Adding to the Perovskite Universe: Inverse-Hybrid Perovskites

Perovskites are a rich family of functional materials. Usually, they contain two cations on the A- and B-sites, surrounded by anions on the X-site, but compounds are also known that invert the ion types (inverse perovskites). Perovskites with one inorganic cation substituted by an organic molecule (hybrid perovskites) are currently intensively studied, due to the promise of CH3NH3PbI3 based solar-cells. We recently combined the concepts of inverse and hybrid perovskites, investigating the properties of inverse-hybrid perovskites by first-principles calculations, adding yet another structural variant to the perovskite universe. Our search discovered a variety of compounds that are computationally predicted to form either as stable perovskites or in a related corner- and edge-sharing phase. We observe materials with electronic properties ranging from metallic systems over small and intermediate band gaps to large band-gap semiconductors. The inverse structure could overcome stability problems of current hybrid perovskite photovoltaics. In addition, inverse-hybrid perovskites show inherent off-center displacement of ions, leading to polar phases.