Electrodeposition of Platinum on Plastic Substrates as Counter Electrodes for Flexible Dye-Sensitized Solar Cells

Platinized electrodes were prepared by two-step constant current electrodeposition of Pt clusters on the Indium tin oxide-coated polyethylene naphthalate (ITO-PEN) substrates for use as counter electrodes in flexible dye-sensitized solar cells (DSSCs). The influence of the deposition conditions of two steps on the surface morphology of the deposited Pt was studied. Scanning electron microscopy and high-resolution transmission electron microscopy images showed the formation of well-separated and uniformly distributed Pt clusters on the substrates at optimum deposition conditions. The mean optical transmittance of the platinized electrodes was greater than 75% in the wavelength of 400-800 nm. The electrocatalytic activity for triiodide reduction was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical reduction was used as an effective post treatment method for further improving the performance of electrocatalytic activity and optical transmittance. X-ray photoelectron spectroscopy analysis reveals an increase of the percentages of Pt(0) on the platinized electrode surface after post-treatment, leading to the improvement of the electrocatalytic activity. The energy conversion efficiency of 6.53 +/- 0.45% for the flexible DSSC based on nanocrystalline TiO2/Ti photoelectrode and electrodeposited Pt/ITO-PEN counter electrode after electrochemical reduction was achieved under back illumination of 100 mW cm(-2) (AM1.5).