Quasi-Vertically Oriented Sb₂Se₃ Thin-Film Solar Cells with Open-Circuit Voltage Exceeding 500 mV Prepared via Close-Space Sublimation and Selenization

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.