near-perfect antireflection coating for silicon solar energy utilization weijian yang department of...
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Near-perfect antireflection coatingfor silicon solar energy utilization
Weijian Yang
Department of Electrical Engineering and Computer Sciences
University of California, Berkeley, CA, 94720, USA
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UC Berkeley 2EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
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.
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UC Berkeley 3EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
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.
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UC Berkeley 4EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
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.
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UC Berkeley 5EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
Graded index
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UC Berkeley 6EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
Moth’s eye
Graded effective medium can reduce index mismatch at the interface and eliminate reflection.
Change air/material ratio gradually.
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UC Berkeley 7EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
Oblique-angle deposition
A random growth fluctuation in the substrate produces a shadow region that the subsequent incident vapor flux cannot reach.
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UC Berkeley 8EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
Graded index AR coating
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UC Berkeley 9EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
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
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UC Berkeley 10EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
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.
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UC Berkeley 11EE 235 Solar Cell Presentation Weijian Yang Mar. 2, 2009
Thank you!
Thank you!