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Disclaimer — This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
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IMPLEMENTATION OF CARBON NANOTUBES AS COUNTER-ELECTRODE
IN DYE-SENSITIZED SOLAR CELLS
Spencer Smith, [email protected], Mena 3pm, Angelo Marsano, [email protected], Budny 10am
Abstract - Our essay focuses on the use of cylindrical carbon
molecules called Carbon Nanotubes (CNTs), which are
known for their extreme strength, unique conductive
properties, and low cost. Specifically, we detail this
material’s implementation into the field of energy in
providing a cheaper, more effective counter electrode in dyesensitized solar cells (DSSCs). These cells capture photons in
sunlight from organic dyes to mimic photosynthetic reaction,
and gain energy without direct sunlight much better than most
cells. Finally, we compared this technology with rivaling
solar energy solutions, and in turn highlighted this method’s
superiority.
We explore the complex electrochemical processes
behind DSSCs using various studies on solar cell
experimentation. We describe the drawbacks to current
methods, and how the adoption of CNTs solves some of these
issues. Finally, we analyze many studies focused on this niche
in solar energy, and compared cost, efficiency, and ethical
implications between CNT technology and other solar cell
types. This showcases the technology’s relevance to the
engineering community and general public alike. The costeffectiveness of CNTs provides an incentive for the
implementation of DSSCs, maximizing their unique
capabilities.
The combination of the polarizing properties of CNTs
proved beneficial in most experiments, providing a valid
replacement for platinum in traditional DSSCs.
Keywords – Carbon nanotubes, dye-sensitized solar cells,
nanomaterials, photoelectrochemical cells, solar energy
JUSTIFICATION OF SOLAR ENERGY
The changing state of the environment on earth and the
atmosphere surrounding it has long been an issue observed by
scientists, engineers, and concerned civilians alike. After
years of debate, fossil fuel emissions have been unanimously
understood as the major contributor to this pollution. The
increase in human industrial tendency using fossil fuels
releases greenhouse gases, such as carbon dioxide, methane,
and Chlorofluorocarbons (CFCs). These chemicals react with
a molecule that which makes up an entire layer of our
atmosphere called ozone [1]. This makes the earth more
University of Pittsburgh Swanson School of Engineering
03.03.2017
1
vulnerable to ultraviolet light from the sun, endangering much
life on earth. The realization of the danger implied by these
processes has led to a spike in incentive to prevent them. In
addition to this, fossil fuels are nonrenewable and
continuously depleting from their finite amount. All of these
traits result in a pattern that is not environmentally sustainable
nor economically sustainable. To be sustainable is to be “of,
relating to, or being a method of harvesting or using a resource
so that the resource is not depleted or permanently damaged,”
[2]. The environmental sustainability of fossil fuels is clearly
not present, while their economic sustainability is shaky due
to the fluctuating costs of the fuels and their continued
depletion. To counter this lack of sustainability of this dirty
form of energy, both corporations and individuals around the
globe have adopted forms of energy such as wind, nuclear,
hydroelectric, and solar power. These are sustainable from an
energy and environmental standpoint and leave less of a
carbon footprint.
While Solar energy does not account for the majority of
energy generated by alternative sources, the pace that it has
been growing at since its invention has been noteworthy.
According to the United States office of energy efficiency and
renewable energy, since 2008, solar energy installations have
grown from 1.2 gigawatts nationally to over 30 gigawatts
today, resulting in around a “seventeen-fold increase,” [3].
