High-efficiency white organic light emitting devices with three separate phosphorescent emission layers

Abstract

We demonstrate high-efficiency white organic light emitting devices (WOLEDs) employing three adjacent phosphorescent emission layers (3-EMLs). The metal-organic dopants for red, green, and blue emissions are each doped in separate hosts, allowing for separate optimization of the three dopant-host material combinations. This structure distributes the exciton generation region across the three hosts to form a stepped progression of highest occupied and lowest unoccupied molecular orbitals. The 3-EML WOLED has a color rendering index of 81 and peak forward-viewing external quantum (EQE) and power efficiencies (PE) of $(16.6\pm 0.8)\%$ and $32\pm 1\mathrm{lm}∕\mathrm{W}$ , respectively, corresponding to a total $\mathrm{EQE}=(28\pm 1)\%$ and a total $\mathrm{PE}=54\pm 3\mathrm{lm}∕\mathrm{W}$ . When an $n$ -doped electron transporting layer is used, the total PE peaks at $64\pm 3\mathrm{lm}∕\mathrm{W}$ , and rolls off to $34\pm 2\mathrm{lm}∕\mathrm{W}$ at $1000\mathrm{cd}∕{\mathrm{m}}^2$ .