New insights into the alkoxy effects on auxiliary adsorption and inhibiting charge recombination in dye-sensitized solar cells with high open circuit voltage: a theoretical investigation

Although introducing an alkoxy group is one of the most popular methods to suppress the interfacial charge recombination process of dye-sensitized solar cells, understanding of its effects is still limited and a microscopic picture of the alkoxy effects is lacking. Two ullazine dyes with distinct alkoxy chains at the donor part are used to investigate the effects of the alkoxy group on the adsorption, dye aggregation and charge recombination process in our study. Different from the usual assumption, we find that alkoxy chains can not only play a shielding role, but can also assist dye adsorption and inhibit the charge recombination process more effectively by covering the TiO2 surface. We also find that the existence of alkyl chains can well inhibit the aggregation of dyes and reduce intermolecular electron transfer. Furthermore, an important structural feature at the interface, the Ti-O interaction between the oxygen atom of the alkoxy group and the Ti atom of the surface is also found to contribute substantially to the interface stability. New insights into the effects of the alkoxy group on auxiliary adsorption and inhibiting charge recombination through reducing the recombination sites pave the way for rational design of sensitizers with high performance.

Automated summary

This study investigates the effects of alkoxy groups on the adsorption, dye aggregation, and charge recombination process in dye-sensitized solar cells. It is found that alkoxy chains can not only shield but also assist dye adsorption and inhibit charge recombination by covering the TiO2 surface effectively. The existence of alkyl chains can also inhibit dye aggregation and reduce intermolecular electron transfer. Additionally, the Ti-O interaction between the alkoxy group and the Ti atom at the surface contributes substantially to interface stability. These findings provide new insights for the rational design of high-performance sensitizers.