Impedance spectroscopic analysis of high-performance dye sensitized solar cells based on nano-clay electrolytes

Abstract

In this work we present quasi-solid state dye-sensitized solar cells obtained employing artificial hydrotalcite nano-clay as electrolyte additive, with a greatly improved photo-energy conversion efficiency of up to 10.9% with respect to the 9.6% obtained for liquid electrolyte ruthenium based reference cell. Through impedance spectroscopy, we have evaluated quantitatively the effects of shifts in the conduction band energy level and variations of electron recombination rates over the photovoltage. We demonstrated that the origin of these changes could be ascribed to the chemical effects induced by the fluctuation of ionic species inside the pores of TiO2 in the presence of nano-clay. These results highlight the dual functionality of clay electrolyte that enables the fabrication of stable solar devices under irradiation tests over 1000 h, and pushes up the photo-energy conversion efficiency up to a record values.