[Type here]
This article is based on the future goals of
highly demanding and super-efficient thin
film solar cells.
Future
Trends Of
Thin Film
Solar Cells
Review Article
Ayesha Tariq
PHYS211501010
Ayesha Tariq
PHYS211501010
Abstract
Solar photovoltaic technology is one of the renewable technologies, which has a
potential to shape a clean, dependable, scalable, and affordable electricity system for
the future. Based on past years review and photovoltaic installations in the year 2014,
the major five leading countries identified are China, Japan, USA, Germany, and
UK. The article also discusses the driving policies, funding and Research and
Development activities: to gauge the reasons behind the success of the leading
countries.
Thin film solar cells are favorable because of their minimum material usage and
rising efficiencies. The three major thin film solar cell technologies include
amorphous silicon, copper indium gallium selenide, and cadmium telluride.
Longevity, reliability, consumer confidence and greater investments must be
established before thin film solar cells are explored on building integrated
photovoltaic systems.
Thin-film solar cells are preferable for their cost-effective nature, least use of
material, and an optimistic trend in the rise of efficiency. The remarkable evolution,
cell configuration, limitations, cell performance, and global market share of each
technology are discussed. The emerging solar cell technologies holding some key
factors and solutions for future development are also mentioned.
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Introduction
As the inevitable scarcity of non-renewable fuels in the coming days, clean power
sources have piqued the attention of researchers, scientists, and investors all over the
globe. Wave power, biopower, geothermal power, tidal power, wind, sun based, and
hydroelectric power are among the new power sources gaining interest. They are
seen as viable alternatives for non-renewable fuels due to their recycling. Sun power
is readily present power sources. [1]
Sun rays are converted into beneficial sources of power, i.e., Electric power or
thermal power, is referred to as sun-based power. A photovoltaic cell, also known
as a sun, based cell or Photovoltaic cell, is a form of invention that converts sunbased power directly into electrical energy. The logic of a PV cell (sun-based cell)
is comparable to those of a conventional p-n junction diode. Photons, or sun-based
power rays, make up photons of visible light. Semiconductor materials in PV cells
gain photons of visible light, which kick out negative charge particles from their
atoms, permit them to pass through the PV and generate Electric power. Sun based
power has gained popularity and widespread use due to its cleanliness, ubiquity,
accessibility, and efficiency. [2]
Many solar technologies including wafer, thin film and organic, have been
researched to achieve reliability, cost-effectiveness, and high efficiency with
enormous success. The amorphous silicon solar cell finds its use in consumer
electronics such as calculators, watches, etc., [3]
Harnessing the sun's energy to produce electricity has proven to be one of the most
promising solutions to the world's energy crisis. However, the device to convert
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sunlight to electricity, a solar cell, must be dependable and cost effective to compete
with conventional sources. Several solar technologies including wafer, thin film and
organic, have been researched to achieve reliability, cost-effectiveness, and high
efficiency with tremendous success for instance, crystalline silicon has been
successful from laboratory to commercial integration, and makes up to 90% of the
global PV market. Both goals need to be met simultaneously to enable the production
of electricity at a low cost and allow high market penetration of solar electricity.
-Si, CdTe and CIGS are the three most widely commercialized thin film solar cells.
When compared to CdTe and CIGS, -Si not only requires a lower amount of silicon
but is also less toxic. CdTe's usage of cadmium proves to be harmful to both the
producer and the consumer, slightly limiting its commercial applications. Despite
this advantage, CIGS and CdTe technologies still lag crystalline silicon solar cell
counterparts in efficiency and reliability. [4]
Scope of Solar Cells in Future
In the coming years, technology improvements will ensure that solar becomes even
cheaper. It could well be that by 2030, solar will have become the most important
source of energy for electricity production in a large part of the world. There is
already a move in place towards higher-efficiency modules, which can generate 1.5
times more power than existing, similarly sized modules today using a technology
called tandem silicon cells. These are going to have a significant impact going
forward.
This means better power electronics and a greater use of low-cost digital
technologies. [5]
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What this means is that solar will reach, in many parts of the world, a levelized cost
of energy that will make it unbeatable compared to fossil fuels.
To outpace current solar cells, a modern design would need to be able to capture
more light, transform light energy to electricity more efficiently, and/or be less
expensive to build than current designs. Energy producers and consumers are more
likely to adopt solar power if the energy it produces is equally or less expensive than
other, often non-renewable, forms of electricity, so any improvement to current solar
cell designs must bring down overall costs to become widely used.
