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.

This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 712949 (TECNIOspring PLUS)" and the Government of Catalonia's Agency for Business Competitiveness(ACCIÓ). This research was also supported by the Spanish Ministry of Science, Innovation and Universities under the WINCOST (ENE2016-80788-C5-1-R) project, and by the European Regional Development Funds (ERDF, FEDER Programa Competitivitat de Catalunya 2007-2013). Authors from IREC and the University of Barcelona belong to the SEMS (Solar Energy and Materials Systems) Consolidated Research Group of the 'Generalitat de Catalunya' (Ref. 2017 SGR 862). Ministry of New and Renewable Energy (MNRE) is very well acknowledged for funding the research activities at SRM IST through the project "Development of Lithium Ion Batteries and Computational Studies for Solar Absorber Layers, (Grant No. 31/03/2014-15/PVSE-R&D).