GRAPHENE SOLAR POWER

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A TECHNICAL SEMINAR REPORT ON
GRAPHENE USE IN SOLAR
PANELS
Submitted by
SIGIRI NAVYASRI -15JJ1A0250
DEPARTMENT OF ELECTRICAL AND
ELECTRONICS ENGINEERING
Jawaharlal Nehru Technological University Hyderabad
College Of Engineering Jagtial

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Nachupally (Kondagattu), Jagtial Dist - 505 501,T.S.
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY
HYDERABAD
COLLEGE OF ENGINEERING JAGTIAL
Nachupally (Kondagattu), Jagtial Dist – 505 501,T.S.
DEPARTMENT OFELECTRICAL AND ELECTRONICS
ENGINEERING
CERTIFICATE
This is to certify that the technical seminar report entitled “GRAPHENE USE IN
SOLAR PANELS” is a bona-fide work carried out by SIGIRI NAVYASRI – 15JJ1A0250 , in
partial fulfilment of the requirements for the degree of BACHELOR OF TECHNOLOGY
in ELECTRICAL AND ELECTRONICS ENGINEERING by the Jawaharlal Nehru
Technological University,Hyderabad duringthe academic year 2015-2019.The seminar
report has been approved as it satisfies the academic requirements in respect of
seminar work prescribed for the degree.

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ACKNOWLEDGEMENT
I am extremely grateful toMr.S. JagadishKumar, Head Ofthe department
Electrical and Electronics Engineering for providing me with best
facilities and encouragement.
I would like to thank my coordinator Mrs. P. Sangeetha, Assistant
professor Department of Electrical and Electronics Engineering for
creative work guidance and encouragement.
Seminar co-ordinator
Mrs. P. Sangeetha(Asst.
Prof)
HOD of EEE
Mr. S. Jagadish Kumar(Asst.
Prof)

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CONTENT
s.no List oftopics Pageno.
1 Introduction 6
2 Grapheneorgraphenes 8
3 Whatisgraphenelike? 8
4 Generalproperties 8
5 Howdowe makegraphene 11
6 Howcanweusegraphene 12
7 Ourgraphenefuture? 14
8 Differentgraphenematerials 14
9 Graphenesolar 18
10 Solarpoweradvantagesanddisadvantages 20
11 Solarpowerapplications 21
12 Grapheneandsolarpanels 21
13 Novelgraphenefilmothernewconceptforsolarenergy 22
14 Deriveenergyfromraindrops 23

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15 Graphenecoulddoubleelectricitygeneratedfromsolar 24
16 Newpropertyrevealedingraphenecouldleadtobetter
performingsolarpanel
27
17 Conclusion 30
18 References 31
Abstract
If the 20th century was the age of plastics, the 21st
century seems set to become the age of graphene
A recently discovered material made from
honeycomb sheets of carbon just one atom thick. Science journals

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have been running out of superlatives for this wondrous stuff: it
is just about the lightest, the strongest, the thinnest, the best heat
and the electricity conducting material ever discovered.
Moreover, if we are to believe the hype, it promises to
revolutionize everything from computing to car tires and solar
cells to smoke detectors.
What! Is this strange and remarkable new stuff? Let us
take a closer look!
Introduction
Graphene, the wonder material of the 21st century discovered amidst
theoretical studies refuting its stability in free form. Attempts to isolate and
characterize graphene began in 1800s, long before the famous discovery by
Geim and Novoselov in 2004. The discovery of graphene opened up a new
world of “flatlands” and a myriad of materials from this class is known today.

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This long list includes hexagonal boron nitride, molybdenum sulphide, di-
chalcogenides, single-atom layers (phosphorene, silicene, borophene, etc.) and
still counting.
What is graphene?
In school we probably learned that carbon comes in two basic but
startlingly different forms (or allotropes), namely graphite (the soft, black stuff
in pencil "leads") and diamond (the super-hard, sparkly crystals in jewellery).
The amazing thing is that both these radically different materials are made of
identical carbon atoms.
So why is graphite different to diamond? The atoms inside the two
materials are arranged in different ways, and this is what gives the two
allotropes their completely different properties: graphite is black, dull, and
relatively soft (soft and hard pencils mix graphite with other materials to make
darker or fainter lines); diamond is transparent and the hardest naturalmaterial
so far discovered.
If that's what we learned in school, probably finished our studies quite a
while ago, because in the last few years scientists have discovered various other
carbon allotropes with even more interesting properties.
There are
1. fullerenes (discovered in 1985; hollow cages of carbon atoms, including
the so-called Buckyball, Buckminsterfullerene, made from a kind of
football-shaped cage of 60 carbon atoms)
2. nanotubes (discovered in 1991; flat sheets of carbon atoms curled into
amazingly thin, hollow tubes one nanometer in diameter)—and (drum
roll) graphene (discovered in 2004).
crystal lattice (another name for a solid's internal, crystalline structure):
lots of atoms arranged in a regular, endlessly repeating, three-dimensional
structure a bit like an atomic climbing frame, only instead of bars there are
invisible bonds between the atoms that hold them together. Diamond and
graphite both have a three-dimensional structure, though it's completely
different: in diamond, the atoms are tightly bonded in three-dimensional
tetrahedrons, whereas in graphite, atoms are bonded tightly in two-
dimensional layers, which are held to the layers above and below by relatively
weak forces.

