Four new bipolar Indolo[3,2-b]carbazole derivatives for blue OLEDs

Abstract Four new indolo [3,2-b]carbazole derivatives containing imidazole-derived moieties, 2,8-bis(4-(9-(4-(tert-butyl)phenyl)-9H-pyreno [4,5-d]imidazol-10-yl)phenyl)-5,11-bis(2-ethylhexyl)-5,11-dihydroindolo [3,2-b]carbazole (Py-ICZ-Py), 2,8-bis(4-(1-(4-(tert-butyl)phenyl)-1H-phenanthro [9,10-d]imidazol-2-yl)phenyl)-5,11-bis(2-ethylhexyl)-5,11-dihydroindolo [3,2-b]carbazole (PI-ICZ-PI), 5,11-bis(2-ethylhexyl)-2,8-bis(4-(1-phenyl-1H-benzo [d]imidazol-2-yl)phenyl)-5,11-dihydroindolo [3,2-b]carbazole (BI-ICZ-BI) and 2,8-bis(4-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenyl)-5,11-bis(2-ethylhexyl)-5,11-dihydroindolo [3,2-b]carbazole (IM-ICZ-IM), were successfully synthesized for highly efficient blue light-emitting devices. The thermal stabilities, photophysical and electrochemical properties of the hybrid compounds were investigated. These hybrid compounds exhibited strong blue emissions in solutions. Furthermore, the vacuum-processed doped devices based on these compounds were fabricated, in which the devices based on the compound PI-ICZ-PI exhibited the best electroluminescence performance with a maximum brightness of 3973 cd/m2, a maximum current efficiency of 3.67 cd/A and a maximum external quantum efficiency (EQE) of 2.64%.