High-Efficiency GaAs Solar Cells on mm and sub-mm Grain-Size Polycrystalline Ge Substrates

    Research output: Contribution to conferencePaper


    GaAs material and device structure optimization studies on optical-grade, millimeter-and-less grain-size polycrystalline Ge substrates are presented. We discuss the growth of high-quality epitaxial layers across various crystalline orientations of a polycrystalline substrate; this is important for obtaining high-performance solar cells. The GaAs solar cell on n-type poly-Ge substrate is a p-on-ntype, with an undoped spacer between the p-emitter and the n-base. An experimental study of dark currents in these junctions, with and without the spacer, as a function of temperatuer (77K to 288K) is presented; this study suggests that the spacer reduces the tunneling contribution to dark current. In addition, we describe device-structure optimization studies that have led us to achieve anopen-circuit voltage (Voc) exceeding 1 Volt and an AM 1.5 efficiency of .apprx. 19% for a 4-cm2-area GaAs cell on sub-mm grain-size poly-Ge. We have also observed an efficiency .apprx. 21% for a 0.25-cm2-area cell on similar small-grain poly-Ge substrates.
    Original languageAmerican English
    Number of pages12
    StatePublished - 1997
    EventNREL/SNL Photovoltaics Program Review: 14th Conference - Lakewood, Colorado
    Duration: 18 Nov 199622 Nov 1996


    ConferenceNREL/SNL Photovoltaics Program Review: 14th Conference
    CityLakewood, Colorado

    Bibliographical note

    Work performed by Research Triangle Institute, Research Triangle Park, North Carolina

    NREL Publication Number

    • NREL/CP-23674


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