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1) Diamond has a strong 3D (three-dimensional) crystal lattice based on a repeating
tetrahedron (left). The red blobs are the carbon atoms and the gray lines are the bonds that
join them together. (Bonds are invisible, but we draw them like this so we can visualize them
more easily.)
2) Graphite has a much weaker structure based on layers of tightly bonded hexagons. The
layers are weakly joined to one another by van der Waals forces (blue dotted lines—only a
few of which are shown for clarity).
Graphene is a single layer of graphite. The remarkable thing about it is
that its crystalline structure is two-dimensional. In other words, the atoms in
graphene are laid out flat, like billiard balls on a table. Just like in graphite, each
layer of graphene is made of hexagonal "rings" of carbon (like lots
of benzene rings connected together, only with more carbon atoms replacing
the hydrogen atoms around the edge), giving a honeycomb-like appearance.
Since the layers themselves are just one atom high, you'd need a stack of about
three million of these layers to make graphene 1mm thick!

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Graphenehasa flatcrystallatticemadefrom interlinkedhexagonsofcarbonatoms(red blobs)
tightly bonded together (black lines).
Graphene or graphenes?
People talk about "graphene" the way they talk about "plastic," but it's
important to remember that scientists are working on many different kinds of
graphene-based materials (just like there are many different kinds of plastics),
all of which are a little bit different and designed to do different things. In this
repot I've followed the convention of calling the material "graphene," but it's as
well to remember that this very new, fast-evolving substance has many
different angles and aspects and the word graphene will ultimately come to
refer to a very wide range of different materials. One day, it may be common to
talk about "graphenes" the way we now speak of "plastics."
What is graphene like?
People are discovering and inventing new materials all the time, but
we seldom hear about them because they're often not thatinteresting. Graphene
was first discovered in 2004, but what's caused such excitement is that its
properties (the way it behaves as a material) are remarkable and exciting.
Briefly, it's super-strong and stiff, amazingly thin, almost completely
transparent, extremely light, and an amazing conductor of electricity and heat.
It also has some extremely unusual electronic properties.
 General properties
Graphene is an amazingly pure substance, thanks largely to its simple,
orderly structure based on tight, regular, atomic bonding, Carbon is a
non-metal, so you might expect graphene to be one too. In fact, it behaves
much more like a metal (though the way it conducts electricity is very
different), and that's led some scientists to describe it as a semimetal or a
semiconductor (a material mid-way between a conductor and an
insulator, such as silicon and germanium). Even so, it's as well to
remember that graphene is extraordinary and quite possibly unique.

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 Strength and stiffness
If you've ever scribbled with a soft pencil (something like a 4B), you'll
know that graphite is horribly soft. That's because the carbon layers
inside a stick of graphite shave off very easily. But the atoms within those
layers are very tightly bonded so, like carbon nanotubes (and unlike
graphite), graphene is super-strong, even stronger than diamond!
Graphene is believed to be the strongest material yet discovered, some
200 times stronger than steel. Remarkably, it's both stiff and elastic
(like rubber), so you can stretch it by an amazing amount (20-25 percent
of its original length) without it breaking. That's because the flat planes
of carbon atoms in graphene can flex relatively easily without the atoms
breaking apart.
No one knows quite what to do with graphene's super-strong properties,
but one likely possibility is mixing it with other materials (such
as plastics) to make composites that are stronger and tougher, but also
thinner and lighter, than any materials we have now. Imagine an energy-
saving car with super-strong, super-thin, super-light plastic body panels
reinforced with graphene; that's the kind of object we might envisage
appearing in a future turned upside down by this amazing material
 Thinness and lightness
Something that's only one atom thick is bound to be pretty light.
Apparently, you could cover a football field with a sheet of graphene
weighing less than a gram although it's pretty unlikely anyone has
actually tried! According to my quick calculations, that means if you
could cover the entire United States with graphene, you'd only need a
mass of around 1500–2000 tons. That might sound a lot, but it's only
about as much as about 1500 cars—and it's completely covering one of
the world's biggest countries
 Heat conductivity
As if super strength and featherweight lightness aren't enough, graphene
is better at carrying heat (it has very high thermal conductivity) than any
other material—better by far than brilliant heat conductors such
as silver and copper, and much better than either graphite or diamond.
Again, we're most likely to discover the benefit of that by using

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graphenes in composite materials, where we could use them to add extra
heat-resistance or conductivity to plastics or other materials.
 Electrical conductivity
This is where graphene starts to get really interesting! Materials that
conduct heat very well also conduct electricity well, because both
processes transport energy using electrons. The flat, hexagonal lattice of
graphene offers relatively little resistance to electrons, which zip through
it quickly and easily, carrying electricity better than even superb
conductors such as copper and almost as well
as superconductors (unlike superconductors, which need to be cooled to
low temperatures, graphene's remarkable conductivity works even at
room temperature). Scientifically speaking, we could say that the
electrons in graphene have a longer mean free path than they have in any
other material (in other words, they can go further without crashing into
things or otherwise being interrupted, which is what causes electrical
resistance). What use is this? Imagine a strong, light, relatively
inexpensive material that can conduct electricity with greatly reduced
energy losses: on a large scale, it could revolutionize electricity
production and distribution from power plants; on a much smaller scale,
it might spawn portable gadgets (such as cellphones) with much
longer battery life.
 Electronic properties
Photos: Advances in nanotechnology, including the development of graphene, will drive faster, smaller, cheaper
computers. Picture by courtesy of Argonne National Laboratory published on Flickr under a Creative Commons
Licence.
Electrical conductivity is just about "ferrying" electricity from one place
to another in a relatively crude fashion; much more interesting is

