Vapor-phase iodination of CdS/Sb2S3 interface for enhanced performance of Sb2S3 solar cells

Antimony sulfide (Sb 2 S 3 ) shows promising potential as a light-absorbing material for thin-film solar cells owing to its quasi-one-dimensional structure and excellent photoelectric properties. However, the performance of Sb 2 S 3 solar cells is limited by various material defects and interfacial energy-level misalignment, resulting in a power conversion efficiency far below the theoretical limit. The interface characteristics between CdS and Sb 2 S 3 are considered to significantly influence these factors and, consequently, the overall device performance. In this work, a vapor-phase iodization process was applied to the CdS film to obtain a high-quality CdS/Sb 2 S 3 heterojunction interface. This process reduces the roughness and improves the hydrophilicity of CdS films, providing favorable conditions for the subsequent deposition of Sb 2 S 3 films. Furthermore, it passivates surface defects of CdS and optimizes the energy band alignment at the CdS/Sb 2 S 3 junction, thereby suppressing non-radiative carrier recombination and effectively improving the heterojunction interface. As a result, Sb 2 S 3 solar cells with the iodine vapor processing achieve a power conversion efficiency ( PCE ) of 6.42%, which represents a 15% enhancement compared to untreated reference devices. This study offers a straightforward gas-phase strategy for interfacial engineering of CdS-based solar cells.