Thin Film Solar Cell Technology Research Articles

Comprehensive Design and Analysis of Thin Film Sb2S3/CIGS Tandem Solar Cell: TCAD Simulation Approach

Abstract This research presents a design and analysis of a tandem solar cell, combining thin film wide bandgap Sb2S3 (1.72 eV) and narrow bandgap CIGS (1.15 eV) for the top and bottom sub-cells, respectively. The integration of all thin film layers enhances flexibility, rendering the tandem solar cell suitable for applications such as wearable electronics. To optimize the power conversion efficiency (PCE) of the tandem solar device, advanced technology computer-aided design (TCAD) simulation tools are employed to estimate loss mechanisms and fine-tune parameters for each layer. An experimentally validated optoelectronic model is introduced, calibrated and validated against fabricated reference solar cells for the individual top and bottom cells. The calibrated model is then utilized to propose optimization routines for the Sb2S3/CIGS tandem solar cell. The initial tandem cell exhibits a JSC of 15.72 mA/cm2 and a PCE of 15.36%. The efficiency drop in the tandem configuration is identified primarily in the top cell. A systematic optimization process for the top cell is initiated, exploring various configurations, including HTL-free and ETL-free setups. Moreover, an np homojunction structure for the top cell is proposed. Optimization routines are applied that involve determining optimal thickness and doping concentration of the n-layer, investigating the effect of p-layer doping concentration, and exploring the influence of the work function of the front contact. As a result, the tandem cell efficiency is significantly improved to 23.33% at the current matching point (CMP), with a JSC of 17.15 mA/cm2. The findings contribute to the advancement of thin-film tandem solar cell technology, showcasing its potential for efficient and flexible photovoltaic applications.

Recent Progress and Challenges in Controlling Secondary Phases in Kesterite CZT(S/Se) Thin Films: A Critical Review

Kesterite-based copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) thin films have attracted considerable attention as promising materials for sustainable and cost-effective thin-film solar cells. However, the successful integration of these materials into photovoltaic devices is hindered by the coexistence of secondary phases, which can significantly affect device performance and stability. This review article provides a comprehensive overview of recent progress and challenges in controlling secondary phases in kesterite CZTS and CZTSe thin films. Drawing from relevant studies, we discuss state-of-the-art strategies and techniques employed to mitigate the formation of secondary phases. These include a range of deposition methods, such as electrodeposition, sol-gel, spray pyrolysis, evaporation, pulsed laser deposition, and sputtering, each presenting distinct benefits in enhancing phase purity. This study highlights the importance of employing various characterization techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, for the precise identification of secondary phases in CZTS and CZTSe thin films. Furthermore, the review discusses innovative strategies and techniques aimed at mitigating the occurrence of secondary phases, including process optimization, compositional tuning, and post-deposition treatments. These approaches offer promising avenues for enhancing the purity and performance of kesterite-based thin-film solar cells. Challenges and open questions in this field are addressed, and potential future research directions are proposed. By comprehensively analyzing recent advancements, this review contributes to a deeper understanding of secondary phase-related issues in kesterite CZT(S/Se) thin films, paving the way for enhanced performance and commercial viability of thin-film solar cell technologies.

Zinc telluride material properties for solar cell application: Absorber layer

Over recent years, Zinc Telluride (ZnTe) has garnered significant interest from researches. This p-type semiconductors boasts a broad band gap, rendering it valuable in various optoelectronic uses like solar cells, LEDs, and laser displays. Given the growing interest in environmentally friendly energy alternatives, exploring the potential of nano-scale semiconducting materials for solar cells is particularly intriguing. ZnTe stands out due to its direct, wide, and adjustable optical band gap, along with its simple doping process, positioning it as a promising candidate for applications in photochemistry. This study aims to consolidate the research conducted by multiple investigators concerning the optical characteristics and electrical attributes of ZnTe thin films. The primary focus is on understanding how deposition methods and doping impacts these properties. The investigation reveals that the diverse doping techniques employed by different researchers have been extensively examined, demonstrating a positive influence of doping on these properties as well. Following the creation of solar cells based on ZnTe, they have emerged as viable and competitive substitutes for silicon solar cells, thanks to their economical nature and stable performance. As a result, there has been notable focus on advancing ZnTe thin film solar cell technology due to their promising capacity to serve as sustainable energy generators.

