Development of Nano-TiO2 Dye Sensitised Solar Cells on High Mobility Transparent Conducting Oxide Thin Films

The optical transmission of dye-sensitised solar cells (DSCs) can be tuned by altering the dye and/or particle size of the mesoporous TiO2 layers, to allow their application as the top device in tandem solar cells. To benefit from this semi-transparency, parasitic optical losses by the transparent electrodes must be minimised. This work investigates the influence of using two different transparent conductors, namely, the high mobility material titanium doped indium oxide (ITiO) and fluorine doped tin oxide (FTO) as electrodes for semi-transparent DSCs. The overall NIR transparency through the DSCs increased significantly as each FTO electrode was replaced by an ITiO electrode. This increase was from 20-45% in the 1300-700 nm wavelength range for fully FTO-based cells, to about 60% for fully ITiO-based cells, across the same spectrum. DSCs prepared on these electrodes exhibited short circuit currents ranging from 14.0-14.9 mA/cm(2). The conversion efficiency of the cell with ITiO as both the front and rear electrodes was 5.8%, which though significant, was lower than the 8-2% attained by the cell using FTO electrodes, as a result of a lower fill factor. Improvements in the ITiO thermal stability and in the processing of the TiO2 interfacial layer are expected to improve the cell efficiency of such single DSC devices. The high current density and optical transparency of ITiO-based DSCs make them an interesting option for tandem solar cells. Copyright (C) 2008 John Wiley & Sons, Ltd.