Bluish‐Green Thermally Activated Delayed Fluorescence Material for Blue‐Hazard Free Hybrid White Organic Light‐Emitting Device with High Color Quality and Low Efficiency Roll‐Off

High color quality and the removal of blue hazard are important for lighting applications. Thermally activated delayed fluorescence (TADF) materials can achieve ≈100% internal quantum efficiency with low cost. However, it is still challenging to achieve high‐color‐quality and blue‐hazard‐free TADF‐based white organic light‐emitting devices (WOLEDs). Here, a bluish‐green TADF material named 10,10′‐[5‐(6‐[1,1′‐biphenyl]‐4‐yl‐2‐phenyl‐4‐pyrimidinyl)‐1,3‐phenylene] bis [9,10‐dihydro‐9,9‐dimethyl‐acridine (DMAC‐BPP) containing two acridines connecting by a phenyl and a pyrimidine is designed and synthesized. Efficient bluish‐green OLED is achieved with DMAC‐BPP emitter. Besides, the yellow and red phosphorescent OLED utilizing DMAC‐BPP as host also shows excellent performance. Thus, a blue‐hazard‐free hybrid WOLED using DMAC‐BPP as host and emitter with maximum external quantum efficiency of 15.6% is achieved. Furthermore, this WOLED shows low efficiency roll‐off and high color quality.