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

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.