DFT study of electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH 3 NH 3 PbX 3 , X = I, Br, Cl)

Abstract

We present the electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH3NH3PbX3, X = I, Br, Cl) using DFT calculations. We find that both CH3NH3PbX3 and CF3NH3PbX3 exhibit direct bandgaps (1.5-2.8 eV) which lies within the suitable bandgap regime for solar cell applications. The carrier mobilities of fluorinated MAPbX3 are much lower than pristine MAPbX3 indicating poor solar cell performance in spite of possible gain in stability due to enhanced hydrophobicity. The fluorination does not affect the chemical stability as is evident from the negative formation and cohesive energies, but an extremely high dipole moment (6.88 Debye) of CH 3 NH 3 + may severely affect the charge carrier pathways.