Light-emitting diodes of poly(3-hexylthiophene) Langmuir-Blodgett films

Poly(3-hexylthiophene) Langmuir-Blodgett films have been used as emitting layers in light-emitting diodes. The effect of the film thickness and additional carrier-transport layers on current-voltage characteristics and quantum efficiency were studied, and the electroluminescence spectra measured. Hole transporting poly(9-vinylcarbazole) was used both as a separate layer in a heterostructure device and in a blend with emitting material. The electron-transport material 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole was used in a blend with the emitting material. The connections between the diode structure and the electro-optical properties as well as operation mechanisms are discussed