Efficiency Of CIGS Solar Cells Research Articles

Impact of graded CIGS absorber layer on Cd-free CIGS thin-film solar cell performance: numerical optimization

Abstract This paper investigates replacing the CdS buffer layer with (Zn, Mg)O and Zn(S, O) double buffer layers. To increase the efficiency of the structure, our strategy involves numerically studying and comparing three types of CIGS bandgap absorber layers: FB (Flat Band), Double Gradient Bandgap (DG) with a high bandgap near the Mo contact (back side), a low bandgap near the buffer layer (front side), and a minimum bandgap between them, and Simple Gradient Bandgap (SG) with a high bandgap near the Mo contact (back side) and a low bandgap near the buffer layer (front side). Each type features different linear graded profiles in the thickness direction to determine the optimal bandgap gradient of the CIGS layer. The performance of the three types is numerically analyzed using the SCAPS-1D simulator. Simulation enables us to test multiple structural combinations efficiently, saving both time and money, while providing results that guide experimental research. The proposed device structure is composed of the following layers: ZnO:Al/n-Zn1-xMgxO/n- ZnSxO1-x/p- Graded-CuIn1-xGaxSe2 /Mo. To study the effects of linear bandgap gradient distribution of Ga⁄((Ga+In) ) ratio according to the thickness direction on CIGS solar cell performance, the electrical properties of the proposed CIGS model were initially matched with experimental data to confirm the structure's accuracy. It was found that the Double Gradient Bandgap (DG), with maxima of 1.44 eV at the back side (near Mo contact), 1.238 eV at the front side (near n-type buffer layer interface), and a minimum of 1.154 eV at a position of 1.7 µm from the back side, has a higher efficiency than the other structures with 26.22% (Voc = 0.8134 V, Jsc = 37.82 mA/cm², FF = 85.21%). Optimizing the bandgap gradient of the CIGS absorber layer helps improve the efficiency of CIGS solar cells. 

Increasing the efficiency of CIGS solar cells due to the reduced graphene oxide field layer of the back surface

Copper indium gallium selenide solar cells (CIGS-SCs) have gained attention due to their cost-effectiveness and environmentally friendly characteristics, making them a promising option for future electricity generation. The efficiency of CIGS-SCs can be enhanced by adding a back surface field layer (BSFL) under the absorber layer to reduce recombination losses. In this study, the electrical parameters, such as the series resistance, shunt resistance, and ideality factor, are calculated for CIGS-SCs with an advanced design, using the SC capacitance simulator (SCAPS) software. The detailed model used in the simulations considers the material properties and fabrication process of BSFL. By utilizing a reduced graphene oxide (rGO) BSFL, a conversion efficiency of 24% and a significant increase in the fill factor are predicted. This increase is primarily attributed to the ability of the rGO layer to mitigate the recombination of charge carriers and establish a quasi-ohmic contact at the metal-semiconductor interface. At higher temperatures, BSFL can become less effective due to an increased recombination and, in turn, a decreased carrier lifetime. Overall, this study provides valuable insights into the underlying physics of CIGS-SCs with BSFL and highlights the potential for improving their efficiency through advanced design and fabrication techniques.

Designing novel plasmonic architectures for highly efficient CIGS solar cells

CIGS solar cells is one of the best thin film solar cells which have efficiency up to 22.6 %. In the recent decades, a lot of attention has been drawn to the methods of increasing solar cells efficiencies. One of the emerging technology for enhancing thin film solar cell efficiencies are using plasmonic effects in the visible or infrared part of the electromagnetic spectrum. Therefore, the primary goal of this study is to use plasmonic nanostructures in the active layer to enhance the absorption and consequently the efficiency of a thin film CIGS solar cell with a 1000 nm thickness. Different factors such as type of material, size and surface occupied with nanostructure can be effect on CIGS solar cell performance. In this research, the solar cell has been optically and electrically characterized in the presence of plasmonic nanostructure by simulations. The efficiency was determined by characteristics parameters such as absorption, quantum efficiency, electron-hole generation rate, current–voltage curve and power-voltage curve. Based on our simulations, the maximum efficiency of 25.61 % was achieved using gold nanocubic structures with dimensions of 100 nm, Occupied Factor of 0.16, positioned at the top of the active layer. This increase is due to increase in optical path of length of scattered light and consequently its absorption in the active layer. Moreover, enhancing carrier generation, decreasing recombination and improving carrier separation can be occurred due to localized surface plasmon resonance and the near-field distribution effect, which effectively scatter light into the active layer.

