Optimizing Sublattice Correlation to Enhance Stability and Charge Carrier Lifetime in Mixed Halide Perovskites
Jiao Wang, Haoran Lu, Xue Tian, Run Long, Oleg V. Prezhdo
Abstract
A-site cations in ABX 3 metal halide perovskites do not contribute to the frontier electronic states. They influence optoelectronic properties indirectly through interaction with the BX 3 sublattice. By systematically investigating correlated motions of Cs cations and the PbX 3 lattice (X = Cl, Br, I), we demonstrate that the interaction between the two subsystems depends on electronegativity and size of the X-site anion. The most electronegative Cl halide minimizes thermal atomic fluctuations, favoring optoelectronic performance. CsPbI 3 is improved by Cl-doping. Nonadiabatic molecular dynamics simulations demonstrate that charge carrier lifetime is extended by nearly an order of magnitude when atomic fluctuations are minimized, due to reduced electron–vibrational interactions, in agreement with experiments. The detailed atomistic examination of the significant impact of correlated motion of the A-site and BX 3 sublattices and its influence on perovskite stability and exciton lifetime offers theoretical guidelines for optimizing perovskite optoelectronic devices.