my oral presentation at jcs spring meeting-2012, tokyo

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

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

Gururaj M. Shivashimpi, Shyam S. Pandey, Rie Watanabe,

Yuhei Ogomi, Yoshihiro Yamaguchi and Shuzi Hayase

Working Principle of DSSCs

SnO2/F

3 I-

I3-

Pt/SnO2/F TiO2 layer: 10-20 μm

Electrolyte layer: 30 μm

TiO2

10-20nm

TiO2

Ru N

N

C O

C O O H

O

Ti

N

N

C O

H O O C

O

Ti

S C N N C S OHP257

e

e

e e

e

e

e

e

e

e

e

e

e

Efficiency > 10 %

Efficiency > 10 %

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

DSSCs based on Squaraine dyes !

Efficiency = 4.5 %

IPCE edge = 700 nm

Yum et al; J. A. Chem. Soc.; 129, 10320-10321, 2007

Efficiency = 3.5 %

IPCE edge = 750 nm

Pandey S. P., et al;

J. Photochem. Photobiol., A.;

214, 269-275, 2010

SQ-5

Efficiency = 1.04 %

IPCE edge = 700 nm

SQ-7

Efficiency = 2.08 %

IPCE edge = 690 nm

Alex S., et al;

J. Photochem. Photobiol., A.;

172, 63-71, 2005

Advantage of Cyanoacrylate Anchoring

Group !

YR-6

Chang, W. K., et al; Org. Lett.; 13, 3880-3883, 2011

Y-R. Shi, et al;

Angew. Chem.; 123, 6749-6751, 2011

Squaraine dyes under present investigation !

SQ-83

SQ-8

SQ-84

Synthesis of SQ-83

Purity: 98% (By HPLC)

FAB-MS: 575.2861 (Observed), 575.2784 (Calculated)

Structure confirmed by 1H-NMR

Electronic Absorption Spectra

Wavelength (nm)

Ab

sorb

an

ce (

No

rm.)

SQ-83 [653 nm]

SQ-84 [663 nm]

SQ-8 [636 nm]

300 400 500 600 7000

0.4

0.8

1.2

Wavelength (nm)

Ab

sorb

an

ce (

No

rm.)

SQ-8

SQ-83

400 500 600 7000

0.5

1

SQ-Dyes in Ethanol Solution SQ-Dyes adsorbed on TiO2

SQ-8 SQ-84 SQ-83

Photovoltaic Characteristics

Cu

rren

t d

ensi

ty (

mA

/cm

2)

Voltage (V)

COOH

Cyanoacrylate

Thiophene-cyanoacrylate

0 0.1 0.2 0.3 0.4 0.5 0.6

2

4

6

8

10

12

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 %

Photovoltaic Parameters

Photocurrent Action Spectra

IPC

E

Wavelength (nm)

COOH

Cyanoacrylate

Thiophene-Cyanoacrylate

300 400 500 600 700 8000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

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.

Conclusions: