Progress in Photovoltaics Research and Applications · 2013 · 33 citations · 52 references
Natural SciencesMaterials EngineeringMaterials ScienceElectronic MaterialsSemiconductor MaterialsThin FilmsSemiconductor Thin FilmsSolar Cell MaterialsSolar CellsThin Film Electrical PropertiesThin-film DepositionThin-film MaterialsChalcogenide Thin FilmsFill FactorGrain Size ImprovementGrain Size VariabilitySecondary Ion Mass SpectrometrySodium FluorideThin-film Solar Cells
Abstract We report on a sodium fluoride (NaF) thickness variation study for the H 2 Se batch furnace selenization of sputtered Cu(In,Ga) films in a wide range of Cu(In,Ga) film compositions to form Cu(In,Ga)Se 2 (CIGSe) films and solar cells. Literature review indicates lack of consensus on the mechanisms involved in Na altering CIGSe film properties. In this work, for sputtered and batch‐selenized CIGSe, NaF addition results in reduced gallium content and an increase in grain size for the top portion of the CIGSe film, as observed by scanning electron microscopy and secondary ion mass spectrometry. The addition of up to 20 nm of NaF resulted in an improvement in all relevant device parameters: open‐circuit voltage, short‐circuit current, and fill factor. The best results were found for 15 nm NaF addition, resulting in solar cells with 16.0% active‐area efficiency (without anti‐reflective coating) at open‐circuit voltage ( V OC ) of 674 mV. Copyright © 2013 John Wiley & Sons, Ltd.
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