed Central

    2015-01-01

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold within the photoactive layer of an opaque perovskite solar cell following a bottom-up approach employing inexpensive and scalable liquid processing techniques. The photovoltaic devices presented herein show high efficiency with tunable color across the visible spectrum. This now imbues the perovskite solar cells with highly desirable properties for cladding in the built environment and encourages design of sustainable colorful buildings and iridescent electric vehicles as future power generation sources. PMID:25650872

  13. Highly efficient perovskite solar cells with tunable structural color.

    PubMed

    Zhang, Wei; Anaya, Miguel; Lozano, Gabriel; Calvo, Mauricio E; Johnston, Michael B; Míguez, Hernán; Snaith, Henry J

    2015-03-11

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold within the photoactive layer of an opaque perovskite solar cell following a bottom-up approach employing inexpensive and scalable liquid processing techniques. The photovoltaic devices presented herein show high efficiency with tunable color across the visible spectrum. This now imbues the perovskite solar cells with highly desirable properties for cladding in the built environment and encourages design of sustainable colorful buildings and iridescent electric vehicles as future power generation sources. PMID:25650872

  14. Mesoporous BaSnO3 layer based perovskite solar cells.

    PubMed

    Zhu, Liangzheng; Shao, Zhipeng; Ye, Jiajiu; Zhang, Xuhui; Pan, Xu; Dai, Songyuan

    2016-01-18

    One of the limitations of TiO2 based perovskite solar cells is the poor electron mobility of TiO2. Here, perovskite oxide BaSnO3 is used as a replacement. It has a higher electron mobility and the same perovskite structure as the light harvesting materials. After optimization, devices based on BaSnO3 showed the best performance of 12.3% vs. 11.1% for TiO2. PMID:26587570

  15. Structured Organic-Inorganic Perovskite toward a Distributed Feedback Laser.

    PubMed

    Saliba, Michael; Wood, Simon M; Patel, Jay B; Nayak, Pabitra K; Huang, Jian; Alexander-Webber, Jack A; Wenger, Bernard; Stranks, Samuel D; Hörantner, Maximilian T; Wang, Jacob Tse-Wei; Nicholas, Robin J; Herz, Laura M; Johnston, Michael B; Morris, Stephen M; Snaith, Henry J; Riede, Moritz K

    2016-02-01

    A general strategy for the in-plane structuring of organic-inorganic perovskite films is presented. The method is used to fabricate an industrially relevant distributed feedback (DFB) cavity, which is a critical step toward all-electrially pumped injection laser diodes. This approach opens the prospects of perovskite materials for much improved optical control in LEDs, solar cells, and also toward applications as optical devices. PMID:26630410

  16. Solid-state NMR characterization of the structure and thermal stability of hybrid organic-inorganic compounds based on a HLaNb2O7 Dion-Jacobson layered perovskite.

    PubMed

    Cattaneo, Alice S; Ferrara, Chiara; Marculescu, Adriana Mossuto; Giannici, Francesco; Martorana, Antonino; Mustarelli, Piercarlo; Tealdi, Cristina

    2016-08-01

    Dion-Jacobson phases, like MLaNb2O7, are an interesting class of ion-exchangeable layered perovskites possessing electronic and photocatalytic properties. Their protonated and organo-modified homologues, in particular, have already been indicated as promising catalysts. However, the structural analysis of these highly tailorable materials is still incomplete, and both the intercalation process and thermal stability of the included organic moieties are far from being completely understood. In this study, we present a thorough solid-state NMR characterization of HLaNb2O7·xH2O intercalated with different amounts of octylamine, or with decylamine. Samples were analyzed as prepared, and after thermal treatment at different temperatures up to 220 °C. The substitution of pristine proton ions was followed via(1)H MAS NMR spectroscopy, whereas the alkyl chains were monitored through (13)C((1)H) CP MAS experiments. The interactions in the interlayer space were explored using (13)C((1)H) 2D heteronuclear correlation experiments. We demonstrate that some of the protons are involved in the functionalization reaction, and some of them are in close proximity to the alkyl ammonium chains. Heating of the hybrid materials leads first to a rearrangement of the alkyl chains and then to their degradation. The spatial arrangement of the chains, their interactions and the thermal behavior of the materials depend on the extent of the functionalization, and on the nature of the intercalated alkyl ammonium ions. PMID:27440133

  17. Layered-structural monoclinic–orthorhombic perovskite La{sub 2}Ti{sub 2}O{sub 7} to orthorhombic LaTiO{sub 3} phase transition and their microstructure characterization

    SciTech Connect

    Herrera, G.; Jiménez-Mier, J.; Chavira, E.

    2014-03-01

    The layered-structural ceramics, such as lanthanum titanate (La{sub 2}Ti{sub 2}O{sub 7}), have been known for their good temperature and low dielectric loss at microwave frequencies that make them good candidate materials for high frequency applications. However, few studies have been conducted on the synthesis optimization by sol gel reaction, in particular by acrylamide polymerization route. The interest in La{sub 2}Ti{sub 2}O{sub 7} ceramic has been greatly increased recently due to the effect of oriented grains. This anisotropy of the microstructure leads to anisotropy in dielectric, electrical and mechanical properties. In this study, grain oriented lanthanum titanate was produced by the sol–gel acrylamide polymerization route. The characterizations of the samples were achieved by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). X-ray diffraction indicates that the formation of monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} nanocrystals is a necessary first step to obtain orthorhombic LaTiO{sub 3} nanocomposites (with space group Pbnm). In this work we identified that the monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} with space group P2{sub 1} transforms its structure into one with the orthorhombic space group Cmc2{sub 1} at approximately 1073 K. The microstructure associated consisted of flaky monoclinic La{sub 2}Ti{sub 2}O{sub 7} nanocomposites in comparison with round-shaped LaTiO{sub 3} nanocomposites. - Highlights: • The flaky-like La{sub 2}Ti{sub 2}O{sub 7} compound was synthesized by sol–gel acrylamide route. • Simultaneous monitoring of the DTA and XRD with temperature was performed. • Phase transformation characterization of La{sub 2}Ti{sub 2}O{sub 7} has been carried out. • The variation of the La{sub 2}Ti{sub 2}O{sub 7} and LaTiO{sub 3} grain morphology has been compared.

  18. High Efficiency Tandem Thin-Perovskite/Polymer Solar Cells with a Graded Recombination Layer.

    PubMed

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

    2016-03-23

    Perovskite-containing tandem solar cells are attracting attention for their potential to achieve high efficiencies. We demonstrate a series connection of a ∼90 nm thick perovskite front subcell and a ∼100 nm thick polymer:fullerene blend back subcell that benefits from an efficient graded recombination layer containing a zwitterionic fullerene, silver (Ag), and molybdenum trioxide (MoO3). This methodology eliminates the adverse effects of thermal annealing or chemical treatment that occurs during perovskite fabrication on polymer-based front subcells. The record tandem perovskite/polymer solar cell efficiency of 16.0%, with low hysteresis, is 75% greater than that of the corresponding ∼90 nm thick perovskite single-junction device and 65% greater than that of the polymer single-junction device. The high efficiency of this hybrid tandem device, achieved using only a ∼90 nm thick perovskite layer, provides an opportunity to substantially reduce the lead content in the device, while maintaining the high performance derived from perovskites. PMID:26918708

  19. Double-layered ZnO nanostructures for efficient perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mahmood, Khalid; S. Swain, Bhabani; Amassian, Aram

    2014-11-01

    To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field.

  20. Double-layered ZnO nanostructures for efficient perovskite solar cells.

    PubMed

    Mahmood, Khalid; S Swain, Bhabani; Amassian, Aram

    2014-12-21

    To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field. PMID:25373624

  1. Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition.

    PubMed

    Lin, Edward L; Edmondson, Bryce I; Hu, Shen; Ekerdt, John G

    2016-01-01

    Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2×1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods. PMID:27501462

  2. Flexible perovskite solar cells based on the metal-insulator-semiconductor structure.

    PubMed

    Wei, Jing; Li, Heng; Zhao, Yicheng; Zhou, Wenke; Fu, Rui; Pan, Huiyue; Zhao, Qing

    2016-09-14

    The metal-insulator-semiconductor (MIS) structure is applied to perovskite solar cells, in which the traditional compact layer TiO2 is replaced by Al2O3 as the hole blocking material to realize an all-low-temperature process. Flexible devices based on this structure are also realized with excellent flexibility, which hold 85% of their initial efficiency after bending 100 times. PMID:27524362

  3. Photoconductive properties of organic-inorganic hybrid films of layered perovskite-type niobate.

    PubMed

    Saruwatari, Kazuko; Sato, Hisako; Idei, Tomochika; Kameda, Jun; Yamagishi, Akihiko; Takagaki, Atsushi; Domen, Kazunari

    2005-06-30

    A hybrid film of layered niobate and an organic amphiphile was prepared by the Langmuir-Blodgett (LB) method. Trimethylammonium-exchanged perovskite-type niobates ((CH(3))(3)NHSr(2)Nb(3)O(10)) were exfoliative to form an aqueous suspension. A monolayer of octadecylamine was produced on such an aqueous dispersion as a template for a hybrid film. A hybrid film was transferred as a Y-type LB film onto a hydrophilic glass plate or an ITO substrate. The structure of a deposited film was investigated with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic force microscopy (AFM) measurements, indicating a layer-by-layer structure with a single or double sheet of niobate as an inorganic composite. From the cyclic voltammogram on an ITO electrode modified with the Y-type 10 layered film, the lower edge of the conduction band of a niobate layer was determined to be - 0.6 V (vs Ag/AgCl). ac impedance and dc measurements were carried out on 1, 5, and 10-layered LB films (2 mm (electrode spacing) x 8 mm (width)) with aluminum electrodes. The freshly deposited samples behaved as an insulator under the illumination of 280 nm light (2.04 x 10(16) quanta s(-1)). Photoconductivities appeared, however, when they were preirradiated with a 150 W Xe lamp (ca. 2 x 10(18) quanta s(-1)) for 0.5-8.5 h. The process was denoted as photomodification. From the FT-IR and XRD results, it was deduced that the photomodification of LB films caused the decomposition of organic templates (octadecylammonium) accompanied by the collapse of layer-by-layer structures. dc analyses on the 5- and 10-layered films after photomodification also showed that they behaved as a photosemiconductor under UV light illumination. PMID:16852536

  4. Highly stable perovskite solar cells with an all-carbon hole transport layer.

    PubMed

    Wang, Feijiu; Endo, Masaru; Mouri, Shinichiro; Miyauchi, Yuhei; Ohno, Yutaka; Wakamiya, Atsushi; Murata, Yasujiro; Matsuda, Kazunari

    2016-06-01

    Nano-carbon materials (carbon nanotubes, graphene, and graphene oxide) have potential application for photovoltaics because of their excellent optical and electronic properties. Here, we demonstrate that a single-walled carbon nanotubes/graphene oxide buffer layer greatly improves the photovoltaic performance of organo-lead iodide perovskite solar cells. The carbon nanotubes/graphene oxide buffer layer works as an efficient hole transport/electron blocking layer. The photovoltaic conversion efficiency of 13.3% was achieved in the organo-lead iodide perovskite solar cell due to the complementary properties of carbon nanotubes and graphene oxide. Furthermore, the great improvement of photovoltaic performance stability in the perovskite solar cells using carbon nanotubes/graphene oxide/polymethyl methacrylate was demonstrated in comparison with that using a typical organic hole transport layer of 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene. PMID:27232674

  5. High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF{sub 3}

    SciTech Connect

    Shirako, Y.; Shi, Y.G.; Aimi, A.; Mori, D.; Kojitani, H.; Yamaura, K.; Inaguma, Y.; Akaogi, M.

    2012-07-15

    NaNiF{sub 3} perovskite was found to transform to post-perovskite at 16-18 GPa and 1273-1473 K. The equilibrium transition boundary is expressed as P (GPa)=-2.0+0.014 Multiplication-Sign T (K). Structure refinements indicated that NaNiF{sub 3} perovskite and post-perovskite have almost regular NiF{sub 6} octahedra consistent with absence of the first-order Jahn-Teller active ions. Both NaNiF{sub 3} perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156 K, and the post-perovskite antiferromagnetic transition at 22 K. Magnetic exchange interaction of NaNiF{sub 3} post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni-F-Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite. - Graphical abstract: Perovskite-post-perovskite transition in NaNiF{sub 3} at high pressure Highlights: Black-Right-Pointing-Pointer NaNiF{sub 3} perovskite (Pv) transforms to post-perovskite (pPv) at 16 GPa and 1300 K. Black-Right-Pointing-Pointer The equilibrium transition boundary is expressed as P (GPa)=-2.0+0.014 T (K). Black-Right-Pointing-Pointer Antiferromagnetic transition occurs at 156 K in Pv and 22 K in pPv.

  6. Highly stable perovskite solar cells with an all-carbon hole transport layer

    NASA Astrophysics Data System (ADS)

    Wang, Feijiu; Endo, Masaru; Mouri, Shinichiro; Miyauchi, Yuhei; Ohno, Yutaka; Wakamiya, Atsushi; Murata, Yasujiro; Matsuda, Kazunari

    2016-06-01

    Nano-carbon materials (carbon nanotubes, graphene, and graphene oxide) have potential application for photovoltaics because of their excellent optical and electronic properties. Here, we demonstrate that a single-walled carbon nanotubes/graphene oxide buffer layer greatly improves the photovoltaic performance of organo-lead iodide perovskite solar cells. The carbon nanotubes/graphene oxide buffer layer works as an efficient hole transport/electron blocking layer. The photovoltaic conversion efficiency of 13.3% was achieved in the organo-lead iodide perovskite solar cell due to the complementary properties of carbon nanotubes and graphene oxide. Furthermore, the great improvement of photovoltaic performance stability in the perovskite solar cells using carbon nanotubes/graphene oxide/polymethyl methacrylate was demonstrated in comparison with that using a typical organic hole transport layer of 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene.Nano-carbon materials (carbon nanotubes, graphene, and graphene oxide) have potential application for photovoltaics because of their excellent optical and electronic properties. Here, we demonstrate that a single-walled carbon nanotubes/graphene oxide buffer layer greatly improves the photovoltaic performance of organo-lead iodide perovskite solar cells. The carbon nanotubes/graphene oxide buffer layer works as an efficient hole transport/electron blocking layer. The photovoltaic conversion efficiency of 13.3% was achieved in the organo-lead iodide perovskite solar cell due to the complementary properties of carbon nanotubes and graphene oxide. Furthermore, the great improvement of photovoltaic performance stability in the perovskite solar cells using carbon nanotubes/graphene oxide/polymethyl methacrylate was demonstrated in comparison with that using a typical organic hole transport layer of 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene. Electronic supplementary information (ESI

  7. Color-Pure Violet-Light-Emitting Diodes Based on Layered Lead Halide Perovskite Nanoplates.

    PubMed

    Liang, Dong; Peng, Yuelin; Fu, Yongping; Shearer, Melinda J; Zhang, Jingjing; Zhai, Jianyuan; Zhang, Yi; Hamers, Robert J; Andrew, Trisha L; Jin, Song

    2016-07-26

    Violet electroluminescence is rare in both inorganic and organic light-emitting diodes (LEDs). Low-cost and room-temperature solution-processed lead halide perovskites with high-efficiency and color-tunable photoluminescence are promising for LEDs. Here, we report room-temperature color-pure violet LEDs based on a two-dimensional lead halide perovskite material, namely, 2-phenylethylammonium (C6H5CH2CH2NH3(+), PEA) lead bromide [(PEA)2PbBr4]. The natural quantum confinement of two-dimensional layered perovskite (PEA)2PbBr4 allows for photoluminescence of shorter wavelength (410 nm) than its three-dimensional counterpart. By converting as-deposited polycrystalline thin films to micrometer-sized (PEA)2PbBr4 nanoplates using solvent vapor annealing, we successfully integrated this layered perovskite material into LEDs and achieved efficient room-temperature violet electroluminescence at 410 nm with a narrow bandwidth. This conversion to nanoplates significantly enhanced the crystallinity and photophysical properties of the (PEA)2PbBr4 samples and the external quantum efficiency of the violet LED. The solvent vapor annealing method reported herein can be generally applied to other perovskite materials to increase their grain size and, ultimately, improve the performance of optoelectronic devices based on perovskite materials. PMID:27336850

  8. Self limiting atomic layer deposition of Al2O3 on perovskite surfaces: a reality?

    NASA Astrophysics Data System (ADS)

    Choudhury, Devika; Rajaraman, Gopalan; Sarkar, Shaibal K.

    2016-03-01

    The feasibility of self-saturated atomic layer deposition of Al2O3 on an organolead halide perovskite (MAPbI3-xClx) surface through a well known trimethylaluminium (TMA)-water (H2O) chemistry is studied. Though the sequential dosages of reactants form films on the perovskite surfaces, a self saturated growth is never observed. Self-saturation leads to the degradation of the material. Both experimental and density functional theory calculations are carried out for complete understanding of the growth mechanism of self-limiting Al2O3 on the perovskite surface.The feasibility of self-saturated atomic layer deposition of Al2O3 on an organolead halide perovskite (MAPbI3-xClx) surface through a well known trimethylaluminium (TMA)-water (H2O) chemistry is studied. Though the sequential dosages of reactants form films on the perovskite surfaces, a self saturated growth is never observed. Self-saturation leads to the degradation of the material. Both experimental and density functional theory calculations are carried out for complete understanding of the growth mechanism of self-limiting Al2O3 on the perovskite surface. Electronic supplementary information (ESI) available: Additional QCM results, FTIR spectra and DFT results. See DOI: 10.1039/c5nr06974b

  9. Structure-property relationships of nanoscale engineered perovskite oxides

    NASA Astrophysics Data System (ADS)

    Tian, Wei

    Recent advances in the synthesis of nanoscale customized structure have demonstrated that reactive molecular beam epitaxy (MBE) can be used to construct nanostructure of oxides with atomic control. The ability to engineer the structure and chemistry of oxides at the nanometer scale makes possible for the creation of new functional materials that can be designed to have exceptional properties. This thesis focused on understanding structure-property relationships of such nanoscale customized oxides utilizing state-of-the-art transmission electron microscopy (TEM). Epitaxial thin films of n = 1--5 members of Ruddlesden-Popper homologous series Srn+1Ti nO3n+1 were synthesized by reactive MBE. We investigated the structure and microstructure of these thin films by x-ray diffraction along with high-resolution transmission electron microscopy (HRTEM) in combination with computer image simulations. We found that the thin films of n = 1--3 members are nearly free of intergrowths, e.g. phase-pure, while n = 4 and 5 thin films contain noticeably more intergrowth defects and anti-phase boundaries in their perovskite sheets. We show that these results are consistent with what is known about the thermodynamics of Sr n+1TinO3 n+1 phases. We also investigated the atomic structure and interfacial structure of artificial PbTiO3/SrTiO3 and BaTiO3/SrTiO 3 superlattices grown by MBE both with and without digital compositional grading. Both of these systems form a solid solution over their entire composition range. Thus, these layered heterostructures are metastable. We demonstrated, however, that the thermodynamically metastable superlattices can be kinetically stabilized via layer-by-layer growth. In addition, we found that the interfaces between two constituents in the heterostructures are atomically-abrupt. The superlattice thin films were made fully coherent with the substrates, resulting in a homogeneous large strain in the BaTiO3 layers due to the lattice mismatch between BaTiO3

  10. Photocatalytic activity of layered perovskite-like oxides in practically valuable chemical reactions

    NASA Astrophysics Data System (ADS)

    Rodionov, I. A.; Zvereva, I. A.

    2016-03-01

    The photocatalytic properties of layered perovskite-like oxides corresponding to the Ruddlesen–Popper, Dion–Jacobson and Aurivillius phases are considered. Of the photocatalytic reactions, the focus is on the reactions of water splitting, hydrogen evolution from aqueous solutions of organic substances and degradation of model organic pollutants. Possibilities to conduct these reactions under UV and visible light in the presence of layered perovskite-like oxides and composite photocatalysts based on them are shown. The specific surface area, band gap energy, particle morphology, cation and anion doping and surface modification are considered as factors that affect the photocatalytic activity. Special attention is paid to the possibilities to enhance the photocatalytic activity by intercalation, ion exchange and exfoliation, which are inherent in this class of compounds. Conclusions are made about the prospects for the use of layered perovskite-like oxides in photocatalysis. The bibliography includes 253 references.

  11. Luminescence processes in A3IILaNb3O12 (AII = Ba, Sr) layered perovskites

    NASA Astrophysics Data System (ADS)

    Chukova, Oksana; Gomenyuk, Olga; Nedilko, Sergiy; Polubinskii, Vitaliy; Scherbatsky, Vasyl; Sheludko, Vadim; Titov, Yuriy

    2014-08-01

    The A3IILaNb3O12 (AII = Sr, Ba) layered perovskites were synthesized by co-precipitation method. Luminescence properties of these compositions have been investigated for the first time. Emission spectra consist of wide bands with maxima located near 430 and 500 nm. Luminescence processes are discussed in connection with features of cation compositions, crystal structure and distortions of the NbO67- groups’ symmetry. Possible scheme of electron states and the lowest allowed electron transitions has been built for the niobate groups of Oh and C3v symmetry. In this scheme, the 430 and 500 nm emission bands were assigned to T1 → A1 and E → A1 electron transitions in the perfect and distorted NbO67- oxyanions, respectively.

  12. Ferromagnetic and Photocatalytic Properties of Layered Perovskite LaBaCo₂O₆ Nanostructures.

    PubMed

    Hu, Yongming; Lei, Jinmei; He, Jing; Li, Yuebin; Wang, Zhao; Wang, Yu; Gu, Haoshuang

    2016-01-01

    Cationic ordered layered tetragonal perovskite phase LaBaCo₂O₆ (LBCO) nanomaterials with irregular shape, and an average diameter of about 100 nm were successfully prepared. A precursor material was annealed in an argon atmosphere at 1100 °C for 48 hours, and then heat treated in an oxygen atmosphere pressure at 800 °C for 12 hours. The resulting LBCO nanomaterials show ferromagnetic transition at about 175 K without any structural changes. They show metallic behavior at below 140 K, and adopt the behavior of soft ferromagnetic materials at 80 K. Cationic ordered LBCO nanomaterials display photocatalytic activities, as they successfully degrade MB solutions under both UV irradiation and visible light. The B-site cations act as the active center, and are located in the centre of BO₆ octahedron units. The various valence states of Co ions in LBCO could contribute to the enhancement of photocatalytic activies. PMID:27398548

  13. Structural, magnetic and magnetocaloric properties of layered perovskite La1.1Bi0.3Sr1.6Mn2O7

    NASA Astrophysics Data System (ADS)

    Oubla, M.; Lamire, M.; Boutahar, A.; Lassri, H.; Manoun, B.; Hlil, E. K.

    2016-04-01

    The La1.1Bi0.3Sr1.6Mn2O7 sample was synthesized by coprecipitation method. Its structure has been characterized by X-ray powder diffraction. The diffraction patterns are consistent with the I4/mmm symmetry, with tetragonal lattice parameters a=3.8750±0.0001 Å and c=20.0456±0.0002 Å. Magnetic measurements have shown a ferromagnetic like ordering with second order magnetic phase transition to paramagnetic states. The magnetic entropy change caused by a magnetic field, (-∆Smax), was estimated on the basis of the Maxwell relation. The maximum magnetic entropy change (-∆Smax) and the relative cooling power (RCP) are, 1.65 J kg-1K-1 and 134.4 J kg-1 respectively, for a 5 T magnetic field change at 340 K.

  14. Structural transformations in cubic structure of Mn/Co perovskites in reducing and oxidizing atmospheres

    NASA Astrophysics Data System (ADS)

    Koponen, Markus J.; Suvanto, Mika; Kallinen, Kauko; Kinnunen, Toni-J. J.; Härkönen, Matti; Pakkanen, Tapani A.

    2006-05-01

    ABO ( A=La, Pr; B=Mn, Co), ABBx'O ( A=La, Pr; B=Mn, Co; B=Co, Pd), and ABCoPdO ( A=La, Pr; B=Fe, Mn) ( x=0.05, 0.37; y=0.38) perovskites were synthesized via malic acid complexation. O 2-TPD, O 2-TPO, and H 2-TPR treatments were carried out to study the oxidation and reduction behavior of the synthesized perovskites. LaCo 0.95Pd 0.05O 3, PrCo 0.95Pd 0.05O 3, and PrCoO 3 perovskites had the highest desorption, oxidation, and reduction activity within the studied perovskite series. Powder XRD studies revealed structural transformation of the cubic structure of all synthesized perovskites except LaFe 0.57Co 0.38Pd 0.05O 3 in H 2/Ar atmosphere when the temperature was over 400 °C. The decomposed structure reverted to the original perovskite structure under oxidizing atmosphere. This reversion was accompanied by increased oxygen desorption activity. It was noticed that the Co and Mn combinations in the B-site of the perovskites structure decreased the thermal stability of the synthesized perovskites.

  15. 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. PMID:27228558

  16. Exclusion of metal oxide by an RF sputtered Ti layer in flexible perovskite solar cells: energetic interface between a Ti layer and an organic charge transporting layer.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Nazeeruddin, Mohammad Khaja; Shin, Hyung-Shik

    2015-04-14

    In this work, the effects of a titanium (Ti) layer on the charge transport and recombination rates of flexible perovskite solar cells were studied. Ti as an efficient barrier layer was deposited directly on PET-ITO flexible substrates through RF magnetic sputtering using a Ti-source and a pressure of ∼5 mTorr. A Ti coated PET-ITO was used for the fabrication of a flexible perovskite solar cell without using any metal oxide layer. The fabricated flexible perovskite solar cell was composed of a PET-ITO/Ti/perovskite (CH3NH3PbI3)/organic hole transport layer of 2,2',7,7'-tetrakis [N,N'-di-p-methoxyphenylamine]-9,9'-spirobifluorene (spiro-OMeTAD)-Li-TFSI/Ag. A high conversion efficiency of ∼8.39% along with a high short circuit current (JSC) of ∼15.24 mA cm(-2), an open circuit voltage (VOC) of ∼0.830 V and a high fill factor (FF) of ∼0.66 was accomplished by the fabricated flexible perovskite solar cell under a light illumination of ∼100 mW cm(-2) (1.5 AM). Intensity-modulated photocurrent (IMPS)/photovoltage spectroscopy (IMVS) studies demonstrated that the fabricated flexible perovskite solar cell considerably reduced the recombination rate. PMID:25747794

  17. Method for fabricating high aspect ratio structures in perovskite material

    DOEpatents

    Karapetrov, Goran T.; Kwok, Wai-Kwong; Crabtree, George W.; Iavarone, Maria

    2003-10-28

    A method of fabricating high aspect ratio ceramic structures in which a selected portion of perovskite or perovskite-like crystalline material is exposed to a high energy ion beam for a time sufficient to cause the crystalline material contacted by the ion beam to have substantially parallel columnar defects. Then selected portions of the material having substantially parallel columnar defects are etched leaving material with and without substantially parallel columnar defects in a predetermined shape having high aspect ratios of not less than 2 to 1. Etching is accomplished by optical or PMMA lithography. There is also disclosed a structure of a ceramic which is superconducting at a temperature in the range of from about 10.degree. K. to about 90.degree. K. with substantially parallel columnar defects in which the smallest lateral dimension of the structure is less than about 5 microns, and the thickness of the structure is greater than 2 times the smallest lateral dimension of the structure.

  18. Efficient hole-blocking layer-free planar halide perovskite thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Ke, Weijun; Fang, Guojia; Wan, Jiawei; Tao, Hong; Liu, Qin; Xiong, Liangbin; Qin, Pingli; Wang, Jing; Lei, Hongwei; Yang, Guang; Qin, Minchao; Zhao, Xingzhong; Yan, Yanfa

    2015-03-01

    Efficient lead halide perovskite solar cells use hole-blocking layers to help collection of photogenerated electrons and to achieve high open-circuit voltages. Here, we report the realization of efficient perovskite solar cells grown directly on fluorine-doped tin oxide-coated substrates without using any hole-blocking layers. With ultraviolet-ozone treatment of the substrates, a planar Au/hole-transporting material/CH3NH3PbI3-xClx/substrate cell processed by a solution method has achieved a power conversion efficiency of over 14% and an open-circuit voltage of 1.06 V measured under reverse voltage scan. The open-circuit voltage is as high as that of our best reference cell with a TiO2 hole-blocking layer. Besides ultraviolet-ozone treatment, we find that involving Cl in the synthesis is another key for realizing high open-circuit voltage perovskite solar cells without hole-blocking layers. Our results suggest that TiO2 may not be the ultimate interfacial material for achieving high-performance perovskite solar cells.

  19. Efficient hole-blocking layer-free planar halide perovskite thin-film solar cells.

    PubMed

    Ke, Weijun; Fang, Guojia; Wan, Jiawei; Tao, Hong; Liu, Qin; Xiong, Liangbin; Qin, Pingli; Wang, Jing; Lei, Hongwei; Yang, Guang; Qin, Minchao; Zhao, Xingzhong; Yan, Yanfa

    2015-01-01

    Efficient lead halide perovskite solar cells use hole-blocking layers to help collection of photogenerated electrons and to achieve high open-circuit voltages. Here, we report the realization of efficient perovskite solar cells grown directly on fluorine-doped tin oxide-coated substrates without using any hole-blocking layers. With ultraviolet-ozone treatment of the substrates, a planar Au/hole-transporting material/CH₃NH₃PbI₃-xClx/substrate cell processed by a solution method has achieved a power conversion efficiency of over 14% and an open-circuit voltage of 1.06 V measured under reverse voltage scan. The open-circuit voltage is as high as that of our best reference cell with a TiO₂ hole-blocking layer. Besides ultraviolet-ozone treatment, we find that involving Cl in the synthesis is another key for realizing high open-circuit voltage perovskite solar cells without hole-blocking layers. Our results suggest that TiO₂ may not be the ultimate interfacial material for achieving high-performance perovskite solar cells. PMID:25798925

  20. Tilt engineering of spontaneous polarization and magnetization above 300 K in a bulk layered perovskite

    NASA Astrophysics Data System (ADS)

    Pitcher, Michael J.; Mandal, Pranab; Dyer, Matthew S.; Alaria, Jonathan; Borisov, Pavel; Niu, Hongjun; Claridge, John B.; Rosseinsky, Matthew J.

    2015-01-01

    Crystalline materials that combine electrical polarization and magnetization could be advantageous in applications such as information storage, but these properties are usually considered to have incompatible chemical bonding and electronic requirements. Recent theoretical work on perovskite materials suggested a route for combining both properties. We used crystal chemistry to engineer specific atomic displacements in a layered perovskite, (CaySr1-y)1.15Tb1.85Fe2O7, that change its symmetry and simultaneously generate electrical polarization and magnetization above room temperature. The two resulting properties are magnetoelectrically coupled as they arise from the same displacements.

  1. Photocatalytic Hydrogen Production over Chromium Doped Layered Perovskite Sr2TiO4.

    PubMed

    Sun, Xiaoqin; Xie, Yinghao; Wu, Fangfang; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

    2015-08-01

    Layered semiconductor photocatalysts have been found to exhibit promising performance levels, probably linked to their interlayer framework that facilitates separation of charge carriers and the reduction/oxidation reactions. Layered titanates, however, generally demonstrate activities under UV irradiation, and therein lies the strong desire to extend their activity into the visible light region. Here, we investigated a series of layered perovskite by doping Sr2TiO4 with Cr and/or La in the hope to improve their visible light responses. Their crystal structures and other physicochemical properties were systematically explored. Our results show that La and Cr can be successfully accommodated in the layered structure and Cr is an efficient dopant for the extension of visible light absorbance. Much enhanced photocatalytic hydrogen evolution was observed after doping and was found to be composition-dependent. The highest hydrogen production rate approaches 97.7 μmol/h for Sr2Ti0.95Cr0.05O4-δ under full range irradiation (λ ≥ 250 nm) and 17 μmol/h for Sr2Ti0.9Cr0.1O4-δ under visible light irradiation (λ ≥ 400 nm), corresponding to an apparent quantum efficiency of 0.16% and 0.05%, respectively. Theoretical calculation reveals that the improved optical and photocatalytic properties are owing to a newly formed spin-polarized valence band from Cr 3d orbitals. The decreased unit cell parameters, reduced band gaps as well as anisotropic properties of layered architectures are likely the reasons for a better activity. Nevertheless, instability of these compounds in the presence of moisture and CO2 was also noticed, suggesting that protective atmospheres are needed for the storage of these photocatalysts. PMID:26171625

  2. Fast Crystallization and Improved Stability of Perovskite Solar Cells with Zn2SnO4 Electron Transporting Layer: Interface Matters.

    PubMed

    Bera, Ashok; Sheikh, Arif D; Haque, Md Azimul; Bose, Riya; Alarousu, Erkki; Mohammed, Omar F; Wu, Tom

    2015-12-30

    Here we report that mesoporous ternary oxide Zn2SnO4 can significantly promotes the crystallization of hybrid perovskite layers and serves as an efficient electron transporting material in perovskite solar cells. Such devices exhibit an energy conversion efficiency of 13.34%, which is even higher than that achieved with the commonly used TiO2 in the similar experimental conditions (9.1%). Simple one-step spin coating of CH3NH3PbI3-xClx on Zn2SnO4 is found to lead to rapidly crystallized bilayer perovskite structure without any solvent engineering. Furthermore, ultrafast transient absorption measurement reveals efficient charge transfer at the Zn2SnO4/perovskite interface. Most importantly, solar cells with Zn2SnO4 as the electron-transporting material exhibit negligible electrical hysteresis and exceptionally high stability without encapsulation for over one month. Besides underscoring Zn2SnO4 as a highly promising electron transporting material for perovskite solar cells, our results demonstrate the significant role of interfaces on improving the perovskite crystallization and photovoltaic performance. PMID:26633572

  3. Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

    PubMed Central

    Choi, Hyosung; Mai, Cheng-Kang; Kim, Hak-Beom; Jeong, Jaeki; Song, Seyeong; Bazan, Guillermo C.; Kim, Jin Young; Heeger, Alan J.

    2015-01-01

    Organic–inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT:PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT:PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells. PMID:26081865

  4. Improve efficiency of perovskite solar cells by using Magnesium doped ZnO and TiO2 compact layers

    NASA Astrophysics Data System (ADS)

    Baktash, Ardeshir; Amiri, Omid; Sasani, Alireza

    2016-05-01

    Here the effect of Magnesium doped TiO2 and ZnO as hole blocking layers (HBLs) are investigated by using solar cell capacitance simulator (SCAPS). The Impact of Magnesium concentration into the TiO2 and ZnO and effect of operating temperature on the performance of the perovskite solar cell are investigated. Best cell performance for both TiO2 and ZnO HBLs (with cell efficiencies of 19.86% and 19.57% respectively) are concluded for the doping level of 10% of Mg into the structure of HBLs. Increase in operating temperature from 300 K to 400 K are decreased the performance of the perovskite solar cell with both pure and Mg-doped HBLs. However, the cells with pure ZnO layer and with Zn0.9 Mg0.1O layer show the highest (with a decline of 8.88% in efficiency) and the lowest stability (with a decline of 50.49% in efficiency) at higher temperatures respectively. Moreover, the cell with Ti0.9 Mg0.1O2 layer shows better stability (with 21.85% reduction in efficiency) than the cell with pure TiO2 compact layer (with 23.28% reduction in efficiency) at higher operating temperatures.

  5. Cation Ordering within the Perovskite Block of a Six-layer Ruddlesden-Popper Oxide from Layer-by-layer Growth

    NASA Astrophysics Data System (ADS)

    Yan, Lei; Niu, H. J.; Rosseinsky, M. J.

    2011-03-01

    The (AO)(A BO3)n Ruddlesden-Popper structure is an archetypal complex oxide consisting of two distinct structural units, an (AO) rock salt layer separating an n-octahedra thick perovskite block. Conventional high-temperature oxide synthesis methods cannot access members with n > 3 , butlowtemperaturelayer - by - layerthinfilmmethodsallowthepreparationofmaterialswiththickerperovskiteblocks , exploitinghighsurfacemobilityandlatticematchingwiththesubstrate . Thispresentationdescribesthegrowthofann = 6 memberCaO / (ABO 3)n (ABO 3 : CaMnO 3 , La 0.67 Ca 0.33 MnO 3 orCa 0.85 Sm 0.15 MnO 3) epitaxialsinglecrystalfilmsonthe (001) SrTiO 3 substrates by pulsed laser deposition with the assistance of a reflection high energy electron diffraction (RHEED).

  6. Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers

    SciTech Connect

    Bell, Christopher

    2011-08-11

    We demonstrate the strain release of LaAlO{sub 3} epitaxial film on SrTiO{sub 3} (001) by inserting ultra-thin 'SrAlO{sub x}' buffer layers. Although SrAlO{sub x} is not a perovskite, nor stable as a single phase in bulk, epitaxy stabilizes the perovskite structure up to a thickness of 2 unit cells (uc). At a critical thickness of 3 uc of SrAlO{sub x}, the interlayer acts as a sliding buffer layer, and abruptly relieves the lattice mismatch between the LaAlO{sub 3} filmand the SrTiO{sub 3} substrate, while maintaining crystallinity. This technique may provide a general approach for strain relaxation of perovskite film far below the thermodynamic critical thickness. A central issue in heteroepitaxial filmgrowth is the inevitable difference in lattice constants between the filmand substrate. Due to this lattice mismatch, thin film are subjected to microstructural strain, which can have a significan effect on the filmproperties. This challenge is especially prominent in the rapidly developing fiel of oxide electronics, where much interest is focused on incorporating the emergent physical properties of oxides in devices. Although strain can be used to great effect to engineer unusual ground states, it is often deleterious for bulk first-orde phase transitions, which are suppressed by the strain and symmetry constraints of the substrate. While there are some reports discussing the control of the lattice mismatch in oxides using thick buffer layers, the materials choice, lattice-tunable range, and control of misfit dislocations are still limited. In this Letter, we report the fabrication of strain-relaxed LaAlO{sub 3} (LAO) thin film on SrTiO{sub 3} (STO) (001) using very thin 'SrAlO{sub x}' (SAO) buffer layers. Whereas for 1 or 2 pseudo-perovskite unit cells (uc) of SAO, the subsequent LAO filmis strained to the substrate, at a critical thickness of 3 uc the SAO interlayer abruptly relieves the lattice mismatch between the LAO and the STO, although maintaining the

  7. Topological Oxide Insulator in Cubic Perovskite Structure

    PubMed Central

    Jin, Hosub; Rhim, Sonny H.; Im, Jino; Freeman, Arthur J.

    2013-01-01

    The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both a large bulk band gap and a high resistivity. Based on first-principles calculations varying the spin-orbit coupling strength, the non-trivial band topology of YBiO3 is investigated, where the spin-orbit coupling of the Bi 6p orbital plays a crucial role. Taking the exquisite synthesis techniques in oxide electronics into account, YBiO3 can also be used to provide various interface configurations hosting exotic topological phenomena combined with other quantum phases. PMID:23575973

  8. Topological Oxide Insulator in Cubic Perovskite Structure

    NASA Astrophysics Data System (ADS)

    Jin, Hosub; Rhim, Sonny H.; Im, Jino; Freeman, Arthur J.

    2013-04-01

    The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both a large bulk band gap and a high resistivity. Based on first-principles calculations varying the spin-orbit coupling strength, the non-trivial band topology of YBiO3 is investigated, where the spin-orbit coupling of the Bi 6p orbital plays a crucial role. Taking the exquisite synthesis techniques in oxide electronics into account, YBiO3 can also be used to provide various interface configurations hosting exotic topological phenomena combined with other quantum phases.

  9. Photovoltaic switching mechanism in lateral structure hybrid perovskite solar cells

    DOE PAGESBeta

    Yuan, Yongbo; Chae, Jungseok; Shao, Yuchuan; Wang, Qi; Xiao, Zhengguo; Centrone, Andrea; Huang, Jinsong

    2015-06-05

    In this study, long range electromigration of methylammonium ions (MA+) in methyl ammonium lead tri-iodide (MAPbI3) film is observed directly using the photo­thermal induced resonance technique. The electromigration of MA+ leads to the formation of a lateral p-i-n structure, which is the origin of the switchable photovoltaic effect in MAPbI3 perovskite devices.

  10. Photovoltaic switching mechanism in lateral structure hybrid perovskite solar cells

    SciTech Connect

    Yuan, Yongbo; Chae, Jungseok; Shao, Yuchuan; Wang, Qi; Xiao, Zhengguo; Centrone, Andrea; Huang, Jinsong

    2015-06-05

    In this study, long range electromigration of methylammonium ions (MA+) in methyl ammonium lead tri-iodide (MAPbI3) film is observed directly using the photo­thermal induced resonance technique. The electromigration of MA+ leads to the formation of a lateral p-i-n structure, which is the origin of the switchable photovoltaic effect in MAPbI3 perovskite devices.

  11. Preparation and optical characteristics of layered perovskite-type lead-bromide-incorporated azobenzene chromophores

    NASA Astrophysics Data System (ADS)

    Sasai, Ryo; Shinomura, Hisashi

    2013-02-01

    Lead bromide-based layered perovskite powders with azobenzene derivatives were prepared by a homogeneous precipitation method. From the diffuse reflectance (DR) and photoluminescence (PL) spectra of the hybrid powder materials, the present hybrids exhibited sharp absorption and PL peaks originating from excitons produced in the PbBr42- layer. When the present hybrid powder was irradiated with UV light at 350 nm, the absorption band from the trans-azobenzene chromophore, observed around 350 nm, decreased, while the absorption band from the cis-azobenzene chromophore, observed around 450 nm, increased. These results indicate that azobenzene chromophores in the present hybrid materials exhibit reversible photoisomerization. Moreover, it was found that the PL intensity from the exciton also varied due to photoisomerization of the azobenzene chromophores in the present hybrid. Thus, for the first time we succeeded in preparing the azobenzene derivative lead-bromide-based layered perovskite with photochromism before and after UV light irradiation.

  12. Transition Metal-Oxide Free Perovskite Solar Cells Enabled by a New Organic Charge Transport Layer.

    PubMed

    Chang, Sehoon; Han, Ggoch Ddeul; Weis, Jonathan G; Park, Hyoungwon; Hentz, Olivia; Zhao, Zhibo; Swager, Timothy M; Gradečak, Silvija

    2016-04-01

    Various electron and hole transport layers have been used to develop high-efficiency perovskite solar cells. To achieve low-temperature solution processing of perovskite solar cells, organic n-type materials are employed to replace the metal oxide electron transport layer (ETL). Although PCBM (phenyl-C61-butyric acid methyl ester) has been widely used for this application, its morphological instability in films (i.e., aggregation) is detrimental. Herein, we demonstrate the synthesis of a new fullerene derivative (isobenzofulvene-C60-epoxide, IBF-Ep) that serves as an electron transporting material for methylammonium mixed lead halide-based perovskite (CH3NH3PbI3-xClx) solar cells, both in the normal and inverted device configurations. We demonstrate that IBF-Ep has superior morphological stability compared to the conventional acceptor, PCBM. IBF-Ep provides higher photovoltaic device performance as compared to PCBM (6.9% vs 2.5% in the normal and 9.0% vs 5.3% in the inverted device configuration). Moreover, IBF-Ep devices show superior tolerance to high humidity (90%) in air. By reaching power conversion efficiencies up to 9.0% for the inverted devices with IBF-Ep as the ETL, we demonstrate the potential of this new material as an alternative to metal oxides for perovskite solar cells processed in air. PMID:26947400

  13. Effect of Morphology Control of Light Absorbing Layer on CH3NH3PbI3 Perovskite Solar Cells.

    PubMed

    Lei, Binglong; Eze, Vincent Obiozo; Mori, Tatsuo

    2016-04-01

    As one of the most significant components of perovskite solar cells, the perovskite light absorbing layer demands high quality to guarantee extraordinary power conversion efficiency (PCE). We have fabricated series of CH3NH3PbI3 perovskite solar cells by virtue of gas-flowing assisting (GFA), spin coating twice for the Pbl2 layer and dipping the semi-samples in a thermal CH3NH3I solution, by which some undesirable perovskite morphologies can be effectively avoided. The modified conductions have also dramatically improved the perovskite layer and elevated the coverage ratio from 53.6% to 79.5%. All the fabrication processes, except the steps for deposition of the hole transport material (HTM) and back gold electrode, have been conducted in air and an average PCE of 6.6% has been achieved by initiatively applying N,N'-bis(1-naphtyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) doped by MoO3 as HTM. The CH3NH3PbI3 perovskite's morphology and its coverage ratio to the underneath TiO2 mesoporic layer are evaluated to account for the cells' performance. It has demonstrated that higher homogeneity and coverage ratio of the CH3NH3PbI3 layer have most significantly contributed to the solar cells' light conversion efficiency. Keywords: Perovskite, Solar Cell, Morphology, Coverage Ratio, Hole Transport Material. PMID:27451600

  14. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D" layer.

    PubMed

    Oganov, Artem R; Ono, Shigeaki

    2004-07-22

    The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3 (ref. 1). But it has not been possible to explain many unusual properties of the lowermost approximately 150 km of the mantle (the D" layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we show that at pressures and temperatures of the D" layer, MgSiO3 transforms from perovskite into a layered CaIrO3-type post-perovskite phase. The elastic properties of the post-perovskite phase and its stability field explain several observed puzzling properties of the D" layer: its seismic anisotropy, the strongly undulating shear-wave discontinuity at its top and possibly the anticorrelation between shear and bulk sound velocities. PMID:15269766

  15. The effect of skin-depth interfacial defect layer in perovskite solar cell

    NASA Astrophysics Data System (ADS)

    Gebremichael, Bizuneh; Mola, Genene Tessema

    2016-08-01

    The hole transport buffer layer (HTL) known as PEDOT:PSS is found to be sensitive to polar solvents often used in the preparation of solution-processed perovskite-based solar cell. We employed {CH}3 {NH}3 {PbI}3 perovskite absorber sandwiched between two charge transport layers to analyze the effect of precursor solvent. By introducing skin-depth interfacial defect layer (IDL) on PEDOT:PSS film we studied the overall performance of the devices using one-dimensional device simulator. Both enhanced conductivity and variations in valence band offset (VBO) of IDL were considered to analyze device performance. A power conversion efficiency (PCE) of the devices was found to grow by 35 % due to increased conductivity of IDL by a factor of 1000. Furthermore, we noted a drastic reduction in PCE of the device by reducing the work function of IDL by more than 0.3eV . The thickness of interfacial defect layer was also analyzed and found to decrease the PCE of the devices by 18 % for fourfold increase in IDL thickness. The analysis was remarkably reproduced the experimentally generated device parameters and will help to understand the underlying physical process in perovskite-based solar cell.

  16. Process for forming epitaxial perovskite thin film layers using halide precursors

    DOEpatents

    Clem, Paul G.; Rodriguez, Mark A.; Voigt, James A.; Ashley, Carol S.

    2001-01-01

    A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

  17. Low-Temperature TiOx Compact Layer for Planar Heterojunction Perovskite Solar Cells.

    PubMed

    Liu, Zonghao; Chen, Qi; Hong, Ziruo; Zhou, Huanping; Xu, Xiaobao; De Marco, Nicholas; Sun, Pengyu; Zhao, Zhixin; Cheng, Yi-Bing; Yang, Yang

    2016-05-01

    Here, we demonstrate an effective low-temperature approach to fabricate a uniform and pinhole-free compact TiO2 layer for enhancing photovoltaic performance of perovskite solar cells. TiCl4 was used to modify TiO2 for efficient charge generation and significantly reduced recombination loss. We found that a TiO2 layer with an appropriate TiCl4 treatment possesses a smooth surface with full coverage of the conductive electrode. Further studies on charge carrier dynamics confirmed that the TiCl4 treatment improves the contact of the TiO2/perovskite interface, facilitating charge extraction and suppressing charge recombination. On the basis of the treatment, we improved the open circuit voltage from 1.01 V of the reference cell to 1.08 V, and achieved a power conversion efficiency of 16.4%. PMID:27058279

  18. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    SciTech Connect

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G.; Posadas, Agham; Demkov, Alexander A.

    2015-12-15

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al{sub 2}O{sub 3} and HfO{sub 2}. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO{sub 3}), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  19. Epitaxial 1D electron transport layers for high-performance perovskite solar cells.

    PubMed

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-10-01

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport. PMID:26324759

  20. The Role of Oxygen in the Degradation of Methylammonium Lead Trihalide Perovskite Photoactive Layers.

    PubMed

    Aristidou, Nicholas; Sanchez-Molina, Irene; Chotchuangchutchaval, Thana; Brown, Michael; Martinez, Luis; Rath, Thomas; Haque, Saif A

    2015-07-01

    In this paper we report on the influence of light and oxygen on the stability of CH3 NH3 PbI3 perovskite-based photoactive layers. When exposed to both light and dry air the mp-Al2 O3 /CH3 NH3 PbI3 photoactive layers rapidly decompose yielding methylamine, PbI2 , and I2 as products. We show that this degradation is initiated by the reaction of superoxide (O2 (-) ) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O2 (-) species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O2 (-) generation is significantly reduced when the mp-Al2 O3 film is replaced with an mp-TiO2 electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH3 NH3 PbI3 to a species without acid protons could improve tolerance to oxygen and enhance stability. PMID:26014846

  1. TiO2 Sub-microsphere Film as Scaffold Layer for Efficient Perovskite Solar Cells.

    PubMed

    Huang, Yang; Zhu, Jun; Ding, Yong; Chen, Shuanghong; Zhang, Changneng; Dai, Songyuan

    2016-03-01

    TiO2 sub-microspheres composed of anatase granular-like nanocrystallines with an average diameter ∼250 nm are synthesized using sol-gel method and employed as the scaffold layer for efficient mesocopic perovskite solar cells. Compared with mesoporous TiO2 films composed of ∼18 nm nanoparticles, the sub-microsphere films show superior light-trapping characteristics and significantly improve the light-harvesting capability of the solar cells. In addition, the charge-transport performance is also dramatically improved according to the transient photocurrent decay despite there being no significant difference in the perovskite layer surface morphology. As a result, an average power conversion efficiency of 15% with a highly uniform distribution is achieved for the solar cells with TiO2 sub-microsphere films, 12% higher than those with TiO2 nanoparticle films. The combination of light-harvesting capability and fast charge transfer make the TiO2 sub-microsphere film a good candidate as the scaffold layer for efficient perovskite solar cells. PMID:26953635

  2. Perovskite-organic hybrid tandem solar cells using a nanostructured perovskite layer as the light window and a PFN/doped-MoO3/MoO3 multilayer as the interconnecting layer

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Lu, Shunmian; Zhu, Lu; Li, Xinchen; Choy, Wallace C. H.

    2016-02-01

    In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL.In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL. Electronic supplementary information (ESI) available. See DOI: 10

  3. New hexagonal perovskite with Mn4+ and Mn5+ at distinct structural positions

    NASA Astrophysics Data System (ADS)

    Tarakina, N. V.; Tyutyunnik, A. P.; Bazuev, G. V.; Vasiliev, A. D.; Berger, I. F.; Gould, C.; Nikolaenko, I. V.

    2015-10-01

    A new hexagonal perovskite, Ba7Li1.75Mn3.5O15.75, has been synthesised using microwave-assisted solid-state synthesis. Its crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. Structural solution based on simultaneous refinement of X-ray and neutron diffraction data shows that Ba7Li1.75Mn3.5O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) Å and c = 16.7467(1) Å (V = 465.063(4) Å3). Columns of face- shared octahedra occupied by Mn4+, Li+ cations and vacancies along the c axis are separated in the ab plane by barium atoms, so that every sixth layer, the coordination of Mn5+ and Li+ changes to tetrahedral. Separation of Mn4+ and Mn5+ cations in two distinct structural positions makes the structure unique. A scanning transmission electron microscopy study revealed the formation of a rhombohedrally centered supercell, which might be attributed to the ordering of manganese and lithium atoms among cationic sites.

  4. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  5. Calcium manganate: A promising candidate as buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems

    SciTech Connect

    Zhao, Pengjun; Wang, Hongguang; Kong, Wenwen; Xu, Jinbao Wang, Lei; Ren, Wei; Bian, Liang; Chang, Aimin

    2014-11-21

    We have systematically studied the feasibility of CaMnO{sub 3} thin film, an n-type perovskite, to be utilized as the buffer layer for hybrid halide perovskite photovoltaic-thermoelectric device. Locations of the conduction band and the valence band, spontaneous polarization performance, and optical properties were investigated. Results indicate the energy band of CaMnO{sub 3} can match up well with that of CH{sub 3}NH{sub 3}PbI{sub 3} on separating electron-hole pairs. In addition, the consistent polarization angle helps enlarge the open circuit voltage of the composite system. Besides, CaMnO{sub 3} film shows large absorption coefficient and low extinction coefficient under visible irradiation, demonstrating high carrier concentration, which is beneficial to the current density. More importantly, benign thermoelectric properties enable CaMnO{sub 3} film to assimilate phonon vibration from CH{sub 3}NH3PbI{sub 3}. All the above features lead to a bright future of CaMnO{sub 3} film, which can be a promising candidate as a buffer layer for hybrid halide perovskite photovoltaic-thermoelectric systems.

  6. Low temperature fabrication of perovskite solar cells with TiO2 nanoparticle layers

    NASA Astrophysics Data System (ADS)

    Kanayama, Masato; Oku, Takeo; Suzuki, Atsushi; Yamada, Masahiro; Sakamoto, Hiroki; Minami, Satoshi; Kohno, Kazufumi

    2016-02-01

    TiO2/CH3NH3PbI3-based photovoltaic devices were fabricated by a spin-coating method using a mixture solution. TiO2 require high-temperature processing to achieve suitably high carrier mobility. TiO2 electron transport layers and TiO2 scaffold layers for the perovskite were fabricated from TiO2 nanoparticles with different grain sizes. The photovoltaic properties and microstructures of solar cells were characterized. Nanoparticle sizes of these TiO2 were 23 nm and 3 nm and the performance of solar cells was improved by combination of two TiO2 nanoparticles

  7. 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. PMID:27386731

  8. Structural phase transitions in EuNbO3 perovskite

    NASA Astrophysics Data System (ADS)

    Kususe, Yoshiro; Yoshida, Suguru; Fujita, Koji; Akamatsu, Hirofumi; Fukuzumi, Masafumi; Murai, Shunsuke; Tanaka, Katsuhisa

    2016-07-01

    The crystal structures of europium niobate, EuNbO3, have been examined over a wide temperature range between 20 and 500 K using synchrotron X-ray diffraction. We have observed two successive structural phase transitions at 360 and 460 K. Below 350 K, EuNbO3 adopts an orthorhombic perovskite structure (space group Imma), which is characterized by NbO6 octahedral tilting about the pseudocubic two-fold axis. The result differs from previous reports in which EuNbO3 was assigned to a cubic aristotype (space group Pm 3 barm) of perovskite at room temperature. At around 360 K, EuNbO3 undergoes a first-order phase transition to a tetragonal symmetry (space group I4/mcm) with the NbO6 octahedral tilting about the pseudocubic four-fold axis. As the temperature is further increased, the I4/mcm tetragonal phase changes into the Pm 3 barm cubic aristotype at 460 K. The tetragonal-to-cubic transformation is characterized as a continuous phase transition.

  9. Structural stability and catalytic activity of lanthanum-based perovskites

    SciTech Connect

    Sergey N. Rashkeev; Lucia M. Petkovic

    2011-05-01

    Perovskite-type oxide materials with a general formula La(1-x)A(x)Fe(1-y)Co(y)O(3-delta), where A is an alkaline earth metal Sr or Ba have been studied as cathode materials for catalytic reduction of oxygen in solid oxide fuel cells (SOFC), as well as combustion catalysts. In this study, we use a combination of temperature programmed reduction measurements, X-ray diffraction, carbon black catalytic oxidation measurements, and first-principles, density-functional-theory (DFT) calculations to elucidate the main processes that contribute into the structural stability and catalytic activity for soot oxidation of these materials. In particular, we investigate the dynamics of the structure reconstruction with oxygen loss during the regulated increase of the temperature. The calculations are in good qualitative agreement with catalytic experiments and allow identify special combinations of the perovskite chemical composition and local surface structures for which one could expect the highest catalytic activity for the soot oxidation process.

