Improved performance of dye-sensitized solar cell with a specially tailored TiO2 compact layer prepared by RF magnetron sputtering

We demonstrate that a graded index TiO2 antireflective compact layer (arc-TiO2) employed by RF sputtering can modulate the optical transmittance and reduce the electron recombination in dye-sensitized solar cell (DSSC). The spectral response of the DSSC is improved, due to higher and red-shifted transmittance spectra in a specific region that favours the sensitization effect of the dye. The effects of arc-TiO2 prepared at various RF sputtering powers to the performances of DSSC were investigated by means of the incident photo to current efficiency (IPCE), open-circuit voltage decay (OCVD) and electrochemical impedance spectroscopy (EIS). The slow decay of the photo-voltage attributed to the desirable merits of the arc-TiO2 compact layer has been evidenced by the OCVD measurement. Meanwhile, the improvement of adhesion between an arc-TiO2 film and porous-TiO2 has decreased the interfacial-charge resistance, R1 in the EIS measurement. This lower R1 then facilitates the charge-transfer process of the electron in the DSSC. At 100 W of RF power, these blended effects improved the overall conversion efficiency of the DSSC by an increase of 42% compared to the cell without the compact layer.