CIGS Cells Research Articles

Numerical Simulation Study of The Increase in Electrical Efficiency of the CIGS-Based Solar Cell by SCAPS-1D

Solar cells are currently the focus of a great deal of research. The aim is to reduce their cost price. To achieve this, we need to reduce the mass of the materials and increase the conversion efficiency of these solar cells. This has motivated research into the use of thin films such as a-Si, CdTe, CIGS. This increase in efficiency requires optimizing the performance of the photovoltaic parameters. In this modeling and simulation work, we use the SCAPS-1D software to study the effect of the recombination speed of the electrons and holes in the CIGS layer, the effect of the thickness of the layers and the effect of the gap energy of each layer of the material used for this solar cell on the short-circuit current Jsc, the open-circuit voltage Voc, the form factor FF and the electrical efficiency η of the CIGS cell for a Mo/p-CIGS/p-Si/In2S3/i-ZnO/Al-ZnO single-junction structure. In this study, we found that recombination speed affects the efficiency of the photovoltaic cell. The gap energy of the absorber layers influences the cell's efficiency, while the other layers (In2S3, ZnO, Al-ZnO) do not have a great influence on solar cell performance and increasing the thickness of the absorber layer has a major influence on efficiency, increasing it up to a certain limit. The thicknesses of the CIGS, p-Si, In2S3, i-ZnO and Al‑ZnO layers need to be in the order of 0.3µm, 0.8µm, 0.05µm, 0.07µm and 0.1µm respectively to achieve better efficiency (31.42%).

Study on the film-forming properties of Mo–Na ceramic targets

In order to provide sufficient and stable Na+ for the CIGS flexible thin film solar cells, Mo–Na ceramic targets were prepared by the plasma-assisted cold sintering process (CSPS). And the film-forming properties of the Mo–Na targets were studied. The Mo–Na targets were prepared with MoO3 as precursor. The Mo–Na targets were successfully prepared with uniformity, compactness and high relative density (98.19 %). Then, the Mo–Na monolayer films were prepared by radio frequency (RF) magnetron sputtering. The results show that Mo–Na monolayer films are homogeneous and compact. Significantly, abundant Na+ are stored in the Mo–Na monolayer films. To verify the application of Mo–Na targets in the CIGS cells, the sandwich structure (Mo/Mo–Na/Mo) films and co-sputtered films were studied. The results show that the co-sputtered films have sufficient Na+, and show good photoelectric and mechanical properties. In addition, after heat treatment, Na+ can diffuse to the surface of the sandwich films, which can provide sufficient and stable Na+ for CIGS thin film cells.

Determination of light-independent shunt resistance in CIGS photovoltaic cells using a collection function-based model

Shunt resistance Rsh is a critical parameter for photovoltaic cells designed for low light indoor applications because it negatively affects the open circuit voltage, fill factor, and conversion efficiency. Standard CIGS cells are known to have low Rsh and are, therefore, unpromising candidates for indoor energy sources. In this paper, we extend the original work of Virtuani et al. by determining the electrical specifications of many CIGS cells with copper contents [Cu]/([Ga]+[In]) as low as 0.33 and gallium contents between 0.28 and 0.81. First, IV data are fitted by a standard single-diode electrical circuit model for each illumination, resulting in light-dependent parameters. Then, we use a procedure based on a single dataset of electrical variables, i.e., independent of light, corrected by the experimental collection function, which captures light-dependent physical mechanisms. In this way, we are able to correctly reproduce the illuminance dependence of the electrical response of the PV cell over three orders of magnitude, in particular with a fixed value of the shunt resistance. The highest Rsh is obtained with a low copper composition of 0.5, regardless of the gallium composition.

