A ZnO nanowire bio-hybrid solar cell

NASA Astrophysics Data System (ADS)

Yaghoubi, Houman; Schaefer, Michael; Yaghoubi, Shayan; Jun, Daniel; Schlaf, Rudy; Beatty, J. Thomas; Takshi, Arash

2017-02-01

Harvesting solar energy as a carbon free source can be a promising solution to the energy crisis and environmental pollution. Biophotovoltaics seek to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. In the current study, we report on a combination of zinc oxide (ZnO) nanowires with monolayers of photosynthetic reaction centers which are self-assembled, via a cytochrome c linker, as photoactive electrode. In a three-probe biophotovoltaics cell, a photocurrent density of 5.5 μA cm-2 and photovoltage of 36 mV was achieved, using methyl viologen as a redox mediator in the electrolyte. Using ferrocene as a redox mediator a transient photocurrent density of 8.0 μA cm-2 was obtained, which stabilized at 6.4 μA cm-2 after 20 s. In-depth electronic structure characterization using photoemission spectroscopy in conjunction with electrochemical analysis suggests that the fabricated photoactive electrode can provide a proper electronic path for electron transport all the way from the conduction band of the ZnO nanowires, through the protein linker to the RC, and ultimately via redox mediator to the counter electrode.

Specifications of ZnO growth for heterostructure solar cell and PC1D based simulations

PubMed Central

Hussain, Babar; Ebong, Abasifreke

2015-01-01

This data article is related to our recently published article (Hussain et al., in press [1]) where we have proposed a new solar cell model based on n-ZnO as front layer and p-Si as rear region. The ZnO layer will act as an active n-layer as well as antireflection (AR) coating saving considerable processing cost. There are several reports presenting use of ZnO as window/antireflection coating in solar cells (Mansoor et al., 2015; Haq et al., 2014; Hussain et al., 2014; Matsui et al., 2014; Ding et al., 2014 [2], [3], [4], [5], [6]) but, here, we provide data specifically related to simultaneous use of ZnO as n-layer and AR coating. Apart from the information we already published, we provide additional data related to growth of ZnO (with and without Ga incorporation) layers using MOCVD. The data related to PC1D based simulation of internal and external quantum efficiencies with and without antireflection effects of ZnO as well as the effects of doping level in p-Si on current–voltage characteristics have been provided. PMID:26587557

Mechanisms of electron transport and recombination in ZnO nanostructures for dye-sensitized solar cells.

PubMed

Vega-Poot, Alberto G; Macías-Montero, Manuel; Idígoras, Jesus; Borrás, Ana; Barranco, Angel; Gonzalez-Elipe, Agustín R; Lizama-Tzec, Francisco I; Oskam, Gerko; Anta, Juan A

2014-04-14

ZnO is an attractive material for applications in dye-sensitized solar cells and related devices. This material has excellent electron-transport properties in the bulk but its electron diffusion coefficient is much smaller in mesoporous films. In this work the electron-transport properties of two different kinds of dye-sensitized ZnO nanostructures are investigated by small-perturbation electrochemical techniques. For nanoparticulate ZnO photoanodes prepared via a wet-chemistry technique, the diffusion coefficient is found to reproduce the typical behavior predicted by the multiple-trapping and the hopping models, with an exponential increase with respect to the applied bias. In contrast, in ZnO nanostructured thin films of controlled texture and crystallinity prepared via a plasma chemical vapor deposition method, the diffusion coefficient is found to be independent of the electrochemical bias. This observation suggests a different transport mechanism not controlled by trapping and electron accumulation. In spite of the quite different transport features, the recombination kinetics, the electron-collection efficiency and the photoconversion efficiency are very similar for both kinds of photoanodes, an observation that indicates that surface properties rather than electron transport is the main efficiency-determining factor in solar cells based on ZnO nanostructured photoanodes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Performance of Dye-Sensitized Solar Cells (DSSCs) Fabricated with Zinc Oxide (ZnO) Nanpowders and Nanorods

NASA Astrophysics Data System (ADS)

Chatterjee, Suman

2018-03-01

Due to their high efficiencies, along with lower production costs, many researchers are working on dye-sensitized solar cells (DSSCs) over last few decades as a substitute technology for nonconventional energy. Nanostructured ZnO has got many interesting properties such as wide band gap, large exciton binding energy, good exciton stability, and high breakdown strength, which are applicable as DSSC electrodes. This present work compares the device properties of DSSC fabricated using ZnO nanorods on a ZnO film and ZnO nanopowders. Different types of ZnO photoanode and dye combinations are used to study the stability and photovoltaic properties of the DSSC cell. The photovoltaic properties of the ZnO-based DSSC samples were systematically investigated. The photovoltaic properties of fabricated cell obtained are discussed in the light of band structure and density of states of different types of ZnO nanolayers. The ZnO nanorods fabricated through the sol-gel route have more uniform thickness resulting in enhanced photovoltaic properties of the fabricated device.

Effect of TiO{sub 2} thickness on nanocomposited aligned ZnO nanorod/TiO{sub 2} for dye-sensitized solar cells

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

Saurdi, I., E-mail: saurdy788@gmail.com; Ishak, A.; UiTM Sarawak Kampus Kota Samarahan Jalan Meranek, Sarawak

2016-07-06

The TiO{sub 2} films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO{sub 2} were formed by deposited the TiO{sub 2} on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO{sub 2} deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO{sub 2} were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO{sub 2}. The dye-sensitized solar cells were fabricated from themore » nanocomposited aligned ZnO nanorod/TiO{sub 2} with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO{sub 2} and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO{sub 2} photoanode-2710µm Dye-Sensitized solar cell.« less

ZnO Hierarchical Nanostructure Photoanode in a CdS Quantum Dot-Sensitized Solar Cell

PubMed Central

Liu, Huan; Zhang, Gengmin; Sun, Wentao; Shen, Ziyong; Shi, Mingji

2015-01-01

A hierarchical array of ZnO nanocones covered with ZnO nanospikes was hydrothermally fabricated and employed as the photoanode in a CdS quantum dot-sensitized solar cell (QDSSC). This QDSSC outperformed the QDSSC based on a simple ZnO nanocone photoanode in all the four principal photovoltaic parameters. Using the hierarchical photoanode dramatically increased the short circuit current density and also slightly raised the open circuit voltage and the fill factor. As a result, the conversion efficiency of the QDSSC based on the hierarchical photoanode was more than twice that of the QDSSC based on the simple ZnO nanocone photoanode. This improvement is attributable to both the enlarged specific area of the photoanode and the reduction in the recombination of the photoexcited electrons. PMID:26379268

Thickness optimization of the ZnO based TCO layer in a CZTSSe solar cell. Evolution of its performance with thickness when external temperature changes.

NASA Astrophysics Data System (ADS)

Chadel, Meriem; Moustafa Bouzaki, Mohammed; Chadel, Asma; Aillerie, Michel; Benyoucef, Boumediene

2017-07-01

The influence of the thickness of a Zinc Oxide (ZnO) transparent conductive oxide (TCO) layer on the performance of the CZTSSe solar cell is shown in detail. In a photovoltaic cell, the thickness of each layer largely influence the performance of the solar cell and optimization of each layer constitutes a complete work. Here, using the Solar Cell Capacitance Simulation (SCAPS) software, we present simulation results obtained in the analyze of the influence of the TCO layer thickness on the performance of a CZTSSe solar cell, starting from performance of a CZTSSe solar cell commercialized in 2014 with an initial efficiency equal to 12.6%. In simulation, the temperature was considered as a functioning parameter and the evolution of tthe performance of the cell for various thickness of the TCO layer when the external temperature changes is simulated and discussed. The best efficiency of the solar cell based in CZTSSe is obtained with a ZnO thickness equal to 50 nm and low temperature. Based on the considered marketed cell, we show a technological possible increase of the global efficiency achieving 13% by optimization of ZnO based TCO layer.

Perovskite solar cells based on nanocolumnar plasma-deposited ZnO thin films.

PubMed

Ramos, F Javier; López-Santos, Maria C; Guillén, Elena; Nazeeruddin, Mohammad Khaja; Grätzel, Michael; Gonzalez-Elipe, Agustin R; Ahmad, Shahzada

2014-04-14

ZnO thin films having a nanocolumnar microstructure are grown by plasma-enhanced chemical vapor deposition at 423 K on pre-treated fluorine-doped tin oxide (FTO) substrates. The films consist of c-axis-oriented wurtzite ZnO nanocolumns with well-defined microstructure and crystallinity. By sensitizing CH3NH3PbI3 on these photoanodes a power conversion of 4.8% is obtained for solid-state solar cells. Poly(triarylamine) is found to be less effective when used as the hole-transport material, compared to 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), while the higher annealing temperature of the perovskite leads to a better infiltration in the nanocolumnar structure and an enhancement of the cell efficiency. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell

PubMed Central

Tsin, Fabien; Venerosy, Amélie; Vidal, Julien; Collin, Stéphane; Clatot, Johnny; Lombez, Laurent; Paire, Myriam; Borensztajn, Stephan; Broussillou, Cédric; Grand, Pierre Philippe; Jaime, Salvador; Lincot, Daniel; Rousset, Jean

2015-01-01

This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>1020 cm−3) and mobilities (up to 20 cm2 V−1 s−1) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell. PMID:25753657

Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell.

PubMed

Tsin, Fabien; Venerosy, Amélie; Vidal, Julien; Collin, Stéphane; Clatot, Johnny; Lombez, Laurent; Paire, Myriam; Borensztajn, Stephan; Broussillou, Cédric; Grand, Pierre Philippe; Jaime, Salvador; Lincot, Daniel; Rousset, Jean

2015-03-10

This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>10(20) cm(-3)) and mobilities (up to 20 cm(2) V(-1) s(-1)) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell.

ZnO transparent conductive oxide for thin film silicon solar cells

NASA Astrophysics Data System (ADS)

Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

2010-03-01

There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

Comparison of TiO₂ and ZnO solar cells sensitized with an indoline dye: time-resolved laser spectroscopy studies of partial charge separation processes.

PubMed

Sobuś, Jan; Burdziński, Gotard; Karolczak, Jerzy; Idígoras, Jesús; Anta, Juan A; Ziółek, Marcin

2014-03-11

Time-resolved laser spectroscopy techniques in the time range from femtoseconds to seconds were applied to investigate the charge separation processes in complete dye-sensitized solar cells (DSC) made with iodide/iodine liquid electrolyte and indoline dye D149 interacting with TiO2 or ZnO nanoparticles. The aim of the studies was to explain the differences in the photocurrents of the cells (3-4 times higher for TiO2 than for ZnO ones). Electrochemical impedance spectroscopy and nanosecond flash photolysis studies revealed that the better performance of TiO2 samples is not due to the charge collection and dye regeneration processes. Femtosecond transient absorption results indicated that after first 100 ps the number of photoinduced electrons in the semiconductor is 3 times higher for TiO2 than for ZnO solar cells. Picosecond emission studies showed that the lifetime of the D149 excited state is about 3 times longer for ZnO than for TiO2 samples. Therefore, the results indicate that lower performance of ZnO solar cells is likely due to slower electron injection. The studies show how to correlate the laser spectroscopy methodology with global parameters of the solar cells and should help in better understanding of the behavior of alternative materials for porous electrodes for DSC and related devices.

Air stable organic-inorganic nanoparticles hybrid solar cells

DOEpatents

Qian, Lei; Yang, Jihua; Xue, Jiangeng; Holloway, Paul H.

2015-09-29

A solar cell includes a low work function cathode, an active layer of an organic-inorganic nanoparticle composite, a ZnO nanoparticle layer situated between and physically contacting the cathode and active layers; and a transparent high work function anode that is a bilayer electrode. The inclusion of the ZnO nanoparticle layer results in a solar cell displaying a conversion efficiency increase and reduces the device degradation rate. Embodiments of the invention are directed to novel ZnO nanoparticles that are advantageous for use as the ZnO nanoparticle layers of the novel solar cells and a method to prepare the ZnO nanoparticles.

Template-free hydrothermal synthesis of beaded nanochain bundles of ZnO and their application as photoanode in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Ballal, Reshma; Shinde, Manish; Waghadkar, Yogesh; Arbuj, Sudhir; Rane, Sunit; Chauhan, Ratna

2018-02-01

ZnO shows promising candidature as photoanode material for dye-sensitized solar cells (DSSCs) due to its high bulk electron mobility and easily tailorable geometrical structures. The objective of this study is to facilitate the development of highly porous hierarchical ZnO for enhanced power conversion efficiency in dye-sensitized solar cells (DSSC) due to its greater dye adsorption. This study investigated the influence of reaction temperatures of 120 °C (sample Z-1) and 180 °C (sample Z-2) in hydrothermal synthesis on structural, morphological and optical properties of resultant ZnO nanostructures and their performance as photoanode material in DSSCs. The synthesized beaded nanochain bundles of ZnO, with multilayered and highly ordered texture, have diameters of several micrometers. Structural and morphological analysis shows that the ZnO beaded nanochain-like architectures possess wurtzite crystalline nature. These morphological improvements (beaded nanochains) of ZnO were found to exhibit higher dye loading and conversion efficiency due to increase in the surface area while reducing charge recombination. The maximum conversion efficiency was obtained with Z-1 and Z-2 is 2.95 and 3.56% with photocurrent of 7.73 and 9.24 mA/cm2, respectively. The obtained results pertaining to the DSSC performance studies were corroborated by the impedance spectroscopy data.

Fabrication of a Combustion-Reacted High-Performance ZnO Electron Transport Layer with Silver Nanowire Electrodes for Organic Solar Cells.

PubMed

Park, Minkyu; Lee, Sang-Hoon; Kim, Donghyuk; Kang, Juhoon; Lee, Jung-Yong; Han, Seung Min

2018-02-28

Herein, a new methodology for solution-processed ZnO fabrication on Ag nanowire network electrode via combustion reaction is reported, where the amount of heat emitted during combustion was minimized by controlling the reaction temperature to avoid damaging the underlying Ag nanowires. The degree of participation of acetylacetones, which are volatile fuels in the combustion reaction, was found to vary with the reaction temperature, as revealed by thermogravimetric and compositional analyses. An optimized processing temperature of 180 °C was chosen to successfully fabricate a combustion-reacted ZnO and Ag nanowire hybrid electrode with a sheet resistance of 30 Ω/sq and transmittance of 87%. A combustion-reacted ZnO on Ag nanowire hybrid structure was demonstrated as an efficient transparent electrode and electron transport layer for the PTB7-Th-based polymer solar cells. The superior electrical conductivity of combustion-reacted ZnO, compared to that of conventional sol-gel ZnO, increased the external quantum efficiency over the entire absorption range, whereas a unique light scattering effect due to the presence of nanopores in the combustion-derived ZnO further enhanced the external quantum efficiency in the 450-550 nm wavelength range. A power conversion efficiency of 8.48% was demonstrated for the PTB7-Th-based polymer solar cell with the use of a combustion-reacted ZnO/Ag NW hybrid transparent electrode.

Orientation-Controllable ZnO Nanorod Array Using Imprinting Method for Maximum Light Utilization in Dye-Sensitized Solar Cells.

PubMed

Jeong, Huisu; Song, Hui; Lee, Ryeri; Pak, Yusin; Kumaresan, Yogeenth; Lee, Heon; Jung, Gun Young

2015-12-01

We present a holey titanium dioxide (TiO2) film combined with a periodically aligned ZnO nanorod layer (ZNL) for maximum light utilization in dye-sensitized solar cells (DSCs). Both the holey TiO2 film and the ZNL were simultaneously fabricated by imprint technique with a mold having vertically aligned ZnO nanorod (NR) array, which was transferred to the TiO2 film after imprinting. The orientation of the transferred ZNL such as laid, tilted, and standing ZnO NRs was dependent on the pitch and height of the ZnO NRs of the mold. The photoanode composed of the holey TiO2 film with the ZNL synergistically utilized the sunlight due to enhanced light scattering and absorption. The best power conversion efficiency of 8.5 % was achieved from the DSC with the standing ZNL, which represented a 33 % improvement compared to the reference cell with a planar TiO2.

SILAR controlled CdSe nanoparticles sensitized ZnO nanorods photoanode for solar cell application: Electrolyte effect.

PubMed

Nikam, Pratibha R; Baviskar, Prashant K; Majumder, Sutripto; Sali, Jaydeep V; Sankapal, Babasaheb R

2018-08-15

Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 °C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (<100 °C). Different characterization techniques viz. X-ray diffractometer, UV-Vis spectrophotometer, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods. Copyright © 2018 Elsevier Inc. All rights reserved.

Tuning of defects in ZnO nanorod arrays used in bulk heterojunction solar cells

PubMed Central

2012-01-01

With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths for the two main defects which make up the visible band, the oxygen vacancy emission wavelength at approximately 530 nm and the zinc vacancy emission wavelength at approximately 630 nm. The precise nature of the defect landscape in the bulk of the nanorods is found to be unimportant to photovoltaic cell performance although the surface structure is more critical. Annealing of the nanorods is optimum at 300°C as this is a sufficiently high temperature to decompose Zn(OH)2 formed at the surface of the nanorods during electrodeposition and sufficiently low to prevent ITO degradation. PMID:23186280

Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

PubMed Central

Selopal, Gurpreet Singh; Wu, Hui-Ping; Lu, Jianfeng; Chang, Yu-Cheng; Wang, Mingkui; Vomiero, Alberto; Concina, Isabella; Diau, Eric Wei-Guang

2016-01-01

We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction. PMID:26738698

Performance of natural-dye-sensitized solar cells by ZnO nanorod and nanowall enhanced photoelectrodes

PubMed Central

Saadaoui, Saif; Ben Youssef, Mohamed Aziz; Ben Karoui, Moufida; Smecca, Emanuele; Strano, Vincenzina; Mirabella, Salvo; Alberti, Alessandra; Puglisi, Rosaria A

2017-01-01

In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N2/H2 95:5) was found to enhance the conductivity by a factor of 103 compared to nitrogen (N2) or oxygen (O2) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO2 layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current J sc by seven times from 2.45 × 10−3 mA/cm2 to 1.70 × 10−2 mA /cm2. PMID:28243567

Performance of natural-dye-sensitized solar cells by ZnO nanorod and nanowall enhanced photoelectrodes.

PubMed

Saadaoui, Saif; Ben Youssef, Mohamed Aziz; Ben Karoui, Moufida; Gharbi, Rached; Smecca, Emanuele; Strano, Vincenzina; Mirabella, Salvo; Alberti, Alessandra; Puglisi, Rosaria A

2017-01-01

In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N 2 /H 2 95:5) was found to enhance the conductivity by a factor of 10 3 compared to nitrogen (N 2 ) or oxygen (O 2 ) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO 2 layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current J sc by seven times from 2.45 × 10 -3 mA/cm 2 to 1.70 × 10 -2 mA /cm 2 .

Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

PubMed Central

Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

2016-01-01

Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400–900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells. PMID:27924911

Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

NASA Astrophysics Data System (ADS)

Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

2016-12-01

Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400-900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells.

Effect of Copper Oxide Nanoparticles as a barrier for Efficiency Improvement in ZnO Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Sonthila, A.; Ruankham, P.; Choopun, S.; Wongratanaphisan, D.; Phadungdhitidhada, S.; Gardchareon, A.

2017-09-01

CuO nanoparticles (CuO NPs) were used as a barrier layer in ZnO dye-sensitized solar cells (DSSCs) to obtain high power conversion efficiency. The barrier layer was investigated in terms of the size of CuO NPs by varying power of pulsed Nd:YAG (1064 nm) laser ablation. Morphological and optical properties of CuO NPs were characterized by transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis) and dynamic light scattering (DLS). It was found that the CuO NPs are rather spherical in shape with diameter in between 20 - 132 nm. In addition, the energy gap of CuO decreases with the increase of CuO NPs size. The power conversion efficiency of ZnO DSSCs was measured under illumination of simulated sunlight obtained from a solar simulator with the radiant power of 100 mW/cm2. The results showed that the ZnO DSSC with the CuO NPs with size of 37 nm exhibits the optimum power conversion efficiency of 1.01% which is higher than that of one without CuO NPs. Moreover, the power conversion efficiency of the ZnO DSSCs decreases with the increase of CuO NPs size.

Ternary Oxides in the TiO2-ZnO System as Efficient Electron-Transport Layers for Perovskite Solar Cells with Efficiency over 15.

PubMed

Yin, Xiong; Xu, Zhongzhong; Guo, Yanjun; Xu, Peng; He, Meng

2016-11-02

Perovskite solar cells, which utilize organometal-halide perovskites as light-harvesting materials, have attracted great attention due to their high power conversion efficiency (PCE) and potentially low cost in fabrication. A compact layer of TiO 2 or ZnO is generally applied as electron-transport layer (ETL) in a typical perovskite solar cell. In this study, we explored ternary oxides in the TiO 2 -ZnO system to find new materials for the ETL. Compact layers of titanium zinc oxides were readily prepared on the conducting substrate via spray pyrolysis method. The optical band gap, valence band maximum and conduction band minimum of the ternary oxides varied significantly with the ratio of Ti to Zn, surprisingly, in a nonmonotonic way. When a zinc-rich ternary oxide was applied as ETL for the device, a PCE of 15.10% was achieved, comparable to that of the device using conventional TiO 2 ETL. Interestingly, the perovskite layer deposited on the zinc-rich ternary oxide is stable, in sharp contrast with that fabricated on a ZnO layer, which will turn into PbI 2 readily when heated. These results indicate that potentially new materials with better performance can be found for ETL of perovskite solar cells in ternary oxides, which deserve more exploration.

Growth and characterization of textured well-faceted ZnO on planar Si(100), planar Si(111), and textured Si(100) substrates for solar cell applications.

PubMed

Tsai, Chin-Yi; Lai, Jyong-Di; Feng, Shih-Wei; Huang, Chien-Jung; Chen, Chien-Hsun; Yang, Fann-Wei; Wang, Hsiang-Chen; Tu, Li-Wei

2017-01-01

In this work, textured, well-faceted ZnO materials grown on planar Si(100), planar Si(111), and textured Si(100) substrates by low-pressure chemical vapor deposition (LPCVD) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathode luminescence (CL) measurements. The results show that ZnO grown on planar Si(100), planar Si(111), and textured Si(100) substrates favor the growth of ZnO(110) ridge-like, ZnO(002) pyramid-like, and ZnO(101) pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100) substrate is slightly larger than that on the planar Si(111) substrate, while both of them are much larger than that on the textured Si(100) substrate. The average grain sizes (about 10-50 nm) of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT) solar cells.

Optical absorption enhancement by inserting ZnO optical spacer in plasmonic organic solar cells

NASA Astrophysics Data System (ADS)

N'Konou, Kekeli; Torchio, Philippe

2018-01-01

Optical absorption enhancement (AE) using coupled optical spacer and plasmonic effects in standard and inverted organic solar cells (OSCs) are demonstrated using the finite-difference time-domain numerical method. The influence of an added zinc oxide (ZnO) optical spacer layer inserted below the active layer in standard architecture is first theoretically investigated while the influence of varying the ZnO cathodic buffer layer thickness in inverted design is studied on AE. Then, the embedding of a square periodic array of core-shell silver-silica nanospheres (Ag@SiO2 NSs) at different positions in standard and inverted OSCs is performed while AE and short-circuit current density (Jsc) are calculated. As a result of previous combined effects, the optimized standard plasmonic OSCs present 15% and 79.45% enhancement in J over the reference with and without ZnO optical spacer layer, respectively, and a 16% increase of AE when Ag@SiO2 NSs are placed on top of the PEDOT:PSS layer. Compared to the inverted OSC reference, the plasmonic OSCs present 26% and 27% enhancement in J and AE, respectively, when the Ag@SiO2 NSs are located on top of the ZnO layer. Furthermore, the spatial position of these NSs in such OSCs is a key parameter for increasing light absorption via enhanced electromagnetic field distribution.

Ultrafast photodynamics of the indoline dye D149 adsorbed to porous ZnO in dye-sensitized solar cells.

PubMed

Rohwer, Egmont; Richter, Christoph; Heming, Nadine; Strauch, Kerstin; Litwinski, Christian; Nyokong, Tebello; Schlettwein, Derck; Schwoerer, Heinrich

2013-01-14

We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I(-)/I(3)(-) redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Screen-Printing of ZnO Nanostructures from Sol-Gel Solutions for Their Application in Dye-Sensitized Solar Cells.

PubMed

Sarkar, Kuhu; Braden, Erik V; Bonke, Shannon A; Bach, Udo; Müller-Buschbaum, Peter

2015-08-24

Diblock copolymers have been used in sol-gel synthesis to successfully tailor the nanoscale morphology of thin ZnO films. As the fabrication of several-micron-thick mesoporous films such as those required in dye-sensitized solar cells (DSSCs) was difficult with this approach, we exploited the benefits of diblock-copolymer-directed synthesis that made it compatible with screen printing. The simple conversion of the diblock copolymer ZnO precursor sol to a screen-printing paste was not possible as it resulted in poor film properties. To overcome this problem, an alternative route is proposed in which the diblock copolymer ZnO precursor sol is first blade coated and calcined, then converted to a screen-printing paste. This allows the benefits of diblock-copolymer-directed particle formation to be compatible with printing methods. The morphologies of the ZnO nanostructures were studied by SEM and correlated with the current density-voltage characteristics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modification of opto-electronic properties of ZnO by incorporating metallic tin for buffer layer in thin film solar cells

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

Deepu, D. R.; Jubimol, J.; Kartha, C. Sudha

2015-06-24

In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin filmmore » solar cells.« less

Assembly and characterization of quantum-dot solar cells

NASA Astrophysics Data System (ADS)

Leschkies, Kurtis Siegfried

Environmentally clean renewable energy resources such as solar energy have gained significant attention due to a continual increase in worldwide energy demand. A variety of technologies have been developed to harness solar energy. For example, photovoltaic (or solar) cells based on silicon wafers can convert solar energy directly into electricity with high efficiency, however they are expensive to manufacture, and thus unattractive for widespread use. As the need for low-cost, solar-derived energy becomes more dire, strategies are underway to identify materials and photovoltaic device architectures that are inexpensive yet efficient compared to traditional silicon solar cells. Nanotechnology enables novel approaches to solar-to-electric energy conversion that may provide both high efficiencies and simpler manufacturing methods. For example, nanometer-size semiconductor crystallites, or semiconductor quantum dots (QDs), can be used as photoactive materials in solar cells to potentially achieve a maximum theoretical power conversion efficiency which exceeds that of current mainstay solar technology at a much lower cost. However, the novel concepts of quantum dot solar cells and their energy conversion designs are still very much in their infancy, as a general understanding of their assembly and operation is limited. This thesis introduces various innovative and novel solar cell architectures based on semiconductor QDs and provides a fundamental understanding of the operating principles that govern the performance of these solar cells. Such effort may lead to the advancement of current nanotechnology-based solar power technologies and perhaps new initiatives in nextgeneration solar energy conversion devices. We assemble QD-based solar cells by depositing photoactive QDs directly onto thin ZnO films or ZnO nanowires. In one scheme, we combine CdSe QDs and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell (QDSSC). An array of ZnO

Optical determination of charge transfer times from indoline dyes to ZnO in solid state dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Meyenburg, I.; Hofeditz, N.; Ruess, R.; Rudolph, M.; Schlettwein, D.; Heimbrodt, W.

2018-05-01

We studied the electron transfer at the interface of organic-inorganic hybrids consisting of indoline derivatives (D149 and D131) on ZnO substrates using a new optical method. We revealed the electron transfer times from the excited dye, e.g. the excitons formed in the dye aggregates to the ZnO substrate by analyzing the photoluminescence transients of the excitons after femtosecond excitation and applying kinetic model calculations. We reveal the changes of the electron transfer times by applying electrical bias. Pushing the Fermi energy of the ZnO substrate towards the excited dye level the transfer time gets longer and eventually the electron transfer is suppressed. The level alignment between the excited dye state and the ZnO Fermi-level is estimated. The excited state of D131 is about 100 meV higher than the respective state of D149 compared to the ZnO conduction band. This leads to shorter electron transfer times and eventually to higher quantum efficiencies of the solar cells.

Flower-shaped ZnO nanocrystallite aggregates synthesized through a template-free aqueous solution method for dye-sensitized solar cells

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

Chang, Wei-Chen, E-mail: changpeter@iner.gov.tw; Institute of Nuclear Energy Research, Atomic Energy Council, Executive Yuan, 1000 Wenhua Rd., Chiaan Village, Lungtan, Taoyuan 325, Taiwan; Chen, Hung-Shuo

Hierarchically structured flower-shaped aggregates composed of ZnO nanocrystals were synthesized through a template-free aqueous solution method. The synthesized nanocrystallite aggregates were demonstrated to be promising photoanode materials for dye-sensitized solar cells (DSSCs). Compared with commercially available ZnO nanoparticles (ZnONPs), the flower-like aggregates (ZnONFs), each having an overall dimension of 400–600 nm, exhibited similar dye loading but higher light-scattering ability, which led to a substantial increase in the light-harvesting efficiency of resulting cells. The unique morphology of ZnONFs also boosted the absorbed photon-to-electric current generation efficiency. Consequently, DSSCs constructed from ZnONFs showed significantly improved photocurrent and achieved an overall conversion efficiency ofmore » 4.42%, which was 47% higher than that attained by ZnONP-based cells.« less

Impedance analysis of PbS colloidal quantum dot solar cells with different ZnO nanowire lengths

NASA Astrophysics Data System (ADS)

Fukuda, Takeshi; Takahashi, Akihiro; Wang, Haibin; Takahira, Kazuya; Kubo, Takaya; Segawa, Hiroshi

2018-03-01

The photoconversion efficiency of colloidal quantum dot (QD) solar cells has been markedly improved by optimizing the surface passivation and device structure, and details of device physics are now under investigation. In this study, we investigated the resistance and capacitance components at the ZnO/PbS-QD interface and inside a PbS-QD layer by measuring the impedance spectrum while the interface area was controlled by changing the ZnO nanowire length. By evaluating the dependence of optical intensity and DC bias voltage on the ZnO nanowire length, only the capacitance was observed to be influenced by the interface area, and this indicates that photoinduced carriers are generated at the surface of PbS-QD. In addition, since the capacitance is proportional to the surface area of the QD, the interface area can be evaluated from the capacitance. Finally, photovoltaic performance was observed to increase with increasing ZnO nanowire length owing to the large interface area, and this result is in good agreement with the capacitance measurement.

New Materials for Chalcogenide Based Solar Cells

NASA Astrophysics Data System (ADS)

Tosun, Banu Selin

Thin film solar cells based on copper indium gallium diselenide (CIGS) have achieved efficiencies exceeding 20 %. The p-n junction in these solar cells is formed between a p-type CIGS absorber layer and a composite n-type film that consists of a 50-100 nm thin n-type CdS followed by a 50-200 nm thin n-type ZnO. This dissertation focuses on developing materials for replacing CdS and ZnO films to improve the damp-heat stability of the solar cells and for minimizing the use of Cd. Specifically, I demonstrate a new CIGS solar cell with better damp heat stability wherein the ZnO layer is replaced with SnO2. The efficiency of solar cells made with SnO2 decreased less than 5 % after 120 hours at 85 °C and 85 % relative humidity while the efficiency of solar cells made with ZnO declined by more than 70 %. Moreover, I showed that a SnO2 film deposited on top of completed CIGS solar cells significantly increased the device lifetime by forming a barrier against water diffusion. Semicrystalline SnO2 films deposited at room temperature had nanocrystals embedded in an amorphous matrix, which resulted in films without grain boundaries. These films exhibited better damp-heat stability than ZnO and crystalline SnO2 films deposited at higher temperature and this difference is attributed to the lack of grain boundary water diffusion. In addition, I studied CBD of Zn1-xCdxS from aqueous solutions of thiourea, ethylenediaminetetraacetic acid and zinc and cadmium sulfate. I demonstrated that films with varying composition (x) can be deposited through CBD and studied the structure and composition variation along the films' thickness. However, this traditional chemical bath deposition (CBD) approach heats the entire solution and wastes most of the chemicals by homogenous particle formation. To overcome this problem, I designed and developed a continuous-flow CBD approach to utilize the chemicals efficiently and to eliminate homogenous particle formation. Only the substrate is heated to

Magnetron sputtered zinc oxide nanorods as thickness-insensitive cathode interlayer for perovskite planar-heterojunction solar cells.

PubMed

Liang, Lusheng; Huang, Zhifeng; Cai, Longhua; Chen, Weizhong; Wang, Baozeng; Chen, Kaiwu; Bai, Hua; Tian, Qingyong; Fan, Bin

2014-12-10

Suitable electrode interfacial layers are essential to the high performance of perovskite planar heterojunction solar cells. In this letter, we report magnetron sputtered zinc oxide (ZnO) film as the cathode interlayer for methylammonium lead iodide (CH3NH3PbI3) perovskite solar cell. Scanning electron microscopy and X-ray diffraction analysis demonstrate that the sputtered ZnO films consist of c-axis aligned nanorods. The solar cells based on this ZnO cathode interlayer showed high short circuit current and power conversion efficiency. Besides, the performance of the device is insensitive to the thickness of ZnO cathode interlayer. Considering the high reliability and maturity of sputtering technique both in lab and industry, we believe that the sputtered ZnO films are promising cathode interlayers for perovskite solar cells, especially in large-scale production.

Synthesis of TiO2 NRs - ZnO Composite for Dye Sensitized Solar Cell Photoanodes

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Ramelan, A. H.; Hidayat, R.; Fadillah, G.; Munawaroh, H.; Saputri, L. N. M. Z.

2017-07-01

Composite of TiO2 NRs - ZnO were synthesized for DSSCs photoanode materials. TiO2 NRs was synthesized from TiO2 anatase by mechanochemical technique using ball milling process with agitation speed of 1000 rpm. While, the further hydrothermal refluxing process was conducted at 120°C under various concentration of NaOH in aqueous solution. The starting material of ZnO was prepared from ZnSO4.7H2O as a precursor. The hydrothermal treated TiO2 was added to the ZnO powder in a certain composition of 1:1, 1:2 and 2:1 (w/w), and the mixtures were then annealed at 400°C. The resulting material was characterized by X-ray diffraction (XRD), Surface area analyzer (SAA), Transmission electron microscopy (TEM), and Thermogravimetry/Differential thermal analysis (TG/DTA). The TiO2 revolution occurs from anatase phase into brookite phase. Rutile TiO2 phase was increasing when the NaOH was added at about 12 M. Nanograf of TEM showed the optimum condition for the formation of TiO2 NRs was obtained when 12 M NaOH was used. Structural transformation to 1D nanorods of TiO2 capable increase surface area up to 79 m2/g. TiO2 NRs-ZnO composite was prepared from TiO2 NRs and ZnO using comparation of TiO2 NRs: ZnO = 1:1, 1:2, dan 2:1. Anatase phase TiO2 as a single phase TiO2 was obtained in the TiO2-ZnO composite (1:1 w/w) upon heating the sample until 400°C. Difference TiO2 NRs-ZnO composite materials were investigated as good photovoltaic materials. Evaluation of the performance of DSSCs was conducted by I-V Keithley 2602A measurement indicate that photoanode built of TiO2 NRs - ZnO thin film has a higher solar cell efficiency than that of TiO2 thin film photoanode.

Energy Conversion: Nano Solar Cell

NASA Astrophysics Data System (ADS)

Yahaya, Muhammad; Yap, Chi Chin; Mat Salleh, Muhamad

2009-09-01

Problems of fossil-fuel-induced climate change have sparked a demand for sustainable energy supply for all sectors of economy. Most laboratories continue to search for new materials and new technique to generate clean energy at affordable cost. Nanotechnology can play a major role in solving the energy problem. The prospect for solar energy using Si-based technology is not encouraging. Si photovoltaics can produce electricity at 20-30 c//kWhr with about 25% efficiency. Nanoparticles have a strong capacity to absorb light and generate more electrons for current as discovered in the recent work of organic and dye-sensitized cell. Using cheap preparation technique such as screen-printing and self-assembly growth, organic cells shows a strong potential for commercialization. Thin Films research group at National University Malaysia has been actively involved in these areas, and in this seminar, we will present a review works on nanomaterials for solar cells and particularly on hybrid organic solar cell based on ZnO nanorod arrays. The organic layer consisting of poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEHPPV) and [6, 6]-phenyl C61-butyric acid 3-ethylthiophene ester (PCBE) was spin-coated on ZnO nanorod arrays. ZnO nanorod arrays were grown on FTO glass substrates which were pre-coated with ZnO nanoparticles using a low temperature chemical solution method. A gold electrode was used as the top contact. The device gave a short circuit current density of 2.49×10-4 mA/cm2 and an open circuit voltage of 0.45 V under illumination of a projector halogen light at 100 mW/cm2.

Organic-inorganic hybrid nanostructures for solar cell applications

NASA Astrophysics Data System (ADS)

AbdulAlmohsin, Samir M.

The enticing electro-optical properties of nanostructured materials such as carbon nanotubes, graphene, CdS nanocrystals and ZnO nanowrie bring new vigor into the innovation of photovoltaics. The main purpose of this dissertation is to develop novel nano-structured materials for low cost solar cell applications. Fabrication, characterization, and solar cell application of organic-inorganic hybrid structures are the main focus of this research. Polyaniline (PANI)/multi-walled carbon nanotube (MWNT) composite films were synthesized by an electrochemical polymerization of aniline with airbrushed MWNTs on ITO substrates. It was found that the incorporation of MWNTs in PANI effectively increase the film conductivity with a percolation threshold of 5% of nanotubes in the composite. The solar cell performance strongly depends on the conductivity of the composite films, which can be tuned by adjusting nanotube concentration. A higher conductivity resulted in a better cell performance, resulting from an efficient charge collection. This study indicates that PANI/MWNT composite films with optimized conductivity are potentially useful for low-cost hybrid solar cell applications. CdS nanocrystal-sensitized solar cells (NCSSCs) were investigated by using polyaniline (PANI) as a replacement for conventional platinum counter electrode. The growth time of the nanocrystals significantly affects the solar cell performance. At an optimum growth, the NCSSCs exhibit 0.83% of the conversion efficiency in comparison to 0.13% for the identical cells without CdS nanocrystals. Electrochemical impedance spectroscopy showed that the charge transfer in the solar cells with CdS nanocrystals was improved. The enhanced overall energy conversion efficiency by nanocrystals is attributed to improved light absorption and suppressed recombination rate of interfacial charges at the injection, resulting in significantly improved charge transfer and electron lifetime. In addition, the PANI electrodes

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

NASA Astrophysics Data System (ADS)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam'an Malik; Mohamad, Dasmawati

2015-04-01

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

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

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo

2015-04-24

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shiftedmore » of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.« less

Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

NASA Astrophysics Data System (ADS)

Ambade, Swapnil B.; Ambade, Rohan B.; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S.; Mane, Rajaram S.; Lee, Soo-Hyoung

2016-02-01

In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM

Thermal Stability-Enhanced and High-Efficiency Planar Perovskite Solar Cells with Interface Passivation.

PubMed

Zhang, Weihai; Xiong, Juan; Jiang, Li; Wang, Jianying; Mei, Tao; Wang, Xianbao; Gu, Haoshuang; Daoud, Walid A; Li, Jinhua

2017-11-08

As the electron transport layer (ETL) of perovskite solar cells, oxide semiconductor zinc oxide (ZnO) has been attracting great attention due to its relatively high mobility, optical transparency, low-temperature fabrication, and good environment stability. However, the nature of ZnO will react with the patron on methylamine, which would deteriorate the performance of cells. Although many methods, including high-temperature annealing, doping, and surface modification, have been studied to improve the efficiency and stability of perovskite solar cells with ZnO ETL, devices remain relatively low in efficiency and stability. Herein, we adopted a novel multistep annealing method to deposit a porous PbI 2 film and improved the quality and uniformity of perovskite films. The cells with ZnO ETL were fabricated at the temperature of <150 °C by solution processing. The power conversion efficiency (PCE) of the device fabricated by the novel annealing method increased from 15.5 to 17.5%. To enhance the thermal stability of CH 3 NH 3 PbI 3 (MAPbI 3 ) on the ZnO surface, a thin layer of small molecule [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) was inserted between the ZnO layer and perovskite film. Interestingly, the PCE of PCBM-passivated cells could reach nearly 19.1%. To our best knowledge, this is the highest PCE value of ZnO-based perovskite solar cells until now. More importantly, PCBM modification could effectively suppress the decomposition of MAPbI 3 and improve the thermal stability of cells. Therefore, the ZnO is a promising candidate of electron transport material for perovskite solar cells in future applications.

Ultrasonic vibration imposed on nanoparticle-based ZnO film improves the performance of the ensuing perovskite solar cell

NASA Astrophysics Data System (ADS)

Miao, Yihe; Du, Peng; Wang, Zhiyu; Chen, Qianli; Eslamian, Morteza

2018-02-01

This work focuses on the development of nearly annealing-free ZnO-based perovskite solar cells (PSCs), suitable for low-cost manufacturing of PSCs on flexible substrates. To this end, thin film of ZnO nanoparticles is employed as the electron transporting layer (ETL), because of its low-temperature solution-processability and high electron mobility. In order to remove the structural and surface defects, ultrasonic vibration is imposed on the substrate of the as-spun wet ZnO films for a short duration of 3 min. It is shown that the ultrasonic excitation bridges the ZnO nanoparticles (cold sintering), and brings about significant improvement in the ZnO film nanostructure and functionality. In addition, ethyl acetate (EA), as an emerging volatile anti-solvent, is employed to deposit the methylammonium (MA) lead halide perovskite thin film atop the ZnO ETL, in order to prepare perovskite layers that only need an annealing time of 30 s. The ZnO-based PSCs, with a simple structure and free of additional treatments, except for the ultrasonic vibration, exhibit a promising performance with a power conversion efficiency (PCE) of over 11%, 40% higher than that of the control device. The ultrasonic vibration treatment is facile, low-cost, environmentally friendly, and compatible with the scalable coating and printing techniques, such as spray and blade coating.

Fabrication of PbS quantum dots and their applications in solar cells based on ZnO nanorod arrays

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Chaudhary, Sujeet; Pandya, Dinesh K.

2018-05-01

An efficient, inexpensive and large area scalable approach based on sol-gel technique is presented to fabricate quantum dots (QDs) of PbS. Size of the QDs is tuned by the varying the bath concentrations in the range of 50-200 mM. Transmission electron microscopy (TEM) studies confirm the growth of spherically shaped ˜5.6 nm QDs at 50 mM bath concentration. The optical bandgap of the QDs is found to be ˜0.9 eV and corresponds to the size obtained from TEM studies. ZnO/PbS solar cells are fabricated by sensitizing the ZnO nanorods with PbS QDs. The fabricated solar cells demonstrate the highest open circuit voltage ˜200 mV and short circuit current density ˜0.81 µA/cm2.

Ultra-fast microwave-assisted hydrothermal synthesis of long vertically aligned ZnO nanowires for dye-sensitized solar cell application.

PubMed

Mahpeykar, S M; Koohsorkhi, J; Ghafoori-Fard, H

2012-04-27

Long vertically aligned ZnO nanowire arrays were synthesized using an ultra-fast microwave-assisted hydrothermal process. Using this method, we were able to grow ZnO nanowire arrays at an average growth rate as high as 200 nm min(-1) for maximum microwave power level. This method does not suffer from the growth stoppage problem at long growth times that, according to our investigations, a normal microwave-assisted hydrothermal method suffers from. Longitudinal growth of the nanowire arrays was investigated as a function of microwave power level and growth time using cross-sectional FESEM images of the grown arrays. Effect of seed layer on the alignment of nanowires was also studied. X-ray diffraction analysis confirmed c-axis orientation and single-phase wurtzite structure of the nanowires. J-V curves of the fabricated ZnO nanowire-based mercurochrome-sensitized solar cells indicated that the short-circuit current density is increased with increasing the length of the nanowire array. According to the UV-vis spectra of the dyes detached from the cells, these increments were mainly attributed to the enlarged internal surface area and therefore dye loading enhancement in the lengthened nanowire arrays.