Thin film Si solar cell and solid oxide fuel cell technologies for a low cost, environmentally friendly and sustainable source of energy

Thin-film solar cell technology based on hydrogenated amorphous silicon has matured over the last two decades and is capable to deliver commercial modules with almost 10 % stabilized efficiency. Moreover attention on hydrogen fuel cells is increasing as the range of potential commercial applications expands, with more than 3800 fuel cell systems being installed and operated worldwide. These systems attain high theoretical efficiencies in the range of 43.7-70.4 %, with an additional 20% as heat recovery, and operating at carbon-free conditions between 50 °C and 900 °C. In this paper the status of thin-film silicon solar cell technology is reviewed by comparing it to other major solar cell technologies. A discussion is also made upon the benefits obtained from the few potential applications, as long-term potential actions for sustainable development, and the future of Solid Oxide Fuel Cells (SOFCs). Applications of thin-film silicon modules and SOFCs are presented. EPIA (European Photovoltaic Industry Association) estimates that half of the growth in the next two years will come from thin-film technology.

Heterostructured CdS Buffer Layer for Sb2Se3 Thin Film Solar Cell

The antimony selenide thin film solar cells technology becomes promising due to its excellent anisotropic charge transport and brilliant light absorption capability. Especially, the device performance heavily relies on the vertically oriented Sb2Se3 grain to promote photoexcited carrier transport. However, crystalline orientation control has been a major issue in Sb2Se3 thin film solar cells. Herein, a new strategy has been developed to tailor the crystal growth of Sb2Se3 ribbons perpendicular to the substrate by using the structural heterostructured CdS buffer layer. The heterostructured CdS buffer layer is formed by a dual layer of CdS nanorods and nanoparticles. The hexagonal CdS nanorods passivated by a thin cubic CdS nanoparticle layer can promote [211] and [221] directional growth of Sb2Se3 ribbons using a close space sublimation approach. The improved buffer/absorber interface, reduced interface defects, and recombination loss contribute to the improved device efficiency of 7.16%. This new structural heterostructured CdS buffer layer can regulate Sb2Se3 nanoribbons crystal growth and pave the way to further improve the low‐dimensional chalcogenide thin film solar cell efficiency.

Experimental and numerical study of the CIGS/CdS heterojunction solar cell

In this paper, we have performed a complementary and comparative analysis between an experimental and simulation study of the CIGS/CdS bulk heterojunction solar cell.The electrical parameters of this heterojunction modeled by a diode in the presence of parasitic resistances (Rs; Rsh), are determined by studying the properties of the (I–V) characteristic in the dark, and at different temperatures from 130 K to 300 K. We used the (ALM) method to determine the parasitic resistances. Also, by using the thermionic emission theory, we have determined other parameters, like ideality factor n, the barrier height φB, and the mobility μ, and we compared these parameters with those determined by using Cheung's method. The ideality factor values at different temperatures which is greater than unity provided us with information about the electronic transport mechanism in the heterojunction.To complete our study, we performed a numerical simulation of the CIGS/CdS structure to determine the efficiency of the solar cell at different temperatures, taking into account the values of the parasitic resistances that we identified earlier. We also explored ways to improve the efficiency of our cell, in particular by using a HTL (NiO) layer. This layer increased the efficiency of the cell from 9.89% to 19.55% at a temperature of 300 K, a significant improvement for the advancement of thin film solar cell technology. In sum, this study makes a valuable contribution to the research field by demonstrating the positive impact of using HTL layers to improve the efficiency of thin film solar cells.

Direct Measurements of Interfacial Photovoltage and Band Alignment in Perovskite Solar Cells Using Hard X-ray Photoelectron Spectroscopy.

A heterojunction is the key junction for charge extraction in many thin film solar cell technologies. However, the structure and band alignment of the heterojunction in the operating device are often difficult to predict from calculations and, due to the complexity and narrow thickness of the interface, are difficult to measure directly. In this study, we demonstrate a technique for direct measurement of the band alignment and interfacial electric field variations of a fully functional lead halide perovskite solar cell structure under operating conditions using hard X-ray photoelectron spectroscopy (HAXPES). We describe the design considerations required in both the solar cell devices and the measurement setup and show results for the perovskite, hole transport, and gold layers at the back contact of the solar cell. For the investigated design, the HAXPES measurements suggest that 70% of the photovoltage was generated at this back contact, distributed rather equally between the hole transport material/gold interface and the perovskite/hole transport material interface. In addition, we were also able to reconstruct the band alignment at the back contact at equilibrium in the dark and at open circuit under illumination.

