496
Y. Ooyama
phthalocyanine αPcS1, which has thiophene units at the non-peripheral (α) positions, showed a higher η value of 5.5% using chenodeoxycholic acid (CDCA) as a
coadsorbent (Yamamoto et al. 2016).
14.2.15 Boron Dipyrromethene (BODIPY) Dyes
Boron dipyrromethene (BODIPY) dyes are fascinating sensitizers for DSSCs because
they have high chemical stability, photostability, and solubility in organic solvents,
in addition to large photoabsorption coefficients in the visible and NIR regions,
strong fluorescence property, and ease of electrochemical modification with electrondonating and electron-accepting groups onto the BODIPY core (Singh and Gayathri
2014; Hattori et al. 2005; Kumaresan et al. 2009; Erten-Ela et al. 2008; Kolemen
et al. 2010, 2011; Mao et al. 2012; Wang et al. 2012). A series of D–π–A BODIPY
dye sensitizers DYE10, DYE11, and PS-1–PS-4, which have two triphenylamine or
trialkoxyphenyl groups as electron donors at the 3- and 5-positions and a carboxylic
acid or cyanoacrylic acid group as an electron acceptor at the 8-position on the
BODIPY core, were developed (Fig. 14.21) (Erten-Ela et al. 2008; Kolemen et al.
2010, 2011). The BODIPY dyes PS-1–PS-4 without two methyl groups at the 1- and
7-positions were designed, because orthogonality between the BODIPY core and
the carboxyphenyl moiety, an electron-accepting and anchoring group, can reduce
the π-conjugation and electron flow from the electron donor to the electron acceptor.
The TiO 2 DSSC using PS-1 yielded an η value of 2.46% with a J sc of 9.17 mA cm
−2 ,
a V oc of 430 mV, and a ff of 0.62.
A series of D–π–A BODIPY dye sensitizers B1–B3 and PB1–PB4, which possess
triphenylamine or 1H-phenanthro[9,10-d]imidazole as an electron donor at the 6position and cyanoacrylic acid as an electron acceptor at the 2-position, were also
designed and synthesized (Fig. 14.21) (Mao et al. 2012; Wang et al. 2012). The
introduction of a substituent at 8-position on the BODIPY core can suppress dye
aggregation and charge recombination between the injected electrons in TiO 2 and
the I 3
– ions, increasing in both J sc and V OC values. In fact, the η value of the TiO 2
DSSC based on B3 with a hexyl group at the 8-position is 1.83%, which is higher
than that of B1 with a methyl group at the 8-position (η = 1.28%). The TiO 2 DSSC
based on PB4 yielded an η value of 2.26% with a J sc value of 5.10 mA cm
−2 , a V oc
value of 610 mV, and a ff value of 0.72.
Kubo et al. designed and developed a series of boron–dibenzopyrromethene dyes
DB1–3 with thienyl-cyanoacrylic acid units (Kubo et al. 2014). The dyes exhibited
intense absorption bands in a long wavelength region with λ max values of 647 nm
(ε = 157000 M
−1 cm
−1 ) for DB1 containing two anchoring units, 660 nm (ε =
109000 M
−1 cm
−1 ) for regioisomer DB2, and 644 nm (ε = 139000 M
−1 cm
−1 ) for
DB3 containing one anchoring unit, although these dyes have no strong electrondonating groups, such as arylamines. The excellent light-harvesting abilities of the
dyes allowed high J sc values in their DSSCs. As a result, the DSSC with butterflyshaped DB2 showed a J sc value of 19.02 mA cm
−2 , a V oc value of 540 mV, and
Y. Ooyama
phthalocyanine αPcS1, which has thiophene units at the non-peripheral (α) positions, showed a higher η value of 5.5% using chenodeoxycholic acid (CDCA) as a
coadsorbent (Yamamoto et al. 2016).
14.2.15 Boron Dipyrromethene (BODIPY) Dyes
Boron dipyrromethene (BODIPY) dyes are fascinating sensitizers for DSSCs because
they have high chemical stability, photostability, and solubility in organic solvents,
in addition to large photoabsorption coefficients in the visible and NIR regions,
strong fluorescence property, and ease of electrochemical modification with electrondonating and electron-accepting groups onto the BODIPY core (Singh and Gayathri
2014; Hattori et al. 2005; Kumaresan et al. 2009; Erten-Ela et al. 2008; Kolemen
et al. 2010, 2011; Mao et al. 2012; Wang et al. 2012). A series of D–π–A BODIPY
dye sensitizers DYE10, DYE11, and PS-1–PS-4, which have two triphenylamine or
trialkoxyphenyl groups as electron donors at the 3- and 5-positions and a carboxylic
acid or cyanoacrylic acid group as an electron acceptor at the 8-position on the
BODIPY core, were developed (Fig. 14.21) (Erten-Ela et al. 2008; Kolemen et al.
2010, 2011). The BODIPY dyes PS-1–PS-4 without two methyl groups at the 1- and
7-positions were designed, because orthogonality between the BODIPY core and
the carboxyphenyl moiety, an electron-accepting and anchoring group, can reduce
the π-conjugation and electron flow from the electron donor to the electron acceptor.
The TiO 2 DSSC using PS-1 yielded an η value of 2.46% with a J sc of 9.17 mA cm
−2 ,
a V oc of 430 mV, and a ff of 0.62.
A series of D–π–A BODIPY dye sensitizers B1–B3 and PB1–PB4, which possess
triphenylamine or 1H-phenanthro[9,10-d]imidazole as an electron donor at the 6position and cyanoacrylic acid as an electron acceptor at the 2-position, were also
designed and synthesized (Fig. 14.21) (Mao et al. 2012; Wang et al. 2012). The
introduction of a substituent at 8-position on the BODIPY core can suppress dye
aggregation and charge recombination between the injected electrons in TiO 2 and
the I 3
– ions, increasing in both J sc and V OC values. In fact, the η value of the TiO 2
DSSC based on B3 with a hexyl group at the 8-position is 1.83%, which is higher
than that of B1 with a methyl group at the 8-position (η = 1.28%). The TiO 2 DSSC
based on PB4 yielded an η value of 2.26% with a J sc value of 5.10 mA cm
−2 , a V oc
value of 610 mV, and a ff value of 0.72.
Kubo et al. designed and developed a series of boron–dibenzopyrromethene dyes
DB1–3 with thienyl-cyanoacrylic acid units (Kubo et al. 2014). The dyes exhibited
intense absorption bands in a long wavelength region with λ max values of 647 nm
(ε = 157000 M
−1 cm
−1 ) for DB1 containing two anchoring units, 660 nm (ε =
109000 M
−1 cm
−1 ) for regioisomer DB2, and 644 nm (ε = 139000 M
−1 cm
−1 ) for
DB3 containing one anchoring unit, although these dyes have no strong electrondonating groups, such as arylamines. The excellent light-harvesting abilities of the
dyes allowed high J sc values in their DSSCs. As a result, the DSSC with butterflyshaped DB2 showed a J sc value of 19.02 mA cm
−2 , a V oc value of 540 mV, and