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TitleLIGHT TRAPPING DESIGNS FOR THIN SILICON SOLAR CELLS by James Gichuhi Mutitu A thesis ...
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Table of Contents
                            ACKNOWLEDGMENTS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
ABSTRACT
                        
Document Text Contents
Page 1

LIGHT TRAPPING DESIGNS FOR THIN SILICON SOLAR CELLS






by


James Gichuhi Mutitu










A thesis submitted to the Faculty of the University of Delaware in partial
fulfillment of the requirements for the degree of Master of Degree in Major





Spring 2010





Copyright 2010 James G. Mutitu
All Rights Reserved

Page 2

LIGHT TRAPPING DESIGNS FOR THIN SILICON SOLAR CELLS



by


James Gichuhi Mutitu






Approved: __________________________________________________________
Dennis W. Prather, Ph.D.
Professor in charge of thesis on behalf of the Advisory Committee



Approved: __________________________________________________________
Kenneth E. Barner, Ph.D.
Chair of the Department of Electrical and Computer Engineering



Approved: __________________________________________________________
Michael J. Chajes, Ph.D.
Dean of the College of Engineering



Approved: __________________________________________________________
Debra Hess Norris, M.S.
Vice Provost for Research and Graduate Studies

Page 47

4.3 Silicon with AR Coating

The second case we consider is one where an antireflection coating has been added to the

bare silicon structure of Fig. 4.1. In this case, for reasons of simplicity, the refractive

index is set as the geometric mean of the index of free space and that of silicon at 0 =

900nm, and the thickness is set to be 0/4n2. With such an AR coating applied, the front

surface reflectance is now reduced to 8% of the total incident power. Similarly the

amount of light absorbed increases, for there is more light that actually enters the active

photovoltaic region than in the previous case. The absorbed light is now 57%, which is

17% more than was absorbed for the bare silicon case. Again, as was anticipated, there is

now more light to transmit, and hence, the transmission increases by 10% to a value of

35%, i.e., when compared to the bare silicon case; as shown in Fig. 4.3. It is interesting to

see just how drastically all the values change when compared to the initial case, and the

characteristic graphs of the two cases are plotted and compared to the total incident flux

in Fig. 4.4. The green graphs in Fig. 4.4 represent the characteristics of the enhanced

(with AR coating) structure. The AR coating allows for 27% more of the incident power

to propagate through the solar cell structure. Of this amount of light, 17% is absorbed by

the active photovoltaic region and 10% is transmitted out of the cell. So, the next logical

step in this train of thought is to minimize the transmission losses.

32

Page 48

Incident Light



Figure 4.3 Schematic of a plane light wave incident on the surface of silicon with an
added AR coating, only 8% of the incident light is now reflected, 57% is absorbed and
35% is transmitted. The Jsc of this structure is 21 mA/cm2.





(a) (b) (c)

Figure 4.4 (a) Plot of the amount of light reflected by the structure of Fig 4.3 (green
plot) when compared to the total light incident (red plot) and the reflectance of the
bare silicon solar cell (blue plot), (b) similar plot illustrating the absorption
characteristics, (c) the transmitted irradiance compared to the incident and bare
silicon transmitted irradiance.



To effectively design an AR coating one has to realize that the refractive index of

materials varies for different wavelengths over the whole solar spectrum and so, one has

Si

Reflected Light

Transmitted

Light

8 %

57%

Absorbed

Light
AR
Coating

Jsc: 21 mA/cm2
35%

400 500 600 700 800 900 1000 1100
0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Wavelength(nm)

Ir
ra

d
ia

n
ce

(
W

c
m

-1
n

m
-1

)




Maximum Power

BaseCase Reflectance
ARStruct Reflectance

400 500 600 700 800 900 1000 1100
0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Wavelength(nm)

Ir
ra

d
ia

n
ce

(
W

c
m

-1
n

m
-1

)




Maximum Power

BaseCase Absorption
ARStruct Absorption

400 500 600 700 800 900 1000 1100
0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Wavelength(nm)

Ir
ra

d
ia

n
ce

(
W

c
m

-1
n

m
-1

)




Maximum Power

BaseCase Transmittance
ARStruct Transmittance

33

Page 93

[13] M. A. Green, Solar Cells : Operating Principles, Technology, and System
Applications. Englewood Cliffs, NJ: Prentice-Hall, 1982, pp. 274.

[14] J. Nelson, The Physics of Solar Cells. London: Imperial College Press, 2003, pp.
363.

[15] M. J. McCann, K. R. Catchpole, K. J. Weber and A. W. Blakers, "A review of thin-
film crystalline silicon for solar cell applications. Part 1: Native substrates," Solar Energy
Materials and Solar Cells, vol. 68, pp. 135-171, 5. 2001.

