Interstitial doping of K and Mn induced structural distortion and electronic properties changes in all‐inorganic CsPbI ₂ Br perovskite

Abstract CsPbI ₂ Br 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 CsPbI ₂ Br remain unclear. Here the structural distortion and the electronic properties changes of CsPbI ₂ Br 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 PbI ₄ Br ₂ octahedrons and dopant-occupied octahedral interstices, as well as density of states and crystal orbital Hamilton population were provided. We found that both the PbI ₄ Br ₂ octahedrons neighboring to Mn atom and the Mn-occupied octahedral interstice undergo a more significant structural distortion than those in the K-doped CsPbI ₂ Br. 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 CsPbI ₂ Br, 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-3 d states) at the CB edge.