Exploring the photovoltaic potential of CuSbS ₂ using SCAPS-1D and DFT simulations

Abstract As the world accelerates its shift toward cleaner, renewable energy, the pursuit of cost-effective, eco-friendly, and highly efficient thin film photovoltaics (TFPV) has become more urgent than ever. In this race, copper antimony sulfide (CuSbS 2 ) stands out with its high absorption coefficient, abundant availability, and low-cost making it a suitable candidate for use as a thin-film absorber layer. However, CuSbS 2 solar cells currently achieve only around 3% efficiency, which is far from sufficient. The challenges lie in improper band offsets, high defect densities in the absorber layer, and suboptimal back metal contacts, all of which hinder the efficiency of CuSbS 2 (CAS) solar cells. In this work, the structural, electronic and optical properties of the CuSbS 2 absorbing layer were thoroughly examined through formation energy, band structure, density of states calculations and absorption coefficient. These analyses reveal that CuSbS 2 is a highly promising photovoltaic material, thanks to its optimal direct electronic band gap. The initial simulations closely matched experimental results, providing a solid foundation for further analysis. Optimizing conduction and valence band offsets, along with the thickness and carrier density in the buffer and hole transport layers, led to an impressive efficiency jump from 3.22% to 9.56%. This study delved into how the thickness, carrier density, and defect concentration in the bulk absorber affect photovoltaic performance, uncovering vital correlations that boost efficiency. Finally, fine-tuning the series and shunt resistance and optimizing the back contact work function resulted in a dramatic improvement, achieving an impressive overall efficiency of 19.23%.