Erratum to Boosting Efficiency of CIGS Solar Cell by Ferroelectric Depolarization Field

Erratum to Boosting Efficiency of CIGS Solar Cell by Ferroelectric Depolarization Field

Investigation on the diffusion mechanism of Ga element and regulation of the V-shaped bandgap in CIGS thin films based on magnetron sputtering with a quaternary target

Gradient bandgap engineering has been acknowledged as an effective approach for improving the efficiency of CIGS solar cells. However, an effective method for achieving gradient bandgap engineering in quaternary sputtered CIGS films has not yet been identified.This is due to the uniform and singular nature of the quaternary target composition, as well as the complex kinetic mechanisms that result in the rearrangement of film elements (particularly Ga) during the annealing process. In this study, a grain boundary migration-driven diffusion mechanism for the Ga element in CIGS thin films was established to address the presented issue. The segregation of Ga element is believed to be caused by the flow velocity field generated from the migration of grain boundaries, and the distribution of Ga element can be precisely calculated using the mass transport equation. By modulating the V-shaped bandgap, a notable enhancement in open-circuit voltage (Voc) was achieved, with an increase from 0.405 V to 0.515 V, leading to an effectively improvement of solar cell's efficiency. By comparing and analyzing the actual performance parameters of the solar cells and the simulated results, we conclude that the increase in Voc is due to the alteration in bandgap structure. This study presents a novel approach to bandgap engineering in quaternary sputtered CIGS films through the quantitative calculation of Ga element distribution.

Theoretical analysis of introducing CeOx as a passivation layer: an innovative approach to boosting CIGS solar cell efficiency

In this paper, we present a novel structure, AZO/CeOx/SnS2/CIGS/a-Si/Ag., simulated using SCAPS-1D. The structure features CeOx as a passivation layer, integrates SnS2 as an auxiliary absorber layer alongside the primary CIGS layer, and employs a-Si as a buffer layer. Our investigation focuses on evaluating the impact of material parameters on various electrical characteristics such as open-circuit voltage (Voc), short-circuit current (Jsc), efficiency (η), and fill factor (FF). We analyze the influence of layer thickness on the aforementioned characteristics and scrutinize the effects of temperature variation and series resistance on cell performance. After detailed calculations, we found that optimizing these parameters led to excellent performances, achieving an efficiency of 30.11%. This achievement was obtained under specific conditions, including the following layer thicknesses: CeOx (0.7 μm), CIGS (1.2 μm), and a-Si (0.1 μm), along with an optimal temperature of 302 K. This study aims to provide valuable insights to device manufacturers for enhancing the efficiency of CIGS solar cells.

Boosting Efficiency of CIGS Solar Cell by Ferroelectric Depolarization Field

AbstractIncreasing the electric field in a solar cell is of importance to alleviate the carrier recombination and thus to increase the power conversion efficiency (PCE). In this paper, a strategy is reported to enhance the internal electric field of Cu(In,Ga)(Se,S)2 (CIGS) solar cells by inserting a ferroelectric BaTiO3 (BTO) layer into the device for the first time. The BTO location in the CIGS solar cell is found to play a vital role in the performances, which is due to the adjustment of the direction of BTO depolarization field. Impressively, the PCE is increased from 4.83% to 16.07% when the BTO depolarization field direction shifts from the opposite to the same direction to the p–n junction electric field. The improved PCE is due to the enhanced open‐circuit voltage (Voc), which suppresses carrier recombination and thus boosts the short‐circuit current density (Jsc) from 14.09 to 32.69 mA cm−2. These results unlock an effective strategy to improve the PCE of a CIGS solar cell by the application of a ferroelectric depolarization field. The facile deposition of BTO via sputtering method at room temperature enables its wide application in other solar cells to boost the PCEs.