Solar energy is also becoming much cheaper to be applied
practically. This is evidenced by a Bloomberg Technology
article by Tom Randall, a writer on renewable energy, which
shows the price advantage of solar versus wind energy, the
previous leader in economical fossil fuel alternatives [5]. The
shrinking costs surrounding solar energy are further
evidenced by Zachary Shanan, the head director of
Cleantechnica, a leading site for clean energy news and
information [4]. In an article on Cleantechnica, Shanan states
that Solar and wind are both cheaper than their fossil fuel
counterparts, with the lowest cost of each being around two
to sixteen dollars less per megawatt-hour when compared. A
reason for the recent boom in solar energy use is the
widespread experimentation being done on the topic,
tweaking many different variables in the process to best meet
goals in both efficiency and sustainability. This work includes
research for the discovery of new forms of solar harvesting,
as well as improvements upon existing solar energy solutions,
Smith
Marsano
scaling from usage in homes to large scale implementations
for areas demanding a larger energy supply. Years of research
have led the industry to some exciting and unique ways to
harvest photons from the sun. The particular advancement
that will be focused on is the Dye-sensitized Solar Cell, a form
of solar cell that uses dyes to mimic photosynthesis in plants.
electrons make their way to the photoelectrode, they are
conducted away to the electrical load of the cell, and the rest
of the circuit. Then, the electrons reach the counter electrode
on the other side of the cell (labeled cathode in this picture,
these terms are interchangeable), and the circuit is closed with
a redox reaction occurs. This reaction reintroduces electrons
into the dye, allowing the reaction to continue, and also
requires a simultaneously unreactive and catalytic material in
its cathode. This overview of the process will aid in the
consideration of appropriate materials for each sector of the
cell.
Possible Shortcomings
Many of the concerns with DSSCs and their impact on
the environment overlap with concerns regarding other
varieties of solar energy. These concerns include land use,
hazardous materials, and global warming emissions from the
production phase [6]. Depending on the type, solar panels can
take up to 16.5 acres per megawatt generated, an amount of
area that proves intrusive on usable land. Although, to counter
this, solar panels will be placed on top of buildings or on land
that is abandoned or otherwise unusable for agriculture or
commercial development. Another key concern is the
widespread use of hazardous materials in the production of
solar panels, particularly the chemicals used in purifying their
semiconductor surface. These chemicals can prove hazardous
to those who are mass-producing solar cells. Another key
concern surrounding solar energy is the carbon dioxide
emissions in the “manufacturing, materials transportation,
installation, maintenance, and decommissioning and
dismantlement processes” [6]. These emissions result in .08
to .2 pounds of carbon dioxide per kilowatt-hour. Compared
to the 1.4 to 3.6 pounds of CO that coal outputs into the
environment per kilowatt-hour, the emissions from the solar
panel process are miniscule, thus proving the environmental
advantages to using various forms of alternative energy in
place of traditional fossil fuels for energy production.
2
FIGURE 1 [6]
Illustration of overall DSSC process
Figure 1 shows the central electrochemical procedure
involved in DSSCs. Light (labeled hv) excites the electrons
within the dye from the S to the S state in the center of the
diagram. S and S are different energy configurations of the
electron, the second being higher energy, and much less stable
and likely to move around. These electrons are injected into
the photoelectrode (TiO in this case), and then sent through
the electrical load, to the counter electrode (cathode). Here, a
redox reaction with an electrolyte occurs, after which the
electrons are transported back to the dye, and the process
repeats.
DYE-SENSITIZED SOLAR CELLS
o
o
The particular mode of alternative energy our work is
concerned with is the Dye-sensitized solar cell (DSSC). The
process behind the energy production, illustrated in Figure 1,
begins with the exciting of electrons by photons from
sunlight. In a study done on DSSCs, Hironori Arakawa of
Tokyo University and Kohijiro Hara of the National Institute
of Advanced Industrial Science likened the process to energy
harnessing in plants. The writers state, “this photon-to-current
conversion mechanism in a DSSC is similar to the mechanism
for photosynthesis in nature, in which chlorophyll functions
as the photosensitizer and charge transport occurs in the
membrane,” [8]. An organic dye within the cell incurs this
photon absorption, which results in an increase in energy.
This allows for the dye to excite some of its electrons to a
higher state. The excited electrons, now a greater distance
from their home nuclei, are then injected into a part of the
DSSC known as the photoelectrode.
