Reduction of the singlet–triplet energy gap of a thermally activated delayed fluorescence emitter by molecular interaction between the host and the emitter†
Abstract
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 ΦTotle, ΦD, and ΦP 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%.