Editorial

Dr.Madhuri Sharon

Research Director

Solar Cells: Convert Sunlight into Electricity:

Our global need of energy is derived from coal, gas, oil, and nuclear power plants. These methods are not

very eco-friendly as well as the fossil fuels like oil is a big cause of political instability and threatens peace in the

world, mainly because of the uneven distribution of the oil around the world. Solar energy is being envisaged as

the alternative methods which could compete with the conventional energy production. Conversion of Sun light

to electricity via photovoltaics is being looked at as promising alternative. Three

types of Solar cells are being researched and developed (i) using crystalline

silicon which is most predominantly used solar cell at the moment (ii) thin film

solar cells which include inorganic semiconductors such as CdTe, CdS, etc, which

are also commercially available and (iii) use of organic and organo-metallic

materials. The major concerns of Solar cell technology are to lower the cost, make

it light weight and easy integration to flexible applications. It will not be improper

to say now that use of Solar cell is a viable method to satisfy a substantial amount

of our energy needs while reducing carbon dioxide pollution, creating jobs and

decreasing market instabilities due to the geopolitics of fossil fuels.

This issue of News Letter is an effort to address and highlight the status of solar cells at present by

staff of wcRnb.

“We have this handy fusion reactor in the sky called the sun, you don’t have

to do anything, it just works. It shows up every day.”

Elon Musk, CEO Tesla Motors

Walchand’s effort in harvesting solar energy

Chinmay Phadke Senior Research Fellow

India can be considered as one

of the wealthiest countries in terms of abundance of

solar energy, a raw income from which lots of

revenue can be generated if one learns to use it

wisely. With future concern, it’s absolutely

necessary to understand and develop the

methodologies to venture into the conservation and

utilization of solar energy. Lately, researchers are

putting great efforts for devising highly efficient

solar cell. Till now, many materials like Graphene,

Carbon Nano Tubes etc. have been used for devising

solar cell.

Apart from researchers, few academic

institutes also have gathered interest and have

undertaken the role in harvesting solar energy.

Among the very few to start, the pioneer of

Walchand institutes, Shreeman Dr.Ranjeet Gandhi

has taken a great initiative by installing water heating

systems based on solar as well as the solar generator.

Girl’s hostel, boy’s hostel and the staff quarters are

furnished with the solar water heating facility, which

includes 10 units, each having capacity of heating

1000 Litres of water per day (Lpd) and recently

installed 8 units having 500 Lpd capacity each. This

suffices the daily need of hot water required by

around 900 hostilities as well as the staff.

Also, the college building of Walchand

Institute of Technology (WIT) is supported by 152

solar panels which have the ability of generating 40

kWp to substitute the 200 kWp required by the

institute, thus covers the 20% of the electricity

required by WIT.

Walchand College of arts & science (WCAS) as well

as WIT campus roads are provided with the solar

power driven lights, which have been installed

throughout campus. With these solar devices lots of

energy or electricity can be redeemed. WCAS and

WIT serves as a noteworthy example for its

contribution in conservation and elegant use of solar

energy.

INCREDIBLE INDIA’S EFFORTS INTO COMMERCIALLY

GENERATING ELECTRICITY BY HARNESSING SOLAR POWER

Nallin Sharma Senior Research Fellow

India is one of leading nation in

every aspect to Humanity, from basic education to

empowering high end industries of world. Demands

of world are again hooked up to Indian Scientists,

Engineers, Doctors and even grass level skilled man-

power to meet the global need in vivid sectors of

engineering like Power/Energy solutions, for

chemical industries, IT & for Mechanical

engineering fields.

Current need to us is green & clean energy

sources, topping in this list is Solar Energy. India is

again a strong contender in world scenario for both

manufacturing Solar panels as well generating &

distributing this clean energy to masses. Twenty first

century is witnessing several large solar projects

being are engineered to fulfill power crisis.