Numerical simulation of germanium selenide heterojunction solar cell

One of the research hotspots in thin film solar cell technology is to seek the suitable absorber layer materials to replace cadmium telluride and copper indium gallium selenium. Recently, germanium selenide (GeSe) with excellent photoelectric property has entered the field of vision of photovoltaic researchers. The main factors affecting the performance of heterojunction solar cell are the material properties of each functional layer, the device configuration, and the interface characteristics at the heterostructure. In this study, we utilize GeSe as the absorber layer, and assemble it with stable TiO<sub>2</sub> as electron transport layer and with Cu<sub>2</sub>O as hole transport layer, respectively, into a heterojunction solar cell with the FTO/TiO<sub>2</sub>/GeSe/Cu<sub>2</sub>O/Metal structure. The TiO<sub>2</sub> and Cu<sub>2</sub>O can form small spike-like conduction band offset and valence band offset with the absorber layer, respectively, which do not hinder majority carrier transport but can effectively suppress carrier recombination at the heterointerface. Subsequently, the wxAMPS software is used to simulate and analyze the effects of functional layer material parameters, heterointerface characteristics, and operating temperature on the performance parameters of the proposed solar cell. Considering the practical application, the relevant material parameters are selected carefully. After being optimized at 300 K, the proposed GeSe heterojunction solar cell can reach an open circuit voltage of 0.752 V, a short circuit current of 40.71 mA·cm<sup>–2</sup>, a filling factor of 82.89%, and a conversion efficiency of 25.39%. It is anticipated from the results that the GeSe based heterojunction solar cell with a structure of FTO/TiO<sub>2</sub>/GeSe/Cu<sub>2</sub>O/Au has the potential to become a high-efficiency, low toxicity, and low-cost photovoltaic device. Simulation analysis also provides some references for designing and preparing the heterojunction solar cells.

Single-component organic solar cells-Perspective on the importance of chemical precision in conjugated block copolymers.

Organic photovoltaics (OPV) present a promising thin-film solar cell technology with particular benefits in terms of weight, aesthetics, transparency, and cost. However, despite being studied intensively since the mid 90's, OPV has not entered the mass consumer market yet. Although the efficiency gap with other thin-film photovoltaics has largely been overcome, active layer stability and performance reproducibility issues have not been fully resolved. State-of-the-art OPV devices employ a physical mixture of electron donor and acceptor molecules in a bulk heterojunction active layer. These blends are prone to morphological changes, leading to performance losses over time. On the other hand, in "single-component" organic solar cells, the donor and acceptor constituents are chemically connected within a single material, preventing demixing and thereby enhancing device stability. Novel single-component materials affording reasonably high solar cell efficiencies and improved lifetimes have recently emerged. In particular, the combination of donor and acceptor structures in conjugated block copolymers (CBCs) presents an exciting approach. Nevertheless, the current CBCs are poorly defined from a structural point of view, while synthetic protocols remain unoptimized. More controlled synthesis followed by proper structural analysis of CBCs is, however, essential to develop rational structure-property-device relations and to drive the field forward. In this perspective, we provide a short overview of the state-of-the-art in single-component organic solar cells prepared from CBCs, reflect on their troublesome characterization and the importance of chemical precision in these structures, give some recommendations, and discuss the potential impact of these aspects on the field.

20%-efficient polycrystalline Cd(Se,Te) thin-film solar cells with compositional gradient near the front junction

Bandgap gradient is a proven approach for improving the open-circuit voltages (VOCs) in Cu(In,Ga)Se2 and Cu(Zn,Sn)Se2 thin-film solar cells, but has not been realized in Cd(Se,Te) thin-film solar cells, a leading thin-film solar cell technology in the photovoltaic market. Here, we demonstrate the realization of a bandgap gradient in Cd(Se,Te) thin-film solar cells by introducing a Cd(O,S,Se,Te) region with the same crystal structure of the absorber near the front junction. The formation of such a region is enabled by incorporating oxygenated CdS and CdSe layers. We show that the introduction of the bandgap gradient reduces the hole density in the front junction region and introduces a small spike in the band alignment between this and the absorber regions, effectively suppressing the nonradiative recombination therein and leading to improved VOCs in Cd(Se,Te) solar cells using commercial SnO2 buffers. A champion device achieves an efficiency of 20.03% with a VOC of 0.863 V.

