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Proceedings Paper

One aspect of solar cell efficiency: multiple wavelengths photon absorption in nano-silicon structures
Author(s): Jaspreet S. Nayyar; Anand Kulkarni
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Paper Abstract

Among several factors, like photon capture, photon reflection, carrier generation by photons, carrier transport and collection, the efficiency also depends on the absorption of photons. The absorption coefficient, α, and its dependence on the wavelength, λ, is of major concern to improve the efficiency. Nano-silicon structures (quantum wells and quantum dots) have a unique advantage that multiple direct and indirect band gaps can be realized by appropriate size control of the quantum wells. This enables multiple wavelength photons of the solar spectrum to be absorbed efficiently. We present a theoretical approach to calculate the absorption coefficient using quantum mechanical calculations on the interaction of photons with the electrons of the valence band. In our model, the oscillator strength of the direct optical transitions is enhanced by the quantum confinement effect in Si nanocrystallites. These kinds of quantum wells can be realized in practice in porous silicon. Our theoretical estimations show the absorption coefficient of silicon quantum dots to be comparable to that of bulk silicon, and is also nearly constant over the visible spectrum.

Paper Details

Date Published: 20 August 2009
PDF: 10 pages
Proc. SPIE 7411, Nanoscale Photonic and Cell Technologies for Photovoltaics II, 74110V (20 August 2009); doi: 10.1117/12.826756
Show Author Affiliations
Jaspreet S. Nayyar, Michigan Technological Univ. (United States)
Anand Kulkarni, Michigan Technological Univ. (United States)

Published in SPIE Proceedings Vol. 7411:
Nanoscale Photonic and Cell Technologies for Photovoltaics II
Loucas Tsakalakos, Editor(s)

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