The photoelectrode is usually a paste that is spread
thickly onto the conductive glass of the cell. Once the excited
*
*
2
Photoelectrode, Dye: other improvements
A popular choice for the photoelectrode is titanium
dioxide (TiO ). This choice is due to the low cost of the
material, as well as its increased absorbing properties. One of
the shortcomings of dye-sensitized solar cells is the efficiency
drop associated with reduced infrared light absorption. The
discovery of TiO ’s ability to ease this efficiency drop makes
it an extremely desirable material for DSSCs. According to
2
2
2
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the American Society of Mechanical Engineer’s writer, Mark
Crawford, the incorporation of titanium dioxide plays a large
role in the push of power conversion efficiencies of dyesensitized solar cells beyond 12% [9]. This only begins to
show the promising future of dye-sensitized solar cells: its
openness and variability in many of its components leaves a
large amount of potential improvement.
The other main components of the process have material
flexibility as well. Variability in dye type has been
experimented with. The results from many different dye types
are found in a summary of recent DSSC lab work, compiled
by Elsa John of the Indian Institute of Technology Bombay
and Maulana Azad National Institute of Technology. The duo
explains wide array of dyes involved in DSSC research, and
the various properties of dyes that tend to affect cells’
performances [10]. There is plenty of activity within this area
of DSSCs; however, an even more popular field of research is
in the counter electrode materials.
DSSCs versus General Solar Energy
There are many comparisons to be made between
DSSCs built with different materials, but perhaps more
important is how the cells’ qualities stack up against standard
commercial solar cells. The most-used type of solar cell is
built on what a CMD College solar energy overview dubs
“silicon wafers”, the popularity of which arises due to high
power efficiencies [12]. Silicon wafers are considered the first
generation of solar cells, which is chronologically followed
by second generation thin film cells. These are known for
their extremely thin light-absorbing layers compared to the
wafer cells (350 micrometers in wafer compared to 1
micrometer in thin), and for requiring much lower
temperatures in manufacturing processes. Their production is
thus much more favorable, and as a result, cheaper [12].
Second generation cells lose out in efficiency compared to
their predecessors, however lack their temperature and
climate restraints. Third generation cells are emerging
technologies, usually incorporating nanomaterials. DSSCs
fall into this category, and the generation of cells are hoped to
be able to exceed the currently unreached 30-40% efficiency
range.
Counter Electrode
The counter electrode located at the conclusion of the
circuit which facilitates the electrolytic reduction that returns
the traveling electrons back into the dye particles. From this
point, the circuit continues to run identically to when it was
first described. There are many different materials available
for use as a counter electrode, all with varied efficiencies,
prices, and properties. In a summary of counter electrode
options by a Nanoscience center, many of these possibilities
are outlined. Platinum is the most popular materials in counter
electrodes for DSSCs in commercial use. The element is inert,
even at extreme conditions, meaning that platinum it is a very
unreactive metal. This is especially beneficial in this situation,
because the counter electrode is responsible for catalysis of
the reaction and helping the redox reaction with the
electrolyte occur, without being oxidized itself. From the
mentioned study, platinum’s popularity is attributed to its
“attractive properties like high catalytic activity [and]
excellent stability towards the iodide redox species,” [11].
This shows two of platinum’s key strengths for use as an
electrode.
There are two varieties of platinum materials used as
counter electrode material, bulk and nanoparticles. Generally,
the second form is far preferred due to its high surface area,
which allots more space for reaction to occur, and beneficial
electrical properties. The downside of platinum in either case
is the low supply of platinum, leading to high prices. This
causes issues for their use within DSSCs, as costeffectiveness is crucial in differentiating different types of
clean energy. Counter electrodes can also be constructed from
carbon-based materials as well. These materials comprise
platinum ideally, lowering price without incurring a dubious
loss in efficiency. Carbon materials’ use will be outlined in a
latter section of this paper.
