CuInSe2 Thin Film Solar Cells Research Articles

Numerical Study of CiS Solar Cell with CuInSe2‐Undoped Layer

Herein, a CuInSe2 thin film solar cell with an intrinsic thin layer (HIT) is modeled and simulated using SCAPS. The HIT is deposited between a thin CdS window layer of reduced thickness of 20 nm to minimize cadmium toxicity and an absorbing layer of variable thickness. The aim is to study the influence of the thickness of absorber and HIT layer, level doping and defect densities of CuInSe2 layer, and high work function (between 5 and 5.6 eV) effect on performance parameters of the solar cell. In general, a significant increase in efficiency is observed. The HIT and the absorber thicknesses are optimized to be 0.3 and 0.5 μm, respectively. A conversion efficiency of 24.2%, a V oc of 0.78 V, J sc of 45.4 mA cm−2, and an FF of 68.3% are obtained for the proposed AZO/ZnO/CdS/CuInSe2/Mo/glass. These simulation results encourage using intrinsic thin layers in CIS solar cell structure.

Radio frequency (RF) sputtered ZrO2-ZnO-TiO2 coating: An example of multifunctional benefits for thin film solar cells on the flexible substrate

A new class of engineered trimetallic oxide nanocomposite coating based on ZrO2, ZnO, and TiO2 (ZZTO) was deposited by radio frequency (RF) sputtering. The prepared ZZTO sputtered coating was characterized by different techniques and finally applied to the CISe thin film solar cells as the antireflective (AR) coating to achieve multifunctional benefits viz. self-cleaning, anticorrosion, and photocatalysis (SAP). ZZTO coating with good optical characteristics and high transmittance was obtained with excellent hydrophobic and corrosion-resistant properties. The fabricated CuInSe2 (CISe) solar cells on the flexible substrates were tested with and without AR coating to assure multifunctionality and improvement in photo conversion efficiency. The suppression of optical loss led to improved light absorption across the wide range of spectrum and boosted the short circuit current density (JSC) from 31.04 to 33.05 mA/cm2, obtaining improved efficiency from 9.11 to 10.24%. It can be ensured from the present research work that engineered ZZTO AR coating can deliver superhydrophobic surface and transparency as high as 91% under mean visible light with excellent photocatalytic and corrosion-resistant properties. Thus, engineered multifunctional ZZTO coating can pave the way to revolutionize the AR material to the extent of an ideal candidate in photovoltaic devices.

Impact of selenization temperature on the performance of sequentially evaporated CuInSe2 thin film solar cells

In the present work, modified stacking of sequentially evaporated metallic precursors and two-step selenization was performed to examine the photovoltaic quality of the copper indium diselenide (CISe) thin films. The photovoltaic device performance as a function of selenization temperatures was investigated. Structural analysis showed that the chalcopyrite CISe thin films' crystallinity steadily improved as selenization temperatures increased from 450 to 550 °C. The grain size of the CISe thin films increased up to 1.0 μm with increasing selenization temperatures. The optical band gap energy fluctuated between 0.99 and 1.02 eV depending upon selenization temperatures. The uniform distribution of elements in the films' depth profile was investigated from secondary ion mass spectroscopy (SIMS). Open circuit voltage (Voc) increased from 258 to 543 mV upon increasing the selenization temperature due to enhanced crystal quality and concentration of sodium diffused through the soda-lime glass (SLG) substrate. A fabricated CISe solar cell attained 9.37% of best conversion efficiency at 550 °C of selenization temperature. These results demonstrate the selenization of evaporated metallic precursors at room temperature to synthesize good quality CISe based absorbers, which substantiate the viability of the proposed approach to obtain solar cells with high efficiency.

