Cadmium-free buffer layers are pivotal for the sustainable development of thin-film photovoltaics. This work numerically investigates SnS₂ as a high-performance, environmentally benign alternative to CdS for antimony selenosulfide (Sb₂(S,Se)₃) solar cells using AFORS-HET software. The SnS₂/Sb₂(S,Se)₃ heterojunction exhibits a significantly lower conduction band offset (CBO ≈ 0.23 eV) than its CdS counterpart (CBO ≈ 0.49 eV), which is identified as the primary factor for suppressed interface recombination and enhanced electron injection efficiency. A comprehensive optimization strategy is presented: tuning the S content in Sb₂(S,Se)₃ to 40% optimizes the trade-off between band gap widening and hole transport barrier at the ETL/absorber interface; adjusting the absorber thickness to 340 nm balances light absorption and carrier collection efficiency; and elevating the SnS₂ carrier concentration to 10²¹ cm⁻³ strengthens the built-in potential and induces a beneficial hole-blocking “spike” at the front contact. The synergistically optimized device achieves a power conversion efficiency (PCE) of 10.39%, a substantial improvement over the 7.56% efficiency of the CdS-based reference cell in our simulation framework.

CuSCN is a low-cost inorganic HTL with potentially better ambient stability than Spiro-OMeTAD according to literature. This study explores copper(I) thiocyanate (CuSCN) as a hole transport layer (HTL) to replace the conventional organic material Spiro-OMeTAD in antimony selenosulfide (Sb₂(S,Se)₃) solar cells. Numerical simulations performed with the Afors-het software reveal that the device structure FTO/CdS/Sb₂(S,Se)₃/CuSCN/Au incorporating CuSCN achieves improved interfacial energy band alignment. Specifically, the valence band offset (VBO) is reduced to −0.2 eV, which substantially enhances hole extraction efficiency and suppresses interface recombination. Through systematic optimization of key structural parameters, including the absorber layer thickness (350 nm), the CuSCN layer thickness (9 nm), and its p-type doping concentration (10¹⁹ cm⁻³), the device attains a maximum power conversion efficiency (PCE) of 12.03%. This work provides a theoretical foundation and a viable device design strategy for developing low-cost, highly stable, and efficient Sb₂(S,Se)₃ solar cells.