共查询到20条相似文献,搜索用时 0 毫秒
1.
Toshiyuki Yamaguchi Yasutaka AsaiNaoyuki Oku Shigetoshi NiiyamaToshito Imanishi Shigeyuki Nakamura 《Solar Energy Materials & Solar Cells》2011,95(1):274-276
Cu(In,Ga)(S,Se)2 thin films with high Ga/III ratio (around 0.8) were prepared by sequential evaporation from CuGaSe2, CuInSe2, In2Se3 and Ga2Se3 compounds and then annealing in H2S gas atmosphere. The annealing temperature was varied from 400 to 500 °C. These samples were characterized by means of XRF, EPMA, XRD and SEM. The S/(S+Se) mole ratio in the thin films increased with increase in the annealing temperature, keeping the Cu, In and Ga contents nearly constant. The open circuit voltage increased and the short circuit current density decreased with increase in the annealing temperature. The best solar cell using Cu(In,Ga)(S,Se)2 thin film with Ga/(In+Ga)=0.79 and S/(S+Se)=0.11 annealed at 400 °C demonstrated Voc=535 mV, Isc=13.3 mA/cm2, FF=0.61 and efficiency=4.34% without AR-coating. 相似文献
2.
D. Abou-Ras J. DietrichJ. Kavalakkatt M. NichterwitzS.S. Schmidt C.T. KochR. Caballero J. KlaerT. Rissom 《Solar Energy Materials & Solar Cells》2011,95(6):1452-1462
The present work gives an overview of how electron microscopy and its related techniques are used to analyze individual layers and their interfaces in Cu(In,Ga)(S,Se)2 thin-film solar cells. Imaging of samples can be performed at scales of down to the (sub)angstroms range. At similar spatial resolutions, information on composition can be gathered by means of energy-dispersive X-ray spectroscopy (EDX) and on spatial distributions of electrostatic Coulomb potentials in the specimen by applying electron holography. Microstructural and compositional properties as well as charge-carrier collection and radiative recombination behavior of the individual layers are accessible by use of electron backscatter diffraction, EDX, electron-beam-induced current (EBIC) and cathodoluminescence measurements, available in scanning electron microscopy. The present contribution gives an overview of the various scanning and transmission electron microscopy techniques applied on Cu(In,Ga)(S,Se)2 thin-film solar cells, examples from case studies, and also demonstrates how these techniques may be combined in order to improve the analysis. Particularly, EBIC results show a reduced charge-carrier collection at Cu(In,Ga)Se2 grain boundaries, while no indication was found for a charge accumulation at the grain boundaries by electron holography. 相似文献
3.
Tokio Nakada Hiroki Ohbo Masakazu Fukuda Akio Kunioka 《Solar Energy Materials & Solar Cells》1997,49(1-4)
The effects of sodium on off-stoichiometric Cu(In,Ga)Se2 (CIGS)-based thin films and solar cells were investigated. The CIGS-based films were deposited with intentionally incorporated Na2Se on Mo-coated SiOx/soda-lime glass substrates by a multi-step process. By sodium control technique high-efficiency ZnO : Al/CdS/CIGS solar cells with efficiencies of 10–13.5% range were obtained over an extremely wide Cu/(In + Ga) ratio range of 0.51–0.96, which has great merit for the large-area manufacturing process. The improved efficiency in the off-stoichiometric regions is mainly attributed to the increased acceptor concentration and the formation of the Cu(In,Ga)3Se5 phase films with p-type conductvity. A new type of solar cell with p-type Cu(In,Ga)3Se5 phase absorber materials is also suggested. 相似文献
4.
