IMPROVED RED DOPANTS FOR ORGANIC ELECTROLUMINESCENT DEVICES

A t-butyl substituted red fluorescent dye, l-6-(1,1,7,7-tetramethyljul olidyl-9-enyl)-4H-pyran (DCJTB), has been found to be an excellent dop ant in AlQ(3) which produces a highly efficient organic EL device with improved red chromaticity. Unlike 4-(dicyanomethylene)-2 l-6-(1,1,7,7 -tetramethyljulolidyl-9-enyl)-4H-pyran (DCJT), DCJTB can be synthesize d in a pure form directly from the unsymmetrical 4-(dicyanomethylene)- 2-(t-butyl)-6-methyl-4H-pyran without the contamination of the non-flu orescent bis-condensation byproduct which is prevalent in the DCJT pre paration. Both photoluminescence and electroluminescence in the solid films of DCJTB in AlQ(3) are modestly enhanced by the extra t-butyl su bstitution as a result of a reduction in the effect of concentration q uenching. The operation stability of the DCJTB doped EL device is supe rior, having a half-life of over 5,000 h driven at an initial brightne ss > 400 cd/m(2).