Crystal growth direction-controlled antimony selenide thin film absorbers produced using an electrochemical approach and intermediate thermal treatment

Sb₂Se₃ is an emerging material among alternative light absorbers for photovoltaic applications. Unlike typical chalcogenides, Sb₂Se₃ is particularly appealing due to its single stable crystal phase, layered structure with loose binding of no dangling bonds. Nevertheless, a cost-effective electrochemical approach for the synthesis of Sb₂Se₃ compounds has not been identified, and the Sb₂Se₃ film with the most favorable [001] preferred orientation has only just been developed. In this study, Sb-rich precursors were prepared electrochemically at −950 mV (vs. Ag/AgCl), and homogeneous Sb₂Se₃ thin films were produced using a pre-thermal treatment process prior to the typical selenization process with additional Se coating. This novel procedure notably suppresses potential Sb dissolution into liquid Se due to the formation of polycrystalline Sb-related crystals. As a result, the Sb-rich precursor was successfully transformed into Sb₂Se₃ thin films with an enhanced perpendicular orientation of the [001] direction. Unfortunately, a high density of voids was produced in the precursor film with two distinguishable layers, and their size increased after selenization. The voids were formed through evolution of H₂Se gas after the initial electrochemical reaction. The resulting photovoltaic cells demonstrated an energy conversion efficiency of 1.8% in a substrate structure consisting of Mo/Sb₂Se₃/CdS/ZnO/ITO.