Liquid Carbazole Substituted with a Poly(ethylene oxide) Group and Its Application for Liquid Organic Light-emitting Diodes

We report efficient carrier injection characteristics in liquid organic light-emitting diodes (OLEDs). The use of a liquid carbazole substituted with a poly(ethylene oxide) (PEO) chain provided a substantial improvement in carrier injection compared to devices constructed with carbazoles without PEO units. The external electroluminescence quantum efficiency (Phi(EL).) of an OLED with the liquid carbazole as an emitting layer resulted in Phi(EL) = 0.75%, 25 times higher Phi(EL) than that of our previous liquid OLED without electrolyte.