Low-Symmetrical Zinc(II) Benzonaphthoporphyrazine Sensitizers for Light-Harvesting in Near-IR Region of Dye-Sensitized Solar Cells.

Two ring-expanded naphthalocyanine-based sensitizers NcS1 and NcS2 have been designed and synthesized to harvest near-IR light energy in dye-sensitized solar cells. Low-symmetrical "push-pull" structures of NcS1 and NcS2 enable the red-shift of absorption spectrum as well as the defined Q-band splitting. The zinc benzonaphthoporphyrazine sensitizer NcS1 possessing one carboxylic acid and six 2,6-diisopropylphenoxy units showed a PCE value of 3.2% when used as a light-harvesting dye on a TiO2 electrode under one sun condition. The NcS1 cell showed a broad photoresponse at wavelengths from 600 to 850 nm.