Enhancing Solar Photovoltaic Cell Efficiency: A Comparative Analysis of Advanced Materials and Manufacturing Techniques

This research paper investigates the enhancement of solar photovoltaic (PV) cell efficiency through a comparative analysis of advanced materials and manufacturing techniques. With the escalating demand for renewable energy solutions, improving the efficiency of solar cells is paramount. This study focuses on several promising materials including silicon, perovskite, CIGS, organic, and dye-sensitized options, alongside innovative manufacturing techniques such as roll-to-roll printing, ultrasonic spraying, and laser scribing. The methodology employed an experimental approach, where various prototypes were fabricated and tested under controlled laboratory conditions. Regression analysis was utilized to examine the impact of different materials and manufacturing techniques on solar cell performance. Key findings revealed that specific manufacturing techniques, particularly laser scribing, significantly enhance the efficiency of silicon-based cells. Moreover, perovskite cells displayed robust performance under varied environmental conditions, suggesting their broader application potential. Material enhancements such as sodium doping in CIGS cells were also shown to substantially increase efficiency. The implications of these findings are significant, offering insights into the effective integration of materials and techniques that could lead to more cost-effective and efficient solar energy systems. This study not only advances the academic understanding of photovoltaic technologies but also guides practical implementations in the solar industry.

Colour-Passive radiative cooling in optoelectronics with Silver/Quantum dot decorated silica multifunctional hybrid structures

The integration of solar cells into the architectural design is hindered by challenges such as passive cooling and colouration appeal. The present study proposes an approach to overcome these obstacles by developing colourful solar cells that maintain optimal performance while addressing limitations related to heat accumulation from plasmon metal nanoparticles and quantum dots (QDs). To attain this, silver/silica microsphere composites combined with CdSe/ZnS core/shell QDs are fabricated with two distinct sizes of Ag nanoparticles embedded around SiO2 microspheres. Upon coating CIGS cells with this hybrid structure, a visually striking vivid green colouration is observed, while ensuring performance efficiency. Furthermore, the radiative cooling capability of these cells is evaluated through indoor and outdoor experiments. Significantly, a substantial temperature reduction of up to 3.2 °C in CIGS cells is achieved when the hybrid structures were applied to the cell's surface under high solar irradiance. The study represents a significant contribution to innovative strategies targeted at achieving passive cooling effect and enhancing aesthetic integration in building-integrated photovoltaics applications.

Proposal and design of organic/CIGS tandem solar cell: Unveiling optoelectronic approaches for enhanced photovoltaic performance

Solar cells are promising devices for converting sunlight into electrical energy. Tandem solar devices, which combine multiple sub cells with complementary absorption spectra, offer a potential strategy to enhance the overall power conversion efficiency (PCE). In this work, the design and performance of organic/CIGS tandem solar devices are investigated. The initial tandem cell comprises two sub cells, namely an organic-based PM6:m-DTC-2 F top cell and CIGS bottom cell. The organic and CIGS cells show a PCE of 12.20% and 20.10%, respectively, where the initial results are based on calibrated cells reproduced from experimental studies. Accordingly, the initial tandem PM6:m-DTC-2 F/CIGS cell shows a PCE of 22.75%. The study focuses on optimizing the PCE via different approaches. Firstly, through the exploration of different hole transport layers (HTLs) of the front cell. Secondly, by investigating the matched current condition between the front and rear cells. Moreover, the doping effect of the CIGS film is investigated. Finally, optimization of the defect concentrations in the absorbers is introduced. These optimizations result in open circuit voltage (Voc) of 1.89 V with short circuit current (Jsc) of 17.55 mA/cm2, and a fill factor (FF) of 82.79%. Consequently, the PCE of the optimized tandem cell is further enhanced to 27.46%. Further, the stability of the proposed tandem cell is evaluated under varying temperatures, and its composition of flexible materials makes it a promising candidate for wearable applications.

Water liquid compatibility as a spectral splitting optical filtration fluid to six types of photovoltaic solar cells under high solar concentrations

