Highly efficient orange fluorescent OLEDs based on the energy transfer from bilayer interface exciplex

•Achieving highly efficient fluorescent OLEDs of 8.1% EQE with rubrene as the emitter.•Utilizing the energy transfer from simple bilayer interface TADF exciplex.•Up-conversion of exciplex triplet excitons and efficient energy transfer play the key role in this system.

We demonstrated highly efficient traditional orange emission fluorescent OLEDs with simple device structure by utilizing energy transfer from bilayer interface TADF exciplex to dopant. With rubrene as the dopant, under the optimized concentration of 1.5%, the device achieved maximum current efficiency, power efficiency and EQE of 25.3 cd/A, 22.6 lm/W and 8.1%, respectively. Even at the luminance of 1000 cd/m2, the EQE also remained 6.9%. The obtainment of so high efficiency could be attributed to highly efficient RISC efficiency of triplet excitons and energy transfer efficiency from TADF exciplex to dopant. The more detailed working mechanism was also argued.

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