Synthesis of Sulfide Perovskites by Sulfurization with Boron Sulfides

Chalcogenide perovskites (CPs), with the general composition ABX₃, where A and B are metals and X = S and Se, have recently emerged as promising materials for application in photovoltaics. However, the development of CPs and their applications has been hindered by the limitations of available preparation methods. Here we present a new approach for the synthesis of CPs, based on the sulfurization of ternary and binary oxides or carbonates with in situ formed boron sulfides. In contrast to the previously described approaches, the method presented here uses chemically stable starting materials and yields pure-phase crystalline CPs within several hours, under low hazard conditions. CP yields over 95% are obtained at temperatures as low as 600 °C. The generality of the approach is demonstrated by the preparation of CPs with compositions BaZrS₃, β-SrZrS₃, BaHfS₃, SrHfS₃, and EuHfS₃. Mechanistic insights about the formation of CPs are discussed.