Angew. Chem., Int. Ed., 2004, 43, 6336; (d) J. Ohshita, K. H. Lee,
K. Kimura and A. Kunai, Organometallics, 2004, 23, 5622; (e)
L. Aubouy, P. Gerbier, N. Huby, G. Wantz, L. Vignau, L. Hirsch
and J. M. Janot, New J. Chem., 2004, 28, 1086; (f) H. Sohn, M. J. Sailor,
D. Magde and W. C. Trogler, J. Am. Chem. Soc., 2003, 125, 3821; (g)
I. Toulokhonova, R. P. Zhao, M. Kozee and R. West, Main Group
Met. Chem., 2001, 24, 737.
(a) J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu,
H. S. Kwok, X. Zhan, Y. Q. Liu, D. B. Zhu and B. Z. Tang, Chem.
Commun., 2001, 1740; (b) M. Freemantle, Chem. Eng. News, 2001, 79,
higher statistic probability of forming D–A interfaces. This is
18
verified by the result of device III: its g
.018 cd/A.
Efficient charge dissociation at the D–A heterojunction interface
is bad for LED but good for PV application and Cz HPS may
C
is as low as merely
0
2
hence show good PV performance. Under the influence of an
applied bias, the dissociated holes and electrons in the respective D
and A domains may steadily migrate along the interfaces to
corresponding electrodes to finish the PV process of converting
light to electricity. We examined the PV responses of the CzHPS-
2
3
41, 29.
(a) J. Chen, C. C. W. Law, J. W. Y. Lam, Y. Dong, S. M. F. Lo,
I. D. Williams, D. B. Zhu and B. Z. Tang, Chem. Mater., 2003, 15,
2
and Cz HPS-based devices (I and II) by shining on them a UV
1
535; (b) Y. Ren, Y. Q. Dong, J. W. Y. Lam, B. Z. Tang and
2
light (365 nm) of low power (15 mW/cm ) under applied biases
K. S. Wong, Chem. Phys. Lett., 2005, 402, 468; (c) Y. Ren, J. W. Y.
Lam, Y. Q. Dong, B. Z. Tang and K. S. Wong, J. Phys. Chem. B, 2005,
and found their external quantum efficiencies (gPV) to be 0.14%
109, 1135; (d) J. W. Chen, Z. L. Xie, J. W. Y. Lam, C. C. W. Law and
and 0.27%, respectively. This confirms that Cz
material than CzHPS.
This conclusion is substantiated by the performance of a series
of PV cells of Cz HPS. As can be seen from Fig. 4B, all of the PV
cells of Cz HPS (devices III–VIII) show good PV efficiencies. The
2
HPS is a better PV
B. Z. Tang, Macromolecules, 2003, 36, 1108; (e) B. Z. Tang, X. W. Zhan,
G. Yu, P. P. S. Lee, Y. Q. Liu and D. B. Zhu, J. Mater. Chem., 2001,
11, 2974; (f) C. C. W. Law, J. Chen, J. W. Y. Lam, H. Peng and
B. Z. Tang, J. Inorg. Organomet. Polym., 2004, 14, 39.
G. Yu, S. Yin, Y. Q. Liu, J. Chen, X. Xu, X. Sun, D. Ma, X. Zhan,
Q. Peng, Z. G. Shuai, B. Z. Tang, D. B. Zhu, W. Fang and Y. Luo,
J. Am. Chem. Soc., 2005, 127, 6335.
5 Z. Li, Y. Q. Dong, B. Mi, Y. H. Tang, M. H a¨ ußler, H. Tong,
Y. P. Dong, J. W. Y. Lam, Y. Ren, H. H. Y. Sung, K. S. Wong, P. Gao,
I. D. Williams, H. S. Kwok and B. Z. Tang, J. Phys. Chem. B, 2005,
2
4
2
best results are obtained with device V, whose short-circuit current
2
density, open-circuit voltage, and fill factor are 96.5 mA/cm , 1.7 V,
and 0.21, respectively. Although the structure of the cell is far from
optimized, it already shows an gPV as high as 2.19%. Optimization
109, 10061.
of the device structure may further boost the gPV of the Cz
based PV cell.
