Highly efficient white electroluminescent devices with hybrid double emitting layers of quantum dots and phosphorescent molecules

Hybrid quantum dot light-emitting diodes (QLEDs) with double emitting layers (EMLs) were developed to achieve highly efficient white emission. The first emitting layer comprised blue and green quantum dots that were deposited by spin-coating, and the second emitting layer comprised red phosphorescent organic molecules that were deposited by thermal evaporation without any buffer layer. These unique trichromatic devices showed three distinct electroluminescent (EL) peaks with similar intensities at 15 V and the variation of the EL spectra with applied voltage was investigated systematically. These hybrid QLEDs for white emission led to high device performance with a maximum luminance of 20453 cd m^-2 and an external quantum efficiency of 9.19%. These results indicate that the unique design of double EMLs is promising for achieving bright and efficient white devices with a high color rendering index.