Efficient Sb2Se3/CdS Planar Heterojunction Solar Cells in Substrate Configuration with (hk0) Oriented Sb2Se3 Thin Films

This work has been published in Solar Energy Materials & Solar Cells 215 (2020) 110603 (DOI: 10.1016/j.solmat.2020.110603). Antimony selenide (Sb₂Se₃) based solar cell technology has experienced rapid development with demonstrated cell efficiency reaching ̴ 9.2% for devices with substrate configuration, hence necessitating more intense research investigation for further progress. Though the effect of crystallographic orientation in this non-cubic material on device performance is now well understood, the influence of composition and intrinsic defects remains debatable. In this work we describe the fabrication and device characteristics of Sb₂Se₃ solar cells designed in the substrate configuration of (SLG/Mo/Sb₂Se₃/CdS/i-ZnO+ITO). Notably, Sb₂Se₃ absorber layers with predominant (hk0) orientation were deposited in a single step by e-beam evaporation of pre synthesized bulk source material. As grown precursor Sb₂Se₃ thin films were subjected to reactive thermal annealing (RTA) treatment in the presence of Se source at different temperatures for enhancing their crystalline quality and balancing their stoichiometry. Analysis of the completed solar cells indicated improved efficiencies post RTA process, with the best performing devices exhibiting a power conversion efficiency (η) of ~ 4.34% for an absorber annealed at a temperature of 350 °C. The improved efficiency is ascribed to the observed changes in chemical composition of the absorber layer and the possible formation of related beneficial antisite defects.