The facile synthesis and high efficiency of the red electroluminescent dopant DCINB: A promising alternative to DCJTB

The cost of manufacturing 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) is prohibitively high because the synthesis of one of the key intermediates, 1,1,7,7-tetramethyljulolidine, is costly, produces by-products and is of low yield. As an alternative low-cost process, a novel red dopant 4-(dicyanomethylene)-2-tert-butyl-6-(8-(4-methyl)phenyl-2,3-dihydro-1H-cyclopenta [3a,8a]indolin-5-enyl)-4H-pyran (DCINB) bearing an indoline unit instead of 1,1,7,7-tetramethyljulolidine as electron donor has been conveniently synthesized in high yield. The dopant exhibited very similar absorption and emission behaviour to DCJTB, but displayed superior fluorescence quantum yield and electroluminescence efficiency, which was attributed to high recombination ratio of excitons imparted by the introduced indoline unit. The synthesis and purification stages are simple and can be scaled-up, thereby offering a possible alternative to the commercial DCJTB.