Effect of cation disorder on electron–phonon coupling in NaBiS2

NaBiS2 has recently emerged as a promising photovoltaic material. When prepared in nano particulate form, its structure is that of a disordered rocksalt (DRX): Na+ and Bi3+ ions are distributed across the cation site, and S2– ions are on the anion site of the Fm-3m rocksalt structure. The presence of occupational and displacive disorder is thought to help localise photoexcited electrons and holes in different parts of the structure. This proposal aims to characterise the lattice dynamics of NaBiS2, its dependence on temperature and also on nanoparticle size. Our aim is to understand the effect of compositional disorder on the vibrational structure of the system, which is key to mediating the relaxation processes that follow photoexcitation. a