Enhancing the efficiency of Sb2(S,Se)3 thin-film solar cells via Li doping in close-spaced sublimation

•Li doping strategy enhances Sb2(S,Se)3 thin-film solar cells via close-spaced sublimation (CSS).•Molten salt treatment ensures uniform Li incorporation.•Improved conductivity and carrier transport boost device efficiency to 6.18%.•Offers new insights for high-performance antimony-based solar cells. Sb2(S,Se)3 is a promising photovoltaic material due to its tunable bandgap, high thermal stability, and low-cost production potential. However, films produced by close-spaced sublimation (CSS) often suffer from defects that reduce efficiency. In this work, lithium (Li) doping was introduced to improve crystal quality, carrier concentration, and conductivity. The lithium was incorporated into the sublimation source via molten salt treatment, resulting in a uniform Li-Sb2(S,Se)3 thin film. The resulting ITO/CdS/Li-Sb2(S,Se)3/PbS/Carbon solar cell achieved a power conversion efficiency of 6.18%, a significant improvement over undoped devices. The study further investigates the optoelectronic properties, revealing that Li doping effectively reduces non-radiative recombination, improves carrier extraction, and increases the valence band maximum (VBM), optimizing energy level alignment for enhanced hole transport. Additionally, the improved surface conductivity and higher carrier concentration due to Li doping contributed to enhanced carrier transport and reduced recombination.This research demonstrates that alkali metal doping can enhance the optoelectronic properties of Sb2(S,Se)3 films, providing a pathway for further efficiency improvements in antimony-based thin-film solar cells.