Surface sulfurization of Cu(In,Ga)Se2 (CIGS) thin films was carried out using two alternative techniques that do not utilize toxic H2S gas; a sequential evaporation of In2S3 after CIGS deposition and the annealing of CIGS thin films in sulfur vapor. A Cu(In,Ga) (S,Se)2 thin layer was grown on the surface of the CIGS thin film after sulfurization using In2S3, whereas this layer was not observed for CIGS thin films after sulfurization using sulfur vapor, although a trace quantity of S was confirmed by AES analysis. In spite of the difference in the surface modification techniques, the cell performance and process yield of the ZnO:Al/CdS/CIGS/Mo/glass thin-film solar cells were remarkably improved by using both surface sulfurization techniques. 相似文献
5.
Shintaro OsadaYasuhiro Abe Takaya AnegawaTakashi Minemoto Hideyuki Takakura 《Solar Energy Materials & Solar Cells》2011,95(1):223-226
Cu(In,Ga)Se2 (CIGS) solar cells with a superstrate structure were fabricated using a lift-off process. To widen the variety of substrate choices for CIGS solar cells, a lift-off process was developed without an intentional sacrificial layer between the CIGS and Mo back-contact layers. The CIGS solar cells fabricated on Mo/soda-lime glass (SLG) were transferred to an alternative SLG substrate. The conversion efficiency of the CIGS solar cells with the superstrate structure was 5.1%, which was almost half that of the CIGS solar cells with a substrate structure prior to the lift-off process. The low conversion efficiency was caused by the high series resistance and low shunt resistance, which would be due to the junction resistance between the CIGS/back contact and cracks introduced during the lift-off process, respectively. 相似文献
6.
Miguel A. Contreras H. Wiesner J. Tuttle K. Ramanathan R. Noufi 《Solar Energy Materials & Solar Cells》1997,49(1-4)
Considering the chalcopyrite/defect-chalcopyrite junction model for Cu(In1−xGax)Se2-based devices and our previously reported findings for the Cu(In1−xGax)3Se5 defect chalcopyrites, we have postulated that uniform high-Ga-content photovoltaic structures (with x > 0.35) do not yield acceptable device performance due to the electrical and structural differences between both types of materials (chalcopyrite and defect-chalcopyrite).In this contribution, the structural properties of the surface region of Ga containing absorber materials have been studied by grazing incidence X-ray diffraction. We find that there are significant differences between surface and bulk. A structural model is proposed for the growth of the chalcopyrite/defect-chalcopyrite junction relative to its Ga content. And we demonstrate that closely lattice matched high-Ga-content structures (x > 0.35) can produce solar cells withv acceptable performances. The high-voltage and low-current electrical outputs from high Ga structures are very desirable in module fabrication because overall resistive losses can be substantially reduced. 相似文献
7.
L. Kronik B. Mishori E. Fefer Y. Shapira W. Riedl 《Solar Energy Materials & Solar Cells》1998,51(1):1126
Surface photovoltage spectroscopy (SPS) has been used for quality control of ZnO/CdS/ Cu(In,Ga)Se2 (CIGS) thin-film solar cells. The results show that SPS makes it possible to detect “hard failures” following CIGS deposition, and both “hard” and “soft” failures following CdS deposition and following ZnO deposition. In addition, a semi-quantitative screening of CdS/CIGS and ZnO/CdS/CIGS samples is possible. Hence, SPS is suggested as a useful tool for in-line monitoring of CIGS-based solar cell production lines. Moreover, SPS is shown to yield important new information regarding CIGS-based solar cells: (a) A deep gap state is found in samples of superior performance. (b) As opposed to the CdS/CIGS structure, a marked decrease in the open-circuit voltage upon Na contamination in ZnO/CIGS structures is found. 相似文献
8.
Shiro Nishiwaki Takuya Satoh Yasuhiro Hashimoto Shin-Ichi Shimakawa Shigeo Hayashi Takayuki Negami Takahiro Wada 《Solar Energy Materials & Solar Cells》2003,77(4):1213
Cu(In,Ga)Se2 (CIGS) surface was modified with Zn doping using vacuum evaporation. Substrate temperatures and exposure times during the Zn evaporation were changed to control a distribution of Zn in the CIGS films. Diffusion of Zn in the CIGS films was observed at the substrate temperature of over 200°C. The diffusion depth of Zn increases with increasing the exposure time at the substrate temperature of 300°C. Solar cells were fabricated using the Zn doped CIGS films. A distribution of the efficiencies decreases with increasing the exposure time of Zn vapor. The doping of Zn at the film surface improved reproducibility of a high fill factor and efficiency. A solar cell fabricated using the CIGS film modified with Zn doping showed an efficiency of 14.8%. 相似文献
9.