Cell
type
Monocrystalli
ne
Thinfilm
CdTe
DSSC
Polymer
Perovskite
Generat
ion
I
II
III
III
III
Energy
efficien
cy
14% 17.5%
9% 11%
1012%
3-10%
31%
Cost
Twice
price of
other
cells
Simila
r price
Simila
r Price
Similar
Price
Similar
Price
Additio
nal
details
Oldest
PV tech
Toxic
due to
cadmi
um
Short
install
time,
large
space
Short
install
time,
large
space
Short
install
time,
small
space
FIGURE 2 [12]
Solar Cell Cost/Efficiency Comparison
The cost and efficiencies of a variety of commercial and
experimental solar cells is displayed in Figure 3. The oldest
cells are shown on the left side of the table, and are
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increasingly new technologies moving toward the right.
Perovskite cells are extremely experimental, and have been
created within the last decade, and have shown severe
stability issues [13].
supply makes their use unideal. The complete adoption of
carbon-based counter electrodes would be economically
unrestrictive, as there are a variety of options that can be
considered for implementation under this umbrella.
One material that has been explored is carbon black,
which is notable for its high surface area-to-volume ratio.
Higher area-to-volume ratios increase reaction rates, because
more individual reactionary collisions can occur
simultaneously, overall boosting the rate. Unfortunately,
carbon black is a byproduct of “the incomplete combustion of
petroleum products,” [12]. This link to a polluting source of
energy does not lend well to the material’s implementation in
environmentally efficient power sources. This ethical
dilemma is best to be avoided, as there are other carbon-based
solutions to embrace.
Mesoporous carbon materials are a large family, which
are known for their application in “batteries, fuel cells, and
supercapacitors,” mostly due to their “electric conductivity,
thermal conductivity, chemical stability, and low density, but
also to their wide availability,” [16]. Mesoporous carbon
materials are known for their nanometre-sized pores, in
addition to high surface area-to-volume ratios, similar to
carbon black. Additionally, materials falling into this group
can be synthesized through less risqué processes. One such
mechanism is pyrolysis of natural materials, which is
decomposition as a result of extremely high temperatures.
A third option is graphene, a carbon lattice structure with
the thickness of one carbon atom. This material is a another
possible counter electrode material due to its impressive
thermal and conductive properties. Graphene is created
through the oxidation of graphite, a natural carbon compound,
and can be utilized within multiple realms, including that of
DSSCs, or in the engineering of new materials altogether [17].
These graphene sheets can then be rolled up into microscopic
tubes, leading to the creation of carbon nanotubes.
The usefulness of CNTs as a nanomaterial rises from
their unique structure and advantageous properties [18]. The
hexagonal pattern of the rolled up graphene sheets results in
both a low mass and strong structure in CNTs, making them
desirable for both industry products and consumer goods alike
[18]. An example of what these sheets look like is shown in
figure 3, displaying what a sheet looks like rolled up, along
with two examples of formations a graphene sheet can take
[18]. Soon after the discovery of CNT, it was revealed that not
only do CNTs conduct electricity, but they also are capable
thermal conductors, highly absorbent, and notably elastic
[21].
In relation to DSSCs, the CNTs’ ability to efficiently
conduct electricity is their most beneficial property. The
ability of a CNT to conduct electricity depends greatly on the
diameter of the substance, with a CNT of smaller diameter
being more conductive than that of a larger one [22].
Additionally, single walled carbon nanotubes, while a bit
more expensive than their multi walled counterpart, are some
of the most conductive materials known. In fact, nanowerk, a
site dedicated to the world of nanotechnology, states that “the
With the wide range of values shown in figure 3, an indepth analysis will likely provide helpful to fully grasp the
benefits and drawbacks to each particular solar energy
solution. As outlined previously, first generation cells are
more expensive, oldest, and become unstable and less
efficient at high temperatures. Thin film cells allow flexibility
of shape, and are much cheaper than crystalline cells;
however, they have toxicity issues due to the presence of
cadmium. Polymer cells have the widest range on this table,
which is attributed to infinite number of polymers that are able
to be synthesized, each containing different functionality. The
higher part of that range is close to what is seen for DSSCs,
whose record high lies at 15% [14].