Now we have more than 200 heavy running

solar panel manufacturing industries, situated all

over India; to name a few:

(i)Vikram Solar of Kolkata W. Bengal; which is

since 2006 having 500MW/annum production and

have installed 120 projects in India. Their future plan

is to enter in producing Nano Carbon incorporated

solar panels for having higher efficiency

(ii)Bergen Associates in Delhi have provided solar

power to 50 villages across India,

(iii)Moser Baer Solar LTD of Delhi

(iv)Tata Power Solar System, Bengaluru, Karnataka,

they coming up with Nano Carbon engineered solar

panels promising in producing energy more

efficiently. According to Ashish Khanna, CEO of

Tata Power Solar; “There are 300 million people in

India without power; 400 million people are supplied

erratic power; more than half the population of India

does not get proper power,” therefore, the

government of India’s ambitious target of achieving

100 GW solar power capacity by 2022 is the need of

the day and future.

(v)Sun solar Techno LTD in Mulund, Mumbai of

Maharashtra,

(vi)Luminous Power Technologies of Pune,

Maharashtra

(vii)Surana solar of Hyderabad, Telangana have also

shown interest in developing Nano Carbon

incorporated solar cell and panels.

(viii)Vorks Energy in Noida, UP

(ix)JJ PV Solar situated in Rajkot Gujarat etc…….

Majority of these companies are specialized

in producing up to 300W Mono & Polycrystalline

panels. They have benchmarked priority not to just

the govt. certifications such as ISO 9000, 9001,

14001; but daily & heavy users also.

Now the challenge is to provide cheaper

installation and production. The next big leap in our

solar distribution is to slash the Rupee 20 per unit

cost to deep down at Rupee 0.2/unit. However, the

current cost as per IREDA is Rupee 5.5 per unit.

Policies have come up to encourage domestic user by

not just providing subsidy but low power consuming

electrical commodities like LED bulbs, low cost

induction heaters, high efficiency electrical

regulators, etc. Tight clashes between Solar powered

Air-conditioner system & reliable Electric vehicle is

one big project where solar power giants are turning

up.

However, summary of study by Deloitte and

Confederation of Indian Industry (CII) has revealed

that though India has installed solar power capacity

by March 2015 is 3,744 MW, still India is not

harvesting even 1% of its total energy. This

statement is disheartening as well as encouraging. It

tells us that we have such a vast store of solar energy

available. And India has to concentrate on policy

issues and challenges, new and emerging

technologies, grid evacuation, availability and load

dispatch and innovative financing models in the solar

power sector.

Dye-Sensitized Solar Cells: A Need for Future Energy Demand

Dr. Rakesh Afre H.O.D Nanotechnology

Dye-sensitized photovoltaic (PV) solar cells

(DSC), a non-conventional PV technology, which

was first reported in 1991, have shown electrical

conversion efficiencies greater than 10% in

laboratory testing. The rising population, rapidly

changing life styles of people, heavy

industrialization and changing landscape of cities has

enormously increased the energy demands. The

present annual worldwide electricity consumption is

12 TW and is expected to become 24 TW by 2050,

leaving a challenging deficit of 12 TW. The present

energy scenario of using fossil fuels to meet the

energy demand is unable to meet the increase in

demand effectively, as these fossil fuel resources are

non-renewable and limited. Also, they cause

significant environmental hazards, like global

warming and the associated climatic issues. Hence,

there is an urgent necessity to adopt renewable

sources of energy, which are eco-friendly and not

extinguishable. Of the various renewable sources

available, such as wind, tidal, geothermal, biomass,

solar, etc., solar serves as the most dependable

option. Solar energy is freely and abundantly

available. Once installed, the maintenance cost is

very low. It is eco-friendly, safely fitting into our

society without any disturbance.

Producing electricity from the Sun requires the

installation of solar panels, which incurs a huge

initial cost and requires large areas of lands for

installation. This is where nanotechnology comes

into the picture and serves the purpose of increasing

the efficiency to higher levels, thus bringing down

the overall cost for energy production. Also,

emerging low-cost solar cell technologies, e.g. thin

film technologies and dye-sensitized solar cells

(DSCs) can help to replace the use of silicon, which

is expensive. Again,

nanotechnological implications can be applied in

these solar cells, to achieve higher efficiencies.

