Carbon dots (CDs) are promising nanomaterials for next-generation lighting and displays due to their tunable bandgap, high photoluminescence quantum yield (PLQY), and high stability. However, the exciton utilization efficiency (EUE) of CD-based films can only reach 25%, fundamentally limiting their application in electroluminescent light-emitting diodes (LEDs). Improving the EUE is therefore of great significance. Herein, we developed composite films containing CDs and poly(9-vinylcarbazole) (PVK). The films were then used to construct a series of high-performance electroluminescent LEDs with tunable emission colors covering the blue to green regions as the concentration of CDs in the films increased, delivering a maximum external quantum efficiency and current efficiency of 2.62% and 5.11 cd/A, respectively. Theoretical calculations and experiments established that the excellent performance at low film PLQY was due to a hot exciton effect in the CDs, achieving nearly 100% EUE. This work provides new design strategies toward high-performance CD-based electroluminescent LEDs.
Keywords: carbon dots; electroluminescence; hot excitons; light-emitting diodes; multicolor.