Color temperature tunable white organic light-emitting diodes

• Color tunable OLEDs were fabricated by stacking two independent OLED panels.
• By operating them individually, it was possible to vary the color temperature.
• We have explored the impact on capping layer thickness effect on transmission and efficiency.
• Our approach offers an effective technical method to achieve color temperature tunability in OLEDs.

In this work, we demonstrated color-tunable white organic light-emitting diodes by stacking upper orange transparent and lower blue bottom emission organic light-emitting diodes (OLEDs). By independently operating each OLED, it was possible to tune the color temperature in a range of 1500–10,000 K, which covers the full Planckian locus in the 1931 CIE space. In designing stable and efficient OLEDs, in addition to the electrical characteristics, the importance of internal microcavity was emphasized and implemented. In fabricating the upper transparent OLED, special attention was paid to the capping layer for enhancing the emission. Our results presented a general guideline that is practically useful in designing high-performance color-tunable OLEDs with transparent OLEDs.

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