Pb-based hybrid perovskite solar cells, despite their advantages, face challenges in commercialization. In recent years, Bi-based chalcohalides are being considered as potential alternative candidates, however, their current device efficiency remains unsatisfactory. Herein, a two-step solution method is developed and applied to the fabrication of BiSI films. The method consists of the formation of Bi2S3 (step I) and its conversion to BiSI (step II). The Bi2S3 was fabricated by a thiol-amine solution process and the BiSI conversion was achieved by chemical reaction between the as-formed Bi2S3 and BiI3. It was found that the formation of BiSI was highly dependent on the Bi:S molar ratio of the Bi2O3-thiourea solution and the number of times of step I. The as-fabricated BiSI film had an optical band gap of 1.61 eV and exhibited nanorod morphology. In addition, the electronic structure is explored and discussed for solar cells applications.
Keywords: Bi2S3; BiSI; bismuth chalcohalides; solar cells; solution process; thiol-amine.