Simulation of antimony chalcogenide thin film solar cell with high-efficiency

Second generation solar cell (TFPV) have captured the attention of the majority of the research community in the energy sector due to dramatic enhancement in its efficiency. Copper Indium Gallium Selenide (CIGS) and Cadmium Telluride (CdTe) have been extensively investigated as light absorbing layer for thin film solar cells since last few years. However, limitations such as low abundance and toxicity of these materials precluded them from being used further in thin film solar cell technology. In this research work, we utilized photovoltaic materials like Sb2Se3 and Sb2S3 to examine the solar cell efficiency by one dimensional solar simulator (SCAPS-1D). A structural device is modelled for optimizing absorber layer thickness, and thus the solar cell efficiency, using various non-toxic buffer layers like CdS, ZnO, In2S3, ZnS, and ZnSe with the thickness of 40 nm. The modelled structure with optimized thickness (2 μm&2.5 μm) resulted in higher efficiency (∼22 %) antimony chalcogenide thin film solar cells.

To grind or not to grind? The influence of mechanical and thermal treatments on the Cu/Zn disorder in Cu2ZnSn(SxSe1-x)4 monograins

Kesterite-type based thin film solar cell technologies are mainly based on polycrystalline absorber layers. A promising low cost alternative technology uses Cu 2 ZnSn(S x Se 1-x ) 4 (CZTSSe) monograins (single crystals of 20–100 μm size) which are fixed in a polymer matrix to form a flexible solar cell. The Cu/Zn disorder is discussed as a possible reason for band tailing causing voltage losses limiting the efficiency of CZTSSe-based devices. The experimental determination of the order parameter Q which is a quantitative measure of Cu/Zn disorder, requires a differentiation between the isoelectronic cations Cu + and Zn 2+ . An in-depth analysis of neutron diffraction data allows the determination of type and concentration of intrinsic point defects including a distinction between Cu and Zn. Neutron diffraction requires large sample volumes, thus monograins offer the unique possibility to correlate structural disorder in CZTSSe with device performance parameters. In this study we tackle the influence of grinding the monograins on stoichiometry deviations, the Cu/Zn disorder as well as intrinsic point defects and optoelectronic properties of CZTSSe monograins. Moreover, an easy methodology based on Raman scattering spectroscopy is proposed for the assessment of Cu/Zn disorder in the CZTSSe compounds. • a significant impact on the order parameter Q in CZTSSe monograins from the “ordering” and “disordering” procedures. • The possibility to develop a fast and easy methodology to estimate the level of Cu/Zn disorder from Raman measurements. • Clear independence of the main structural, compositional and optoelectronic properties from the mechanical treatment.

PMMA Lens Arrays for Micro Concentrator Solar Cells Produced by Hot Embossing

The rising energetical needs of modern society have been increasingly pushing for the improvement in energy efficiency. Thin-film solar cell technology encompasses several types of devices whose purpose is to gather energy emitted from a luminous source and convert it into usable electrical energy for a variety of applications, particularly low-powered devices. Micro concentrator solar cells are promising devices to solve the materials availability problem and address the power conversion efficiency simultaneously. Since the energy conversion efficiency for this type of solar cell is not particularly high, it stands out to benefit greatly from using an optical concentrator element to increase the light intensity reaching the active surface. The micro-concentrator element is comprised of a micro-lens array, which can be manufactured by different technologies, such as polymer injection moulding, extrusion, or hot embossing. In this work, we explore how hot embossing can be used to inexpensively produce spherical lenses with Ø 1 mm in an array according to micro concentrator solar cell requirements. A simple compression system coupled with an infrared lamp heat chamber was used to emboss PMMA disks. Different mould insert manufacturing technologies were used and different hot embossing parameters were assessed. The process replicability of the micro-lens cavities was determined by infinite focus microscopy and optical microscopy. The most promising lens array was achieved with a mould insert produced by μ-EDM (with Ra and Rz values of 0.6 μm and 4.58 μm, respectively).

