A-sites join the band edge

Solar Cells The band edge of hybrid organic-inorganic perovskites, which have the general formula ABX3, is mainly controlled by the inorganic X anions (such as chloride) and the B cation (such as lead). Organic A-site cations usually only exert indirect structural effects because their electronic levels lie far from the band edge. Xue et al. show that cations with large π-conjugated structures can interact with inorganic frontier molecular orbitals. A surface layer of ethylammonium pyrene, which had an optimal intercalation distance, increased hole mobilities and power conversion efficiencies relative to a reference inorganic perovskite and also improved device stability. Science , this issue p. [636][1] [1]: /lookup/doi/10.1126/science.abd4860