Perovskite-inspired low-dimensional hybrid azetidinium bismuth halides: [(CH2)3NH2]3Bi2X9 (X = I, Br, Cl)

Bi-based halide perovskites have been considered as alternatives to Pb-based perovskites with the intention of avoiding the use of lead in the field of photovoltaics. Over the last few years, novel Bi-based halide perovskites have shown potential in reaching good photovoltaic performance, as suggested by their similar electronic structure to Pb-based perovskites. Nevertheless, their lower dimensionality entails poor charge carrier transport. It has been consistently stated that the role of the A-site should be further studied. To explore this proposition, we have synthesized three different Bi-based halides with substitution on the A-site by azetidinium cations. In this contribution we report fundamental observations of azetidinium bismuth halides, [(CH2)3NH2]3Bi2I9, [(CH2)3NH2]3Bi2Br9, and [(CH2)3NH2]3Bi2Cl9 with prospects in optoelectronics and photovoltaics. These new materials exhibit 0D and 2D crystal structures at a molecular level and the optical feature of an excitonic band state.