  10. Epitaxial 1D electron transport layers for high-performance perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Han, Gill Sang; Chung, Hyun Suk; Kim, Dong Hoe; Kim, Byeong Jo; Lee, Jin-Wook; Park, Nam-Gyu; Cho, In Sun; Lee, Jung-Kun; Lee, Sangwook; Jung, Hyun Suk

    2015-09-01

    We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport.We demonstrate high-performance perovskite solar cells with excellent electron transport properties using a one-dimensional (1D) electron transport layer (ETL). The 1D array-based ETL is comprised of 1D SnO2 nanowires (NWs) array grown on a F:SnO2 transparent conducting oxide substrate and rutile TiO2 nanoshells epitaxially grown on the surface of the 1D SnO2 NWs. The optimized devices show more than 95% internal quantum yield at 750 nm, and a power conversion efficiency (PCE) of 14.2%. The high quantum yield is attributed to dramatically enhanced electron transport in the epitaxial TiO2 layer, compared to that in conventional nanoparticle-based mesoporous TiO2 (mp-TiO2) layers. In addition, the open space in the 1D array-based ETL increases the prevalence of uniform TiO2/perovskite junctions, leading to reproducible device performance with a high fill factor. This work offers a method to achieve reproducible, high-efficiency perovskite solar cells with high-speed electron transport

  11. Electro- and photoluminescence imaging as fast screening technique of the layer uniformity and device degradation in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Soufiani, Arman Mahboubi; Tayebjee, Murad J. Y.; Meyer, Steffen; Ho-Baillie, Anita; Sung Yun, Jae; MacQueen, Rowan W.; Spiccia, Leone; Green, Martin A.; Hameiri, Ziv

    2016-07-01

    In this study, we provide insights into planar structure methylammonium lead triiodide (MAPbI3) perovskite solar cells (PSCs) using electroluminescence and photoluminescence imaging techniques. We demonstrate the strength of these techniques in screening relatively large area PSCs, correlating the solar cell electrical parameters to the images and visualizing the features which contribute to the variation of the parameters extracted from current density-voltage characterizations. It is further used to investigate one of the major concerns about perovskite solar cells, their long term stability and aging. Upon storage under dark in dry glovebox condition for more than two months, the major parameter found to have deteriorated in electrical performance measurements was the fill factor; this was elucidated via electroluminescence image comparisons which revealed that the contacts' quality degrades. Interestingly, by deploying electroluminescence imaging, the significance of having a pin-hole free active layer is demonstrated. Pin-holes can grow over time and can cause degradation of the active layer surrounding them.

  12. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D'' layer.

    NASA Astrophysics Data System (ADS)

    Oganov, Artem R.

    2005-03-01

    The Earth's lower mantle, the largest region within our planet (670-2890 km depths), is believed to contain ˜75 vol.% of (Mg,Fe)SiO3 perovskite, ˜20% (Mg,Fe)O, and ˜5% CaSiO3. This mineralogy was unable to explain many unusual properties of the D'' layer, the lowermost ˜150 km of the mantle. Using ab initio simulations and high-pressure experiments we have demonstrated [1] that at pressures and temperatures of the D'' layer, MgSiO3 transforms from perovskite into a layered CaIrO3--type structure (space group Cmcm); this structure was also independently found in [2]. The elastic properties of the new phase and its stability field explain most of the previously puzzling properties of the D'' layer: its seismic anisotropy [3], strongly undulating shear-wave discontinuity at its top^ [4], and the anticorrelation between shear and bulk sound velocities [5]. This new phase is therefore likely to be a major Earth-forming mineral, and its discovery will change our understanding of the deep Earth's interior. Latest studies of the effects of impurities [6,7] on the stability of this phase, and similar phases of other compounds will be discussed. REFERENCES: 1. Oganov A.R., Ono S. (2004). Nature 430, 445-448. 2. Murakami M., et al. (2004). Science 304, 855-858. 3. Panning M., Romanowicz B. (2004). Science 303, 351-353. 4. Sidorin I., et al. D.V. (1999). Science 286, 1326-1331. 5. Su W.J., Dziewonski A.M. (1997). Phys. Earth Planet. Inter. 100, 135-156. 6. Mao W.L., et al. (2004). Proc. Natl. Acad. Sci. 101, 15867-15869. 7. Ono S., Oganov A.R., Ohishi Y. (2004). Submitted.

  13. Perovskite-organic hybrid tandem solar cells using a nanostructured perovskite layer as the light window and a PFN/doped-MoO3/MoO3 multilayer as the interconnecting layer.

    PubMed

    Liu, Jian; Lu, Shunmian; Zhu, Lu; Li, Xinchen; Choy, Wallace C H

    2016-02-14

    In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL. PMID:26809656

  14. Ba4Ru3O10.2(OH)1.8: a new member of the layered hexagonal perovskite family crystallised from water.

    PubMed

    Hiley, Craig I; Lees, Martin R; Hammond, David L; Kashtiban, Reza J; Sloan, Jeremy; Smith, Ronald I; Walton, Richard I

    2016-05-11

    A new barium ruthenium oxyhydroxide Ba4Ru3O10.2(OH)1.8 crystallises under hydrothermal conditions at 200 °C: powder neutron diffraction data show it adopts an 8H hexagonal perovskite structure with a new stacking sequence, while high resolution electron microscopy reveals regions of ordered layers of vacant Ru sites, and magnetometry shows antiferromagnetism with TN = 200(5) K. PMID:27074292

  15. Null current hysteresis for acetylacetonate electron extraction layer in perovskite solar cells.

    PubMed

    Bin Mohd Yusoff, Abd Rashid; Teridi, Mohd Asri Mat; Jang, Jin

    2016-03-28

    Solution processed zirconium acetylacetonate (Zr(acac)) is successfully employed as an electron extraction layer, replacing conventional titanium oxide, in planar CH3NH3PbI3 perovskite solar cells. The as-prepared Zr(acac) film possesses high transparency, high conductivity, a smooth morphology, high wettability, compatibility with PbI2 DMF solution, and an energy level matching that of CH3NH3PbI3 perovskite material. An average power conversion efficiency of about 11.93%, along with a high fill factor of 74.36%, an open circuit voltage of 1.03 V, and a short-circuit current density of 15.58 mA cm(-2) is achieved. The overall performance of the devices is slight better than that of cells using ruthenium acetylacetonate (Ru(acac)). The differences between solar cells with different electron extraction layers in charge recombination, charge transport and transfer and lifetime are further explored and it is demonstrate that Zr(acac) is a more effective and promising electron extraction layer. This work provides a simple, and cost effective route for the preparation of an effective hole extraction layer. PMID:26489053

  16. Null current hysteresis for acetylacetonate electron extraction layer in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mohd Yusoff, Abd. Rashid Bin; Mat Teridi, Mohd Asri; Jang, Jin

    2016-03-01

    Solution processed zirconium acetylacetonate (Zr(acac)) is successfully employed as an electron extraction layer, replacing conventional titanium oxide, in planar CH3NH3PbI3 perovskite solar cells. The as-prepared Zr(acac) film possesses high transparency, high conductivity, a smooth morphology, high wettability, compatibility with PbI2 DMF solution, and an energy level matching that of CH3NH3PbI3 perovskite material. An average power conversion efficiency of about 11.93%, along with a high fill factor of 74.36%, an open circuit voltage of 1.03 V, and a short-circuit current density of 15.58 mA cm-2 is achieved. The overall performance of the devices is slight better than that of cells using ruthenium acetylacetonate (Ru(acac)). The differences between solar cells with different electron extraction layers in charge recombination, charge transport and transfer and lifetime are further explored and it is demonstrate that Zr(acac) is a more effective and promising electron extraction layer. This work provides a simple, and cost effective route for the preparation of an effective hole extraction layer.

  17. Perovskite solar cell using a two-dimensional titania nanosheet thin film as the compact layer.

    PubMed

    Li, Can; Li, Yahui; Xing, Yujin; Zhang, Zelin; Zhang, Xianfeng; Li, Zhen; Shi, Yantao; Ma, Tingli; Ma, Renzhi; Wang, Kunlin; Wei, Jinquan

    2015-07-22

    The compact layer plays an important role in conducting electrons and blocking holes in perovskite solar cells (PSCs). Here, we use a two-dimensional titania nanosheet (TNS) thin film as the compact layer in CH3NH3PbI3 PSCs. TNS thin films with thicknesses ranging from 8 to 75 nm were prepared by an electrophoretic deposition method from a dilute TNS/tetrabutylammonium hydroxide solution. The TNS thin films contact the fluorine-doped tin oxide grains perfectly. Our results show that a 8-nm-thick TNS film is sufficient for acting as the compact layer. Currently, the PSC with a TNS compact layer has a high efficiency of 10.7% and relatively low hysteresis behavior. PMID:26158908

  18. 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.

  19. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-07-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials.

  20. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells.

    PubMed

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-01-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials. PMID:27411487

  1. A composite light-harvesting layer from photoactive polymer and halide perovskite for planar heterojunction solar cells

    PubMed Central

    Wang, Heming; Rahaq, Yaqub; Kumar, Vikas

    2016-01-01

    A new route for fabrication of photoactive materials in organic-inorganic hybrid solar cells is presented in this report. Photoactive materials by blending a semiconductive conjugated polymer with an organolead halide perovskite were fabricated for the first time. The composite active layer was then used to make planar heterojunction solar cells with the PCBM film as the electron-acceptor. Photovoltaic performance of solar cells was investigated by J-V curves and external quantum efficiency spectra. We demonstrated that the incorporation of the conjugated photoactive polymer into organolead halide perovskites did not only contribute to the generation of charges, but also enhance stability of solar cells by providing a barrier protection to halide perovskites. It is expected that versatile of conjugated semi-conductive polymers and halide perovskites in photoactive properties enables to create various combinations, forming composites with advantages offered by both types of photoactive materials. PMID:27411487

  2. Room-Temperature Optical Tunability and Inhomogeneous Broadening in 2D-Layered Organic-Inorganic Perovskite Pseudobinary Alloys.

    PubMed

    Lanty, Gaëtan; Jemli, Khaoula; Wei, Yi; Leymarie, Joël; Even, Jacky; Lauret, Jean-Sébastien; Deleporte, Emmanuelle

    2014-11-20

    We focus here our attention on a particular family of 2D-layered and 3D hybrid perovskite molecular crystals, the mixed perovskites (C6H5-C2H4-NH3)2PbZ4(1-x)Y4x and (CH3-NH3)PbZ3(1-x)Y3x, where Z and Y are halogen ions such as I, Br, and Cl. Studying experimentally the disorder-induced effects on the optical properties of the 2D mixed layered materials, we demonstrate that they can be considered as pseudobinary alloys, exactly like Ga1-xAlxAs, Cd1-xHgxTe inorganic semiconductors, or previously reported 3D mixed hybrid perovskite compounds. 2D-layered and 3D hybrid perovskites afford similar continuous optical tunability at room temperature. Our theoretical analysis allows one to describe the influence of alloying on the excitonic properties of 2D-layered perovskite molecular crystals. This model is further refined by considering different Bohr radii for pure compounds. This study confirms that despite a large binding energy of several 100 meV, the 2D excitons present a Wannier character rather than a Frenkel character. The small inhomogeneous broadening previously reported in 3D hybrid compounds at low temperature is similarly consistent with the Wannier character of free excitons. PMID:26276477

  3. Improving the performance of perovskite solar cells with glycerol-doped PEDOT:PSS buffer layer

    NASA Astrophysics Data System (ADS)

    Jian-Feng, Li; Chuang, Zhao; Heng, Zhang; Jun-Feng, Tong; Peng, Zhang; Chun-Yan, Yang; Yang-Jun, Xia; Duo-Wang, Fan

    2016-02-01

    In this paper, we investigate the effects of glycerol doping on transmittance, conductivity and surface morphology of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)) (PEDOT:PSS) and its influence on the performance of perovskite solar cells. . The conductivity of PEDOT:PSS is improved obviously by doping glycerol. The maximum of the conductivity is 0.89 S/cm when the doping concentration reaches 6 wt%, which increases about 127 times compared with undoped. The perovskite solar cells are fabricated with a configuration of indium tin oxide (ITO)/PEDOT:PSS/CH3NH3PbI3/PC61BM/Al, where PEDOT:PSS and PC61BM are used as hole and electron transport layers, respectively. The results show an improvement of hole charge transport as well as an increase of short-circuit current density and a reduction of series resistance, owing to the higher conductivity of the doped PEDOT:PSS. Consequently, it improves the whole performance of perovskite solar cell. The power conversion efficiency (PCE) of the device is improved from 8.57% to 11.03% under AM 1.5 G (100 mW/cm2 illumination) after the buffer layer has been modified. Project supported by the National Natural Science Foundation of China (Grant Nos. 61264002, 61166002, 91333206, and 51463011), the Natural Science Foundation of Gansu Province, China (Grant No. 1308RJZA159), the New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-13-0840), the Research Project of Graduate Teacher of Gansu Province, China (Grant No. 2014A-0042), and the Postdoctoral Science Foundation from Lanzhou Jiaotong University, China.

  4. Carbon nanotube/polymer composites as a highly stable hole collection layer in perovskite solar cells.

    PubMed

    Habisreutinger, Severin N; Leijtens, Tomas; Eperon, Giles E; Stranks, Samuel D; Nicholas, Robin J; Snaith, Henry J

    2014-10-01

    Organic-inorganic perovskite solar cells have recently emerged at the forefront of photovoltaics research. Power conversion efficiencies have experienced an unprecedented increase to reported values exceeding 19% within just four years. With the focus mainly on efficiency, the aspect of stability has so far not been thoroughly addressed. In this paper, we identify thermal stability as a fundamental weak point of perovskite solar cells, and demonstrate an elegant approach to mitigating thermal degradation by replacing the organic hole transport material with polymer-functionalized single-walled carbon nanotubes (SWNTs) embedded in an insulating polymer matrix. With this composite structure, we achieve JV scanned power-conversion efficiencies of up to 15.3% with an average efficiency of 10 ± 2%. Moreover, we observe strong retardation in thermal degradation as compared to cells employing state-of-the-art organic hole-transporting materials. In addition, the resistance to water ingress is remarkably enhanced. These are critical developments for achieving long-term stability of high-efficiency perovskite solar cells. PMID:25226226

  5. Thermally Induced Structural Evolution and Performance of Mesoporous Block Copolymer-Directed Alumina Perovskite Solar Cells

    PubMed Central

    2015-01-01

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI3–xClx) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI3–xClx material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance. PMID:24684494

  6. Green, Orange, and Magenta Luminescence in Strontium Stannates with Perovskite-Related Structures

    NASA Astrophysics Data System (ADS)

    Ueda, Kazushige; Yamashita, Takahiro; Nakayashiki, Kensuke; Goto, Katsuhiko; Maeda, Tsuyoshi; Furui, Koji; Ozaki, Koichiro; Nakachi, Yutaka; Nakamura, Satoshi; Fujisawa, Masaru; Miyazaki, Takato

    2006-09-01

    Intense green, orange or magenta luminescence was observed in rare-earth doped alkaline earth (Ca, Sr, and Ba) stannates, particularly strontium stannates with perovskite-related structures. Tb-Mg codoped SrSnO3 showed sharp emission lines corresponding to Tb ions as a green phosphor. Sm doped Sr3Sn2O7 exhibited sharp pairs of emission lines corresponding to Sm ions as an orange phosphor. Eu-Ti codoped Sr2SnO4 as a magenta phosphor showed sharp red luminescent lines corresponding to Eu ions as well as a broad blue emission band corresponding to Ti-related complexes. It was suggested that codoping and/or layered structures in these phosphors are closely related to the increase in luminescence intensity from these rare-earth ions.

  7. Doped hole transport layer for efficiency enhancement in planar heterojunction organolead trihalide perovskite solar cells

    DOE PAGESBeta

    Wang, Qi; Bi, Cheng; Huang, Jinsong

    2015-05-06

    We demonstrated the efficiency of a solution-processed planar heterojunction organometallic trihalide perovskite solar cell can be increased to 17.5% through doping the hole transporting layer for reducing the resistivity. Doped Poly(triaryl amine) (PTAA) by 2,3,5,6-Tetrafluoro-7,7,8,8-Tetracyanoquinodimethane (F4-TCNQ) reduced device series resistance by three-folds, increasing the device fill factor to 74%, open circuit voltage to 1.09 V without sacrificing the short circuit current. As a result, this study reveals that the high resistivity of currently broadly applied polymer hole transport layer limits the device efficiency, and points a new direction to improve the device efficiency.

  8. Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction

    SciTech Connect

    Lu, Fengqi; Kuang, Xiaojun

    2015-01-15

    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 instability 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.

  9. The essential role of the poly(3-hexylthiophene) hole transport layer in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Liu, Wenqiang; Tan, Furui; Gu, Yuzong

    2015-01-01

    The compact and oriented TiO2 films are prepared by a solvothermal method, and used as electron transporting layers in perovskite CH3NH3PbI3-xClx based solar cells incorporating poly(3-hexylthiophene-2,5-diyl) (P3HT) as the hole transporting material layer. The devices with P3HT exhibit a substantial increase in power conversion efficiency, open circuit voltage, and fill factor, compared with the reference device without P3HT. Impedance spectroscopy measurements demonstrate that the present P3HT layer decreases the internal resistance in solar cells and allows the interface between oriented TiO2 and CH3NH3PbI3-xClx to form more perfect in electronics. It is also found that the electron lifetime in the devices with P3HT is much longer than that of the device without P3HT. Thus, the charge collection efficiency of the device with P3HT is markedly enhanced, compared with the devices without P3HT. Analysis of the energy levels of the involved materials indicates that the P3HT film between the CH3NH3PbI3-xClx layer and the Au electrode provides a better energy level matching for efficient transporting holes to the anode. Meanwhile, the stability of such P3HT solar cells is enhanced because of the compact and oriented TiO2 film preventing the possible interaction between TiO2 and perovskite as time went on.

  10. Well-Defined Nanostructured, Single-Crystalline TiO2 Electron Transport Layer for Efficient Planar Perovskite Solar Cells.

    PubMed

    Choi, Jongmin; Song, Seulki; Hörantner, Maximilian T; Snaith, Henry J; Park, Taiho

    2016-06-28

    An electron transporting layer (ETL) plays an important role in extracting electrons from a perovskite layer and blocking recombination between electrons in the fluorine-doped tin oxide (FTO) and holes in the perovskite layers, especially in planar perovskite solar cells. Dense TiO2 ETLs prepared by a solution-processed spin-coating method (S-TiO2) are mainly used in devices due to their ease of fabrication. Herein, we found that fatal morphological defects at the S-TiO2 interface due to a rough FTO surface, including an irregular film thickness, discontinuous areas, and poor physical contact between the S-TiO2 and the FTO layers, were inevitable and lowered the charge transport properties through the planar perovskite solar cells. The effects of the morphological defects were mitigated in this work using a TiO2 ETL produced from sputtering and anodization. This method produced a well-defined nanostructured TiO2 ETL with an excellent transmittance, single-crystalline properties, a uniform film thickness, a large effective area, and defect-free physical contact with a rough substrate that provided outstanding electron extraction and hole blocking in a planar perovskite solar cell. In planar perovskite devices, anodized TiO2 ETL (A-TiO2) increased the power conversion efficiency by 22% (from 12.5 to 15.2%), and the stabilized maximum power output efficiency increased by 44% (from 8.9 to 12.8%) compared with S-TiO2. This work highlights the importance of the ETL geometry for maximizing device performance and provides insights into achieving ideal ETL morphologies that remedy the drawbacks observed in conventional spin-coated ETLs. PMID:27183030

  11. Highly stable, luminescent core-shell type methylammonium-octylammonium lead bromide layered perovskite nanoparticles.

    PubMed

    Bhaumik, Saikat; Veldhuis, Sjoerd A; Ng, Yan Fong; Li, Mingjie; Muduli, Subas Kumar; Sum, Tze Chien; Damodaran, Bahulayan; Mhaisalkar, Subodh; Mathews, Nripan

    2016-06-01

    A new protocol for the synthesis of a highly stable (over 2 months under ambient conditions) solution-processed core-shell type structure of mixed methylammonium-octylammonium lead bromide perovskite nanoparticles (5-12 nm), having spherical shape, color tunability in the blue to green spectral region (438-521 nm) and a high photoluminescence quantum yield (PLQY) of up to 92% is described. The color tunability, high PLQY and stability are due to the quantum confinement imparted by the crystal engineering associated with core-shell nanoparticle formation during growth. PMID:27165565

  12. Significant enhancement of photovoltage in artificially designed perovskite oxide structures

    NASA Astrophysics Data System (ADS)

    Zhou, Wen-jia; Jin, Kui-juan; Guo, Hai-zhong; He, Xu; He, Meng; Xu, Xiu-lai; Lu, Hui-bin; Yang, Guo-zhen

    2015-03-01

    La0.9Sr0.1MnO3/insulator/SrNb0.007Ti0.993O3 multilayer and La0.9Sr0.1MnO3/SrNb0.007Ti0.993O3/In2O3:SnO2(ITO)/La0.9Sr0.1MnO3/SrNb0.007Ti0.993O3 multilayer structures were designed to enhance the photovoltage. The photovoltages of these two structures under an illumination of 308 nm laser are 410 and 600 mV, respectively. The latter is 20 times larger than that (30 mV) observed in La0.9Sr0.1MnO3/SrNb0.007Ti0.993O3 single junction. The origin of such significant enhancement of photovoltage is discussed in this letter. These results suggest that the photoelectric property of perovskite oxides could be much improved by artificial structure designing. The enhanced photovoltaic effects have potential applications in the ultraviolet photodetection and solar cells.

  13. Tailoring of Electron-Collecting Oxide Nanoparticulate Layer for Flexible Perovskite Solar Cells.

    PubMed

    Shin, Seong Sik; Yang, Woon Seok; Yeom, Eun Joo; Lee, Seon Joo; Jeon, Nam Joong; Joo, Young-Chang; Park, Ik Jae; Noh, Jun Hong; Seok, Sang Il

    2016-05-19

    Low-temperature-processed perovskite solar cells (PSCs), especially those fabricated on flexible substrates, exhibit device performance that is worse than that of high-temperature-processed PSCs. One of the main reasons for the inferior performance of low-temperature-processed PSCs is the loss of photogenerated electrons in the electron collection layer (ECL) or related interfaces, i.e., indium tin oxide/ECL and ECL/perovskite. Here, we report that tailoring of the energy level and electron transporting ability in oxide ECLs using Zn2SnO4 nanoparticles and quantum dots notably minimizes the loss of photogenerated electrons in the low-temperature-fabricated flexible PSC. The proposed ECL with methylammonium lead halide [MAPb(I0.9Br0.1)3] leads to fabrication of significantly improved flexible PSCs with steady-state power conversion efficiency of 16.0% under AM 1.5G illumination of 100 mW cm(-2) intensity. These results provide an effective method for fabricating high-performance, low-temperature solution-processed flexible PSCs. PMID:27117778

  14. Atomic force microscopy surface analysis of layered perovskite La2Ti2O7 particles grown by molten flux method

    NASA Astrophysics Data System (ADS)

    Orum, Aslihan; Takatori, Kazumasa; Hori, Shigeo; Ikeda, Tomiko; Yoshimura, Masamichi; Tani, Toshihiko

    2016-08-01

    Rectangular platelike particles of La2Ti2O7, a layered perovskite, were synthesized in KCl, NaCl, and LiCl by the molten flux method. The formation mechanism of the equilibrium shape in these alkali chloride fluxes was discussed in terms of the surface and interfacial energies of crystallographic planes. The atomic force microscopy (AFM) observations revealed that the developed plane of the platelike particles is along the interlayers in the {110}-type layered crystal structure, and is considered to represent the lowest surface energy plane in which strong, periodic Ti–O bond chains terminate. Herein, for the first time, a growth mechanism for La2Ti2O7 particles is proposed and discussed. Triangular prism structures along the c-axis were observed on the developed planes of KCl-grown particles whereas no such structures were found on those of LiCl-grown ones. AFM measurements suggest that the prism facets are {210}-La2Ti2O7, which results in lower interfacial energy within KCl.

  15. 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

    2015-01-01

    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

    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

  17. 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.

  18. Magnetic materials. Tilt engineering of spontaneous polarization and magnetization above 300 K in a bulk layered perovskite.

    PubMed

    Pitcher, Michael J; Mandal, Pranab; Dyer, Matthew S; Alaria, Jonathan; Borisov, Pavel; Niu, Hongjun; Claridge, John B; Rosseinsky, Matthew J

    2015-01-23

    Crystalline materials that combine electrical polarization and magnetization could be advantageous in applications such as information storage, but these properties are usually considered to have incompatible chemical bonding and electronic requirements. Recent theoretical work on perovskite materials suggested a route for combining both properties. We used crystal chemistry to engineer specific atomic displacements in a layered perovskite, (Ca(y)Sr(1- y))(1.15)Tb(1.85)Fe2O7, that change its symmetry and simultaneously generate electrical polarization and magnetization above room temperature. The two resulting properties are magnetoelectrically coupled as they arise from the same displacements. PMID:25613888

  19. Crystallographic and Electronic Structure of the Sr3Sb2CoO9 Triple Perovskite

    NASA Astrophysics Data System (ADS)

    González, W.; Cardona, R.; Landínez Téllez, D. A.; Roa-Rojas, J.

    2014-04-01

    Compounds The perovskites are materials with physical and chemical characteristics that make them optimal for application in the technological and scientist. When the ideal formula of perovskite ABO3 is modified by introducing a special structural arrangement can get to get triple perovskites, which correspond to the formula A3B2B'O9. In this work we report the synthesis process and the study of electronic structure and crystal Sr3Sb2CoO9 new triple perovskite. From the experiments of X-ray Diffraction and the application of the Rietveld refinement method was revealed that the system crystallizes in a perovskite structure with a characteristic triple given by the space group Immm (#71) and lattice parameters a=9.791(9) Å, b=5.656(7) Å and c=16.957(8) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system by using the Quantum EXPRESSO code. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization. ©2013 Elsevier Science. All rights reserved.

  20. Polymer/Perovskite-type nanoparticle multilayers with multielectric properties prepared from ligand addition-induced layer-by-layer assembly.

    PubMed

    Kim, Younghoon; Kook, Kyungyun; Hwang, Sun Kak; Park, Cheolmin; Cho, Jinhan

    2014-03-25

    We introduce an adsorption mechanism for a layer-by-layer (LbL) assembly (i.e., a ligand addition-induced LbL assembly) and demonstrate that the (polymer/perovskite nanoparticle (NP))n nanocomposite films based on the ligand addition LbL exhibit ferroelectric and resistive switching properties. Oleic acid (OA)-stabilized BaTiO3 NPs (OA-BTO NPs) with a size of approximately 8 nm were LbL-assembled with amine-functionalized dendrimers (NH2-dendrimers) using the high affinity between NH2 moieties and Ti ions. The ferroelectric properties of the (NH2-dendrimer/OA-BTO NP)n multilayers were generated by the Ti disorder in the OA-BTO NP unit cell despite the use of sub-10 nm OA-BTO NPs (i.e., OA-BTO NPs), which are near the critical size for ferroelectric properties. Additionally, the (NH2-dendrimer/OA-BTO NP)n multilayers sandwiched between the bottom (platinum) and top (silver or tungsten) electrodes exhibited a resistive switching memory at a relatively low operating voltage below 2 V with a switching speed of approximately 100 ns and an ON/OFF current ratio of approximately 10(4). Furthermore, the ferroelectric and resistive switching properties could be further improved by controlling the bilayer number (n). We believe that our approach can provide a basis for designing and exploiting multifunctional memory electronics based on a variety of perovskite NPs with ferroelectric properties. PMID:24571293

  1. Tailoring of energy levels in lead chloride based layered perovskites and energy transfer between the organic and inorganic planes

    NASA Astrophysics Data System (ADS)

    Braun, M.; Tuffentsammer, W.; Wachtel, H.; Wolf, H. C.

    1999-04-01

    Excitonic inter-layer energy transfer is proved in a system consisting of bimolecular layers of organic dyes (benzyl, naphthyl, or anthryl) in lead chloride perovskites. By a systematic variation of the dye molecules we place the inorganic exciton band of lead chloride energetically beneath, above or between the singlet and triplet levels of the dye. Therefore we observe emission from that exciton band, the molecular singlet or triplet level due to energy transfer between the inorganic and organic layers. In the case of the layered perovskite (C 6H 5-CH 2-NH 3) 2PbCl 4 we succeeded in energetically matching the inorganic exciton band with the molecular triplet level.

  2. Effect of Electron Transporting Layer on Bismuth-Based Lead-Free Perovskite (CH3NH3)3 Bi2I9 for Photovoltaic Applications.

    PubMed

    Singh, Trilok; Kulkarni, Ashish; Ikegami, Masashi; Miyasaka, Tsutomu

    2016-06-15

    Methylammonium iodo bismuthate ((CH3NH3)3Bi2I9) (MBI) perovskite is a promising alternative to rapidly progressing hybrid organic-inorganic lead perovskites because of its better stability and low toxicity compared to lead-based perovskites. Solution-processed perovskite fabricated by single-step spin-coating and subsequent heating produced polycrystalline films of hybrid perovskite (CH3NH3)3Bi2I9), whose morphology was influenced drastically by the nature of substrates. The optical measurements showed a strong absorption band around 500 nm. The devices made on anatase TiO2 mesoporous layer showed good performance with current density over 0.8 mA cm(-2) while the devices on brookite TiO2 layer and planar (free of porous layer) was inefficient. However, all the MBI devices were stable to ambient conditions for more than 10 weeks. PMID:27225529

  3. Electrodeposited Ultrathin TiO2 Blocking Layers for Efficient Perovskite Solar Cells

    PubMed Central

    Su, Tzu-Sen; Hsieh, Tsung-Yu; Hong, Cheng-You; Wei, Tzu-Chien

    2015-01-01

    In this study, the electrodeposition (ED) of ultrathin, compact TiO2 blocking layers (BLs) on fluorine-doped tin oxide (FTO) glass for perovskite solar cells (PSCs) is evaluated. This bottom-up method allows for controlling the morphology and thickness of TiO2 films by simply manipulating deposition conditions. Compared with BLs produced using the spin-coating (SC) method, BLs produced using ED exhibit satisfactory surface coverage, even with a film thickness of 29 nm. Evidence from cyclic voltammetry shows that an ED BL suppresses interfacial recombination more profoundly than an SC BL does, consequently improving the photovoltaic properties of the PSC significantly. A PSC equipped with an ED TiO2 BL having a 13.6% power conversion efficiency is demonstrated. PMID:26526771

  4. An Azaacene Derivative as Promising Electron-Transport Layer for Inverted Perovskite Solar Cells.

    PubMed

    Gu, Pei-Yang; Wang, Ning; Wu, Anyang; Wang, Zilong; Tian, Miaomiao; Fu, Zhisheng; Sun, Xiao Wei; Zhang, Qichun

    2016-08-01

    It is highly desirable to develop novel n-type organic small molecules as an efficient electron-transport layer (ETL) for the replacement of PCBM to obtain high-performance metal-oxide-free, solution-processed inverted perovskite solar cells (PSCs) because this type of solar cells with a low-temperature and solution-based process would make their fabrication more feasible and practical. In this research, the new azaacene QCAPZ has been synthesized and employed as non-fullerene ETL material for inverted PSCs through a solution-based process without the need for additional dopants or additives. The as-fabricated inverted PSCs show a power conversion efficiency up to 10.26 %. Our results clearly suggest that larger azaacenes could be promising electron-transport materials to achieve high-performance solution-processed inverted PSCs. PMID:27378599

  5. Electrodeposited Ultrathin TiO2 Blocking Layers for Efficient Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Su, Tzu-Sen; Hsieh, Tsung-Yu; Hong, Cheng-You; Wei, Tzu-Chien

    2015-11-01

    In this study, the electrodeposition (ED) of ultrathin, compact TiO2 blocking layers (BLs) on fluorine-doped tin oxide (FTO) glass for perovskite solar cells (PSCs) is evaluated. This bottom-up method allows for controlling the morphology and thickness of TiO2 films by simply manipulating deposition conditions. Compared with BLs produced using the spin-coating (SC) method, BLs produced using ED exhibit satisfactory surface coverage, even with a film thickness of 29 nm. Evidence from cyclic voltammetry shows that an ED BL suppresses interfacial recombination more profoundly than an SC BL does, consequently improving the photovoltaic properties of the PSC significantly. A PSC equipped with an ED TiO2 BL having a 13.6% power conversion efficiency is demonstrated.

  6. Electrodeposited Ultrathin TiO2 Blocking Layers for Efficient Perovskite Solar Cells.

    PubMed

    Su, Tzu-Sen; Hsieh, Tsung-Yu; Hong, Cheng-You; Wei, Tzu-Chien

    2015-01-01

    In this study, the electrodeposition (ED) of ultrathin, compact TiO2 blocking layers (BLs) on fluorine-doped tin oxide (FTO) glass for perovskite solar cells (PSCs) is evaluated. This bottom-up method allows for controlling the morphology and thickness of TiO2 films by simply manipulating deposition conditions. Compared with BLs produced using the spin-coating (SC) method, BLs produced using ED exhibit satisfactory surface coverage, even with a film thickness of 29 nm. Evidence from cyclic voltammetry shows that an ED BL suppresses interfacial recombination more profoundly than an SC BL does, consequently improving the photovoltaic properties of the PSC significantly. A PSC equipped with an ED TiO2 BL having a 13.6% power conversion efficiency is demonstrated. PMID:26526771

  7. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    PubMed Central

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid bin; Jang, Jin

    2016-01-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL. PMID:27277388

  8. Low-temperature solution-processed tin oxide as an alternative electron transporting layer for efficient perovskite solar cells.

    PubMed

    Ke, Weijun; Fang, Guojia; Liu, Qin; Xiong, Liangbin; Qin, Pingli; Tao, Hong; Wang, Jing; Lei, Hongwei; Li, Borui; Wan, Jiawei; Yang, Guang; Yan, Yanfa

    2015-06-01

    Lead halide perovskite solar cells with the high efficiencies typically use high-temperature processed TiO2 as the electron transporting layers (ETLs). Here, we demonstrate that low-temperature solution-processed nanocrystalline SnO2 can be an excellent alternative ETL material for efficient perovskite solar cells. Our best-performing planar cell using such a SnO2 ETL has achieved an average efficiency of 16.02%, obtained from efficiencies measured from both reverse and forward voltage scans. The outstanding performance of SnO2 ETLs is attributed to the excellent properties of nanocrystalline SnO2 films, such as good antireflection, suitable band edge positions, and high electron mobility. The simple low-temperature process is compatible with the roll-to-roll manufacturing of low-cost perovskite solar cells on flexible substrates. PMID:25987132

  9. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid Bin; Jang, Jin

    2016-06-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL.

  10. High-performance and environmentally stable planar heterojunction perovskite solar cells based on a solution-processed copper-doped nickel oxide hole-transporting layer.

    PubMed

    Kim, Jong H; Liang, Po-Wei; Williams, Spencer T; Cho, Namchul; Chueh, Chu-Chen; Glaz, Micah S; Ginger, David S; Jen, Alex K-Y

    2015-01-27

    An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated. Perovskite solar cells based on using Cu-doped NiOx HTL show a remarkably improved power conversion efficiency up to 15.40% due to the improved electrical conductivity and enhanced perovskite film quality. General applicability of Cu-doped NiOx to larger bandgap perovskites is also demonstrated in this study. PMID:25449020

  11. Fabrication and characterization of perovskite-type solar cells with Nb-doped TiO2 layers

    NASA Astrophysics Data System (ADS)

    Saito, Jo; Oku, Takeo; Suzuki, Atsushi; Akiyama, Tsuyoshi

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing perovskite CH3NH3PbI3 using Nb-doped TiO2 as an electron-transporting layer were fabricated and characterized. Nb-doped TiO2 layer showed an improvement of the short-circuit current density and power conversion efficiency using Ti0.95Nb0.05O2.

  12. Electrosynthesis and crystal structure of the new 15R hexagonal perovskite Ba 5MnNa 2V 2O 13

    NASA Astrophysics Data System (ADS)

    Bendraoua, Abdelaziz; Quarez, Eric; Abraham, Francis; Mentré, Olivier

    2004-04-01

    A new manganese oxide Ba 5MnNa 2V 2O 13 with an original structure closely related to the cubic perovskite has been prepared by electrosynthesis in molten NaOH. Its crystal structure has been refined from single crystal X-ray diffraction in the R 3¯m space group, a=5.8490(6) Å, c=36.856(5) Å, Z=3, R1=4.72%, w R2=10.56%. The crystal structure is a rhombohedral 15R polytype and exhibits a close packed structure built up from [BaO 3- δ] ( c) and [BaO 2] ( c') layers within a ( ccc' cc) 3 stacking sequence. The resulting three-dimensional edifice is formed by Ba(Mn 0.33Na 0.67)O 3 cubic perovskite blocks separated by double sheets of V 5+O 4 tetrahedra pointing towards the central [BaO 2] c' layer. In the perovskite blocks, 1/6 of oxygen deficient vacancies located on layers surrounding manganese involve a Mn(IV) valence, in square pyramids rather than octahedra. On the same layers along c, the barium atom split from a central (0,0, z) position to close ( x,- x, z) positions as a compensation of the oxygen deficiency. In this work, a review of the Mn-related perovskite materials found in the literature is reported showing the wide variety of materials adopting related structural polytypes. A building scheme from simple to more complex edifices is also presented by successive intercalation of [BaO n] ( n=1, 2) in order to visualize topological relationships between the number of possible hexagonal perovskite series members.

  13. Perovskite Solar Cells: Moth-Eye TiO2 Layer for Improving Light Harvesting Efficiency in Perovskite Solar Cells (Small 18/2016).

    PubMed

    Kang, Seong Min; Jang, Segeun; Lee, Jong-Kwon; Yoon, Jungjin; Yoo, Dong-Eun; Lee, Jin-Wook; Choi, Mansoo; Park, Nam-Gyu

    2016-05-01

    A moth-eye patterned mesoporous (mp) TiO2 layer is fabricated in the form of submicron scale by using lithography, nano-imprinting and polydimethyl siloxane (PDMS) stamping methods. On page 2443, M. Choi, N.-G. Park, and co-workers demonstrate an excellent light harvesting property of perovskite solar cell by employing the moth-eye nanostructured mp-TiO2 film. These novel fabrication methods are expected to be optically beneficial to opto-electronic devices. PMID:27151831

  14. Structure constraints and instability leading to the post-perovskite phase transition of MgSiO 3

    NASA Astrophysics Data System (ADS)

    Martin, C. David; Parise, John B.

    2008-01-01

    Recent experience with Rietveld refinement of structural analogues and literature surveys, suggests anion-anion repulsion limits the stability of the perovskite phase, including in the MgSiO 3 perovskite to post-perovskite transition. Assuming rigid octahedral coordination, still to be tested experimentally, the critical point where intra- and inter-octahedral anion-anion distances are equal provides a useful metric for predicting the pressure of the perovskite/post-perovskite transition and the Clapeyron slope of the phase boundary, once pressure and temperature derivatives of relevant structure parameters are known. The inter-octahedral anion-anion distances and the polyhedral volume ratio are rigorously formulated as a function of octahedral rotation in this work, assuming the orthorhombic ( Pbnm) perovskite structure, where regular octahedra share each corner and conform to the in- and anti-phase rotation schemes designated by space group symmetry. These mathematical expressions are consistent with structure data from 70 perovskite-structured materials surveyed in the literature at ambient as well as extreme conditions and define structure constraints, such as the minimum polyhedral volume ratio, which must be reached before the phase transition to the post-perovskite structure-type can proceed. The formalism we present is general for perovskite ( Pbnm) and dependent on the accuracy with which structures can be determined from, sometimes compromised, high pressure diffraction data.

  15. Perovskite-supported palladium for methane oxidation - structure-activity relationships.

    PubMed

    Eyssler, Arnim; Lu, Ye; Matam, Santhosh Kumar; Weidenkaff, Anke; Ferri, Davide

    2012-01-01

    Palladium is the precious metal of choice for methane oxidation and perovskite-type oxides offer the possibility to stabilize it as PdO, considered crucial for catalytic activity. Pd can adopt different oxidation and coordination states when associated with perovskite-type oxides. Here, we review our work on the effect of perovskite composition on the oxidation and coordination states of Pd and its influence on catalytic activity for methane oxidation in the case of typical Mn, Fe and Co perovskite-based oxidation catalysts. Especially X-ray absorption near edge structure (XANES) spectroscopy is shown to be crucial to fingerprint the different coordination states of Pd. Pd substitutes Fe and Co in the octahedral sites but without modifying catalytic activity with respect to the Pd-free perovskite. On LaMnO(3) palladium is predominantly exposed at the surface thus bestowing catalytic activity for methane oxidation. However, the occupancy of B-cation sites of the perovskite structure by Pd can be exploited to cyclically activate Pd and to protect it from particle growth. This is explicitly demonstrated for La(Fe, Pd)O(3), where catalytic activity for methane oxidation is enhanced under oscillating redox conditions at 500 °C, therefore paving the way to the practical application in three-way catalysts for stoichiometric natural gas engines. PMID:23211725

  16. Novel CdS Hole-Blocking Layer for Photostable Perovskite Solar Cells.

    PubMed

    Hwang, Insung; Yong, Kijung

    2016-02-17

    Currently, the stability issue of the perovskite solar cells (PSCs) is one of the most critical obstacles in the commercialization of PSCs. Although incredible advances in the photovoltaic efficiencies of PSCs have been achieved in the past few years, research on the stability of PSCs has been relatively less explored. In this study, a new kind of CdS hole-blocking layer replacing the traditional compact TiO2 layer is developed to improve the photostability of PSCs because the intrinsic oxygen vacancies of the TiO2 surface are suspected to be the main cause for the photoinduced degradation of PSCs. As a result, PSCs with the CdS layer exhibit considerably improved photostability, maintaining over 90% of the initial efficiency after continuous sunlight illumination for 12 h, while the TiO2 PSC retains only 18% of the initial efficiency under the same conditions. Charge-transfer characteristics related to photodegradation are investigated by various analyses including electrochemical impedance spectroscopy and open-circuit voltage decay and time-resolved photoluminescence decay measurements. the CdS PSC exhibits negligible degradation in the charge-carrier dynamics, while the TiO2 PSC suffers from severely damaged characteristics like increased charge recombination rate, charge-transfer resistance, and reduced charge extraction rate. PMID:26809352

  17. Layered oxygen-deficient double perovskite as an efficient and stable anode for direct hydrocarbon solid oxide fuel cells.

    PubMed

    Sengodan, Sivaprakash; Choi, Sihyuk; Jun, Areum; Shin, Tae Ho; Ju, Young-Wan; Jeong, Hu Young; Shin, Jeeyoung; Irvine, John T S; Kim, Guntae

    2015-02-01

    Different layered perovskite-related oxides are known to exhibit important electronic, magnetic and electrochemical properties. Owing to their excellent mixed-ionic and electronic conductivity and fast oxygen kinetics, cation layered double perovskite oxides such as PrBaCo2O5 in particular have exhibited excellent properties as solid oxide fuel cell oxygen electrodes. Here, we show for the first time that related layered materials can be used as high-performance fuel electrodes. Good redox stability with tolerance to coking and sulphur contamination from hydrocarbon fuels is demonstrated for the layered perovskite anode PrBaMn2O5+δ (PBMO). The PBMO anode is fabricated by in situ annealing of Pr0.5Ba0.5MnO3-δ in fuel conditions and actual fuel cell operation is demonstrated. At 800 °C, layered PBMO shows high electrical conductivity of 8.16 S cm(-1) in 5% H2 and demonstrates peak power densities of 1.7 and 1.3 W cm(-2) at 850 °C using humidified hydrogen and propane fuels, respectively. PMID:25532072

  18. Layered oxygen-deficient double perovskite as an efficient and stable anode for direct hydrocarbon solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Sengodan, Sivaprakash; Choi, Sihyuk; Jun, Areum; Shin, Tae Ho; Ju, Young-Wan; Jeong, Hu Young; Shin, Jeeyoung; Irvine, John T. S.; Kim, Guntae

    2015-02-01

    Different layered perovskite-related oxides are known to exhibit important electronic, magnetic and electrochemical properties. Owing to their excellent mixed-ionic and electronic conductivity and fast oxygen kinetics, cation layered double perovskite oxides such as PrBaCo2O5 in particular have exhibited excellent properties as solid oxide fuel cell oxygen electrodes. Here, we show for the first time that related layered materials can be used as high-performance fuel electrodes. Good redox stability with tolerance to coking and sulphur contamination from hydrocarbon fuels is demonstrated for the layered perovskite anode PrBaMn2O5+δ (PBMO). The PBMO anode is fabricated by in situ annealing of Pr0.5Ba0.5MnO3-δ in fuel conditions and actual fuel cell operation is demonstrated. At 800 °C, layered PBMO shows high electrical conductivity of 8.16 S cm-1 in 5% H2 and demonstrates peak power densities of 1.7 and 1.3 W cm-2 at 850 °C using humidified hydrogen and propane fuels, respectively.

  19. Tackling pseudosymmetry problems in electron backscatter diffraction (EBSD) analyses of perovskite structures

    NASA Astrophysics Data System (ADS)

    Mariani, Elisabetta; Kaercher, Pamela; Mecklenburgh, Julian; Wheeler, John

    2016-04-01

    Perovskite minerals form an important mineral group that has applications in Earth science and emerging alternative energy technologies, however crystallographic quantification of these minerals with electron backscatter diffraction (EBSD) is not accurate due to pseudosymmetry problems. The silicate perovskite Bridgmanite, (Mg,Fe)SiO3, is understood to be the dominant phase in the Earth's lower mantle. Gaining insight into its physical and rheological properties is therefore vital to understand the dynamics of the Earth's deep interior. Rock deformation experiments on analogue perovskite phases, for example (Ca,Sr)TiO3, combined with quantitative microstructural analyses of the recovered samples by EBSD, yield datasets that can reveal what deformation mechanisms may dominate the flow of perovskite in the lower mantle. Additionally, perovskite structures have important technological applications as new, suitable cathodes for the operation of more efficient and environmentally-friendly solid oxide fuel cells (SOFC). In recent years they have also been recognised as a potential substitute for silicon in the next generation of photovoltaic cells for the construction of economic and energy efficient solar panels. EBSD has the potential to be a valuable tool for the study of crystal orientations achieved in perovskite substrates as crystal alignment has a direct control on the properties of these materials. However, perovskite structures currently present us with challenges during the automated indexing of Kikuchi bands in electron backscatter diffraction patterns (EBSPs). Such challenges are represented by the pseudosymmetric character of perovskites, where atoms are subtly displaced (0.005 nm to 0.05 nm) from their higher symmetry positions. In orthorhombic Pbnm perovskites, for example, pseudosymmetry may be evaluated from the c/a unit cell parameter ratio, which is very close to 1. Two main types of distortions from the higher symmetry structure are recognised: a

  20. Structure, Growth Process, and Growth Mechanism of Perovskite in High-Titanium-Bearing Blast Furnace Slag

    NASA Astrophysics Data System (ADS)

    Liu, Lu; Hu, Meilong; Xu, Yuzhou; Bai, Chenguang; Gan, Yunhua

    2015-08-01

    The isothermal crystallization of perovskite in TiO2-CaO-SiO2-Al2O3-MgO high-titanium-bearing blast furnace slag was observed in situ at 1698 K (1425 °C) using a confocal scanning laser microscope. The dendrite structure of perovskite (CaTiO3) thus obtained showed vividly the primary dendrite trunks and secondary dendrite arms. Furthermore, the dendritic growth of perovskite in liquid slag was clearly observed on line. The results showed that the dendrite arrays in which the primary dendrite trunks observed on slag surface were parallel with each other grew toward the same direction. The secondary dendrite arms grew in the perpendicular direction with the primary trucks and stopped growing when they encounter. The perovskite dendrites showed a linear growth at two stages. The dendrites grew faster at early stage at about 5 to 7 μm/s and grew with a lower growth rate at about 1 to 2 μm/s in later stage. Finally, the growth mechanism of perovskite in melt was analyzed with the solidification theory. Based on the theoretical calculation of equilibrium phases in slag, the initial slag could be considered as a binary component system. One component was perovskite and the other component was the sum of all the other species that did not attend the crystallization of perovskite (included SiO2, Al2O3, and MgO, as well as CaO and TiO2 that were not involved in the solid formation). The formation of perovskite required the diffusion of CaO and TiO2 to the solid/liquid interface and the rejection of the other species from the interface. The solid/liquid equilibrium schematic diagram was made based on the calculation.

  1. Artificial layered perovskite oxides A(B{sub 0.5}B′{sub 0.5})O{sub 3} as potential solar energy conversion materials

    SciTech Connect

    Chen, Hungru; Umezawa, Naoto

    2015-02-07

    Perovskite oxides with a d{sup 0} electronic configuration are promising photocatalysts and exhibit high electron mobilities. However, their band gaps are too large for efficient solar energy conversion. On the other hand, transition metal cations with partially filled d{sup n} electronic configurations give rise to visible light absorption. In this study, by using hybrid density functional theory calculations, it is demonstrated that the virtues of the two categories of materials can be combined in perovskite oxide A(B{sub 0.5}B′{sub 0.5})O{sub 3} with a layered B-site ordering along the [001] direction. The electronic structures of the four selected perovskite oxide compounds, La(Ti{sub 0.5}Ni{sub 0.5})O{sub 3}, La(Ti{sub 0.5}Zn{sub 0.5})O{sub 3}, Sr(Nb{sub 0.5}Cr{sub 0.5})O{sub 3}, and Sr(Nb{sub 0.5}Fe{sub 0.5})O{sub 3} are calculated and discussed.

  2. Lattice instability and competing spin structures in the double perovskite insulator Sr2FeOsO6.

    PubMed

    Paul, Avijit Kumar; Reehuis, Manfred; Ksenofontov, Vadim; Yan, Binghai; Hoser, Andreas; Többens, Daniel M; Abdala, Paula M; Adler, Peter; Jansen, Martin; Felser, Claudia

    2013-10-18

    The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron-osmium layers along the tetragonal c axis. Neutron powder diffraction experiments, 57Fe Mössbauer spectra, and density functional theory calculations suggest that this behavior arises because a lattice instability resulting in alternating iron-osmium distances fine-tunes the balance of competing exchange interactions. Thus, Sr2FeOsO6 is an example of a double perovskite, in which the electronic phases are controlled by the interplay of spin, orbital, and lattice degrees of freedom. PMID:24182298

  3. Perovskite Solar Cells Based on Low-Temperature Processed Indium Oxide Electron Selective Layers.

    PubMed

    Qin, Minchao; Ma, Junjie; Ke, Weijun; Qin, Pingli; Lei, Hongwei; Tao, Hong; Zheng, Xiaolu; Xiong, Liangbin; Liu, Qin; Chen, Zhiliang; Lu, Junzheng; Yang, Guang; Fang, Guojia

    2016-04-01

    Indium oxide (In2O3) as a promising n-type semiconductor material has been widely employed in optoelectronic applications. In this work, we applied low-temperature solution-processed In2O3 nanocrystalline film as an electron selective layer (ESL) in perovskite solar cells (PSCs) for the first time. By taking advantages of good optical and electrical properties of In2O3 such as high mobility, wide band gap, and high transmittance, we obtained In2O3-based PSCs with a good efficiency exceeding 13% after optimizing the concentration of the precursor solution and the annealing temperature. Furthermore, to enhance the performance of the In2O3-based PSCs, a phenyl-C61-butyric acid methyl ester (PCBM) layer was introduced to modify the surface of the In2O3 film. The PCBM film could fill up the pinholes or cracks along In2O3 grain boundaries to passivate the defects and make the ESL extremely compact and uniform, which is conducive to suppressing the charge recombination. As a result, the efficiency of the In2O3-based PSC was improved to 14.83% accompanied with VOC, JSC, and FF being 1.08 V, 20.06 mA cm(-2), and 0.685, respectively. PMID:26996215

  4. Syntheses, structures, and ionic conductivities of perovskite-structured lithium–strontium–aluminum/gallium–tantalum-oxides

    SciTech Connect

    Phraewphiphat, Thanya; Iqbal, Muhammad; Suzuki, Kota; Matsuda, Yasuaki; Yonemura, Masao; Hirayama, Masaaki; Kanno, Ryoji

    2015-05-15

    The ionic conductivities of new perovskite-structured lithium–strontium–aluminum/gallium–tantalum oxides were investigated. Solid solutions of the new perovskite oxides, (Li{sub x}Sr{sub 1−x})(Al{sub (1−x)/2}Ta{sub (1+x)/2})O{sub 3} and (Li{sub x}Sr{sub 1−x})(Ga{sub (1−x)/2}Ta{sub (1+x)/2})O{sub 3}, were synthesized using a ball-milled-assisted solid-state method. The partial substitution of the smaller Ga{sup +3} for Ta{sup +5} resulted in new compositions, the structures of which were determined by neutron diffraction measurements using a cubic perovskite structural model with the Pm−3m space group. Vacancies were introduced into the Sr(Li) sites by the formation of solid solutions with compositions (Li{sub x}Sr{sub 1−x−y}☐{sub y})(Ga{sub [(1−x)/2]−y}Ta{sub [(1+x)/2]+y})O{sub 3}, where the composition range of 0≤y≤0.20 was examined for x=0.2 and 0.25. The highest conductivity, 1.85×10{sup −3} S cm{sup −1} at 250 °C, was obtained for (Li{sub 0.25}Sr{sub 0.625}☐{sub 0.125})(Ga{sub 0.25}Ta{sub 0.75})O{sub 3} (x=0.25, y=0.125). Enhanced ionic conductivities were achieved by the introduction of vacancies at the A-sites. - Graphical abstract: Novel lithium-conducting oxides with the cubic perovskite structure (Li{sub x}Sr{sub 1−x−y}☐{sub y})(Ga{sub [(1−x)/2]−y}Ta{sub [(1+x)/2]+y})O{sub 3} provide a specific solid-solution region with various x and y values, exhibiting the highest ionic conductivity (1.85 S cm{sup −1} at 250 °C) for (Li{sub 0.25}Sr{sub 0.625}☐{sub 0.125})(Ga{sub 0.25}Ta{sub 0.75})O{sub 3} (x=0.25, y=0.125 in (Li{sub x}Sr{sub 1−x−y}☐{sub y})(Ga{sub [(1−x)/2]−y}Ta{sub [(1+x)/2]+y})O{sub 3}). The vacancies (☐) introduced into the A-sites contribute to the enhancement of lithium diffusion in the perovskite structure because of the enlargement of the bottleneck size and suppression of the interaction between lithium and oxygen. - Highlights: • The perovskite-structured novel Li

  5. Low-temperature processed electron collection layers of graphene/TiO2 nanocomposites in thin film perovskite solar cells.

    PubMed

    Wang, Jacob Tse-Wei; Ball, James M; Barea, Eva M; Abate, Antonio; Alexander-Webber, Jack A; Huang, Jian; Saliba, Michael; Mora-Sero, Iván; Bisquert, Juan; Snaith, Henry J; Nicholas, Robin J

    2014-02-12

    The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 °C. This is unfavorable for low-cost production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 °C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells. PMID:24341922

  6. Moth-Eye TiO2 Layer for Improving Light Harvesting Efficiency in Perovskite Solar Cells.

    PubMed

    Kang, Seong Min; Jang, Segeun; Lee, Jong-Kwon; Yoon, Jungjin; Yoo, Dong-Eun; Lee, Jin-Wook; Choi, Mansoo; Park, Nam-Gyu

    2016-05-01

    A moth-eye nanostructured mp-TiO2 film using conventional lithography, nano-imprinting and polydimethyl-siloxane (PDMS) stamping methods is demonstrated for the first time. Power conversion efficiency of the moth-eye patterned perovskite solar cell is improved by ≈11%, which mainly results from increasing light harvesting efficiency by structural optical property. PMID:26990492

  7. Preparation of ultra-thin and high-quality WO3 compact layers and comparision of WO3 and TiO2 compact layer thickness in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Jincheng; Shi, Chengwu; Chen, Junjun; Wang, Yanqing; Li, Mingqian

    2016-06-01

    In this paper, the ultra-thin and high-quality WO3 compact layers were successfully prepared by spin-coating-pyrolysis method using the tungsten isopropoxide solution in isopropanol. The influence of WO3 and TiO2 compact layer thickness on the photovoltaic performance of planar perovskite solar cells was systematically compared, and the interface charge transfer and recombination in planar perovskite solar cells with TiO2 compact layer was analyzed by electrochemical impedance spectroscopy. The results revealed that the optimum thickness of WO3 and TiO2 compact layer was 15 nm and 60 nm. The planar perovskite solar cell with 15 nm WO3 compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO2 compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency.

  8. Single-Layer Light-Emitting Diodes Using Organometal Halide Perovskite/Poly(ethylene oxide) Composite Thin Films.

    PubMed

    Li, Junqiang; Bade, Sri Ganesh R; Shan, Xin; Yu, Zhibin

    2015-09-16

    Organometal halide perovskite and poly(ethylene oxide) composite thin films are studied. Single-layer light-emitting diodes using the composite thin film sandwiched between indium tin oxide and indium-gallium eutectic alloy exhibit a low turn-on voltage and high brightness because of the ionic conductivity of the composite film and the formation of a p-i-n homojunction. PMID:26247326

  9. Synthesis and thermal stability studies of a series of metastable Dion–Jacobson double-layered neodymium-niobate perovskites

    SciTech Connect

    Josepha, Elisha A.; Farooq, Sara; Mitchell, Cinnamon M.; Wiley, John B.

