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

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 1000 cd/m(2) to 5000 cd/m(2) with power efficiency of 38.7 lm/W and current efficiency of 46.4 cd/A at 1000 cd/m(2). In addition, negligible color changes were observed by delaying red dopant saturation time using optimum red dopant concentration. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.