International Journal of Renewable Energy Development


Int. Journal of Renewable Energy Development 4 (2) 2015:77-93 
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© IJRED – ISSN: 2252-4940, July 15,2015, All rights reserved 

 Contents list available at IJRED website 
 

Int. Journal of Renewable Energy Development (IJRED) 
 
Journal homepage: http://ejournal.undip.ac.id/index.php/ijred 

 

Historic Developments, Current Technologies and Potential of 
Nanotechnology to Develop Next Generation Solar Cells with 

Improved Efficiency 

Nisith Raval and Ajay Kumar Gupta*  

 
Centre of Excellence in Nanotechnology (CoE-NT), Confederation of Indian Industry (CII), CII House, Gulbai Tekra Road, Near Panchavati, Ahmedabad - 

380006. Gujarat, India. 

 

Abstract: Sun is the continuous source of renewable energy, from where we can get abundant of solar energy. Concept of conversion of 

solar energy into heat was used back in 200 B.C. since then, the solar cells have been developed which can convert solar energy into the 

electrical energy and these systems have been produced commercially. The technologies to enhance the power conversion efficiency (PCE) 

have been continuously improved. Different technologies used for developing solar cells can be categorized either on the basis of material 

used or techniques of technology development which is further termed as ‘first generation’ (e.g. crystalline silicon), ‘second generation’ 

(thin films of Amorphous silicon, Copper indium gallium selenide, Cadmium telluride), ‘Third generation’ (Concentrated, Organic and Dye 

sensitize solar cell). These technologies give PCE up to 25% depending on the technology and the materials used. Nanotechnology enables 

the use of nanomaterial whose size is below 100 nm with extraordinary properties which has the capability to enhance the PCE to greater 

extent. Various nanomaterials like quantum dots, quantum well, carbon nanotubes, nanowire and graphene have been used to make 

efficient and economical solar cells, which not only provide high conversion efficiency economically but also are easy to produce. Today, 

by using nanotechnology, conversion efficiency up to 44.7 % has been achieved by Fraunhofer Institute at Germany. In this review article, 

we have reviewed the literature including various patents and publications, summarized the history of solar cell development, development 

of different technologies and rationale of their development highlighting the advantages and challenges involved in their development for 

commercial purpose. We have also included the recent developments in solar cell research where different nanomaterials have been 

designed and used successfully to prove their superiority over conventional systems. 
 
Keywords: Solar cell, Nanotechnology, Renewable energy, Photovoltaic, Power conversion efficiency 

 

Article History: Received March 20, 2015; Received in revised form May 12, 2015; Accepted June 10, 2015; Available online 
How to Cite This Article: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to 
Develop Next Generation Solar Cells with Improved Efficiency, 4(2), 77-93.  
http://dx.doi.org/10.14710/ijred.4.2-77-93 
 

 

                                                           
*
Ajay Gupta: Phone: +917940279996; Fax : +917940279999  

Email: ajay.gupta@cii.in 

1. Solar cell: historic developments and the current 
scenario 

By the year 2050, global energy demand will be 
more than two times and it may be three times by the 
end of this century. The Scope, to compete these 
increasing demand is the major challenges for achieving 
technological advancements, economic growth, and 
political stability. Advancement of existing technologies 
will not bridge the gaps between today’s need and 
tomorrow’s requirements. It must require additional 
source of energy and technologies to harvest the energy 
efficiency from these source over the next half-century 

with the capacity to double the today’s energy output. 
The sun is the natural source of energy which delivers 
more energy to the earth in an hour than we use in a 
year from fossil, nuclear, and all other renewable 
sources together. Currently we are using only 0.1 % of 
our primary energy from sunlight. 

In the last few decades, there had been growing 
research and developments in the area of solar cell 
technologies where the sunlight can be used as a source 
to generate electricity through photovoltaic effect. 
However this concept of solar technology is not new 
and find references as early as in centuries Before 
Christ (B.C.). In 3rd Century B.C., burning mirrors were 

http://dx.doi.org/10.14710/ijred.4.2-77-93


Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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© IJRED – ISSN: 2252-4940, July 15, 2015, All rights reserved 

used to light torches by Greeks and Romans for 
religious purposes (Anuradha, Lovish & Pranjal 2013). 
Later, in 212 B.C., the Greek scientist, Archimedes used 
sunlight to set fire to wooden ships by using the 
reflective properties of bronze shields. During the era of 
1st to 17th centuries, there were many reports indicating 
the use of solar energy in houses and public buildings 
for getting the warmth in winter seasons. 

During the next two centuries (i.e. 18th and 19th 
century), there had been many developments and 
breakthroughs in the use of solar technologies. These 
developments are reported in the Table 1. All these 
milestones utilize different processes / technologies to 
harvest solar energy for use by the society (U.S 
Department of Energy 2015). However, still there was 
no scientific discovery or mechanism available which 
could be used at a commercial scale by mass public. 

Table 1 
History of solar cell (1700 – 1899) 
Sr. No. Year Historical Developments / Milestones 

1 1767  World’s first solar collector / cooker 
was developed to cook the foods by 
Swiss scientist Horace de Saussure. 

2 1816  Robert Stirling and Lord Kelvin 
developed a thermo-solar cell to 
concentrate sun’s thermal energy to 
produce power. 

3 1839  French scientist Edmon Becquerel 
discovered the photovoltaic effect for 
the first time by using an electrolytic 
cell using electrolysis phenomenon.  

4 1860  French August Mouchet developed the 
solar powered steam engine for 
industrial applications. 

5 1873  W. Smith discovered the 
photoconductivity of selenium. 

6 1876  William Grylls Adams and Richard E. 
Day discovered the concept of 
selenium based solar cells and later in 
year 1883 Charles Fritts developed 
the first selenium wafer based solar 
cells. 

7 1880  Samuel P Langley invented bolometer 
to measure light from the sunrays. 

8 1891  C. Kemp patented the first commercial 
solar water heater. 

9 1888 –1897  Several scientists granted patents on 
solar cells. 

 
However, at the same time (during the 18th and 19th 

century) several significant developments took place in 
the form of the industrial revolution which includes the 
machine based process, new chemical manufacturing, 
efficient hydro power production, increase the 
acceptance of steam and coal as a fuel source. However, 
as the industrialization progressed across the sectors, 
demand for the energy kept on rising. Earlier, the 
machines were operated manually which gradually 
started shifting to automatic operation where human 
intervention was minimal. These modern machines 
required energy (e.g. electrical, hydrothermal, steam 
engines, etc.). Due to this, there was growing need of 
energy for industry as well as society. 

1.1 Birth of modern technology 
In order to fulfil the future energy requirements, it 

was highly desirable to develop the technologies and 
devices which can capture the sun light and convert it 
into the form which can be put to use by the society. The 
beginning of 20th century brought more knowledge and 
improvement in the technologies used to harvest solar 
energy.  Table 2 gives the glimpse of the developments 
happened during the century (U.S Department of 
Energy 2015; Affordable solar 2015; Wikipedia, 
Timeline of solar cell 2015; Experience 2015). 

 
Table 2 
History of solar cell (1900 – 2010) 

Sr. 
No. 

Year 
Historical Developments / 

Milestones 
1 1900 –1950  Albert Einstein discovered the 

photo-electric effect (Year 1905). 
 Carnegie steel company invents 

copper coil based solar collector 
(year 1908). 

 Silicon (single crystalline) was 
developed by Jan Czochralski, a 
polish scientist (year 1918). 

 Photovoltaic effect was discovered 
in cadmium sulfide based solar cell 
by Audobert and Stora (year 1932). 

 Passive solar building in US was 
built (year 1947). 

2 1951 – 1960  Bell Labs invented solar cell 
(silicone) with about 6% efficiency 
to run daily equipment’s (year 
1954). 

 Western Electric licenses 
commercial solar cell technologies 
(year 1955). 

 Between years 1957 – 1960, 
Hoffman electronics achieved 8 – 
14 % efficient in solar cell. 

 Silicon sensors started producing 
selenium and silicon solar cells 
(year 1960). 

3 1961 – 1970  The Telstar communications 
satellite is powered by solar cells 
(year 1962). 

 Sharp Corporation produces a 
module of silicon based solar cells 
(year 1963). 

 Japan installed a 242 watt solar cell 
array on a light house (year 1963) 

 First manned spacecraft (Soyuz 1) 
was powered by solar cells (year 
1967). 

 Exon Corporation produced 
cheaper solar cells which could be 
used in remote locations where grid 
connections were not feasible (year 
1970). 

4 1971 – 1980  First amorphous silicon solar cells 
were created by David Carlson and 
Christopher Wronski, with 1.1% 
efficiency (year 1976). 

 The world production of 
photovoltaic cells exceeded 500 kW 
(year 1977). 

