Solid state electrochemical reaction in photocells made using conducting polyaniline and sensitized with methylene blue

Abstract.

The effect of small concentration of methylene blue (MB) on photocurrents was studied in solid state photoelectrochemical cells fabricated using conducting polyaniline (PANI) coated electrodes sandwiched with a solid polymer electrolyte, viz. poly(vinyl alcohol) (PVA) with phosphoric acid. These exhibit good photoresponse to visible light (maximum photosensitivity factor of the order of 10). The current-voltage (I-V) characteristics in such cells reveal that the charge transport is ohmic. Also, an electrochemical reaction (motion of Cl^– from SPE+MB to PANI) is observed at 1.2–1.3 V, which gives rise to a sudden increase of current at this particular voltage. The presence of illumination enhances this electrochemical reaction. The combined effect, i.e. ohmic charge transport and an electrochemical reaction, is observed in the I-V characteristics. Along with the dye concentration, the photosensitivity is observed to be field/voltage dependent. The sensitization effects are due to lowering of the potential barrier formed at the PANI/SPE+MB interface under illumination.