Management of charge carriers and excitons for efficient and color-stable white phosphorescent organic light-emitting diodes with simplified structure

• We proposed an original device concept for simplified WOLEDs to achieve good color-stability.
• The two-color and three-color WOLEDs achieve maximum power efficiencies of 45.5 lm/W and 32.8 lm/W.
• The reason of the superior color-stability of the WOLEDs is discussed.
• The mixed host structure plays key roles in achieving excellent color stability.

We have demonstrated color-stable and highly efficient simplified white phosphorescent organic light-emitting diodes. The key feature is the use of a novel approach to confine the distribution of charge carriers and excitons across the whole blue emission layer. The resulting two-color white device has the maximum power efficiency and current efficiency of 45.5 lm/W and 43.5 cd/A with a very low color shift over a wide range of luminance. By systematically investigating the working mechanisms, we found that the ambipolar charge carrier transport ability of co-host layer which ensures the distribution of excitons to form in the whole blue emission layer was the critical factors for constructing color-stable white devices. Our results show that simplified white devices based on two organic materials achieving excellent color stability are possible.

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