Synthesis and electrochemical properties of platinum-based films used as cathode materials in dye - Sensitized solar cells

Comparative investigation of platinum (Pt) and platinum/carbon nanotube (Pt/CNT) films used as cathodes in dye-sensitized solar cells (DSCs) has been carried out. Nanostructured Pt films on a conductive glass substrate were prepared by polyol reduction (PR-Pt), electrode-position (ED-Pt) and thermal decomposition (TD-Pt). The morphology, crystal structure and electrochemical behavior of the synthesized films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energydispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DSCs using the synthesized Pt-based cathodes were characterized by I-V curve measurement. DSCs with TD-Pt counter electrode show the best performance with stable photovoltaic characteristics. The energy conversion efficiency (ν) of DSCs used synthesized cathode materials decreased in the order TDPt> ED-Pt>PR-Pt. Energy conversion efficiency (ν) of 5% and more can be obtained for DSCs with ED-Pt and TD-Pt counter electrodes, while the DSCs based on PR-Pt attained efficiency less than 3%. The highest catalytic activity for triiodide/iodide (I3 ^-/I^-) redox reaction was observed for the ED-Pt film, that exhibits highest peak current densities and lowest charge transfer resistance. Meanwhile the reduction of I3 ^- ions may occur on the TD-Pt film with the lowest over-potential and less irreversible, compared with ED-Pt and PR-Pt electrode. The synthesized Pt/CNT film showed comparatively high catalytic performance for I3 ^-/I^- redox reaction; however its adhesion to the glass substrate is poor for the DSCs fabrication.