A key step in industrialization of photovoltaics (PV) is the development of low-cost and large-area metallization processes to substitute the standard screen-printing process of silver paste. Thus Cu and Ni metallization processes enabled by laser patterning have been widely pursued in passivated-emitter rear-cell (PERC) technology. However, the undesirable opto-thermal side-effects of laser processing have so far hindered using similar processes for metallization of Si heterojunction (SHJ) solar cells due to the relatively high sensitivity of SHJ cells to thermal shocks. Here an innovative process is described, in which the laser damage to the SHJ cell is minimized by using a double-mask layer that optically and thermally isolates the device from the laser beam. As a proof of concept, Si heterojunction solar cells of 235 cm2 surface area are metallized using this method and >19% power conversion efficiencies are achieved. This process is applicable to any temperature-sensitive electronic device with front conductive surface, such as perovskite/Si multi-junction and semi-transparent perovskite solar cells.