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Modeling of defect tolerance of IMM multijunction photovoltaics for space application
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Paper Abstract

Reduction of defects by use of thick sophisticated graded metamorphic buffers in inverted metamorphic solar cells has been a requirement to obtain high efficiency devices. With increase in number of metamorphic junctions to obtain higher efficiencies, these graded buffers constitute a significant part of growth time and cost for manufacturer of the solar cells. It's been shown that ultrathin 3 and 4 junction IMM devices perform better in presence of dislocations or/and radiation harsh environment compared to conventional thick IMM devices. Thickness optimization of the device would result in better defect and radiation tolerant behavior of 0.7ev and 1.0ev InGaAs sub-cells which would in turn require thinner buffers with higher efficiencies, hence reducing the total device thickness. It is also shown that for 3 and 4 junc. IMM, with an equivalent 1015 cm-2 1 MeV electron fluence radiation, very high EOL efficiencies can be afforded with substantially higher dislocation densities (<2×107 cm-2) than those commonly perceived as acceptable for IMM devices with remaining power factor as high as 0.85. The irregular radiation degradation behavior in 4-junc IMM is also explained by back photon reflection from gold contacts and reduced by using thickness optimization of 0.7ev and 1.0ev InGaAs sub-cells.

Paper Details

Date Published: 25 March 2013
PDF: 8 pages
Proc. SPIE 8620, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices II, 86200V (25 March 2013); doi: 10.1117/12.2004600
Show Author Affiliations
Akhil Mehrotra, Univ. of Houston (United States)
Alex Freundlich, Univ. of Houston (United States)

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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