Solar Cell Technology
LIU ZHI1
Department of Mechanical Engineering, National University of Singapore
21 Lower Kent Ridge Road, Singapore 119077
ABSTRACT
This UROP project is mainly discussed about the general principles and applications of solar
cell technology. It starts from the photon emission by the diffusion reaction in the sun to the
generation of electricity by solar panel, and finally application of solar cell into common device for
daily use. 1
The outcome of this UROP project is to let me get a deep understanding of the general
principles of how solar cell generates electricity from sunlight. Meanwhile, third generation of solar
cell which is thin film, its working principle, efficiency and future development, will also be
investigated.
1. Introduction
This UROP project is mainly discussed about the genral principles and applications of solar
cell technology. It starts from the photon emission by the diffusion reaction in the sun to the
generation of electricity by solar panel, and finally application of solar cell into common device for
daily use.
After completing this UROP project, I get a deep understanding of the general principles of
how solar cell generates electricity from sunlight. Meanwhile, I also touched a little bit on the third
generation of solar cell which is thin film, its working principle, efficiency and future development.
1.1 Proposal
Before I started the project, I set a plan to do this research. And the general information is as follows:
Four areas I intend to research in my UROP project.
1) Get to know the basic knowledge of the sun and the sunlight generation. (photons generation and
its energy level of different wavelength)
2) Understand solar cell technology and the principle of electricity generation.
1
Student
3) Get to know the latest technology on solar cell manufacturing process, and do a research on its
production cost and how to minimize this cost.
4) Do a research on the areas of applications of solar cell technology(which industry or civil
equipments are suitable for using solar energy )
Six processes I intend to follow during the UROP project:
1) Research on sunlight generation. Know the principles that how solar technology convert into
electricity or thermal energy.
2) Research on various usage of solar energy worldwide and each technology’s efficiency of
converting solar energy.
3) Get to know different kinds of solar cell (monocrystalline, multicrystalline, solar cell
concentrator technology, electrochemical PV cells, and thin film solar cells) and advantage and
disadvantage of each cell. And cost and percentage of usage of each solar cell.
4) Research on the solar cell manufacturing processes and its techniques on various cells mentioned
above. Try to find one or two ways to lower the cost of these cells.
5) Research on various equipments which are suitable to use solar cell.
6) If possible, I want to make a solar cell module myself and implement it into the equipment.
1.2 Methodology
Most of the information is from the internet because it is the easiest way. There is also a
shortcoming because it is not academically reliable. I also searched some academic papers in NUS
database, and some of them are very profound for me. I think as my study goes deeper and deeper in
this area, I will be capable to read academic journals on this topic. This report is just a conclusion of
what I have learned and experienced so far, and also some of my thoughts during the learning
processes.
2. Results and Discussion
2.1 Photons generation
Study solar cell technology, I think the first step is to study the sun, where the photon source
comes from. So I searched a lot of information on the internet, such as the composition of the sun,
structure of the sun, general condition of the sun and fusion reaction in the sun, which is the most
important step for photon generation. Energy crisis let us shift our focus from oil to sunlight, which
is a renewable, stable and environmental friendly energy resource. Firstly, the sun will spend around
10 billion years as a main sequence star before it stops its fusion reaction. Secondly, the generation
of electromagnetic wave is stable and continuously emitted to the space. Thirdly, through the solar
cell technology, all we need to do is to put the solar cell under the sun and it will generate electricity
automatically. Compared with other energy generation, it does not have any emission or consume
any natural resources on the earth, so we call it environmental friendly energy.
Below are some statistics about photon generation and energy received on the earth.
Fusion reaction inside the sun:
4H+2He
2He + E (E is released in the form of electromagnetic wave, photon)
The life of the sun: 10 billion years
Solar energy power measured by satellite around the earth: 1366 w/m
w 2 Cross section of the earth
127400000km2
Total power earth received from the sun: 1.74*1017W, plus or minus 3.5%
In 2005, total worldwide energy consumption was 500 EJ (= 5 x 1020J) .This is equivalent to an
average energy consumption rate of 15 TW (= 1.5 x 1013 W).
0.01% energy from the sun can fulfill the whole world energy consumption.
2.2 Photovoltaic
voltaic technology (solar cell)
This is the core technology I need to research in my project. Nowadays, a lot of energy
research companies or institutions study on this topic and new technologies in this area developed
very fast. The only problem to prevent this solar cell from largely implemented into daily
d
use is the
cost. Researchers use various methods to make cheaper solar cell. Such as thin film solar cell,
organic/ polymer solar cell, but the energy conversion efficiency will decreased
decreased as the cost
decreasing.
