Improvement of efficiency of dye-sensitized solar cells by reduction of internal resistance

With the aim of increasing conversion efficiency, the series-internal resistance of dye-sensitized solar cells (DSCs) was investigated with electrochemical impedance spectroscopy measurement based on an equivalent circuit of DSCs. It was found that series-internal resistance correlates positively with the sheet resistance of the transparent conducting oxide and the thickness of the electrolyte layer and negatively with the roughness factor of the platinum counter electrode. A cell sensitized with a black dye with series-internal resistance of $1.8\Omega {\mathrm{cm}}^2$ was fabricated and showed conversion efficiency of 10.2% when measured with a metal mask under an air mass of 1.5 sunlight.