Time evolution of the electric field at electrode interfaces with conducting polymers

Time-resolved scanning Kelvin probe microscopy (SKPM) and Raman microscopy have been used to investigate processes occurring at the interface between indium tin oxide (ITO) electrodes and inkjet printed polyethylenedioxythiophene: polystyrene sulphonic acid (PEDOT:PSS). SKPM reveals a slow, reversible polarisation process (time constant similar to12 s) occurring at the electrodes caused by the drift of Na+ and/or H+ ions in the polymer. Raman microscopy shows that the resulting field enhancement at the electrodes increases the concentration of holes in the polymer at the anode, while at the cathode there is a significant reduction in hole concentration. Such effects have implications for both the short- and long-term stability of devices utilising PEDOT:PSS. (C) 2004 American Institute of Physics.