Admittance electrical model of polyfluorene based organic light emitting diodes

In order to obtain an AC electrical model of polyfluorene-PEDOT poly(3,4-ethylenedioxythiophene) based organic light emitting diodes, different devices have been realized using three PEDOT dispersions. Static current-voltage characteristics have revealed exponential like transport in all the samples and the bias has shown no dependence on admittance spectra. An electrical model is proposed and the estimated capacitance has been analyzed in terms of polyfluorene bulk intra-gap state distribution obtaining a state density of about 10 16 eV −1 cm −3 . The hypothesis of a space charge involving completely the polyfluorene layer has been discussed.