70,907 research outputs found

    High efficiency, low cost thin GaAs solar cells

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    The feasibility of fabricating space-resistant, high efficiency, light-weight, low-cost GaAs shallow-homojunction solar cells for space application is demonstrated. This program addressed the optimal preparation of ultrathin GaAs single-crystal layers by AsCl3-GaAs-H2 and OMCVD process. Considerable progress has been made in both areas. Detailed studies on the AsCl3 process showed high-quality GaAs thin layers can be routinely grown. Later overgrowth of GaAs by OMCVD has been also observed and thin FaAs films were obtained from this process

    Shallow-homojunction GaAs solar cells

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    Single-crystal GaAs shallow-homojunction solar cells on GaAs or Ge substrates, without Ga sub 1-x Al sub x As window layers, that have conversion efficiencies exceeding 20% at AM1 (17% at AMO). Using a simple theoretical model, good fits were obtained between computer calculations and experimental data for external quantum efficiency and conversion efficiency of cells with different values of n+ layer thickness. The calculations not only yield values for material properties of the GaAs layers composing the cells but will also permit the optimization of cell designs for space and terrestrial applications. Preliminary measurements indicate that the shallow-homojunction cells are resistant to electron irradiation. In the best test so far, bombardment with 1 x 10 to the 16th power/sq cm fluence of 1 MeV electrons reduced the short-circuit current by only about 6%

    THE LUXURY AXIOM, THE WEALTH PARADOX, AND CHILD LABOR

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    Basu and Van (1998) present a fundamental framework of child labor with two important axioms: the luxury axiom and the substitution axiom. A number of empirical studies, however, reveal a ¡°wealth paradox¡±. The current paper has two aims. First, it develops a model that provides an explanation for ¡°the wealth paradox¡± in light of the luxury axiom and the substitution axiom. Second, it helps understand the relationship between the luxury axiom and the substitution axiom.Child Labor, Luxury Axiom, Wealth Paradox, Substitution Axiom
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