[16] K. R. Catchpole, M. J. McCann, K. J. Weber and A. W. Blakers, "A review of thin-
film crystalline silicon for solar cell applications. Part 2: Foreign substrates," Solar
Energy Materials and Solar Cells, vol. 68, pp. 173-215, 5. 2001.

[17] M. A. Green, Third Generation Photovoltaics : Advanced Solar Energy Conversion.
, vol. 12, Berlin ; New York: Springer, 2003, pp. 160.

[18] M. A. Green, Silicon Solar Cells, Advanced Principles and Practice. University of
New South Wales: Center for Photovoltaic Devices and Systems, University of New
South Wales, 1995,

[19] E. Yablonovitch, "INTENSITY ENHANCEMENT IN TEXTURED OPTICAL
SHEETS FOR SOLAR CELLS." in Conference Record of the 16th IEEE Photovoltaic
Specialists Conference - 1982. 1982, pp. 501-506.

[20] J. G. Mutitu, S. Shi, C. Chen, T. Creazzo, A. Barnett, C. Honsberg and D. W.
Prather, "Thin film silicon solar cell design based on photonic crystal and diffractive
grating structures," Optics Express, vol. 16, pp. 15238-15248, 2008.

[21] C. Balanis, Advanced Engineering Electromagnetics. John Wiley and Sons, 1989,

[22] L. Rayleigh, "On the reflection of vibrations at the confines of two media between
which the transition is gradual," Proceedings of the London Mathematics Society, vol. 11,
pp. 51-59, 1879.

[23] J. Müller, B. Rech, J. Springer and M. Vanecek, "TCO and light trapping in silicon
thin film solar cells," Solar Energy, vol. 77, pp. 917-930, 12. 2004.

[24] H. A. Macleod, Thin-Film Optical Filters. ,2.th ed.New York; London: Macmillan;
A. Hilger Ltd., 1986, pp. 519.

[25] E. Loewen and E. Popov, Diffraction Gratings and Applications. New York, New
York: Marcel Dekker Inc, 1997,

78

Page 94

79


[26] C. Heine, "Submicrometer Gratings for Solar Cell Applications," Applied Optics, pp.
2476-2482, 1995.

[27] X. Hu, "Particle Swarm Optimization," 2006.

[28] J. G. Mutitu, S. Shi, C. Chen, A. Barnett, C. Honsberg and D. W. Prather, "Light
trapping designs for thin film silicon solar cells," in IGERT: Solar Hydrogen Conference,
2008,

[29] J. D. Joannopoulos, S. G. .Johnson, J. N. Winn and R. D. Meade, Photonic Crystals:
Molding the Flow of Light. ,2nd ed.Princeton University Press, 2008,

[30] D. W. Prather, S. Shi, A. Sharkawy, J. Murakowski and G. Schneider, Photonic
Crystals: Theory Applications and Fabrication. John Wiley and Sons, 2009,

[31] J. M. Gee, "Optically enhanced absorption in thin silicon layers using photonic
crystals," in 29th IEEE Photovoltaic Specialists Conference, may 19,2002 - may 24,
2002, pp. 150-153.

[32] L. Zeng, Y. Yi, C. Hong, B. A. Alamariu, J. Liu, X. Duan and L. C. Kimerling,
"New solar cells with novel light trapping via textured photonic crystal back reflector," in
2005 MRS Fall Meeting, November 28,2005 - December 01, 2006, pp. 251-256.

[33] L. Zeng, Y. Yi, C. Hong, J. Liu, N. Feng, X. Duan, L. C. Kimerling and B. A.
Alamariu, "Efficiency enhancement in Si solar cells by textured photonic crystal back
reflector," Appl. Phys. Lett., vol. 89, 2006.

[34] P. Bermel, C. Luo, L. Zeng, L. C. Kimerling and J. D. Joannopoulos, "Improving
thin-film crystalline silicon solar cell efficiencies with photonic crystals," Optics Express,
vol. 15, pp. 16986-17000, 2007.

[35] S. Venkataraman, "Fabrication of Two-Dimensional and Tree-Dimensional Photonic
Crystal Devices for Applications in Chip-Scale Optical interconnects," 2005.

[36] Department of Energy, "Solar History Timeline," 2009.

[37] M. A. Green, K. Emery, Y. Hishikawa and W. Warta, "Solar cell efficiency tables
(Version 33)," Prog Photovoltaics Res Appl, vol. 17, pp. 85-94, 2009.

[38] A. V. Shah, H. Schade, M. Vanecek, J. Meier, E. Vallat-Sauvain, N. Wyrsch, U.
Kroll, C. Droz and J. Bailat, "Thin-film silicon solar cell technology," Prog Photovoltaics
Res Appl, vol. 12, pp. 113-142, 2004.

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