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manipulating the flow of electrons that carry electricity, which is
what electronics is all about. As you might expect from its other amazing
abilities, the electronic properties of graphene are also highly unusual.
First off, the electrons are faster and much more mobile, which opens up
the possibility of computer chips that work more quickly (and with less
power) than the ones we use today. Second, the electrons move through
graphene a bit like photons (wave-like particles of light), at speeds close
enough to the speed of light (about 1 million meters per second, in fact)
that they behave according to both the theories of relativity and quantum
mechanics, where simple certainties are replaced by puzzling
probabilities. That means simple bits of carbon (graphene, in other
words) can be used to test aspects of those theories on the table top,
instead of by using blisteringly expensive particle accelerators or vast,
powerful space telescopes.
 Optical properties
As a general rule, the thinner something is, the more likely it is to be
transparent (or translucent), and it's easy to see why: with fewer atoms
to battle, photons are more likely to penetrate through thin objects than
thick ones. As you might expect, super-thin graphene, being only one
atom thick, is almost completely transparent; in fact, graphene transmits
about 97–98 percent of light (compared to about 80–90 percent for a basic,
single pane of window glass). Bearing in mind that graphene is also an
amazing conductor of electricity, you can startto understand why people
who make solar panels, LCDs, and touchscreens are getting very excited:
a material than combines amazing transparency, superb electrical
conductivity, and high strength is a perfect starting point for applications
like these.
 Impermeability
Sheets of graphene have such closely knit carbon atoms that they can
work like super-fine atomic nets, stopping other materials from getting
through. That means graphene is useful for trapping and detecting gases
but it might also have promising applications holding gases (such as
hydrogen) that leak relatively easily from conventional containers. One
of the drawbacks of using hydrogen as a fuel (in electric cars) is the

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difficulty of storing it safely. Graphenes, potentially, could help to
make fuel-cell cars running on hydrogen a more viable prospect.
On the other hand, if you pepper tiny holes into graphene to make it
porous, you get make a meshlike material called holey graphene that can
work like an electrical semiconductor or a very fine, physical sieve. Still
very new, it's already starting to find exciting applications in new forms
of energy storage (such as supercapacitors) and water filters that could
reduce pressure on the planet by helping us turn ocean water into safe,
clean drinking water.
How do we make graphene?
Photo: Vapor deposition is usedto create a layer of graphene on another surface (known as a substrate). Picture by
Warren Gretz courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).
Take a pencil and some sticky tape. Stick the tape to the graphite, peel it away,
and you'll get a layer of graphite made up of multiple layers of carbon atoms.
Repeat the process very carefully, over and over again, and you'll (hopefully)
end up with carbon so thin that it'll contain just one layer of atoms. That's your
graphene! This rather crude method goes by the technical name of mechanical
exfoliation. An alternative method involves loading up a super-precise atomic
force microscope with a piece of graphite and then rubbing it very precisely on
something so that single layers of graphene flake off, a bit like graphite from a
pencil lead only one layer at a time. Techniques like this are fiddly and
intricate and explain why graphene is currently the most expensive material
on the planet

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These methods are fine for making tiny test samples of graphene in a
laboratory, but there's no way we could make graphene like this on the kind of
industrial scale on which it's likely to be required.
So how do you make lots of graphene? One approach is to put an organic
(carbon-based) gas such as methane into a closed container with something like
a piece of copper in the bottom, then monkey with the temperature and
pressure until a layer of graphene is formed on it. Because the graphene is
formed by depositing layers of a chemical from a gas (vapor), this method is
called chemical vapor deposition (CVD). Another approach involves growing
crystals of graphene starting from a carbon-rich solid, such as sugar.
How can we use graphene?
We can answer that question in at least three different ways.
 First, because graphene has so many excellent properties, and because
all those properties probably aren't needed in the same material (for the
same applications), it makes sense to start talking about different types
of graphene (or even different graphenes) that are being used in different
ways or being optimized for particular purposes. So we're likely to see
some graphenes being developed for structural uses (in composites
materials), some being optimized to make the most of their
extraordinary electron-carrying properties (for use in electronic
components), others where we make the most of low-resistivity (in
energy-saving power systems), and still others where excellent
transparency and electrical conductivity are the important things (in
solar cells and computer displays).

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Photo: Computer memory chips like this might become smaller and faster if graphene replaces the silicon we
currently use.
 Second, we can see graphene as an exciting replacement for existing
materials that have been pushed to their physical limits.
Silicon transistors (the switching devices used as memories and
"decision-making" logic gates in computers), for example, have
consistently become smaller and more powerful over the last few
decades, following a trend known as Moore's law, but computer
scientists have long expressed concerns that the same rate of progress
can't continue as we approach basic limitations imposed by the laws of
physics.
Some scientists are already imagining smaller and faster transistors in
which silicon is replaced by graphene, taking computer devices even
closer to the absolute limits of physics. In theory, we could use graphene
to make ballistic transistors that store information or switch on and off
at super-high speeds by manipulating single electrons. In much the same
way, graphene could revolutionize other areas of technology
constrained by conventional materials. For example, it could spawn
lighter and stronger airplanes (by replacing composite materials or metal
alloys), cost-competitive and more efficient solar panels (replacing
silicon again), more energy-efficient power transmission equipment (in
place of superconductors), and supercapacitors with thinner plates that
can be charged in seconds and store more energy in a smaller space than
has ever previously been possible (replacing ordinary, chemical batteries
entirely).

