Substitutional Chemistry of MAPbI3: Gaining Control over Material Photostability and Photovoltaic Performance via Pb2+ Replacement

The strategy of partial Pb²⁺ substitution is applied, in prototypical MAPbI₃ perovskite, with a large array of metal cations in order to comprehensively explore their possible incorporation in the perovskite lattice at Pb²⁺ sites and thus obtain improved photostability of the absorber. An analysis of lattice parameters and optoelectronic properties of MAPb_1-xM_xI_∼3 compositions allowed authors to deduce which metal cations are partially incorporated in the perovskite structure and which are expelled in the form of secondary phases. Curious effects of metal incorporation are observed, such as a decrease in the tetragonal distortion ratio and a change in the band gap. This work reveals that the doping of 11 metal cations significantly improves the photostability of the MAPbI₃ films. Multiple MAPb_1-xM_xI_∼3 formulations deliver superior power conversion efficiencies (PCEs) in solar cells. The DFT calculations further demonstrate a complex relationship between the synthetic conditions and doping patterns. The performed study is thus a stepping stone in the development of more stable perovskite absorbers with superior photovoltaic properties.