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Ray optical light trapping in silicon microwires: exceeding the 2n^2 intensity limit

Kosten, Emily D. and Warren, Emily L. and Atwater, Harry A. (2011) Ray optical light trapping in silicon microwires: exceeding the 2n^2 intensity limit. Optics Express, 19 (4). pp. 3316-3331. ISSN 1094-4087. doi:10.1364/OE.19.003316.

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We develop a ray optics model of a silicon wire array geometry in an attempt to understand the very strong absorption previously observed experimentally in these arrays. Our model successfully reproduces the n^2 ergodic limit for wire arrays in free space. Applying this model to a wire array on a Lambertian back reflector, we find an asymptotic increase in light trapping for low filling fractions. In this case, the Lambertian back reflector is acting as a wide acceptance angle concentrator, allowing the array to exceed the ergodic limit in the ray optics regime. While this leads to increased power per volume of silicon, it gives reduced power per unit area of wire array, owing to reduced silicon volume at low filling fractions. Upon comparison with silicon microwire experimental data, our ray optics model gives reasonable agreement with large wire arrays (4 μm radius), but poor agreement with small wire arrays (1 μm radius). This suggests that the very strong absorption observed in small wire arrays, which is not observed in large wire arrays, may be significantly due to wave optical effects.

Item Type:Article
Related URLs:
URLURL TypeDescription
Warren, Emily L.0000-0001-8568-7881
Atwater, Harry A.0000-0001-9435-0201
Additional Information:© 2011 Optical Society of America. Received 22 Nov 2010; accepted 25 Jan 2011; published 4 Feb 2011. The authors thank M. Kelzenberg for provision of data and insightful discussion, D. Callahan for advice on the manuscript and E.Warmann for assistance with figures. This material is based upon work supported as part of the Light Matter Interaction in Energy Conversion, an Energy Frontier Research Center funded by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001293.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0001293
Subject Keywords:Solar Energy
Issue or Number:4
Classification Code:OCIS Codes: (080.0080) Geometric optics; (350.6050) Solar energy; (000.6590) Statistical mechanics; (030.5630) Radiometry; (260.6970) Total internal reflection
Record Number:CaltechAUTHORS:20110415-155438432
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Official Citation:Emily D. Kosten, Emily L. Warren, and Harry A. Atwater, "Ray optical light trapping in silicon microwires: exceeding the 2n2 intensity limit," Opt. Express 19, 3316-3331 (2011)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23348
Deposited On:20 Apr 2011 17:17
Last Modified:09 Nov 2021 16:13

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