    2014-08-15

    The Dion–Jacobson double-layered perovskite, RbNdNb{sub 2}O{sub 7}, is used as a precursor to synthesize the series ANdNb{sub 2}O{sub 7} (A=H, Li, Na, K, NH{sub 4}, Ag), and (MCl)NdNb{sub 2}O{sub 7} (M=Mn, Fe, Cu) through ion-exchange reactions ≤400 °C. Thermal stability studies indicated that most of these compounds are metastable. A combination of X-ray powder diffraction and differential thermal analysis were used to determine various low temperature decomposition pathways; these pathways were very dependent on the interlayer species. Overall the ANdNb{sub 2}O{sub 7} series was found to be less stable than the corresponding lanthanides, ALaNb{sub 2}O{sub 7}. - Graphical abstract: A new series of topochemically-prepared metastable neodymium-containing layered perovskites are studied. - Highlights: • A series of new layered neodymium containing perovskites were synthesized by ion exchange. • Products were studied by variable temperature X-ray diffraction and thermal analysis. • Most of the series are metastable showing exothermic transitions on decomposition. • The Nd compounds are less stable due to the smaller size of the Nd relative to La.

  10. Magnetic and dielectric properties of layered perovskite Gd2Ti2O7 thin film epitaxially stabilized on a perovskite single crystal

    NASA Astrophysics Data System (ADS)

    Ukita, Takashi; Hirose, Yasushi; Ohno, Sawako; Hatabayashi, Kunitada; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2012-04-01

    Layered perovskite (LP) titanates, Ln2Ti2O7 (Ln = lanthanoids), are ferroelectric materials containing magnetic Ln3+ ions at A-site. Metastable LP-Gd2Ti2O7 was fabricated in epitaxial thin film form on lattice-matched perovskite substrates and its dielectric and magnetic properties were investigated. The (100)-oriented LP-Gd2Ti2O7 films were epitaxially grown on (110) plane of (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) and Nb-doped SrTiO3 by using a pulsed laser deposition method. Piezoresponse force microscope measurements revealed that LP-Gd2Ti2O7 has spontaneous polarization along the b-axis at room temperature, strongly suggesting room temperature ferroelectricity. Magnetization measurements showed paramagnetic behavior with weak antiferromagnetic interaction around 2 K. Small positive magneto-dielectric effect (Δɛ/ɛ ˜ 10-5 order) was also confirmed at 10 K.

  11. Composition and crystal structure of perovskite films attained from electrodes of used car battery

    NASA Astrophysics Data System (ADS)

    Dhiaputra, Ilham; Permana, Bayu; Maulana, Yusep; Inayatie, Yuniar Dwi; Purba, Yonatan R.; Bahtiar, Ayi

    2016-02-01

    Perovskite solar cells have been intensively investigated for high performance and low-cost solid-state solar cells. Perovskite based-lead materials are commonly used as active material for high power conversion efficiency solar cells. Herein, we report our study on the development of used electrodes car battery as a cheap raw lead material to be converted into lead (II) iodide PbI2 by using simple chemical method. We have successfully obtained PbI2 material with purity higher than 85% and its crystal structure is comparable with that of commercial product. The perovskite CH3NH3PbI3 film was prepared by spin-coating of PbI2 solution and followed by spin-coating two-times of methylamonium iodide (MAI) solution. In this paper, the crystal structure of perovskite film attained from used car battery is shown and compared with that of prepared from commercial PbI2. By utilizing the used car battery into perovskite valuable material for high performance solar cells, we can not only improve the economical value (added-value) of wasted car battery but also we can simultaneously save the environment.

  12. Interplay of octahedral distortions in electronic and structural phase transitions in ABO3 perovskites

    NASA Astrophysics Data System (ADS)

    Balachandran, Prasanna V.; Rondinelli, James M.

    2013-03-01

    In this work, we investigate group-subgroup relationships afforded to ABO3 perovskites from combinations of BO6 distortions - bond stretching and bond angle rotations - with the objective of identifying new pathways for tuning their properties through electron-lattice interactions. Using nickelate and bismuthate perovskite compounds as a template, we decompose their low-symmetry structures into orthonormal symmetry-breaking lattice modes of the parent cubic space group. Statistical analysis of mode decomposition data uncovers previously unappreciated relationships between microscopic octahedral distortion modes and macroscopic physical properties. Finally, we propose novel crystal engineering strategies to study perovskites near phase boundaries that are otherwise extremely difficult to probe experimentally. This project is supported by The Defense Advanced Research Projects Agency (grant no. N66001-12-4224). The views, opinions, and/or findings reported here are solely those of the authors and do not represent official views of DARPA or DOD.

  13. Exploring the Electronic Band Structure of Organometal Halide Perovskite via Photoluminescence Anisotropy of Individual Nanocrystals.

    PubMed

    Täuber, Daniela; Dobrovolsky, Alexander; Camacho, Rafael; Scheblykin, Ivan G

    2016-08-10

    Understanding electronic processes in organometal halide perovskites, flourishing photovoltaic, and emitting materials requires unraveling the origin of their electronic transitions. Light polarization studies can provide important information regarding transition dipole moment orientations. Investigating individual methylammonium lead triiodide perovskite nanocrystals enabled us to detect the polarization of photoluminescence intensity and photoluminescence excitation, hidden in bulk samples by ensemble averaging. Polarization properties of the crystals were correlated with their photoluminescence spectra and electron microscopy images. We propose that distortion of PbI6 octahedra leads to peculiarities of the electronic band structure close to the band-edge. Namely, the lowest band transition possesses a transition dipole moment along the apical Pb-I-Pb bond resulting in polarized photoluminescence. Excitation of photoluminescence above the bandgap is unpolarized because it involves molecular orbitals delocalized both in the apical and equatorial directions of the perovskite octahedron. Trap-assisted emission at 77 K, rather surprisingly, was polarized similar to the bandgap emission. PMID:27462927

  14. The Electronic Structure of Iron in Aluminous (Mg,Fe)SiO3 Perovskite at High-Pressures and Temperatures

    NASA Astrophysics Data System (ADS)

    Jackson, J. M.; Sturhahn, W.; Lerche, M.; Li, J.

    2006-12-01

    Knowledge of iron valences and spin states in silicate perovskite is relevant to our understanding of the physical and chemical properties of Earth's lower mantle such as transport properties, mechanical behavior, and element partitioning. Recent studies have proposed that aluminous ferromagnesium silicate perovskite (Al- Pv) is the principle sink for ferric iron in Earth's lower mantle [e.g. 1]. Also of geophysical interest is the electronic spin state of Al-Pv under lower mantle conditions. To date, simultaneous high-pressure and high- temperature measurements of the hyperfine parameters to identify the valence and spin states of iron in Al-Pv have not been reported. In this study, we have measured the electronic structure of the iron component of an aluminous Fe-bearing silicate perovskite sample, (Mg0.88Fe0.09)(Si0.94Al0.10)O3, close to a pyrolite composition, using synchrotron Mössbauer spectroscopy (SMS) and laser heated diamond anvil cells. Recent developments in SMS have enabled in situ measurements of small samples (< 10 μm) with relatively low 57Fe contents (< 10 at.%) to Mbar pressures [e.g. 2,3]. The samples were first synthesized in a multi-anvil apparatus [3], and the perovskite structure was confirmed by X-ray diffraction. The sample was loaded into a diamond anvil cell sandwiched between NaCl insulating layers. Measurements were carried out to 65 GPa and up to 2000 K at beamline 3-ID of the Advanced Photon Source. Spectra were collected before, during, and after laser heating, at each pressure point. Synchrotron Mössbauer spectra were also collected on decreasing pressure. Evaluation of the spectra provided the isomer shift (relative to stainless steel) and the quadrupole splitting of the iron component in silicate perovskite, which gives information on valence and spin states under lower mantle conditions. This work is supported by NSF through COMPRES and the U.S. DOE-BES, Office of Science, under Contract No. W-31-109-ENG-38. [1] Mc

  15. Two-Step Physical Deposition of a Compact CuI Hole-Transport Layer and the Formation of an Interfacial Species in Perovskite Solar Cells.

    PubMed

    Gharibzadeh, Saba; Nejand, Bahram Abdollahi; Moshaii, Ahmad; Mohammadian, Nasim; Alizadeh, Amir Hossein; Mohammadpour, Rahele; Ahmadi, Vahid; Alizadeh, Abdolali

    2016-08-01

    A simple and practical approach is introduced for the deposition of CuI as an inexpensive inorganic hole-transport material (HTM) for the fabrication of low cost perovskite solar cells (PSCs) by gas-solid phase transformation of Cu to CuI. The method provides a uniform and well-controlled CuI layer with large grains and good compactness that prevents the direct connection between the contact electrodes. Solar cells prepared with CuI as the HTM with Au electrodes displays an exceptionally high short-circuit current density of 32 mA cm(-2) , owing to an interfacial species formed between the perovskite and the Cu resulting in a long wavelength contribution to the incident photon-to-electron conversion efficiency (IPCE), and an overall power conversion efficiency (PCE) of 7.4 %. The growth of crystalline and uniform CuI on a low roughness perovskite layer leads to remarkably high charge extraction in the cells, which originates from the high hole mobility of CuI in addition to a large number of contact points between CuI and the perovskite layer. In addition, the solvent-free method has no damaging side effect on the perovskite layer, which makes it an appropriate method for large scale applications of CuI in perovskite solar cells. PMID:27357330

  16. Structural and electronic properties of organo-halide hybrid perovskites from ab initio molecular dynamics.

    PubMed

    Quarti, Claudio; Mosconi, Edoardo; De Angelis, Filippo

    2015-04-14

    The last two years have seen the unprecedentedly rapid emergence of a new class of solar cells, based on hybrid organic-inorganic halide perovskites. The success of this class of materials is due to their outstanding photoelectrochemical properties coupled to their low cost, mainly solution-based, fabrication techniques. Solution processed materials are however often characterized by an inherent flexible structure, which is hardly mapped into a single local minimum energy structure. In this perspective, we report on the interplay between structural and electronic properties of hybrid lead iodide perovskites investigated using ab initio molecular dynamics (AIMD) simulations, which allow the dynamical simulation of disordered systems at finite temperature. We compare the prototypical MAPbI3 (MA = methylammonium) perovskite in its cubic and tetragonal structure with the trigonal phase of FAPbI3 (FA = formamidinium), investigating different starting arrangements of the organic cations. Despite the relatively short time scale amenable to AIMD, typically a few tens of ps, this analysis demonstrates the sizable structural flexibility of this class of materials, showing that the instantaneous structure could significantly differ from the time and thermal averaged structure. We also highlight the importance of the organic-inorganic interactions in determining the fluxional properties of this class of materials. A peculiar spatial localization of the valence and conduction band edges is also found, with a dynamics in the range of 0.1 ps, which is associated with the positional dynamics of the organic cations within the cubo-octahedral perovskite cage. This asymmetry in the spatial localization of the band edges is expected to ease exciton dissociation and assist the initial stages of charge separation, possibly constituting one of the key factors for the impressive photovoltaic performances of hybrid lead-iodide perovskites. PMID:25766785

  17. Structural, Optical, and Electronic Properties of Wide Bandgap Perovskites: Experimental and Theoretical Investigations.

    PubMed

    Kumawat, Naresh K; Tripathi, Madhvendra Nath; Waghmare, Umesh; Kabra, Dinesh

    2016-06-01

    Wide bandgap hybrid halide perovskites based on bromine and chlorine halide anions have emerged as potential candidates for various optoelectronic devices. However, these materials are relatively less explored than the iodine-based perovskites for microscopic details. We present experiment and first-principles calculations to understand the structural, optical, and electronic structure of wide bandgap CH3NH3Pb(Br1-xClx)3 (x = 0, 0.33, 0.66, and 1) 3D hybrid perovskite materials. We substituted Br(-) with Cl(-) to tune the bandgap from 2.4 eV (green emissive) to 3.2 eV (blue (UV) emissive) of these materials. We correlate our experimental results with first-principles theory and provide an insight into important parameters like lattice constants, electronic structure, excitonic binding energy (EX), dielectric constant, and reduced effective mass (μr) of charge carriers in these perovskite semiconductors. Electronic structure calculations reveal that electronic properties are mainly governed by Pb 6p and halide p orbitals. Our estimates of EX within a hydrogen model suggest that an increase in EX by increasing the Cl(-) (chlorine) concentration is mainly due to a decrease in the dielectric constant with x and almost constant value of μr close to the range of 0.07me. PMID:27203800

  18. Polar-axis-oriented crystal growth of tetragonal PZT films on stainless steel substrate using pseudo-perovskite nanosheet buffer layer

    NASA Astrophysics Data System (ADS)

    Minemura, Yoshiki; Ichinose, Daichi; Nagasaka, Kohei; Kim, Jin Woon; Shima, Hiromi; Nishida, Ken; Kiguchi, Takanori; Konno, Toyohiko J.; Oshima, Naoya; Funakubo, Hiroshi; Uchida, Hiroshi

    2015-07-01

    Lead zirconate titanate (PZT) film with polar axis orientation was grown on a SUS 316L stainless steel substrate with the help of a Ca2Nb3O10 nanosheet (ns-CN) layer that had a pseudo-perovskite-type crystal structure. The ns-CN buffer layer was supported on a platinized SUS 316L (Pt/SUS) substrate, followed by chemical solution deposition (CSD) of the PZT films with tetragonal symmetry (Zr/Ti =40/60). The PZT films consisting of c-domain, with [001]-axis orientation of the perovskite unit cell, were deposited on the ns-CN/Pt/SUS substrate owing to (i) epitaxial lattice matching between the unit cell of PZT and substrate surface and (ii) in-plane thermal stress applied to the PZT film during cooling-down step of CSD procedure. The c-domain-oriented PZT film on ns-CN/Pt/SUS substrate exhibited enhanced remanent polarization of approximately 52 μC/cm2 and lowered dielectric permittivity of approximately 230, which are superior to those of conventional PZT films with random crystal orientation and comparable to those of epitaxial PZT films grown on (100)SrRuO3//(100)SrTiO3 substrates.

  19. Epitaxial stabilization of (110)-layered perovskites of the RE{sub 2}Ti{sub 2}O{sub 7} (RE=La, Nd, Sm, Gd) family

    SciTech Connect

    Havelia, S.; Wang, S.; Balasubramaniam, K.R.; Salvador, P.A.

    2009-07-15

    Thin films of RE{sub 2}Ti{sub 2}O{sub 7} (RE=La, Nd, Sm, Gd) were deposited on single crystal SrTiO{sub 3} (110) substrates at 900 deg. C using pulsed laser deposition. X-ray diffraction (XRD) results showed sharp (00k) peaks (in theta-2theta scans) with narrow rocking curves (omega-scan peak widths of 0.4-0.9{sup o}), indicating that all compositions adopted the (110)-layered perovskite structure. While this is the stable structure for RE=La and Nd, it is metastable for RE=Sm and Gd. The metastable compounds are formed directly through epitaxial stabilization at these high temperatures and are shown to be isostructural to monoclinic La{sub 2}Ti{sub 2}O{sub 7}. The a, b, and c lattice parameters decreased monotonically with decreasing size of the RE cation, while the monoclinic angle remained fairly constant. The epitaxial relationship between the (110)-layered RE{sub 2}Ti{sub 2}O{sub 7} films and the SrTiO{sub 3}(110) substrate was found by XRD and transmission electron microscopy to be {l_brace}001{r_brace}<010>{sub film}||{l_brace}110{r_brace}<11-bar0>{sub SrTiO{sub 3}}. The single-phase, metastable, epitaxial, 100 nm thick films maintained the layered perovskite structure even after annealing at 900 deg. C for two hours in 200 Torr of oxygen. - Graphical abstract: Epitaxial thin films of RE{sub 2}Ti{sub 2}O{sub 7} (RE=Gd, Sm, Nd, and La) were deposited on single crystal SrTiO{sub 3} (110) substrates using pulsed laser deposition (PLD). All compositions adopted the monoclinic (110)-layered perovskite structure, which is the stable phase for La{sub 2}Ti{sub 2}O{sub 7} and Nd{sub 2}Ti{sub 2}O{sub 7} but is metastable with respect to the pyrochlore phase for Sm{sub 2}Ti{sub 2}O{sub 7} and Gd{sub 2}Ti{sub 2}O{sub 7}.

  20. Luminescence studies of perovskite structured titanates: A review

    NASA Astrophysics Data System (ADS)

    Nag Bhargavi, G.; Khare, Ayush

    2015-06-01

    Apart from widely known dielectric and ferroelectric properties, the perovskite type materials also constitute a class of materials, which are recently investigated for their optical properties. These materials are being used for fabrication of various microelectronics and optoelectronic devices. Photoluminescence (PL), mechanoluminescence (ML) and thermoluminescence (TL) are such phenomena offering numerous applications in different fields like electro-optics, flat panel displays, LED technology, sensors, dynamic visualization etc. This paper briefly reviews the status and new progress in luminescence studies of ferroelectric materials like barium titanate (BT), barium zirconate titanate (BZT), calcium titanate (CT), calcium zirconate titanate (CZT), lead titanate (PT), lead zirconate titanate (PZT), etc., prepared through various methods.

  1. Perovskites: transforming photovoltaics, a mini-review

    SciTech Connect

    Chilvery, Ashwith; Batra, Ashok; Yang, Bin; Xiao, Kai; Guggilla, Padmaja; Aggarwal, Mohan; Surabhi, Raja; Lal, Ravi; Currie, James; Penn, Benjamin

    2015-01-01

    The recent power-packed advent of perovskite solar cells is transforming photovol- taics (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 article provides a detailed insight of the organometal halide based perovskite structure, its unique stoichiometric design, and its underlying principles for PV applications. The compatibility of various PV layers and its fab- rication methods is also discussed.

  2. Perovskites: transforming photovoltaics, a mini-review

    DOE PAGESBeta

    Chilvery, Ashwith Kumar; Batra, Ashok K.; Yang, Bin; Xiao, Kai; Guggilla, Padmaja; Aggarwal, Mohan D.; Surabhi, Raja; Lal, Ravi B.; Currie, James R.; Penn, Benjamin G.

    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.

  3. Synthesis, structural and optical properties of perovskite type CH3NH3PbI3 nanorods

    NASA Astrophysics Data System (ADS)

    Rajamanickam, N.; Rajashabala, S.; Ramachandran, K.

    2015-06-01

    Perovskite type methyl ammonium lead triiodide (CH3NH3PbI3) thin films were prepared by coprecipitation method. The structural and optical properties were investigated by XRD, SEM, Raman and UV-Vis spectroscopy. Perovskite structured tetragonal phase was observed by XRD. The UV spectrum exhibits a band gap of 1.63 eV. The nanorods are arranged in flower like structure distinguished by SEM. Raman spectrum of this organo-halide perovskite was studied for the full exploitation in solar cells.

  4. Perovskite LaRhO{sub 3} as a p-type active layer in oxide photovoltaics

    SciTech Connect

    Nakamura, Masao Krockenberger, Yoshiharu; Fujioka, Jun; Kawasaki, Masashi; Tokura, Yoshinori

    2015-02-16

    Perovskite-type transition-metal oxides have a wide variety of physical properties and triggered intensive research on functional devices in the form of heteroepitaxial junctions. However, there is a missing component that is a p-type conventional band semiconductor. LaRhO{sub 3} (LRO) is one of very few promising candidates having its bandgap between filled t{sub 2g} and empty e{sub g} of Rh in low-spin state, but there has been no report on the synthesis of large-size single crystals or thin films. Here, we report on the junction properties of single-crystalline thin films of LRO grown on (110) oriented Nb-doped SrTiO{sub 3} substrates. The external quantum efficiency of the photo-electron conversion exceeds 1% in the visible-light region due to the wide depletion layer and long diffusion length of minority carriers in LRO. Clear indication of p-type band semiconducting character in a perovskite oxide of LRO will pave a way to explore oxide electronics of perovskite heterostructures.

  5. Graphene oxide/PEDOT:PSS composite hole transport layer for efficient and stable planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Da-Young; Na, Seok-In; Kim, Seok-Soon

    2016-01-01

    We investigated a graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composite as a promising candidate for the practical application of a 2-D carbonaceous hole transport layer (HTL) to planar heterojunction perovskite solar cells (PeSCs) consisting of a transparent electrode/HTL/perovskite/fullerene/metal electrode. Both the insulating properties of GO and the non-uniform coating of the transparent electrode with GO cause the poor morphology of perovskite induced low power conversion efficiency (PCE) of 6.4%. On the other hand, PeSCs with a GO/PEDOT:PSS composite HTL, exhibited a higher PCE of 9.7% than that of a device fabricated with conventional PEDOT:PSS showing a PCE of 8.2%. The higher performance is attributed to the decreased series resistance (RS) and increased shunt resistance (RSh). The well-matched work-function between GO (4.9 eV) and PEDOT:PSS (5.1 eV) probably results in more efficient charge transport and an overall decrease in RS. The existence of GO with a large bandgap of ~3.6 eV might induce the effective blocking of electrons, leading to an increase of RSh. Moreover, improvement in the long-term stability under atmospheric conditions was observed.

  6. Formation Dynamics of CH3NH3PbI3 Perovskite Following Two-Step Layer Deposition.

    PubMed

    Patel, Jay B; Milot, Rebecca L; Wright, Adam D; Herz, Laura M; Johnston, Michael B

    2016-01-01

    Hybrid metal-halide perovskites have emerged as a leading class of semiconductors for optoelectronic devices because of their desirable material properties and versatile fabrication methods. However, little is known about the chemical transformations that occur in the initial stages of perovskite crystal formation. Here we follow the real-time formation dynamics of MAPbI3 from a bilayer of lead iodide (PbI2) and methylammonium iodide (MAI) deposited through a two-step thermal evaporation process. By lowering the substrate temperature during deposition, we are able to initially inhibit intermixing of the two layers. We subsequently use infrared and visible light transmission, X-ray diffraction, and photoluminescence lifetime measurements to reveal the room-temperature transformations that occur in vacuum and ambient air, as MAI diffuses into the PbI2 lattice to form MAPbI3. In vacuum, the transformation to MAPbI3 is incomplete as unreacted MAI is retained in the film. However, exposure to moist air allows for conversion of the unreacted MAI to MAPbI3, demonstrating that moisture is essential in making MAI more mobile and thus aiding perovskite crystallization. These dynamic processes are reflected in the observed charge-carrier lifetimes, which strongly fluctuate during periods of large ion migration but steadily increase with improving crystallinity. PMID:26667323

  7. Electronic structure and band alignment at an epitaxial spinel/perovskite heterojunction.

    PubMed

    Qiao, Liang; Li, Wei; Xiao, Haiyan; Meyer, Harry M; Liang, Xuelei; Nguyen, N V; Weber, William J; Biegalski, Michael D

    2014-08-27

    The electronic properties of solid-solid interfaces play critical roles in a variety of technological applications. Recent advances of film epitaxy and characterization techniques have demonstrated a wealth of exotic phenomena at interfaces of oxide materials, which are critically dependent on the alignment of their energy bands across the interface. Here we report a combined photoemission and electrical investigation of the electronic structures across a prototypical spinel/perovskite heterojunction. Energy-level band alignment at an epitaxial Co3O4/SrTiO3(001) heterointerface indicates a chemically abrupt, type I heterojunction without detectable band bending at both the film and substrate. The unexpected band alignment for this typical p-type semiconductor on SrTiO3 is attributed to its intrinsic d-d interband excitation, which significantly narrows the fundamental band gap between the top of the valence band and the bottom of the conduction band. The formation of the type I heterojunction with a flat-band state results in a simultaneous confinement of both electrons and holes inside the Co3O4 layer, thus rendering the epitaxial Co3O4/SrTiO3(001) heterostructure to be a very promising material for high-efficiency luminescence and optoelectronic device applications. PMID:25075939

  8. An efficient electron transport material of tin oxide for planar structure perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Murugadoss, Govindhasamy; Kanda, Hiroyuki; Tanaka, Soichiro; Nishino, Hitoshi; Ito, Seigo; Imahoric, Hiroshi; Umeyama, Tomokazu

    2016-03-01

    The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 film prepared at low temperature using different solvents was investigated. SnO2 was selected as an electron conducting medium due to its superior properties over TiO2, such as better antireflective properties, higher electron mobility, more suitable band edges and a wider band gap. A SnO2 layer was developed by spin-coating SnCl2 solution followed by annealing at 200 °C in air. The low-temperature (200 °C) annealed SnO2 layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology using ethanol as a solvent rather than water. Solid state CuSCN hole conductor was used as HTM for reducing the device cost. A planar solar cell fabricated with CH3NH3PbI3 perovskite infiltrated SnO2 showed a power conversion efficiency of 8.38% with short-circuit current density of 18.99 mA cm-2, an open-circuit voltage of 0.96 mV and a fill factor of 45%. The devices were fabricated at >60% humidity level at room temperature. The results suggest that SnO2 is an effective charge collection system for CH3NH3PbI3 based planar perovskite solar cells. In addition, these results provide a new direction for the future improvement of perovskite solar cells using new electron conducting layers.

  9. Di-hydrogen contact induced lattice instabilities and structural dynamics in complex hydride perovskites.

    PubMed

    Schouwink, P; Hagemann, H; Embs, J P; D'Anna, V; Černý, R

    2015-07-01

    The structural phase transitions occurring in a series of perovskite-type complex hydrides based on the tetrahydroborate anion BH4(-) are investigated by means of in situ synchrotron x-ray powder diffraction, vibrational spectroscopy, thermal methods and ab initio calculations in the solid state. Structural dynamics of the BH4 anion are followed with quasi-elastic neutron scattering. We show that unexpected temperature-induced lattice instabilities in perovskite-type ACa(BH4)3 (A = K, Rb, Cs) have their origin in close hydridic di-hydrogen contacts. The rich lattice dynamics lead to coupling between internal B-H vibrations and phonons, resulting in distortions in the high-temperature polymorph that are identical in symmetry to well-known instabilities in oxide perovskites, generally condensing at lower temperatures. It is found that anion-substitution BH4(-) <-> (X = Halide) can relax distortions in ACa(BH4)3 by eliminating coulomb repulsive H(-)···H(-) effects. The interesting nature of phase transition in ACa(BH4)3 enters an unexplored field of weak interactions in ceramic-like host lattices and is the principal motivation for this study. Close di-hydrogen contacts suggest new concepts to tailor crystal symmetries in complex hydride perovskites in the future. PMID:26076047

  10. Pressure-induced conductivity and yellow-to-black piezochromism in a layered Cu-Cl hybrid perovskite.

    PubMed

    Jaffe, Adam; Lin, Yu; Mao, Wendy L; Karunadasa, Hemamala I

    2015-02-01

    Pressure-induced changes in the electronic structure of two-dimensional Cu-based materials have been a subject of intense study. In particular, the possibility of suppressing the Jahn-Teller distortion of d(9) Cu centers with applied pressure has been debated over a number of decades. We studied the structural and electronic changes resulting from the application of pressures up to ca. 60 GPa on a two-dimensional copper(II)-chloride perovskite using diamond anvil cells (DACs), through a combination of in situ powder X-ray diffraction, electronic absorption and vibrational spectroscopy, dc resistivity measurements, and optical observations. Our measurements show that compression of this charge-transfer insulator initially yields a first-order structural phase transition at ca. 4 GPa similar to previous reports on other Cu(II)-Cl perovskites, during which the originally translucent yellow solid turns red. Further compression induces a previously unreported phase transition at ca. 8 GPa and dramatic piezochromism from translucent red-orange to opaque black. Two-probe dc resistivity measurements conducted within the DAC show the first instance of appreciable conductivity in Cu(II)-Cl perovskites. The conductivity increases by 5 orders of magnitude between 7 and 50 GPa, with a maximum measured conductivity of 2.9 × 10(-4) S·cm(-1) at 51.4 GPa. Electronic absorption spectroscopy and variable-temperature conductivity measurements indicate that the perovskite behaves as a 1.0 eV band-gap semiconductor at 39.7 GPa and has an activation energy for electronic conduction of 0.232(1) eV at 40.2 GPa. Remarkably, all these changes are reversible: the material reverts to a translucent yellow solid upon decompression, and ambient pressure powder X-ray diffraction data taken before and after compression up to 60 GPa show that the original structure is maintained with minimal hysteresis. PMID:25580620

  11. Thermal and Environmental Stability of Semi-Transparent Perovskite Solar Cells for Tandems Enabled by a Solution-Processed Nanoparticle Buffer Layer and Sputtered ITO Electrode.

    PubMed

    Bush, Kevin A; Bailie, Colin D; Chen, Ye; Bowring, Andrea R; Wang, Wei; Ma, Wen; Leijtens, Tomas; Moghadam, Farhad; McGehee, Michael D

    2016-05-01

    A sputtered oxide layer enabled by a solution-processed oxide nanoparticle buffer layer to protect underlying layers is used to make semi-transparent perovskite solar cells. Single-junction semi-transparent cells are 12.3% efficient, and mechanically stacked tandems on silicon solar cells are 18.0% efficient. The semi-transparent perovskite solar cell has a T 80 lifetime of 124 h when operated at the maximum power point at 100 °C without additional sealing in ambient atmosphere under visible illumination. PMID:26880196

  12. The ordered double perovskite PrBaCo2O6: Synthesis, structure, and magnetism

    NASA Astrophysics Data System (ADS)

    Motin Seikh, Md.; Pralong, V.; Lebedev, O. I.; Caignaert, V.; Raveau, B.

    2013-07-01

    The stoichiometric layered perovskite cobaltite PrBaCo2O6 has been synthesized using an oxidative reaction of PrBaCo2O5.80 by sodium hypochlorite. The ferromagnetic properties of this oxide, which exhibits the highest TC of 210 K among the "112" layered cobaltites, are interpreted by double exchange mechanism. In contrast, the creation of oxygen vacancies in this framework leads for the oxides PrBaCo2O5+δ (0.80 ≤ δ < 1) to a strong competition between ferromagnetism and antiferromagnetism due to the appearance of superexchange Co3+—O—Co3+ antiferromagnetic interactions.

  13. Application of Electron Structure Calculations to the Migration of Oxygen through a Perovskite Membrane

    NASA Astrophysics Data System (ADS)

    Wood, Douglas A.

    The focus of this thesis is the application of electron structure calculations, particularly density functional theory, to the analysis of the process by which oxygen is able to migrate through a perovskite crystal. This property creates the possibility of using perovskite membranes to separate oxygen from air. This could be applied to the generation of syngas directly from natural gas without the need for a separate air separation unit. A perovskite has the nominal formula ABO3 where A is a rare earth type cation and B is a transition type cation. The structure consists of the B cations arranged in a cube with the A cation in the center. The oxygen ions are located at the midpoint of each B-B cube edge and form an octahedron centered on each B cation. Any real perovskite crystal will contain a certain fraction of vacancies at the oxygen sites. Oxygen migrates through the crystal by jumping from a neighboring site to the vacancy. The permeability of the crystal is thus a function of the concentration of vacancies and the activation energy of the jump from a neighboring site to the vacancy. These properties can be modified by adding dopants for the A and B cations. The literature contains a substantial amount of experimental work on the effect of such dopants. The overall migration process can be divided into components (i) the concentration of oxygen vacancies, (ii) the activation energy for a neighboring on-site oxygen atom to jump to the vacant site, (iii) the concentration of surface vacancies, and (iv) the processes by which oxygen ions transfer back and forth between the perovskite surface and the contiguous vapor space. Using SrTiO3 and LaCoO3 as model compounds, DFT calculations have been used to (i) calculate various properties of the perovskite crystal, (ii) estimate the activation energy of a jump between an occupied oxygen site and an adjacent vacant oxygen site, (iii) predict the effects of various dopants at the A and B site and (iv) analyze the

  14. Using an airbrush pen for layer-by-layer growth of continuous perovskite thin films for hybrid solar cells.

    PubMed

    Ramesh, Mohan; Boopathi, Karunakara Moorthy; Huang, Tzu-Yen; Huang, Yu-Ching; Tsao, Cheng-Si; Chu, Chih-Wei

    2015-02-01

    In this manuscript we describe hybrid heterojunction solar cells, having the device architecture glass/indium tin oxide/poly(3,4-ethylenedioxythiopene)/poly(styrenesulfonic acid)/perovskite/[6,6]-phenyl-C61-butyric acid methyl ester/C60/2,9-dimethyl- 4,7-diphenyl-1,10-phenanthroline/Al, fabricated using lead halide perovskite obtained through spray-coating at a low precursor concentration. To study the relationship between the morphology and device performance, we recorded scanning electron microscopy images of perovskite films prepared at various precursor ratios, spray volumes, substrate temperatures, and postspray annealing temperatures. Optimization of the spray conditions ensured uniform film growth and high surface area coverage at low substrate temperatures. Lead halide perovskite solar cells prepared under the optimal conditions displayed an average power conversion efficiency (PCE) of approximately 9.2%, with 85% of such devices having efficiencies of greater than 8.3%. The best-performing device exhibited a short-circuit current density of 17.3 mA cm(-2), a fill factor of 0.63, and an open-circuit voltage of 0.93 V, resulting in a PCE of 10.2%. Because spray-coating technology allows large-area deposition, we also fabricated devices having areas of 60 and 342 mm(2), achieving PCEs with these devices of 6.88 and 4.66%, respectively. PMID:25562387

  15. Investigation of growth of thin layers of perovskite on native silicon dioxide by a combination of atomic force microscopy and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Taghi Khani, A.; Walther, T.

    2013-11-01

    Thin layers of (Sr,Ba)TiO3 perovskite have been grown on native silicon dioxide by pulsed laser deposition at the Technical University of Darmstadt, Germany. Atomic force microscopy (AFM) has been used to investigate the surfaces of the native silicon oxide before and after over-growth by the perovskite in plan-view. Bright-field and dark-field scanning transmission electron microscopy (STEM) in a JEOL 2010F field-emission transmission electron microscope have been combined to investigate the layer stacks of Si/SiO2/(Ba,Sr)TiO3 in cross-section. The aim is to correlate surface roughnesses in plan-view geometry with interface roughness in cross-sectional geometry, with an emphasis on detecting percolation in the perovskite layers if they approach thicknesses of only a few unit cells.

  16. Distribution change of oxygen vacancies in layered perovskite type(Sr, La){sub n+1}Fe{sub n}O{sub 3n+1} (n=3)

    SciTech Connect

    Kagomiya, Isao Jimbo, Keigo; Kakimoto, Ken-ichi

    2013-11-15

    To elucidate characteristic oxygen vacancy formation in layered perovskite (Sr, La){sub n+1}Fe{sub n}O{sub 3n+1} with the perovskite layer number: n=3, oxygen vacancy content δ of the (Sr{sub 0.775}La{sub 0.225}){sub 4}Fe{sub 3}O{sub 10−δ} (SLF4310) was investigated using a titration technique and a thermogravimetric analysis. The equilibrium constant K for the reduction reaction: Oo{sup ×}+2Fe{sub Fe}{sup ∙} (Fe{sup 4+})=1/2O{sub 2}+Vo{sup ∙∙}+2Fe{sub Fe}{sup ×}(Fe{sup 3+}) was estimated using the vacancy content δ. The Arrhenius plot of the K reveals slope change at approximately 775 °C. From the Rietveld analysis, the oxygen vacancies are the most remarkable at the O2 (O4) sites at lower (higher) temperatures than about 800 °C, which temperature is approximately comparable with that of slope change in the K. These facts mean that distribution of vacancy sites in the SLF4310 changes at approximately 775 °C, accompanying no structural phase transition. The vacancy distribution change affects to the ion conductivity of the SLF4310. - Graphical abstract: Crystal structure of (Sr{sub 0.775}La{sub 0.225}){sub 4}Fe{sub 3}O{sub 10−δ} (SLF4310) at 1000 °C. Display Omitted - Highlights: • Distribution change of oxygen vacancies is appeared at approximately 775 °C. • The distribution change with no structure phase transition is the first observation. • The vacancy distribution change affects the ion conductivity of the SLF4310.

  17. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    PubMed

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-01

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise. PMID:27295399

  18. Mechanism of biphasic charge recombination and accumulation in TiO2 mesoporous structured perovskite solar cells.

    PubMed

    Wang, Hao-Yi; Wang, Yi; Yu, Man; Han, Jun; Guo, Zhi-Xin; Ai, Xi-Cheng; Zhang, Jian-Ping; Qin, Yujun

    2016-04-28

    Organic-inorganic halide perovskite solar cells are becoming the next big thing in the photovoltaic field owing to their rapidly developing photoelectric conversion performance. Herein, mesoporous structured perovskite devices with various perovskite grain sizes are fabricated by a sequential dropping method, and the charge recombination dynamics is investigated by transient optical-electric measurements. All devices exhibit an overall power conversion efficiency around 15%. More importantly, a biphasic trap-limited charge recombination process is proposed and interpreted by taking into account the specific charge accumulation mechanism in perovskite solar cells. At low Fermi levels, photo-generated electrons predominately populate in the perovskite phase, while at high Fermi levels, most electrons occupy traps in mesoporous TiO2. As a result, the dynamics of charge recombination is, respectively, dominated by the perovskite phase and mesoporous TiO2 in these two cases. The present work would give a new perspective on the charge recombination process in meso-structured perovskite solar cells. PMID:27076212

  19. Cuprous Oxide as a Potential Low-Cost Hole-Transport Material for Stable Perovskite Solar Cells.

    PubMed

    Nejand, Bahram Abdollahi; Ahmadi, Vahid; Gharibzadeh, Saba; Shahverdi, Hamid Reza

    2016-02-01

    Inorganic hole-transport materials are commercially desired to decrease the fabrication cost of perovskite solar cells. Here, Cu2O is introduced as a potential hole-transport material for stable, low-cost devices. Considering that Cu2O formation is highly sensitive to the underlying mixture of perovskite precursors and their solvents, we proposed and engineered a technique for reactive magnetron sputtering. The rotational angular deposition of Cu2O yields high surface coverage of the perovskite layer for high rate of charge extraction. Deposition of this Cu2O layer on the pinhole-free perovskite layer produces devices with power conversion efficiency values of up to 8.93%. The engineered Cu2O layers showed uniform, compact, and crack-free surfaces on the perovskite layer without affecting the perovskite structure, which is desired for deposition of the top metal contact and for surface shielding against moisture and mechanical damages. PMID:26748959

  20. Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskites

    PubMed Central

    Giovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

    2016-01-01

    Ultrafast spin manipulation for opto–spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorganic semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile solution processability, can offer breakthroughs in this area. We demonstrate novel room-temperature, strong ultrafast spin-selective optical Stark effect in solution-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ~6.3 meV using circularly polarized optical pulses without any external photonic cavity (that is, corresponding to a Rabi energy of ~55 meV and equivalent to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and organic replacement in these perovskites affords control of the dielectric confinement and thus presents a straightforward strategy for tuning light-matter coupling strength. PMID:27386583

  1. Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskites.

    PubMed

    Giovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

    2016-06-01

    Ultrafast spin manipulation for opto-spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorganic semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile solution processability, can offer breakthroughs in this area. We demonstrate novel room-temperature, strong ultrafast spin-selective optical Stark effect in solution-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ~6.3 meV using circularly polarized optical pulses without any external photonic cavity (that is, corresponding to a Rabi energy of ~55 meV and equivalent to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and organic replacement in these perovskites affords control of the dielectric confinement and thus presents a straightforward strategy for tuning light-matter coupling strength. PMID:27386583

  2. Determination of stoichiometry and concentration of trace elements in thin BaxSr1-xTiO3 perovskite layers.

    PubMed

    Becker, J S; Boulyga, S F

    2001-07-01

    This paper describes an analytical procedure for determining the stoichiometry of BaxSr1-xTiO3 perovskite layers using inductively coupled plasma mass spectrometry (ICP-MS). The analytical results of mass spectrometry measurements are compared to those of X-ray fluorescence analysis (XRF). The performance and the limits of solid-state mass spectrometry analytical methods for the surface analysis of thin BaxSr1-xTiO3 perovskite layers sputtered neutral mass spectrometry (SNMS)--are investigated and discussed. PMID:11496982

  3. 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

  4. 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.

  5. Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2016-04-01

    Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

  6. Novel Combination of Efficient Perovskite Solar Cells with Low Temperature Processed Compact TiO2 Layer via Anodic Oxidation.

    PubMed

    Du, Yangyang; Cai, Hongkun; Wen, Hongbin; Wu, Yuxiang; Huang, Like; Ni, Jian; Li, Juan; Zhang, Jianjun

    2016-05-25

    In this work, a facile and low temperature processed anodic oxidation approach is proposed for fabricating compact and homogeneous titanium dioxide film (AO-TiO2). In order to realize morphology and thickness control of AO-TiO2, the theory concerning anodic oxidation (AO) is unveiled and the influence of relevant parameters during the process of AO such as electrolyte ingredient and oxidation voltage on AO-TiO2 formation is observed as well. Meanwhile, we demonstrate that the planar perovskite solar cells (p-PSCs) fabricated in ambient air and utilizing optimized AO-TiO2 as electron transport layer (ETL) can deliver repeatable power conversion efficiency (PCE) over 13%, which possess superior open-circuit voltage (Voc) and higher fill factor (FF) compared to its counterpart utilizing conventional high temperature processed compact TiO2 (c-TiO2) as ETL. Through a further comparative study, it is indicated that the improvement of device performance should be attributed to more effective electron collection from perovskite layer to AO-TiO2 and the decrease of device series resistance. Furthermore, hysteresis effect about current density-voltage (J-V) curves in TiO2-based p-PSCs is also unveiled. PMID:27150310

  7. A composite nanostructured electron-transport layer for stable hole-conductor free perovskite solar cells: design and characterization

    NASA Astrophysics Data System (ADS)

    Yu, Zhenhua; Qi, Fei; Liu, Pei; You, Sujian; Kondamareddy, Kiran Kumar; Wang, Changlei; Cheng, Nian; Bai, Sihang; Liu, Wei; Guo, Shishang; Zhao, Xing-Zhong

    2016-03-01

    A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility.A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility. Electronic supplementary information (ESI) available: Details of the experimental section and ESI figures. See DOI: 10.1039/c5nr09045h

  8. Room-temperature, solution-processable organic electron extraction layer for high-performance planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Jong H.; Chueh, Chu-Chen; Williams, Spencer T.; Jen, Alex K.-Y.

    2015-10-01

    In this work, we describe a room-temperature, solution-processable organic electron extraction layer (EEL) for high-performance planar heterojunction perovskite solar cells (PHJ PVSCs). This EEL is composed of a bilayered fulleropyrrolidinium iodide (FPI)-polyethyleneimine (PEIE) and PC61BM, which yields a promising power conversion efficiency (PCE) of 15.7% with insignificant hysteresis. We reveal that PC61BM can serve as a surface modifier of FPI-PEIE to simultaneously facilitate the crystallization of perovskite and the charge extraction at FPI-PEIE/CH3NH3PbI3 interface. Furthermore, the FPI-PEIE can also tune the work function of ITO and dope PC61BM to promote the efficient electron transport between ITO and PC61BM. Based on the advantages of room-temperature processability and decent electrical property of FPI-PEIE/PC61BM EEL, a high-performance flexible PVSC with a PCE ~10% is eventually demonstrated. This study shows the potential of low-temperature processed organic EEL to replace transition metal oxide-based interlayers for highly printing compatible PVSCs with high-performance.In this work, we describe a room-temperature, solution-processable organic electron extraction layer (EEL) for high-performance planar heterojunction perovskite solar cells (PHJ PVSCs). This EEL is composed of a bilayered fulleropyrrolidinium iodide (FPI)-polyethyleneimine (PEIE) and PC61BM, which yields a promising power conversion efficiency (PCE) of 15.7% with insignificant hysteresis. We reveal that PC61BM can serve as a surface modifier of FPI-PEIE to simultaneously facilitate the crystallization of perovskite and the charge extraction at FPI-PEIE/CH3NH3PbI3 interface. Furthermore, the FPI-PEIE can also tune the work function of ITO and dope PC61BM to promote the efficient electron transport between ITO and PC61BM. Based on the advantages of room-temperature processability and decent electrical property of FPI-PEIE/PC61BM EEL, a high-performance flexible PVSC with a PCE ~10% is

  9. Formation of perovskite BiFeO3(001) films on refined Pt(111) electrode layer with reduced thickness on glass substrates

    NASA Astrophysics Data System (ADS)

    Chang, H. W.; Yuan, F. T.; Tien, S. H.; Tu, K. T.; Wang, C. R.; Jen, S. U.

    2014-05-01

    Structure and ferroelectric properties of multiferroic BiFeO3 (001) films grown on Pt(111) buffer layer with thicknesses of 5-50 nm on glass substrate at 500 °C have been studied. (001) texture of the perovskite BiFeO3 (BFO) could be developed. Grain size and morphology of the BFO(001) films were closely related to those of Pt electrode although no epitaxial growth was evidenced. The optimized BFO layer which exhibited the ferroelectric performance comparable to those with SrRuO3 under layer could be achieved in the samples with Pt thickness in the range of 10 to 20 nm. Different from the polycrystalline BFO/SrRuO3 films, large grain size for 50-nm-thick Pt underlayer causes degeneration of both the ferroelectric properties and the (001)-texture due to the formation of the secondary B2O3 phase. On the other hand, reducing Pt thickness to 5 nm resulted in the induction of the pinholes and thus the increase of the leakage current density. The presented results reveal that a smooth interface between the Pt electrode and BFO layer is essential to achieve good ferroelectric properties.

  10. The Structural Disorder and Lattice Stability of (Ba,Sr)(Co,Fe)O3 Complex Perovskites

    SciTech Connect

    S.N.Rashkeev

    2011-05-01

    The structural disorder and lattice stability of complex perovskite (Ba,Sr)(Co,Fe)O3, a promising cathode material for solid oxide fuel cells and oxygen permeation membranes, is explored by means of first principles DFT calculations. It is predicted that Ba and Sr ions easily exchange their lattice positions (A-cation disorder) similarly to Co and Fe ions (B-cation disorder). The cation antisite defects (exchange of A- and B-type cations) have a relatively high formation energy. The BSCF is predicted to exist in an equilibrium mixture of several phases and can decompose exothermically into the Ba- and Co-rich hexagonal (Ba,Sr)CoO3 and Sr- and Fe-rich cubic (Ba,Sr)FeO3 perovskites.

  11. Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO{sub 3}

    SciTech Connect

    Dixon, Charlotte A.L.; Kavanagh, Christopher M.; Knight, Kevin S.; Kockelmann, Winfried; Morrison, Finlay D.; Lightfoot, Philip

    2015-10-15

    The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO{sub 3} has been studied in detail by powder neutron diffraction in the temperature range 25perovskite LaFeO{sub 3} is rationalized from a detailed powder neutron diffraction study. - Highlights: • Crystal structure of the perovskite LaFeO{sub 3} studied in detail by powder neutron diffraction. • Unusual thermal evolution of lattice metrics rationalized. • Contrasting behavior to Bi-doped LaFeO{sub 3}. • Octahedral distortion/tilt parameters explain unusual a and c lattice parameter behavior.

  12. Highly Efficient, Reproducible, Uniform (CH3 NH3 )PbI3 Layer by Processing Additive Dripping for Solution-Processed Planar Heterojunction Perovskite Solar Cells.

    PubMed

    Kim, Hansol; Jeong, Hanbin; Lee, Jae Kwan

    2016-09-01

    A processing additive dripping (PAD) approach to forming highly efficient (CH3 NH3 )PbI3 (MAPbI3 ) perovskite layers was investigated. A MAPbI3 (CB/DIO) perovskite film fabricated by this approach, which included briefly dripping chlorobenzene incorporating a small amount of diiodooctane (DIO) during casting of a MAPbI3 perovskite precursor dissolved in dimethylformamide, exhibited superior smooth, uniform morphologies with high crystallinity and large grains and revealed completely homogeneous surface coverage. The surface coverage and morphology of the substrate significantly affected the photovoltaic performance of planar heterojunction (PHJ) perovskite solar cells (PrSCs), resulting in a power conversion efficiency of 11.45 % with high open-circuit voltage of 0.91 V and the highest fill factor of 80.87 %. Moreover, the PAD approach could effectively provide efficient MAPbI3 (CB/DIO) perovskite layers for highly efficient, reproducible, uniform PHJ PrSC devices without performance loss or variation even over larger active areas. PMID:27414840

  13. Nanometer-scale separation of d(10) Zn(2+)-layers and twin-shift competition in Ba8ZnNb6O24-based 8-layered hexagonal perovskites.

    PubMed

    Lu, Fengqi; Wang, Xiaoming; Pan, Zhengwei; Pan, Fengjuan; Chai, Shiqiang; Liang, Chaolun; Wang, Quanchao; Wang, Jing; Fang, Liang; Kuang, Xiaojun; Jing, Xiping

    2015-08-01

    The 8-layered shifted hexagonal perovskite compound Ba8ZnNb6O24 was isolated via controlling the ZnO volatilization, which features long-range B-cation ordering with nanometer-scale separation by ∼1.9 nm of octahedral d(10) cationic (Zn(2+)) layers within the purely corner-sharing octahedral d(0) cationic (Nb(5+)) host. The long-range ordering of the B-site vacancy and out-of-center distortion of the highly-charged d(0) Nb(5+) that is assisted by the second-order Jahn-Teller effect contribute to this unusual B-cation ordering in Ba8ZnNb6O24. A small amount (∼15%) of d(10) Sb(5+) substitution for Nb(5+) in Ba8ZnNb6-xSbxO24 dramatically transformed the shifted structure to a twinned structure, in contrast with the Ba8ZnNb6-xTaxO24 case requiring 50% d(0) Ta(5+) substitution for Nb(5+) for such a shift-to-twin transformation. Multiple factors including B-cationic sizes, electrostatic repulsion forces, long-range ordering of B-site vacancies, and bonding preferences arising from a covalent contribution to the B-O bonding that includes out-of-center octahedral distortion and the B-O-B bonding angle could subtly contribute to the twin-shift phase competition of B-site deficient 8-layered hexagonal perovskites Ba8B7O24. The ceramics of new shifted Ba8ZnNb6O24 and twinned Ba8ZnNb5.1Sb0.9O24 compounds exhibited good microwave dielectric properties (εr ∼ 35, Qf ∼ 36 200-43 400 GHz and τf ∼ 38-44 ppm/°C). PMID:26110444

  14. First principle study of band structure of SrMO3 perovskites

    NASA Astrophysics Data System (ADS)

    Daga, Avinash; Sharma, Smita

    2016-05-01

    First principle study of band structure calculations in the local density approximations (LDA) as well as in the generalized gradient approximations (GGA) have been used to determine the electronic structure of SrMO3 where M stands for Ti, Zr and Mo. Occurrence of band gap proves SrTiO3 and SrZrO3 to be insulating. A small band gap is observed in SrMoO3 perovskite signifies it to be metallic. Band structures are found to compare well with the available data in the literature showing the relevance of this approach. ABINIT computer code has been used to carry out all the calculations.

  15. CaTiO.sub.3 Interfacial template structure on semiconductor-based material and the growth of electroceramic thin-films in the perovskite class

    DOEpatents

    McKee, Rodney Allen; Walker, Frederick Joseph

    1998-01-01

    A structure including a film of a desired perovskite oxide which overlies and is fully commensurate with the material surface of a semiconductor-based substrate and an associated process for constructing the structure involves the build up of an interfacial template film of perovskite between the material surface and the desired perovskite film. The lattice parameters of the material surface and the perovskite of the template film are taken into account so that during the growth of the perovskite template film upon the material surface, the orientation of the perovskite of the template is rotated 45.degree. with respect to the orientation of the underlying material surface and thereby effects a transition in the lattice structure from fcc (of the semiconductor-based material) to the simple cubic lattice structure of perovskite while the fully commensurate periodicity between the perovskite template film and the underlying material surface is maintained. The film-growth techniques of the invention can be used to fabricate solid state electrical components wherein a perovskite film is built up upon a semiconductor-based material and the perovskite film is adapted to exhibit ferroelectric, piezoelectric, pyroelectric, electro-optic or large dielectric properties during use of the component.

  16. Strong coupling of exciton and photon modes in photonic crystal infiltrated with organic-inorganic layered perovskite

    NASA Astrophysics Data System (ADS)

    Sumioka, Kazuhiro; Nagahama, Hiroyuki; Tsutsui, Tetsuo

    2001-03-01

    Large vacuum Rabi-splitting, the evidence of strong coupling of photon and exciton modes, was observed at room temperature in an ordered array of silica microspheres infiltrated with organic-inorganic layered perovskite. By natural sedimentation of a colloidal suspension of monodispersed silica microspheres with a diameter of 256 nm, three-dimensional ordered array of silica microspheres (silica opal) were prepared. Into an air space of the silica opal, organic-inorganic perovskite, bis-(phenethylammonium) tetraiodoplumbate (PAPI), which exhibits intense exciton absorption at 2.40 eV, was infiltrated. The silica opal infiltrated with PAPI (23% of air space was filled) exhibited a stop band at 2.13 eV, when observed at a normal direction to the sample surface. By changing the observation angle, the coupling of the stop band at around 2.1-2.4 eV and the exciton band at 2.40 eV due to PAPI was attained. From angle-tuning measurements of reflection spectra, a vacuum Rabi-splitting of 240 meV was evaluated.

  17. Synthesis, crystal structure and magnetic properties of a new pillared perovskite La{sub 5}Mo{sub 2.75}V{sub 1.25}O{sub 16}

    SciTech Connect

    Ramezanipour, Farshid; Derakhshan, Shahab; Greedan, John E. Cranswick, Lachlan M.D.

    2008-12-15

    A new pillared perovskite compound La{sub 5}Mo{sub 2.76(4)}V{sub 1.25(4)}O{sub 16}, has been synthesized by solid-state reaction and its crystal structure has been characterized using powder X-ray and neutron diffraction. The magnetic properties of this compound have been investigated using SQUID magnetometry, and the magnetic structure has been studied using neutron diffraction data. A theoretical calculation of relative strengths of spin interactions among different magnetic ions and through different pathways has been performed using extended Hueckel, spin dimer analysis. The crystal structure of this material contains perovskite-type layers that are connected through edge-sharing dimeric units of octahedra. The structure is described in space group C2/m with unit cell parameters a=7.931(2) A, b=7.913(2) A, c=10.346(5) A and {beta}=95.096(5){sup o}. The material shows both short-range ferrimagnetic correlations from {approx}200 to 110 K and long-range antiferromagnetic order below T{sub c}{approx}100 K. The magnetic structure was investigated by neutron diffraction and is described by k=(0 0 1/2 ) as for other pillared perovskites. It consists of a ferrimagnetic arrangement of Mo and V within the layers that are coupled antiferromagnetically between layers. This is the first magnetic structure determination for any Mo-based pillared perovskite. - Graphical abstract: Long-range magnetic order below 100 K in the pillared perovskite La{sub 5}Mo{sub 2.75}V{sub 1.25}O{sub 16}. The magnetic structure is shown in the inset.

  18. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    SciTech Connect

    Katayama, Tsukasa; Chikamatsu, Akira Kamisaka, Hideyuki; Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2015-10-15

    The substitution of hydride anions (H{sup −}) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoO{sub x}H{sub y} thin films via the topotactic hydride doping of brownmillerite SrCoO{sub 2.5} epitaxial thin films with CaH{sub 2}. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H{sup −}-Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO{sub 3−x}H{sub x} (M = Cr, Ti, V). The SrCoO{sub x}H{sub y} thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  19. Crystal structure of post-perovskite-type CaIrO3 reinvestigated: new insights into atomic thermal vibration behaviors

    PubMed Central

    Nakatsuka, Akihiko; Sugiyama, Kazumasa; Yoneda, Akira; Fujiwara, Keiko; Yoshiasa, Akira

    2015-01-01

    Single crystals of the title compound, the post-perovskite-type CaIrO3 [calcium iridium(IV) trioxide], have been grown from a CaCl2 flux at atmospheric pressure. The crystal structure consists of an alternate stacking of IrO6 octa­hedral layers and CaO8 hendeca­hedral layers along [010]. Chains formed by edge-sharing of IrO6 octa­hedra (point-group symmetry 2/m..) run along [100] and are inter­connected along [001] by sharing apical O atoms to build up the IrO6 octa­hedral layers. Chains formed by face-sharing of CaO8 hendeca­hedra (point-group symmetry m2m) run along [100] and are inter­connected along [001] by edge-sharing to build up the CaO8 hendeca­hedral layers. The IrO6 octa­hedral layers and CaO8 hendeca­hedral layers are inter­connected by sharing edges. The present structure refinement using a high-power X-ray source confirms the atomic positions determined by Hirai et al. (2009 ▸) [Z. Kristallogr. 224, 345–350], who had revised our previous report [Sugahara et al. (2008 ▸). Am. Mineral. 93, 1148–1152]. However, the displacement ellipsoids of the Ir and Ca atoms based on the present refinement can be approximated as uniaxial ellipsoids elongating along [100], unlike those reported by Hirai et al. (2009 ▸). This suggests that the thermal vibrations of the Ir and Ca atoms are mutually suppressed towards the Ir⋯Ca direction across the shared edge because of the dominant repulsion between the two atoms. PMID:26396860

  20. Perovskite solar cells with a planar heterojunction structure prepared using room-temperature solution processing techniques

    NASA Astrophysics Data System (ADS)

    Liu, Dianyi; Kelly, Timothy L.

