Fully screen-printed PERC cells with laser-fired contacts — An industrial cell concept with 19.5% efficiency

The introduction of a dielectric rear side passivation with local contacts (PERC) opens a path for improvements in the cost of crystalline silicon photovoltaics. First, the cell efficiency is increased by higher internal rear side reflectance and better passivation. Second, the elimination of the cell bow allows the use of thinner wafers to reduce the silicon consumption. While the PERC cell concept is well known, there is still no favorable industrial solution for the rear side metallization. Currently, there are two candidates for industrially relevant processes: The i-PERC process, where the dielectric is opened before the application of the rear-side metallization, and laser-fired contacts (LFC), where the contacts are laser-fused after metallization. LFC promises good process robustness. However, so far, state-of-the-art efficiencies were only reported with evaporated Al rear-side metallization (PVD). Nevertheless, near-term introduction of the PERC concept would favor a fully screen-printed (SP) metallization to maintain compatibility with established process equipment. We report on the development of a fully screen-printed PERC cell with LFC. The optimization of the cell performance requires a co-optimization of both the passivation stack and the rear-side metallization.