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Companies such as Samsung, Nokia, and IBM are already developing
graphene-based replacements for such things as touchscreens,
transistors, and flash memories, though the work is at a very early stage.
 Third, and most exciting of all, is the likelihood that we'll develop all
kinds of brand-new, currently unimaginable technologies that take
advantage of graphene's amazing properties. In the 20th century,
plastics didn't simply replace older materials such as metal and wood:
for better or worse, they completely changed our culture into one where
disposability and convenience overtook durability. If graphenes lead us
to ultra-light, ultra-thin, strong, transparent, optically and electrically
conducting materials, who knows what possibilities might lie ahead.
How about super-lightweight clothes made of graphenes, wired to
batteries, that change color at the flick of a switch? Or an emergency
house built for disaster areas, with graphene walls so strong and light
that you can fold it up and carry it in a backpack?
Our graphene future?
Is it full-steam ahead to a future where graphene rules the world?
Maybe or maybe not. It's important not to get carried away with the hype: most
of the exciting work on graphene has so far been done on a very small scale in
chemical and physics laboratories. Most of the research is still what we'd
describe as "blue sky": it could be many years or even decades before it can be
developed practically, let along cost-effectively. By the same token, it's still very
early days for basic scientific research into graphene. Forgetting all the amazing
applications for a moment, there's doubtless much more exciting science to
emerge. For example, we don't yet know if graphene is the only material with
a two-dimensional crystal lattice—or if similar but even more extraordinary

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materials are just waiting to be discovered. One thing we do know is that this
is a very exciting time for materials science
Different Graphene Materials
Mentions of graphene often refer to a graphene sheet—a single layer of carbon
atoms in a perfect honeycomb lattice. The term graphene, however, is used to
describe an entire family of materials that are different in structure and
properties.
Monolayer graphene sheets, often made by vacuum processes like CVD
(depositing gaseous reactants onto a substrate), are considered to be
high-quality materials with electronic properties that are potentially
valuable in a number of applications – like energy storage and
generation, solar cells, and more. However, since the process is wasteful
and requires expensive machinery, such materials are still expensive and
are mainly used in research activities - although commercial applications
are slowly appearing.
Bilayer graphene (Stacking two sheets of graphene one on top of the
other). It turns out that this material differs from monolayer graphene in
its electrical properties. Just like graphene, it has a zero bandgap, but a
controllable bandgap can be introduced by applying an electric
displacement field to the two layers. A bandgap can also be introduced
by stacking the two layers in a specific arrangement. These materials are
also mainly used today in various research activities.
Few-layer graphene (FLG) (Three or more sheets of graphene can be
used to create materials - and these are referred to collectively ).
When you reach about thirty layers, the properties start to resemble graphite.
The terms graphene, FLG, bi-layer graphene and graphite are not clearly
defined in a standardized manner, which is one of the causes of confusion in
the industry that is nowadays being addressed in various standardisation
efforts.
Graphene Nanoribbons (GNRs)

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GNRs are thin (under 50 nm) strips of graphene. These have interesting
electronic properties, which depend on the width and edge type of the
material (zigzag type or armchair type). In fact, GNRs can be metals,
semiconductors, half metals, ferromagnets and antiferromagnets—
depending on the width, shape, edge structures and chemical
termination. Basically, GNRs are semiconductors with an energy gap that
scales (inversely) with the width of the ribbon.
An armchair graphene ribbon (left) and a zigzag ribbon (right).
GNRs have been the focus of intensive research due to their interesting
electronic and spintronics features. GNRs have also been used to develop
several transistor designs, DNA sequencing approaches, and more.
Producing GNRs with perfect edges (zigzag or armchair) is difficult. You
can start with a graphene sheet and cut it into the desired shape. Another
possible production method is “opening” (also called
“unzipping”) carbon nanotubes (CNTs), which are rolled up sheets of
graphene. Whether these methods are cost-effective and efficient ways to
produce GNRs or CNTs is yet to be seen. GNRs today are still mainly
used in small quantities for research activities.
Graphene Flakes / NanoPlatelets (GNFs / GNPs)
Producing and handling large graphene sheets is very difficult. Making
tiny “flakes” of graphene, in powder or solution form, is much easier.
These graphene flakes (GNFs) can retain some of graphene’s mechanical,
thermal and electrical properties. It is possible to synthesise GNFs in
different sizes and shapes (but not easy, however, to maintain

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consistency), which changes their properties—as different sized particles
behave differently in a matrix. So, a triangle flake will behave differently
than a round one, and you can also make them in different sizes.
Graphene flakes in dispersion, on paper.
Some GNFs are made from single-layer graphene flakes, and some are
stacked graphene flakes (few-layer graphene flakes, in fact). GNFs can be
made in different shapes, and this gives them a degree of engineering
freedom you cannot achieve with larger graphene sheets. Graphene
flakes are sometimes marketed as graphene nanoplatelets – or GNPs. A
nanoplatelet is a small round disk-shaped particle (named after its plate-
shape structure). In theory, graphene nanoplatelets are disk-shaped
graphene sheets (or stacks of sheets) - so a GNP is a type of graphene
flake. In practice, it is very difficult to create round-shaped graphene
platelets—even if they are artificiallysynthesised. Virtually all GNPs are
not technically disk-shaped, and should therefore be called GNFs.
GNFs are a relatively low-cost form of graphene, and found in growing
use in various composite materials.
Graphene Oxide (GO)