Potassium Iodide-Modified Lead-Free Cs3Bi2I9 Perovskites for Enhanced High-Efficiency Solar Cells.

Lead-free, bismuth-based perovskite solar cells (PSCs) are promising, non-toxic, and stable alternatives to lead-based PSCs, which are environmentally harmful and highly unstable under deprived air conditions. However, bismuth-based PSCs still suffer from low-power-conversion efficiency (PCE) due to their large bandgap and poor film morphology. Their poor film-forming ability is the greatest obstacle to Cs₃Bi₂I₉ progress in thin-film solar cell technology. This study synthesizes novel, lead-free perovskites with a small bandgap, excellent stability, and highly improved photovoltaic performance by integrating different amounts of potassium iodide (KI) into a perovskite precursor solution. KI incorporation improves the crystallinity of the perovskite, increases the grain size, and decreases the potential contact distribution, which is demonstrated by X-ray diffraction, electronic scanning microscopy, atomic force microscopy, and ultraviolet-visible spectroscopy. The Cs₃Bi₂I₉ PSC device with 2 vol. % incorporation of KI shows the highest PCE of 2.81% and Voc of 1.01 V as far as all the Bi-based cells fabricated for this study are concerned. The study demonstrates that incorporating KI in the Cs₃Bi₂I₉ perovskite layer highly stabilizes the resultant PSC device against humidity to the extent that it maintains 98% of the initial PCE after 90 days, which is suitable for solar cell applications. The devices also demonstrate greater resistance to airborne contaminants and high temperatures without encapsulation, opening up new possibilities for lead-free Cs₃Bi₂I₉ PSCs in future commercialization.

Structural and Morphological Properties of Single and Mixed Halide Pb-Based Perovskites

Single and mixed-halide perovskite solar cells have attracted much research attention in recent years due to the conditions of low-cost thin film solar cell technology. For this current research, perovskite materials CH3NH3PbCl3, CH3NH3PbI2Cl, CH3NH3PbICl2, and CH3NH3PbI3 have been synthesized and deposited on clean glass substrates by spin coating process. The structural and morphological properties of the prepared thin films have been studied by X-ray diffraction and Scanning electron microscopy. All the perovskite showed fine crystallinity, possessing a tetragonal phase. The average crystallite sizes of the prepared samples are obtained to be 20.77 nm, 30.18 nm, 31.11 nm, and 42.23 nm, respectively. The lattice strain decreased with increasing crystallite size. A drastic change was observed in the morphological properties of the perovskites. The perovskite grains change from microrods to microcube by substituting iodine with chlorine ions.

A study on influence of potential defects and optimization of device structure for CuSbS2 based thin film solar cell using SCAPS – 1D simulator

Copper antimony sulphide (CuSbS2) is a benign material for next generation thin film solar cell technology due to its non-toxicity, low cost, and earth abundant ingredients. The noteworthy features of CuSbS2 are its high absorption coefficient and suitable bandgap. In this work, we computationally analyzed the CuSbS2 thin film solar cell using SCAPS-1D simulation software in order to boost the performance of CuSbS2 solar cell by exploring the individual and integrated effects of stoichiometric defects and interface defects, CuSbS2 layer thickness, auger hole capture coefficient, CdS layer thickness, back contact materials and parasitic resistances. The study reveals that stoichiometric (CuSb and VS) and interface defects affect perniciously on the solar cell parameters. The optimum thickness of CuSbS2 and CdS layer is 500 nm and 60 nm, respectively. In addition to the investigations with CdS as a buffer layer, we also carried out a comparative study on performance of CuSbS2 based thin film solar cell by changing the buffer layer material to Zn(O,S) and found that the device with CdS as a buffer layer gives marginally better efficiency and particularly higher short-circuit current as compared to that with Zn(O,S) as a buffer layer.

