Andreas Bornschlegl, LMU München
Nanospectroscopy Group in Nano-Institute
Perovskite nanocrystals (PNCs) have exceptional light-emitting properties, including wide spectral tunability and high quantum yields. To realize efficient devices, it is imperative to understand how carrier transport progresses in PNC thin films. Spatially and temporally resolved optical microscopy was used to map exciton diffusion in PNC thin films for different temperatures (9K-320K) and NC sizes. The results of these measurements can be attributed to the coexistance of excitons and free electron hole-pairs inside the individual PNCs. This coexistence is quantified by the exciton binding energy and thus by the NC size, which turns out to be a critical factor in the diffusion of excitons in PNCs, even more so than the film quality. During measurements at cryogenic temperatures, it was also discovered, that there are both slow-emitting dark and fast-emitting bright excitons in PNCs. This behavior again depends strongly on the PNC size.
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