Energetic Stability and Band-Edge Orbitals of Layered Inorganic Perovskite Compounds for Solar Energy Applications

Halide and oxide perovskite semiconductors (e.g., CsPbI₃ and SrTiO₃) have been widely studied for solar energy conversion applications. The optoelectronic properties and performance of these compounds can be tuned through the growth of layered perovskite superstructures. While oxides are quite varied in the compositions and geometries taken up by layered perovskites, halides have proven much more limited. In this paper, we use density functional theory calculations and chemical intuition to explore why this is the case. We show that, in general, the thermodynamic stability or instability of layered perovskite superstructures depends on the interplay of their ionic and covalent character and, just as importantly, on the features of other competing phases.