(
1H, m), 3.84–3.89 (1H, m), 3.95–3.98 (2H, m), 4.74 (2H, s), 4.95–4.99
due to the blocking effect of the charge recombination between
À
(1H, m), 7.02–7.04 (3H, m), 7.09 (1H, s), 7.14–7.16 (2H, m), 7.20–7.22
2H, m), 7.29–7.37 (5H, m), 7.41–7.49 (5H, m) and 7.71 (1H, s) ppm;
I
3
2
and electrons injected in the nanocrystalline-TiO electro-
(
1
3
des. Therefore, the VOC variation observed in Fig. 3 indicates
that the charge recombination was impeded by the
blocking effect, due to the combination of the n-octyl chain
and CDCA.
C NMR (DMSO-d
26.3 (1C), 28.5 (1C), 28.6 (1C), 31.2 (1C), 32.9 (1C), 34.9 (1C), 44.0
1C), 44.3 (1C), 46.1 (1C), 68.6 (1C), 92.7 (1C), 108.1 (1C), 112.5 (1C),
6
): d 14.0 (1C), 22.1 (1C), 23.9 (1C), 26.2 (1C),
(
1
1
19.4 (2C), 123.8 (1C), 126.9 (2C), 127.1 (1C), 127.4 (1C), 127.7 (1C),
28.4 (3C), 129.2 (2C), 129.7 (2C), 130.4 (2C), 131.5 (1C), 132.9 (1C),
Without CDCA, the variation of JSC by n-octyl substitution
on the rhodanine ring was small (0.5% of JSC). However, with
CDCA, the effect of the n-octyl chain was apparent and the
substitution of the n-octyl chain (from D149 to D205) with
CDCA decreased the JSC by 5.9%. The effect of n-octyl
substitution and CDCA on the FF was similarly small. Without
CDCA, the n-octyl substitution decreased the FF by 0.6%.
With CDCA, the n-octyl substitution increased the FF by 1.9%.
Without CDCA, the improvement in Z from D149 to D205
was only by 2.1%. With CDCA, the improvement in Z from
D149 to D205 by 6.2% was significant. The resulting average
Z value of D205 with CDCA was an outstanding 9.40%
134.9 (1C), 136.6 (1C), 139.4 (1C), 140.2 (1C), 140.3 (1C), 142.6 (1C),
46.2 (1C), 149.0 (1C), 166.1 (1C), 166.2 (1C), 168.0 (1C) and 189.0
1C) ppm.
1
(
1
2
¨ ¨
B. O’Regan and M. Gratzel, Nature, 1991, 353, 737; M. Gratzel,
Nature, 2001, 414, 338; F. Gao, Y. Wang, J. Zhang, D. Shi, M.
Wang, R. Humphry-Baker, P. Wang, S. M. Zakeeruddin and M.
Gratzel, Chem. Commun., 2008, 2635.
¨
(a) Chiba A. Islam, Y. Watanabe, R. Komiya, N. Koide and L.
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De Angelis, S. Fantacci, A. Selloni, G. Viscardi, P. Liska, S.
Ito, B. Takeru and M. Gra
6835.
(a) Z.-S. Wang, F.-Y. Li and C.-H. Huang, J. Phys. Chem. B, 2001,
05, 9210; (b) D. P. Hagberg, T. Edvinsson, T. Marinado, G.
Boschloo, A. Hagfeldt and L. Sun, Chem. Commun., 2006, 2245;
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¨
tzel, J. Am. Chem. Soc., 2005, 127,
1
3
1
(
Table 1). The highest Z value of 9.52% was achieved with a
À2
(
DSC based on D205 (JSC: 18.56 mA cm , VOC: 0.717 V, and
FF: 0.716). Reproducible efficiencies from 9.3% to 9.5% were
obtained with the solar cell based on D205.
Commun., 2005, 4098; (d) H. Tian, X. Yang, R. Chen, Y. Pan, L. Li,
A. Hagfeldt and L. Sun, Chem. Commun., 2007, 3741; (e) S.-L. Li,
K.-J. Jiang, K.-F. Shao and L.-M. Yang, Chem. Commun., 2006,
2792; (f) T. Kitamura, M. Ikeda, K. Shigaki, T. Inoue, N. A.
Anderson, X. Ai, T. Lian and S. Yanagida, Chem. Mater., 2004, 16,
In summary, a new indoline dye exhibiting an Z value of
.52% has been demonstrated, which is the highest efficiency
9
obtained so far among DSCs based on organic dye photo-
1
806; (g) K. Hara, M. Kurashige, S. Ito, A. Shinpo, S. Suga, K.
Sayama and H. Arakawa, Chem. Commun., 2003, 252; (h) K. Hara,
T. Sato, R. Katoh, A. Furube, T. Yoshihara, M. Murai, M.
Kurashige, S. Ito, A. Shinpo, S. Suga and H. Arakawa, Adv. Funct.
Mater., 2005, 15, 246; (i) W. M. Campbell, K. W. Jolley, P. Wagner,
K. Wagner, P. J. Walsh, K. C. Gordon, L. Schmidt-Mende, Md. K.
À2
sensitizers under AM 1.5 radiation (100 mW cm ). This
efficiency rivals the highest value (11.18%) obtained with a
DSC based on the Ru dye N719 under the same measurement
2b
conditions. It was confirmed that the control of dye-
aggregation by the combination between CDCA and substitu-
tion of the n-octyl chain on the rhodanine ring was the key
factor in obtaining a high-efficiency organic dye-sensitized
solar cell. These results strongly indicate that the application
of organic dye photosensitizers in DSCs is promising with
regard to high solar cell performance, low-cost production and
recyclability. However, the detailed mechanisms of dye-
aggregation for DSC photovoltaics are still undetermined. In
¨
Nazeeruddin, Q. Wang, M. Gratzel and D. L. Officer, J. Phys.
