Front and Rear Pressure Contact Degradation in Solar Modules Due to Thermal Cycle Treatment

Abstract

Front and rear pressure contact is essential for low contact resistance between solar cell and interconnection ribbon after module fabrication. However, the contact resistivity increases due to thermal cycle treatment. Therefore, the influence of soldering failures on series resistance of one-cell modules is investigated by a variation of number and position of intended soldering failures. At initial state, all samples are of similar performance. The degradation of these test modules due to thermal cycle treatment occurs soldering number and position dependent. The degradation curves are fitted by varying the pressure contact resistivity between interconnection ribbon and front and rear metallization, respectively. Simulations reveal an increasing pressure contact resistivity for front and rear side and for the rear side an increase of the metal layer sheet resistance due to thermal cycle treatment. After 400 thermal cycles the pressure contact resistivity increases by two orders of magnitude from 1 to 85 mΩcm² for front and from 4 to 250 mΩcm² for rear side.