Photoelectrochemical properties of MWCNT–TiO2 hybrid materials as a counter electrode for dye-sensitized solar cells

The MWCNT–TiO2 hybrid materials were prepared by a simply mixing method and used as a counter electrode (CE) for dye-sensitized solar cells. Compared with the platinum CE, MWCNT–TiO2 CE has the similar redox voltage and current response in the cyclic voltammetry. The electrochemical catalytic activity was characterized by the electrochemical impedance spectroscopy and Tafel curve, including the equivalent circuit, the exchange current density, the limiting diffusion current density, and the diffusion coefficient of triiodide/iodide redox species. The results indicate that the reduction process from triiodide to iodide is determined by the kinetic-controlled and diffusion-limited processes. The device performance is optimal based on the MWCNT–TiO2 (mass ratio of 2:1) CE, such as the open-circuit voltage of 0.72 V, the short-circuit photocurrent density of 15.71 mA/cm2, the fill factor of 0.68, and the photon-to-electron conversion efficiency of 7.69%.

The results of the electrochemical impedance spectroscopy and Tafel measurements indicate that the reduction process from triiodide to iodide at the counter electrode surface is determined by the kinetic-controlled and diffusion-limited processes.Figure optionsDownload as PowerPoint slide