Synergistic effects of ZnO compact layer and TiCl4 post-treatment for dye-sensitized solar cells

The interaction between ZnO compact layer and TiCl4 post-treatment on TiO2 photoelectrode for dye sensitized solar cell (DSSC) is investigated. Photoelectrode combined the two modifications is designated as ZnO + 2l + TiCl4. It is found that after the TiCl4 treatment the ZnO compact layer transforms to a bi-functional layer, which suppresses back electrons transfer from FTO to electrolyte and reduces the FTO/TiO2 interfacial resistance. In addition, the newly formed TiO2 coating generated by TiCl4 post-treatment contains abundant and well dispersed Zn element, which further facilitates electron transfer at TiO2 layer. Meanwhile, the electron lifetime in ZnO + 2l + TiCl4 is the longest. Consequently, the overall energy conversion efficiency of the cell with ZnO + 2l + TiCl4 is significantly enhanced to 8.9%, which is 8.8% higher than that with pure TiCl4 post-treatment and 17.7% higher than that without any treatment. These results are verified by material characterization and corresponding opto-electrical properties measurements. Experimental results demonstrate this facile method is a more promising alternative to the conventional interface and surface modification in high efficient DSSCs.

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► We combined a basic ZnO compact layer with an acid TiCl4 post-treatment.
► The FTO/TiO2 interfacial resistance has been reduced when comparing with single treatment and untreated photoelectrodes.
► The newly formed TiO2 coating by the combined modification contained abundant and well dispersed Zn element.
► The photoelectrode with the combined modification has the lowest resistance for electron transport and the longest electron lifetime for recombination.
► The overall energy conversion efficiency was highly enhanced by the combined modification.