Simultaneous high efficiency/CRI/spectral stability and low efficiency roll-off hybrid white organic light-emitting diodes via simple insertion of ultrathin red/green phosphorescent emitters in a blue exciplex

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Abstract
The simultaneous achievement of high efficiency, low efficiency roll-off, good spectral stability and a high color rendering index (CRI) is still a challenge in hybrid white organic light-emitting diodes (WOLEDs). In this paper, we strategically design a device structure by simply inserting ultrathin red/green phosphorescent emitters in a blue exciplex to efficiently utilize excitons for light emission. The resulting WOLEDs not only exhibit high efficiency and low efficiency roll-off, but also maintain a high CRI and stable spectral emission. The maximum power efficiency (PE), current efficiency (CE) and external quantum efficiency (EQE) reached 66.2 lm W−1, 50.6 cd A−1 and 21.2% and remained at 50.9 lm W−1, 45.2 cd A−1 and 18.3% at 100 cd m−2 and 34.6 lm W−1, 35.5 cd A−1 and 15.8% at 1000 cd m−2, respectively. In addition, the electroluminescence (EL) spectra were also extremely stable with a high CRI of 86 and Commission Internationale de L’Eclairage (CIE) coordinates of (0.40 ± 0.01, 0.46 ± 0.01) from 500 to 10 000 cd m−2. The achievement of good comprehensive performance is attributed to the efficient device structure of ultrathin phosphors in the exciplex that can realize 100% exciton utilization without affecting the electrical properties.
Funding Information
  • National Natural Science Foundation of China (21788102, 51333007, 51673067, 91433201, 11661131001)
  • Guangzhou Municipal Science and Technology Program key projects (201707020040)

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