The impressively high efficiency seen on this table is for
another third-generation energy type, perovskite solar cells,
which have seen massive growth since their discovery in
2009. While these cell’s efficiencies are dazzling, a study
done by Xing Zhao and Nam-Gyu Park of Sungkyunkwan
University (S. Korea) have found flaws in the cells’ stability.
Their study details the issues that arise in the presence of
humidity, and through a series of decomposition reactions,
efficiency can be lessened [13]. Many of the reagents exist
naturally at room temperature in gaseous forms, making the
breaking down of the process nearly impossible to avoid.
Thus, this seemingly standout cell is not the godsend of a solar
cell it may seem to be.
Overall, DSSCs fall in the above-average range for solar
energy, and have much less dramatic flaws than some other
forms. DSSCs have most of their issues in the electrolyte, as
low temperatures can cause freezing and physical damage to
the cell. The electrolyte within the cell must also be sealed,
and dyes can sometimes be harmful to humans, depending on
which variety is used [15]. One other gripe that some have
with DSSCs is price, however, the substitution of the platinum
electrode for a carbon material-based one decreases the price
significantly.
Carbon materials
Among the candidates to replace the current norm of
platinum in dye-sensitized solar cells are carbon materials.
Carbon-based counter electrodes are ideal for production due
to their natural abundance: according to an article fronted by
Sara Thomas on carbon nanotube counter electrodes,
“Carbon, which is the sixth most abundant material in the
Earth's crust, is the best material to replace Pt,” [12]. Carbon,
with a high supply and minimal corrosive properties, is an
ideal substitute for the rare, albeit efficient, platinum.
Efficiencies for these cells do not reach the levels their
platinum peers do, however the platinum’s diminishing
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resistivity of the single walled nanotubes ropes was of the
order of 10 ohm-cm at 27°C” [21]. A statistic such as this
makes single walled carbon nanotubes the “most conductive
carbon fiber known” [21]. This conductivity in turn led
experimentation regarding the application of CNTs in
products such as batteries, various electronic devices, and in
the interests of this research, dye-sensitized solar cells.
only usable on rooftops. This opens an absolutely massive
array of options for CNT-based DSSCs to be applied within.
For example, thin, clear sheets of DSSCs can be placed
in between glass window panes to harvest energy throughout
the day. Instead of the long installation processes associated
with consumer use of normal, rigid solar panels, this
application has the potential to be store bought, or at least
installed with ease. Another potential use for DSSCs is their
integration into small consumer electronic products, such as
cell phones, in order to extend battery life without requiring
frequent recharges. This particular use would only be
applicable with DSSCs due to their ability to harvest light
more efficiently in areas that are not as exposed to sunlight as
those used with traditional solar panels. Both of these possible
applications display the ability of DSSCs to be implemented
simultaneously in both small and large-scale energy
generation operations; all the while, proving more applicable
due to the cost advantage of using CNTs in place of platinum
as a counter electrode.
The use of CNTs as a counter electrode in place of
platinum is essential to the economical sustainability of
DSSCs in a large sense. Having a cost-efficient counter
electrode gives DSSCs a greater chance of being considered
a major player in solar cells and solar energy alike, expanding
the potential uses to a wider variety of devices and
applications. The continuous improvements upon DSSCs as a
technology ensures that they remain relevant as an alternative
to not only fossil fuels, but other forms of solar cells as well.
By being economically sustainable with the implementation
of CNTs, this guarantees that DSSCs will have the ability to
thrive, helping our planet to become and remain
environmentally sustainable.
