Quantum Dot to Nanorod Transition for Efficient White-Light-Emitting Diodes with Suppressed Absorption Losses

Colloidal nanocrystals have great potential for next-generation solid-state lighting due to their outstanding emission and absorption tunability via size and morphology, narrow emission linewidth, and high photoluminescence quantum yield (PLQY). However, the losses due to self-and interabsorption among multitudes of nanocrystals significantly decrease external quantum yield levels of light-emitting diodes (LEDs). Here, we demonstrate efficient white LEDs via CdSe/CdS dot to dot-in-rod transition that enabled a large Stokes shift of 780 meV and significantly reduced absorption losses when used in conjunction with near-unity PLQY ZnCdSe/ZnSe quantum dots (QDs) emitting at the green spectral range. The optimized incorporation of nanocrystals in a liquid state led to the white LEDs with an ultimate external quantum efficiency (EQE) of 42.9%, with a net increase of EQE of 10.3% in comparison with white LEDs using CdSe/CdS dots. Therefore, combinations of nanocrystals with different nanomorphologies hold high promise for efficient white LEDs.

Automated summary

This study demonstrates efficient white LEDs by utilizing the dot to dot-in-rod transition of CdSe/CdS and near-unity PLQY ZnCdSe/ZnSe quantum dots (QDs). The combination significantly reduces absorption losses and improves the external quantum efficiency of white LEDs.