Tri-Spiral Donor for High Efficiency and Versatile Blue Thermally Activated Delayed Fluorescence Materials.

Blue thermally activated delayed fluorescence (TADF) emitters that can simultaneously achieve high efficiency in doped and nondoped organic light-emitting diodes (OLEDs) are rarely reported. Reported here is a strategy using a tri-spiral donor for such versatile blue TADF emitters. Impressively, by simply extending the nonconjugated fragment and molecular length, aggregation-caused emission quenching (ACQ) can be greatly alleviated to achieve as high as a 90 % horizontal orientation dipole ratio and external quantum efficiencies (EQEs) of up to 33.3 % in doped and 20.0 % in nondoped sky-blue TADF-OLEDs. More fascinatingly, a high-efficiency purely organic white OLED with an outstanding EQE of up to 22.8 % was also achieved by employing TspiroS-TRZ as a blue emitter and an assistant host. This compound is the first blue TADF emitter that can simultaneously achieve high electroluminescence (EL) efficiency in doped, nondoped sky-blue, and white TADF-OLEDs.