Reduction of Bulk and Interface Defects via Photo-annealing Treatment for High-efficiency Antimony Selenide Solar Cells

Antimony selenide (Sb2Se3) exhibits outstanding photoelectric characteristics and has significant potential for application in photovoltaic devices. However, Sb2Se3 solar cells are hindered by severe carrier combinations at both the heterojunction interface and within the Sb2Se3 bulk, thereby limiting the improvement of device power conversion efficiency (PCE). This study presents a novel strategy for regulating the interface of the Sb2Se3/CdS heterojunction using a photo-annealing treatment. During this process, element substitution near the heterojunction efficiently prompts atomic rearrangement, leading to improved lattice matching at the interface and a reduction in the density of interface defects. Furthermore, the diffusion of Cd into the Sb2Se3 absorber facilitated the passivation of deep antisite and vacancy defects in the bulk of Sb2Se3. The photo-annealing process effectively enables the reduction of interface defects at the heterojunction interface and deep-level traps in the bulk of Sb2Se3. Consequently, this enhances the quality of the Sb2Se3/CdS heterojunction and facilitates the transport and collection of photo-generated carriers in the device. The resultant Sb2Se3/CdS heterojunction solar cells achieve a PCE of up to 10.58% (certified efficiency of 10.18%), making them the most efficient Sb2Se3 solar cells ever recorded. This work provides novel insights into the passivation of defects at the heterojunction and within the absorber bulk, highlighting pathways to enhance the photovoltaic performance of Sb2Se3 solar cells.