Interfacial Engineering towards Enhanced Photovoltaic Performance of Sb2Se3 Solar Cell

Antimony selenide (Sb2Se3) 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 Sb2Se3 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 Sb2Se3 solar cells. Herein, an interfacial engineering method is developed by antimony chloride (SbCl3) on CdS films with post-annealing treatment to improve the quality of both interface and absorber thin film. It is found that the SbCl3 treatment resulted in 1) transformation of the CdS/Sb2Se3 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 Sb2Se3 film on the high-purity hexagonal CdS. As a result, the Sb2Se3 solar cell treated with SbCl3 achieves a top efficiency of 6.89% in superstrate planar heterojunction Sb2Se3 solar cell. This study provides a new interfacial post-treatment method for the preparation of high-performance Sb2Se3 planar heterojunction solar cells.