Optimisation of Sb₂S₃ thin-film solar cells via Sb₂Se₃ post-treatment

In this work, Sb₂S₃ thin films are prepared by Vapour Transport Deposition (VTD) and solar cell devices with the superstrate structure of ITO/CdS/Sb₂S₃/Au are fabricated. In particular, an effective Sb₂Se₃ post-treatment method is developed for the optimisation of Sb₂S₃ thin-film cells without modifying the Sb₂S₃ main structure and phase. A device efficiency of 4.02% is reached by optimising the time of Sb₂Se₃ post-treatment with the augment of short-circuit current density (J_sc) and fill factor (FF). Comparative studies of the electrical properties, carrier transport, and carrier recombination of cells with and without Sb₂Se₃ post-treatment are carried out in detail, including current density versus voltage (J-V) measurements under both light and dark conditions, energy-dispersive X-ray spectroscopy (EDX), deep-level transient spectroscopy (DLTS), and open-circuit voltage measurements at various temperatures and light intensity levels. The best-performing cells are Sb₂Se₃ post-treated cells, which have the least amount of parallel current pathways, the smallest amount of trap-assisted recombination, longer carrier lifetimes, and a benign distribution of elements with S-rich features. This study provides a unique strategy for realising the greater potential of chalcogenide thin-film solar cells.