CdS/CdSe quantum dot shell decorated vertical ZnO nanowire arrays by spin-coating-based SILAR for photoelectrochemical cells and quantum-dot-sensitized solar cells.

PubMed

Zhang, Ran; Luo, Qiu-Ping; Chen, Hong-Yan; Yu, Xiao-Yun; Kuang, Dai-Bin; Su, Cheng-Yong

2012-04-23

A CdS/CdSe composite shell is assembled onto the surface of ZnO nanowire arrays with a simple spin-coating-based successive ionic layer adsorption and reaction method. The as-prepared photoelectrode exhibit a high photocurrent density in photoelectrochemical cells and also generates good power conversion efficiency in quantum-dot-sensitized solar cells. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of iodine dopant amount effects on dye-sensitized hierarchically structured ZnO solar cells

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

Zheng, Yan-Zhen; Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029; Ding, Haiyang

2014-07-01

Highlights: • The effect of I amount on the photovoltaic performance was investigated. • The enhancement in η of ZnO:I DSSCs was from 38% to 77% compared with ZnO DSSCs. • Appropriate I doping enhanced light harness and inhibited charge recombination. - Abstract: We prepare a series of iodine doped zinc oxide monodisperse aggregates (ZnO:I) with various iodine concentrations as the photoanodes of dye-sensitized solar cells (DSSCs) to study iodine dopant amount-dependent photovoltaic performance. The iodine-doped DSSCs achieve overall conversion efficiency (η) of 3.6–4.6%. The enhancement in η of ZnO:I DSSCs is from 38% to 77% as compared to undopedmore » ZnO DSSCs. The significantly enhanced η of DSSCs is found to be correlated with iodine dopant amount. The optimum iodine dopant amount is determined to be 2.3 wt% by X-ray photoelectron spectroscopy. Furthermore, the incident photon to current conversion efficiency and electrochemical impedance spectroscopy data reveal a systematic correlation between photovoltaic properties and the iodine dopant amount. The enhancement of open-circuit potential of ZnO:I cells is arising from negative shift of their flat-band potential, as demonstrated by Mott–Schottky measurement.« less

Exceptionally omnidirectional broadband light harvesting scheme for multi-junction concentrator solar cells achieved via ZnO nanoneedles

NASA Astrophysics Data System (ADS)

Yeh, Li-Ko; Tian, Wei-Cheng; Lai, Kun-Yu; He-Hau, Jr.

2016-12-01

GaInP/GaAs/Ge triple-junction concentrator solar cells with significant efficiency enhancement were demonstrated with antireflective ZnO nanoneedles. The novel nanostructure was attained with a Zn(NO3)2-based solution containing vitamin C. Under one sun AM 1.5G solar spectrum, conversion efficiency of the triple-junction device was improved by 23.7% via broadband improvement in short-circuit currents of 3 sub-cells after the coverage by the nanoneedles with a graded refractive index profile. The efficiency enhancement further went up to 45.8% at 100 suns. The performance boost through the nanoneedles also became increasingly pronounced in the conditions of high incident angles and the cloudy weather, e.g. 220.0% of efficiency enhancement was observed at the incident angle of 60°. These results were attributed to the exceptional broadband omnidirectionality of the antireflective nanoneedles.

Al-/Ga-Doped ZnO Window Layers for Highly Efficient Cu₂ZnSn(S,Se)₄ Thin Film Solar Cells.

PubMed

Seo, Se Won; Seo, Jung Woo; Kim, Donghwan; Cheon, Ki-Beom; Lee, Doh-Kwon; Kim, Jin Young

2018-09-01

The successful use of Al-/Ga-doped ZnO (AGZO) thin films as a transparent conducting oxide (TCO) layer of a Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell is demonstrated. The AGZO thin films were prepared by radio frequency (RF) sputtering. The structural, crystallographic, electrical, and optical properties of the AGZO thin films were systematically investigated. The photovoltaic properties of CZTSSe thin film solar cells incorporating the AGZO-based TCO layer were also reported. It has been found that the RF power and substrate temperature of the AGZO thin film are important factors determining the electrical, optical, and structural properties. The optimization process involving the RF power and the substrate temperature leads to good electrical and optical transmittance of the AGZO thin films. Finally, the CZTSSe solar cell with the AGZO TCO layer demonstrated a high conversion efficiency of 9.68%, which is higher than that of the conventional AZO counterpart by 12%.

Nanostructured ZnO - its challenging properties and potential for device applications

NASA Astrophysics Data System (ADS)

Dimova-Malinovska, D.

2017-01-01

Nanostructured ZnO possessing interesting structural and optical properties offers challenging opportunities for innovative applications. In this lecture the review of the optical and structural properties of ZnO nanostructured layers is presented. It is shown that they have a direct impact on the parameters of devices involving ZnO. An analysis of current trends in the photovoltaic (PV) field shows that improved light harvesting and efficiency of solar cells can be obtained by implementing nanostructured ZnO layers to process advanced solar cell structures. Because of amenability to doping, high chemical stability, sensitivity to different adsorbed gases, nontoxicity and low cost ZnO attracted much attention for application as gas sensors. The sensitivity of nano-grain ZnO gas elements is comparatively high because of the grain-size effect. Application of nanostructured ZnO for gas sensors and for increasing of light harvesting in solar cells is demonstrated.

Co-sensitization of ZnO by CdS quantum dots in natural dye-sensitized solar cells with polymeric electrolytes to improve the cell stability

NASA Astrophysics Data System (ADS)

Junhom, W.; Magaraphan, R.

2015-05-01

The CdS quantum dots (QDs) were deposited on ZnO layer by chemical bath deposition method to absorb light in the shorter wavelength region and used as photoanode in the dye sensitized solar cell (DSSCs) with natural dye extracted from Noni leaves. Microstructures of CdS-ZnO from various dipping time were characterized by XRD, FE-SEM and EDX. The results showed that the CdS is hexagonal structure and the amount of CdS increases when the dipping time increases. The maximal conversion efficiency of 0.292% was achieved by the DSSCs based on CdS QDs-sensitized ZnO film obtained from 9 min-dipping time. Furthermore, the stability of DSSCs was improved by using polymeric electrolyte. Poly (acrylic acid) (PAA) and Polyacrylamide (PAM) were introduced to CdS QDs-sensitized ZnO film from 9 min-dipping time. Each polymeric electrolyte was prepared by swelling from 0.1-2.0 %w in H2O. The maximal conversion efficiency of 0.207% was achieved for DSSCs based on CdS QDs-sensitized ZnO film with PAM 1.0% and the conversion efficiency was decreased 25% when it was left for1 hr.

Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

2015-04-01

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

Full coverage of perovskite layer onto ZnO nanorods via a modified sequential two-step deposition method for efficiency enhancement in perovskite solar cells

NASA Astrophysics Data System (ADS)

Ruankham, Pipat; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Choopun, Supab; Sagawa, Takashi

2017-07-01

Full coverage of perovskite layer onto ZnO nanorod substrates with less pinholes is crucial for achieving high-efficiency perovskite solar cells. In this work, a two-step sequential deposition method is modified to achieve an appropriate property of perovskite (MAPbI3) film. Surface treatment of perovskite layer and its precursor have been systematically performed and their morphologies have been investigated. By pre-wetting of lead iodide (PbI2) and letting it dry before reacting with methylammonium iodide (MAI) provide better coverage of perovskite film onto ZnO nanorod substrate than one without any treatment. An additional MAI deposition followed with toluene drop-casting technique on the perovskite film is also found to increase the coverage and enhance the transformation of PbI2 to MAPbI3. These lead to longer charge carrier lifetime, resulting in an enhanced power conversion efficiency (PCE) from 1.21% to 3.05%. The modified method could been applied to a complex ZnO nanorods/TiO2 nanoparticles substrate. The enhancement in PCE to 3.41% is observed. These imply that our introduced method provides a simple way to obtain the full coverage and better transformation to MAPbI3 phase for enhancement in performances of perovskite solar cells.

Plasmon Enhanced Hetero-Junction Solar Cell

NASA Astrophysics Data System (ADS)

Long, Gen; Ching, Levine; Sadoqi, Mostafa; Xu, Huizhong

2015-03-01

Here we report a systematic study of plasmon-enhanced hetero-junction solar cells made of colloidal quantum dots (PbS) and nanowires (ZnO), with/without metal nanoparticles (Au). The structure of solar cell devices was characterized by AFM, SEM and profilometer, etc. The power conversion efficiencies of solar cell devices were characterized by solar simulator (OAI TriSOL, AM1.5G Class AAA). The enhancement in the photocurrent due to introduction of metal nanoparticles was obvious. We believe this is due to the plasmonic effect from the metal nanoparticles. The correlation between surface roughness, film uniformity and device performance was also studied.

Limits of ZnO Electrodeposition in Mesoporous Tin Doped Indium Oxide Films in View of Application in Dye-Sensitized Solar Cells

PubMed Central

Dunkel, Christian; von Graberg, Till; Smarsly, Bernd M.; Oekermann, Torsten; Wark, Michael

2014-01-01

Well-ordered 3D mesoporous indium tin oxide (ITO) films obtained by a templated sol-gel route are discussed as conductive porous current collectors. This paper explores the use of such films modified by electrochemical deposition of zinc oxide (ZnO) on the pore walls to improve the electron transport in dye-sensitized solar cells (DSSCs). Mesoporous ITO film were dip-coated with pore sizes of 20–25 nm and 40–45 nm employing novel poly(isobutylene)-b-poly(ethylene oxide) block copolymers as structure-directors. After electrochemical deposition of ZnO and sensitization with the indoline dye D149 the films were tested as photoanodes in DSSCs. Short ZnO deposition times led to strong back reaction of photogenerated electrons from non-covered ITO to the electrolyte. ITO films with larger pores enabled longer ZnO deposition times before pore blocking occurred, resulting in higher efficiencies, which could be further increased by using thicker ITO films consisting of five layers, but were still lower compared to nanoporous ZnO films electrodeposited on flat ITO. The major factors that currently limit the application are the still low thickness of the mesoporous ITO films, too small pore sizes and non-ideal geometries that do not allow obtaining full coverage of the ITO surface with ZnO before pore blocking occurs. PMID:28788618

Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer

NASA Astrophysics Data System (ADS)

Yang, Xiaokun; Hu, Long; Deng, Hui; Qiao, Keke; Hu, Chao; Liu, Zhiyong; Yuan, Shengjie; Khan, Jahangeer; Li, Dengbing; Tang, Jiang; Song, Haisheng; Cheng, Chun

2017-04-01

Comparing with hot researches in absorber layer, window layer has attracted less attention in PbS quantum dot solar cells (QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on. Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V oc of 18%, J sc of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.

Inverted polymer solar cell based on MEH-PPV/PC61BM coupled with ZnO nanoparticles as electron transport layer

NASA Astrophysics Data System (ADS)

Salem, A. M. S.; El-Sheikh, S. M.; Harraz, Farid A.; Ebrahim, S.; Soliman, M.; Hafez, H. S.; Ibrahim, I. A.; Abdel-Mottaleb, M. S. A.

2017-12-01

In this work, we demonstrate the use of annealed sol-gel derived ZnO nanoparticles acting as electron transport layer (ETL) in inverted bulk heterojunction (BHJ) polymer solar cells (PSCs). We have examined the photovoltaic performance of devices based on poly(2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV):(6,6)-phenyl-C61-butyric acid methyl ester (PC61BM) blend system employing the ZnO nanoparticles as an ETL with CuI as hole transport layer (HTL) in comparison to the case of using the conventional HTL of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) sulfonic acid (PEDOT:PSS). The effect of the presence of another layer of ZnO macrospheres attached to the ZnO nanoparticles is also investigated. The highest power conversion efficiency (PCE) value of 1.35% was achieved for device: ITO/ZnO nanoparticles/MEH-PPV:PC61BM/CuI/Ag, which is 275% more the value obtained when CuI was replaced by PEDOT:PSS. The comprehensive analyses on structural and optical characteristics including SEM, XRD, FTIR, PL and UV-vis spectroscopy indicated that the use of the ZnO nanoparticles alone as ETL, together with the CuI as HTL could effectively reduce trap-assisted recombination and charge accumulation at the interface, which is beneficial for the enhanced device performance.

Preparation and characterization of nanorod-like TiO2 and ZnO films used for charge-transport buffer layers in P3HT based organic solar cells

NASA Astrophysics Data System (ADS)

Thao, Tran Thi; Long, Dang Dinh; Truong, Vo-Van; Dinh, Nguyen Nang

2016-08-01

With the aim of findingout the appropriate buffer layers for organic solar cells (OSC), TiO2 and ZnO on ITO/glass were prepared as nanorod-like thin films. The TiO2 films were crystallyzed in the anatase phase and the ZnO films, in the wurtzite structure. The nanorods in both the fims have a similar size of 15 to 20 nm in diameter and 30 to 50 nm in length. The nanorods have an orientation nearly perpendicular to the ITO-substrate surface. From UV-Vis data the bandgap of the TiO2 and ZnO films were determined tobe 3.26 eV and 3.42 eV, respectively. The laminar organic solar cells with added TiO2 and ZnO, namely ITO/TiO2/P3HT:PCBM/LiF/Al (TBD) and ITO/ZnO/P3HT:PCBM/LiF/Al (ZBD)were made for characterization of the energy conversion performance. As a result, comparing to TiO2,the nanorod-likeZnO filmwas found to be a much better buffer layer that made the fill factor improve from a value of 0.60 for TBD to 0.82 for ZBD, and consequently thePCE was enhanced from 0.84 for TBD to 1.17% for ZBD.

Co-sensitization of ZnO by CdS quantum dots in natural dye-sensitized solar cells with polymeric electrolytes to improve the cell stability

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

Junhom, W.; Magaraphan, R.

2015-05-22

The CdS quantum dots (QDs) were deposited on ZnO layer by chemical bath deposition method to absorb light in the shorter wavelength region and used as photoanode in the dye sensitized solar cell (DSSCs) with natural dye extracted from Noni leaves. Microstructures of CdS-ZnO from various dipping time were characterized by XRD, FE-SEM and EDX. The results showed that the CdS is hexagonal structure and the amount of CdS increases when the dipping time increases. The maximal conversion efficiency of 0.292% was achieved by the DSSCs based on CdS QDs-sensitized ZnO film obtained from 9 min-dipping time. Furthermore, the stability ofmore » DSSCs was improved by using polymeric electrolyte. Poly (acrylic acid) (PAA) and Polyacrylamide (PAM) were introduced to CdS QDs-sensitized ZnO film from 9 min-dipping time. Each polymeric electrolyte was prepared by swelling from 0.1-2.0 %w in H2O. The maximal conversion efficiency of 0.207% was achieved for DSSCs based on CdS QDs-sensitized ZnO film with PAM 1.0% and the conversion efficiency was decreased 25% when it was left for1 hr.« less

Electrical characterization of dye sensitized nano solar cell using natural pomegranate juice as photosensitizer

NASA Astrophysics Data System (ADS)

Adithi, U.; Thomas, Sara; Uma, V.; Pradeep, N.

2013-02-01

This paper shows Electrical characterization of Dye Sensitized Solar Cell using natural dye, extracted from the pomegranate as a photo sensitizer and ZnO nanoparticles as semiconductor. The constituents of fabricated dye sensitized solar cell were working electrode, dye, electrolyte and counter electrode. ZnO nanoparticles were synthesized and used as semiconductor in working electrode. Carbon soot was used as counter electrode. The resistance of ZnO film on ITO film was found out. There was an increase in the resistance of the film and film changes from conducting to semiconducting. Photovoltaic parameters of the fabricated cell like Short circuit current, open circuit voltage, Fill factor and Efficiency were found out. This paper shows that usage of natural dyes like pomegranate juice as sensitizer enables faster and simpler production of cheaper and environmental friendly solar cell.

The result of synthesis analysis of the powder TiO{sub 2}/ZnO as a layer of electrodes for dye sensitized solar cell applications

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

Retnaningsih, Lilis, E-mail: lilisretna@gmail.com; Muliani, Lia

2016-04-19

This study has been conducted synthesis of TiO{sub 2} nanoparticle powders and ZnO nanoparticle powder into a paste to be in this research, dye-sensitive solar cells (DSSC) was produced by TiO{sub 2} nanopowder and ZnO nanopowder synthesis to make paste that is applied as electrode. This electrode works based on photon absorbed by dye and transferred to different composition of TiO{sub 2}/ ZnO particle. Properties of DSSC are affected by fabrication method, parameter and dimension of TiO{sub 2} / ZnO nanoparticles, technique and composition of TiO{sub 2} / ZnO paste preparation is important to get the higher performance of DSSC.more » Doctor blade is a method for electrode coating on glass substrate. The electrode was immersed into dye solution of Z907 and ethanol. From the experiment, the effect of TiO{sub 2} and ZnO nanopowder mixture for electrode was investigated. XRD characterization show anatase and rutile phase, which sintered TiO{sub 2}/ZnO has intensity more than 11,000. SEM characterization shows the composition of 20% TiO{sub 2} / 80% ZnO has better porosity. Higher efficiency that is investigated by I-V measurement using Sun Simulator.« less

Decreased Charge Transport Barrier and Recombination of Organic Solar Cells by Constructing Interfacial Nanojunction with Annealing-Free ZnO and Al Layers.

PubMed

Liu, Chunyu; Zhang, Dezhong; Li, Zhiqi; Zhang, Xinyuan; Guo, Wenbin; Zhang, Liu; Ruan, Shengping; Long, Yongbing

2017-07-05

To overcome drawbacks of the electron transport layer, such as complex surface defects and unmatched energy levels, we successfully employed a smart semiconductor-metal interfacial nanojunciton in organic solar cells by evaporating an ultrathin Al interlayer onto annealing-free ZnO electron transport layer, resulting in a high fill factor of 73.68% and power conversion efficiency of 9.81%. The construction of ZnO-Al nanojunction could effectively fill the surface defects of ZnO and reduce its work function because of the electron transfer from Al to ZnO by Fermi level equilibrium. The filling of surface defects decreased the interfacial carrier recombination in midgap trap states. The reduced surface work function of ZnO-Al remodulated the interfacial characteristics between ZnO and [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM), decreasing or even eliminating the interfacial barrier against the electron transport, which is beneficial to improve the electron extraction capacity. The filled surface defects and reduced interfacial barrier were realistically observed by photoluminescence measurements of ZnO film and the performance of electron injection devices, respectively. This work provides a simple and effective method to simultaneously solve the problems of surface defects and unmatched energy level for the annealing-free ZnO or other metal oxide semiconductors, paving a way for the future popularization in photovoltaic devices.

Hybrid nanostructure heterojunction solar cells fabricated using vertically aligned ZnO nanotubes grown on reduced graphene oxide.

PubMed

Yang, Kaikun; Xu, Congkang; Huang, Liwei; Zou, Lianfeng; Wang, Howard

2011-10-07

Using reduced graphene oxide (rGO) films as the transparent conductive coating, inorganic/organic hybrid nanostructure heterojunction photovoltaic devices have been fabricated through hydrothermal synthesis of vertically aligned ZnO nanorods (ZnO-NRs) and nanotubes (ZnO-NTs) on rGO films followed by the spin casting of a poly(3-hexylthiophene) (P3HT) film. The data show that larger interfacial area in ZnO-NT/P3HT composites improves the exciton dissociation and the higher electrode conductance of rGO films helps the power output. This study offers an alternative to manufacturing nanostructure heterojunction solar cells at low temperatures using potentially low cost materials.

Zinc Oxide Grown by CVD Process as Transparent Contact for Thin Film Solar Cell Applications

NASA Astrophysics Data System (ADS)

Faÿ, S.; Shah, A.

Metalorganic chemical vapor deposition of ZnO films (MOCVD) [1] started to be comprehensively investigated in the 1980s, when thin film industries were looking for ZnO deposition processes especially useful for large-scale coatings at high growth rates. Later on, when TCO for thin film solar cells started to be developed, another advantage of growing TCO films by the CVD process has been highlighted: the surface roughness. Indeed, a large number of studies on CVD ZnO revealed that an as-grown rough surface cn be obtained with this deposition process [2-4]. A rough surface induces a light scattering effect, which can significantly improve light trapping (and therefore current photo-generation) within thin film silicon solar cells. The CVD process, indeed, directly leads to as-grown rough ZnO films without any post-etching step (the latter is often introduced to obtain a rough surface, when working with as-deposited flat sputtered ZnO). This fact could turn out to be a significant advantage when upscaling the manufacturing process for actual commercial production of thin film solar modules. The zinc and oxygen sources for CVD growth of ZnO films are given in Table 6.1.

Development of n-ZnO/p-Si single heterojunction solar cell with and without interfacial layer

NASA Astrophysics Data System (ADS)

Hussain, Babar

The conversion efficiency of conventional silicon (Si) photovoltaic cells has not been improved significantly during last two decades but their cost decreased dramatically during this time. However, the higher price-per-watt of solar cells is still the main bottleneck in their widespread use for power generation. Therefore, new materials need to be explored for the fabrication of solar cells potentially with lower cost and higher efficiency. The n-type zinc oxide (n-ZnO) and p-type Si (p-Si) based single heterojunction solar cell (SHJSC) is one of the several attempts to replace conventional Si single homojunction solar cell technology. There are three inadequacies in the literature related to n-ZnO/p-Si SHJSC: (1) a detailed theoretical analysis to evaluate potential of the solar cell structure, (2) inconsistencies in the reported value of open circuit voltage (VOC) of the solar cell, and (3) lower value of experimentally achieved VOC as compared to theoretical prediction based on band-bending between n-ZnO and p-Si. Furthermore, the scientific community lacks consensus on the optimum growth parameters of ZnO. In this dissertation, I present simulation and experimental results related to n-ZnO/p-Si SHJSC to fill the gaps mentioned above. Modeling and simulation of the solar cell structure are performed using PC1D and AFORS-HET software taking practical constraints into account to explore the potential of the structure. Also, unnoticed benefits of ZnO in solar cells such as an additional antireflection (AR) effect and low temperature deposition are highlighted. The growth parameters of ZnO using metal organic chemical vapor deposition and sputtering are optimized. The structural, optical, and electrical characterization of ZnO thin films grown on sapphire and Si substrates is performed. Several n-ZnO/p-Si SHJSC devices are fabricated to confirm the repeatability of the VOC. Moreover, the AR effect of ZnO while working as an n-type layer is experimentally verified

ZnO Photoanode Effect on the Efficiency Performance of Organic Based Dye Sensitized Solar Cell

NASA Astrophysics Data System (ADS)

Mohamad, I. S.; Ismail, S. S.; Norizan, M. N.; Murad, S. A. Z.; Abdullah, M. M. A.

2017-06-01

Dye sensitized solar cell has been emerged as one of the most promising candidates for photovoltaics applications in good quality of their low manufacturing cost and impressive conversion energy. Titanium dioxide (TiO2) which is used as photoanode in the market has the advantage of wide bandgap energy but low in electron mobility (∼10 cm2/(V.s)). Ruthenium in the other hand, as the dye sensitizer is a rare noble metal and harmful to human health. Thus, this article reveals the performance of photo-to-electric conversion efficiency with the usage of Zinc Oxide as photoanode with higher electron mobility (155 cm2/(V.s)) compared to TiO2 utilizing three natural fruit dyes of Prunus domestica, Magnifera indica and Citrus limon. ZnO and TiO2 photoanodes were fabricated using sol gel and dr blade method respectively. The morphology of the photoanodes were characterized using Scanning Electron Microscope and the efficiency of the complete DSSC with all different fruit dyes were characterized using Semiconductor Parametric Analyzer. The different property of electron mobility photoanodes effect in DSSC proved to give better performance with the photoconversion efficiency of 3.082% using ZnO with Prunus domestica dye. This article also reveals that pH indicator does not affect the selection and the performance of DSSC.

Microwave-assisted synthesis of C-doped TiO2 and ZnO hybrid nanostructured materials as quantum-dots sensitized solar cells

NASA Astrophysics Data System (ADS)

Rangel-Mendez, Jose R.; Matos, Juan; Cházaro-Ruiz, Luis F.; González-Castillo, Ana C.; Barrios-Yáñez, Guillermo

2018-03-01

The microwave-assisted solvothermal synthesis of C-doped TiO2 and ZnO hybrid materials was performed. Saccharose, titanium isopropoxide and zinc acetate were used as organic and inorganic sources for the synthesis. The influence of temperature and reaction time on the textural and optoelectronic properties of the hybrid materials was verified. Carbon quantum-dots of TiO2 and ZnO nanostructured spheres were obtained in a second pot by controlled calcination steps of the precursor hybrid materials. A carefully characterization by adsorption-desorption N2 isotherms, XRD, XPS, SEM, UV-vis/DR and electro- and photo-electrochemistry properties of the carbon quantum-dots TiO2 and ZnO spheres was performed. The photoelectrochemical activity of TiO2-C and ZnO-C films proved to be dependent on the conditions of synthesis. It was found a red-shift in the energy band gap of the semiconductors with values of 3.02 eV and 3.13 eV for the TiO2-C and ZnO-C, respectively, clearly lower than those on bare semiconductors, which is associated with the C-doping effect. From the photo-electrochemistry characterization of C-doped TiO2 and ZnO films can be concluded that the present materials have potential applications as photoelectrodes for quantum-dots sensitized solar cells.

Efficient Solar-Induced Photoelectrochemical Response Using Coupling Semiconductor TiO2-ZnO Nanorod Film

PubMed Central

Abd Samad, Nur Azimah; Lai, Chin Wei; Lau, Kung Shiuh; Abd Hamid, Sharifah Bee

2016-01-01

Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl2 and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO2 into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO2 loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm2 (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm2 (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3–4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination. PMID:28774068

Numerical modelling of CIGS/CdS solar cell

NASA Astrophysics Data System (ADS)

Devi, Nisha; Aziz, Anver; Datta, Shouvik

2018-05-01

In this work, we design and analyze the Cu(In,Ga)Se2 (CIGS) solar cell using simulation software "Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D)". The conventional CIGS solar cell uses various layers, like intrinsic ZnO/Aluminium doped ZnO as transparent oxide, antireflection layer MgF2, and electron back reflection (EBR) layer at CIGS/Mo interface for good power conversion efficiency. We replace this conventional model by a simple model which is easy to fabricate and also reduces the cost of this cell because of use of lesser materials. The new designed model of CIGS solar cell is ITO/CIGS/OVC/CdS/Metal contact, where OVC is ordered vacancy compound. From this simple structure, even at very low illumination we are getting good results. We simulate this CIGS solar cell model by varying various physical parameters of CIGS like thickness, carrier density, band gap and temperature.

Enhancement of Energy Conversion Efficiency for Dye Sensitized Solar Cell Using Zinc Oxide Photoanode

NASA Astrophysics Data System (ADS)

Jamalullail, N.; Smohamad, I.; Nnorizan, M.; Mahmed, N.

2018-06-01

Dye sensitized solar cell (DSSC) is a third generation solar cell that is well known for its low cost, simple fabrication process and promised reasonable energy conversion efficiency. Basic structure of DSSC is composed of photoanode, dye sensitizer, electrolyte that is sandwiched together in between two transparent conductive oxide (TCO) glasses. Each of the components in the DSSC contributes important role that affect the energy conversion efficiency. In this research, the commonly used titanium dioxide (TiO2) photoanode has previously reported to have high recombination rate and low electron mobility which caused efficiency loss had been compared with the zinc oxide (ZnO) photoanode with high electron mobility (155 cm2V-1s-1). Both of these photoanodes had been deposited through doctor blade technique. The electrical performance of the laboratory based DSSCs were tested using solar cell simulator and demonstrated that ZnO is a better photoanode compared to TiO2 with the energy conversion efficiency of 0.34% and 0.29% respectively. Nanorods shape morphology was observed in ZnO photoanode with average particle size of 41.60 nm and average crystallite size of 19.13 nm. This research proved that the energy conversion efficiency of conventional TiO2 based photoanode can be improved using ZnO material.

Simulation approach for optimization of ZnO/c-WSe{}_{2} heterojunction solar cells

NASA Astrophysics Data System (ADS)

Huang, Shihua; Li, Qiannan; Chi, Dan; Meng, Xiuqing; He, Lü

2017-04-01

Taking into account defect density in WSe{}2, interface recombination between ZnO and WSe{}2, we presented a simulation study of ZnO/crystalline WSe{}2 heterojunction (HJ) solar cell using wxAMPS simulation software. The optimal conversion efficiency 39.07% for n-ZnO/p-c-WSe{}2 HJ solar cell can be realized without considering the impact of defects. High defect density (> 1.0× {10}11 cm{}-2) in c-WSe{}2 and large trap cross-section (> 1.0 × 10{}-10 cm{}2) have serious impact on solar cell efficiency. A thin p-WSe{}2 layer is intentionally inserted between ZnO layer and c-WSe{}2 to investigate the effect of the interface recombination. The interface properties are very crucial to the performance of ZnO/c-WSe{}2HJ solar cell. The affinity of ZnO value range between 3.7-4.5 eV gives the best conversion efficiency. Project supported by the Natural Science Foundation of Zhejiang Province (No. LY17F040001), the Open Project Program of Surface Physics Laboratory (National Key Laboratory) of Fudan University (No. KF2015_02), the Open Project Program of National Laboratory for Infrared Physics, Chinese Academy of Sciences (No. M201503), the Zhejiang Provincial Science and Technology Key Innovation Team (No. 2011R50012), and the Zhejiang Provincial Key Laboratory (No. 2013E10022).

Printable CIGS thin film solar cells

NASA Astrophysics Data System (ADS)

Fan, Xiaojuan

2014-03-01

Among the various thin film solar cells in the market, CuInGaSe thin film cells have been considered as the most promising alternatives to silicon solar cells because of their high photo-electricity efficiency, reliability, and stability. However, many fabrication of CIGS thin film are based on vacuum processes such as evaporation sputtering techniques which are not cost efficient. This work develops a method using paste or ink liquid spin-coated on glass that would be to conventional ways in terms of cost effective, non-vacuum needed, quick processing. A mixture precursor was prepared by dissolving appropriate amounts of chemicals. After the mixture solution was cooled, a viscous paste prepared and ready for spin-coating process. A slight bluish CIG thin film substrate was then put in a tube furnace with evaporation of metal Se by depositing CdS layer and ZnO nanoparticle thin film coating to a solar cell fabrication. Structure, absorption spectrum, and photo-conversion efficiency for the as-grown CIGS thin film solar cell under study.

Preparation of Zinc Oxide (ZnO) Thin Film as Transparent Conductive Oxide (TCO) from Zinc Complex Compound on Thin Film Solar Cells: A Study of O2 Effect on Annealing Process

NASA Astrophysics Data System (ADS)

Muslih, E. Y.; Kim, K. H.

2017-07-01

Zinc oxide (ZnO) thin film as a transparent conductive oxide (TCO) for thin film solar cell application was successfully prepared through two step preparations which consisted of deposition by spin coating at 2000 rpm for 10 second and followed by annealing at 500 °C for 2 hours under O2 and ambient atmosphere. Zinc acetate dehydrate was used as a precursor which dissolved in ethanol and acetone (1:1 mol) mixture in order to make a zinc complex compound. In this work, we reported the O2 effect, reaction mechanism, structure, morphology, optical and electrical properties. ZnO thin film in this work shows a single phase of wurtzite, with n-type semiconductor and has band gap, carrier concentration, mobility, and resistivity as 3.18 eV, 1.21 × 10-19cm3, 11 cm2/Vs, 2.35 × 10-3 Ωcm respectively which is suitable for TCO at thin film solar cell.

Theoretical study of electronic transfer current rate at dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

AL-Agealy, Hadi J. M.; AlMaadhede, Taif Saad; Hassooni, Mohsin A.; Sadoon, Abbas K.; Ashweik, Ahmed M.; Mahdi, Hind Abdlmajeed; Ghadhban, Rawnaq Qays

2018-05-01

In this research, we present a theoretical study of electronic transfer kinetics rate in N719/TiO2 and N719/ZnO dye-sensitized solar cells (DSSC) systems using a simple model depending on the postulate of quantum mechanics theory. The evaluation of the electronic transition current rate in DSSC systems are function of many parameters such that; the reorientation transition energies ΛSe m D y e , the transition coupling parameter ℂT(0), potential exponential effect e-(E/C-EF ) kBT , unit cell volume VSem, and temperature T. Furthermore, the analysis of electronic transfer current rate in N719/TiO2 and N719/ZnO systems show that the rate upon dye-sensitization solar cell increases with increases of transition coupling parameter, decreasing potential that building at interface a results of different material in this devices and increasing with reorientation transition energy. On the other hand, we can find the electronic transfer behavior is dependent of the dye absorption spectrum and mainly depending on the reorientation of transition energy. The replacement of the solvents in both DSSC system caused increasing of current rates dramatically depending on polarity of solvent in subset devices. This change in current rate of electron transfer were attributed to much more available of recombination sites introduced by the solvents medium. The electronic transfer current dynamics are shown to occurs in N719/TiO2 system faster many time compare to ocuures at N719/ZnO system, this indicate that TiO2 a is a good and active material compare with ZnO to using in dye sensitized solar cell devices. In contrast, the large current rate in N719/TiO2 comparing to ZnO of N719/ZnO systems indicate that using TiO2 with N719 dye lead to increasing the efficiency of DSSC.

Enhancement of photovoltaic performance of flexible perovskite solar cells by means of ionic liquid interface modification in a low temperature all solution process

NASA Astrophysics Data System (ADS)

Chu, Weijing; Yang, Junyou; Jiang, Qinghui; Li, Xin; Xin, Jiwu

2018-05-01

The quality of interface between the electron transport layer (ETL) and perovskite is very crucial to the photovoltaic performance of a flexible perovskite solar cell fabricated under low-temperature process. This work demonstrates a room temperature ionic liquid modification strategy to the interface between ZnO layer and MAPbI3 film for high performance flexible perovskite solar cells based on a PET substrate. [BMIM]BF4 ionic liquid modification can significantly improve the surface quality and wettability of the ZnO ETL, thus greatly increase the charge mobility of ZnO ETL and improve the crystalline of perovskite film based on it. Moreover, the dipolar polarization layer among the ZnO ETL with perovskite, built by modification, can adjust the energy level between the ZnO ETL and perovskite and facilitates the charge extraction. Therefore, an overall power conversion efficiency (PCE) of 12.1% have been achieved under standard illumination, it increases by 1.4 times of the flexible perovskite solar cells on a pristine ZnO ETL.

Disinfection of Multidrug Resistant Escherichia coli by Solar-Photocatalysis using Fe-doped ZnO Nanoparticles.

PubMed

Das, Sourav; Sinha, Sayantan; Das, Bhaskar; Jayabalan, R; Suar, Mrutyunjay; Mishra, Amrita; Tamhankar, Ashok J; Stålsby Lundborg, Cecilia; Tripathy, Suraj K

2017-03-07

Spread of antibiotic resistant bacteria through water, is a threat to global public health. Here, we report Fe-doped ZnO nanoparticles (Fe/ZnO NPs) based solar-photocatalytic disinfection (PCD) of multidrug resistant Escherichia coli (MDR E. coli). Fe/ZnO NPs were synthesized by chemical precipitation technique, and when used as photocatalyst for disinfection, proved to be more effective (time for complete disinfection = 90 min) than ZnO (150 min) and TiO 2 (180 min). Lipid peroxidation and potassium (K + ) ion leakage studies indicated compromisation of bacterial cell membrane and electron microscopy and live-dead staining confirmed the detrimental effects on membrane integrity. Investigations indicated that H 2 O 2 was the key species involved in solar-PCD of MDR E. coli by Fe/ZnO NPs. X-ray diffraction and atomic absorption spectroscopy studies showed that the Fe/ZnO NPs system remained stable during the photocatalytic process. The Fe/ZnO NPs based solar-PCD process proved successful in the disinfection of MDR E. coli in real water samples collected from river, pond and municipal tap. The Fe/ZnO NPs catalyst made from low cost materials and with high efficacy under solar light may have potential for real world applications, to help reduce the spread of resistant bacteria.

Understanding the role of silica nanospheres with their light scattering and energy barrier properties in enhancing the photovoltaic performance of ZnO based solar cells.

PubMed

Banik, Avishek; Ansari, Mohammad Shaad; Sahu, Tushar Kanta; Qureshi, Mohammad

2016-10-12

The present study discusses the design and development of a dye sensitized solar cell (DSSC) using a hybrid composite of ZnO nanoparticles (ZnO NP) and silica nanospheres (SiO 2 NS). A ≈22% enhancement in the overall power conversion efficiency (PCE, η) was observed for the device fabricated with a binary hybrid composite of 1 wt% SiO 2 NS and ZnO NP compared to the pristine ZnO NP device. A systematic investigation revealed the dual function of the silica nanospheres in enhancing the device efficacy compared to the bare ZnO NP based device. Sub-micron sized SiO 2 NS can boost the light harvesting efficiency of the photoanode by optical confinement, resulting in increased propagation length of the incident light by multiple internal reflections, which was confirmed by UV-Vis diffused reflectance spectroscopy. Electrochemical impedance spectroscopic (EIS) analysis showed a reduced recombination of photo-generated electrons to the I - /I 3 - redox shuttle in the case of the composite photoanode. The higher recombination resistance (R ct ) in the case of a 1 wt% composite indicates that the SiO 2 NS serves as a partial energy barrier layer to retard the interfacial recombination (back transfer) of photo-generated electrons at the working electrode/electrolyte interface, increasing the device efficiency.

Natural dye extracted from karkadah and its application in dye-sensitized solar cells: experimental and density functional theory study.

PubMed

Reda, S M; Soliman, K A

2016-02-01

This work presents an experimental and theoretical study of cyanidin natural dye as a sensitizer for ZnO dye-sensitized solar cells. ZnO nanoparticles were prepared using ammonia and oxalic acid as a capping agent. The calculated average size of the synthesized ZnO with different capping agents was found to be 32.1 nm. Electronic properties of cyanidin and delphinidin dye were studied using density functional theory (DFT) and time-dependent DFT with a B3LYP/6-31G(d,p) level. By comparing the theoretical results with the experimental data, the cyanidin dye can be used as a sensitizer in dye-sensitized solar cells. An efficiency of 0.006% under an AM-1.5 illumination at 100  mW/cm(2) was attained. The influence of dye adsorption time on the solar cell performance is discussed.

Enhanced photovoltaic performance utilizing effective charge transfers and light scattering effects by the combination of mesoporous, hollow 3D-ZnO along with 1D-ZnO in CdS quantum dot sensitized solar cells.

PubMed

Chetia, Tridip Ranjan; Barpuzary, Dipankar; Qureshi, Mohammad

2014-05-28

A combination of 3-dimensional (3D) hollow mesoporous ZnO microspheres (ZnO HMSP) and vertically grown one-dimensional ZnO nanowires (1D ZnO NWs) on a fluorine doped tin oxide (FTO) coated glass substrate has been investigated as a photoanode for a CdS quantum dot-sensitized solar cell (QSSC). A comparative study of the photovoltaic performance of the solar cell with devices fabricated with pristine ZnO HMSPs and ZnO NWs was carried out. The proposed photovoltaic device exhibits an enhancement in power conversion efficiency (PCE) upto ∼74% and ∼35%, as compared to the 1D ZnO NW and ZnO HMSP based solar cells. The maximum incident photon-to-current conversion efficiency (IPCE) for the solar cell was observed to be ∼40%, whereas for the devices fabricated with bare ZnO HMSP and ZnO NW the IPCE were only ∼32% and ∼19%, respectively. The enhanced photovoltaic performance of the solar cell is attributed to the high Brunauer-Emmett-Teller (BET) surface area, efficient light-scattering effects and facilitated diffusion of the electrolyte for better functioning of the redox couple (S(2-)/Sn(2-)) in the hybrid photoanode. Moreover, a faster electron transport through 1D ZnO NWs provides better charge collection from the photoactive layer, which leads to an increase in the short circuit current density of the device. The present study highlights the design and development of a new hybrid photoanode for solar harvesting.

Chemically Deposited Thin-Film Solar Cell Materials

NASA Technical Reports Server (NTRS)

Raffaelle, R.; Junek, W.; Gorse, J.; Thompson, T.; Harris, J.; Hehemann, D.; Hepp, A.; Rybicki, G.

2005-01-01

We have been working on the development of thin film photovoltaic solar cell materials that can be produced entirely by wet chemical methods on low-cost flexible substrates. P-type copper indium diselenide (CIS) absorber layers have been deposited via electrochemical deposition. Similar techniques have also allowed us to incorporate both Ga and S into the CIS structure, in order to increase its optical bandgap. The ability to deposit similar absorber layers with a variety of bandgaps is essential to our efforts to develop a multi-junction thin-film solar cell. Chemical bath deposition methods were used to deposit a cadmium sulfide (CdS) buffer layers on our CIS-based absorber layers. Window contacts were made to these CdS/CIS junctions by the electrodeposition of zinc oxide (ZnO). Structural and elemental determinations of the individual ZnO, CdS and CIS-based films via transmission spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy and energy dispersive spectroscopy will be presented. The electrical characterization of the resulting devices will be discussed.

Low resistivity ZnO-GO electron transport layer based CH{sub 3}NH{sub 3}PbI{sub 3} solar cells

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

Ahmed, Muhammad Imran, E-mail: imranrahbar@scme.nust.edu.pk, E-mail: amirhabib@scme.nust.edu.pk; Hussain, Zakir; Mujahid, Mohammad

Perovskite based solar cells have demonstrated impressive performances. Controlled environment synthesis and expensive hole transport material impede their potential commercialization. We report ambient air synthesis of hole transport layer free devices using ZnO-GO as electron selective contacts. Solar cells fabricated with hole transport layer free architecture under ambient air conditions with ZnO as electron selective contact achieved an efficiency of 3.02%. We have demonstrated that by incorporating GO in ZnO matrix, low resistivity electron selective contacts, critical to improve the performance, can be achieved. We could achieve max efficiency of 4.52% with our completed devices for ZnO: GO composite. Impedancemore » spectroscopy confirmed the decrease in series resistance and an increase in recombination resistance with inclusion of GO in ZnO matrix. Effect of temperature on completed devices was investigated by recording impedance spectra at 40 and 60 {sup o}C, providing indirect evidence of the performance of solar cells at elevated temperatures.« less

Solution-Processed Small-Molecule Bulk Heterojunctions: Leakage Currents and the Dewetting Issue for Inverted Solar Cells.

PubMed

Destouesse, Elodie; Chambon, Sylvain; Courtel, Stéphanie; Hirsch, Lionel; Wantz, Guillaume

2015-11-11

In organic photovoltaic (PV) devices based on solution-processed small molecules, we report here that the physicochemical properties of the substrate are critical for achieving high-performances organic solar cells. Three different substrates were tested: ITO coated with PSS, ZnO sol-gel, and ZnO nanoparticles. PV performances are found to be low when the ZnO nanoparticles layer is used. This performance loss is attributed to the formation of many dewetting points in the active layer, because of a relatively high roughness of the ZnO nanoparticles layer, compared to the other layers. We successfully circumvented this phenomenon by adding a small quantity of polystyrene (PS) in the active layer. The introduction of PS improves the quality of film forming and reduces the dark currents of solar cells. Using this method, high-efficiency devices were achieved, even in the case of substrates with higher roughness.

Fe-tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs

NASA Astrophysics Data System (ADS)

Çakar, Soner; Özacar, Mahmut

2016-06-01

In this paper we have synthesized different morphological ZnO nanostructures via microwave hydrothermal methods at low temperature within a short time. We described different morphologies of ZnO at different Zn(NO3)2/KOH mole ratio. The ZnO nanostructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry. All ZnO structures have hexagonal wurtzite type structures. The FESEM images showed various morphologies of ZnO such as plate, rod and nanoparticles. Dye sensitized solar cells have been assembled by these different morphological structures photo electrode and tannic acid or Fe-tannic acid complex dye as sensitizer. We have achieved at maximum efficiencies of photovoltaic cells prepared with ZnO plate in all dye systems. The conversion efficiencies of dye sensitized solar cells are 0.37% and 1.00% with tannic acid and Fe-tannic acid complex dye, respectively.

