Efficient quantum capacitance enhancement in DSSC by gold nanoparticles plasmonic effect

Charge collection, transport and the recombination, which can be described by a capacitance of the device, in a dye-sensitized solar cell determine the performance of the device. High capacitance renders efficient charge collection, transport and suppressing the recombination in the device. Here, we report the existence of quantum capacitance or electrochemical capacitance like phenomenon effect in the improvement of the performance of the DSSC device in the presence of Au nanoparticles. By comparing the photovoltaic performances of plasmonic DSSC (ITO|TiO2:Au:dye(N719)|Iodolyte|Pt) with normal DSSC (without gold nanoparticles), it is found that the power conversion efficiency is enhanced by 15.23%, namely from 4.07 to 4.69%, when the Au nanoparticles presence in the device. Electrochemical impedance and optical absorption and X-ray photoelectron spectroscopy analysis suggested that the improvement of the device performance is related to the enhancement of the optical activity of the TiO2 nanostructure via plasmonic effect and defect or oxygen vacancy density modification and the enhancement of carrier transport due to existence of the quantum capacitance effect in the device. The mechanism of the performance enhancement will be discussed in detail.