CONTACT TAPES ATTACHED TO CIGS MODULES BY ULTRASONIC WELDING

摘要

Al-plated Cu contact tapes were attached to the Mo back contact of 10×10 cm~2, 30×30 cm~2, and 60×120 cm~2 CIGS solar modules by ultrasonic welding of single welding points. The connection occurred between the Al cladding and the Mo or MoSe_x surface ("configuration M") which is exposed by removing the overlying ZnO/CIGS layer on top of it by mechanical scraping. The average peel strength of the welding points ranges between 1 and 7 N, depending on the welding force, power and energy. For increasing welding forces, the peel strength is controlled successively by the adhesion of the interfaces Al/Mo, Al/Cu and Mo/glass. The contact resistance of about 75 mΩ per welding point, corresponding to a resistivity of 1.8 mΩcm~2, was quite stable in the damp-heat (DH) and thermal-cycling (TC) tests. The corrosion sensitivity of the selenised Mo layer, with its MoSe_x surface, was significantly reduced compared to pure Mo. The efficiencies of the ultrasonically welded and encapsulated CIGS modules remained very stable during the DH and TC tests, showing no negative effects which could be attributed to the welding procedure. The number and characteristics of glass outbreaks were evaluated among several thousand welding points. The defect rate could be reduced to about 0.2% by employing an appropriate fixation of the modules and a sufficiently moderate welding force and energy. Glass outbreaks occurred mainly when the welding points were located at small cracks, holes, or cavities at the Mo/glass surface.