Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)
Publication date: 11th May 2021
Modification of the dye structure used in the construction of dye-sensitized solar cells (DSSCs) has been one of the most important challenge in recent years. One way is a change in the anchoring groups that take part in the chemical bonds between the titania surface and dye molecules. Recently, a series of organic dyes modified with the alkoxysilyl anchoring group, instead of carboxyl one, has been proposed [1, 2, 3]. The carboxyl as an anchoring group is the most popular, however the long-time stability of the solar cells working with the dyes with carboxyl group is not satisfactory, especially in the presence of water-based electrolyte.
The replacement by the trimethoxysilyl anchoring group was done for D205 dye belonging to the indoline class of dye [4]. Desorption of the dyes with alkoksysilyl group from titania surface is more difficult than with carboxyl one. Theoretical calculations provide that both for D205 and the modified dye (D205Si) the LUMO level is higher than the conduction band (CB) edge of titania resulting the thermodynamic driving force for the efficient electron injection from the excited state of dye to the CB of titania. Moreover, the HOMO of both dyes is mainly localized over the indoline and the LUMO on the rhodamine moiety. For D205 the LUMO is localized closer to the anchoring group (carboxyl) than for D205Si (trimethoxysilyl group links to the chromophore via the phenyl-amide moiety resulting only in small electron distribution around the anchoring group).
This study was supported by the research grants No. 2015/18/E/ST4/00196 (SONATA BIS) from The National Science Centre of Poland (NCN). All theoretical calculations were performed at the PL-Grid project.