Efficient and stable flexible Sb2Se3 thin film solar cells enabled by an epitaxial CdS buffer layer

Abstract Recently, Sb2Se3, an Earth-abundant constituents compound, has emerged as a promising low-cost thin film photovoltaic material. The Sb2Se3 solar cells with a polycrystalline CdS buffer layer suffer from unsatisfactory photoexcitation stability. Herein, we fabricate flexible Sb2Se3 thin film solar cells by utilizing the transferable van der Waals epitaxial CdS on mica as a buffer layer. Compared to the nonepitaxial CdS buffer layer, the epitaxial CdS can significantly reduce the interface defects and interfacial diffusion. With the improved Sb2Se3/CdS interface, we obtained a power conversion efficiency of 7.15%, and the flexible Sb2Se3 solar cell exhibits an excellent stability under the continuous illumination. In addition, after 1000 bending cycles with a 50° bending angle, the flexible device maintained over 90% of the initial efficiency. These encouraging results demonstrate a potential application of Sb2Se3 solar cells in flexible, lightweight, and wearable power supply.