The inductive-effect of electron withdrawing trifluoromethyl for thermally activated delayed fluorescence: tunable emission from tetra- to penta-carbazole in solution processed blue OLEDs

The non-conjugated inductive effect of trifluoromethyl (CF3) was found to be a new acceptor instead of other conjugated moieties. Two blue emissive compounds, 4CzCF3Ph and 5CzCF3Ph, were synthesized using a simple catalyst-free C–N coupling reaction. Solution-processed TADF devices based on the 5CzCF3Ph dopant exhibit significantly higher efficiency (11.8 cd A−1, 5.2%) than 4CzCF3Ph (1.03 cd A−1, 0.67%) due to the smaller ΔEST value for efficient RISC.