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Comparison of the device physics principles of planar and radial p-n junction nanorod solar cells

Kayes, Brendan M. and Atwater, Harry A. and Lewis, Nathan S. (2005) Comparison of the device physics principles of planar and radial p-n junction nanorod solar cells. Journal of Applied Physics, 97 (11). Art. No. 114302. ISSN 0021-8979. http://resolver.caltech.edu/CaltechAUTHORS:KAYjap05

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Abstract

A device physics model has been developed for radial p-n junction nanorod solar cells, in which densely packed nanorods, each having a p-n junction in the radial direction, are oriented with the rod axis parallel to the incident light direction. High-aspect-ratio (length/diameter) nanorods allow the use of a sufficient thickness of material to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers in a direction normal to the light absorption. The short collection lengths facilitate the efficient collection of photogenerated carriers in materials with low minority-carrier diffusion lengths. The modeling indicates that the design of the radial p-n junction nanorod device should provide large improvements in efficiency relative to a conventional planar geometry p-n junction solar cell, provided that two conditions are satisfied: (1) In a planar solar cell made from the same absorber material, the diffusion length of minority carriers must be too low to allow for extraction of most of the light-generated carriers in the absorber thickness needed to obtain full light absorption. (2) The rate of carrier recombination in the depletion region must not be too large (for silicon this means that the carrier lifetimes in the depletion region must be longer than ~10 ns). If only condition (1) is satisfied, the modeling indicates that the radial cell design will offer only modest improvements in efficiency relative to a conventional planar cell design. Application to Si and GaAs nanorod solar cells is also discussed in detail.


Item Type:Article
Additional Information:©2005 American Institute of Physics. Received 7 October 2004; accepted 15 March 2005; published online 23 May 2005. This work was supported by the National Renewable Energy Laboratory.
Subject Keywords:silicon; gallium arsenide; elemental semiconductors; III-V semiconductors; solar cells; minority carriers; diffusion; semiconductor device models; carrier lifetime
Record Number:CaltechAUTHORS:KAYjap05
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:KAYjap05
Alternative URL:http://dx.doi.org/10.1063/1.1901835
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4165
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Aug 2006
Last Modified:26 Dec 2012 08:58

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