High-performance blue organic light-emitting diodes with 20% external electroluminescence quantum efficiency based on pyrimidine-containing thermally activated delayed fluorescence emitters

We report here high-performance pure blue thermally activated delayed fluorescence (TADF) molecules based on a central pyrimidine acceptor (A) core with peripheral diphenylacridan donor (D) units. A design motif of highly twisted D-A-D architectures having a small singlet-triplet energy splitting allows for the production of efficient pure blue TADF with high quantum efficiencies exceeding 90%. An OLED based on the blue pyrimidine-based TADF emitter exhibits a high maximum external quantum efficiency of 20.8% and a high power efficiency of 31.5 lm W-1.