The first option, adding hardware that allows the solar cells to capture more light,
does not actually require that we abandon current solar cell designs. Another route
to improving the performance of solar cells is to target their efficiency so they are
better at converting energy in sunlight to electricity. Solar cells with more than one
layer of light-capturing material can capture more photons than solar cells with only
a single layer. Recently, lab-tested solar cells with four layers can capture 46% of
the incoming light energy that hit them. These «thin-film solar cells» use a layer of
material to harvest light energy that is only 2 to 8 micrometers thick, only about 1%
of what is used to make a traditional solar cell. Much like cells with multiple layers,
thin-film solar cells are a bit tricky to manufacture, which limits their application,
but research is ongoing.
In the immediate future, silicon solar cells are likely to continue to decrease in cost
and be installed in large numbers. [6]
We concentrate on the use of grid-connected solar-powered generators to replace
conventional sources of electricity. For the more than one billion people in the
developing world who lack access to a reliable electric grid, the cost of small-scale
PV generation is often outweighed by the extremely high value of access to
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electricity for lighting and charging mobile telephone and radio batteries. In
addition, in some developing nations it may be economic to use solar generation to
reduce reliance on imported oil, particularly if that oil must be moved by truck to
remote generator sites. A companion working paper discusses both these valuable
roles for solar energy in the developing world.
The Solar Futures Study explores solar energy’s role in transitioning to a carbonfree electric grid. Produced by the U.S.
Line chart showing how the Solar Futures Study predicts that solar deployment will
grow from 2020-2050
The Solar Futures Study modeled the deployment of solar necessary for a
decarbonized grid. Preliminary modeling shows that decarbonizing the entire energy
system could result in as much as 3,000 GW of solar due to increased electrification.
[7]
To reach these levels, solar deployment will need to grow by an average of thirty
gigawatts alternating current each year between now and 2025 and ramp up to 60
GW per year between 2025 and 2030—four times its current deployment rate—to
total 1,000 GW ac of solar deployed by 2035. By 2050, solar capacity would need
to reach 1,600 GW ac to achieve a zero-carbon grid with enhanced electrification of
end uses.
Solar continues to grow and advance as innovations in nanotechnology increase its
effectiveness, doubling the electrical capabilities of solar power systems. Developers
of solar energy are now able to take an old glass panel and turn it back into a new
solar panel. From large, utility-scale projects to multiple, small-scale solar sites,
Lamp Rynearson professionals assist clients with the process of bringing this type
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of energy to municipalities of all sizes. What started as a client referral has turned
into multiple large utility-scale solar energy projects for Lamp Rynearson, ranging
from 500 KW to 300 MW. [8]
Perovskite Solar Cells
A perovskite solar cell is a type of solar cell which includes a perovskite-structured
compound, most commonly a hybrid organic-inorganic lead or tin halide-based
material, as the light-harvesting active layer. Perovskite solar cells have therefore
been the fastest-advancing solar technology as of 2016. With the potential of
achieving even higher efficiencies and exceptionally low production costs,
perovskite solar cells have become commercially attractive.
The name 'perovskite solar cell' is derived from the ABX3 crystal structure of the
absorber materials, which is referred to as perovskite structure and where A and B
are cations and X is an anion. A cation with radii between 1.60 Å and 2.50 Å were
found to form perovskite structures. The most studied perovskite absorber is
methylammonium lead trihalide, with an optical bandgap between ~1.55 and 2.3 eV
depending on halide content. The first use of perovskite in a solid-state solar cell
was in a dye-sensitized cell using CsSnI3 as a p-type hole transport layer and
absorber. [9]
Perovskite solar cell. Much of the recent work on perovskite solar cells has been
dominated by absorber materials based on methylammonium lead halide. Although
perovskite materials have been studied for more than a century, initial studies on
methylammonium lead halides for semiconductor applications started in the past two
decades. Initial applications of perovskite absorbers in solar cells occurred in 2006
and were published in 2009. [10]
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A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide
perovskite materials has attracted great attention from the researchers all over the
world and is one of the top ten scientific breakthroughs in 2013. The photoelectric
power conversion efficiency of the perovskite solar cells has increased from 3.8%
in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate
for the new generation of solar cells to replace traditional silicon solar cells in the
future. [11]
Unlike silicon solar cells, PSCs are less expensive, and fabrication can be done by
simple wet chemical process. In addition to that the instability and poor lifetime are
the other serious threats for the commercialization of PSCs. This chapter discusses
the various reported standard fabrication techniques for the deposition of
photoanode, perovskite layer, electron/hole transport layers, counter electrode, and
factors affecting the stability and lifetime of PSCs. By the end of this chapter the
readers will be able to get a clear idea about the fabrication methods, and stability
and lifetime of PSCs. [12]
Perovskite solar cells can be manufactured using simple, additive deposition
techniques, like printing, for a fraction of the cost and energy. In 2012, researchers
first discovered how to make a stable, thin-film perovskite solar cell with light
photon-to-electron conversion efficiencies over 10%, using lead halide perovskites
as the light-absorbing layer. Since then, the sunlight-to-electrical-power conversion
efficiency of perovskite solar cells has skyrocketed, with the laboratory record
standing at 25.2%. Researchers are also combining perovskite solar cells with
conventional silicon solar cells – record efficiencies for these «perovskite on silicon»
tandem cells are currently 29.1% and rising rapidly.