Over 15% efficient wide-band-gap Cu(In,Ga)S2 solar cell: Suppressing bulk and interface recombination through composition engineering

Over 15% efficient wide-band-gap Cu(In,Ga)S2 solar cell: Suppressing bulk and interface recombination through composition engineering

Stacking fault reduction during annealing in Cu-poor CuInSe2 thin film solar cell absorbers analyzed by in situ XRD and grain growth modeling

Buried wurtzite structures composed by stacking faults of the {111} planes in zinc-blende and {112} planes in chalcopyrite structures can result in barriers for charge carrier transport. A precise understanding of stacking fault annihilation mechanisms is therefore crucial for the development of effective deposition processes. During co-evaporation of Cu(In,Ga)Se2—a photovoltaic absorber material showing record efficiencies of up to 22.9% for thin film solar cells—a reduction of stacking faults occurs at the transition from a Cu-poor to a Cu-rich film composition, parallel to grain growth, which is suggesting that the two phenomena are coupled. Here, we show by in situ synchrotron X-ray diffraction during annealing of Cu-poor CuInSe2 thin films that stacking faults can be strongly reduced through annealing, without passing through a Cu-rich film composition. We simulate the evolution of the X-ray diffraction stacking fault signal with a simple numerical model of grain growth driven by stacking fault energy and grain boundary curvature. The results support the hypothesis that the stacking fault reduction can be explained by grain growth. The model is used to make predictions on annealing times and temperatures required for stacking fault reduction and could be adapted for polycrystalline thin films with similar morphology.

Studies on the graded band-gap copper indium di-selenide thin film solar cells prepared by electrochemical route

A graded band-gap CuInSe2 (CIS) thin film solar cell (TFSC) having glass/FTO/CdS/CIS multilayer/Au structure has been fabricated. A simple and low-cost electrodeposition technique is used to deposit the multilayers of CIS onto fluorine doped tin oxide (FTO) coated glass substrate. A conventional three-electrode geometry consisting, FTO, graphite and Ag/AgCl as a working, counter and reference electrodes, respectively was used for electrodeposition. Structural characterization was carried out using X-ray diffraction (XRD) and Raman spectroscopy, which revealed the chalcopyrite tetragonal CIS structure with a quite Cu-rich surface which reduces upon selenization. The morphology of the as grown and selenized CIS multilayer thin films was studied by using atomic force microscopy (AFM) which shows the compact and uniform layer formation. The depth profile distribution of individual elements in both as-grown and selenized CIS multilayer thin films has been determined using secondary ion mass spectroscopy (SIMS). SIMS results revealed that the proposed graded band gap structure is retained even after selenization. The presence of Cu+, In3+ and Se2− oxidation states were confirmed using X-ray photoelectron spectroscopy (XPS). A single layer and multilayer CIS solar cell devices yielded ∼5.10% and ∼7.20% power conversion efficiency, respectively. In the present work, pH 3 buffer solution helps to improve the morphology of CIS layer which gives the better power conversion efficiency as compared to the previously reported value.

Simulation of Tandem Thin-Film Solar Cell on the Basis of CuInSe2

CuInSe2 thin-film solar cells are promising materials for photovoltaic devices. One of the main tasks of researchers is to find ways to increase the solar cells efficiency. In this paper we propose an original structure of a thin-film solar cell based on a tandem connection of a photoelectric converter and a thermoelectric layer based on CuInSe2. The photoelectric converter consists of CuInSe2 and CdS layers. A 3D model of the proposed thin-film solar cell was implemented in the COMSOL Multiphysics environment with using the Heat Transfer module. The simulation was carried out taking into account the diurnal and seasonal variations of both the ambient temperature and the power density of the AM1.5 solar spectrum for the geographical coordinates of Minsk. The solar radiation power density of about 500 kW/m2 can be achieved by using concentrators. The temperature pattern and temperature gradients are calculated in each layer of the solar cell without and with the temperature stabilization of the substrate back side as well as without and with the thermal insulation of the substrate ends. Graphs of the temperature gradients of the thermoelectric layer and the temperature variations of the photoelectric converter of the solar cell are given. As a result of the simulation, it is shown how the uneven heating of both the surface of a thin-film solar cell and its layers occur under conditions of diurnal and seasonal variations of both the ambient temperature and the solar radiation power density. Under concentrated solar radiation exposure, the photoelectric converter surface can be heated up to 700 °C without temperature stabilization of the solar cell substrate. The operating temperature of the photoelectric converter was maintained at no more than 2.35 °C in January and at no more than 14.23 °C in July due to the temperature stabilization of the substrate back side of the proposed device. This made it possible to achieve an increase in the output power of the solar cell both by summing the photoand thermoelectric output voltages and by the concentration of solar radiation.

