2. Introduction
Adverse effect on the climate change of the globe
the average increment of temperature of the globe
below 2°C
As suggested by many studies improving the energy
efficiency of the machinery used and avoiding rampant
use of devices causing emission of green house gases
fossil fuels which is taking the major toll on the earth’s
climate, by virtue of emission of gases like CO2, N2O and
Methane
3. Introduction
Use of non-conventional sources of energy like solar
energy, wind energy and biomass has become the
need of the hour for the mankind. At this juncture, such
measures are imperative and indispensible for two
important reasons
It is required to explore for renewable sources of energy
as the fossil fuels are continuously depleting.
Minimizing the use of fossil fuels is highly essential to cut
down the carbonemissions in the interest of the climate
of the planet earth.
6. Sources of Renewable Energy and
importance of solar energy
The recent expert analysis states that the global
Green House Gas (GHG) emissions may be reduced
by 35%, if renewable energy generation targets are
met by 2030 [*]
There are different types of renewable sources of
energy or non-conventional sources of energy which
do not have any direct contribution in the increment
of green house emissions
* Energy and Climate Change: World Energy Outlook Special Report, 2015.
12. First Generation Solar Cells:
The solar cells based on monocrystalline and
polycrystalline Silicon constitute the first generation solar
cells
Advantages: raw material availability, highefficiency
and long term stability, very well developed Silicon
processing technology
the physics of these solar cells is well understood
efficiency of ~24%
13. First Generation Solar Cells:
Disadvantages:cost effectiveness
Silicon being an indirect band gap material has a low light absorption
coefficient.
Such a property of silicon requires larger thickness of material for
better optical absorption.
Thicker material films when used in the device, demand longer charge
diffusion lengths which put a constraint on the quality of the material.
That means, the material films used in solar cell application are ought
to be defect free to attain better efficiency.
The fluctuations in the availability of solar grade silicon have impeded
the pace of
expansion of the solar cell installations.
14. First Generation Solar Cells:
Challenges
Silicon in its monocrystalline and polycrystalline forms is
inevitable
reduce the cost or explore for new materials
This naturally gave birth to a new generation namely the
second generation of solar cells
15. Second Generation of Solar Cells:
Amorphous Silicon apparently seemed to emerge as a solution to the cost
factor from its crystalline counter parts
Amorphous silicon solar cells suffer from staebler wronskieffect
Due to this deleterious effect the solar cell performance temporally
degrades under illumination
In this effect, the incident photons create electron-hole pairs due to the
breakage of si-si bonding in a-Si resulting in dangling bonds
These appear as sub-band gap states leading to recombination of
electrons and so decreased performance of the
cellmodule efficiency of around 8.5%
16. Cu2S/CdS based solar cells
Advantages:
These cells contain active polycrystalline CIGS layers with Mo coated
glass
sheets or steel substrates using energy economic methods.
Flexible substrates may be used to make solar cells using these materials.
These are relatively environmentally friendly solar cells as they employ
very
little cadmium in the form of CdS
17. Disadvantages:
These are not as efficient as crystalline silicon based solar cells
Manufacturing complexities still exist due to these being ternary and
quartenary
compounds
The prices are not competitive as compared to CdTe
Also use rare elements like Indium giving rise to more practical difficulties.
18. Cadmium Telluride solar cells have the following advantages and
disadvantages:
Advantages:
These cells in combination with CdS, match better with the solar
spectrum
Cadmium is an abundant metal.
19. Disadvantages:
It has lower device efficiency as compared to crystalline silicon
Tellurium is a very rare element raising doubts over the CdTe PV
expansion.
Cadmium is highly cytotoxic and CdTe is also a toxic compound if
ingested.
In all, it may be concluded that, second generation solar cells have not
really been
successful in finding alternative technologies to silcon solar cells.