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/m2 to 5000 cd/m2 with power efficiency of 38.7 lm/W and current efficiency of 46.4 cd/A at 1000 cd/m2. In addition, negligible color changes were observed by delaying red dopant saturation time using optimum red dopant concentration.

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► Color-stable white OLEDs with a double emitting layer structure were demonstrated.
► Deep hole trapping of red and green dopants could restrict exciton generation zone movement.
► The current and power efficiencies of 40.4 lm/W and 46.8 cd/A were achieved with (0.39, 0.39) color coordinates.