Towards industrialization of a-Si:H/c-Si heterojunction cells: From 20.5% record cells to 19.8% efficiency on industry compatible 148.5cm2 Cz wafers

In this paper, we present our recent work concerning the industrialization of hydrogenated amorphous/crystalline silicon heterojunction cells (a-Si:H/c-Si HET). Indeed, if efficiencies up to 20.5% have already been announced by INES solar cell group, not all developed processes are fully compatible with industrial constraints because of cost and throughput concerns mainly. Thus, we propose to analyze further, step by step, the process adaptations needed to be compatible with industry requirements. Performing in-house experiments, we can estimate properly main efficiency loss steps (wafer quality, metallization...etc.) and propose solutions to maximize solar cell batch performance, uniformity, repeatability and costs. Based on all this learning, fully industry compatible a-Si:H/c-Si HET solar cells on 148.5cm² Cz wafers have been processed with demonstrated efficiencies up to 19.8%. For specific bifacial HET solar cells, efficiency up to 19.4% has been measured, with bifacial ratio higher than 90% (illuminated back side efficiency compared to standard front side illumination efficiency).