Introduction What is Solar Cell? History of Solar Cell How is it work? Generation of Solar Cell Efficiency chart Advantage of Solar Cell

1. Introduction to Solar Cell
Keshav Kumar Sharma
PhD Scholar
Department of Physics

2. Outlines
 Introduction
 What is Solar Cell?
 History of Solar cell
 Solar Cell: How is it Work?
 Generation of Solar Cell
 Solar cells: Efficiency Chart
 Advantage and Disadvantage of solar cells

3. Introduction: What is Solar Energy?
 Originates with the thermonuclear fusion reactions
occurring in the sun.
 Represents the entire electro-magnetic radiation
(visible light, infrared, ultraviolet, x-rays, and radio
waves).
 This energy consists of radiant light and heat energy
from the sun.
 Out of all energy emitted by sun only a small fraction
of energy is absorbed by the earth.
https://en.wikipedia.org/wiki/Sun
https://en.wikipedia.org/wiki/Solar_energy

4. Breakdown of Incoming Solar Energy
https://en.wikipedia.org/wiki/File:Breakdown_of_the_incoming_solar_energy.jpg
The surface receives about
47% of the total solar
energy that reaches the
Earth. Only this amount is
usable.

5. Solar Energy Distribution
https://www.cloudynights.com/topic/728286-smoky-day-solar-observing/

6. Air Mass
 “Air Mass" measures how much
atmosphere sunlight has to pass through.
 Since atmosphere absorbs and scatters
solar radiation, a larger air mass means
less insolation.
 When the sun is lower in the sky, the
sunlight has to pass through more
atmosphere and so the air mass is greater
Air mass = 1/cos(ZA°)
where "ZA" stands for "zenith angle" which is how
far away from directly overhead the sun is.
http://www.ftexploring.com/solar-energy/air-mass-and-insolation2.htm

7. Solar Energy Harvesting Using Different Paths
 Solar Thermal Energy
 Solar Heating
 Solar Water Heating
 Solar Space Heating
 Solar Space Cooling
 Solar Photovoltaic
 Solar Concentrators
Solar Thermal Plant
Solar Water Heating Solar Photovoltaic Plant Solar Concentrators Plant
https://www.volksenergie.in/solar-water-heaters.php https://doi.org/10.1007/978-3-030-02236-5_2
https://en.wikipedia.org/wiki/Serpa_solar_power_plant
https://energyvulture.com/2016/07/15/

8. Solar Energy can be used to generate electricity in three
ways:
 Solar Photovoltaic Energy:
Using solar energy for the direct generation of electricity
using photovoltaic phenomenon.
 Solar Thermal Energy:
Using solar thermal technologies for heating fluids or gases
which can be used as a heat source or to run turbines to
generate electricity.
 Passive Solar Energy:
Solar can be used for direct heating of buildings in winter by
using the right orientation of windows and heat collecting
surfaces.
Electricity Generation from Solar Energy
http://www.mydiysolarhouse.com/solar-power-defined/

9. Solar’s Share in India’s Installed Power Capacity
https://mercomindia.com/solar-share-in-india/
India – Cumulative Installed power capacity Mix (%) in 2020
https://www.irena.org/solar
Solar Installed Power Capacity in 2019
Installed
Power
Capacity
(MW)
India, 2019
Solar Thermal – 6,289 MW
Solar PV – 578,533 MW
Total - 584,822 MW

10. What is Solar Cell?
 It is an electric device which converts solar energy into electricity and is
based on the Photovoltaic effect.
 Photo + voltaic = convert light to electricity.
Sunlight
https://www.emworks.com/application/solar-cell

11. History of Solar Cell
 1839: French scientist Edmond Becquerel first discovered the photovoltaic effect.
 1873-1876: Willoughby Smith, an English electrical engineer, discovered
the photoconductivity of selenium.
 1883: New York inventor Charles Fritts created the first solar cell by coating selenium
with a thin layer of gold. This cell achieved an energy conversion rate of 1-2 %.
 1887: German physicist Heinrich Hertz first observed the photoelectric effect.
 1905: Einstein explained the photoelectric effect He received the Nobel prize in 1921.
 1953-1956: Silicon solar cells are produced commercially- now 6% efficient.
 1958: The first solar-powered satellite, Vanguard 1, was launched from NASA.
 1982: Arco Solar built the first solar park — a solar power plant of 1 megawatt— in
Hesperia, California.
 1995: first times solar cells were used in recreational vehicles.
 1994-1999: National Renewable Energy Laboratory developed a new solar cell from
gallium indium phosphide and gallium arsenide that exceeded 30% conversion efficiency.
 2005: DIY solar panels become popular.
 2015: Flexible printed solar panels created- 20% power conversion efficiency.
 2016: Sunless solar power is discovered- thermo-photovoltaic cells.

12. Solar Cell: How is It Works?

13. Energy Band Formation in Solids
 Each isolated atom has discrete energy level, with two electrons of opposite spin
occupying a state.
 When atoms are brought into close contact, these energy levels split.
 If there are a large number of atoms, the discrete energy levels form a “continuous”
band. https://sites.google.com/site/puenggphysics/home/unit-5/band-theory-in-solids

14. Energy Band Diagram
~ 9 eV
~ 1eV
https://electricalvoice.com/material-classification-based-energy-band-diagram/

15. Silicon: Intrinsic and Extrinsic
Eg = 1.1 eV Eg = 1.1 eV
~ 0.05 eV
Eg = 1.1 eV
~ 0.05 eV
Intrinsic Semiconductor N- type Semiconductor P- type Semiconductor
 Doping silicon lattice with group V elements can creates extra electrons in the conduction band — negative
charge carriers (n-type), As- donor.
 Doping silicon with group III elements can creates empty holes in the conduction band — positive charge
carriers (p-type), B-(acceptor)

16. PN Junction Diode
 A p-n junction is a junction formed by combining p-type and n-type
semiconductors together in very close contact.
 In p-n junction, the current is only allowed to flow along one direction from p-
type to n- type materials.

