High efficiency white organic light-emitting devices incorporating yellow phosphorescent platinum(II) complex and composite blue host

Abstract

A new class of charge neutral, strongly luminescent cyclometalated platinum(II) complexes supported by dianionic tetradentate ligand are synthesized. One of these platinum(II) complexes, Y-Pt, displays a high photoluminescence quantum yield of 86% and electroluminescence efficacy (ηpower) of up to 52 lm W-1, and is utilized as a yellow phosphorescent dopant in the fabrication of white organic light-emitting devices (WOLEDs). WOLEDs based on conventional structures with yellow emission from Y-Pt in combination with blue emission from bis(4,6-difluorophenyl- pyridinato-N,C2′) (picolinate) iridium(III) (FIrpic) show a total ηpower of up to 31 lm W-1. A two-fold increase in ηpower by utilizing a modified WOLED structure comprising of a composite blue host is realized. With this modified device structure, the total ηpower and driving voltage at a luminance of 1000 cd m -2 can be improved to 61 lm W-1 and 7.5 V (i.e., 10 V for control devices). The performance improvement is attributed to an effectively broaden exciton formation-recombination zone and alleviation of localized exciton accumulation within the FIrpic-doped composite host for reduced triplet-triplet annihilation, yielding blue light-emission with enhanced intensity. The modified device structure can also adopt a higher concentration of Y-Pt towards its optimal value, leading to WOLEDs with high efficiency. An effective and simple approach for boosting the performance of white organic light-emitting devices (WOLEDs) is demonstrated. A modified device structure consisting of a composite blue host that can significantly improve both device efficiency and efficiency roll-off is developed. With the modified structure, a WOLED exhibiting twofold enhancement in the total efficacy from 31 up to 61 lm W-1 is realized. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.