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.