World Journal Of Engineering
Carbon nanotube fiber for Photovoltaic Application
Tao Chen, Zhibin Yang, Huisheng Peng
Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of
Macromolecular Science, and Laboratory of Advanced Materials, Fudan University, Shanghai
200438, China. *E-mail: taochenm@163.com
Introduction
Materials
Transparent conducting oxide (TCO, F-doped
SnO2, 15 Ω/square, Nippon Sheet Glass Co.)
coated glass or Polyethylene naphthalene2,6-dicarboxylate (PEN, 12 ohm/square,
Peccell Co., Japan) was used as the conductibe
substrate. N719 were purchased from
Solaronix SA without further purification. The
redox electrolyte consists of 0.1 M LiI, 0.05 M
I2, 0.6 M dimethyl-3-n-propyl-imidazolium
iodide and 0.5 M 4-tert butyl-pyridine in
dehydrated acetonitrile. Surlyn sheets were
used for device sealing.
Because of their excellent electrical and
mechanical properties and large specific area,
carbon nanotubes (CNTs) have been widely
introduced into organic solar cells to improve
their photovoltaic performance by three main
methods, i.e., solution blending, melt blending,
and in-situ preparation [1]. Unfortunately, the
electrical or mechanical properties of CNT
composite materials have not been improved
greatly as expected due to aggregation and
random dispersion of CNTs inside. Therefore,
the photovoltaic performance of solar cell can
not achieve a high improvement. CNTs fibers
with high aligned CNTs inside show excellent
mechanical (e.g., strength about 0.2-8.8 GPa)
and electrical properties (e.g., conductivity on
level of 10-103 S cm-1), which are very
promising in various applications such as
structural
materials,
strong
and
high-conductive cables, photoelectric and
electrochemical devices due to their flexible,
high-strength, high-conductivity and weavable
nature[2].
Device Fabrication Process
CNT arrays were synthesized by a typical
chemical vapor deposition in a quartz tube
furnace
using
catalyst
of
Fe(1nm)/Al2O3(10nm) on silicon wafer with
ethylene as the carbon source. The CNT fibers
were directly spun onto the conductive surface
of TCO from the CNT array with rotation
speed of the microprobe typically ranging
from 1000 to 3000 rad/min. The CNT fibers
on the TCO conductive glass (or the
ITO–PEN substrates) were used as working
electrode after sensitized in a solution of N719
(0.3 mM in CH3CN). The CNT fiber working
electrode and counter electrode (Pt coated
TCO) were sealed with a Surlyn frame as
spacer by pressing them at 100 oC. Then, the
redox electrolyte was injected into the cell
through the hole on the back of the counter
electrode. Finally, the holes were sealed by
Herein, CNT fibers with highly aligned CNTs
inside are used to fabricate novel organic solar
cells, in which the CNT fibers are used as both
the
semiconductive
materials
for
photo-sensitized dyes and electrons injection
materials. The photovoltaic performances of
solar cells are carefully investigated [3].
Experiment
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World Journal Of Engineering
covering a Surlyn sheet and a piece of
microscope objective glass at 100 oC.
power conversion efficiency (η) can be then
calculated to be 3.93%.
Results and Discussion
The interactions between N719 molecules and
CNTs were confirmed by Raman spectra
shown as Figure 1(excited at 514 nm). For
instance, the characteristic peak of NCS group
shifted from 2104 cm-1 for pure N719 to 2098
cm-1 for N719/CNT composite fibers, and the
bipyridine vibration at 1540 cm-1 for pure
N719 shifted to 1534 cm-1 for N719/nanotube
composites; both D-band and G-band at 1344
and 1576 cm-1 for pure CNTs shifted to 1347
and 1580 cm-1 for N719/CNT composite fibers,
respectively, and the intensity ratios between
G-band and D-band decreased from 1.69 for
pure CNT fibers to 1.55 for N719/CNT
composite fibers. Note that for a pure CNT
fiber, the G band is much stronger than that of
the D band, which indicated that the building
CNTs were very clean with less amorphous
carbon or other impurities.
Fig.2 J-V curve of a solar cell being simulated
under 100 mW/cm2 illumination.
Conclusion
The N719/CNT composite fibers have been
successfully prepared by directly immersing
CNT fibers into N719 solution followed by
evaporation of solvent. The photovoltaic
performance of novel organic solar cell using
this N719/CNT composite fiber as working
electrode has been studied.
Reference
1.
2.
Fig.1 Raman spectra of pure CNT fiber, N719
powder, and CNT/N719 composite fiber.
3.
Figure 2 shows a typical curve of the current
versus voltage with a composite fiber (5 mm
in length and 10 μm in diameter). The
short-circuit current density (Jsc), open-circuit
voltage (Voc) and fill factor (FF) are 7.1
mA/cm2, 0.38 V, and 0.43, respectively. The
192
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Chou T.-W., Gao L., Thostenson E. T.,
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