92nd Japanese Chemical Society Spring Meeting-2012, oral presentation on influence of nature of anchoring group in photo sensitization behavior of unsymmetrical squaraine dyes

1. 非対称スクアリル色素におけるアンカーの影響と光増感作用
Influence of Nature of Anchoring Group in
Photosensitization Behaviour of Unsymmetrical
Squaraine Dyes
Gururaj M. Shivashimpi, Shyam S. Pandey, Rie Watanabe,
Yuhei Ogomi, Yoshihiro Yamaguchi and Shuzi Hayase
Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196, Japan
Nippon Steel Chemical Co. Ltd., 46-80 Nakabaru, Sakinohama, Tobata, Kitakyushu 804-8503, Japan

2. Working Principle of DSSCs
Ti Ti
O O
CO CO
e e N N
HO OC N N CO OH
Ru
e e OHP257 SCN NCS
e
-
Efficiency > 10 %
3I e
e I - e
3
TiO2 TiO2
e e
10-20nm
e TiO2 layer: 10-20 μm
Pt/SnO2/F
e e
SnO2/F Electrolyte layer: 30 μm

3. Efficiency > 10 %

5. Development of NIR Dyes !
Potentiality of Phthalocyanine, Cyanine and
Squaraine sensitizers
1. Sharp, narrow and Intense light absorption
2. High molar extinction coefficient
3. Capability of sensitization of wide band gap semiconductors
4. Possibility to tailor the optical absorption window from
visible to NIR wavelength region

6. DSSCs based on Squaraine dyes !
SQ-5 Efficiency = 3.5 %
Efficiency = 1.04 % IPCE edge = 750 nm
IPCE edge = 700 nm Pandey S. P., et al;
J. Photochem. Photobiol., A.;
214, 269-275, 2010
SQ-7
Efficiency = 2.08 %
IPCE edge = 690 nm
Efficiency = 4.5 %
Alex S., et al; IPCE edge = 700 nm
J. Photochem. Photobiol., A.; Yum et al; J. A. Chem. Soc.; 129, 10320-10321, 2007
172, 63-71, 2005

7. Advantage of Cyanoacrylate Anchoring
Group !
YR-6
Y-R. Shi, et al;
Angew. Chem.; 123, 6749-6751, 2011
Chang, W. K., et al; Org. Lett.; 13, 3880-3883, 2011

8. Squaraine dyes under present investigation !
SQ-8
SQ-83
SQ-84

9. Synthesis of SQ-83
Purity: 98% (By HPLC)
FAB-MS: 575.2861 (Observed), 575.2784 (Calculated)
Structure confirmed by 1H-NMR

10. Electronic Absorption Spectra
SQ-8 SQ-84 SQ-83
1.2
SQ-83 [653 nm] 1
SQ-84 [663 nm]
Absorbance (Norm.)
Absorbance (Norm.)
SQ-8 [636 nm]
0.8 SQ-8
SQ-83
0.5
0.4
0 0
300 400 500 600 700 400 500 600 700
Wavelength (nm) Wavelength (nm)
SQ-Dyes in Ethanol Solution SQ-Dyes adsorbed on TiO2

11. Photovoltaic Characteristics
12
Current density (mA/cm2)
10 COOH
Cyanoacrylate
Thiophene-cyanoacrylate
8
6
4
2
0 0.1 0.2 0.3 0.4 0.5 0.6
Voltage (V)
Photovoltaic Parameters
Dyes Jsc (mA/cm2) Voc (V) FF Efficiency
SQ-8 6.71 0.58 0.72 2.82 %
SQ-83 11.53 0.63 0.69 5.03 %
SQ-84 6.93 0.58 0.66 2.67 %

12. Photocurrent Action Spectra
0.7
COOH
Cyanoacrylate
0.6
Thiophene-Cyanoacrylate
0.5
IPCE
0.4
0.3
0.2
0.1
0
300 400 500 600 700 800
Wavelength (nm)

13. Conclusions:
1. Novel Indole donor based unsymmetrical squaraine dyes with varying
anchoring groups have been synthesized and characterized.
2. Cyanoacrylate functionality leads not only to the red-shift in absorption spectra
but pronounced spectral broadening as well as photon harvesting as compared
to –COOH anchoring group.
3. Introduction of additional spacer between cyanoacrylate anchoring group and
conjugated chromophore leads to hampered photon harvesting.