480
Y. Ooyama
7.7% with a J sc value of 14.0 mA cm
−2 , a V oc value of 740 mV, and a ff value of
0.74. The IPCE value reached nearly 80% in the visible region.
14.2.5 Hemicyanine Dyes
Hemicyanine dye sensitizers, which are efficient in TiO 2 DSSCs, are cationic dyes
based on D–π–A structures composed of a p-dialkylaminophenyl group as an
electron-donating part, a cationic moiety including benzo- and naphthothiazolium,
pyridinium, and indolium salts as a strong electron accepting part, and a methane (–
CH=CH–) unit as a π-conjugated bridge between the electron-donating and accepting
parts (Fig. 14.9) (Wang et al. 2000; Chen et al. 2005a; Yao et al. 2003). A series of
benzothiazolium hamicyanine dye sensitizers (HC1–HC5) and naphthothiazolium
hemicyanine (HC6) were designed to bear sulfonate (–SO 3
− ), carboxyl (–COOH),
and/or hydroxyl (–OH) groups as anchoring parts. The IPCE spectra of the TiO 2
DSSCs using these hemicyanine dyes were strongly affected by the anchoring groups,
and the η values decreased in the order of carboxyl and hydroxyl > carboxyl >
sulfonate and hydroxyl. This result indicates the importance of anchoring groups for
the photovoltaic performances of DSSCs. The highest η value of 5.2% and IPCE
Fig. 14.9 Chemical structures of hemicyanine dye sensitizers for TiO 2 DSSCs
Y. Ooyama
7.7% with a J sc value of 14.0 mA cm
−2 , a V oc value of 740 mV, and a ff value of
0.74. The IPCE value reached nearly 80% in the visible region.
14.2.5 Hemicyanine Dyes
Hemicyanine dye sensitizers, which are efficient in TiO 2 DSSCs, are cationic dyes
based on D–π–A structures composed of a p-dialkylaminophenyl group as an
electron-donating part, a cationic moiety including benzo- and naphthothiazolium,
pyridinium, and indolium salts as a strong electron accepting part, and a methane (–
CH=CH–) unit as a π-conjugated bridge between the electron-donating and accepting
parts (Fig. 14.9) (Wang et al. 2000; Chen et al. 2005a; Yao et al. 2003). A series of
benzothiazolium hamicyanine dye sensitizers (HC1–HC5) and naphthothiazolium
hemicyanine (HC6) were designed to bear sulfonate (–SO 3
− ), carboxyl (–COOH),
and/or hydroxyl (–OH) groups as anchoring parts. The IPCE spectra of the TiO 2
DSSCs using these hemicyanine dyes were strongly affected by the anchoring groups,
and the η values decreased in the order of carboxyl and hydroxyl > carboxyl >
sulfonate and hydroxyl. This result indicates the importance of anchoring groups for
the photovoltaic performances of DSSCs. The highest η value of 5.2% and IPCE
Fig. 14.9 Chemical structures of hemicyanine dye sensitizers for TiO 2 DSSCs