Indium oxide as a high-performance ETL for CuInS₂ thin-film solar cells

This paper presents an extensive numerical analysis of CuInS₂-based thin-film solar cell design incorporating indium oxide (In₂O₃), used as a cadmium-free electron transport layer (ETL). In₂O₃, with its wide bandgap, high electronic mobility, and chemical stability, offers an eco-friendly alternative to conventional CdS, TiO₂, and SnO₂ ETLs. The proposed Al/FTO/In₂O₃/CuInS₂/a-Si:H/Ni structure was optimized through SCAPS-1D simulations by varying absorber thickness, doping concentration, defect density, and operating temperature. This study identifies an optimal absorber thickness of ∼1 μm. While higher doping improves open-circuit voltage and fill factor, excessive defect density induces Shockley–Read–Hall recombination, degrading performance. Temperature-dependent simulations highlight the need for effective thermal management to mitigate carrier lifetime and efficiency losses at elevated temperatures. The optimised device structure shows a peak power conversion efficiency of 29.79%, indicating that In₂O₃ has significant promise as a high performance, environmentally friendly ETL in the next generation of CuInS₂ thin-film photovoltaics.