Dye-sensitized solar cells based on porous conjugated polymer counter electrodes

• Poly-3-methyl-thiophene (P3MT) layers were grown using electrochemical deposition method.
• By controlling the growth conditions, porous P3MT can be produced.
• Grown P3MT layers can be used as counter electrodes in dye-sensitized solar cells.
• The growth rate of P3MT layers plays an essential role in the cell performance.

In this paper, we report platinum-free dye-sensitized solar cells that were fabricated using a grown porous poly-3-methyl-thiophene (P3MT) counter electrode. The growing of the porous P3MT was performed by an electrochemical deposition method. This method is easy and affordable unlike the common expensive deposition methods. The morphology of P3MT films was studied by scanning electron microscopy images. It was observed that polymer layers grown with a current density of 2 mA/cm2 have a clear porous and rough structure as compared to layers grown with a lower current density. To understand the reaction kinetics and the catalytic activities of the counter electrodes with P3MT for 3I−/I3− redox reaction, cyclic voltammetry (CV) was performed. Based on the analysis of CV, it was shown that this layer can be used as a counter electrode for dye-sensitized solar cells. The electro deposition conditions during the growth of polymer layers such as current density, the morphology of polymer films and the duration of polymerization have a significant role in the current–voltage characterization of the fabricated solar cells. The performance of the fabricated solar cells was improved by optimization of these parameters. The highest efficiency of 2.76% was obtained by using porous P3MT in the counter electrode.