Numerical investigation and experimental validation of CFTS/CdS heterojunction solar cells via structural and material parameter optimization using SCAPS-1D

Abstract In this research, p-type Cu 2 FeSnS 4 (CFTS) thin-film solar cells were fabricated using a cost-effective chemical spray pyrolysis technique with a p-CFTS/n-CdS/FTO architecture. The as-deposited CFTS films exhibited a tetragonal stannite phase with an average crystallite size of 18 nm and a direct bandgap of 1.54 eV. Experimental performance showed an efficiency of 5.23% for a 510 nm absorber thickness. To explore the theoretical potential, a comprehensive optimization was conducted using SCAPS-1D, focusing on absorber/buffer thickness, bandgap grading, and carrier concentration. The optimization identified a critical absorber thickness of 5.0 μm to maximize photon absorption while minimizing recombination. The ultimate simulated device achieved a benchmark efficiency of 25.52%, with V OC of 1.17 V and J SC of 26.89 mA/cm 2 , providing a roadmap for future experimental scaling of CFTS-based photovoltaics. Graphical abstract