The alignment of these beneficial properties make
carbon nanotubes virtually destined for application within
dye-sensitized solar cells: combining the ideal conductive and
catalytic properties with extreme affordability, this carbon
compound provides an ideal substitute for both the pricier first
and second generation solar cells, as well as other DSSCs with
pricier counter electrodes implemented within them. Platinum
usually has a higher efficiency, but is about five times the
price of CNTs, for a few percent difference. The use of a
synthesized material, engineered with plentiful and costeffective components effectively satisfies all of the drawbacks
of the less ideal, more expensive platinum counter electrode.
Almost all available studies on these two different cells use
qualitative statements, while never addressing real price
figures for platinum and carbon nanotubes, so there is no
direct price comparison within this paper. This hole in
knowledge is unfortunate, but given platinum’s expensive
per-ounce price (about $1000 per oz.), and CNTs’ very
moderate price (about $15 per oz.), the substantial gap in price
is easy to visualize [20, 25].
-4
FIGURE 3 [19]
Structure of graphene sheets
Figure 3 shows the structure of graphene sheets and how they
appear not only flat, but also rolled into carbon nanotube
form. Two hexagonal patterns are shown below the image,
showing the different ways that CNTs can be structured on
the surface. The different arrangement of the patterns can
affect the conductivity of the CNTs, with the armchair variety
being more conductive out of the two displayed here.
CARBON NANOTUBES IN DYESENSITIZED SOLAR CELLS
The advantages of CNTs in DSSCs comes from the
improvements that CNTs provide to a solar energy option that
already proves interesting and versatile. Many of the
advantages of DSSCs come from their low cost and low
weight, along with their flexibility, thinness, and ability to
generate significant power from sunlight [23]. These features
set DSSCs apart from other solar cells, giving them access to
different energy harvesting opportunities, which prove even
more useful due to the implementation of CNTs as a counter
electrode. One such application is “building-integrated
photovoltaics,” [23]. The idea behind building-integrated
photovoltaics is the practice of implementing DSSCs on a
building in places other than rooftops, heightening the amount
of opportunities to generate light from these devices. This can
be done because of DSSCs’ ability to harvest energy
efficiently in non-direct sunlight, a feature that cannot be said
about traditional silicon-based solar cells, which are typically
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Figure 4 provides a direct comparison between DSSCs with
Pt counter electrodes and CNT counter electrodes. The
numbers show the minimal difference between a lot of the
figures, including the fill factor (FF), which is most literally a
judge of solar cells’ quality. The calculation divides the
highest achieved power with the theoretical highest power
(the product of the max voltage and the max current). The fill
factor gives a picture of how much the cell is reaching its
potential. The η values, or standing for efficiency, also show
the small extent of the differences between these two types of
DSSCs.
technology as a whole, as research and development can be
reallocated to areas like the synthesis of more ideal dyes, the
discovery usable solid electrolytes, or the creation more
conductive glass on the edges of the cell.
With this being said, no energy solution is perfect and
they all come with flaws. As stated earlier, DSSCs have some
competition with other forms of solar energy that may have
some advantages over them, but these other solutions are not
without their own flaws that hold them back from being the
perfect answer. DSSCs themselves come with their own
ethical issues regarding poisonous substances from the
electrolyte, a toxin that could harm those manufacturing and
handling the cells. Even with these ethical issues related to
some toxic substances used in this component of DSSCs, they
are still a less harmful energy solution than typical fossil fuels.
The importance of cleaner sources of energy cannot be
stressed enough after the damage fossil fuels have already
done on our environment and atmosphere. It can be
discouraging to think of one perfect solution to the issue that
is dirty energy, but a wide variety of sustainable options are
available to implement in order to do just that. While the sheer
number of options can be daunting to consider, we believe
that DSSCs with CNTs as counter-electrodes are a worthy
addition to the options available.