A dye sensitized solar cell is based on a

semiconductor formed between a photo-sensitized

anode and an electrolyte, a photo-electrochemical

system. Dye sensitized cells are used for converting

sunlight into electrical energy across a wide intensity

range by using a dye, which is absorbed in titanium

oxide semiconductor. A dye sensitized cell has

several attractive features such as semi-flexibility

and semi-transparency, which offers a variety of

uses. In the current scenario, dye sensitized cells are

the most efficient third generation solar technology

available. Dye sensitized cells can be a suitable

option as a replacement for existing technologies in

low density applications such as rooftop solar

collectors. However, use of liquid electrolyte in dye

sensitized cell design is a major drawback, as it has

temperature stability problems. In the last 5-10 years,

solid-state dye sensitized solar cells have been

developed. In this case the liquid electrolyte is

replaced by one of the several solid hole-conducting

materials. During this period, the efficiency of solid

state dye sensitized solar cell has increased from 4%

to 15%.

Based on application, the global dye sensitized cell

market is segmented into different categories:

building-integrated photovoltaics, indoor

application, retail application, emergency power and

military application, and others. Building-integrated

photovoltaics are further sub-segmented into BIPV

glass and solar roofs. Indoor application is further

Green House using Dye-sensitized Solar

Cell

sub-segmented into three categories: solar chargers,

wireless keyboards, and others. Retail application is

further sub-segmented into three categories: indoor

and outdoor advertising, point-of-purchase displays,

and others.

The need to replace fossil fuels with renewable and

sustainable energy sources is more exigent than ever,

in order to reduce CO2 emissions causing climatic

change and guarantee the further development of

mankind in harmony with our natural environment.

Can Silicon solar cell be replaced by Carbon solar cell?

Prof. Dr. Maheshwar Sharon Joint Research Director

Conversion of Solar energy to electricity is

now a viable method with many advantages over

conversion of fossil energy to electricity such as

reduced carbon dioxide pollution, creating jobs and

decreasing market instabilities due to the geopolitics

of fossil fuels. Moreover fossil fuel supplies are

rapidly diminishing.

The first credit for developing a Solar Cell

goes to Becqurel who discovered photovoltaic effect

in selenium way back in 1839. Other early

contributors were W. Zerassky (1908), who built a

solar thermoelectric device by welding two

dissimilar metals i.e. zinc antimony alloy and silver

plated alloy. Hailing the solar energy as Green

technology and need of the day Daryl Chapin, Calvin

Fuller and Gerald Pearson of Bell Laboratories

developed the first solar cells in 1954. Now the

efforts are on to achieve commercially competitive

electricity generation with sources such as oil or coal.

The requirements for grid parity vary widely,

depending on local factors such as the annual number

of Sun hours as well as the local costs of competing

technologies to get higher conversion of sun light. It

is theoretically predicted that photovoltaic cell can

give efficiency up to 30%. Successful use of Solar

Cell was in 1959 when Vanguard satellite carried

first 108 solar photovoltaic chips to power its radio.

It must be mentioned here that for such project cost

of Solar cell was immaterial.

When scientists realized that the petrol and

other fossil fuels from which electrical power is

being generated has limited availability, they

indulged in developing photovoltaic Solar Cell that

will be useful for terrestrial application. Initially the

cost of Solar Cell was very high ($1000/w).

However, with consistent effort of scientists it was

reduced to about $100/w by 1970; and now it is

around $5/w. Efforts are now made to develop

silicon solar cell from amorphous silicon so that

flexible type solar cell could be possible. Efforts are

also made to develop materials other than silicon like

CdSe,CuInSe2 etc for making solar cell. These solar

cells are also known as solid state solar cell formed

by joining n- and p-type of these materials like n-Si

with p-Si. Anew class of solar cell was developed

during 1966 when a semiconductor-metal could form

similar junction as p;n junction. This discovery was

made by Walter H. Schottky and is classified as

metal-Schottky type junction. Fujishima and Honda

in 1972 showed a possibility of making similar solar

cell by using electrolyte in between the two materials

i.e. n-Si/electrolyte/metal. Such cells were classified

as wet type solar cell or Photoelectrochemical solar

cell.

This discovery gave the birth to a concept

that a metal-Semiconductoor Schottky type junction

could also be formed by bringing a suitable

electrolyte in between either two semiconductors

(i.e. p-type and n-type) or in between semiconductor

and metal. Global scientists while working on this

type cell realised that though it was possible to

fabricate wet type cell which could compete with

photovoltaic solar cell, but unfortunately there is non

inorganic semiconductor material which could be

electrochemically and photoelectrochemically stable

in aquous solution for more than few hours to few

months. This was the biggest hurdle towards the

development of wet type solar cell.