This work investigates NaF, on Mo coated sodium barrier glass, as a sodium precursor for the growth of Cu(In, Ga)Se2 for thin film solar cells. These precursor layers are investigated by X-ray photoelectron spectroscopy (XPS) before and after annealing, and after exposure to selenium. XPS is also performed on the Cu(In, Ga)Se2 layer, deposited with NaF. The influence of the NaF on the absorber growth is studied by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The electrical properties are investigated by cell fabrication and characterization. Cell results are comparable when NaF or out-diffusion of sodium from the soda lime glass are used. 相似文献
10.
Udai P. Singh William N. Shafarman Robert W. Birkmire 《Solar Energy Materials & Solar Cells》2006,90(5):623-630
Sulfurization of copper indium gallium diselenide (CIGS) thin films solar cell absorber has been used to enhance the open-circuit voltage of the device by increasing the band gap of the absorber near the interface. Sulfurization of a homogeneous co-evaporated Cu(InGa)Se2 thin film was studied in hydrogen sulfide and in a mixture of hydrogen sulfide and hydrogen selenide gases with the inclusion of oxygen. The structural and compositional properties of the absorber layer were investigated by XRD, EDS and AES. Sulfurization in hydrogen sulfide gas forms a fully converted sulfide layer at the top of the absorber layer, which in turn forms a barrier for the current collection. Sulfurization in a mixture of hydrogen sulfide and hydrogen selenide gases forms a wide band gap Cu(InGa)(SeS)2 layer at the surface, but at the same time there is Ga diffusion away from the surface with the inclusion of sulfur at the surface. 相似文献
11.
The reversible persistent changes of the fill factor (FF) induced by the illumination and voltage bias along with changes in the electronic properties of the ZnO/CdS/Cu(In,Ga)Se2 photovoltaic devices have been studied. Admittance spectroscopy and capacitance–voltage characterization reveal a correlation between the FF and the space charge distribution within the absorber. Our experiments provide evidence that a major source of FF loss in efficient devices is caused by excess negative charge close to the interface. We explain the persistent changes in the net acceptor concentration in the interface region by the relaxation effects due to compensating donors—the same mechanism, which leads to metastable changes of the doping level in the bulk of the absorber. 相似文献
12.
Tokio Nakada Yutaka Hirabayashi Takehito Tokado Daiske Ohmori Takahiro Mise 《Solar Energy》2004,77(6):739-747
Cu(In1−xGax)Se2 (CIGS)-based thin film solar cells fabricated using transparent conducting oxide (TCO) front and back contacts were investigated. The cell performance of substrate-type CIGS devices using TCO back contacts was almost the same as that of conventional CIGS solar cells with metallic Mo back contacts when the CIGS deposition temperatures were below 500 °C for SnO2:F and 520 °C for ITO. CIGS thin film solar cells fabricated with ITO back contacts had an efficiency of 15.2% without anti-reflection coatings. However, the cell performance deteriorated at deposition temperatures above 520 °C. This is attributed to the increased resistivity of the TCO’s due to the removal of fluorine from SnO2 or undesirable formation of a Ga2O3 thin layer at the CIGS/ITO interface. The formation of Ga2O3 was eliminated by inserting an intermediate layer such as Mo between ITO and CIGS. Furthermore, bifacial CIGS thin film solar cells were demonstrated as being one of the applications of semi-transparent CIGS devices. The cell performance of bifacial devices was improved by controlling the thickness of the CIGS absorber layer. Superstrate-type CIGS thin film solar cells with an efficiency of 12.8% were fabricated using a ZnO:Al front contact. Key techniques include the use of a graded band gap Cu(In,Ga)3Se5 phase absorber layer and a ZnO buffer layer along with the inclusion of Na2S during CIGS deposition. 相似文献
13.
