- Carbon nanotubes are being used in solar panel technology to improve efficiency by allowing the panels to utilize infrared radiation. The nanotubes act as photoconversion sites and help transport charge carriers. This can increase theoretical efficiency to 80%. - Double-walled carbon nanotubes are directly incorporated into thin film solar cells, creating a p-n heterojunction with silicon. Nanotubes serve as both a light absorber and charge transport layer. Initial tests show an efficiency over 1%. - Advantages of carbon nanotube solar panels include improved efficiency, ability to operate at night, increased output voltage, and reduced material needs. However, the technology remains in the experimental stage.

1. G.NARAYANAMMA INSTITUTE OF
TECHNOLOGY AND SCIENCES
CARBON NANOTUBES IN SOLAR PANEL
TECHNOLOGY
1yenigalla.srujana, 2k.shoushya, 3k.sowmya
1srujana.yenigalla95@gmail.com, 2shamm1722@gmail.com, 3kerelli.sowmya@gmail.com
Abstract-
This paper introduces the advancement in the solar
panel technology. It presents about the usage of the
carbon nanotubes or graphite instead of silicon in solar
panels. These carbon nanotubes are used for photo
conversion and a counter electrode construction, which
are placed in liquid electrolyte through a (reduction and
oxidation) redox reaction. The silicon semiconductors
in a solar cell are geared toward taking infrared light
and converting it directly to electricity. Meanwhile, the
visible spectrum is lost as heat and longer wavelengths
pass through unexploited. A new nano-material being
developed by a group of researchers spread across
the country could act as a “thermal emitter,” making
solar power significantly more efficient by scooping
up more of that wasted energy. The infrared part of
light is relatively easy for conventional high-efficiency
solar cells to convert to electricity, and the thermal
emitter approach works within that framework. A
thermal emitter isn’t a parallel system for deriving
electricity directly from the sun’s rays. Instead, this
is an application or so called thermo photovoltaic
principals. Researchers have estimated a theoretical
80% efficiency rating — much higher than the mid-30s
where most silicon-based solar panels are stuck.
Index terms- solar panels, carbon nanotubes, thermal
emitter, photovoltaic principals.
I. INTRODUCTION
The need for power in remote locations has
given rise to the need for a more portable solar cell.
Organic solar cells have shown great potential for
the solution. The problem lies in the inadequate
efficiency currently found in organic solar cells.
There is more to solar radiation than meets the
eye: sun- burn develops from unseen UV radiation,
while we sense infrared radiation as heat on our skin,
though invisible to us. Solar cells also ‘see’ only a
portion of solar radiation: approximately 20 percent
of the energy contained in the solar spectrum is
unavailable to cells made of silicon – they are unable
to utilize a part of the infrared radiation, the short-
wavelength IR radiation, for generating power.
II. SOLAR PANNELS
Fig.1: An installation of 24 solar modules in rural Mongolia
A solar panel is a set of solar
photovoltaic modules electrically connected and
mounted on a supporting structure. A photovoltaic
module is a packaged, connected assembly
of solar cells. The solar panel can be used as a
component of a larger photovoltaic system to
generate and supply electricity in commercial and
residential applications. Each module is rated by
its DC output power under standard test conditions
(STC), and typically ranges from 100 to 320 watts.
The efficiency of a module determines the area
of a module given the same rated output - an 8%
efficient 230 watt module will have twice the area
of a 16% efficient 230 watt module. A single solar
module can produce only a limited amount of
power; most installations contain multiple modules.
A photovoltaic system typically includes a panel or
an array of solar modules, an inverter, and sometimes
a battery and/or solar tracker and interconnection
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2. wiring.
Fig.2: A solar photovoltaic module is composed of individual PV
cells. This crystalline-silicon module has an aluminium frame and
glass on the front.
III. CARBON NANOTUBES
Carbon nanotubes (CNTs) are allotropes of
carbon with a cylindrical nanostructure. Nanotubes
have been constructed with length-to-diameter ratio
of up to 132,000,000:1, significantly larger than
for any other material. These cylindrical nanotubes
have unusual properties, which are valuable for
nanotechnology, electronics, optics and other
fields of technology. In particular, owing to their
extraordinary thermal conductivity and mechanical
and electrical properties, carbon nanotubes find
applications as additives to various structural
materials. For instance, nanotubes form a tiny portion
of the material(s) in some (primarily carbon fiber)
baseball bats, golf clubs, or car parts.