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With this rapid surge in cell efficiency, perovskite solar cells and perovskite tandem
solar cells may soon become cheap, highly efficient alternatives to conventional
silicon solar cells. A cross-section of a perovskite solar cell.
While perovskite solar cells, including perovskite on silicon tandems, are being
commercialized by dozens of companies worldwide, there are still basic science and
engineering challenges to address that can improve their performance, reliability,
and manufacturability. Some perovskite researchers continue to push conversion
efficiencies by characterizing defects in the perovskite.
Perovskite crystals often exhibit atomic-scale defects that can reduce solar
conversion efficiency. Department of Energy’s Solar Energy Technologies Office to
develop new passivation strategies and added charge collecting materials, allowing
perovskite solar cells to reach their full efficiency potential while remaining
compatible with low-cost manufacturing. Chemistry professor Daniel Gamelan and
his group aim to modify silicon solar cells with perovskite coatings to collect highenergy photons of blue light more efficiently, bypassing the theoretical limit of 33%
conversion for conventional silicon cells. With funding from SETO, Gamelan and
Blue Dot are developing deposition techniques to create thin films of perovskite
materials for large-area solar cells and for enhancing conventional silicon solar cells.
At the Washington Clean Energy Testbeds, an open-access lab facility operated by
CEI, researchers and entrepreneurs can utilize state-of-the-art equipment to develop,
test, and scale technologies like perovskite solar cells. Using the roll-to-roll printer
at the Testbeds, perovskite inks can be printed at low temperatures onto flexible
substrates. One of his group’s most active projects, also funded by SETO, is
developing in situ instruments that can measure the growth of perovskite crystals as
they are being rapidly deposited during roll-to-roll printing. With support from the
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Joint Center for the Development and Research of Earth Abundant Materials,
Mackenzie’s group is also using the world’s highest resolution printer to develop
new electrodes to pull electrical current out of perovskite solar cells without blocking
sunlight from entering the cell.
Flexible thin film Solar Cells
A thin-film solar cell is a second-generation solar cell that is made by depositing one
or more thin layers, or thin film of photovoltaic material on a substrate, such as glass,
plastic or metal. Thin-film solar cells are commercially used in several technologies,
including cadmium telluride, copper indium gallium Di selenide, and amorphous
thin-film silicon. Film thickness varies from a few nanometers to tens of
micrometers, much thinner than thin-film's rival technology, the conventional, firstgeneration crystalline silicon solar cell, that uses wafers of up to 200 µm thick. This
allows thin film cells to be flexible, and lower in weight.
It is used in building-integrated photovoltaics and as semi-transparent, photovoltaic
glazing material that can be laminated onto windows. Other commercial applications
use rigid thin film solar panels in some of the world's largest photovoltaic power
stations. Despite these enhancements, the market-share of thin-film never reached
more than 20 percent in the last two decades and has been declining in recent years
to about 9 percent of worldwide photovoltaic installations in 2013. [14]
Thin-film solar cells were originally introduced in the 1970s by researchers at the
Institute of Energy Conversion at the University of Delaware in the United States.
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Several types of thin-film solar cells are widely used because of their relatively low
cost and their efficiency in producing electricity.
Cadmium telluride thin-film solar cells are the most common type available. They
are less expensive than the more standard silicon thin-film cells. Copper indium
gallium selenide is another type of semiconductor used to manufacture thin-film
solar cells. CIGS thin-film solar cells have reached 21.7 percent efficiency in
laboratory settings and 18.7 percent efficiency in the field, making CIGS a leader
among alternative cell materials and a promising semiconducting material in thinfilm technologies.
