0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1-eV)/GaInAs(0.7-eV) Four-Junction Solar Cell: Preprint

    Research output: Contribution to conferencePaper

    Abstract

    We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga0.5In0.5P/GaAs/Ga0.75In0.25As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga0.75In0.25As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, alower-bandgap GaxIn1-xAs fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the GaxIn1-xAs fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At abandgap of 0.88 eV, junctions were obtained with very encouraging~80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved inpractice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.
    Original languageAmerican English
    Number of pages7
    StatePublished - 2006
    Event2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4) - Waikoloa, Hawaii
    Duration: 7 May 200612 May 2006

    Conference

    Conference2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4)
    CityWaikoloa, Hawaii
    Period7/05/0612/05/06

    NREL Publication Number

    • NREL/CP-520-39913

    Keywords

    • bandgap
    • four-junction
    • open-circuit voltages
    • PV
    • quantum efficiency (QE)
    • solar cells

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