Highly efficient and color-stable white organic light-emitting diode based on a novel blue phosphorescent host

Highly efficient phosphorescent white organic light-emitting devices (WOLEDs) have been fabricated by using two complementary blue and yellow emitting layers, in which the blue guest iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2′] picolinate (Firpic) was doped in a novel blue phosphorescent host. The efficiencies and spectra of WOLEDs can be easily tuned by inserting an ultrathin interlayer between the two emitters and adjusting the thickness of the yellow emitting layer (Y-EML). The device with 1 nm thick interlayer and 3 nm thick (Y-EML) obtains very high efficiencies of 42.4 cd/A and 47.6 lm/W and a luminance of 1144 cd/m2 was realized at a low voltage of 3.6 V. In addition, another device with 2 nm thick interlayer and 5 nm thick Y-EML exhibited nearly voltage-independent electroluminescent (EL) spectra. Commission International de L’Eclairage (CIE) coordinates of this device only changes from (0.333, 0.436) at a luminance of 100 cd/m2 to (0.330, 0.434) at that of 10,000 cd/m2, nearly independent of the driving voltage.