Analysis and design of p-n homojunction Sb2Se3 solar cells by numerical simulation

Antimony selenide (Sb2Se3) is considered a promising candidate utilized as an absorber in thin film solar cell (TFSC) technology thanks to its non-toxic and earth-abundant nature besides its reported high absorption coefficient. To enhance the power conversion efficiency (PCE) of Sb2Se3 solar cells, we report some design suggestions by applying device simulation. The numerical model is firstly validated by calibration of simulation results vs those from an experimental Sb2Se3 solar cell structure composed of FTO/CdS/Sb2Se3/Au where CdS serves as an electron transport layer (ETL). Then, the cell is modified to include an embedded p-n homojunction. In contrast to the conventional heterostructure design, a homojunction structure has crucial benefits in terms of both electronic and optoelectronic characteristics such as the extra produced built-in electric field which can increase the transport of photogenerated carriers. Three device configurations are presented and compared. The first and the second cases are when using CdS and ZnOS as ETLs. Utilizing ZnOS ternary compound is found to be more beneficial as its conduction band offset with the absorber layer could be tuned to attain a proper cliff-like band alignment. The third case is when considering homojunction design free from all carrier transport layers. Possible paths for device optimization are investigated to boost the efficiency in a try to overcome the efficiency bottleneck encountered in the Sb2Se3-based quasi homojunction solar cells. All simulations, performed in this study, are done by SCAPS device simulation software under standard AM1.5G one Sun illumination.

Numerical analysis of hole transport layer-free antimony selenide solar cells: Possible routes for efficiency promotion

Amongst the numerous absorbers confronted in thin-film solar cell technology, antimony selenide (Sb2Se3) is regarded as an extremely promising contender as it is a non-toxic and earth-abundant besides its high-level absorption coefficient. To boost the power conversion efficiency (PCE) of Sb2Se3 solar cells, we report some design recommendations by utilizing device simulation. The device model is firstly validated by calibration of an experimental cell having a configuration of FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au. Then, the optimization of a hole transport layer (HTL) free structure is carried out by tuning the conduction band offset between the electron transport layer (ETL) and the Sb2Se3 absorber and by inspecting the key absorber parameters to get the maximum available power conversion efficiency. In this context, the ternary compound material ZnMgO is found to match the optimum band alignment. Moreover, the impact of ETL parameters, like thickness, doping, and surface treatment by ammonia etching, has been analyzed to understand its underlying physics and to provide possible ways for device efficiency promotion. All simulations, conducted in this paper, are accomplished by SCAPS device simulation software under standard one Sun (AM1.5G, 100 mW/cm2) illumination at 300 K.

창호용 블라인드 태양광 모듈의 설계

We propose an indoor blind-type solar module that can be applied to the windows of buildings. A comparative study was conducted with solar modules by alternatively assuming crystalline silicon, CIGS, or amorphous silicon thin film solar cell technology. It is self-evident that the output power of the crystalline silicon solar cell module is the largest, but the power gap between modules is smaller than that predicted from the cell efficiency because the module power loss in thin film solar cell modules is comparatively small. In addition, since the temperature coefficient of the thin film solar cell is smaller than that of the crystalline silicon solar cell, the output power gap between the crystalline silicon and thin film solar cell modules is further reduced when operating in a high temperature environment. It is expected that this blind-type solar module would contribute about 10% reduction of the existing fossil energy generation, and about 50% of electricity consumption per household as an urban auxiliary power source.

Comprehensive study on CdSe thin film as potential window layer on CdTe solar cell by SCAPD-1D

Photovoltaics significantly contributes towards the emerging renewable energy drive. Amongst the available thin film solar cell technologies, presently CdTe is leading at commercial state. CdS is being widely used as window layer in CdTe solar cell but challenged with toxicity. Therefore, this project explores the feasibility of CdSe as alternative window layer in CdTe solar cell. The CdSe is optimized to determine the best complete CdTe based solar cell. The study also compares the device performance of proposed CdSe/CdTeSe/CdTe solar cell with other reported CdSe/CdTe and CdS/CdSe solar cells. While degerming the optimized thickness of CdTe solar cell with respect to different prospective window layer materials, the simulation results reveal that CdTe thickness can significantly reduce, at least by 500 nm, with only 1% reduction in PCE by replacing conventional CdS window layer with CdSe layer. Furthermore, while determining the appropriate Se composition on CdSexTe1-x as this layer forms between CdTe and CdSe layer during the fabrication, it has been found that 18% efficiency can be obtained in CdTe solar cell if the stoichiometry of CdSexTe1-x can be maintained as CdSe0.3Te0.7 during the device fabrication.