Significant Enhancement of Blue OLED Performances through Molecular Engineering of Pyrimidine‐Based Emitter

Although pyrimidine‐based emitters are one of the most promising classes of compounds, a structure–property relationship for an effective molecular design strategy has not yet been elucidated. In this study, the authors develop three types of blue pyrimidine emitters for high‐performance thermally activated delayed fluorescence (TADF) organic light‐emitting devices (OLEDs). 2,4,6‐triphenylpyrimidine is used as an acceptor, and tri‐ or penta‐substituted acridine as a donor unit for the blue TADF emitters. The authors investigate the effects of the nitrogen position on the photophysical properties and OLED performances, and develop a blue device with a high external quantum efficiency close to 25%. The device performances are among the best so far for blue TADF OLEDs.