To unlock the full performance potential of silicon heterojunction solar cells requires reductions of parasitic absorption and shadowing losses. Yet the translation of the hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) window layer and copper-plated electrodes to a cost-effective and scalable production-relevant context remains one of the largest roadblocks towards mainstream adoption of silicon heterojunction technology. Here we address the first challenge by developing an industrial-scale high-frequency plasma-enhanced chemical vapour deposition system with a minimized standing wave effect, enabling the deposition of doped nc-SiOx:H with excellent electron selectivity, low parasitic absorption and high uniformity. Next, we demonstrate seed-free copper plating, resulting in grids with a high aspect ratio and low metal fraction. By implementing the doped nc-SiOx:H window layer, certified efficiencies of 25.98% and 26.41% are obtained for M6-size bifacial silicon heterojunction devices with screen-printed silver electrodes and copper-plated electrodes, respectively. These results underline the performance potential of silicon heterojunction technology and lower the threshold towards their mass manufacturing.