Exciton Transport in Disordered Perovskite Nanocrystal Solids

Solution-processed thin films of colloidal lead halide perovskite (LHP) nanocrystals (NCs) show great potential for next-generation optoelectronic devices. However, these NC solids exhibit non-negligible size and shape polydispersity, which introduces both structural and energetic disorder. Here we resolve the exciton dynamics in space, time, and energy to elucidate the impact of disorder on exciton transport. We show that the disorder depends sensitively on the alkylamine ligand used in the synthesis. While shorter alkyl chain lengths lead to high polydispersity, longer alkyl chains lead to a narrower size distribution and smaller particles where quantum confinement becomes more pronounced, consequently leading to increased energetic disorder. Strikingly, we find that exciton transport is less efficient in NC solids with long alkyl chains, despite the fact that they have significantly more narrowly size-distributed ensembles. This demonstrates that energetic disorder rather than structural disorder is the dominant factor for predicting exciton transport within these disordered systems.