Strategy to improve the efficiency of solution-processed phosphorescent organic light-emitting devices by modified TADF host with tert-butyl carbazole

Abstract A new bipolar host material t3Cz-SO was designed and synthesized by introducing tert-butyl carbazole unit to the peripheral of parent TADF units. The calculated triplet energy and ΔEST of t3Cz-SO are 2.85 and 0.11 eV, respectively. Moreover, t3Cz-SO exhibited excellent film-forming ability and morphological stability, which are suitable for the fabrication of solution-processed OLEDs. The FIrpic-based device host with t3Cz-SO achieved low turn-on voltage of 3.5 V and high power efficiency of 16.5 lm W−1, which is almost ten times higher than the unmodified parent TADF molecule. This study shows that the introduction of tert-butyl carbazole unit to the periphery of small molecular TADF emitter is an effective method for the development of efficient electroluminescent materials.