Synthesis and Characterization of ZnO/polymer planar heterojunction solar cells

NASA Astrophysics Data System (ADS)

Gutierrez, Leandro; Manners, William; Nabizadeh, Arya; Albers, Patrick; Duran, Jesus; Scudieri, Anthony; Isah, Anne; McDougall, Michael; Sahiner, Mehmet; Wang, Weining

2014-03-01

ZnO/polymer heterojunction has been studied by many groups for its potential application in solar cell, LED, UV photodetection and other applications. However, there are few studies on ZnO/polymer heterojunction by synthesizing ZnO using pulsed laser deposition (PLD). Comparing with other methods, PLD has the advantage of congruent evaporation, and being able to grow high quality thin films at relatively low temperature. In our previous work in pulsed-laser-deposited (PLD) ZnO/PEDOT:PSS heterojunction, correlations between the annealing conditions of pulsed laser deposition and the electrical performance of solar cells have been observed. In this work, we report two new studies: 1) Studies on how the performance of the PLD-ZnO /PEDOT:PSS heterojunction depends on polymer conductivity; 2) Comparison studies on PLD-ZnO/PEDOT:PSS and PLD-ZnO/P3HT heterojunction. We studied how the performance of ZnO/polymer solar cells depend on the polymer work function and conductivities and deposition condition of ZnO. X-ray diffraction (XRD) and scanning electron microscopy were used to characterize the PLD-ZnO film. The correlation between the solar cell electrical performance and the polymer conductivity and pulsed laser deposition conditions will be discussed.

Comprehensive Study of Sol-Gel versus Hydrolysis-Condensation Methods To Prepare ZnO Films: Electron Transport Layers in Perovskite Solar Cells.

PubMed

Zhao, Yu-Han; Zhang, Kai-Cheng; Wang, Zhao-Wei; Huang, Peng; Zhu, Kai; Li, Zhen-Dong; Li, Da-Hua; Yuan, Li-Gang; Zhou, Yi; Song, Bo

2017-08-09

Owing to the high charge mobility and low processing temperature, ZnO is regarded as an ideal candidate for electron transport layer (ETL) material in thin-film solar cells. For the film preparation, the presently dominated sol-gel (SG) and hydrolysis-condensation (HC) methods show great potential; however, the effect of these two methods on the performance of the resulting devices has not been investigated in the same frame. In this study, the ZnO films made through SG and HC methods were applied in perovskite solar cells (Pero-SCs), and the performances of corresponding devices were compared under parallel conditions. We found that the surface morphologies and the conductivities of the films prepared by SG and HC methods showed great differences. The HC-ZnO films with higher conductivity led to relatively higher device performance, and the best power conversion efficiencie (PCE) of 12.9% was obtained; meanwhile, for Pero-SCs based on SG-ZnO, the best PCE achieved was 10.9%. The better device performance of Pero-SCs based on HC-ZnO should be attributed to the better charge extraction and transportation ability of HC-ZnO film. Moreover, to further enhance the performance of Pero-SCs, a thin layer of pristine C 60 was introduced between HC-ZnO and perovskite layers. By doing so, the quality of perovskite films was improved, and the PCE was elevated to 14.1%. The preparation of HC-ZnO film involves relatively lower-temperature (maximum 100 °C) processing; the films showed better charge extraction and transportation properties and can be a more promising ETL material in Pero-SCs.

Research on ZnO/Si heterojunction solar cells

NASA Astrophysics Data System (ADS)

Chen, Li; Chen, Xinliang; Liu, Yiming; Zhao, Ying; Zhang, Xiaodan

2017-06-01

We put forward an n-ZnO/p-Si heterojunction solar cell model based on AFORS-HET simulations and provide experimental support in this article. ZnO:B (B-doped ZnO) thin films deposited by metal-organic chemical vapor deposition (MOCVD) are planned to act as electrical emitter layer on p-type c-Si substrate for photovoltaic applications. We investigate the effects of thickness, buffer layer, ZnO:B affinity and work function of electrodes on performances of solar cells through computer simulations using AFORS-HET software package. The energy conversion efficiency of the ZnO:B(n)/ZnO/c-Si(p) solar cell can achieve 17.16% ({V}{oc}: 675.8 mV, {J}{sc}: 30.24 mA/cm2, FF: 83.96%) via simulation. On a basis of optimized conditions in simulation, we carry out some experiments, which testify that the ZnO buffer layer of 20 nm contributes to improving performances of solar cells. The influences of growth temperature, thickness and diborane (B2H6) flow rates are also discussed. We achieve an appropriate condition for the fabrication of the solar cells using the MOCVD technique. The obtained conversion efficiency reaches 2.82% ({V}{oc}: 294.4 mV, {J}{sc}: 26.108 mA/cm2, FF: 36.66%). Project supported by the State Key Development Program for Basic Research of China (Nos. 2011CBA00706, 2011CBA00707), the Tianjin Applied Basic Research Project and Cutting-Edge Technology Research Plan (No. 13JCZDJC26900), the Tianjin Major Science and Technology Support Project (No. 11TXSYGX22100), the National High Technology Research and Development Program of China (No. 2013AA050302), and the Fundamental Research Funds for the Central Universities (No. 65010341).

Efficiency enhancement of ZnO nanostructure assisted Si solar cell based on fill factor enlargement and UV-blue spectral down-shifting

NASA Astrophysics Data System (ADS)

Gholizadeh, A.; Reyhani, A.; Parvin, P.; Mortazavi, S. Z.

2017-05-01

ZnO nanostructures (including nano-plates and nano-rods (NRs)) are grown in various temperatures and Ar/O2 flow rates using thermal chemical vapor deposition, which affect the structure, nano-plate/NR population, and the quality of ZnO nanostructures. X-ray diffraction (XRD) attests that the peak intensity of the crystallographic plane (1 0 0) is correlated to nano-plate abundance. Moreover, optical properties elucidate that the population of nano-plates in samples strongly affect the band gap, binding energy of the exciton, and UV-visible (UV-vis) absorption and spectral luminescence emissions. In fact, the exciton binding energy reduces from ~100 to 80 meV when the population of nano-plates increases in samples. Photovoltaic characteristics based on the drop-casting on Si solar cells reveals three dominant factors, namely, the equivalent series resistance, decreasing reflectance, and down-shifting, in order to scale up the absolute efficiency by 3%. As a consequence, the oxygen vacancies in ZnO nanostructures give rise to the down-shifting and increase of free-carriers, leading to a reduction in the equivalent series resistance and an enlargement of fill factor. To obtain a larger I sc, reduction of spectral reflectance is essential; however, the down-shifting process is shown to be dominant by lessening the surface electron-hole recombination rate over the UV-blue spectral range.

Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Gur, Emre; Kocak, Yusuf

2018-01-01

Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires' layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm2 under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%) . The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.

Enhancing the Durability and Carrier Selectivity of Perovskite Solar Cells Using a Blend Interlayer.

PubMed

Sin, Dong Hun; Jo, Sae Byeok; Lee, Seung Goo; Ko, Hyomin; Kim, Min; Lee, Hansol; Cho, Kilwon

2017-05-31

A mechanically and thermally stable and electron-selective ZnO/CH 3 NH 3 PbI 3 interface is created via hybridization of a polar insulating polymer, poly(ethylene glycol) (PEG), into ZnO nanoparticles (NPs). PEG successfully passivates the oxygen defects on ZnO and prevents direct contact between CH 3 NH 3 PbI 3 and defects on ZnO. A uniform CH 3 NH 3 PbI 3 film is formed on a soft ZnO:PEG layer after dispersion of the residual stress from the volume expansion during CH 3 NH 3 PbI 3 conversion. PEG also increases the work of adhesion of the CH 3 NH 3 PbI 3 film on the ZnO:PEG layer and holds the CH 3 NH 3 PbI 3 film with hydrogen bonding. Furthermore, PEG tailors the interfacial electronic structure of ZnO, reducing the electron affinity of ZnO. As a result, a selective electron-collection cathode is formed with a reduced electron affinity and a deep-lying valence band of ZnO, which significantly enhances the carrier lifetime (473 μs) and photovoltaic performance (15.5%). The mechanically and electrically durable ZnO:PEG/CH 3 NH 3 PbI 3 interface maintains the sustainable performance of the solar cells over 1 year. A soft and durable cathodic interface via PEG hybridization in a ZnO layer is an effective strategy toward flexible electronics and commercialization of the perovskite solar cells.

Hybrid polymer/ZnO solar cells sensitized by PbS quantum dots

PubMed Central

2012-01-01

Poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylene)]/ZnO nanorod hybrid solar cells consisting of PbS quantum dots [QDs] prepared by a chemical bath deposition method were fabricated. An optimum coating of the QDs on the ZnO nanorods could strongly improve the performance of the solar cells. A maximum power conversion efficiency of 0.42% was achieved for the PbS QDs' sensitive solar cell coated by 4 cycles, which was increased almost five times compared with the solar cell without using PbS QDs. The improved efficiency is attributed to the cascade structure formed by the PbS QD coating, which results in enhanced open-circuit voltage and exciton dissociation efficiency. PMID:22313746

Role of ZnO photoanode nanostructures and sensitizer deposition approaches on the photovoltaic properties of CdS/CdSe and CdS1-xSex quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Şişman, İlkay; Tekir, Oktay; Karaca, Hüseyin

2017-02-01

Hierarchical bundle-like ZnO nanorod arrays (BNRs) were synthesized by a one-pot hydrothermal method based on two consecutive temperature steps for cascade CdS/CdSe and ternary CdS1-xSex alloy quantum dot-sensitized solar cells (QDSSCs) as photoanode. The CdS/CdSe and CdS1-xSex QDs were deposited on the surface of the ZnO BNRs by conventional and modified successive ionic-layer adsorption and reaction (SILAR) methods, respectively. Using the ZnO BNRs/CdS/CdSe photoanode, the power conversion efficiency reaches 2.08%, which is 1.8 times higher than that of pristine ZnO nanorods/CdS/CdSe photoanode, while by applying ZnO BNRs/CdS1-xSex, the power conversion efficiency improves 2.52%. The remarkably improved photovoltaic performance is mainly derived from the bundle-like nanorod arrays structure, which increases the QDs loading amount and the scattering effect for light absorption, and the appropriate conduction band energy, sufficient Se amount and well coverage of the ternary CdS1-xSex QDs result in enhanced photogenerated electron injection, high light absorption and reduced recombination, respectively. As a result, ZnO BNRs/CdS1-xSex combination can significantly improve performance of QDSSCs.

A simulation study to improve the efficiency of ZnO1-xSx/Cu2ZnSn (Sy, Se1-y)4 solar cells by composition-ratio control

NASA Astrophysics Data System (ADS)

Sharbati, S.; Norouzzadeh, E.; Mohammadi, S.

2018-04-01

This work investigates the impact of the conduction-band offset (CBO) and valence band offset (VBO) on the performance of Zn (O, S)/Cu2ZnSn (S, Se)4 solar cells by numerical simulations. The band gap alignment at the buffer-CZTS layer interface are controlled by the sulfur-to-oxygen and sulfur-to-selenium ratios. The simulation results show that the high sulfur content in the Zn (O, S) layer makes a big offset in the conduction band and high oxygen content in the in the Zn (O, S) layer eventuates in large valence band offset, that descends Cu2ZnSn (S, Se)4 solar cell performance. We established an initial device model based on an experimental device with world record efficiencies of 12.6%. This study shows that most suitable heterojunction for ZnO1-xSx/Cu2ZnSn (Sy, Se1-y)4 solar cells is when sulfur content ranging 19%-50% in the Zn (O, S) and 30%-50% in the CZTSSe. The efficiency of Cu2ZnSn (S, Se)4 solar cells will be achieved to 14.3%.

Mesoporous multi-shelled ZnO microspheres for the scattering layer of dye sensitized solar cell with a high efficiency

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

Xia, Weiwei; Mei, Chao; Zeng, Xianghua, E-mail: xhzeng@yzu.edu.cn

2016-03-14

Both light scattering and dye adsorbing are important for the power conversion efficiency PCE performance of dye sensitized solar cell (DSSC). Nanostructured scattering layers with a large specific surface area are regarded as an efficient way to improve the PCE by increasing dye adsorbing, but excess adsorbed dye will hinder light scattering and light penetration. Thus, how to balance the dye adsorbing and light penetration is a key problem to improve the PCE performance. Here, multiple-shelled ZnO microspheres with a mesoporous surface are fabricated by a hydrothermal method and are used as scattering layers on the TiO{sub 2} photoanode ofmore » the DSSC in the presence of N719 dye and iodine–based electrolyte, and the results reveal that the DSSCs based on triple shelled ZnO microsphere with a mesoporous surface exhibit an enhanced PCE of 7.66%, which is 13.0% higher than those without the scattering layers (6.78%), indicating that multiple-shelled microspheres with a mesoporous surface can ensure enough light scattering between the shells, and a favorable concentration of the adsorbed dye can improve the light penetration. These results may provide a promising pathway to obtain the high efficient DSSCs.« less

Optimization of processing parameters on the controlled growth of ZnO nanorod arrays for the performance improvement of solid-state dye-sensitized solar cells

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

Lee, Yi-Mu, E-mail: ymlee@nuu.edu.t; Yang, Hsi-Wen

2011-03-15

High-transparency and high quality ZnO nanorod arrays were grown on the ITO substrates by a two-step chemical bath deposition (CBD) method. The effects of processing parameters including reaction temperature (25-95 {sup o}C) and solution concentration (0.01-0.1 M) on the crystal growth, alignment, optical and electrical properties were systematically investigated. It has been found that these process parameters are critical for the growth, orientation and aspect ratio of the nanorod arrays, showing different structural and optical properties. Experimental results reveal that the hexagonal ZnO nanorod arrays prepared under reaction temperature of 95 {sup o}C and solution concentration of 0.03 M possessmore » highest aspect ratio of {approx}21, and show the well-aligned orientation and optimum optical properties. Moreover the ZnO nanorod arrays based heterojunction electrodes and the solid-state dye-sensitized solar cells (SS-DSSCs) were fabricated with an improved optoelectrical performance. -- Graphical abstract: The ZnO nanorod arrays demonstrate well-alignment, high aspect ratio (L/D{approx}21) and excellent optical transmittance by low-temperature chemical bath deposition (CBD). Display Omitted Research highlights: > Investigate the processing parameters of CBD on the growth of ZnO nanorod arrays. > Optimization of CBD process parameters: 0.03 M solution concentration and reaction temperature of 95 {sup o}C. > The prepared ZnO samples possess well-alignment and high aspect ratio (L/D{approx}21). > An n-ZnO/p-NiO heterojunction: great rectifying behavior and low leakage current. > SS-DSSC has J{sub SC} of 0.31 mA/cm{sup 2} and V{sub OC} of 590 mV, and an improved {eta} of 0.059%.« less

Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties

NASA Astrophysics Data System (ADS)

Ibrayev, N. Kh.; Ilyassov, B. R.; Afanasyev, D. A.

2017-03-01

Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

Demonstration of a 100-kWth high-temperature solar thermochemical reactor pilot plant for ZnO dissociation

NASA Astrophysics Data System (ADS)

Koepf, E.; Villasmil, W.; Meier, A.

2016-05-01

Solar thermochemical H2O and CO2 splitting is a viable pathway towards sustainable and large-scale production of synthetic fuels. A reactor pilot plant for the solar-driven thermal dissociation of ZnO into metallic Zn has been successfully developed at the Paul Scherrer Institute (PSI). Promising experimental results from the 100-kWth ZnO pilot plant were obtained in 2014 during two prolonged experimental campaigns in a high flux solar simulator at PSI and a 1-MW solar furnace in Odeillo, France. Between March and June the pilot plant was mounted in the solar simulator and in-situ flow-visualization experiments were conducted in order to prevent particle-laden fluid flows near the window from attenuating transparency by blocking incoming radiation. Window flow patterns were successfully characterized, and it was demonstrated that particle transport could be controlled and suppressed completely. These results enabled the successful operation of the reactor between August and October when on-sun experiments were conducted in the solar furnace in order to demonstrate the pilot plant technology and characterize its performance. The reactor was operated for over 97 hours at temperatures as high as 2064 K; over 28 kg of ZnO was dissociated at reaction rates as high as 28 g/min.

Progress in nanostructured photoanodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Liu, Xueyang; Fang, Jian; Liu, Yong; Lin, Tong

2016-09-01

Solar cells represent a principal energy technology to convert light into electricity. Commercial solar cells are at present predominately produced by single- or multi-crystalline silicon wafers. The main drawback to silicon-based solar cells, however, is high material and manufacturing costs. Dye-sensitized solar cells (DSSCs) have attracted much attention during recent years because of the low production cost and other advantages. The photoanode (working electrode) plays a key role in determining the performance of DSSCs. In particular, nanostructured photoanodes with a large surface area, high electron transfer efficiency, and low electron recombination facilitate to prepare DSSCs with high energy conversion efficiency. In this review article, we summarize recent progress in the development of novel photoanodes for DSSCs. Effect of semiconductor material (e.g. TiO2, ZnO, SnO2, N2O5, and nano carbon), preparation, morphology and structure (e.g. nanoparticles, nanorods, nanofibers, nanotubes, fiber/particle composites, and hierarchical structure) on photovoltaic performance of DSSCs is described. The possibility of replacing silicon-based solar cells with DSSCs is discussed.

Impact of solar UV radiation on toxicity of ZnO nanoparticles through photocatalytic reactive oxygen species (ROS) generation and photo-induced dissolution

EPA Science Inventory

The present study investigated the impact of solar UV radiation on ZnO nanoparticle toxicity through photocatalytic ROS generation and photo-induced dissolution. Toxicity of ZnO nanoparticles to Daphnia magna was examined under laboratory light versus simulated solar UV radiatio...

Hybrid zinc oxide/graphene electrodes for depleted heterojunction colloidal quantum-dot solar cells.

PubMed

Tavakoli, Mohammad Mahdi; Aashuri, Hossein; Simchi, Abdolreza; Fan, Zhiyong

2015-10-07

Recently, hybrid nanocomposites consisting of graphene/nanomaterial heterostructures have emerged as promising candidates for the fabrication of optoelectronic devices. In this work, we have employed a facile and in situ solution-based process to prepare zinc oxide/graphene quantum dots (ZnO/G QDs) in a hybrid structure. The prepared hybrid dots are composed of a ZnO core, with an average size of 5 nm, warped with graphene nanosheets. Spectroscopic studies show that the graphene shell quenches the photoluminescence intensity of the ZnO nanocrystals by about 72%, primarily due to charge transfer reactions and static quenching. A red shift in the absorption peak is also observed. Raman spectroscopy determines G-band splitting of the graphene shell into two separated sub-bands (G(+), G(-)) caused by the strain induced symmetry breaking. It is shown that the hybrid ZnO/G QDs can be used as a counter-electrode for heterojunction colloidal quantum-dot solar cells for efficient charge-carrier collection, as evidenced by the external quantum efficiency measurement. Under the solar simulated spectrum (AM 1.5G), we report enhanced power conversion efficiency (35%) with higher short current circuit (80%) for lead sulfide-based solar cells as compared to devices prepared by pristine ZnO nanocrystals.

High work function transparent middle electrode for organic tandem solar cells

NASA Astrophysics Data System (ADS)

Moet, D. J. D.; de Bruyn, P.; Blom, P. W. M.

2010-04-01

The use of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) in combination with ZnO as middle electrode in solution-processed organic tandem solar cells requires a pH modification of the PEDOT:PSS dispersion. We demonstrate that this neutralization leads to a reduced work function of PEDOT:PSS, which does not affect the performance of polythiophene:fullerene solar cells, but results in a lower open-circuit voltage of devices based on a polyfluorene derivative with a higher ionization potential. The introduction of a thin layer of a perfluorinated ionomer recovers the anode work function and gives an open-circuit voltage of 1.92 V for a double junction polyfluorene-based solar cell.

Materials, device, and interface engineering to improve polymer-based solar cells

NASA Astrophysics Data System (ADS)

Hau, Steven Kin

The continued depletion of fossil fuel resources has lead to the rise in energy production costs which has lead to the search for an economically viable alternative energy source. One alternative of particular interest is solar energy. A promising alternative to inorganic materials is organic semiconductor polymer solar cells due to their advantages of being cheaper, light weight, flexible and made into large areas by roll-to-roll processing. In this dissertation, an integrated approach is taken to improve the overall performance of polymer-based solar cells by the development of new polymer materials, device architectures, and interface engineering of the contacts between layers. First, a new class of metallated conjugated polymers is explored as potential solar cell materials. Systematic modifications to the molecular units on the main chain of amorphous metallated Pt-polymers show a correlation that improving charge carrier mobility also improves solar cell performance leading to mobilities as high as 1 x 10-2 cm2/V·s and efficiencies as high as 4.1%. Second, an inverted device architecture using a more air stable electrode (Ag) is demonstrated to improve the ambient stability of unencapsulated P3HT:PCBM devices showing over 80% efficiency retention after 40 days of exposure. To further demonstrate the potential for roll-to-roll processing of polymer solar cells, solution processed Ag-nanoparticles were used to replace the vacuum deposited Ag anode electrode for inverted solar cells showing efficiencies as high as 3%. In addition, solution processed polymer based electrodes were demonstrated as a replacement to the expensive and brittle indium tin oxide showing efficiencies of 3% on flexible substrate solar cells. Third, interface engineering of the n-type (high temperature sol-gel processed TiO2 or ZnO, low temperature processed ZnO nanoparticles) electron selective metal oxide contacts in inverted solar cells with self-assembled monolayers (SAM) show improved

Studies on graphene zinc-oxide nanocomposites photoanodes for high-efficient dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Effendi, N. A. S.; Samsi, N. S.; Zawawi, S. A.; Hassan, O. H.; Zakaria, R.; Yahya, M. Z. A.; Ali, A. M. M.

2017-09-01

A dye-sensitized solar cells (DSSCs) using a nanocomposite (NC) semiconductor film, consisting of graphene layer and ZnO nanosheets (Gr-ZnO) is fabricated by electrodeposition process. The DSSCs based on Gr-ZnO NC were determined via electrochemical impedance spectra (EIS), UV-Visible diffused reflectance spectroscopy (UV-Vis), and photovoltaic performances J-V curves to substantiate the explanations. Impedance spectra shows that a smaller charge transport time constant occurs in DSSCs based on Gr-ZnO NC comparing to ZnO. This improved the electron collecting efficiency significantly, resulting in high open circuit voltage. Moreover, Gr-ZnO NC shows an efficient photoinduced charge separation and transportation can be achieved at the interface thus exhibit excellent potential for photocurrent generation compared with sole ZnO. Gr-ZnO NC obtained a maximum photocurrent response for an open-circuit voltage and a power conversion efficiency of 0.96 V and 7.01% respectively, which is doubled from sole ZnO. The fabricated Gr-ZnO NC cells show better performances compared to conventional ZnO structure reference cell.

The influence of anatase-rutile mixed phase and ZnO blocking layer on dye-sensitized solar cells based on TiO2nanofiberphotoanodes

PubMed Central

2013-01-01

High performance is expected in dye-sensitized solar cells (DSSCs) that utilize one-dimensional (1-D) TiO2 nanostructures owing to the effective electron transport. However, due to the low dye adsorption, mainly because of their smooth surfaces, 1-D TiO2 DSSCs show relatively lower efficiencies than nanoparticle-based ones. Herein, we demonstrate a very simple approach using thick TiO2 electrospun nanofiber films as photoanodes to obtain high conversion efficiency. To improve the performance of the DSCCs, anatase-rutile mixed-phase TiO2 nanofibers are achieved by increasing sintering temperature above 500°C, and very thin ZnO films are deposited by atomic layer deposition (ALD) method as blocking layers. With approximately 40-μm-thick mixed-phase (approximately 15.6 wt.% rutile) TiO2 nanofiber as photoanode and 15-nm-thick compact ZnO film as a blocking layer in DSSC, the photoelectric conversion efficiency and short-circuit current are measured as 8.01% and 17.3 mA cm−2, respectively. Intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy measurements reveal that extremely large electron diffusion length is the key point to support the usage of thick TiO2 nanofibers as photoanodes with very thin ZnO blocking layers to obtain high photocurrents and high conversion efficiencies. PMID:23286741

Enhanced light absorption of silicon solar cells with dielectric nanostructured back reflector

NASA Astrophysics Data System (ADS)

Ren, Rui; Zhong, Zheng

2018-06-01

This paper investigates the light absorption property of nanostructured dielectric reflectors in silicon thin film solar cells using numerical simulation. Flat thin film solar cell with ZnO nanostructured back reflector can produce comparable photocurrent to the control model with Ag nanostructured back reflector. Furthermore, when it is integrated with nano-pillar surface decoration, a photocurrent density of 29.5 mA/cm2 can be achieved, demonstrating a photocurrent enhancement of 5% as compared to the model with Ag nanostructured back reflector.

Enhanced Efficiency of Dye-Sensitized Solar Cells with Mesoporous-Macroporous TiO2 Photoanode Obtained Using ZnO Template

NASA Astrophysics Data System (ADS)

Pham, Trang T. T.; Mathews, Nripan; Lam, Yeng-Ming; Mhaisalkar, Subodh

2017-06-01

Improved light harvesting efficiency can be achieved by enhancing the optical properties of the titanium dioxide (TiO2) photoanode in dye-sensitized solar cells (DSSCs), leading to higher power conversion efficiency. By incorporating submicrometer cavities in TiO2 mesoporous film, using zinc oxide (ZnO) particles as a template, a bimodal pore size structure has been created, called a mesoporous-macroporous nanostructure. This photoanode structure consists of 20-nm TiO2 nanoparticles with two kinds of pores with size of 20 nm (mesopores) and 500 nm (macropores). Energy-dispersive x-ray spectroscopy and x-ray diffraction studies showed no trace of ZnO in the TiO2 after removal by TiCl4 treatment. Higher diffuse transmittance of this film compared with the standard transparent photoanode provides evidence of improved light scattering. When employed in a device, the incident-photon-to-current efficiency of ZnO-assisted devices showed enhancement at longer wavelengths, corresponding to the Mie light scattering effect with the macropores as scattering centers. This resulted in overall higher power conversion efficiency of the DSSC. In this work, a nonvolatile gel ionic liquid was used as the electrolyte to also demonstrate the benefit of this structure in combination with a viscous electrolyte and its promising application to prolong the stability of DSSCs.

Flexible hybrid energy cell for simultaneously harvesting thermal, mechanical, and solar energies.

PubMed

Yang, Ya; Zhang, Hulin; Zhu, Guang; Lee, Sangmin; Lin, Zong-Hong; Wang, Zhong Lin

2013-01-22

We report the first flexible hybrid energy cell that is capable of simultaneously or individually harvesting thermal, mechanical, and solar energies to power some electronic devices. For having both the pyroelectric and piezoelectric properties, a polarized poly(vinylidene fluoride) (PVDF) film-based nanogenerator (NG) was used to harvest thermal and mechanical energies. Using aligned ZnO nanowire arrays grown on the flexible polyester (PET) substrate, a ZnO-poly(3-hexylthiophene) (P3HT) heterojunction solar cell was designed for harvesting solar energy. By integrating the NGs and the solar cells, a hybrid energy cell was fabricated to simultaneously harvest three different types of energies. With the use of a Li-ion battery as the energy storage, the harvested energy can drive four red light-emitting diodes (LEDs).

Dye sensitized solar cells using catalytically active CuO-ZnO nanocomposite synthesized by single step method

NASA Astrophysics Data System (ADS)

Abraham, Nelsa; Rufus, Alex; Unni, C.; Philip, Daizy

2018-07-01

In the present paper we report a low cost, single step preparation method for the synthesis of CuO-ZnO nanocomposite through simple co-precipitation technique using oxalic acid. To have a better idea about the deviations brought about by the inclusion of CuO in ZnO lattice, pure ZnO nanoparticles synthesized from 0.1 M solutions were also investigated. X-ray diffraction studies showed that the composite contains only hexagonal wurtzite ZnO and monoclinic CuO structures. The magnetic studies of CuO-ZnO heterostructures were also conducted in order to elucidate the source of the ferromagnetism observed at room temperature. The catalytic efficiency of the as prepared nanocomposite was estimated by the degradation of methylene blue and eosin yellowish which also shows its suitability as a promising candidate in waste water treatment. The effect of chenodeoxycholic acid as a co-adsorbent in the performance of dye sensitized solar cells fabricated using the synthesized ZnO and the nanocomposite was also studied and significant improvement in photovoltaic performance has been obtained for nanocomposite based solar cell.

Molecular and Nanoscale Engineering of High Efficiency Excitonic Solar Cells

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

Jenekhe, Samson A.; Ginger, David S.; Cao, Guozhong

We combined the synthesis of new polymers and organic-inorganic hybrid materials with new experimental characterization tools to investigate bulk heterojunction (BHJ) polymer solar cells and hybrid organic-inorganic solar cells during the 2007-2010 period (phase I) of this project. We showed that the bulk morphology of polymer/fullerene blend solar cells could be controlled by using either self-assembled polymer semiconductor nanowires or diblock poly(3-alkylthiophenes) as the light-absorbing and hole transport component. We developed new characterization tools in-house, including photoinduced absorption (PIA) spectroscopy, time-resolved electrostatic force microscopy (TR-EFM) and conductive and photoconductive atomic force microscopy (c-AFM and pc-AFM), and used them to investigatemore » charge transfer and recombination dynamics in polymer/fullerene BHJ solar cells, hybrid polymer-nanocrystal (PbSe) devices, and dye-sensitized solar cells (DSSCs); we thus showed in detail how the bulk photovoltaic properties are connected to the nanoscale structure of the BHJ polymer solar cells. We created various oxide semiconductor (ZnO, TiO 2) nanostructures by solution processing routes, including hierarchical aggregates and nanorods/nanotubes, and showed that the nanostructured photoanodes resulted in substantially enhanced light-harvesting and charge transport, leading to enhanced power conversion efficiency of dye-sensitized solar cells.« less

ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation.

PubMed

Hsueh, Yi-Huang; Ke, Wan-Ju; Hsieh, Chien-Te; Lin, Kuen-Song; Tzou, Dong-Ying; Chiang, Chao-Lung

2015-01-01

Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5-10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.

ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation

PubMed Central

Hsueh, Yi-Huang; Ke, Wan-Ju; Hsieh, Chien-Te; Lin, Kuen-Song; Tzou, Dong-Ying; Chiang, Chao-Lung

2015-01-01

Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5–10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles. PMID:26039692

Impact of solar UV radiation on toxicity of ZnO nanoparticles through photocatalytic reactive oxygen species (ROS) generation and photo-induced dissolution.

PubMed

Ma, Hongbo; Wallis, Lindsay K; Diamond, Steve; Li, Shibin; Canas-Carrell, Jaclyn; Parra, Amanda

2014-10-01

The present study investigated the impact of solar UV radiation on ZnO nanoparticle toxicity through photocatalytic ROS generation and photo-induced dissolution. Toxicity of ZnO nanoparticles to Daphnia magna was examined under laboratory light versus simulated solar UV radiation (SSR). Photocatalytic ROS generation and particle dissolution were measured on a time-course basis. Two toxicity mitigation assays using CaCl2 and N-acetylcysteine were performed to differentiate the relative importance of these two modes of action. Enhanced ZnO nanoparticle toxicity under SSR was in parallel with photocatalytic ROS generation and enhanced particle dissolution. Toxicity mitigation by CaCl2 to a less extent under SSR than under lab light demonstrates the role of ROS generation in ZnO toxicity. Toxicity mitigation by N-acetylcysteine under both irradiation conditions confirms the role of particle dissolution and ROS generation. These findings demonstrate the importance of considering environmental solar UV radiation when assessing ZnO nanoparticle toxicity and risk in aquatic systems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fabrication and Characterization of Hybrid Organic-Inorganic Electron Extraction Layers for Polymer Solar Cells toward Improved Processing Robustness and Air Stability.

PubMed

Fredj, Donia; Pourcin, Florent; Alkarsifi, Riva; Kilinc, Volkan; Liu, Xianjie; Ben Dkhil, Sadok; Boudjada, Nassira Chniba; Fahlman, Mats; Videlot-Ackermann, Christine; Margeat, Olivier; Ackermann, Jörg; Boujelbene, Mohamed

2018-05-23

Organic-inorganic hybrid materials composed of bismuth and diaminopyridine are studied as novel materials for electron extraction layers in polymer solar cells using regular device structures. The hybrid materials are solution processed on top of two different low band gap polymers (PTB7 or PTB7-Th) as donor materials mixed with fullerene PC 70 BM as the acceptor. The intercalation of the hybrid layer between the photoactive layer and the aluminum cathode leads to solar cells with a power conversion efficiency of 7.8% because of significant improvements in all photovoltaic parameters, that is, short-circuit current density, fill factor, and open-circuit voltage, similar to the reference devices using ZnO as the interfacial layer. However when using thick layers of such hybrid materials for electron extraction, only small losses in photocurrent density are observed in contrast to the reference material ZnO of pronounced losses because of optical spacer effects. Importantly, these hybrid electron extraction layers also strongly improve the device stability in air compared with solar cells processed with ZnO interlayers. Both results underline the high potential of this new class of hybrid materials as electron extraction materials toward robust processing of air stable organic solar cells.

Vertical growth of ZnO nanorods on ZnO seeded FTO substrate for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2018-04-01

Zinc oxide (ZnO) nanorods (NRs) were electrochemically grown on fluorine doped tin oxide (FTO) and ZnO seeded FTO substrates. X-ray diffraction (XRD) patterns, Raman spectra and photoluminescence (PL) spectra reveal that the hexagonal wurtzite structured ZnO grown on a seeded FTO substrate has a high crystallinity, crystal quality and less atomic defects. Felid emission scanning electron microscope (FE-SEM) images display a high growth density of NRs grown on seeded FTO substrate compared to NRs grown on FTO substrate. The efficiency of the DSSCs based on NRs grown on FTO and seeded FTO substrates is 0.85 and 1.52 %, respectively. UV-Vis absorption spectra and electrochemical impedance spectra depict that the NRs grown on seeded FTO photoanode have higher dye absorption and charge recombination resistance than that of the NRs grown on FTO substrate.

The influence of material type and composition of TiO2- ZnO on manufacturing of paste for the application of DSSC

NASA Astrophysics Data System (ADS)

Retnaningsih, L.; Muliani, L.; Aggraini, P. N.; Hidayat, J.

2016-11-01

Research, fabrication and material selection for the application of Dye- sensitized solar cell (DSSC) has been performed on glass FTO (Flour Tin Oxide). The material is used in the form of TiO2 paste, TiO2 powder and ZnO powder. Dye-sensitized solar cell (DSSC), is a fotoelektrokimia-based solar cells where the absorption process light done by the dye molecules and the process of separation of inorganic semiconductor materials by charge of Titanium dioxide (TiO2) and Zinc oxide (ZnO). The purpose of this research is to know the exact composition of TiO2 and ZnO materials in order to produce the best efficiency with DSSC. On this research was done making prototype dye-sensitized solar cell using dye Z 907, and semiconductor nanoparticles TiO2 and ZnO powder that is made into a paste by mixing different composition in two variations of samples: A = ZnO (powder) + 40% TiO2 (powder) and B = 60% TiO2 (powder) (40%) + TiO2 (pasta) 60%. The second variation of this high efficiency is value at sample B i.e. TiO2 (powder) + 40% TiO2 (paste) of 60%.

Preparation of Ga-doped ZnO films by pulsed dc magnetron sputtering with cylindrical rotating target for thin film solar cell applications

NASA Astrophysics Data System (ADS)

Shin, Beom-Ki; Lee, Tae-Il; Park, Ji-Hyeon; Park, Kang-Il; Ahn, Kyung-Jun; Park, Sung-Kee; Lee, Woong; Myoung, Jae-Min

2011-11-01

Applicability of Ga-doped ZnO (GZO) films for thin film solar cells (TFSCs) was investigated by preparing GZO films via pulsed dc magnetron sputtering (PDMS) with rotating target. The GZO films showed improved crystallinity and increasing degree of Ga doping with increasing thickness to a limit of 1000 nm. The films also fulfilled requirements for the transparent electrodes of TFSCs in terms of electrical and optical properties. Moreover, the films exhibited good texturing potential based on etching studies with diluted HCl, which yielded an improved light trapping capability without significant degradation in electrical propreties. It is therefore suggested that the surface-textured GZO films prepared via PDMS and etching are promising candidates for indium-free transparent electrodes for TFSCs.

Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices.

PubMed

Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T; Durrant, James R

2015-10-15

Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced "burn-in" effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions.

The Fate of ZnO Nanoparticles Administered to Human Bronchial Epithelial Cells

PubMed Central

Gilbert, Benjamin; Fakra, Sirine C.; Xia, Tian; Pokhrel, Suman; Mädler, Lutz; Nel, André E.

2014-01-01

A particular challenge for nanotoxicology is the evaluation of the biological fate and toxicity of nanomaterials that dissolve in aqueous fluids. Zinc oxide nanomaterials are of particular concern because dissolution leads to release of the toxic divalent zinc ion. Although dissolved zinc ions have been implicated in ZnO cytotoxicity, direct identification of the chemical form of zinc taken up by cells exposed to ZnO nanoparticles, and its intracellular fate, has not yet been achieved. We combined high resolution X-ray spectromicroscopy and high elemental sensitivity X-ray microprobe analyses to determine the fate of ZnO and less soluble iron-doped ZnO nanoparticles following exposure to cultures of human bronchial epithelial cells, BEAS-2B. We complemented two-dimensional X-ray imaging methods with atomic force microscopy of cell surfaces to distinguish between nanoparticles that were transported inside the cells from those that adhered to the cell exterior. The data suggest cellular uptake of ZnO nanoparticles is a mechanism of zinc accumulation in cells. Following uptake, ZnO nanoparticles dissolved completely generating intracellular Zn2+ complexed by molecular ligands. These results corroborate a model for ZnO nanoparticle toxicity that is based on nanoparticle uptake followed by intracellular dissolution. PMID:22646753

Improving scattering layer through mixture of nanoporous spheres and nanoparticles in ZnO-based dye-sensitized solar cells.

PubMed

Kim, Chohui; Choi, Hongsik; Kim, Jae Ik; Lee, Sangheon; Kim, Jinhyun; Lee, Woojin; Hwang, Taehyun; Kang, Suji; Moon, Taeho; Park, Byungwoo

2014-01-01

A scattering layer is utilized by mixing nanoporous spheres and nanoparticles in ZnO-based dye-sensitized solar cells. Hundred-nanometer-sized ZnO spheres consisting of approximately 35-nm-sized nanoparticles provide not only effective light scattering but also a large surface area. Furthermore, ZnO nanoparticles are added to the scattering layer to facilitate charge transport and increase the surface area as filling up large voids. The mixed scattering layer of nanoparticles and nanoporous spheres on top of the nanoparticle-based electrode (bilayer geometry) improves solar cell efficiency by enhancing both the short-circuit current (J sc) and fill factor (FF), compared to the layer consisting of only nanoparticles or nanoporous spheres.

Plasmon-Assisted Efficiency Enhancement of Eu3+-Doped Tellurite Glass-Covered Solar Cells

NASA Astrophysics Data System (ADS)

Lima, Bismarck C.; Gómez-Malagón, L. A.; Gomes, A. S. L.; Garcia, J. A. M.; Kassab, L. R. P.

2017-12-01

Rare-earth-doped tellurite glass containing metallic nanoparticles can be exploited to manage the solar spectrum in order to increase solar cell efficiency. It is therefore possible to modify the incident solar spectrum profile to the spectrum that optimizes the solar cell recombination process by covering the solar cell with plasmonic luminescent downshifting layers. With this approach, the losses due to thermalization are minimized and the efficiency is increased. Due to the down-conversion process that couples the plasmon resonance of the metallic nanoparticles and the rare-earth electronic energy levels, it is possible to convert photons from the ultraviolet region to the visible and near-band-gap region of the semiconductor. It is demonstrated here that plasmon-assisted efficiency enhancements of 14.0% and 34.5% can be obtained for commercial Si and GaP solar cells, respectively, covered with Eu3+-doped TeO2-ZnO glass containing silver nanoparticles.

Development of nanostructured and surface modified semiconductors for hybrid organic-inorganic solar cells.

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

Hsu, Julia, W. P.

2008-09-01

Solar energy conversion is increasingly being recognized as one of the principal ways to meet future energy needs without causing detrimental environmental impact. Hybrid organic-inorganic solar cells (SCs) are attracting particular interest due to the potential for low cost manufacturing and for use in new applications, such as consumer electronics, architectural integration and light-weight sensors. Key materials advantages of these next generation SCs over conventional semiconductor SCs are in design opportunities--since the different functions of the SCs are carried out by different materials, there are greater materials choices for producing optimized structures. In this project, we explore the hybrid organic-inorganicmore » solar cell system that consists of oxide, primarily ZnO, nanostructures as the electron transporter and poly-(3-hexylthiophene) (P3HT) as the light-absorber and hole transporter. It builds on our capabilities in the solution synthesis of nanostructured semiconducting oxide arrays to this photovoltaic (PV) technology. The three challenges in this hybrid material system for solar applications are (1) achieving inorganic nanostructures with critical spacing that matches the exciton diffusion in the polymer, {approx} 10 nm, (2) infiltrating the polymer completely into the dense nanostructure arrays, and (3) optimizing the interfacial properties to facilitate efficient charge transfer. We have gained an understanding and control over growing oriented ZnO nanorods with sub-50 nm diameters and the required rod-to-rod spacing on various substrates. We have developed novel approaches to infiltrate commercially available P3HT in the narrow spacing between ZnO nanorods. Also, we have begun to explore ways to modify the interfacial properties. In addition, we have established device fabrication and testing capabilities at Sandia for prototype devices. Moreover, the control synthesis of ZnO nanorod arrays lead to the development of an efficient anti

Facile synthesis of one dimensional ZnO nanostructures for DSSC applications

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2016-05-01

Development of zinc oxide (ZnO) nanostructure based third generation dye sensitized solar cell is interesting compared to conventional silicon solar cells. ZnO nanostructured thin films were electrochemically deposited onto fluorine doped tin oxide (FTO) glass substrate. The effect of ethylene-diamine-tetra-acetic acid (EDTA) on structural, morphological and optical properties is investigated using X-ray diffraction (XRD) meter, field emission scanning electron microscope (FE-SEM) and micro Raman spectroscopy. XRD patterns reveal that the prepared nanostructures are hexagonal wutrzite structures with (101) plane orientation, the nanostructure prepared using EDTA exhibits better crystallinity. FE-SEM images illustrate that the morphological changes are observed from nanorod structure to cauliflower like structure as EDTA is added. Micro Raman spectra predict that cauliflower like structure possesses a higher crystalline nature with less atomic defects compared to nanorod structures. Dye sensitized solar cell (DSSC) is constructed for the optimized cauliflower structure, and open circuit voltage, short circuit density, fill factor and efficiency are estimated from the J-V curve.

Dielectric Scattering Patterns for Efficient Light Trapping in Thin-Film Solar Cells.

PubMed

van Lare, Claire; Lenzmann, Frank; Verschuuren, Marc A; Polman, Albert

2015-08-12

We demonstrate an effective light trapping geometry for thin-film solar cells that is composed of dielectric light scattering nanocavities at the interface between the metal back contact and the semiconductor absorber layer. The geometry is based on resonant Mie scattering. It avoids the Ohmic losses found in metallic (plasmonic) nanopatterns, and the dielectric scatterers are well compatible with nearly all types of thin-film solar cells, including cells produced using high temperature processes. The external quantum efficiency of thin-film a-Si:H solar cells grown on top of a nanopatterned Al-doped ZnO, made using soft imprint lithography, is strongly enhanced in the 550-800 nm spectral band by the dielectric nanoscatterers. Numerical simulations are in good agreement with experimental data and show that resonant light scattering from both the AZO nanostructures and the embedded Si nanostructures are important. The results are generic and can be applied on nearly all thin-film solar cells.