17. Solar Cell Working Principle
Light photon excite electron from V.B. to
C.B.
Leaving equal no. of holes behind.
Electron-hole generated in the depletion
region move to opposite direction due to
barrier field.
Electron toward n-side and holes toward p-
side. Positive and Negative charge formed at
p and n-side respectively.
Photo-voltage set-up across the junction.
Photo-current flows when external load
connected.
https://www.researchgate.net/publication/322628682_Solar_Tree_Project/figures?lo=1
Cross sectional view of Solar Cell

18. I-V Characteristic of Solar Cell
 Graph obtained for Solar Cell is in fourth quadrant.
 Solar Cell Parameters:
1. Short circuit current (Jsc)
2. Open circuit voltage (Voc)
3. Fill factor (FF)
4. Efficiency ( 𝜂)

19. Generation of Solar Cells
Classification of Solar Cell
First Generation
 Mono Crystalline Si
 Polo Crystalline Si
Second Generation
 Amorphous Silicon
 CIGS
 CdTe
 CZTS
Third Generation
 Organic Solar Cell
 Perovskite
 DSSC
 Quantum Dots
Price Vs Efficiency among the different
generation solar cells
https://doi.org/10.1016/S1369-7021(07)70278-X

20. Solar Cells: First Generation
 89.6 % of 2019 Production
45.2 % Single Crystalline Si
42.2 % Ploy Crystalline Si
 Limit efficiency 31%
 Single crystal silicon - 16-19% efficiency
 Multi-crystal silicon - 14-15% efficiency
https://jlankatech.com/generations-of-solar-cells/

21. Solar Cells: Second Generation
https://www.nanowerk.com/news/newsid=21691.php
DOI:dx.doi.org/10.1016/j.solmat.2012.01.001
https://sites.google.com/site/thetanggroupur/research/cdte
Amorphous Silicon
CZTS
CdTe CIGS
 Amorphous Si
(Efficiency = 7%)
 CdTe
(Efficiency = 22.6 %)
 CZTS
(Efficiency = 12.6 %)
 CIGS
(Efficiency = 23 %)

22. Solar Cells: Third Generation
https://www.nrel.gov/pv/organic-photovoltaic-solar-cells.html https://energynext.co.th/2020/07/why-perovskite-solar-cells-are-intrinsically-
unstable/
•DOI: 10.1088/1757-899X/374/1/012048
https://sinovoltaics.com/learning-center/solar-cells/quantum-dot-solar-cell/
Perovskite solar Cell (Efficiency = 25.2 %)
Quantum dots Solar cell (Efficiency = 16.6 %)
Organic Solar Cell (Efficiency = 17.4 %)
DSSC (Efficiency = 12.3 %)

23. Tandem Solar Cells
 One method to increase the efficiency of a solar cell is to split the spectrum and use a solar cell that is
optimized to each section of the spectrum.
https://www.pveducation.org/pvcdrom/tandem-cells
https://metsolar.eu/blog/what-are-tandem-cells-introduction-to-solar-
technology-part-3/
Perovskite Silicon Tandem Cell
Some Examples of Tandem Solar Cell:
• DSSC/DSSC (7.1 % efficiency)
• DSSC/CIGS (12.35 % efficiency)
• DSSC/GaAs (7.63 % efficiency)
• DSSC/c-Si (17.23% efficiency)
• a-Si/DSSC (12.31% efficiency)
• Perovskite/c-Si (26.4% efficiency) (mechanically stacked)
• Perovskite/c-Si (23.6% efficiency) (monolithic tandem)
• CZTS/c-Si (16.8% efficiency)

24. Multi- Junction Solar Cells
 Multi-junction (MJ) solar cells are solar cells with multiple p–n junctions made of different
semiconductor materials.
 Each material's p-n junction will produce electric current in response to different wavelengths of light.
Electrical circuit equivalent
diagram
Layers and band diagram of the
tunnel junction.
Structure of an MJ solar cell
https://en.wikipedia.org/wiki/Multi-junction_solar_cell
•DOI: 10.1039/b809257e
 Highest efficiency ( 47.1%) achieved for 6 junction at NREL.

25. Solar Cells: Efficiency Chart

26. Solar Cells: Efficiency Chart

27. Solar Cells: Efficiency Chart

28. Solar Cells: Efficiency Chart

29. Solar Cells: Efficiency Chart

30. Solar Cells: Efficiency Chart

31.  Advantages
•Consumes no fuel
•No pollution
•Wide power-handling capabilities
•High power-to-weight ratio
 Disadvantages
•The main disadvantage of solar cell is the initial cost. Most types of
solar cell require large areas of land to achieve average efficiency.
•Air pollution and weather can also have a large effect on the efficiency
of the cells.
•The silicon used is also very expensive and the solar cells can only ever
generate electricity during the daytime.
Advantage and Disadvantage of Solar Cell
https://www.greenmatch.co.uk/blog/2014/08/5-advantages-and-5-disadvantages-of-solar-energy