Selenization of electrochemically synthesized copper-indium layers from non-aqueous solution for solar cell application

Abstract A simple two-step, electrodeposition of copper-indium (Cu-In) intermetallic alloy thin films followed by selenization process was employed for the synthesis and development of CuInSe2 (CIS) thin film solar cells (TFSC). The co-deposition of Cu and In in ethylene glycol at 130 °C was studied using the cyclic voltammetry (CV) to obtain a stable Cu-In phase. A wide window of deposition potentials from −0.7 V to −1.5 V versus Ag/AgCl reference electrode was optimized. Three different potentials, −0.7 V, −1.0 V and −1.3 V are chosen to deposit the Cu-In intermetallic alloy thin films, which were further selenized in controlled selenium ambient at 400 °C. The selenization effect is studied extensively on structural, morphological, optical and compositional properties of selenized Cu-In (CIS) thin films. Polycrystalline CIS layers with tetragonal crystal structure are obtained upon selenization of Cu-In thin films. Three prominent reflections of CIS, (112), (204/220) and (312/116) are exhibited in all selenized Cu-In layers. Additional secondary phases of CuxSe1-x are attributed for the layers grown at −0.7 and −1.0 V. Compact and void-free surface morphology with particle size ∼1–2 μm was observed for all selenized samples. The selenized Cu-In layer sample deposited at −1.3 V measure ∼1.06 eV energy band gap with polycrystalline tetragonal chalcopyrite crystal structure of CIS. The photoelectrochemical measurement confirms the growth of p-type material. A selenized Cu-In layer deposited at −1.3 V with CdS window layer measured power conversion efficiency 5.44%.

High‐performance low bandgap thin film solar cells for tandem applications

AbstractThin film tandem solar cells provide a promising approach to achieve high efficiencies. These tandem cells require at least a bottom low bandgap and an upper high bandgap solar cell. In this contribution, 2 high‐performance Cu(In,Ga)Se2 cells with bandgaps as low as 1.04 and 1.07 eV are presented. These cells have shown certified efficiencies of 15.7% and 16.6% respectively. Measuring these cells under a 780‐nm longpass filter, corresponding to the bandgap of a typical top cell in tandem applications (1.57 eV), they achieved efficiencies of 7.9% and 8.3%. Admittance measurements showed no recombination active deep defects. One additional high‐performance CuInSe2 thin film solar cell with bandgap of 0.95 eV and efficiency of 14.1% is presented. All 3 cells have the potential to be integrated as bottom low bandgap cells in thin film tandem applications achieving efficiencies around 24% stacked with an efficient high bandgap top cell.

Correction to “Potassium Fluoride ex-situ Treatment on both Cu-rich and Cu-poor CuInSe2 Thin Film Solar Cells” [Mar 17 684-689

Presents corrections to the paper, “Potassium fluoride ex situ treatment on both Cu-Rich and Cu-Poor CuInSe2 thin film solar cells,” (Elanzeery, H., et al), IEEE J. Photovolt., vol. 7, no. 2, pp. 684–689, Mar. 2017.

