Concurrent Design of Alloy Compositions of CZTSSe and CdZnS Using SCAPS Simulation: Potential Routes to Overcoming VOC Deficit

Abstract

Solar energy is the most used renewable energy source. CZTSSe uses earth-abundant elements and has promising optoelectronic properties, resulting in becoming a viable alternative to thin film PV. This work provides design guidelines for CZTSSe-based solar cells, where CZTSSe has a tunable affinity and energy gap. The analysis is based on incorporating a ternary compound material to serve as an electron transport material (ETM). In this regard, CdZnS is a potential candidate that can be utilized as an electron transport layer whose affinity and energy gap can be tuned to adjust the band alignment at the ETL/CZTSSe interface. In order to design a high-efficiency solar cell, one has to tune both the ETL and absorber layers to have a suitable conduction band offset (CBO), thereby minimizing the non-radiative recombination which, in turn, boosts the power conversion efficiency (PCE). Thus, in our presented simulation study, we provide a codesign of alloy compositions of both the CZTSSe photoactive layer and the CdZnS ETL using SCAPS-1D simulation. It is found that using the codesign of alloy compositions of the ternary compound ETL and the absorber enhances the PCE by about 2% and, more importantly, overcomes the main issue in CZTSSe which is its open-circuit voltage (VOC) deficit. Furthermore, upon optimizing the thickness and doping of both the ETL and absorber layer, as well as the bulk defect of the absorber layer, a PCE of 17.16% is attained in this study, while the calibrated PCE based on a previously published experimental work was 12.30%.

Influence of Bulk Defect Density on the Efficiency of CIGS Based Photovoltaic Cell/Solar Cell

“…Literature confirms that impurities [32, 33, 35,] and defects [36,37] strongly influence properties of CIGS absorbers. Iimpurities or defects can be added to either increase conductivity or control charge carrier lifetime and recent studies reveals that defects are closely linked to film growth mechanisms in CIGS that include but are not limited to gravitational sedimentation [37], inertial impaction [38] and Brownian diffusion [39], mixed induction by turbulent flow [40], electrostatic precipitation [41], interception [42] and in part by elongation of particles [43]. Some impurities cause imperfections in a lattice crystal and end up acting as recombination sites which explains the reduction in photon absorption by the photocell.…”

Numerical Study and Optimization of CZTS-Based Thin-Film Solar Cell Structure with Different Novel Buffer-Layer Materials Using SCAPS-1D Software

“…The buffer layer aligns the bands between the CZTS and the window layer while also reducing flaws and interfacial strain caused by the window layer [20]. Among different buffer layer materials, cadmium sulfide (CdS) [21] [22], zinc sulfide (ZnS) [23] [24] and ternary alloy cadmium zinc sulfide (CdZnS) [25] [26] [27] have been attracted more attention to the researchers because of their unique optical and electrical properties suitable for thin-film solar cell structure. CdS has a bandgap of 2.42 eV so that absorbs photons with wavelengths less than 590 nm, therefore covering 24% of the solar spectrum.…”