First-Principles\nHybrid Functional Study of the Organic–Inorganic\nPerovskites CH₃NH₃SnBr₃ and CH₃NH₃SnI₃

Abstract

We\nstudied the structural and electronic properties of the hybrid\nperovskites CH₃NH₃SnI₃ and CH₃NH₃SnBr₃ as well as their band alignments\nwith respect to the electron-conducting TiO₂ electrode\nusing first-principles electronic structure calculations. Our hybrid\nfunctional calculations yielded band gaps of 1.3 and 1.84 eV for CH₃NH₃SnI₃ and CH₃NH₃SnBr₃, respectively, which are consistent with experimental\nvalues. In addition, our calculations show that the organic cation\n[CH₃NH₃]⁺ does not take part in the\nformation of the valence band nor the conduction band and only plays\na role in donating one electron in each material. Our band alignment\ncalculations show that introducing substitutional Br dopants for I\nanions in CH₃NH₃SnI₃ could facilitate\ncharge transfer from the hybrid perovskite to the TiO₂ electrode,\nenabling the development of more efficient solar cell architectures.