Methylammonium cation deficient surface for enhanced binding stability at TiO₂/CH₃NH₃PbI₃ interface

Heterojunction interfaces in perovskite solar cells play an important role in enhancing their photoelectric properties and stability. Till date, the precise lattice arrangement at TiO₂/CH₃NH₃PbI₃ heterojunction interfaces has not been investigated clearly. Here, we examined a TiO₂/CH₃NH₃PbI₃ interface and found that a heavy atomic layer exists in such interfaces, which is attributed to the vacancies of methylammonium (MA) cation groups. Further, first-principles calculation results suggested that an MA cation-deficient surface structure is beneficial for a strong heterogeneous binding between TiO₂ and CH₃NH₃PbI₃ to enhance the interface stability. Our research is helpful for further understanding the detailed interface atom arrangements and provides references for interfacial modification in perovskite solar cells.