Designing Atomic Interface in Sb₂S₃/CdS Heterojunction for Efficient Solar Water Splitting

AbstractIn the emerging Sb2S3‐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 Sb2S3/CdS interface induces detrimental defects but is often overlooked. Designing a stable interface in the Sb2S3/CdS heterojunction is essential to achieve high solar energy conversion efficiency. As a proof of concept, this study reports that the modification of the Sb2S3/CdS heterojunction with an ultrathin Al2O3 interlayer effectively suppresses the interfacial defects by preventing the diffusion of Cd2+ cations into the Sb2S3 layer. As a result, a water‐splitting photocathode based on Ag:Sb2S3/Al2O3/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:Sb2S3/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.