    2014-02-01

    Organic-inorganic hybrid solar cells that combine a mesoporous scaffold, a perovskite light absorber and an organic hole transporter have emerged at the forefront of solution-processable photovoltaic devices; however, they require processing temperatures of up to 500 °C to sinter the mesoporous metal-oxide support. Here, we report the use of a thin film of ZnO nanoparticles as an electron-transport layer in CH3NH3PbI3-based solar cells; in contrast to mesoporous TiO2, the ZnO layer is both substantially thinner and requires no sintering. We took advantage of these facts to prepare flexible solar cells with power-conversion efficiencies in excess of 10%. The use of ZnO also results in improvements to device performance for cells prepared on rigid substrates. Solar cells based on this design exhibit power-conversion efficiencies as high as 15.7% when measured under AM1.5G illumination, which makes them some of the highest-performing perovskite solar cells reported to date.

  1. Scalable fabrication of efficient organolead trihalide perovskite solar cells with doctor-bladed active layers

    DOE PAGESBeta

    Deng, Yehao; Peng, Edwin; Shao, Yuchuan; Xiao, Zhengguo; Dong, Qingfeng; Huang, Jinsong

    2015-03-25

    Organolead trihalide perovskites (OTPs) are nature abundant materials with prospects as future low-cost renewable energy sources boosted by the solution process capability of these materials. Here we report the fabrication of efficient OTP devices by a simple, high throughput and low-cost doctor-blade coating process which can be compatible with the roll-to-roll fabrication process for the large scale production of perovskite solar cell panels. The formulation of appropriate precursor inks by removing impurities is shown to be critical in the formation of continuous, pin-hole free and phase-pure perovskite films on large area substrates, which is assisted by a high deposition temperaturemore » to guide the nucleation and grain growth process. The domain size reached 80–250 μm in 1.5–2 μm thick bladed films. By controlling the stoichiometry and thickness of the OTP films, highest device efficiencies of 12.8% and 15.1% are achieved in the devices fabricated on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and cross-linked N4,N4'-bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyl)phenyl)–N4,N4'-diphenylbiphenyl-4,4'-diamine covered ITO substrates. Furthermore, the carrier diffusion length in doctor-bladed OTP films is beyond 3.5 μm which is significantly larger than in the spin-coated films, due to the formation of crystalline grains with a very large size by the doctor-blade coating method.« less

  2. Scalable fabrication of efficient organolead trihalide perovskite solar cells with doctor-bladed active layers

    SciTech Connect

    Deng, Yehao; Peng, Edwin; Shao, Yuchuan; Xiao, Zhengguo; Dong, Qingfeng; Huang, Jinsong

    2015-03-25

    Organolead trihalide perovskites (OTPs) are nature abundant materials with prospects as future low-cost renewable energy sources boosted by the solution process capability of these materials. Here we report the fabrication of efficient OTP devices by a simple, high throughput and low-cost doctor-blade coating process which can be compatible with the roll-to-roll fabrication process for the large scale production of perovskite solar cell panels. The formulation of appropriate precursor inks by removing impurities is shown to be critical in the formation of continuous, pin-hole free and phase-pure perovskite films on large area substrates, which is assisted by a high deposition temperature to guide the nucleation and grain growth process. The domain size reached 80–250 μm in 1.5–2 μm thick bladed films. By controlling the stoichiometry and thickness of the OTP films, highest device efficiencies of 12.8% and 15.1% are achieved in the devices fabricated on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and cross-linked N4,N4'-bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyl)phenyl)–N4,N4'-diphenylbiphenyl-4,4'-diamine covered ITO substrates. Furthermore, the carrier diffusion length in doctor-bladed OTP films is beyond 3.5 μm which is significantly larger than in the spin-coated films, due to the formation of crystalline grains with a very large size by the doctor-blade coating method.

  3. Single step deposition of an interacting layer of a perovskite matrix with embedded quantum dots

    NASA Astrophysics Data System (ADS)

    Ngo, Thi Tuyen; Suarez, Isaac; Sanchez, Rafael S.; Martinez-Pastor, Juan P.; Mora-Sero, Ivan

    2016-07-01

    Hybrid lead halide perovskite (PS) derivatives have emerged as very promising materials for the development of optoelectronic devices in the last few years. At the same time, inorganic nanocrystals with quantum confinement (QDs) possess unique properties that make them suitable materials for the development of photovoltaics, imaging and lighting applications, among others. In this work, we report on a new methodology for the deposition of high quality, large grain size and pinhole free PS films (CH3NH3PbI3) with embedded PbS and PbS/CdS core/shell Quantum Dots (QDs). The strong interaction between both semiconductors is revealed by the formation of an exciplex state, which is monitored by photoluminescence and electroluminescence experiments. The radiative exciplex relaxation is centered in the near infrared region (NIR), ~1200 nm, which corresponds to lower energies than the corresponding band gap of both perovskite (PS) and QDs. Our approach allows the fabrication of multi-wavelength light emitting diodes (LEDs) based on a PS matrix with embedded QDs, which show considerably low turn-on potentials. The presence of the exciplex state of PS and QDs opens up a broad range of possibilities with important implications in both LEDs and solar cells.Hybrid lead halide perovskite (PS) derivatives have emerged as very promising materials for the development of optoelectronic devices in the last few years. At the same time, inorganic nanocrystals with quantum confinement (QDs) possess unique properties that make them suitable materials for the development of photovoltaics, imaging and lighting applications, among others. In this work, we report on a new methodology for the deposition of high quality, large grain size and pinhole free PS films (CH3NH3PbI3) with embedded PbS and PbS/CdS core/shell Quantum Dots (QDs). The strong interaction between both semiconductors is revealed by the formation of an exciplex state, which is monitored by photoluminescence and

  4. Identifying the Molecular Structures of Intermediates for Optimizing the Fabrication of High-Quality Perovskite Films.

    PubMed

    Cao, Jing; Jing, Xiaojing; Yan, Juanzhu; Hu, Chengyi; Chen, Ruihao; Yin, Jun; Li, Jing; Zheng, Nanfeng

    2016-08-10

    During the past two years, the introduction of DMSO has revolutionized the fabrication of high-quality pervoskite MAPbI3 (MA = CH3NH3) films for solar cell applications. In the developed DMSO process, the formation of (MA)2Pb3I8·2DMSO (shorted as Pb3I8) has well recognized as a critical factor to prepare high-quality pervoskite films and thus accomplish excellent performances in perovskite solar cells. However, Pb3I8 is an I-deficient intermediate and must further react with methylammonium iodide (MAI) to be fully converted into MAPbI3. By capturing and solving the molecular structures of several intermediates involved in the fabrication of perovskite films, we report in this work that the importance of DMSO is NOT due to the formation of Pb3I8. The use of different PbI2-DMSO ratios leads to two different structures of PbI2-DMSO precursors (PbI2·DMSO and PbI2·2DMSO), thus dramatically influencing the quality of fabricated perovskite films. However, such an influence can be minimized when the PbI2-DMSO precursor films are thermally treated to create mesoporous PbI2 films before reacting with MAI. Such a development makes the fabrication of high-quality pervoskite films highly reproducible without the need to precisely control the PbI2:DMSO ratio. Moreover, the formation of ionic compound (MA)4PbI6 is observed when excess MAI is used in the preparation of perovskite film. This I-rich phase heavily induces the hysteresis in PSCs, but is readily removed by isopropanol treatment. On the basis of all these findings, we develop a new effective protocol to fabricate high-performance PSCs. In the new protocol, high-quality perovskite films are prepared by simply treating the mesoporous PbI2 films (made from PbI2-DMSO precursors) with an isopropanol solution of MAI, followed by isopropanol washing. The best efficiency of fabricated MAPbI3 PSCs is up to 19.0%. As compared to the previously reported DMSO method, the devices fabricated by the method reported in this work

  5. Magnetization and magneto-transport staircaselike behavior in layered perovskite Sr2CoO4 at low temperature

    NASA Astrophysics Data System (ADS)

    Li, Qiuhang; Yuan, Xueping; Xing, Lei; Xu, Mingxiang

    2016-06-01

    Polycrystalline layered perovskite Sr2CoO4 sample was synthesized by high temperature and high pressure method. The staircaselike behavior has been observed in the magnetization and resistivity versus field curves of Sr2CoO4 at low temperature. The main features of the steps can be obtained from the measured results: (i) the positions of the external magnetic field at which steps occur are varying in different measurement runs, (ii) the steps only appear at low temperature and disappear with a slight increase of the temperature, (iii) the steps are dependent on the temperature and field sweep rate. Based on the features of the magnetization and magneto-transport staircaselike behavior in Sr2CoO4, the unusual phenomenon can be ascribed to an avalanche of flipping domains in terms of the random field theory.

  6. Magnetization and magneto-transport staircaselike behavior in layered perovskite Sr2CoO4 at low temperature

    PubMed Central

    Li, Qiuhang; Yuan, Xueping; Xing, Lei; Xu, Mingxiang

    2016-01-01

    Polycrystalline layered perovskite Sr2CoO4 sample was synthesized by high temperature and high pressure method. The staircaselike behavior has been observed in the magnetization and resistivity versus field curves of Sr2CoO4 at low temperature. The main features of the steps can be obtained from the measured results: (i) the positions of the external magnetic field at which steps occur are varying in different measurement runs, (ii) the steps only appear at low temperature and disappear with a slight increase of the temperature, (iii) the steps are dependent on the temperature and field sweep rate. Based on the features of the magnetization and magneto-transport staircaselike behavior in Sr2CoO4, the unusual phenomenon can be ascribed to an avalanche of flipping domains in terms of the random field theory. PMID:27293142

  7. A composite nanostructured electron-transport layer for stable hole-conductor free perovskite solar cells: design and characterization.

    PubMed

    Yu, Zhenhua; Qi, Fei; Liu, Pei; You, Sujian; Kondamareddy, Kiran Kumar; Wang, Changlei; Cheng, Nian; Bai, Sihang; Liu, Wei; Guo, Shishang; Zhao, Xing-zhong

    2016-03-21

    A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility. PMID:26932777

  8. Magnetization and magneto-transport staircaselike behavior in layered perovskite Sr2CoO4 at low temperature.

    PubMed

    Li, Qiuhang; Yuan, Xueping; Xing, Lei; Xu, Mingxiang

    2016-01-01

    Polycrystalline layered perovskite Sr2CoO4 sample was synthesized by high temperature and high pressure method. The staircaselike behavior has been observed in the magnetization and resistivity versus field curves of Sr2CoO4 at low temperature. The main features of the steps can be obtained from the measured results: (i) the positions of the external magnetic field at which steps occur are varying in different measurement runs, (ii) the steps only appear at low temperature and disappear with a slight increase of the temperature, (iii) the steps are dependent on the temperature and field sweep rate. Based on the features of the magnetization and magneto-transport staircaselike behavior in Sr2CoO4, the unusual phenomenon can be ascribed to an avalanche of flipping domains in terms of the random field theory. PMID:27293142

  9. Efficient All-Vacuum Deposited Perovskite Solar Cells by Controlling Reagent Partial Pressure in High Vacuum.

    PubMed

    Hsiao, Sheng-Yi; Lin, Hong-Lin; Lee, Wei-Hung; Tsai, Wei-Lun; Chiang, Kai-Ming; Liao, Wei-Yu; Ren-Wu, Chen-Zheng; Chen, Chien-Yu; Lin, Hao-Wu

    2016-08-01

    All-vacuum-deposited perovskite solar cells produced by controlling reagent partial pressure in high vacuum with newly developed multi-layer electron and hole transporting structures show outstanding power conversion efficiency of 17.6% and smooth, pinhole-free, micrometer-sized perovskite crystal grains. PMID:27226143

  10. Room-Temperature Solution-Processed NiOx:PbI2 Nanocomposite Structures for Realizing High-Performance Perovskite Photodetectors.

    PubMed

    Zhu, Hugh Lu; Cheng, Jiaqi; Zhang, Di; Liang, Chunjun; Reckmeier, Claas J; Huang, He; Rogach, Andrey L; Choy, Wallace C H

    2016-07-26

    While methylammonium lead iodide (MAPbI3) with interesting properties, such as a direct band gap, high and well-balanced electron/hole mobilities, as well as long electron/hole diffusion length, is a potential candidate to become the light absorbers in photodetectors, the challenges for realizing efficient perovskite photodetectors are to suppress dark current, to increase linear dynamic range, and to achieve high specific detectivity and fast response speed. Here, we demonstrate NiOx:PbI2 nanocomposite structures, which can offer dual roles of functioning as an efficient hole extraction layer and favoring the formation of high-quality MAPbI3 to address these challenges. We introduce a room-temperature solution process to form the NiOx:PbI2 nanocomposite structures. The nanocomposite structures facilitate the growth of the compact and ordered MAPbI3 crystalline films, which is essential for efficient photodetectors. Furthermore, the nanocomposite structures work as an effective hole extraction layer, which provides a large electron injection barrier and favorable hole extraction as well as passivates the surface of the perovskite, leading to suppressed dark current and enhanced photocurrent. By optimizing the NiOx:PbI2 nanocomposite structures, a low dark current density of 2 × 10(-10) A/cm(2) at -200 mV and a large linear dynamic range of 112 dB are achieved. Meanwhile, a high responsivity in the visible spectral range of 450-750 nm, a large measured specific detectivity approaching 10(13) Jones, and a fast fall time of 168 ns are demonstrated. The high-performance perovskite photodetectors demonstrated here offer a promising candidate for low-cost and high-performance near-ultraviolet-visible photodetection. PMID:27340899

  11. Single step deposition of an interacting layer of a perovskite matrix with embedded quantum dots.

    PubMed

    Ngo, Thi Tuyen; Suarez, Isaac; Sanchez, Rafael S; Martinez-Pastor, Juan P; Mora-Sero, Ivan

    2016-08-14

    Hybrid lead halide perovskite (PS) derivatives have emerged as very promising materials for the development of optoelectronic devices in the last few years. At the same time, inorganic nanocrystals with quantum confinement (QDs) possess unique properties that make them suitable materials for the development of photovoltaics, imaging and lighting applications, among others. In this work, we report on a new methodology for the deposition of high quality, large grain size and pinhole free PS films (CH3NH3PbI3) with embedded PbS and PbS/CdS core/shell Quantum Dots (QDs). The strong interaction between both semiconductors is revealed by the formation of an exciplex state, which is monitored by photoluminescence and electroluminescence experiments. The radiative exciplex relaxation is centered in the near infrared region (NIR), ≈1200 nm, which corresponds to lower energies than the corresponding band gap of both perovskite (PS) and QDs. Our approach allows the fabrication of multi-wavelength light emitting diodes (LEDs) based on a PS matrix with embedded QDs, which show considerably low turn-on potentials. The presence of the exciplex state of PS and QDs opens up a broad range of possibilities with important implications in both LEDs and solar cells. PMID:27437778

  12. The electronic structure of metal oxide/organo metal halide perovskite junctions in perovskite based solar cells

    PubMed Central

    Dymshits, Alex; Henning, Alex; Segev, Gideon; Rosenwaks, Yossi; Etgar, Lioz

    2015-01-01

    Cross-sections of a hole-conductor-free CH3NH3PbI3 perovskite solar cell were characterized with Kelvin probe force microscopy. A depletion region width of about 45 nm was determined from the measured potential profiles at the interface between CH3NH3PbI3 and nanocrystalline TiO2, whereas a negligible depletion was measured at the CH3NH3PbI3/Al2O3 interface. A complete solar cell can be realized with the CH3NH3PbI3 that functions both as light harvester and hole conductor in combination with a metal oxide. The band diagrams were estimated from the measured potential profile at the interfaces, and are critical findings for a better understanding and further improvement of perovskite based solar cells. PMID:25731963

  13. High temperature neutron diffraction studies of PrInO3 and the measures of perovskite structure distortion.

    PubMed

    Baszczuk, A; Dabrowski, B; Avdeev, M

    2015-06-21

    The crystal structure of PrInO(3) was investigated in the temperature range 303-1123 K by high-resolution neutron-powder diffraction. The PrInO(3) adopts a highly distorted variant of the perovskite structure with the orthorhombic Pnma space group in the whole temperature range investigated. The bond length and bond-angle analysis revealed a very slow tendency to decrease structural distortion with increasing temperature. Comparison of different parameters quantifying perovskite structure distortion calculated for PrInO(3) and the similar PrAlO(3) and PrGaO(3) shows the advantage of using the tolerance factor t12 calculated for the 12-fold coordinated Pr by geometrical averaging of the individual interatomic distances. An additional advantage of the tolerance factor method results from the possibility of extending it to predict the average structural distortion and the geometrical stability of the perovskites at various temperatures once the accurate dependence of t(x,T,d) on the composition, temperature and oxygen content is found. By comparing PrInO(3) with several AMO(3) perovskites containing ions in the fixed oxidation state on the A and M crystal sites it was found that structural distortion and the tolerance factor t12 for PrInO(3) are consistent with the empirical thermal expansion coefficient based on the bond strength calculation [R. M. Hazen, and C. T. Prewitt, Am. Mineral., 1977, 62(3-4), 309]. In contrast to perovskites AMO(3-d) containing mixed-valent M ions, which allow for a wide range of changes of the tolerance factor t(12)(T,d) as a function of oxygen content, perovskites AMO(3) with M ions in the fixed oxidation state show much less flexibility. This flexibility is further reduced for the A(3+)M(3+)O(3) perovskites like PrInO(3) for which even a large change of the synthesis temperature has a minor effect on controlling the resulting t(12)(T) and the structural phase in comparison with A(2+)M(4+)O3 perovskites. The only parameter left for A(3+)M

  14. Application of mesoporous SiO2 layer as an insulating layer in high performance hole transport material free CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Cheng, Nian; Liu, Pei; Bai, Sihang; Yu, Zhenhua; Liu, Wei; Guo, Shi-Shang; Zhao, Xing-Zhong

    2016-07-01

    A mesoporous SiO2 layer is successfully introduced into the hole transport material free perovskite solar cells by spin-coating a SiO2 paste onto the TiO2 scaffold layer. This SiO2 layer can act as an insulating layer and effectively inhibit the charge recombination between the TiO2 layer and carbon electrode. The variation of power conversion efficiencies with the thickness of SiO2 layer is studied here. Under optimized SiO2 thickness, perovskite solar cell fabricated on the TiO2/SiO2 film shows a superior power conversion efficiency of ∼12% and exhibits excellent long time stability for 30 days.

  15. Structural determination and electronic properties of the 4d perovskite SrPdO3

    NASA Astrophysics Data System (ADS)

    He, Jiangang; Franchini, Cesare

    2014-01-01

    The structure and ground state electronic structure of the recently synthesized SrPdO3 perovskite [A. Galal et al. J. Power Sources 195, 3806 (2010), 10.1016/j.jpowsour.2009.12.091] have been studied by means of screened hybrid functional and the GW approximation with the inclusion of electron-hole interaction within the test-charge/test-charge scheme. By conducting a structural search based on lattice dynamics and group theoretical method we identify the orthorhombic phase with Pnma space group as the most stable crystal structure. The phase transition from the ideal cubic perovskite structure to the Pnma one is explained in terms of the simultaneous stabilization of the antiferrodistortive phonon modes R4+ and M3+. Our results indicate that SrPdO3 exhibits an insulating ground state, substantiated by a GW0 gap of about 1.1 eV. Spin polarized calculations suggest that SrPdO3 adopts a low spin state (t2g↑↓↑↓↑↓eg0), and is expected to exhibit spin excitations and spin state crossovers at finite temperature, analogous to the case of 3d isoelectronic LaCoO3. This would provide another playground for the study of spin state transitions in 4d oxides and an opportunity to design multifunctional materials based on the 4d Pnma building block.

  16. Structure-property relationships of BaCeO perovskites for the oxidative dehydrogenation of alkanes

    SciTech Connect

    Nenoff, T.M.; Jackson, N.B.; Miller, J.E.; Sault, A.G.; Trudell, D.

    1997-12-01

    The oxidative dehydrogenation (ODH) reactions for the formation of two important organic feedstocks ethylene and propylene are of great interest because of the potential in capital and energy savings associated with these reactions. Theoretically, ODH can achieve high conversions of the starting materials (ethane and propane) at lower temperatures than conventional dehydrogenation reactions. The important focus in this study of ODH catalysts is the development of a structure-property relationship for catalyst with respect to selectivity, so as to avoid the more thermodynamically favorable combustion reaction. Catalysts for the ODH reaction generally consist of mixed metal oxides. Since for the most selective catalyst lattice oxygen is known to participate in the reaction, catalysts are sought with surface oxygen atoms that are labile enough to perform dehydrogenation, but not so plentiful or weakly bound as to promote complete combustion. Also, catalysts must be able to replenish surface oxygen by transport from the bulk. Perovskite materials are candidates to fulfill these requirements. The authors are studying BaCeO{sub 3} perovskites doped with elements such as Ca, Mg, and Sr. During the ODH of the alkanes at high temperatures, the perovskite structure is not retained and a mixture of carbonates and oxides is formed, as revealed by XRD. While the Ca doped materials showed enhanced total combustion activity below 600 C, they only showed enhanced alkene production at 700 C. Bulk structural and surface changes, as monitored by powder X-ray diffraction, and X-ray photoelectron spectroscopy are being correlated with activity in order to understand the factors affecting catalyst performance, and to modify catalyst formulations to improve conversion and selectivity.

  17. Modeling of optical losses in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Taghavi, M. Javad; Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.

    2016-09-01

    The optical losses within the structure of hybrid perovskite solar cells are investigated using only the optical properties of each layer e.g. refractive index and extinction coefficient. This model allows calculating the transmission/reflection rates at the interfaces and absorption loss within any layer. Then, the short circuit current density and loss percentage are calculated versus the perovskite and TiO2 thicknesses from 50 nm to 150 nm. To make our calculations closer to reality, we extracted the optical properties of each device component from the literature reports on glass/TCO/TiO2/perovskite/metal. The simulations were fitted with the experimental results of some relevant references. Our simulations show that ITO transmits the light better than SnO2 as the TCO front electrode, and the light reflection at both sides of the perovskite layer, e.g. at TiO2/perovskite and perovskite/Spiro-OMeTAD, is lower than 25%. The light interference and multiple reflections have been accounted in our calculations and finally we showed that a thicker TiO2 and perovskite cause more optical loss in current density due to stronger absorption.

  18. Revised structural phase transitions in the archetype KMnF3 perovskite crystal

    NASA Astrophysics Data System (ADS)

    Kapusta, Joanna; Daniel, Philippe; Ratuszna, Alicja

    1999-06-01

    Reinvestigation of the structural and vibrational properties of the typical perovskite KMnF3, exhibiting two antiferrodistortive structural phase transitions, was performed using x-ray powder diffraction and Raman spectroscopy in the range between 30 and 300 K. The x-ray-diffraction work has unambiguously shown that a monoclinic distortion (ra-b+c- tilt system P21/m space group) is observed at low temperature below TC2=91 K. This result corresponds with the Raman temperature study which shows that this transition, in spite of its first-order character, can be associated with a group-subgroup relation between tetragonal and monoclinic symmetries. Additionally, existence of a large structural disorder far above the cubic to tetragonal transition (TC1=186 K) is suggested by the two following experimental indications: (i) persistence of hard modes of the tetragonal phase in the cubic symmetry, and (ii) existence of Raman broad bands in normally inactive ideal cubic phase, which are interpreted by the folding of the whole phonons branches of the cubic Brillouin zone. This last observation allows us to follow the evolution of the cubic R'15 soft mode versus temperature, based only on the Raman-scattering data, in full agreement with previous inelastic neutron data. The results of Raman investigations into KMnF3 are discussed in more general framework of structural disorder in perovskite systems which exhibit anisotropic correlation between octahedra.

  19. High-pressure synthesis, crystal structure and magnetic properties of TlCrO3 perovskite.

    PubMed

    Yi, Wei; Matsushita, Yoshitaka; Katsuya, Yoshio; Yamaura, Kazunari; Tsujimoto, Yoshihiro; Presniakov, Igor A; Sobolev, Alexey V; Glazkova, Yana S; Lekina, Yuliya O; Tsujii, Naohito; Nimori, Shigeki; Takehana, Kanji; Imanaka, Yasutaka; Belik, Alexei A

    2015-06-21

    TlMO(3) perovskites (M(3+) = transition metals) are exceptional members of trivalent perovskite families because of the strong covalency of Tl(3+)-O bonds. Here we report on the synthesis, crystal structure and properties of TlCrO(3) investigated by Mössbauer spectroscopy, specific heat, dc/ac magnetization and dielectric measurements. TlCrO(3) perovskite is prepared under high pressure (6 GPa) and high temperature (1500 K) conditions. The crystal structure of TlCrO(3) is refined using synchrotron X-ray powder diffraction data: space group Pnma (no. 62), Z = 4 and lattice parameters a = 5.40318(1) Å, b = 7.64699(1) Å and c = 5.30196(1) Å at 293 K. No structural phase transitions are found between 5 and 300 K. TlCrO(3) crystallizes in the GdFeO(3)-type structure similar to other members of the perovskite chromite family, ACrO(3) (A(3+) = Sc, In, Y and La-Lu). The unit cell volume and Cr-O-Cr bond angles of TlCrO(3) are close to those of DyCrO(3); however, the Néel temperature of TlCrO(3) (TN≈ 89 K) is much smaller than that of DyCrO(3) and close to that of InCrO(3). Isothermal magnetization studies show that TlCrO(3) is a fully compensated antiferromagnet similar to ScCrO(3) and InCrO(3), but different from RCrO(3) (R(3+) = Y and La-Lu). Ac and dc magnetization measurements with a fine step of 0.2 K reveal the existence of two Néel temperatures with very close values at T(N2) = 87.0 K and T(N1) = 89.3 K. Magnetic anomalies near T(N2 )are suppressed by static magnetic fields and by 5% iron doping. PMID:25730286

  20. Temperature and Pressure Sensors Based on Spin-Allowed Broadband Luminescence of Doped Orthorhombic Perovskite Structures

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I. (Inventor); Chambers, Matthew D. (Inventor)

    2014-01-01

    Systems and methods that are capable of measuring pressure or temperature based on luminescence are discussed herein. These systems and methods are based on spin-allowed broadband luminescence of sensors with orthorhombic perovskite structures of rare earth aluminates doped with chromium or similar transition metals, such as chromium-doped gadolinium aluminate. Luminescence from these sensors can be measured to determine at least one of temperature or pressure, based on either the intense luminescence of these sensors, even at high temperatures, or low temperature techniques discussed herein.

  1. Plasmonic Structure Enhanced Exciton Generation at the Interface between the Perovskite Absorber and Copper Nanoparticles

    PubMed Central

    Lin, Kuen-Feng; Chiang, Chien-Hung; Wu, Chun-Guey

    2014-01-01

    The refractive index and extinction coefficient of a triiodide perovskite absorber (TPA) were obtained by fitting the transmittance spectra of TPA/PEDOT:PSS/ITO/glass using the transfer matrix method. Cu nanoplasmonic structures were designed to enhance the exciton generation in the TPA and to simultaneously reduce the film thickness of the TPA. Excitons were effectively generated at the interface between TPA and Cu nanoparticles, as observed through the 3D finite-difference time-domain method. The exciton distribution is advantageous for the exciton dissociation and carrier transport. PMID:25295290

  2. Controlling the Cavity Structures of Two-Photon-Pumped Perovskite Microlasers.

    PubMed

    Zhang, Wei; Peng, Lan; Liu, Jie; Tang, Aiwei; Hu, Jin-Song; Yao, Jiannian; Zhao, Yong Sheng

    2016-06-01

    Low-threshold two-photon-pumped (TPP) perovskite microcavity lasers are achieved in crystal perovskite 1D or 2D microstructures fabricated through a liquid-phase self-assembly method assisted by two distinct surfactant soft templates. The lasing actions from the perovskite materials exhibit a shape-dependent microcavity effect, which is subsequently utilized for the modulation of the lasing modes and for the achievement of two-photon-pumped single-mode perovskite microlasers. PMID:27007487

  3. "Ba6Nb4RuO18" and "LaBa4Nb3RuO15" - The structural consequences of substituting paramagnetic cations into AnBn-1O3n cation-deficient perovskite oxides

    NASA Astrophysics Data System (ADS)

    Kamil, Elynor L.; Morgan, Harry W. T.; Hayward, Michael A.

    2016-06-01

    The B-cation deficient perovskite phases Ba6Nb4RuO18 and LaBa4Nb3RuO15 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 Ba6Nb4TiO18 and LaBa4Nb3TiO15) they adopt 5-layer and 4-layer B-cation deficient perovskite structures respectively, and are better described as Ba5Nb3.33Ru0.81O15 and Ba3.16La0.84Nb2.36Ru0.72O12. The factors that lead to the compositionally analogous Nb/Ru and Nb/Ti phases adopting different structures are discussed on the basis of the difference between d0 and non-d0 transition metal cations.

  4. 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

    2014-01-01

    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. PMID:24751601

  5. Dielectric response of double layered perovskite Sr3MnTiO7

    NASA Astrophysics Data System (ADS)

    Chowki, S.; Sahu, B.; Singh, A. K.; Mohapatra, N.

    2016-05-01

    The results of dielectric and resistivity measurements on the Ruddlesden-Popper (RP) type compound Sr3MnTiO7 (SMTO) is presented here. The dielectric response of the compound was recorded in the temperature range 10-300 K with the probing frequency from 500 Hz-5 MHz. We observe a broad anomaly at ~ 200 K in the temperature dependence of dissipation factor (tanδ) and corresponding change in slope in the dielectric constant ɛr'(T) which may be attributed to a difference in the conduction mechanism below and above 200 K. The overall dielectric dispersion of SMTO resembles to that of the double perovskites Sr2MnTiO6 and La2NiMnO6 which follows the modified Debye relaxation equation. This indicates a relaxor type dielectric behavior of SMTO may be due to the contribution of grain boundary effects.

  6. A layered perovskite with alternating Cu-O 2 and C-O planes

    NASA Astrophysics Data System (ADS)

    Matacotta, F. C.; Pal, D.; Mertelj, T.; Sˇtˇastný, P.; Nozar, P.; Mateev, D.; Ganguly, P.

    1992-11-01

    We have found a double perovskite compound corresponding to the composition Ba 1.5Sr 0.5CuO 3.CO 2. It is characterized by the alternation of Cu-O 2 and C-O planes and it forms at relatively low annealing temperatures(T<900°C)in presence of CO 2 gas. The stability of this compound seems to be related to the intersection point of the a and b lattice parameters dependence in the A 2CuO 3 series, where A is any mixture of two alkaline earths Ca, Sr, Ba. Preliminary results show that it is possible to replace the CO 2 molecule with other simple organic moities from room temperature dry solutions.

  7. Electro-spray deposition of a mesoporous TiO2 charge collection layer: toward large scale and continuous production of high efficiency perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Min-Cheol; Kim, Byeong Jo; Yoon, Jungjin; Lee, Jin-Wook; Suh, Dongchul; Park, Nam-Gyu; Choi, Mansoo; Jung, Hyun Suk

    2015-12-01

    The spin-coating method, which is widely used for thin film device fabrication, is incapable of large-area deposition or being performed continuously. In perovskite hybrid solar cells using CH3NH3PbI3 (MAPbI3), large-area deposition is essential for their potential use in mass production. Prior to replacing all the spin-coating process for fabrication of perovskite solar cells, herein, a mesoporous TiO2 electron-collection layer is fabricated by using the electro-spray deposition (ESD) system. Moreover, impedance spectroscopy and transient photocurrent and photovoltage measurements reveal that the electro-sprayed mesoscopic TiO2 film facilitates charge collection from the perovskite. The series resistance of the perovskite solar cell is also reduced owing to the highly porous nature of, and the low density of point defects in, the film. An optimized power conversion efficiency of 15.11% is achieved under an illumination of 1 sun; this efficiency is higher than that (13.67%) of the perovskite solar cell with the conventional spin-coated TiO2 films. Furthermore, the large-area coating capability of the ESD process is verified through the coating of uniform 10 × 10 cm2 TiO2 films. This study clearly shows that ESD constitutes therefore a viable alternative for the fabrication of high-throughput, large-area perovskite solar cells.The spin-coating method, which is widely used for thin film device fabrication, is incapable of large-area deposition or being performed continuously. In perovskite hybrid solar cells using CH3NH3PbI3 (MAPbI3), large-area deposition is essential for their potential use in mass production. Prior to replacing all the spin-coating process for fabrication of perovskite solar cells, herein, a mesoporous TiO2 electron-collection layer is fabricated by using the electro-spray deposition (ESD) system. Moreover, impedance spectroscopy and transient photocurrent and photovoltage measurements reveal that the electro-sprayed mesoscopic TiO2 film

  8. Design of a dual-layer ceramic interconnect based on perovskite oxides for segmented-in-series solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Park, Beom-Kyeong; Kim, Dae-Wi; Song, Rak-Hyun; Lee, Seung-Bok; Lim, Tak-Hyoung; Park, Seok-Joo; Park, Chong-Ook; Lee, Jong-Won

    2015-12-01

    A segmented-in series (SIS) SOFC consists of segmented unit cells connected in electrical series and shows improved stack efficiency over conventional SOFCs. In this design, a thin interconnect film provides both electrical contact and sealing between the anode of one cell and the cathode of the next; thus, it should have high conductivity and chemical/structural stability in both reducing and oxidizing atmospheres as well as impermeability to gases. Here, we report a dual-layer interconnect film for SIS-SOFCs comprising perovskite-type oxides, Sr0.7La0.2TiO3 (exposed to a reducing atmosphere) and La0.8Sr0.2FeO3 (exposed to an oxidizing atmosphere). The interconnect film is not only very dense but also highly conductive and stable under SOFC operating conditions; in particular, it shows an area-specific resistance of 19.6 mΩ cm2 at 800 °C, which is much lower than the generally accepted limit for SOFCs. A flat-tubular SIS-SOFC fabricated using these interconnect films exhibits a power density as high as 340 mW cm-2, which proves the feasibility of the dual-layer interconnect design.

  9. Tomographic reconstruction of layered tissue structures

    NASA Astrophysics Data System (ADS)

    Hielscher, Andreas H.; Azeez-Jan, Mohideen; Bartel, Sebastian

    2001-11-01

    In recent years the interest in the determination of optical properties of layered tissue structure has resurfaced. Applications include, for example, studies on layered skin tissue and underlying muscles, imaging of the brain underneath layers of skin, skull, and meninges, and imaging of the fetal head in utero beneath the layered structures of the maternal abdomen. In this work we approach the problem of layered structures in the framework of model-based iterative image reconstruction schemes. These schemes are currently developed to determine the optical properties inside tissue from measurement on the surface. If applied to layered structure these techniques yield substantial improvements over currently available semi-analytical approaches.

  10. Structural and electric evidence of ferrielectric state in Pb₂MnWO₆ double perovskite system.

    PubMed

    Orlandi, Fabio; Righi, Lara; Cabassi, Riccardo; Delmonte, Davide; Pernechele, Chiara; Bolzoni, Fulvio; Mezzadri, Francesco; Solzi, Massimo; Merlini, Marco; Calestani, Gianluca

    2014-10-01

    In this paper we describe the new ferri-electric compound Pb2MnWO6 (PMW), a double perovskite that can be considered as a novel structural prototype showing complex nuclear structure and interesting electric properties. According to single-crystal synchrotron data, PMW crystallizes in the noncentrosymmetric polar group Pmc21, in which the two symmetry-independent lead atoms give rise to a ferrielectric arrangement. The accurate crystallographic characterization indicates the presence of a complex distortion of the perovskite lattice driven by the local instability induced by the 6s(2) lone pair of the lead atoms. These peculiar structural features are confirmed by the complete electrical characterization of the system. Dielectric and transport measurements indicate an insulating character of the sample, while pyroelectric measurements point out a ferrielectric state characterized by different contributions. The magnetic transition at 45 K is accompanied by a magnetostrictive effect indicating a probable spin-lattice coupling. The characterizations carried out on PMW, showing the evidence of a coexistence of antiferromagnetism and ferrielectricity at low temperature, could lead to the definition of a new class of multiferroic materials. PMID:25197959

  11. Doped perovskite-based ruthenates: Structure, electrical, magnetic and magnetoresistive properties

    NASA Astrophysics Data System (ADS)

    Mamchik, Alexander Ivanovich

    2003-10-01

    The electric and magnetic properties of ruthenium-containing ABO 3 oxides with perovskite structure are intimately connected with their structure and composition. Even a slight perturbation caused by doping can significantly modify the electrical conductivity and the magnetic ground state of these compounds. In this thesis the structural, electronic, and magnetic properties of several perovskite ruthenate solid solutions, based on SrRuO 3 and CaRuO3, and containing Fe or Co on the B-sites, are presented. In the Fe-containing compounds, Ru preserves its 4+ valence state, while in the Co-doped compounds there is an order-dependent charge transfer between Ru and Co, leading to some Ru in the 5+ state. Saturation magnetization of solid solutions initially increases with both Fe and Co concentration, indicating the formation of large local magnetic moments around these cations. At higher Fe and Co substitution level, a spin glass state develops and a gradual metal/insulator transition occurs. At the same time, a large negative magnetoresistance emerges. These solid solutions are analogous to Mn-doped diluted magnetic semiconductors that contain giant local moments around Mn impurities, which themselves interact antiferromagnetically. Similar magnetic and magnetoresistive behavior is expected in other conducting ruthenates, and possibly other 4d and 5d conducting oxides that are doped with 3d transition metals.

  12. Enhanced photoelectrical performance of dye-sensitized solar cells with double-layer TiO2 on perovskite SrTiO3 substrate

    NASA Astrophysics Data System (ADS)

    Liu, Qiuhong; Sun, Qiong; Zhang, Min; Li, Yang; Zhao, Mei; Dong, Lifeng

    2016-04-01

    In this research, perovskite SrTiO3 particles are synthesized by a hydrothermal method, and TiO2 with a double-layer structure is grown on the SrTiO3 surface by a hydrolysis-condensation process. Structural characterizations reveal that TiO2 comprises of two phases: anatase film at the bottom and single-crystal rutile nanorods grown along the [110] direction on top. The TiO2-SrTiO3 composite film is investigated as photoanode material for dye-sensitized solar cells. In comparison with pure TiO2 and SrTiO3, the composite photoanode shows a much better performance in photoelectric conversion efficiency (1.35 %), which is about 2 and 100 times as efficient as pure TiO2 and SrTiO3, respectively. This indicates that the composite structure can facilitate charge carrier transfer and reduce electron-hole recombination to enhance photoelectrical properties of TiO2-based photoanode materials.

  13. Study of Local Structure in Selected Organic-Inorganic Perovskites in the Pm3⁻m Phase

    SciTech Connect

    Worhatch, Richard J; Kim, HyunJeong; Swainson, Ian P; Yonkeu, Andre L; Billinge, Simon J.L.

    2008-06-30

    The local structures of the inorganic component of selected organic-inorganic perovskites (OIPs) are studied by analyzing the X-ray pair distribution function. Whereas the long-range structure of each perovskite is the untilted Pm3m phase, all the OIPs showed significant internal distortion of the octahedra. Varying the halide has a significant impact on the lattice constant. There is evidence of local lone-pair distortions for certain compositions. The most complex case of disorder appears to be that of CH3NH3SnBr3.

  14. Buffer layer for thin film structures

    DOEpatents

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

    2006-10-31

    A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

  15. Buffer layer for thin film structures

    DOEpatents

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

    2010-06-15

    A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

  16. Interfacial structure in epitaxial perovskite oxides on (001) Ge crystal

    SciTech Connect

    Shen, Xuan; Ahmadi-Majlan, K.; Ngai, Joseph H.; Wu, Di; Su, Dong

    2015-01-19

    We investigated the interfacial structure of hetero-epitaxial SrZr{sub 0.68}Ti{sub 0.32}O{sub 3} thin film deposited on (001) Ge single crystal via transmission electron microscopy (TEM). The results from high-resolution scanning TEM and electron energy-loss spectroscopy show an atomically abrupt interface without secondary phase. We found misfit dislocations with Burgers vector of 1/2a 〈111〉 and threading dislocations with Burgers vector of a 〈100〉. Furthermore, we observed the coupling between dislocation half-loop and anti-phase boundary induced by the lattice terrace of Ge along 〈100〉 direction and their decoupling after annealing. We proposed models based on half-loop theory to interpret the coupling and the dislocation reactions.

  17. Bright Visible-Infrared Light Emitting Diodes Based on Hybrid Halide Perovskite with Spiro-OMeTAD as a Hole-Injecting Layer.

    PubMed

    Jaramillo-Quintero, Oscar A; Sanchez, Rafael S; Rincon, Marina; Mora-Sero, Ivan

    2015-05-21

    Hybrid halide perovskites that are currently intensively studied for photovoltaic applications, also present outstanding properties for light emission. Here, we report on the preparation of bright solid state light emitting diodes (LEDs) based on a solution-processed hybrid lead halide perovskite (Pe). In particular, we have utilized the perovskite generally described with the formula CH3NH3PbI(3-x)Cl(x) and exploited a configuration without electron or hole blocking layer in addition to the injecting layers. Compact TiO2 and Spiro-OMeTAD were used as electron and hole injecting layers, respectively. We have demonstrated a bright combined visible-infrared radiance of 7.1 W·sr(-1)·m(-2) at a current density of 232 mA·cm(-2), and a maximum external quantum efficiency (EQE) of 0.48%. The devices prepared surpass the EQE values achieved in previous reports, considering devices with just an injecting layer without any additional blocking layer. Significantly, the maximum EQE value of our devices is obtained at applied voltages as low as 2 V, with a turn-on voltage as low as the Pe band gap (V(turn-on) = 1.45 ± 0.06 V). This outstanding performance, despite the simplicity of the approach, highlights the enormous potentiality of Pe-LEDs. In addition, we present a stability study of unsealed Pe-LEDs, which demonstrates a dramatic influence of the measurement atmosphere on the performance of the devices. The decrease of the electroluminescence (EL) under continuous operation can be attributed to an increase of the non-radiative recombination pathways, rather than a degradation of the perovskite material itself. PMID:26263264

  18. Strontium superstoichiometry and defect structure of SrCeO3 perovskite.

    PubMed

    Mather, Glenn C; Figueiredo, Filipe M; Paz, Julio Romero de; García-Martín, Susana

    2008-02-01

    Strontium cerate (SrCeO(3)) is the parent phase of a family of prototype proton-conducting perovskites with important potential applications as electrolytes in protonic ceramic fuel cells, hydrogen-separation membranes, and sensors for hydrogen and humidity. Apparent nonstoichiometric behavior and the microstructure of SrCeO(3) have been investigated. Phase analysis by X-ray diffraction indicates that single-phase material in the system Sr(1+x)CeO(3+)delta is obtained for compositions x = 0.02-0.03 and that nominally stoichiometric SrCeO(3) (x = 0) synthesized by either solid-state reaction or the citrate method is Sr-rich. Selected area electron diffraction confirms that the system crystallizes with the GdFeO(3)-type orthorhombic perovskite structure (space group Pnma). Structural defects characterized by high-resolution transmission electron microscopy include twin domain boundaries and SrO-rich, Ruddlesden-Popper-type planar defects. Magnetic susceptibility measurements down to 2 K indicate that the Ce(3+) content is minor ( approximately 0.01 mol per formula unit for slow-cooled material) and does not influence the observed nonstoichiometry. PMID:18166041

  19. Structures of ordered tungsten- or molybdenum-containing quaternary perovskite oxides

    SciTech Connect

    Day, Bradley E.; Bley, Nicholas D.; Jones, Heather R.; McCullough, Ryan M.; Eng, Hank W.; Porter, Spencer H.; Woodward, Patrick M.; Barnes, Paris W.

    2012-01-15

    The room temperature crystal structures of six A{sub 2}MMoO{sub 6} and A{sub 2}MWO{sub 6} ordered double perovskites were determined from X-ray and neutron powder diffraction data. Ba{sub 2}MgWO{sub 6} and Ba{sub 2}CaMoO{sub 6} both adopt cubic symmetry (space group Fm3-bar m, tilt system a{sup 0}a{sup 0}a{sup 0}). Ba{sub 2}CaWO{sub 6} has nearly the same tolerance factor (t=0.972) as Ba{sub 2}CaMoO{sub 6} (t=0.974), yet it surprisingly crystallizes with I4/m symmetry indicative of out-of-phase rotations of the MO{sub 6} octahedra about the c-axis (a{sup 0}a{sup 0}c{sup -}). Sr{sub 2}ZnMoO{sub 6} (t=0.979) also adopts I4/m symmetry; whereas, Sr{sub 2}ZnWO{sub 6} (t=0.976) crystallizes with monoclinic symmetry (P2{sub 1}/n) with out-of-phase octahedral tilting distortions about the a- and b-axes, and in-phase tilting about the c-axis (a{sup -}a{sup -}c{sup +}). Ca{sub 2}CaWO{sub 6} (t=0.867) also has P2{sub 1}/n symmetry with large tilting distortions about all three crystallographic axes and distorted CaO{sub 6} octahedra. Analysis of 93 double perovskites and their crystal structures showed that while the type and magnitude of the octahedral tilting distortions are controlled primarily by the tolerance factor, the identity of the A-cation acts as the secondary structure directing factor. When A=Ba{sup 2+} the boundary between cubic and tetragonal symmetries falls near t=0.97, whereas when A=Sr{sup 2+} this boundary falls somewhere between t=1.018 and t=0.992. - Graphical abstract: A survey of the tolerance factor of 41 Mo/W- and 52 Nb/Ta-containing quaternary perovskites plotted as a function of the difference between the two six-coordinate M-cation ionic radii. Compounds with cubic symmetry are represented by diamonds, those with tetragonal symmetry are represented by squares, those with I2/m monoclinic symmetry are represented by Multiplication-Sign , and those with P2{sub 1}/n monoclinic symmetry are represented by triangles. White symbols represent

  20. Polar and Magnetic Layered A Site and Rock Salt B Site-Ordered NaLnFeWO6 (Ln = La, Nd) Perovskites

    SciTech Connect

    Tetuerto, Maria; Li, Mang-Rong; Ignatov, Alexander; Croft, Mark; Ramanujachary, Kandalam V.; Chi, Songxue; Hodges, Jason P; Dachraoui, W.; Hadermann, Joke; Thao Tran, T.; Shiv Halasyamani, P.; Grams, C.; Hemberger, J.; Greenblatt, M.

    2013-01-01

    We have expanded the double perovskite family of materials with the unusual combination of layered order in the A sublattice and rock salt order over the B sublattice to compounds NaLaFeWO6 and NaNdFeWO6. The materials have been synthesized and studied by powder X-ray diffraction, neutron diffraction, electron diffraction, magnetic measurements, X-ray absorption spectroscopy, dielectric measurements, and second harmonic generation. At room temperature, the crystal structures of both compounds can be defined in the noncentrosymmetric monoclinic P21 space group resulting from the combination of ordering both in the A and B sublattices, the distortion of the cell due to tilting of the octahedra, and the displacement of certain cations. The magnetic studies show that both compounds are ordered antiferromagnetically below TN 25 K for NaLaFeWO6 and at 21 K for NaNdFeWO6. The magnetic structure of NaNdFeWO6 has been solved with a propagation vector k = (1/2 0 1/2) as an antiferromagnetic arrangement of Fe and Nd moments. Although the samples are potential multiferroics, the dielectric measurements do not show a ferroelectric response.

  1. Si-compatible candidates for high-K dielectrics with the Pbnm perovskite structure

    SciTech Connect

    Coh, Sinisa; Heeg, Tassilo; Haeni, Jeffery; Biegalski, Michael D; Letteri, James; Bernhagen, M; Reiche, Paul; O'brien, Kevin; Uecker, Rinhold; Trolier-McKinstry, Susan; Schlom, Darrell; Vanderbilt, David

    2010-01-01

    We analyze both experimentally (where possible) and theoretically from first-principles the dielectric tensor components and crystal structure of five classes of Pbnm perovskites. All of these materials are believed to be stable on silicon and are therefore promising candidates for high-K dielectrics. We also analyze the structure of these materials with various simple models, decompose the lattice contribution to the dielectric tensor into force constant matrix eigenmode contributions, explore a peculiar correlation between structural and dielectric anisotropies in these compounds and give phonon frequencies and infrared activities of those modes that are infrared-active. We find that CaZrO3, SrZrO3, LaHoO3, and LaYO3 are among the most promising candidates for high-K dielectrics among the compounds we considered.

  2. Trace surface-clean palladium nanosheets as a conductivity enhancer in hole-transporting layers to improve the overall performances of perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Cao, Jing; Mo, Shiguang; Jing, Xiaojing; Yin, Jun; Li, Jing; Zheng, Nanfeng

    2016-02-01

    Surface-clean Pd nanosheets were synthesized and embedded in a hole transport material (HTM) matrix to improve the conductivity of the HTM layer. Applying only a trace amount of Pd nanosheets readily led to a remarkably enhanced performance of perovskite solar cells (PSCs). This finding provides an effective strategy to build efficient charge-transport materials for improving the overall performance of PSCs.Surface-clean Pd nanosheets were synthesized and embedded in a hole transport material (HTM) matrix to improve the conductivity of the HTM layer. Applying only a trace amount of Pd nanosheets readily led to a remarkably enhanced performance of perovskite solar cells (PSCs). This finding provides an effective strategy to build efficient charge-transport materials for improving the overall performance of PSCs. Electronic supplementary information (ESI) available: Details of the XRD, UV-vis spectra, cross-sectional SEM images and the EQE spectra of the cells. See DOI: 10.1039/c5nr07789c

  3. Light Harvesting and Charge Recombination in CH3NH3PbI3 Perovskite Solar Cells Studied by Hole Transport Layer Thickness Variation.

    PubMed

    Marinova, Nevena; Tress, Wolfgang; Humphry-Baker, Robin; Dar, M Ibrahim; Bojinov, Vladimir; Zakeeruddin, Shaik Mohammed; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

    2015-04-28

    A tailored optimization of perovskite solar cells requires a detailed understanding of the processes limiting the device efficiency. Here, we study the role of the hole transport layer (HTL) spiro-MeOTAD and its thickness in a mesoscopic TiO2-based solar cell architecture. We find that a sufficiently thick (200 nm) HTL not only increases the charge carrier collection efficiency but also the light harvesting efficiency. This is due to an enhanced reflection of a smooth HTL/Au-electrode interface. The rough CH3NH3PbI3 perovskite surface requires an HTL thickness of >400 nm to avoid surface recombination and guarantee a high open-circuit voltage. Analyses of the electroluminescence efficiency and the diode ideality factor show that the open-circuit voltage becomes completely limited by trap-assisted recombination in the perovskite for a thick HTL. Thus, spiro-MeOTAD is a very good HTL choice from the device physics' point of view. The fill factor analyzed by the Suns-Voc method is not transport limited, but trap-recombination limited as well. Consequently, a further optimization of the device has to focus on defects in the polycrystalline perovskite film. PMID:25769194

  4. Enhanced performance of CH3NH3PbI3-x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface.

    PubMed

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-12-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3-x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3-x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3-x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices. PMID:27356563

  5. Enhanced performance of CH3NH3PbI3- x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface

    NASA Astrophysics Data System (ADS)

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-06-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3- x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3- x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3- x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.

  6. Hybrid functional band gap calculation of SnO{sub 6} containing perovskites and their derived structures

    SciTech Connect

    Lee, Hyewon; Cheong, S.W.; Kim, Bog G.

    2015-08-15

    We have studied the properties of SnO{sub 6} octahedra-containing perovskites and their derived structures using ab initio calculations with different density functionals. In order to predict the correct band gap of the materials, we have used B3LYP hybrid density functional, and the results of B3LYP were compared with those obtained using the local density approximation and generalized gradient approximation data. The calculations have been conducted for the orthorhombic ground state of the SnO{sub 6} containing perovskites. We also have expended the hybrid density functional calculation to the ASnO{sub 3}/A'SnO{sub 3} system with different cation orderings. We propose an empirical relationship between the tolerance factor and the band gap of SnO{sub 6} containing oxide materials based on first principles calculation. - Graphical abstract: (a) Structure of ASnO{sub 3} for orthorhombic ground state. The green ball is A (Ba, Sr, Ca) cation and the small (red) ball on edge is oxygen. SnO{sub 6} octahedrons are plotted as polyhedron. (b) Band gap of ASnO{sub 3} as a function of the tolerance factor for different density functionals. The experimental values of the band gap are marked as green pentagons. (c) ASnO{sub 3}/A'SnO{sub 3} superlattices with two types cation arrangement: [001] layered structure and [111] rocksalt structure, respectively. (d) B3LYP hybrid functional band gaps of ASnO{sub 3}, [001] ordered superlattices, and [111] ordered superlattices of ASnO{sub 3}/A'SnO{sub 3} as a function of the effective tolerance factor. Note the empirical linear relationship between the band gap and effective tolerance factor. - Highlights: • We report the hybrid functional band gap calculation of ASnO{sub 3} and ASnO{sub 3}/A'SnO{sub 3}. • The band gap of ASnO{sub 3} using B3LYP functional reproduces the experimental value. • We propose the linear relationship between the tolerance factor and the band gap.

  7. NaIrO{sub 3}-A pentavalent post-perovskite

    SciTech Connect

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-03-15

    Sodium iridium (V) oxide, NaIrO{sub 3,} was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO{sub 3}, the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO{sub 3}. Among the oxide post-perovskites, NaIrO{sub 3} is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO{sub 6} octahedra separated by layers of NaO{sub 8} bicapped trigonal prisms. NaIrO{sub 3} shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO{sub 3}, synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO{sub 3} post-perovskite. Research highlights: {yields} NaIrO{sub 3} post-perovskite stabilized by pressure. {yields} First example of a pentavalent oxide post-perovskite. {yields} Non-metallic and non-magnetic behavior of NaIrO{sub 3}.

  8. Reported and predicted structures of Ba(Co,Nb)(1-δ)O₃ hexagonal perovskite phases.

    PubMed

    Bradley, Kathryn A; Collins, Christopher; Dyer, Matthew S; Claridge, John B; Darling, George R; Rosseinsky, Matthew J

    2014-10-21

    The Extended Module Materials Assembly computational method for structure solution and prediction has been implemented for close-packed lattices. Exploring the family of B-site deficient materials in hexagonal perovskite barium cobalt niobates, it is found that the EMMA procedure returns the experimental structures as the most stable for the known compositions of Ba3CoNb2O9, Ba5Nb4O15 and Ba8CoNb6O24. The unknown compositions Ba11Co2Nb8O33 and Ba13CoNb10O39, having longer stacking sequences, are predicted to form as intergrowths of Ba3CoNb2O9 and Ba5Nb4O15, and are found to have similar stability to pure Ba3CoNb2O9 and Ba5Nb4O15, indicating that it is likely they can be synthesised. PMID:24871400

  9. A First-Principles Study on the Structural and Electronic Properties of Sn-Based Organic-Inorganic Halide Perovskites

    NASA Astrophysics Data System (ADS)

    Ma, Zi-Qian; Pan, Hui; Wong, Pak Kin

    2016-08-01

    Organic-inorganic halide perovskites have attracted increasing interest on solar-energy harvesting because of their outstanding electronic properties. In this work, we systematically investigate the structural and electronic properties of Sn-based hybrid perovskites MASnX3 and FASnX3 (X = I, Br) based on density-functional-theory calculations. We find that their electronic properties strongly depend on the organic molecules, halide atoms, and structures. We show that there is a general rule to predict the band gap of the Sn-based hybrid perovskite: its band gap increases as the size of halide atom decreases as well as that of organic molecule increase. The band gap of high temperature phase (cubic structure) is smaller than that of low temperature phase (orthorhombic structure). The band gap of tetragonal structure (medium-temperature phase) may be larger or smaller than that of cubic phase, depending on the orientation of the molecule. Tunable band gap within a range of 0.73-1.53 eV can be achieved by choosing halide atom and organic molecule, and controlling structure. We further show that carrier effective mass also reduces as the size of halide atom increases and that of molecule decreases. By comparing with Pb-based hybrid perovskites, the Sn-based systems show enhanced visible-light absorption and carrier mobility due to narrowed band gap and reduced carrier effective mass. These Sn-based organic-inorganic halide perovskites may find applications in solar energy harvesting with improved performance.