Investigation of the effect of different back contacts on the growth and efficiency of cigs solar cells

Herein, 〖Cu(In〗_(1-x) Ga_(1-x))(〖S,Se)〗_2 films were successfully deposited onto different back contacts: fluorite tin oxide (ITO), Indium doped Tin Oxide (FTO), and Molybdenum Mo by spray pyrolysis technique. The effect of back contacts on the structural and optical properties of CIGS was investigated. The X-ray patterns reveal crystalline phases with preferred phase orientations (112), (220), (220/214), and (312/116) for the different samples and a (110) phase of MoS2, particularly for the molybdenum back contact. SEM showed good crystallinity of the deposit films, especially for CIGS deposited at FTO back contact shows less porosity, homogenous surface, and good crystal size. Optical analyses for different back contacts provided bandgaps of 1.2 eV, 1.4 eV, and 1.64 eV for the films deposited on Mo, FTO, and ITO, respectively. SCAPS-1D simulator was used to exhibit the electrical characteristics of each cell according to the CIGS-deposition results. Among the different back contacts used, Mo showed the best efficiency of 22.93%. For FTO and ITO back contacts, the additional interfacial layer (MoS2 or MoSe2) between the absorber and the back contact shows an improvement in the efficiency from 22.59% to 23,97% and from 13.8% to 14.05%, respectively.

Effect of Temperature to Fabrication Cigs Solar Cell Using the Sputtering Method

Copper-indium-gallium diselenide (CuInGaSe2) or CIGS is one of the most promising materials for thin film solar cell applications. CIGS solar cells were deposited by sputtering method on ZnO/ZnS/CIGS/Mo arrays. Various parameters in sputtering greatly influence the efficiency of CIGS solar cells such as temperature. Thermal parameters are used to compare the effect of the CIGS layer on optimizing the efficiency of CIGS solar cells. The results show that the CIGS layer deposited using temperature has a crystalline structure, besides that the resulting efficiency is also higher than CIGS solar cells deposited without temperature, namely 0.177%.

First investigation into the physical characteristics of GO-Doped CuO-ZnO thin films as a secondary absorption layer in CIGS solar cells

In this work, undoped and graphene oxide (Go) doped CuO-ZnO mixed oxide thin films were deposited on glass substrates by spray pyrolysis technique. The effect of doping concentration on the physical properties of the deposited layers, had been investigated. XRD results of graphene doped CuO-ZnO mixed oxide flms show crystallized graphene phase for high doping percentage of 8 %. The morphological characterization revealed a good homogeneity at the surface with good dispersion of graphene nanoparticles over the entire surface. Optical measurements indicated an increase in transmission and in the band gap energy up to 75 % and 2.75 eV, respectively, occurring as the doping rate increased to the values. The new graphene oxide (Go) doped CuO-ZnO mixed oxide thin films were used to improve the efficiency of CIGS solar cell. The new simulated solar cell FTO/ZnO/CdS/CZO:Go /CIGS/MO,With CZO:Go /CIGS represent the double absorber layer, was studied. An increase in efficiency from 21.5 to 29.68 % was achieved after adding CZO:Go as a second absorber layer which can be explained by the possibility of the second absorber layer to absorb more photons and by band gap engeneering structure of the proposed solar cell.

Chemical Trend of Nonradiative Recombination in Cu(In,Ga)Se2 Alloys

Understanding nonradiative recombination is important for improving semiconductor devices. For Cu(In,Ga)Se${}_{2}$ (CIGS) solar cells, antisite defects have long been considered the main recombination centers, yet the underlying mechanism has remained elusive. Here first-principles calculations show that these ``killer centers'' themselves cannot capture holes efficiently for effective recombination. However, internal conversion to the distorted neutral DX center does open an efficient hole-capture pathway, and DX's stability in CIGS increases with Ga concentration, which resolves the longstanding issue of why the efficiency of CIGS solar cells decreases at high Ga concentration.

Effects of annealing temperature and atmosphere on performances of Zn0.9Mg0.1O buffer layers for CIGS solar cell

Zn 0.9 Mg 0.1 O (ZMO) thin films were fabricated by magnetron co-sputtering without substrates heating. Annealing process was introduced to reduce the defect density and improve the photoelectric performances. The effects of annealing temperature and atmosphere on the crystallization, defect density, and photoelectric performances of ZMO films were investigated. The variation mechanisms for intrinsic point defects in ZMO films during the annealing process were discussed. The results show that annealing reduces the defect-bound emission and improves the crystallization. And annealing promotes the desorption of adsorbed oxygen and the diffusion of oxygen in air. Besides, the near-band-edge emission peak shifts to shorter wavelengths and the band gap ( E g) increases, which should be attributed to the changes in the position of Mg atoms. And the common increase of the Hall mobility and carrier concentration of the ZMO films, which leads to a decrease in the resistivity. Finally, after annealing in air and Ar atmosphere, the resistivity of ZMO films is 63.8 and 2.2 Ω.cm, and the value of E g is 3.42 and 3.39 eV, respectively. And based on the performance optimization of ZMO films, the efficiency of CIGS solar cells with ZMO buffer layers reaches up to 12.9%. These results are helpful for the application of ZMO buffer layers on CIGS solar cells to improve cell efficiency.