High Short-Circuit Current Density in CIS Solar Cells by a Simple Two-Step Selenization Process With a KF Postdeposition Treatment

In this work, we present a CuInSe2 (CIS) thin-film solar cell with 14.7% efficiency and 40.2-mA/cm 2 short-circuit current. The samples were fabricated by the selenization of stacked elemental layers under selenium vapor in atmospheric ambient within a simple graphite box. Some samples were treated with a postdeposition treatment (PDT) with potassium fluoride (KF), whereas some were not, thus allowing for useful comparison. The use of the KF PDT led to two interesting improvements on our samples: formation of a hole-blocking layer between CdS/CIS interface, which reduces the tunneling recombination and significantly increases the open-circuit voltage. In addition, the KF PDT clearly reduces the symmetry of the nonohmic shunt leakage at low forward bias and reverse bias, which can be explained by a space-charge-limited current model, indicative of metal–semiconductor–metal (MSM) shunts. Discussion is presented to understand possible defects introduced during our processing steps and the physical origin of the shunt paths and why they might be of the MSM type. New directions to improve the performance of CIS solar cells are presented for future work using this very simple fabrication technique.

Effects of Annealing Pressure on Microstructure and Conversion Efficiency for Electrodeposited CuInSe₂ Absorbers.

As-deposited CuInSe₂ thin films by electrodeposition method are usually accompanied with amorphous structure which is regarded detrimental for solar cell conversion efficiency. In this work, we proposed an annealing method under high pressure for improving the conversion efficiency of electrodeposited CuInSe₂ thin film solar cells, and the microstructure of high-pressure annealed CuInSe₂ films were also investigated. The annealing pressure was set from 100 kPa to 250 kPa, and the annealed CuInSe₂ thin films were then fabricated into solar cell using standard process. Field-emission scanning electron microscopy (FESEM) images show that CuInSe₂ films with higher annealing pressure demonstrate denser and smoother surface morphology. Results from X-ray diffraction (XRD) and Raman spectra indicate that annealing under high pressure enhanced the (1 1 2) preferential orientation of CuInSe₂ films and also eliminated binary Cu–Se phases. Finally, through annealing CuInSe₂ absorber layer under 200 kPa, the fill factor of the CuInSe₂ solar cell was found to be improved from 28.4% to 55% and the efficiency from 2.77% to 6.91%.

Formation of CuInSe2 Printable Solar Cell Using Aqueous Phase Synthesized CuIn Alloy Nanoparticles

Actualization of environmental problems has induced the utilization of natural energy, such as solar energy. On the other hand, it is true that minimum energy payback time of Si solar cell is long, and dramatic improvement of Si based solar battery’s efficiency is not easy since its efficiency come closed to theoretical value. Therefore, various type solar battery has vigorously researched Since CuInSe2 (CIS) based solar battery, one of the attractive solar cell materials, shows the maximum efficiency reached up to 20.9% and long life time at large scale modules, commercialization of CIS based solar battery is stimulated. However, it is also true that these cell are deposited in high vacuum condition, which lead the loss of natural resources and also energy. So, various researches were vigorously researched of chemical reduction method since it is ecological and also economical technique. Ye et al. synthesized Cu-In alloy particles by using chemical reduction method in organic solvent and the Cu-In alloy precursor films were transformed to CuInSe2 films by selenization [1]. The resulting cells demonstrate a maximum energy conversion efficiency of 3.92 %. However, total cost of this method is not low since organic solvent should be used. On the other hand, until now, we reported that the synthesis of uniform and well crystallized alloy nanoparticles, such as Pd20Te7 and also CuIn alloy nanoparticles by restrict controlling the homogenization of metallic complexes in the aqueous solution under room temperature [2]. In this method, reduction rate of the metal species can be controlled under the room temperature, nevertheless ternary, or more, alloy nano materials with uniform and well crystallized structure was not synthesized until now. Therefore, in this study, these Cu-In (CI) alloy precursor materials were applied to the synthesis of CIS printable solar cell. CI alloy nanoparticles were synthesized and size controlled by chemical reduction method under ambient conditions using metal chlorides as metal sources and sodium borohydride as a reducing agent. Dispersion of synthesized CI nanoparticles were printed onto Mo-sputtered glass substrates, and selenized at 575 ºC for 60min to form of CIS solar cells. By obeying the calculation results and also electrochemical potential measurement, CI nanoparticles can be successfully synthesized in aqueous solution under room temperature. After selenization, CI was transformed into CuInSe2 thin film solar cells. The CuInSe2 thin film solar cells synthesized by this method exhibited a photovoltaic conversion efficiency of 2.3% under AM 1.5 G illumination. From the relationship between open circuit potential, short circuit current density, and fill factor, it indicated that smoothing of CIS films and improvement of the crystallinity and thickness should need to increase the solar cells properties. This work has been supported by the Grant-in-Aid for Scientific Research (B) (No. 26281054). [1] Ye Seul Lim, et.,al, J. Phys. Chem. C, 2013, 117 (23), pp 11930–11940, [2] H. Takahashi et.,al, Applied Catalysis A: General 392 (2011) 80–85.

