Long‐Range Resonant Energy Transfer from Blue Thermally Activated Delayed Fluorescence Emitter to Red Quantum‐Dot for Efficient Electroluminescence

Enhancing exciton utilization is crucial for boosting the performance of colloidal quantum‐dot light‐emitting diodes (QLEDs). The authors introduced a deep‐blue thermally activated delayed fluorescence emitter, 10‐(2,12‐di‐tert‐butyl‐5,9‐dioxa‐13b‐boranaphtho(3,2,1‐de)anthracen‐7‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridine (TDBA‐Ac), as a sensitizer doped in the hole transport layer to activate long‐range resonant energy transfer to the quantum‐dot‐based emission layer. Photophysical and device characterization demonstrated that TDBA‐AC can effectively harvest the excitons via reverse intersystem crossing and subsequently transfer the energy to the adjacent quantum‐dot layer, thereby enhancing the utilization of excitons. A reduction of the hole injection barrier between the HTL and EML also achieves because of the deeper highest occupied molecular orbital of TDBA‐Ac. As a result, the power efficiency and the external quantum efficiency of the sensitized red CdSe/ZnS QLEDs reach 42.8 lm W −1 and 26.9%, respectively, accompanied with a significantly low efficiency roll‐off. The universality of this approach is also confirmed in the InP‐based QLEDs.