Na Impurity Chemistry in Photovoltaic CIGS Thin Films: An Investigation with X-ray Photoelectron Spectroscopy

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    Abstract

    Thermal processing of Cu(In1-xGax)Se2 thin-films grown as part of photovoltaic devices on soda-lime glass leads to the incorporation of Na impurity atoms in the Cu(In1-xGax)Se2. Na contamination increases the photovoltaic efficiency of Cu(In1-xGax)Se2-based devices. The purpose of this investigation is to develop a model for the chemistry of Na in Cu(In1-xGax)Se2 in an effort to understand how itimproves performance. An analysis of x-ray photoelectron spectroscopy data shows that the Na concentration is equivalent 0.1 at. % in the bulk of Cu(In1-xGax)Se2 thin films and that the Na is bound to Se. The authors propose a model invoking the replacement of column III elements by Na during the growth of Cu(In1-xGax)Se2 thin films. Na on In and Ga sites would act as acceptor states to enhancephotovoltaic device performance.
    Original languageAmerican English
    Pages (from-to)3044-3049
    Number of pages6
    JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
    Volume15
    Issue number6
    DOIs
    StatePublished - 1997

    NREL Publication Number

    • NREL/JA-530-22781

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