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Graphite is a 3D material composed of many layers of graphene.
Graphite oxide is a compound of graphite (carbon), hydrogen and
oxygen. In graphite oxide, the carbon layers (the graphene sheets) are
separated by oxygen molecules. When graphite oxide is placed in water,
it is easily separated into graphene sheets – to get graphene oxide (GO) -
single sheets of carbon, oxygen and hydrogen.
Graphene Oxide flakes.
Graphene oxide has properties quite different from those of graphene.
For example, it is dispersible in water and other organic solvents (as well
as in different matrices), whereas graphene is not. On the other hand, in
terms of electrical conductivity, graphene oxide is much less conductive
than graphene and is often described as an electrical insulator.
Graphene oxide’s unique properties make it suitable for different
applications than graphene. It is heavily studied for uses that rely on its
hydrophilic nature and lack of electrical conductivity, like water
treatment membranes, medical applications and various composite
materials. Use of graphene oxide however, is still mostly limited to R&D
activity.
Reduced Graphene Oxide
Graphene oxide sheets can be reduced (which means removing the
oxygen and hydrogen) to get regular graphene sheets (called reduced
graphite oxide sheets, referred to as r-GO).
While this is a rather easy way to produce graphene sheets, those sheets
usually contain many chemical and structural defects. The chosen
process of reduction (and there are many methods, as well as the
materials used) has a great impact on the quality of the resulting rGO,

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and some of these can sometimes be quite close in properties to pristine
graphene.
Besides lower prices and relative ease of production, a major advantage
of rGO is the ability to scale-up its production and make it in large
quantities. High-quality rGO basically has properties similar to CVD
graphene, so it is naturally suitable for similar applications. However, the
advantages listed above (like lower price and scalability) often make it
attractive when thinking of commercialisation, and so rGO is used
heavily in development work.
Graphene Quantum Dots (GQDs)
A quantum dot (QD) is a tiny semiconductor that has electronic
properties between those of bulk semiconductors and of discrete
molecules. QDs are being studied for several applications (including
transistors, solar panels, LEDs and even quantum computing) and are
recently being adopted in high-end LCD TVs.
A graphene quantum dot. (Source: Aalto University)
The size and shape of the quantum dot control its electronic
characteristics. For example, if you use a QD to emit light in a LED-like
application, the size determines the color (wavelength) of the light. The
dot's size and bandgap are inversely related.
Graphene quantum dots (GQDs) are ultra-small graphene flakes, usually
made by cutting GNRs into 100 nanometer-long pieces. Like GNRs,
GQDs are semiconductors and have a bandgap. As in all quantum dots,
the electronic properties are related to the size and shape of the dot.
Additional Graphene Materials
There are additional graphene intermediary materials (such as inks and
coatings) and graphene-like materials. Reviewing the different materials
makes it clear that choosing the right one for a specific project is a vital

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first step, as these have different properties and behaviors. Hopefully,
graphene will continue its development and live up to its potential by
being integrated into more commercial products and projects
Graphene Solar
What is a solar panel?

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Solar panel electricity systems, also known as solar photovoltaics (PV), capture
the sun’s energy (photons) and convert it into electricity. PV cells are made from
layers of semiconducting material, and produce an electric field across the
layers when exposed to sunlight.
When light reaches the cell, some of it is absorbed into the semiconducting
material and causes electrons to break loose and flow. This flow of electrons is
an electric current, that can be drawn out and used for powering outside
devices. This current, along with the cell’s voltage (a result of built-in electric
fields), define the power that the solar cell is capable of producing. It is worth
mentioning that a PV cell can produce electricity without direct sunlight, but
more sunshine equals more electricity.
A module, or panel, is a group of cells connected electrically and packaged
together. several panels can also form an array, which can provide more
electricity and be used for powering larger instruments and devices.
Different kinds of Solar cells
Solar cells are roughly divided into three categories: Monocrystalline,
Polycrystalline and Thin Film.
Most of the world’s PVs are based on a variation of silicon. The purity of the
silicon, or the more perfectly aligned silicon molecules are, affects how good it
will be at converting solar energy.

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Monocrystalline solar cells (Mono-Si, or single-crystal-Si) go through a
process of cutting cylindrical ingots to make silicon wafers, which gives
the panels their characteristiclook. They have external even coloring that
suggests high-purity silicon, thus having the highest efficiency rates
(typically 15-20%). They are also space efficient (their efficiency allows
them to be small) and live longer than other kinds of solar panels. Alas,
they are more expensive than other kinds and tend to be damaged by
external dirt or snow.
Polycrystalline silicon (p-Si or mc-Si) solar cells do not go through the
abovementioned process, and so are simpler and cost less than
Monocrystalline ones. Their typical efficiency is 13-16%, due to lower
silicon purity. They are also bigger and take up more space.
Thin-Film solar cells (TFSC), are made by depositing one or several thin
layers of photovoltaic material onto a substrate. Different types of TFSCs
are categorized by which photovoltaic material is deposited onto the
substrate: Amorphous silicon (a-Si), cadmium telluride (CdTe), copper
indium gallium selenide (CIS/CIGS), polymer solar panels and organic
photovoltaic cells (OPC). Thin-film modules have reached efficiencies of
7-13%. Their mass production is simple, they can be made flexible and
are potentially cheaper to manufacture than crystalline-based solar cells.
They do, however, take up a lot of space (hampering their use in
residential applications) and tend to degrade faster than crystalline solar
panels.
Solar power advantages and disadvantages
Solar power is free and infinite, and solar energy use indeed has major
advantages.
It is an eco-friendly, sustainable way of energy production. Solar energy
systems today are also much cheaper than they were 20 years ago, and save
money in electricity expenses. In addition, it is a much environmentally cleaner
form of energy production that helps reduce global warming and coal
pollution. It does not waste water like coal and nuclear power plants and is also
considered to be a form of energy that is much safer for use.

