The design and simulation of thin film silicon solar cells studied using FDTD method.

1. By
S. Saravanan
Design and Analysis of Thin Film Silicon Solar
cells Using FDTD Method
Under the guidance of
Dr. R. S. Dubey
Head
Department of Nanotechnology,
Advanced Research Laboratory for Nanomaterials &
Devices
Swarnandhra College of Engineering & Technology
Narsapur (A.P.)
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2. OutlinesOutlines
 Introducion
 Why thin film for solar cells?
Why light trapping?
Photonic Crystals ?
Designing Apporaoch
 Results
 Conclusion
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3. Today also main energy source is the fossil fuel which has
disadvantage of emission of the greenhouse gases: a major
factor for increasing global warming.
Renewable energy sources such as sunlight, wind, rain, tides,
and geothermal heat are the best alternative of the fossil fuel.
Among all these renewable energy sources, solar energy
utilization is only 0.05% which is very less as compared to the
total energy received from the sun.
As per literature, we can generate 13 TW energy by only
covering 0.1% of earth’s surface with 10% efficiency solar
cells.
Introduction

4.  Silicon is an attractive photovoltaic material because of its natural
abundance, compatible with existing process technology and its
appropriate band gap.
 But the cost of c-silicon is also an important issue at mass scale
production. One approach to significantly lower the cost of c-silicon
solar cells is the use of thin silicon films.
 Thin film technology have some advantages e.g. less amount of material
needed, allows material with shorter carrier diffusion lengths, low
energy consumption for device fabrication and light-weight.
 But silicon thin film based solar cells have weak absorption in longer
wavelength.
 Hence, novel optical engineering schemes are needed to overcome such
low absorption such as patterned structures, diffraction grating, a
reflector at the back side of silicon solar cell, metal nanoparticles etc.
Why Thin Films for Solar Cells?

5. Why Light
Trapping?
The purpose of light trapping is to prevent the entered photons
into the solar cell with the probability to absorb within the active
region.
This requirement can be fulfilled by two mechanisms:
1. Diffraction or scattering which can change the direction of
incident photons so that as much as of photons can propagate at
higher angles with prolonged path length within the cell.
2. Coupling of incident photons provided with the guided mode in
the active region of solar cell with a confinement of light.
In simple words, once the incident photons entered into the
device their mean residing time in active region must be long
enough and they are absorbed before escaping the device.
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6. PhotonicPhotonic CrystalsCrystals??
Artificial Dielectric StructuresArtificial Dielectric Structures
Photonic BandgapPhotonic Bandgap
Dielectric ContrastDielectric Contrast
DependentDependent
Light propagation prohibited without
absorption within bandgap.
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7. Designing Approach
The short circuit current calculated from above equation contributes to the
calculation of efficiency as:
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The designing of thin film solar cells is simulated using FDTD
method.
A long wavelength light range will not be absorbed by the solar
cell due to weak absorption limitation of the silicon solar cells.
The ratio of maximum power that can be derived from solar device to the
product of short circuit current and open circuit voltage which can be
expressed as:
(1)
(2)
(3)

8. Electric field Analysis
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9. Results
ARC refractive index Anti-reflection layer thickness
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10. Analysis of Grating and DBR layer
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11. Absorption
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12. Comparison of Cell Efficiency & J-V
Curve
Cell efficiency . Short-circuit current of solar cells based
on DBR and diffraction grating.
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13. Types of Structure
Solar Cell Structure
Short circuit
current
(mA/cm2
)
Efficiency
(%)
Relative
enhanced
efficiency
(%)
Reference
Designed 5 µm cell
thickness (ARC only)
21.3 14 -
5 µm cell thickness
(ARC+DBR+GRA)
30.2 20 42.8
10 µm cell thickness
(ARC+DBR+GRA)
33.1 21.7 57.1
20 µm cell thickness
(ARC+DBR+GRA)
35.47 23.3 64.2
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14. The design and simulation of thin film solar cells using FDTD method is
presented.
It is found that three DBR pairs with 0.8μm center wavelength was good
choice for optimal perforamance of solar cell.
We have compared the cell efficiency of single and binary grating layer
based solar cells and observed an enhancement in later one.
A relative enhancement in short circuit current is observed i.e. 29.6, 32.9
and 34.6 mA/cm2
of 5, 10 and 20 μm cell thicknesses which indicates the
enhanced absorption in the wavelength 450-1100nm.
Finally, binary grating based solar cell designing is more efficient for
light trapping which yields maximum quantum efficiency.
ConclusionsConclusions
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15. Scope of my work
To investigate grating parameters such as grating period, duty cycle,
grating height and width in order to achieve a better performance of solar
cells.
Further, ARC layer can be replaced with nanoparticles to have minimum
reflection at the top surface.
To investigate light trapping and plasmonic effects in silicon thin film
solar cells based on metal nanoparticles.
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16. References
Peter Bermel, Chiyan Luo, Lirong Zeng, Lionel C. Kimerling, John D.
Joannopoulos, 2007.Improving Thin-film Crystalline Silicon Solar Cell
Efficiencies with Photonic Crystals. Optics Express 15, 16896-17000.
M. Y. Kuo, J. Y. Hsing, T. T. Chiu, C. N. Li, W. T. Kuo, T. S. Lay, M. H.
Shih, 2012.Quantum Efficiency Enhancement in Selectively Transparent
Silicon Thin Film Solar Cells by Distributed Bragg Reflectors.Optics
Express 20, A828-835 .
Ning-Ning Feng, Michel, J., Lirong Zeng, Jifeng Liu, Ching-Yin
Hong, Kimerling, L.C., Duan, Xiaoman, 2007.Design of Highly Efficient
Light-Trapping Structures for Thin-Film Crystalline Silicon Solar Cells.
IEEE Transactions on Electron Devices 54, 1926-1932.
James G. Mutitu, Shouyan Shi, Caihua Chen, Timothy Crezzo, Allen
Barnett, Christaina Honsberg, Dennis W. Prather, 2008.Thin film silicon
solar cell design based on photoniccrystal and diffraction grating structure.
Optics Express 16. 15238-15248.
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17. Acknowledgements
The financial support provided by Defence Research and
Development Organisation (DRDO), New Delhi, INDIA is
highly acknowledged.
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18. Questions?
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19. Thank You For Your Kind
Attention !