Dynamic Disorder Dominates Delocalization, Transport, and Recombination in Halide Perovskites

The remarkable efficiency of halide perovskite photovoltaic devices can be traced to their curiously long charge-carrier lifetimes and high mobilities, but the underlying origins of these properties and their ability to tolerate defects from solution processing remain unclear. Elucidating these origins is particularly important for efforts to develop new perovskite materials that are more stable and that avoid toxic components such as lead. We reveal that localization of charge carriers into electronic states known as large polarons slows their recombination through a combination of reduced wavefunction overlap and the formation of energetic barriers to electron-hole recombination. Importantly, this localization is mediated by thermally induced dynamic disorder of the anharmonic perovskite lattice. These findings reveal pathways to vary the composition of halide perovskites to tune the interplay between charge transport and recombination to optimize their optoelectronic properties.