Synthesis and Size Control of CuIn Alloy Nanoparticles in Aqueous Solution and Its Application for CuInSe2 Solar Cell

Since CIS (CuInSe2) solar cell, one of the attractive solar cell materials, shows the maximum efficiency reached up to 20.9%, CIS/CIGS solar cell is considered to comparable with that of Si solar cells. However, it is also true that these cell are deposited in high vacuum condition, which lead the loss of natural resources and also energy. So, various researches were vigorously researched of chemical reduction method since it is ecological and also economical technique. Ye et al.[1] synthesized Cu-In alloy particles by using chemical reduction method in organic solvent and the Cu-In alloy precursor films were transformed to CuInSe2films by selenization. The resulting cells demonstrate a maximum energy conversion efficiency of 3.92 %. However, total cost of this method is not low since organic solvent should be used. On the other hand, until now, we reported that the synthesis of uniform and well crystallized alloy nanoparticles, such as Pd20Te7 and Bi2Te3by restrict controlling the homogenization of metallic complexes in the aqueous solution under room temperature [2]. In this method, reduction rate of the metal species can be controlled under the room temperature, nevertheless ternary, or more, alloy nano materials with uniform and well crystallized structure was not synthesized until now. Therefore, in this study, CIS solar cell was tried to construct by using Cu-In (CI) alloy precursors prepared in aqueous phase by our method. CI alloy nanoparticles were synthesized and size controlled by chemical reduction method under ambient conditions using metal chlorides as metal sources and sodium borohydride as a reducing agent. Synthesized CI nanoparticles (0.4 g ) was dispersed in 4 mL of various solution to make a sample dispersion. CI alloy nanoparticles dispersion was coated onto Mo-sputtered glass substrates by spin coat to make CI alloy precursor films. The desiccated thin films were selenized at temperatures ranging from 300 ºC to 575 ºC for 60min. By obeying the calculation results and also electrochemical potential measurement, various copper complexes was successfully restricted to single species, and relationship between stability constants of complex reagents and reduction potential were summarized. As a results, CI nanoparticles can be successfully synthesized. XRD mesurments shows that synthesized materials were single phase of CuInSe alloy at selenization at 575 ºC. The CuInSe2 thin film solar cells synthesized by this method exhibited a photovoltaic conversion efficiency of 0.5 % under AM 1.5 G illumination. However, many pinhole, which lead defective contact of electrode and causes a decrease in efficiency, was formed on the CuInSe2thin film surface at this treatment condition. Therefore, in order to form pinhole-free films by spin coat, particle size of Cu-In ally nanoparticles precursor was controlled to have narrow particle size distribution. As a result, diameter of Cu-In particles become 30-70 nm. By using these size and distribution controlled CI nanoparticles, photovoltaic conversion efficiency was increased to 1.5 %. Other results will reported in our presentation. This work has been supported by the Grant-in-Aid for Scientific Research (B) (No. 26281054). [1] Ye Seul Lim, et.,al, J. Phys. Chem. C, 2013, 117 (23), pp 11930–11940, [2] H. Takahashi et.,al, Applied Catalysis A: General 392 (2011) 80–85.