 Salyut-1, Skylab, Florida Solar 
Energy Centre, The University of 
Delaware’s “Solar One” residential 
building, Solar Energy Research 



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Institute at Colorado, Solar panels 
in White House, USA, Calculators 
etc. powered by solar energy were 
developed in this decade.    

 First thin film solar cell was 
developed by University of 
Delaware with 10% efficiency using 
Cu2S/CdS technology (year 1980). 

5 1981 – 1990  ARCO Solar produces > 1 MW of 
solar modules/year in California 
(year 1982). 

 Volkswagen, Germany tested solar 
arrays on the roof of Dasher station 
wagons (year 1982). 

 Global photovoltaic production 
exceeds 21.3 megawatts (year 
1983). 

 Centre for Photovoltaic Engineering 
created 20% efficient silicon cells at 
the University of New South Wales 
(year 1985). 

 World’s largest solar thermal 
facility located in Kramer Junction, 
CA, was commissioned (year 1986). 

 ARCO Solar released first thin film 
power module (year 1986). 

 Michael Gratzel and Brian O'Regan 
created world cheapest dye 
sensitize solar cell (year 1988). 

 Dr. Alvin Marks granted patents for 
Lepcon and Lumeloid (year 1988). 

6 1991 – 2000  National Renewable Energy 
Laboratory was established by 
President George H. W. Bush (year 
1991 – 1994). 

 University of South Florida 
achieved 15.89 % efficient in thin-
film cell (year 1992). 

 NREL achieve 30 % efficiency using  
GaInP/GaAs two - terminal   
concentrator cell  (year 1994). 

 Graetzel, Switzerland achieves 11% 
efficient energy conversion using a 
photo electrochemical effect in dye-
sensitized cells that (year 1996). 

 Total worldwide installed 
photovoltaic power reaches 1,000 
megawatts (year 1999).  

 Spectrolabs, Inc. and NREL 
developed solar cells with an 
efficiency of 32.3% (year 1999).  

 NREL achieved 18.8% efficient in 
thin film solar cells (year 1999). 

7 2001 – 2010   BP Solarex developed highest solar 
modules of 10.8 % conversion 
efficiency achieved by 0.5 Sq. meter 
and 10.6 % achieved by 0.9 Sq. 
meter (year 2000). 

 Terra Sun LLC developed unique 
method holographic films to 
concentrate sunlight onto a solar 
cell (year2001). 

 Power Light Corporation developed 
word largest hybrid system (Wind 
and solar energy) to maximize the 
power generation (year 2001). 

 The University of Delaware 
achieved a new efficiency of 42.8% 
(year 2007). 

 China produced nearly half (1700 
MW) of the world production (3800 
MW) of solar panels (year 2007). 

 The installation cost of PV modules 
decreased from 16000 $/KW in 
1990’s to 6000 $/KW (year 2008). 

 World solar cell production reached 
9,340 MW (year 2009). 

 

Solar cell is an electrical device which converts the 
light energy into electric energy by photovoltaic effect. 
In simple words, upon exposure of solar cell with light, 
it can generate an electric current without being 
attached to any external voltage source. But do require 
an external load for power consumption. Recent 
technologies like screen printing and solar fabric can 
enable to install the solar cell inside the house, even on 
the roof. Today International market have opened up, in 
which solar panels manufacturer are now playing a key 
role in the solar power industry. 

2. Solar Cell Technology 

Photovoltaic (PV) is a similar term of solar cells, as 
an electronic devices that convert sunlight directly into 
electricity. The modern age solar cell was invented at 
Bell Telephone Laboratories in 1954. A solar cell are 
grouped together to form a solar module. Auxiliary 
components of solar cell (i.e. balance of system - BOS) 
comprise inverter, controls, etc. Today, solar cell is one 
of the fastest growing renewable energy technologies 
and in the present context, solar cell systems may be 
considered as one of the most abundant renewable 
technologies (IRENA 2012). This is because of the 
availability of innovative technologies, which makes it 
feasible to develop efficient modular size with ever 
increasing power conversion efficiency that they are 
within the reach of individuals, co-operative societies 
and small businesses who can install these modules for 
electricity generation and manage to lock-in prices. 
Over other conventional technologies solar cell 
technology offers additional benefits like renewable 
source of energy, readily available across the globe, 
small and highly modular sizes of solar devices can be 
installed anywhere at shade-free locations e.g. roofs, 
gardens etc. Solar cell generate electricity by harvesting 
sunlight and hence require no fossil fuels like nuclear, 
oil, coal, gas etc., thereby requires relatively low 
production, operation and maintenance costs. Today, 
wide ranges of technologies are available using different 
types of materials in solar cell. Hence with the huge 
scope, the future of solar cell is looking bright. Solar cell 
technologies are categories into three generations, viz. 
first-generation, second generation and third 
generation based on the material used.  

2.1.  First generation technologies 

Silicon is a semi-conductive material widely use in 
solar cell applications. Energy band gap of crystalline 
silicon is about 1.1 eV, which make crystalline silicon 
more suitable for conversion of sun energy into electric 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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energy. Out of all other materials tried till now, silicon 
have achieved conversion efficiency around 15 to 20 % 
at commercial scale (Kenneth & Paul 1982). This 
technology has a long history of reliable performance 
with lifetime of more than 25 years. First-generation 
solar systems use single types of material i.e. crystalline 
silicon (c-Si), either as single crystalline (SC-Si) or as 
multicrystalline (mc-Si). Single crystalline silicon 
wafers, which are cut from single crystal silicon ingots 
to make monocrystalline solar cell. Comparatively 
monocrystalline silicon has capacity to higher efficiency, 
but it is very difficult to produce from ingot silicon 
crystal. Hence it is very energy intensive and expensive 
to grow. While multicrystalline wafers are cut 
directionally solidified blocks or grown in thin sheet so 
it is easy to build up and they are less expensive. To 
prepare single crystal silicon from multicrystalline 
silicon, first and foremost requirement is molten state 
of silicon and follow by solidification in a manner to 
arrange the silicon atoms themselves in a perfect lattice 
as occur naturally. General procedure requires initial 
contact of single crystal seed of silicon with the molten 
state and enables to cool down slowly. As the single-
crystal silicon is grown, appropriate substances or 
dopants are like to introduce to tune the material 
electric behavior as per requirement. Dopants like 
boron and phosphorus have been used to obtain 
electron donor and electron acceptor to complete the 
photoelectric circuit (Kenneth & Paul 1982). 
Advantages of monocrystalline silicon are that the 
monocrystalline cells have the highest efficiency, very 
stable and are simple type of solar cell. Drawback of 
these monocrystalline silicon based solar cells is that 
they are more expensive and they do not perform 
efficiently at elevated temperatures (Wide Bay Burnett 
Conservation Council Inc. WBBCC 2010). Crystalline 
silicon solar cells and modules have dominated 
photovoltaic technology from the beginning of solar cell 
history and contribute around 90 % in solar cell market. 
In 1996, electric output of single crystalline solar cell 
was 48.7 MW, which share 55 % of global solar cell 
market (Kenneth & Paul 1982). Multicrystalline solar 
cell output was 28.4 MW and occupies 32 % global solar 
cell market. In 2000, single crystalline cell output 
decreased to 32 % and for multicrystalline it increased 
to 51%. Such changes were observed because of 
expensive method of fabrication for single crystalline 
silicon solar cell. In 2004, china enters into the mass 
production of solar cell technology leads to capture 70 
% of total market of solar cell technology. So in 2013, 
monocrystalline wafer based technology holds 90 % of 
total market, while multicrystalline about 55 % 
(Fraunhofer Institute of Solar Energy System 2014). 

 
2.2. Second generation technologies 

Thin film solar cell as second generation technology, 
was developed to produce low cost electricity as 
compared to first generation solar cell. Thin film solar 

cell technology involve the deposition of a thin layer of 
about 4 µm thickness of photovoltaic material on 
substrates like steel, glass or plastic. As a result, very 
less amount of photovoltaic material is required to 
produce solar cells with good conversion efficiency 
which makes them feasible for commercial production. 
Thin film solar cells technology utilize non-crystalline 
material, has lower conversion efficiency ranging from 
4 to 12 %. Hence its power conversion efficiency is 
significantly lower in comparison with crystalline solar 
cells (International Energy Agency 2013). Photovoltaic 
materials like Amorphous silicon (a-si), Cadmium 
Telluride (CdTe), Copper indium selenide (CIS) and 
Copper Indium Gallium Diselenide (CIGS) are widely 
used to make thin film solar cell. Despite their lower 
efficiency, thin film solar cells enjoy good stability as 
well as good shelf-life comparable to c-Si module. In 
addition, they have short energy pay-back times which 
may be less than 1 year.  

