Suppressing Oxygen-Induced Deterioration of Metal Halide Perovskites by Alkaline Earth Metal Doping: A Quantum Dynamics Study.

Exposure to oxygen undermines stability and charge transport in metal halide perovskites, because molecular oxygen, as well as photogenerated superoxide and peroxide, erodes the perovskite lattice and creates charge traps. We demonstrate that alkaline earth metals passivate the oxygen species in CH 3 NH 3 PbI 3 by breaking the O-O bond and forming new bonds with the oxygen atoms, shifting the trap states of the antibonding O-O orbitals from inside the bandgap into the bands. In addition to eliminating the oxidizing species and the charge traps, doping with the alkaline earth metals slightly increases the bandgap and partially localizes the electron and hole wavefunctions, weakening the electron-hole and charge-phonon interactions and making the charge carrier lifetimes longer than even those in pristine CH 3 NH 3 PbI 3 . Relative to CH 3 NH 3 PbI 3 exposed to oxygen and light, the charge carrier lifetime of the passivated CH 3 NH 3 PbI 3 increases by 2-3 orders of magnitude. The ab initio quantum dynamics simulations demonstrate that alkaline earth metals passivate efficiently not only intrinsic perovskite defects, but also the foreign species, providing a viable strategy to suppress perovskite degradation.