Efficient deep-blue organic light-emitting diodes: Arylamine-substituted oligofluorenes

Abstract

Novel deep-blue-light-emitting diphenylamino and triphenylamino end-capped oligofluorenes were synthesized by double palladium-catalyzed Suzuki cross- coupling of dibromo-oligofluorene with the corresponding boronic acid as a key step. These oligofluorenes exhibit deep-blue emission (lambda(em)(max) = 429-432 nm), low and reversible electrochemical oxidation (highest occupied molecular orbital = 5.15-5.20 eV), high fluorescence quantum yield (Phi(FL) = 0.61-0.93), and good thermal properties (glass-transition temperature, T-g = 99-195 degrees C and decomposition temperature, T-dec > 450 degrees C). Remarkably, saturated deep-blue organic light-emitting diodes, made from these oligofluorenes as dopant emitters, have been achieved with excellent performance and maximum efficiencies up to 2.9 cd A(-1) at 2 mA cm(-2) (external quantum efficiency of 4.1 %) and with Commission Internationale de l'Eclairage (x,y) coordinates of (0.152,0.08), which is very close to the National Television System Committee standard blue.