Doped red organic electroluminescent devices based on a cohost emitter system

We have developed an efficient red emitter in organic light-emitting diodes based on the fluorescent dye 4-(dicyanomethylene)-2-$t$ -butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-$\text{4H}$ -pyran doped in a cohost emitter system of 5,6,11,12-tetraphenylnathacene/tris(8-hydroxyquinolinato)aluminum which achieved an electroluminescence (EL) efficiency of 4.4 cd/A and 2.1 lm/W at 20 ${\mathrm{mA/cm}}^2$ and 6.8 V, with a near saturated Commission Internationale d’Eclairage coordinates $\text{(x=0.65,}$ $\text{y=0.35).}$ This cohost emitter system has the advantage of alleviating the current-induced fluorescence quenching often encountered in red organic EL devices and greatly improves the EL efficiency over a wide range of drive current conditions. From accelerated degradation tests, a device half-life of about 33 800 h can be projected in this system at an initial device luminance of 100 ${\mathrm{cd/m}}^2.$