  10. Influence of surface and finite size effects on the structural and magnetic properties of nanocrystalline lanthanum strontium perovskite manganites

    SciTech Connect

    Žvátora, Pavel; Veverka, Miroslav; Veverka, Pavel; Knížek, Karel; Závěta, Karel; Pollert, Emil; Goglio, Graziella; Duguet, Etienne; Kaman, Ondřej

    2013-08-15

    Syntheses of nanocrystalline perovskite phases of the general formula La{sub 1−x}Sr{sub x}MnO{sub 3+δ} were carried out employing sol–gel technique followed by thermal treatment at 700–900 °C under oxygen flow. The prepared samples exhibit a rhombohedral structure with space group R3{sup ¯}c in the whole investigated range of composition 0.20≤x≤0.45. The studies were aimed at the chemical composition including oxygen stoichiometry and extrinsic properties, i.e. size of the particles, both influencing the resulting structural and magnetic properties. The oxygen stoichiometry was determined by chemical analysis revealing oxygen excess in most of the studied phases. The excess was particularly high for the samples with the smallest crystallites (12–28 nm) while comparative bulk materials showed moderate non-stoichiometry. These differences are tentatively attributed to the surface effects in view of the volume fraction occupied by the upper layer whose atomic composition does not comply with the ideal bulk stoichiometry. - Graphical abstract: Evolution of the particle size with annealing temperature in the nanocrystalline La{sub 0.70}Sr{sub 0.30}MnO{sub 3+δ} phase. Display Omitted - Highlights: • The magnetic behaviour of nanocrystalline La{sub 1−x}Sr{sub x}MnO{sub 3+δ} phases was analyzed on the basis of their crystal structure, chemical composition and size of the particles. • Their Curie temperature and magnetization are markedly affected by finite size and surface effects. • The oxygen excess observed in the La{sub 1−x}Sr{sub x}MnO{sub 3+δ} nanoparticles might be generated by the surface layer with deviated oxygen stoichiometry.

  11. Layered manganites : magnetic structure at extreme doping levels.

    SciTech Connect

    Mitchell, J. F.

    1998-09-11

    We report powder neutron diffraction results on the crystal and magnetic structures of the bilayer Ruddlesden-Popper phase Sr{sub 3}Mn{sub 2}O{sub 7{minus}{delta}} ({delta} = 0.0, 0.45) and correlate these structures with their magnetic and transport properties. The {delta} = 0.45 compound contains a large number of oxygen vacancies that are disordered in the MnO{sub 2} planes. As a result of this disordered vacancy structure, Sr{sub 3}Mn{sub 2}O{sub 6.55} is a nonmagnetic insulator. Sr{sub 3}Mn{sub 2}O{sub 7.0} ({delta} = 0) is an antiferromagnetic insulator whose magnetic structure is related to that of the SrMnO{sub 3} perovskite. Comparison of this end-member compound to its doped congeners in the La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} series highlights the extreme sensitivity of magnetic structure to dopant concentration in these layered materials.

  12. Triple-layered perovskite niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y): new self-activated oxides.

    PubMed

    Qin, Lin; Wei, Donglei; Huang, Yanlin; Kim, Sun Il; Yu, Young Moon; Seo, Hyo Jin

    2013-09-16

    Niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y) were prepared by conventional high-temperature solid-state reaction. The formation of a single-phase compound with triple-layered perovskite-type structure was verified through X-ray diffraction (XRD) studies. The luminescence characteristics such as photoluminescence excitation and emission spectra, X-ray-excited luminescence (XEL), Stokes shift, decay curves, and color coordinates were investigated. The niobates can be efficiently excited by UV light and present luminescence behaviors with rich luminescence colors. Under excitation by ultraviolet radiation, CaRNb3O10 (R = La, Gd, Yb, or Y) exhibits strong blue luminescence due to the self-activation center of the octahedral NbO6 groups, even at room temperature. For the materials of composition CaRNb3O10 (R = Sm, Eu, Dy, or Er), the excitation at the host band produces a characteristic luminescence of rare earth ions, indicating a host-guest energy transfer process. CaRNb3O10 (R = Eu) has the strongest luminescence intensity, which can be efficiently excitated by near UV wavelength. It could be suggested to be a potential candidate for the application on near-UV excited white LEDs. PMID:23977903

  13. Characterization of organic-inorganic hybrid layered perovskite and intercalated compound (n-C12H25NH3)2ZnCl4

    NASA Astrophysics Data System (ADS)

    Abdel-Kader, M. M.; Aboud, A. I.; Gamal, W. M.

    2016-05-01

    We report on some electrical properties and solid-solid phase transitions of organic-inorganic hybrid layered halide perovskite and intercalated compound (n-C12H25NH3)2ZnCl4 which is one member of the long-chain compounds of the series (n-CnH2n+1NH3)2,(n = 8-18). The complex dielectric permittivity ɛ*(ω,T) and the ac conductivity σ (ω,T) were measured as functions of temperature 100 K < T < 390 K and frequency 5 kHz < f < 100 kHz. Moreover, the differential scanning calorimetery and the differential thermal analysis thermograms were performed. The analysis of our data confirms the existence of a structural phase transition at T ≈ (362 ± 2) K, where the compound changes its state from intercalation to non-intercalation with a drastic increase in the c-axis by about 16.4%. The behavior of the frequency-dependent conductivity follows the Jonscher universal power law: σ (ω, T) αῳs(ῳ,T). The mechanism of electrical conduction in the low-temperature phase (phase II) can be described as quantum mechanical tunneling model.

  14. Industrial-grade rare-earth and perovskite oxide for high-performance electrolyte layer-free fuel cell

    NASA Astrophysics Data System (ADS)

    Xia, Chen; Wang, Baoyuan; Ma, Ying; Cai, Yixiao; Afzal, Muhammad; Liu, Yanyan; He, Yunjuan; Zhang, Wei; Dong, Wenjing; Li, Junjiao; Zhu, Bin

    2016-03-01

    In the present work, we report a composite of industrial-grade material LaCePr-oxide (LCP) and perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for advanced electrolyte layer-free fuel cells (EFFCs). The microstructure, morphology, and electrical properties of the LCP, LSCF, and LCP-LSCF composite were investigated and characterized by XRD, SEM, EDS, TEM, and EIS. Various ratios of LCP to LSCF in the composite were modulated to achieve balanced ionic and electronic conductivities. Fuel cell with an optimum ratio of 60 wt% LCP to 40 wt% LSCF reached the highest open circuit voltage (OCV) at 1.01 V and a maximum power density of 745 mW cm-2 at 575 °C, also displaying a good performance stability. The high performance is attributed to the interfacial mechanisms and electrode catalytic effects. The findings from the present study promote industrial-grade rare-earth oxide as a promising new material for innovative low temperature solid oxide fuel cell (LTSOFC) technology.

  15. Low thermal budget, photonic-cured compact TiO2 layers for high-efficiency perovskite solar cells

    DOE PAGESBeta

    Das, Sanjib; Gu, Gong; Joshi, Pooran C.; Yang, Bin; Aytug, Tolga; Rouleau, Christopher M.; Geohegan, David B.; Xiao, Kai

    2016-05-25

    Rapid advances in organometallic trihalide perovskite solar cells (PSCs) have positioned them to be one of the leading next generation photovoltaic technologies. However, most of the high-performance PSCs, particularly those using compact TiO2 as an electron transport layer, require a high-temperature sintering step, which is not compatible with flexible polymer-based substrates. Considering the materials of interest for PSCs and corresponding device configurations, it is technologically imperative to fabricate high-efficiency cells at low thermal budget so that they can be realized on low-temperature plastic substrates. In this paper, we report on a new photonic curing technique that produces crystalline anatase-phase TiO2more » films on indium tin oxide-coated glass and flexible polyethylene terephthalate (PET) substrates. Finally, the planar PSCs, using photonic-cured TiO2 films, exhibit PCEs as high as 15.0% and 11.2% on glass and flexible PET substrates, respectively, comparable to the device performance of PSCs incorporating furnace annealed TiO2 films.« less

  16. High Performance Perovskite Hybrid Solar Cells with E-beam-Processed TiOx Electron Extraction Layer.

    PubMed

    Meng, Tianyu; Liu, Chang; Wang, Kai; He, Tianda; Zhu, Yu; Al-Enizi, Abdullah; Elzatahry, Ahmed; Gong, Xiong

    2016-01-27

    Perovskite hybrid solar cells (pero-HSCs) have drawn great attention in the last 5 years. The efficiencies of pero-HSCs have been boosted from 3.8% to over 20%. However, one of the bottlenecks for commercialization of pero-HSCs is to make a high electrical conductive TiOx electron extraction layer (EEL). In this study, we report high performance pero-HSCs with TiOx EEL, where the TiOx EEL is fabricated by electron beam (e-beam) evaporation, which has been proved to be a well-developed manufacturing process. The resistance of the e-beam evaporated TiOx EEL is smaller than that of sol-gel processed TiOx EEL. Moreover, the dark current densities and interfacial charge carrier recombination of pero-HSCs incorporated with e-beam processed TiOx EEL is also smaller than that of pero-HSCs incorporated with sol-gel processed TiOx EEL. All these result in efficient pero-HSCs with high reproducibility. These results demonstrate that our method provides a simple and facile way to approach high performance pero-HSCs. PMID:26727027

  17. Low-Temperature and Solution-Processed Amorphous WO(x) as Electron-Selective Layer for Perovskite Solar Cells.

    PubMed

    Wang, Kai; Shi, Yantao; Dong, Qingshun; Li, Yu; Wang, Shufeng; Yu, Xufeng; Wu, Mengyao; Ma, Tingli

    2015-03-01

    The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL. PMID:26262648

  18. Room temperature oxidative intercalation with chalcogen hydrides: Two-step method for the formation of alkali-metal chalcogenide arrays within layered perovskites

    SciTech Connect

    Ranmohotti, K.G. Sanjaya; Montasserasadi, M. Dariush; Choi, Jonglak; Yao, Yuan; Mohanty, Debasish; Josepha, Elisha A.; Adireddy, Shiva; Caruntu, Gabriel; Wiley, John B.

    2012-06-15

    Highlights: ► Topochemical reactions involving intercalation allow construction of metal chalcogenide arrays within perovskite hosts. ► Gaseous chalcogen hydrides serve as effect reactants for intercalation of sulfur and selenium. ► New compounds prepared by a two-step intercalation strategy are presented. -- Abstract: A two-step topochemical reaction strategy utilizing oxidative intercalation with gaseous chalcogen hydrides is presented. Initially, the Dion-Jacobson-type layered perovskite, RbLaNb{sub 2}O{sub 7}, is intercalated reductively with rubidium metal to make the Ruddlesden-Popper-type layered perovskite, Rb{sub 2}LaNb{sub 2}O{sub 7}. This compound is then reacted at room-temperature with in situ generated H{sub 2}S gas to create Rb-S layers within the perovskite host. Rietveld refinement of X-ray powder diffraction data (tetragonal, a = 3.8998(2) Å, c = 15.256(1) Å; space group P4/mmm) shows the compound to be isostructural with (Rb{sub 2}Cl)LaNb{sub 2}O{sub 7} where the sulfide resides on a cubic interlayer site surrounded by rubidium ions. The mass increase seen on sulfur intercalation and the refined S site occupation factor (∼0.8) of the product indicate a higher sulfur content than expected for S{sup 2−} alone. This combined with the Raman studies, which show evidence for an H-S stretch, indicate that a significant fraction of the intercalated sulfide exists as hydrogen sulfide ion. Intercalation reactions with H{sub 2}Se{sub (g)} were also carried out and appear to produce an isostructural selenide compound. The utilization of such gaseous hydride reagents could significantly expand multistep topochemistry to a larger number of intercalants.

  19. 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.

  20. Crystalline, Magnetic and Electronic Structure of the Ba2DySbO6 Complex Perovskite

    NASA Astrophysics Data System (ADS)

    Cardona, R.; Moreno Mendoza, R.; Carrero Bermúdez, L. A.; Landínez Téllez, D. A.; Roa-Rojas, J.

    2016-01-01

    In this work, we report the synthesis of the Ba2DySbO6 new double perovskite by means of the solid-state reaction recipe from high-purity oxide powders of BaCO3, Dy2O3, and Sb2O5. The analysis of the crystal structure was carried out through the X-ray diffraction technique with posterior Rietveld refinement of the experimental diffraction data by the GSAS code. Results reveal that the Ba2DySbO6 material crystallizes in a rhombohedral perovskite structure, belonging to the R-3 (#148) space group with lattice parameter a = 5.96260(5) Å, and angle α = 60.008°. The magnetic characterization was performed by measurements of magnetic susceptibility as a function of temperature. The behavior observed in the temperature regime from 4 K up to 300 K was paramagnetic. The characteristic magnetic parameters were obtained from the fitting with the Curie equation, obtaining the values of susceptibility independent of temperature 0.00633 emu/mol and effective magnetic moment 8.9 \\upmu B, which is 84 % in agreement with the expected value predicted by the Hund's rules. The electronic structure was calculated by means of linearized augmented plane waves in the framework of the density functional theory (DFT). This study considers the cohesion energies as a function of the lattice parameter, with a lattice constant a, whose value is 98 % in agreement with the experimental result. Curves of density of states as a function of the wave number reveal that this material behaves as an insulator with energy gap 3.65 eV. This result was corroborated by diffuse reflectance experiments adjusted to the Kubelka-Munk equation. The effective magnetic moment obtained from the DFT calculations was 7.7 \\upmu B.

  1. 4-fold photocurrent enhancement in ultrathin nanoplasmonic perovskite solar cells.

    PubMed

    Cai, Boyuan; Peng, Yong; Cheng, Yi-Bing; Gu, Min

    2015-11-30

    Although perovskite materials have been widely investigated for thin-film photovoltaic devices due to the potential for high efficiency, their high toxicity has pressed the development of a solar cell structure of an ultra-thin absorber layer. But insufficient light absorption could be a result of ultra-thin perovskite films. In this paper, we propose a new nanoplasmonic solar cell that integrates metal nanoparticles at its rear/front surfaces of the perovskite layer. Plasmon-enhanced light scattering and near-field enhancement effects from lumpy sliver nanoparticles result in the photocurrent enhancement for a 50 nm thick absorber, which is higher than that for a 300 nm thick flat perovskite solar cell. We also predict the 4-fold photocurrent enhancement in an ultrathin perovskite solar cell with the absorber thickness of 10 nm. Our results pave a new way for ultrathin high-efficiency solar cells with either a lead-based or a lead-free perovskite absorption layer. PMID:26698816

  2. Structural phase transition in perovskite metal-formate frameworks: a Potts-type model with dipolar interactions.

    PubMed

    Šimėnas, Mantas; Balčiūnas, Sergejus; Ma Combining Cedilla Czka, Mirosław; Banys, Jūras; Tornau, Evaldas E

    2016-07-21

    We propose a combined experimental and numerical study to describe an order-disorder structural phase transition in perovskite-based [(CH3)2NH2][M(HCOO)3] (M = Zn(2+), Mn(2+), Fe(2+), Co(2+) and Ni(2+)) dense metal-organic frameworks (MOFs). The three-fold degenerate orientation of the molecular (CH3)2NH2(+) (DMA(+)) cation implies a selection of the statistical three-state model of the Potts type. It is constructed on a simple cubic lattice where each lattice point can be occupied by a DMA(+) cation in one of the available states. In our model the main interaction is the nearest-neighbor Potts-type interaction, which effectively accounts for the H-bonding between DMA(+) cations and M(HCOO)3(-) cages. The model is modified by accounting for the dipolar interactions which are evaluated for the real monoclinic lattice using density functional theory. We employ the Monte Carlo method to numerically study the model. The calculations are supplemented with the experimental measurements of electric polarization. The obtained results indicate that the three-state Potts model correctly describes the phase transition order in these MOFs, while dipolar interactions are necessary to obtain better agreement with the experimental polarization. We show that in our model with substantial dipolar interactions the ground state changes from uniform to the layers with alternating polarization directions. PMID:27341447

  3. The thermal equation of state of (Mg, Fe)SiO3 bridgmanite (perovskite) and implications for lower mantle structures

    NASA Astrophysics Data System (ADS)

    Wolf, Aaron S.; Jackson, Jennifer M.; Dera, Przemeslaw; Prakapenka, Vitali B.

    2015-11-01

    The high-pressure/high-temperature equation of state (EOS) of synthetic 13% Fe-bearing bridgmanite (Mg silicate perovskite) is measured using powder X-ray diffraction in a laser-heated diamond anvil cell with a quasi-hydrostatic neon pressure medium. We compare these results, which are consistent with previous 300 K sound speed and compression studies, with a reanalysis of Fe-free Mg end-member data from Tange et al. (2012) to determine the effect of iron on bridgmanite's thermoelastic properties. EOS parameters are incorporated into an ideal lattice mixing model to probe the behavior of bridgmanite at deep mantle conditions. With this model, a nearly pure bridgmanite mantle composition is shown to be inconsistent with density and compressibility profiles of the lower mantle. We also explore the buoyant stability of bridgmanite over a range of temperatures and compositions expected for Large Low-Shear Velocity Provinces, concluding that bridgmanite-dominated thermochemical piles are more likely to be passive dense layers externally supported by convection, rather than internally supported metastable domes. The metastable dome scenario is estimated to have a relative likelihood of only 4-7%, given the narrow range of compositions and temperatures consistent with seismic constraints. If buoyantly supported, such structures could not have remained stable with greater thermal contrast early in Earth's history, ruling out formation scenarios involving a large concentration of heat producing elements.

  4. Pyrolysis preparation of WO3 thin films using ammonium metatungstate DMF/water solution for efficient compact layers in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Jincheng, Zhang; Chengwu, Shi; Junjun, Chen; Chao, Ying; Ni, Wu; Mao, Wang

    2016-03-01

    The tungsten trioxide (WO3) thin films were firstly prepared by spin-coating-pyrolysis methods using the ammonium metatungstate ((NH4)6H2W12O40) DMF/water solution, and successfully applied as the efficient compact layers for the planar perovskite solar cells. The influence of the WO3 film thickness and the rinsing treatment of CH3NH3PbI3 thin film with isopropanol on the photovoltaic performance of the corresponding perovskite solar cells was systematically investigated. The results revealed that the perovskite solar cell with a 62 nm thick WO3 compact layer achieved a photoelectric conversion efficiency of 5.72%, with a short circuit photocurrent density of 17.39 mA/cm2, an open circuit voltage of 0.58 V and a fill factor of 0.57. The photoelectric conversion efficiency was improved from 5.72% to 7.04% by the isopropanol rinsing treatment. Project supported by the National Natural Science Foundation of China (Nos. 51472071, 512720616, 51072043), and the National Basic Research Program of China (No. 2011CBA00700).

  5. Structural and optical characterization of DyAlO3 perovskite powders obtained by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Saji S., K.; Raju, K.; Wariar, P. R. S.

    2016-05-01

    Phase pure Dysprosium monoaluminate has been prepared from Dysprosium oxide and Aluminium nitrate by auto-ignition citrate complex combustion process. The phase formation has been investigated using X-ray diffraction analysis (XRD), Thermo-Gravimetric/Differential Thermal Analysis (TGA/DTA) and Fourier Transform Infrared (FT-IR) spectroscopy analysis. X-ray diffraction analysis (XRD) revealed that DyAlO3 has an orthorhombic perovskite structure. From Transmission Electron Microscopy (TEM) studies, average particle-size has been found to be as low as 45 nm. The absorption spectrum of the DyAlO3 nanoparticles shows characteristic absorption bands of Dy atom. The optical band gap of the material was found to be 5.15eV, which corresponds to direct allowed transitions.

  6. Optical and Structural Study of Organometal Halide Materials for Applications in Perovskite-Based Solar Cells

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh Tu; Phan Vu, Thi Van; Bui, Bao Thoa; Luong, Thu Trang; Nguyen, Minh Hieu; Hoang Ngoc, Lam Huong; Bui, Van Diep; Truong, Thanh Tu; Nguyen-Tran, Thuat

    2016-05-01

    CH3NH3PbI3 and CH3NH3PbI2Br crystal powders and thin films with chemical formula CH3NH3PbI3- x Br x have been synthesized by reacting methylammonium bromide/iodide with lead iodide. The films were fabricated by a low-temperature solution process using the spin-coating method followed by thermal annealing, which is an effective means for controlling the composition and morphology of the CH3NH3PbI3- x Br x thin films. The resulting perovskite films exhibit good optical absorption and crystalline structure, being promising for potential application as light absorbers in future solar cells.

  7. Enhanced Efficiency and Stability of Inverted Perovskite Solar Cells Using Highly Crystalline SnO2 Nanocrystals as the Robust Electron-Transporting Layer.

    PubMed

    Zhu, Zonglong; Bai, Yang; Liu, Xiao; Chueh, Chu-Chen; Yang, Shihe; Jen, Alex K-Y

    2016-08-01

    Highly crystalline SnO2 is demonstrated to serve as a stable and robust electron-transporting layer for high-performance perovskite solar cells. Benefiting from its high crystallinity, the relatively thick SnO2 electron-transporting layer (≈120 nm) provides a respectable electron-transporting property to yield a promising power conversion efficiency (PCE)(18.8%) Over 90% of the initial PCE can be retained after 30 d storage in ambient with ≈70% relative humidity. PMID:27168338

  8. 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

  9. High-performance inverted planar heterojunction perovskite solar cells based on a solution-processed CuOx hole transport layer

    NASA Astrophysics Data System (ADS)

    Sun, Weihai; Li, Yunlong; Ye, Senyun; Rao, Haixia; Yan, Weibo; Peng, Haitao; Li, Yu; Liu, Zhiwei; Wang, Shufeng; Chen, Zhijian; Xiao, Lixin; Bian, Zuqiang; Huang, Chunhui

    2016-05-01

    During the past several years, methylammonium lead halide perovskites have been widely investigated as light absorbers for thin-film photovoltaic cells. Among the various device architectures, the inverted planar heterojunction perovskite solar cells have attracted special attention for their relatively simple fabrication and high efficiencies. Although promising efficiencies have been obtained in the inverted planar geometry based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) sulfonic acid (PEDOT:PSS) as the hole transport material (HTM), the hydrophilicity of the PEDOT:PSS is a critical factor for long-term stability. In this paper, a CuOx hole transport layer from a facile solution-processed method was introduced into the inverted planar heterojunction perovskite solar cells. After the optimization of the devices, a champion PCE of 17.1% was obtained with an open circuit voltage (Voc) of 0.99 V, a short-circuit current (Jsc) of 23.2 mA cm-2 and a fill factor (FF) of 74.4%. Furthermore, the unencapsulated device cooperating with the CuOx film exhibited superior performance in the stability test, compared to the device involving the PEDOT:PSS layer, indicating that CuOx could be a promising HTM for replacing PEDOT:PSS in inverted planar heterojunction perovskite solar cells.During the past several years, methylammonium lead halide perovskites have been widely investigated as light absorbers for thin-film photovoltaic cells. Among the various device architectures, the inverted planar heterojunction perovskite solar cells have attracted special attention for their relatively simple fabrication and high efficiencies. Although promising efficiencies have been obtained in the inverted planar geometry based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) sulfonic acid (PEDOT:PSS) as the hole transport material (HTM), the hydrophilicity of the PEDOT:PSS is a critical factor for long-term stability. In this paper, a CuOx hole transport layer from a

  10. Crystal Structure of Pure and Aluminous Calcium Silicate Perovskites at Mantle Related Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Chen, H.; Shim, S. H.; Leinenweber, K. D.; Meng, Y.; Prakapenka, V.

    2015-12-01

    CaSiO3-perovskite (CaPv) is believed to be the third most abundant mineral (5 wt%) in the Earth's lower mantle (LM). Subducted slabs contain 23 wt% CaPv at the LM related pressure (P) and temperature (T), where Al2O3 could be incorporated into the crystal structure of CaPv (AlCaPv). However, there remains important discrepancy between computations and experiments on the crystal structure of CaPv at high P and low T. Some computations have predicted a tetragonal I4/mcm structure with a pseudo-cubic axial ratio (cp/ap) greater than 1, while X-ray diffraction (XRD) studies have suggested a tetragonal P4/mmm structure with cp/ap ~ 0.995. Using Ne as a pressure medium, we conducted in-situ XRD of CaSiO3 and 5 wt% Al-bearing CaSiO3 in the laser heated diamond anvil cell at the GSECARS and HPCAT sectors of the Advanced Photon Source. Rietveld refinements are performed on the diffraction patterns of CaPv at 300 K and 20-60 GPa. Similar to previous studies, we observed splitting of the 200 and 211 peaks after T-quench in pure CaPv. However, unlike previous experiments, diffraction patterns were more consistent with a tetragonal I4/mcm structure with cp/ap ~ 1.005 than P4/mmm. All the previous diffraction patterns have been measured with an Ar or MgO medium, or even without a medium, while we used more hydrostatic Ne medium. Considering the small free energy differences among different perovskite structures, the crystal structure of CaPv may be very sensitive to non-hydrostatic stresses. In runs with AlCaPv, asymmetrical 200 peaks are found up to 60 GPa and 2200 K, showing that non-cubic could be still stable at mantle geotherm temperatures in AlCaPv. The extreme sensitivity of CaPv on deviatoric stresses may have important implications for the elastic properties of the mantle regions with strong deformations, because the elastic anisotropy can change with the crystal structure of CaPv.

  11. Layer like porous materials with hierarchical structure.

    PubMed

    Roth, Wieslaw J; Gil, Barbara; Makowski, Wacław; Marszalek, Bartosz; Eliášová, Pavla

    2016-06-13

    Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks. PMID:26489452

  12. 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. PMID:27214091

  13. Degradation of Methylammonium Lead Iodide Perovskite Structures through Light and Electron Beam Driven Ion Migration

    PubMed Central

    2016-01-01

    Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques. PMID:26804213

  14. Degradation of Methylammonium Lead Iodide Perovskite Structures through Light and Electron Beam Driven Ion Migration.

    PubMed

    Yuan, Haifeng; Debroye, Elke; Janssen, Kris; Naiki, Hiroyuki; Steuwe, Christian; Lu, Gang; Moris, Michèle; Orgiu, Emanuele; Uji-I, Hiroshi; De Schryver, Frans; Samorì, Paolo; Hofkens, Johan; Roeffaers, Maarten

    2016-02-01

    Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques. PMID:26804213

  15. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D'' diversity.

    PubMed

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q R

    2014-01-01

    Recent studies show that the D'' layer, just above the Earth's core-mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D'' diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D'' discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D'' layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific. PMID:24670790

  16. Two layer structure for reinforcing pothole repair

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Yuan, Kuo-Yao; Zou, Linhua; Yang, Jenn-Ming; Ju, Jiann-Wen; Kao, Wei; Carlson, Larry

    2013-04-01

    We have applied dicyclopentadiene (DCPD) resin for reinforcing pothole patch materials due to its unique properties - low cost, low viscosity at beginning and ultra-toughness after curing, chemical compatibility with tar, tunable curing profile through catalyst design. In this paper, we have designed a two layer structure - well compacted base layer and DCPD reinforced 1-1.5" top layer - for pothole repair. By choosing two graded asphalt mixes, a porous top layer and fully compacted base layer was prepared after compaction and ready for DCPD resin infiltration. The DCPD curing and infiltration profile within this porous top layer was measured with thermocouples. The rutting resistance was tested with home-made wheel rutter. The cage effect due to the p-DCPD wrapping was characterized with wheel penetration test. The results showed that this two layer structure pothole repair has greatly improved properties and can be used for pothole repair to increase the service life.

  17. Simulation of plasma double-layer structures

    NASA Technical Reports Server (NTRS)

    Borovsky, J. E.; Joyce, G.

    1982-01-01

    Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2 dimensional particle in cell method. The investigation of planar double layers indicates that these one dimensional potential structures are susceptible to periodic disruption by instabilities in the low potential plasmas. Only a slight increase in the double layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double layer electric field alignment of accelerated particles and strong magnetization results in their magnetic field alignment. The numerical simulations of spatially periodic two dimensional double layers also exhibit cyclical instability. A morphological invariance in two dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron beam excited electrostatic electron cyclotron waves and (ion beam driven) solitary waves are present in the plasmas adjacent to the double layers.

  18. Simulation of Sintering of Layered Structures

    SciTech Connect

    OLEVSKY,EUGENE; TIKARE,VEENA; GARINO,TERRY J.; BRAGINSKY,MICHAEL V.

    2000-11-22

    An integrated approach, combining the continuum theory of sintering and Potts model based mesostructure evolution analysis, is used to solve the problem of bi-layered structure sintering. Two types of bi-layered structures are considered: layers of the same material with different initial porosity, and layers of two different materials. The effective sintering stress for the bi-layer powder sintering is derived, both at the meso- and the macroscopic levels. Macroscopic shape distortions and spatial distributions of porosity are determined as functions of the dimensionless specific time of sintering. The effect of the thickness of the layers on shrinkage, warpage, and pore-grain structure is studied. Ceramic ZnO powders are employed as a model experimental system to assess the model predictions.

  19. An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Seo, Seongrok; Park, Ik Jae; Kim, Myungjun; Lee, Seonhee; Bae, Changdeuck; Jung, Hyun Suk; Park, Nam-Gyu; Kim, Jin Young; Shin, Hyunjung

    2016-06-01

    NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis.NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01601d

  20. Niobium Doping Effects on TiO2 Mesoscopic Electron Transport Layer-Based Perovskite Solar Cells.

    PubMed

    Kim, Dong Hoe; Han, Gill Sang; Seong, Won Mo; Lee, Jin-Wook; Kim, Byeong Jo; Park, Nam-Gyu; Hong, Kug Sun; Lee, Sangwook; Jung, Hyun Suk

    2015-07-20

    Perovskite solar cells (PSCs) are the most promising candidates as next-generation solar energy conversion systems. To design a highly efficient PSC, understanding electronic properties of mesoporous metal oxides is essential. Herein, we explore the effect of Nb doping of TiO2 on electronic structure and photovoltaic properties of PSCs. Light Nb doping (0.5 and 1.0 at %) increased the optical band gap slightly, but heavy doping (5.0 at %) distinctively decreased it. The relative Fermi level position of the conduction band is similar for the lightly Nb-doped TiO2 (NTO) and the undoped TiO2 whereas that of the heavy doped NTO decreased by as much as ∼0.3 eV. The lightly doped NTO-based PSCs exhibit 10 % higher efficiency than PSCs based on undoped TiO2 (from 12.2 % to 13.4 %) and 52 % higher than the PSCs utilizing heavy doped NTO (from 8.8 % to 13.4 %), which is attributed to fast electron injection/transport and preserved electron lifetime, verified by transient photocurrent decay and impedance studies. PMID:25891531

  1. Magnetic order and electronic structure of the 5 d3 double perovskite Sr2ScOsO6

    NASA Astrophysics Data System (ADS)

    Taylor, A. E.; Morrow, R.; Singh, D. J.; Calder, S.; Lumsden, M. D.; Woodward, P. M.; Christianson, A. D.

    2015-03-01

    The magnetic susceptibility, crystal and magnetic structures, and electronic structure of the double perovskite Sr2ScOsO6 are reported. Using both neutron and x-ray powder diffraction we find that the crystal structure is monoclinic P 21/n from 3.5 to 300 K. Magnetization measurements indicate an antiferromagnetic transition at TN=92 K , one of the highest transition temperatures of any double perovskite hosting only one magnetic ion. Type I antiferromagnetic order is determined by neutron powder diffraction, with an Os moment of only 1.6 (1 ) μB , close to half the spin-only value for a crystal field split 5 d electron state with a t2g 3 ground state. Density functional calculations show that this reduction is largely the result of strong Os-O hybridization, with spin-orbit coupling responsible for only a ˜0.1 μB reduction in the moment.

  2. Rapid Microwave-Assisted Grafting of Layered Perovskites with n-Alcohols.

    PubMed

    Boykin, Joshua R; Smith, Luis J

    2015-05-01

    Dion-Jacobson layered niobates have been extensively researched in recent years because of a variety of useful properties such as dielectric behavior, proton conduction, and solid acid catalysis. The behavior of these materials is strongly dependent on the elemental composition and, more specifically, the interlayer surface environment. A novel method of partial grafting of n-alcohols into the interlayer of HSr2Nb3O10 with approximately 40% conversion has been developed using microwave irradiation to generate high temperatures. This method has reduced the grafting reaction time by more than 97% while maintaining conversion rates consistent with previous methods. PMID:25906189

  3. Layered perovskite oxide: a reversible air electrode for oxygen evolution/reduction in rechargeable metal-air batteries.

    PubMed

    Takeguchi, Tatsuya; Yamanaka, Toshiro; Takahashi, Hiroki; Watanabe, Hiroshi; Kuroki, Tomohiro; Nakanishi, Haruyuki; Orikasa, Yuki; Uchimoto, Yoshiharu; Takano, Hiroshi; Ohguri, Nobuaki; Matsuda, Motofumi; Murota, Tadatoshi; Uosaki, Kohei; Ueda, Wataru

    2013-07-31

    For the development of a rechargeable metal-air battery, which is expected to become one of the most widely used batteries in the future, slow kinetics of discharging and charging reactions at the air electrode, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively, are the most critical problems. Here we report that Ruddlesden-Popper-type layered perovskite, RP-LaSr3Fe3O10 (n = 3), functions as a reversible air electrode catalyst for both ORR and OER at an equilibrium potential of 1.23 V with almost no overpotentials. The function of RP-LaSr3Fe3O10 as an ORR catalyst was confirmed by using an alkaline fuel cell composed of Pd/LaSr3Fe3O10-2x(OH)2x·H2O/RP-LaSr3Fe3O10 as an open circuit voltage (OCV) of 1.23 V was obtained. RP-LaSr3Fe3O10 also catalyzed OER at an equilibrium potential of 1.23 V with almost no overpotentials. Reversible ORR and OER are achieved because of the easily removable oxygen present in RP-LaSr3Fe3O10. Thus, RP-LaSr3Fe3O10 minimizes efficiency losses caused by reactions during charging and discharging at the air electrode and can be considered to be the ORR/OER electrocatalyst for rechargeable metal-air batteries. PMID:23802735

  4. Magnetic and structural properties of NaLnMnWO{sub 6} and NaLnMgWO{sub 6} perovskites

    SciTech Connect

    King, Graham; Wayman, Lora M.; Woodward, Patrick M.

    2009-06-15

    We have prepared 14 new AA'BB'O{sub 6} perovskites which possess a rock salt ordering of the B-site cations and a layered ordering of the A-site cations. The compositions obtained are NaLnMnWO{sub 6} (Ln=Ce, Pr, Sm, Gd, Dy, and Ho) and NaLnMgWO{sub 6} (Ln=Ce, Pr, Sm, Eu, Gd, Tb, Dy, and Ho). The samples were structurally characterized by powder X-ray diffraction which has revealed metrically tetragonal lattice parameters for compositions with Ln=Ce, Pr and monoclinic symmetry for compositions with smaller lanthanides. Magnetic susceptibility vs. temperature measurements have found that all six NaLnMnWO{sub 6} compounds undergo antiferromagnetic ordering at temperatures between 10 and 13 K. Several compounds show signs of a second magnetic phase transition. One sample, NaPrMnWO{sub 6}, appears to pass through at least three magnetic phase transitions within a narrow temperature range. All eight NaLnMgWO{sub 6} compounds remain paramagnetic down to 2 K revealing that the ordering of the Ln{sup 3+} cations in the NaLnMnWO{sub 6} compounds is induced by the ordering of the Mn{sup 2+} sub-lattice. - Graphical abstract: Evidence for multiple magnetic phase transitions in the A and B-site ordered perovskite NaPrMnWO{sub 6}.

  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. PMID:26717046

  6. Pressure dependent structural changes and predicted electrical polarization in perovskite RMnO3

    NASA Astrophysics Data System (ADS)

    Wu, T.; Chen, H.; Gao, P.; Yu, T.; Chen, Z.; Liu, Z.; Ahn, K. H.; Wang, X.; Cheong, S.-W.; Tyson, T. A.

    2016-02-01

    High pressure x-ray diffraction measurements on perovskite RMnO3 (R  =  Dy, Ho and Lu) reveal that varying structural changes occur for different R ions. Large lattice changes (orthorhombic strain) occur in DyMnO3 and HoMnO3 while the Jahn-Teller (JT) distortion remains stable. Conversely, in the small R-ion system LuMnO3, Mn-O bond distortions are observed between 4 and 8 GPa with a broad minimum in the JT distortion. High pressure infrared measurements indicate that a phonon near 390 cm-1 corresponding to the complex motion of the Mn and O ions changes anomalously for LuMnO3. It softens in the 4-8 GPa region, which is consistent with the structural change in Mn-O bonds and then hardens at higher pressures. By contrast, the phonons continuously harden with increasing pressure for DyMnO3 and HoMnO3. Density functional theory methods show that E-phase LuMnO3 is the most stable phase up to the 10 GPa pressure examined. Simulations indicate that the distinct structural change under pressure in LuMnO3 can possibly be used to optimize the electric polarization by pressure/strain.

  7. Local structure of the metal-organic perovskite dimethylammonium manganese(ii) formate.

    PubMed

    Duncan, Helen D; Dove, Martin T; Keen, David A; Phillips, Anthony E

    2016-03-14

    We report total neutron scattering measurements on the metal-organic perovskite analogue dimethylammonium manganese(ii) formate, (CD3)2ND2[Mn(DCO2)3]. Reverse Monte Carlo modelling shows that, in both the disordered high-temperature and ordered low-temperature phases, the ammonium moiety forms substantially shorter hydrogen bonds (N...O = 2.4 Å and 2.6 Å) than are visible in the average crystal structures. These bonds result from a pincer-like motion of two adjacent formate ions about the dimethylammonium ion in such a way that the framework can adjust independently to the positions of nearest-neighbour dimethylammonium ions. At low temperatures the shortest hydrogen bond is less favourable, apparently because it involves a greater distortion of the framework. Furthermore, in the high-temperature phase, in addition to the three disordered nitrogen positions expected from the average crystal structure, there appear to be also smaller probability maxima between these positions, corresponding to orientations in which the dimethylammonium is hydrogen-bonded to the two oxygen atoms of a single formate ion. The spontaneous strain across the phase transition reveals a contraction of the framework about the dimethylammonium cation, continuing as the material is cooled below the transition temperature. These results provide direct evidence of the local atomic structure of the guest-framework hydrogen bonding, and in particular the distortions of the framework responsible for the phase transition in this system. PMID:26763144

  8. Solution-Based Fabrication of Perovskite Multilayers and Superlattices Using Nanosheet Process

    NASA Astrophysics Data System (ADS)

    Li, Bao-Wen; Osada, Minoru; Akatsuka, Kosho; Ebina, Yasuo; Ozawa, Tadashi C.; Sasaki, Takayoshi

    2011-09-01

    We report a solution-based fabrication of perovskite multilayers and superlattices using perovskite nanosheets. Perovskite nanosheets (LaNb2O7, Ca2Nb3O10, and Sr2Nb3O10) were prepared by delaminating layered perovskites. A layer-by-layer approach using Langmuir-Blodgett deposition was effective for fabricating high-quality nanofilms of perovskite nanosheets on various substrates, such as quartz glass, Si, and SrRuO3. Structural characterizations by X-ray diffraction, transmission electron microscopy, and hard X-ray photoelectron spectroscopy revealed that these perovskite nanofilms are composed of a well-ordered lamellar structure with an atomically sharp interface. The multilayer films exhibited a stable dielectric response inherent to the perovskite nanosheet. We also found that the superlattices of (LaNb2O7/Ca2Nb3O10)5 and (Sr2Nb3O10/Ca2Nb3O10)5 possess strong interface coupling, which gives rise to enhanced dielectric constant.

  9. NaIrO3—A Pentavalent Post-perovskite

    SciTech Connect

    M Bremholm; S Dutton; P Stephens; R Cava

    2011-12-31

    Sodium iridium (V) oxide, NaIrO{sub 3}, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO{sub 3}, the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO{sub 3}. Among the oxide post-perovskites, NaIrO{sub 3} is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO{sub 6} octahedra separated by layers of NaO{sub 8} bicapped trigonal prisms. NaIrO{sub 3} shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides.

  10. Ultrathin efficient perovskite solar cells employing a periodic structure of a composite hole conductor for elevated plasmonic light harvesting and hole collection

    NASA Astrophysics Data System (ADS)

    Long, Mingzhu; Chen, Zefeng; Zhang, Tiankai; Xiao, Yubin; Zeng, Xiaoliang; Chen, Jian; Yan, Keyou; Xu, Jianbin

    2016-03-01

    We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a Voc of 1.05 V, Jsc of 22.9 mA cm-2, FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer.We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure

  11. Stabilization of Organic-Inorganic Perovskite Layers by Partial Substitution of Iodide by Bromide in Methylammonium Lead Iodide.

    PubMed

    Ruess, Raffael; Benfer, Felix; Böcher, Felix; Stumpp, Martina; Schlettwein, Derck

    2016-05-18

    Thin films of the methylammonium lead halides CH3 NH3 Pb(I1-x Brx )3 are prepared on fluorine-doped tin oxide substrates and exposed to humid air in the dark and under illumination. To characterize the stability of the materials, UV/Vis spectra are acquired at fixed intervals, accompanied by XRD, energy-dispersive X-ray spectroscopy, SEM, and confocal laser scanning microscopy. Different degradation mechanisms are observed depending on the environmental conditions. It is found that bromide can successfully suppress the transformation of the perovskite into the monohydrate, presumably owing to stronger hydrogen-bonding interactions with the organic cation. However, under illumination in humid air, rather rapid decomposition of the perovskites was still observed, which is due to phase segregation. The use of increased bromide content in methylammonium lead halide absorbers is discussed in terms of their application in perovskite solar cells. PMID:26853438

  12. The effect of moisture on the structures and properties of lead halide perovskites: a first-principles theoretical investigation.

    PubMed

    Zhang, Lei; Ju, Ming-Gang; Liang, WanZhen

    2016-08-17

    With efficiencies exceeding 20% and low production costs, lead halide perovskite solar cells (PSCs) have become potential candidates for future commercial applications. However, there are serious concerns about their long-term stability and environmental friendliness, heavily related to their commercial viability. Herein, we present a theoretical investigation based on the ab initio molecular dynamics (AIMD) simulations and the first-principles density functional theory (DFT) calculations to investigate the effects of sunlight and moisture on the structures and properties of MAPbI3 perovskites. AIMD simulations have been performed to simulate the impact of a few water molecules on the structures of MAPbI3 surfaces terminated in three different ways. The evolution of geometric and electronic structures as well as the absorption spectra has been shown. It is found that the PbI2-terminated surface is the most stable while both the MAI-terminated and PbI2-defective surfaces undergo structural reconstruction, leading to the formation of hydrated compounds in a humid environment. The moisture-induced weakening of photoabsorption is closely related to the formation of hydrated species, and the hydrated crystals MAPbI3·H2O and MA4PbI6·2H2O scarcely absorb the visible light. The electronic excitation in the bare and water-absorbed MAPbI3 nanoparticles tends to weaken Pb-I bonds, especially those around water molecules, and the maximal decrease of photoexcitation-induced bond order can reach up to 20% in the excited state in which the water molecules are involved in the electronic excitation, indicating the accelerated decomposition of perovskites in the presence of sunlight and moisture. This work is valuable for understanding the mechanism of chemical or photochemical instability of MAPbI3 perovskites in the presence of moisture. PMID:27499005

  13. Ferroelectric Phase Transition and Photoinduced Cooperative Phenomena in Bi-Layered Perovskite Pb2Bi4Ti5O18 Ceramics Studied by Brillouin Scattering

    NASA Astrophysics Data System (ADS)

    Takesada, Masaki; Ueki, Ayaka; Onodera, Akira; Noguchi, Yuji; Miyayama, Masaru

    2010-09-01

    The ferroelectric phase transition mechanism and ultraviolet (UV) photoexcition effect have been investigated in the bismuth layered perovskite Pb2Bi4Ti5O18 by Brillouin scattering using a Sandercock-type tandem Fabry-Perot interferometer. The temperature dependences of Brillouin spectra both with and without UV irradiation were observed around phase transition points. The observed Brillouin spectra include a central peak component that shows an anomaly in the ferroelectric phase transition point TC=450 K. The central peak spectra show narrowing under UV irradiation. The correlation length of the ferroelectric dipole fluctuation should be enhanced with the UV irradiation effect below TC.

  14. Photoinduced cooperative phenomena in ferroelectric layered perovskites Pb2Bi4Ti5O18 studied by high resolution Raman scattering

    NASA Astrophysics Data System (ADS)

    Takesada, Masaki; Ueki, Ayaka; Onodera, Akira

    2009-02-01

    The UV photo induced effect in bismuth layered perovskite Pb2Bi4Ti5O18 has been investigated by a low frequency Raman scattering. The temperature dependences of Raman spectra both under and without a UV irradiation were observed around the ferroelectric to relaxor phase transition temperature. The central peak in the Raman spectrum shows narrowing under a UV irradiation below Tc. The correlation length of the ferroelectric fluctuation should be enhanced as a UV photo induced effect in the ferroelectric state.

  15. An easy-to-fabricate low-temperature TiO2 electron collection layer for high efficiency planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Conings, B.; Baeten, L.; Jacobs, T.; Dera, R.; D'Haen, J.; Manca, J.; Boyen, H.-G.

    2014-08-01

    Organometal trihalide perovskite solar cells arguably represent the most auspicious new photovoltaic technology so far, as they possess an astonishing combination of properties. The impressive and brisk advances achieved so far bring forth highly efficient and solution processable solar cells, holding great promise to grow into a mature technology that is ready to be embedded on a large scale. However, the vast majority of state-of-the-art perovskite solar cells contains a dense TiO2 electron collection layer that requires a high temperature treatment (>450 °C), which obstructs the road towards roll-to-roll processing on flexible foils that can withstand no more than ˜150 °C. Furthermore, this high temperature treatment leads to an overall increased energy payback time and cumulative energy demand for this emerging photovoltaic technology. Here we present the implementation of an alternative TiO2 layer formed from an easily prepared nanoparticle dispersion, with annealing needs well within reach of roll-to-roll processing, making this technology also appealing from the energy payback aspect. Chemical and morphological analysis allows to understand and optimize the processing conditions of the TiO2 layer, finally resulting in a maximum obtained efficiency of 13.6% for a planar heterojunction solar cell within an ITO/TiO2/CH3NH3PbI3-xClxpoly(3-hexylthiophene)/Ag architecture.

  16. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodong; Lei, Ming; Zhou, Yi; Song, Bo; Li, Yongfang

    2015-08-01

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH3NH3PbI3-XClX. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (Jsc). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  17. An easy-to-fabricate low-temperature TiO{sub 2} electron collection layer for high efficiency planar heterojunction perovskite solar cells

    SciTech Connect

    Conings, B.; Baeten, L.; Jacobs, T.; Dera, R.; D’Haen, J.; Manca, J.; Boyen, H.-G.

    2014-08-01

    Organometal trihalide perovskite solar cells arguably represent the most auspicious new photovoltaic technology so far, as they possess an astonishing combination of properties. The impressive and brisk advances achieved so far bring forth highly efficient and solution processable solar cells, holding great promise to grow into a mature technology that is ready to be embedded on a large scale. However, the vast majority of state-of-the-art perovskite solar cells contains a dense TiO{sub 2} electron collection layer that requires a high temperature treatment (>450 °C), which obstructs the road towards roll-to-roll processing on flexible foils that can withstand no more than ∼150 °C. Furthermore, this high temperature treatment leads to an overall increased energy payback time and cumulative energy demand for this emerging photovoltaic technology. Here we present the implementation of an alternative TiO{sub 2} layer formed from an easily prepared nanoparticle dispersion, with annealing needs well within reach of roll-to-roll processing, making this technology also appealing from the energy payback aspect. Chemical and morphological analysis allows to understand and optimize the processing conditions of the TiO{sub 2} layer, finally resulting in a maximum obtained efficiency of 13.6% for a planar heterojunction solar cell within an ITO/TiO{sub 2}/CH{sub 3}NH{sub 3}PbI{sub 3-x}Cl{sub x}poly(3-hexylthiophene)/Ag architecture.

  18. An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells.

    PubMed

    Seo, Seongrok; Park, Ik Jae; Kim, Myungjun; Lee, Seonhee; Bae, Changdeuck; Jung, Hyun Suk; Park, Nam-Gyu; Kim, Jin Young; Shin, Hyunjung

    2016-06-01

    NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis. PMID:27216291

  19. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    SciTech Connect

    Liu, Xiaodong; Zhou, Yi E-mail: songbo@suda.edu.cn Song, Bo E-mail: songbo@suda.edu.cn; Lei, Ming; Li, Yongfang E-mail: songbo@suda.edu.cn

    2015-08-10

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH{sub 3}NH{sub 3}PbI{sub 3−X}Cl{sub X}. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (J{sub sc}). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  20. Activity and structure of perovskites as diesel reforming catalysts for solid oxide fuel cells.

    SciTech Connect

    Liu, D.-J.; Krumpelt, M.; Chemical Engineering

    2005-01-01

    Recent progress in developing perovskite materials as more cost-effective catalysts in autothermal reforming (ATR) of diesel fuel to hydrogen-rich reformate for solid oxide fuel cell (SOFC) application is reported. Perovskite-type metal oxides with B sites partially exchanged by ruthenium were prepared and evaluated under ATR reaction conditions. The hydrogen yield, reforming efficiency, and CO{sub x} selectivity of these catalysts were investigated using diesel surrogate fuel with 50 ppm sulfur. The catalyst performances have approached or exceeded a benchmark, high-cost rhodium-based material. In parallel with the reactivity study, we also investigated the physical properties of B-site doped perovskites and their impact on the reforming performance using various characterization techniques such as BET, X-ray powder diffraction, temperature programmable reduction, scanning electron microscopy, and synchrotron X-ray absorption spectroscopy. We found that ruthenium is highly dispersed into perovskite lattice and its redox behavior is directly associated with reforming activity.

  1. The Kinematics of Turbulent Boundary Layer Structure

    NASA Technical Reports Server (NTRS)

    Robinson, Stephen Kern

    1991-01-01

    The long history of research into the internal structure of turbulent boundary layers has not provided a unified picture of the physics responsible for turbulence production and dissipation. The goals of the present research are to: (1) define the current state of boundary layer structure knowledge; and (2) utilize direct numerical simulation results to help close the unresolved issues identified in part A and to unify the fragmented knowledge of various coherent motions into a consistent kinematic model of boundary layer structure. The results of the current study show that all classes of coherent motion in the low Reynolds number turbulent boundary layer may be related to vortical structures, but that no single form of vortex is representative of the wide variety of vortical structures observed. In particular, ejection and sweep motions, as well as entrainment from the free-streem are shown to have strong spatial and temporal relationships with vortical structures. Disturbances of vortex size, location, and intensity show that quasi-streamwise vortices dominate the buffer region, while transverse vortices and vortical arches dominate the wake region. Both types of vortical structure are common in the log region. The interrelationships between the various structures and the population distributions of vortices are combined into a conceptual kinematic model for the boundary layer. Aspects of vortical structure dynamics are also postulated, based on time-sequence animations of the numerically simulated flow.

  2. Pressure-Induced Structural and Electronic Transition in Sr2ZnWO6 Double Perovskite.

    PubMed

    Li, Nana; Manoun, Bouchaib; Tang, Lingyun; Ke, Feng; Liu, Fengliang; Dong, Haini; Lazor, Peter; Yang, Wenge

    2016-07-01

    High-pressure structural and electrical properties of Sr2ZnWO6 double perovskite were investigated using in situ angle-dispersive synchrotron X-ray diffraction (XRD), Raman, and alternating current (AC) impedance spectroscopy. A structural transition from monoclinic (P21/n) to triclinic (P1̅) phase around 9 GPa was observed due to the pressure-induced distortion of (W, Zn)O6 octahedron. In situ high-pressure Raman spectroscopy showed the increasing interaction among O-W-O in WO6 octahedron with pressure and a transition pressure consistent with the XRD results. From the AC impedance spectroscopy measurements, the resistivity increased steeply by ∼1 order of magnitude around 11 GPa, indicating an electronic transition accompanying the symmetry change. The increase in the interaction among O-W-O enhances the attraction of O(2-) electrons toward W(6+), thus increasing the covalence, which in turn lowers the charge transfer energy between O(2-) and W(6+) and induces the resistivity increase under high pressure. PMID:27308777

  3. Correlating structure and electronic band-edge properties in organolead halide perovskites nanoparticles.

    PubMed

    Zhu, Qiushi; Zheng, Kaibo; Abdellah, Mohamed; Generalov, Alexander; Haase, Dörthe; Carlson, Stefan; Niu, Yuran; Heimdal, Jimmy; Engdahl, Anders; Messing, Maria E; Pullerits, Tonu; Canton, Sophie E

    2016-06-01

    After having emerged as primary contenders in the race for highly efficient optoelectronics materials, organolead halide perovskites (OHLP) are now being investigated in the nanoscale regime as promising building blocks with unique properties. For example, unlike their bulk counterpart, quantum dots of OHLP are brightly luminescent, owing to large exciton binding energies that cannot be rationalized solely on the basis of quantum confinement. Here, we establish the direct correlation between the structure and the electronic band-edge properties of CH3NH3PbBr3 nanoparticles. Complementary structural and spectroscopic measurements probing long-range and local order reveal that lattice strain influences the nature of the valence band and modifies the subtle stereochemical activity of the Pb(2+) lone-pair. More generally, this work demonstrates that the stereochemical activity of the lone-pair at the metal site is a specific physicochemical parameter coupled to composition, size and strain, which can be employed to engineer novel functionalities in OHLP nanomaterials. PMID:27189431

  4. Structural and magnetic properties of double perovskite oxide Ba2CeSbO6

    NASA Astrophysics Data System (ADS)

    Dutta, Alo; Mukhopadhyay, P. K.; Sinha, T. P.; Das, Dipankar; Shannigrahi, Santiranjan

    2016-08-01

    The structural and magnetic properties of a double perovskite oxide Ba2CeSbO6 (BCSO) synthesized by solid state reaction technique have been investigated. The Rietveld refinement of the X-ray diffraction pattern of BCSO suggests the monoclinic crystal structure at room temperature with P21/n space group. The vibrational properties of BCSO are investigated by the Fourier transform Infrared and Raman spectroscopy. The Raman spectrum confirms the B-site ordering of cations in BCSO. The temperature dependent magnetic susceptibility data in the field cooled mode show the anti-ferromagnetic behaviour of BCSO below 59 K. The core level X-ray photoemission (XPS) spectrum of Ce-3d and Sb-3d states confirms the presence of multiple oxidation states of these cations. The presence of both the Ce3+ and Ce4+ ions in BCSO gives the 4f4-δ intermediate valence state which may reduce the effective magnetic moment with respect to the system having single valence Ce3+ ion.

  5. Pressure-Induced Structural and Optical Properties of Organometal Halide Perovskite-Based Formamidinium Lead Bromide.

    PubMed

    Wang, Lingrui; Wang, Kai; Zou, Bo

    2016-07-01

    Organometal halide perovskites (OMHPs) are attracting an ever-growing scientific interest as photovoltaic materials with moderate cost and compelling properties. In this Letter, pressure-induced optical and structural changes of OMHP-based formamidinium lead bromide (FAPbBr3) were systematically investigated. We studied the pressure dependence of optical absorption and photoluminescence, both of which showed piezochromism. Synchrotron X-ray diffraction indicated that FAPbBr3 underwent two phase transitions and subsequent amorphization, leading directly to the bandgap evolution with redshift followed by blueshift during compression. Raman experiments illustrated the high pressure behavior of organic cation and the surrounding inorganic octahedra. Additionally, the effect of cation size and the different intermolecular interactions between organic cation and inorganic octahedra result in the fact that FAPbBr3 is less compressible than the reported methylammonium lead bromide (MAPbBr3). High pressure studies of the structural evolution and optical properties of OMHPs provide important clues in optimizing photovoltaic performance and help to design novel OMHPs with higher stimuli-resistant ability. PMID:27321024

  6. Electronic structure investigation of the cubic inverse perovskite Sc3AlN

    NASA Astrophysics Data System (ADS)

    Magnuson, Martin; Mattesini, Maurizio; Höglund, Carina; Abrikosov, Igor A.; Birch, Jens; Hultman, Lars

    2008-12-01

    The electronic structure and chemical bonding of the recently discovered inverse perovskite Sc3AlN , in comparison to those of ScN and Sc metal, have been investigated by bulk-sensitive soft-x-ray emission spectroscopy. The measured ScL , NK , AlL1 , and AlL2,3 emission spectra are compared with calculated spectra using first-principles density-functional theory including dipole transition-matrix elements. The main Sc3d-N2p and Sc3d-Al3p chemical bond regions are identified at -4 and -1.4eV below the Fermi level, respectively. A strongly modified spectral shape of 3s states in the AlL2,3 emission from Sc3AlN in comparison to that for pure Al metal is found, which reflects the Sc3d-Al3p hybridization observed in the AlL1 emission. The differences between the electronic structures of Sc3AlN , ScN, and Sc metal are discussed in relation to the change in the conductivity and elastic properties.

  7. Effect of sintering time on structural, microstructural and chemical composition of Ni-doped lanthanum gallate perovskites

    NASA Astrophysics Data System (ADS)

    Colomer, M. T.; Kilner, J. A.

