High-brightness white light-emitting organic electroluminescent devices using poly(N-vinylcarbazole) as a hole-transporter

A white light-emitting organic electroluminescent (EL) device with multilay er thin-film structure, which shows high-brightness and high-efficiency, is demonstrated. The device structure of glass substrate/indium-tin oxide/pol y(N-vinylcarbazole) (PVK)/1,1,4,4-tetraphenyl-1,3-butadiene/8-(quinolinolat e)-aluminum (Alq) doped with 5,6,11,12-tetraphenylnaphthacene/Alq/Mg/Al was employed. The turn-on voltage is as low as 2.5 V. The white light emission covers a wide range of the visible region, and the Commission Internationa le de 1' Eclairage coordinates of the emitted light are (0.319, 0.332) at 1 0 V. Bright white light, over 20 000 cd/m(2), was successfully obtained at about 18 V, and the maximum efficiency reaches to 1.24 lm/W at 9 V. The rea sons of obtaining high level EL properties of our device have been discusse d.