Identifying Short-Range Disorder in Crystalline Bulk Cu₂SnS₃ Phases: A Solid-State Nuclear Magnetic Resonance Spectroscopic Investigation

Cu₂SnS₃ has recently attracted attention as a low-cost, earth-abundant absorber material for thin-film solar cells. Unfortunately, multiple Cu₂SnS₃ structures exist and the conditions under which different structures form are poorly defined. The structures of tetragonal and monoclinic Cu₂SnS₃ phases are clarified by use of solid-state nuclear magnetic resonance spectroscopy (ssNMR). The monoclinic Cu₂SnS₃ phase is shown to form under Sn-rich, Cu-poor conditions and the tetragonal Cu₂SnS₃ phase forms under Cu-rich, Sn-poor conditions, indicating that there is a composition difference between the structures that has not previously been reported. Furthermore, the monoclinic phase is destabilized at temperatures between 200 and 345 °C, when the material becomes tetragonal.