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Although solar power production is widely considered to be a positive thing,
some downsides require mentioning. The initial cost of purchasing and
installing solar panels can be substantial, despite widespread government
subsidy programs and tax initiatives. Sun exposure is critical and so location
plays a significant role in the generation of electricity. Areas that are cloudy or
foggy for long periods of time will produce much less electricity. Other
commonly argues disadvantages regard insufficiency of produced electricity
and reliability issues.
Solar power applications
Common solar energy applications include various residential uses such as
solar lighting, heating and ventilation systems. Many small appliances utilize
solar energy for operation, like calculators, scales, toys and more. Agriculture
and horticulture also employ solar energy for the operation of different aids like
water pumps and crop drying machines. The field of transportation has been
interested in solar powered vehicles for many years, including cars, planes and
boats that are vigorously researched and developed. Solar energy also has
various industrial applications, ranging from powering remote locations as
well as space and satellite systems, to powering transportation signals,
lighthouses, offshore navigation systems and many more.
Solar technologies are vigorously researched, aiming to lower costs and
improve existing products as well as integrate PV systems in innovative
products like PV-powered curtains, clothes and laptop cases.
Graphene and solar panels

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Graphene is made of a single layer of carbon atoms that are bonded together in
a repeating pattern of hexagons. It is a 2 dimensional material with amazing
characteristics, which grant it the title “wonder material”. It is extremely strong
and almost entirely transparent and also astonishingly conductive and flexible.
Graphene is made of carbon, which is abundant, and can be a relatively
inexpensive material. Graphene has a seemingly endless potential for
improving existing products as well as inspiring new ones.
Solar cells require materials that are conductive and allow light to get through,
thus benefiting from graphene's superb conductivity and transparency.
Graphene is indeed a great conductor, but it is not very good at collecting the
electrical current produced inside the solar cell. Hence, researchers are looking
for appropriate ways to modify graphene for this purpose. Graphene Oxide
(GO), for example, is less conductive but more transparent and a better charge
collector which can be useful for solar panels.
The conductive Indium Tin Oxide (ITO) is used with a non-conductive glass
layer as the transparent electrodes in most organic solar panels to achieve these
goals, but ITO is rare, brittle and makes solar panels expensive. Many
researches focus on graphene as a replacement for ITO in transparent electrodes
of OPVs. Others search for ways of utilizing graphene in improving overall
performance of photovoltaic devices, mainly OPVs, as well as in electrodes,
active layers, interfacial layers and electron acceptors.
Commercialization efforts

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Novel graphene film offers new concept for solar energy
Researchers at Swinburne, the University of Sydney and Australian National
University have collaborated to develop a solar absorbing, ultra-thin graphene-
based film with unique properties that has great potential for use in solar
thermal energy harvesting.
The 90 nanometre material is said to be a 1000 times finer than a human hair
and is able to rapidly heat up to 160°C under natural sunlight in an open
environment.
The team stated that this new graphene-based material may also open new
avenues in:
thermophotovoltaics (the direct conversion of heat to electricity)
solar seawater desalination
infrared light source and heater
optical components: modulators and interconnects for communication
devices
photodetectors
colorful display
It could possibly lead to the development of ‘invisible cloaking technology’
through developing large-scale thin films enclosing the objects to be ‘hidden’.
The researchers have developed a 2.5cm x 5cm working prototype to
demonstrate the photo-thermal performance of the graphene-based

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metamaterial absorber. They have also proposed a scalable manufacturing
strategy to fabricate the proposed graphene-based absorber at low cost.
The reduced graphene oxide layer and grating structures were coated with a
solution and fabricated by a laser nanofabrication method respectively, which
are both scalable and low cost.
“Our cost-effective and scalable graphene absorber is promising for integrated,
large-scale applications that require polarisation-independent, angle
insensitive and broad bandwidth absorption, such as energy-harvesting,
thermal emitters, optical interconnects, photodetectors and optical modulators,
Fabrication on a flexible substrate and the robustness stemming from graphene
make it suitable for industrial use. The physical effect causing this outstanding
absorption in such a thin layer is quite general and thereby opens up a lot of
exciting applications
Derive energy from raindrops
Solar panels today work best during periods of strong sunlight, but start to
wane when it gets cloudy or rainy. A breakthrough in graphene-based solar
panels could change all that, by allowing solar panels to generate electricity
during inclement weather.
Graphene-based solar cells, say the researchers from the Ocean University of
China, would be able to derive energy from raindrops that happen to fall on the
panel, by taking advantage of the various salts present within the liquid.
The graphene sheets that make up the solar cells would be able to separate the
positively charged ions in rainwater, including sodium, calcium and
ammonium. These positive ions bind to the ultra-thin layer of graphene to form
a double layer (also called a pseudocapacitor) with the electrons already
present. The potential energy difference between the two layers is what
generates the electrical current.
The researchers have tested a prototype by using slightly salty water to
simulate rain, and a thin-film photovoltaic cell called a dye-sensitised solar cell.

