Realization of Thermally Stimulated Delayed Phosphorescence in Arylgold(III) Complexes and Efficient Gold(III) Based...

To address and overcome the difficulties associated with the increased reactivity and susceptibility of blue emitters to deactivation pathways arising from the high-lying triplet excited states, we have successfully demonstrated an innovative strategy of harvesting triplet emission via the "thermally stimulated delayed phosphorescence" mechanism, where thermal up-conversion of excitons from the lower-energy triplet excited states (T₁) to higher-energy triplet excited states (T₁') are observed to generate blue emission. The lower-lying T₁ excited state could serve as a mediator to populate the emissive T₁' state by up-conversion via reverse internal conversion, which could enhance the photoluminescence quantum yield by over 20-folds. Organic light-emitting devices with respectable external quantum efficiencies of up to 7.7% and sky-blue emission with CIE coordinates of (0.17, 0.37) have been realized. The operational stability for the device based on complex 1 has also been explored, and the device is found to show fairly respectable lifetime. This work opens up a new avenue to the design and synthesis of blue phosphorescent emitters.