Takayuki Negami Yasuhiro Hashimoto Shiro Nishiwaki 《Solar Energy Materials & Solar Cells》2001,67(1-4)
An efficiency of over 18% have been achieved in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Solar cell parameters were estimated for the cells with efficiencies of more and less than 18%. A diode quality factor n and forward current (saturated current) J0 of the cell with over 18% efficiency are lower than those with below 18% efficiency. This would be attributed to sufficient coverage of the CdS film with excellent uniformity as a buffer and/or window layer over the CIGS film because the process of CdS film formation was improved. 相似文献
14.
To reduce cracks caused by the lift-off process in a Cu(In,Ga)Se2 (CIGS) layer, we focused on increasing the transferred layer thickness. We investigated the relationship between crack formation and the transferred layer thickness which is controlled by a Mo back electrode thickness. We found that the cracks were reduced by increasing the back electrode thickness. We suggest that the dominant factor of the crack reduction is attributed to the increase of the film hardness by increasing the Mo back electrode thickness. Next, we applied this crack reduction method to the solar cell fabrication. From the comparison of the 0.2-μm-thick Au single and 0.2-μm-thick Au/1.6-μm-thick Mo stacked back electrode lift-off CIGS solar cells, we investigated advantages of our crack reduction method. The crack formation was reduced only for the stacked back electrode lift-off solar cell. From the spatial distribution evaluation of an external quantum efficiency (EQE), we found that the crack reduction leads to not only the increase of an average EQE but also the decrease of EQE dispersion. In the solar cell parameters, the stacked back electrode lift-off solar cell without cracks showed the short-circuit current density and fill factor higher than those of the single back electrode lift-off solar cell with cracks. As a result, the conversion efficiency improvement as high as approximately 1% (an absolute value) was obtained. Moreover, the stacked back electrode lift-off solar cell showed the diode parameters (the diode ideality factor, the saturation current density, and series resistance) better than those of the single back electrode lift-off solar cell in the dark current density-voltage characteristics. We concluded that this high fill factor was attributed to the better diode performance. We therefore found that the stacked back electrode structure was very effective for improving the solar cell performance using the lift-off process. 相似文献
15.
S. Nishiwaki T. Satoh S. Hayashi Y. Hashimoto S. Shimakawa T. Negami T. Wada 《Solar Energy Materials & Solar Cells》2001,67(1-4)
Improved preparation process of a device quality Cu(In,Ga)Se2 (CIGS) thin film was proposed for production of CIGS solar cells. In–Ga–Se layer were deposited on Mo-coated soda-lime glass, and then the layer was exposed to Cu and Se fluxes to form Cu–Se/In–Ga–Se precursor film at substrate temperature of over 200°C. The precursor film was annealed in Se flux at substrate temperature of over 500°C to obtain high-quality CIGS film. The solar cell with a MgF2/ITO/ZnO/CdS/CIGS/Mo/glass structure showed an efficiency of 17.5% (Voc=0.634 V, Jsc=36.4 mA/cm2, FF=0.756). 相似文献
16.
