Efficient blue organic light-emitting diodes using newly-developed pyrene-based electron transport materials

We synthesized new kinds of pyrene-based electron transport materials: 1,6-di(pyridin-3-yl)-3,8-di(naphthalen-1-yl)pyrene (N1PP) and 1,6-di(pyridin-3-yl)-3,8-di(naphthalen-2-yl)pyrene (N2PP). The external quantum efficiencies of the device with these electron transport materials increase by more than 50% at 1 mA cm−2 compared with those of the device with representative Alq3 as an electron transport material. The enhanced quantum efficiency is due to a balanced charge recombination in an emissive layer. Electron mobilities in N1PP and N2PP films are three times higher than that in Alq3. Highly enhanced power efficiency is achieved due to a low electron injection barrier and a high electron mobility. We find that the luminance degradation in the blue OLEDs is correlated with the HOMO energy levels of electron transport materials.