Synthesis of Specific Solvatochromic D-π-A Dyes with Pyridinium Ring as Electron-Withdrawing Group for Dye-Sensitized Solar Cells.

Specific solvatochromic D-π-A-type pyridinium dyes were designed and developed as photosensitizers for dye-sensitized solar cells (DSSCs). The dyes have N-sulfobutylpyridinium or N-(carboxybutyl)pyridinium bromide as an electron-withdrawing anchoring group. The two dyes show specific solvatochromism, leading to a large bathochromic shift of the absorption band in halogenated solvents. Moreover, a dye-adsorbed TiO₂ film immersed into halogenated solvents exhibits specific solvatochromism, as does a dye solution of halogenated solvents. DSSCs based on specific solvatochromic D-π-A-type pyridinium dyes and halogenated solvents as electrolyte solvent were prepared and their photovoltaic performance investigated. It was found that the appropriate combination of solvatochromic dyes with electrolyte solution and the effective interaction between solvatochromic dyes and TiO₂ surface can lead to not only an enhancement of light-harvesting efficiency (LHE), but also efficient electron injection from the dye to the conduction band (CB) of TiO₂. This work demonstrates that the solvatochromism of organic dyes is a key consideration for high-performance DSSCs based on organic dye sensitizers. [ABSTRACT FROM AUTHOR]