Energy localization vs. charge funneling in aggregates of CsPbBr3 perovskite nanocrystals

We studied photoluminescence (PL) and electroluminescence (EL) on single aggregates composed of tens to hundreds of nanocrystals (NCs) of the halide perovskite CsPbBr3. Energy landscape of the aggregate caused by size distribution of the NCs leads to funneling of charges towards and EL from the largest NC. This phenomenon results in pronounced blinking of the aggregate EL. In PL, on the other hand, the absorbed light energy is localized and reemitted on individual NCs, without significant redistribution by energy/exciton transfer. As a result the PL of individual aggregates does not show any blinking. We further investigated the effect of externally applied de voltage on PL of the aggregates in a capacitance-like device and observed an intriguing phenomenon of large oscillations of PL intensity that occur with a period of seconds and are correlated between different aggregates across micrometer distances.