Integration and reliability of ultra thin silicon solar cells and modules fabricated using SOM® technology

Thin crystalline silicon solar cells are of interest due to significant material cost reduction and potentially high conversion efficiency. We have previously demonstrated a patented, novel exfoliation technology capable of producing large area (156×156 mm) 25 µm thin flexible mono c-Si cells with high efficiencies. In this paper we address the mechanical strength and handling requirements of these foils during wafer transfer, cell processing and module integration. Based on a bi-material foil composed of thin monocrystalline silicon and a supporting substrate fabricated using our novel SOM^® (Semiconductor on Metal) kerf-less exfoliation process, closed-form mechanical analyses are introduced and developed to evaluate their strength and fracture behaviors. These analyses include the thermal stresses in the composite films and the effect of surface texturing on the fracture behavior of silicon in these foils. Functional cells were fabricated and module reliability results that include thermal shock and highly accelerated stress tests (HAST) are also shown in this paper.