Phosphonic acid anchored ruthenium complexes for ZnO-based dye-sensitized solar cells

We report on the development of ruthenium dyes for the application in flexible ZnO based dye-sensitized solar cells. The ZnO based solar cells were prepared by electrodeposition using eosin Y as a structure-directing agent. The newly synthesized ruthenium dyes differed in the complexity of the extended π-donor-system and in their anchor moieties. As alternatives to carboxylic acids as anchor groups, dyes carrying phosphonic acids were studied. Comparison of the dyes contrary to what could be expected showed that the phosphonic acid anchored dyes were not superior to the carboxylic anchored dyes. A surprising second effect was that the dyes with the least sophisticated ligands performed best. Exploring possible reasons we established a simple model that allows pre-evaluation of the applicability of the dyes before testing them in real solar cells.