A hybrid white organic light-emitting diode with above 20% external quantum efficiency and extremely low efficiency roll-off
Recently, the combination of blue fluorescent emitter with long wavelength phosphorescent emitters in the so-called hybrid white organic light-emitting diodes (WOLEDs) has attracted significant attention. However, compared to the previously reported all-phosphor WOLEDs, the efficiencies of hybrid WOLEDs are still unsatisfactory. In this work, through a delicate design of the device structure, nearly all generated excitons are harnessed for light emission in the hybrid WOLED. The hybrid device shows excellent electroluminescence (EL) performance with a forward-viewing maximum external quantum efficiency (EQE), current efficiency (CE) and power efficiency (PE) of 21.2%, 49.6 cd A−1 and 40.7 lm W−1, respectively, which then slightly decreases to 20.0%, 49.5 cd A−1 and 37.1 lm W−1 at 1000 cd m−2, which are the highest levels reported so far. This work opens up an avenue for the development of blue fluorescent emitter together with a novel device structural design for ultrahigh performance hybrid WOLEDs in the future.