Theoretical investigation of the structural and electronic properties of Al-decorated TiO2/perovskite interfaces

Methylammonium lead iodide perovskites, CH3NH3PbI3, possess excellent photoelectric conversion properties and can be potentially applied as the next-generation light-harvesting layer of solar cells. However, the stability problems have been hindering their practical applications. The density-functional theory calculations have been performed to investigate the structural and electronic properties of Al-decorated TiO2/perovskite interfaces. Combined with the density derived electrostatic and chemical method, the bonding characteristics around the interfaces are explored. It is found that both interfacial Pb-O and Ti-I bonds are responsible for the stability of the interfaces, especially the interfacial Pb atoms making the formation of oxygen vacancies harder, which is beneficial for the performance of the solar cells. Furthermore, our calculations have shown that the properties of the TiO2/perovskite interfaces could be well improved by Al modification. The corresponding atomistic mechanisms that govern the stabilities of the TiO2/perovskite interfaces are also discussed.