Abstract
The emerging thermally activated delayed fluorescence materials have great potential for efficiencies in organic light-emitting diodes by optimizing molecular structures of the emitter system. However, it is still challenging in the device structural design to achieve high efficiency and stable device operation in white organic light-emitting diodes. Here we propose a universal design strategy for thermally activated delayed fluorescence emitter-based fluorescent white organic light-emitting diodes, establishing an advanced system of “orange thermally activated delayed fluorescence emitter sensitized by blue thermally activated delayed fluorescence host” combined with an effective exciton-confined emissive layer. Compared to reference single-layer and double-layer emissive devices, the external quantum efficiency improves by 31 and 45%, respectively, and device operational stability also shows nearly fivefold increase. Additionally, a detailed optical simulation for the present structure is made, indicating the validity of the design strategy in the fluorescent white organic light-emitting diodes.
Highlights
The emerging thermally activated delayed fluorescence materials have great potential for efficiencies in organic light-emitting diodes by optimizing molecular structures of the emitter system
There is still a bottleneck to simultaneously realize high efficiency and long device lifetime in phosphorescent White organic light-emitting diodes (WOLEDs), which is restricted by the absence of the efficient and stable blue phosphorescent emitters
Because the energy gap between the singlet excited state and triplet excited state is sufficiently small in thermally activated delayed fluorescence (TADF) processes, the generated nonradiative triplet excitons can be efficiently upconverted into the radiative singlet excitons by the reverse intersystem crossing (RISC) process[27,28,29,30,31]
Summary
The emerging thermally activated delayed fluorescence materials have great potential for efficiencies in organic light-emitting diodes by optimizing molecular structures of the emitter system. It is still challenging in the device structural design to achieve high efficiency and stable device operation in white organic light-emitting diodes. We propose a universal design strategy for thermally activated delayed fluorescence emitter-based fluorescent white organic light-emitting diodes, establishing an advanced system of “orange thermally activated delayed fluorescence emitter sensitized by blue thermally activated delayed fluorescence host” combined with an effective exciton-confined emissive layer.
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