Simulation and Optimization of CdTe and CIGS Thin-Film Solar Cells with Dual ETLS (CdS, ZnO) Using SCAPS-1D: A Comparative Approach

Abstract

Thin-film solar cells offer promising alternatives to crystalline silicon photovoltaics, combining reduced material consumption with flexibility and cost-effectiveness. Among them, cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) remain the most commercially successful technologies, though their performance depends strongly on structural and electronic parameters. This work employs SCAPS-1D simulations to investigate CdTe- and CIGS-based devices incorporating two electron transport layers (ETLs), cadmium sulfide (CdS) and zinc oxide (ZnO). The analysis explores absorber and ETL thickness, doping concentration, interface defect density, and bulk defect density. Baseline simulations show that CdTe devices achieved efficiencies of 18.7% (Voc = 0.59 V, Jsc = 43 mA/cm²), while CIGS devices reached up to 35.1% efficiency (Voc = 1.37 V, Jsc = 28 mA/cm²). Correlation studies reveal that CdTe efficiency improvements are mainly linked to doping-driven increases in Voc and FF, whereas CIGS efficiency is governed by Jsc enhancements from optimized thickness. CdTe demonstrated tolerance to interface and defect variations, in contrast to CIGS, which exhibited efficiency collapse under high recombination conditions. The novelty of this study lies in its comparative and integrated optimization of CdTe and CIGS using two ETLs under identical SCAPS-1D conditions, bridging a gap in prior literature where these absorbers are typically studied separately. The findings highlight a trade-off: CIGS provides higher efficiencies but requires strict defect and interface control, while CdTe offers robustness under fabrication variability. These results inform both material selection and device engineering strategies for advancing scalable thin-film photovoltaic technologies.