Amorphous silicon (a-Si) 

In thin film solar cell technology, maximum efficiency 
was achieved with amorphous silicon as a photovoltaic 
material. Defective structure of amorphous silicon leads 
to high band gap 1.7 eV which in turn increases the 
absorptivity of sun light to almost 40 times as compared 
to monocrystalline silicon solar cell (Abdin et al. 2013). 
However, the main problem with amorphous silicon is 
the degradation of silicon in sun light, so overall 
efficiency of solar cell diminishes as a function of time. 
Various approaches have been utilized to overcome the 
above problems. One of the approach is the deposition 
of amorphous silicon material by plasma vapor 
deposition technique with as minimum thickness as 
possible as to strengthen the electric field across the 
material and its stability (Anas I.A.T. 2007). But as the 
thickness of the film decreases, light absorption 
capacity decreased and hence cell efficiency also got 
reduced. So to overcome the lower absorption and 
conversion efficiency, double, triple or multi junction 
thin film silicon solar cell approaches were explored. 
Such approaches comprised of the use of thin layer of 
amorphous silicon and subsequent layer of 
microcrystalline silicon on to the amorphous silicon. In 
year 2009, amorphous silicon panels achieved efficiency 
of 6-9 % (Green et al. 2011). Afterwards, Switzerland 
based company Oerlikon announced test panels that can 
reach power conversion efficiency of around 11 % using 
a multifunction technology (Greentechmedia 2009). 
Advantage of using amorphous silicon in producing thin 
film solar cell is that, it is not only very economical but 
also compatible with other materials.  
 
Cadmium Telluride (CdTe) 

Cadmium is a by-product of zinc during mining and 
tellurium is a by-product of copper processing. 
Cadmium telluride thin film is the most economical thin 



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film technology out of currently available technologies. 
Its band gap is about 1.5 eV, which match with the solar 
spectrum. In 2011, CdTe thin film achieved very high 
efficiencies up to 16.7% with low production cost than 
other thin-film technologies (International Energy 
Agency 2013). Efficiency of CdTe solar cells depend on 
various parameters e.g. deposition technique, substrate 
and deposition temperature etc. Its band gap can be 
varied by using various approaches like hetero-junction 
or multi-junction solar cell which lead to increase in 
efficiency up to 18% (Noufi & Zweibel 2006). Various 
methods are available to deposit CdTe on substrate as 
mentioned in table 3 (Koch et al. 2011). A potential 
problem of cadmium telluride is the production 
quantity of telluride and availability, which is depend on 
extraction, refining and recycling yield of copper 
industry. Toxicity of telluride is another problem for 
solar cell industry. 

Table 3 
Thin Film deposition technique (Koch W et al 2011) 

Sr. No. Name of CdTe thin-film deposition techniques 

1 Close space sublimation 
2 Vapor transport deposition 
3 Physical vapor deposition 
4 Sputter deposition 
5 Electrode deposition 
6 Metal organic chemical vapor deposition 
7 Spray deposition 
8 Screen print deposition 

 

Copper Indium Gallium Selenide (CIGS) 

As CIGS is a new technology so still it is in developing 
stage and is set to compete with other technologies. 
Solar cells based on CIGS offer the highest efficiencies 
among all thin-film Solar cell technologies. Power 
conversion efficiency of solar cell have been achieved up 
to 20 % at laboratory scale and 7 to 16% was achieve at 
commercial scale which is close to that of crystalline 
Silicon cells (International Energy Agency 2013). In this 
case, band gap can be modified by varying the Group III 
cations from Indium, Gallium, and Aluminum and the 
anions between Selenium and Sulfur. Using 
combinations of different compositions enable to make 
wider the range of energy band gap. Semi conductive 
materials like CuInSe2 (CIS), Cu(InGa)Se2 (CIGS) and 
CdTe are widely accepted because of their high 
efficiency, long-term stable performance and potential 
for low-cost production (Noufi & Zweibel 2006). Thin 
layer of around 2 mm is sufficient enough to absorb the 
useful part of the solar spectrum because of its high 
absorbing power. As compared to other technologies, 
the manufacturing process is more complex and costly. 
Hence, by replacing indium with low cost materials 
could help to reduce the cost. Currently, researchers are 
more attracted towards the application of 
multicrystalline solar cell for space applications due to 
its excellent photovoltaic effect than silicon. However, 

thin film manufacturers start adopting modification in 
existing technology because of low cost crystalline 
silicon modules are available in the market. Four 
different types of thin film solar cell with power 
conversion efficiencies are described below in Fig 1 
(EPIA- Europian Photovoltaic Industry Association 
2011). 
 

 
Fig 1: Second generation solar cell efficiency for laboratory scale and 
commercial scale. 

2.3. Third generation solar cell 

Third generation solar cell technologies includes 
concentrating PV (CPV), Dye sensitize solar cell and 
organic solar cells. Even with extensive efforts these 
technologies are still under demonstration and have not 
yet been widely commercialized.  

Concentrated photovoltaic cell (CPV) 

Concentrated photovoltaic (CPV) cell enable to 
concentrate a large amount of sunlight onto a small area 
of solar photovoltaic (PV) cells to generate electricity 
using optics as a main component which includes lenses 
or curved mirrors. A concentrator is usually made up of 
relatively inexpensive materials such as plastic / glass 
lenses to capture the sunlight falling on a large area and 
concentrate that energy onto absorbent (IRENA - 
International Renewable Energy Agency 2013). CPV 
technology has many advantages like it can operate at 
elevated temperature, produce more power in 
minimum time, have slow degradation compared to 
earlier generation solar technologies and have much 
higher power conversion efficiency. Mirrors or lenses 
decrease the cost of solar cell significantly than other 
expensive solar cell (IRENA - International Renewable 
Energy Agency 2013). CPV systems are classified 
according to the amount of the concentrated solar 
energy, measured in ‘suns’ (the square of the 
magnification): (I) Low concentration PV systems with a 
solar concentration of 2-100 suns, (II) Medium 
concentration PV systems with a solar concentrations of 
100 to 300 suns and (III) High concentration 
photovoltaic (HCPV) systems with a solar 
concentrations of 1000 suns or more (Wikipedia, 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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Concentrated photovoltaic 2015) . Today’s CPV systems 
have system efficiencies almost 30%, which incorporate 
highly efficient III-V silicon solar-cells. The installation 
costs of CPV systems today are very competitive to flat-
plate PV systems. At commercial scale silicon based CPV 
have achieved 20 to 25% power conversion efficiency 
(Robert & Vasilis 2012). At laboratory scale, more than 
40% of power conversion efficiency was achieved using 
III-V semiconductors in multi-junction CPV. Their 
higher efficiency and the smaller PV surface area 
required may eventually reduce the overall costs. For 
techno-commercial reasons, the utility market is the 
most popular market for CPV companies. In 2008, 
according to a Green media survey there were 10, 38, 
and 46 companies available in the market with their 
CPV products in residential, commercial and utility 
segment respectively (Sorin, Elizabeth & Travis . 2008). 
SOITEC in Europe is another firm with multi junction 
cells announced for 4-junction devices, at 43.6% 
conversion efficiency under 319 suns (Solar server 
2013). In 2012, the Fraunhofer Institute for Solar 
Energy Systems fabricated multi-junction photovoltaic 
cell with 44.7% power conversion efficiency and 
breaking its own record of 43.6% set just four months 
prior (Maria 2013). 

Dye sensitized solar cell (DSSC) 

Dye-sensitized solar cells combining the unique 
properties of both the organic compound and inorganic 
compound have attracted the attention of scientists in 
the recent years. In the conventional solar cell systems, 
semiconductor material plays the dual role of photon 
absorber and charge carrier. On the other hand, DSSC 
separate these two functions to two different materials, 
i.e. the organic molecule usually a dye as a sensitizer 
absorbs sunlight and the second inorganic molecule 
then transforms solar energy into electric energy. First, 
light is illuminated onto a dye which in turn excites 
electrons in the dye. The excited electrons further excite 
the electrons in titanium dioxide (TiO2) film and 
ultimately reaching the electrode through diffusion. On 
the counter electrode, generated electrons reduce I3

－ 

ions to I－ ions and diffuse in the solution, reach the dye, 

give up electrons, and are oxidized forming I3
－ ions 

(Tomohiro & Hirohiko 2009). Numerous metal 
complexes and organic dyes have been used as 
sensitizers in solar cell. Photo excitation at a monolayer 
of organic dye results in the injection of an electron into 
the conduction band of oxide. Then, organic dye 
restores its original electron configuration by electron 
donation from the electrolyte, usually an organic system 
containing redox couples. N3 dye, RuL2(NCS)2, and 
Black dye, RuL(NCS)3, are the most commonly used as 
an organic dyes in DSCs. Main drawback with organic 
dye based DSSC is the toxicity of organic dye as well as 
the stability of electrolyte at elevated temperature. Such 
problem can be solved by using natural dye because 

they are biodegradable, cheap and abundant. By using 
synthetic organic dyes in DSSC, highest efficiency of 11-
12 % have been achieved, while with natural dyes 9.8% 
was achieved. Natural dyes from flower, fruit or 
vegetable are capable to act as a photo sensitive 
material in DSSC. Highest efficiency of 7.6 % have been 
achieved by using coumarin as a natural dye (Souad et 
al. 2013). However DSSC have certain drawbacks e.g. 
low stability of dye and electrolyte solution at elevated 
temperature and lesser efficiency compared to other 
solar cell technologies. Need of the hours is to find out 
the solutions to increase the stability of dyes and 
electrolytes in these DSSC and at the same time increase 
the efficiency. Despite these problems, it is expected 
that the DSSC will become the future of solar cells 
technologies to provide the cheap energy due with high 
conversion efficiency.  

