3424
T.-C. Chao et al. / Tetrahedron Letters 50 (2009) 3422–3424
ene-based
sults indicate that their hole mobilities are influenced strongly by
the length and rigidity of their -conjugated backbones and by
p-conjugated materials are reported first time, the re-
p
the structures of the peripheral substituents. Hole mobilities of
up to 10ꢀ3 cm2 Vꢀ1 sꢀ1 were observed for a rigid, coplanar indeno-
thiophene-based derivative (4PP) bearing small, uniform periphe-
ral aryl substituents.
Acknowledgments
Figure 3. Frontier molecular orbitals HOMO (left) and LUMO (right) of 4TT
computed using the DFT (B3LYP/631G) method.
We thank Mr. Wei-Guang Liu for the aid in molecular calcula-
tion on the reorganization energy. The financial support of this re-
search was from the National Science Council of Taiwan.
Table 1
GDM carrier transport parameters for 4PP, 4PT, and 4TT
Supplementary data
Hole
l0 (ꢁ10ꢀ3 cm2/V s)
r
(ꢁ10ꢀ2 eV)
R
C (ꢁ10ꢀ4
)
Supplementary data associated with this article can be found, in
4PP
4PT
4TT
15
10
3
8.00
7.80
7.75
1.65
1.63
1.58
4
3.7
4.5
References and notes
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dependent hole mobility measurements of 4PP, 4PT, and 4TT
(Fig. S3, supplementary data). The obtained carrier mobilities agree
with the prediction of Gaussian disorder model (GDM)8,12, which
assumes that charge transport in amorphous organic solids occurs
by means of hopping among uncorrelated localized sites with
Gaussian-distributed energetic disorder and intermolecular posi-
tional disorder. Table 1 summarizes the extracted data: disorder-
free mobility (
parameter of positional disorder (
dependent hole mobilities using Bässler formalism described as:
l0), degree of energetic disorder (
r), and the
R) from temperature- and field-
0 2
3
1
!
!
2
ꢀ
ꢁ
2
pffiffiffi
2
3kBT
r
r
kBT
@ 4
5
A
l
ðE; TÞ ¼
l
0 exp
ꢀ
exp
C
ꢀ
R2
E
where E is electric field, T is temperature, kB is the Boltzmann con-
stant, C is an empirical constant.
The obtained data indicate that the nature of peripheral substi-
tutions exhibits negligible influence on the energetic disorder, as
well as on the positional disorder. More significantly, the results
of temperature-dependent mobility measurement suggest that
the relative magnitudes of carrier mobility of a common indenothi-
ophene backbone with different substitutions are mainly governed
by l0 (4PP > 4PT > 4TT) (i.e., intrinsic intermolecular charge-trans-
fer characteristics), which is consistent with those observed for
mobilities.
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2005, 87, 052103; (b) Fong, H. H.; So, S. K.; Sham, W. Y.; Lo, C. F.; Wu, Y. S.;
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In summary, TOF measurements of the non-dispersive hole
mobilities of a homologous series of amorphous indenothioph-