Improved performances of organic light-emitting diodes with metal oxide as anode buffer

We demonstrate extremely stable and highly efficient organic light-emitting diodes (OLEDs) based on molybdenum oxide $(MoO3)$ as a buffer layer on indium tin oxide (ITO). The significant features of $MoO3$ as a buffer layer are that the OLEDs show low operational voltage, high electroluminescence (EL) efficiency and good stability in a wide range of $MoO3$ thickness. A green OLED with structure of $ITO∕MoO3∕N,N′$-di(naphthalene-1-yl)-$N,N′$-diphenyl-benzidene (NPB)∕NPB: tris(8-hydroxyquinoline) aluminum $(Alq3)$⁠:10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-$1H$⁠, $5H$⁠, $11H$-(1)-benzopyropyrano(6,7-8-$i$⁠,$j$⁠)quinolizin-11-one (C545T)∕$Alq3∕LiF∕Al$ shows a long lifetime of over $50000h$ at $100cd∕m2$ initial luminance, and the power efficiency reaches $15lm∕W$⁠. The turn-on voltage is $2.4V$⁠, and the operational voltage at $1000cd∕m2$ luminance is only $6.9V$⁠. The significant enhancement of the EL performance is attributed to the improvement of hole injection and interface stability at anode.