The spectral-splitting optical filtration (SSOF) technique has attracted a lot of attention as a solution to the unnecessary portion of solar irradiation that can be stored as heat in the cells of conventional photovoltaic (PV) and photovoltaic/thermal (PV/T) systems. Transmitting the effective portion according to the SSOF fluid optical range and the spectral response of the integrated cell was the key solution proposed by this technique. The present study investigates the numerical feasibility of using liquid water, under six distinct solar concentration ratios, as a SSOF fluid for incident radiation on six types of PV cells with different spectral response ranges. For the 36 cases, the performance of PV and hybrid PV/T systems, represented as PV/Cooling fluid (PV/CF), with SSOF was evaluated and compared to their original performance without SSOF. In mid-July in Dhahran, Saudi Arabia, the functionality of each system was determined by analyzing the generated electrical and thermal energy over the course of a full day. In addition, the electrical efficiency and average PV temperature of the systems were estimated. In terms of spectral compatibility, the water SSOF was more compatible with three PV cells, out of the examined cells. At specified solar concentrations, depending on the engaged PV cell, the results demonstrated that integrating SSOF into the conventional PV and hybrid PV/CF systems produced more electricity at reduced PV temperatures, compared to the corresponding conventional system. In addition, the functionality was extended to increased solar concentrations. Due to the discrepancy in their spectral responses, the electrical energy and efficiency outputs of each cell type varied. When conventional systems were combined with SSOF, the spectral transmittance range of the liquid and the distinct spectral response ranges of the cells increased the number of possible combinations. p-Si and CIGS cells performed comparably in standalone PV and hybrid PV/CF systems, while CIGS and Perovskite cells performed comparably with SSOF. The m-Si and p-Si cells provided the most electrical energy and efficiency, while the a-Si cells were the least efficient, which thereafter influenced the selection of the highly functional system suitable for the PV cell type. At 8.2 suns and above, the hybrid SSOF/PV/CF system had the highest overall energy output and electrical efficiency, for all the examined cells, due to enhanced cooling and reduced solar radiation exposure.

Fundamental Mechanisms Behind the Reverse Characteristic of Cu(In,Ga)Se2 Solar Cells

Partial shading of PV modules can lead to degradation of the shaded cells. The degradation originates from a reverse bias voltage over the shaded cells. In order to mitigate reverse bias damage in Cu(In,Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) modules, a good understanding of the fundamental mechanisms governing the reverse characteristic is required. In this study, a model is introduced that describes this behavior for CIGS cells. In this model, the low and non-Ohmic leakage current is accounted for by the space charge limited current component. A sharp increase in current that is typically observed in the CIGS reverse characteristics can be described by Fowler–Nordheim tunneling. This model has been validated against measurements performed at different temperatures and illumination intensities, and is able to describe the dependencies of the reverse bias behavior on both temperature and illumination.

Routes for Metallization of Perovskite Solar Cells.

The application of metallic nanoparticles leads to an increase in the efficiency of solar cells due to the plasmonic effect. We explore various scenarios of the related mechanism in the case of metallized perovskite solar cells, which operate as hybrid chemical cells without p-n junctions, in contrast to conventional cells such as Si, CIGS or thin-layer semiconductor cells. The role of metallic nano-components in perovskite cells is different than in the case of p-n junction solar cells and, in addition, the large forbidden gap and a large effective masses of carriers in the perovskite require different parameters for the metallic nanoparticles than those used in p-n junction cells in order to obtain the increase in efficiency. We discuss the possibility of activating the very poor optical plasmonic photovoltaic effect in perovskite cells via a change in the chemical composition of the perovskite and through special tailoring of metallic admixtures. Here we show that it is possible to increase the absorption of photons (optical plasmonic effect) and simultaneously to decrease the binding energy of excitons (related to the inner electrical plasmonic effect, which is dominant in perovskite cells) in appropriately designed perovskite structures with multishell elongated metallic nanoparticles to achieve an increase in efficiency by means of metallization, which is not accessible in conventional p-n junction cells. We discuss different methods for the metallization of perovskite cells against the background of a review of various attempts to surpass the Shockley–Queisser limit for solar cell efficiency, especially in the case of the perovskite cell family.

Electrical Efficiency Increase in CPVT Collectors by Spectral Splitting

Concentrating photovoltaic-thermal (CPVT) collectors have to face the challenge of contrary temperature requirements in the single receiver parts. The PV cells require low temperatures to achieve high efficiency, whereas the thermal part should generate high temperatures for providing industrial heat. The approach of “Spectral Splitting” can offer a solution for compact CPVT receivers; however, a clear quantification of the expected conversion efficiency is difficult. Therefore, this paper describes a modelling methodology for obtaining electrical and thermal performance parameters for a Spectral Splitting configuration using semiconductor-doped glass combined with appropriate heat transfer fluid. The PV technologies c-Si, CIGS and CdTe are considered. The presented model yields distinct results for maximising the electrical efficiency, calculates the reduction in waste heat dissipation within the cells and assesses the impacts of concentration factor and cell temperature. An optimised configuration could be found with CIGS cells, impinged by a selected wavelength spectrum between 868 nm and 1100 nm, where the theoretical efficiency reaches 42.9%. The waste heat dissipation within the cells is reduced by 84.9%, compared to a full-spectrum operation. The depicted CPVT receiver design using bendable thin-film PV cells will be realised as a prototype in a subsequent project phase.

