We fabricated 2-stack white organic light-emitting diode (WOLED) structure with luminance efficiency of 27.4 cd/A and color point of (0.32, 0.29) where one unit device emitted blue color and the other emitted red and green colors. Comparing with other configurations possible for 2-stack WOLED, it was found that our structure had merits of higher color gamut and lower power consumption, in spite of low luminance efficiency. In our 2-stack structure, we found that the blue efficiency which determines the power consumption of panel was strongly dependent on the position of the blue emitting layer. Based on an optical simulation and a viewing-angle analysis, we proved that the change of the luminance of blue color came from the microcavity effect depending on the distances between anode and cathode and between blue emitting layer and cathode.
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