Coexistence of large polaron and polaronic exciton in hybrid lead halide perovskite nanocrystals

Abstract

In this work, we probe the relationship between perovskite material microstructure and the nature of the photogenerated polarons. We prepare formamidinium lead iodide quantum dot films in two forms with distinctive inter-QD interactions. Using a combination of time-resolved spectroscopies, we observe a competition between carrier thermalization into polaronic excitons and ultrafast hot-carrier transport between QDs, with the balance between channels set by the excess photon energy and connectivity between QDs. These results underscore the importance of microscopic structure in steering the ultrafast processes which determines the fate of photoexcitations in perovskite materials.