Circularly Polarized Electroluminescence of Thermally Activated Delayed Fluorescence-Active Chiral Binaphthyl-Based Luminogens

Two pairs of thermally activated delayed fluorescence (TADF)-active chiral luminogens (R/S-1 and R/S-2) can be achieved by introducing D-A-type groups to chiral BINOL skeletons. The resulting chiral luminogens can exhibit aggregation-induced emission properties in THF-water mixtures and TADF emission in a doped-film state. The absolute photoluminescence quantum yield (ΦPL) and delayed fluorescence lifetimes (τdelayed) were measured to be 18.5% and 1.03 μs for R-1 and 15.7% and 0.97 μs for R-2. However, only R/S-1 with the fixed conjugation structure can emit circularly polarized luminescence signals, and glum can reach 1.6 × 10-3 in toluene solution and 9.2 × 10-4 in the neat film. Most importantly, R/S-1 was chosen as the emitting layers for orange-red circularly polarized organic light-emitting diodes, which can display low turn-on voltage (Von) of 3.4 V, high maximum brightness (Lmax) up to 40 470 cd m-2, moderate external quantum efficiency of 4.1%, as well as circularly polarized electroluminescence signal with gEL = -0.9 × 10-3/+1.0 × 10-3.