These carbon nanotubes are now used in the
technology of solar panels to increase the efficiency
of the solar panels up to 80%. The discussion
mentioned ahead will help in understanding how
these carbon nanotubes can be used in solar panels.
Fig.3: A scanning electron microscopy image of carbon nanotubes
bundles.
Fig.4: Multi walled carbon nanotube
IV. HISTORY OF CNT SOLAR
PANNELS
Stanford University scientists have built the first
solar cell made entirely of carbon, a promising
alternative to the expensive materials used in
photovoltaic devices today.The results are published
in today's online edition of the journal ACS Nano.
It was later also developed by the scientists in
MIT. They could tap the unused energy of infrared
radiations in the modified solar cells using carbon
nanotubes.
• Usage Of Carbon Nanotubes In Solar
Pannels Helping In Improving The
Efficiency
Fig.5: Fullerences (C60), Bunkyball.
The new cell is made of two exotic forms of carbon:
carbon nanotubes and C60, otherwise known as
bucky balls. This is the first all-carbon photovoltaic
cell, a feat made possible by new developments in the
large-scale production of purified carbon nanotubes.
It has only been within the last few years or so that
it has been possible to hand someone a vial of just
one type of carbon nanotube. In order for the new
solar cells to work, the nanotubes have to be very
pure, and of a uniform type: single-walled, and all
of just one of nanotube two possible symmetrical
configurations. Other groups have made photovoltaic
(PV) cells using carbon nanotubes, but only by
using a layer of polymer to hold the nanotubes in
position and collect the electrons knocked loose
when they absorb sunlight. But that combination adds
extra steps to the production process, and requires
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3. extra coatings to prevent degradation with exposure
to air. The new all-carbon PV cell appears to be
stable in air. The carbon-based cell is most effective
at capturing sunlight in the near-infrared region.
Because the material is transparent to visible light,
such cells could be overlaid on conventional solar
cells, creating a tandem device that could harness
most of the energy of sunlight.
V.Construction Of Carbon
Solar Cell
Fig.6: construction of the solar cell
• In conventional solid-state photovoltaic
cells three different tasks are generally
expected to be fulfilled simultaneously by
the material.
• Light absorption to generate electric charge
carriers, charge carrier separation and charge
transport to the electrodes.
• We use a mixture of a stable photoactive
light absorbing dye molecule with carbon
nanotubes introduced to a conjugated
polymer matrix to perform these tasks.
• Charge separation at the interface, electron
transport through the carbon nanotube
acceptors and hole transport from the dye to
the polymer backbone is expected to occur.
• In this system, differences in work function
between outer materials (metal contacts)
will create the necessary asymmetry to cause
electric charges to flow and inject into the
contacts to the external circuit. The general
device geometry and method of fabrication
is as follows.
• Transparent FTO coated glass (conducting
glass) is to be used as bottom electrode. The
composite material dissolved in chloroform
or toluene and sonicated. The active layer
can then be deposited by spin coating from
the solution.
• Complete device is obtained by depositing
the top metal electrode by either evaporation
or sputtering techniques.
• It is easy to see the attractiveness of
Organic Solar Cells (OSCs) from the fact
that the fabrication procedure is this simple
and inexpensive.
• Carbon is a remarkable element existing
in a variety of stable forms ranging
from insulator/semiconductor diamond
to metallic/semi-metallic graphite to
conducting/semi-conducting nano/micro
tubes to fullerences of highest order of
symmetry, which shows many interesting
physico-opto-electronic properties.
• In addition, it is also possible that many
more forms of carbon are yet to be
discovered. The various forms of carbon
have attracted a great deal of interest
in recent years because of their unique
structure and properties. Among various
application of carbonaceous material, recent
study of heterojunction diodes and solar
cells are quite interesting in terms of its
electronic application.
• Recent results on semiconducting
camphoric carbon and photovoltaic cell
promote carbon material to be one of the
future scopes of economically viable high
efficiency solar cell.
VI.WORKING OF CARBON
SOLAR PANNEL
Solar panels works on the principal of photovoltaic
effect.
PHOTOVOLTAIC EFFECT: It is the creation of
an electrical voltage or rather the electric current
flowing in a closed loop, here referred to in a solar
panel. This process is somewhat related to the
photoelectric effect; although these are different
processes altogether. The electrons that are generated
when the solar panels are exposed to a stream
of photons are transferred between the different
bands of energy inside the atom to which they are
bound. Typically, the transition of the energy state
of electrons takes place from valence band to the
conduction band, but within the material that is used
in the solar panels. This transfer of electrons makes
them accumulate in order to cause a buildup of
voltage between the two electrodes.
