Substitution effect on band structure shape of of hybrid perovskite CH3NH3PbI3

Introduction: Recently inorganic-organic halide perovskites have emerged as highly efficient materials for developing ‎photovoltaic and optoelectronic devices. The specific properties like good charge carrier mobilities, high ‎quantum efficiency, tunable band gap of these perovskites have made good candicates for using as photon ‎absorbers in solar cells, light-emitting diodes photovoltaics (PVs) and photodetection devices [1]. Among ‎various perovskites, the CH3NH3PbI3 with a direct band gap of almost 1.6 eV has been studied over ‎recent years for solar cell applications. Hence, understanding the electronic and optical properties is ‎crucially important for designing novel materials based on hybrid perovskites. In this study, fluorine and ‎chlorine doping effect on the band gap and electronic properties of CH3NH3PbI3 have been investigated.‎Materials and Methods: All calculations have been done using density functional theory (DFT) based first principles calculations. ‎The GGA proposed by PBE is used as the exchange-correlation functional. The role of fluorine and ‎chlorine substuition is considered, with emphasis on electronic properties of CH2FNH3PbI3 and ‎CHFClNH3PbI3. ‎Results and Conclusion: The band structurea of CH3NH3PbI3, CH2FNH3PbI3 and CHFClNH3PbI3 are compared in Fig.1, which in ‎point Γ, the direct band gap is observed. Our results demonsrates that fluorine and chlorine doping ‎narrows the band gap and affects the composition of the valence band maximum, hence the effective ‎mass of the holes in the valance band will be changed. The changes in the conduction band in the presence ‎of fluorine and chlorine is ignorable which means that this substitution does not considerably affect the ‎effective mass of the electrons.

Keywords:

Perovskite , DFT , Electronic Properties , Band Gap