Reduction of the singlet-triplet energy gap of a thermally activated delayed fluorescence emitter by molecular interaction between the host and the emitter

摘要

We reported the comparative effect of 1,3-bis(9H-carbazol-9-yl) benzene (mCP) and 1,3,5-tris(N-phenylbenzimidazole-2-yl) benzene (TPBI) hosts on the PL characteristics of 2-phenyl-4'-carbazole-9H-thioxanthen- 9-one-10,10-dioxide (TXO-PhCz). Strong interaction between TXO-PhCz and TPBI can be observed, leading to the lower singlet-triplet energy gap of 8.8 meV and non-monotonic increase of Phi(Totle), Phi(D), and Phi(P) with temperature. OLEDs based on TXO-PhCz: TPBI films afford a maximum current efficiency of 71.9 cd A(-1), a maximum power efficiency of 45.2 lm W-1, and a maximum EQE of 23.2%.