Organic solar cell (OPV) 

Within the last three decades, tremendous effort 
have been made to develop organic solar cells common 
materials used for photovoltaic devices are inorganic. 
The incorporation of semiconducting polymers into 
organic solar cells resulted in remarkable 
improvements within last few years. The sp2-
hybridization of carbon atom of semiconducting organic 
materials is responsible for the absorption of visible 
solar region and to transport the electrons to generate 
the electricity. Basically, four consecutive steps are 
involved towards working principle of organic solar cell 
i.e. light absorption, excitation, charge transport and 
collection (Myung 2009). Organic solar cells are 
classified on the bases of number of electron 
transporting layer available in the device namely single, 
double and triple layer organic solar cell (Daniel & 
Darren 2013). In 1994 A.D. R. N. Marks et al. prepared 
an organic solar cell having poly (p-phenylene vinylene) 
of 50-320 nm thickness in sandwiched manner between 
Indium titanium oxide (ITO) and cathode with 0.1% 
power conversion efficiency under 0.1mW/cm2 
intensity. The reason behind such low efficiency is due 
to intrinsically low mobility of charges through 
semiconducting organic. Organic solar cells have unique 
and significant advantage like these devices are not only 
low costs per module, but also their thinness and 
extremely small mass could also reduce the costs 
associated with transportation and installation of 
modules. So aim of the electronic segment is to set the 
application of electronics everywhere for the 
development of next generation. With these, semi 
conductive organic industry will play a vital role in 
upcoming future technologies. Multidisciplinary 
approach of organic solar cell with other components 
like batteries, in fuel cell etc. will enhance their 
production efficiency. This integration of organic solar 
cells into many products will be their technological 
advantage. Owing to the lack of scalable high 



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performance donor materials, conversion efficiency of 
OPV is usually lower than other available solar 
technologies. Studies on mass-produced organic 
photovoltaic (OPV) devices lag far behind that on lab-
scale devices. Power conversion efficiencies (PCE) of 6–
7% have been achieved for OPV devices based on 
different active layers using different organic polymers. 
Recently it has been reported that 8.4% efficient 
fullerene-free organic solar cells were developed which 
exploited long-range exciton energy transfer. In one 
study PCE as high as 15% has also been reported and 
the technology was already patented by the inventors 
(Ning et al. 2013). Glimpse of power conversion 
efficiency (PCE) of all three generation technologies for 
solar cells in terms of laboratory scale and commercial 
scale as mentioned in Table 4 (Georg, Enrico, & Yoann 
2012). 

Table 4 
The list of technologies with efficiency at laboratory Vs. commercial 
scale with their market share 

Technology Material PCE at 
Labor
atory 
scale 
(%) 

PCE at 
Comm
ercial 
scale 
(%) 

Market 
share 
(%) 

First 
generation 

Crystalline 
Silicon (Multi 
crystalline 
and Mono 
crystalline) 

28 16-20 85 

Second 
generation 

Amorphous 
Silicon 

10 8 14 

CdTe 16 11 

Cu(InGa)Se2 20 12 

Third 
generation 

Organic Solar 
cell 

12 8 1 

Dye Sensitize 
solar cell 
(DSSC) 

10 – 
15 

11 

Concentrated 
Solar cell 

43.6 31.8 

3. Current trends towards applications of 
Nanotechnology in solar cell 

Current solar cell technologies have two major 
drawbacks i.e. low conversion efficiencies and high 
manufacturing cost for generation of electricity at 
commercial scale.  Nanotechnology is an emerging 
technology that has the potential to provide solution to 
above problems. As the nanotechnology make use of 
materials, which are very small in size (less than 100 
nm) having very large surface area. Such properties can 
enhance the efficiency manifold and also at the same 
time reduce the sizes of the devices. Currently, most 
commercial solar cell utilize silicon based semiconductor 
materials. But in the past few years, scientists have been 
investigating to increase the efficiency of solar cell using 
nanotechnology. Use of nanomaterial would provide the 
new ways to capture, store and exchange energy. Three 

basic advantage have been offered by nanotechnology 
based solar cell. First advantage is the large surface area 
offer enhanced solar absorption. Second, light generated 
electrons and holes need to travel over a much shorter 
path and thus recombination losses are greatly reduced. 
Third  the tunable energy band gap by varying the size of 
nanoparticles. This allows for the much needed 
flexibility in designing of solar cells. Currently various 
nanomaterials have been explored to develop the solar 
cells. Among these materials quantum dots, quantum 
wells, carbon nanotubes and nanowires are most widely 
studied (Abdin et al. 2013). 

3.1 Quantum dots (QDs) 

Quantum dots are minute crystal composites of size 
less than 10 nm are having tremendous semi conductive 
properties. These properties are responsible due to their 
ability to enhance light absorption and absorb the 
infrared range. Quantum dots has potential to tune the 
band gap upto optimum value to enhance the maximum 
efficiency. It can be applied to single junction solar cells 
with different band gap to form a tandem cells. Due to 
significant properties like significant absorption of 
infrared radiation, at higher temperatures it increase the 
photo current and efficient radiation hardness. 
Theoritically it was predicted that the efficiency of QDs 
can be achieve up to ~64% for a well-adjusted 
intermediate band in a solar cell. A solar cell uses 
quantum dots as the light absorbing material can be use 
rather than known bulk materials such as silicon, copper 
indium gallium selenide (CIGS), TiO2, ZnO or CdTe (Sethi, 
Mukesh, & Priti 2011). 

Silicon based QDs have been proved to provide better 
power conversion efficiency as compare to bulk Silicon 
due to the following reasons that (Georg, Enrico, & 
Yoann 2012): 

[1] Increase in the energy gap with decrease in the size 
of the QDs. Due to enhanced energy gap, widening in 
the distance between the energy states occurs. As a 
result, the relaxation of the excited carrier is slow 
down with respect to bulk silicon (Hot carrier solar 
cell). 

[2] Si QDs exhibit strong photoluminescence in the 
visible red region of the solar spectrum. QDs can 
generate multiple excitons in silicon atom with 
twice or more energy than the band gap, thereby 
splitting the excited exciton into ‘n’ excitons without 
losing the excess energy in the form of heat. 

QDs have many advantages like size dependent 
tunable energy band gap, strong photoluminescence, 
generation of multiple excitons etc. Various approaches 
have been tried by using QDs for solar cell in order to 
increase power conversion efficiency like (a) QDSSCs 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
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(Quantum dot sensitize solar cell), here QDs act as an 
alternative to the dye molecule in Dye sensitized solar 
cell. (b) Crystal QDs.to combine the quantum dots 
inherent tunability with a simple manufacturing process 
in order to reduce the cost. (c) Multi junction solar cell 
(d) Organic solar cell: 

Developments of solar cell using quantum dots (QDs) 

According to US patent US20100012168, 
US20130042906, US8395042, a quantum dot sensitized 
solar cell including an anode, a cathode and an 
electrolyte is provided. The anode includes a 
semiconductor electrode adsorbed with a plurality of 
quantum dots. This include a tunable electron conductor 
that permits greater choices in quantum dots, thereby 
providing solar cells that can be constructed to utilize a 
broad light absorption range that covers the ultraviolet, 
visible and infrared regions leading to an improved 
conversion efficiency of the solar cell. The size and 
composition of a quantum dot can determine its band 
gap and Fermi level (Mihai, Viorel-Georgel, Cornel, 
Mircea , Bogdan-Catalin 2010; Ming-Way 2013; Neil, 
Friedrich, Timothy, & James, 2013). Various approaches 
have been explored to increase power conversion 
efficiency like QD’s core-shell structure, QD’s absorb 
light and emit red shifted light which can absorb by 
active layer and by depositing QD’s on CNT/ Nanowire, 
20nm ZnO mesoporous photo anode to achieve 12 % 
which was claimed by US patent application 
US2008/000183, US20120132891 and CN2011/000860 
(Istvan et al 2006; Troy 2008; Prashant K. et al 2008; 
Mircea, Bogdan-Catalin, 2010; Leonard & Jeeseong, 
2012; Robert et al 2012; Mihai, Viorel-Georgel, Cornel, 
Chunhui  2013). Material used for QD’s solar cell are 
CdSe, ZnS, CdSe, InGaAs, InGa, InAs, Germanium, CdS, 
PdS and InP as per US8658889, US20110146772, 
US8072039, US20050155641, EP2442326 and 
US8574685 (Hiroaki 2011; Kyung-Sang, Byung-ki. 2011; 
Simon 2011; Anna, Zhi, Linan, Marilyn, 2013 & Jason, 
Xiaomei 2013; Kun-Ping 2014). Porphyrin-sensitized 
solar cells with cobalt (ii/iii)–based redox electrolyte 
and zinc porphyrin dye as sensitizer were succeeded to 
achieve 12.3% efficiency (Aswani et al. 2014). 

