Transcript Slide 1
Near-perfect antireflection coating
for silicon solar energy utilization
Weijian Yang
Department of Electrical Engineering and Computer Sciences
University of California, Berkeley, CA, 94720, USA
Motivation
AR coating can improve solar collection efficiency.
Solar radiation
Broadband spectrum.
Incident angle changes within a day.
An idea AR coating should maintain a low
reflectance for a broadband spectrum and all
angles of incidence.
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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AR coating
Fresnel reflection
Traditional quarter-wave AR coating suffers from a small
range of optical spectrum and incident angle.
Grade index nanorod thin film structure.
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Graded Index
Reflectance of the AR coating depends on
smoothness of the index profile.
Minimize the differential reflectance at each
interface of the multilayer structure.
n ni ( ns ni ) z
n ni ( ns ni )(3 z 2 2 z 3 )
n ni ( ns ni )(10z 3 15z 4 6 z 5 )
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Graded index
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Moth’s eye
Graded effective medium can reduce index
mismatch at the interface and eliminate reflection.
Change air/material ratio gradually.
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Oblique-angle deposition
A random growth fluctuation
in the substrate produces a
shadow region that the
subsequent incident vapor
flux cannot reach.
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Graded index AR coating
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Comparison
Structure
Ave. Reflection Ave. Transmission
Si
32.6%
67.4%
Single layer quarter
wavelength
18.8%
81.2%
Graded index
3.79%
96.12
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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References
M. Kuo, et.al., Opt. Lett., 33, 2527, 2008.
J. Xi, et.al., Nature Photonics, 1, 176, 2007.
J. Xi, et.al., Opt. Lett., 5, 601, 2006.
S. Kennedy, et.al., Appl. Opt., 42, 4573, 2003.
www.physorg.com.
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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Thank you!
Thank you!
UC Berkeley
EE 235 Solar Cell Presentation Weijian Yang
Mar. 2, 2009
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