Investigation of local nanoscale electronic variation and photo excited carrier dynamics in hybrid organic-inorganic mixed cation perovskite films

Hybrid organic-inorganic perovskite materials are promising materials for photovoltaic applications, due to high efficiencies of light collection along with simple and cost effective production methods. One challenge arising in prepared films of hybrid perovskites are the presence of micro- and nano-scale variations that may affect properties desirable for solar cell applications. For example, spatial variations observed in the photoluminescence yield will affect the overall efficiency of devices. In order to understand the electronic effects of such variations, we employ time resolved photoemission electron microscopy (TR-PEEM) to investigate the electronic states and photo excited carrier dynamics with spatial resolution of several tens of nanometers in mixed cation cesium formamidinium methylammonium lead triiodide (CsFAMAPbI3) films. Our initial findings show evidence for occupied mid-gap states that occur in localized spots in the films. Further, we observe the different photo excited behaviors at these local areas.