A challenge for x-ray photoelectron spectroscopy characterization of Cu(In, Ga)Se2 absorbers: The accurate quantification of Ga/(Ga plus In) ratio

THIN SOLID FILMS

卷:669

Article; Proceedings Paper

Bechu, Solene^1,2  Loubat, Anais^1,2  Bouttemy, Muriel^1,2  Vigneron, Jackie^1,2  Gentner, Jean-Louis³  Etcheberry, Arnaud^1,2 

[1] Inst Photovolta Ile de France IPVF, 30 RD 128, F-91120 Palaiseau, France

[2] Univ Paris Saclay, CNRS, UVSQ, ILV, 45 Av Etats Unis, F-78035 Versailles, France

[3] Almae Technol SAS, Route Nozay, F-91460 Marcoussis, France

关键词: Copper indium gallium selenide;    X-ray photoelectron spectroscopy;    Surface composition;    Gallium;    Indium;    Surface chemical engineering;   

DOI  :  10.1016/j.tsf.2018.11.029

来源: Elsevier

【 摘 要 】

CIGS (Cu(In, Ga) Se-2) layers are among the more efficient photovoltaic absorbers for thin film solar cells and remain competitive in the worldwide landscape of solar cells devices and modules with also new emerging markets (flexible or metallic substrates, tandem, low or high band gap CIGS.). Their properties are governed by different key composition parameters, and among them the GGI ratio ([Ga]/([Ga] + [In])) which controls the gap value. Indeed, the GGI determination is an important metrological challenge at the surface of the CIGS layer, particularly before the buffer deposition. Using X-Ray Photoelectron Spectroscopy (XPS), we propose here a specific methodology to determine this ratio at the surface. In order to, a surface preparation of the CIGS by chemical treatments, combining an initial flattening by HBr:Br-2:H2O etching with a finishing step performed in KCN:H2O, is implemented. This chemical engineering leads to a quasi perfectsurface, flattened and cleared from surface oxide and selenide phase on which our XPS methodology for GGI determination is tested. The photopeaks choice to obtain the most coherent GGI ratio quantification is discussed. In particular we focus on the Ga3d-In4d region, situated in narrow binding energy domain, and discuss why this photopeak combination can be considered as the most adapted for a representative GGI determination. Quantitative fitting procedure of the Ga3d-In4d region is qualified on a reference epitaxial InxGa1-xAs layer and its implementation in the CIGS case is shown.

【 授权许可】

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