Quasi-Vertically Oriented Sb<sub>2</sub>Se<sub>3</sub> Thin-Film Solar Cells with Open-Circuit Voltage Exceeding 500 mV Prepared via Close-Space Sublimation and Selenization
Ping Fan, Guojie Chen, Shuo Chen, Zhuanghao Zheng, Muhammad Azam, Nafees Ahmad, Zhenghua Su, Guangxing Liang, Xianghua Zhang, Zhi‐Gang Chen
Abstract
Sb2Se3, one of the most desirable absorption materials for next-generation thin-film solar cells, has an excellent photovoltaic characteristic. The [hk1]-oriented (quasi-vertically oriented) Sb2Se3 thin film is more beneficial for promoting efficient carrier transport than the [hk0]-oriented Sb2Se3 thin film. Controlling thin-film orientation remains the main obstacle to the further improvement in the efficiency of Sb2Se3-based solar cells. In this work, the controlled [hk0] or [hk1] orientation of the Sb2Se3 precursor is readily adjusted by tuning the substrate temperature and the distance between the source and the sample in close-space sublimation (CSS). Well-crystallized stoichiometric Sb2Se3 thin films with the desired orientation and large crystal grains are successfully prepared after selenization. Sb2Se3 thin-film solar cells in a substrate configuration of glass/Mo/Sb2Se3/CdS/ITO/Ag are fabricated with a power conversion efficiency of 4.86% with a record open-circuit voltage (VOC) of 509 mV. The significant improvement in VOC is closely related to the quasi-vertically oriented Sb2Se3 absorber layer with reduced deep-level defect density in the bulk and defect passivation at the Sb2Se3/CdS heterojunction. This work indicates that CSS and selenization show a remarkable potential for the fabrication of high-efficiency Sb2Se3 solar cells.