Revealing two heat-annealing related photoproduct systems and widely existed subgrain domains in organolead perovskite

Abstract

For highly interested organolead perovskite based solar cells, the photoproducts are regarded as the co-existed exciton and free carriers. In this study, we carefully re-examined this conclusion with our recently developed density-resolved spectroscopic method. Heat-annealing related two photoproduct systems are observed. We found that the widely accepted model is only true for single crystal and freshly made films without heat-annealing. For those sufficiently heat-annealed films, another system presenting significant emissive exciton-carrier collision (ECC) is discovered. In addition, the appearing of ECC indicates the emerging of an internal morphology after heat annealing, which is assigned to a recently discussed twinning subgrain structure. We proved that such subgrain structures broadly exist in perovskite films. This finding could prove the morphological basis for high performance of perovskite working layers.

18pages, 3 figures. supporting info supplied