Efficient white organic light-emitting devices based on a novel phosphine oxide host with low driving voltage and excellent color stability

摘要

Efficient phosphorescent white organic light-emitting devices (WOLEDs) based on a novel phosphine oxide host, 4,6-bis(diphenylphosphoryl)dibenzofuran (DBFDPO), with particularly low turn-on voltage and high color stability are reported. Without any electrical doping (p-doing or n-doping) strategies, the simplified optimal WOLEDs utilizing DBFDPO as the same host for blue/yellow emitters show low operating voltages, 1 cd/m(2) at 2.5 V (turn-on voltage), 46 cd/m(2) at 3 V and 2787 cd/m(2) at 5 V, and 12840 cd/m(2) at 7 V, respectively. A forward-viewing current efficiency (CE) of 413 cd/A (power efficiency (PE) of 34.0 lm/W) is achieved at the luminance of 673.4 cd/m(2) without any out-coupling enhancement structures. Furthermore, improved color stability is achieved through adjusting the yellow emitting layer. The Commission Internationale de I'Eclairage coordinates (CIE) of the optimal WOLED merely shift from (0.330, 0.405) to (0.327, 0.400) over a wide range of luminance (10-10,000 cd/m(2)). We have revealed that the competition of the two mechanisms of energy transfer and carrier-trapping/-assist transport severely impact on the spectra stability. (C) 2016 Elsevier B.V. All rights reserved.