Spectrum-stable tetra-chromatic white organic light-emitting diodes with red emitter outside the exciton recombination zone

Abstract

Achieving the stable spectrum in complementary-color white organic light-emitting diodes (WOLEDs) with multiple emitters is a challenge. Here, on the basis of ultrathin emitters and spacers, we were successful in achieving a four-chromatic (Blue-Green-Red-Orange) WOLED with superior spectral stability. By placing the red emitter outside the exciton recombination zone, but within the energy transfer radius, the carrier trapping effect from the red dye which is extremely detrimental to spectral stability, is minimized. By adjusting the orange emitter and the unipolar spacer layer adjacent to the red emitter, the red emission from the energy transfer mechanism which is insensitive to voltage is further increased, resulting in further improvement of the spectral stability. When the brightness changed in the range of 1000 cdm-2 to 10000 cdm-2, the color coordinate change of the device with the most stable spectrum is only (0.004,0.006). Simultaneously, the color rendering index (CRI) of this device is up to 86.