Optical simulation and investigation of different coating methods CdS&TiO2 for buffer layer in CIGS solar cell efficiency

Optical simulation and investigation of different coating methods CdS&TiO2 for buffer layer in CIGS solar cell efficiency

Performance optimization of single graded CIGS absorber and buffer layers for high efficiency: A numerical approach

We present a numerical simulation based study of single graded Cu(In,Ga)Se2 (Copper Indium Gallium Diselenide) thin film solar cell. In this work, initially a basic CIGS single graded cell structure is optimized in terms of thickness, band-gap and doping concentration. CdS is kept as the buffer layer, which is widely used for high efficiency CIGS solar cells. In the next step, CdS is replaced with ZnMgO as the buffer layer in order to exploit its greater photon absorption ability due to its higher band-gap which further enhances the cell efficiency. A thorough analysis is carried out on the solar cell parameters open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and quantum efficiency (η) of the photovoltaic cell structure. An intermediate layer of p-type MoS2 is inserted in between the single graded CIGS absorber layers. The objective is to limit the unintentional Ga inter diffusion and maintain the desired grading during the high temperature annealing for the absorber preparation. The power conversion efficiency of the bilayer device structure with Ga fraction x=(0.31) of the top absorber layer along with Ga fraction y=(0.25) of the bottom absorber layer exhibits an improved efficiency from 24.02% (CdS as the buffer layer) to 25.37% (ZnMgO as buffer layer). An excellent power efficiency of η = 26.78% is reported after adding the intermediate layer of p-type MoS2 and optimizing its thickness and the carrier concentration.

Impact of doping concentration, thickness, and band-gap on individual layer efficiency of CIGS solar cell

An investigation with the individual layer physical property of the CIGS solar cells is a significant parameter to design and fabricate highly efficient devices. Therefore, this work demonstrates the thickness and carrier concentrations doping dependence simulations using SCAPS 1D software. The optimized CIGS solar cells different layer properties such as short-circuit current density ([Formula: see text], open-circuit voltage ([Formula: see text], Fill Factor (FF) and conversion efficiency ([Formula: see text] with varying thickness and doped concentration are presented. This optimized layer by layer simulation work would be useful to build a suitable CIGS solar cell structure. This simulation investigation showed that an optimal CIGS device structure can be fabricated possessing the configuration of a window layer ZnO : Al thickness 0.02 [Formula: see text]m, ZnO layer thickness 0.01 [Formula: see text] m with [Formula: see text] = 10[Formula: see text] cm[Formula: see text] and [Formula: see text] = 10[Formula: see text] cm[Formula: see text], a CdS buffer layer thickness 0.01 [Formula: see text]m with [Formula: see text] = 10[Formula: see text] cm[Formula: see text] and absorber layer CIGS in the thickness range of 1–4 [Formula: see text]m with the doping level range [Formula: see text] = 10[Formula: see text]–10[Formula: see text] cm[Formula: see text], along with the optimal CIGS energy bandgap range of 1.3–1.45 eV. According to optimized simulation results, a CIGS solar cell device can possess electric efficiency 26.61%, FF 82.96%, current density of 38.21 mA/cm2with the open circuit voltage 0.7977 eV. Hence, these optimized simulation findings could be helpful to provide a path to design and fabricate highly efficient CIGS solar cells devices.

Unraveling the cause of degradation in Cu(In,Ga)Se2 photovoltaics under potential induced degradation

AbstractCopper indium gallium diselenide (CIGS) based technology is actively competing in the global photovoltaic market with high conversion efficiency. Commercial CIGS modules are anticipated to perform on rated output in the field condition for 20 years. Potential induced degradation (PID) is considered as one of the critical concerns among all the current reliability assessment issues. PID accelerated tests have been performed on pre‐commercial CIGS modules to investigate reduction in electrical performance. We report the severe reduction in electrical performance after PID is correlated to the microstructural and chemical properties of the constituent materials. Under extreme PID stress, the cell surface reveals various defects including crater formation. The aim of this article is to explore the consequences of PID induced craters on the efficiency of CIGS solar cells by investigating material degradation kinetics. In this perspective, we present the root cause of PID in CIGS thin‐film modules in relation to microstructural defects by detailed investigation using J‐V analysis, field emission scanning electron microscope (FESEM), Raman spectroscopy, X‐Ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). This analysis can provide more effective and sustainable research strategies to cultivate more efficient and reliable CIGS technologies in the long run.