While scientists were looking for the

solution to this problem, discovery of fulleren by

Kroto et al in 1985 (Kroto along with Smalley and

Robert Curl got Nobel prize in 1996 for this

discovery) gave a light of hope that carbon

nanomaterial could be a good choice for devloping

wet type solar cell, because carbon material is

expectd to be stable in acidic as well as alkaline

media.

Considering this Sharon’s group got

indulged in early nineteen nintees into developing

semiconducting carbon for its application in wet

type of cell. Sharon’s group questioned that if

elecrolyte can give a Schottky type junction then why

not it can also formed ohmic type junction. Answer

to this question resulted in developing solar

chargeable battery, which they coined as Saur

Viddyut Kosh) and Sharon-Schottky Juntion.

The challenge to get a material, which is

electrochemically and photoelectrochemically

stable, remained a challenge when it was realised that

almost all semiconducting nano carbon materials

possess zero band gap (indirect band gap). Though

Sharon’s group could find a synthethetic process to

develop carbon of direct band gap 1.4 eV (which is

most suitable band gap for wet type solar cell), but

presence of zero indrect band gap caused the major

hurdle in decreasing the concentration of minority

carrier. However, they are the only group in the

world to have developed a Homojunction Carbon

Solar Cell with an efficiency of 4%, but unless the

zero indirect band gap is either destroyed or its band

gap is increased to some reasonable value, future of

carbon photovoltaic solar cell remain as biggest

hurdle in competeing with silicon solar cell. This

group no doubt is still working with a hope to solve

this problem, only time will give the real answer of

their success.

Some humble efforts of our group: 1. M. Sharon; Solar Galvanic Cell, Industrial Research. May, 1976 (USA).

2. M. Sharon, S. G. Saran, A. Sinha & B. M. Prasad; A Saur Viddyut Kosh-Solar Photogalvanic Cell - II., J.

Electrochem. Soc. 30(3), 200-203, 1981.

3. M. Sharon & A. Sinha; A rechargeable Photoelectrochemical Solar Cells., Int. J. Hydrogen Energy, 7,

557-562, 1982.

4. M. Sharon, S. Kumar & S. R. Jawalekar; Saur Viddyut Kosh-IV, Study of a rechargeable solar battery

with n-Pb3O4 electrodes., Solar Cells. 12-4, 353 - 361, 1984

5. M. Sharon & G. R. Rao, Photoelectrochemical cell with liquid- (ohmic)-semiconductor- liquid (Schottky

Barrier) system, Ind. J. Chem. 25A, 170 - 172, 1986.

6. M. Sharon, P. Veluchamy, C. Natrajan & D. Kumar, Review Article - Solar Rechargeable Battery -

Principle and Materials, Electrochimica Acta 36 (7), 1107 -11026, 1991.

7. M. Sharon, K. Mukhopadhyay, K. M. Krishna, Fullerenes from camphor: A Natural Source., Phys.

Rev. Lett. 72(20), 3182 – 3185, 1994

8. M. Sharon, I. Mukhopadhyay and K. Mukhopadhyay, A Photoelectrochemical Solar Cells from p-Carbon

semiconductor, Sol. Energy Mat. Sol. Cells, 45, 35-41, 1997

9. M. Sharon, K. Mukhopadhyay, I. Mukhopadhyay, T. Soga and M. Umeno, Carbon Photovoltaic cell,

Carbon, 35, 863-864, 1997

10. M. Sharon, K. M. Krishna, T. Soga, K. Mukhopadhyay, M. Umeno, Photovoltaic solar cell from

camphoric carbon. A natural Carbon, Solar Energy Materials and Solar cells, 48, 1-4, 25-33, 1997

