Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO(2) photoanodes

We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO(2)) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiO(x) or TiCl(4) precursor solutions to create a blocking layer before tape casting the SnO(2) mesoporous anode. In addition, SnO(2) photoelectrodes were treated with the same precursor solutions to deposit a TiO(2) passivating layer covering the SnO(2) particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl(4) treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO(2) anode by titania can play a major role in maximizing the photo conversion efficiency.