CIGS cells traditionally have been more costly than other types of cells on the
market, and for that reason they are not widely used. Gallium arsenide thin-film solar
cells have reached 30 percent efficiency in laboratory environments, but they are
very expensive to manufacture.
Applications of thin-film solar cells began in the 1980s with small strips that were
used for calculators and watches. Except for cadmium telluride thin-films,
nonflexible photovoltaic cells have faster payback times, and their construction is
more durable, which has advantages in many applications. Sheets of thin films may
be used to generate electricity increasingly in places where other photovoltaic cells
cannot be used, such as on curved surfaces on buildings or cars or even on clothing
to charge handheld devices. [15]
Nanostructured metal back reflectors are playing a significant role in thin-film solar
cells, which facilitates an increased optical path length within a relatively thin
absorbing layer. The solar cells with BRs demonstrate an excellent light harvesting
capability in the long-wavelength region. Compared to the reference cells, the three
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devices with plasmonic BRs show lower parasitic absorptions with different
individual absorption distributions. [16]
Thin-film flexible solar cells are lightweight and mechanically robust. Substrate
materials reviewed include metals, ceramics, glasses, and plastics. For electrode
materials, transparent conducting oxides, thin metal films/nanowires, nanocarbons,
and conducting polymers. [17]
The substrate is embossed with an acetate structure of «microgrooves, » each just a
few micrometers thick. With this embossed substrate, Power Roll first deposits
transport layers onto the sides of the grooves using a vacuum cooling process, and
then a photo-active cell material is printed onto the surface using roll-to-roll, slotdie coating. In pilot production, the company plans to work with a perovskite as the
cell material, though potentially it could make use of any other solar-absorbing ink
compatible with the printing processes. Each of the microgrooves acts as an
individual solar cell.
This means that any device would have strong resistance to shading or small area
defects. Finally, the device is encapsulated to protect its inner workings. « We do
not need a transparent conducting layer, we don’t need any complex cell
interconnection features, » Power Roll CEO Neil Spann told PV magazine.
Power Roll’s approach offers scope for flexibility in the size and shape of devices.
«The first application areas we’re looking at are non-load bearing rooftops and
buildings as a whole,» said Spann. [18]
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Tandem Thin Film Solar Cells
Seeking high power conversion efficiency is always a striving pathway for many
researchers to commercialize organic solar cells. Thus, it is essential to achieve high
conversion efficiency to make solar oriented devices as truly green energy resource.
In this paper, we report novel tandem structures based on organic materials in which
homo and hybrid schemes are utilized. The loss of photons may be due to smaller
photon energy compared to the bandgap of active material, which generally transmit
through the cell without being absorbed.
To counter these issues, tandem structure plays an important key role. In tandem
structure multi-stacking layer structure is used which compose of different absorber
layers either connected in series or in parallel. The series connected multilayer
structure provide an efficient mode to extract high value of and Voc . The different
absorber layers with different absorption coefficient are responsible for the
absorption of photons with different energies levels.
Various polymers and molecules combined to form bulk material to make strong and
broad spectral coverage. So, tandem structures configured with multi absorber layers
provide enhance absorption of photons. However, the tandem structure based on
organic material has not been studied intensively due to complexity, so there is a
great room to improve the performance of such tandem based organic devices. From
the survey, we concluded that low efficiency is currently the main challenge in
organic solar cells, which need to be countered for the advancement in organic
photovoltaic technology. [19]
By piling several solar devices one over the other, a tandem cell is obtained. The
light which is not absorbed in the lower cell can be absorbed in the upper cell. [20]
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The nm-scale features of transparent conductive oxide front electrode and μm-scale
features of textured glass form a multi-scale texturing scheme, which is potentially
beneficial to the longer wavelength absorption in mc-Si cell and hence increase the
total current of the tandem solar cell. Conformal growth model was applied
successfully to analyze thin film growth on textured glass in this work. Power
conversion efficiency improvements of ∼1.0% and ∼0.8% have been achieved with
solar cells on sandblasting and cream-etching textured glass, respectively. The
improvement of conversion efficiency is crucial to the future potential market of aSi/mc-Si thin-film tandem solar modules.
