Improved red dopants for organic electroluminescent devices

A t-butyl substituted red fluorescent dye, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), has been found to be an excellent dopant in AlQ(3) which produces a highly efficient organic EL device with improved red chromaticity. Unlike 4-(dicyanomethylene)-2 methyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJT), DCJTB can be synthesized in a pure form directly from the unsymmetrical 4-(dicyanomethylene)-2-(t-butyl)-6-methyl-4H-pyran without the contamination of the non-fluorescent bis-condensation byproduct which is prevalent in the DCJT preparation. Both photoluminescence and electroluminescence in the solid films of DCJTB in AlQ(3) are modestly enhanced by the extra t-butyl substitution as a result of a reduction in the effect of concentration quenching. The operation stability of the DCJTB doped EL device is superior, having a half-life of over 5,000 h driven at an initial brightness > 400 cd/m(2).