Hybrid Tandem White OLED with Long Lifetime and 150 Lm W-1in Luminous Efficacy Based on TADF Blue Emitter Stabilized with Phosphorescent Red Emitter

Modern lighting requires high efficiency and long lifetime simultaneously. In this paper, highly efficient white organic light emitting diodes (WOLEDs) are demonstrated based on a modified hybrid tandem structure constructed with a phosphorescent yellow-red unit using an exciplex host and a blue-red unit based on a thermally activated delayed fluorescence (TADF) blue emitter, and the devices are properly built with internal and external light extraction structures. The resulting four-color WOLED exhibits an external quantum efficiency and luminous efficacy of 126.2% and 150.7 Lm W-1, respectively, and the color rendering index is close to 80 at a brightness of 1000 cd m(-2). This device also shows a very good color stability with increasing luminance up to 15 000 cd m(-2)and there is only a small angular color variation for viewing angles changing from 0 degrees to 70 degrees. The T(50)lifetime (defined as the time corresponding to 50% decrease in luminance from an initial value) of the WOLED at an initial luminance of 1000 cd m(-2)is extrapolated as 12 600 h.