    2015-08-01

    This work reports the effect of two different sintering times, 6 and 48 h on the structural, microstructural, and chemical features of Ni-doped La0.90Sr0.10GaO3.00-δ. Independently of the sintering time, La0.90Sr0.10Ga1-xNixO3.00-δ (where x=0.10, and 0.20 (mol)) presents a rhombohedral symmetry with a lattice volume that decreases when NiO dopant increases. Besides the perovskite, LaSrGa3.00O7.00 (nominal composition) is present as second phase in all cases. When the samples are doped with NiO, the peaks of this second phase are shifted with respect to the peaks of the pure phase. These shifts suggest that this second phase could admit some Ni ions in its structure. According to the XRD patterns, the amount of the latter phase is larger when sintering time is increased. Electron probe microanalysis (EPMA) indicated that the matrix of the samples sintered for 6 h is constituted by a perovskite with an experimental composition very close to the nominal one. However, when the samples are sintered for 48 h the matrix of each sample is constituted by two perovskites; both with compositional deviations with respect to their nominal one. In particular, a significant Sr depletion compensated by a La increment in the A site is observed. Those compositional deviations could be mainly due to the diffusion of the cations in the bulk and/or from the bulk to the surface of the samples. That diffusion can favour the formation, not only, of a second perovskite with a different composition in relation with the first one formed, but also, the formation of second phases. In addition, a very slight broadening of Bragg peaks of the perovskites sintered for 48 h is observed by XRD and can be related to the presence of two different perovskites in each sample according to EPMA results. By BSEM and EPMA analyses La4.00Ga2.00O9.00 (nominal composition) is also observed as second phase when samples are treated for 48 h.

  8. Structure of the low latitude boundary layer

    NASA Technical Reports Server (NTRS)

    Sckopke, N.; Paschmann, G.; Haerendel, G.; Sonnerup, B. U. O.; Bame, S. J.; Forbes, T. G.; Hones, E. W., Jr.; Russell, C. T.

    1980-01-01

    Observations at high temporal resolution of the frontside magnetopause and plasma boundary layer, made with the LASL/MPE fast plasma analyzer onboard the ISEE 1 and 2 spacecraft, revealed a complex quasiperiodic structure of some of the observed boundary layers. A cool tailward streaming boundary layer plasma was seen intermittently, with intervening periods of hot tenuous plasma which has properties similar to the magnetospheric population. While individual encounters with the boundary layer plasma last only a few minutes, the total observation time may extend over one hour or more.

  9. Perovskite Solar Cells with Large-Area CVD-Graphene for Tandem Solar Cells.

    PubMed

    Lang, Felix; Gluba, Marc A; Albrecht, Steve; Rappich, Jörg; Korte, Lars; Rech, Bernd; Nickel, Norbert H

    2015-07-16

    Perovskite solar cells with transparent contacts may be used to compensate for thermalization losses of silicon solar cells in tandem devices. This offers a way to outreach stagnating efficiencies. However, perovskite top cells in tandem structures require contact layers with high electrical conductivity and optimal transparency. We address this challenge by implementing large-area graphene grown by chemical vapor deposition as a highly transparent electrode in perovskite solar cells, leading to identical charge collection efficiencies. Electrical performance of solar cells with a graphene-based contact reached those of solar cells with standard gold contacts. The optical transmission by far exceeds that of reference devices and amounts to 64.3% below the perovskite band gap. Finally, we demonstrate a four-terminal tandem device combining a high band gap graphene-contacted perovskite top solar cell (Eg = 1.6 eV) with an amorphous/crystalline silicon bottom solar cell (Eg = 1.12 eV). PMID:26266857

  10. Charge Carriers in Planar and Meso-Structured Organic-Inorganic Perovskites: Mobilities, Lifetimes, and Concentrations of Trap States.

    PubMed

    Hutter, Eline M; Eperon, Giles E; Stranks, Samuel D; Savenije, Tom J

    2015-08-01

    Efficient solar cells have been obtained using thin films of solution-processed organic-inorganic perovskites. However, there remains limited knowledge about the relationship between preparation route and optoelectronic properties. We use complementary time-resolved microwave conductivity (TRMC) and photoluminescence (PL) measurements to investigate the charge carrier dynamics in thin planar films of CH3NH3PbI(3-x)Cl(x), CH3NH3PbI3, and their meso-structured analogues. High mobilities close to 30 cm(2)/(V s) and microsecond-long lifetimes are found in thin films of CH3NH3PbI(3-x)Cl(x), compared to lifetimes of only a few hundred nanoseconds in CH3NH3PbI3 and meso-structured perovskites. We describe our TRMC and PL experiments with a global kinetic model, using one set of kinetic parameters characteristic for each sample. We find that the trap density is less than 5 × 10(14) cm(-3) in CH3NH3PbI(3-x)Cl(x), 6 × 10(16) cm(-3) in the CH3NH3PbI3 thin film and ca. 10(15) cm(-3) in both meso-structured perovskites. Furthermore, our results imply that band-to-band recombination is enhanced by the presence of dark carriers resulting from unintentional doping of the perovskites. Finally, our general approach to determine concentrations of trap states and dark carriers is also highly relevant to other semiconductor materials. PMID:26267206

  11. Laser Crystallization of Organic-Inorganic Hybrid Perovskite Solar Cells.

    PubMed

    Jeon, Taewoo; Jin, Hyeong Min; Lee, Seung Hyun; Lee, Ju Min; Park, Hyung Il; Kim, Mi Kyung; Lee, Keon Jae; Shin, Byungha; Kim, Sang Ouk

    2016-08-23

    Organic-inorganic hybrid perovskites attract enormous research interest for next generation solar energy harvest. Synergistic crystalline structures comprising organic and inorganic components enable solution processing of perovskite films. A reliable crystallization method for perovskites, compatible with fast continuous process over large-area flexible substrates, is crucial for high performance solar cell production. Here, we present laser crystallization of hybrid perovskite solar cells using near-infrared (NIR) laser (λ = 1064 nm). Crystalline morphology of CH3NH3PbI3 (MAPbI3) perovskite films are widely controllable with laser irradiation condition while maintaining film uniformity. Photothermal heating effectively assisted by interfacial photoconversion layers is critical for phase transformation without beam damage of multilayered device structures. Notably, laser crystallization attains higher device performances than conventional thermal annealing. Fast laser crystallization with manufacture level scan rate (1 m min(-1)) demonstrates inverted-type perovskite solar cells with 11.3 and 8.0% efficiencies on typical glass and flexible polymer substrates, respectively, without rigorous device optimization. PMID:27377145

  12. Enhanced charge collection with ultrathin AlOx electron blocking layer for hole-transporting material-free perovskite solar cell.

    PubMed

    Wei, Huiyun; Shi, Jiangjian; Xu, Xin; Xiao, Junyan; Luo, Jianheng; Dong, Juan; Lv, Songtao; Zhu, Lifeng; Wu, Huijue; Li, Dongmei; Luo, Yanhong; Meng, Qingbo; Chen, Qiang

    2015-02-21

    An ultrathin AlOx layer has been deposited onto a CH3NH3PbI3 film using atomic layer deposition technology, to construct a metal-insulator-semiconductor (MIS) back contact for the hole-transporting material-free perovskite solar cell. By optimization of the ALD deposition cycles, the average power conversion efficiency (PCE) of the cell has been enhanced from 8.61% to 10.07% with a highest PCE of 11.10%. It is revealed that the improvement in cell performance with this MIS back contact is mainly attributed to the enhancement in charge collection resulting from the electron blocking effect of the AlOx layer. PMID:25594083

  13. Power Conversion Efficiency and Device Stability Improvement of Inverted Perovskite Solar Cells by Using a ZnO:PFN Composite Cathode Buffer Layer.

    PubMed

    Jia, Xiaorui; Zhang, Lianping; Luo, Qun; Lu, Hui; Li, Xueyuan; Xie, Zhongzhi; Yang, Yongzhen; Li, Yan-Qing; Liu, Xuguang; Ma, Chang-Qi

    2016-07-20

    We have demonstrated in this article that both power conversion efficiency (PCE) and performance stability of inverted planar heterojunction perovskite solar cells can be improved by using a ZnO:PFN nanocomposite (PFN: poly[(9,9-bis(3'-(N,N-dimethylamion)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl)-fluorene]) as the cathode buffer layer (CBL). This nanocomposite could form a compact and defect-less CBL film on the perovskite/PC61BM surface (PC61BM: phenyl-C61-butyric acid methyl ester). In addition, the high conductivity of the nanocomposite layer makes it works well at a layer thickness of 150 nm. Both advantages of the composite layer are helpful in reducing interface charge recombination and improving device performance. The power conversion efficiency (PCE) of the best ZnO:PFN CBL based device was measured to be 12.76%, which is higher than that of device without CBL (9.00%), or device with ZnO (7.93%) or PFN (11.30%) as the cathode buffer layer. In addition, the long-term stability is improved by using ZnO:PFN composite cathode buffer layer when compare to that of the reference cells. Almost no degradation of open circuit voltage (VOC) and fill factor (FF) was found for the device having ZnO:PFN, suggesting that ZnO:PFN is able to stabilize the interface property and consequently improve the solar cell performance stability. PMID:27349330

  14. Total energy study of the microscopic structure and electronic properties of tetragonal perovskite SrTiO{sub 3}

    SciTech Connect

    Rubio-Ponce, A.; Olguín, D.

    2014-05-15

    To study the structural and electronic properties of cubic perovskite SrTiO{sub 3} and its stress-induced tetragonal phase, we have performed total energy calculations and studied the effect of oxygen vacancies on the electronic properties of tetragonal perovskite SrTiO{sub 3}. The method used was the relativistic full-potential linearized augmented plane wave (FLAPW) method. To obtain the geometry that minimizes the total energy, we relaxed the internal atomic sites of the tetragonal cell. As a result of this procedure, we have found that the titanium atoms move toward the plane of the vacancy by 0.03 Å, and the apical oxygen atoms move to the same plane by approximately 0.14 Å. These results are discussed in comparison with experimental data.

  15. Perovskite solar cells: High voltage from ordered fullerenes

    NASA Astrophysics Data System (ADS)

    Yan, Yanfa

    2016-01-01

    The open-circuit voltage is one of the parameters determining the efficiency of solar cells in converting solar radiation to electricity. Reducing the structural disorder in fullerene electron-transport layers is now shown to significantly improve the open-circuit voltage of perovskite solar cells.

  16. Influence of structural distortions on the Ir magnetism in Ba2-xSrxYIrO6 double perovskites

    NASA Astrophysics Data System (ADS)

    Phelan, Brendan F.; Seibel, Elizabeth M.; Badoe, Daniel; Xie, Weiwei; Cava, R. J.

    2016-06-01

    We explore the relative strengths of spin orbit coupling and crystal field splitting in the Ir5+ compounds Ba2-xSrxYIrO6. In the case of strong spin orbit coupling and regular Ir5+ octahedra, one expects a non-magnetic J=0 state; in the case of distorted octahedra where crystal field effects dominate, the t2g manifold splits into a magnetic ground state. We report the results of continuously transitioning from the cubic Ba2YIrO6 double perovskite with ideal octahedra to the monoclinic Sr2YIrO6 double perovskite with distorted octahedra. We see no emergence of an enhanced Ir5+ magnetic moment in the series on increasing the structural distortions, as would have been the case for significant crystal field splitting. The near-constant magnetic moment observed through the Ba2-xSrxYIrO6 series reinforces the notion that spin-orbit coupling is the dominant force in determining the magnetism of iridium-oxygen octahedra in perovskite-like structures.

  17. Perovskite-structure TlMnO₃: a new manganite with new properties.

    PubMed

    Yi, Wei; Kumagai, Yu; Spaldin, Nicola A; Matsushita, Yoshitaka; Sato, Akira; Presniakov, Igor A; Sobolev, Alexey V; Glazkova, Yana S; Belik, Alexei A

    2014-09-15

    We synthesize a new member of the AMnO3 perovskite manganite family (where A is a trivalent cation)--thallium manganite, TlMnO3--under high-pressure (6 GPa) and high-temperature (1500 K) conditions and show that the structural and magnetic properties are distinct from those of all other AMnO3 manganites. The crystal structure of TlMnO3 is solved and refined using single-crystal X-ray diffraction data. We obtain a triclinically distorted structure with space group P1̅ (No. 2), Z = 4, and lattice parameters a = 5.4248(2) Å, b = 7.9403(2) Å, c = 5.28650(10) Å, α = 87.8200(10)°, β = 86.9440(10)°, and γ = 89.3130(10)° at 293 K. There are four crystallographic Mn sites in TlMnO3 forming two groups based on the degree of their Jahn-Teller distortions. Physical properties of insulating TlMnO3 are investigated with Mössbauer spectroscopy and resistivity, specific heat, and magnetization measurements. The orbital ordering, which persists to the decomposition temperature of 820 K, suggests A-type antiferromagnetic ordering with the ferromagnetic planes along the [-101] direction, consistent with the measured collinear antiferromagnetism below the Néel temperature of 92 K. Hybrid density functional calculations are consistent with the experimentally identified structure, insulating ground state, and suggested magnetism, and show that the low symmetry originates from the strongly Jahn-Teller distorted Mn(3+) ions combined with the strong covalency of the Tl(3+)-O bonds. PMID:25163034

  18. Controlling the Electronic Structures of Perovskite Oxynitrides and their Solid Solutions for Photocatalysis.

    PubMed

    Umezawa, Naoto; Janotti, Anderson

    2016-05-10

    Band-gap engineering of oxide materials is of great interest for optoelectronics, photovoltaics, and photocatalysis applications. In this study, electronic structures of perovskite oxynitrides, LaTiO2 N and SrNbO2 N, and solid solutions, (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x , are investigated using hybrid density functional calculations. Band gaps of LaTiO2 N and SrNbO2 N are much smaller than that of SrTiO3 owing to the formation of a N 2p band, which is higher in energy than the O 2p band. The valence- and conduction-band offsets of SrTiO3 /LaTiO2 N and SrTiO3 /SrNbO2 N are computed, and the adequacy for H2 evolution is analyzed by comparing the positions of the band edges with respect to the standard hydrogen electrode (SHE). The band gap of (SrTiO3 )1-x (LaTiO2 N)x and (SrTiO3 )1-x (SrNbO2 N)x solid solutions are also discussed. PMID:27072042

  19. Structural and impedance analysis of Co-doped SrTiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Echeverri, E.; Arnache, O.

    2016-02-01

    SrTi1-xCoxO3 (0.2≥x≥0) polycrystalline samples were prepared by solid-state reaction. X-ray diffraction (XRD) analysis shown the perovskite type structure is conserved for all samples without impurities. A small increase in the lattice parameters were observed for x≥0.05. Morphology and composition were analysed by scanning electron microscopy (SEM- EDX). Impedance spectroscopy measurements form 50Hz to 1MHz were made at different temperatures (25-400°C). The spectra were analysed by Z' vs Z'' plots, which reveal 3 contributions associated to electrodes, grain boundary and grain. From the fits the frequency f) and times relaxation (τ) of the grain were estimated, with values of f∼15KHz and τ∼67µs for 20% Co samples at RT. A dispersion in the permittivity ε* at low frequency (<300Hz) were observed, which increase with the temperature. Each component of ε* converge for frequencies up to ∼300kHz. Finally, a behaviour and activation energy analysis of the electrical conductivity is presented from ln(σ) vs 1/T plots.

  20. Electronic structure studies of high-T/sub c/ perovskites and related materials

    SciTech Connect

    Wachs, A.L.; Turchi, P.E.A.; Kaiser, J.H.; West, R.N.; Howell, R.H.; Jean, Y.C.; Merkle, K.L.; Revcolevschi, A.; Fluss, M.J.

    1988-10-01

    We have performed 2D-ACPAR measurements on La/sub 2/CuO/sub 4/ and NiO. The ACPAR distributions were very isotropic, with small anisotropic deviations on the order of 10% of the total counts. It was not possible to clearly discern a Fermi surface in either set of data, nor was it possible to identify any features with the symmetry and periodicity of the crystalline reciprocal lattices. Attempts to model both systems by starting with a localized ionic picture and allowing covalency overlap to take place among the atoms comprising an isolated metal atom-oxygen octahedral cluster have proven successful. This result suggests that it might be appropriate for analyses of the electronic structure for high-T/sub c/ perovskites to begin with the ansatz of localized electronic states. This approach has worked very well for the transition-metal monoxides. Finally, application of the LCW formalism to data from both systems yields a result very close to filled-band behavior. We believe the deviations from the latter are significant, but that they originate from positronic wavefunction mixing of the electronic states and not from a Fermi surface. 9 refs., 3 figs.

  1. Disproportionation, dopant incorporation, and defect clustering in Perovskite-structured NdCoO3.

    PubMed

    Tealdi, Cristina; Malavasi, Lorenzo; Fisher, Craig A J; Islam, M Saiful

    2006-03-23

    Atomistic simulation techniques are used to examine the defect chemistry of perovskite-structured NdCoO(3), a material whose electrochemical properties make it attractive for use in heterogeneous oxidation catalysis, as well as in gas sensors and mixed ionic/electronic conductors. In practice, dopants are added to NdCoO(3) to obtain the desired properties, such as high electrical conductivity and rapid gas adsorption/desorption; thus, a wide range of dopants substituted on both Nd and Co sites are examined. Charge compensation for aliovalent dopants is predicted to occur via formation of oxide ion vacancies; these are understood to be key sites with respect to catalytic and sensor activity. Low activation energies calculated for oxide ion migration are consistent with high oxygen mobilities measured experimentally. Sr and Ca, which occupy Nd sites in the lattice, are found to be the most soluble of the alkaline earth metals, in agreement with experiment. These two dopant ions also have the weakest binding energies for dopant-vacancy cluster formation. Mechanisms of electronic defect formation, critical to the overall transport properties of the material, are also considered. The results suggest that disproportionation of the Co ion to form small polaron species is the most favorable intrinsic defect process. In doped compounds, formation of electronic holes via uptake of oxygen at vacant sites is found to be a low energy process. PMID:16539474

  2. Integrated perovskite/bulk-heterojunction toward efficient solar cells.

    PubMed

    Liu, Yongsheng; Hong, Ziruo; Chen, Qi; Chang, Weihsuan; Zhou, Huanping; Song, Tze-Bin; Young, Eric; Yang, Yang Michael; You, Jingbi; Li, Gang; Yang, Yang

    2015-01-14

    We successfully demonstrated an integrated perovskite/bulk-heterojunction (BHJ) photovoltaic device for efficient light harvesting and energy conversion. Our device efficiently integrated two photovoltaic layers, namely a perovskite film and organic BHJ film, into the device. The device structure is ITO/TiO2/perovskite/BHJ/MoO3/Ag. A wide bandgap small molecule DOR3T-TBDT was used as donor in the BHJ film, and a power conversion efficiency (PCE) of 14.3% was achieved in the integrated device with a high short circuit current density (JSC) of 21.2 mA cm(-2). The higher JSC as compared to that of the traditional perovskite/HTL (hole transporting layer) device (19.3 mA cm(-2)) indicates that the BHJ film absorbs light and contributes to the current density of the device. Our result further suggests that the HTL in traditional perovskite solar cell, even with good light absorption capability, cannot contribute to the overall device photocurrent, unless this HTL becomes a BHJ layer (by adding electron transporting material like PC71BM). PMID:25513830

  3. Self-formed grain boundary healing layer for highly efficient CH3 NH3 PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Son, Dae-Yong; Lee, Jin-Wook; Choi, Yung Ji; Jang, In-Hyuk; Lee, Seonhee; Yoo, Pil J.; Shin, Hyunjung; Ahn, Namyoung; Choi, Mansoo; Kim, Dongho; Park, Nam-Gyu

    2016-07-01

    Perovskite solar cells have attracted significant research efforts due to their remarkable performance, with certified power conversion efficiency now reaching 22%. Solution-processed perovskite thin films are polycrystalline, and grain boundaries are thought to be responsible for causing recombination and trapping of charge carriers. Here we report an effective and reproducible way of treating grain boundaries in CH3NH3PbI3 films deposited by means of a Lewis acid–base adduct approach. We show by high-resolution transmission electron microscopy lattice images that adding 6 mol% excess CH3NH3I to the precursor solution resulted in a CH3NH3I layer forming at the grain boundaries. This layer is responsible for suppressing non-radiative recombination and improving hole and electron extraction at the grain boundaries by forming highly ionic-conducting pathways. We report an average power conversion efficiency of 20.1% over 50 cells (best cell at 20.4%) together with significantly reduced current–voltage hysteresis achieved by this grain boundary healing process.

  4. Perovskites: transforming photovoltaics, a mini-review

    NASA Astrophysics Data System (ADS)

    Chilvery, Ashwith Kumar; Batra, Ashok K.; Yang, Bin; Xiao, Kai; Guggilla, Padmaja; Aggarwal, Mohan D.; Surabhi, Raja; Lal, Ravi B.; Currie, James R.; Penn, Benjamin G.

    2015-01-01

    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 article provides a detailed insight of the organometal halide based perovskite structure, its unique stoichiometric design, and its underlying principles for PV applications. The compatibility of various PV layers and its fabrication methods is also discussed.

  5. Structure of relaminarizing turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Ramesh, O.; Patwardhan, Saurabh

    2014-11-01

    Relaminarization of a turbulent boundary layer in a strongly accelerated flow has received a great attention in recent times. It has been found that such relaminarization is a general and regularly occurring phenomenon in the leading-edge region of a swept wing of an airplane (van Dam et al., 1993). In this work, we investigate the effect of initial Reynolds number on the process of relaminarization in turbulent boundary layers. The experimental and numerical investigation of relaminarizing turbulent boundary layers undergoing same history reveals that the boundary layer with higher initial Reynolds number relaminarizes at a lower pressure gradient value compared to the one with lower Reynolds number. This effect can be explained on the inviscid theory proposed earlier in the literature. Further, various parameter criteria proposed to predict relaminarization, are assessed and the structure of relaminarizing boundary layers is investigated. A mechanism for stabilization of near-wall low speed streaks is proposed.

  6. Selective Precipitation and Concentrating of Perovskite Crystals from Titanium-Bearing Slag Melt in Supergravity Field

    NASA Astrophysics Data System (ADS)

    Gao, Jintao; Zhong, Yiwei; Guo, Zhancheng

    2016-06-01

    Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study. Since perovskite was the first precipitated phase from the slag melt during the cooling process, and a greater precipitation quantity and larger crystal sizes of perovskite were obtained at 1593 K to 1563 K (1320 °C to 1290 °C), concentrating of perovskite crystals from the slag melt was carried out at this temperature range in the supergravity field, at which the perovskite transforms into solid particles while the other minerals remain in the liquid melt. The layered structures appeared significantly in the sample obtained by supergravity treatment, and all the perovskite crystals moved along the supergravity direction and concentrated as the perovskite-rich phase in the bottom area, whereas the molten slag concentrated in the upper area along the opposite direction, in which it was impossible to find any perovskite crystals. With the gravity coefficient of G = 750, the mass fraction of TiO2 in the perovskite-rich phase was up to 34.65 wt pct, whereas that of the slag phase was decreased to 12.23 wt pct, and the recovery ratio of Ti in the perovskite-rich phase was up to 75.28 pct. On this basis, an amplification experimental centrifugal apparatus was exploited and the continuous experiment with larger scale was further carried out, the results confirming that selective precipitation and concentrating of perovskite crystals from the titanium-bearing slag melt by supergravity was a feasible method.

  7. Selective Precipitation and Concentrating of Perovskite Crystals from Titanium-Bearing Slag Melt in Supergravity Field

    NASA Astrophysics Data System (ADS)

    Gao, Jintao; Zhong, Yiwei; Guo, Zhancheng

    2016-08-01

    Selective precipitation and concentrating of perovskite crystals from titanium-bearing slag melt in the supergravity field was investigated in this study. Since perovskite was the first precipitated phase from the slag melt during the cooling process, and a greater precipitation quantity and larger crystal sizes of perovskite were obtained at 1593 K to 1563 K (1320 °C to 1290 °C), concentrating of perovskite crystals from the slag melt was carried out at this temperature range in the supergravity field, at which the perovskite transforms into solid particles while the other minerals remain in the liquid melt. The layered structures appeared significantly in the sample obtained by supergravity treatment, and all the perovskite crystals moved along the supergravity direction and concentrated as the perovskite-rich phase in the bottom area, whereas the molten slag concentrated in the upper area along the opposite direction, in which it was impossible to find any perovskite crystals. With the gravity coefficient of G = 750, the mass fraction of TiO2 in the perovskite-rich phase was up to 34.65 wt pct, whereas that of the slag phase was decreased to 12.23 wt pct, and the recovery ratio of Ti in the perovskite-rich phase was up to 75.28 pct. On this basis, an amplification experimental centrifugal apparatus was exploited and the continuous experiment with larger scale was further carried out, the results confirming that selective precipitation and concentrating of perovskite crystals from the titanium-bearing slag melt by supergravity was a feasible method.

  8. Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air.

    PubMed

    Hu, Hang; Dong, Binghai; Hu, Huating; Chen, Fengxiang; Kong, Mengqin; Zhang, Qiuping; Luo, Tianyue; Zhao, Li; Guo, Zhiguang; Li, Jing; Xu, Zuxun; Wang, Shimin; Eder, Dominik; Wan, Li

    2016-07-20

    In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability. PMID:27340730

  9. Hexagonal β-NaYF4:Yb(3+), Er(3+) Nanoprism-Incorporated Upconverting Layer in Perovskite Solar Cells for Near-Infrared Sunlight Harvesting.

    PubMed

    Roh, Jongmin; Yu, Haejun; Jang, Jyongsik

    2016-08-10

    Hexagonal β-NaYF4:Yb(3+), Er(3+) nanoprisms, successfully prepared using a hydrothermal method, were incorporated into CH3NH3PbI3 perovskite solar cells (PSCs) as an upconverting mesoporous layer. Due to their near-infrared (NIR) sunlight harvesting, the PSCs based on the upconverting mesoporous layer exhibited a power conversion efficiency of 16.0%, an increase of 13.7% compared with conventional TiO2 nanoparticle-based PSCs (14.1%). This result suggests that the hexagonal β-NaYF4:Yb(3+), Er(3+) nanoprisms expand the absorption range of the PSC via upconversion photoluminescence, leading to an enhancement of the photocurrent. PMID:27472304

  10. Ultrathin efficient perovskite solar cells employing a periodic structure of a composite hole conductor for elevated plasmonic light harvesting and hole collection.

    PubMed

    Long, Mingzhu; Chen, Zefeng; Zhang, Tiankai; Xiao, Yubin; Zeng, Xiaoliang; Chen, Jian; Yan, Keyou; Xu, Jianbin

    2016-03-28

    We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a V(oc) of 1.05 V, J(sc) of 22.9 mA cm(-2), FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer. PMID:26377231

  11. Perovskite: A Structure of Great Interest to Geophysics and Materials Science

    NASA Astrophysics Data System (ADS)

    Navrotsky, Alexandra; Weidner, Donald J.

    Perovskite, CaTiO3, was discovered and named in 1839 by Gustav Rose, German chemist and mineralogist (1798-1873), the year he was appointed professor at Berlin University. To Rose we owe sanidine (1808), anorthite (1823), and cancrinite (1859) as well. Alexander von Humboldt whom the Tsar of Russia had asked to explore the far reaches of his empire chose Rose as a fellow traveller. Rose's report "Reise nach dem Ural, Altai und dem Kaspischen Meer", was published in Berlin between 1837 and 1842. It is presumably there that Rose first mentioned perovskite.

  12. Cobalt based layered perovskites as cathode material for intermediate temperature Solid Oxide Fuel Cells: A brief review

    NASA Astrophysics Data System (ADS)

    Pelosato, Renato; Cordaro, Giulio; Stucchi, Davide; Cristiani, Cinzia; Dotelli, Giovanni

    2015-12-01

    Nowadays, the cathode is the most studied component in Intermediate Temperature-Solid Oxide Fuel Cells (IT-SOFCs). Decreasing SOFCs operating temperature implies slow oxygen reduction kinetics and large polarization losses. Double perovskites with general formula REBaCo2O5+δ are promising mixed ionic-electronic conductors, offering a remarkable enhancement of the oxygen diffusivity and surface exchange respect to disordered perovskites. In this review, more than 250 compositions investigated in the literature were analyzed. The evaluation was performed in terms of electrical conductivity, Area Specific Resistance (ASR), chemical compatibility with electrolytes and Thermal Expansion Coefficient (TEC). The most promising materials have been identified as those bearing the mid-sized rare earths (Pr, Nd, Sm, Gd). Doping strategies have been analyzed: Sr doping on A site promotes higher electrical conductivity, but worsen ASR and TECs; B-site doping (Fe, Ni, Mn) helps lowering TECs, but is detrimental for the electrochemical properties. A promising boost of the electrochemical activity is obtained by simply introducing a slight Ba under-stoichiometry. Still, the high sensitivity of the electrochemical properties against slight changes in the stoichiometry hamper a conclusive comparison of all the investigated compounds. Opportunities for an improvement of double perovskite cathodes performance is tentatively foreseen in combining together the diverse effective doping strategies.

  13. Investigations of the magnetic properties and structures of the pillared perovskites, La{sub 5}Re{sub 3}MO{sub 16} (M=Co, Ni)

    SciTech Connect

    Cuthbert, Heather L. . E-mail: cuthbehl@mcmaster.ca; Greedan, John E.; Cranswick, Lachlan

    2006-07-15

    La{sub 5}Re{sub 3}CoO{sub 16} and La{sub 5}Re{sub 3}NiO{sub 16} were synthesized by solid-state reaction and studied by SQUID magnetometry, heat capacity and powder neutron diffraction measurements. These two compounds belong to a series of isostructural Re-based pillared perovskites [Chi et al. J. Solid State Chem. 170 (2003) 165]. Magnetic susceptibility measurements indicate apparent short-range ferri or ferromagnetic correlations and possible long-range antiferromagnetic order for La{sub 5}Re{sub 3}CoO{sub 16} at 35K, and at 38 and 14K for La{sub 5}Re{sub 3}NiO{sub 16}. Heat capacity measurements of the Co compound show a lambda anomaly, typical of long-range magnetic order, at 32K. In contrast, the Ni compound displays a broader, more symmetric feature at 12K in the heat capacity data, indicative of short-range magnetic order. Low-temperature powder neutron diffraction revealed contrasting magnetic structures. While both show an ordering wave vector, k=(0,0,1/2), in La{sub 5}Re{sub 3}CoO{sub 16}, the Co{sup 2+} and Re{sup 5+} moments are ordered ferrimagnetically within the corner-shared octahedral layers, while the layers themselves are coupled antiferromagnetically along the c-axis, as also found in La{sub 5}Re{sub 3}MnO{sub 16} and La{sub 5}Re{sub 3}FeO{sub 16}. In the case of the Ni material, the Re{sup 5+} and Ni{sup 2+} moments in the perovskite layers couple ferromagnetically and are canted 30 deg. away from the c-axis, angled 45 deg. in the ab-plane. The layers then couple antiferromagnetically at low temperature, a unique magnetic structure for this series. The properties of the La{sub 5}Re{sub 3}MO{sub 16} series, with M=Mn, Fe, Co, Ni and Mg are also reviewed.

  14. Nanomanufacturing : nano-structured materials made layer-by-layer.

    SciTech Connect

    Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto; Reedy, Earl David, Jr.; Fan, Hongyou; Schunk, Peter Randall; Chandross, Michael Evan; Roberts, Scott A.

    2011-10-01

    Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

  15. Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

    DOE PAGESBeta

    Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; Jones, Jacob L.; Maria, Jon-Paul; Trolier-McKinstry, Susan

    2016-07-05

    Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties withmore » decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling

  16. From Morphology to Interfaces to Tandem Geometries: Enhancing the Performance of Perovskite/Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Russell, Thomas

    We have taken a new approach to develop mesoporous lead iodide scaffolds, using the nucleation and growth of lead iodide crystallites in a wet film. A simple time-dependent growth control enabled the manipulation of the mesoporous lead iodide layer quality in a continuous manner. The morphology of lead iodide is shown to influence the subsequent crystallization of methyamoniumleadiodide film by using angle-dependent grazing incidence x-ray scattering. The morphology of lead iodide film can be fine-tuned, and thus the methyamoniumleadiodide film quality can be effectively controlled, leading to an optimization of the perovskite active layer. Using this strategy, perovskite solar cells with inverted PHJ structure showed a PCE of 15.7 per cent with little hysteresis. Interface engineering is critical for achieving efficient solar cells, yet a comprehensive understanding of the interface between metal electrode and electron transport layer (ETL) is lacking. A significant power conversion efficiency (PCE) improvement of fullerene/perovskite planar heterojunction solar cells was achieved by inserting a fulleropyrrolidine interlayer between the silver electrode and electron transport layer. The interlayer was found to enhance recombination resistance, increases electron extraction rate and prolongs free carrier lifetime. We also uncovered a facile solution-based fabrication of high performance tandem perovskite/polymer solar cells where the front sub-cell consists of perovskite and the back sub-cell is a polymer-based layer. A record maximum PCE of 15.96 per cent was achieved, demonstrating the synergy between the perovskite and semiconducting polymers. This design balances the absorption of the perovskite and the polymer, eliminates the adverse impact of thermal annealing during perovskite fabrication, and affords devices with no hysteresis. This work was performed in collaboration with Y. Liu, Z. Page, D. Venkataraman and T. Emrick (UMASS), F. Liu (LBNL) and Q. Hu and R

  17. Elastic anisotropy of experimental analogues of perovskite and post-perovskite help to interpret D′′ diversity

    PubMed Central

    Yoneda, Akira; Fukui, Hiroshi; Xu, Fang; Nakatsuka, Akihiko; Yoshiasa, Akira; Seto, Yusuke; Ono, Kenya; Tsutsui, Satoshi; Uchiyama, Hiroshi; Baron, Alfred Q. R.

    2014-01-01

    Recent studies show that the D′′ layer, just above the Earth's core–mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D′′ diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Our results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D′′ discontinuity. Considering the relation between lattice preferred orientation and seismic anisotropy in the D′′ layer, we suggest that the c axis of post-perovskite MgSiO3 aligns vertically beneath the Circum-Pacific rim, and the b axis vertically beneath the Central Pacific. PMID:24670790

  18. Electronic band structure trends of perovskite halides: Beyond Pb and Sn to Ge and Si

    NASA Astrophysics Data System (ADS)

    Huang, Ling-yi; Lambrecht, Walter R. L.

    2016-05-01

    The trends in electronic band structure are studied in the cubic A B X3 halide perovskites for A =Cs ; B =Pb , Sn, Ge, Si; and X =I , Br, Cl. The gaps are found to decrease from Pb to Sn and from Ge to Si, but increase from Sn to Ge. The trend is explained in terms of the atom s levels of the group-IV element and the atomic sizes which changes the amount of hybridization with X -p and hence the valence bandwidth. Along the same series spin-orbit coupling also decreases and this tends to increase the gap because of the smaller splitting of the conduction band minimum. Both effects compensate each other to a certain degree. The trend with halogens is to reduce the gap from Cl to I, i.e., with decreasing electronegativity. The role of the tolerance factor in avoiding octahedron rotations and octahedron edge sharing is discussed. The Ge containing compounds have tolerance factor t >1 and hence do not show the series of octahedral rotation distortions and the existence of edge-sharing octahedral phases known for Pb and Sn-based compounds, but rather a rhombohedral distortion. CsGeI3 is found to have a suitable gap for photovoltaics both in its cubic (high-temperature) and rhombohedral (low-temperature) phases. The structural stability of the materials in the different phases is also discussed. We find the rhombohedral phase to have lower total energy and slightly larger gaps but to present a less significant distortion of the band structure than the edge-sharing octahedral phases, such as the yellow phase in CsSnI3. The corresponding silicon based compounds have not yet been synthesized and therefore our estimates are less certain but indicate a small gap for cubic CsSiI3 and CsSiBr3 of about 0.2 ±0.2 eV and 0.8 ±0.6 eV for CsSiCl3. The intrinsic stability of the Si compounds is discussed.

  19. A quaternary lead based perovskite structured materials with diffuse phase transition behavior

    SciTech Connect

    Puli, Venkata Sreenivas; Martinez, R.; Kumar, Ashok; Scott, J.F.; Cavendish Laboratory, Dept. Physics, University of Cambridge, Cambridge CB0 3HE ; Katiyar, Ram S.

    2011-12-15

    Graphical abstract: (a) Curie-Weiss plot for the inverse of the relative dielectric permittivity and (b) log (1/{epsilon} - 1/{epsilon}{sub m}) as function of log (T - T{sub m}) for ceramics at 1 kHz. Highlights: Black-Right-Pointing-Pointer Retaining phase pure structure with quaternary complex stoichiometric compositions. Black-Right-Pointing-Pointer P-E loops with good saturation polarization (P{sub s} {approx} 30.7 {mu}C/cm{sup 2}). Black-Right-Pointing-Pointer Diffused relaxor phase transition behavior with {gamma} estimated is {approx}1.65. -- Abstract: A lead based quaternary compound composed of 0.25(PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}) + 0.25(PbFe{sub 0.5}Ta{sub 0.5}O{sub 3}) + 0.25 (PbF{sub 0.67}W{sub 0.33}O{sub 3}) + 0.25(PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}) - (PZT-PFT-PFW-PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature {approx}261 K and other above {approx}410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm-3 {mu}m. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P{sub s} {approx} 30.68 {mu}C/cm{sup 2}) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT-PFT-PFW-PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/{epsilon} versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The

  20. TiO2 quantum dots as superb compact block layers for high-performance CH3NH3PbI3 perovskite solar cells with an efficiency of 16.97%

    NASA Astrophysics Data System (ADS)

    Tu, Yongguang; Wu, Jihuai; Zheng, Min; Huo, Jinghao; Zhou, Pei; Lan, Zhang; Lin, Jianming; Huang, Miaoliang

    2015-12-01

    A compact TiO2 layer is crucial to achieve high-efficiency perovskite solar cells. In this study, we developed a facile, low-cost and efficient method to fabricate a pinhole-free and ultrathin blocking layer based on highly crystallized TiO2 quantum dots (QDs) with an average diameter of 3.6 nm. The surface morphology of the blocking layer and the photoelectric performance of the perovskite solar cells were investigated by spin-coating with three different materials: colloidal TiO2 QDs, titanium precursor solution, and aqueous TiCl4. Among these three treatments, the perovskite solar cell based on the TiO2 QD compact layer offered the highest power conversion efficiency (PCE) of 16.97% with a photocurrent density of 22.48 mA cm-2, a photovoltage of 1.063 V and a fill factor of 0.71. The enhancement of PCE mainly stems from the small series resistance and the large shunt resistance of the TiO2 QD layer.A compact TiO2 layer is crucial to achieve high-efficiency perovskite solar cells. In this study, we developed a facile, low-cost and efficient method to fabricate a pinhole-free and ultrathin blocking layer based on highly crystallized TiO2 quantum dots (QDs) with an average diameter of 3.6 nm. The surface morphology of the blocking layer and the photoelectric performance of the perovskite solar cells were investigated by spin-coating with three different materials: colloidal TiO2 QDs, titanium precursor solution, and aqueous TiCl4. Among these three treatments, the perovskite solar cell based on the TiO2 QD compact layer offered the highest power conversion efficiency (PCE) of 16.97% with a photocurrent density of 22.48 mA cm-2, a photovoltage of 1.063 V and a fill factor of 0.71. The enhancement of PCE mainly stems from the small series resistance and the large shunt resistance of the TiO2 QD layer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05563f

  1. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-15

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer (S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  2. Identifying layers in random multiphase structures

    NASA Astrophysics Data System (ADS)

    Mader, Kevin; Stampanoni, Marco

    2016-01-01

    X-Ray microscopic methods, benefiting from the large penetration depth of X-rays in many materials, enable 3D investigation of a wide variety of samples. This allows for a wide variety of physical, chemical, and biological structures to be seen and explored, in some cases even in real time. Such measurements have lead to insights into paleontology, vulcanology, genetics, and material science. The ability to see and visualize complex systems can provide otherwise unobtainable information on structure, interactions, mechanical behavior, and evolution. The field has, however, led to a massive amount of new, heterogenous, difficult to process data. We present a general, model-free approach for characterizing multiphase 3D systems and show how the method can be applied to experimental X-ray microscopy data to better understand and quantify layer structure in two typical systems: investigation of layered fibers and clay samples.

  3. Selective Deposition of Insulating Metal Oxide in Perovskite Solar Cells with Enhanced Device Performance.

    PubMed

    Yue, Youfeng; Yang, Xudong; Wu, Yongzhen; Salim, Noviana Tjitra; Islam, Ashraful; Noda, Takeshi; Han, Liyuan

    2015-08-24

    We report a simple methodology for the selective deposition of an insulating layer on the nanoparticulate TiO2 (np-TiO2) mesoporous layer of perovskite solar cells. The deposited MgO insulating layer mainly covered the bottom part of the np-TiO2 layer with less coverage at the top. The so-called quasi-top-open structure is introduced to act as an efficient hole-blocking layer to prevent charge recombination at the physical contact of the transparent conducting oxide with the perovskite. This leads to an open-circuit voltage higher than that of the reference cell with a compact TiO2 hole-blocking layer. Moreover, such a quasi-top-open structure can facilitate the electron injection from perovskite into the np-TiO2 mesoporous layer and improve the spectral response at longer wavelength because of the less covered insulating layer at the top. This work provides an alternative way to fabricate perovskite solar cells without the need to use a conventional compact TiO2 layer. PMID:26230988

  4. Persistent Structures in the Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Palumbo, Dan; Chabalko, Chris

    2005-01-01

    Persistent structures in the turbulent boundary layer are located and analyzed. The data are taken from flight experiments on large commercial aircraft. An interval correlation technique is introduced which is able to locate the structures. The Morlet continuous wavelet is shown to not only locates persistent structures but has the added benefit that the pressure data are decomposed in time and frequency. To better understand how power is apportioned among these structures, a discrete Coiflet wavelet is used to decompose the pressure data into orthogonal frequency bands. Results indicate that some structures persist a great deal longer in the TBL than would be expected. These structure contain significant power and may be a primary source of vibration energy in the airframe.

  5. Structural and transport properties of double perovskite Dy{sub 2}NiMnO{sub 6}

    SciTech Connect

    Chanda, Sadhan Saha, Sujoy; Dutta, Alo; Sinha, T.P.

    2015-02-15

    Highlights: • Sol–gel citrate method is used to prepare the double perovskite Dy{sub 2}NiMnO{sub 6}. • Structure and dielectric relaxation of the sample are studied for nano and bulk phases. • The relaxation mechanism of the sample is modeled by Cole–Cole equation. • With increasing sintering temperature conductivity increases. • Electronic structures and magnetic properties have been studied by DFT calculations. - Abstract: The double perovskite oxide Dy{sub 2}NiMnO{sub 6} (DNMO) is synthesized in nano and bulk phase by the sol–gel citrate method. The Rietveld refinement of X-ray diffraction pattern of the sample at room temperature shows the monoclinic P2{sub 1}/n phase. Dielectric relaxation of the sample is investigated in the impedance and electric modulus formalisms in the frequency range from 50 Hz to 1 MHz and in the temperature range from 253 to 415 K. The Cole–Cole model is used to explain the relaxation mechanism in DNMO. The frequency-dependent maxima in the imaginary part of impedance are found to obey an Arrhenius law with activation energy of 0.346 and 0.344 eV for nano and bulk DNMO, respectively. A significant increase in conductivity of bulk DNMO has been observed than that of the nanoceramic. Electronic structures and magnetic properties of DNMO have been studied by performing first principles calculation based on density functional theory.

  6. Quasiparticle band gap of organic-inorganic hybrid perovskites: Crystal structure, spin-orbit coupling, and self-energy effects

    NASA Astrophysics Data System (ADS)

    Gao, Weiwei; Gao, Xiang; Abtew, Tesfaye; Sun, Yiyang; Zhang, Shengbai; Zhang, Peihong

    The quasiparticle band gaps of organic-inorganic hybrid perovskites are often determined (and can be controlled) by various factors, complicating predictive materials optimization. Here we report a comprehensive investigation on the band gap formation mechanism in CH3NH3PbI3 by decoupling various contributing factors which ultimately determine their electronic structure and quasiparticle band gap. Four major factors, namely, quasiparticle self-energy, spin-orbit coupling, volume (lattice constant) effects, and structural distortions due to the presence of organic molecules, and their influences on the quasiparticle band structure of organometal hybrid perovskites are illustrated. We find that although methylammonium cations do not contribute directly to the electronic states near band edges, they play an important role in defining the band gap through a lattice distortion mechanism and by controlling the overall lattice constants (thus the chemical bonding of the optically active PbI3-). The spin-orbit coupling effects drastically reduce the electron and hole effective masses in these systems, which is beneficial for high carrier mobilities and small exciton binding energies. This work is supported by the National Natural Science Foundation of China (Grant No. 11328401), NSF (Grant No. DMR-0946404 and DMR-1506669), and the SUNY Networks of Excellence.

  7. Magnetic order and electronic structure of 5d3 double perovskite Sr2ScOsO6

    DOE PAGESBeta

    Taylor, A. E.; Morrow, R.; Singh, D. J.; Calder, S.; Lumsden, M. D.; Woodward, P. M.; Christianson, A. D.

    2015-03-01

    The magnetic susceptibility, crystal and magnetic structures, and electronic structure of double perovskite Sr2ScOsO6 are reported. Using both neutron and x-ray powder diffraction we find that the crystal structure is monoclinic P21/n from 3.5 to 300 K. Magnetization measurements indicate an antiferromagnetic transition at TN=92 K, one of the highest transition temperatures of any double perovskite hosting only one magnetic ion. Type I antiferromagnetic order is determined by neutron powder diffraction, with an Os moment of only 1.6(1) muB, close to half the spin-only value for a crystal field split 5d electron state with t2g^3 ground state. Density functional calculationsmore » show that this reduction is largely the result of strong Os-O hybridization, with spin-orbit coupling responsible for only a ~0.1 muB reduction in the moment.« less

  8. Synthesis of novel perovskite crystal structure phase of strontium doped rare earth manganites using sol gel method

    NASA Astrophysics Data System (ADS)

    Abdel-Latif, I. A.; Ismail, Adel A.; Bouzid, Houcine; Al-Hajry, A.

    2015-11-01

    In the present work, polycrystalline perovskites of R0.6Sr0.4MnO3 nanocomposites (R=La, Nd, or Sm) were synthesized using the sol-gel method in the presence of citric acid and polyethylene glycol as chelating and structure directing agents respectively. The synthesized gel was calcined at 800 °C for 5 h. The XRD revealed that the obtained nanocrystalline R0.6Sr0.4MnO3 is monoclinic crystal structure of space group (I2/a). TEM images showed that the prepared perovskites are homogeneous and uniform with particle sizes in a range 20-40 nm and the HR-TEM images and lattice fringes displayed the monoclinic structure. IV measurements showed that Nd0.6Sr0.4MnO3 has semiconducting properties at room temperature. With applying low magnetic field, a transition from semiconductor behavior to Ohmic resistivity was observed. The static resistance of Nd0.6Sr0.4MnO3 was calculated to be ~2.985 TΩ for semiconductor phase and the resistance increased 1000 times that gives rise to negative magnetoresistance (MR). The value of MR of Nd0.6Sr0.4MnO3 equals to 99.84%, which leads to the use of these materials in fabrication of magnetic devices in the industrial scale.

  9. Organic-inorganic heterostructure electroluminescent device using a layered perovskite semiconductor (C6H5C2H4NH3)2PbI4

    NASA Astrophysics Data System (ADS)

    Era, M.; Morimoto, S.; Tsutsui, T.; Saito, S.

    1994-08-01

    Using the combination of a layered perovskite compound (C6H5C2H4NH3)2PbI4 (PAPI), which forms a stable exciton with a large binding energy owing to its low-dimensional semiconductor nature and exhibits sharp and strong photoluminescence from the exciton band, and an electron-transporting oxadiazole derivative, we fabricated an organic-inorganic heterostructure electroluminescent (EL) device. The EL spectrum of the device corresponded well to the photoluminescence spectrum of the PAPI film; the emission was peaking at 520 nm and half-width of the emission was about 10 nm at liquid-nitrogen temperature. Further, highly intense EL of more than 10 000 cd m-2 was performed at 2 A cm-2 at liquid-nitrogen temperature in the device.

  10. Electronic structure of ferromagnetic semiconductor material on the monoclinic and rhombohedral ordered double perovskites La{sub 2}FeCoO{sub 6}

    SciTech Connect

    Fuh, Huei-Ru; Chang, Ching-Ray; Weng, Ke-Chuan; Wang, Yin-Kuo

    2015-05-07

    Double perovskite La{sub 2}FeCoO{sub 6} with monoclinic structure and rhombohedra structure show as ferromagnetic semiconductor based on density functional theory calculation. The ferromagnetic semiconductor state can be well explained by the superexchange interaction. Moreover, the ferromagnetic semiconductor state remains under the generalized gradient approximation (GGA) and GGA plus onsite Coulomb interaction calculation.

  11. Role of bromine doping on the photovoltaic properties and microstructures of CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsushi; Okada, Hiroshi; Oku, Takeo

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing CH3NH3PbI3 perovskite compound were fabricated using mesoporous TiO2 as the electronic transporting layer and spirobifluorence as the hole-transporting layer. The purpose of the present study is to investigate role of bromine (Br) doping on the photovoltaic properties and microstructure of CH3NH3PbI3 perovskite solar cells. Photovoltaic, optical properties and microstructures of perovskite-based solar cells were investigated. The X-ray diffraction identified crystal structure of the perovskite layer doped with Br in the solar cell. Scanning electron microscopy observation showed a different behavior of surface morphology and the perovskite crystal structure on the TiO2 mesoporous structure depending on extent amount of hydrogen doping of Br. The role of bromide halogen doping on the perovskite crystal structure and photovoltaic properties was due to improvement of carrier mobility, optimization of electron structure, band gap related with the photovoltaic parameters of Voc, Jsc and η. Energy diagram and photovoltaic mechanism of the perovskite solar cells varied with halogen doping was discussed by experimental results.

  12. 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.

  13. Mechanism of charge recombination in meso-structured organic-inorganic hybrid perovskite solar cells: A macroscopic perspective

    SciTech Connect

    Yang, Wenchao; Yao, Yao Wu, Chang-Qin

    2015-04-21

    In the currently popular organic-inorganic hybrid perovskite solar cells, the slowness of the charge recombination processes is found to be a key factor for contributing to their high efficiencies and high open circuit voltages, but the underlying recombination mechanism remains unclear. In this work, we investigate the bimolecular recombination (BR) and the trap-assisted monomolecular recombination (MR) in meso-structured perovskite solar cells under steady state working condition, and try to reveal their roles on determining the device performance. Some interfacial effects such as the injection barriers at the selective contacts are examined as well. Based on the macroscopic device modeling, the recombination resistance-voltage (R{sub rec}−V) and the current density-voltage (J–V) curves are calculated to characterize the recombination mechanism and describe the device performance, respectively. Through comparison with the impedance spectroscopy extracted R{sub rec} data, it is found that under the typical BR reduction factor and deep trap densities observed in experiments, the MR dominates the charge recombination in the low voltage regime, while the BR dominates in the high voltage regime. The short circuit current and the fill factor could be reduced by the significant MR but the open circuit voltage is generally determined by the BR. The different electron injection barriers at the contact can change the BR rate and induce different patterns for the R{sub rec}–V characteristics. For the perovskites of increased band gaps, the R{sub rec}'s are significantly enhanced, corresponding to the high open circuit voltages. Finally, it is revealed that the reduced effective charge mobility due to the transport in electron and hole transporting material makes the R{sub rec} decrease slowly with the increasing voltage, which leads to increased open circuit voltage.

  14. Mechanism of charge recombination in meso-structured organic-inorganic hybrid perovskite solar cells: A macroscopic perspective

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Yao, Yao; Wu, Chang-Qin

    2015-04-01

    In the currently popular organic-inorganic hybrid perovskite solar cells, the slowness of the charge recombination processes is found to be a key factor for contributing to their high efficiencies and high open circuit voltages, but the underlying recombination mechanism remains unclear. In this work, we investigate the bimolecular recombination (BR) and the trap-assisted monomolecular recombination (MR) in meso-structured perovskite solar cells under steady state working condition, and try to reveal their roles on determining the device performance. Some interfacial effects such as the injection barriers at the selective contacts are examined as well. Based on the macroscopic device modeling, the recombination resistance-voltage (Rrec-V) and the current density-voltage (J-V) curves are calculated to characterize the recombination mechanism and describe the device performance, respectively. Through comparison with the impedance spectroscopy extracted Rrec data, it is found that under the typical BR reduction factor and deep trap densities observed in experiments, the MR dominates the charge recombination in the low voltage regime, while the BR dominates in the high voltage regime. The short circuit current and the fill factor could be reduced by the significant MR but the open circuit voltage is generally determined by the BR. The different electron injection barriers at the contact can change the BR rate and induce different patterns for the Rrec-V characteristics. For the perovskites of increased band gaps, the Rrec's are significantly enhanced, corresponding to the high open circuit voltages. Finally, it is revealed that the reduced effective charge mobility due to the transport in electron and hole transporting material makes the Rrec decrease slowly with the increasing voltage, which leads to increased open circuit voltage.

  15. Bright light-emitting diodes based on organometal halide perovskite

    NASA Astrophysics Data System (ADS)

    Tan, Zhi-Kuang; Moghaddam, Reza Saberi; Lai, May Ling; Docampo, Pablo; Higler, Ruben; Deschler, Felix; Price, Michael; Sadhanala, Aditya; Pazos, Luis M.; Credgington, Dan; Hanusch, Fabian; Bein, Thomas; Snaith, Henry J.; Friend, Richard H.

    2014-09-01

    Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15 nm layer of CH3NH3PbI3-xClx perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9‧-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2 W sr-1 m-2 at a current density of 363 mA cm-2, with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364 cd m-2 at a current density of 123 mA cm-2, giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.

  16. Plane mixing layer vortical structure kinematics

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.

    1993-01-01

    The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.

  17. Structural properties of PbVO3 perovskites under hydrostatic pressure conditions up to 10.6 GPa.

    PubMed

    Zhou, Wei; Tan, Dayong; Xiao, Wansheng; Song, Maoshuang; Chen, Ming; Xiong, Xiaolin; Xu, Jian

    2012-10-31

    High-pressure synchrotron x-ray powder diffraction experiments were performed on PbVO(3) tetragonal perovskite in a diamond anvil cell under hydrostatic pressures of up to 10.6 GPa at room temperature. The compression behavior of the PbVO(3) tetragonal phase is highly anisotropic, with the c-axis being the soft direction. A reversible tetragonal to cubic perovskite structural phase transition was observed between 2.7 and 6.4 GPa in compression and below 2.2 GPa in decompression. This transition was accompanied by a large volume collapse of 10.6% at 2.7 GPa, which was mainly due to electronic structural changes of the V(4+) ion. The polar pyramidal coordination of the V(4+) ion in the tetragonal phase changed to an isotropic octahedral coordination in the cubic phase. Fitting the observed P-V data using the Birch-Murnaghan equation of state with a fixed [Formula: see text] of 4 yielded a bulk modulus K(0) = 61(2) GPa and a volume V(0) = 67.4(1) Å(3) for the tetragonal phase, and the values of K(0) = 155(3) GPa and V(0) = 58.67(4) Å(3) for the cubic phase. The first-principles calculated results were in good agreement with our experiments. PMID:23041755

  18. Design, synthesis, crystal structure and magnetic properties of novel osmium-based B-site ordered double perovskites

    NASA Astrophysics Data System (ADS)

    Russell, David D.

    Transition metal oxides (TMOs) with face centered cubic arrangement of magnetic ions are composed of triangular sub-lattices. When antiferromagnetic (AFM) interactions of the same strengths between all three pathways in triangular settings are in place, spin constraints cannot be fulfilled simultaneously and the system undergoes geometric magnetic frustration (GMF). The purpose of the work presented in this thesis is to better understand the criteria for a system to undergo GMF. To achieve this, the novel B-site ordered double perovskites Ca2ScOsO6 and Ca2.2Mg0.8 OsO6 were synthesized in polycrystalline form utilizing the conventional solid-state method. The crystal structure of these compounds were characterized through X-ray diffraction, and magnetic properties were explored through magnetic susceptibility measurements. Employing the spin-dimer analysis method, relative magnetic exchange interactions were calculated and modeled. These novel osmium-based B-site ordered double perovskites were then compared to isostructural compounds to study the effects of the osmium oxidation state on crystal structure and the exhibited properties.