ZnO/p-GaN heterostructure for solar cells and the effect of ZnGa2O4 interlayer on their performance.

PubMed

Nam, Seung Yong; Choi, Yong Seok; Lee, Ju Ho; Park, Seong Ju; Lee, Jeong Yong; Lee, Dong Seon

2013-01-01

We report the usage of ZnO material as an alternative for n-GaN for realizing III-nitride based solar cell. The fabricated solar cell shows large turn-on voltage of around 8 volts and a rapid decrease of photocurrent at low bias voltage under darkness and 1-sun illumination conditions, respectively. This phenomenon can be attributed to the formation of high-resistive ultra-thin layers at the ZnO/ p-GaN junction interface during high temperature deposition. Transmission electron microscopy (TEM) studies carried out on the grown samples reveals that the ultra-thin layer consists of ZnGa2O4. It is found that the presence of insulating ZnGa2O4 film is detrimental in the performance of proposed heterostructure for solar cells.

Potassium-doped zinc oxide as photocathode material in dye-sensitized solar cells.

PubMed

Bai, Jie; Xu, Xiaobao; Xu, Ling; Cui, Jin; Huang, Dekang; Chen, Wei; Cheng, Yibing; Shen, Yan; Wang, Mingkui

2013-04-01

ZnO nanoparticles are doped with K and applied in p-type dye-sensitized solar cells (DSCs). The microstructure and dynamics of hole transportation and recombination are investigated. The morphology of the K-doped ZnO nanoparticles shows a homogeneous distribution with sizes in the range 30-40 nm. When applied in p-type DSCs in combination with C343 as sensitizer, the K-doped ZnO nanoparticles achieve a photovoltaic power conversion efficiency of 0.012 % at full-intensity sunlight. A further study on the device by transient photovoltage/photocurrent decay measurements shows that the K-doped ZnO nanoparticles have an appreciable hole diffusion coefficient (ca. 10(-6) cm(2) s(-1) ). Compared to the widely used p-type NiO nanoparticles, this advantage is crucial for further improving the efficiency of p-type DSCs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

NASA Astrophysics Data System (ADS)

Edley, Michael

Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination

Nanostructured Electron-Selective Interlayer for Efficient Inverted Organic Solar Cells.

PubMed

Song, Jiyun; Lim, Jaehoon; Lee, Donggu; Thambidurai, M; Kim, Jun Young; Park, Myeongjin; Song, Hyung-Jun; Lee, Seonghoon; Char, Kookheon; Lee, Changhee

2015-08-26

We report a unique nanostructured electron-selective interlayer comprising of In-doped ZnO (ZnO:In) and vertically aligned CdSe tetrapods (TPs) for inverted polymer:fullerene bulkheterojunction (BHJ) solar cells. With dimension-controlled CdSe TPs, the direct inorganic electron transport pathway is provided, resulting in the improvement of the short circuit current and fill factor of devices. We demonstrate that the enhancement is attributed to the roles of CdSe TPs that reduce the recombination losses between the active layer and buffer layer, improve the hole-blocking as well as electron-transporting properties, and simultaneously improve charge collection characteristics. As a result, the power conversion efficiency of PTB7:PC70BM based solar cell with nanostructured CdSe TPs increases to 7.55%. We expect this approach can be extended to a general platform for improving charge extraction in organic solar cells.

Dye-sensitized solar cell employing zinc oxide aggregates grown in the presence of lithium

DOEpatents

Zhang, Qifeng; Cao, Guozhong

2013-10-15

Provided are a novel ZnO dye-sensitized solar cell and method of fabricating the same. In one embodiment, deliberately added lithium ions are used to mediate the growth of ZnO aggregates. The use of lithium provides ZnO aggregates that have advantageous microstructure, morphology, crystallinity, and operational characteristics. Employing lithium during aggregate synthesis results in a polydisperse collection of ZnO aggregates favorable for porosity and light scattering. The resulting nanocrystallites forming the aggregates have improved crystallinity and more favorable facets for dye molecule absorption. The lithium synthesis improves the surface stability of ZnO in acidic dyes. The procedures developed and disclosed herein also help ensure the formation of an aggregate film that has a high homogeneity of thickness, a high packing density, a high specific surface area, and good electrical contact between the film and the fluorine-doped tin oxide electrode and among the aggregate particles.

Self-assembly synthesis of precious-metal-free 3D ZnO nano/micro spheres with excellent photocatalytic hydrogen production from solar water splitting

NASA Astrophysics Data System (ADS)

Guo, Si-yao; Zhao, Tie-jun; Jin, Zu-quan; Wan, Xiao-mei; Wang, Peng-gang; Shang, Jun; Han, Song

2015-10-01

A simple and straightforward solution growth routine is developed to prepare microporous 3D nano/micro ZnO microsphere with a large BET surface area of 288 m2 g-1 at room temperature. The formation mechanism of the hierarchical 3D nano/micro ZnO microsphere and its corresponding hydrogen evolution performance has been deeply discussed. In particular, this novel hierarchical 3D ZnO microspheres performs undiminished hydrogen evolution for at least 24 h under simulated solar light illumination, even under the condition of no precious metal as cocatalyst. Since the complex production process of photocatalysts and high cost of precious metal cocatalyst remains a major constraint that hinders the application of solar water splitting, this 3D nano/micro ZnO microspheres could be expected to be applicable in the precious-metal-free solar water splitting system due to its merits of low cost, simple procedure and high catalytic activity.

Zinc Oxide/TiO2 Bilayer Heterojunction as a Working Electrode in Quasi Solid Dye Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Aprilia, A.; Safriani, L.; Arsyad, Wa Ode S.; Syakir, N.; Susilawati, T.; Mulyana, C.; Fitrilawati; Hidayat, R.

2017-07-01

Bilayer heterojunction of aluminium doped zinc oxide (AZO) and titanium dioxide (TiO2) mesoporous has been successfully deposited on fluorine tin oxide (FTO) substrate as working electrode in dye sensitized solar cell. This layer was used as working electrode in quasi solid dye sensitized solar cell. The solar cell structure is FTO/ZnO/TiO2/PGE/Pt/FTO using polymer gel electrolyte (PGE). In polymer gel electrolyte system, hybrid copolymer based on poly-TMSPMA (3-methoxysilyl propyl methacrylate) was used as a matrix to trap ionic liquid. An addition of aluminum as atom dopant also studied to observe the physical properties changes of photoanode related to solar cell performance. AlCl3 was used as dopant material with the concentrations at 0.5 weight % and 1.0 weight% of zinc acetate dehydrate as raw material. Based on our previous result, the existence of Al dopant would decrease the surface roughness of ZnO layer, reduce the grain size of ZnO particles, transmittance at visible light increase and also change the charge carrier density. Nevertheless, the highest efficiency was achieved for undoped ZnO/TiO2 photoanode (η=0.67%). Based on current-voltage measurement data analysis (using diode model equation) the ideality factor (n) of device using undoped ZnO was smaller (n=2.96) than AZO 0.5 wt% and 1.0 wt% (n=∼4), indicate better quality of undoped ZnO/TiO2 interfaces rather than AZO/TiO2.

Low temperature grown ZnO@TiO{sub 2} core shell nanorod arrays for dye sensitized solar cell application

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

Goh, Gregory Kia Liang; Le, Hong Quang, E-mail: lehq@imre.a-star.edu.sg; Huang, Tang Jiao

High aspect ratio ZnO nanorod arrays were synthesized on fluorine-doped tin oxide glasses via a low temperature solution method. By adjusting the growth condition and adding polyethylenimine, ZnO nanorod arrays with tunable length were successfully achieved. The ZnO@TiO{sub 2} core shells structures were realized by a fast growth method of immersion into a (NH{sub 4}){sub 2}·TiF{sub 6} solution. Transmission electron microscopy, X-ray Diffraction and energy dispersive X-ray measurements all confirmed the existence of a titania shell uniformly covering the ZnO nanorod's surface. Results of solar cell testing showed that addition of a TiO{sub 2} shell to the ZnO nanorod significantlymore » increased short circuit current (from 4.2 to 5.2 mA/cm{sup 2}), open circuit voltage (from 0.6 V to 0.8 V) and fill factor (from 42.8% to 73.02%). The overall cell efficiency jumped from 1.1% for bare ZnO nanorod to 3.03% for a ZnO@TiO{sub 2} core shell structured solar cell with a 18–22 nm shell thickness, a nearly threefold increase. - Graphical abstract: The synthesis process of coating TiO{sub 2} shell onto ZnO nanorod core is shown schematically. A thin, uniform, and conformal shell had been grown on the surface of the ZnO core after immersing in the (NH{sub 4}){sub 2}·TiF{sub 6} solution for 5–15 min. - Highlights: • ZnO@TiO{sub 2} core shell nanorod has been grown on FTO substrate using low temperature solution method. • TEM, XRD, EDX results confirmed the existing of titana shell, uniformly covered rod's surface. • TiO{sub 2} shell suppressed recombination, demonstrated significant enhancement in cell's efficiency. • Core shell DSSC's efficiency achieved as high as 3.03%, 3 times higher than that of ZnO nanorods.« less

Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

NASA Astrophysics Data System (ADS)

Chen, Yang; Lu, Chunxiao; Tang, Liang; Song, Yahui; Wei, Shengnan; Rong, Yang; Zhang, Zhaohong; Wang, Jun

2016-12-01

In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

Improved efficiency of ZnO hierarchical particle based dye sensitized solar cell by incorporating thin passivation layer in photo-anode

NASA Astrophysics Data System (ADS)

Das, Priyanka; Mondal, Biswanath; Mukherjee, Kalisadhan

2018-01-01

Present article describes the DSSC performances of photo-anodes prepared using hydrothermal route derived ZnO particles having dissimilar morphologies i.e. simple micro-rod and nano-tips decorated micro-rod. The surface of nano-tips decorated micro-rod is uneven and patterned which facilitate more dye adsorption and better scattering of the incident light resulting superior photo-conversion efficiency (PCE) ( η 1.09%) than micro-rod ZnO ( η 0.86%). To further improve the efficiency of nano-tips decorated micro-rod ZnO based DSSC, thin passivation layer of ZnO is introduced in the corresponding photo-anode and a higher PCE ( η 1.29%) is achieved. The compact thin passivation layer here expedites the transportation of photo-excited electrons, restricts the undesired recombination reactions and prevents the direct contact of electrolyte with conducting substrates. Attempt is made to understand the effect of passivation layer on the transportation kinetics of photo-excited electrons by analyzing the electrochemical impedance spectra of the developed cells.

Bioanalytical system for detection of cancer cells with photoluminescent ZnO nanorods

NASA Astrophysics Data System (ADS)

Viter, R.; Jekabsons, K.; Kalnina, Z.; Poletaev, N.; Hsu, S. H.; Riekstina, U.

2016-11-01

Using photoluminescent ZnO nanorods and carbohydrate marker SSEA-4, a novel cancer cell recognition system was developed. Immobilization of SSEA-4 antibodies (αSSEA-4) on ZnO nanorods was performed in buffer solution (pH = 7.1) over 2 h. The cancer cell line probes were fixed on the glass slide. One hundred microliters of ZnO-αSSEA-4 conjugates were deposited on the cell probe and exposed for 30 min. After washing photoluminescence spectra were recorded. Based on the developed methodology, ZnO-αSSEA-4 probes were tested on patient-derived breast and colorectal carcinoma cells. Our data clearly show that the carbohydrate SSEA-4 molecule is expressed on cancer cell lines and patient-derived cancer cells. Moreover, SSEA-4 targeted ZnO nanorods bind to the patient-derived cancer cells with high selectivity and the photoluminescence signal increased tremendously compared to the signal from the control samples. Furthermore, the photoluminescence intensity increase correlated with the extent of malignancy in the target cell population. A novel portable bioanalytical system, based on optical ZnO nanorods and fiber optic detection system was developed. We propose that carbohydrate SSEA-4 specific ZnO nanorods could be used for the development of cancer diagnostic biosensors and for targeted therapy.

Hybrid structure of polyaniline/ZnO nanograss and its application in dye-sensitized solar cell with performance improvement

NASA Astrophysics Data System (ADS)

Zhu, Shibu; Wei, Wei; Chen, Xiangnan; Jiang, Man; Zhou, Zuowan

2012-06-01

Polyaniline (PANI) hybridized ZnO photoanode for dye-sensitized solar cell (DSSC) was primarily prepared via a two-step process which involved hydrothermal growth of ZnO nanograss on the fluorine-doped tin oxide (FTO) substrate and subsequently chemisorption of PANI on the surfaces of the ZnO nanorods. The PANI hybridized ZnO nanograss films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), and the results indicated that there were chemical interactions between PANI and ZnO. Both pure ZnO nanograss and PANI hybridized ZnO nanograss were applied to DSSC. The results of photoelectrochemical measurement showed that the photocurrent density of PANI (100 mg/L) hybridized ZnO nanograss photoanode was significantly enhanced, and the overall light-conversion efficiency increased by 60%. The electrochemical impedance spectra (EIS) displayed that the electron densities in photoanodes of PANI hybridized ZnO nanograss were larger than that in pure ZnO nanograss. This is ascribed to more effective charge separation and faster interfacial charge transferring occurred in the hybrid photoanode.

Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2 to MDCK kidney cells: Size matters.

PubMed

Kononenko, Veno; Repar, Neža; Marušič, Nika; Drašler, Barbara; Romih, Tea; Hočevar, Samo; Drobne, Damjana

2017-04-01

In the present study, we evaluated the roles that ZnO particle size and Zn ion release have on cyto- and genotoxicity in vitro. The Madin-Darby canine kidney (MDCK) cells were treated with ZnO nanoparticles (NPs), ZnO macroparticles (MPs), and ZnCl 2 as a source of free Zn ions. We first tested cytotoxicity to define sub-cytotoxic exposure concentrations and afterwards we performed alkaline comet and cytokinesis-block micronucleus assays. Additionally, the activities of both catalase (CAT) and glutathione S-transferase (GST) were evaluated in order to examine the potential impairment of cellular stress-defence capacity. The amount of dissolved Zn ions from ZnO NPs in the cell culture medium was evaluated by an optimized voltammetric method. The results showed that all the tested zinc compounds induced similar concentration-dependent cytotoxicity, but only ZnO NPs significantly elevated DNA and chromosomal damage, which was accompanied by a reduction of GST and CAT activity. Although Zn ion release from ZnO NPs in cell culture medium was significant, our results show that this reason alone cannot explain the ZnO genotoxicity seen in this experiment. We discuss that genotoxicity of ZnO NPs depends on the particle size, which determines the physical principles of their dissolution and cellular internalisation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of substrate morphology slope distributions on light scattering, nc-Si:H film growth, and solar cell performance.

PubMed

Kim, Do Yun; Santbergen, Rudi; Jäger, Klaus; Sever, Martin; Krč, Janez; Topič, Marko; Hänni, Simon; Zhang, Chao; Heidt, Anna; Meier, Matthias; van Swaaij, René A C M M; Zeman, Miro

2014-12-24

Thin-film silicon solar cells are often deposited on textured ZnO substrates. The solar-cell performance is strongly correlated to the substrate morphology, as this morphology determines light scattering, defective-region formation, and crystalline growth of hydrogenated nanocrystalline silicon (nc-Si:H). Our objective is to gain deeper insight in these correlations using the slope distribution, rms roughness (σ(rms)) and correlation length (lc) of textured substrates. A wide range of surface morphologies was obtained by Ar plasma treatment and wet etching of textured and flat-as-deposited ZnO substrates. The σ(rms), lc and slope distribution were deduced from AFM scans. Especially, the slope distribution of substrates was represented in an efficient way that light scattering and film growth direction can be more directly estimated at the same time. We observed that besides a high σ(rms), a high slope angle is beneficial to obtain high haze and scattering of light at larger angles, resulting in higher short-circuit current density of nc-Si:H solar cells. However, a high slope angle can also promote the creation of defective regions in nc-Si:H films grown on the substrate. It is also found that the crystalline fraction of nc-Si:H solar cells has a stronger correlation with the slope distributions than with σ(rms) of substrates. In this study, we successfully correlate all these observations with the solar-cell performance by using the slope distribution of substrates.

Seed mediated synthesis of nanosized zinc oxide and its electron transporting activity in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Rajkumar, C.; Arulraj, Arunachalam

2018-01-01

A zinc oxide (ZnO) nanoparticle has been synthesized using seed mediated method at a low temperature of 90 °C. To understand its optical, structural and morphological properties of as-synthesized ZnO, it was characterized using various analytical techniques. The obtained result reveals that ZnO nanoparticles possess hexagonal wurtzite crystal structure with an average crystallite size of ˜40 nm. The presence of hydroxyl, amine and alkyl groups was confirmed from Fourier transform infrared analysis. Furthermore, the synthesized ZnO powder has employed as photoanode for the fabrication of dye-sensitized solar cells using Doctor-blade technique. To evaluate its photo-conversion efficiency, the device has been assembled into a cell module and illuminated with the light intensity of 100 mW cm-2. The device exhibits the photo-conversion efficiency of 1.85% with the current density of 4.532 mA cm-2 and voltage of 0.61 V.

Cu2O-based solar cells using oxide semiconductors

NASA Astrophysics Data System (ADS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2016-01-01

We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu2O heterojunction solar cells fabricated using p-type Cu2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa2O4 thin-film layer. In most of the Cu2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga2O3-Al2O3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (Voc) were obtained by using a relatively small amount of MgO or Al2O3, e.g., (ZnO)0.91-(MgO)0.09 and (Ga2O3)0.975-(Al2O3)0.025, respectively. When Cu2O-based heterojunction solar cells were fabricated using Al2O3-Ga2O3-MgO-ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Voc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu2O heterojunction solar cells fabricated using Na-doped Cu2O (Cu2O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a Voc of 0.84 V were obtained in a MgF2/AZO/n-(Ga2O3-Al2O3)/p-Cu2O:Na heterojunction solar cell fabricated using a Cu2O:Na sheet with a resistivity of approximately 10 Ω·cm and a (Ga0.975Al0

The influence of annealing temperature on the interface and photovoltaic properties of CdS/CdSe quantum dots sensitized ZnO nanorods solar cells.

PubMed

Qiu, Xiaofeng; Chen, Ling; Gong, Haibo; Zhu, Min; Han, Jun; Zi, Min; Yang, Xiaopeng; Ji, Changjian; Cao, Bingqiang

2014-09-15

Arrays of ZnO/CdS/CdSe core/shell nanocables with different annealing temperatures have been investigated for CdS/CdSe quantum dots sensitized solar cells (QDSSCs). CdS/CdSe quantum dots were synthesized on the surface of ZnO nanorods that serve as the scaffold via a simple ion-exchange approach. The uniform microstructure was verified by scanning electron microscope and transmission electron microscope. UV-Visible absorption spectrum and Raman spectroscopy analysis indicated noticeable influence of annealing temperature on the interface structural and optical properties of the CdS/CdSe layers. Particularly, the relationship between annealing temperatures and photovoltaic performance of the corresponding QDSSCs was investigated employing photovoltaic conversion, quantum efficiency and electrochemical impedance spectra. It is demonstrated that higher cell efficiency can be obtained by optimizing the annealing temperature through extending the photoresponse range and improving QD layer crystal quality. Copyright © 2014 Elsevier Inc. All rights reserved.

High efficiency and stability of quasi-solid-state dye-sensitized ZnO solar cells using graphene incorporated soluble polystyrene gel electrolytes

NASA Astrophysics Data System (ADS)

Bi, Shi-Qing; Meng, Fan-Li; Zheng, Yan-Zhen; Han, Xue; Tao, Xia; Chen, Jian-Feng

2014-12-01

We report on the preparation of highly effective composite electrolytes by combining the two-dimensional graphene (Gra) and soluble polystyrene (PS) nanobeads on Pt counter electrode for the quasi-solid-state electrolytes of ZnO based dye-sensitized solar cells (DSCs). Under an optimized Gra/electrolyte ratio of 12 mg mL-1, the ionic conductivity (σ) of Gra-PS electrolyte was significantly improved from 32.8 mS cm-1 to 39.8 mS cm-1. And the electrochemical impedance spectroscopy (EIS) analysis proved that the ZnO-DSC with the optimized composite electrolyte possessed the lowest impedance value. As a result, the overall power conversion efficiencies (PCEs) of quasi-solid-state ZnO-DSCs significantly enhanced to 5.08% from initial 4.09%. Moreover, the results of long-term stability assays showed that the gel-state Gra-PS ZnO-DSC could retain over 90% of its initial PCE after radiation of 1000 h under full sunlight outdoors. It is anticipated that this work may provide an effective way to increase the cell efficiency by the introduction of Gra into gel electrolyte as well as a great potential for practical application.

Preferential cytotoxicity of ZnO nanoparticle towards cervical cancer cells induced by ROS-mediated apoptosis and cell cycle arrest for cancer therapy

NASA Astrophysics Data System (ADS)

Sirelkhatim, Amna; Mahmud, Shahrom; Seeni, Azman; Kaus, Noor Haida Mohd

2016-08-01

The present study aimed to synthesize multifunctional ZnO-NP samples, namely ZnO-20, ZnO-40, and ZnO-80 nm, using different approaches, to be used as efficient anticancer agents. Systematic characterizations revealed their particle sizes and demonstrated nanostructures of nanorods (ZnO-80 nm) and nanogranules (ZnO-20 and ZnO-40 nm). They exhibited significant ( p < 0.05) toxicity to HeLa cancer cells. HeLa cell viabilities at 1 mM dose reduced to 37, 32, 15 %, by ZnO-80, ZnO-40, and ZnO-20 nm, respectively, at 48 h. However, the same dose exerted different effects of 79.6, 76, and 75 % on L929 normal cells at 48 h. Measurement of reactive oxygen species (ROS) showed a considerable ROS yields on HeLa cells by all samples with a pronounced percentage (50 %) displayed by ZnO-20 nm. Moreover, ROS-mediated apoptosis induction and blocked cell cycle progression in the S, G2/M, and G0/G1 phases significantly ( p < 0.05). Apoptosis induction was further confirmed by DNA fragmentation and Hoechst-PI costained images viewed under fluorescence microscope. Additionally, morphological changes of HeLa cells visualized under light microscope showed assortment of cell death involved shrinkage, vacuolization and apoptotic bodies' formation. Most importantly, results exposed the impact of size and morphology of ZnO samples on their toxicity to Hela cells mediated mainly by ROS production. ZnO-20 nm in disk form with its nanogranule shape and smallest particle size was the most toxic sample, followed by ZnO-40 nm and then ZnO-80 nm. An additional proposed mechanism contributed in the cell death herein was ZnO decomposition producing zinc ions (Zn2+) into the acidic cancer microenvironment due to the smaller sizes of ZnO-NPs. This mechanism has been adopted in the literatures as a size-dependent phenomenon. The emerged findings were suggested to provide new platforms in the development of therapeutics as selective agents to the fatal cervical cancer, and to benefit from the

Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers.

PubMed

Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

2015-02-18

Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers

NASA Astrophysics Data System (ADS)

Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

2015-02-01

Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

Responses of human cells to ZnO nanoparticles: a gene transcription study†

PubMed Central

Moos, Philip J.; Olszewski, Kyle; Honeggar, Matthew; Cassidy, Pamela; Leachman, Sancy; Woessner, David; Cutler, N. Shane; Veranth, John M.

2013-01-01

The gene transcript profile responses to metal oxide nanoparticles was studied using human cell lines derived from the colon and skin tumors. Much of the research on nanoparticle toxicology has focused on models of inhalation and intact skin exposure, and effects of ingestion exposure and application to diseased skin are relatively unknown. Powders of nominally nanosized SiO2, TiO2, ZnO and Fe2O3 were chosen because these substances are widely used in consumer products. The four oxides were evaluated using colon-derived cell lines, RKO and CaCo-2, and ZnO and TiO2 were evaluated further using skin-derived cell lines HaCaT and SK Mel-28. ZnO induced the most notable gene transcription changes, even though this material was applied at the lowest concentration. Nano-sized and conventional ZnO induced similar responses suggesting common mechanisms of action. The results showed neither a non-specific response pattern common to all substances nor synergy of the particles with TNF-α cotreatment. The response to ZnO was not consistent with a pronounced proinflammatory signature, but involved changes in metal metabolism, chaperonin proteins, and protein folding genes. This response was observed in all cell lines when ZnO was in contact with the human cells. When the cells were exposed to soluble Zn, the genes involved in metal metabolism were induced but the genes involved in protein refoldling were unaffected. This provides some of the first data on the effects of commercial metal oxide nanoparticles on human colon-derived and skin-derived cells. PMID:21769377

Semiconductor hierarchically structured flower-like clusters for dye-sensitized solar cells with nearly 100% charge collection efficiency.

PubMed

Xin, Xukai; Liu, Hsiang-Yu; Ye, Meidan; Lin, Zhiqun

2013-11-21

By combining the ease of producing ZnO nanoflowers with the advantageous chemical stability of TiO2, hierarchically structured hollow TiO2 flower-like clusters were yielded via chemical bath deposition (CBD) of ZnO nanoflowers, followed by their conversion into TiO2 flower-like clusters in the presence of TiO2 precursors. The effects of ZnO precursor concentration, precursor amount, and reaction time on the formation of ZnO nanoflowers were systematically explored. Dye-sensitized solar cells fabricated by utilizing these hierarchically structured ZnO and TiO2 flower clusters exhibited a power conversion efficiency of 1.16% and 2.73%, respectively, under 100 mW cm(-2) illumination. The intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) studies suggested that flower-like structures had a fast electron transit time and their charge collection efficiency was nearly 100%.

Perovskite-based solar cells with inorganic inverted hybrid planar heterojunction structure

NASA Astrophysics Data System (ADS)

Lai, Wei-Chih; Lin, Kun-Wei; Guo, Tzung-Fang; Chen, Peter; Liao, Yuan-Yu

2018-01-01

We demonstrated the good performance of inorganic inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with glass/ITO/NiOx/CH3NH3PbI3 perovskite/C60/ room temperature (RT)-sputtered ZnO/Al structure. We adopted spin coating and RT sputtering for the deposition of NiOx and ZnO, respectively. The inorganic hole and electron transport layer of NiOx and RT-sputtered ZnO, respectively, could improve the open-circuit voltage (VOC), short-circuit current density (JSC), and power conversion efficiency (η%) of the SCs. We obtained inorganic inverted CH3NH3PbI3 perovskite-based SCs with a JSC of 21.96 A/cm2, a VOC of 1.02 V, a fill factor (FF%) of 68.2%, and an η% of 15.3% despite the sputtering damage of the RT-sputtered ZnO deposition. Moreover, the RT-sputtered ZnO could function as a diffusion barrier for Al, moisture, and O2. The inorganic inverted CH3NH3PbI3 perovskite-based SCs demonstrated improved storage reliability.

In vitro toxicity of different-sized ZnO nanoparticles in Caco-2 cells

NASA Astrophysics Data System (ADS)

Kang, Tianshu; Guan, Rongfa; Chen, Xiaoqiang; Song, Yijuan; Jiang, Han; Zhao, Jin

2013-11-01

There has been rapid growth in nanotechnology in both the public and private sectors worldwide, but concern about nanosafety exists. To assess size-dependent cytotoxicity on human cancer cells, we studied the cytotoxic effect of three kinds of zinc oxide nanoparticles (ZnO NPs) on human epithelial colorectal adenocarcinoma (Caco-2) cells. Nanoparticles were first characterized by size, distribution, and intensity. Multiple assays have been adopted to measure the cell activity and oxidative stress. The cytotoxicity of ZnO NPs was time dependent and dose dependent. The 24-h exposure was chosen to confirm the viability and accessibility of the cells and taken as the appropriate time for the following test system. The IC50 value was found at a low concentration. The oxidative stress elicited a significant reduction in glutathione with increase in reactive oxygen species and lactate dehydrogenase. The toxicity resulted in a deletion of cells in the G1 phase and an accumulation of cells in the S and G2/M phases. One type of metallic oxide (ZnO) exerted different cytotoxic effects according to different particle sizes. Data from the previous experiments showed that 26-nm ZnO NPs appeared to have the highest toxicity to Caco-2 cells. The study demonstrated the toxicity of ZnO NPs to Caco-2 cells and the impact of particle size, which could be useful in the medical applications.

Calculation of DSSC parameters based on ZnO nanorod/TiO2 mesoporous photoanode

NASA Astrophysics Data System (ADS)

Safriani, L.; Nurrida, A.; Mulyana, C.; Susilawati, T.; Bahtiar, A.; Aprilia, A.

2017-07-01

Photoanode of dye sensitized solar cell (DSSC) plays an important role as electron transport media to accept photogenerated electron from excited state of dye. There are several physical properties that are required from photoanode of DSSC. It should be highly transparent, have large surface area, has a conduction band lower than LUMO of dye molecule, has high charge carrier mobility and finally has a good stability in redox electrolyte process. In this work, DSSC with structure FTO/ZnO nanorod/TiO2 mesoporous/Ru-dye/gel electrolyte/ Pt/FTO has been fabricated. In order to modified the structures of photoanode, ZnO nanorod was grown on aluminium doped ZnO seed layer by variation concentration of Al (0 wt%, 0.5 wt% and 1.0 wt%). Zinc nitrate hexahydrate and hexamethylenetetramine used as raw materials for ZnO nanorod growth solution and deposited by self-assembly methods on FTO/Al doped ZnO seed layer. It is then followed by deposition of titania (TiO2) paste by screen printing methods. DSSC parameters i.e. ideally factor (n), series resistance (RS ), and shunt resistance (RSH ) was derived from current density-voltage (I-V) curve using the simplify equation of ideal diode model. The influences of ZnO photoanode structures to the solar cell performance will be completely discussed.

Nonlinear Optical Properties of ZnO for BioimagingCell and Cell Destruction

NASA Astrophysics Data System (ADS)

Urban, Ben; Chakki, Samudyatha; Senthilkumar, Os; Senthilkumar, Kasilingam; Fujita, Yasuhisa; Neogi, Arup

2011-03-01

As of recent years nanotechnology has been at the forefront of scientific research. It promises to have a broad range of applications from turning unhealthy foods into health foods, making computers faster and curing cancer. We present results on using nonlinear optical processes of ZnO nano-crystals to detect, track and destroy cells. By incorporating ZnO into a hydrophobic nano-hydrogel matrix with trace amounts of H2 O2 , we can attach antibodies or microRNA for specific cell targeting and, using the heat generating properties of the third order nonlinear process, release H2 O2 in the cell causing instant cell death. Theoretically, with the appropriate sequence for microRNA or the appropriate antibodies, we could target cancer cells in the body and destroy them. This presentation gives our results until now.

Efficient inverted polymer solar cells based on conjugated polyelectrolyte and zinc oxide modified ITO electrode

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

Yuan, Tao; Zhu, Xiaoguang; Tu, Guoli, E-mail: tgl@hust.edu.cn

Efficient inverted polymer solar cells (PSCs) were constructed by utilizing a conjugated polyelectrolyte PF{sub EO}SO{sub 3}Na and zinc oxide to modify the indium tin oxide (ITO) electrode. The ITO electrode modified by PF{sub EO}SO{sub 3}Na and zinc oxide possesses high transparency, increased electron mobility, smoothened surface, and lower work function. PTB7:PC{sub 71}BM inverted PSCs containing the modified ITO electrode achieved a high power conversion efficiency (PCE) of 8.49%, exceeding that of the control device containing a ZnO modified ITO electrode (7.48%). Especially, PCE-10:PC{sub 71}BM inverted polymer solar cells achieved a high PCE up to 9.4%. These results demonstrate a usefulmore » approach to improve the performance of inverted polymer solar cells.« less

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2017-12-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage (J-V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density (J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance (R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode (C μ ) and electron lifetime (t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2018-03-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage ( J- V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density ( J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance ( R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode ( C μ ) and electron lifetime ( t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

An over 18%-efficiency completely buffer-free Cu(In,Ga)Se2 solar cell

NASA Astrophysics Data System (ADS)

Ishizuka, Shogo; Nishinaga, Jiro; Koida, Takashi; Shibata, Hajime

2018-07-01

In this letter, an independently certified photovoltaic efficiency of 18.4% demonstrated from a completely buffer-layer-free Cu(In,Ga)Se2 (CIGS) solar cell is reported. A Si-doped CIGS thin film was used as the photoabsorber layer and a conductive B-doped ZnO (BZO) front electrode layer was directly deposited on the CIGS layer. Metastable acceptor activation by heat-light soaking treatment was performed to maximize the efficiency. The results presented here are expected to serve as a benchmark for simplified-structure CIGS devices as well as a reference for discussions on the role of buffer layers used in conventional CIGS solar cells.

Enhanced fill factor of tandem organic solar cells incorporating a diketopyrrolopyrrole-based low-bandgap polymer and optimized interlayer.

PubMed

Wang, Dong Hwan; Kyaw, Aung Ko Ko; Park, Jong Hyeok

2015-01-01

We demonstrate that reproducible results can be obtained from tandem solar cells based on the wide-bandgap poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2',1',3'-benzothiadiazole] (PCDTBT) and the diketopyrrolopyrrole (DPP)-based narrow bandgap polymer (DT-PDPP2T-TT) with a decyltetradecyl (DT) and an electron-rich 2,5-di-2-thienylthieno[3,2-b]thiophene (2T-TT) group fabricated using an optimized interlayer (ZnO NPs/ph-n-PEDOT:PSS) [NPs: nanoparticles; ph-n: pH-neutral PEDOT: poly(3,4-ethylenedioxythiophene); PSS: polystyrene sulfonate]. The tandem cells are fabricated by applying a simple process without thermal annealing. The ZnO NP interlayer operates well when the ZnO NPs are dispersed in 2-methoxyethanol, as no precipitation and chemical reactions occur. In addition to the ZnO NP film, we used neutral PEDOT:PSS as a second interlayer which is not affect to the sequential deposited bulk heterojunction (BHJ) active layer of acidification. The power conversion efficiency (PCE) of a tandem device reaches 7.4 % (open-circuit voltage VOC =1.53 V, short-circuit current density JSC =7.3 mA cm(-2) , and fill factor FF=67 %). Furthermore, FF is increased to up to 71 % when another promising large bandgap (bandgap ∼1.94 eV) polymer (PBnDT-FTAZ) is used. The surface of each layer with nanoscale morphology (BHJ1/ZnO NPs film/ph-n-PEDOT:PSS/BHJ2) was examined by means of AFM analysis during sequential processing. The combination of these factors, efficient DPP-based narrow bandgap material and optimized interlayer, leads to the high FF (average approaches 70 %) and reproducibly operating tandem BHJ solar cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational Study of Ternary Devices: Stable, Low-Cost, and Efficient Planar Perovskite Solar Cells

NASA Astrophysics Data System (ADS)

Sajid, Sajid; Elseman, Ahmed Mourtada; Ji, Jun; Dou, Shangyi; Wei, Dong; Huang, Hao; Cui, Peng; Xi, Wenkang; Chu, Lihua; Li, Yingfeng; Jiang, Bing; Li, Meicheng

2018-07-01

Although perovskite solar cells with power conversion efficiencies (PCEs) more than 22% have been realized with expensive organic charge-transporting materials, their stability and high cost remain to be addressed. In this work, the perovskite configuration of MAPbX (MA = CH3NH3, X = I3, Br3, or I2Br) integrated with stable and low-cost Cu:NiO x hole-transporting material, ZnO electron-transporting material, and Al counter electrode was modeled as a planar PSC and studied theoretically. A solar cell simulation program (wxAMPS), which served as an update of the popular solar cell simulation tool (AMPS: Analysis of Microelectronic and Photonic Structures), was used. The study yielded a detailed understanding of the role of each component in the solar cell and its effect on the photovoltaic parameters as a whole. The bandgap of active materials and operating temperature of the modeled solar cell were shown to influence the solar cell performance in a significant way. Further, the simulation results reveal a strong dependence of photovoltaic parameters on the thickness and defect density of the light-absorbing layers. Under moderate simulation conditions, the MAPbBr3 and MAPbI2Br cells recorded the highest PCEs of 20.58 and 19.08%, respectively, while MAPbI3 cell gave a value of 16.14%. [Figure not available: see fulltext.

Light trapping in thin-film solar cells measured by Raman spectroscopy

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

Ledinský, M., E-mail: ledinsky@fzu.cz; Photovoltaics and Thin Film Electronics Laboratory, Institute of Microengineering; Moulin, E.

2014-09-15

In this study, Raman spectroscopy is used as a tool to determine the light-trapping capability of textured ZnO front electrodes implemented in microcrystalline silicon (μc-Si:H) solar cells. Microcrystalline silicon films deposited on superstrates of various roughnesses are characterized by Raman micro-spectroscopy at excitation wavelengths of 442 nm, 514 nm, 633 nm, and 785 nm, respectively. The way to measure quantitatively and with a high level of reproducibility the Raman intensity is described in details. By varying the superstrate texture and with it the light trapping in the μc-Si:H absorber layer, we find significant differences in the absolute Raman intensity measured in the near infraredmore » wavelength region (where light trapping is relevant). A good agreement between the absolute Raman intensity and the external quantum efficiency of the μc-Si:H solar cells is obtained, demonstrating the validity of the introduced method. Applications to thin-film solar cells, in general, and other optoelectronic devices are discussed.« less

ZnO Nanoparticles Treatment Induces Apoptosis by Increasing Intracellular ROS Levels in LTEP-a-2 Cells.

PubMed

Wang, Caixia; Hu, Xiaoke; Gao, Yan; Ji, Yinglu

2015-01-01

Owing to the wide use of novel nanoparticles (NPs) such as zinc oxide (ZnO) in all aspects of life, toxicological research on ZnO NPs is receiving increasing attention in these days. In this study, the toxicity of ZnO NPs in a human pulmonary adenocarcinoma cell line LTEP-a-2 was tested in vitro. Log-phase cells were exposed to different levels of ZnO NPs for hours, followed by colorimetric cell viability assay using tetrazolium salt and cell survival rate assay using trypan blue dye. Cell morphological changes were observed by Giemsa staining and light microscopy. Apoptosis was detected by using fluorescence microscopy and caspase-3 activity assay. Both intracellular reactive oxygen species (ROS) and reduced glutathione (GSH) were examined by a microplate-reader method. Results showed that ZnO NPs (≥ 0.01 μg/mL) significantly inhibited proliferation (P < 0.05) and induced substantial apoptosis in LTEP-a-2 cells after 4 h of exposure. The intracellular ROS level rose up to 30-40% corresponding to significant depletion (approximately 70-80%) in GSH content in LTEP-a-2 cells (P < 0.05), suggesting that ZnO NPs induced apoptosis mainly through increased ROS production. This study elucidates the toxicological mechanism of ZnO NPs in human pulmonary adenocarcinoma cells and provides reference data for application of nanomaterials in the environment.

Highly Transparent and UV-Resistant Superhydrophobic SiO2-Coated ZnO Nanorod Arrays

PubMed Central

2015-01-01

Highly transparent and UV-resistant superhydrophobic arrays of SiO2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 °C) steps on both glass and thin sheets of PET (2 × 2 in.2), and the superhydrophobic nanocomposite is shown to have minimal impact on solar cell device performance under AM1.5G illumination. Flexible plastics can serve as front cell and backing materials in the manufacture of flexible displays and solar cells. PMID:24495100

Insights into collaborative separation process of photogenerated charges and superior performance of solar cells

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

Liu, Xiangyang, E-mail: lxy081276@126.com; Wang, Shun; Zheng, Haiwu

2016-07-25

ZnO nanowires/Cu{sub 4}Bi{sub 4}S{sub 9} (ZnO/CBS) and ZnO nanowires/CBS-graphene nanoplates (ZnO/CBS-GNs), as well as two types of solar cells were prepared. The photovoltaic responses of CBS-GNs and ZnO/CBS-GNs can be improved with incorporation of GNs. The transient surface photovoltage (TPV) can provide detailed information on the separation and transport of photogenerated carriers. The multichannel separation process from the TPVs indicates that the macro-photoelectric signals can be attributed to the photogenerated charges separated at the interface of CBS/GNs, rather than CBS/ZnO. The multi-interfacial recombination is the major carrier loss, and the hole selective p-V{sub 2}O{sub 5} can efficiently accelerate the chargemore » extraction to the external circuit. The ZnO/CBS-GNs cell exhibits the superior performance, and the highest efficiency is 10.9%. With the adequate interfaces of CBS/GNs, GNs conductive network, energy level matching, etc., the excitons can easily diffuse to the interface of CBS/GNs, and the separated electrons and holes can be collected quickly, inducing the high photoelectric properties. Here, a facile strategy for solid state solar cells with superior performance presents a potential application.« less

Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

PubMed

Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

2015-07-29

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a

Room temperature enhanced red emission from novel Eu(3+) doped ZnO nanocrystals uniformly dispersed in nanofibers.

PubMed

Zhang, Yongzhe; Liu, Yanxia; Li, Xiaodong; Wang, Qi Jie; Xie, Erqing

2011-10-14

Achieving red emission from ZnO-based materials has long been a goal for researchers in order to realize, for instance, full-color display panels and solid-state light-emitting devices. However, the current technique using Eu(3+) doped ZnO for red emission generation has a significant drawback in that the energy transfer from ZnO to Eu(3+) is inefficient, resulting in a low intensity red emission. In this paper, we report an efficient energy transfer scheme for enhanced red emission from Eu(3+) doped ZnO nanocrystals by fabricating polymer nanofibers embedded with Eu(3+) doped ZnO nanocrystals to facilitate the energy transfer. In the fabrication, ZnO nanocrystals are uniformly dispersed in polymer nanofibers prepared by the high electrical field electrospinning technique. Enhanced red emission without defect radiation from the ZnO matrix is observed. Three physical mechanisms for this observation are provided and explained, namely a small ZnO crystal size, uniformity distribution of ZnO nanocrystals in polymers (PVA in this case), and strong bonding between ZnO and polymer through the -OH group bonding. These explanations are supported by high resolution transmission emission microscopy measurements, resonant Raman scattering characterizations, photoluminescence spectra and photoluminescence excitation spectra measurements. In addition, two models exploring the 'accumulation layer' and 'depletion layer' are developed to explain the reasons for the more efficient energy transfer in our ZnO nanocrystal system compared to that in the previous reports. This study provides an important approach to achieve enhanced energy transfer from nanocrystals to ions which could be widely adopted in rare earth ion doped materials. These discoveries also provide more insights into other energy transfer problems in, for example, dye-sensitized solar cells and quantum dot solar cells.

Efficient inverted bulk-heterojunction polymer solar cells with self-assembled monolayer modified zinc oxide.

PubMed

Kim, Wook Hyun; Lyu, Hong-Kun; Han, Yoon Soo; Woo, Sungho

2013-10-01

The performance of poly(3-hexylthiophen) (P3HT) and [6, 6]phenyl C61 butyric acid methyl ester ([60]PCBM)-based inverted bulk-heterojunction (BHJ) polymer solar cells (PSCs) is enhanced by the modification of zinc oxide (ZnO)/BHJ interface with carboxylic-acid-functionalized self-assembled monolayers (SAMs). Under simulated solar illumination of AM 1.5 (100 mW/cm2), the inverted devices fabricated with SAM-modified ZnO achieved an enhanced power conversion efficiency (PCE) of 3.34% due to the increased fill factor and photocurrent density as compared to unmodified cells with PCE of 2.60%. This result provides an efficient method for interface engineering in inverted BHJ PSCs.