Patent US7402832 claimed that core-shell defect free 
silicon quantum dot exhibits photoluminescence with 
power conversion efficiency is greater than 10 % 
(Howard & Hoon 2008). Light scattering Silicon and Gold 
Nanoparticle shown improved performance of quantum-
well solar cells with a 17% power conversion efficiency 
(Derkacs et al. 2008). 94% of the light can absorb by 280 
nm thick hydrogenated amorphous silicon (A-Si:h) layer 
in nano dome based solar cell. It is higher than the 65% 
absorption of flat film devices, due to efficient light 
management and self-cleaning concept (Ekins-daukes et 
al. 2010). Facilitation of significant electric interaction 
provided by P3HT−CdSe nanocomposites having well-

defined interface. It also promoting the dispersion of 
CdSe within the P3HT matrix efficiently (Xu et al. 2007). 
Power conversion efficiency about 6 % was achieved 
using co-polymer, poly [n-9-hepta-decanyl-2, 7-
carbazole-alt-5, 5-(4', 7’-di-2-thienyl-2', 1’, 3’-
benzothiadiazole) (PCDTBT) in bulk heterojunction 
composites with the fullerene derivative [6, 6]-phenyl 
c70-butyric acid methyl ester (PC70BM). Conversion of 
sunlight to electricity to supply for future generation is 
considered to be a major task. To address a future need 
of electricity, the cost of solar energy will have to be 
significantly lower and the efficiency will have to be 
increase significantly. So with these requirements, 
research on nanostructure Si QDs for application in solar 
cell has enormously increased. However, a deep 
scientific investigation of using these structures is 
required to outperform the C-Si solar cells to meet future 
energy needs. 

3.2 Quantum well (QW) 

Barnham and co-workers at Imperial College 
proposed and demonstrated the first quantum well solar 
cells (QWSCs) a decade ago. It was based on the 
hypothesis that quantum wells could extend the spectral 
response and increase the photocurrent of solar cells 
without degrading their voltage characteristics. Hence 
initial proposal for these devices was motivated by the 
goal of enhanced energy efficiency. Early experiments on 
AlGaAs-based cells indeed revealed that introduction of 
GaAs quantum wells enhanced both the photocurrent 
and power conversion efficiency under broadband 
illumination. These results motivate the researcher to 
explore quantum well phenomenon to enhance power 
conversion efficiency (Keith et al. 1997). 

In the past few years researcher are more attracted 
towards quantum well solar cells (QWSC). Quantum well 
solar cells (QWSC) is a thin layer of material posing a 
lower band gap than the surrounding barrier or host 
material. Quantum well must be sufficient thin to bring 
about quantum effect through the confinement of 
electron and holes, so its dimension is in range of few 
nanometers. Hence its novel structure has potential to 
achieve high efficiency if the absorption spectra of 
absorbing material is wide by photo-generated electrons 
and holes escape from the wells and increase the output 
current. A QWSC consists of a p–i–n-junction 
constructed from high band-gap semiconductor with 
thin layers of lower band-gap semiconductor to form 
potential wells, as shown in Fig 2. By the recombination 
in the bulk material, the open circuit voltage can be still 
controlled which is known as barriers. While the 
sections of lower band-gap material absorb low-energy 
photons that the barrier material which is known as 
well. For light with energy greater than the band-gap (E) 
the quantum-well (QW) cell behave like a conventional 
solar cell. However, light with energy below and above 



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the energy band-gap (Eg), can be absorbed in the 
quantum wells.  

In 2009, a single junction GaAsP/InGaAs quantum 
well solar cell attained a peak efficiency of 28.3% under 
solar concentration (Ekins-Daukes et al. 2013). Major 
benefit of incorporating a quantum well stack into a 
multi-junction solar cell is to increase the photocurrent 
up to 40 % with InGaP/ MQW/Ge. Hence additional 
current flow through the top and middle cells to increase 
the efficiency. Presently, QWSC efficiencies of 
approximately 20–25% are achievable. While in future, 
it can be expected that 35% efficiency or beyond is 
achievable using strain-balanced tandem QWSC in order 
to extend the spectral range (Rault & Zahed 2003). For 
single junction QWSC optical band gap can tune the 
thickness and composition to get highest efficiency 
efficiencies. 

 
Fig 2: Quantum well based solar cell. 

 

Development of solar cell using quantum well (QW) 

Prof Keith Barnham of Imperial College London 
invented the QW solar cell in 1989, which operated at 
high current and was made of alternating layers of 
InGaAs and GaAsP wile p and n layer are made from 
GaAs. In 2009, Prof Keith Barnham achieved the highest 
efficiency of a nano structure solar cell at 30.6 % 
obtained from a tandem junction QW solar cell at a 
concentration of 54 suns (Mazzer et al 2006). 

US patent US5496415 and US4688068 describe a 
solar cell formed from a semiconductor having a relative 
wide band-gap characterized by a multi-quantum well 
system incorporated in the depletion region of the cell. 
These quantum wells comprise regions of 
semiconductor with a smaller band gap. Material used 
for smaller band gap is InGaA, GaAs, GaP, and GaN 
(Gordon 1986; Keith  1996; Alexandre 2000; Liang, Ilyas 
& Masud 2013; Roger). These kinds of quantum well 
were able to achieve 12 % power conversion efficiency. 
It has been also discovered that the power conversion 
efficiency of InGaN/GaN based quantum well sola cell 
are inversely proportional to temperature (Ramesh et al 
2013). InGaN/GaN multiple quantum well (MQW) solar 

cells with enhanced power conversion efficiency using 
colloidal CdS quantum dots (QDs) and back-side 
distributed Bragg reflectors (DBRs) up to 20.7% (Yu-Lin 
et al. 2013). 

Patent US20120167973, EP2595193 and US8101856 
describe that solar cell were designed by using quantum 
well which is made up of polycrystalline silicon, 
germanium or GaP-Si. By incorporating hydrogenated 
nano crystalline silicon (nc-Si:H) and a-Si:H (nc-Si:H/a-
Si:H) multiple quantum wells (MQW) in the intrinsic 
region, absorption coefficient increases in three steps 
starting from 1.0 × 104 cm−1 to 3.0 × 104 cm-1 for photon 
energy of 1.2 eV to 1.4 eV, respectively. Therefore 
number of incorporation is directly related with the 
efficiency of solar cell (Ankur, Manvendra, Pratibha 
2014). 

The mitigation of the thermal scattering as well as the 
control of the light absorption range of quantum energy 
level is considered as a driving force for next generation 
solar cell. Multiple quantum wells (MQW) utilize 
absorbing material with multiple band gap to achieve 
higher conversion efficiency. This MQW thickness of the 
well layer (5-10 nm) is important to form quantized 
energy state in the well. MQW based solar cells 
demonstrate good temperature stability because of 
multi band gap structures. Due to this feature of MQWs 
they are also suitable thermo-photovoltaic applications, 
where heat generated from combustion process can be 
converted into electricity. These cells can also be used 
for spaces applications (Seung 2007). 

3.3 Carbon nanotube (CNT) 

Carbon nano tube (CNT) is made up of graphite sheet, 
which are rolled like a straw. It may be single rolled 
sheet single wall carbon nano tube (SWCNT) or multiple 
rolled sheet i.e. multiple wall carbon nano tube 
(MWCNT). Carbon nanotubes is considered as ideal 
material for solar cell due to wide range of direct band 
gaps from infrared to ultraviolet and high carrier 
mobility with reduced carrier transport scattering, 
which make themselves ideal photovoltaic material. 
Secondary advantage of carbon nanotubes is earth 
abundant, possess high optical absorption, and superior 
thermal and photo stability. The extraordinary 
properties of CNTs such as light weight, excellent 
mechanical strength, three dimensional flexibility and 
outstanding electro catalytic property, can improve the 
performance of solar cells. CNT nanostructured surface 
can also enhance the performance of both charge 
separation and electron transportation, so they can be 
applied as either a working electrode or counter 
electrode, or even as the conductive substrate as shown 
in fig 3. Electron mobility’s on the order of 10,000 
cm2/Vs have been measured for both metallic and 
semiconducting tubes. These extraordinary electronic 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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properties are due to low defect density and the one 
dimensional geometry (Yan et al. 2013).  