  19. Coupling and electrical control of structural, orbital and magnetic orders in perovskites

    PubMed Central

    Varignon, Julien; Bristowe, Nicholas C.; Bousquet, Eric; Ghosez, Philippe

    2015-01-01

    Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials. The key to the functional electronic properties exhibited by perovskites is often the so-called Jahn-Teller distortion. For applications, an electrical control of the Jahn-Teller distortions, which is so far out of reach, would therefore be highly desirable. Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations. The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity. Thanks to the intimate coupling between Jahn-Teller distortions and electronic degrees of freedom, the electric field control of Jahn-Teller distortions is of general relevance and may find broad interest in various functional devices. PMID:26482414

  20. Efficient conversion from UV light to near-IR emission in Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10}

    SciTech Connect

    Lu, Yuting; Li, Yuze; Qin, Lin; Huang, Yanlin; Qin, Chuanxiang; Tsuboi, Taiju; Huang, Wei

    2015-04-15

    Graphical abstract: CaRNb{sub 3}O{sub 10} is a self-activated oxide due to charge transfer transition in octahedral NbO{sub 6} groups. CaLaNb{sub 3}O{sub 10}:Yb{sup 3+} presents intense IR emission due to the cooperative energy transfer from host (NbO{sub 6}) to Yb{sup 3+} is responsible. It could be expected to be potentially applicable for enhancing photovoltaic conversion efficiency of Si-based solar cells. - Abstract: Yb{sup 3+}-doped triple-layered perovskite CaLaNb{sub 3}O{sub 10} micro-particles were synthesized via the solid-state reaction method. The crystal structure and morphology of the polycrystalline samples were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurements, respectively. The reflectance spectra, photoluminescence (PL) excitation and emission spectra, the decay curves, and the absolute quantum efficiency (QE) of the near-infrared (NIR) emission (910–1100 nm) were measured. Under excitation of UV light, Yb{sup 3+}-doped perovskite shows an intense NIR emission attributed to the {sup 2}F{sub 5/2} → {sup 2}F{sub 7/2} transitions of Yb{sup 3+} ions, which could match maximum spectral response of a Si-based solar cell. This is beneficial for its possible application in an enhancement of the photovoltaic conversion efficiency of solar energy utilization. The efficient energy transfer in Yb{sup 3+}-doped CaLaNb{sub 3}O{sub 10} from NbO{sub 6} groups into Yb{sup 3+} ions was confirmed by the spectra and fluorescent decay measurements. Cooperative energy transfer (CET) was supposed to be the NIR emission mechanism.

  1. Enhanced magnetization in ultrathin manganite layers via structural ``delta-doping'' of octahedral rotations

    NASA Astrophysics Data System (ADS)

    Moon, Eun Ju; Kirby, Brian J.; May, Steven J.

    The design of rotations and distortions of the corner-shared BO6 octahedra has emerged as an exciting platform to control electronic or magnetic behavior in ABO3 perovskite heterostructures. Recent work has shown that purely structural effects can be used to spatially confined magnetism in oxide heterostructures and point to the design of rotational gradients as routes to realize novel electronic or ferroic states in oxide superlattices [Nat. Comm. 5, 5710 (2014)]. Here, we demonstrate a structural ``delta doping'' approach for controlling magnetism in ultrathin layers within isovalent manganite superlattices. Polarized neutron reflectivity and temperature dependent magnetization measurements are used to correlate enhanced magnetization with local regions of suppressed octahedral rotations in the heterostructures. This work was supported by the U. S. Army Research Office under Grant No. W911NF-15-1-0133.

  2. Effect of cation arrangement on the electronic structures of the perovskite solid solutions (SrTiO3)1 -x(LaCrO3)x from first principles

    NASA Astrophysics Data System (ADS)

    Chen, Hungru; Umezawa, Naoto

    2014-07-01

    The electronic structures of [SrTiO3]1 -x[LaCrO3]x perovskite solid solutions are studied using hybrid density functional calculations to investigate their potential photocatalytic activity. The introduction of Cr3 + into SrTiO3 not only creates occupied states inside the band gap but can adversely narrow the conduction band. However, if Cr3 + and Ti4 + ions are segregated in alternating [001] layers, the conduction band remains highly dispersive. This suggests that the electronic structure can be tuned by controlling the cation arrangement. We predict that [SrTiO3]0.5[LaCrO3]0.5 with alternating TiO2 and CrO2 layered along the [001] direction, which has not been experimentally realized yet, will exhibit strong absorption of visible light response and excellent electronic transport properties.

  3. Structural and Optoelectronic Properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) Anti-Perovskite Compounds

    NASA Astrophysics Data System (ADS)

    Ullah, Imran; Murtaza, G.; Khenata, R.; Mahmood, Asif; Muzzamil, M.; Amin, N.; Saleh, M.

    2016-01-01

    We employed first-principles calculations to predict the structural and optoelectronic properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) anti-perovskite compounds using an all-electron full-potential linearized augmented plane-wave method. Optimized structural parameters are found to be in good agreement with the available experimental measurements. The electronic band structure is calculated using different exchange-correlation potentials which reveal that the investigated compounds are narrow direct band gap semiconductors. A direct narrow band gap at the center of the Brillouin zone emphasises the optical activity of these compounds. Prediction of the optical properties, such as the real and imaginary parts of the dielectric function and refractive index along with reflectivity and optical conductivity, reveals the importance of these compounds in the visible and near UV optoelectronic devices industry.

  4. Structural and Optoelectronic Properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) Anti-Perovskite Compounds

    NASA Astrophysics Data System (ADS)

    Ullah, Imran; Murtaza, G.; Khenata, R.; Mahmood, Asif; Muzzamil, M.; Amin, N.; Saleh, M.

    2016-06-01

    We employed first-principles calculations to predict the structural and optoelectronic properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) anti-perovskite compounds using an all-electron full-potential linearized augmented plane-wave method. Optimized structural parameters are found to be in good agreement with the available experimental measurements. The electronic band structure is calculated using different exchange-correlation potentials which reveal that the investigated compounds are narrow direct band gap semiconductors. A direct narrow band gap at the center of the Brillouin zone emphasises the optical activity of these compounds. Prediction of the optical properties, such as the real and imaginary parts of the dielectric function and refractive index along with reflectivity and optical conductivity, reveals the importance of these compounds in the visible and near UV optoelectronic devices industry.

  5. Structure, magnetic, magnetocaloric and magnetoresistance properties of Pr 1-xPb xMnO 3 perovskites

    NASA Astrophysics Data System (ADS)

    Hanh, D. T.; Chau, N.; Luong, N. H.; Tho, N. D.

    2006-09-01

    In our previous work, we have studied structure and properties of La 1-xPb xMnO 3 perovskites. Variation of doping content leads to alternating structure and magnetic properties of materials. In this paper, the investigation of structure, magnetic, magnetocaloric and magnetoresistance properties of family Pr 1-xPb xMnO 3 ( x=0.1-0.5) is presented. The grain size of samples increases with Pb content. The FC and ZFC thermomagnetic curves measured at low field and low temperatures exhibit the spin-glass-like behavior. The magnetic entropy changes, |Δ Sm( T)|, were determined and showed belong to GMCE. The resistance measurements indicated that first two samples exhibited semiconducting conductivity in the whole measured temperature range, whereas in the rest of samples there is insulator-metallic transition on R( T) curves. Magnetoresistance measurements have also been performed.

  6. Stabilization of Highly Polar BiFeO3 -like Structure: A New Interface Design Route for Enhanced Ferroelectricity in Artificial Perovskite Superlattices

    NASA Astrophysics Data System (ADS)

    Wang, Hongwei; Wen, Jianguo; Miller, Dean J.; Zhou, Qibin; Chen, Mohan; Lee, Ho Nyung; Rabe, Karin M.; Wu, Xifan

    2016-01-01

    In ABO3 perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in BiFeO3 with an R 3 c structure [1] but suppress ferroelectricity in CaTiO3 with a P b n m symmetry [2]. For many CaTiO3-like perovskites, the BiFeO3 structure is a metastable phase. Here, we report the stabilization of the highly polar BiFeO3-like phase of CaTiO3 in a BaTiO3/CaTiO3 superlattice grown on a SrTiO3 substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk CaTiO3 to a different pattern that is characteristic of a BiFeO3 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 CaTiO3 structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].

  7. Effects of the post-perovskite phase transition properties on the stability and structure of primordial reservoirs in the lower mantle of the Earth

    NASA Astrophysics Data System (ADS)

    Li, Yang; Deschamps, Frédéric; Tackley, Paul J.

    2015-12-01

    Two key features of the lowermost Earth's mantle are the presence of Large Low Shear Velocity Provinces (LLSVPs), which may be reservoirs of primordial, chemically distinct material, and the phase change from perovskite (pv) to post-perovskite (pPv), which may occur at lowermost mantle conditions. However, the influence of this phase change on the shape, dynamics, and stability of chemically distinct reservoirs is not well constrained. Here, we performed numerical experiments of thermo-chemical convection in 2-D spherical annulus geometry to investigate the effects on thermo-chemical structure in the lower mantle of three parameters affecting the pPv phase change: the core-mantle boundary (CMB) temperature (TCMB), the viscosity ratio between pv and pPv (ΔηpPv), and the Clapeyron slope of the pPv phase transition (ΓpPv). Our results indicate that increasing CMB temperature increases the wavelength of the primordial reservoirs. Furthermore, a high CMB temperature promotes the development of plumes outside the reservoir of primordial material. High CMB temperature and large Clapeyron slope both favour the formation of pPv patches and of a double-crossing of the phase boundary, thus preventing the formation of continuous layer of pPv above the CMB. Combined with a low CMB temperature and/or a low Clapeyron slope of the pPv phase transition, a full layer of weak pPv above the CMB strongly enhances the mixing efficiency of primordial material with ambient regular mantle material, which may not allow the generation of large reservoirs. Based on our experiments, we conclude that the models of convection best describing the Earth's mantle dynamics include a large pPv Clapeyron slope (typically in the range of 13-16 MPa/K), and a moderate CMB temperature (around 3750 K). Our models do not provide further constraints on the value of the pPv viscosity, both regular and low values giving similar results on stability and structure of large primordial reservoirs for models

  8. TiO2 quantum dots as superb compact block layers for high-performance CH3NH3PbI3 perovskite solar cells with an efficiency of 16.97.

    PubMed

    Tu, Yongguang; Wu, Jihuai; Zheng, Min; Huo, Jinghao; Zhou, Pei; Lan, Zhang; Lin, Jianming; Huang, Miaoliang

    2015-12-28

    A compact TiO(2) layer is crucial to achieve high-efficiency perovskite solar cells. In this study, we developed a facile, low-cost and efficient method to fabricate a pinhole-free and ultrathin blocking layer based on highly crystallized TiO(2) quantum dots (QDs) with an average diameter of 3.6 nm. The surface morphology of the blocking layer and the photoelectric performance of the perovskite solar cells were investigated by spin-coating with three different materials: colloidal TiO(2) QDs, titanium precursor solution, and aqueous TiCl(4). Among these three treatments, the perovskite solar cell based on the TiO(2) QD compact layer offered the highest power conversion efficiency (PCE) of 16.97% with a photocurrent density of 22.48 mA cm(-2), a photovoltage of 1.063 V and a fill factor of 0.71. The enhancement of PCE mainly stems from the small series resistance and the large shunt resistance of the TiO(2) QD layer. PMID:26585357

  9. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure.

    PubMed

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-01-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa. PMID:26671171

  10. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.

  11. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    PubMed Central

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-01-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa. PMID:26671171

  12. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    DOE PAGESBeta

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-16

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. We find, consistent withmore » PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.« less

  13. Structure, magnetic, magnetocaloric and magnetoresistance properties of La 1- xPb xMnO 3 perovskite

    NASA Astrophysics Data System (ADS)

    Chau, Nguyen; Nhat, Hoang Nam; Luong, Nguyen Hoang; Minh, Dang Le; Tho, Nguyen Duc; Chau, Nguyen Ngoc

    2003-04-01

    La 1- xPb xMnO 3 ( x=0.1, 0.2, 0.3, 0.4, and 0.5) perovskites were prepared by a solid-state reaction. Except for x=0.5 (cubic) and x=0.4 (rhombohedral), the structure of the other compositions was pseudo-rhombohedral with P1 symmetry. The particle size of the grains is depending on the Pb content of the samples. The Curie temperature Tc increases from 235 K for x=0.1-310 K for x=0.2 and is almost constant (about 360 K) for x⩾0.3. The field-cooled and zero-field-cooled thermomagnetic curves measured at low field show a split below a so-called irreversibility temperature Tr, which is somewhat smaller than Tc except for x=0.1, where it is 270 K. From a series of magnetic isotherms the magnetic entropy changes Δ S( T) were determined for a field step of 500 Oe. The maximum value of Δ Smax increases with increasing x till x=0.3 and then decreases with further increasing x. The conductivity of perovskites is metallic at low temperatures and semiconducting at high temperatures. Magnetoresistance measurements have been performed.

  14. Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.

    PubMed

    Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

    2014-06-14

    The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell. PMID:24736900

  15. Interface and Composition Analysis on Perovskite Solar Cells.

    PubMed

    Matteocci, Fabio; Busby, Yan; Pireaux, Jean-Jacques; Divitini, Giorgio; Cacovich, Stefania; Ducati, Caterina; Di Carlo, Aldo

    2015-12-01

    Organometal halide (hybrid) perovskite solar cells have been fabricated following four different deposition procedures and investigated in order to find correlations between the solar cell characteristics/performance and their structure and composition as determined by combining depth-resolved imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and analytical scanning transmission electron microscopy (STEM). The interface quality is found to be strongly affected by the perovskite deposition procedure, and in particular from the environment where the conversion of the starting precursors into the final perovskite is performed (air, nitrogen, or vacuum). The conversion efficiency of the precursors into the hybrid perovskite layer is compared between the different solar cells by looking at the ToF-SIMS intensities of the characteristic molecular fragments from the perovskite and the precursor materials. Energy dispersive X-ray spectroscopy in the STEM confirms the macroscopic ToF-SIMS findings and allows elemental mapping with nanometer resolution. Clear evidence for iodine diffusion has been observed and related to the fabrication procedure. PMID:26523427

  16. Crystal Structure of Calcium Silicate Perovskite Synthesized under Water Saturated Conditions at Mantle Related Pressure-Temperature

    NASA Astrophysics Data System (ADS)

    Chen, H.; Shim, S. H. D.; Leinenweber, K. D.; Meng, Y.; Prakapenka, V.

    2014-12-01

    Perovskite-structured CaSiO3 (Ca-Pv) is the third most abundant mineral in the lower mantle. However, its crystal structure is still under debate and the solubility of H2O in Ca-Pv is not well constrained. We have conducted in situ X-ray diffraction measurements on Ca-Pv under H2O saturated conditions in the laser-heated diamond-anvil cell at the GSECARS and HPCAT sectors of the Advanced Photon Source. Glass starting materials were mixed with platinum powder (10 wt%) for laser coupling and internal pressure scale. Cold compressed foils of the mixtures were loaded in the diamond-anvil cell together with Ne or water. The X-ray diffraction patterns of the Ca-Pv sample synthesized in a Ne medium are consistent with a cubic perovskite structure at both 300 K and high temperatures up to 2,400 K at 50 GPa. No clear peak splittings were observed within the resolution of the angle-dispersive powder diffraction technique. However, in the experiments with water, clear splitting of the 200 diffraction line appears during heating to temperatures over 2000 K and remain after temperature quench at 32 GPa. The peak splittings were clearly observed at high temperatures to 2400 K, which is close to the melting point of water at the pressure. The different structural behaviors of Ca-Pv depending on media (Ne and water) may suggest that OH might enter into the crystal structure of nominally anhydrous Ca-Pv phase at high pressure and high temperature.

  17. Tunable Photonic Devices in Ferroelectric-Based Layered Structures

    NASA Astrophysics Data System (ADS)

    Xin, Jianzhuo

    This thesis presents the studies on the optical properties of perovskite ferroelectric thin films, as well as the preparation and applications of ferroelectrics in tunable photonic devices. Ba(Zr,Ti)O3 (BZT) thin films with different Zr concentration were grown on MgO substrates by pulsed laser deposition, and their structural and optical properties in the visible range were systematically characterized, including the out-of-plane lattice constant, grain size, refractive index, optical band gap energy, electro-optic coefficient, optical loss and absorption coefficient. The obtained results provide information for the design of BZT thin film-based optical devices. One-dimensional photonic crystal filter working in the terahertz (THz) range was studied. The transmission properties of SrTiO3 (STO) crystals were first characterized by THz time-domain spectroscopy. Si/STO multilayers with different STO defect thicknesses were designed by the transfer matrix method and then constructed by polishing and stacking. The shift of defect mode was observed and comparable with the calculations. Two-dimensional photonic structures in the optical and infra-red range were then attempted. A combination of nanoimprint lithography and inductively coupled plasma etching were investigated on (Ba,Sr)TiO3 thin films. Then, in order to simplify the nanoimprint process and allow thick metal sacrificial layer deposition for high aspect-ratio etching, a transfer imprint lithography technique was developed. Finally, surface plasmon resonance (SPR) tuning via thermally-induced refractive index changes in ferroelectrics was investigated. Ag stripes with periodicity 750 nm were fabricated on flat BST surface by nanoimprint lithography and subsequent lift-off. (-1), (2) and (-2) SP modes from Ag/BST interface were observed in visible range. Red shift of the modes up to 3.9 nm was obtained with increasing temperature. Then continuous Au film on corrugated BST surface with periodicity of 1 mum was

  18. Flexible Hybrid Organic-Inorganic Perovskite Memory.

    PubMed

    Gu, Chungwan; Lee, Jang-Sik

    2016-05-24

    Active research has been done on hybrid organic-inorganic perovskite materials for application to solar cells with high power conversion efficiency. However, this material often shows hysteresis, which is undesirable, shift in the current-voltage curve. The hysteresis may come from formation of defects and their movement in perovskite materials. Here, we utilize the defects in perovskite materials to be used in memory operations. We demonstrate flexible nonvolatile memory devices based on hybrid organic-inorganic perovskite as the resistive switching layer on a plastic substrate. A uniform perovskite layer is formed on a transparent electrode-coated plastic substrate by solvent engineering. Flexible nonvolatile memory based on the perovskite layer shows reproducible and reliable memory characteristics in terms of program/erase operations, data retention, and endurance properties. The memory devices also show good mechanical flexibility. It is suggested that resistive switching is done by migration of vacancy defects and formation of conducting filaments under the electric field in the perovskite layer. It is believed that organic-inorganic perovskite materials have great potential to be used in high-performance, flexible memory devices. PMID:27093096

  19. Vacancy-type defects and electronic structure of perovskite-oxide SrTiO3 from positron annihilation

    NASA Astrophysics Data System (ADS)

    Hamid, A. S.; Uedono, A.; Chikyow, T.; Uwe, K.; Mochizuki, K.; Kawaminami, S.

    2006-02-01

    The vacancy-type defects in Nb-doped SrTiO3 and in undoped SrTiO3, annealed in H2 flow, were investigated by means of positron lifetime and 2D angular correlation of annihilation radiation (ACAR) experiments. The calculations of the lifetime of positron were performed by using atomic superposition (AT-SUP) method. The results showed that positrons annihilate from a free state in the Nb-doped SrTiO3. The trapping centers in the annealed sample were found to be oxygen vacancies VO associated with relaxation of the surrounding ions. Moreover, the momentum distributions of the samples studied were correlated to the variation of their electronic structure. It was proposed from the drastic change in the momentum distribution upon introduction of VO, that 2D-ACAR technique is a sensitive tool for acquiring information on the electronic and bond structure of the perovskite-oxides.

  20. Single Cesium Lead Halide Perovskite Nanocrystals at Low Temperature: Fast Single-Photon Emission, Reduced Blinking, and Exciton Fine Structure

    PubMed Central

    2016-01-01

    Metal-halide semiconductors with perovskite crystal structure are attractive due to their facile solution processability, and have recently been harnessed very successfully for high-efficiency photovoltaics and bright light sources. Here, we show that at low temperature single colloidal cesium lead halide (CsPbX3, where X = Cl/Br) nanocrystals exhibit stable, narrow-band emission with suppressed blinking and small spectral diffusion. Photon antibunching demonstrates unambiguously nonclassical single-photon emission with radiative decay on the order of 250 ps, representing a significant acceleration compared to other common quantum emitters. High-resolution spectroscopy provides insight into the complex nature of the emission process such as the fine structure and charged exciton dynamics. PMID:26771336

  1. Ligand-Stabilized Reduced-Dimensionality Perovskites.

    PubMed

    Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H

    2016-03-01

    Metal halide perovskites have rapidly advanced thin-film photovoltaic performance; as a result, the materials' observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions. These drive an increased formation energy and should therefore improve material stability. Here we report reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieve the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity. PMID:26841130

  2. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  3. Damage modes in dental layer structures.

    PubMed

    Jung, Y G; Wuttiphan, S; Peterson, I M; Lawn, B R

    1999-04-01

    Natural teeth (enamel/dentin) and most restorations are essentially layered structures. This study examines the hypothesis that coating thickness and coating/substrate mismatch are key factors in the determination of contact-induced damage in clinically relevant bilayer composites. Accordingly, we study crack patterns in two model "coating/substrate" bilayer systems conceived to simulate crown and tooth structures, at opposite extremes of elastic/plastic mismatch: porcelain on glass-infiltrated alumina ("soft/hard"); and glass-ceramic on resin composite ("hard/soft"). Hertzian contacts are used to investigate the evolution of fracture damage in the coating layers, as functions of contact load and coating thickness. The crack patterns differ radically in the two bilayer systems: In the porcelain coatings, cone cracks initiate at the coating top surface; in the glass-ceramic coatings, cone cracks again initiate at the top surface, but additional, upward-extending transverse cracks initiate at the internal coating/substrate interface, with the latter dominant. The substrate is thereby shown to have a profound influence on the damage evolution to ultimate failure in the bilayer systems. However, the cracks are highly stabilized in both systems, with wide ranges between the loads to initiate first cracking and to cause final failure, implying damage-tolerant structures. Finite element modeling is used to evaluate the tensile stresses responsible for the different crack types. The clinical relevance of these observations is considered. PMID:10326733

  4. Correlations of Optical Absorption, Charge Trapping, and Surface Roughness of TiO2 Photoanode Layer Loaded with Neat Ag-NPs for Efficient Perovskite Solar Cells.

    PubMed

    Yang, Dongwook; Jang, Jae Gyu; Lim, Joohyun; Lee, Jin-Kyu; Kim, Sung Hyun; Hong, Jong-In

    2016-08-24

    We systematically investigated the effect of silver nanoparticles (Ag-NPs) on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Neat, spherical Ag-NPs at loading levels of 0.0, 0.5, 1.0, and 2.0 wt % were embedded into the titanium dioxide (TiO2) photoanode layer. The plasmonic effect of the Ag-NPs strongly enhanced the incident light absorption over a wide range of the visible wavelength region in addition to the inherent absorbance of the perovskite sensitizer. The low conduction energy level of the Ag-NPs compared to that of TiO2 provides trap sites for free charge carriers. Thus, the correlation between the enhancement of the optical absorption and the number of charge traps provided by the Ag-NPs is critical to determine the device performance, especially current density (Jsc) and PCE. This is confirmed by the quantitative comparison of the incident light absorption and the time-resolved photoluminescence decay according to the loading levels of the Ag-NPs in the TiO2 layer. The absorption enhancement from 380 to 750 nm in the UV-visible spectrum is proportional to the increase in the loading levels of the Ag-NPs. However, the Jsc increases with the device with 0.5 wt % Ag-NPs and gradually decreases with increases in the loading level above 0.5 wt % because of the different contributions to the absorbance and the charge trapping by different Ag-NP loading levels. In addition, the suppression of the surface roughness with dense packing by the Ag-NPs helps to improve the Jsc and the following PCE. Consequently, the PCE of the PSC with 0.5 wt % Ag-NPs is increased to 11.96%. These results are attributed to the balance between increased absorbance by the localized surface plasmon resonance and the decreased charge trapping as well as the decreased surface roughness of the TiO2 layer with the Ag-NPs. PMID:27471777

  5. Synthesis, structural and dielectric properties of double perovskite Ho2FeMnO6

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tirthankar; Elizabeth, Suja

    2016-05-01

    A new double perovskite Ho2FeMnO6 was grown by nitrate route. Temperature dependent dielectric response was recorded at different frequencies. Relaxor-like-behavior is observed whose activation energy was calculated using Arrhenius equation. The dispersion is very small at room temperature. The Nyquist plot over a broad frequency range at room temperature provides evidence for the presence of three relaxations from sample electrode interface, grain boundary and grain. The corresponding values of resistance and capacitance were calculated from the equivalent circuit model analysis of the Nyquist plot.

  6. Effects of post-perovskite phase transition properties on the stability and structure of primordial reservoirs in the lower mantle of the Earth

    NASA Astrophysics Data System (ADS)

    Tackley, P.; Li, Y.; Deschamps, F.; Manatschal, G.

    2015-12-01

    Two key features of the lowermost Earth's mantle are the presence of the large low shear-wave velocity provinces (LLSVPs), which may be reservoirs of primordial, chemically distinct material, and the phase change from perovskite (pv) to post-perovskite (ppv), which may occur at lowermost mantle conditions. However, the influence of this phase change on the shape, dynamics, and stability of chemically distinct reservoirs are not well constrained. Here we performed numerical experiments of thermo-chemical convection in 2-D spherical annulus geometry to investigate the effects on thermo-chemical structure in the lower mantle of three parameters affecting the pPv phase change: the core-mantle (CMB) temperature, the viscosity ratio between pv and pPv, and the Clapeyron slope of the pPv phase transition. Our results indicate that increasing CMB temperature increases the wavelength of the primordial reservoirs by preventing the phase transition from pv to pPv to occur. Furthermore, a high CMB temperature promotes the development of plumes outside the reservoirs of primordial material. High CMB temperature and large Clapeyron slope both favor the formation of pPv patches and of a double-crossing of the phase boundary, thus preventing the formation of continuous layer of pPv above the CMB. Combined with a low CMB temperature and/or a low Clapeyron slope of the pPv phase transition, a full layer of weak pPv above CMB strongly enhances the mixing efficiency of primordial material with ambient regular mantle material, which may not allow the generation of large reservoirs. Based on our experiments, we conclude that the models of convection best describing the Earth's mantle dynamics include a large pPv Clapeyron slope (typically in the range of 13-16 MPa/K), and a moderate CMB temperature (around 3750 K). We also find that the phase change from pv to pPv may occur within the large reservoirs in the form of small discontinuous patches at the base when using critical values of

  7. Perovskite photovoltaics featuring solution-processable TiO2 as an interfacial electron-transporting layer display to improve performance and stability

    NASA Astrophysics Data System (ADS)

    Yu, Yang-Yen; Chiang, Rih-Sheng; Hsu, Hsiang-Lin; Yang, Chun-Chen; Chen, Chih-Ping

    2014-09-01

    In this study we used solution-processable crystalline TiO2 nanoparticles as an interfacial modified layer between the active layer and aluminum cathode to fabricate CH3NH3PbI3/PCBM-based planar heterojunction perovskite photovoltaic (PPV) devices. We optimized the performance of the PPV device prepared without TiO2 by varying the preheating temperature of the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT) substrate, obtaining a power conversion efficiency (PCE) of 6.3% under simulated AM 1.5 G irradiation (100 mW cm-2). After incorporating the TiO2 layer, we obtained a much higher PCE of 7.0%. The TiO2-containing PPV device exhibited extremely high stability (retaining ~96% of its PCE after 1000 h) under long-term storage in a dark N2-filled glove box; the unencapsulated device retained approximately 80% of its original efficiency (T80) after 1 week under ambient conditions (ISOS-D-1; defined as 23 °C/50% RH). In contrast, the normal device was sensitive to ambient conditions with a value of T80 at only 3 h. We attributed the improved device performance (PCE, stability) to the enhanced electron transporting, hole blocking, and barrier properties arising from the presence of the TiO2 layer.In this study we used solution-processable crystalline TiO2 nanoparticles as an interfacial modified layer between the active layer and aluminum cathode to fabricate CH3NH3PbI3/PCBM-based planar heterojunction perovskite photovoltaic (PPV) devices. We optimized the performance of the PPV device prepared without TiO2 by varying the preheating temperature of the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT) substrate, obtaining a power conversion efficiency (PCE) of 6.3% under simulated AM 1.5 G irradiation (100 mW cm-2). After incorporating the TiO2 layer, we obtained a much higher PCE of 7.0%. The TiO2-containing PPV device exhibited extremely high stability (retaining ~96% of its PCE after 1000 h) under long-term storage in a dark N2-filled

  8. Simulation of polarization and butterfly hysteresis loops in bismuth layer-structured ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Ye, Z.; Tang, M. H.; Cheng, C. P.; Zhou, Y. C.; Zheng, X. J.; Hu, Z. S.

    2006-11-01

    Modeling of the hysteresis loop of ferroelectric thin films has been thought very difficult owing to its nonlinear and history-dependent electric field effects. Here we extend the Preisach model [Z. Phys. 94, 277 (1935)] by using the distribution function integral and superposition method. The model shows improved hysteresis loop that agrees reasonably well with the experimental data measured from the bismuth layer-structured ferroelectric thin films. Compared with the previous model, the current model provides polarization-field (P-E) loop with full and symmetric shape, suitable coercive field (Ec), and few undesirable parameters. The butterfly loop of perovskite-type ferroelectric thin films is also simulated. Additionally, the approach is able to describe the unsaturated loops obtained under various ac electric fields, which is very useful in circuit simulation of ferroelectric field effect transistor or ferroelectric capacitor.

  9. Structure-property Relationships of Layered Oxypnictides

    NASA Astrophysics Data System (ADS)

    Muir, Sean W.

    Investigating the structure-property relationships of solid state materials can help improve many of the materials we use each day in life. It can also lead to the discovery of materials with interesting and unforeseen properties. In this work the structure property relationships of newly discovered layered oxypnictide phases are presented and discussed. There has generally been worldwide interest in layered oxypnictide materials following the discovery of superconductivity up to 55 K for iron arsenides such as LnFeAsO 1-xFx (where Ln = Lanthanoid). This work presents efforts to understand the structure and physical property changes which occur to LnFeAsO materials when Fe is replaced with Rh or Ir and when As is replaced with Sb. As part of this work the solid solution between LaFeAsO and LaRhAsO was examined and superconductivity is observed for low Rh content with a maximum critical temperature of 16 K. Ln RhAsO and LnIrAsO compositions are found to be metallic; however Ce based compositions display a resistivity temperature dependence which is typical of Kondo lattice materials. At low temperatures a sudden drop in resistivity occurs for both CeRhAsO and CeIrAsO compositions and this drop coincides with an antiferromagnetic transition. The Kondo scattering temperatures and magnetic transition temperatures observed for these materials can be rationalized by considering the expected difference in N(EF) J parameters between them, where N(EF) is the density of states at the Fermi level and J represents the exchange interaction between the Ce 4f1 electrons and the conduction electrons. In addition to studying these 4d and 5d substituted systems the LaFeSbO compositional system was investigated. While LaFeSbO has not been successfully synthesized the transition metal free layered oxypnictide composition La2SbO 2 was discovered and its structural and physical properties have been examined along with the properties of La2BiO2. Density functional theory was used to

  10. Cycling Performance of a Columnar-Structured Complex Perovskite in a Temperature Gradient Test

    NASA Astrophysics Data System (ADS)

    Schlegel, N.; Sebold, D.; Sohn, Y. J.; Mauer, G.; Vaßen, R.

    2015-10-01

    To increase the efficiency of turbines for the power generation and the aircraft industry, advanced thermal barrier coatings (TBCs) are required. They need to be long-term stable at temperatures higher than 1200 °C. Nowadays, yttria partially stabilized zirconia (YSZ) is applied as standard TBC material. But its long-term application at temperatures higher than 1200 °C leads to detrimental phase changes and sintering effects. Therefore, new materials have to be investigated, for example, complex perovskites. They provide high melting points, high thermal expansion coefficients and thermal conductivities of approx. 2.0 W/(m K). In this work, the complex perovskite La(Al1/4Mg1/2Ta1/4)O3 (LAMT) was investigated. It was deposited by the suspension plasma spraying (SPS) process, resulting in a columnar microstructure of the coating. The coatings were tested in thermal cycling gradient tests and they show excellent results, even though some phase decomposition was found.

  11. PbnI4n+2(2n+2)- ribbons (n = 3, 5) as dimensional reductions of 2D perovskite layers in cystamine cation based hybrids, also incorporating iodine molecules or reversible guest water molecules.

    PubMed

    Louvain, Nicolas; Bi, Wenhua; Mercier, Nicolas; Buzaré, Jean-Yves; Legein, Christophe; Corbel, Gwenaël

    2007-03-01

    Pb(n)I(4n+2)((2n+2)-) (n = 3, 5) ribbons, which can be regarded as dimensional reductions of 2D perovskite layers, are stabilized by diprotonated cystamine cations in (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(4)Pb(3)I(14),I(2) (1) and (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).4H(2)O (2). Both 1 and 2 have interesting structural characteristics; it is unprecedented that the ribbons are linked via I(2) molecules incorporated in the lattice of 1, while tetrameric water clusters are trapped in the structure of 2. 2 undergoes a (reversible) water desorption process at 310 K leading to (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).2H(2)O (3). The electrical behavior of 2 and 3 has been investigated in the ranges 293-310 K and 310-358 K respectively. Above 310 K, the electronic contribution remains constant while the ionic transference number tends towards unity showing almost pure ionic transport at 360 K (6 x 10(-7) S cm(-1) at 330 K) originating probably from the migration of protons through the hydrogen bonds connecting the water molecules to the cystamine counter cations. PMID:17308677

  12. Solution-processed flexible planar perovskite solar cells: A strategy to enhance efficiency by controlling the ZnO electron transfer layer, PbI2 phase, and CH3NH3PbI3 morphologies

    NASA Astrophysics Data System (ADS)

    Jung, Kyungeun; Lee, Jeongwon; Kim, Joosun; Chae, Weon-Sik; Lee, Man-Jong

    2016-08-01

    This paper reports a synergistic strategy to enhance the power conversion efficiency (PCE) of flexible planar perovskite solar cells (PSCs) by controlling the thickness of the ZnO electron transport layer (ETL), PbI2 phase, and size/morphology of the perovskite (MAPbI3) absorber layer. To optimize the size/morphology of MAPbI3 via a two-step spin coating process, various volumes of CH3NH3I precursor solutions with a constant concentration were continuously coated, which greatly affected the grain growth condition of the MAPbI3. In addition, the remnant PbI2 phase in the MAPbI3, which acted as a recombination barrier, was simultaneously controlled. This strategic method to synergistically combine the major factors affecting the final PCE resulted in the best efficiency of 12.3%, which is the highest efficiency among ZnO-ETL-based flexible planar PSCs to date.

  13. Hydrolysis preparation of the compact TiO2 layer using metastable TiCl4 isopropanol/water solution for inorganic-organic hybrid heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Xiaoyan, Dai; Chengwu, Shi; Yanru, Zhang; Ni, Wu

    2015-07-01

    A hydrolysis process was applied to prepare the compact TiO2 layer using the fresh metastable TiCl4 isopropanol/water solution as the precursor solution for the preparation of the inorganic-organic hybrid heterojunction perovskite solar cells. The optimal compact TiO2 layer prepared from the aqueous solution of 2 mol/L TiCl4 diluted in isopropanol at 1 : 3 by volume as precursor solution was uniform and with a film thickness of 126 nm. The corresponding perovskite solar cell gave a photovoltaic conversion efficiency of 10.61%. Project supported by the National Natural Science Foundation of China (Nos. 51472071, 51272061, 51072043), and the National Basic Research Program of China (No. 2011CBA00700).

  14. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties.

    PubMed

    Jaffe, Adam; Lin, Yu; Beavers, Christine M; Voss, Johannes; Mao, Wendy L; Karunadasa, Hemamala I

    2016-04-27

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3 (+), X = Br(-) or I(-)) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites' precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material's resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(Br x I1-x )3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors. PMID:27163050

  15. High-efficiency bulk heterojunction memory devices fabricated using organometallic halide perovskite:poly(N-vinylcarbazole) blend active layers.

    PubMed

    Wang, Cheng; Chen, Yu; Zhang, Bin; Liu, Shanshan; Chen, Qibin; Cao, Yaming; Sun, Sai

    2016-01-14

    A solution-processed organometallic halide perovskite-based bulk heterojunction (BHJ) memory device with a configuration of indium-doped tin oxide (ITO)/CH3NH3PbI3:PVK/Al has been successfully fabricated. Under a threshold voltage of -1.57 V, this device shows a nonvolatile write-once read-many-times (WORM) memory effect, with a maximum ON/OFF current ratio exceeding 10(3). In contrast, the ITO/CH3NH3PbI3/Al device showed only conductor characteristics, while the PVK-based device exhibited insulator behavior. Upon being subjected to voltages, an interesting filamentary nature of the CH3NH3PbI3:PVK film was also observed in situ at the microscopic nanometer level using a conductive atomic force microscopy (C-AFM) technique with a device configuration of Si/Pt/CH3NH3PbI3:PVK/Pt. The mechanism associated with the memory effect is discussed. The electric-field-induced intermolecular charge transfer effect between CH3NH3PbI3 and PVK, and the possible conformational ordering of the PVK side-chains/backbone under an applied bias voltage, may cause the electrical conductivity switching and WORM effect in the reported BHJ device. PMID:26645358

  16. Investigation on structural, optical and magnetic properties of double perovskite Gd{sub 2}NiMnO{sub 6}

    SciTech Connect

    Mohapatra, S. R.; Sahu, B.; Raut, S.; Singh, A. K.; Kaushik, S. D.

    2015-06-24

    Single phase double perovskite Gd{sub 2}NiMnO{sub 6} was prepared by conventional solid state reaction route. X-ray diffraction (XRD) result reveals that the compound possess monoclinic structure with space group P2{sub 1}/n. Optical characterization performed at room temperature via UV-visible spectroscopy confirms Gd{sub 2}NiMnO{sub 6} as a direct band-gap material with band gap of ∼1.5 eV. Magnetization measurement in Zero field cooled (ZFC) condition at H = 100 Oe shows magnetic transition at ∼ 125 K. Due to competing interactions between magnetic ions (Ni{sup 2+} and Mn{sup 4+}), we could observe two magnetic transition below 40 K.

  17. Dominance of interface chemistry over the bulk properties in determining the electronic structure of epitaxial metal/perovskite oxide heterojunctions

    SciTech Connect

    Chambers, Scott A.; Du, Yingge; Gu, Meng; Droubay, Timothy C.; Hepplestone, Steven; Sushko, Petr

    2015-06-09

    We show that despite very similar crystallographic properties and work function values in the bulk, epitaxial Fe and Cr metallizations on Nb:SrTiO3(001) generate completely different heterojunction electronic properties. Cr is Ohmic whereas Fe forms a Schottky barrier with a barrier height of 0.50 eV. This contrast arises because of differences in interface chemistry. In contrast to Cr [Chambers, S. A. et al., Adv. Mater. 2013, 25, 4001.], Fe exhibits a +2 oxidation state and occupies Ti sites in the perovskite lattice, resulting in negligible charge transfer to Ti, upward band bending, and Schottky barrier formation. The differences between Cr and Fe are understood by performing first-principles calculations of the energetics of defect formation which corroborate the observed interface chemistry and structure.

  18. Structure and magnetic properties of spinel-perovskite nanocomposite thin films on SrTiO3 (111) substrates

    NASA Astrophysics Data System (ADS)

    Kim, Dong Hun; Yang, Junho; Kim, Min Seok; Kim, Tae Cheol

    2016-09-01

    Epitaxial CoFe2O4-BiFeO3 nanocomposite thin films were synthesized on perovskite structured SrTiO3 (001) and (111) substrates by combinatorial pulsed laser deposition and characterized using scanning electron microscopy, x-ray diffraction, and vibrating sample magnetometer. Triangular BiFeO3 nanopillars were formed in a CoFe2O4 matrix on (111) oriented SrTiO3 substrates, while CoFe2O4 nanopillars with rectangular or square top surfaces grew in a BiFeO3 matrix on (001) substrates. The magnetic hysteresis loops of nanocomposites on (111) oriented SrTiO3 substrates showed isotropic properties due to the strain relaxation while those of films on SrTiO3 (001) substrates exhibited a strong out-of-plane anisotropy originated from shape and strain effects.

  19. New routes to synthesizing an ordered perovskite CaCu3Fe2Sb2O12 and its magnetic structure by neutron powder diffraction.

    PubMed

    Larregola, Sebastian A; Zhou, Jianshi; Alonso, Jose A; Pomjakushin, Vladimir; Goodenough, John B

    2014-05-01

    The search for new double-perovskite oxides has grown rapidly in recent years because of their interesting physical properties like ferroelectricity, magnetism, and multiferroics. The synthesis of double perovskites, especially the A-site-ordered perovskites, in most cases needs to be made under high pressure, which is a drawback for applying these materials. Here we have demonstrated synthetic routes at ambient pressure by which we have obtained a high-quality duo-sites-ordered double perovskite, CaCu3Fe2Sb2O12, which has been previously synthesized under high pressure. The availability of a large quantity of the powder sample allows us to determine the crystal and magnetic structures by neutron powder diffraction (NPD) at 300 and 1.3 K. Measurements of the magnetization and heat capacity showed a ferrimagnetic transition at 160 K. A ferrimagnetic structure consisting of the uncompensated antiferromagnetic coupling between neighboring collinear copper and iron spins has been resolved from the low-temperature NPD data. PMID:24716725

  20. Structural investigations of (Ca,Sr)ZrO3 and Ca(Sn,Zr)O3 perovskite compounds

    NASA Astrophysics Data System (ADS)

    Tarrida, Martine; Larguem, H.; Madon, M.

    2009-07-01

    (Ca x ,Sr1- x )ZrO3 and Ca(Sn y ,Zr1- y )O3 solid solutions were synthesized by solid-state reaction at high temperature before to be studied by powder X-ray diffraction and Raman Spectroscopy. Diffraction data allow the distortion of the ABO3 perovskite structure to be investigated according to cations substitution on A and B-sites. It is shown that distortion, characterized by Φ, the tilt angle of BO6 octahedra, slightly increases with decreasing y content in Ca(Sn y ,Zr1- y )O3 compounds and strongly decreases with decreasing x content in (Ca x ,Sr1- x )ZrO3 compounds. Such results are discussed in view of the relative A and B cation sizes. Raman data show that vibrational spectra are strongly affected by the cation substitution on A-site; the frequencies of most vibrational modes increase with increasing x content in (Ca x ,Sr1- x )ZrO3 compounds, i.e. with the decreasing mean size of the A-cation; the upper shift is observed for the 358 cm-1 mode (∂ ν/∂r = -60.1 cm-1/Å). On the other hand, the cation substitution on B-sites, slightly affect the spectra; it is shown that in most cases, the frequency of vibrational modes increases with increasing y content in Ca(Sn y ,Zr1- y )O3 compounds, i.e. with the decreasing mean size of the B-cation, but that two modes (287 and 358 cm-1) behave differently: their frequencies decrease with the decreasing mean size of the B-cation, with a shift respectively equal to +314 and +162 cm-1/Å. Such results could be used to predict the location of different elements such as trivalent cations or radwaste elements on A- or B-site, in the perovskite structure.

  1. Synthesis of LaYbO3 perovskite through modified Pechini method: Structural, electric and magnetic characterization

    NASA Astrophysics Data System (ADS)

    Jaramillo P, J. A.; Landínez Téllez, D. A.; Roa-Rojas, J.; Parra Vargas, C. A.; Barrera, E. W.

    2015-10-01

    Single phase LaYbO3 lanthanide-based perovskite powder was synthesized by modified Pechini method, which is based on polyesterification of metal-citrate complexes in aqueous solution. Complexes were formed in aqueous solution and after polyalcohol addition and slow water evaporation, bond formation is allowed and a macroscopic polymeric network was produced, where cations are embedded and uniformly distributed. Finally, through several pyrolysis steps, microcrystalline oxide particles were obtained. Structural characterization was performed by means the powder X-ray diffraction (XRD) technique. The obtained patterns were indexed and refined to reveal that the LaYbO3 simple perovskite crystallizes in an orthorhombic structure, belonging to the Pnma (#62) space group, with lattice constants a = 6.0327 Å, b = 8.4138 Å and c = 5.8307 Å. Studies of electron dispersive X-ray spectroscopy show that the LaYbO3 is free of impurities. Electric response was evaluated by electric polarization measurements as a function of applied electric fields. Obtained curves show evidence of a hysteretic behavior related with dielectric losses which are characteristics of insulator materials. From the saturation values of electric charge, the relative dielectric constant was determined to be 22.6. The magnetic behavior was examined by means of the curves of magnetic susceptibility as a function of temperature. The fit with the Curie equation is in agreement with a typical paramagnetic feature with effective magnetic moment μ = 4.9 μB, which is close to the theoretical expected value from the Hund’s rules.

  2. Synthesis, structure, and magnetic properties of novel B-site ordered double perovskites, SrLaMReO6 (M = Mg, Mn, Co and Ni).

    PubMed

    Thompson, Corey M; Chi, Lisheng; Hayes, John R; Hallas, Alannah M; Wilson, Murray N; Munsie, Timothy J S; Swainson, Ian P; Grosvenor, Andrew P; Luke, Graeme M; Greedan, John E

    2015-06-21

    Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P2(1)/n structure type, which consists of alternately corner-shared octahedra of MO(6) and ReO(6). Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites. Bond valence sum calculations (BVS) suggest all M and Re ions are 2+ and 5+, respectively, and for the Mn-containing phase this is also supported by XANES measurements. All of the materials are paramagnetic at room-temperature and their Curie-Weiss temperatures are positive (except for Mg) indicating net ferromagnetic interactions. No evidence for long-range magnetic order is evident in the dc magnetic susceptibility and μSR measurements for SrLaMgReO(6) to 2 K. The Mn-phase shows long-range order at T(C) = 190 K and neutron diffraction revealed a ferromagnetic structure with a refined net moment of ∼3.7μ(B). Both Co- and Ni-containing phases exhibit spin glass behavior at T(G) = 23 and 30 K, respectively, which is supported by neutron diffraction and a.c. susceptibility data. The structure and physical properties of these four new rhenium based ordered double perovskites are compared to the closely related "pillared perovskites", La(5)Re(3)MO(16), the isoelectronic Os(6+) (5d(2)) double perovskite Sr(2)CoOsO(6), and the Re(6+) (5d(1)) double perovskites, Sr(2)MReO(6), (M = Mg, Ca, Mn, Co, Ni). PMID:25740594

  3. Krypton irradiation damage in Nd-doped zirconolite and perovskite

    NASA Astrophysics Data System (ADS)

    Davoisne, C.; Stennett, M. C.; Hyatt, N. C.; Peng, N.; Jeynes, C.; Lee, W. E.

    2011-08-01

    Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts for plutonium disposition is necessary to evaluate their long-term behaviour during geological disposal. Polycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex situ with 2 MeV Kr + at a dose of 5 × 10 15 ions cm -2 to simulate recoil of Pu nuclei during alpha decay. The feasibility of thin section preparation of both pristine and irradiated samples by Focused Ion Beam sectioning was demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region separated from the pristine material by a thin (40-60 nm) damaged interface. The zirconolite lattice was lost in the damaged interface, but the fluorite sublattice was retained. The Nd-doped perovskite contained a defined irradiated layer composed of an amorphous region surrounded by damaged but still crystalline layers. The structural evolution of the damaged regions is consistent with a change from orthorhombic to cubic symmetry. In addition in Nd-doped perovskite, the amorphisation dose depended on crystallographic orientation and possibly sample configuration (thin section or bulk). Electron Energy Loss Spectroscopy revealed Ti remained in the 4+ oxidation state but there was a change in Ti coordination in both Nd-doped perovskite and Nd-doped zirconolite associated with the crystalline to amorphous transition.

  4. Synthesis, structure, chemical stability, and electrical properties of Nb-, Zr-, and Nb-codoped BaCeO3 perovskites.

    PubMed

    Bhella, Surinderjit Singh; Fürstenhaupt, Tobias; Paul, Reginald; Thangadurai, Venkataraman

    2011-07-18

    We report the effect of donor-doped perovskite-type BaCeO(3) on the chemical stability in CO(2) and boiling H(2)O and electrical transport properties in various gas atmospheres that include ambient air, N(2), H(2), and wet and dry H(2). Formation of perovskite-like BaCe(1-x)Nb(x)O(3±δ) and BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) (x = 0.1; 0.2) was confirmed using powder X-ray diffraction (XRD) and electron diffraction (ED). The lattice constant was found to decrease with increasing Nb in BaCe(1-x)Nb(x)O(3±δ), which is consistent with Shannon's ionic radius trend. Like BaCeO(3), BaCe(1-x)Nb(x)O(3±δ) was found to be chemically unstable in 50% CO(2) at 700 °C, while Zr doping for Ce improves the structural stability of BaCe(1-x)Nb(x)O(3±δ). AC impedance spectroscopy was used to estimate electrical conductivity, and it was found to vary with the atmospheric conditions and showed mixed ionic and electronic conduction in H(2)-containing atmosphere. Arrhenius-like behavior was observed for BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) at 400-700 °C, while Zr-free BaCe(1-x)Nb(x)O(3±δ) exhibits non-Arrhenius behavior at the same temperature range. Among the perovskite-type oxides investigated in the present work, BaCe(0.8)Zr(0.1)Nb(0.1)O(3±δ) showed the highest bulk electrical conductivity of 1.3 × 10(-3) S cm(-1) in wet H(2) at 500 °C, which is comparable to CO(2) and H(2)O unstable high-temperature Y-doped BaCeO(3) proton conductors. PMID:21692498

  5. Improving the efficiency of perovskite solar cells through optimization of the CH3NH3PbI3 film growth in solution process method

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Liu, Jian; Lu, Xinrong; Gao, Yandong; You, Xiaozeng; Xu, Xiangxing

    2015-12-01

    Perovskite-structured organic-inorganic materials such as CH3NH3PbI3 are attracting much interest in the scientific community because of their abilities to function as revolutionary light harvesters and charge transfer materials for solar cells. To achieve high power conversion efficiency (PCE), it is critical to optimize the perovskite film layer. This paper reports the temperature and concentration controls on the two-step solution process. A diffusion-controlled growth mechanism is proposed for this process in tuning the morphology and purity of the perovskite film, which are proven to be important factors contributing to the photovoltaic performance. The highest PCE of 11.92% is achieved with an optimized perovskite crystal size of ∼150 nm and an appropriate amount of residual PbI2. This study sheds light on the design and fabrication of highly efficient, low-cost, solution-processed perovskite solar cells.

  6. Interface Energetics in Organo-Metallic Halide Perovskite-based Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Schulz, Philip

    2015-03-01

    In my presentation I will talk about the most recent findings on the electronic structure of methylammonium lead tri-halide (MAPbX3, X =I, Br) perovskite films and their interfaces to adjacent transport layers. Intricate knowledge of the electronic alignment at the contact interfaces in perovskite solar cells is essential for the understanding of the working principle as well as improving design and thus performance of respective devices. In our studies we employ ultra-violet, X-ray and inverse photoemission spectroscopy (UPS, XPS, IPES) to directly determine valence and conduction band offsets. In this way we are able to report a direct measurement of the electronic band gap as well as ionization energy and electron affinity found for perovskite surfaces. Furthermore, our findings indicate that the electronic energy level alignment of adjacent organic hole transport layers, such as spiro-MeOTAD, can limit the maximum attainable open circuit voltage (Voc) in solar cells if the highest occupied molecular orbital of the hole transport material is not well aligned to the valence band maximum of the perovskite layer. Using better suited hole transporters, like CBP, values for Voc larger than 1.5 V could be achieved in the case of MAPbBr3 based devices. More recently, inverted perovskite solar cells based on nickel oxide bottom anodes have been reported to yield viable power conversion efficiencies and stability. We find that the interface between the p-doped NiO surface and the MAPbI3 layer on top lead to p-type perovskite filsm while the same material deposited on TiO2 in the conventional cell geometry turns out to be n-type. A further investigation of a C60 layer deposited on top of p-type perovskite films reveals an ideal alignment between the lowest unoccupied molecular orbital of the organic electron transport materials and the conduction band minimum of the perovskite film underneath. These results explain why the inverted solar cell structure could achieve

  7. Structure-property relations in the distorted ordered double perovskite Sr2InReO6

    NASA Astrophysics Data System (ADS)

    Gao, Haitao; Llobet, Anna; Barth, Joachim; Winterlik, Jürgen; Felser, Claudia; Panthöfer, Martin; Tremel, Wolfgang

    2011-04-01

    The rock-salt ordered type double perovskite Sr2InReO6 is systematically investigated by means of powder x-ray diffraction, neutron powder diffraction, temperature-dependent electrical transport, heat capacity and magnetic susceptibility measurements, and electronic band structure calculations. The crystal structure of Sr2InReO6 is revised to be monoclinic (cryolite structure type, space group P21/n) with all structural distortions according to the high-symmetry aristotype due to tilting of the InO6 and ReO6 octahedra, respectively. Sr2InReO6 is a Mott insulator with variable-range hopping. Two 5d electrons are unpaired and localized on the Re5+ ions. Although there are antiferromagnetic interactions, the fcc arrangement of the Re5+ cations (5d2) leads to a geometrically frustrated spin system that does not achieve full magnetic order. The experimental findings are in line with the results of electronic structure computation using the WIEN2K program within the GGA + U approximation exclusively on the basis of the revised crystal structure model.

  8. Analysing the effect of crystal size and structure in highly efficient CH3NH3PbI3 perovskite solar cells by spatially resolved photo- and electroluminescence imaging

    NASA Astrophysics Data System (ADS)

    Mastroianni, S.; Heinz, F. D.; Im, J.-H.; Veurman, W.; Padilla, M.; Schubert, M. C.; Würfel, U.; Grätzel, M.; Park, N.-G.; Hinsch, A.

    2015-11-01

    CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as well as light beam induced current measurements (LBIC). It was found that the most efficient cell shows the highest luminescence and the least efficient cell is most strongly limited by non-radiative recombination. Crystal size, morphology and distribution in the capping layer and in the porous scaffold strongly affect the non-radiative recombination. Moreover, the very non-uniform crystal structure with multiple facets, as evidenced by SEM images of the 0.032 M device, suggests the creation of a large number of grain boundaries and crystal dislocations. These defects give rise to increased trap-assisted non-radiative recombination as is confirmed by high-resolution μ-PL images. The different imaging techniques used in this study prove to be well-suited to spatially investigate and thus correlate the crystal morphology of the perovskite layer with the electrical and radiative properties of the solar cells and thus with their performance.CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as

  9. Structural and magnetic characterization of the new GdMn1-xFexO3 perovskite material

    NASA Astrophysics Data System (ADS)

    Cardona Vasquez, J. A.; Landínez Téllez, D. A.; Collazos, C. A.; Roa Rojas, J.

    2016-02-01

    In this paper we presents the synthesis process of the GdMn1-xFexO3 perovskite material by conventional solid state reaction method. Crystalline phase evolution during the synthesis was studied by X-ray Diffraction (XRD) in powder of the materials, observing that the chemical reaction of the precursor oxides was significant above 1000°C. Rietveld refinement of DRX patterns shows a perovskite structure with octahedral distortions (space group Pbnm, # 62) for studied values of x (0, 0.1 and 0.2). The degree of substitution generates an increasing tendency on lattice parameters a and c, while for b is decreasing just as for the volume of the unit cell. The effect of the change in the lattice parameters directly affects the octahedral distortions, ie, with increasing degree of substitution (increased parameter c) octahedra tend to arrange one above the other aligned with the c axis. Magnetization measurements as a function of temperature were performed above room temperature between 300K and 860K with an applied field of 20Oe and below room temperature in Field Cooling (FC) and Zero Field Cooling modes (ZFC) between 4.2K and 300K with an applied field of 200Oe. Magnetic behavior above room temperature is paramagnetic for used values of x, on the other hand at low temperatures (T<30K) magnetic phase transitions associated to the apparition of an antiferromagnetic phase are observed. In addition for x=0.1 the derivative of magnetization shows a peak around 31K, associated to the ferrimagnetic transition for this material. Curie-Weiss fit reveals the antiferromagnetic (ferrimagnetic) behavior of the materials, also shows that the configurations with x=0 and x=0.2 have an effective magnetic moment very similar to the reported value of undoped material, while for x=0.1 a higher value is observed confirming the ferrimagnetic behavior of this configuration.

  10. Synthesis, characterization and phase transitions in the inorganic-organic layered perovskite-type hybrids [(CnH2n+1NH3)2PbI4], n = 4, 5 and 6.