The efficiencies of Cu(In,Ga)Se2/CdS/ZnO solar cell devices in which the absorbers are produced by classical two-step processes are significantly lower that those in which co-evaporated absorbers are used. A significant problem related to two-step growth processes is the reported segregation of Ga towards the Mo back contact, resulting in separate CuInSe2 and CuGaSe2 phases. Furthermore, it is often reported that material losses (especially In and Ga) occur during high-temperature selenization of metallic precursors. In this study, X-ray fluorescence (XRF) analysis was used to study the diffusion behaviour of the chalcopyrite elements in single-stage and two-stage processed Cu(In,Ga)Se2 thin films. This relatively simple characterization technique proved to be very reliable in determining the degree of selenium incorporation, possible material losses and the in-depth compositional uniformity of samples at different stages of processing. This information is especially important in the case of two-stage growth processes, involving high-temperature selenization steps of metallic precursors. Device quality Cu(In,Ga)Se2 thin films were prepared by a relatively simple and reproducible two-step growth process in which all the metals were evaporated from one single crucible in a selenium-containing environment. The precursors were finally treated in an H2Se/Ar atmosphere to produce fully reacted films. XRF measurement indicated no loss of In or Ga during this final selenization step, but a significant degree of element diffusion which depended on the reaction temperature. It was also possible to produce Cu(In,Ga)Se2 thin films with an appreciable amount of Ga in the near-surface region without separated CuInSe2 and CuGaSe2 phases. 相似文献
17.
J. Bekker 《Solar Energy Materials & Solar Cells》2009,93(5):539-543
Thin films based on CuInSe2 have become very successful as absorber layers for solar cells. It is only in the recent past that gallium (Ga) and sulfur (S) were incorporated into CuInSe2 in order to increase the energy band gap of the film to an optimum value with the ultimate aim of producing more efficient devices. This paper focuses on the incorporation of S into partly selenized CuInSe2 films in order to produce CuIn(Se,S)2 films with varying S/Se+S ratios, resulting in different band-gap energies. This was achieved by varying the conditions when selenizing Cu/In alloys in H2Se/Ar, and then exposing these various partly selenized films to H2S/Ar under identical conditions. 相似文献
18.
Thin films of Cu(In,Ga)Se2 were prepared by thermal crystallization on the sputtered Mo/substrate and characterized. MoSe2 layer was formed at the interface between Cu(In,Ga)Se2 and Mo layers after the thermal crystallization. The graded Ga concentration in crystallized Cu(In,Ga)Se2 thin films was confirmed. Cu(In,Ga)Se2 thin films prepared on the Mo/soda-lime glass had large and columnar grains rather than those on the Mo/quartz substrate. 相似文献
19.
M. E. Calixto R. N. Bhattacharya P. J. Sebastian A. M. Fernandez S. A. Gamboa R. N. Noufi 《Solar Energy Materials & Solar Cells》1998,55(1-2)
CuIn1−xGaxSe2 (CIGS) thin films were formed from an electrodeposited CuInSe2 (CIS) precursor by thermal processing in vacuum in which the film stoichiometry was adjusted by adding In, Ga and Se. The structure, composition, morphology and opto-electronic properties of the as-deposited and selenized CIS precursors were characterized by various techniques. A 9.8% CIGS based thin film solar cell was developed using the electrodeposited and processed film. The cell structure consisted of Mo/CIGS/CdS/ZnO/MgF2. The cell parameters such as Jsc, Voc, FF and η were determined from I–V characterization of the cell. 相似文献
20.
Illumination intensities in indoor environments are usually given in terms of lux, a unit of measurement which only takes into account the spectral distribution of the light source in the sensitivity range of the human eye (380–780 nm). At a given level of illuminance, however, the performance of a solar cell will strongly depend on the spectral distribution of the incoming light and on its spectral response. This work considers the spectral distribution of some typical light sources encountered in indoor environments (natural daylight/AM 1.5, fluorescent tube, halogen lamp with and without cold reflector, and the common incandescent lamp) and calculates the actual amount of light available to a generic solar cell. We then calculate the performance for different indoor illumination levels and spectra of a Cu(In,Ga)Se2 solar cell especially optimised for low-irradiance conditions. Considering as a reference the performance of the cell under a AM 1.5 spectrum at a given level of illuminance, we can expect the performance of the cell to be reduced by a factor 3 and 2, respectively, when using a fluorescent tube and a halogen lamp with cold reflector as the light source, and to be increased by a factor 2 to 3 if the cell is operated under a halogen/incandescent lamp. 相似文献