Utilizing the concept of the photo induced charge 
transfer between organic conjugated polymers as a 
donor and nanotubes as acceptor, CNTs and different 
polymers have been used extensively with an aim to 
increase the efficiency by three times. Hence CNT are 
considering as a promising candidate for solar cell by 
increasing conversion efficiency, increasing stability and 
decreasing cost (Maciej et al. 2011). 
 

 
Fig 3: Dye sensitize solar cell containing CNT as charge transfer layer 

 

Development of solar cell using carbon nanotube (CNT) 

Their low-cost processing is expected to become a 
method for commercially realistic energy conversion 
efficiency and the most probable technology to 
significantly contribute to renewable electricity 
generation in the coming years. Due to their electro 
catalytic properties carbon nanotube as an electrode 
increase power energy conversion of solar cell up to 7-9 
% (Chen et al. 2012). Recently, a dye-sensitized solar cell 
with a tube like structure achieves 4.16 % conversion 
efficiency, which is different from the sandwich 
structure of the traditional dye-sensitized solar cell 
(Yongping et al. 2012). 

So far, CNTs have been utilized in solar cell as a 
substitute of TiO2 either in counter electrode or photo 
anode with simple mixing in solid state electrolyte and 
with an engineered interfacial layer. Recently various 
approaches utilizing CNTs have been explored to 
increase the conversion efficiency of solar cell. TiO2 is 
considered to be a versatile candidate for the photo 
electrochemical (PECH) application due to its ability to 
improve the light absorption in visible region (Cheng et 
al. 2013). A titanium dioxide nanoparticle is dispersed 
on single wall carbon nanotube (SWCNT) films to 
improve photo induced charge separation and transport 
of carriers to the collecting electrode surface. As far as 
photoelectron-chemical is concern, charge equilibrium 
between TiO2 and single wall carbon nanotube is a 

prime important factor to improve the efficiency of solar 
cell (Yongping et al. 2012). However, in case of Multi 
Wall Carbon Nano Tube (MWCNT), a controlled layer of 
multi-wall carbon nanotubes (MWCNT) is usually grown 
directly on top of fluorine-doped tin oxide (FTO) or 
other glass electrodes as a surface modifier for 
improving the performance of organic solar cells by 2% 
(Capassoa et al. 2014). Charge transport properties 
enhance the charge collection efficiency of dye sensitized 
solar cells (DSSC) by incorporating oriented TiO2 
nanotube arrays consisting of closely packed nanotubes 
having several micrometers in length with typical wall 
thicknesses, inter tube spacing of 8−10 nm and pore size 
diameters of about 30 nm (Kai et al. 2007). Recent 
patent applications (IN2010/000023 and 
JP2013118127) describe that using TiO2 carbon nano 
tube (MWCNT) nanocomposites comprised DSSC 
prepared by using hydrothermal route leads to the 
increased efficiency of the DSSC (Brian et al. 2005; 
Subas, Vivek, Sarfraj, Mujavar, 2010; Kiyoshige 2013). 

Recently, several polymers having conducting 
properties have gained popularity in designing cheap, 
lightweight, flexible and affordable solar cells. Several 
investigations in this regard have been done by various 
researchers. For example, single-wall carbon nanotube 
(SWCNT)–polymer solar cells were constructed with 
region regular poly (3-octylthiophene)-(P3OT) with 
purity >95% w/w, laser-generated SWNTS (Michael c/o 
Stuttgart Technology Center Dürr, Gabriele c/o Stuttgart 
Technology Center Nelles, Akio Stuttgart Technology 
Center Yasuda 2005). Another invention mentioned in 
Patent EP1507298 describes that solar cell comprising 
carbon nanotubes (CNT) as an electron conductor and 
organic substance like polymethacrylate’s for hole’s to 
get photovoltaic effect (Michael c/o Stuttgart 
Technology Center Dürr, Gabriele c/o Stuttgart 
Technology Center Nelles, Akio Stuttgart Technology 
Center Yasuda 2005). In another such research, by using 
concentric electro spinning of poly (methyl 
methacrylate) as a core precursor and polyacrylonitrile 
as a shell precursor to prepare a hollow active carbon 
nanofiber have been used. Such nanofiber with 190 and 
270 nm for core and shell diameter showed excellent 
mesoporous structure, and 1-D conducting pathway in 
employing as catalysts of counter electrodes (CEs) for 
dye-sensitized solar cells (DSSC). In other developments 
involving the development of high efficiency solar cells 
various semiconducting materials have been deployed. 
Patent US20130092236 and US2011/054301 describe 
such devices where absorbing layer are composed of 
Gallium Arsenide (GaAs), Copper Indium Selenide 
(CuInSe) etc. to achieve high efficiency with low cost 
(Ranga, Christopher, Claire, Bhaskar, Omkaram, Srikant, 
Gaurav, Sanjayan, Kaushal; Robert 2012). It was also 
demonstrated in one of the study that acid infiltration of 
nanotube networks significantly boosts the cell 
efficiency to enhance charge separation and transport by 
reducing the internal resistance to improve the fill factor 



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and by forming photo-electrochemical units. Here the 
efficiency of about 13.8% was achieved by combining 
carbon nanotubes and silicon (Yi et al. 2011). Other 
materials such as silver, palladium, Germanium, 
Platinum etc. were also used as conductive adhesives. 
Conductive adhesive enables interconnection of new 
cells and interconnector concepts, such as 
heterojunction solar cells with their heat sensitive 
surface (Zemena et al 2013). Palladium nanocrystallite 
decorated TiO2 nanotubes (Pd/TNTs) improve the light 
absorption in visible region which enhance photo 
catalytic activity of solar cells (Cheng et al. 2013). In 
another study a composite film composed of platinum 
nanoparticles and carbon fibers was coated on FTO glass 
as a counter electrode in dye-sensitized solar cell (DSSC) 
shown 7.77% efficiency (Cai, Chen & Peng 2010). Patent 
No 20100089447 describes the use of conductive layers 
prepared of Silver nanoparticles or Magnesium nano 
layer (1-20 nm) thereof mixture (Takahito, Chihaya, 
2007; Bulent, Burak, Richard, 2010). The purpose of 
carbon nanotube (CNT) based conductive adhesive was 
to increase the reliability and also to replace these costly 
heavy metals. 

Defect rich edge planes of bamboo like structure 
carbon nanotube enable the electron transfer kinetics at 
the interface of counter electrode and electrolyte and 
result in improvement of fill factor due to low charge 
transfer resistance. So in combination with a dye-
sensitized TiO2 photo anode and an organic liquid 
electrolyte, a multi-wall carbon nanotube (CNT) 
counter-electrode DSSC shows 7.7% energy conversion 
efficiency. Uniform distribution of multiwall carbon 
nanotubes within the heterojunction organic solar cell 
are shown to increase in cell fill factor of 50–60% 
(Anthony, Ross, Ravi 2006). It has been reported that 
CNT incorporated with TiO2 structure could play an 
important role in transporting the photo generated 
electrons towards the conductive supports, with the 
addition of SWCNTs, the incident power conversion 
efficiency 7.3 % to 16 %. CNTs can be used for the 
development of flat solar cells and flexible solar cells, 
where the latter are light weight and have the advantage 
for signal transmission and PV self-power generation. In 
the flexible solar cells, rigid substrate made of 
transparent conducting oxides (TCO) has been replaced 
and it has more power conversion efficiency. The flexible 
solar cells can be generated through carbon fibers, wire 
shaped CNT-CNT solar cell and carbon nanoyarn. In 
addition, the carbon nanostructures due to their efficient 
power conversion efficiency and 3D bendable structure 
can be used for various engineering applications such as 
fiber textile, composites etc. A further research is 
required, where new designs functional materials with 
smaller band gaps may enhance power conversion 
efficiency. Wire shaped DSSCs with above mentioned 
characteristics and stability under different 
environments may be used for various engineering 
applications. 