Effect of Buffer Layer on Cu (In, Ga)Se2 Solar Cell Performance

Search of sustainable energy resources is continued from the decades. The industrialization growth in various domains and socio-economic developments created huge demand of electrical power while the conventional resources are shrinking. This opens doors for research and developments in renewable energy resources such as, Solar, Wind, Hydro and Geothermal Energy sectors. Among these energy solar energy emerged as one of the sustainable energy resource. This research work targeted to improve the efficiency of thin film flexible Copper Indium Gallium Di-Selenide abbreviated as CIGS cell through optimization of buffer layer parameters. The proposed model used zinc sulphide (ZnS) as a potential buffer layer to make the solar cell free from toxic Cadmium (CdS) sulphide. Further the doping profile and width of buffer layers are investigated along with corresponding change in energy states and electrical permittivity of the material. The complete solar cell model is simulated using MATLAB scripting and SCAPS model. the results are compared with the existing result of CdS-CIGS. The ZnS-CIGS model is simulated with variation in thickness of buffer layer and optimized material parameters are determined.

Numerical optimization of ultrathin CIGS solar cells with rear surface passivation

We use Silvaco-TCAD tools to optimize ultrathin Cu (In1-xGax) Se2 solar cells with rear surface passivation. First of all, the single CIGS structure was performed and calibrated with the electrical and optical output of the experimental results. Based on the simulation and example results, considering the variety of carrier’s transport mechanism at the heterointerface CdS/CIGS shows a significant impact on cell performance. The proposed rear passivated ultrathin CIGS structure consists the following configuration: MgF2 (120 nm)/ZnO:Al (300 nm)/ZnO(100 nm)/CdS(50 nm)/CIGS(500 nm)/Al2O3/Ag/glass-substrate. The effect of the rear-passivated, absorber thickness (CIGS), and cell pitch on ultrathin CIGS cell performance is analyzed and studied under AM 1.5G, 1 sun illumination. This increases the model’s total implied photocurrent density from 21.1 to 29.1 mA/cm2. The simulations show that the ultrathin CIGS cell efficiencies of up to 13% can be obtained. The results from these simulations are compared with the measured characteristics of the fabricated cell.

A Review of CZTS Thin Film Solar Cell Technology

Copper Zinc Tin Sulfide (CZTS) solar cells have recently attracted attention as a potential low-cost earth abundant replacement for CIGS cells. This is due to their constituent’s Zn and Sn are non-toxic and earth-abundant compare to the elements of In and Ga in CIGS. Thus, aiming to analyse solar cells free from the environmental contaminant, CZTS is viewed as a potential candidate as the absorber for the next generation thin film solar cells. However, the conversion efficiency of CZTS based solar cells reported which is relatively low (highest conversion efficiency recorded is 12.5%) from the theoretical conversion efficiency limit of 32.2%. This is due to the low fill factor (FF), open circuit voltage (Voc) and current density (Jsc). In this study analysis of the different CZTS based solar cells and its synthesis methods will be reviewed. The effect of the compositional change and various structure in the CZTS, different buffer layers with their interfaces are thoroughly studied. The challenges regarding improving the conversion efficiency of CZTS solar cells and their future in the thin film solar cell application are discussed.

Graded bandgap nanostructured SnS-based photocells

Tin sulfide SnS, SnS2 thin films have been fabricated and investigated for solar cell application as prospective inexpensive and environmentally safe material. Today, SnSx-based single bandgap and tandem solar cell designs demonstrate promising results as environment-friendly and cheap alternative to common Si, CdTe, CIGS cells. To enhance further the solar spectrum utilization, the graded bandgap structures are preffered. The chemical deposition of tin sulfide films presents a low-cost and scalable processing for thin-film solar cells mass production. In the paper, the successive ionic layer adsorption and reaction (SILAR) technique was used to produce SnSx layers, including successive cyclic dipping into Na2S and SnCl2 + NaCl + triethanolamine solutions. The XRD measurements reveal the SnS, SnS2 layers formation with nanograins micromorphology. The optical transmission measurements show the variable bandgap values depending, presumably, on the nanograins size. In this study, we propose and analyse, using SCAPS code simulation, a simple graded bandgap heterostructure solar cell structure based on nanostructured bandgap-engineered SnS/SnS2 active layers showing conversion efficiency up to ~ 14% for non-graded and ~ 16% for graded bandgap heterostructure.

