Enhanced Driving Performance of Organic Light-Emitting Diodes with All Carrier Ohmic-Contacts

Abstract

This paper elucidates the enhancement of the optoelectronic properties of organic light-emitting diodes (OLEDs) by the p-doping effect of molybdenum oxide -doped -tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA). The device performance strongly depends on both the thickness and the doping concentration of the -doped 2-TNATA. As the doping concentration is increased from 25 to 75%, the hole ohmic properties of the hole-only device with the glass/indium tin oxide -doped 2-TNATA structure were improved, due to the increase in the p-type doping effect. Also, the photoemission spectra revealed that the p-type doping effects cause the lowering of the hole-injecting barrier height, as well as the improvement of the hole conductivity. This improvement is caused by the formation of the charge transfer complex that is generated by doping into 2-TNATA, markedly increasing the number of hole carriers. With -doped 2-TNATA as a hole ohmic contact and fullerene /lithium fluoride (LiF) as an electron ohmic contact, the OLED with the glass/ITO/-doped 2-TNATA (75%, )/NPB structure showed both a maximum luminance of at and power efficiency of at about .