First-Principles Modeling of Bismuth Doping in the MAPbI3 Perovskite

Heterovalent doping in lead halide perovskites was only marginally explored. Particular attention was focused on Bi3+ dopant, which was found to increase the α-phase stability for CsPbI3, leading to high efficiency of fully inorganic perovskite solar cells. It was recently demonstrated that the absorption onset red-shift of the Bi-doped perovskite is due to the increased number of defect states and a significant increase in the sub-band-gap density of states. Here we computationally simulated the electronic properties of the Bi-doped MAPbI3 (MA = CH3NH3+) perovskite to gain insight into the electronic structure modifications occurring upon heterovalent doping. Our results confirm the presence of deep trap states induced by the Bi dopant, with the Bi3+ acting as deep electron trap. The absorption onset red-shift observed upon Bi-doping of MAPbI3 is mainly related to transitions to the Bi defect states, while the perovskite band gap is essentially unaltered.