Basically, the principles of all kinds of solar cells are the same, it is photovoltaic effect. To
explain the photovoltaic solar panel more simply, photons from sunlight knock electrons into a
higher state of energy level, create electricity. Photons heat the solar cell, and make the electrons
move in the connected line and generate electricity. We can also use the conventional silicon as an
example; use the p-type
type silicon and n-type
n
silicon make a p-nn junction (actually it is a doping process,
dope n-type into the p-type
type wafer). When the photons
photo hit on the n-type
type silicon and make the
electrons into activated state, these electrons break the bonding of the atoms and travel to the pp-type
side, meanwhile, holes left on the n--type
type side. There are two modes of charge carrier separation. One
is drift,, which is driven by an electrostatic field. And another is diffusion, charge carrier diffuse from
high concentration to low concentration. Then the current will be formed if using the circuit to
connect two sides of the panel. The resulting circuit of solar
sol cell is show below:
Fig 2.1
All photovoltaic devices are some type of photodiode.
Fig 2.2
Depletion region: the depletion region, also called depletion layer, depletion zone, junction
region or the space charge region, is an insulating region within a conductive, dope
doped semiconductor
material where the charge carriers have diffused away, or have been forced away by an electric static
field.
The uncompensated ions are positive on the N side and negative on the P side. This cr
creates an
electric field that provides a force opposing the continued diffusion of charge carriers. When the
electric field is sufficient to arrest further transfer of holes and electrons, the depletion region has
reached its equilibrium dimensions. Integrating the electric field across the depletion region
determines what is called the built-in voltage (also called the junction voltage or barrier voltage or
contact potential
Much of the solar radiation reaching the earth is composed of photons with energies greater
than the band gap of the silicon. So the electrons in the silicon just absorb enough activate energy to
break the atomic bonding and form current. The difference of the energy emitted and absorbed is
converted into heat via lattice vibration.
Solar cell is usually connected in series to create an addictive voltage. Connecting in parallel
will yield a high current. These are very basic stuff I have learned in year 1. However, during my
research, some common rule of thumb comes into my picture which I cannot learn from the textbook.
For example, the average power is equal to 20% of peak power, so that each peak kilowatt of solar
array output power corresponds to energy production of 4.8kWh per day.
2.3 Various usages of solar energy and each technology’s converting efficiency
Besides solar cell converting electricity, there are various ways of converting solar power for
our daily use. I just use a short paragraph to conclude solar energy use in human history.
The oldest way of solar energy use should be evaporation ponds, which is used to obtain salt
from sea water. As time passed, more and more new technology come out, people use plastic bottle
and sunlight to disinfection drink water in Indonesia. 70GW solar water heating system implemented
in China in 2006. Solar chemical process also was studied since 1970. Solar energy can also be used
to desalinate saline or brackish water. Then it comes to the solar panel, most interested part of solar
energy use for scientists nowadays. From the usage on satellites in 1960s, the cost of solar panel was
decreased from 286USD/watt to 2USD/watt today or even less. The efficiency increased from 4.5%
to around 30% today. Meanwhile, the application of solar power is shifting from satellites to
domestic electricity generation, solar powered vehicles, railroad crossings and so on. As the shortage
of fossil energy today, people pay more and more attention on solar energy study and more and more
solar cells are implemented in the equipment for our daily use.
2.4 A close look at different kinds of solar cells, advantages and disadvantages of each kind
solar cell.
So far, there are basically three generations of solar cells exist. They all based on the
photovoltaic effect to generate electricity. The first generation is crystalline silicon, which can
approach 33% converting efficiency. Second generation is the thin film generation. This kind of solar
cells are all consists of thin film made from certain chemical composite. Typical examples are CdTe,
CIS, CIGS. Compared with the first generation, it has the lower producing cost, but lower efficiency.
The third generation is also based on thin film technology; current research is aiming to increase
converting efficiency to 30%-60% while maintaining the costs.
So let me start from the basic silicon p-n junction solar cell. This kind of solar cell divided into
monocrytalline silicon, polycrystalline silicon and ribbon silicon, usually the monocrystalline has the
highest efficiency but also highest production cost. Ribbon has lower efficiency than polycrystalline,
but it is the cheapest among the 3 types. Those p-n junction silicon solar cells accounts for 89.6%
market ratio in 2007.