Improving conversion efficiency of co-electrodeposited CuInSe2 thin film solar cells with substrate and solution heating

As-prepared electrodeposited CuInSe2 film is amorphous and rough. After CuInSe2 films growth, cadmium sulfide layers are deposited by chemical bath. The interface between the CuInSe2 layer and the CdS layer is a p–n junction for high-efficiency solar cells. The CuInSe2 layer must be defect-free and smooth to make a junction. In this work, CuInSe2 films with a smooth surface are obtained by heating the substrate and solution, and the solar cell of open circuit voltage is improved from 69 to 371 mV, the fill factor from 26.3 to 52 % and the conversion efficiency from 0.49 to 6.46 %. The structural properties of these selenized films are investigated using X-ray diffraction (XRD). Field-emission scanning electron microscopy images indicate that the ordered copper indium diselenide thin films are entirely filled. XRD results show that the copper indium diselenide thin films are crystalline with highly preferential orientation. Energy-dispersive spectroscopy analysis was used to determine the composition of the films.

Structural properties of In2Se3 precursor layers deposited by spray pyrolysis and physical vapor deposition for CuInSe2 thin-film solar cell applications

The structural properties of In2Se3 precursor thin films grown by chemical spray pyrolysis (CSP) and physical vapor deposition (PVD) methods were compared. This is to investigate the feasibility to substitute PVD process of CuInSe2 (CISe) films by CSP films as precursor layer, thus decreasing the production cost by increasing material-utilization efficiency. Both films of 1μm thickness were deposited at the same substrate temperature of 380°C. X-ray diffraction and Raman spectra confirm the formation of γ-In2Se3 crystalline phase for both films. The PVD and CSP films exhibited (110) and (006) preferred orientations, respectively. The PVD films showed a smaller full width at half maximum value (0.09°) compared with CSP layers (0.1°). Films with the same crystalline phase but with different orientations are normally used in the preparation of high quality CISe films by 3-stage process. Scanning electron microscope cross-section images showed an important difference in grain size with well-defined larger grains of size 1–2μm in the PVD films as compared to CSP layers (600nm). Another important characteristic that differentiates the two precursor films is the oxygen contamination. X-ray photoelectron spectroscopy showed the presence of oxygen in CSP films. The oxygen atoms could be bonded to indium by replacing Se vacancies, which are formed during CSP deposition. Taking account of the obtained results, such CSP films can be used as precursor layer in a PVD process in order to produce CISe absorber films.

Selenization of printed Cu–In–Se alloy nanopowder layers for fabrication of CuInSe2 thin film solar cells

One of the promising low cost and non-vacuum approaches for the fabrication of semiconductor CuInSe2 and Cu(In,Ga)(S,Se)2 thin film absorbers is the printing of precursor materials followed by a sintering/selenization process. The selenization process parameters such as temperature, duration, and selenium vapor pressure strongly influence the morphology and electronic properties of the absorber film. In this study, the effect of pre-annealing in an inert atmosphere and selenization on printed mechanically synthesized CuInSe0.5 alloy nanopowder precursor films was investigated. 1–2μm thick CuInSe0.5 alloy nanopowder layers were deposited on a Mo-sputtered glass substrate by means of doctor blade coating of a nanopowder based precursor suspension. Pre-annealing was performed on a hot plate inside a nitrogen gas filled glove box. Selenization was performed in a home-made rapid thermal processing (RTP) furnace with two RTP heating zones for independent temperature control of the selenium source and the coated substrate. The temperature of the selenium source was fixed at 390–410°C during the selenization to provide a constant supply of selenium vapor. A two-step process, i.e., a pre-annealing in nitrogen atmosphere at 400°C for 30min followed by selenization at 530°C for 15min was found to result in better densification and grain growth of the CuInSe2 phase, compared to a single step selenization at 530°C for 15min. The solar cell fabricated by the two-step process had an efficiency of 5.4% and a fill factor of 52%, while the device fabricated by the single step selenization had an efficiency of 1.1% and a fill factor of 31%.

