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Published January 2012 | Supplemental Material
Journal Article Open

Solar Cell Light Trapping beyond the Ray Optic Limit


In 1982, Yablonovitch proposed a thermodynamic limit on light trapping within homogeneous semiconductor slabs, which implied a minimum thickness needed to fully absorb the solar spectrum. However, this limit is valid for geometrical optics but not for a new generation of subwavelength solar absorbers such as ultrathin or inhomogeneously structured cells, wire-based cells, photonic crystal-based cells, and plasmonic cells. Here we show that the key to exceeding the conventional ray optic or so-called ergodic light trapping limit is in designing an elevated local density of optical states (LDOS) for the absorber. Moreover, for any semiconductor we show that it is always possible to exceed the ray optic light trapping limit and use these principles to design a number of new solar absorbers with the key feature of having an elevated LDOS within the absorbing region of the device, opening new avenues for solar cell design and cost reduction.

Additional Information

© 2011 American Chemical Society. Received: September 26, 2011. Revised: December 2, 2011. Publication Date (Web): December 12, 2011. The authors acknowledge helpful discussions with S. Burgos, E. Feigenbaum, E. Kosten, J. Fakonas, D. O'Carroll, J. Grandidier, V. E. Ferry, and K. Aydin. This work was supported by the Energy Frontier Research Center program of the Office of Science of the Department of Energy under Grant DESC0001293 (J.N.M. and H.A.A.) and by Department of Energy under Grant DOE DE-FG02-07ER46405 (D.M.C.).

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