Chem. C, 2007, 11, 11760; (j) N. Koumura, Z.-S. Wang, S. Mori,
M. Miyashita, E. Suzuki and K. Hara, J. Am. Chem. Soc., 2006,
128, 14256; (k) Z.-S. Wang, Y. Cui, Y. Dan-oh, C. Kasada, A.
Shinpo and K. Hara, J. Phys. Chem. C, 2007, 111, 7224; (l) S. Ito, S.
M. Zakeeruddin, R. Humphry-Baker, P. Liska, R. Charvet, P.
Comte, Md. K. Nazeeruddin, P. Pechy, M. Takata, H. Miura, S.
´
Uchida and M. Gratzel, Adv. Mater., 2006, 18, 1202; (m) S. Hwang,
¨
J. H. Lee, C. Park, H. Lee, C. Kim, C. Park, M.-H. Lee, W. Lee, J.
Park, K. Kim, N.-G. Park and C. Kim, Chem. Commun., 2007,
4887.
4 E. E. Jelly, Nature, 1936, 138, 1009T. H. James, The Theory of the
Photographic Process, Macmillan Inc., London–New York, 1977,
p. 219.
2
order to supersede the results of ruthenium complexes (11%),
advanced studies to understand molecular aggregation with an
electron-dynamics study (e.g. photovoltage decay) will be
presented in a forthcoming paper.
5 A. C. Khazraji, S. Hotchandani, S. Das and P. V. Kamat, J. Phys.
Chem. B, 1999, 103, 4693.
6
7
¨
A. Kay and M. Gratzel, J. Phys. Chem., 1993, 97, 6272.
T. Horiuchi, H. Miura, K. Sumioka and S. Uchida, J. Am. Chem.
Soc., 2004, 126, 12218.
This work was supported by a grant from the Swiss Federal
Energy Office (OFEN) and Nissan Science Foundation.
8
K. Sayama, S. Tsukagoshi, K. Hara, Y. Ohga, A. Shinpou, Y.
Abe, S. Suga and H. Arakawa, J. Phys. Chem. B, 2002, 106, 1363.
Notes and references
9 D. Kuang, S. Uchida, R. Humphry-Baker, S. M. Zakeeruddin and
M. Gratzel, Angew. Chem., Int. Ed., 2008, 47, 1923.
10 J. D. Mee (Eastman Kodak Co.), US Pat., 5 679 795, 1997.
11 S. Ito, T. N. Murakami, P. Comte, P. Liska, C. Gratzel, Md. K.
Nazeeruddin and M. Gratzel, Thin Solid Films, 2008, 516,
4613.
12 S. Ito, M. K. Nazeeruddin, P. Liska, P. Comte, R. Charvet, P.
Pechy, M. Jirousek, A. Kay, S. M. Zakeeruddin and M. Gratzel,
Prog. Photovoltaics: Res. Appl., 2006, 14, 589.
¨
À1
w (2) IR (KBr): n 1534, 1676, 1744, 1767, 2852, 2922, and 2955 cm
;
1
3
H NMR (CDCl ): d 0.88 (3H, t, J = 6.9 Hz), 1.26–1.33 (10H, m), 1.35
¨
(3H, t, J = 7.2 Hz), 1.64–1.71 (2H, m), 3.89 (2H, s), 4.05 (2H, t, J =
¨
13
7
.7 Hz), 4.31 (2H, q, J = 7.2 Hz), and 4.68 (2H, s) ppm; C NMR
): d 14.1 (1C), 14.1 (1C), 22.6 (1C), 26.8 (1C), 26.8 (1C), 29.1
1C), 29.1 (1C), 31.2 (1C), 31.7 (1C), 44.9 (1C), 45.3 (1C), 62.9 (1C),
(CDCl
3
(
´
¨
9
1
4.8 (1C), 150.0 (1C), 165.9 (1C), 167.5 (1C), 172.6 (1C), and
89.3 (1C) ppm.
13 S. Ito, H. Matsui, K. Okada, S. Kusano, T. Kitamura, Y.
Wada and S. Yanagida, Sol. Energy Mater. Sol. Cells, 2004, 82,
421.
4
(
3) mp: 4250 1C; UV-Vis (CHCl
3
): lmax = 554 nm; e = 7.47 Â 10 ;
+
47 3 4 3
ESI-TOFMS: m/z calcd for C48H N O S [M] : 825.2723; meas.:
8
25.2697; IR (KBr): n 1486, 1508, 1541, 1564, 1576, 1675, 1702, 2855
14 J. E. Kroeze, N. Hirata, S. Koops, Md. K. Nazeeruddin, L.
¨
Schmidt-Mende, M. Gratzel and J. R. Durrant, J. Am. Chem.
Soc., 2006, 128, 16376.
À1
1
and 2925 cm
1
;
.25–1.28 (11H, m), 1.60–1.69 (4H, m), 1.75–1.84 (2H, m), 1.99–2.12
H NMR (DMSO-d
6
): d 0.85 (3H, t, J = 6.8 Hz),
5
196 | Chem. Commun., 2008, 5194–5196
This journal is ꢀc The Royal Society of Chemistry 2008