| dc.description.abstract | The compact layers used to improve the performance of dye-sensitized solar cells have been reported by Petra J. Cameron et al.. In our study, we applied a new TiO2 compact layer in the interface between the transparent fluorine doped SnO2 (FTO) anode and the electrolyte in order to reduce charge recombination losses. TiO2 compact layers were prepared by the sputtering and thermal oxidations instead of spray pyrolysis.
The dye-sensitized solar cells with a TiO2 compact layer fabricated in this study, the solar energy conversion efficiency is about 2%~4%.According to this result, we prepared the compact layer with crystal structures as Anatase and Rutile. The thicknesses were varied from 20nm, 50nm, to 100nm.
Solar cells without the compact layer, their short circuit current and the solar energy conversion efficiency were 5.3±0.35mA/cm2 and 2.1±0.2% respectively. After adding the compact layer, the short circuit current and the solar energy conversion efficiency were both increased, especially for those solar cells with compact layer thinner than 50nm. For the device with 20nm thickness Anatase type TiO2 compact layer, the short circuit current and the solar energy conversion efficiency of the cells were 7.95±0.35mA/cm2 and 3.7±0.2% respectively. For the device with 50nm thickness Rutile type TiO2 compact layer, the short circuit current and the solar energy conversion efficiency of the cells were 8.98±0.57mA/cm2 and 3.8±0.2% respectively. When the compact layer about 100nm thick, the solar energy conversion efficiency of the cell was lower than the thinner compact layer cells.
Measurements of AC impedance in the Nyquist polt were found that the Rh and R1 in the dye-sensitized solar cell could be reduced by applying the TiO2 compact layer, no matter if the TiO2 compact layer is Anatase type or Rutile type. That is, the contact resistance of the FTO substrate and the charge transfer resistance of the interface between TiO2 compact layer and the TiO2 phtoelectrode were both reduced.
By comparing the electrical properties of the dye-sensitized solar cells with and without TiO2 compact layer, we also found that the dark current was greatly reduced (68μA/cm2) in the device with TiO2 compact layer with 0.4V forward bias voltage. The dark current density of the cell without compact layer was 625μA/cm2.
In conclusion, the TiO2 compact layer does prevent the back reaction between the interface of FTO substrate and electrolyte. | en_US |