3.4 Nanowire (NW) 

Nanowires are defined as metallic or semiconducting 
particles having a cross sectional diameters <1 nm, and 
submicron size length. Ideal material for nanowires 
would have a band gap of around 1.55 eV (Qifeng, et al. 
2012). The nanowire geometry provides potential 
advantages like optimum tunable band gap, better light 
trapping, increase defect tolerance and reduce reflection 
to increase the efficiency and reduce the cost. 1-D 
nanowire arrays as photo-electrodes have been widely 
investigated to provide a rapid collection of carriers and 
affording large junction areas with less reflectance loss. 
Nanowires are composed of n-type and p-type material, 
arrange in such a way that one material rolled over 
another material, so as an when photons irradiate on it 
then hole and charge move in equal and opposite 
direction as shown in Fig 4. 

 Nanowires of Si, Ge, GaN and InAs have high electron 
mobility in the axial direction. Therefore nanowires 
show comparable to or even over the best reported for 
solar cell efficiency (Benjamin & Peidong 2009). One of 
the most successful methods employed for nanowire 
synthesis is based on chemical vapor deposition (CVD). 
Nanowires grown by CVD employ a so called vapor 
liquid Solid (VLS) growth mechanism. Vertically aligned 
oxide nanowire comprising solar cell allows the light to 
be absorbed in the vertical direction and prevent exciton 
diffusion to improve the efficiency. In addition, the use of 
inexpensive, environmentally benign, and stable oxide 
materials suggests that a device constructed in this 
manner could have an excellent working lifetime at a 
fraction of the cost of existing solar cells. 

 
Figure 4. Charge Transfer in Nanowire based solar cell 

The x and y axis directions are much smaller than z 
axis direction of nanowire, which enable to impart 
nanowires with various applications in electronic and 
optoelectronic devices. It was found in dye sensitized 
solar cells (DSSC) that, the nanowires provide electron 
transport 100 times faster than conventional cell by 
providing direct pathways for electron conduction. 
Semiconducting nanowire (NWs) present a fascinating 
potential opportunity for developing high efficiency, 
low-cost solar cells by decoupling light absorption and 
carrier separation. Ordered arrays of vertical nanowires 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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with radial junctions has advantages like optical, 
electrical, strain relaxation, charge separation 
mechanisms and product cost than thin film solar cell 
with planner junction. In addition to playing a role in 
providing direct pathways for electron transport, 
compared to planar film, the nanowires contribute to 
enhancing the optical absorption and hence increase the 
solar cells efficiency (Sharma & Juhi 2013). 

Development of solar cell using Nanowire (NW) 

According to patent US7893348, solar cell 
comprising silicon (si) nanowires as active elements 
have been designed (Bastiaan & Loucas 2011). Patent 
US201102847230 describe that patterning planar 
photo-absorbing materials into arrays of nanowires is 
demonstrated as a method for increasing the total 
photon absorption in a given thickness of absorbing 
material (Chang & Yue, 2010; Robert & William 2011). 
By varying the wire length alters the wire filling ratio 
required to achieve the same amount of light absorption. 
Optimal designs for antireflective Silicon nanowire 
based solar cells achieve 11% power conversion 
efficiency (Jin et al 2013). Radial growth of 
hydrogenated amorphous silicon over p-doped 
crystalline silicon nanowires using plasma enhanced 
chemical vapor deposition technique on glass substrates 
achieves 5.6 % efficiency (Erik & Peidong 2010).  

As with CNTs, solar cells have been fabricated using 
various other materials like Silver, Gold, Titanium, ZnO, 
TiO2, InGaN, GaN, GaAs, and GaInP etc. or in combination 
with silicon nanowires (Fei, Siguang, Kang, 2007; Lars, 
Martin, Federico, 2009; Juneui, Jihyun, Sangwoo 2010; 
Yijie, Anjia, James, Shu, Paul 2012; Siegfried, 2012; Tae, 
Joo, Jae, Jae, Won 2012; Zetian 2013). By using TiO2 and 
Germanium Arsenide (GaAs) nanowire either with 
polymer as composite or as an electrode it can achieve 
even higher power conversion efficiency of 9.2 % (Jiun, 
Shu, Ching 2012; Hong, Shu, Ching 2012; Sin K. et al 
2014). Patent applications IB2013/050943 and 
US20120202314 describe that solar cell comprised of a 
layer of p/n-doped semiconductor nanowires with 
embedded polymer layer (Samson, Hao, Felix, 2012; 
Silke, Boer, Gerhardus, 2013). Based on a heterojunction 
between the vertically aligned GaAs/ Ag nanowires and 
polymers like poly (3, 4-ethylenedioxythiophene): poly 
(styrenesulfonate) and/or incorporating poly (3-
hexylthiophene) electron blocking layer have been 
designed to achieved power conversion efficiency of 
9.2% (Jiun, Shu, Ching 2012; Hong, Shu, Ching 2012). In 
another breakthrough, highly flexible and cost-efficient 
brush painting of flexible organic solar cells (FOSCs) 
used same material. 

In addition, it provides an opportunities to fabricate 
complex single crystalline semi-conductors devices 
directly in low cost subtract and electrodes such as Al 
foil, stainless-steel and conductive glass. Nano wire 
based solar cell can be fabricated using a wide variety of 

materials ranging from Si, Zn, CdTe, CuO2, Tio2, in and 
many other polymer NW combination. Power 
conversion efficiency from these nanowires can be 
achieved close to 10%. These nanowire provide high 
efficiency due to their unique geometry for example (a) 
Periodic array of nanowire with radial junctions give the 
advantage such as reduced reflation, maximum light 
trapping, radial charge separation and single crystalline 
synthesis on known epitaxial subtracts (b) Axial junction 
loss the radial charge separation benefit but keep the 
others. (C) Substrate junction lack the radial charge 
separation benefit and cannot be removed the substrate 
for testing as single nanowire solar cell. These nanowire 
have been synthesized by using two most common 
techniques i.e. chemical vapor deposition and pattern 
chemical etching. The surface property of the materials, 
dopant profiling and incorporation of catalyst during 
growth of NWs has been found to affect the electrical 
properties, charge mobility and diameters. The above 
factors promised to lower the cost of solar cell by 
reducing the amount of material needed. It is expected 
that the cost of multifunction solar cell fabrication using 
nanowire can be as low as to that of traditional thin film 
solar cell cost without compromising the power 
conversion efficiency. However there are many 
challenges which needs to be addressed before the 
benefits can be realized commercially, These challenges 
includes surface characteristics of the material, 
mechanical and chemical stability, doping control, 
nanowire array uniformity and scalability. 

3.5 Graphene 
Graphene is the two dimensional (2D) building block 

for Sp2 carbon allotropes. A flat monolayer of carbon 
atoms tightly packed into a two dimensional (2D) 
honeycomb lattice is known as Graphene. It is generally 
wrapped up into zero dimension (0D) fullerenes, rolled 
into one dimension (1D) nanotubes or stacked into 3D 
graphite. Hence it can be used as a lubricant due to its 
loosely bonded layered planar structure with the planes 
of carbon atoms. 

History of Graphene 

History of Graphene is incomplete without describing 
Graphene oxide (GO). Graphene are called as reduced 
Graphene oxide. Which was extensively studied in back 
1840s (Daniel, Rodney, Christopher 2010). Timeline of 
selected events occurred in the history of Graphene as 
mentioned below Table 5. 

Table 5 
Historical development of Graphene for solar cell (Daniel, Rodney, 
Christopher 2010) 

Year Events 

1987 The name “Graphene” was first mentioned by S. Mouras 
and co-workers to describe the graphite layers that had 
various compounds inserted between them forming the 
so-called Graphite Intercalation compounds or GIC’s. 

1999 Ruoff and coworkers micromechanically exfoliate 



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© IJRED – ISSN: 2252-4940, July 15,2015, All rights reserved 

Graphene into thin lamella comprised of multiple layer of 
Graphene. 

2003 In 2003, Andre and Kostya succeeded in producing the 
first isolated Graphene flakes and this work was 
published in 2004. 

2005 The first major result on the electronic properties was 
the anomalous quantum Hall effect in Graphene reported 
around the same time by Andre and Kostya and by Philip 
Kim’s group at Columbia University. 

2010 Andre and Kostya were awarded the 2010 Nobel prize in 
physics for this work and are continuing to unveil new 
and exciting properties in graphene and other related 
two dimensional crystal materials. 

2014 Jonathan Coleman and colleagues from Trinity College 
Dublin were able to create Graphene by mixing the 
proper amount of graphite powder, water and 
dishwashing liquid in a high-powered blender. 

 

Potential for solar cell 

Graphene has very high electrical conductivity due 
to it contains both holes and electrons as charge carriers. 
The Graphene with each absorb photon it generate an 
electron hole pair. It was said that graphene’s electrons 
has similar mobility as photon due to their lack of mass. 
Graphene electrons require to travel sub-micrometer 
distances without scattering i.e. ballistic transport 
phenomenon. Graphene is used as a light absorbent can 
able to increase efficiency of solar cell by enhancing 
absorption capacity. Graphene is the strongest material 
ever discovered with a tensile strength of 300 x 108 
Pascal’s which is 4 x 108 times stronger than A36 
structural steel. The reason behind its strength is 0.142 
Nm-long carbon bonds. Hence graphene is a strong 
candidate for solar cell (Yanwu et al. 2010). 

