Electrochemical doping of conjugated polymers is a complex process, which forms the basis for both characterisation and applications of this class of materials. The high electron affinityof poly(quinoxaline vinylene)s and poly(pyridopyrazine)s, two types of polymers with potential use as electron acceptors in organic photodiodes, has been demonstrated with cyclic voltamrnetry. A large number of substituted polythiophenes were studied with the same technique and their electrochemical bandgaps were calculated on the basis of the n- and p-doping processes. The agreement with their optical bandgaps was sometimes poor, why we conclude that the common combination of electrochemical evaluation of the energy of the band edges with optical bandgaps may be misleading.

Associated with the electrochemical doping is a huge change in the conductivity. Solid state electrochemical cells were used to determine the conductivity in de-doped PEDOT, a polymer usually found in its doped state. The lowest conductivities found in PEDOT , and possible tostudy in these devices, are higher than expected by comparison to related materials. Such high conductivities allow the possibility of electrodeless electrochemistry, where the polymer under study is its own current collector. This demonstrates the use of a doped conjugated polymer film to act as its own working electrode for further doping. One way of demonstrating this phenomenon is to initialise the doping process in one end of a conjugated polymer film, being the working electrode in an electrochemical cell, and observe how the doped area gradually grows. An analysis of this propagation together with electrochemical data can be used to calculate the conductivity of the film in its doped state, and to characterisethe doping process.

The propagation of zones for electrochemical conversion in solid state two electrode cells also give evidence for doping as a part of the mechanism in polymer light emitting electro chemicalcells. These were constructed with oligoethylene substituted polythiophene mixed with an electrolyte as the active layer between two ITO electrodes. Also the use of poly(3,4-ethylenedioxythiophene), PEDOT, both as electron and hole injection electrode in lightemitting devices, was demonstrated.