Improved Efficiency of a Large-Area Cu(In,Ga)Se2 Solar Cell by a Nontoxic Hydrogen-Assisted Solid Se Vapor Selenization Process

A nontoxic hydrogen-assisted solid Se vapor selenization process (HASVS) technique to achieve a large-area (40 × 30 cm(2)) Cu(In,Ga)Se2 (CIGS) solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for active area) was demonstrated. The remarkable improvement of efficiency and fill factor comes from improved open circuit voltage (Voc) and reduced dark current due to (1) decreased interface recombination raised from the formation of a widened buried homojunction with n-type Cd(Cu) participation and (2) enhanced separation of electron and hole carriers resulting from the accumulation of Na atoms on the surface of the CIGS film. The effects of microstructural, compositional, and electrical characteristics with hydrogen-assisted Se vapor selenization, including interdiffusion of atoms and formation of buried homojunction, were examined in detail. This methodology can be also applied to CIS (CuInSe2) thin film solar cells with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area) and provides a facile approach to improve quality of CIGS and stimulate the nontoxic progress in the large scale CIGS PV industry.

Fabrication of CuInSe2 thin film solar cell with selenization of double layered precursors from Cu2Se and In2Se3 binary

CuInSe2 (CIS) films on Mo/soda-lime glass were prepared by selenization of sputtered precursors from Cu2Se and In2Se3 binary targets. Cu–In–Se precursors were sequentially sputtered with double-layered structure of both Cu2Se/In2Se3 and In2Se3/Cu2Se. The structural, compositional and electrical properties of annealed Cu–In–Se precursors were investigated for solar cell applications. Better adhesion between CIS and Mo back contact was observed in the double-layered structure of Cu2Se/In2Se3 at all working pressures. Less MoSe2 phase on both structures was generated at a lower working pressure of 0.67Pa. A CIS solar cell with Al/Al-doped ZnO/i-ZnO/CdS/CIS (900nm, Cu2Se/In2Se3 at 0.67Pa)/Mo/soda-lime glass was continuously fabricated, and its conversion efficiency was 4.6%, with 346mV of open circuit voltage, 30.5mA/cm2 of short circuit current density and 43.5% fill factor.

Study on the Buffer Layer of CIS Thin Film Solar Cell by Separate-Melting Chemical Bath Deposition Methods

In this work, cadmium sulphide (CdS) buffer layer of CuInSe2 (CIS) thin film solar cell is fabricated by separate-melting Chemical Bath Deposition (CBD) methods. The reason of adopting the CdS thin film as the buffer layer of CIS thin film solar cell is that the CdS can act as energy gap buffer and reduce the band-offset between CIS absorbing layer and the Transparent Conductive Oxide layer. The CdS thin films are generated by the separate-melting CBD methods in situation of atmosphere. In order to analyze the characteristics of the CdS thin films conveniently, the CdS thin films are firstly fabricated on Soda-lime, and the final found optimal CdS thin film is fabricated on the CIS/Mo/Soda-lime glasses. Then the p-n diode characteristic of the CdS/CIS/Mo/Soda-lime glasses is measured by four-point probe. And the CdS thin films are fabricated by the separate-melting CBD methods through various combinations of time interval from 40 and 60 minutes and temperature range from 70,75,80 and 85°C. It is found that the combination of 85°C and 60 minutes is optimal to obtain smoother surface and more uniform thickness of CdS thin film. Additionally from optical characteristic analysis, in situation of emitted light wave length 500 nm, the transmittance of the cadmium sulphide thin film is 61%. Meanwhile, the band gap is close to theoretical value of 2.4 eV.