Development of solar cell using Graphene 

Stanford University scientists have developed the 
first solar cell made entirely of carbon, which is a 
cheaper alternative to the expensive, silicon based solar 
cell (Standford 2012). Bao and her colleagues use 
Graphene sheets as dual material (active layer and 
electrode). It primarily absorbs near-infrared 
wavelengths of light so it power conversion efficiency is 
less than 1% (Standford 2012). The University of Florida 
achieves 8.6 % power conversion efficiency by using 
graphene doped with trifluoromethanesulfonyl-amide 
(TFSA) coated silicon wafer material. With celebrative 
research of universitat Jaume I in Castello and Oxford 
University, they claimed 15.6% power conversion 
efficiency by combining titanium oxide and graphene as 
a charge collector and perovskite as a sunlight absorber. 
Its production costs are very low, enable to make it 
possible for the technology to be used on flexible plastics 
(Gizma 2015). If plasmonic nanostructures of graphene 
were optimized, it should be possible for falling photon 
on graphene is converted into current and increase the 
efficiency of solar cell. That is what industry want to 
produce said by Alexander Grigorenko of Manchester 

(Physic world 2011). 
Soitec Germany- As recently developed, a word class 

four junction solar cell grown on different III-V 
compound materials using CPV technology gives an 
outstanding 43.6 % PCE. This technology was developed 
in collaboration with the Fraunhofer institute of solar 
energy system and the Helmholt zentrum fur 
materialien und Energie in berline. This allows optimal 
band gap combinations to capture the maximum 
sunlight’s. Recently, multi-junction solar cells with 
concentrator photovoltaic (CPV) systems have 
demonstrated solar conversion efficiency over 40. It is 
cost effective because of broad geographic areas for 
solar absorption. For metamorphic 3-junction 
GaInP/GaInAs/Ge solar cell, its power conversion 
efficiency was about 41.6% at 484 suns, the highest 
efficiency yet demonstrated for this type of cells.   

Professor Ravi Silva from the University of Surrey 
outlined his definition for 4th generation (4G) solar cells, 
capable to improve the power conversion efficiency of 
existing 3rd generation solar cell. 4th generation (4G) 
solar cells comprise single layer of conducting polymer 
films (organic) i.e. cheap and flexibility with novel 
nanostructures (inorganic) i.e. lifetime stability 
(Anthony, Ross, Ravi 2006). 

3.6 Nanofabrication: Roll to Roll process 

Three dimensional (3-D) nanomaterial has potential 
to boost up the performance of solar cell owing to the 
power conversion efficiency. However the cost effective 
production with mass production having unchanged 
optical and physical properties are still remain challenge 
for the present technology. Though, polymeric solar cell 
up to some extent are able to overcome the current 
challenges like high manufacturing cost, lack of ability 
for mass production or restricted application etc. So in 
modern scenario, researchers are adopting 
multidisciplinary approach by combining the 
nanofabrication technique and polymeric solar cell 
concept to beneficiate the solar industry. 
Nanofabrication is the technique to manipulate the 
component or material in controllable manner at 
nanometer scale in 1, 2 or 3 dimension. Such technique 
gives value addition to the manufacturing process due to 
change in electronic property of the material at 
nanometer scale. In last few years, electronic industry 
has attracted much towards the nanofabrication 
technique to produce electronic circuits or boards with 
extraordinary electric performance. Now a day’s same 
concept was applied for solar cell using roll to roll 
process. Roll to roll is the process to deposit, assemble or 
coat the material on substrate for mass production of 
industrial product. It has been already used by coating 
industry to beneficiate of time saving mass production. 
While in solar industry, roll to roll process is unable to 
fulfill the prior requirement of power conversion 
efficiency. By coupling nanofabrication and roll to roll 



Citation: Raval, N. and Gupta, A.K. (2015) Historic Developments, Current Technologies and Potential of Nanotechnology to Develop Next Generation Solar Cells 
with Improved Efficiency, 4(2),77-93, dx.doi.org/10.14710/ijred.4.2.77-93  

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© IJRED – ISSN: 2252-4940, July 15, 2015, All rights reserved 

method it is possible to open a wide scope of 
opportunity for manufacturing paradigm and industrial 
requirements. Nanofabricated roll to roll technique 
provides a flexible, transparent and light weight 
substrate for the manufacturing of solar cell. At 
development stage, materials like silicon, group I-V and 
polymeric nanoparticles have been investigated as an 
absorbing component, while plastic or metal strip have 
been used as a substrate of solar cell. As roll to roll 
technology for solar cell industry is less mature enough 
technology than other technologies and hence the power 
conversion efficiency of solar device achieved very low. 
The list of different methods of roll to roll process are 
comprising nanofabrication with their power conversion 
efficiency in solar cell as shown in Table 11. With 
extensive research and development in last few years 
power conversion efficiency of flexible solar cell using 
CIGS is 14.1 %, CdTe is 11.4 %, a-silicon is 12 % and TiO2 
is 8 % on plastic substrate at laboratory scale. While at 
industrial scale for CIGS is 17.5 %, CdTe is 8 % and a-
silicon is 8 % (Razykov et al 2011). However inherent 
stability and less production cost indicate a promising 
potential for these technology. Various types of 
nanofabrication process are available like nano-
imprinting, nano-lithography, self-assembling, molecular 
engineering etc. Hence, large scale flexible solar cell will 
grove into a billion dollars industry over the next few 
years and will change our view of electronics. The photo-
electric market in 2010 with about 2 billion USD of 
which 20% is flexible. It was projected that by 2020, it 
rises to almost 60 billion USD, of which 75 % is of 
flexible (IDTechEx 2009-2029 market report 2009). 

 

Table 6 
List of roll to roll methods with their PCE (%) (Markus H. 2013)   
Sr. 
no. 

Technology Material Power 
conversion 
efficiency 

(%) 
1 Slot die coating PEDOT:PSS, 

P3HT:PCBM 
1.74 

2 Doctor blading POD2T-
DTBT:PCBM 

6.74 

3 Spray Coating P1:PCBM 5.1 
4 Screen printing Ag 20.3 
5 Flexo printing Ag 18.1 
6 Gravure printing PEDOT:PSS, 

P3HT:PCBM 
2.8 

7 Inkjet printing Ag 4.91 

4. Future aspects 

Researchers succeed to demonstrate the conversion of 

solar energy to electric energy after the extensive research 

of 60 year. Today also we are facing crucial limitations like 

manufacturing cost and poor power conversion efficiency. 

Hence, it is not sufficient to replace the consumption 

demand of fossil fuel with solar energy. Innovative solar 

cell technologies that utilize nanostructured materials offer 

great technological potential due to their attractive 

properties. The late noble physicist Richard smalley saw a 

potential in nanomaterial to bring revolution in energy 

sector by modifying the fundamentals component of solar 

cell using value adding property of nanotechnology to 

make better solar cell. To overcome the problem of 

reflection, anti-reflecting coating has been used, which 

increase the cost of solar cell. Recently, nonporous material 

was coated on solar cell surface which is known as black 

silicon. It increased the 20% power conversion efficiency 

from conventional solar cell. However, efficiency of solar 

cell is not only the advantage of nanotechnology. Another 

value addition of nanotechnology is to produce ultra-thin 

and flexible solar cell, which cross limit of rooftop solar 

panels. New solar cells are based on films formed by roll-

to-roll process technology of nanomaterial enabling high 

surface area, transparency, excellent stability and good 

electrical conductivity and are ideal for solar applications. 

It also opens the opportunity to produce cheaper and 

environmental friendly solar cells. Availability of 

electricity is the major challenge for developing countries, 

due to lack of fossil fuel and high global price of crude oil. 

So, nanotechnology has potential to decrease the cost of 

solar cell and allow to achieve good power conversion 

efficiency. It also enables to meet the increasing demand of 

electricity and also accessible for those people. Today 

researchers started exploring nanotechnology in different 

way to develop the solar cell. Therefore, the use of 

nanotechnology appears to provide a ladder to develop 

newer solar cell with much high PCE at cheaper cost and 

bring revolution in the solar cell industry in future. 

5. Acknowledgement 

The authors are grateful to the Confederation of Indian 

Industry and Govt. of Gujarat for their financial support 

(Ref. No.: IC/INC/CoE/SANCTION/667493) in 

establishing the CoE-NT at Ahmedabad, Gujarat, India. NR 

is also thankful to the Institute of pharmacy, Nirma 

University, Ahmedabad for their support by providing 

library facility.  

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