CARBON NANOTUBES: A POTENTIAL MEMBER IN THE SOLAR ENERGY

TECHNOLOGY

Isaac Nandgavkar Junior Research Fellow

Carbon nanotubes (CNTs)

are allotropes of carbon having dimension in the

nanometer range. They have tube-like structure

composed of carbon atoms linked in hexagonal

shapes with each covalently bonded to 3 other carbon

atoms. Carbon Nanotubes have many structures,

differing in length, thickness, and in the type of

helicity and number of layers. As a group, CNTs

typically have diameters ranging from <1 nm up to

50 nm. Their lengths are typically several microns,

but recent advancements have made the nanotubes

much longer measuring in centimeters. Overall,

Carbon Nanotubes show a unique combination of

stiffness, strength, and tenacity compared to other

fiber materials which usually lack one or more of

these properties. Thermal and electrical conductivity

are also very high and comparable to other

conductive materials. CNTs are from the fullerene

family whose name is derived from the long, hollow

structure with the walls formed by one-atom-thick

sheets of carbon, called graphene. These sheets are

rolled at specific and chiral angles, and the

combination of the rolling angle and radius decides

the CNT’s properties; for example, whether the CNT

is a metal or semiconductor.

Entry of CNT in Solar Cell Arena

CNTs possess a wide range of direct band

gaps matching the solar spectrum, strong photo

absorption, from infrared to ultraviolet, high carrier

mobility and reduced carrier transport scattering,

apart from this, they are also lighter, more flexible

and cheaper than conventional solar-cell materials

thus ideal for photovoltaic technology. But research

stalled when CNTs proved to be inefficient,

converting far less sunlight into power than other

methods.

In the earlier years, the researchers tended to

choose one particular chirality with good

semiconducting properties and build an entire solar

cell out of that one. But the problem is that each CNT

chirality absorbs a narrow range of optical

wavelengths. So if the CNTs of a single chiral

structure is used it would mean throwing way all the

other solar energy. In the preceding paragraphs some

milestone achievement in recent years are presented

Researchers at Umeå University in Sweden

[March 2014] have discovered that controlled

placement of the CNTs into nano-structures

produces a huge boost in electronic performance. For

the first time, the researchers show that CNTs can be

engineered into complex network architectures, and

with controlled nano-scale dimensions inside a

polymer matrix. The high degree of control of the

method enables production of highly efficient CNTs

networks with a very small amount of CNTs

compared to other conventional methods, thereby

strongly reducing materials costs. The resulting nano

networks possess exceptional ability to transport

charges, up to 100 million times higher than

previously measured CNT random networks

produced by conventional methods.

There has been a breakthrough for the CNTs,

paving their way back into the field of solar

technology in September 2014, when few

researchers in Northwestern University published

about polychiral semiconducting CNTs solar cells

having higher efficiency than predecessors.

Addressing the problem of single chiral not able to

absorbs wide range of wavelengths, these researchers

synthesized a polychiral CNT which maximized the

amount of photocurrent produced by absorbing a

broader range of solar-spectrum wavelengths. The

cells significantly absorbed near-infrared

wavelengths, a range that has been inaccessible to

many leading thin-film technologies.

A new technique is developed in November

2014 using hydrogen fluoride and electric current to

remove oxygen from CNTs which resulted in high

power conversion efficiencies, a measure of how

efficiently a solar cell converts sunlight to electric

energy.

As reported in a published article in

ChemNanoMat in February 2015, a thin conducting

polymer interlayer significantly improves

photovoltaic performance by creating a better

depletion layer within the underlying silicon. With

the addition of a top antireflection layer, a

photovoltaic device, silicon-poly(3,4-

ethylenedioxythiophene): poly(styrene sulfonate)–

carbon nanotube–poly(styrene) has been fabricated

with a photovoltaic conversion efficiency of 8.7 %.

In February 2015, researchers in Japan

demonstrated a significant improvement in the CNT

solar cells by the use of metal oxide layers for

efficient carrier transport. As a result the power

conversion efficiency improved up to 17% in

CNT/Si solar cells.

Researchers at the University of Cincinnati

(March 2015) presented on how a blend of

conjugated polymers resulted in structural and

electronic changes that increased the efficiency

three-fold, by incorporating pristine graphene into

the active layer of the carbon-based materials. This

research has shown potential for constructing

flexible solar cells using CNTs, researchers have

found that wrapping carbon nanotubes in non-

covalently bonded polymers improves their

photovoltaic functions in solar cells.

