Production of thin (70-100 μm) crystalline silicon cells for conformable modules

PhosTop solar cells, having a back Al alloy p-n junction with a Ag/SiN_x/n⁺np⁺/Al structure, were fabricated from dendritic web silicon substrates 70-100 μm thick. High-throughput, automated production tools (screen printers, belt furnaces, etc.) were used to produce 3.3 cm × 10.0 cm cells. Cell blanks remained essentially flat throughout the process, in spite of full back coverage by screen-printed and alloyed aluminum. The ability of thin web substrates to remain flat is tentatively attributed to three factors: the open structure of the aluminum layer (89% packing factor), the relatively small thickness of the aluminum layer (17 μm), and the effective stiffening of the web substrate by slip dislocations pushed against internal twin planes. Cell efficiencies up to 14.1%, with excellent IQE, were obtained. These thin web cells were found to conform comfortably to the curved surface of a cylinder 15 cm in diameter. Demonstration modules, designed to fit around a pole 50 cm in diameter, were also fabricated.