Color stable phosphorescent white organic light-emitting diodes with double emissive layer structure

Abstract

In this paper, we report color stable phosphorescent white organic light-emitting diodes (OLEDs) based on a double emissive layer (EML) structure composed of blue and red/green phosphorescent units. Deep hole trapping situation of red and green dopants at the red/green EML could induce less voltage dependent white spectral characteristics by restricting the change of exciton generation zone. A wide band-gap host material, 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy), was used for achieving such deep-trap generation. Fabricated phosphorescent white OLED shows a slight color coordinate change of (−0.002, +0.002) from 1000cd/m2 to 5000cd/m2 with power efficiency of 38.7lm/W and current efficiency of 46.4cd/A at 1000cd/m2. In addition, negligible color changes were observed by delaying red dopant saturation time using optimum red dopant concentration.