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Cavities observed in PV modules induced by the tabbing and stringing process

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By Eric Pilat, CEA-INES, LMPV (Module Laboratory); Manuel Hidalgo, Senior Research Scientist, ARKEMA Sollia Laboratory, LMPV; Dominque Thil, ARKEMA Sollia Laboratory, LMPV; Marion Vite, CEA-INES, LMPV (Module Laboratory)

A major cause of failure in PV modules is related to the penetration of the module by moisture and its retention within. The presence of moisture results in corrosion of metallic contacts or accelerates the molecular degradation of the encapsulant, causing a loss of transparency and in some cases the development of yellowing. The moisture penetration may be intrinsic to the resin itself, but most often it will occur at the interfaces. As a consequence, the adhesion of the resin to glass, metallization, cell and backsheet surfaces may be affected. Engineers involved in the assembly of PV modules used to link adhesion degradation issues to poor conditions for storing polymeric materials, especially the encapsulation resin and the backsheet. In this paper another cause, which has not yet been studied by specialists, is discussed. It is shown that the welding of copper strips can induce residues which prevent the satisfactory adhesion of the resin, resulting in elamination. This phenomenon is identified by ‘spots’ along the busbars after lamination. The study highlights the possible consequences of these defects for a module’s performance, after consecutive thermal cycling, damp-heat and humidity-freeze testing. Recommendations are also given for choosing a suitable solder flux and optimizing the soldering process, in order to maintain satisfactory control over potential delamination problems.

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For manufacturers who had their heads in the bunker during 2012, fighting falling ASPs and eroding margins, the nineteenth edition brings you details of what lies in store for this coming year. Wright Williams & Kelly return in this issue with their popular analysis of payback on technology buys; crucially they analyze n-type wafers, Al2O3 passivation and copper metallization. SERIS shows us how to achieve 18.7% efficiencies using low-cost etching techniques on diffused wafers. We also have two important technology roundups: CIGS from Helmholtz Berlin, and PV module encapsulation techniques from Fraunhofer ISE.

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