Superstrate glass/transparent conductive oxide can improve cell efficiency through
modified reflection properties at interfaces or increased transmission or light
trapping in the high-index Si layers. 2–6 In industry, light trapping is normally
realized with textured TCO on flat glass, e.g., ten multi-scale light-trapping scheme
has been introduced to improve light trapping in multi-crystalline Si wafer based
solar cells - «black Si». Si thin film growth mechanisms on textured glass and
electrical results for the Si tandem solar cells were also discussed. [20]
A promising way to enhance the efficiency of CIGS solar cells is by combining them
with perovskite solar cells in tandem devices. Here, a process for the fabrication of
NIR-transparent perovskite solar cells is presented, which enables power conversion
efficiencies up to 12.1% combined with an average sub-band gap transmission of
71% for photons with wavelength between 800 and 1000 nm. Future developments
of perovskite/CIGS tandem devices are discussed and prospects for devices with
efficiency toward and above 27% are given. [21]
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Benefits of Solar Cells
 A
CLEAN
AND
GREEN
ENERGY
SOURCE
The most prominent advantage of PV cells is the clean and green energy it
provides.
 FREE
RAW
MATERIALS
PV cells depend on solar energy to produce electricity, which is freely
available in abundance around you. While you will have to make an initial
investment in the system, solar power is natural, free, and available in
abundance for a long time.
 VERSATILITY
Solar PV cells can generate electricity anywhere.
 SIGNIFICANT IMPACT ON SMART ENERGY NETWORKS
Solar PV has an integral role in smart energy networks, which work on
distributed power generation. DPGs are exceptionally environmentally
friendly because it helps reduce the production of electricity at centralized
power plants.
 REDUCED
COSTS
About costs, while solar panels Columbia Mo were indeed once expensive, its
rates are expected to reduce substantially within the next few years. The
financial incentives offered makes solar energy panels an attractive
investment alternative.
 INTERMITTENCY
ISSUES
Like all other renewable energy sources, solar energy and PV cells have
intermittency problems.
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 ADDITIONAL
INVESTMENTS
PV cells require an additional investment in inverters and storage
batteries. This additional investment can, however, provide a solution for the
PV cells’ intermittency issues.
 USES
A
LARGE
AREA
That’s why it’s vital that you wisely select a spot for the solar energy
system, and why many people install it upon their roofs. [22]
 Environmentally
Friendly
Energy
With solar cells occurs almost no pollution, and this is a great advantage. The
discharge of waste and pollution is unavoidable in relation to the production
of solar cells, the transport of these, and when you install them.
 Innovative
Energy
Photovoltaics is a popular topic in green energy and is a good solution to
prevent climate change. It has already made an innovative branch of study
under continuous research and development. So, another advantage of the
solar cell industry is the job opportunities it can provide in case the
investments continue.
 High
Investment
One of the most important disadvantages of solar cells is the high installation
cost of solar panels. For example, the estimated cost of a 5kW solar PV system
is around £7000 - £9000, depending on your roof type and other conditions.
[23]
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References
[1] https://bit.ly/2WNK2x8
[2] https://bit.ly/2WSdHp7
[3] http://www.elsevier.com/locate/rser
[4]
https://www.weforum.org/agenda/2020/01/the-future-looks-bright-for-solarenergy/#:~:text=In%20the%20coming%20years%2C%20technology,the%20envir
onment%20and%20climate%20change.
[5] https://sitn.hms.harvard.edu/flash/2019/future-solar-bright/
[6] https://energy.mit.edu/research/future-solar-energy/
[7] https://www.energy.gov/eere/solar/solar-futures-study
[8] https://lamprynearson.com/the-scope-the-future-of-solar-is-bright/
[9] https://en.wikipedia.org/wiki/Perovskite_solar_cell
[10] https://www.energy.gov/eere/solar/perovskite-solar-cells
[11] https://www.hindawi.com/journals/jnm/2018/8148072/
[12] https://www.sciencedirect.com/topics/engineering/perovskite-solar-cells
[13] https://www.cei.washington.edu/education/science-of-solar/perovskite-solarcell/
[14] https://en.wikipedia.org/wiki/Thin-film_solar_cell
[15] https://www.britannica.com/technology/thin-film-solar-cell
[16] https://pubs.acs.org/doi/10.1021/acsami.0c05330
[17] https://www.sciencedirect.com/science/article/pii/S266693582030001X
[18] https://www.pv-magazine.com/2021/03/27/the-weekend-read-new-pathwaysin-flexible-thin-film-pv/
[19] https://ieeexplore.ieee.org/document/9069278
[20] https://www.sciencedirect.com/topics/chemistry/tandem-solar-cell
[21] https://pubs.acs.org/doi/10.1021/acs.jpclett.5b01108
[22] https://mosolarapps.com/the-eight-pros-and-four-cons-of-solar-photovoltaiccells/
[23] https://www.greenmatch.co.uk/blog/2015/06/advantages-and-disadvantagesof-solar-cells
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