Solar panels contain a system of solar cells
that are interconnected so that they can transfer the
induced voltage/current between one another so that
the required parameters can pile up and a suitable
throughout can be obtained. Series connections of
solar cells in solar panels help add up the voltage
and the same is true for solar cells connected using
3

4. parallel connection.
Another fact is that solar panels produce much
lesser efficiency as compared to when their basic
components viz. solar cells are used independently
without any interconnections. Typically, solar
panels that are available commercially are only
able to depict their best efficiency as low as 21%.
Due to the significant impact of efficiency, a
number of techniques are used in order to tweak the
performance of solar cells.
VII.WORKING OF DOUBLE
WALLED CARBON
NANOTUBE USED IN
SOLAR/PHOTOVOLTAIC
CELL:
The directly configured double-walled carbon
nanotubes as energy conversion materials to fabricate
thin-film solar cells, with nanotubes serving as
both photo generation sites and a charge carriers
collecting/transport layer. The solar cells consist of a
semitransparent thin film of nanotubes conformally
coated on a n-type crystalline silicon substrate to
create high-density p−n heterojunctions between
nanotubes and n-Si to favor charge separation
and extract electrons (through n-Si) and holes
(through nanotubes). Initial tests have shown a
power conversion efficiency of >1%, proving that
DWNTs-on-Si is a potentially suitable configuration
for making solar cells. Our devices are distinct
from previously reported organic solar cells based
on blends of polymers and nanomaterials, where
conjugate polymers generate excitons and nanotubes
only serve as a transport path.
Fig.7: working of solar panel.
NANOTUBE PROPERTIES USEFUL FOR SOLAR
PANNELS
• High carrier mobilities (~1,20,000 cm2 V-1 s-
1)
• Large surface areas (~1600 m2 g-1)
• Absorption in the IR range (Eg: 0.48 to 1.37
eV)
• Conductance - Independent of the channel
length
• Enormous current carrying capability – 109
A cm-2
• Semiconducting CNTs – Ideal solar cells
• Mechanical strength & Chemical stability
PERFORMANCE OF CNT’S :
When the CNT is used instead of the pure polymer
substances the performance of the solar cell is as
shown below:
It shows about the linear variation of the V-I
characteristics of the output produced in the process
of conversion of the light energy to electrical energy.
Fig.8: performance of the carbon solar panel depending on the
light emission of the singled walled carbon nanotube.
The variation of the wavelength, light energy
which is inputted to the panel with the transmittance
of that energy.
Fig. 9: variation of the wavelength over percentage transmittance.
4
y = 0.0038x - 1E-06
-0.005
-0.004
-0.003
-0.002
-0.001
0
0.001
0.002
0.003
0.004
0.005
-1.5 -1 -0.5 0 0.5 1 1.5
V
A
Device 4 dark
Linear (Device 4 dark)

5. VIII.ADVANTAGES OF USING
CNT IN A SOLAR PANNEL
° The efficiency of the system can be
improved.
° As the CNT solar panels uses infrared rays
including visible range of sunlight they can
work at night times.
° They remain stable at ambience temperature
about 1600oF .
° The amount of the material to be used for
the construction will also be reduced
° As the mobility of the electrons is more
in the case of the CNT the output voltage
produced is drastically increased.
CONCLUSION:
Carbon nanotube technology is the
upcoming technology in the field of solar panels
which is under experimental stage. This seems like
a very promising direction that will eventually allow
for nanotubes promise to be more fully harnessed.
It helps in increasing the efficiency, reliability of the
panel.
REFERENCES:
• Physical Properties of Carbon
Nanotubes (1998), Imperial College Press,
UK, R. Saito, M.S. Dresselhaus,
G.Dresselhaus
• Optical and Electronic Properties of
Fullerenes and Fullerene-Based Materials,
Marcel Dekker, Inc(1999),Eds. J. Shinar et al
• The Science and Technology of Carbon
Nanotubes, (1999) Elsevier, Eds. K.
Tanaka, T. Yamabe and K. Yamabe
• Science of Fullerenes and Carbon
Nanotubes, (1996), Academic Press,
M. S. Dresselhaus, G. Dresselhaus and
P. C. Eklund
• Carbon Nanotubes (2001), Springer, Berlin,
Eds. M. S. Dresselhaus, G.Dresselhaus.
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