Thermally Activated Delayed Fluorescence Materials Based on Homoconjugation Effect of Donor–Acceptor Triptycenes

Donor–acceptor
triptycences, TPA-QNX­(CN)­2 and TPA-PRZ­(CN)­2,
were synthesized and their emissive properties were studied. They
exhibited a blue-green fluorescence with emission lifetimes on the
order of a microsecond in cyclohexane at room temperature. The long
lifetime emission is quenched by O2 and is attributed to
thermally activated delayed florescence (TADF). Unimolecular TADF
is made possible by the separation and weak coupling due to homoconjugation
of the HOMO and LUMO on different arms of the three-dimensional donor–acceptor
triptycene. Organic light emitting devices (OLEDs) were fabricated
using TPA-QNX­(CN)­2 and TPA-PRZ­(CN)­2 as emitters which displayed electroluminescence
with efficiencies as high as 9.4% EQE.