Direct synthesis of vertically aligned ZnO nanowires on FTO substrates using a CVD method and the improvement of photovoltaic performance

PubMed Central

2012-01-01

In this work, we report a direct synthesis of vertically aligned ZnO nanowires on fluorine-doped tin oxide-coated substrates using the chemical vapor deposition (CVD) method. ZnO nanowires with a length of more than 30 μm were synthesized, and dye-sensitized solar cells (DSSCs) based on the as-grown nanowires were fabricated, which showed improvement of the device performance compared to those fabricated using transferred ZnO nanowires. Dependence of the cell performance on nanowire length and annealing temperature was also examined. This synthesis method provided a straightforward, one-step CVD process to grow relatively long ZnO nanowires and avoided subsequent nanowire transfer process, which simplified DSSC fabrication and improved cell performance. PMID:22673046

Surface structure, optoelectronic properties and charge transport in ZnO nanocrystal/MDMO-PPV multilayer films.

PubMed

Lian, Qing; Chen, Mu; Mokhtar, Muhamad Z; Wu, Shanglin; Zhu, Mingning; Whittaker, Eric; O'Brien, Paul; Saunders, Brian R

2018-05-07

Blends of semiconducting nanocrystals and conjugated polymers continue to attract major research interest because of their potential applications in optoelectronic devices, such as solar cells, photodetectors and light-emitting diodes. In this study we investigate the surface structure, morphological and optoelectronic properties of multilayer films constructed from ZnO nanocrystals (NCs) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). The effects of layer number and ZnO concentration (C ZnO ) used on the multilayer film properties are investigated. An optimised solvent blend enabled well-controlled layers to be sequentially spin coated and the construction of multilayer films containing six ZnO NC (Z) and MDMO-PPV (M) layers (denoted as (ZM) 6 ). Contact angle data showed a strong dependence on C ZnO and indicated distinct differences in the coverage of MDMO-PPV by the ZnO NCs. UV-visible spectroscopy showed that the MDMO-PPV absorption increased linearly with the number of layers in the films and demonstrates highly tuneable light absorption. Photoluminescence spectra showed reversible quenching as well as a surprising red-shift of the MDMO-PPV emission peak. Solar cells were constructed to probe vertical photo-generated charge transport. The measurements showed that (ZM) 6 devices prepared using C ZnO = 14.0 mg mL -1 had a remarkably high open circuit voltage of ∼800 mV. The device power conversion efficiency was similar to that of a control bilayer device prepared using a much thicker MDMO-PPV layer. The results of this study provide insight into the structure-optoelectronic property relationships of new semiconducting multilayer films which should also apply to other semiconducting NC/polymer combinations.

Intrinsic and extrinsic doping of ZnO and ZnO alloys

NASA Astrophysics Data System (ADS)

Ellmer, Klaus; Bikowski, André

2016-10-01

In this article the doping of the oxidic compound semiconductor ZnO is reviewed with special emphasis on n-type doping. ZnO naturally exhibits n-type conductivity, which is used in the application of highly doped n-type ZnO as a transparent electrode, for instance in thin film solar cells. For prospective application of ZnO in other electronic devices (LEDs, UV photodetectors or power devices) p-type doping is required, which has been reported only minimally. Highly n-type doped ZnO can be prepared by doping with the group IIIB elements B, Al, Ga, and In, which act as shallow donors according to the simple hydrogen-like substitutional donor model of Bethe (1942 Theory of the Boundary Layer of Crystal Rectifiers (Boston, MA: MIT Rad Lab.)). Group IIIA elements (Sc, Y, La etc) are also known to act as shallow donors in ZnO, similarly explainable by the shallow donor model of Bethe. Some reports showed that even group IVA (Ti, Zr, Hf) and IVB (Si, Ge) elements can be used to prepare highly doped ZnO films—which, however, can no longer be explained by the simple hydrogen-like substitutional donor model. More probably, these elements form defect complexes that act as shallow donors in ZnO. On the other hand, group V elements on oxygen lattice sites (N, P, As, and Sb), which were viewed for a long time as typical shallow acceptors, behave instead as deep acceptors, preventing high hole concentrations in ZnO at room temperature. Also, ‘self’-compensation, i.e. the formation of a large number of intrinsic donors at high acceptor concentrations seems to counteract the p-type doping of ZnO. At donor concentrations above about 1020 cm-3, the electrical activation of the dopant elements is often less than 100%, especially in polycrystalline thin films. Reasons for the electrical deactivation of the dopant atoms are (i) the formation of dopant-defect complexes, (ii) the compensation of the electrons by acceptors (Oi, VZn) or (iii) the formation of secondary phases, for

Effect of Temperature and Growth Time on Vertically Aligned ZnO Nanorods by Simplified Hydrothermal Technique for Photoelectrochemical Cells.

PubMed

Mohd Fudzi, Laimy; Zainal, Zulkarnain; Lim, Hong Ngee; Chang, Sook-Keng; Holi, Araa Mebdir; Sarif Mohd Ali, Mahanim

2018-04-29

Despite its large band gap, ZnO has wide applicability in many fields ranging from gas sensors to solar cells. ZnO was chosen over other materials because of its large exciton binding energy (60 meV) and its stability to high-energy radiation. In this study, ZnO nanorods were deposited on ITO glass via a simple dip coating followed by a hydrothermal growth. The morphological, structural and compositional characteristics of the prepared films were analyzed using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). Photoelectrochemical conversion efficiencies were evaluated via photocurrent measurements under calibrated halogen lamp illumination. Thin film prepared at 120 °C for 4 h of hydrothermal treatment possessed a hexagonal wurtzite structure with the crystallite size of 19.2 nm. The average diameter of the ZnO nanorods was 37.7 nm and the thickness was found to be 2680.2 nm. According to FESEM images, as the hydrothermal growth temperature increases, the nanorod diameter become smaller. Moreover, the thickness of the nanorods increase with the growth time. Therefore, the sample prepared at 120 °C for 4 h displayed an impressive photoresponse by achieving high current density of 0.1944 mA/cm².

Interface Engineering through Atomic Layer Deposition towards Highly Improved Performance of Dye-Sensitized Solar Cells

PubMed Central

Lu, Hao; Tian, Wei; Guo, Jun; Li, Liang

2015-01-01

A composite photoanode comprising ultralong ZnO nanobelts and TiO2 nanoparticles was prepared and its performance in dye-sensitized solar cells (DSSCs) was optimized and compared to the photoanode consisting of conventional TiO2 nanoparticles. The ultralong ZnO nanobelts were synthesized in high yield by a facile solution approach at 90 oC followed by annealing at 500 oC. The effect of the ratio of ZnO nanobelts to TiO2 nanoparticles on the light scattering, specific surface area, and interface recombination were investigated. An optimum amount of ZnO nanobelts enhanced the photon-conversion efficiency by 61.4% compared to that of the conventional TiO2 nanoparticles. To further reduce the recombination rate and increase the carrier lifetime, Atomic Layer Deposition (ALD) technique was utilized to coat a continuous TiO2 film surrounding the ZnO nanobelts and TiO2 nanoparticles, functioning as a barrier-free access of all electrons to conductive electrodes. This ALD treatment improved the interface contact within the whole photoanode system, finally leading to significant enhancement (137%) in the conversion efficiency of DSSCs. PMID:26238737

Involvement of PINK1/parkin-mediated mitophagy in ZnO nanoparticle-induced toxicity in BV-2 cells.

PubMed

Wei, Limin; Wang, Jianfeng; Chen, Aijie; Liu, Jia; Feng, Xiaoli; Shao, Longquan

2017-01-01

With the increasing application of zinc oxide nanoparticles (ZnO NPs) in biological materials, the neurotoxicity caused by these particles has raised serious concerns. However, the underlying molecular mechanisms of the toxic effect of ZnO NPs on brain cells remain unclear. Mitochondrial damage has been reported to be a factor in the toxicity of ZnO NPs. PINK1/parkin-mediated mitophagy is a newly emerging additional function of autophagy that selectively degrades impaired mitochondria. Here, a PINK1 gene knockdown BV-2 cell model was established to determine whether PINK1/parkin-mediated mitophagy was involved in ZnO NP-induced toxicity in BV-2 cells. The expression of total parkin, mito-parkin, cyto-parkin, and PINK1 both in wild type and PINK1 -/- BV-2 cells was evaluated using Western blot analysis after the cells were exposed to 10 μg/mL of 50 nm ZnO NPs for 2, 4, 8, 12, and 24 h. The findings suggested that the downregulation of PINK1 resulted in a significant reduction in the survival rate after ZnO NP exposure compared with that of control cells. ZnO NPs were found to induce the transportation of parkin from the cytoplasm to the mitochondria, implying the involvement of mitophagy in ZnO NP-induced toxicity. The deletion of the PINK1 gene inhibited the recruitment of parkin to the mitochondria, causing failure of the cell to trigger mitophagy. The present study demonstrated that apart from autophagy, PINK1/parkin-mediated mitophagy plays a protective role in ZnO NP-induced cytotoxicity.

Involvement of PINK1/parkin-mediated mitophagy in ZnO nanoparticle-induced toxicity in BV-2 cells

PubMed Central

Wei, Limin; Wang, Jianfeng; Chen, Aijie; Liu, Jia; Feng, Xiaoli; Shao, Longquan

2017-01-01

With the increasing application of zinc oxide nanoparticles (ZnO NPs) in biological materials, the neurotoxicity caused by these particles has raised serious concerns. However, the underlying molecular mechanisms of the toxic effect of ZnO NPs on brain cells remain unclear. Mitochondrial damage has been reported to be a factor in the toxicity of ZnO NPs. PINK1/parkin-mediated mitophagy is a newly emerging additional function of autophagy that selectively degrades impaired mitochondria. Here, a PINK1 gene knockdown BV-2 cell model was established to determine whether PINK1/parkin-mediated mitophagy was involved in ZnO NP-induced toxicity in BV-2 cells. The expression of total parkin, mito-parkin, cyto-parkin, and PINK1 both in wild type and PINK1−/− BV-2 cells was evaluated using Western blot analysis after the cells were exposed to 10 μg/mL of 50 nm ZnO NPs for 2, 4, 8, 12, and 24 h. The findings suggested that the downregulation of PINK1 resulted in a significant reduction in the survival rate after ZnO NP exposure compared with that of control cells. ZnO NPs were found to induce the transportation of parkin from the cytoplasm to the mitochondria, implying the involvement of mitophagy in ZnO NP-induced toxicity. The deletion of the PINK1 gene inhibited the recruitment of parkin to the mitochondria, causing failure of the cell to trigger mitophagy. The present study demonstrated that apart from autophagy, PINK1/parkin-mediated mitophagy plays a protective role in ZnO NP-induced cytotoxicity. PMID:28331313

Impedance measurement of Cobalt doped ZnO Quantum dots

NASA Astrophysics Data System (ADS)

Tiwari, Ram; Kaphle, Amrit; Hari, Parameswar

We investigated structural, thermal and electrical properties of ZnO Quantum dots grown by precipitation method. QDs were spin coated on ITO and annealed at various temperatures ranging from 1000C to 300 0C. ZnO QDs were doped with cobalt for concentration ranging from 0-15%. XRD measurement showed increase in bond length, strain, dislocation density and Cell volume as the doping level varied from 0% to 15%. Impedance Spectroscopy measurements represented by Cole-Cole plot showed reduction in resistance as the cobalt doping concentration increased from 0-15%. Thermal activation energy was obtained by plotting resistivity Vs temperature for doped samples at temperatures from 1000C to 3000C. The thermal activation energy decreased from 85.13meV to 58.21meV as doping increased from 0-15%. Relaxation time was extracted by fitting data to RC model. Relaxation time varied from 61.57 ns to 3.76 ns as the cobalt concentration increased from 0% to 15%. We will also discuss applications of cobalt doped ZnO QDs on improving conversion efficiency of solar cells.

Eosin-Y sensitized core-shell TiO2-ZnO nano-structured photoanodes for dye-sensitized solar cell applications.

PubMed

Manikandan, V S; Palai, Akshaya K; Mohanty, Smita; Nayak, Sanjay K

2018-06-01

In the current investigation, TiO 2 and TiO 2 -ZnO (core-shell) spherical nanoparticles were synthesized by simple combined hydrolysis and refluxing method. A TiO 2 core nanomaterial on the shell material of ZnO was synthesized by utilizing variable ratios of ZnO. The structural characterization of TiO 2 -ZnO core/shell nanoparticles were done by XRD analysis. The spherical structured morphology of the TiO 2 -ZnO has been confirmed through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies. The UV-visible spectra of TiO 2 -ZnO nanostructures were also compared with the pristine TiO 2 to investigate the shift of wavelength. The TiO 2 -ZnO core/shell nanoparticles at the interface efficiently collect the photogenarated electrons from ZnO and also ZnO act a barrier for reduced charge recombination of electrolyte and dye-nanoparticles interface. This combination improved the light absorption which induced the charge transfer ability and dye loading capacity of core-shell nanoparticles. An enhancement in the short circuit current (J sc ) from 1.67 mA/cm 2 to 2.1 mA/cm 2 has been observed for TiO 2 -ZnObased photoanode (with platinum free counter electrode), promises an improvement in the energy conversion efficiency by 57% in comparison with that of the DSSCs based on the pristine TiO 2 . Henceforth, TiO 2 -ZnO photoelectrode in ZnO will effectively act as barrier at the interface of TiO 2 -ZnO and TiO 2 , ensuring the potential for DSSC application. Copyright © 2018 Elsevier B.V. All rights reserved.

Semitransparent Flexible Organic Solar Cells Employing Doped-Graphene Layers as Anode and Cathode Electrodes.

PubMed

Shin, Dong Hee; Jang, Chan Wook; Lee, Ha Seung; Seo, Sang Woo; Choi, Suk-Ho

2018-01-31

Semitransparent flexible photovoltaic cells are advantageous for effective use of solar energy in many areas such as building-integrated solar-power generation and portable photovoltaic chargers. We report semitransparent and flexible organic solar cells (FOSCs) with high aperture, composed of doped graphene layers, ZnO, P3HT:PCBM, and PEDOT:PSS as anode/cathode transparent conductive electrodes (TCEs), electron transport layer, photoactive layer, and hole transport layer, respectively, fabricated based on simple solution processing. The FOSCs do not only harvest solar energy from ultraviolet-visible region but are also less sensitive to near-infrared photons, indicating semitransparency. For the anode/cathode TCEs, graphene is doped with bis(trifluoromethanesulfonyl)-amide or triethylene tetramine, respectively. Power conversion efficiency (PCE) of 3.12% is obtained from the fundamental FOSC structure, and the PCE is further enhanced to 4.23% by adding an Al reflective mirror on the top or bottom side of the FOSCs. The FOSCs also exhibit remarkable mechanical flexibilities through bending tests for various curvature radii.

Role of organic interfacial modifiers in inverted polymers solar cells: An in-depth analysis of perylene vs fullerene organic modifiers

NASA Astrophysics Data System (ADS)

Kumar, S.; Panigrahi, D.; Dhar, A.

2018-03-01

Interfacial issues can significantly restrict the performance of photovoltaic devices by exacerbating the charge recombination channels, macroscopic phase separation, and providing a non-ideal contact for selective extraction of charges particularly in photovoltaic devices using organic and inorganic materials together. Organic interfacial modifiers (IMs) are often used to mitigate these issues by modifying the organic-inorganic interface. In order to extricate the role of these IMs on the photovoltaic performance we have made a comprehensive study on the application of perylene-based and fullerene small molecules having different molecular origin as organic IMs on ZnO electron extracting layers in inverted BHJs photovoltaic devices. We report an elaborate study on the electronic and surface altering properties of these IMs and correlated their effect on the different PV performance parameters of the inverted BHJ solar cells employing P3HT: PCBM photoactive layer. Our investigations demonstrate the role of these organic IMs in reducing the ZnO cathode work function and increasing its electron transportation property along with the passivation of superficial traps states present on ZnO which helps in selective extraction of charge carriers from the devices and minimize the recombination losses. These different aspects of IMs compete and their balanced effect decides the final outcome. As a result, we obtain a substantial improvement in the device performance with power conversion efficiency (PCE) of 3.0% for the C70/ZnO cathode device which shows over 60% improvement in contrast to the devices without any ZnO surface modification. The present investigation intents to exhibit the feasibility of vacuum sublimated organic small molecules in performance improvement in BHJ solar cells utilizing the ZnO ETLs and contrast their efficacy for the purpose rather than setting any benchmark device performance although the efficiencies obtained are typical for the active layer

Nanostructured Solar Cells.

PubMed

Chen, Guanying; Ning, Zhijun; Ågren, Hans

2016-08-09

We are glad to announce the Special Issue "Nanostructured Solar Cells", published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3-B2O3-ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance

NASA Astrophysics Data System (ADS)

Kim, Bit-Na; Kim, Hyeong Jun; Chang, Hyo Sik; Hong, Hyun Seon; Ryu, Sung-Soo; Lee, Heon

2013-10-01

In this study, eco-friendly Pb-free Bi2O3-B2O3-ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

A study on the optics of copper indium gallium (di)selenide (CIGS) solar cells with ultra-thin absorber layers.

PubMed

Xu, Man; Wachters, Arthur J H; van Deelen, Joop; Mourad, Maurice C D; Buskens, Pascal J P

2014-03-10

We present a systematic study of the effect of variation of the zinc oxide (ZnO) and copper indium gallium (di)selenide (CIGS) layer thickness on the absorption characteristics of CIGS solar cells using a simulation program based on finite element method (FEM). We show that the absorption in the CIGS layer does not decrease monotonically with its layer thickness due to interference effects. Ergo, high precision is required in the CIGS production process, especially when using ultra-thin absorber layers, to accurately realize the required thickness of the ZnO, cadmium sulfide (CdS) and CIGS layer. We show that patterning the ZnO window layer can strongly suppress these interference effects allowing a higher tolerance in the production process.

Toxicity of nano- and micro-sized ZnO particles in human lung epithelial cells

NASA Astrophysics Data System (ADS)

Lin, Weisheng; Xu, Yi; Huang, Chuan-Chin; Ma, Yinfa; Shannon, Katie B.; Chen, Da-Ren; Huang, Yue-Wern

2009-01-01

This is the first comprehensive study to evaluate the cytotoxicity, biochemical mechanisms of toxicity, and oxidative DNA damage caused by exposing human bronchoalveolar carcinoma-derived cells (A549) to 70 and 420 nm ZnO particles. Particles of either size significantly reduced cell viability in a dose- and time-dependent manner within a rather narrow dosage range. Particle mass-based dosimetry and particle-specific surface area-based dosimetry yielded two distinct patterns of cytotoxicity in both 70 and 420 nm ZnO particles. Elevated levels of reactive oxygen species (ROS) resulted in intracellular oxidative stress, lipid peroxidation, cell membrane leakage, and oxidative DNA damage. The protective effect of N-acetylcysteine on ZnO-induced cytotoxicity further implicated oxidative stress in the cytotoxicity. Free Zn2+ and metal impurities were not major contributors of ROS induction as indicated by limited free Zn2+ cytotoxicity, extent of Zn2+ dissociation in the cell culture medium, and inductively-coupled plasma-mass spectrometry metal analysis. We conclude that (1) exposure to both sizes of ZnO particles leads to dose- and time-dependent cytotoxicity reflected in oxidative stress, lipid peroxidation, cell membrane damage, and oxidative DNA damage, (2) ZnO particles exhibit a much steeper dose-response pattern unseen in other metal oxides, and (3) neither free Zn2+ nor metal impurity in the ZnO particle samples is the cause of cytotoxicity.

Thin-film copper indium gallium selenide solar cell based on low-temperature all-printing process.

PubMed

Singh, Manjeet; Jiu, Jinting; Sugahara, Tohru; Suganuma, Katsuaki

2014-09-24

In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol-gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm(2), and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C.

Effect of polyvinyl alcohol on electrochemically deposited ZnO thin films for DSSC applications

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2017-05-01

Nanostructures of zinc oxide (ZnO) thin film are electrochemically deposited in the absence and presence of polyvinyl alcohol (PVA) on fluorine doped tin oxide (FTO) substrate. X-ray diffraction (XRD) patterns and Raman spectroscopy confirmed the formation of hexagonal structure of ZnO. The film prepared in the presence of PVA showed a better crystallinity and its crystalline growth along the (002) plane orientation. Field emission scanning electron microscope (FE-SEM) images display nanowire arrays (NWAs) and sponge like morphology for films prepared in the absence and presence of PVA, respectively. Photoluminescence (PL) spectra depict the film prepared in the presence PVA having less atomic defects with good crystal quality compared with other film. Dye sensitized solar cell (DSSC) is constructed using low cost eosin yellow dye and current-voltage (J-V) curve is recorded for optimized sponge like morphology based solar cell.

High efficiency copper indium gallium diselenide (CIGS) thin film solar cells

NASA Astrophysics Data System (ADS)

Rajanikant, Ray Jayminkumar

pressure of 10-5 mbar. The thickness of the film was kept 1 mum for the solar cell device preparation. Rapid Thermal Annealing (RTA) is carried out of CIGS thin film at 500 °C for 2 minutes in the argon atmosphere. Annealing process mainly improves the grain growth of the CIGS and, hence the surface roughness, which is essential for a multilayered semiconductor structure. Thin layer of n-type highly resistive cadmium sulphide (CdS), generally known as a "buffer" layer, is deposited on CIGS layer by thermal and flash evaporation method at the substrate temperature of 100 °C. The CdS thin film plays a crucial role in the formation of the p-n junction and thus the solar cell device performance. The effect of CdS film substrate temperature ranging from 50 °C to 200 °C is observed. At the 100 °C substrate temperature, CdS thin film shows the near to 85 % of transmission in the visible region and resistivity of the order of greater then 20 x 109 Ocm, which are the essential characteristics of buffer layer. The bi-layer structure of ZnO, containing 70 nm i-ZnO and 500 nm aluminum (Al) doped ZnO, act as a transparent front-contact for CIGS thin film solar cell. These layers were deposited using RF magnetron sputtering. i-ZnO thin film acts as an insulating layer, which prevents the recombination of the photo-generated carries and also minimizes the lattice miss match defects between CdS and Al-ZnO. The resistivity of iZnO and Al-ZnO is of the order of 1012 Ocm and 10-4 Ocm, respectively. Al-ZnO thin films act as transparent conducting top electrode having transparency of about 85 % in the visible region. On Al-ZnO layer the finger-type grid pattern of silver (Ag), 200 nm thick, is deposited for the collection of photo-generated carriers. The thin film based multilayered structure Mo / CIGS / CdS / i-ZnO / Al-ZnO / Ag grid of CIGS solar cell is grown one by one on a single glass substrate. As-prepared CIGS solar cell device shows a minute photovoltaic effect. For the further

Physico-chemical characteristics of ZnO nanoparticles-based discs and toxic effect on human cervical cancer HeLa cells

NASA Astrophysics Data System (ADS)

Sirelkhatim, Amna; Mahmud, Shahrom; Seeni, Azman; Kaus, Noor Haida Mohd.; Sendi, Rabab

2014-10-01

In this study, we investigated physico-chemical properties of zinc oxide nanoparticles (ZnO NPs)-based discs and their toxicity on human cervical cancer HeLa cell lines. ZnO NPs (80 nm) were produced by the conventional ceramic processing method. FESEM analysis indicated dominant structure of nanorods with dimensions 100-500 nm in length, and 20-100 nm in diameter. The high content of ZnO nanorods in the discs probably played significant role in toxicity towards HeLa cells. Structural defects (oxygen vacancies and zinc/oxygen interstitials) were revealed by PL spectra peaks at 370-376 nm and 519-533 nm for the ZnO discs. The structural, optical and electrical properties of prepared sample have influenced the toxicological effects of ZnO discs towards HeLa cell lines via the generation of reactive oxygen species (ROS), internalization, membrane damage, and eventually cell death. The larger surface to volume area of the ZnO nanorods, combined with defects, stimulated enhanced toxicity via ROS generation hydrogen peroxide, hydroxyl radicals, and superoxide anion. The preliminary results confirmed the ZnO-disc toxicity on HeLa cells was significantly associated with the unique physicochemical properties of ZnO NPs and to our knowledge, this is the first cellular study for treatment of HeLa cells with ZnO discs made from 80 nm ZnO particles.

Photosensitization of ZnO nanowires with CdSe quantum dots for photovoltaic devices.

PubMed

Leschkies, Kurtis S; Divakar, Ramachandran; Basu, Joysurya; Enache-Pommer, Emil; Boercker, Janice E; Carter, C Barry; Kortshagen, Uwe R; Norris, David J; Aydil, Eray S

2007-06-01

We combine CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell. An array of ZnO nanowires was grown vertically from a fluorine-doped tin oxide conducting substrate. CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot-nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. With a liquid electrolyte as the hole transport medium, quantum-dot-sensitized nanowire solar cells exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuit voltages of 0.5-0.6 V when illuminated with 100 mW/cm2 simulated AM1.5 spectrum. Internal quantum efficiencies as high as 50-60% were also obtained.

Understanding chemically processed solar cells based on quantum dots

PubMed Central

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Abstract Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum. PMID:28567179

Understanding chemically processed solar cells based on quantum dots

NASA Astrophysics Data System (ADS)

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-12-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

Understanding chemically processed solar cells based on quantum dots.

PubMed

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO 2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

Enhanced performance of P3HT/(PCBM:ZnO:TiO{sub 2}) blend based hybrid organic solar cells

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

Ikram, M., E-mail: mianraj.1981@gmail.com; Murray, R.; Imran, M.

Highlights: • We fabricated hybrid bulk heterojunction organic solar cells. • TiO{sub 2} and ZnO nanoparticles replace PCBM with fixed amount of P3HT in active layer • PCE was significantly improved by the introduction of TiO{sub 2} and ZnO. • A possible route toward low-cost OPV. • To the best of my knowledge, this work is the first time going to report. - Abstract: Quaternary blend hybrid organic solar cells enjoy both an increased light absorption range and an easy method to fabricate because of the simple structure. In this study effects of mixing inorganic metal oxides (ZnO and TiO{submore » 2}) nanoparticles to the active layer of organic photovoltaics devices were investigated. The active layer primarily consists of various ratios of electron donor poly (3-hexylthiophene) (P3HT) and an electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) together with nanostructured ZnO and TiO{sub 2} dispersed in chlorobenzene (CB) and 1,2-dichlorobenzene (DCB). The ratio of PCBM to nanoparticles was varied keeping the ratio of P3HT to acceptor material constant. Mixing of nanoparticle plays a significant role in the resulting power conversion efficiency (PCE) of the devices. An increased PCE for ZnO/TiO{sub 2} doped devices can be attributed to increased absorption in the visible region and enhanced charge collection due to the percolation networks formed by metal oxides nanoparticles.« less

Optimalization activity of ZnO NR/TiO2 NR-P3HT as an active layer based on hybrid bulk heterojunction on dye sensitized solar cell (DSSC)

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

Saputri, Liya Nikmatul Maula Zulfa; Ramelan, Ari Handono; Hanif, Qonita Awliya

2016-04-19

Dye sensitized solar cell (DSSC) with metal inorganic and conjugated organic polymer mixture, ZnO NR/TiO{sub 2} NR-P3HT as an active layer based on hybrid bulk heterojunction has been studied. The hybrid material was used to optimize DSSC performs for better efficiency than only TiO{sub 2} as an electrode. Synthesis of TiO{sub 2} nanorods (NR) was conducted by ball milling 1000 rpm for 4 hours and strong base reaction by hydrothermal process at 120 °C overnight. And the ZnO NR was synthesized from Zn(NO{sub 3}){sub 2}.4H{sub 2}O precusor by hydrotermal process at 90 °C for 5 hours and calcined on various temperaturemore » s of 400, 600, and 800 °C. ZnO NR was coated into an Tndium Tin Oxide (TTO) glass to collecting electron s effectively, where TiO{sup 2} NR were incorporated with poly(3 -hexylthiophene) (P3HT) on various concentration s of 5, 10, 15 mg/mL to obtain a larger surface area. Material characterization were performed by X -Ray Diffraction (XRD) and Uv-Vis spectrophotometer. For an application of DSSC were measured by T-V Keithley Multimeter and the efficiency of DSSC at various P3HT’s concentrations of 5, 10, 15 mg/mL were 7.44 × 10{sup −3}, 0.0114, 0.0104, respectively. The maximum efficiency of DSSC was showed when TiO{sup 2} NR-P3HT’s concentration was 10 mg/mL.« less

Electrodeposition and characterization of ZnO thin films using sodium thiosulfate as an additive for photovoltaic solar cells

NASA Astrophysics Data System (ADS)

Rahal, Hassiba; Kihal, Rafiaa; Affoune, Abed Mohamed; Ghers, Mokhtar; Djazi, Faycal

2017-06-01

Zinc oxide thin films have been grown by electrodeposition technique onto Cu and ITO-coated glass substrates from an aqueous zinc nitrate solution with addition of sodium thiosulfate at 90 °C. The effects of sodium thiosulfate on the electrochemical deposition of ZnO were investigated by cyclic voltammetry and chronoamperometry techniques. Deposited films were obtained at -0.60 V vs. SCE and characterized by XRD, SEM, FTIR, optical, photoelectrochemical and electrical measurements. Thickness of the deposited film was measured to be 357 nm. X-ray diffraction results indicated that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along (002) plane. FTIR results confirmed the presence of ZnO films at peak 558 cm-1. SEM images showed uniform, compact morphology without any cracks and films composed of large flower-like ZnO agglomerates with star-shape. Optical properties of ZnO reveal a high optical transmission (> 80 % ) and high absorption coefficient (α > {10}5 {{cm}}-1) in visible region. The optical energy band gap was found to be 3.28 eV. Photoelectrochemical measurements indicated that the ZnO films had n-type semiconductor conduction. Electrical properties of ZnO films showed a low electrical resistivity of 6.54 {{Ω }}\\cdot {cm}, carrier concentration of -1.3× {10}17 {{cm}}-3 and mobility of 7.35 cm2 V-1 s-1. Project supported by the Algerian Ministry of Higher Education and Scientific Research, Algeria (No. J0101520090018).

Facile synthesis of Zn1-xCoxO/ZnO core/shell nanostructures and their application to dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Manthina, Venkata; Agrios, Alexander G.

2017-04-01

Heterostructures consisting of Co-doped ZnO nanorod cores encased in an undoped ZnO shell were successfully synthesized to serve as photoanodes for dye-sensitized solar cells (DSSCs) by a two-step chemical bath deposition (CBD) technique. This yields a highly favorable structure in which electrons injected from the dye into the ZnO then step down in energy into the Co-doped core, where the electron is transported to the collector while the ZnO shell acts as a barrier to recombination with the electrolyte. Incorporation of the core/shell structures into DSSCs resulted in large improvements in photocurrent and photovoltage in comparison to pure ZnO nanorod-based DSSCs. SEM and XRD characterization indicate incorporation of the Co2+ into the ZnO matrix, without separation of the Co into other phases, providing no energy barriers. In addition, the ability of these heterostructures to reduce recombination rates in redox couples with fast recombination rates was probed by comparing DSSC device performance in both iodide/triiodide-based and ferrocene/ferrocenium-based electrolytes.

All-inorganic large-area low-cost and durable flexible perovskite solar cells using copper foil as a substrate.

PubMed

Abdollahi Nejand, B; Nazari, P; Gharibzadeh, S; Ahmadi, V; Moshaii, A

2017-01-05

Here, a low-cost perovskite solar cell using CuI and ZnO as the respective inorganic hole and electron transport layers is introduced. Copper foil is chosen as a cheap and low-weight conductive substrate which has a similar work function to ITO. Besides, copper foil is an interesting copper atom source for the growth of the upper cuprous iodide layer on copper foil. A spray coating of a transparent silver nanowire electrode is used as a top contact. The prepared device shows a maximum power conversion efficiency of 12.80% and long-term durability providing an environmentally and market friendly perovskite solar cell.

Efficient dye-sensitized solar cells from mesoporous zinc oxide nanostructures sensitized by N719 dye

NASA Astrophysics Data System (ADS)

Kumara, G. R. A.; Deshapriya, U.; Ranasinghe, C. S. K.; Jayaweera, E. N.; Rajapakse, R. M. G.

2018-03-01

Dye-sensitized solar cells (DSCs) have attracted a great deal of attention due to their low-cost and high power conversion efficiencies. They usually utilize an interconnected nanoparticle layer of TiO2 as the electron transport medium. From the fundamental point of view, faster mobility of electrons in ZnO is expected to contribute to better performance in DSCs than TiO2, though the actual practical situation is quite the opposite. In this research, we addressed this problem by first applying a dense layer of ZnO on FTO followed by a mesoporous layer of interconnected ZnO nanoparticle layer, both were prepared by spray pyrolysis technique. The best cell shows a power conversion efficiency of 5.2% when the mesoporous layer thickness is 14 μm and the concentration of the N719 dye in dye coating solution is 0.3 mM, while a cell without a dense layer shows 4.2% under identical conditions. The surface concentration of dye adsorbed in the cell with a dense layer and that without a dense layer are 5.00 × 10‑7 and 3.34 × 10‑7 mol/cm2, respectively. The cell with the dense layer has an electron lifetime of 54.81 ms whereas that without the dense layer is 11.08 ms. As such, the presence of the dense layer improves DSC characteristics of ZnO-based DSCs.

ZnO thin films and nanostructures for emerging optoelectronic applications

NASA Astrophysics Data System (ADS)

Rogers, D. J.; Teherani, F. H.; Sandana, V. E.; Razeghi, M.

2010-02-01

ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO.

Synthesis and characterization of ZnO/ZnSe NWs/PbS QDs solar cell

NASA Astrophysics Data System (ADS)

Kamruzzaman, M.; Zapien, J. A.

2017-04-01

The capture of solar energy has gained the attention for the next generation solar cell. ZnO/ZnSe NW arrays were synthesized on an FTO glass substrate using a simple and facile hydrothermal and ion-exchange approaches. The lead sulfide (PbS) QDs was infiltrated into ZnO/ZnSe NWs via SILAR method for making inorganic quantum dot sensitized ZnO/ZnSe/PbS QDs solar cell. The surface morphology, structural, optical, and J-V characteristics have been investigated. The ZnO/ZnSe NW is a core-shell like structure, and the absorption edge shifted from the UV region (ZnO NWs) to the near infrared region for ZnO/ZnSe NWs/PbS QDs. For PbS QDs-sensitized solar cell, the obtained value of η = 1.1%, J sc = 20.60 mA/cm2, V oc = 155 mV, and FF = 34.7%, respectively. The photovoltaic performance of the device in this study is still inferior. However, it is the first report regarding to ZnO/ZnZe NWs/PbS QDs solar cell. The achieving high absorption and large short circuit current density may interest in further improvement of the device performance by suppressing surface defects, optimizing the quality of ZnO/ZnSe NWs and PbS QDs.

Rapid green synthesis of ZnO nanoparticles using a hydroelectric cell without an electrolyte

NASA Astrophysics Data System (ADS)

Shah, Jyoti; Kumar Kotnala, Ravinder

2017-09-01

In this study, zinc oxide (ZnO) nanoparticles were synthesized using a novel environmentally friendly hydroelectric cell without an electrolyte or external current source. The hydroelectric cell comprised a nanoporous Li substituted magnesium ferrite pellet in contact with two electrodes, with zinc as the anode and silver as an inert cathode. The surface unsaturated cations and oxygen vacancies in the nanoporous ferrite dissociated water molecules into hydronium and hydroxide ions when the hydroelectric cell was dipped into deionized water. Hydroxide ions migrated toward the zinc electrode to form zinc hydroxide and the hydronium ions were evolved as H2 gas at the silver electrode. The zinc hydroxide collected as anode mud was converted into ZnO nanoparticles by heating at 250 °C. Structural analysis using Raman spectroscopy indicated the good crystallinity of the ZnO nanoparticles according to the presence of a high intensity E2-(high) mode. The nanoparticle size distribution was 5-20 nm according to high resolution transmission electron microscopy. An indirect band gap of 2.75 eV was determined based on the Tauc plot, which indicated the existence of an interstitial cation level in ZnO. Near band edge and blue emissions were detected in photoluminescence spectral studies. The blue emissions obtained from the ZnO nanoparticles could potentially have applications in blue lasers and LEDs. The ZnO nanoparticles synthesized using this method had a high dielectric constant value of 5 at a frequency of 1 MHz, which could be useful for fabricating nano-oscillators. This facile, clean, and cost-effective method obtained a significant yield of 0.017 g for ZnO nanoparticles without applying an external current source.

Fullerene derivative-doped zinc oxide nanofilm as the cathode of inverted polymer solar cells with low-bandgap polymer (PTB7-Th) for high performance.

PubMed

Liao, Sih-Hao; Jhuo, Hong-Jyun; Cheng, Yu-Shan; Chen, Show-An

2013-09-14

Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

PubMed Central

Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M.A.; Ahamed, Maqusood

2015-01-01

We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33–55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved. PMID:26347142

Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

NASA Astrophysics Data System (ADS)

Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M. A.; Ahamed, Maqusood

2015-09-01

We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells.

PubMed

Akhtar, Mohd Javed; Alhadlaq, Hisham A; Alshamsan, Aws; Majeed Khan, M A; Ahamed, Maqusood

2015-09-08

We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of Al(x)Zn(1-x)O nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 &caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

Quantitative analysis of optical and recombination losses in Cu(In,Ga)Se{sub 2} thin-film solar cells

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

Kosyachenko, L. A., E-mail: lakos@chv.ukrpack.net; Lytvynenko, V. Yu.; Maslyanchuk, O. L.

2016-04-15

Optical and recombination losses in a Cu(In,Ga)Se{sub 2} thin-film solar cell with a band gap of 1.36–1.38 eV are theoretically analyzed. The optical transmittance of the ZnO and CdS layers through which the radiation penetrates into the absorbing layer is determined. Using optical constants, the optical loss caused by reflection at the interfaces (7.5%) and absorption in the ZnO and CdS layers (10.2%) are found. To calculate the recombination loss, the spectral distribution of the quantum efficiency of CdS/CuIn{sub 1–x}Ga{sub x}Se{sub 2} is investigated. It is demonstrated that, taking the drift and diffusion components of recombination at the front andmore » rear surfaces of the absorber into account, the quantum efficiency spectra of the investigated solar cell can be analytically described in detail. The real parameters of the solar cell are determined by comparing the calculated results and experimental data. In addition, the losses caused by the recombination of photogenerated carriers at the front and rear surfaces of the absorbing layer (1.8% and <0.1%, respectively), at its neutral part (7.6%), and in the space-charge region of the p–n heterojunction (1.0%) are determined. A correction to the parameters of Cu(In,Ga)Se{sub 2} is proposed, which enhances the charge-accumulation efficiency.« less

Delocalization of π electrons and trapping action of ZnO nanoparticles in PPY matrix for hybrid solar cell application

NASA Astrophysics Data System (ADS)

Singh, Rajinder; Choudhary, Ram Bilash; Kandulna, Rohit

2018-03-01

Polypyrrole (PPY)-Zinc Oxide (ZnO) nanocomposites with varying concentration of ZnO (1:1-1:4) were prepared via in-situ polymerization technique by using pyrrole monomer in the presence of ammonium persulphate (APS) as oxidant. Globular morphology of PPY and sheet like structure of ZnO was examined using FESEM and EDAX. FTIR showed the presence of vibration modes in fingerprint region (1500 cm-1-500 cm-1) for metal oxides confirming the presence and interaction of ZnO with the polymer matrix in nanocomposites. Amorphous nature of PPY and hexagonal wurtzite structure of ZnO was confirmed using XRD with average crystallite size within 20 nm-30 nm. PANI-ZnO (1:1) exhibited blue shift in comparison to PPY (neat) and optimized optical band gap ∼ 1.81 eV. The effect of carrier concentration was investigated using electrochemical analyzer and maximum current was recorded for PANI-ZnO (1:1). The highest conductance was calculated for PANI-ZnO (1:1) ∼ 7.3242 × 10-3 S using current -voltage characteristics. Thermal stability was found to be increasing with the increase in ZnO concentration PANI-ZnO nanocomposite.

Enhanced performance of porphyrin sensitized solar cell based on graphene quantum dots decorated photoanodes

NASA Astrophysics Data System (ADS)

Sehgal, Preeti; Narula, Anudeep Kumar

2018-05-01

Porphyrin sensitized solar cells (PSSC) has been successfully fabricated composed of graphene quantum dots (GQD) functionalized ZnO photoanodes, zinc tetrakis (4-carboxy phenyl)porphyrin (TCPPZn) as sensitizer and polypyrrole coated oxidised multiwalled carbon nanotubes (PPy/OMWCNT) as counter electrode. The effect of the concentration of GQD on the structural, morphological, photophysical and photovoltaic properties of GQD@ZnO, and GQD@ZnO/TCPPZn nanocomposites has also been investigated. Studies indicate that TCPPZn adsorbed on the surface on GQD@ZnO. Hot electron injection mechanism and multiple exciton generation from GQD to ZnO were mainly responsible for the photoexcitation response in PSSC. This study indicates that GQD can play role of sensitizer to some extent. The time decay measurements reveals the evidences of FRET mechanism, and synergistic interaction between GQD and TCPPZn. The Jsc, Voc, PCE of the corresponding PSSC devices enhanced initially and then decreased. Among all the devices fabricated, the PSSC with a 40% amount of GQD (GQD@ZnO/TCPPZn 40%) attains the best performance with the Jsc = 10.1 mA/cm2, Voc = 0.48, PCE = 2.45% FF = 0.507 higher than ZnO@TCPPZn device fabricated without GQD. Overall, this design provides a new concept for the development of photoanodes which derive better efficiency for dye sensitized solar cell (DSSC) and PSSC at economical low cost.

Effects of substrate conductivity on cell morphogenesis and proliferation using tailored, atomic layer deposition-grown ZnO thin films

PubMed Central

Choi, Won Jin; Jung, Jongjin; Lee, Sujin; Chung, Yoon Jang; Yang, Cheol-Soo; Lee, Young Kuk; Lee, You-Seop; Park, Joung Kyu; Ko, Hyuk Wan; Lee, Jeong-O

2015-01-01

We demonstrate that ZnO films grown by atomic layer deposition (ALD) can be employed as a substrate to explore the effects of electrical conductivity on cell adhesion, proliferation, and morphogenesis. ZnO substrates with precisely tunable electrical conductivity were fabricated on glass substrates using ALD deposition. The electrical conductivity of the film increased linearly with increasing duration of the ZnO deposition cycle (thickness), whereas other physical characteristics, such as surface energy and roughness, tended to saturate at a certain value. Differences in conductivity dramatically affected the behavior of SF295 glioblastoma cells grown on ZnO films, with high conductivity (thick) ZnO films causing growth arrest and producing SF295 cell morphologies distinct from those cultured on insulating substrates. Based on simple electrostatic calculations, we propose that cells grown on highly conductive substrates may strongly adhere to the substrate without focal-adhesion complex formation, owing to the enhanced electrostatic interaction between cells and the substrate. Thus, the inactivation of focal adhesions leads to cell proliferation arrest. Taken together, the work presented here confirms that substrates with high conductivity disturb the cell-substrate interaction, producing cascading effects on cellular morphogenesis and disrupting proliferation, and suggests that ALD-grown ZnO offers a single-variable method for uniquely tailoring conductivity. PMID:25897486

Chemical Etching of Zinc Oxide for Thin-Film Silicon Solar Cells

PubMed Central

Hüpkes, Jürgen; Owen, Jorj I; Pust, Sascha E; Bunte, Eerke

2012-01-01

Abstract Chemical etching is widely applied to texture the surface of sputter-deposited zinc oxide for light scattering in thin-film silicon solar cells. Based on experimental findings from the literature and our own results we propose a model that explains the etching behavior of ZnO depending on the structural material properties and etching agent. All grain boundaries are prone to be etched to a certain threshold, that is defined by the deposition conditions and etching solution. Additionally, several approaches to modify the etching behavior through special preparation and etching steps are provided. PMID:22162035

Investigation of photocalalytic activity of ZnO prepared by spray pyrolis with various precursors

NASA Astrophysics Data System (ADS)

Bourfaa, F.; Lamri Zeggar, M.; A, A.; Aida, M. S.; Attaf, N.