    PubMed

    Billing, David G; Lemmerer, Andreas

    2007-10-01

    Three inorganic-organic layered perovskite-type hybrids of the general formula [(C(n)H(2n+1)NH(3))(2)PbI(4)], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C(4)H(9)NH(3))(2)PbI(4)] has a single phase transition, [(C(5)H(11)NH(3))(2)PbI(4)] has two phase transitions and [(C(6)H(13)NH(3))(2)PbI(4)] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C(4)H(9)NH(3))(2)PbI(4)] and [(C(6)H(13)NH(3))(2)PbI(4)], and from orange to red for [(C(5)H(11)NH(3))(2)PbI(4)]. The structural details associated with this phase transition have been investigated via single-crystal X-ray diffraction, SC-XRD, for all three compounds. PMID:17873443

  11. Performance enhancement of perovskite solar cells with Mg-doped TiO2 compact film as the hole-blocking layer

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Qin, Minchao; Tao, Hong; Ke, Weijun; Chen, Zhao; Wan, Jiawei; Qin, Pingli; Xiong, Liangbin; Lei, Hongwei; Yu, Huaqing; Fang, Guojia

    2015-03-01

    In this letter, we report perovskite solar cells with thin dense Mg-doped TiO2 as hole-blocking layers (HBLs), which outperform cells using TiO2 HBLs in several ways: higher open-circuit voltage (Voc) (1.08 V), power conversion efficiency (12.28%), short-circuit current, and fill factor. These properties improvements are attributed to the better properties of Mg-modulated TiO2 as compared to TiO2 such as better optical transmission properties, upshifted conduction band minimum (CBM) and downshifted valence band maximum (VBM), better hole-blocking effect, and higher electron life time. The higher-lying CBM due to the modulation with wider band gap MgO and the formation of magnesium oxide and magnesium hydroxides together resulted in an increment of Voc. In addition, the Mg-modulated TiO2 with lower VBM played a better role in the hole-blocking. The HBL with modulated band position provided better electron transport and hole blocking effects within the device.

  12. ESR Studies of Layered-Perovskite Manganites R0.5Sr1.5MnO4 (R = La, Nd)

    NASA Astrophysics Data System (ADS)

    Marumoto, Kazuhiro; Soda, Kazuya; Kuroda, Shin-ichi; Moritomo, Yutaka

    2003-03-01

    ESR studies have been performed on single crystals of layered-perovskite manganites R0.5Sr1.5MnO4 (R = La, Nd). An anisotropic ESR signal with extremely broad linewidth is observed and ascribed to the single-ion-anisotropic D term. For La0.5Sr1.5MnO4, the spin susceptibility χs deviates from the Curie-Weiss-like behavior and the peak-to-peak linewidth Δ Hpp shows a broad maximum at the charge-ordering temperature Tco (≈ 217 K). With further decrease of temperature below 160 K, χs decreases and Δ Hpp increases rapidly due to the spin order at the Néel temperature TN (≈ 110 K). These anomalies are absent in Nd0.5Sr1.5MnO4, which does not show the charge-ordering nor the spin-ordering. On the basis of these experimental data, we will discuss the charge and spin order of La0.5Sr1.5MnO4.

  13. Performance enhancement of perovskite solar cells with Mg-doped TiO{sub 2} compact film as the hole-blocking layer

    SciTech Connect

    Wang, Jing; Qin, Minchao; Tao, Hong; Ke, Weijun; Chen, Zhao; Wan, Jiawei; Qin, Pingli; Lei, Hongwei; Fang, Guojia; Xiong, Liangbin; Yu, Huaqing

    2015-03-23

    In this letter, we report perovskite solar cells with thin dense Mg-doped TiO{sub 2} as hole-blocking layers (HBLs), which outperform cells using TiO{sub 2} HBLs in several ways: higher open-circuit voltage (V{sub oc}) (1.08 V), power conversion efficiency (12.28%), short-circuit current, and fill factor. These properties improvements are attributed to the better properties of Mg-modulated TiO{sub 2} as compared to TiO{sub 2} such as better optical transmission properties, upshifted conduction band minimum (CBM) and downshifted valence band maximum (VBM), better hole-blocking effect, and higher electron life time. The higher-lying CBM due to the modulation with wider band gap MgO and the formation of magnesium oxide and magnesium hydroxides together resulted in an increment of V{sub oc}. In addition, the Mg-modulated TiO{sub 2} with lower VBM played a better role in the hole-blocking. The HBL with modulated band position provided better electron transport and hole blocking effects within the device.

  14. Solid State Structure-Reactivity Studies on Bixbyites, Fluorites and Perovskites Belonging to the Vanadate, Titanate and Cerate Families

    NASA Astrophysics Data System (ADS)

    Shafi, Shahid P.

    This thesis primarily focuses on the systematic understanding of structure-reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in-situ techniques including powder x-ray diffraction and thermogravimetric-differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure-reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite-type oxide ion conductor Ce1-xInxO2-delta (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO 3-delta perovskites and the subsequent CO2-capture reaction

  15. Structural manipulation and tailoring of dielectric properties in SrTi1-xFexTaxO3 perovskites: Design of new lead free relaxors.

    PubMed

    Shukla, R; Patwe, S J; Deshpande, S K; Achary, S N; Krishna, P S R; Shinde, A B; Gopalakrishnan, J; Tyagi, A K

    2016-01-01

    We report composition dependent structure evolution from SrTiO3 to SrFe0.5Ta0.5O3 by powder X-ray and neutron diffraction studies of SrTi1-2xFexTaxO3 (0.00 ≤ × ≤ 0.50) compositions. Structural studies reveal cubic (Pm3m) perovskite-type structure of the parent SrTiO3 for x up to 0.075 and cation disordered orthorhombic (Pbnm) perovskite-type structure for x ≥ 0.33. A biphasic region consisting of a mixture of cubic and orthorhombic structures is found in the range for 0.10 ≤ × ≤ 0.25. Dielectric studies reveal transformation from a normal dielectric to relaxor like properties with increasing Fe(3+) and Ta(5+) concentration. Dielectric response is maximum at x = 0.33 in the series. The results establish a protocol for designing new lead-free relaxor materials based on the co-substitution of Fe(3+) and Ta(5+) for Ti(4+) in SrTiO3. A complex interplay of strain effects arising from distribution of cations at the octahedral sites of the perovskite structure controls the dielectric properties. PMID:27514668

  16. Structural manipulation and tailoring of dielectric properties in SrTi1−xFexTaxO3 perovskites: Design of new lead free relaxors

    PubMed Central

    Shukla, R.; Patwe, S. J.; Deshpande, S. K.; Achary, S. N.; Krishna, P. S. R.; Shinde, A. B.; Gopalakrishnan, J.; Tyagi, A. K.

    2016-01-01

    We report composition dependent structure evolution from SrTiO3 to SrFe0.5Ta0.5O3 by powder X-ray and neutron diffraction studies of SrTi1−2xFexTaxO3 (0.00 ≤ × ≤ 0.50) compositions. Structural studies reveal cubic (Pm3m) perovskite-type structure of the parent SrTiO3 for x up to 0.075 and cation disordered orthorhombic (Pbnm) perovskite-type structure for x ≥ 0.33. A biphasic region consisting of a mixture of cubic and orthorhombic structures is found in the range for 0.10 ≤ × ≤ 0.25. Dielectric studies reveal transformation from a normal dielectric to relaxor like properties with increasing Fe3+ and Ta5+ concentration. Dielectric response is maximum at x = 0.33 in the series. The results establish a protocol for designing new lead-free relaxor materials based on the co-substitution of Fe3+ and Ta5+ for Ti4+ in SrTiO3. A complex interplay of strain effects arising from distribution of cations at the octahedral sites of the perovskite structure controls the dielectric properties. PMID:27514668

  17. Functionalization of perovskite thin films with moisture-tolerant molecules

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Wang, Yun; Liu, Porun; Cheng, Yi-Bing; Zhao, Hui Jun; Yang, Hua Gui

    2016-02-01

    Organic-inorganic hybrid perovskites are particularly suited as light-harvesting materials in photovoltaic devices. The power conversion efficiency of perovskite solar cells has reached certified values of over 20% in just a few years. However, one of the major hindrances for application of these materials in real-world devices is the performance degradation in humid conditions, leading to a rapid loss of photovoltaic response. Here, we demonstrate that hydrophobic tertiary and quaternary alkyl ammonium cations can be successfully assembled on the perovskite surface as efficient water-resisting layers via a facile surface functionalization technique. Such layers can protect the perovskite film under high relative humidity (90 ± 5%) over 30 days. More importantly, devices based on such films can retain the photovoltaic capacities of bulk perovskites, with power conversion efficiencies over 15%. Improving the humidity tolerance of perovskite materials is a necessary step towards large-scale production of high-performance perovskite-based devices under ambient humidity.

  18. Magnetic order and electronic structure of 5d3 double perovskite Sr2ScOsO6

    SciTech Connect

    Taylor, A. E.; Morrow, R.; Singh, D. J.; Calder, S.; Lumsden, M. D.; Woodward, P. M.; Christianson, A. D.

    2015-03-01

    The magnetic susceptibility, crystal and magnetic structures, and electronic structure of double perovskite Sr2ScOsO6 are reported. Using both neutron and x-ray powder diffraction we find that the crystal structure is monoclinic P21/n from 3.5 to 300 K. Magnetization measurements indicate an antiferromagnetic transition at TN=92 K, one of the highest transition temperatures of any double perovskite hosting only one magnetic ion. Type I antiferromagnetic order is determined by neutron powder diffraction, with an Os moment of only 1.6(1) muB, close to half the spin-only value for a crystal field split 5d electron state with t2g^3 ground state. Density functional calculations show that this reduction is largely the result of strong Os-O hybridization, with spin-orbit coupling responsible for only a ~0.1 muB reduction in the moment.

  19. Using Low Temperature Photoluminescence Spectroscopy to Investigate CH₃NH₃PbI₃ Hybrid Perovskite Degradation.

    PubMed

    Jemli, Khaoula; Diab, Hiba; Lédée, Ferdinand; Trippé-Allard, Gaelle; Garrot, Damien; Geffroy, Bernard; Lauret, Jean-Sébastien; Audebert, Pierre; Deleporte, Emmanuelle

    2016-01-01

    Investigating the stability and evaluating the quality of the CH₃NH₃PbI₃ perovskite structures is quite critical both to the design and fabrication of high-performance perovskite devices and to fundamental studies of the photophysics of the excitons. In particular, it is known that, under ambient conditions, CH₃NH₃PbI₃ degrades producing some PbI₂. We show here that low temperature Photoluminescence (PL) spectroscopy is a powerful tool to detect PbI₂ traces in hybrid perovskite layers and single crystals. Because PL spectroscopy is a signal detection method on a black background, small PbI₂ traces can be detected, when other methods currently used at room temperature fail. Our study highlights the extremely high stability of the single crystals compared to the thin layers and defects and grain boundaries are thought to play an important role in the degradation mechanism. PMID:27399669

  20. High-pressure synthesis, crystal structure and magnetic properties of double perovskite oxide Ba{sub 2}CuOsO{sub 6}

    SciTech Connect

    Feng, Hai L.; Arai, Masao; Matsushita, Yoshitaka; Tsujimoto, Yoshihiro; Yuan, Yahua; Sathish, Clastin I.; He, Jianfeng; Tanaka, Masahiko; Yamaura, Kazunari

    2014-09-15

    A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} was synthesized under high-pressure (6 GPa) and high-temperature (1500 °C) conditions. The polycrystalline Ba{sub 2}CuOsO{sub 6} was characterized by synchrotron X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility, isothermal magnetization, and specific heat measurements. The oxide crystallizes in a double-perovskite structure with an I4/m space group, in which Os(VI) and Cu(II) are ordered in the perovskite B-site. Ba{sub 2}CuOsO{sub 6} is electrically insulating with an activation energy of 0.813(2) eV and shows antiferromagnetic-like characteristics at temperatures of ∼55 K and ∼70 K. The results of the first-principle calculation suggested that the spin–orbit interaction of Os(VI) plays a substantial role in the insulating state. The Jahn–Teller distortion of CuO{sub 6} octahedra influences the magnetic characteristics with regard to possible two-dimensional magnetic correlations. - Graphical abstract: A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} synthesized by a high-pressure (6 GPa) and high-temperature (1500 °C) method. - Highlights: • A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} was synthesized. • Ba{sub 2}CuOsO{sub 6} is electrically insulating and antiferromagnetic below ∼70 K. • The Jahn–Teller distortion of CuO{sub 6} has relevance to possible magnetic anisotropy.

  1. High efficiency sequentially vapor grown n-i-p CH3NH3PbI3 perovskite solar cells with undoped P3HT as p-type heterojunction layer

    NASA Astrophysics Data System (ADS)

    Abbas, Hisham A.; Kottokkaran, Ranjith; Ganapathy, Balaji; Samiee, Mehran; Zhang, Liang; Kitahara, Andrew; Noack, Max; Dalal, Vikram L.

    2015-01-01

    Photovoltaic devices with perovskite materials as light absorbing material were fabricated through sequential vapor deposition of lead iodide and methylammonium iodide with undoped poly3hexylthiophene (P3HT) as a hole transporting layer. The sequential vapor deposition process produced films and devices with the large grains and low defect densities, very small values of dark current, and high open circuit voltages. The thickness of the P3HT layer was a critical parameter for achieving high solar conversion efficiencies of 13.7%. The vapor deposition process also produced devices with a tight distribution of performance characteristics and very high open circuit voltages (0.99 V).

  2. Structural Characterization of Layered Morphologies in Precise Copolymers

    NASA Astrophysics Data System (ADS)

    Trigg, Edward; Gaines, Taylor; Wagener, Kenneth; Winey, Karen

    2015-03-01

    Layered morphologies have been observed in precise polyethylene-based copolymers that contain acid, charged, or polar functional groups precisely spaced along a linear alkane chain. Sufficiently long alkane segments form structures resembling orthorhombic polyethylene crystals, while the functional groups form 2-D layers that disrupt the alkane crystal structure to varying degrees. Here, layered morphologies in precise copolymers containing acrylic acid, phosphonic acid, imidazolium bromide, and sulfone groups are studied via X-ray scattering. Specifically, the composition profiles of the layered structures are obtained by Fourier synthesis, and the coherence length is investigated using peak width analysis. This analysis indicates that the layers of functional groups are frequently bordered by two crystallites, which suggests different dynamics relative to layers bordered by one crystalline and one amorphous microdomain. Detailed understanding of the structure of the layered morphologies will allow for a systematic investigation of proton and ion conductivity mechanisms, which are expected to occur through the high-dielectric layers.

  3. Low-temperature sputtered nickel oxide compact thin film as effective electron blocking layer for mesoscopic NiO/CH3NH3PbI3 perovskite heterojunction solar cells.

    PubMed

    Wang, Kuo-Chin; Shen, Po-Shen; Li, Ming-Hsien; Chen, Shi; Lin, Ming-Wei; Chen, Peter; Guo, Tzung-Fang

    2014-08-13

    We introduce the use of low temperature sputtered NiOx thin film, which substitutes the PEDOT-PSS and solution-processed NiOx as an effective electron blocking layer for mesoscopic NiO/CH3NH3PbI3 perovskite solar cells. The influences of film thickness and oxygen doping on the photovoltaic performances are scrutinized. The cell efficiency has been improved from 9.51 to 10.7% for devices using NiOx fabricated under pure argon atmosphere. With adequate doping under 10% oxygen flow ratio, we achieved power conversion efficiency of 11.6%. The procedure is large area scalable and has the advantage for cost-effective perovskite-based photovoltaics. PMID:25054484

  4. Amorphous Inorganic Electron-Selective Layers for Efficient Perovskite Solar Cells: Feasible Strategy Towards Room-Temperature Fabrication.

    PubMed

    Wang, Kai; Shi, Yantao; Li, Bo; Zhao, Liang; Wang, Wei; Wang, Xiangyuan; Bai, Xiaogong; Wang, Shufeng; Hao, Ce; Ma, Tingli

    2016-03-01

    Inorganic electron-selective layers (ESLs) are fabricated at extremely low temperatures of 70°C or even 25°C by a simple solution route. This is of great significance because the attained PCEs confirm the feasibility of room-temperature coating of inorganic amorphous ESLs through a solution method for the first time. PMID:26708492

  5. Monolayer and Few-Layer All-Inorganic Perovskites as a New Family of Two-Dimensional Semiconductors for Printable Optoelectronic Devices.

    PubMed

    Song, Jizhong; Xu, Leimeng; Li, Jianhai; Xue, Jie; Dong, Yuhui; Li, Xiaoming; Zeng, Haibo

    2016-06-01

    Printed flexible photodetectors based on 2D inorganic perovskites with atomic thickness show excellent photosensing with fast rise and decay response times. As-synthesized nanosheets can easily be dispersed in various solvents, leading to large-area, crack-free, low-roughness, flexible films after printing. This study demonstrates that all-inorganic perovskite CsPbX3 nanosheets as a new class of 2D semiconductors have huge potential for flexible optoelectronic applications. PMID:27110705

  6. Double perovskite structure: a vibrational and luminescence investigation providing a perspective on crystal field strength.

    PubMed

    Li, Wenyu; Ning, Lixin; Tanner, Peter A

    2012-07-12

    The luminescence spectra of Eu(3+) doped in a series of double perovskite lattices Ba(2)LnMO(6) (Ln = Y, Gd; M = Nb, Ta) have been recorded at room temperature and 10 K. Together with FT-IR and FT-Raman spectra and aided by DFT vibrational energy calculations, assignments have been made for the crystal field levels of the (5)D(J) (J = 0,1) and (7)F(J) (J = 0-2) multiplets. The luminescence spectra are consistent with monoclinic symmetry of these systems. The crystal field parameters from the fitting of the energy level data set of Ba(2)YNbO(6):Eu(3+) enable the crystal field strength to be calculated, and the order of magnitude is Cl(-) < O(2-) < F(-) for the EuX(6)(n-) (n = 6 for halogen, 9 for oxide) moieties. For these systems, an empirical linear relationship between crystal field strength and electronegativity of ligand X has been found. By contrast, the nephelauxetic series from the depression of the Slater parameter F(2) is Cl(-) ≈ O(2-) > F(-) > free ion for these systems. PMID:22703165

  7. Elucidating the Reaction Pathways in the Synthesis of Organolead Trihalide Perovskite for High-Performance Solar Cells

    PubMed Central

    Wang, Baohua; Young Wong, King; Xiao, Xudong; Chen, Tao

    2015-01-01

    The past two years have witnessed unprecedentedly rapid development of organic–inorganic halide perovskite–based solar cells. The solution–processability and high efficiency make this technology extraordinarily attractive. The intensive investigations have accumulated rich experiences in the perovskite fabrication; while the mechanism of the chemical synthesis still remains unresolved. Here, we set up the chemical equation of the synthesis and elucidate the reactions from both thermodynamic and kinetic perspectives. Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and “collision” probability synergistically determine the reaction rate. These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature. This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high–efficiency perovskite photoactive layer. PMID:26020476

  8. Perovskite-Type LaSrMnO Electrocatalyst with Uniform Porous Structure for an Efficient Li-O2 Battery Cathode.

    PubMed

    Yang, Yanbing; Yin, Wei; Wu, Shiting; Yang, Xiangdong; Xia, Wei; Shen, Yue; Huang, Yunhui; Cao, Anyuan; Yuan, Quan

    2016-01-26

    Perovskite is an excellent candidate as low cost catalyst for Li-O2 cells. However, the limited porosity, which impedes molecular transport, and the inherent low electronic conductivity are the main barriers toward production of high-performance electrodes. Here, we designed a hierarchical porous flexible architecture by coating thin mesoporous yet crystalline LaSrMnO layers throughout a graphene foam to form graphene/meso-LaSrMnO sandwich-like nanosheets. In this well-designed system, the macropore between nanosheets facilitates O2 and Li(+) diffusion, the mesopore provides large surface area for electrolyte immersion and discharge products deposition, the perovskite phase catalyst decreases reactive overpotential, and the graphene serves as conductive network for electrons transport. When used as a freestanding electrode of Li-O2 cell, it shows high specific capacity, superior rate capability, and cyclic stability. Combination of mesoporous perovskites with conductive graphene networks represents an effective strategy for developing efficient electrodes in various energy storage systems. PMID:26679735

  9. Hydrogen in magnesium palladium thin layer structures

    NASA Astrophysics Data System (ADS)

    Kruijtzer, G. L.

    2008-02-01

    In this thesis, the study of hydrogen storage, absorption and desorption in magnesium layers is described. The magnesium layers have a thickness of 50-500 nm and are covered by a palladium layer which acts as a hydrogen dissociation/association catalyst. The study was preformed under ultra high vacuum conditions to avoid oxygen contamination. The main analysis techniques were RBS, ERD and TDS.

  10. Structural and superconducting properties of vanadium substituted Y Ba 2 (Cu 1-x V x) 3 O 9 perovskite oxide system

    NASA Astrophysics Data System (ADS)

    Al-Dallal, S.; Khan, M. N.; Memon, A.

    1991-12-01

    The superconducting properties YBaCuVO system has been studied. It was found that upon substituation of copper by vanadium, the critical temperature decreases linearly for the whole compositional range under investigation (0.2 ⩾ × ⩾ 0.001). X-ray diffraction analysis reveals that the structure of these compounds changes systematicaly from orthorhombic which corresponds to oxygen difficient perovskite to tetragonal.

  11. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties

    PubMed Central

    2016-01-01

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3+, X = Br– or I–) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites’ precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material’s resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(BrxI1–x)3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors. PMID:27163050

  12. Conversion efficiency improvement of inverted CH3NH3PbI3 perovskite solar cells with room temperature sputtered ZnO by adding the C60 interlayer

    NASA Astrophysics Data System (ADS)

    Lai, Wei-Chih; Lin, Kun-Wei; Guo, Tzung-Fang; Chen, Peter; Wang, Yuan-Ting

    2015-12-01

    We have demonstrated the performance of inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with a room temperature (RT) sputtered ZnO electron transport layer by adding fullerene (C60) interlayer. ZnO exhibits a better matched conduction band level with perovskite and Al work function and around energy offset of 2.2 eV between highest occupied molecular orbital level of CH3NH3PbI3 perovskite and valance band level of ZnO. However, the CH3NH3PbI3 perovskite layer will be damaged during direct RT sputtering deposition of ZnO. Therefore, the C60 interlayer having matched conduction band level with ZnO and CH3NH3PbI3 perovskite added between the CH3NH3PbI3 perovskite and RT sputtered ZnO layers for protection prevents sputtering damages on the CH3NH3PbI3 perovskite layer. The short-circuit current density (JSC, 19.41 mA/cm2) and open circuit voltage (VOC, 0.91 V) of the SCs with glass/ITO/poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS)/perovskite/C60/RT sputtered ZnO/Al structure is higher than the JSC (16.23 mA/cm2) and VOC (0.90 V) of the reference SC with glass/ITO/PEDOT:PSS/perovskite/C60/bathocuproine (BCP)/Al structure. Although the SCs with the former structure has a lower fill factor (FF%) than the SCs with the latter structure, its conversion efficiency η% (10.93%) is higher than that (10.6%) of the latter.

  13. Effects of Bi doping on structural and magnetic properties of double perovskite oxides Sr2FeMoO6

    NASA Astrophysics Data System (ADS)

    Lan, Yaohai; Feng, Xiaomei; Zhang, Xin; Shen, Yifu; Wang, Ding

    2016-08-01

    A new series of double perovskite compounds Sr2 - δBixFeMoO6 have been synthesized by solid-state reaction. δ refers to the nominal doping content of Bi (δ = 0, 0.1, 0.2, 0.3, 0.4, 0.5), while the Bi content obtained by the Rietveld refinement is x = 0, 0.01, 0.05, 0.08, 0.10 and 0.12. Their crystal structure and magnetic properties are investigated. Rietveld analysis of the room temperature XRD data shows all the samples crystallize in the cubic crystal structure with the space group Fm 3 ‾ m and have no phase transition. SEM images show that substituted samples present a denser microstructure and bigger grains than Sr2FeMoO6, which is caused by a liquid sintering process due to the effumability of Bi. The unit cell volume increases with augment of Bi3+ concentration despite the smaller ionic radius Bi3+ compared with the Sr2+, which is attributed to the electronic effect. The degree of Fe/Mo order (η) increases first and then decreases to almost disappearance with augment of Bi doping, which is the result of contribution from electronic effect. Calculated saturation magnetization Ms(3) according to our phase separation likeness model matches well with the experimental ones. The observed variations of magnetoresistance (MR) are consistent with the Fe/Mo order (η) due to the internal connection with anti-site defect (ASD).

  14. Structural and optoelectronic properties of the zinc titanate perovskite and spinel by modified Becke-Johnson potential

    NASA Astrophysics Data System (ADS)

    Ali, Zahid; Ali, Sajad; Ahmad, Iftikhar; Khan, Imad; Rahnamaye Aliabad, H. A.

    2013-07-01

    Structural and electronic properties of the cubic perovskite ZnTiO3 and spinel Zn2TiO4 are theoretically studied by the modified Becke-Johnson (mBJ) potential within the framework of density functional theory (DFT). The calculated lattice constants are found to be consistent with the experimental results. The electronic band structures of both the materials reveal that ZnTiO3 is an indirect band gap while Zn2TiO4 is a direct band gap semiconductor. The calculated fundamental band gaps of these compounds are 2.7 eV and 3.18 eV, which are consistent with the experimental band gaps of 2.9 eV and 3.1 eV, respectively. Zn2TiO4 is a wide and direct band gap compound and hence is an attractive material for optoelectronic applications, especially in near ultraviolet (UV) optoelectronics. Keeping in view the importance of Zn2TiO4 in low frequency UV devices its optical properties like dielectric functions, refractive index, reflectivity and energy loss function are also evaluated and discussed in detail.

  15. Structure and thermodynamic stability of hydrogen interstitials in BaZrO3 perovskite oxide from density functional calculations.

    PubMed

    Björketun, Mårten E; Sundell, Per G; Wahnström, Göran

    2007-01-01

    Density functional calculations have been used to study the electronic structure, preferred sites in the lattice, formation energies and vibrational frequencies for hydrogen interstitials in different charge states in the cubic phase of perovskite-structured BaZrO3. By combining ab initio results with thermodynamic modeling, defect formation at finite temperature and pressure has been investigated. We demonstrate how the site selectivity and spatial distribution of dopant atoms in the lattice can be affected by changes in the environmental conditions (atomic chemical potentials, oxygen partial pressure and temperature) used during processing of the material. In addition, we have calculated the thermodynamic parameters of the water uptake reaction for an acceptor-doped BaZrO3 crystal in equilibrium with a humid atmosphere. The interaction energies between a protonic defect and the investigated Ga, Gd, In, Nd, Sc, and Y dopants were found to be attractive, and we show that a simple model of defect association may reproduce an experimentally observed trend in the hydration enthalpy. PMID:17326572

  16. Ab initio study of structural, mechanical, thermal and electronic properties of perovskites Sr(Li,Pd)H3

    NASA Astrophysics Data System (ADS)

    Benlamari, S.; Amara Korba, S.; Lakel, S.; Meradji, H.; Ghemid, S.; El Haj Hassan, F.

    2016-01-01

    The structural, elastic, thermal and electronic properties of perovskite hydrides SrLiH3 and SrPdH3 have been investigated using the all-electron full-potential linear augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). For the exchange-correlation potential, local-density approximation (LDA) and generalized gradient approximation (GGA) have been used to calculate theoretical lattice parameters, bulk modulus, and its pressure derivative. The present results are in good agreement with available theoretical and experimental data. The three independent elastic constants (C11, C12 and C44) are also reported. From electronic band structure and density of states (DOSs), it is found that SrLiH3 is an insulator characterized by an indirect gap of 3.48 eV, while SrPdH3 is metallic with a calculated DOSs at Fermi energy of 0.745 states/eV-unit cell. Poisson’s ratio (σ), Young’s modulus (E), shear modulus (G), anisotropy factor (A), average sound velocities (vm) and density (ρ) of these compounds are also estimated for the first time. The Debye temperature is deduced from the average sound velocity. Variation of elastic constants and bulk modulus of these compounds as a function of pressure is also reported. Pressure and thermal effects on some macroscopic properties are predicted using the quasi-harmonic Debye model.

  17. Structural and magnetic properties of RTiNO{sub 2} (R=Ce, Pr, Nd) perovskite nitride oxides

    SciTech Connect

    Porter, Spencer H.; Huang, Zhenguo; Cheng, Zhenxiang; Avdeev, Maxim; Chen, Zhixin; Dou, Shixue; Woodward, Patrick M.

    2015-03-15

    Neutron powder diffraction indicates that CeTiNO{sub 2} and PrTiNO{sub 2} crystallize with orthorhombic Pnma symmetry (Ce: a=5.5580(5), b=7.8369(7), and c=5.5830(4) Å; Pr: a=5.5468(5), b=7.8142(5), and c=5.5514(5) Å) as a result of a{sup –}b{sup +}a{sup –} tilting of the titanium-centered octahedra. Careful examination of the NPD data, confirms the absence of long range anion order in both compounds, while apparent superstructure reflections seen in electron diffraction patterns provide evidence for short range anion order. Inverse magnetic susceptibility plots reveal that the RTiNO{sub 2} (R=Ce, Pr, Nd) compounds are paramagnetic with Weiss constants that vary from −28 to −42 K. Effective magnetic moments for RTiNO{sub 2} (R=Ce, Pr, Nd) are 2.43 μ{sub B}, 3.63 μ{sub B}, and 3.47 μ{sub B}, respectively, in line with values expected for free rare-earth ions. Deviations from Curie–Weiss behavior that occur below 150 K for CeTiNO{sub 2} and below 30 K for NdTiNO{sub 2} are driven by magnetic anisotropy, spin–orbit coupling, and crystal field effects. - Graphical abstract: The structure and magnetism of the oxide nitride perovskites RTiNO{sub 2} (R=Ce, Pr, Nd) have been explored. The average symmetry is shown to be Pnma with a random distribution of oxide and nitride ions and a{sup −}b{sup +}a{sup −} tilting of the titanium-centered octahedra, but electron diffraction shows evidence for short range anion order. All three compounds are paramagnetic but deviations from the Curie Weiss law are seen below 150 K for R=Ce and below 30 K for R=Nd. - Highlights: • The oxide nitride perovskites RTiNO{sub 2} (R=Ce, Pr) have been prepared and their structures determined. • Diffraction measurements indicate short range cis-order of O and N, but no long range order. • Compounds are paramagnetic with Weiss constants that vary from −28 to −42 K. • CeTiO{sub 2}N and NdTiO{sub 2}N deviate from Curie–Weiss behavior below 150 and 30 K, respectively.

  18. B-site ordered perovskite LaSrMnNbO{sub 6}: Synthesis, structure and antiferromagnetism

    SciTech Connect

    Yang Tao; Perkisas, Tyche; Hadermann, Joke; Croft, Mark; Ignatov, Alexander; Greenblatt, Martha

    2010-11-15

    LaSrMnNbO{sub 6} has been synthesized by high temperature solid state reaction under 1% H{sub 2}/Ar dynamic flow. The structure is determined by Rietveld refinement of the powder X-ray diffraction data. It crystallizes in the monoclinic space group P2{sub 1}/n with the unit cell parameters: a=5.69187(12), b=5.74732(10), c=8.07018(15) A and {beta}=90.0504(29){sup o}, which were also confirmed by electron diffraction. The Mn{sup 2+} and Nb{sup 5+} ions, whose valence states are confirmed by X-ray absorption near-edge spectroscopy, are almost completely ordered over the B-site (<1% inversion) of the perovskite structure due to the large differences of both cationic size (0.19 A) and charge. The octahedral framework displays significant tilting distortion according to Glazer's tilt system a{sup -}b{sup -}c{sup +}. Upon heating, LaSrMnNbO{sub 6} decomposes at 690 {sup o}C under O{sub 2} flow or at 775 {sup o}C in air. The magnetic susceptibility data indicate the presence of long-range antiferromagnetic ordering at T{sub N}=8 K; the experimentally observed effective paramagnetic moment, {mu}{sub eff}=5.76 {mu}{sub B} for high spin Mn{sup 2+} (3d{sup 5}, S=5/2) is in good agreement with the calculated value ({mu}{sub calcd}=5.92 {mu}{sub B}). -- Graphical abstract: An ordered double perovskite, LaSrMnNbO{sub 6} has been synthesized in the monoclinic space group P2{sub 1}/n. The Mn{sup 2+} and Nb{sup 5+} ions, whose valence states are confirmed by X-ray absorption near-edge spectroscopy, are ordered over the B-site. The magnetic susceptibility data indicate long-range antiferromagnetic ordering at T{sub N}=8 K. Display Omitted

  19. Hybrid germanium iodide perovskite semiconductors: active lone pairs, structural distortions, direct and indirect energy gaps, and strong nonlinear optical properties.

    PubMed

    Stoumpos, Constantinos C; Frazer, Laszlo; Clark, Daniel J; Kim, Yong Soo; Rhim, Sonny H; Freeman, Arthur J; Ketterson, John B; Jang, Joon I; Kanatzidis, Mercouri G

    2015-06-01

    The synthesis and properties of the hybrid organic/inorganic germanium perovskite compounds, AGeI3, are reported (A = Cs, organic cation). The systematic study of this reaction system led to the isolation of 6 new hybrid semiconductors. Using CsGeI3 (1) as the prototype compound, we have prepared methylammonium, CH3NH3GeI3 (2), formamidinium, HC(NH2)2GeI3 (3), acetamidinium, CH3C(NH2)2GeI3 (4), guanidinium, C(NH2)3GeI3 (5), trimethylammonium, (CH3)3NHGeI3 (6), and isopropylammonium, (CH3)2C(H)NH3GeI3 (7) analogues. The crystal structures of the compounds are classified based on their dimensionality with 1–4 forming 3D perovskite frameworks and 5–7 1D infinite chains. Compounds 1–7, with the exception of compounds 5 (centrosymmetric) and 7 (nonpolar acentric), crystallize in polar space groups. The 3D compounds have direct band gaps of 1.6 eV (1), 1.9 eV (2), 2.2 eV (3), and 2.5 eV (4), while the 1D compounds have indirect band gaps of 2.7 eV (5), 2.5 eV (6), and 2.8 eV (7). Herein, we report on the second harmonic generation (SHG) properties of the compounds, which display remarkably strong, type I phase-matchable SHG response with high laser-induced damage thresholds (up to ∼3 GW/cm(2)). The second-order nonlinear susceptibility, χS(2), was determined to be 125.3 ± 10.5 pm/V (1), (161.0 ± 14.5) pm/V (2), 143.0 ± 13.5 pm/V (3), and 57.2 ± 5.5 pm/V (4). First-principles density functional theory electronic structure calculations indicate that the large SHG response is attributed to the high density of states in the valence band due to sp-hybridization of the Ge and I orbitals, a consequence of the lone pair activation. PMID:25950197

  20. Fabrication of nanofibrous A- or B-sites substituted LaCoO{sub 3} perovskites with macroscopic structures and their catalytic applications

    SciTech Connect

    Wu, Qiang; Zhao, Li; Wu, Meixia; Yao, Weifeng; Qi, Meixue; Shi, Xiaoyan

    2014-03-01

    Graphical abstract: Fabrication of nanofibrous La{sub 1−x}Ce{sub x}CoO{sub 3} (x = 0.05, 0.1, 0.2) and LaMn{sub x}Co{sub 1−x}O{sub 3} (x = 0.2, 0.5, 0.8) perovskite-type oxides with macroscopic structures can be successfully achieved by using carbon nanofibers (CNFs) as templates. Furthermore, their application for the combustion of carbon black (CB), which is a model of particulate matter exhausted from diesel engines, was demonstrated. - Highlights: • Nanofibrous perovskites with macroscopic shapes were successfully obtained. • CNFs template method used here is facile, effective and reproducible. • This method might be applicable to other novel material fabrication. • The obtained materials show superior catalytic activity in soot combustion. - Abstract: Fabrication of nanofibrous La{sub 1−x}Ce{sub x}CoO{sub 3} (x = 0.05, 0.1, 0.2) and LaMn{sub x}Co{sub 1−x}O{sub 3} (x = 0.2, 0.5, 0.8) perovskite-type oxides with macroscopic structures can be successfully achieved by using carbon nanofibers (CNFs) as templates. Field emission scanning electron microscopy (FE-SEM), coupled with X-ray diffraction (XRD) analysis confirmed the template effect and formation of the perovskite-type oxides on the macroscopic substrate. It turned out that this facile method can ensure the desired single-phase perovskite-type oxides formation by controlling the corresponding metal ratio during the preparation procedure. In addition, the immobilized nanofibrous La{sub 1−x}Ce{sub x}CoO{sub 3} (x = 0.05) and LaMn{sub x}Co{sub 1−x}O{sub 3} (x = 0.5) perovskite-type oxides can greatly decrease the combustion temperature of nanosized carbon black particles, which has the high potential application prospects in the treatment of diesel soot particles.

  1. Structural and magnetic study of Yb{sup 3+} in the perovskites Sr{sub 2}YbMO{sub 6} (M=Nb, Ta, Sb)

    SciTech Connect

    Coomer, Fiona C.; Campbell, John; Giordano, Nico; Collins, Oonagh M.; Cussen, Edmund J.

    2015-01-15

    The compounds Sr{sub 2}YbNbO{sub 6}, Sr{sub 2}YbTaO{sub 6} and Sr{sub 2}YbSbO{sub 6} have been prepared using solid state methods by heating pelleted reagents in air at temperatures up to 1400 °C. Rietveld refinement against room temperature neutron powder diffraction data show that all three compounds crystallise with a cation-ordered variant of the perovskite structure in the P2{sub 1}/n space group. Complete cation ordering occurs between M{sup 5+} and Yb{sup 3+} over two octahedrally-coordinated sites in the structure and all compounds are stoichiometric in oxygen. The Sb–O bond lengths are similar to related perovskite compounds but differ slightly from those indicated by bond valence sums. Magnetic susceptibility data resemble Curie–Weiss paramagnetic behaviour, but can be better understood as arising from the effect of the octahedral crystal field on the {sup 2}F{sub 5/2} ground state of Yb{sup 3+} leading to a temperature dependent magnetic moment on this ion below 100 K. - Graphical abstract: The magnetic susceptibility of the face-centred cubic Yb{sup 3+} lattice is dominated by the temperature dependent single-ion moment below 100 K. - Highlights: • Cation-ordered perovskites are studied using neutron diffraction and magnetometry. • Yb{sup 3+} cations form a pseudo face centred cubic lattice in a distorted structure. • Sb{sup 5+} cation is slightly overbonded as observed in related perovskites. • Crystal field splitting of 4f{sup 13} Yb{sup 3+} giving a temperature dependent moment. • Magnetic susceptibility reproduces theoretical predictions below 100 K.

  2. PrBa0.5Sr0.5Co2O5+δ layered perovskite cathode for intermediate temperature solid oxide fuel cells

    SciTech Connect

    Ding, Hanping; Xue, Xingjian

    2010-02-06

    Layered perovskite oxides have ordered A-cations localizing oxygen vacancies, and may potentially improve oxygen ion diffusivity and surface exchange coefficient. The A-site-ordered layered perovskite PrBa0.5Sr0.5Co2O5+δ (PBSC) was evaluated as new cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The material was characterized using electrochemical impedance spectroscopy in a symmetrical cell system (PBSC/Ce0.9Sm0.1O1.9 (SDC)/PBSC), exhibiting excellent performance in the intermediate temperature range of 500–700 °C. An area-specific-resistance (ASR) of 0.23 Ω cm2 was achieved at 650 °C for cathode polarization. The low activation energy (Ea) 124 kJ mol-1 is comparable to that of La0.8Sr0.2CoO3-δ. A laboratory-scaled SDC-based tri-layer cell of Ni-SDC/SDC/PBSC was tested in intermediate temperature conditions of 550 to 700 °C. A maximum power density of 1045 mW cm-2 was achieved at 700 °C. The interfacial polarization resistance is as low as 0.285, 0.145, 0.09 and 0.05 Ω cm2 at 550, 600, 650 and 700 °C, respectively. Layered perovskite PBSC shows promising performance as cathode material for IT-SOFCs.

  3. The performance of La0.6Sr1.4MnO4 layered perovskite electrode material for intermediate temperature symmetrical solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Chen, Gang; Wu, Kai; Cheng, Yonghong

    2014-12-01

    A layered perovskite electrode material, La0.6Sr1.4MnO4+δ (LSMO4), has been studied for intermediate temperature symmetrical solid oxide fuel cells (IT-SSOFCs) on La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte. The chemical compatibility tests indicate that no reaction occurred between LSMO4 oxide and LSGM electrolyte at temperature up to 1000 °C both in air and 5% H2. The lower conductivity in 5% H2 and higher conduction activation energy than those in air would be caused by poorer overlap of both σ and π bonds. DFT + U calculations also show that oxygen vacancies which formed in reducing atmosphere may block the 3D hopping path for electrons or holes through Mn-O-Mn chains. For LSMO4 electrode, SEM results indicate that the electrode formed good contact with the electrolyte after being sintered at 900 °C for 2 h. At 800 °C, the polarization resistance of the LSMO4 cathode is about 0.87 Ω cm2 in air, while the polarization resistance of the LSMO4 anode is about 2.07 Ω cm2 in 5% H2. LSMO4 exhibits better electrochemical activity for oxygen reduction than that for hydrogen oxidation. A cell with LSGM electrolyte, LSMO4-LSGM mixture as anode and cathode simultaneously displays a maximum power density of 59 mW cm-2 at 800 °C.

  4. Efficient charge-transport in hybrid lead iodide perovskite solar cells.

    PubMed

    Zhao, Jinjin; Wang, Peng; Wei, Liyu; Liu, Zhenghao; Fang, Xueqian; Liu, Xianglin; Ren, Deliang; Mai, Yaohua

    2015-10-14

    Recently, highly efficient solar cells based on organic-inorganic perovskites have been intensively studied for developing fabricating methods and device structures. To improve the performance of perovskite film devices, delicate control of charge transfer material interconnectivity is required. Here, controlling the mesoporous TiO2 structure improves their charge collection and injection rate, and allows substantial enhancement of the corresponding device performance. We found that increasing the TiCl4 processing time deteriorates the device performance by introducing a large amount of excessively large perovskite particles, surface roughness and charge recombination. Proper TiCl4 processing dramatically improves the charge transport within the electron transfer layer, explaining the efficient performance of meso-superstructured solar cells. PMID:26356533

  5. Structural and magnetic states in layered manganites: An expanding view of the phase diagram

    SciTech Connect

    Mitchell, J. F.; Millburn, J. E.; Ling, C.; Argyriou, D. N.; Bordallo, H. N.

    2000-01-05

    Colossal magnetoresistive (CMR) manganites display a spectacular range of structural, magnetic, and electronic phases as a function of hole concentration, temperature, magnetic field, etc. A1though the bulk of research has concentrated on the 3-D perovskite manganites, the ability to study anisotropic magnetic and electronic interactions made available in reduced dimensions has accelerated interest in the layered Ruddlesden-Popper (R-P) phases of the manganite class. The quest for understanding the coupling among lattice, spin, and electronic degrees of freedom (and dimensionality) is driven by the availability of high quality materials. In this talk, the authors will present recent results on synthesis and magnetic properties of layered manganites from the La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} series in the Mn{sup 4+}-rich regime x >0.5. This region of the composition diagram is populated by antiferromagnetic structures that evolve from the A-type layered order to G-type ''rocksalt'' order as x increases. Between these two regimes is a wide region (0.7 < x < 0.9) where an incommensurate magnetic structure is observed. The IC structure joins spin canting and phase separation as a mode for mixed-valent manganites to accommodate FM/AF competition. Transport in these materials is dominated by highly insulating behavior, although a region close to x = 0.5 exhibits metal-nonmetal transitions and an extreme sensitivity to oxygen content. They suggest two possible explanations for this transport behavior at doping just above x = O.5: localization by oxygen defects or charge ordering of Mn{sup 3+}/Mn{sup 4+}sites.

  6. Large Grained Perovskite Solar Cells Derived from Single-Crystal Perovskite Powders with Enhanced Ambient Stability.

    PubMed

    Yen, Hung-Ju; Liang, Po-Wei; Chueh, Chu-Chen; Yang, Zhibin; Jen, Alex K-Y; Wang, Hsing-Lin

    2016-06-15

    In this study, we demonstrate the large grained perovskite solar cells prepared from precursor solution comprising single-crystal perovskite powders for the first time. The resultant large grained perovskite thin film possesses a negligible physical (structural) gap between each large grain and is highly crystalline as evidenced by its fan-shaped birefringence observed under polarized light, which is very different from the thin film prepared from the typical precursor route (MAI + PbI2). PMID:27224963

  7. Effect of Structural Phase Transition on Charge-Carrier Lifetimes and Defects in CH3NH3SnI3 Perovskite.

    PubMed

    Parrott, Elizabeth S; Milot, Rebecca L; Stergiopoulos, Thomas; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

    2016-04-01

    Methylammonium tin triiodide (MASnI3) has been successfully employed in lead-free perovskite solar cells, but overall power-conversion efficiencies are still significantly lower than for lead-based perovskites. Here we present photoluminescence (PL) spectra and time-resolved PL from 8 to 295 K and find a marked improvement in carrier lifetime and a substantial reduction in PL line width below ∼110 K, indicating that the cause of the hindered performance is activated at the orthorhombic to tetragonal phase transition. Our measurements therefore suggest that targeted structural change may be capable of tailoring the relative energy level alignment of defects (e.g., tin vacancies) to reduce the background dopant density and improve charge extraction. In addition, we observe for the first time an above-gap emission feature that may arise from higher-lying interband transitions, raising the prospect of excess energy harvesting. PMID:26990282

  8. Reduced ultraviolet light induced degradation and enhanced light harvesting using YVO{sub 4}:Eu{sup 3+} down-shifting nano-phosphor layer in organometal halide perovskite solar cells

    SciTech Connect

    Chander, Nikhil; Chandrasekhar, P. S.; Thouti, Eshwar; Swami, Sanjay Kumar; Dutta, Viresh; Komarala, Vamsi K.; Khan, A. F.

    2014-07-21

    We report a simple method to mitigate ultra-violet (UV) degradation in TiO{sub 2} based perovskite solar cells (PSC) using a transparent luminescent down-shifting (DS) YVO{sub 4}:Eu{sup 3+} nano-phosphor layer. The PSC coated with DS phosphor showed an improvement in stability under prolonged illumination retaining more than 50% of its initial efficiency, whereas PSC without the phosphor layer degraded to ∼35% of its initial value. The phosphor layer also provided ∼8.5% enhancement in photocurrent due to DS of incident UV photons into additional red photons. YVO{sub 4}:Eu{sup 3+} layer thus served a bi-functional role in PSC by reducing photo-degradation as well as enhancing energy conversion efficiency.

  9. Compositional and Structural Versatility in an Unusual Family of anti-Perovskite Fluorides: [Cu(H2O)4]3[(MF6)(M'F6)].

    PubMed

    Felder, Justin B; Yeon, Jeongho; Smith, Mark D; Zur Loye, Hans-Conrad

    2016-07-18

    A series of six anti-perovskite fluorides of the type [Cu(H2O)4]3(M1-xM'xF6)2 (where M and M' = V, Cr, Mn, Fe as well as M = Fe and M' = V and Cr) was synthesized as high-quality single crystals via a mild hydrothermal route. These materials belong to a class of perovskite-based structures in which the anions and cations of the regular ABX3 perovskite structure have exchanged positions. Two complex anions, MF6(3-) and M'F6(3-), occupy the normal A and B cation positions, while three complex cations, [Cu(H2O)4](2+), occupy the normally anionic X positions. As in the ABX3 compositions, the A and B positions can be occupied by different complex anions, allowing for the preparation of a wide range of compositions. Magnetic property measurements were performed on all six phases, and complex magnetic behavior was observed at low temperatures in the Mn, Fe, and bimetallic Fe/V and Fe/Cr phases. PMID:27367900

  10. Optical properties and structural phase transitions of lead-halide based inorganic-organic 3D and 2D perovskite semiconductors under high pressure

    NASA Astrophysics Data System (ADS)

    Matsuishi, K.; Ishihara, T.; Onari, S.; Chang, Y. H.; Park, C. H.

    2004-11-01

    Optical absorption, photoluminescence and Raman scattering of lead-halide based inorganic-organic perovskite semiconductors were measured under quasi-hydrostatic pressure at room temperature. For the 3D perovskite semiconductor, (CH3NH3)PbBr3, the free exciton photoluminescence band exhibits red-shifts with pressure, and jumps to a higher energy by 0.07 eV at 0.8 GPa, which is associated with a phase transition from a cubic to an orthorhombic structure confirmed by Raman scattering. Above the phase transition pressure, the exciton band shows blue-shifts with further increasing pressure, and eventually disappears above 4.7 GPa. The results are compared with those for the 2D perovskite semiconductor, (C4H9NH3)2PbI4. First principles pseudopotential calculations were performed to investigate changes in octahedral distortion and electronic band structures with pressure. The calculations have explained the origins of the intriguing changes in the electronic states with pressure in view of bonding characters between atomic orbitals in octahedra.

  11. Composite S-layer lipid structures.

    PubMed

    Schuster, Bernhard; Sleytr, Uwe B

    2009-10-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

  12. Composite S-layer lipid structures

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2010-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

  13. The structure of nanoscale polaron correlations in the layered manganites

    NASA Astrophysics Data System (ADS)

    Campbell, Branton

    2002-03-01

    Recent x-ray and neutron scattering experiments have uncovered nanoscale polaron correlations that play an essential role in the colossal magnetoresistive (CMR) behavior of the perovskite manganites. Short-range polaronic order decreases the charge-carrier mobility of the high-temperature paramagnetic state, and subsequently becomes unstable at the ferromagnetic transition, contributing to a pronounced resistivity decrease at T_C. In the bilayered perovskite system La_2-2xSr_1+2xMn_2O7 (0.3 < x < 0.5), weak x-ray diffuse scattering maxima reveal a one-dimensional incommensurate structural modulation with wavevector q = (0.3, 0, ± 1) and a correlation length of 10 to 30 Angstroms. A crystallographic analysis of the diffuse satellite intensities yields a longitudinal Jahn-Teller stretch mode suggestive of charge-density-wave fluctuations. Within the correlated regions, polaronic eg electrons form a striped pattern of occupied d(3x^2-r^2) orbitals. Dynamic polaron correlations of the zig-zag orbital type are also observed above TC and exhibit distinctly glassy behavior. These structures provide unique insights into the nature of strongly correlated polaronic systems. Collaborators: R. Osborn, D.N. Argyriou, S. Rosenkranz, L. Vasiliu-Doloc, J.F. Mitchell, S.K. Sinha, J.W. Lynn, C.D. Ling, Z. Islam, U. Ruett, and A. Berger. This work was supported by the U.S. DOE Office of Science contract No. W-31-109-ENG-38.

  14. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    DOE PAGESBeta

    Pilania, G.; Uberuaga, B. P.

    2015-03-19

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositionsmore » in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. As a result, the computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.« less

  15. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    SciTech Connect

    Pilania, G.; Uberuaga, B. P.

    2015-03-19

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. As a result, the computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.

  16. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl{sub 6}

    SciTech Connect

    Pilania, G. Uberuaga, B. P.

    2015-03-21

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl{sub 6} using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl{sub 3} and RbZnCl{sub 3}) forming the double perovskite exhibit a stark contrast. While CsCaCl{sub 3} is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl{sub 3} is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl{sub 6} can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. The computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.

  17. Atomic structure of metal-halide perovskites from first principles: The chicken-and-egg paradox of the organic-inorganic interaction

    NASA Astrophysics Data System (ADS)

    Li, Jingrui; Rinke, Patrick

    2016-07-01

    We have studied the prototype hybrid organic-inorganic perovskite CH3NH3PbI3 and its three close relatives, CH3NH3SnI3 ,CH3NH3PbCl3 , and CsPbI3, using relativistic density function theory. The long-range van der Waals (vdW) interactions were incorporated into the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional using the Tkatchenko-Scheffler pairwise scheme. Our results reveal that hydrogen bonding, which is well described by the PBE functional, plays a decisive role for the structural parameters of these systems, including the position and orientation of the organic cation as well as the deformation of the inorganic framework. The magnitude of the inorganic-framework deformation depends sensitively on the orientation of the organic cation, and directly influences the stability of the hybrid perovskites. Our results suggest that the organic and the inorganic components complement each other; the low symmetry of the organic cation is the origin of the inorganic-framework deformation, which then aids the overall stabilization of the hybrid perovskite structure. This stabilization is indirectly affected by vdW interactions, which lead to smaller unit-cell volumes than in PBE and therefore modulate the interaction between the organic cation and the inorganic framework. The vdW-induced lattice-constant corrections are system dependent and lead to PBE+vdW lattice constants in good agreement with experiment. Further insight is gained by analyzing the vdW contributions. In all iodide-based hybrid perovskites, the interaction between the organic cation and the iodide anions provides the largest lattice-constant change, followed by iodine-iodine and the organic cation—heavy-metal cation interaction. These corrections follow an almost linear dependence on the lattice constant within the range considered in our study and are therefore approximately additive.

  18. Low temperature thermoelastic and structural properties of LaGaO{sub 3} perovskite in the Pbnm phase

    SciTech Connect

    Knight, Kevin S.

    2012-10-15

    The thermoelastic and structural properties of LaGaO{sub 3} perovskite have been studied using high resolution neutron diffractometry at 158 temperatures between 11 K and 548 K. Data collected in 2 K intervals between 410 K and 430 K show no evidence for an intermediate phase between the low temperature phase in space group Pbnm and the high temperature phase in space group F3{sup Macron }2/n. From a simultaneous fit of the unit cell volume and the isochoric heat capacity, the phonon density of states in the Pbnm phase is shown to be approximated by a two-term Debye model, with characteristic temperatures 294(1) K and 831(1) K. Vibrational Debye temperatures, determined from fitting the temperature variation of the atomic displacement parameters, show the cations to be more associated with the lower characteristic temperature, whilst that for the anions, is closer to the higher characteristic temperature. Structural parameters are presented as the amplitudes of the seven symmetry-adapted basis-vectors of the aristotype phase, and a structural basis for the temperature-dependence of the bond lengths is outlined. The phase transition in both temperature and pressure arises when a non-bonded La-O distance approaches the La coordination sphere. - Graphical abstract: The weight fraction of the rhombohedral phase of LaGaO{sub 3} from the onset of the phase transition at 408 K to its completion at 430 K. Highlights: Black-Right-Pointing-Pointer Thermoelastic properties of LaGaO{sub 3} analyzed as a two-term Debye model. Black-Right-Pointing-Pointer Crystal structure and bonding analyzed in terms of symmetry-adapted basis-vectors. Black-Right-Pointing-Pointer Consistency between calorimetric and crystallographic measurements.

  19. Nanocrystalline rutile electron extraction layer enables low-temperature solution processed perovskite photovoltaics with 13.7% efficiency.

    PubMed

    Yella, Aswani; Heiniger, Leo-Philipp; Gao, Peng; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

    2014-05-14

    We demonstrate low-temperature (70 °C) solution processing of TiO2/CH3NH3PbI3 based solar cells, resulting in impressive power conversion efficiency (PCE) of 13.7%. Along with the high efficiency, a strikingly high open circuit potential (VOC) of 1110 mV was realized using this low-temperature chemical bath deposition approach. To the best of our knowledge, this is so far the highest VOC value for solution-processed TiO2/CH3NH3PbI3 solar cells. We deposited a nanocrystalline TiO2 (rutile) hole-blocking layer on a fluorine-doped tin oxide (FTO) conducting glass substrate via hydrolysis of TiCl4 at 70 °C, forming the electron selective contact with the photoactive CH3NH3PbI3 film. We find that the nanocrystalline rutile TiO2 achieves a much better performance than a planar TiO2 (anatase) film prepared by high-temperature spin coating of TiCl4, which produces a much lower PCE of 3.7%. We attribute this to the formation of an intimate junction of large interfacial area between the nanocrystalline rutile TiO2 and the CH3NH3PbI3 layer, which is much more effective in extracting photogenerated electrons than the planar anatase film. Since the complete fabrication of the solar cell is carried out below 100 °C, this method can be easily extended to plastic substrates. PMID:24628563

  20. Effects of pyrolysis temperature on structural, Raman, and infrared properties of perovskite PbTiO3 nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, Sun A.; Kim, Byung Hoon; Cho, Sam Yeon; Han, Jin Kyu; Bu, Sang Don; Choi, Yong Chan

    2016-02-01

    In this work, we investigated the effects of the pyrolysis temperature on the structural, Raman, and infrared properties of PbTiO3 nanotubes (PTO-NTs). The PTO-NTs were synthesized by spin coating a sol-gel solution on porous anodic alumina membranes, followed by the pyrolysis step at 400 - 600 ℃. Then, PTO-NTs were finally crystallized at 600 - 700 ℃ in an oxygen atmosphere to get the perovskite phase. The PTO-NTs had an outer diameter of about 420 nm and a wall thickness of about 10 nm. X-ray diffraction patterns showed that the tetragonality ( c/ a) increased from 1.019 to 1.028 as the pyrolysis temperature was increased from 400 to 600 ℃. Raman spectroscopy showed that the phonon modes of A 1( nTO) and E( nTO) increased with a redshift of the A 1(3TO) mode as the pyrolysis temperature was increased. In the Fourier-transform infrared spectra of PTO-NTs embedded in the porous anodic alumina membrane, the transmittance of the band at 499 cm-1 increased as the pyrolysis temperature was increased, which might be due to an increase in the tetragonality.