506
Y. Ooyama
TiO 2 electrode and low light-harvesting efficiency, lowering the photovoltaic performances of the DSSCs. In this context, Goutsolelos et al. designed and developed a
“spider-shaped” porphyrin dye sensitizer 1PV-Zn-Por with four phenylenevinylene
groups, eight long dodecyloxy chains, and four pyridyl groups, which exhibited a
high dye loading value (1.9 × 10
17 molecules per cm
2 ) due to the increased basicity
of the pyridyl groups (Stangel et al. 2014). Consequently, the DSSC using 1PV-ZnPor yielded an η value of 5.12%. Grätzel and co-workers also developed the highest
performance DSSC with an η value of 8.2% based on MH-3 (Mai et al. 2015).
On the other hand, Ooyama et al. designed and developed a D–π–A-type BODIPY
dye sensitizer YH-1 with two pyridyl groups as electron-withdrawing and anchoring
groups at the end of the 3- and 5-positions and a carbazole–diphenylamine moiety
as an electron-donating group at the 8-position on the BODIPY core (Fig. 14.26).
YH-1 showed a good light-harvesting efficiency in the red/NIR region and a good
adsorption ability on the TiO 2 surface (Ooyama et al. 2013b). It was demonstrated that
the extended π-conjugated system by the introduction of the two thienylpyridines at
the 3- and 5-positions and the carbazole–diphenylamine moiety through a thiophene
unit at the 8-position on the BODIPY core can cause red-shift and broadening of
the photoabsorption band in the red/NIR region. The DSSC using YH-1 yielded an
incident photon-to-current conversion efficiency of ca. 10% over 500–700 nm with
an onset at 800 nm. Using a coadsorbent of CDCA to prevent dye aggregation on the
TiO 2 surface, the DSSC based on YH-1 showed a J sc value of 1.85 mA cm
−2 and an
η value of 0.39%. The relatively low photovoltaic performance of YH-1 is attributed
to not only the formation of strongly π-stacked aggregates, the low LUMO energy
level, and the radiationless relaxation of the photoexcited state, which reduce the
electron injection yield but also the fast charge recombination between the injected
electrons and the I 3
− ions, which decreases the V oc value (320–350 mV). Moreover,
Ooyama et al. designed and synthesized a (D) 2 –π–A-type BODIPY dye OMK-PY
with two diphenylamine–thienylcarbazole moieties at the 3- and 5-positions and a
pyridyl group at the end of the 8-position on the BODIPY core (Ooyama et al. 2017a).
The DSSC based on OMK-PY showed a J sc value of 1.08 mA cm
−2 , a V oc value of
335 mV, and a ff value of 0.53, corresponding to an η value of 0.19%.
Furthermore, Ooyama et al. designed and developed a new-type of D–π–A dye
sensitizers with azine rings such as pyridine, pyrazine, triazine, and pyridinium ring,
as electron-withdrawing and anchoring groups (Figs. 14.26, 14.28) (Ooyama et al.
2010c, 2013c, 2014a, b, 2015a, b, c, d, 2016a, b, c; Harima et al. 2013, 2015; Adachi
et al. 2016). It was revealed that the D–π–A dye sensitizers with azine rings can
adsorb onto the TiO 2 surface by the formation of hydrogen bonding or azinium ion
at the Brønsted acid sites or coordination bonding at the Lewis acid sites on the TiO 2
surface, which enables efficient electron injection from the dyes to the CB of the
TiO 2 electrode. As a result, azine rings were demonstrated to be one of the most
promising components of dye sensitizers for DSSCs.
Y. Ooyama
TiO 2 electrode and low light-harvesting efficiency, lowering the photovoltaic performances of the DSSCs. In this context, Goutsolelos et al. designed and developed a
“spider-shaped” porphyrin dye sensitizer 1PV-Zn-Por with four phenylenevinylene
groups, eight long dodecyloxy chains, and four pyridyl groups, which exhibited a
high dye loading value (1.9 × 10
17 molecules per cm
2 ) due to the increased basicity
of the pyridyl groups (Stangel et al. 2014). Consequently, the DSSC using 1PV-ZnPor yielded an η value of 5.12%. Grätzel and co-workers also developed the highest
performance DSSC with an η value of 8.2% based on MH-3 (Mai et al. 2015).
On the other hand, Ooyama et al. designed and developed a D–π–A-type BODIPY
dye sensitizer YH-1 with two pyridyl groups as electron-withdrawing and anchoring
groups at the end of the 3- and 5-positions and a carbazole–diphenylamine moiety
as an electron-donating group at the 8-position on the BODIPY core (Fig. 14.26).
YH-1 showed a good light-harvesting efficiency in the red/NIR region and a good
adsorption ability on the TiO 2 surface (Ooyama et al. 2013b). It was demonstrated that
the extended π-conjugated system by the introduction of the two thienylpyridines at
the 3- and 5-positions and the carbazole–diphenylamine moiety through a thiophene
unit at the 8-position on the BODIPY core can cause red-shift and broadening of
the photoabsorption band in the red/NIR region. The DSSC using YH-1 yielded an
incident photon-to-current conversion efficiency of ca. 10% over 500–700 nm with
an onset at 800 nm. Using a coadsorbent of CDCA to prevent dye aggregation on the
TiO 2 surface, the DSSC based on YH-1 showed a J sc value of 1.85 mA cm
−2 and an
η value of 0.39%. The relatively low photovoltaic performance of YH-1 is attributed
to not only the formation of strongly π-stacked aggregates, the low LUMO energy
level, and the radiationless relaxation of the photoexcited state, which reduce the
electron injection yield but also the fast charge recombination between the injected
electrons and the I 3
− ions, which decreases the V oc value (320–350 mV). Moreover,
Ooyama et al. designed and synthesized a (D) 2 –π–A-type BODIPY dye OMK-PY
with two diphenylamine–thienylcarbazole moieties at the 3- and 5-positions and a
pyridyl group at the end of the 8-position on the BODIPY core (Ooyama et al. 2017a).
The DSSC based on OMK-PY showed a J sc value of 1.08 mA cm
−2 , a V oc value of
335 mV, and a ff value of 0.53, corresponding to an η value of 0.19%.
Furthermore, Ooyama et al. designed and developed a new-type of D–π–A dye
sensitizers with azine rings such as pyridine, pyrazine, triazine, and pyridinium ring,
as electron-withdrawing and anchoring groups (Figs. 14.26, 14.28) (Ooyama et al.
2010c, 2013c, 2014a, b, 2015a, b, c, d, 2016a, b, c; Harima et al. 2013, 2015; Adachi
et al. 2016). It was revealed that the D–π–A dye sensitizers with azine rings can
adsorb onto the TiO 2 surface by the formation of hydrogen bonding or azinium ion
at the Brønsted acid sites or coordination bonding at the Lewis acid sites on the TiO 2
surface, which enables efficient electron injection from the dyes to the CB of the
TiO 2 electrode. As a result, azine rings were demonstrated to be one of the most
promising components of dye sensitizers for DSSCs.