Structure engineering of solution-processed precursor films for low temperature fabrication of CuIn(S,Se)2 solar cells

Fabrication of flexible Cu(In,Ga)(S,Se)2 (CIGS) thin-film solar cell via precursor solution is a promising approach due to its perfect compatibility with roll-to-roll production. So far, polyimide (PI) is the most suitable substrate for flexible CIGS solar cell because of many advantages such as low cost, light weight, good insulativity and free of metallic impurities. However, PI has not been used in solution-processed approach because PI cannot tolerate the annealing process (selenization) at high temperature (≥550 °C) which is normally required for most of highly efficient CIGS solar cells fabricated via precursor solution. Here, we report low temperature (450 °C) fabrication of CuIn(S,Se)2 (CISSe) absorber by carefully engineering the structure of solution-processed precursor film. By adding extra Cu2S into solution-processed CuInS2 (CIS) precursor films through structure engineering of Mo/In2S3/Cu2S (bilayer), Mo/CIS/Cu2S/(CIS/Cu2S)3/CIS (multilayer), enough Cu2−xSe is formed in low temperature selenization which facilitates the formation process of CISSe absorber. Characterizations using XRD, Raman, SEM and EDX show that absorbers fabricated from precursor films with new structures favor the sufficient selenization, resulting in much better morphology and higher photovoltaic performance than the absorber fabricated from precursor film with normal structure of Mo/CIS (single layer). After preliminary optimization, efficiencies of 5.01% and 6.13% have been achieved in CISSe solar cells fabricated from precursor films with new structures which is only 3.83% from normal structure. Our results demonstrate the feasibility of fabricating efficient chalcopyrite solar cells via precursor solution in low temperature selenization.

Analysis of the Heavy Alkali Element Postdeposition Treatment: Which Factors Determine the Electronic Structure and Transport Properties of the Heterojunction in CIGS Thin Film Solar Cells

The remarkable efficiency of CIGS solar cells has been continuously broken in recent years due to the postdeposition treatment of heavy alkali elements (Alkali-PDT). At present, a large number of e...

Influence of back surface field layer on enhancing the efficiency of CIGS solar cell

The main objective of this research work is to improve the efficiency of conventional baseline structured CIGS solar cells by adding a Back surface field (PbS) layer between the CIGS absorber and the Mo back contact. The possible effect of the p-PbS layer on the photovoltaic parameters of the CIGS thin-film solar cell has been investigated by SCAPS-1D. The simulation of J-V characteristics showed that conversion efficiency of the conventional solar cell (Al/ITO/Al-ZnO/i-ZnO/CIGS/Mo/Substrate) is 22.67% (3 µm CIGS layer) and an improved conversion efficiency of 24.22% has been gained after adding the BSF (PbS) layer. The PbS layer between CIGS and Mo back contact provides an additional hole tunneling action that form a quasi ohmic contact from a schottkey type near the back region and this quasi ohmic contact improves the efficiency of carrier collection as well as BSF action reduces the back surface recombination. Besides thickness, energy band gap, electron affinity of the PbS layer were varied and optimized. Again, operating temperature on the overall performance of the proposed solar cell was also investigated. These findings are very promising for future performance and cost effective solar cell.

Optimization of Ga content gradient in Cu(In,Ga)Se<sub>2</sub> solar cells through machine learning and device simulation

Cu(In,Ga)Se<sub>2</sub> (CIGS) solar cell is a kind of highly efficient thin film solar cell, for which Ga ratio (Ga/(Ga+In), GGI) gradient engineering is an efficient approach to achieving high open circuit voltage under no short circuit current loss. In this work, we firstly evaluate the room and the strategies for improving the device performance of the CIGS solar cells based on the comparison among their theoretical efficiency limits. Then we investigate the different schemes of “V” type GGI gradient and their effects on device performance through machine learning and device simulation. Based on these studies, we optimize the scheme of “V” type GGI gradient and obtain a high efficiency of 26% from device simulation. The carrier kinetics for the effect of modifying GGI gradient on device performance are analyzed. This work provides an approach to optimizing the GGI gradient to obtain highly efficient CIGS solar cells, which is referable for experimental optimization.