29 | P a g e
The researchers modified the cell by adding a layer of graphene, then mounting
it on a transparent backing of indium tin oxide and plastic. This dual-function
solar cell concept could then be used to produce power from both sunshine and
the simulated rainwater.
Graphene as a material is both strong and light, and can hold energy better than
graphite. It is also being developed into anti-reflection coatings for solar cells,
so the integration of graphene into solar applications is not unheard of.
By extending the role of graphene to actively harvest energy from rainwater,
the researchers were able to generate hundreds of microvolts from the water,
and achieve a 6.53 percent solar-to-electricity conversion efficiency from the
solar panel.
While these results are impressive for a conceptual prototype, there’s more
work to be done in order to raise efficiency to commercially-viable levels. One
particular problem is the relatively low concentrations of ions in raindrops,
which make it a challenge to generate enough electricity. The researchers are
also working to adjust the technology so it can handle a variety of different
types of rainwater with different ion mixtures.
However, the researchers hope their findings can guide the design of future
solar cells, and open up thinking about alternative electricity generating
capabilities for solar cells. For example, it may be possible to create solar cells
that are able to harvest energy from ambient heat and light, to boost their
performance indoors.
The wider use of solar panels, such as integrating them into roofs, walls and
windows of buildings, as well as the movement to provide decentralised
storage of power generated by solar panels via battery systems.
Graphene Could Double Electricity Generated From
Solar
The amount of sunlight that hits the Earth every 40 minutes is enough to meet
global energy demands for an entire year. The trick, of course, is harnessing it
and converting it into useful electricity. A new study has revealed that
tweaking graphene allows it to generate two electrons for every photon of light

30 | P a g e
it receives. This could double the amount of electricity currently converted in
photovoltaic devices.
Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern. It
is incredibly light, flexible, exponentially stronger than steel, and capable of
conducting electricity even better than copper. In order to make it useful in
photovoltaic devices, the researchers needed to have a better idea of graphene’s
mechanism for converting light into electricity. This process takes only a femto-
second (10-15 sec), which is too quick to easily study.
To learn more about how this energy conversion takes place, the graphene was
subjected to a treatment called “ultrafast time- and angle-resolved
photoemission spectroscopy” (trARPES).
The material was placed in an ultra-high vacuum chamber and blasted with
ultrafast laser light, which excited the electrons and made them more capable
of carrying an electrical current. A second laser emitted pulses of light,
recording the current energy level of each electron in each pulse. These images
were then put together, kind of like a flip book, to portray the action that
happens on such a short timescale.
The researchers facilitated the conversion process by ‘doping’ the graphene.
That is, they improved the material’s photovoltaic prowess by chemically
altering the number of electrons, thereby exciting them. When a photon comes
and knocks an electron back to the ground state, that one electron is able to
excite two more, generating the electric current.
“This indicates that a photovoltaic device using doped graphene could show
significant efficiency in converting light to electricity”
Doped graphene appears to be a great material to easily release the electrons
and use extra energy to excite other electrons, rather than waste the energy as
heat. Unfortunately, the material needs a little help in absorbing light; a key
requirement for photovoltaic devices. Graphene will need to be combined with
other ultra-thin materials, such as tungsten diselenide or molybednium
disulphide, like has been attempted in previous studies. This could possibly be
the key in bumping solar energy conversion from its assumed plateau of 32%

31 | P a g e
up to an astonishing 60%; an increase that could revolutionize solar energy.
Moving forward, the researchers are planning to use similar measures to
investigate the photovoltaic properties of other ultra-thin materials, including
molybednium disulphide.
By connecting a graphene layer with atomic layers of molybdenum diselenide
and tungsten disulfide, researchers were able to boost the material's carrier
lifetime.
Researchers have discovered a method to increase the carrier lifetime of
graphene, a development which says could ultimately lead to the development
of ultrathin, flexible solar cells using graphene.
Graphene can transport a charge much faster than most other materials, which
would make it an excellent solar cell material. However, it is held back by its
extremely short carrier lifetime, which means that electrons excited by sunlight
only remain mobile for one picosecond (one millionth of a millionth of a
second).

32 | P a g e
To overcome this problem, the researchers looked at methods to suppress
recombination of the electrons, and keep them mobile for long enough to create
a charge.
The method used, Unipolar optical doping and extended photocarrier lifetime
in graphene by band alignment engineering, published in the journal Nano
Futures, connects a graphene layer with two other atomic material layers –
molybdenum diselenide (MoSe2) and tungsten disulfide (WS2).
Combining the materials in this way, the researchers were able to increase the
carrier lifetime of the material from 1 to around 400 picoseconds. Their
experiment used a 0.1 picosecond laser pulse to ‘excite’ some electrons in the
molybdenum disulfide layer, and monitoring them using a second laser pulse.
“We can think of the MoSe2 and graphene layers as two classrooms full of
students all sitting, while the middle WS2 layer acts as a hallway separating the
two rooms,” he explains.
“When light strikes the sample, some of the electrons in MoSe2 are liberated.
They are allowed to go across the WS2-layer hallway to enter the other room,
which is graphene.
However, the hallway is carefully designed so that the electrons have to leave
their seats in MoSe2. Once in graphene, they have no choice but to stay mobile
and hence contribute to electric currents, because their seats are no longer
available to them.”
The researchers now plan to experiment with different material layers in
combination with graphene, to gain better control over the lifetime of the
excited electrons.
Researchers recently made a discovery using MoSe2 and similar compounds,
known as van der Waals materials, and is continuing research to gain better
control over electron excitation.
New property revealed in graphene could lead to better performing
solar panels

