Development of highly stable organic electroluminescent devices with a doped co-host emitter system

Efficient red organic light-emitting devices based on the fluorescent dye “4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped in co-host emitter (CHE) systems of rubrene/tris(8-hydroxyquinolinato)aluminum (Alq3) [60/40] and of 9,10-di(2-naphthyl)anthracene (ADN)/Alq3 [60/40] which achieved a luminance efficiency of 4.2-5.5 cd/A at 20 mA/cm2 with Commission Internationale d'Eclairage coordinates of [0.64, 0.35]-[0.62, 0.37]. At high rubrene or ADN concentration (>60%), this DCJTB doped CHE system has the advantage of alleviating the current-induced fluorescence quenching problem often encountered in red organic electroluminescence (EL) devices and greatly improves the EL efficiency over a wide range of drive current conditions.