A FUTURE FOR ALTERNATIVE ENERGY
SOURCES
It is now obvious that alternative energy not only has the
potential to be, but currently is a major player in the
distribution of power around the world. While the
implementation of various forms of renewable energy
becomes more prominent along with the global focus on a
sustainable environmental state, the widespread use of solar
energy continues to grow. We are confident that along with
the growth of solar energy, the usage and prevalence of
DSSCs grows with the field. As displayed through our
research, DSSCs have statistics and research to justify their
implementation into the multitude of solar cell varieties. This
acceptance of DSSCs will lead to an even greater opportunity
for solar energy to play a major role in the spread of
alternative energy solutions, with more and more
geographical locations looking to go green. For these
locations, having the practical option of DSSCs for their solar
panels will increase the interest for solar energy as a preferred
power source.
Not only do we think that DSSCs should play a major
role in the diverse array of solar energy options, but we
believe that carbon compounds have the ability to make a
substitute for platinum as the default counter electrode
material in DSSCs. While the substitution for an already
functional counter electrode may seem strange, this would not
only make room for research in other parts of the cell, but also
make the price factor of the cells much more attractive to
those interested in solar energy. The designation of a material
as a standard is beneficial for the advancement of the
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https://climate.nasa.gov/causes/
[2] “Sustainable.” Merriam-Webster. Accessed 1.28.2017.
https://www.merriam-webster.com/dictionary/sustainable
[3] “Solar Energy in the United States” Office of Energy
Efficiency and Renewable Energy. 2014. Accessed
2.26.2017. https://energy.gov/eere/solarpoweringamerica/so
lar-energy-united-states
[4] Zachary Shanan. “Low Costs of Solar Power & Wind
Power Crush Coal, Crush Nuclear, & Beat Natural Gas”
Cleantechnica.
12.25.2016.
Accessed
2.26.2017.
https://cleantechnica.com/2016/12/25/cost-of-solar-powervs-cost-of-wind-power-coal-nuclear-natural-gas/
[5] T. Randall. “Bloomberg World Energy Hits a Turning
Point:
Solar
That's
Cheaper
Than
Wind”
BloombergTechology. 12.15.2016. Accessed 2.12.2017.
https://www.bloomberg.com/news/articles/2016-1215/world-energy-hits-a-turning-point-solar-that-s-cheaperthan-wind
[6] “Environmental Impacts of Solar Power.” Union of
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[7] J. Yum, E. Baranoff, S. Wenger, Md. K. Nazeeruddin, M.
Gratzel. “Panchromatic engineering for dye-sensitized solar
cells.” Royal Society of Chemistry. 12.21.2010. Accessed
2.27.2017.
Material
Current
(mA)
Voltage
(V)
FF
ηefficiency
(%)
Price
per
ounce
Pt
4.67
0.713
0.747
9.95%
~$1000
CNT
4.35
0.711
0.727
8.99%
~$15
FIGURE 4 [20, 24, 25]
Comparison of Platinum/CNT-based cells
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Marsano
[18] S. Iijima. “The Discovery of Carbon Nanotubes”
International Balzan Prize Foundation. 11.22.2007. Accessed
1.23.2017.
http://www.balzan.org/en/prizewinners/sumioiijima/the-discovery-of-carbon-nanotubes-iijima
[19] B. Dumé. “Unzipped Graphene Reveals its Secrets”
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unzipped-graphene-reveals-its-secrets
[20] “Multi Walled Carbon Nanotubes 50nm.” CheapTubes.
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[21] “Electrical Conductivity” Nanowerk. Accessed
2.26.2017
http://www.nanowerk.com/nanotechnology/introduction/intr
oduction_to_nanotechnology_26.php
[22] S. Gong, Z. H. Zhu, and S. A. Meguid. “Carbon nanotube
agglomeration effect on piezoresistivity of polymer
nanocomposites”
ResearchGate.
10.2014.
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ACKNOWLEDGEMENTS
We would like to thank Emelyn Haft, our co-chair who
helped edit this research essay, and met with us consistently.
We would also like to extend our thanks to writing instructor,
Joshua Zelesnick, for assisting us in clarifying our vision of
the paper, and clarifying all misunderstandings we had along
the way.
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