Reproducible and High-Performance WOLEDs Based on Independent High-Efficiency Triplet Harvesting of Yellow Hot-Exciton ESIPT and Blue TADF Emitters

Hot exciton organic light-emitting diode (OLED) emitters can balance the high performance of a device and reduce efficiency roll-off by fast reverse intersystem crossing from high-lying triplets (hRISC). In this study, an excited-state intramolecular proton transfer (ESIPT) fluorophore of 2-(benzo[d]thiazol-2-yl)-4-(pyren-1-yl)phenol (PyHBT) with the typical characteristic properties of a hot exciton is developed. With high efficiency of utilization of the exciton (91%), its yellow OLED exhibited high external quantum efficiency (EQE) of 5.6%, current efficiency (CE) of 16.8 cd A-1, and power efficiency (PE) of 17.3 lm W-1. The performance of the yellow emissive "hot exciton" ESIPT fluorophores is among the highest recorded. Due to the large Stokes shift of the ESIPT emitter, non-energy-transferred high-performance white OLEDs (WOLEDs) are developed, which are reproducible and highly efficient. This is possible because of the independent harvesting of most of the triplets in both complementary-color emitters without the interference of energy transfer. The PyHBT-based WOLEDs exhibit a maximum EQE of 14.3% and CE of 41.1 cd A-1, which facilitates the high-yield mass production of inexpensive WOLEDs. A high-performance excited-state intramolecular proton transfer (ESIPT) electroluminescent yellow emitter has been demonstrated via high-level reverse intersystem crossing with highly efficient exciton utilization (91%). Further by using blue thermally activated delayed fluorescence (TADF) emitters, reproducible and high-efficiency white organic light-emitting diodes (WOLEDs) based on blocking-energy-transfer mechanism have been fabricated, by independent highly efficient exciton harvesting in both emitters.image