Efficient, color stable white organic light-emitting diode based on high energy level yellowish-green dopants

A study was conducted to demonstrate the fabrication of efficient, color-stable, multi-emitting layer (EML) white organic light-emitting diodes (WOLED) using high energy level yellowish-green phosphorescent dopants. The WOLEDs exhibited maximum external quantum efficiency of 11.7% and maximum luminance efficiency of 13.21mW^-1, respectively. The results of the study show that the WOLEDs also exhibited high CRI over 87 and the color temperature of about 4300 k. The dopants have higher LUMO and HOMO levels than the host so that the dopants behave as hole traps and electron scattering centers. As a result the recombination ratio in each EML was maintained constant with increasing voltage to keep the CIE almost constant. The middle green emitting layer also improves the electron and hole balance in the EMLs to improve the device efficiency. The study also suggests that these WOLEDs have sufficient potential for solid-state lighting applications.