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Optical transmission as a fast and non-destructive tool for determination of ethylene-co-vinyl acetate curing state in photovoltaic modules

Authors

  • Heng-Yu Li,

    1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Neuchâtel, Switzerland
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  • Laure-Emmanuelle Perret-Aebi,

    1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Neuchâtel, Switzerland
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  • Ricardo Théron,

    1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Neuchâtel, Switzerland
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    • now with Gadir Solar, 11510 Puerto Real, Cádiz, Spain.
  • Christophe Ballif,

    1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Neuchâtel, Switzerland
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  • Yun Luo,

    Corresponding author
    • 3S Modultec, Lyss, Switzerland
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  • Ronald F. M. Lange

    1. 3S Modultec, Lyss, Switzerland
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    • now with 9-om ag, Wiesenstrasse 26, CH-3073 Gümligen, Switzerland.

Correspondence: Yun Luo, 3S Modultec, Schachenweg 24, CH-3250 Lyss, Switzerland.

E-mail: yun.luo@3-s.ch

ABSTRACT

Poly(ethylene-co-vinyl acetate) (EVA) is the primary polymer used for encapsulation of photovoltaic (PV) modules. Its degree of cross-linking (gel content) is taken as a major quality reference. The EVA gel content is normally measured by Soxhlet extraction and more recently also by Differential Scanning Calorimetry (DSC). The DSC method is proven here to be fast and effective but is, as the Soxhlet extraction method, destructive to the PV module. With the aim of developing a fast and non-destructive method to determine the gel content, a number of analytical techniques are presented. The most promising method is ultraviolet/visible/near-infrared (UV/Vis/NIR) optical transmission. The measured diffuse transmission reflects the EVA crystallite size, which is related to the EVA gel content. This opens the possibility to apply an in-line analysis of every PV module immediately after the lamination step and could significantly contribute to the process quality control that is needed in future high-throughput production lines of PV modules. Copyright © 2011 John Wiley & Sons, Ltd.

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