Laser-Powered Co-Firing Process for Highly Efficient Si Solar Cells

This article presents a successful laser-powered cofiring process for highly efficient Si solar cells as a more compact and energy-efficient alternative to the conventional firing process in an infrared (IR) lamp-powered heat chamber.The best cell group reaches with laser firing only 0.1% abs lower cell efficiency compared to the best group with conventional firing, demonstrating the industrial potential of this laser firing technology.Adding the laser enhanced contact optimization (LECO) process after firing improves the cell efficiency for laser firing to the level of conventional firing, demonstrating the potential of the combination of the laser firing and the LECO process.Index Terms-Alternative firing, firing process, laser enhanced contact optimization (LECO), short-circuit effect, silicon solar cells, thermography, vertical cavity surface-emitting laser (VCSEL). I. INTRODUCTIONT HE contact firing is a well-established process in the in- dustrial silicon solar cell production [1].The firing process divides into a low temperature burnout phase, where the binders of the metal pastes burn out, and a high temperature peak phase, where the cell contacts are co-formed on both sides [2].The industrial firing process (further called "conventional firing") takes place in a conveyor belt furnace, where the wafers are thermally processed in an isolated infrared (IR) lamp-powered chamber.The working principle of this chamber is high air temperature and homogenization of the lamp radiation via reflective walls [1].The resulting mix of convective and reflective radiative heating leads to a substantial amount of wasted energy that is not heating the wafer-namely the energy needed for heating