화학공학소재연구정보센터
Thin Solid Films, Vol.517, No.17, 5293-5297, 2009
Enhancement of efficiency of white organic light-emitting diodes with p-type hole injection layer
This study elucidates the optoelectronic properties of high-efficiency p-i-n white organic light-emitting diodes (WOLEDs) with molybdenum oxide (MoO(x))-doped 4,4',4 ''-tris[2-naphthyl(phenyl)amino] triphenylamine (2-TNATA) as a p-doping hole injection layer (p-HIL). Devices with 10 wt.% MoO(x) doping in 2-TNATA had electroluminescent (EL) efficiencies of 7.71 cd/A and 4.32 lm/W, respectively, at a driving voltage of 5.65 V and current density of 20 mA/cm(2). The X-ray photoelectron spectroscopy (XPS) and UV-vis-NIR absorption spectra of MoO(x)-doped 2-TNATA layers revealed that MoOx-doped 2-TNATA p-HIL had an improvement on hole conductivity. Such the improvement is caused by the formation of the charge transfer (CT) complex (MoO(x)(-)/2-TNATA(+)) that is generated by doping MoO(x) into 2-TNATA, markedly increasing the number of hole carriers, improving the balance of the electrons and holes in the recombination zone. Additionally, annealing improves the morphological stability of the p-HIL and extends the lifetime of the p-i-n WOLED. (C) 2009 Elsevier B.V. All rights reserved.