Preventing Superoxide Generation on Molecule-Protected CH3NH3PbI3 Perovskite: A Time-Domain Ab Initio Study.

Metal halide perovskites are promising materials for photovoltaics and optoelectronics. However, transfer of an electron from perovskite to oxygen leads to the formation of superoxide that significantly decreases the stability and charge carrier lifetime of perovskites, which constitutes major issues for real applications. Using nonadiabatic (NA) molecule dynamics simulations, we demonstrate that the introduction of a perylene diimide (PDI) molecule into the CH3NH3PbI3 system adsorbed with an oxygen molecule creates a midgap state above the trap state generated by the oxygen molecule, and thus the PDI midgap state can rapidly capture the photogenerated electron of perovskite at about 100 ps prior to the O2-related trap state, which takes about double the time. The route simultaneously avoids the formation of superoxide and enhances the stability of perovskites. The fast electron trapping originates from the strong NA coupling and small energy gap between the PDI midgap state and the CH3NH3PbI3 conduction band minimum. Our simulations suggest that a rational choice an electron-accepting molecule can improve the stability and performance of perovskite solar cells and photoelectric devices.