White light from an electroluminescent diode made from poly[3(4-octylphenyl)-2,2′-bithiophene] and an oxadiazole derivative

We report on an electroluminescent diode emitting red, green, and blue light simultaneously. The device is based on a thin polymer layer, poly[3-(4-octylphenyl)-2,2′-bithiophene] and a thick molecular layer, 2-(4-biphenylyl)-5-(4-tertbutyl-phenyl)1,3,5-oxadiazole. The quantum efficiency for light conversion is 0.3% and the turn-on voltage for light emission is 7 V. In this article we present electric and spectroscopic characterizations. A mechanism for the light emission, based on electron and hole recombination between the two organic layers, is proposed.