The effect of driving voltage on the electroluminescent property of a blend of poly(9-vinylcarbazole) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole

The impact of driving voltage on the electroluminescence (EL) from organic light emitting diode with ITO/PVK:PBD:TBAPF6(10:10:1)/Al structure was analyzed by the method of Gaussian fitting. Indium tin oxide (ITO) was used as anode, poly(9-vinylcarbazole) (PVK) as polymeric host, 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as electron-transporting molecule, tetrabutylammonium hexafluorophosphate (TBAPF6) as organic salt and aluminium (Al) as cathode. A broad EL has been observed and it could be attributed to the overlap of emission from four different excited state complexes, including PVK:PBD exciplex, PVK:PBD electroplex, PBD electromer and PVK electromer. The EL spectra shifted to longer wavelength with the increase of driving voltage. The ratio of PVK electromer to PVK:PBD exciplex emission intensity first declined slightly and then increased remarkably, while the relative intensity of combination of PVK:PBD electroplex and PBD electromer emission remained unchanged when the voltage was increased.