Effect of dye aggregation on the photosensitization effect of conducting polypyrrole sensitized with Prussian Blue

The effect of dye aggregation at the small concentration (0–4 mM/monomer) of dispersed Prussian Blue (PB) on the photocurrents were studied in solid state cells fabricated using conducting polypyrrole (Ppy) coated electrodes sandwiched with solid polymer electrolytes viz. polyvinyl alcohol (PVA) with phosphoric acid. These exhibit good photoresponse to visible light: photocurrents being 25 times more than that of the dark current values depending on the concentration of the sensitizer and the applied field. The sensitization increases with concentration of the dye at low concentrations but at high concentration formation of dye aggregates (H-type) has a negative impact on the photosensitization process. The current–voltage (I–V) characteristics in such cells reveal that the charge transport is mainly governed by the space charge effects and the sensitization effects are due to the lowering of the potential barrier formed at the Ppy/PVA+PB interface under photoexcitation.