Optimizing Crystal Orientation and Defect Mitigation in Antimony Selenide Thin‐Film Solar Cells through Buffer Layer Energy Band Adjustment

Antimony selenide (Sb₂Se₃) has sparked significant interest in high-efficiency photovoltaic applications due to its advantageous material and optoelectronic properties. In recent years, there has been considerable development in this area. Nonetheless, defects and suboptimal [hk0] crystal orientation expressively limit further device efficiency enhancement. This study used Zinc (Zn) to adjust the interfacial energy band and strengthen carrier transport. For the first time, it is discovered that the diffusion of Zn in the cadmium sulfide (CdS) buffer layer can affect the crystalline orientation of the Sb₂Se₃ thin films in the superstrate structure. The effect of Zn diffusion on the morphology of Sb₂Se₃ thin films with Cd_xZn_1-xS buffer layer has been investigated in detail. Additionally, Zn doping promotes forming Sb₂Se₃ thin films with the desired [hk1] orientation, resulting in denser and larger grain sizes which will eventually regulate the defect density. Finally, based on the energy band structure and high-quality Sb₂Se₃ thin films, this study achieves a champion power conversion efficiency (PCE) of 8.76%, with a V_OC of 458 mV, a J_SC of 28.13 mA cm^-2, and an FF of 67.85%. Overall, this study explores the growth mechanism of Sb₂Se₃ thin films, which can lead to further improvements in the efficiency of Sb₂Se₃ solar cells.