33 | P a g e
Shining light on graphene: Although graphene has been studied vigorously
for more than a decade, new measurements on high-performance graphene
devices have revealed yet another unusual property. In ultra-clean graphene
sheets, energy can flow over great distances, giving rise to an unprecedented
response to light.
Discovered a new mechanism for ultra-efficient charge and energy flow in
graphene, opening up opportunities for developing new types of light-
harvesting devices.
The researchers fabricated pristine graphene- graphene with no impurities into
different geometric shapes, connecting narrow ribbons and crosses to wide
open rectangular regions. They found that when light illuminated constricted
areas, such as the region where a narrow ribbon connected two wide regions,
they detected a large light-induced current, or photocurrent.
The finding that pristine graphene can very efficiently convert light into
electricity could lead to the development of efficient and ultrafast
photodetectors and potentially more efficient solar panels.
Graphene, a 1-atom thick sheet of carbon atoms arranged in a hexagonal lattice,
has many desirable material properties, such as high current-carrying capacity
and thermal conductivity. In principle, graphene can absorb light at any
frequency, making it ideal material for infrared and other types of

34 | P a g e
photodetection, with wide applications in bio-sensing, imaging, and night
vision.
In most solar energy harvesting devices, a photocurrent arises only in the
presence of a junction between two dissimilar materials, such as "p-n" junctions,
the boundary between two types of semiconductor materials. The electrical
current is generated in the junction region and moves through the distinct
regions of the two materials.
"But in graphene, everything changes," said Nathaniel Gabor, an associate
professor of physics at UCR, who co-led the research project. "We found that
photocurrents may arise in pristine graphene under a special condition in
which the entire sheet of graphene is completely free of excess electronic charge.
Generating the photocurrent requires no special junctions and can instead be
controlled, surprisingly, by simply cutting and shaping the graphene sheet into
unusual configurations, from ladder-like linear arrays of contacts, to narrowly
constricted rectangles, to tapered and terraced edges."
Pristine graphene is completely charge neutral, meaning there is no excess
electronic charge in the material. When wired into a device, however, an
electronic charge can be introduced by applying a voltage to a nearby metal.
This voltage can induce positive charge, negative charge, or perfectly balance
negative and positive charges so the graphene sheet is perfectly charge neutral.
"The light-harvesting device we fabricated is only as thick as a single atom,"
Gabor said. "We could use it to engineer devices that are semi-transparent.
These could be embedded in unusual environments, such as windows, or they
could be combined with other more conventional light-harvesting devices to
harvest excess energy that is usually not absorbed. Depending on how the
edges are cut to shape, the device can give extraordinarily different signals."
The research team reports this first observation of an entirely new physical
mechanism a photocurrent generated in charge-neutral graphene with no need
for p-n junctions in Nature Nanotechnology today.
Previous work by the Gabor lab showed a photocurrent in graphene results
from highly excited "hot" charge carriers.

35 | P a g e
When light hits graphene, high-energy electrons relax to form a population of
many relatively cooler electrons, Gabor explained, which are subsequently
collected as current. Even though graphene is not a semiconductor, this light-
induced hot electron population can be used to generate very large currents.
"All of this behavior is due to graphene's unique electronic structure," he said.
"In this 'wonder material,' light energy is efficiently converted into electronic
energy, which can subsequently be transported within the material over
remarkably long distances."
He explained that, about a decade ago, pristine graphene was predicted to
exhibit very unusual electronic behavior: electrons should behave like a liquid,
allowing energy to be transferred through the electronic medium rather than
by moving charges around physically.
"But despite this prediction, no photocurrent measurements had been done on
pristine graphene devices until now," he said.
The new work on pristine graphene shows electronic energy travels great
distances in the absence of excess electronic charge.
The research team has found evidence that the new mechanism results in a
greatly enhanced photoresponse in the infrared regime with an ultrafast
operation speed.
"We plan to further study this effect in a broad range of infrared and other
frequencies, and measure its response speed”.

36 | P a g e
CONCLUSION
Solar power is looking more and more attractive, as other power
generation methods such as fossil fuels and nuclear power come under
increasing scrutiny
Nano material solar cells shows special promise to both enhance
efficiency of solar energy conservation and alsoreduce the manufacturing
cost

37 | P a g e
It increase efficiently by the absorption of light as well as the overall
radiation to electricity would help preserve the environment, decrease
wastage, provide electricity for rural areas, and have a wide array of
commercial applications due to its capabilities
References
https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.201100119

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https://www.azonano.com/article.aspx?ArticleID=4565
http://www.iosrjournals.org/iosr-jmce/papers/vol11-issue6/Version-
2/J011627181.pdf
http://news.mit.edu/2017/mit-researchers-develop-graphene-based-
transparent-flexible-solar-cells-0728
https://www.sciencedirect.com/science/article/pii/S221128551830115
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