Laser-formed stencils for printed silicon solar cells

In this paper, we demonstrate the utility of laser machining stainless steel stencils for printed silicon solar cells. Laser-formed stencils are potentially cheaper than foils and screens formed by lithographic processes and may have some advantage in terms of durability, and they may also have some advantage for alignment between stencil printed features and other laser processed features on the silicon wafer. The standard laser scribing tool used for buried contact solar cell fabrication at UNSW is capable of cutting features of less than 35 microns in stencil foils 80 microns thick. By serendipity, the scribing process converts the slag by-product to an iron compound that can be selectively etched, leaving clean, well-formed stencil features. The foils have proved to be printable, with reasonably well formed features in printed and fired pastes. Initial solar cells have demonstrated efficiencies of 13.5%.