A method for forming SbSI thin films is formed. In the first step of the method, a substrate (14) is provided. Next a buffer layer (16) is formed on the substrate (14). Then, a SbSI source (12) is provided. The SbSI source (12) and buffer layer (16) with substrate (14) are placed in an ampoule (10). The ampoule is heated in a two-zone furnace (11). This causes the SbSI source (12) to form a vapor which reacts with the buffer layer (14) to form a thin film of SbSI.