Thin film solar cell is the newly emerged technology. Due to its relatively low cost compared
with silicon, it got a market share of 5.2% in 2007 and will be increased in the following years. The
conventional thin film has the lower efficiency than p-n junction silicon; new technologies create
multi-layer thin films which can better absorb the coming sunlight. Thus, it has even high converting
efficiency than bulk silicon.
Some typical thin film solar cells are as follows:
Thin film solar cell mainly consists of CdTe, CIS, CIGS and GaAs. Compared with other thin
film, CdTe is easier to deposit and more suitable for mass production. The only shortcoming is
the toxicity of cadmium, a heavy metal that is a cumulative poison. It has already proved that
cadmium released to the atmosphere is relatively lower than other thin film solar cells.
• CIS and CIGS are two similar thin film, the only difference is that CIGS use Ga substitute for In
in the CIS. This method can reduce the cost because of limited availability of In, meanwhile, it
also increase the optical band gap of the cell. The efficiency will also be increased. The best
conversion deficiency for flexible CIGS cells is 14.1% in 2006, and it was increased to 19.9% on
March 2008. The only disadvantage of this technology is the manufacturing cost.
• GaAs is the lowest cost alternative in terms of $/kWh and $/W. This kind of semiconductor are
carefully chosen to absorb nearly the entire solar spectrum, thus, it has the higher efficiency. It
has reached a record high of 40.7% under solar concentration and laboratory conditions. Same
disadvantage as other thin film, high production cost.
Other kind of technology such as light-absorbing dyes has a very low producing cost. However,
the dyes in these cells suffer from degradation under heat and UV light. The cell casing is difficult to
seal due to the solvents used in assembly.
•
•
•
Organic/polymer solar cell is a whole new concept of solar cell. It does not like the bulk silicon,
the charge carrier is by drifting, and it absorbs light and activates electrons into activated state.
Due to the concentration gradient created, the electrons will diffuse into the holes and generate
electricity. The highest efficiency so far is 6.5%. But it is very fit for the applications where
mechanical flexibility and disposability are important.
Silicon thin film is made of amorphous silicon, photocrytalline silicon or nanocrystalline silicon.
It tends to be less efficient than bulk silicon but also less expensive to produce. With some new
methods, the conversion efficiency can be largely increased. For example, Amorphous silicon
has a higher band gap (1.7 eV) than crystalline silicon (c-Si) (1.1 eV), which means it absorbs
the visible part of the solar spectrum more strongly than the infrared portion of the spectrum. As
nc-Si has about the same band gap as c-Si, the two materials can be combined in thin layers,
creating a layered cell called a tandem cell. The top cell in a-Si absorbs the visible light and
leaves the infrared part of the spectrum for the bottom cell in nanocrystalline Si.
There are also some other kind of solar cell, like nanocrystalline solar cell, concentrating
photovoltaics (it is a method to increase the efficiency of solar cell while keep the low usage of solar
panel use).
2.5 Manufacturing Processes
This part is mainly discussed about various manufacturing method of solar cell. There are
generally two kinds of solar cell. One is based on the traditional silicon bulk, p-n junction solar cell;
it is divided into monocrystalline and multicrystalline. And another is thin film solar cell, the main
production of this generation solar cell includes CIGS, CdTe, and GaAs as discussed in the previous
part.
Monocrystalline and Multicrystalline Solar Cell
Because this kind of solar cells are semiconductor devices, they share many of the same
processing and manufacturing techniques as other semiconductor devices such as computer and
memory chips. However, the stringent requirements for cleanliness and quality control are more
relaxed for solar cells. Most large-scale commercial solar cell factories today make screen printed
poly-crystalline silicon solar cells. Single crystalline wafers which are used in the semiconductor
industry can be made into excellent high efficiency solar cells, but they are generally considered to
be too expensive for large-scale mass production.
Poly-crystalline silicon wafers are made by wire-sawing block-cast silicon ingots into very thin
(180 to 350 micrometer) slices or wafers. The wafers are usually lightly p-type doped. To make a
solar cell from the wafer, a surface diffusion of n-type dopants is performed on the front side of the
wafer. This forms a p-n junction a few hundred nanometers below the surface.
