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CPV Cell Infant Mortality Study: Preprint

Description: Six hundred and fifty CPV cells were characterized before packaging and then after a four-hour concentrated on-sun exposure. An observed fielded infant mortality failure rate was reproduced and attributed to epoxy die-attach voiding at the corners of the cells. These voids increase the local thermal resistance allowing thermal runaway to occur under normal operation conditions in otherwise defect-free cells. FEM simulations and experiments support this hypothesis. X-ray transmission imaging of the affected assemblies was not found capable of detecting all suspect voids and therefore cannot be considered a reliable screening technique in the case of epoxy die-attach.
Date: May 1, 2011
Creator: Bosco, N.; Sweet, C.; Silverman, T. & Kurtz, S.
Partner: UNT Libraries Government Documents Department

Phase Separation and Facet Formation during the Growth of (GaAs)1-x(Ge2)x Alloy Layers by Metal Organic Vapour Phase Epitaxy

Description: Metal organic vapour phase epitaxy (GaAs)1-x(Ge2)x alloy layers, 0<x<0.22, were grown at temperatures between 640 and 690 C, on vicinal (001) GaAs substrates. Phase separation occurred in all the layers. The phase-separated microstructure changed with alloy composition, growth temperature, and substrate orientation. In x {approx} 0.1 layers grown at 640 C, Ge segregation occurred on {l_brace}115{r_brace}B planes associated with a {l_brace}115{r_brace}B surface faceting. Increase in growth temperature led to the formation of large, (001)-oriented, irregular-shaped platelets of Ge-rich material. Growth on {l_brace}115{r_brace}B substrates resulted in a ''natural superlattice'' of GaAs/Ge along the growth direction.
Date: September 13, 1999
Creator: Norman, A. G.; Olson, J. M.; Geisz, J. F.; Moutinho, H. R.; Mason, A.; Al-Jassim, M. M. et al.
Partner: UNT Libraries Government Documents Department

III-V Growth on Silicon Toward a Multijunction Cell

Description: A III-V on Si multijunction solar cell promises high efficiency at relatively low cost. The challenges to epitaxial growth of high-quality III-Vs on Si, though, are extensive. Lattice-matched (LM) dilute-nitride GaNPAs solar cells have been grown on Si, but their performance is limited by defects related to the nitrogen. Advances in the growth of lattice-mismatched (LMM) materials make more traditional III-Vs, such as GaInP and GaAsP, very attractive for use in multijunction solar cells on silicon.
Date: November 1, 2005
Creator: Geisz, J.; Olson, J.; McMahon, W.; Friedman, D.; Kibbler, A.; Kramer, C. et al.
Partner: UNT Libraries Government Documents Department

High performance anti-reflection coatings for broadband multi-junction solar cells

Description: The success of bandgap engineering has made high efficiency broadband multi-junction solar cells possible with photo-response out to the band edge of Ge. Modeling has been conducted which suggests that current double layer anti-reflection coating technology is not adequate for these devices in certain cases. Approaches for the development of higher performance anti-reflection coatings are examined. A new AR coating structure based on the use of Herpin equivalent layers is presented. Optical modeling suggests a decrease in the solar weighted reflectance of over 2.5{percent} absolute as a result. This structure requires no additional optical material development and characterization because no new optical materials are necessary. Experimental results and a sensitivity analysis are presented.
Date: February 23, 2000
Partner: UNT Libraries Government Documents Department