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

Abstract

AbstractHot 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.