Antireflection coatings, which increase the amount of light coupled into the solar cell, are
typically next applied. Over the past decade, silicon nitride has gradually replaced titanium dioxide
as the antireflection coating of choice because of its excellent surface passivation qualities. It is
typically applied in a layer several hundred nanometers thick using plasma-enhanced chemical vapor
deposition. Some solar cells have textured front surfaces that, like antireflection coatings, serve to
increase the amount of light coupled into the cell. Such surfaces can usually only be formed on
single-crystal silicon, though in recent years methods of forming them on multicrystalline silicon
have been developed.
Czochralski Process
After some research online, I have found the manufacturing method to produce
monocrystalline silicon is Czochralski Process. Czochralski process is a method of crystal growth
used to obtain single crystals of semiconductors, metals, salts, and synthetic gemstones. It is named
after Polish scientist Jan Czochralski, who discovered the method in 1916 while investigating the
crystallization rates of metals.
The process is generally like this: A seed crystal, mounted on a rod, is dipped into the molten
silicon. The seed crystal's rod is pulled upwards and rotated at the same time. By precisely
controlling the temperature gradients, rate of pulling and speed of rotation, and then it can extract a
large, single-crystal, cylindrical ingot from the melt. By investigating and visualizing the temperature
and velocity fields during the crystal growth process, occurrence of unwanted instabilities in the melt
can be avoided. This process is normally performed in an inert atmosphere, such as argon, and in an
inert chamber, such as quartz. After the growth of large cylindrical ingots, A commercial HCT saw
with high-speed wires and SiC slurry makes precision cuts to slice them to the specified cross section.
Prepare for the monocrystalline silicon solar cell production.
Multicrystalline silicon solar cell production procedure
•
A series of controls ensure that silicon feedstock meets the strict purity requirements necessary
to produce solar grade silicon ingots.
•
The silicon is melted down in a GT Solar Directional Solidification System (DSS) furnace.
•
A PLC program controls the entire process of melting, directional solidification, and cooling to
optimize the process based on the type of silicon feedstock and the production requirements.
•
The electric furnace combined with the PLC controls ensures efficient production and
minimizes environmental impact.
•
A commercial HCT saw with high-speed wires and SiC slurry makes precision cuts to slice
them into 16 bricks according to the specified cross section.
•
8 bricks at a time are sliced into extremely thin wafers that are ready for solar cell production.
8 bricks can yield approximately 3,000 wafers.
•
The wafers then move on to the automated production line. Etching and texturing of wafers
removes any saw damage and creates a surface that reduces solar reflection in order to capture
as much light as possible.
•
A high temperature phosphorus diffusion process creates the p/n junction necessary to produce
photovoltaic electricity.
•
The solar cells are then coated with an anti-reflective coating to enhance their light capturing
capability.
•
Finally, a state-of-the-art automated printing line applies the silver bus strips and coats the
backside with aluminum.
Manufacturing process of thin film
There are basically two methods to manufacturing thin film solar cells like CIGS. The first one
is sequential deposition of Cu, Ga and In and a post treatment in Se and S atmosphere. The second
method is the co-evaporation method, which makes a one step in-line process possible.
For CdTe thin film production. In the fabrication process, all the layers are grown by vacuum
evaporation. Commercially available soda-lime glass coated with fluorine doped tin oxide was used
as substrates. CdS layers were grown in a high vacuum evaporation chamber at a substrate
temperature of 150℃ and subsequently annealed at 450℃ for recrystallizaiton. Without breaking
the vacuum CdTe was then deposited at a substrate temperature of 300℃. Vacuum evaporation was
used for the deposition of 600 nm CdCl2 layers on CdTe and the stacks were annealed at 430℃ for
30 min in air.
2.6 Various Application of Solar Cell
Recent years have seen rapid growth in the number of installations of PV on to buildings that
are connected to the electricity grid. This area of demand has been stimulated in part by government
subsidy programmes (especially Japan and Germany) and by green pricing policies of utilities or
electricity service providers (e.g. in Switzerland and the USA). The central driving force though
comes from the desire of individuals or companies to obtain their electricity from a clean,
non-polluting, renewable source for which they are prepared to pay a small premium.
In these grid-connected systems, PV System supplies electricity to the
building and any day-time excess may be exported to the grid. Batteries
are not required because the grid supplies any extra demand. However, if
you want to be independent of the grid supply you will need battery
storage to provide power outside daylight hours.
Solar PV modules can be retrofitted on to a pitched roof above the
existing roof-tiles, or the tiles replaced by specially designed PV roof-tiles or roof-tiling systems. If
you are planning to put a PV system on to a building and have it connected to the grid supply there
are likely to be local regulations that need to be met, and permission required from your utility or
electricity service provider. The level of credit for any exported electricity will vary depending on
local schemes in place.