Self-aligned concentrating immersion-lens arrays for patterning and efficiency recovery in scaffold-reinforced perovskite solar cells

Unlike existing silicon, CIGS, and multi-junction cells that exhibit remarkable mechanical durability, perovskite solar cells have been shown to delaminate when subjected to the mechanical loads that occur during processing and field exposures, limiting their potential as a reliable solar technology. Mechanical reinforcement is thus essential for durable and reliable perovskite technologies. A recent strategy to overcome the thermomechanical fragility of perovskite solar cells is to extrinsically shield them by introducing reinforcing scaffolds which partition the cell into many distinct microcells, but improvements in mechanical stability coincide with a reduced device efficiency due to parasitic absorption by the scaffold. We address this reduced efficiency by integrating concentrating immersion-lens arrays (CILAs) into scaffold-reinforced solar cells. These scaffolds are lithographically patterned by a maskless process, in which ultraviolet light is used to pattern the scaffolds through the CILAs, ensuring self-alignment and optical contact with the microcells. This process creates mm-scale scaffold patterns with a line edge roughness of 17.5 ± 4.3 µm and line width roughness of 26.4 ± 8.5 µm. Perovskite devices are deposited into the microcells, and during operation, light is concentrated into the microcells and away from the insulating scaffolds, resulting in mechanically resilient solar cells with efficiencies comparable to planar devices. The devices with the strongest lenses—i.e., lower radius of curvature—recover up to 89 ± 15% of photocurrent and 91 ± 29% power conversion efficiency that would have been otherwise lost to parasitic absorption. Ray-tracing simulations of the CILAs also demonstrate passive tracking of incident light which is critical for optimal power output as the sun moves across the sky during the day. In these simulations, devices with CILAs showed improved passive tracking compared to devices without CILAs out to 60° off-normal. The UV stability of CILAs are experimentally verified through aging tests which show no change in their mechanical integrity after 1000 h of UV exposure. The simplicity of the fabrication process and the efficiency of the resulting scaffolded devices show that a lens-integrated scaffold-reinforced structure is a potential pathway to high-performance, robust, commercially viable perovskite solar cells.

Damage-free patterning of thermally sensitive CIGS thin-film solar cells: Can nanosecond pulses outperform ultrashort laser pulses?

Nanosecond pulses are usually not considered as a suitable candidate for low-damage processing of heat-sensitive materials due to high thermal effects and significant melt formation. Many studies have shown, that CIGS is thermally sensitive material and ultrashort lasers have been chosen as the primary source for the processing of CIGS cells. However, we report on the P3 scribing of CIGS thin-film solar cells with the ns pulse duration at the wavelength of 2.5 µm – a wavelength close to the mid-infrared region and compare the results with the ps pulses covering traditional wavelengths of 355 nm, 532 nm, 1064 nm, and 1342 nm. In our case, 6 ns pulses at 2.5 µm wavelength outperformed the picosecond laser sources operating at VIS and NIR wavelength range. The minimal P3 scribe conductivity of 4.7 mS/m was achieved for ns laser patterning, corresponding to simulated CIGS module efficiency loss of just 0.01%. We proposed that high absorption in the transparent conductive oxide - TCO efficiently shielded the underlying CIGS with only a fraction of energy reaching the back-contact. Finally, results show that nanosecond pulses can be as competitive as picosecond ones for P3 processing of high-efficiency CIGS devices.