In a recent effort in April 2015 Schottky

diodes and solar cells are statistically created in the

contact area between two macroscopic films of

single-walled carbon nanotubes (SWCNTs) at the

junction of semiconducting and quasi-metallic

bundles consisting of several high quality tubes. The

n-doping of one of the films allows for photovoltaic

action, owing to an increase in the built-in potential

at the bundle-to-bundle interface. Statistical analysis

demonstrates that the Schottky barrier device

contributes significantly to the I-V characteristics,

compared to the p-n diode. The upper limit of

photovoltaic conversion efficiency has been

estimated at ∼20%, demonstrating that the light

energy conversion is very efficient for such a unique

solar cell. While there have been multiple studies on

rectifying SWNT diodes in the nanoscale

environment, this is the first report of a macroscopic

all-CNT diode and solar cell.

In September 2015, for the first time,

scientists have created a solar energy collector using

CNTs that can directly convert optical light in to a

direct current. It is hoped these optical rectennas may

one day rival established technologies, such as the

silicon solar cell.

One of the most recent outcome of improving

power conversion efficiency (PCE) of organic solar

cells by the addition of small quantities (0.02%–

0.04%) of pristine single-walled carbon nanotubes

(SWCNTs) in the active-layer is reported in this

month of December 2015. A single diode model of

a solar cell was used to extract the cell parameters

and understand the effect of SWNTs. Based on

experimental data and it's fitting to the single diode

model, they proposed that SWCNT improved the

transport and extraction of photo generated charges

within the solar cell device.

GRAPHENE – A 2-DIMENSIONAL CARBON TO ENHANCE

THE SOLAR ENERGY CONVERSION CAPACITY TO ELECTRICITY

Farha Modi Junior Research Fellow

Graphene, the pure carbon

material that is just one atom thick and nearly

transparent when laid out in sheets, manages to be

roughly 200 times stronger than steel. It is also an

excellent conductor of energy and can be synthesized

from unique carbon sources, anything from pencil

lead and it has thousands of applications like in

batteries, computer circuits, smartphones, energy

cells, etc. When you search “graphene” on the web,

the most common picture you’ll see is a molecular

lattice that resembles a honeycomb. In reality, this

depiction of graphene is perhaps the best way to

understand its incredible properties. The structure is

remarkably strong and efficient. As such, graphene

is the most chemically reactive form of carbon,

which also makes the material highly conductive and

flexible, as well as strong. Graphene is an insanely

amazing conductor of heat and electricity but, up till

now it wasn’t very good at absorbing light. A very

big problem currently with a graphene based solar

panel design is the fact that the edges of the graphene

sheet are highly reactive, so harvesting the current

would prove to be much more of a challenge.

One of the major reasons that solar panels are

facing such hurdles to replace conventional

electricity sources is because they are very

inefficient. The most efficient and the most

expensive panel is currently somewhere around 32%

efficiency. However, scientists in Switzerland, Ecole

Polytechnique Federale de Lausanne (EPFL) have

figured out a way to utilize Graphene in solar panel

design, raising its efficiency to an absolutely

staggering 60 % - a finally feasible amount.

A few years ago in April 2012, scientists

from Michigan Technological University found out

that incorporating graphene, one of the coolest new

nanomaterial of the 21st century could increase the

cell’s conductivity and also boost the efficiency of

the next generation of solar panels, bringing 52.4%

more current into the circuit.

Last year in January, 2014, Juan Bisquert,

Professor of Applied physics at University of Jaume

I in Castello, created and characterized a

photovoltaic device based on a combination of

titanium oxide and graphene- a charge collector and

perovskite as sunlight absorber. The device is

manufactured at low temperatures and has a high

efficiency. Researchers from University of Illinois

College of Engineering had achieved new levels of

performance (March 24, 2014]) for seed-free and

substrate-free arrays of nanowires from class of

materials called III-V directly on graphene. These

semiconductor compounds hold particular promise

for applications involving light, such as Solar cells or

lasers.

In this image,

imagine a field of small

wires, standing at

attention like a tiny

field of wheat,

gathering the Sun’s rays

as the first step in Solar

energy conversion.