Industrial usage
Solar Energy has been the power supply of choice for industrial applications, where power is
required at remote locations. This means in these applications that solar power is economic, without
subsidy. Most systems in individual uses require a few kilowatts of power.
The examples are powering repeater stations for microwave, TV and radio, telemetry and radio
telephones.
Solar energy is also frequently used on transportation signal. E.g. offshore navigation buoys,
lighthouses, aircraft warning lights on pylons or structures, and increasingly in road traffic warning
signals. Solar is used to power environmental and situation monitoring equipment and corrosion
protection systems for pipelines, well-heads, and bridges or other structures. As before, for larger
electrical loads it can be cost effective to configure a hybrid power system that links the PV with a
small diesel generator.
Solar cell’s great benefit here is that it is highly reliable and requires little maintenance
In remote area
Apart from off-grid homes, other remote buildings such as schools, community halls, and
clinics can all benefit from electrification with Solar Energy. This can power TV, video, telephony
and a range of refrigeration equipment. Rather than base solar power generation on individual
dwellings, it is also possible to configure central village power plants that can either power homes
via a local wired network, or act as a battery charging station where members of the community can
bring batteries to be recharged.
PV Systems can be used to pump water in remote areas e.g. as part of a
portable water supply system. Specialized solar water pumps are designed
for submersible use or to float on open water. Usually, the ability to store
water in a tank means that battery power storage is unnecessary. Large-scale
desalination plants can also be PV powered. Larger off-grid systems can be
constructed to power larger and more sophisticated electrical loads by using
an array of PV modules and having more battery storage capacity.
Commercial buildings
On an office building, atria can be covered with glass/glass PV modules, which can be
semi-transparent to provide shaded light. On a factory, large roof areas have been the best location
for solar modules. If they are flat, then arrays can be mounted using techniques that do not breach the
weatherproof roof membrane. Also, skylights can be covered partially with PV.
The vertical walls of office buildings provide several opportunities for PV incorporation. The
first is as a "curtain wall system" that constitutes the weather barrier of the building. The second is an
underlying weather barrier that provides the insulation and sealing of the building.
The third option is to create sunshades or balconies incorporating a PV System. Sunshades
may have the PV System mounted externally to the building or have PV cells specially mounted
between glass sheets comprising the window.
Solar vehicles
Solar powered cars are cars which are powered by an array of photovoltaic cells. The
electricity created by the solar cells either directly powers the vehicle through a motor, or goes into a
storage battery. Even if a vehicle is completely covered in solar cells, it will only receive a smaller
amount of solar energy and will be able to convert only a small amount of that to useful energy.
Because of this, most solar powered vehicles are only used in research, educational tools or to
compete in the various races for solar powered vehicles.
Helios UAV in solar powered flight
In 1974, the unmanned Sunrise II plane inaugurated the era of solar flight. In 1980, the
Gossamer Penguin made the first piloted flights powered solely by photovoltaics. This was quickly
followed by the Solar Challenger which demonstrated a more airworthy design with its crossing of
the English Channel in July 1981. Developments then turned back to unmanned aerial vehicles
(UAV) with the Pathfinder (1997) and subsequent designs, culminating in the Helios which set the
altitude record for a non-rocket-propelled aircraft at 29,524 metres (96,860 ft) in 2001. The Zephyr,
developed by BAE Systems, is the latest in a line of record-breaking solar aircraft, making a 54-hour
flight in 2007, and month-long flights are envisioned by 2010.
Some small appliance for our daily use
Solar Powered Calculators
Solar Powered Watch
Electrical Power Charger
2.7 Asian Youth Energy Summit
On 30 and 31 Oct. 2008. I attended Asian Youth Energy Summit Conference. It was held in
NUS international Conference Center by Energy Carta, which is a non-profit organization that seeks
to educate and engage students and young professionals with industry and other stakeholders about
issues related to Sustainable Development and Energy.
It is a quite meaningful conference for me. That’s because I have learned a lot of things during
this two-day conference, and also get interactions with some green energy enthusiasts, great person
in this industry. An undergraduate student from Rice University gave us an impressive presentation
on solar cells. It encourages me to keep on studying in this area. I think I can also achieve what he
has done because we are all undergraduates.