2016-03-01

Semiconductor photocatalysts such as ZnO has attracted much attention in recent years due to their various applications for the degradation of organic pollutants in water, air and in dye sensitized photovoltaic solar cell. In the present work, ZnO thin films were prepared by ultrasonic spray pyrolysis by using different precursors namely: acetate, chloride and zinc nitrate in order to investigate their influence on ZnO photocatalytic activity. The films crystalline structure was studied by mean of X- ray diffraction measurements (XRD) and the films surface morphology by Scanning Electron Microscopy (SEM). The films optical properties were studied by mean of UV-visible spectroscopy. The prepared films were tested for the degradation of the red reactive dye largely used in textile industry. As a result, we found that the zinc nitrate is the best precursor to prepare ZnO thin films suitable for a good photocatalytic activity.

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

NASA Astrophysics Data System (ADS)

Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

2016-04-01

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm-1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

Transparent and conducting ZnO films grown by spray pyrolysis

NASA Astrophysics Data System (ADS)

Hadjeris, Lazhar; Herissi, Labidi; Badreddine Assouar, M.; Easwarakhanthan, Thomas; Bougdira, Jamal; Attaf, Nadhir; Salah Aida, M.

2009-03-01

ZnO films were prepared using the simple, flexible and cost-effective spray pyrolysis technique at different substrate temperatures and precursor molarity values. The films' structural, optical and electrical properties were investigated by x-ray diffraction, UV-VIS transmittance spectroscopy, profilometry and voltage-current-temperature (VIT) measurements. The films prepared at substrate temperatures above 400 °C appear better crystallized with (0 0 2) preferred orientation and exhibit higher visible transmittance (65-80%), higher electrical n-type semiconductor conductivity (10-50 (Ω cm)-1), lower activation energy (<0.35 eV) and smaller Urbach energy (80 meV). These results indicate that such sprayed ZnO films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition of the precursor droplets. ZnO films having desired optical and electrical properties for cheaper large-area solar cells may thus be tailored through the substrate temperature and the precursor molarity.

Au nanorods-incorporated plasmonic-enhanced inverted organic solar cells

NASA Astrophysics Data System (ADS)

Peng, Ling; Mei, Yang; Chen, Shu-Fen; Zhang, Yu-Pei; Hao, Jing-Yu; Deng, Ling-Ling; Huang, Wei

2015-11-01

The effect of Au nanorods (NRs) on optical-to-electric conversion efficiency is investigated in inverted polymer solar cells, in which Au NRs are sandwiched between two layers of ZnO. Accompanied by the optimization of thickness of ZnO covered on Au NRs, a high-power conversion efficiency of 3.60% and an enhanced short-circuit current density (JSC) of 10.87 mA/cm2 are achieved in the poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC60BM)-based inverted cell and the power conversion efficiency (PCE) is enhanced by 19.6% compared with the control device. The detailed analyses of the light absorption characteristics, the simulated scattering induced by Au NRs, and the electromagnetic field around Au NRs show that the absorption improvement in the photoactive layer due to the light scattering from the longitudinal axis and the near-field increase around Au NRs induced by localized surface plasmon resonance plays a key role in enhancing the performances. Project supported by the Ministry of Science and Technology, China (Grant No. 2012CB933301), the National Natural Science Foundation of China (Grant Nos. 61274065, 51173081, 61136003, BZ2010043, 51372119, and 51172110), and the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions and Synergetic Innovation Center for Organic Electronics and Information Displays, China.

High-Performance Dye-Sensitized Solar Cells Based on Morphology-Controllable Synthesis of ZnO–ZnS Heterostructure Nanocone Photoanodes

PubMed Central

Rouhi, Jalal; Mamat, Mohamad Hafiz; Ooi, C. H. Raymond; Mahmud, Shahrom; Mahmood, Mohamad Rusop

2015-01-01

High-density and well-aligned ZnO–ZnS core–shell nanocone arrays were synthesized on fluorine-doped tin oxide glass substrate using a facile and cost-effective two-step approach. In this synthetic process, the ZnO nanocones act as the template and provide Zn2+ ions for the ZnS shell formation. The photoluminescence spectrum indicates remarkably enhanced luminescence intensity and a small redshift in the UV region, which can be associated with the strain caused by the lattice mismatch between ZnO and ZnS. The obtained diffuse reflectance spectra show that the nanocone-based heterostructure reduces the light reflection in a broad spectral range and is much more effective than the bare ZnO nanocone and nanorod structures. Dye-sensitized solar cells based on the heterostructure ZnO–ZnS nanocones are assembled, and high conversion efficiency (η) of approximately 4.07% is obtained. The η improvement can be attributed primarily to the morphology effect of ZnO nanocones on light-trapping and effectively passivating the interface surface recombination sites of ZnO nanocones by coating with a ZnS shell layer. PMID:25875377

Nanostructured zinc oxide photoelectrodes by green routes M-SILAR and electrodeposition for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Gaikwad, M. A.; Suryawanshi, M. P.; Maldar, P. S.; Dongale, T. D.; Moholkar, A. V.

2018-04-01

Surfactant-free, ultrasound assisted modified successive ionic layer adsorption and reaction (M-SILAR) method and home-made microcontroller based low-cost potentiostat system are employed to prepare zinc oxide (ZnO) nanostructure based thin films. The comparison between physicochemical as well as photoelectrochemical (PEC) properties of the nanostructures prepared via two different template free, simplistic and cost-effective green routes have been discussed in detail. X-ray diffraction and Raman analysis confirm the formation of phase pure ZnO with the hexagonal crystal structure. Surface morphology significantly affects the physicochemical as well as PEC properties of ZnO thin films. Nanorods (NRs) and nanosheets (NSs) based ZnO thin films sensitized with N3 dye have been directly used as photoelectrodes in the dye-sensitized solar cell (DSSC). The power conversion efficiency (PCE) of 0.59% is achieved with Jsc of 4.04 mA/cm2 and Voc of 0.44 V for the DSSC in which the M-SILAR deposited 1-D ZnO NRs based thin film is used as the photoanode. While relatively less PCE of 0.29% with Jsc of 2.53 mA/cm2 and Voc of 0.36 V is obtained for DSSC prepared using electrodeposited 2-D ZnO NSs. In the NSs like 2-D surface morphology, the presence of multiple grain boundaries are acted as traps for the diffusing electrons, which reduces the electron mobility through it.

Complete transformation of ZnO and CuO nanoparticles in culture medium and lymphocyte cells during toxicity testing.

PubMed

Ivask, Angela; Scheckel, Kirk G; Kapruwan, Pankaj; Stone, Vicki; Yin, Hong; Voelcker, Nicolas H; Lombi, Enzo

2017-03-01

Here, we present evidence on complete transformation of ZnO and CuO nanoparticles, which are among the most heavily studied metal oxide particles, during 24 h in vitro toxicological testing with human T-lymphocytes. Synchrotron radiation-based X-ray absorption near edge structure (XANES) spectroscopy results revealed that Zn speciation profiles of 30 nm and 80 nm ZnO nanoparticles, and ZnSO 4 - exposed cells were almost identical with the prevailing species being Zn-cysteine. This suggests that ZnO nanoparticles are rapidly transformed during a standard in vitro toxicological assay, and are sequestered intracellularly, analogously to soluble Zn. Complete transformation of ZnO in the test conditions was further supported by almost identical Zn spectra in medium to which ZnO nanoparticles or ZnSO 4 was added. Likewise, Cu XANES spectra for CuO and CuSO 4 -exposed cells and cell culture media were similar. These results together with our observation on similar toxicological profiles of ZnO and soluble Zn, and CuO and soluble Cu, underline the importance of dissolution and subsequent transformation of ZnO and CuO nanoparticles during toxicological testing and provide evidence that the nano-specific effect of ZnO and CuO nanoparticles is negligible in this system. We strongly suggest to account for this aspect when interpreting the toxicological results of ZnO and CuO nanoparticles.

Photovoltaic solar cell

DOEpatents

Nielson, Gregory N.; Gupta, Vipin P.; Okandan, Murat; Watts, Michael R.

2015-09-08

A photovoltaic solar concentrator is disclosed with one or more transverse-junction solar cells (also termed point contact solar cells) and a lens located above each solar cell to concentrate sunlight onto the solar cell to generate electricity. Piezoelectric actuators tilt or translate each lens to track the sun using a feedback-control circuit which senses the electricity generated by one or more of the solar cells. The piezoelectric actuators can be coupled through a displacement-multiplier linkage to provide an increased range of movement of each lens. Each lens in the solar concentrator can be supported on a frame (also termed a tilt plate) having three legs, with the movement of the legs being controlled by the piezoelectric actuators.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

2013-05-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

PubMed Central

2013-01-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration. PMID:23680100

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

PubMed Central

Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

2016-01-01

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm−1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls. PMID:27071382

Optical characterization of pure and Al-doped ZnO prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Belka, Radosław; Keczkowska, Justyna; Kasińska, Justyna

2016-09-01

In this paper the preparation process and optical characterization of pure and Al3+ doped zinc oxide (Al:ZnO) coatings will be presented. ZnO based materials have been studied extensively due to their potential applications in optoelectronic devices as conductive gas sensors, transparent conductive, electrodes, solar cell windows, varistors, UVfilters or photovoltaic cells. It is II-VI semiconductor with wide-band gap of 3.37 eV and large exciton binding energy of 60meV. It is possible to improve the conductivity of ZnO coating by intentionally doping ZnO with aluminium ions during preparation process. Such transparent and conducting thin films, known as AZO (Aluminium Zinc Oxide) films, are very good candidate for application as transparent conducting materials in many optoelectronic devices. The well-known sol-gel method is used for preparation of solution, coated on glass substrates by dip coating process. Prepared samples were investigated by Raman and UV-VIS spectroscopy. Transmittance as well as specular and diffuse reflectance spectroscopy methods were used for studies of optical parameters. We found that Al admixture influences on optical bandgap of ZnO.

Control of ZnO Nanorod Defects to Enhance Carrier Transportation in p-Cu₂O/i-ZnO Nanorods/n-IGZO Heterojunction.

PubMed

Ke, Nguyen Huu; Trinh, Le Thi Tuyet; Mung, Nguyen Thi; Loan, Phan Thi Kieu; Tuan, Dao Anh; Truong, Nguyen Huu; Tran, Cao Vinh; Hung, Le Vu Tuan

2017-01-01

The p-Cu₂O/i-ZnO nanorods/n-IGZO heterojunctions were fabricated by electrochemical and sputtering method. ZnO nanorods were grown on conductive indium gallium zinc oxide (IGZO) thin film and then p-Cu₂O layer was deposited on ZnO nanorods to form the heterojunction. ZnO nanorods play an important role in carrier transport mechanisms and performance of the junction. The changing of defects in ZnO nanorods by annealing samples in air and vacuum have studied. The XRD, photoluminescence (PL) spectroscopy, and FTIR were used to study about structure, and defects in ZnO nanorods. The SEM, i–V characteristics methods were also used to define structure, electrical properties of the heterojunctions layers. The results show that the defects in ZnO nanorods affected remarkably on performance of heterojunctions of solar cells.

Effects of subtoxic concentrations of TiO{sub 2} and ZnO nanoparticles on human lymphocytes, dendritic cells and exosome production

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

Andersson-Willman, Britta; Gehrmann, Ulf; Cansu, Zekiye

Metal oxide nanoparticles are widely used in the paint and coating industry as well as in cosmetics, but the knowledge of their possible interactions with the immune system is very limited. Our aims were to investigate if commercially available TiO{sub 2} and ZnO nanoparticles may affect different human immune cells and their production of exosomes, nano-sized vesicles that have a role in cell to cell communication. We found that the TiO{sub 2} or ZnO nanoparticles at concentrations from 1 to 100 μg/mL did not affect the viability of primary human peripheral blood mononuclear cells (PBMC). In contrast, monocyte-derived dendritic cellsmore » (MDDC) reacted with a dose dependent increase in cell death and caspase activity to ZnO but not to TiO{sub 2} nanoparticles. Non-toxic exposure, 10 μg/mL, to TiO{sub 2} and ZnO nanoparticles did not significantly alter the phenotype of MDDC. Interestingly, ZnO but not TiO{sub 2} nanoparticles induced a down regulation of FcγRIII (CD16) expression on NK-cells in the PBMC population, suggesting that subtoxic concentrations of ZnO nanoparticles might have an effect on FcγR-mediated immune responses. The phenotype and size of exosomes produced by PBMC or MDDC exposed to the nanoparticles were similar to that of exosomes harvested from control cultures. TiO{sub 2} or ZnO nanoparticles could not be detected within or associated to exosomes as analyzed with TEM. We conclude that TiO{sub 2} and ZnO nanoparticles differently affect immune cells and that evaluations of nanoparticles should be performed even at subtoxic concentrations on different primary human immune cells when investigating potential effects on immune functions. -- Highlights: ► ZnO nanoparticles induce cell death of MDDC but not of PBMC. ► ZnO nanoparticles induce caspase activation and DNA fragmentation in MDDC. ► TiO{sub 2} nanoparticles are taken up by MDDC but have no effect on their phenotype. ► ZnO nanoparticles induce a significant reduction of CD16

Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

NASA Astrophysics Data System (ADS)

Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

2016-03-01

Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

Thin Film Solar Cells: Organic, Inorganic and Hybrid

NASA Technical Reports Server (NTRS)

Dankovich, John

2004-01-01

Thin film solar cells are an important developing resource for hundreds of applications including space travel. In addition to being more cost effective than traditional single crystal silicon cells, thin film multi-crystaline cells are plastic and light weight. The plasticity of the cells allows for whole solar panels to be rolled out from reams. Organic layers are being investigated in order to increase the efficiency of the cells to create an organic / inorganic hybrid cell. The main focus of the group is a thin film inorganic cell made with the absorber CuInS2. So far the group has been successful in creating the layer from a single-source precursor. They also use a unique method of film deposition called chemical vapor deposition for this. The general makeup of the cell is a molybdenum back contact with the CuInS2 layer, then CdS, ZnO and aluminum top contacts. While working cells have been produced, the efficiency so far has been low. Along with quantum dot fabrication the side project of this that is currently being studied is adding a polymer layer to increase efficiency. The polymer that we are using is P3OT (Poly(3-octylthiopene-2,5-diyll), retroregular). Before (and if) it is added to the cell, it must be understood in itself. To do this simple diodes are being constructed to begin to look at its behavior. The P3OT is spin coated onto indium tin oxide and silver or aluminum contacts are added. This method is being studied in order to find the optimal thickness of the layer as well as other important considerations that may later affect the composition of the finished solar cell. Because the sun is the most abundant renewable, energy source that we have, it is important to learn how to harness that energy and begin to move away from our other depleted non-renewable energy sources. While traditional silicon cells currently create electricity at relatively high efficiencies, they have drawbacks such as weight and rigidness that make them unattractive

Amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Takahashi, K.; Konagai, M.

The fabrication, performance, and applications of a-Si solar cells are discussed, summarizing the results of recent experimental investigations and trial installations. Topics examined include the fundamental principles and design strategies of solar power installations; the characteristics of monocrystalline-Si solar cells; techniques for reducing the cost of solar cells; independent, linked, and hybrid solar power systems; proposed satellite solar power systems; and the use of solar cells in consumer appliances. Consideration is given to the history of a-Si, a-Si fabrication techniques, quality criteria for a-Si films, solar cells based on a-Si, and techniques for increasing the efficiency and lowering the cost of a-Si solar cells. Graphs, diagrams, drawings, and black-and-white and color photographs are provided.

Light Trapping for Silicon Solar Cells: Theory and Experiment

NASA Astrophysics Data System (ADS)

Zhao, Hui

Crystalline silicon solar cells have been the mainstream technology for photovoltaic energy conversion since their invention in 1954. Since silicon is an indirect band gap material, its absorption coefficient is low for much of the solar spectrum, and the highest conversion efficiencies are achieved only in cells that are thicker than about 0.1 mm. Light trapping by total internal reflection is important to increase the optical absorption in silicon layers, and becomes increasingly important as the layers are thinned. Light trapping is typically characterized by the enhancement of the absorptance of a solar cell beyond the value for a single pass of the incident beam through an absorbing semiconductor layer. Using an equipartition argument, in 1982 Yablonovitch calculated an enhancement of 4n2 , where n is the refractive index. We have extracted effective light-trapping enhancements from published external quantum efficiency spectra in several dozen silicon solar cells. These results show that this "thermodynamic" enhancement has never been achieved experimentally. The reasons for incomplete light trapping could be poor anti-reflection coating, inefficient light scattering, and parasitic absorption. We report the light-trapping properties of nanocrystalline silicon nip solar cells deposited onto two types of Ag/ZnO backreflectors at United Solar Ovonic, LLC. We prepared the first type by first making silver nanparticles onto a stainless steel substrate, and then overcoating the nanoparticles with a second silver layer. The second type was prepared at United Solar using a continuous silver film. Both types were then overcoated with a ZnO film. The root mean square roughness varied from 27 to 61 nm, and diffuse reflectance at 1000 nm wavelength varied from 0.4 to 0.8. The finished cells have a thin, indium-tin oxide layer on the top that acts as an antireflection coating. For both backreflector types, the short-circuit photocurrent densities J SC for solar

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).

Solar Photovoltaic Cells.

ERIC Educational Resources Information Center

Mickey, Charles D.

1981-01-01

Reviews information on solar radiation as an energy source. Discusses these topics: the key photovoltaic material; the bank theory of solids; conductors, semiconductors, and insulators; impurity semiconductors; solid-state photovoltaic cell operation; limitations on solar cell efficiency; silicon solar cells; cadmium sulfide/copper (I) sulfide…

Cu(In,Ga)Se2 Solar Cells with Amorphous In2O3-Based Front Contact Layers.

PubMed

Koida, Takashi; Ueno, Yuko; Nishinaga, Jiro; Higuchi, Hirohumi; Takahashi, Hideki; Iioka, Masayuki; Shibata, Hajime; Niki, Shigeru

2017-09-06

Amorphous (a-) In 2 O 3 -based front contact layers composed of transparent conducting oxide (TCO) and transparent oxide semiconductor (TOS) layers were proved to be effective in enhancing the short-circuit current density (J sc ) of Cu(In,Ga)Se 2 (CIGS) solar cells with a glass/Mo/CIGS/CdS/TOS/TCO structure, while maintaining high fill factor (FF) and open-circuit voltage (V oc ). An n-type a-In-Ga-Zn-O layer was introduced between the CdS and TCO layers. Unlike unintentionally doped ZnO broadly used as TOS layers in CIGS solar cells, the grain-boundary(GB)-free amorphous structure of the a-In-Ga-Zn-O layers allowed high electron mobility with superior control over the carrier density (N). High FF and V oc values were achieved in solar cells containing a-In-Ga-Zn-O layers with N values broadly ranging from 2 × 10 15 to 3 × 10 18 cm -3 . The decrease in FF and V oc produced by the electronic inhomogeneity of solar cells was mitigated by controlling the series resistance within the TOS layer of CIGS solar cells. In addition, a-In 2 O 3 :H and a-In-Zn-O layers exhibited higher electron mobilities than the ZnO:Al layers conventionally used as TCO layers in CIGS solar cells. The In 2 O 3 -based layers exhibited lower free carrier absorption while maintaining similar sheet resistance than ZnO:Al. The TCO and TOS materials and their combinations did not significantly change the V oc of the CIGS solar cells and the mini-modules.

Preparation and photovoltaic properties of perovskite solar cell based on ZnO nanorod arrays

NASA Astrophysics Data System (ADS)

Xu, Yang; Liu, Tian; Li, Zhaosong; Feng, Bingjie; Li, Siqian; Duan, Jinxia; Ye, Cong; Zhang, Jun; Wang, Hao

2016-12-01

A careful control of ZnO nanorod arrays with various densities and thickness were achieved by hydrothermal method. An obvious increase in the ZnO nanorod density is observed as the concentrations of zinc acetate dropped as expected through the surface SEM images. On the other hand, samples with and without TiO2 compact layer were also studied and results had been analyzed to seek for an optimized substrate structure for light absorbing layer and increase the efficiency. What's more, a deep research for the drying temperature for perovskite layer was also conducted. As a result, SEM images discribe a promising surface appearance of perovskite layer which is finely attached onto the nanorod structure. Final power conversion efficiency (PCE) of FTO/ZnO seed layer/ZnO nanorods/perovskite/spiro-OMe-TAD/Au electrode photovoltaic device reached ∼9.15% together with open-circuit voltage of 957 mV, short-circuit current density of 17.8 mA/cm2 and fill factor of 0.537.

Effect of indium on photovoltaic property of n-ZnO/p-Si heterojunction device prepared using solution-synthesized ZnO nanowire film

NASA Astrophysics Data System (ADS)

Kathalingam, Adaikalam; Kim, Hyun-Seok; Park, Hyung-Moo; Valanarasu, Santiyagu; Mahalingam, Thaiyan

2015-01-01

Preparation of n-ZnO/p-Si heterostructures using solution-synthesized ZnO nanowire films and their photovoltaic characterization is reported. The solution-grown ZnO nanowire film is characterized using scanning electron microscope, electron dispersive x-ray, and optical absorption studies. Electrical and photovoltaic properties of the fabricated heterostructures are studied using e-beam-evaporated aluminum as metal contacts. In order to use transparent contact and to simultaneously collect the photogenerated carriers, sandwich-type solar cells were fabricated using ZnO nanorod films grown on p-silicon and indium tin oxide (ITO) coated glass as ITO/n-ZnO NR/p-Si. The electrical properties of these structures are analyzed from current-voltage (I-V) characteristics. ZnO nanowire film thickness-dependent photovoltaic properties are also studied. Indium metal was also deposited over the ZnO nanowires and its effects on the photovoltaic response of the devices were studied. The results demonstrated that all the samples exhibit a strong rectifying behavior indicating the diode nature of the devices. The sandwich-type ITO/n-ZnO NR/p-Si solar cells exhibit improved photovoltaic performance over the Al-metal-coated n-ZnO/p-Si structures. The indium deposition is found to show enhancement in photovoltaic behavior with a maximum open-circuit voltage (Voc) of 0.3 V and short-circuit current (Isc) of 70×10-6 A under ultraviolet light excitation.

Graphene-Based Transparent Electrodes for Dye Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Al-Rawashdeh, Nathir A. F.; Albiss, Borhan A.; Yousef, Mo'ath H. I.

2018-02-01

Several Zinc Oxide (ZnO) photo-anodes were prepared with different morphologies. For each morphology, two composites containing graphene oxide (GO) were prepared. ZnO sheet-flowers attained the highest efficiency among control samples, owing to the light diffraction that may be caused by such morphology. On the other hand, ZnO rods achieved lower performance than ZnO sheet-flowers, but higher than ZnO flowers, due to their porosity and structure, which may scatter light effectively. The effect of including GO in the photoanode matrix was studied and the results demonstrate a significant increase in short circuit current density (JSC). The addition of GO suggested an overall positive effect on cell performance, where samples of ZnO rods and Flowers had the most significant increase in their performance, due to the inhibition of charge recombination by GO.

The application of sensitizers from red frangipani flowers and star gooseberry leaves in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Almaz Dhafina, Wan; Salleh, Hasiah; Zalani Daud, Muhamad; Ali, Nora’aini

2018-05-01

Nowadays natural based dyes for dye-sensitized solar cells (DSSCs) have been in research field attention due to its advantages over other type of dyes such as low-cost, low-toxicity, completely biodegradable and abundance of resources. Natural dyes can be produced via the simple extraction method of pigments from plant parts such as flower, fruits, leaves, tuber etc. In this feature article, the natural dyes which composed of anthocyanin pigment from red frangipani flowers and chlorophyll from star gooseberry leaves were applied in zinc oxide, (ZnO) based-DSSC. The ZnO photoanode of the DSSCs sample were sensitized in each dye with different duration. It was observed that DSSCs which has chlorophyll pigment as dye had better performance with power conversion efficiency (PCE) of 0.007%.

Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires.

PubMed

He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

2017-06-16

In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g -1 at a scan rate of 20 mV s -1 , which is almost twice that of ZnO NWs (191.5 F g -1 ). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g -1 at a current density of 1.33 A g -1 with an energy density of 25.2 W h kg -1 at the power density of 896.44 W kg -1 . In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires

NASA Astrophysics Data System (ADS)

He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

2017-06-01

In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g-1 at a scan rate of 20 mV s-1, which is almost twice that of ZnO NWs (191.5 F g-1). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g-1 at a current density of 1.33 A g-1 with an energy density of 25.2 W h kg-1 at the power density of 896.44 W kg-1. In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

Controllable synthesis of mesoporous multi-shelled ZnO microspheres as efficient photocatalysts for NO oxidation

NASA Astrophysics Data System (ADS)

Chen, Xiaolang; Zhang, Huiqiang; Zhang, Dieqing; Miao, Yingchun; Li, Guisheng

2018-03-01

The successful application of hierarchically porous structure in environmental treatment has provided new insights for solving environmental problems. Hierarchically structured semiconductor materials were considered as promising photocatalysts for NO oxidation in gas phase. Multi-shelled ZnO microspheres (MMSZ) were controllably shaped with hierarchically porous structures via a facile hydrothermal route using amino acid (N-Acetyl-D-Proline) as template and post-calcination treatment. Symmetric Ostwald ripening was used to explain the morphological evolution of hierarchical nanostructure. MMSZ was proved highly efficient for oxidizing NO (400 ppb) in gas phase under UV light irradiation with a much higher photocatalytic removal rate (77.3%) than that of the as-obtained ZnO crystals with other hierachically porous structures, owing to its higher photocurrent intensity. Such greatly enhanced photocatalytic activity can be assigned to the enhanced crystallinity of ZnO, mesopores and unique multi-shelled structure. Enhanced crystallinity promotes photogenerated charges under light irradiation. Mesoporous porosity can ensure enough light scattering between the shells. Multi-shelled structure endows ZnO with higher specific surface area and high frequency of multiple light reflection, resulting in more exposed active sites, higher light utilization efficiency, and fast separation efficiency of photogenerated charge carriers. The experimental results demonstrated that the photogenerated holes (h+) are the main active species. Hierarchically structured ZnO is not only contributed to directly use solar energy to solving various problems caused by atmospheric pollution, but also has potential applications in energy converse and storage including solar cells, lithium batteries, water-splitting, etc.

Solar cell shingle

NASA Technical Reports Server (NTRS)

Forestieri, A. F.; Ratajczak, A. F.; Sidorak, L. G. (Inventor)

1977-01-01

A solar cell shingle was made of an array of solar cells on a lower portion of a substantially rectangular shingle substrate made of fiberglass cloth or the like. The solar cells may be encapsulated in flourinated ethylene propylene or some other weatherproof translucent or transparent encapsulant to form a combined electrical module and a roof shingle. The interconnected solar cells were connected to connectors at the edge of the substrate through a connection to a common electrical bus or busses. An overlap area was arranged to receive the overlap of a cooperating similar shingle so that the cell portion of the cooperating shingle may overlie the overlap area of the roof shingle. Accordingly, the same shingle serves the double function of an ordinary roof shingle which may be applied in the usual way and an array of cooperating solar cells from which electrical energy may be collected.

Cytotoxicity of zinc oxide (ZnO) nanoparticles is influenced by cell density and culture format.

PubMed

Heng, Boon Chin; Zhao, Xinxin; Xiong, Sijing; Ng, Kee Woei; Boey, Freddy Yin-Chiang; Loo, Joachim Say-Chye

2011-06-01

A parameter that has often been overlooked in cytotoxicity assays is the density and confluency of mammalian cell monolayers utilized for toxicology screening. Hence, this study investigated how different cell seeding densities influenced their response to cytotoxic challenge with ZnO nanoparticles. Utilizing the same volume (1 ml per well) and concentration range (5-40 μg/ml) of ZnO nanoparticles, contradictory results were observed with higher-density cell monolayers (BEAS-2B cells) obtained either by increasing the number of seeded cells per well (50,000 vs. 200,000 cells per well of 12-well plate) or by seeding the same numbers of cells (50,000) within a smaller surface area (12-well vs. 48-well plate, 4.8 vs. 1.2 cm(2), respectively). Further experiments demonstrated that the data may be skewed by inconsistency in the mass/number of nanoparticles per unit area of culture surface, as well as by inconsistent nanoparticle to cell ratio. To keep these parameters constant, the same number of cells (50,000 per well) were seeded on 12-well plates, but with the cells being seeded at the edge of the well for the experimental group (by tilting the plate) to form a dense confluent monolayer, as opposed to a sparse monolayer for the control group seeded in the conventional manner. Utilizing such an experimental set-up for the comparative evaluation of four different cell lines (BEAS-2B, L-929, CRL-2922 and C2C12), it was observed that the high cell density monolayer was consistently more resistant to the cytotoxic effects of ZnO nanoparticles compared to the sparse monolayer for all four different cell types, with the greatest differences being observed above a ZnO concentration of 10 μg/ml. Hence, the results of this study demonstrate the need for the standardization of cell culture protocols utilized for toxicology screening of nanoparticles, with respect to cell density and mass/number of nanoparticles per unit area of culture surface.

Perspective: Maintaining surface-phase purity is key to efficient open air fabricated cuprous oxide solar cells

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

Hoye, Robert L. Z., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk; Ievskaya, Yulia; MacManus-Driscoll, Judith L., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk

2015-02-01

Electrochemically deposited Cu{sub 2}O solar cells are receiving growing attention owing to a recent doubling in efficiency. This was enabled by the controlled chemical environment used in depositing doped ZnO layers by atomic layer deposition, which is not well suited to large-scale industrial production. While open air fabrication with atmospheric pressure spatial atomic layer deposition overcomes this limitation, we find that this approach is limited by an inability to remove the detrimental CuO layer that forms on the Cu{sub 2}O surface. Herein, we propose strategies for achieving efficiencies in atmospherically processed cells that are equivalent to the high values achievedmore » in vacuum processed cells.« less

Substrate-oriented nanorod scaffolds in polymer-fullerene bulk heterojunction solar cells.

PubMed

Ogawa, Yuta; White, Matthew S; Sun, Lina; Scharber, Markus C; Sariciftci, Niyazi Serdar; Yoshida, Tsukasa

2014-04-14

The use of a p-type inorganic semiconductor to form a nanorod scaffold within a polymer-fullerene bulk heterojunction solar cell is reported. The performance of this cell is compared to those made of the commonly used n-type scaffold of ZnO, which has been reported many times in the literature. The scaffold is designed to improve charge-carrier collection by increased mobility in thicker samples. Observations show that generally the device performance shows a negative correlation to nanorod length. By using CuSCN as a p-type inorganic scaffold, a very similar trend is observed. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

New Thin-Film Solar Cells Compared to Normal Solar Cells

NASA Image and Video Library

1966-06-21

Adolph Spakowski, head of the Photovoltaic Fundamentals Section at the National Aeronautics and Space Administration (NASA) Lewis Research Center, illustrated the difference between conventional silicon solar cells (rear panel) and the new thin-film cells. The larger, flexible thin-film cells in the foreground were evaluated by Lewis energy conversion specialists for possible future space use. The conventional solar cells used on most spacecraft at the time were both delicate and heavy. For example, the Mariner IV spacecraft required 28,000 these solar cells for its flyby of Mars in 1964. NASA Lewis began investigating cadmium sulfide thin-film solar cells in 1961. The thin-film cells were made by heating semiconductor material until it evaporated. The vapor was then condensed onto an electricity-producing film only one-thousandth of an inch thick. The physical flexibility of the new thin-film cells allowed them to be furled, or rolled up, during launch. Spakowski led an 18-month test program at Lewis to investigate the application of cadmium sulfide semiconductors on a light metallized substrate. The new thin-film solar cells were tested in a space simulation chamber at a simulated altitude of 200 miles. Sunlight was recreated by a 5000-watt xenon light. Two dozen cells were exposed to 15 minutes of light followed by 15 minutes of darkness to test their durability in the constantly changing illumination of Earth orbit.

Impact of the electron-transport layer on the performance of solution-processed small-molecule organic solar cells.

PubMed

Long, Guankui; Wan, Xiangjian; Kan, Bin; Hu, Zhicheng; Yang, Xuan; Zhang, Yi; Zhang, Mingtao; Wu, Hongbing; Huang, Fei; Su, Shijian; Cao, Yong; Chen, Yongsheng

2014-08-01

Although the performance of polymer solar cells has been improved significantly recently through careful optimization with different interlayers for the same materials, more improvement is needed in this respect for small-molecule-based solar cells, particularly for the electron-transport layers (ETLs). In this work, three different solution-processed ETLs, PFN, ZnO nanoparticles, and LiF, were investigated and compared in the performance of small-molecule-based devices, and power conversion efficiencies (PCEs) of 8.32, 7.30, and 7.38% were achieved, respectively. The mechanism for the ETL-induced enhancement has been studied, and different ETLs have a significantly different impact on the device performance. The clearly improved performance of PFN is attributed to the combination of reduced bimolecular recombination and increased effective photon absorption in the active layer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aerosolized ZnO nanoparticles induce toxicity in alveolar type II epithelial cells at the air-liquid interface

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

Xie, Yumei; Williams, Nolann G.; Tolic, Ana

The majority of in vitro studies characterizing the impact of engineered nanoparticles (NPs) on cells that line the respiratory tract were conducted in cells exposed to NPs in suspension. This approach introduces processes that are unlikely to occur during inhaled NP exposures in vivo, such as the shedding of toxic doses of dissolved ions. ZnO NPs are used extensively and pose significant sources for human exposure. Exposures to airborne ZnO NPs can induce adverse effects, but the relevance of the dissolved Zn2+ to the observed effects in vivo is still unclear. Our goal was to mimic in vivo exposures tomore » airborne NPs and decipher the contribution of the intact NP from the contribution of the dissolved ions to airborne ZnO NP toxicity. We established the exposure of alveolar type II epithelial cells to aerosolized NPs at the air-liquid interface (ALI), and compared the impact of aerosolized ZnO NPs and NPs in suspension at the same cellular doses, measured as the number of particles per cell. By evaluating membrane integrity and cell viability 6 and 24 hours post exposure we found that aerosolized NPs induced toxicity at the ALI at doses that were in the same order of magnitude as doses required to induce toxicity in submersed cultures. In addition, distinct patterns of oxidative stress were observed in the two exposure systems. These observations unravel the ability of airborne ZnO NPs to induce toxicity without the contribution of dissolved Zn2+ and suggest distinct mechanisms at the ALI and in submersed cultures.« less

Roles of interfacial modifiers in hybrid solar cells: inorganic/polymer bilayer vs inorganic/polymer:fullerene bulk heterojunction.

PubMed

Eom, Seung Hun; Baek, Myung-Jin; Park, Hanok; Yan, Liang; Liu, Shubin; You, Wei; Lee, Soo-Hyoung

2014-01-22

Hybrid solar cells (HSCs) incorporating both organic and inorganic materials typically have significant interfacial issues which can significantly limit the device efficiency by allowing charge recombination, macroscopic phase separation, and nonideal contact. All these issues can be mitigated by applying carefully designed interfacial modifiers (IMs). In an attempt to further understand the function of these IMs, we investigated two IMs in two different HSCs structures: an inverted bilayer HSC of ZnO:poly(3-hexylthiophene) (P3HT) and an inverted bulk heterojunction (BHJ) solar cell of ZnO/P3HT:[6,6]-phenyl C61-butyric acid methyl ester (PCBM). In the former device configuration, ZnO serves as the n-type semiconductor, while in the latter device configuration, it functions as an electron transport layer (ETL)/hole blocking layer (HBL). In the ZnO:P3HT bilayer device, after the interfacial modification, a power conversion efficiency (PCE) of 0.42% with improved Voc and FF and a significantly increased Jsc was obtained. In the ZnO/P3HT:PCBM based BHJ device, including IMs also improved the PCE to 4.69% with an increase in Voc and FF. Our work clearly demonstrates that IMs help to reduce both the charge recombination and leakage current by minimizing the number of defect sites and traps and to increase the compatibility of hydrophilic ZnO with the organic layers. Furthermore, the major role of IMs depends on the function of ZnO in different device configurations, either as n-type semiconductor in bilayer devices or as ETL/HBL in BHJ devices. We conclude by offering insights for designing ideal IMs in future efforts, in order to achieve high-efficiency in both ZnO:polymer bilayer structure and ZnO/polymer:PCBM BHJ devices.

Asymmetric ZnO panel-like hierarchical architectures with highly interconnected pathways for free-electron transport and photovoltaic improvements.

PubMed

Shi, Yantao; Zhu, Chao; Wang, Lin; Li, Wei; Fung, Kwok Kwong; Wang, Ning

2013-01-02

Through a rapid and template-free precipitation approach, we synthesized an asymmetric panel-like ZnO hierarchical architecture (PHA) for photoanodes of dye-sensitized solar cells (DSCs). The two sides of the PHA are constructed differently using densely interconnected, mono-crystalline and ultrathin ZnO nanosheets. By mixing these PHAs with ZnO nanoparticles (NPs), we developed an effective and feasible strategy to improve the electrical transport and photovoltaic performance of the composite photoanodes of DSCs. The highly crystallized and interconnected ZnO nanosheets largely minimized the total grain boundaries within the composite photoanodes and thus served as direct pathways for the transport and effective collection of free electrons. Through low-temperature (200 °C) annealing, these novel composite photoanodes achieved high conversion efficiencies of up to 5.59% for ZnO-based quasi-solid DSCs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetron sputtering fabrication and photoelectric properties of WSe2 film solar cell device

NASA Astrophysics Data System (ADS)

Mao, Xu; Zou, Jianpeng; Li, Hongchao; Song, Zhengqi; He, Siru

2018-06-01

Tungsten diselenide (WSe2) films with different growing orientations exhibit diverse photoelectric properties. The WSe2 film with C-axis⊥substrate texture has been prepared and applied to thin-film solar cells. W nanofilms with a thickness of 270 nm were deposited onto the Mo bottom electrode and then heat-treated in selenium vapor to synthesize WSe2 films with a thickness of 1 μm. ZnO films were deposited onto WSe2 films to form a P-N junction and ITO films were deposited subsequently as the conductive layer. X-ray diffractometry, scanning electron microscopy and UV-vis-NIR spectro-analysis instrument were employed to analyze the phase composition, optical absorptivity and micromorphology of WSe2 films and the WSe2 solar cell device. WSe2 films exhibit excellent photoelectric performance with an optical absorption coefficient greater than 105 cm-1 across the visible spectrum. The calculated direct and indirect band gap of the WSe2 films is 1.48 eV and 1.25 eV, respectively. With the application of standard glass/Mo/WSe2/ZnO/ITO/Ag device structure, the open-circuit voltage of the battery device is 82 mV. The short-circuit current density is 2.98 mA/cm2 and the filling factor is 0.32. The photoelectric conversion efficiency of the WSe2 film solar cell device is 0.79%.

Inverted polymer solar cells with enhanced fill factor by inserting the potassium stearate interfacial modification layer

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

Li, Jiangsheng; Faculty of Materials Science and Chemical Engineering, Ningbo University, No. 818 Fenghua Road, Ningbo 315211; Jiu, Tonggang, E-mail: jiutonggang@nimte.ac.cn, E-mail: fangjf@nimte.ac.cn

2016-05-02

A thin potassium stearate (KSt) film combined with an optimized ZnO film was introduced to improve the fill factor (FF) of highly efficient inverted polymer solar cells (PSCs). Atomic force microscopy and contact angle measurements were used to show that the introduction of KSt did not change the morphology of interlayer. On the contrary, it is beneficial for the spread of the active layer on the interlayer. The origin of enhanced FF was systematically studied by the ideal current-voltage model for a single heterojunction solar cell and electrochemical impedance spectroscopy. On the basis of the data analysis, the reduced chargemore » recombination loss was responsible for this improved FF. At last, when KSt was replaced by sodium stearate (NaSt), the similar experiment phenomenon was observed. This indicates that inserting a metallic stearate modified layer is a promising strategy to enhance inverted PSCs performance.« less

Enhanced charge transport and photovoltaic performance of PBDTTT-C-T/PC70BM solar cells via UV-ozone treatment.

PubMed

Adhikary, Prajwal; Venkatesan, Swaminathan; Adhikari, Nirmal; Maharjan, Purna P; Adebanjo, Olusegun; Chen, Jihua; Qiao, Qiquan

2013-10-21

In this work, the electron transport layer of PBDTTT-C-T/PC70BM polymer solar cells were subjected to UV-ozone treatment, leading to improved cell performances from 6.46% to 8.34%. The solar cell efficiency reached a maximum of 8.34% after an optimal 5 minute UV-ozone treatment, and then decreased if treated for a longer time. To the best of our knowledge, the mechanism behind the effects of UV-ozone treatment on the improvement of charge transport and cell performance is not fully understood. We have developed a fundamental understanding of the UV-ozone treatment mechanism, which explains both the enhancements in charge transport and photovoltaic performance at an optimal treatment time, and also the phenomenon whereby further treatment time leads to a drop in cell efficiency. Transient photocurrent measurements indicated that the cell charge transport times were 1370 ns, 770 ns, 832 ns, 867 ns, and 1150 ns for the 0 min, 5 min, 10 min, 15 min, and 20 min UV-ozone treatment times, respectively. Therefore the 5 min UV-ozone treatment time led to the shortest transport time and the most efficient charge transport in the cells. The 5 min UV-ozone treated sample exhibited the highest peak intensity (E2) in the Raman spectra of the treated films, at about 437 cm(-1), indicating that it possessed the best wurtzite phase crystallinity of the ZnO films. Further increasing the UV-ozone treatment time from 5 to 20 min induced the formation of p-type defects (e.g. interstitial oxygen atoms), pushing the ZnO Fermi-level further away from the vacuum level, and decreasing the wurtzite crystallinity.

Development and validation of TOF-SIMS and CLSM imaging method for cytotoxicity study of ZnO nanoparticles in HaCaT cells.

PubMed

Lee, Pei-Ling; Chen, Bo-Chia; Gollavelli, Ganesh; Shen, Sin-Yu; Yin, Yu-Sheng; Lei, Shiu-Ling; Jhang, Cian-Ling; Lee, Woan-Ruoh; Ling, Yong-Chien

2014-07-30

Zinc oxide nanoparticles (ZnO NPs) exhibit novel physiochemical properties and have found increasing use in sunscreen products and cosmetics. The potential toxicity is of increasing concern due to their close association with human skin. A time-of-flight secondary ion mass spectrometry (TOF-SIMS) and confocal laser scanning microscopy (CLSM) imaging method was developed and validated for rapid and sensitive cytotoxicity study of ZnO NPs using human skin equivalent HaCaT cells as a model system. Assorted material, chemical, and toxicological analysis methods were used to confirm their shape, size, crystalline structure, and aggregation properties as well as dissolution behavior and effect on HaCaT cell viability in the presence of various concentrations of ZnO NPs in aqueous media. Comparative and correlative analyses of aforementioned results with TOF-SIMS and CLSM imaging results exhibit reasonable and acceptable outcome. A marked drop in survival rate was observed with 50μg/ml ZnO NPs. The CLSM images reveal the absorption and localization of ZnO NPs in cytoplasm and nuclei. The TOF-SIMS images demonstrate elevated levels of intracellular ZnO concentration and associated Zn concentration-dependent (40)Ca/(39)K ratio, presumably caused by the dissolution behavior of ZnO NPs. Additional validation by using stable isotope-labeled (68)ZnO NPs as tracers under the same experimental conditions yields similar cytotoxicity effect. The imaging results demonstrate spatially-resolved cytotoxicity relationship between intracellular ZnO NPs, (40)Ca/(39)K ratio, phosphocholine fragments, and glutathione fragments. The trend of change in TOF-SIMS spectra and images of ZnO NPs treated HaCaT cells demonstrate the possible mode of actions by ZnO NP involves cell membrane disruption, cytotoxic response, and ROS mediated apoptosis. Copyright © 2014 Elsevier B.V. All rights reserved.

