Selective Laser Melting of Metal Foils for Ultrathin Patterned Contacts in Silicon Solar Cells

The vast majority of today's solar modules are produced using screen printing of silver pastes, which places a heavy burden on the supply of this increasingly expensive metal. The expected growth in photovoltaic electricity generation requires alternative metallisation techniques that minimise or eliminate the use of silver, which today accounts for up to one quarter of the non-silicon cost of cell production. To address this pressing need this work describes a novel way of producing silicon-metal interfaces via selective laser melting of foils. We apply the recent innovations of laser assisted additive manufacturing of metals to the production of finger contacts in silicon solar cells. We demonstrate that fingers as thin as 15 mu m can be laser melted and contacted to the surface of a textured and oxidised silicon surface, directly from a metal foil. We perform scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements of these contacts to demonstrate the potential of this new technique. The process described here uses readily available metal foils, and low-cost, high-throughput laser equipment, which can be easily integrated into the manufacture of PERC-like device architectures. The implementation of this metal printing technique could lead to an extremely promising new method of manufacturing ultrathin and high aspect ratio contacts for silicon solar cells.