Divalent Anionic Doping in Perovskite Solar Cells for Enhanced Chemical Stability

The chemical stabilities of hybrid perovskite materials demand further improvement toward long-term and large-scale photovoltaic applications. Herein, the enhanced chemical stability of CH₃NH₃PbI₃ is reported by doping the divalent anion Se²⁻ in the form of PbSe in precursor solutions to enhance the hydrogen-bonding-like interactions between the organic cations and the inorganic framework. As a result, in 100% humidity at 40 °C, the 10% w/w PbSe-doped CH₃NH₃PbI₃ films exhibited >140-fold stability improvement over pristine CH₃NH₃PbI₃ films. As the PbSe-doped CH₃NH₃PbI₃ films maintained the perovskite structure, a top efficiency of 10.4% with 70% retention after 700 h aging in ambient air is achieved with an unencapsulated 10% w/w PbSe:MAPbI₃-based cell. As a bonus, the incorporated Se²⁻ also effectively suppresses iodine diffusion, leading to enhanced chemical stability of the silver electrodes.