Interfacial Engineering towards Enhanced Photovoltaic Performance of Sb2Se3 Solar Cell

Abstract Antimony selenide (Sb 2 Se 3 ) is a kind of emerging candidate for the application in low‐cost and high‐efficiency thin film solar cells owing to its non‐toxicity, earth‐abundance, and unique quasi‐1D crystal structure. In this photovoltaic material, quasi‐vertically oriented Sb 2 Se 3 thin films can transfer photocarriers efficiently along the [ hk1 ]‐orientation. However, the crystal orientation control in thin films is still the main obstacle to improve the efficiency of Sb 2 Se 3 solar cells. Herein, an interfacial engineering method is developed by antimony chloride (SbCl 3 ) on CdS films with post‐annealing treatment to improve the quality of both interface and absorber thin film. It is found that the SbCl 3 treatment resulted in 1) transformation of the CdS/Sb 2 Se 3 interface from “cliff” to “spike” like energy band alignments; 2) improved surface morphology of CdS surface, and 3) suppressed cubic structure of CdS structure and thus generating improved [ hk1 ]‐oriented Sb 2 Se 3 film on the high‐purity hexagonal CdS. As a result, the Sb 2 Se 3 solar cell treated with SbCl 3 achieves a top efficiency of 6.89% in superstrate planar heterojunction Sb 2 Se 3 solar cell. This study provides a new interfacial post‐treatment method for the preparation of high‐performance Sb 2 Se 3 planar heterojunction solar cells.