Mr. Dipal Barua, who is the managing director of Grameen Shakti, gave us an amazing talk on
what he has done in his home country, Bengal. Because most of the areas in Bengal are still
uncovered by the electrical grid, so he develops a new product, simple solar module powering
system. He recruited women in the rural area, and assembly this solar modules. Each set of modules
can power TV for 2 or 3 hours and light for 5 to 6 hours after sunset. Of course, in the daytime, it can
fully power all these devices. It brought a lot of convenience for the local people and meanwhile, it
also creates hundreds of jobs for women in the rural area. Actually, Professor Muhamad Yunus and
Grameen Bank received the Nobel Prize in 2006 for its contribution to poverty reduction and peace.
I joined Professor Luther’s discussion panel, who is the CEO of Solar Energy Research
Institute of Singapore (SERIS), which is a National Lab based in NUS. Christophe Inglin, who is the
Managing Director of Phoenix Solar in Singapore. They gave us a brief view for the solar technology
development in the next decade. They mainly focused on the amorphous silicon and thin film solar
cell development. The transforming efficiency has researched to 14% for CIGS now, and can be
achieved for higher efficiency.
Another discussion panel was held by NUS Prof Chou Siaw Kiang, who is executive director
of Energy Studies Institute. Benjamin K. Sovacool, research fellow of Lee Kuan Yew School of
public Policy. They gave us a whole new perspective on solar cell development. They start from the
economic side and political side. As I have discussed previously, during the 1970s and 1980s oil
shortage crisis, large amount of research fund and incentive policy were going to solar cell industry.
However, after the crisis, people shifted their focus back on the fossil fuel area. Solar cell keeps on
growing 14% each year till 2000. The main point here is that whether this technology can be
developed largely depends on the government policy. That’s because its high costs compared with
the grid electricity. Singapore government aims to grow the Clean Energy industry to generate a total
of S$1.7 billion in value-added and 7000 jobs by 2015. Good news is that Norway’s Renewable
Energy Corp decided to build the world’s largest solar plant at a cost of $6.3 billion in Singapore. So
I can see I have a bright future if I put myself into this industry.
3. Conclusion
This is the first time I make extensive study on a specific area. I get most of the information
from internet, conference handout, and research papers. Some of the information may be not reliable.
However, I get to know the basic concept of the solar cell technology, various kinds of solar cell and
their applications. Also I find out each kind solar cell’s working principle. The market share of each
kind of solar cell has also been investigated. In the second half of the project, I focused my study on
the manufacturing process of the solar panels, get a deep understanding that how the silicon or thin
film solar cells were made. Due to the knowledge constrains, I cannot provide any suggestions for
the manufacturing methods discussed above. After discussing about the manufacturing methods, I
did an intensive study on the application of solar cell. There are really a lot. Almost all the electrical
device can be powered by solar cell. We just need to consider the efficiency and the economic
optimization of each kind of solar cell application. In my proposal, I intend to buy a solar cell and
implement it into a device for daily use. However, due to the school lab condition and time
constrains, I cannot put all my thoughts into practice.
Asian Youth Energy Summit really helps me a lot on this project. I get to know the latest
technology and research direction in this area. And also some other consideration, such as economy
and public policy also come into my mind. So I can see a clearer picture of solar cell technology. On
the conference, I also make some friends who are enthusiasm in the renewable energy area. We
exchanged our thoughts and ideas on it, and it is really fantastic conference. I also got interactions
with professional people in this area, like Christophe Inglin, who is managing director of Phoenix
Solar Pte.
I joined Professor Hawlader’s FYP students meeting weekly. Get to know more about what
my seniors is doing now. Each of them has their presentation every week. They shared their thoughts
and results on their study field, and Porf Hawlader gave them many valuable suggestions. I also
shared with them what I have done in the past week, and ask them for some suggestions. It is really
happy to work with them, and I like that style. Meanwhile, I have learned a lot from this kind of
meeting.
Above all, from UROP study, I have learned the basic principle of solar cell and their future
development. It is really an enriching experience for me. I also make some friends and get to know
some big person in this area. Besides technology, there are also some factors, such as economy and
public policies, come into my mind. It lets me to view the full picture that how a technology is
promoted into the society. I like to thank my mentor, Professor M.N.A Hawlader, who gives me
tremendous help and valuable suggestions in this UROP project. Let me join their FYP meeting, and
take their time to listen to my presentation. It is a quite happy journey in my university life.
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M. Powalla, B.(2002) Development of large-area CIGS modules Solar Energy Materials and Solar
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