Abstract:
Light weight photovoltaic (PV) modules have advantages both to reduce costs of PV installations as well as to enhance their further integration with building and other urban structures such as roofs of public parking areas and bus stations. Polycarbonate (PC) materials have been studied before as glass or front sheet replacement, but recently the PC-PC module design (where both front and back sheets are made of PC) has gained attractions both in industry as well as in research. It offers further additional benefits, such as improved reliability (in terms of silicon cell cracks) and enhanced ease of integration into not only flat surfaces, but also curved ones such as integrated PV in cars, trucks, and boats. These benefits may enable more aesthetic design that can increase the appeal of the PV technology. However, a few technological issues stand between the current forms of PC-PC PV module design and the increasing market demands for more aesthetically pleasing and contour-confirming PV integrations. Two of the most important ones are the silicon sensitivity against fracture (especially in bending mode) and interface delamination (especially between PC and the encapsulants). Both are driven by mechanical stresses in the silicon cells as well as in other materials in the PV module/package design. Having published widely our studies in stresses in silicon solar cells in PV module design, both experimentally as well as computationally as shown in the literature review of this manuscript, our research group has obtained unique insights in the primary driving forces of failures in the typical PV module design (glass-back sheet). In the present manuscript, we use the Width Tapered Cantilever Beam (WTCB) method to investigate the interfacial delamination issues systematically. We found that the energy release rate for delamination or fracture at the interfaces between PC and EVA (Ethylene Vinyl Acetate) was fairly low (i.e. low adhesion strength), but could be enhanced with process parameters during the PV lamination step or separate thermal treatment. Hence, this could be taken advantage for enabling unique and highly innovative PV modules based on PC, and for aesthetic purposes for the wider applications of PV technology.
