CsPbI2Br and its derivatives are promising light harvesters for all-inorganic perovskite photovoltaic devices, whereas the effects of doping on local lattice structures and electronic properties of CsPbI2Br remain unclear. Here the structural distortion and the electronic properties changes of CsPbI2Br caused by the interstitial alkali-metal K and transition-metal Mn dopants were investigated from first-principles calculations. The bond lengths, bond angles, distortion magnitude and volume of both PbI4Br2 octahedrons and dopant-occupied octahedral interstices, as well as density of states and crystal orbital Hamilton population were provided. We found that both the PbI4Br2 octahedrons neighboring to Mn atom and the Mn-occupied octahedral interstice undergo a more significant structural distortion than those in the K-doped CsPbI2Br. Contrary to the exothermic K-doping, the endothermic Mn-doping reduces the volume of Mn-occupied octahedral interstice by shrinking Mn-Br-I atomic plane and elongating Cs-Cs interatomic distance. The interstitial K-doping has little effect on the position and orbital component of valance band (VB) maximum and conduction band (CB) minimum of CsPbI2Br, while the interstitial Mn-doping can not only shift up the VB edge by 0.41 eV but also introduce new unoccupied gap states (Mn-3d states) at the CB edge.

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