Correlative Light-Electron Microscopy Shows RGD-Targeted ZnO Nanoparticles Dissolve in the Intracellular Environment of Triple Negative Breast Cancer Cells and Cause Apoptosis with Intratumor Heterogeneity.

PubMed

Othman, Basmah A; Greenwood, Christina; Abuelela, Ayman F; Bharath, Anil A; Chen, Shu; Theodorou, Ioannis; Douglas, Trevor; Uchida, Maskai; Ryan, Mary; Merzaban, Jasmeen S; Porter, Alexandra E

2016-06-01

ZnO nanoparticles (NPs) are reported to show a high degree of cancer cell selectivity with potential use in cancer imaging and therapy. Questions remain about the mode by which the ZnO NPs cause cell death, whether they exert an intra- or extracellular effect, and the resistance among different cancer cell types to ZnO NP exposure. The present study quantifies the variability between the cellular toxicity, dynamics of cellular uptake, and dissolution of bare and RGD (Arg-Gly-Asp)-targeted ZnO NPs by MDA-MB-231 cells. Compared to bare ZnO NPs, RGD-targeting of the ZnO NPs to integrin αvβ3 receptors expressed on MDA-MB-231 cells appears to increase the toxicity of the ZnO NPs to breast cancer cells at lower doses. Confocal microscopy of live MDA-MB-231 cells confirms uptake of both classes of ZnO NPs with a commensurate rise in intracellular Zn(2+) concentration prior to cell death. The response of the cells within the population to intracellular Zn(2+) is highly heterogeneous. In addition, the results emphasize the utility of dynamic and quantitative imaging in understanding cell uptake and processing of targeted therapeutic ZnO NPs at the cellular level by heterogeneous cancer cell populations, which can be crucial for the development of optimized treatment strategies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploration of Al-Doped ZnO in Photovoltaic Thin Films

NASA Astrophysics Data System (ADS)

Ciccarino, Christopher; Sahiner, M. Alper

The electrical properties of Al doped ZnO-based thin films represent a potential advancement in the push for increasing solar cell efficiency. Doping with Aluminum will theoretically decrease resistivity of the film and therefore achieve this potential as a viable option in the P-N junction phase of photovoltaic cells. The n-type semi-conductive characteristics of the ZnO layer will theoretically be optimized with the addition of Aluminum carriers. In this study, Aluminum doping concentrations ranging from 1-3% by mass were produced, analyzed, and compared. Films were developed onto ITO coated glass using the Pulsed Laser Deposition technique. Target thickness was 250 nm and ellipsometry measurements showed uniformity and accuracy in this regard. Active dopant concentrations were determined using Hall Effect measurements. Efficiency measurements showed possible applications of this doped compound, with upwards of 7% efficiency measured, using a Keithley 2602 SourceMeter set-up. XRD scans showed highly crystalline structures, with effective Al intertwining of the hexagonal wurtzile ZnO molecular structure. This alone indicates a promising future of collaboration between these two materials.

Four-cell solar tracker

NASA Technical Reports Server (NTRS)

Berdahl, C. M.

1981-01-01

Forty cm Sun tracker, consisting of optical telescope and four solar cells, stays pointed at Sun throughout day for maximum energy collection. Each solar cell generates voltage proportional to part of solar image it receives; voltages drive servomotors that keep image centered. Mirrored portion of cylinder extends acquisition angle of device by reflecting Sun image back onto solar cells.

Heterojunction solar cell

DOEpatents

Olson, Jerry M.

1994-01-01

A high-efficiency single heterojunction solar cell wherein a thin emitter layer (preferably Ga.sub.0.52 In.sub.0.48 P) forms a heterojunction with a GaAs absorber layer. The conversion effiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer.

Solar cells

NASA Astrophysics Data System (ADS)

Cuquel, A.; Roussel, M.

The physical and electronic characteristics of solar cells are discussed in terms of space applications. The principles underlying the photovoltaic effect are reviewed, including an analytic model for predicting the performance of individual cells and arrays of cells. Attention is given to the effects of electromagnetic and ionizing radiation, micrometeors, thermal and mechanical stresses, pollution and degassing encountered in space. The responses of different types of solar cells to the various performance-degrading agents are examined, with emphasis on techniques for quality assurance in the manufacture and mounting of Si cells.

Origin of Photovoltage Enhancement via Interfacial Modification with Silver Nanoparticles Embedded in an a-SiC:H p-Type Layer in a-Si:H Solar Cells.

PubMed

Li, Tiantian; Zhang, Qixing; Ni, Jian; Huang, Qian; Zhang, Dekun; Li, Baozhang; Wei, Changchun; Yan, Baojie; Zhao, Ying; Zhang, Xiaodan

2017-03-29

We used silver nanoparticles (Ag-NPs) embedded in the p-type semiconductor layer of hydrogenated amorphous silicon (a-Si:H) solar cells in the Schottky barrier contact design to modify the interface between aluminum-doped ZnO (ZnO:Al, AZO) and p-type hydrogenated amorphous silicon carbide (p-a-SiC:H) without plasmonic absorption. The high work function of the Ag-NPs provided a good channel for the transport of photogenerated holes. A p-type nanocrystalline SiC:H layer was used to compensate for the real surface defects and voids on the surface of Ag-NPs to reduce recombination at the AZO/p-type layer interface, which then enhanced the photovoltage of single-junction a-Si:H solar cells to values as high as 1.01 V. The Ag-NPs were around 10 nm in diameter and thermally stable in the p-type a-SiC:H film at the solar-cell process temperature. We will also show that a wide range of photovoltages between 1.01 and 2.89 V could be obtained with single-, double-, and triple-junction solar cells based on the single-junction a-Si:H solar cells with tunable high photovoltage. These solar cells are suitable photocathodes for solar water-splitting applications.

Heterojunction solar cell

DOEpatents

Olson, J.M.

1994-08-30

A high-efficiency single heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer. 1 fig.

Investigation of the phototoxic effect of ZnO nanorods on fibroblasts and melanoma human cells

NASA Astrophysics Data System (ADS)

Kishwar, S.; Siddique, M.; Israr-Qadir, M.; Nur, O.; Willander, M.; Öllinger, K.

2014-11-01

Photocytotoxic effects of as-grown and zinc oxide (ZnO) nanorods coated with 5-aminolevulinic acid (ALA) have been studied on human cells, i.e. melanoma and foreskin fibroblast, under dark and ultraviolet light exposures. Zinc oxide nanorods have been grown on the very sharp tip (diameter = 700 nm) of borosilicate glass pipettes and then were coated by the photosensitizer for targeted investigations inside human cells. The coated glass pipette’s tip with photosensitizer has been inserted inside the cells with the help of a micro-manipulator and irradiated through ultraviolet light (UVA), which reduces the membrane potential of the mitochondria leading to cell death. Cell viability loss has been detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay when exposed to the dissolved ZnO nanorods and the production of the reactive oxygen species (ROS) has been detected along with the enhanced cytotoxic effect under UVA irradiation. Additionally, the influence of the lipid soluble antioxidant vitamin E and water-soluble N-acetyl-cysteine toward the enhancement or reduction of the toxicity has been investigated. A comparative analysis of the toxic nature of ZnO nanorods has been drawn between normal human fibroblast and melanoma cells, which can be favorable for understanding the clinical setting for killing tumor cells.

Dependence of lattice strain relaxation, absorbance, and sheet resistance on thickness in textured ZnO@B transparent conductive oxide for thin-film solar cell applications.

PubMed

Kou, Kuang-Yang; Huang, Yu-En; Chen, Chien-Hsun; Feng, Shih-Wei

2016-01-01

The interplay of surface texture, strain relaxation, absorbance, grain size, and sheet resistance in textured, boron-doped ZnO (ZnO@B), transparent conductive oxide (TCO) materials of different thicknesses used for thin film, solar cell applications is investigated. The residual strain induced by the lattice mismatch and the difference in the thermal expansion coefficient for thicker ZnO@B is relaxed, leading to an increased surface texture, stronger absorbance, larger grain size, and lower sheet resistance. These experimental results reveal the optical and material characteristics of the TCO layer, which could be useful for enhancing the performance of solar cells through an optimized TCO layer.

Photovoltaic solar cell

DOEpatents

Nielson, Gregory N; Cruz-Campa, Jose Luis; Okandan, Murat; Resnick, Paul J

2014-05-20

A photovoltaic solar cell for generating electricity from sunlight is disclosed. The photovoltaic solar cell comprises a plurality of spaced-apart point contact junctions formed in a semiconductor body to receive the sunlight and generate the electricity therefrom, the plurality of spaced-apart point contact junctions having a first plurality of regions having a first doping type and a second plurality of regions having a second doping type. In addition, the photovoltaic solar cell comprises a first electrical contact electrically connected to each of the first plurality of regions and a second electrical contact electrically connected to each of the second plurality of regions, as well as a passivation layer covering major surfaces and sidewalls of the photovoltaic solar cell.

Photovoltaic solar cell

DOEpatents

Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J

2013-11-26

A photovoltaic solar cell for generating electricity from sunlight is disclosed. The photovoltaic solar cell comprises a plurality of spaced-apart point contact junctions formed in a semiconductor body to receive the sunlight and generate the electicity therefrom, the plurality of spaced-apart point contact junctions having a first plurality of regions having a first doping type and a second plurality of regions having a second doping type. In addition, the photovoltaic solar cell comprises a first electrical contact electrically connected to each of the first plurality of regions and a second electrical contact electrically connected to each of the second plurality of regions, as well as a passivation layer covering major surfaces and sidewalls of the photovoltaic solar cell.

Surface Coverage and Metallicity of ZnO Surfaces from First-Principles Calculations

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Schleife, Andre; The Schleife research Group Team

Zinc oxide (ZnO) surfaces are widely used in different applications such as catalysis, biosensing, and solar cells. These surfaces are, in many cases, chemically terminated by hydroxyl groups. In experiment, a transition of the ZnO surface electronic properties from semiconducting to metallic was reported upon increasing the hydroxyl coverage to more than approximately 80 %. The reason for this transition is not well understood yet. We report on first-principles calculations based on density functional theory for the ZnO [ 10 1 0 ] surface, taking different amounts of hydroxyl coverage into account. We calculated band structures for fully relaxed configurations and verified the existence of this transition. However, we only find the fully covered surface to be metallic. We thus explore the possibility for clustering of the surface-terminating hydroxyl groups based on total-energy calculations. We also found that the valence band maximum consists of oxygen p states from both the surface hydroxyl groups and the surface oxygen atoms of the material. The main contribution to the metallicity is found to be from the hydroxyl groups.

Electrical properties of TiO2 at different deposition frequencies and their application in ZnO/TiO2 based dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Saurdi, I.; Shafura, A. K.; Mamat, M. H.; Ishak, A.; Rusop, M.

2018-05-01

In this work, the titanium oxide (TiO2) films were deposited on glass substrate at different deposition frequencies (1, 2, 3 and 4 times) and therefore different of thicknesses been produced by using spin coating technique and their electrical and structural properties were investigated. The thicknesses of TiO2 films at different deposition frequencies (1, 2, 3 and 4 times) were 900μm, 1815μm, 2710μm and 3620μm respectively. Meanwhile, the resistivities of TiO2 films at different deposition frequencies (1, 2, 3 and 4 times) were 5.41 × 106Ωcm, 2.28 × 106Ωcm, 2.78 × 105Ωcm and 8.37 × 106Ωcm, respectively. The ZnO/TiO2 composite for ZnO nanorod and TiO2 been produced by deposited the TiO2 on top of ZnO nanorod at different deposition frequencies on ITO-coated glass substrate. The fabricated dye-sensitized solar cells of ZnO nanorod without TiO2, ZnO/TiO2 with a TiO2 thickness 900μm, ZnO/TiO2 with a TiO2 thickness 1815μm, ZnO/TiO2 with a TiO2 thickness 2710μm, ZnO/TiO2 with a TiO2 thickness 3620μm on top of ZnO nanorod were investigated. From the solar simulator measurement under AM 1.5 the solar energy conversion efficiency (η) of ZnO nanorod without TiO2, ZnO/TiO2- 900μm, ZnO/TiO2-1815μm, ZnO/TiO2-2710μm and ZnO/TiO2-3620μm were 0.99%, 1.87%, 2.11%, 2.54%, 2.27%, respectively. The DSSCs ZnO/TiO2 show better of efficiency as compared to ZnO nanorod without TiO2. Furthermore, the enhancement of ZnO/TiO2-2710μm DSSC also closely related with the improvement of electrical and structural properties of TiO2 at 3 deposition frequencies as compared with TiO2 at 1, 2 and 4 deposition frequencies.

Modification of electron states in CdTe absorber due to a buffer layer in CdTe/CdS solar cells

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

Fedorenko, Y. G., E-mail: y.fedorenko@liverpool.ac.uk; Major, J. D.; Pressman, A.

2015-10-28

By application of the ac admittance spectroscopy method, the defect state energy distributions were determined in CdTe incorporated in thin film solar cell structures concluded on ZnO, ZnSe, and ZnS buffer layers. Together with the Mott-Schottky analysis, the results revealed a strong modification of the defect density of states and the concentration of the uncompensated acceptors as influenced by the choice of the buffer layer. In the solar cells formed on ZnSe and ZnS, the Fermi level and the energy position of the dominant deep trap levels were observed to shift closer to the midgap of CdTe, suggesting the mid-gapmore » states may act as recombination centers and impact the open-circuit voltage and the fill factor of the solar cells. For the deeper states, the broadening parameter was observed to increase, indicating fluctuations of the charge on a microscopic scale. Such changes can be attributed to the grain-boundary strain and the modification of the charge trapped at the grain-boundary interface states in polycrystalline CdTe.« less

Vertically building Zn2SnO4 nanowire arrays on stainless steel mesh toward fabrication of large-area, flexible dye-sensitized solar cells.

PubMed

Li, Zhengdao; Zhou, Yong; Bao, Chunxiong; Xue, Guogang; Zhang, Jiyuan; Liu, Jianguo; Yu, Tao; Zou, Zhigang

2012-06-07

Zn(2)SnO(4) nanowire arrays were for the first time grown onto a stainless steel mesh (SSM) in a binary ethylenediamine (En)/water solvent system using a solvothermal route. The morphology evolution following this reaction was carefully followed to understand the formation mechanism. The SSM-supported Zn(2)SnO(4) nanowire was utilized as a photoanode for fabrication of large-area (10 cm × 5 cm size as a typical sample), flexible dye-sensitized solar cells (DSSCs). The synthesized Zn(2)SnO(4) nanowires exhibit great bendability and flexibility, proving potential advantage over other metal oxide nanowires such as TiO(2), ZnO, and SnO(2) for application in flexible solar cells. Relative to the analogous Zn(2)SnO(4) nanoparticle-based flexible DSSCs, the nanowire geometry proves to enhance solar energy conversion efficiency through enhancement of electron transport. The bendable nature of the DSSCs without obvious degradation of efficiency and facile scale up gives the as-made flexible solar cell device potential for practical application.

Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation

NASA Astrophysics Data System (ADS)

Zhu, Hua-Yue; Jiang, Ru; Fu, Yong-Qian; Li, Rong-Rong; Yao, Jun; Jiang, Sheng-Tao

2016-04-01

Novel multifunctional NiFe2O4/ZnO hybrids were prepared by a hydrothermal method and their physicochemical properties were characterized by XRD, SEM, TEM, TGA, VSM, BET and UV-vis DRS. The adsorption and photocatalytic performance of NiFe2O4/ZnO hybrids were systematically investigated using congo red as a model contaminant. With the introduction of NiFe2O4, NiFe2O4/ZnO hybrids can absorb the whole light from 300 nm to 700 nm. The adsorption capacity (221.73 mg g-1) of NiFe2O4/ZnO hybrids is higher than those of NiFe2O4, ZnO and mechanically mixed NiFe2O4/ZnO hybrids. The removal of congo red solution (20 mg L-1) by NiFe2O4/ZnO hybrids was about 94.55% under simulated solar light irradiation for 10 min. rad OH and h+ play important roles in the decolorization of congo red solution by NiFe2O4/ZnO hybrids under simulated solar light irradiation. The decolorization efficiency of congo red solution is 97.23% for the fifth time by NiFe2O4/ZnO hybrids under simulate solar light irradiation, indicating the high photostability and durability. NO3- and Cl- anions which are ubiquitous components in dye-containing wastewater have negligible influence on the effectiveness of NiFe2O4/ZnO hybrids. Moreover, the magnetic NiFe2O4/ZnO hybrids can be easily separated from the reacted solution by an external magnet.

In vitro evaluation of cellular responses induced by ZnO nanoparticles, zinc ions and bulk ZnO in fish cells.

PubMed

Fernández, Dolores; García-Gómez, Concepción; Babín, Mar

2013-05-01

Zinc oxide nanoparticles (ZnO-NPs) are inevitably released into the environment and are potentially dangerous for aquatic life. However, the potential mechanisms of cytotoxicity of zinc nanoparticles remain unclear. Studying the toxicity of ZnO-NPs with In vitro systems will help to determine their interactions with cellular biomolecules. The aim of this study was to evaluate the cytotoxic potentials of ZnO-NPs in established fish cell lines (RTG-2, RTH-149 and RTL-W1) and compare them with those of bulk ZnO and Zn(2+) ions. Membrane function (CFDA-AM assay), mitochondrial function (MTT assay), cell growth (KBP assay), cellular stress (β-galactosidase assay), reductase enzyme activity (AB assay), reactive oxygen species (ROS), total glutathione cellular content (tGSH assay) and glutathione S-transferase (GST) activities were assessed for all cell lines. ZnO-NPs cytotoxicity was greater than those of bulk ZnO and Zn(2+). ZnO-NPs induced oxidative stress is dependent on their dose. Low cost tests, such as CFDA-AM, ROS, GST activity and tGSH cell content test that use fish cell lines, may be used to detect oxidative stress and redox status changes. Particle dissolution of the ZnO-NPs did not appear to play an important role in the observed toxicity in this study. Published by Elsevier B.V.

In situ detection of the Zn(2+) release process of ZnO NPs in tumour cells by confocal laser scanning fluorescence microscopy.

PubMed

Song, Wenshuang; Tang, Xiaoling; Li, Yong; Sun, Yang; Kong, Jilie; Qingguang, Ren

2016-08-01

The use of zinc oxide (ZnO) nanoparticles (NPs) for cancer is not yet clear for human clinical applications, which is primarily due to the lack of a better understanding of the action mechanisms and cellular consequences of the direct exposure of cells to these NPs. In this work, the authors have selected zinquin ethyl ester, a Zn(2+)-specific fluorescent molecular probe, to efficiently differentiate ZnO NPs and Zn(2+), and combined with confocal laser scanning microscopy (CLSM) to in situ study the Zn(2+) release process of ZnO NPs in cancer cell system through detecting the change of Zn(2+) level over time. During the experiments, the authors have designed the test group ZnO-2 in addition to assess the influence of a long-term storage on the characteristics of ZnO NPs in aqueous solution, and the Zn(2+) release process of ZnO NPs in cancer cell system. After three-month storage at room temperature, the release process became earlier and faster, which was consistent with previous results of transmission electron microscope, UV-Vis and PL spectra. It is a good detection method that combination of Zn(2+)-specific fluorescent molecular probe and CLSM, which will be helpful for ZnO NPs using in clinical research.

Heterostructure solar cells

NASA Technical Reports Server (NTRS)

Chang, K. I.; Yeh, Y. C. M.; Iles, P. A.; Morris, R. K.

1987-01-01

The performance of gallium arsenide solar cells grown on Ge substrates is discussed. In some cases the substrate was thinned to reduce overall cell weight with good ruggedness. The conversion efficiency of 2 by 2 cm cells under AMO reached 17.1 percent with a cell thickness of 6 mils. The work described forms the basis for future cascade cell structures, where similar interconnecting problems between the top cell and the bottom cell must be solved. Applications of the GaAs/Ge solar cell in space and the expected payoffs are discussed.

Plasmonically sensitized metal-oxide electron extraction layers for organic solar cells.

PubMed

Trost, S; Becker, T; Zilberberg, K; Behrendt, A; Polywka, A; Heiderhoff, R; Görrn, P; Riedl, T

2015-01-16

ZnO and TiOx are commonly used as electron extraction layers (EELs) in organic solar cells (OSCs). A general phenomenon of OSCs incorporating these metal-oxides is the requirement to illuminate the devices with UV light in order to improve device characteristics. This may cause severe problems if UV to VIS down-conversion is applied or if the UV spectral range (λ < 400 nm) is blocked to achieve an improved device lifetime. In this work, silver nanoparticles (AgNP) are used to plasmonically sensitize metal-oxide based EELs in the vicinity (1-20 nm) of the metal-oxide/organic interface. We evidence that plasmonically sensitized metal-oxide layers facilitate electron extraction and afford well-behaved highly efficient OSCs, even without the typical requirement of UV exposure. It is shown that in the plasmonically sensitized metal-oxides the illumination with visible light lowers the WF due to desorption of previously ionosorbed oxygen, in analogy to the process found in neat metal oxides upon UV exposure, only. As underlying mechanism the transfer of hot holes from the metal to the oxide upon illumination with hν < Eg is verified. The general applicability of this concept to most common metal-oxides (e.g. TiOx and ZnO) in combination with different photoactive organic materials is demonstrated.

Solar cell radiation handbook

NASA Technical Reports Server (NTRS)

Tada, H. Y.; Carter, J. R., Jr.; Anspaugh, B. E.; Downing, R. G.

1982-01-01

The handbook to predict the degradation of solar cell electrical performance in any given space radiation environment is presented. Solar cell theory, cell manufacturing and how they are modeled mathematically are described. The interaction of energetic charged particles radiation with solar cells is discussed and the concept of 1 MeV equivalent electron fluence is introduced. The space radiation environment is described and methods of calculating equivalent fluences for the space environment are developed. A computer program was written to perform the equivalent fluence calculations and a FORTRAN listing of the program is included. Data detailing the degradation of solar cell electrical parameters as a function of 1 MeV electron fluence are presented.

Improved photovoltaic properties of ZnTeO-based intermediate band solar cells

NASA Astrophysics Data System (ADS)

Tanaka, Tooru; Saito, Katsuhiko; Guo, Qixin; Yu, Kin Man; Walukiewicz, Wladek

2018-02-01

Highly mismatched ZnTe1-xOx (ZnTeO) alloy is one of the potential candidates for an absorber material in a bulk intermediate band solar cell (IBSC) because a narrow, O-derived intermediate band IB (E-) is formed well below the conduction band CB (E+) edge of the ZnTe. We have previously demonstrated the generation of photocurrent induced by two-step photon absorption (TSPA) in ZnTeO IBSCs using n-ZnO window layer. However, because of the large conduction band offset (CBO) between ZnTe and ZnO, only a small open circuit voltage (Voc) was observed in this structure. Here, we report our recent progress on the development of ZnTeO IBSCs with n-ZnS window layer. ZnS has a large direct band gap of 3.7 eV with an electron affinity of 3.9 eV that can realize a smaller CBO with ZnTe. We have grown n-type ZnS thin films on ZnTe substrates by molecular beam epitaxy (MBE), and demonstrated ZnTe solar cells and ZnTeO IBSCs using n-ZnS window layer with an improved VOC. Especially, a n-ZnS/i-ZnTe/p-ZnTe solar cell showed an improved Voc of 0.77 V, a large short-circuit current density of 6.7 mA/cm2 with a fill factor of 0.60, yielding the power conversion efficiency of 3.1 %, under 1 sun illumination.

Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint

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

Pern, F. J.; Noufi, R.

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. Themore » best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ≥ 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ≥ 70/70. At T/RH = 85/70, substantial blistering of BZO layers on

Synthesis of biocompatible SiO2 coated ZnO quantum dots for cell imaging

NASA Astrophysics Data System (ADS)

Zhang, Min; Wang, Qian; Chen, Haiyan; Gu, Yueqing

2014-09-01

Quantum dots (QDs) is a promising candidate for biomedical imaging. However, the bio-toxicity of traditional quantum dots obstructed their further application seriously. In this work, a simple solution growth method was utilized to synthesize ZnO QDs. However, their self-assemble feature makes them unstable in aqueous solution. Furthermore, (3-Aminopropyl) triethoxysilane was selected as a capping agent to stabilize ZnO QDs and then ZnO@SiO2 nanoparticles were obtained. They dispersed excellently in water and exhibited favorable fluorescence properties owing to the protection of silane. The biocompatability of ZnO@SiO2 nanoparticles was verified by MTT assy. The cell affinity studies demonstrated that ZnO@SiO2 nanoparticles could be uptaken by cells efficiently. Therefore, the as-prepared ZnO@SiO2 nanoparticles is a promising candidate for applications in cell imaging.

GaAs Solar Cell Radiation Handbook

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.

1996-01-01

History of GaAs solar cell development is provided. Photovoltaic equations are described along with instrumentation techniques for measuring solar cells. Radiation effects in solar cells, electrical performance, and spacecraft flight data for solar cells are discussed. The space radiation environment and solar array degradation calculations are addressed.

The effects of electron and hole transport layer with the electrode work function on perovskite solar cells

NASA Astrophysics Data System (ADS)

Deng, Quanrong; Li, Yiqi; Chen, Lian; Wang, Shenggao; Wang, Geming; Sheng, Yonglong; Shao, Guosheng

2016-09-01

The effects of electron and hole transport layer with the electrode work function on perovskite solar cells with the interface defects were simulated by using analysis of microelectronic and photonic structures-one-dimensional (AMPS-1D) software. The simulation results suggest that TiO2 electron transport layer provides best device performance with conversion efficiency of 25.9% compared with ZnO and CdS. The threshold value of back electrode work function for Spiro-OMeTAD, NiO, CuI and Cu2O hole transport layer are calculated to be 4.9, 4.8, 4.7 and 4.9 eV, respectively, to reach the highest conversion efficiency. The mechanisms of device physics with various electron and hole transport materials are discussed in details. The device performance deteriorates gradually as the increased density of interface defects located at ETM/absorber or absorber/HTM. This research results can provide helpful guidance for materials and metal electrode choice for perovskite solar cells.

Module level solutions to solar cell polarization

DOEpatents

Xavier, Grace , Li; Bo, [San Jose, CA

2012-05-29

A solar cell module includes interconnected solar cells, a transparent cover over the front sides of the solar cells, and a backsheet on the backsides of the solar cells. The solar cell module includes an electrical insulator between the transparent cover and the front sides of the solar cells. An encapsulant protectively packages the solar cells. To prevent polarization, the insulator has resistance suitable to prevent charge from leaking from the front sides of the solar cells to other portions of the solar cell module by way of the transparent cover. The insulator may be attached (e.g., by coating) directly on an underside of the transparent cover or be a separate layer formed between layers of the encapsulant. The solar cells may be back junction solar cells.

GaAs Solar Cell Radiation Handbook

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.

1996-01-01

The handbook discusses the history of GaAs solar cell development, presents equations useful for working with GaAs solar cells, describes commonly used instrumentation techniques for assessing radiation effects in solar cells and fundamental processes occurring in solar cells exposed to ionizing radiation, and explains why radiation decreases the electrical performance of solar cells. Three basic elements required to perform solar array degradation calculations: degradation data for GaAs solar cells after irradiation with 1 MeV electrons at normal incidence; relative damage coefficients for omnidirectional electron and proton exposure; and the definition of the space radiation environment for the orbit of interest, are developed and used to perform a solar array degradation calculation.

Assembling solar-cell arrays

NASA Technical Reports Server (NTRS)

Bloch, J. T.; Hanger, R. T.; Nichols, F. W.

1979-01-01

Modified 70 mm movie film editor automatically attaches solar cells to flexible film substrate. Machine can rapidly and inexpensively assemble cells for solar panels at rate of 250 cells per minute. Further development is expected to boost production rate to 1000 cells per minute.

Optical design of ZnO-based antireflective layers for enhanced GaAs solar cell performance.

PubMed

Lee, Hye Jin; Lee, Jae Won; Kim, Hee Jun; Jung, Dae-Han; Lee, Ki-Suk; Kim, Sang Hyeon; Geum, Dae-myeong; Kim, Chang Zoo; Choi, Won Jun; Baik, Jeong Min

2016-01-28

A series of hierarchical ZnO-based antireflection coatings with different nanostructures (nanowires and nanosheets) is prepared hydrothermally, followed by means of RF sputtering of MgF2 layers for coaxial nanostructures. Structural analysis showed that both ZnO had a highly preferred orientation along the 〈0001〉 direction with a highly crystalline MgF2 shell coated uniformly. However, a small amount of Al was present in nanosheets, originating from Al diffusion from the Al seed layer, resulting in an increase of the optical bandgap. Compared with the nanosheet-based antireflection coatings, the nanowire-based ones exhibited a significantly lower reflectance (∼2%) in ultraviolet and visible light wavelength regions. In particular, they showed perfect light absorption at wavelength less than approximately 400 nm. However, a GaAs single junction solar cell with nanosheet-based antireflection coatings showed the largest enhancement (43.9%) in power conversion efficiency. These results show that the increase of the optical bandgap of the nanosheets by the incorporation of Al atoms allows more photons enter the active region of the solar cell, improving the performance.

Achieving 15% Tandem Polymer Solar Cells

DTIC Science & Technology

2015-06-23

solar cell structures – both polymer only and hybrid tandem cells to constantly pushing the envelope of solution processed solar cell ...performance – 11.6% polymer tandem cell , 7% transparent tandem polymer cell , and over 10% PCE hybrid tandem solar cells were achieved. In addition, AFOSR’s...final support also enabled us to explore novel hybrid perovskite solar cells in depth. For example, single junction cell efficiency

Influence of the layer parameters on the performance of the CdTe solar cells

NASA Astrophysics Data System (ADS)

Haddout, Assiya; Raidou, Abderrahim; Fahoume, Mounir

2018-03-01

Influence of the layer parameters on the performances of the CdTe solar cells is analyzed by SCAPS-1D. The ZnO: Al film shows a high efficiency than SnO2:F. Moreover, the thinner window layer and lower defect density of CdS films are the factor in the enhancement of the short-circuit current density. As well, to increase the open-circuit voltage, the responsible factors are low defect density of the absorbing layer CdTe and high metal work function. For the low cost of cell production, ultrathin film CdTe cells are used with a back surface field (BSF) between CdTe and back contact, such as PbTe. Further, the simulation results show that the conversion efficiency of 19.28% can be obtained for the cell with 1-μm-thick CdTe, 0.1-μm-thick PbTe and 30-nm-thick CdS.

Positron annihilation spectroscopy: Applications to Si, ZnO, and multilayer semiconductor structures

NASA Astrophysics Data System (ADS)

Schaffer, J. P.; Rohatgi, A.; Dewald, A. B.; Frost, R. L.; Pang, S. K.

1989-11-01

The potential of positron annihilation spectroscopy (PAS) for defect characterization at the atomic scale in semiconductors is demonstrated for Si, ZnO, and multilayer structures, such as an AlGaAs/GaAs solar cell. The types of defects discussed include: i) vacancy complexes, oxygen impurities and dopants, ii) the influence of cooling rates on spatial non-uniformities in defects, and iii) characterization of buried interfaces. In sev-eral instances, the results of the PAS investigations are correlated with data from other established semiconductor characterization techniques.

Solar cell circuit and method for manufacturing solar cells

NASA Technical Reports Server (NTRS)

Mardesich, Nick (Inventor)

2010-01-01

The invention is a novel manufacturing method for making multi-junction solar cell circuits that addresses current problems associated with such circuits by allowing the formation of integral diodes in the cells and allows for a large number of circuits to readily be placed on a single silicon wafer substrate. The standard Ge wafer used as the base for multi-junction solar cells is replaced with a thinner layer of Ge or a II-V semiconductor material on a silicon/silicon dioxide substrate. This allows high-voltage cells with multiple multi-junction circuits to be manufactured on a single wafer, resulting in less array assembly mass and simplified power management.

A Hybrid Tandem Solar Cell Combining a Dye-Sensitized and a Polymer Solar Cell.

PubMed

Shao, Zhipeng; Chen, Shuanghong; Zhang, Xuhui; Zhu, Liangzheng; Ye, Jiajiu; Dai, Songyuan

2016-06-01

A hybrid tandem solar cell was assambled by connecting a dye sensitized solar cell and a polymer solar cell in series. A N719 sensitized TiO2 was used as photocathode in dye-sensitized subcell, and a MEH-PPV/PCBM composite was used as active layer in the polymer subcell. The polymer subcell fabricated on the counter electrode of the dye sensitized solar cell. A solution processed TiO(x) layer was used as electron collection layer of the polymer sub cell and the charge recombination layer. The effects of the TiO(x) interlayer and the spectral overlap between the two sub cells have been studied and optimized. The results shows that a proper thickness of the TiO(x) layer is needed for tandem solar cells. Thick TiO(x) will enhance the series resistance, but too thin TiO(x), layer will damage the hole blocking effect and its hydrophilic. The resulting optimized tandem solar cells exhibited a power conversion efficiency of 1.28% with a V(oc) of 0.95 V under simulated 100 mW cm(-2) AM 1.5 illumination.

Solar cell array interconnects

DOEpatents

Carey, Paul G.; Thompson, Jesse B.; Colella, Nicolas J.; Williams, Kenneth A.

1995-01-01

Electrical interconnects for solar cells or other electronic components using a silver-silicone paste or a lead-tin (Pb-Sn) no-clean fluxless solder cream, whereby the high breakage of thin (<6 mil thick) solar cells using conventional solder interconnect is eliminated. The interconnects of this invention employs copper strips which are secured to the solar cells by a silver-silicone conductive paste which can be used at room temperature, or by a Pb-Sn solder cream which eliminates undesired residue on the active surfaces of the solar cells. Electrical testing using the interconnects of this invention has shown that no degradation of the interconnects developed under high current testing, while providing a very low contact resistance value.

High-Temperature Solar Cell Development

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Raffaelle, Ryne P.; Merritt, Danielle

2004-01-01

The vast majority of satellites and near-earth probes developed to date have relied upon photovoltaic power generation. If future missions to probe environments close to the sun will be able to use photovoltaic power, solar cells that can function at high temperatures, under high light intensity, and high radiation conditions must be developed. For example, the equilibrium temperature of a Mercury surface station will be about 450 C, and the temperature of solar arrays on the proposed "Solar Probe" mission will extend to temperatures as high as 2000 C (although it is likely that the craft will operate on stored power rather than solar energy during the closest approach to the sun). Advanced thermal design principles, such as replacing some of the solar array area with reflectors, off-pointing, and designing the cells to reflect rather than absorb light out of the band of peak response, can reduce these operating temperature somewhat. Nevertheless, it is desirable to develop approaches to high-temperature solar cell design that can operate under temperature extremes far greater than today's cells. Solar cells made from wide bandgap (WBG) compound semiconductors are an obvious choice for such an application. In order to aid in the experimental development of such solar cells, we have initiated a program studying the theoretical and experimental photovoltaic performance of wide bandgap materials. In particular, we have been investigating the use of GaP, SiC, and GaN materials for space solar cells. We will present theoretical results on the limitations on current cell technologies and the photovoltaic performance of these wide-bandgap solar cells in a variety of space conditions. We will also give an overview of some of NASA's cell developmental efforts in this area and discuss possible future mission applications.

CdS/CdSe quantum dots and ZnPc dye co-sensitized solar cells with Au nanoparticles/graphene oxide as efficient modified layer.

PubMed

Chen, Cong; Cheng, Yu; Jin, Junjie; Dai, Qilin; Song, Hongwei

2016-10-15

Co-sensitization by using two or more sensitizers with complementary absorption spectra to expand the spectral response range is an effective approach to enhance device performance of quantum dot sensitized solar cells (QDSSCs). To improve the light-harvesting in the visible/near-infrared (NIR) region, organic dye zinc phthalocyanine (ZnPc) was combined with CdS/CdSe quantum dots (QDs) for co-sensitized solar cells based on ZnO inverse opals (IOs) as photoanode. The resulting co-sensitized device shows an efficient panchromatic spectral response feature to ∼750nm and presents an overall conversion efficiency of 4.01%, which is superior to that of the individual ZnPc-sensitized solar cells and CdS/CdSe-sensitized solar cells. Meanwhile, an Au nanoparticles/graphene oxide (Au NPs/GO) composite layer was successfully prepared to modify Cu2S counter electrode for the co-sensitized solar cells. Reducing the carrier recombination process by GO and catalytic process of Au NPs leads to increased power conversion efficiency(PCE) from 4.01 to 4.60% and sustainable stability remains ∼85% of its original value after 60min light exposure. In this paper, introduction of the organic dyes as co-sensitizer and Au NPs/GO as counter electrode modified layer has been proved to be an effective route to improve the performance of QDSSCs. Copyright © 2016 Elsevier Inc. All rights reserved.

A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities.

PubMed

Lu, Yi-Hsuan; Lin, Wei-Hao; Yang, Chao-Yao; Chiu, Yi-Hsuan; Pu, Ying-Chih; Lee, Min-Han; Tseng, Yuan-Chieh; Hsu, Yung-Jung

2014-08-07

An environmentally benign antisolvent method has been developed to prepare Cu(2+)-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu(2+) ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu(2+) introduction, resulting in the formation of Cu(2+)-doped ZnO nanocrystals. The as-prepared Cu(2+)-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu(2+) may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu(2+)-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu(2+). A further increase in the Cu(2+) concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu(2+). The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu(2+)-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu(2+) doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.

Investigation into the effects of surface stripping ZnO nanosheets.

PubMed

Barnett, Chris J; Jackson, Georgina; Jones, Daniel R; Lewis, Aled R; Welsby, Kathryn; Evans, Jon E; McGettrick, James D; Watson, Trystan; Maffeis, Thierry G G; Dunstan, Peter R; Barron, Andrew R; Cobley, Richard J

2018-04-20

ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

Investigation into the effects of surface stripping ZnO nanosheets

NASA Astrophysics Data System (ADS)

Barnett, Chris J.; Jackson, Georgina; Jones, Daniel R.; Lewis, Aled R.; Welsby, Kathryn; Evans, Jon E.; McGettrick, James D.; Watson, Trystan; Maffeis, Thierry G. G.; Dunstan, Peter R.; Barron, Andrew R.; Cobley, Richard J.

2018-04-01

ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

Enhanced optical band-gap of ZnO thin films by sol-gel technique

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

Raghu, P., E-mail: dpr3270@gmail.com; Naveen, C. S.; Shailaja, J.

2016-05-06

Transparent ZnO thin films were prepared using different molar concentration (0.1 M, 0.2 M & 0.8 M) of zinc acetate on soda lime glass substrates by the sol-gel spin coating technique. The optical properties revealed that the transmittance found to decrease with increase in molar concentration. Absorption edge showed that the higher concentration film has increasingly red shifted. An increased band gap energy of the thin films was found to be direct allowed transition of ∼3.9 eV exhibiting their relevance for photovoltaic applications. The extinction coefficient analysis revealed maximum transmittance with negligible absorption coefficient in the respective wavelengths. The resultsmore » of ZnO thin film prepared by sol-gel technique reveal its suitability for optoelectronics and as a window layer in solar cell applications.« less

Comparison of CIGS solar cells made with different structures and fabrication techniques

DOE PAGES

Mansfield, Lorelle M.; Garris, Rebekah L.; Counts, Kahl D.; ...

2016-11-03

Cu(In, Ga)Se2 (CIGS)-based solar cells from six fabricators were characterized and compared. The devices had differing substrates, absorber deposition processes, buffer materials, and contact materials. The effective bandgaps of devices varied from 1.05 to 1.22 eV, with the lowest optical bandgaps occurring in those with metal-precursor absorber processes. Devices with Zn(O, S) or thin CdS buffers had quantum efficiencies above 90% down to 400 nm. Most voltages were 250-300 mV below the Shockley-Queisser limit for their bandgap. Electroluminescence intensity tracked well with the respective voltage deficits. Fill factor (FF) was as high as 95% of the maximum for each device'smore » respective current and voltage, with higher FF corresponding to lower diode quality factors (~1.3). An in-depth analysis of FF losses determined that diode quality reflected in the quality factor, voltage-dependent photocurrent, and, to a lesser extent, the parasitic resistances are the limiting factors. As a result, different absorber processes and device structures led to a range of electrical and physical characteristics, yet this investigation showed that multiple fabrication pathways could lead to high-quality and high-efficiency solar cells.« less

Comparison of CIGS solar cells made with different structures and fabrication techniques

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

Mansfield, Lorelle M.; Garris, Rebekah L.; Counts, Kahl D.

Cu(In, Ga)Se2 (CIGS)-based solar cells from six fabricators were characterized and compared. The devices had differing substrates, absorber deposition processes, buffer materials, and contact materials. The effective bandgaps of devices varied from 1.05 to 1.22 eV, with the lowest optical bandgaps occurring in those with metal-precursor absorber processes. Devices with Zn(O, S) or thin CdS buffers had quantum efficiencies above 90% down to 400 nm. Most voltages were 250-300 mV below the Shockley-Queisser limit for their bandgap. Electroluminescence intensity tracked well with the respective voltage deficits. Fill factor (FF) was as high as 95% of the maximum for each device'smore » respective current and voltage, with higher FF corresponding to lower diode quality factors (~1.3). An in-depth analysis of FF losses determined that diode quality reflected in the quality factor, voltage-dependent photocurrent, and, to a lesser extent, the parasitic resistances are the limiting factors. As a result, different absorber processes and device structures led to a range of electrical and physical characteristics, yet this investigation showed that multiple fabrication pathways could lead to high-quality and high-efficiency solar cells.« less

Solar cell array interconnects

DOEpatents

Carey, P.G.; Thompson, J.B.; Colella, N.J.; Williams, K.A.

1995-11-14

Electrical interconnects are disclosed for solar cells or other electronic components using a silver-silicone paste or a lead-tin (Pb-Sn) no-clean fluxless solder cream, whereby the high breakage of thin (<6 mil thick) solar cells using conventional solder interconnect is eliminated. The interconnects of this invention employs copper strips which are secured to the solar cells by a silver-silicone conductive paste which can be used at room temperature, or by a Pb-Sn solder cream which eliminates undesired residue on the active surfaces of the solar cells. Electrical testing using the interconnects of this invention has shown that no degradation of the interconnects developed under high current testing, while providing a very low contact resistance value. 4 figs.

Origin of Open-Circuit Voltage Loss in Polymer Solar Cells and Perovskite Solar Cells.

PubMed

Kim, Hyung Do; Yanagawa, Nayu; Shimazaki, Ai; Endo, Masaru; Wakamiya, Atsushi; Ohkita, Hideo; Benten, Hiroaki; Ito, Shinzaburo

2017-06-14

Herein, the open-circuit voltage (V OC ) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of V OC to discuss the difference in the primary loss mechanism of V OC between them. As a result, the photon energy loss for polymer solar cells is in the range of about 0.7-1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms, while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of V OC in both solar cells are further discussed on the basis of the experimental data.

Solar-cell defect analyzer

NASA Technical Reports Server (NTRS)

Gauthier, M. K.; Miller, E. L.; Shumka, A.

1980-01-01

Laser-Scanning System pinpoints imperfections in solar cells. Entire solar panels containing large numbers of cells can be scanned. Although technique is similar to use of scanning electron microscope (SEM) to locate microscopic imperfections, it differs in that large areas may be examined, including entire solar panels, and it is not necessary to remove cover glass or encapsulants.

Solar cell with back side contacts

DOEpatents

Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J; Wanlass, Mark Woodbury; Clews, Peggy J

2013-12-24

A III-V solar cell is described herein that includes all back side contacts. Additionally, the positive and negative electrical contacts contact compoud semiconductor layers of the solar cell other than the absorbing layer of the solar cell. That is, the positive and negative electrical contacts contact passivating layers of the solar cell.

