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Two-Junction GaAs/Ge Cells With Three Terminals for PV and CPV Applications

Published online by Cambridge University Press:  31 January 2011

Mahieddine Emziane
Mahieddine Emziane*
Affiliation:
emziane@mit.edumemziane@masdar.ae, Masdar Institute, Materials, POBox 54224, Abu Dhabi, POBox 54224, United Arab Emirates, +971 2698 8016, +971 2698 8121
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Abstract

The present investigation deals with a two-junction device having GaAs as the top cell and Ge for the bottom cell on a Ge substrate. Compared with the conventional two-terminal device configuration, three terminals avoid the loss due to current mismatching between the cells, and the resistance loss originating from the tunnel junction between the cells. Device structures were investigated and optimized with regard to the thicknesses and doping levels of both top and bottom active junctions that lead to the highest device performance. Due to the split of the incident solar spectrum between GaAs and Ge cells, the latter only receives the light to which the former is transparent (mainly in the near infrared) and therefore behaves differently from a single-junction Ge cell. Optimal current-voltage and power-voltage characteristics were generated for individual cells together with the corresponding device PV parameters. The predictions show that an extended spectral coverage is achieved leading to an enhanced overall power output from the devices. The potential applications of these devices in conventional as well as concentrator PV were assessed and discussed as a function of the simulated concentration ratio of the incident light under AM1.5 illumination conditions. We have shown that a relatively thin double-junction GaAs/Ge device can achieve a remarkably high power output.

Keywords

devicesphotovoltaicthin film
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1165: Symposium M – Thin-Film Compound Semiconductor Photovoltaics–2009 , 2009 , 1165-M08-13
Copyright
Copyright © Materials Research Society 2009

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