Surface and interfacial heterogeneities in hybrid perovskite solar cells*

Hybrid organic-inorganic perovskites are promising candidates for photovoltaic and optoelectronic applications with power conversion efficiencies over 25%. There remain unanswered questions about the fundamental reasons for such high efficiencies and widespread disparities observed in experiments. We elucidate the reasons for the observed heterogeneity in the properties of perovskite solar cells by performing first-principles investigations of surfaces and interfaces in methylammonium lead halides. We find a considerable spread in the value of the Rashba spin splitting [1], band alignments, and defect formation energies depending on the surface facet and termination. Our calculations explain some of the disparities in experimental literature. We also provide design guidelines to maximize the efficiencies of perovskite solar cells through control of surfaces and interfaces during synthesis.