Non-destructive testing of crystalline silicon photovoltaic back-contact modules

Abstract

One-step module encapsulation and interconnection using conductive back sheet foils and conductive adhesives has advantages including i) fast module assembly, ii) limiting cell handling to a one time pick-and-place, and iii) low temperature (<;160°C) processing. Drawback of the integrated module production, however, is that interconnected cells can only be inspected after the module has been laminated. Furthermore, because all electrical interconnections are located between the cells and the conductive foil, non-destructive test methods are required for the inspection of photovoltaic (PV) modules produced with this method. In this contribution complimentary non-destructive test methods, including lock-in thermography using a forward bias in the dark (power is dissipated) are compared as methods for testing back-contact modules allowing i) the accurate discrimination of failed and functioning interconnections between cells and the conductive foils, and ii) the detection of delamination of the back side foil. Included in the comparison are electroluminescence, infrared thermography, X-ray scanning, and ultrasonic inspection. Drawbacks and benefits of each test method are summarized and this shows that lock-in thermography is a fast, accurate, and economical non-destructive test method that can be applied for back-contact modules.