Photo- and electro-luminescence properties of two coumarin-triarylimidazole hybrid derivatives

Two coumarin-triarylimidazole hybrid derivatives with an N,N-diethylamine at the 7-position and a triaryl-substituted imidazole at the 3-position on the coumarin core, 3-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-Bu) and 3-(1-(4-cyanophenyl)-4,5-diphenyl-1H-imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one (C-IM-CN), were successfully synthesized for application in organic-light emitting devices. Their photophysical and electrochemical properties, thermal stability and electroluminescence properties were investigated. The results showed that these compounds have excellent thermal stability, and exhibit strong blue-green emission in dichloromethane solution and green emission in thin solid films. Further, the solution-processed doped devices based on the compounds were fabricated, in which the devices fabricated from C-IM-CN exhibited the best device performance with a turn-on voltage of 3.6 V, a maximum brightness of 6896 cd m(-2), a maximum current efficiency of 6.39 cd A(-1) and a maximum external quantum efficiency of 2.92%.