First-Principles Hybrid Functional Study of the Organic-Inorganic Perovskites CH3NH3SnBr3 and CH3NH3SnI3

We studied the structural and electronic properties of the hybrid perovskites CH3NH3SnI3 and CH3NH3SnBr3 as well as their band alignments with respect to the electron-conducting TiO2 electrode using first-principles electronic structure calculations. Our hybrid functional calculations yielded band gaps of 1.3 and 1.84 eV for CH3NH3SnI3 and CH3NH3SnBr3, respectively, which are consistent with experimental values. In addition, our calculations show that the organic cation [CH3NH3](+) does not take part in the formation of the valence band nor the conduction band and only plays a role in donating one electron in each material. Our band alignment calculations show that introducing substitutional Br dopants for I anions in CH(3)NH3SnI3 could facilitate charge transfer from the hybrid perovskite to the TiO2 electrode, enabling the development of more efficient solar cell architectures.