Manufacturing of High-Efficiency Bi-Facial Tandem Concentrator Solar Cells: February 20, 2009--August 20, 2010

    Research output: NRELSubcontract Report

    Abstract

    Spire Semiconductor made concentrator photovoltaic (CPV) cells using a new bi-facial growth process and met both main program goals: a) 42.5% efficiency 500X (AM1.5D, 25C, 100mW/cm2); and b) Ready to supply at least 3MW/year of such cells at end of program. We explored a unique simple fabrication process to make a N/P 3-junction InGaP/GaAs/InGaAs tandem cells . First, the InGaAs bottom cell isgrown on the back of a GaAs wafer. The wafers are then loaded into a cassette, spin-rinsed to remove particles, dipped in dilute NH4OH and spin-dried. The wafers are then removed from the cassette loaded the reactor for GaAs middle and InGaP top cell growth on the opposite wafer face (bi-facial growth). By making the epitaxial growth process a bit more complex, we are able to avoid more complexprocessing (such as large area wafer bonding or epitaxial liftoff) used in the inverted metamorphic (IMM) approach to make similar tandem stacks. We believe the yield is improved compared to an IMM process. After bi-facial epigrowth, standard III-V cell steps (back metal, photolithography for front grid, cap etch, AR coat, dice) are used in the remainder of the process.
    Original languageAmerican English
    Number of pages35
    StatePublished - 2011

    Bibliographical note

    Work performed by Spire Semiconductior Corporation, LLC, Hudson, New Hampshire

    NREL Publication Number

    • NREL/SR-5200-51767

    Keywords

    • bi-facial tandem
    • CPV
    • IMM
    • solar cells

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