Zinc Chloride-Treated Indium Sulfide as Buffer Layer for Cd-Free Antimony Selenide Solar Cells

In2S3, as a promising environmentally benign semiconductor, is used as a buffer layer in thin-film solar cells due to its high electron mobility, low toxicity, and excellent thermal and chemical stability. The preparation of a high-quality In2S3 film is crucial for the improvement of its carrier extraction ability and subsequent deposition of absorber layers. Herein, it is demonstrated for the first time that a posttreatment of In2S3 film with ZnCl2 solution is able to serve as buffer layer for constructing superstrate Sb2Se3 solar cells. The posttreatment with ZnCl2 not only prevents In2S3 from excessive oxidation during annealing process, but also facilitates the growth of (hk1) orientation of Sb2Se3, thereby improving the interfacial contact of In2S3/Sb2Se3. The improved heterojunction quality suppresses the carrier recombination at the interface, and enhances the charge extraction ability of In2S3. As a result, the power conversion efficiency of Sb2Se3 solar cell increases from 2.63% to 5.00%. Herein, a facile and effective strategy is provided for the application of In2S3 as the buffer layer in inorganic chalcogenide solar cells.