Scientist at Michigan Technological

University (August, 2014) tried to overcome few

drawbacks of solar cells by replacing platinum ( a

key material in dye-sensitized solar cells) with a new,

3-D form of graphene made from carbon monoxide

and lithium oxide with virtually no loss in electrical

generating capacity.

Very recently in November, 2015 it is

reported that a Researcher at the Hong Kong

Polytechnic University has developed a first-ever

made semitransparent perovskite solar cells with

graphene as electrode. With simple processing

techniques, solar cells with high power conversion

efficiencies can be fabricated at low cost. The power

conversion efficiencies of this novel invention was

around 12% when they were illuminated from

Fluorine-doped Tin Oxide bottom electrodes (FTO)

or the graphene top electrodes, compared with 7% of

conventional semitransparent solar cells. Its potential

low cost of less than HK$0.5/Watt, more than 50%

reduction compared with the existing cost of silicon

solar cells, will enable it to be widely used in the

future. Semitransparent solar cell technology can be

integrated into the building design, replacing

conventional building material, such as facades,

shelters, windows and rooftops, etc.

The “Super material” isn’t ready yet,

but it is going to make future technologies so awesome.

DYE SENSITIZED SOLAR CELL – A THIN FILM SOLAR CELL

Prerak Patel Junior Research Fellow

A dye-sensitized solar cell (DSSC), also s referred to

as dye sensitized cells (DSC) is a low-cost solar cell

belonging to the group of thin film solar cells. These

are a third generation photovoltaic (solar) cell that

converts any visible light into electrical energy. This

new class of advanced

solar cell can be likened to

artificial photosynthesis

due to the way in which it

mimics nature’s absorption

of light energy.

It is based on a

semiconductor formed between a photo-sensitized

anode and an electrolyte, a photo electrochemical

system. The modern version of a dye solar cell, also

known as the Grätzel cell, was originally invented in

1988 by Brian O'Regan and Michael Grätzel at UC

Berkeley and this work was later developed by the

afore mentioned scientists at the École

Polytechnique Fédérale de Lausanne until the

publication of the first high efficiency DSSC in 1991.

Michael Grätzel has been awarded the 2010

Millennium Technology Prize for this invention.

DSSC is a disruptive technology that can be

used to produce electricity in a wide range of light

conditions, indoors and outdoors, enabling the user

to convert both artificial and natural light into energy

to power a broad range of electronic devices.

Dye-sensitized solar cells have gained

widespread attention in recent years because of their

low production costs, ease of fabrication and tunable

optical properties, such as color and transparency. In

DSSC, electrodes consist of sintered semiconducting

nanoparticles, mainly TiO2 or ZnO. These

nanoparticle DSSCs rely on trap-limited diffusion

through the semiconductor nanoparticles for the

electron transport.

This limits the device efficiency since it is a

slow transport mechanism. Recombination is more

likely to occur at longer wavelengths of radiation.

Moreover, sintering of nanoparticles requires a high

temperature of about 450°C, which restricts the

fabrication of these cells to robust, rigid solid

substrates. It has been proved that there is increase in

the efficiency of DSSC, if the sintered nanoparticle

electrode is replaced by a specially designed

electrode possessing an exotic 'nanoplant-like'

morphology.

Some of the recent mile-stone out puts in DSSC

are enumerated below:

2010

The world witnessed a major breakthrough

when researchers at the École Polytechnique

Fédérale de Lausanne and at the University du

Québec à Montréal claim to have overcome two of

the challenges faced in DSC's (i) "New molecules"

were created for the electrolyte, resulting in a liquid

or gel that is transparent and non-corrosive, which

can increase the photo voltage and improve the cell's

output and stability; (ii) At the cathode, platinum was

replaced by cobalt sulfide, which is far less

expensive, more efficient, more stable and easier to

produce in the laboratory.

2011

World´s largest dye sensitized photovoltaic

module, printed onto steel in a continuous line was

announced by Dyesol and Tata Steel Europe in June.

Immediately after that in October Dyesol and CSIRO

announced a successful completion of Second

Milestone that was explained by Dyesol Director

Gordon Thompson as, "The materials developed

during this joint collaboration have the potential to

significantly advance the commercialization of DSC

in a range of applications where performance and

stability are essential requirements. Dyesol is

extremely encouraged by the breakthroughs in the

chemistry allowing the production of the target

molecules. This creates a path to the immediate

commercial utilization of these new materials."

