TADF material with non-conjugated rigid donor for high-performance full-color phosphorescent OLEDs: Effects of triplet harvest and charge transport on efficiency

Abstract

Host materials play a crucial role in developing highly efficient OLEDs, of which universal host materials for full-color OLEDs are in great demand. Herein, two wide band-gap thermally activated delayed fluorescence (TADF) host materials based on diphenylsulfone derivatives were developed by rationally tuning the TADF characteristic and charge transport ability through electron-donor engineering. Owning to the non-conjugated rigid donor 9,9-dimethylacridine, mSOAD showed obvious superiority in pronounced TADF effect with an extra small singlet-triplet energy split of 0.02 eV and balanced carrier transport properties. Full-color phosphorescent OLEDs based on mSOAD were achieved with impressive efficiencies of 65.52 cd/A, 66.51 lm/W and 19.00% for green OLED, 36.19 cd/A, 32.46 lm/W and 16.7% for blue OLED and 32.65 cd/A, 30.99 lm/W, and 20.31% for red OLED, respectively. Our results revealed the key effect of efficient triplet harvest and balanced charge transport ability of TADF host materials in high efficiency and low efficiency roll-off in OLEDs.