Sensitization effect in doped and undoped state of polypyrrole by methylene blue in solid state electrochemical cells

Methylene blue (MB) at small concentration is used as a photosensitizer in the solid state photoelectrochemical cells fabricated using doped and undoped polypyrrole (Ppy) coated electrodes sandwiched with solid polymer electrolyte (SPE) viz. polyvinylalcohol (PVA) doped with phosphoric acid. Different sensitization effects are observed for the same polymer–dye combination. MB sensitizes Ppy in doped state more efficiently as compared to undoped state of the polymer. The actual placement of the energy levels of dye with respect to polymer and ease with which polymer transports photogenerated charge carriers without recombination are observed to be important in such sensitization processes and governs the overall process.