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Proceedings Paper

Carrier collection efficiency in multiple quantum well solar cells
Author(s): Hiromasa Fujii; Kasidit Toprasertpong; Kentaroh Watanabe; Masakazu Sugiyama; Yoshiaki Nakano
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Paper Abstract

The present paper proposes Carrier Collection Efficiency (CCE) as a useful evaluation measure to investigate the carrier transport in quantum well solar cells. CCE is defined as the ratio of the carriers extracted as photocurrent to the total number of the carriers that are photo-excited in the p-n junction area, and can be easily calculated by normalizing the collected current, i.e. the difference between the current under light irradiation and that in the dark, to its saturation value at reverse bias. By measuring CCE as a function of the irradiation wavelength and the applied bias, we can directly and quantitatively evaluate the efficiency of the carrier extraction under operation of the cell, and clarify the underlying problem of the carrier transport. The proposed derivation procedure of CCE is based on the assumption that the saturation of the collected current at reverse bias indicates 100% collection of the photo-excited carriers. We validated this hypothesis by studying the balance between the number of the photo-excited carriers that can be collected at a sufficiently large reverse bias and the number of the photons absorbed in the wells. As a result, the absorption fraction in the MQW region well agreed with the saturated external quantum efficiency as we predicted, indicating CCE defined in this study is an appropriate approximation for the collection efficiency of the carrier generated in the active region of a solar cell device.

Paper Details

Date Published: 25 March 2013
PDF: 8 pages
Proc. SPIE 8620, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices II, 86201F (25 March 2013); doi: 10.1117/12.2003287
Show Author Affiliations
Hiromasa Fujii, The Univ. of Tokyo (Japan)
Kasidit Toprasertpong, The Univ. of Tokyo (Japan)
Kentaroh Watanabe, Research Ctr. for Advanced Science and Technology (Japan)
Masakazu Sugiyama, The Univ. of Tokyo (Japan)
Yoshiaki Nakano, The Univ. of Tokyo (Japan)
Research Ctr. for Advanced Science and Technology (Japan)


Published in SPIE Proceedings Vol. 8620:
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices II
Alexandre Freundlich; Jean-Francois Guillemoles, Editor(s)

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