Realization
of Thermally Stimulated Delay Phosphorescence
in Arylgold(III) Complexes and Efficient Gold(III) Based Blue-Emitting
Organic Light-Emitting Devices
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.