First principles study on organic cation A-site doping in CsPbI3 perovskite

• Formation energy and Goldschmidt tolerance factor of cation doped CsPbI 3 are calculated. • PBE, PBE + SOC and HSE06 are used to calculate the band structure. • Light absorption spectra of the doped CsPbI 3 all shows red shift. Among all inorganic perovskite, CsPbI 3 has the closest ideal bang gap for solar cells. However, the instability of metal halides hinders its commercial application. The doping of A-site organic cations might improve the stability of perovskite and also make the bandgap adjustable, thus enhance its photoelectric properties. In this paper, the structure stability, electronic structure and optical properties of CsPbI 3 with five different organic cations (H 3 NNH 2 + , CH 3 NH 3 + , C 3 H 6 NH 2 + , CH 3 NH 2 CH 3 + , CH 3 CH 2 NH 3 + ) partially alternative doping instead the A site cation have been studied by using the first principles within density functional theory. In order to get accurate description of the bandstructure information, different exchange–correlation functions, e. g. PBE, PBE + SOC and HSE were used to describe the calculated systems, our calculation results indicated that the PBE exchange–correlation function can describe the electronic properties of the systems very well in this paper. Formation energy calculation indicates that all the doping systems are thermally stable; and all the doped CsPbI 3 show good tolerance factor according Goldschmidt rule. Among the five different doping systems, the bandgap of doped H 3 NNH 2 + will decrease to 1.28 eV, while the bandstructure of other doped cations will widen the bandgap. The maximum bandgap increased to 1.65 eV with doping C 3 H 6 NH 2 + . However, all the band structures are mainly contributed by inorganic framework. The results suggest that the structure doped organic cations can be exited stably, and the band edge of the optical absorption spectrum will be redshifted. These properties can provide research ideas for the subsequent research of A-site doping organic cations.