Designing Atomic Interface in Sb2 S3 /CdS Heterojunction for Efficient Solar Water Splitting

Abstract

In the emerging Sb₂ S₃ -based solar energy conversion devices, a CdS buffer layer prepared by chemical bath deposition is commonly used to improve the separation of photogenerated electron-hole pairs. However, the cation diffusion at the Sb₂ S₃ /CdS interface induces detrimental defects but is often overlooked. Designing a stable interface in the Sb₂ S₃ /CdS heterojunction is essential to achieve high solar energy conversion efficiency. As a proof of concept, this study reports that the modification of the Sb₂ S₃ /CdS heterojunction with an ultrathin Al₂ O₃ interlayer effectively suppresses the interfacial defects by preventing the diffusion of Cd²⁺ cations into the Sb₂ S₃ layer. As a result, a water-splitting photocathode based on Ag:Sb₂ S₃ /Al₂ O₃ /CdS heterojunction achieves a significantly improved half-cell solar-to-hydrogen efficiency of 2.78% in a neutral electrolyte, as compared to 1.66% for the control Ag:Sb₂ S₃ /CdS device. This work demonstrates the importance of designing atomic interfaces and may provide a guideline for the fabrication of high-performance stibnite-type semiconductor-based solar energy conversion devices.

Keywords: Al2O3 interlayer; Sb2S3/CdS heterojunction; defect passivation; interface engineering; photoelectrochemical water splitting.