Dyesol and Tata Steel Europe in November 2011

achieved the targeted development of Grid Parity

Competitive BIPV solar steel that does not require

government subsidized feed in tariffs. TATA-Dyesol

"Solar Steel" Roofing is currently being installed on

the Sustainable Building Envelope Centre (SBEC) in

Shotton, Wales.

2012

Northwestern University researchers

announced a solution to a primary problem of DSSCs

that of difficulties in using and containing the liquid

electrolyte and the consequent relatively short useful

life of the device. This is achieved through the use of

nanotechnology and the conversion of the liquid

electrolyte to a solid. The current efficiency is about

half that of silicon cells, but the cells are lightweight

and potentially of much lower cost to produce.

2013

During the last 5–10 years, a new kind of

DSSC has been developed - the solid state dye-

sensitized solar cell. In this case the liquid electrolyte

is replaced by one of several solid hole conducting

materials. From 2009 to 2013 the efficiency of Solid

State DSSCs has dramatically increased from 4% to

15%. Michael Graetzel announced the fabrication of

Solid State DSSCs with 15.0% efficiency, reached

by the means of a hybrid perovskite CH3NH3PbI3

dye, subsequently deposited from the separated

solutions of CH3NH3I and PbI2.

2014

At University Malaya, Dr. Wee Siong Chiu

and colleagues were working on controlling the

secondary nucleation and self-assembly in zinc oxide

(ZnO), a material which is currently being

scrutinized for its potential applications in dye-

sensitized solar cells as well as photo catalytic

reactions to generate clean electricity by splitting

water under sunlight. In this work, Dr. Chiu and

Alireza Yaghoubi demonstrated a new route for

synthesis of various zinc oxide nanostructures using

the lipophilic interactions between a novel precursor

and a number of fatty acids. They are hoping to

further use this method to increase the efficiency of

photo catalysts in the visible regime where most of

the sunlight energy lies. According to the

researchers, if this approach is successful, generating

electricity is as easy as pouring some bio-inert

nonmaterial into a lake and fusing the split oxygen

and hydrogen atoms back into water in a photo

electrochemical cell.

2015

Yiying Wu, professor of Chemistry &

Biochemistry at Ohio State University have

developed the first aqueous flow battery with solar

capability. This solar flow battery design can

potentially be applied for grid-scale solar energy

conversion and storage, as well as producing

‘electrolyte fuels’ that might be used to power future

electric vehicles,” In tests, the researchers compared

the solar flow battery’s performance to that of a

typical lithium-iodine battery. They charged and

discharged the batteries 25 times. Each time, both

batteries discharged around 3.3 volts. The difference

was that the solar flow battery could produce the

same output with less charging. The typical battery

had to be charged to 3.6 volts to discharge 3.3 volts.

The solar flow battery was charged to only 2.9 volts,

because the solar panel made up the difference.

That’s an energy savings of nearly 20 percent. This

Solar panel is called dye-sensitized solar cell or, as

Wu and his team have dubbed it, the first “aqueous

solar flow battery.”

“Prototype aqueous solar

flow battery under

development at The Ohio

State University. The square

piece of solar cell is red,

because the researchers are

using a red dye to tune the

wavelength of light it

absorbs and converts to

electrons.”

Giuseppe Calogero and his team have developed

vegetable based dye-sensitized solar cells. Vegetable

dyes, extracted from algae, flowers, fruit and leaves,

are being used as sensitizers in DSSCs. Thus far,

anthocyanin and betalain extracts together with

selected chlorophyll derivatives are the most

successful vegetable sensitizers

Contact Information

Address: Walchand Centre for Research in Nanotechnology

& Bio-nanotechnology, Walchand College of Arts & Science,

W.H. Marg, Ashok Chowk, Solapur – 413006.

Website: www.wcrnb.com

Email: info@wcrnb.com Office No.: 0217-2651863

(A leading Institution Developing Nanotechnology)

Of

Walchand College of Arts & Science, Solapur

is starting M.Sc. in Nanotechnology from June 2016

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