| Summary: | High efficiency monochrome red and white OLEDs were realized through the control of dopant concentration by employing the exciplex mCP:PO-T2T as host. The red OLED based on exciplex host achieved the maximum external quantum efficiency (EQE) of 21%, a 44% increase compared with traditional CBP single host. Further, the white OLED with maximum current efficiency, power efficiency and EQE of 41.2 cd/A, 43.1 lm/W, and 19.5%, respectively, was obtained by decreasing the dopant concentration to achieve the simultaneous emission of exciplex host and dopant emitter. The results demonstrate that the barrier-free charge injection, balanced charge transport/recombination, and high triplet excition harvest are responsible for the high efficiency.
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