An efficient dual-emissive-layer white organic light emitting-diode: Insight into device working mechanism and origin of color-shift

•A dual-emissive-layer white organic light emitting-diode is demonstrated.•The peak power efficiency of the device is 44.1 ± 2.3 lm/W.•A detailed analysis of the device working principle is performed.•The voltage-dependent color shift of the device is quantitatively described.

By using a single host for both blue and orange phosphorescent dopants, a simple and efficient white organic light emitting-diode is reported. The dual-emissive-layer white device achieves a peak external quantum efficiency of 16.9 ± 0.9% and power efficiency of 44.1 ± 2.3 lm/W without out-coupling enhancement. Analysis of the device working mechanism determines that the blue dopant molecules can form a bridge to facilitate electron transport into the adjacent orange emitting-layer. The orange emission originates from both the direct electron trapping by the orange dopant and incomplete blue–orange energy transfer mechanisms. The origin of the voltage-dependent color shift of the device is quantitatively determined according to the working mechanism. Possible solution to reducing the color-shift is also provided based on the calculation and analytical results.

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