Spatial Mapping of Electrochemical Hole Injection into Supercrystals of Perovskite Nanocrystals

Lead halide perovskite nanocrystals are of interest for application as an emissive layer in light-emitting diodes (LEDs) due to their high photoluminescence quantum yield, their color tunability, and their defect tolerance. For the application in LEDs, charges need to be easily transferred from the charge transport layers to the nanocrystal core without compromising the optoelectronic properties. While charging of nanocrystals can be studied by spectroelectrochemistry (SEC) in general, in this work, we combine SEC with diffraction-limited optical resolution. This allows us to study hole injection into self-assembled supercrystals of CsPbBr3 nanocrystals and determine the spatially dependent potential for this action. We find an overall brightening of the photoluminescence, which is gradually shifting from the edges to the supercrystal center, and a generally greater resistance toward electrochemical degradation in the supercrystals.