Two New Dyes with Carboxypyridinium Regioisomers as Anchoring Groups for Dye-Sensitized Solar Cells

Two new organic dye-sensitized solar cell (DSSC) sensitizers bearing regioisomeric carboxyl-N-methylpyridinium moieties were prepared and fully characterized. Based on TD-DFT calculations, they were anticipated to show a significantly red-shifted absorption spectrum compared to normal carboxypyridines and other regioisomeric pyridinium salts. Although this prediction was met, the two regioisomers unexpectedly showed very different stabilities upon adsorption on TiO2.