Violet–blue electroluminescent diodes utilizing conjugated polymer blends

We report violet–blue emission from light-emitting diodes (LEDs) fabricated by dispersing a soluble conjugated polymer poly(2,5-dibutoxyphenylene) (PPP) and an organic electron-transporting material 2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) into a hole-transporting polymer poly(N-vinylcarbazole) (PVK). The emission film can be spin-coated by the blend solution. The air-stable aluminum is used as the cathode material. The electroluminescent efficiency of the device reaches 1.2%, which is more than 100 times that of the device made with only PPP. The LEDs turn on at about 20 V and have a peak emission wavelength in the violet–blue region at 424 nm.