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Title:
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Reliability of back-contact MWT modules under hot and humid conditions
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Author(s):
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Bandou, F.; Hadj Arab, A.; Belkaid, M.S.; Rosca, V.; Guichoux, M.G.; Eerenstein, W.; Roosmalen, J.A.M. van; Logerais, P.O.
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Published by:
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Publication date:
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ECN
Solar Energy
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18-11-2015
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ECN report number:
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Document type:
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ECN-W--15-037
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Article (scientific)
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Number of pages:
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10
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Published in: British Journal of Applied Science & Technology (Sciencedomain International), , 2016, Vol.13, p.1-10.
Abstract:
Aims: Back-contact metallization-wrap-through (MWT) modules made with different materials were
manufactured and tested at ECN in The Netherlands.
Study Design: Damp heat testing (DH, 85°C and 85% relative humidi ty) was performed to
investigate the effect of the module materials and potential failure mechanisms on electrical
performance degradation.
Place and Duration of Study: ECN Solar Energy, P.O.Box 1, 1755 ZG Petten, Netherlands and
Centre de Développement des Energies Renouvelables, Division Energie Solaire Photovoltaïque,
Route de l'Observatoire, BP 62, Bouzaréah, 16340, Alger, Algeria, between June 2011 and March
2015.
Methodology: Fourteen back-contact MWT modules with different combinations of four conductive
backsheet foils (inner isolation layers, also referred to as inner layer dielectric, ILD), two electrically
conductive adhesives (CA) and two encapsulants were tested.
Results: Results reveal that modules which combine conductive backsheet foil with two types of
ILD and ethylene-vinyl-acetate (EVA) showed the highest degradation levels. It is suggested that
effects of moisture in EVA cause a weakening of the adhesion strength at the ILD/Cu interface and
then delamination between conductive adhesive and Ag-plated contacts applied to the copper
interconnection foil. Removal of ILD significantly improves the stability of back-contact modules.
Enhanced reliability is observed for modules which combine ILD-free foil Cu backsheet, conductive
adhesive and polyolefin or EVA as encapsulant.
Conclusion: Removal of ILD is the most interesting approach and is currently adopted by foil
manufacturers. Importantly, the modules built with ILD-free backsheet and either polyolefin
encapsulant or EVA showed respectively only 0.3% and 1.6% maximum power loss after 2000
hours of damp heat which is well below the requirement of the IEC 61215 standard.
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