2
HPS-
6 Y. Q. Dong, J. W. Y. Lam, Z. Li, H. Tong, Y. P. Dong, X. D. Feng
and B. Z. Tang, J. Inorg. Organomet. Polym. Mater., 2005, 15, 287.
7
C. P.-Y. Chan, M. H a¨ ußler, B. Z. Tang, Y. Q. Dong, K.-K. Sin,
W.-C. Mak, D. Trau, M. Seydack and R. Renneberg, J. Immunol.
Methods, 2004, 295, 111.
In summary, in this work, we synthesized Cz(2)HPS’s comprised
of carbazolyl donors and silolyl acceptors. The HPS derivative
with two Cz groups, i.e. Cz HPS, is thermolytically resistant
2
8 (a) H. Chen, J. Chen, C. Qiu, B. Z. Tang, M. Wong and H. S. Kwok,
IEEE J. Sel. Top. Quantum Electron., 2004, 10, 10; (b) J. Chen, H. Peng,
C. C. W. Law, Y. Dong, J. W. Y. Lam, I. D. Williams and B. Z. Tang,
Macromolecules, 2003, 36, 4319.
(
T
d
360 uC) and morphologically stable (T
g
m
129 uC, T 298 uC),
thanks to the strong D–A interaction in the carbazolylsilole. We
have proved the concept that a silole can be made PV-active by
9
H. Chen, J. W. Y. Lam, J. Luo, Y. Ho, B. Z. Tang, D. B. Zhu,
M. Wong and H. S. Kwok, Appl. Phys. Lett., 2002, 81, 574.
attaching donor groups to the silolyl ring. The PV cells of Cz HPS
2
perform well and offer an gPV as high as 2.19%. To our knowledge,
these are the first PV cells based on a low molar mass silole. The
10 H. Murata, Z. H. Kafafi and M. Uchida, Appl. Phys. Lett., 2002, 80,
89.
1 e.g.: (a) K. Tamao, M. Uchida, T. Izumizawa, K. Furukawa and
1
1
2
fact that Cz HPS performs better than CzHPS suggests that
S. Yamaguchi, J. Am. Chem. Soc., 1996, 118, 11974; (b) J. Ohshita,
K. Kai, A. Takata, T. Iida, A. Kunai, N. Ohta, K. Komaguchi,
M. Shiotani, A. Adachi, K. Sakamaki and K. Okita, Organometallics,
introduction of more Cz groups will make silole more photo-
responsive. Based on the structural insight gained in this study, we
anticipate that an HPS derivative with its silole core fully covered
by six Cz peripheral groups will show excellent PV performance.
Work along these lines is currently being undertaken in our
laboratories.
2
001, 20, 4800.
2 (a) J. L. Segura, N. Martin and D. M. Guldi, Chem. Soc. Rev., 2005, 34,
1; (b) P. Peumans, A. Yakimov and S. R. Forrest, J. Appl. Phys., 2003,
93, 3693.
13 (a) W. U. Huynh, J. J. Dittmer and A. P. Alivisatos, Science, 2002, 295,
425; (b) L. Schmidt-Mende, A. Fechtenkotter, K. Mullen, E. Moons,
1
3
2
We are grateful to the Research Grants Council of Hong Kong
R. H. Friend and J. D. MacKenzie, Science, 2001, 293, 1119; (c) G. Yu,
J. Gao, J. C. Hummelen, F. Wudl and A. J. Heeger, Science, 1995, 270,
1789.
(603304, 604903, 6085/02P, and 6121/01P), the Natural Science
Foundation of China (N_HKUST606_03), the Ministry of Science
and Technology of China (973 Program), and the Cao Guangbiao
Foundation of Zhejiang University.