Influence of size and shape of sub-micrometer light scattering centers in ZnO-assisted TiO2 photoanode for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Pham, Trang T. T.; Mathews, Nripan; Lam, Yeng-Ming; Mhaisalkar, Subodh

2018-03-01

Sub-micrometer cavities have been incorporated in the TiO2 photoanode of dye-sensitized solar cell to enhance its optical property with light scattering effect. These are large pores of several hundred nanometers in size and scatter incident light due to the difference refraction index between the scattering center and the surrounding materials, according to Mie theory. The pores are created using polystyrene (PS) or zinc oxide (ZnO) templates reported previously which resulted in ellipsoidal and spherical shapes, respectively. The effect of size and shape of scattering center was modeled using a numerical analysis finite-difference time-domain (FDTD). The scattering cross-section was not affected significantly with different shapes if the total displacement volume of the scattering center is comparable. Experiments were carried out to evaluate the optical property with varying size of ZnO templates. Photovoltaic effect of dye-sensitized solar cells made from these ZnO-assisted films were investigated with incident-photon-to-current efficiency to understand the effect of scattering center size on the enhancement of absorption. With 380 nm macropores incorporated, the power conversion efficiency has increased by 11% mostly thanks to the improved current density, while 170 nm and 500 nm macropores samples did not have increment in sufficiently wide range of absorbing wavelengths.

Progress in a-SiOx:H thin film solar cells with patterned MgF2 dielectric for top cell of multi-junction system

NASA Astrophysics Data System (ADS)

Kang, Dong-Won; Sichanugrist, Porponth; Konagai, Makoto

2016-07-01

We successfully designed and experimentally demonstrated an application of patterned MgF2 dielectric material at rear Al-doped ZnO (AZO)/Ag interface in thin film amorphous silicon oxide ( a-SiOx:H) solar cells. When it was realized in practical device process, MgF2 coverage with patterned morphology was employed to allow for current flow between the AZO and Ag against highly resistive MgF2 material. On the basis of the suggested structure, we found an improvement in quantum efficiency of the solar cells with the patterned MgF2. In addition, an enhancement of open circuit voltage ( V oc ) and fill factor ( FF) was observed. A remarkable increase in shunt resistance of the cells with the MgF2 would possibly indicate that the highly resistive MgF2 layer can partly suppress physical shunting across top and bottom electrodes caused by very thin absorber thickness of only 100 nm. The approach showed that our best-performing device revealed an essential improvement in conversion efficiency from 7.83 to 8.01% with achieving markedly high V oc (1.013 V) and FF (0.729). [Figure not available: see fulltext.

A three solar cell system based on a self-supporting, transparent AlGaAs top solar cell

NASA Technical Reports Server (NTRS)

Negley, Gerald H.; Rhoads, Sandra L.; Terranova, Nancy E.; Mcneely, James B.; Barnett, Allen M.

1989-01-01

Development of a three solar cell stack can lead to practical efficiencies greater than 30 percent (1x,AM0). A theoretical efficiency limitation of 43.7 percent at AM0 and one sun is predicted by this model. Including expected losses, a practical system efficiency of 36.8 percent is anticipated. These calculations are based on a 1.93eV/1.43eV/0.89eV energy band gap combination. AlGaAs/GaAs/GaInAsP materials can be used with a six-terminal wiring configuration. The key issues for multijunction solar cells are the top and middle solar cell performance and the sub-bandgap transparency. AstroPower has developed a technique to fabricate AlGaAs solar cells on rugged, self-supporting, transparent AlGaAs substrates. Top solar cell efficiencies greater than 11 percent AM0 have been achieved. State-of-the-art GaAs or InP devices will be used for the middle solar cell. GaInAsP will be used to fabricate the bottom solar cell. This material is lattice-matched to InP and offers a wide range of bandgaps for optimization of the three solar cell stack. Liquid phase epitaxy is being used to grow the quaternary material. Initial solar cells have shown open-circuit voltages of 462 mV for a bandgap of 0.92eV. Design rules for the multijunction three solar cell stack are discussed. The progress in the development of the self-supporting AlGaAs top solar cell and the GaInAsP bottom solar cell is presented.

Solar power satellites - Heat engine or solar cells

NASA Technical Reports Server (NTRS)

Oman, H.; Gregory, D. L.

1978-01-01

A solar power satellite is the energy-converting element of a system that can deliver some 10 GW of power to utilities on the earth's surface. We evaluated heat engines and solar cells for converting sunshine to electric power at the satellite. A potassium Rankine cycle was the best of the heat engines, and 50 microns thick single-crystal silicon cells were the best of the photovoltaic converters. Neither solar cells nor heat engines had a clear advantage when all factors were considered. The potassium-turbine power plant, however, was more difficult to assemble and required a more expensive orbital assembly base. We therefore based our cost analyses on solar-cell energy conversion, concluding that satellite-generated power could be delivered to utilities for around 4 to 5 cents a kWh.

Determination of Carrier Lifetimes in Organic-Inorganic Hybrid Solar Cells Based on Sb2S3 by Using the Time-Resolved Photocurrent

NASA Astrophysics Data System (ADS)

Jo, Hyun-Jun; Mun, Young Hee; Kim, Jong Su; Kim, Seung Hyun; Lee, Sang-Ju; Sung, Shi-Joon; Kim, Dae-Hwan

2018-03-01

This paper presents organic-inorganic hybrid solar cells (SCs) based on ZnO/Sb2S3/P3HT heterojunctions. The ZnO and the Sb2S3 layers were grown using atomic layer deposition (ALD). Although four cells were fabricated on one substrate by using the same process, their open-circuit voltages ( V OC ) and short-circuit current densities ( J SC ) were different. The SC with a high V OC has a low J SC . The causes of the changes in the V OC and the JSC were investigated by using photoluminescence (PL) spectroscopy and optically-biased time-resolved photocurrent (TRPC) measurements. The PL results at 300 K showed that the emission positions of the Sb2S3 layers in all cells were similar at approximately 1.71 eV. The carrier lifetime of the SCs was calculated from the TRPC results. The lifetime of cell 4 with the highest J SC decreased drastically with increasing intensity of the continuous-wave optical bias beam. Therefore, the defect states in the ZnO layer contribute to the J SC , but degrade the V OC .

High efficiency solar cells combining a perovskite and a silicon heterojunction solar cells via an optical splitting system

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

Uzu, Hisashi, E-mail: Hisashi.Uzu@kaneka.co.jp, E-mail: npark@skku.edu; Ichikawa, Mitsuru; Hino, Masashi

2015-01-05

We have applied an optical splitting system in order to achieve very high conversion efficiency for a full spectrum multi-junction solar cell. This system consists of multiple solar cells with different band gap optically coupled via an “optical splitter.” An optical splitter is a multi-layered beam splitter with very high reflection in the shorter-wave-length range and very high transmission in the longer-wave-length range. By splitting the incident solar spectrum and distributing it to each solar cell, the solar energy can be managed more efficiently. We have fabricated optical splitters and used them with a wide-gap amorphous silicon (a-Si) solar cellmore » or a CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cell as top cells, combined with mono-crystalline silicon heterojunction (HJ) solar cells as bottom cells. We have achieved with a 550 nm cutoff splitter an active area conversion efficiency of over 25% using a-Si and HJ solar cells and 28% using perovskite and HJ solar cells.« less

Solar cell radiation handbook

NASA Technical Reports Server (NTRS)

Tada, H. Y.; Carter, J. R., Jr.

1977-01-01

Solar cell theory cells are manufactured, and how they are modeled mathematically is reviewed. The interaction of energetic charged particle radiation with solar cells is discussed in detail and the concept of 1 MeV equivalent electron fluence is introduced. The space radiation environment is described and methods of calculating equivalent fluences for the space environment are developed. A computer program was written to perform the equivalent fluence calculations and a FORTRAN listing of the program is included. Finally, an extensive body of data detailing the degradation of solar cell electrical parameters as a function of 1 MeV electron fluence is presented.

Self-Assembly of ZnO-Nanorods and Its Performance in Quasi Solid Dye Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Aprilia, A.; Erdienzy, A.; Bahtiar, A.; Safriani, L.; Syakir, N.; Risdiana; Saragi, T.; Hidayat, S.; Fitrilawati; Hidayat, R.; Siregar, R. E.

2017-07-01

Zinc oxide (ZnO) nanorods (NRs) were successfully prepared by self-assembly methods using zinc nitrate hexahydrate and hexamethylenetetramine as raw materials. ZnO-NRs were grown on FTO/ZnO seed layer and to enhance dye adsorption it was continued by deposition of titania (TiO2) paste by screen printing method. Deposition time of ZnO-NRs were varied, for 120, 150 and 180 minutes and subsequently stacked with one layer of TiO2 mesoporous. The resulting heterojunction layers of FTO/ZnO-Nrs/TiO2 was then applied as a photoanode in quasi-solid dye sensitized solar cell (QS- DSSC) with polymer gel electrolyte (PGE) as a hole conductor. UV-Vis spectrometer was used to investigate the changes of dye adsorption in photoanode with/without inserting titania mesoporous. Characterizations of scanning electron microscopy (SEM) and X-ray diffraction was carried out and the results shows that increasing the deposition time produces a smaller average grain size, diameter and denser layer of ZnO-nanorods. From current-voltage measurement, higher efficiency (η = 2.53%) was obtained for 120 min ZnO nanorods with short circuit current density (Jsc ) of 2.84 mA/cm2 and open circuit voltage (Voc) of 0.7 V. The combination of TiO2 and ZnO-NRs shows a better performance in solar cells characteristics due to increases of dye adsorption on photoanode and high photogenerated electron transport rate. This work emphasizes an optimum condition of ZnO-NRs in combination with TiO2 mesoporous as an alternative photoanode in QS-DSSC.

Comparison of the in vitro and in vivo toxic effects of three sizes of zinc oxide (ZnO) particles using flounder gill (FG) cells and zebrafish embryos

NASA Astrophysics Data System (ADS)

Han, Li; Zhai, Yanan; Liu, Yang; Hao, Linhua; Guo, Huarong

2017-02-01

Nano-sized zinc oxide (nZnO) particles are one kind of the most commonly used metal oxide nanoparticles (NPs). This study compared the cytotoxic and embryotoxic effects of three increasing sized ZnO particles (ϕ 30 nm, 80-150 nm and 2 μm) in the flounder gill (FG) cells and zebrafish embryos, and analyzed the contribution of size, agglomeration and released Zn2+ to the toxic effects. All the tested ZnO particles were found to be highly toxic to both FG cells and zebrafish embryos. They induced growth inhibition, LDH release, morphological changes and apoptosis in FG cells in a concentration-, size- and time-dependent manner. Moreover, the release of LDH from the exposed FG cells into the medium occurred before the observable morphological changes happened. The ultrasonication treatment and addition of serum favored the dispersion of ZnO particles and alleviated the agglomeration, thus significantly increased the corresponding cytotoxicity. The released Zn2+ ions from ZnO particles into the extracellular medium only partially contributed to the cytotoxicity. All the three sizes of ZnO particles tested induced developmental malformations, decrease of hatching rates and lethality in zebrafish embryos, but size- and concentration- dependent toxic effects were not so obvious as in FG cells possibly due to the easy aggregation of ZnO particles in freshwater. In conclusion, both FG cells and zebrafish embryos are sensitive bioassay systems for safety assessment of ZnO particles and the environmental release of ZnO particles should be closely monitored as far as the safety of aquatic organisms is concerned.

Coupling of Luminescent Solar Concentrators to Plasmonic Solar Cells

NASA Astrophysics Data System (ADS)

Wang, Shu-Yi

To make inexpensive solar cells is a continuous goal for solar photovoltaic (PV) energy industry. Thin film solar cells of various materials have been developed and continue to emerge in order to replace bulk silicon solar cells. A thin film solar cell not only uses less material but also requires a less expensive refinery process. In addition, other advantages coming along with small thickness are higher open circuit voltage and higher conversion efficiency. However, thin film solar cells, especially those made of silicon, have significant optical losses. In order to address this problem, this thesis investigates the spectral coupling of thin films PV to luminescent solar concentrators (LSC). LSC are passive devices, consisting of plastic sheets embedded with fluorescent dyes which absorb part of the incoming radiation spectrum and emit at specific wavelength. The emitted light is concentrated by total internal reflection to the edge of the sheet, where the PVs are placed. Since the light emitted from the LSC edge is usually in a narrow spectral range, it is possible to employ diverse strategies to enhance PV absorption at the peak of the emission wavelength. Employing plasmonic nanostructures has been shown to enhance absorption of thin films via forward scattering, diffraction and localized surface plasmon. These two strategies are theoretically investigated here for improving the absorption and elevating the output power of a thin film solar cell. First, the idea of spectral coupling of luminescent solar concentrators to plasmonic solar cells is introduced to assess its potential for increasing the power output. This study is carried out employing P3HT/PC60BM organic solar cells and LSC with Lumogen Red dyes. A simplified spectral coupling analysis is employed to predict the power density, considering the output spectrum of the LSC equivalent to the emission spectrum of the dye and neglecting any angular dependence. Plasmonic tuning is conducted to enhance

New mounting improves solar-cell efficiency

NASA Technical Reports Server (NTRS)

Shepard, N. F., Jr.

1980-01-01

Method boosts output by about 20 percent by trapping and redirecting solar radiation without increasing module depth. Mounted solar-cell array is covered with internally reflecting plate. Plate is attached to each cell by transparent adhesive, and space between cells is covered with layer of diffusely reflecting material. Solar energy falling on space between cells is diffused and reflected internally by plate until it is reflected onto solar cell.

Mechanism of Zn Particle Oxidation by H2O and CO2 in the Presence of ZnO

PubMed Central

2014-01-01

In this work we investigate the mechanism of Zn oxidation with CO2 and/or H2O to produce solar derived fuels (CO and/or H2) as part of the Zn/ZnO thermochemical redox cycle. It has been observed that the ZnO contamination of Zn produced by solar thermal reduction of ZnO (solar Zn) facilitates oxidation of the metallic Zn by CO2 and H2O, allowing for nearly complete conversion at temperatures as low as 350 °C. Reaching the same reaction extent starting with pure Zn requires considerably higher temperatures which imposes use of unconventional hard-to-operate reaction configurations utilizing Zn as vapor. The mechanism of this enhancement is investigated by studying the oxidation of solid Zn diluted with ZnO or Al2O3 at 350–400 °C utilizing thermogravimetry. It is found that ZnO acts as the site for the oxidation of Zn originating from the vapor phase, thereby serving as a sink for Zn vapor and maintaining the driving force for sustainable Zn sublimation. As this Zn sublimation competes with the growth of an impervious ZnO scale over the surface of the remaining solid Zn, the presence of the ZnO increases the reaction extent according to the magnitude of its surface area. This mechanism is supported by energy-dispersive X-ray (EDX) spectroscopy, revealing a substantial deposition of produced ZnO over the surface of the ZnO-seeded Al2O3 diluent. PMID:26692637

Mechanism of Zn Particle Oxidation by H2O and CO2 in the Presence of ZnO.

PubMed

Weibel, David; Jovanovic, Zoran R; Gálvez, Elena; Steinfeld, Aldo

2014-11-25

In this work we investigate the mechanism of Zn oxidation with CO 2 and/or H 2 O to produce solar derived fuels (CO and/or H 2 ) as part of the Zn/ZnO thermochemical redox cycle. It has been observed that the ZnO contamination of Zn produced by solar thermal reduction of ZnO (solar Zn) facilitates oxidation of the metallic Zn by CO 2 and H 2 O, allowing for nearly complete conversion at temperatures as low as 350 °C. Reaching the same reaction extent starting with pure Zn requires considerably higher temperatures which imposes use of unconventional hard-to-operate reaction configurations utilizing Zn as vapor. The mechanism of this enhancement is investigated by studying the oxidation of solid Zn diluted with ZnO or Al 2 O 3 at 350-400 °C utilizing thermogravimetry. It is found that ZnO acts as the site for the oxidation of Zn originating from the vapor phase, thereby serving as a sink for Zn vapor and maintaining the driving force for sustainable Zn sublimation. As this Zn sublimation competes with the growth of an impervious ZnO scale over the surface of the remaining solid Zn, the presence of the ZnO increases the reaction extent according to the magnitude of its surface area. This mechanism is supported by energy-dispersive X-ray (EDX) spectroscopy, revealing a substantial deposition of produced ZnO over the surface of the ZnO-seeded Al 2 O 3 diluent.

Interfacial engineering of electron transport layer using Caesium Iodide for efficient and stable organic solar cells

NASA Astrophysics Data System (ADS)

Upama, Mushfika Baishakhi; Elumalai, Naveen Kumar; Mahmud, Md Arafat; Wright, Matthew; Wang, Dian; Xu, Cheng; Haque, Faiazul; Chan, Kah Howe; Uddin, Ashraf

2017-09-01

Polymer solar cells (PSCs) have gained immense research interest in the recent years predominantly due to low-cost, solution process-ability, and facile device fabrication. However, achieving high stability without compromising the power conversion efficiency (PCE) serves to be an important trade-off for commercialization. In line with this, we demonstrate the significance of incorporating a CsI/ZnO bilayer as electron transport layer (ETL) in the bulk heterojunction PSCs employing low band gap polymer (PTB7) and fullerene (PC71BM) as the photo-active layer. The devices with CsI/ZnO interlayer exhibited substantial enhancement of 800% and 12% in PCE when compared to the devices with pristine CsI and pristine ZnO as ETL, respectively. Furthermore, the UV and UV-ozone induced degradation studies revealed that the devices incorporating CsI/ZnO bilayer possess excellent decomposition stability (∼23% higher) over the devices with pristine ZnO counterparts. The incorporation of CsI between ITO and ZnO was found to favorably modify the energy-level alignment at the interface, contributing to the charge collection efficiency as well as protecting the adjacent light absorbing polymer layers from degradation. The mechanism behind the improvement in PCE and stability is analyzed using the electrochemical impedance spectroscopy and dark I-V characteristics.

Band alignment and charge transfer predictions of ZnO/ZnX (X = S, Se or Te) interfaces applied to solar cells: a PBE+U theoretical study.

PubMed

Flores, Efracio Mamani; Gouvea, Rogério Almeida; Piotrowski, Maurício Jeomar; Moreira, Mário Lucio

2018-02-14

The engineering of semiconductor materials for the development of solar cells is of great importance today. Two topics are considered to be of critical importance for the efficiency of Grätzel-type solar cells, the efficiency of charge separation and the efficiency of charge carrier transfer. Thus, one research focus is the combination of semiconductor materials with the aim of reducing charge recombination, which occurs by spatial charge separation. From an experimental point of view, the combining of materials can be achieved by decorating a core with a shell of another material resulting in a core-shell system, which allows control of the desired photoelectronic properties. In this context, a computational simulation is mandatory for the atomistic understanding of possible semiconductor combinations and for the prediction of their properties. Considering the construction of ZnO/ZnX (X = S, Se or Te) interfaces, we seek to investigate the electronic influence of the shell (ZnX) on the core (ZnO) and, consequently, find out which of the interfaces would present the appropriate properties for (Grätzel-type) solar cell applications. To perform this study, we have employed density functional theory (DFT) calculations, considering the Perdew-Burke-Ernzerhof (PBE) functional. However, it is well-known that plain DFT fails to describe strong electronic correlated materials where, in general, an underestimation of the band gap is obtained. Thus, to obtain the correct description of the electronic properties, a Hubbard correction was employed, i.e. PBE+U calculations. The PBE+U methodology provided the correct electronic structure properties for bulk ZnO in good agreement with experimental values (99.4%). The ZnO/ZnX interfaces were built and were composed of six ZnO layers and two ZnX layers, which represents the decoration process. The core-shell band gap was 2.2 eV for ZnO/ZnS, ∼1.71 eV for ZnO/ZnSe and ∼0.95 eV for ZnO/ZnTe, which also exhibited a type-II band

Plasmonically sensitized metal-oxide electron extraction layers for organic solar cells

PubMed Central

Trost, S.; Becker, T.; Zilberberg, K.; Behrendt, A.; Polywka, A.; Heiderhoff, R.; Görrn, P.; Riedl, T.

2015-01-01

ZnO and TiOx are commonly used as electron extraction layers (EELs) in organic solar cells (OSCs). A general phenomenon of OSCs incorporating these metal-oxides is the requirement to illuminate the devices with UV light in order to improve device characteristics. This may cause severe problems if UV to VIS down-conversion is applied or if the UV spectral range (λ < 400 nm) is blocked to achieve an improved device lifetime. In this work, silver nanoparticles (AgNP) are used to plasmonically sensitize metal-oxide based EELs in the vicinity (1–20 nm) of the metal-oxide/organic interface. We evidence that plasmonically sensitized metal-oxide layers facilitate electron extraction and afford well-behaved highly efficient OSCs, even without the typical requirement of UV exposure. It is shown that in the plasmonically sensitized metal-oxides the illumination with visible light lowers the WF due to desorption of previously ionosorbed oxygen, in analogy to the process found in neat metal oxides upon UV exposure, only. As underlying mechanism the transfer of hot holes from the metal to the oxide upon illumination with hν < Eg is verified. The general applicability of this concept to most common metal-oxides (e.g. TiOx and ZnO) in combination with different photoactive organic materials is demonstrated. PMID:25592174

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility

NASA Astrophysics Data System (ADS)

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J.

2014-07-01

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

PubMed

Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J

2014-08-07

To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

Organic solar cells and physics education

NASA Astrophysics Data System (ADS)

Csernovszky, Zoltán; Horváth, Ákos

2018-07-01

This paper explains the operational principles of a home-made organic solar cell with the representation of an electron-cycle on an energy-level diagram. We present test data for a home-made organic solar cell which operates as a galvanic cell and current source in an electrical circuit. To determine the maximum power of the cell, the optimal current was estimated with a linear approximation. Using different light sources and dyes, the electrical properties of organic solar cells were compared. The solar cells were studied by looking at spectrophotometric data from different sensitizer dyes, generated by a do-it-yourself diffraction grating spectroscope. The sensitizer dyes of solar cells were tested by the diffraction grating spectroscope. The data were analysed on a light-intensity‑wavelength diagram to discover which photons were absorbed and to understand the colours of the fruits containing these dyes. In terms of theoretical applications, the paper underlines the analogous nature of organic solar cells, a conventional single p‑n junction solar cell and the light-dependent reactions of photosynthesis, using energy-level diagrams of electron-cycles. To conclude, a classification of photon‑electron interactions in molecular systems and crystal lattices is offered, to show the importance of organic solar cells.

AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

NASA Technical Reports Server (NTRS)

Dinetta, L. C.; Hannon, M. H.; Mcneely, J. B.; Barnett, A. M.

1991-01-01

The AstroPower self-supporting, transparent AlGaAs top solar cell can be stacked upon any well-developed bottom solar cell for improved system performance. This is an approach to improve the performance and scale of space photovoltaic power systems. Mechanically stacked tandem solar cell concentrator systems based on the AlGaAs top concentrator solar cell can provide near term efficiencies of 36 percent (AMO, 100x). Possible tandem stack efficiencies greater than 38 percent (100x, AMO) are feasible with a careful selection of materials. In a three solar cell stack, system efficiencies exceed 41 percent (100x, AMO). These device results demonstrate a practical solution for a state-of-the-art top solar cell for attachment to an existing, well-developed solar cell.

A low-temperature ZnO nanowire ethanol gas sensor prepared on plastic substrate

NASA Astrophysics Data System (ADS)

Lin, Chih-Hung; Chang, Shoou-Jinn; Hsueh, Ting-Jen

2016-09-01

In this work, a low-temperature ZnO nanowire ethanol gas sensor was prepared on plastic substrate. The operating temperature of the ZnO nanowire ethanol gas sensor was reduced to room temperature using ultraviolet illumination. The experimental results indicate a favorable sensor response at low temperature, with the best response at 60 °C. The results also reveal that the ZnO nanowire ethanol gas sensor can be easily integrated into portable products, whose waste heat can improve sensor response and achieve energy savings, while energy consumption can be further reduced by solar irradiation.

Complete transformation of ZnO and CuO nanoparticles in ...

EPA Pesticide Factsheets

Here, we present evidence on complete transformation of ZnO and CuO nanoparticles, which are among the most heavily studied metal oxide particles, during 24 h in vitro toxicological testing with human T-lymphocytes. Synchrotron radiation-based X-ray absorption near edge structure (XANES) spectroscopy results revealed that Zn speciation profiles of 30 nm and 80 nm ZnO nanoparticles, and ZnSO4- exposed cells were almost identical with the prevailing species being Zn-cysteine. This suggests that ZnO nanoparticles are rapidly transformed during a standard in vitro toxicological assay, and are sequestered intracellularly, analogously to soluble Zn. Complete transformation of ZnO in the test conditions was further supported by almost identical Zn spectra in medium to which ZnO nanoparticles or ZnSO4 was added. Likewise, Cu XANES spectra for CuO and CuSO4-exposed cells and cell culture media were similar. These results together with our observation on similar toxicological profiles of ZnO and soluble Zn, and CuO and soluble Cu, underline the importance of dissolution and subsequent transformation of ZnO and CuO nanoparticles during toxicological testing and provide evidence that the nano-specific effect of ZnO and CuO nanoparticulates is negligible in this system. We strongly suggest to account for this aspect when interpreting the toxicological results of ZnO and CuO nanoparticles. Although a number of studies have discussed the transformation of nanoparticles during

Surface coatings of ZnO nanoparticles mitigate differentially a host of transcriptional, protein and signalling responses in primary human olfactory cells

PubMed Central

2013-01-01

Background Inhaled nanoparticles have been reported in some instances to translocate from the nostril to the olfactory bulb in exposed rats. In close proximity to the olfactory bulb is the olfactory mucosa, within which resides a niche of multipotent cells. Cells isolated from this area may provide a relevant in vitro system to investigate potential effects of workplace exposure to inhaled zinc oxide nanoparticles. Methods Four types of commercially-available zinc oxide (ZnO) nanoparticles, two coated and two uncoated, were examined for their effects on primary human cells cultured from the olfactory mucosa. Human olfactory neurosphere-derived (hONS) cells from healthy adult donors were analyzed for modulation of cytokine levels, activation of intracellular signalling pathways, changes in gene-expression patterns across the whole genome, and compromised cellular function over a 24 h period following exposure to the nanoparticles suspended in cell culture medium. Results ZnO nanoparticle toxicity in hONS cells was mediated through a battery of mechanisms largely related to cell stress, inflammatory response and apoptosis, but not activation of mechanisms that repair damaged DNA. Surface coatings on the ZnO nanoparticles mitigated these cellular responses to varying degrees. Conclusions The results indicate that care should be taken in the workplace to minimize generation of, and exposure to, aerosols of uncoated ZnO nanoparticles, given the adverse responses reported here using multipotent cells derived from the olfactory mucosa. PMID:24144420

Fluorinated copper phthalocyanine nanowires for enhancing interfacial electron transport in organic solar cells.

PubMed

Yoon, Seok Min; Lou, Sylvia J; Loser, Stephen; Smith, Jeremy; Chen, Lin X; Facchetti, Antonio; Marks, Tobin J; Marks, Tobin

2012-12-12

Zinc oxide is a promising candidate as an interfacial layer (IFL) in inverted organic photovoltaic (OPV) cells due to the n-type semiconducting properties as well as chemical and environmental stability. Such ZnO layers collect electrons at the transparent electrode, typically indium tin oxide (ITO). However, the significant resistivity of ZnO IFLs and an energetic mismatch between the ZnO and the ITO layers hinder optimum charge collection. Here we report that inserting nanoscopic copper hexadecafluorophthalocyanine (F(16)CuPc) layers, as thin films or nanowires, between the ITO anode and the ZnO IFL increases OPV performance by enhancing interfacial electron transport. In inverted P3HT:PC(61)BM cells, insertion of F(16)CuPc nanowires increases the short circuit current density (J(sc)) versus cells with only ZnO layers, yielding an enhanced power conversion efficiency (PCE) of ∼3.6% vs ∼3.0% for a control without the nanowire layer. Similar effects are observed for inverted PTB7:PC(71)BM cells where the PCE is increased from 8.1% to 8.6%. X-ray scattering, optical, and electrical measurements indicate that the performance enhancement is ascribable to both favorable alignment of the nanowire π-π stacking axes parallel to the photocurrent flow and to the increased interfacial layer-active layer contact area. These findings identify a promising strategy to enhance inverted OPV performance by inserting anisotropic nanostructures with π-π stacking aligned in the photocurrent flow direction.

High saturation solar light beam induced current scanning of solar cells.

PubMed

Vorster, F J; van Dyk, E E

2007-01-01

The response of the electrical parameters of photovoltaic cells under concentrated solar irradiance has been the subject of many studies performed in recent times. The high saturation conditions typically found in solar cells that are subjected to highly concentrated solar radiation may cause electrically active cell features to behave differently than under monochromatic laser illumination, normally used in light beam induced current (LBIC) investigations. A high concentration solar LBIC (S-LBIC) measurement system has been developed to perform localized cell characterization. The responses of silicon solar cells that were measured qualitatively include externally biased induced cell current at specific cell voltages, I(V), open circuit voltage, V(oc), and the average rate of change of the cell bias with the induced current, DeltaV/DeltaI(V), close to the zero bias region. These images show the relative scale of the parameters of a cell up to the penetration depth of the solar beam and can be obtained with relative ease, qualifying important electrical response features of the solar cell. The S-LBIC maps were also compared with maps that were similarly obtained using a high intensity He-Ne laser beam probe. This article reports on the techniques employed and initial results obtained.

Alternative buffer layer development in Cu(In,Ga)Se2 thin film solar cells

NASA Astrophysics Data System (ADS)

Xin, Peipei

Cu(In,Ga)Se2-based thin film solar cells are considered to be one of the most promising photovoltaic technologies. Cu(In,Ga)Se2 (CIGS) solar devices have the potential advantage of low-cost, fast fabrication by using semiconductor layers of only a few micrometers thick and high efficiency photovoltaics have been reported at both the cell and the module levels. CdS via chemical bath deposition (CBD) has been the most widely used buffer option to form the critical junction in CIGS-based thin film photovoltaic devices. However, the disadvantages of CdS can’t be ignored - regulations on cadmium usage are getting stricter primarily due to its toxicity and environmental impacts, and the proper handling of the large amount of toxic chemical bath waste is a massive and expensive task. This dissertation is devoted to the development of Cd-free alternative buffer layers in CIGS-based thin film solar cells. Based on the considerations of buffer layer selection criteria and extensive literature review, Zn-compound buffer materials are chosen as the primary investigation candidates. Radio frequency magnetron sputtering is the preferred buffer deposition approach since it’s a clean and more controllable technique compared to CBD, and is readily scaled to large area manufacturing. First, a comprehensive study of the ZnSe1-xOx compound prepared by reactive sputtering was completed. As the oxygen content in the reactive sputtering gas increased, ZnSe1-xOx crystallinity and bandgap decreased. It’s observed that oxygen miscibility in ZnSe was low and a secondary phase formed when the O2 / (O2 + Ar) ratio in the sputtering gas exceeded 2%. Two approaches were proposed to optimize the band alignment between the CIGS and buffer layer. One method focused on the bandgap engineering of the absorber, the other focused on the band structure modification of the buffer. As a result, improved current of the solar cell was achieved although a carrier transport barrier at the junction

Photovoltaic Properties in Interpenetrating Heterojunction Organic Solar Cells Utilizing MoO3 and ZnO Charge Transport Buffer Layers

PubMed Central

Hori, Tetsuro; Moritou, Hiroki; Fukuoka, Naoki; Sakamoto, Junki; Fujii, Akihiko; Ozaki, Masanori

2010-01-01

Organic thin-film solar cells with a conducting polymer (CP)/fullerene (C60) interpenetrating heterojunction structure, fabricated by spin-coating a CP onto a C60 deposit thin film, have been investigated and demonstrated to have high efficiency. The photovoltaic properties of solar cells with a structure of indium-tin-oxide/C60/poly(3-hexylthiophene) (PAT6)/Au have been improved by the insertion of molybdenum trioxide (VI) (MoO3) and zinc oxide charge transport buffer layers. The enhanced photovoltaic properties have been discussed, taking into consideration the ground-state charge transfer between PAT6 and MoO3 by measurement of the differential absorption spectra and the suppressed contact resistance at the interface between the organic and buffer layers. PMID:28883360

Scale-Up of the Electrodeposition of ZnO/Eosin Y Hybrid Thin Films for the Fabrication of Flexible Dye-Sensitized Solar Cell Modules.

PubMed

Bittner, Florian; Oekermann, Torsten; Wark, Michael

2018-02-02

The low-temperature fabrication of flexible ZnO photo-anodes for dye-sensitized solar cells (DSSCs) by templated electrochemical deposition of films was performed in an enlarged and technical simplified deposition setup to demonstrate the feasibility of the scale-up of the deposition process. After extraction of eosin Y (EY) from the initially deposited ZnO/EY hybrid films, mesoporous ZnO films with an area of about 40 cm² were reproducibly obtained on fluorine doped tin oxide (FTO)-glass as well as flexible indium tin oxide (ITO)-polyethylenterephthalate (PET) substrates. With a film thickness of up to 9 µm and a high specific surface area of up to about 77 m²·cm -3 the ZnO films on the flexible substrates show suitable properties for DSSCs. Operative flexible DSSC modules proved the suitability of the ZnO films for use as DSSC photo-anodes. Under a low light intensity of about 0.007 sun these modules achieved decent performance parameters with conversion efficiencies of up to 2.58%. With rising light intensity the performance parameters deteriorated, leading to conversion efficiencies below 1% at light intensities above 0.5 sun. The poor performance of the modules under high light intensities can be attributed to their high series resistances.

Scale-Up of the Electrodeposition of ZnO/Eosin Y Hybrid Thin Films for the Fabrication of Flexible Dye-Sensitized Solar Cell Modules

PubMed Central

Oekermann, Torsten

2018-01-01

The low-temperature fabrication of flexible ZnO photo-anodes for dye-sensitized solar cells (DSSCs) by templated electrochemical deposition of films was performed in an enlarged and technical simplified deposition setup to demonstrate the feasibility of the scale-up of the deposition process. After extraction of eosin Y (EY) from the initially deposited ZnO/EY hybrid films, mesoporous ZnO films with an area of about 40 cm2 were reproducibly obtained on fluorine doped tin oxide (FTO)-glass as well as flexible indium tin oxide (ITO)–polyethylenterephthalate (PET) substrates. With a film thickness of up to 9 µm and a high specific surface area of up to about 77 m2·cm−3 the ZnO films on the flexible substrates show suitable properties for DSSCs. Operative flexible DSSC modules proved the suitability of the ZnO films for use as DSSC photo-anodes. Under a low light intensity of about 0.007 sun these modules achieved decent performance parameters with conversion efficiencies of up to 2.58%. With rising light intensity the performance parameters deteriorated, leading to conversion efficiencies below 1% at light intensities above 0.5 sun. The poor performance of the modules under high light intensities can be attributed to their high series resistances. PMID:29393910

Quantum Dots for Solar Cell Application

NASA Astrophysics Data System (ADS)

Poudyal, Uma

Solar energy has been anticipated as the most important and reliable source of renewable energy to address the ever-increasing energy demand. To harvest solar energy efficiently, diverse kinds of solar cells have been studied. Among these, quantum dot sensitized solar cells have been an interesting group of solar cells mainly due to tunable, size-dependent electronic and optical properties of quantum dots. Moreover, doping these quantum dots with transition metal elements such as Mn opens avenue for improved performance of solar cells as well as for spin based technologies. In this dissertation, Mn-doped CdSe QDs (Mn-CdSe) have been synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method. They are used in solar cells to study the effect of Mn doping in the performance of solar cells. Incident photon to current-conversion efficiency (IPCE) is used to record the effect of Mn-doping. Intensity modulated photovoltage and photocurrent spectroscopy (IMVS/PS) has been used to study the carrier dynamics in these solar cells. Additionally, the magnetic properties of Mn-CdSe QDs is studied and its possible origin is discussed. Moreover, CdS/CdSe QDs have been used to study the effect of liquid, gel and solid electrolyte in the performance and stability of the solar cells. Using IPCE spectra, the time decay measurements are presented and the possible reactions between the QD and the electrolytes are explained.

Recent advances of flexible hybrid perovskite solar cells

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Efficient indium-tin-oxide free inverted organic solar cells based on aluminum-doped zinc oxide cathode and low-temperature aqueous solution processed zinc oxide electron extraction layer

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

Chen, Dazheng; Zhang, Chunfu, E-mail: cfzhang@xidian.edu.cn; Wang, Zhizhe

Indium-tin-oxide (ITO) free inverted organic solar cells (IOSCs) based on aluminum-doped zinc oxide (AZO) cathode, low-temperature aqueous solution processed zinc oxide (ZnO) electron extraction layer, and poly(3-hexylthiophene-2, 5-diyl):[6, 6]-phenyl C{sub 61} butyric acid methyl ester blend were realized in this work. The resulted IOSC with ZnO annealed at 150 °C shows the superior power conversion efficiency (PCE) of 3.01%, if decreasing the ZnO annealing temperature to 100 °C, the obtained IOSC also shows a PCE of 2.76%, and no light soaking issue is observed. It is found that this ZnO film not only acts as an effective buffer layer but also slightlymore » improves the optical transmittance of AZO substrates. Further, despite the relatively inferior air-stability, these un-encapsulated AZO/ZnO IOSCs show comparable PCEs to the referenced ITO/ZnO IOSCs, which demonstrates that the AZO cathode is a potential alternative to ITO in IOSCs. Meanwhile, this simple ZnO process is compatible with large area deposition and plastic substrates, and is promising to be widely used in IOSCs and other relative fields.« less

Hybrid Perovskites: Prospects for Concentrator Solar Cells.

PubMed

Lin, Qianqian; Wang, Zhiping; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

2018-04-01

Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley-Queisser limit stipulated for a single-junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge-carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy-conversion efficiencies under solar concentration, where they are able to exceed the Shockley-Queisser limit and exhibit strongly elevated open-circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications.

Flexible inverted polymer solar cells fabricated in air at low temperatures

NASA Astrophysics Data System (ADS)

Kuwabara, Takayuki; Wang, Xiaofan; Kusumi, Takuji; Yamaguchi, Takahiro; Taima, Tetsuya; Takahashi, Kohshin

2016-08-01

A series of modified indium tin oxide (ITO) materials, including sol-gel zinc-oxide-coated ITO (ITO/ZnO), ZnO nanoparticle-coated ITO (ITO/ZnO-NP), 1,4-bis(3-aminopropyl)piperazine (BAP)-modified ITO, and polyethylenimine ethoxylated (PEIE)-modified ITO, were used for electron-collection electrodes in inverted polymer solar cells (PSCs). The modified ITO electrodes were prepared in air at temperatures below 100 °C, using various ITO films on flexible poly(ethylene terephthalate) substrates (PET-ITO) with sheet resistances ranging from 12 to 60 Ω sq-1. The PET-ITO (12 Ω sq-1)/ZnO-NP PSC exhibited an improved power conversion efficiency (PCE) (2.93%), and this PCE was ˜90% of that observed for a cell using glass-ITO/ZnO-NP (sheet resistance = 10 Ω sq-1 PCE = 3.28%). Additionally, we fabricated a flexible inverted ZnO-NP PSC using an indene-C60 bisadduct (ICBA) as the acceptor material in place of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and obtained a PCE of 4.18%.

Variation of solar cell sensitivity and solar radiation on tilted surfaces

NASA Technical Reports Server (NTRS)

Klucher, T. M.

1978-01-01

The validity is studied that one of various insolation models used to compute solar radiation incident on tilted surfaces from global data measured on horizontal surfaces. The variation of solar cell sensitivity to solar radiation is determined over a wide range of atmospheric condition. A new model was formulated that reduced the deviations between measured and predicted insolation to less than 3 percent. Evaluation of solar cell sensitivity data indicates small change (2-3 percent) in sensitivity from winter to summer for tilted cells. The feasibility of using such global data as a means for calibrating terrestrial solar cells is discussed.

Bactericidal impact of Ag, ZnO and mixed AgZnO colloidal nanoparticles on H37Rv Mycobacterium tuberculosis phagocytized by THP-1 cell lines.

PubMed

Jafari, Alireza; Mosavari, Nader; Movahedzadeh, Farahnaz; Nodooshan, Saeedeh Jafari; Safarkar, Roya; Moro, Rossella; Kamalzadeh, Morteza; Majidpour, Ali; Boustanshenas, Mina; Mosavi, Tahereh

2017-09-01

The purpose of this research project was to infection of human macrophages (THP-1) cell lines by H 37 Rv strain of Mycobacterium tuberculosis (H 37 RvMTB) and find out the ratio/dilution of mixture silver (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) whose ability to eliminate phagocytized bacteria compared to rifampicin. The colloidal Ag NPs and ZnO NPs were synthesized and their characteristics were evaluated. The THP-1 cell lines were infected with different concentration of H 37 RvMTB. Next, the infected cells were treated with different ratios/dilutions of Ag NPs, ZnO NPs and rifampicin. The THP-1 were lysed and were cultured in Lowenstein-Jensen agar medium, for eight weeks. The TEM and AFM images of NPs and H 37 RvMTB were supplied. It is observed that Ag NPs, 2 Ag :8 ZnO and 8 Ag :2 ZnO did not have any anti-tubercular effects on phagocytized H 37 RvMTB. Conversely, ZnO NPs somehow eliminated 18.7 × 10 4  CFU ml -1 of H 37 RvMTB in concentration of ∼ 0.468 ppm. To compare with 40 ppm of rifampicin, ∼ 0.663 ppm of 5 Ag :5 ZnO had the ability to kill of H 37 RvMTB, too. Based on previous research, ZnO NPs had strong anti-tubercular impact against H 37 RvMTB to in-vitro condition, but it was toxic in concentration of ∼ 0.468 ppm to both of THP-1 and normal lung (MRC-5) cell lines. It also seems that 5 Ag :5 ZnO is justified because in concentration of ∼ 0.663 ppm of 5 Ag :5 ZnO , phagocytized H 37 RvMTB into the THP-1 had died without any toxicity effects against THP-1 and also MRC-5 cell lines. It is obvious that the mixture of colloidal silver and zinc oxide NPs with ratio of 5 Ag :5 ZnO would be trustworthy options as anti-tubercular nano-drugs in future researches. Copyright © 2017. Published by Elsevier Ltd.

Silicon solar cells as a high-solar-intensity radiometer

NASA Technical Reports Server (NTRS)

Spisz, E. W.; Robson, R. R.

1971-01-01

The characteristics of a conventional, 1- by 2-cm, N/P, gridded silicon solar cell when used as a radiometer have been determined for solar intensity levels to 2800 mW/sq cm (20 solar constants). The short-circuit current was proportional to the radiant intensity for levels only to 700 mW/sq cm (5 solar constants). For intensity levels greater than 700 mW/sq cm, it was necessary to operate the cell in a photoconductive mode in order to obtain a linear relation between the measured current and the radiant intensity. When the solar cell was biased with a reverse voltage of -1 V, the measured current and radiant intensity were linearly related over the complete intensity range from 100 to 2800 mW/sq cm.

Enhancing Solar Cell Efficiencies through 1-D Nanostructures

PubMed Central

2009-01-01

The current global energy problem can be attributed to insufficient fossil fuel supplies and excessive greenhouse gas emissions resulting from increasing fossil fuel consumption. The huge demand for clean energy potentially can be met by solar-to-electricity conversions. The large-scale use of solar energy is not occurring due to the high cost and inadequate efficiencies of existing solar cells. Nanostructured materials have offered new opportunities to design more efficient solar cells, particularly one-dimensional (1-D) nanomaterials for enhancing solar cell efficiencies. These 1-D nanostructures, including nanotubes, nanowires, and nanorods, offer significant opportunities to improve efficiencies of solar cells by facilitating photon absorption, electron transport, and electron collection; however, tremendous challenges must be conquered before the large-scale commercialization of such cells. This review specifically focuses on the use of 1-D nanostructures for enhancing solar cell efficiencies. Other nanostructured solar cells or solar cells based on bulk materials are not covered in this review. Major topics addressed include dye-sensitized solar cells, quantum-dot-sensitized solar cells, and p-n junction solar cells.