Enhancing passive radiative cooling properties of flexible CIGS solar cells for space applications using single layer silicon oxycarbonitride films

Satellites in lower earth orbits have been primarily powered by photovoltaic modules. With growing power demand for new satellite concepts, solar cells are required to be flexible and ultra-lightweight to decrease launch costs. CIGS thin film solar technology is a promising candidate, since it can be manufactured on flexible substrates and possesses high radiation hardness. Poor radiative properties of CIGS on the other hand, lead to high temperatures and therefore power loss. High emissivity coatings on CIGS have already been reported but the influence on thermal and electrical aspects have not been addressed. Here we present the optical properties of silicon-oxycarbonitride coatings and their effect on electrical parameters on CIGS cells to be used for the DLR's GoSolAr power sail mission. We show that the single layer coating can significantly increase emissivity from 0.3 to 0.72, with minimal spectral losses and negligible impact on the functioning of the underlying CIGS cell. We simulated the thermal impact of the coating on solar cells in orbit and can predict that the maximum temperature of the cells is reduced by 30 °C, resulting in a significant power gain. Additionally, the coating has an emissivity of 0.87 in the atmospheric window of 8–13 μm making it a very good passive radiative cooler for terrestrial solar cells. The low-cost coating can replace glass and the process can be scaled up for large CIGS modules. The coating can also significantly increase the power to mass ratio of solar modules, reducing costs for space applications.

Enhanced Transmittance and Photoelectrochemical 2D Nanostructured N-Type Semiconductor ZnS Thin Film Prepared by One-Step Electrodeposition in a Non-Vacuum-Processed CIGS Cell

Two-dimensional N-type semiconductor nanostructured ZnS films for use in optical semiconductor applications were fabricated via a comparatively facile and low-cost electrodeposition method. Electrodeposition was carried out at a current density of 1.5 mA cm–2 at 60°C. ZnS was produced and deposited on the cathode, and crystalline grains developed. Subsequently, islands of discontinuous N-type semiconductor nanoparticles grew, which decreased the cathode conductivity to control the thickness of the film within the nanometer range. To characterize the structure, composition and chemical state of the nano-film, scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were employed. The results showed that the ZnS nano-film was successfully prepared, with uniform and dense surface morphology and a wurtzite structure. The 4-min electrodeposition resulted in a ZnS nano-film with thickness of 89.15 nm. The band gap of the ZnS nano-film of the N-type semiconductor was 3.75 eV.

Performance Enhancement Strategy of Ultra-Thin CIGS Solar Cells

In this article, numerical modeling and simulation using SCAPS-1D software has been used to explore the performance of CIGS-based solar cells when some parameters are modified. Starting from a baseline model that rigorously reproduces the experimental results, the absorber properties such as defect density, band-gap and acceptor concentration have been investigated and the optimal values to obtain high-efficiency CIGS-base solar cells have been proposed. The optimal parameters obtained are used to develop a new ultra-thin CIGS cell architecture. The results suggest that the use of 1000 nm Electron Back Reflector (EBR) layer with 1.3 eV band-gap at the CIGS/Mo interface provides higher electrical parameters than standard cells and materials such as MoS2, AgO, SnS, Cu2Te, CdSnP2, CuIn5S8, PbCuSbS3 can be successful EBR in ultra-thin CIGS solar cells. This optimized structure provides a serious pathway toward the development of ultra-thin cells with performance close to the best CIGS cells with standard thicknesses.

Performance Optimization of ZnS/CIGS Solar Cell with over 25% Efficiency Enabled by Using a CuIn3Se5 OVC Layer

Chalcopyrite CIGS solar cells have been demonstrated with the highest efficiency for thin-film solar cell families. Herein, the effects of thickness and bandgap of cadmium (Cd) free ZnS buffer layer grown on CIGS absorber with an ordered vacancy compound (OVC) at buffer/absorber interface in CIGS solar cell structure have been investigated using ADEPT 2.1 simulator. The ZnS buffer possesses a wider energy bandgap than the traditional CdS buffer layer, which substantiates the higher conversion efficiency of this solar cell, allowing the photons of lower wavelength into the CIGS layer. Besides, CuIn 3 Se 5 has been used as an OVC layer that assists to improve the conversion efficiency to an optimized level of over 25% by reducing the recombination rate. Moreover, the optimized short circuit current (J sc ) and corresponding open-circuit voltage (V oc ) yield a higher fill factor (FF) of 86.22%, which, therefore, results in an optimum efficiency of the CIGS cell estimated as 25.68% under AM 1.5 irradiance.