14 (a) B. Z. Tang, H. Z. Chen, R. S. Xu, J. W. Y. Lam, K. K. L. Cheuk,
H. N. C. Wong and M. Wang, Chem. Mater., 2000, 12, 213; (b)
J. W. Y. Lam and B. Z. Tang, J. Polym. Sci., Part A: Polym. Chem.,
2
003, 41, 2607.
5 M. Hissler, P. Dyer and R. Reau, Coord. Chem. Rev., 2003, 244, 1.
6 I. B. Berlman, Handbook of Fluorescence Spectra of Aromatic Molecules,
Academic Press, New York, 1971.
1
1
Notes and references
{
Crystal data for CzHPS: C53
H39NSi, M 5 717.94, monoclinic, Cc,
˚
a 5 14.3168(12), b 5 14.7242(12), c 5 18.7652(15) A, b 5 102.536(2)u,
17 Device I: ITO/NPB(700 A)/CzHPS(200 A)/Alq (200 A)/LiF(7 A)/Al;
3
˚ ˚ ˚
˚
˚
˚
˚
3
23
21
˚
V 5 3861.5(5) A , Z 5 4, D
00(2) K, 2hmax 5 25.00u, 9454 reflections collected, 5093 independent
reflections (Rint 5 0.0537), R 5 0.0554 and wR 5 0.0928 [I . 2s(I)],
5 0.0776 and wR
c
5 1.235 Mg m , m 5 0.100 mm , T 5
˚
device II: ITO/NPB(500 A)/Cz HPS(300 A)/TPBI(100 A)/Alq (50 A)/
2
3
1
˚
LiF(7 A)/Al, where ITO 5 indium-tin oxide, NPB 5 N,N9-bis(1-
naphthyl)-N,N9-diphenyl-1,19-biphenyl-4,49-diamine, andTPBI52,29,20-
1
2
23
˚
R
1
2
5 0.0994 (all data), De +0.296 and 20.245 e A .
(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole).
CCDC 270218. See http://www.rsc.org/suppdata/cc/b5/b505683g/index.sht
for crystallographic data in CIF or other electronic format.
˚ ˚ ˚
˚
2
HPS(300 A)/
1
8 Device III: ITO/NPB(0 A)/Alq :5% Cz HPS(300 A)/Alq (50 A)/
3 2 3
˚
LiF(7 A)/Al; device IV: ITO/NPB(50 A)/Alq
˚
3
:5% Cz
˚
˚
˚
Alq
Cz HPS(300 A)/Alq
˚ ˚ ˚
2 3
Alq :5% Cz HPS(300 A)/Alq (50 A)/LiF(7 A)/Al; device VII: ITO/NPB
3
(50 A)/LiF(7 A)/Al; device V: ITO/NPB(200 A)/Alq :5%
3
˚
˚ ˚ ˚
3
(50 A)/LiF(7 A)/Al; device VI: ITO/NPB(400 A)/
1
e.g.: (a) H. J. Tracy, J. L. Mullin, W. T. Klooster, J. A. Martin, J. Haug,
S. Wallace, I. Rudloe and K. Watts, Inorg. Chem., 2005, 44, 2003; (b)
J. H. Lee, Q. D. Liu, D. R. Bai, Y. J. Kang, Y. Tao and S. N. Wang,
Organometallics, 2004, 23, 6205; (c) A. J. Boydston and B. L. Pagenkopf,
2
3
˚
˚
˚ ˚
(200 A)/Alq :5% Cz
3
2
HPS(300 A)/Alq
˚ ˚
3
:5% Cz HPS(300 A)/Alq (100 A)/LiF(7 A)/Al.
3
(10 A)/LiF(7 A)/Al; device VIII:
˚
˚
ITO/NPB(200 A)/Alq
3
2
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Chem. Commun., 2005, 3583–3585 | 3585