Imec, SolarWorld, and Solvay debut 100-μm thin PV cell



Click image to enlarge: iPERC thin solar wafer

This year's European Photovoltaic Solar Energy Conference and Exhibition saw Belgium's research laboratory Imec, SolarWorld, and Solvay present a 100-μm thick, 156- x 156-mm PERC (passivated emitter and rear cell)-type mono-silicon solar cell integrated in a 255 Wp class-A module. The PERC-based modules, developed by Imec and SolarWorld, were manufactured on SolarWorld's fully automated production line without significant wafer breakage. proving the robustness of PERC technology and the high quality of SolarWorld's module manufacturing. PERC-type silicon solar cells are promising candidates for next-generation cells for mass production because of high conversion efficiencies combined with a reduced amount of silicon. Although the price of silicon feedstock for PV has come down significantly, it still makes sense for cost and performance reasons to explore technology for thin, high-efficiency crystalline Si solar cells. The production yield for thin cells is typically an obstacle hindering full industrial adoption. In addition to increasing the conversion efficiency for thin cells by improving surface passivation, PERC technology also reduces the internal stress in the cells, potentially enabling less critical handling of the thin wafers in manufacturing. Imec and SolarWorld's modules each contain 60 randomly selected i-PERC cells, co-fabricated by Imec's PV research group and SolarWorld Innovations (SWIN), starting from 120-μm thin Cz-silicon wafer material. After surface decoupling and junction formation at SWIN, imec performed rear side passivation and rear laser ablation. The rear aluminum metallization was deposited at SWIN, while imec conducted the silver screen-printing, co-firing and characterization. Cell efficiencies have measured an average 18.5% with a best cell performing at 19% efficiency. Finally, enough cells for module production with 18.5% 0.2% were implemented in 60-cell class-A standard modules using SolarWorld's module manufacturing line. Imec and SolarWorld's modules demonstrated a power higher than 255 Wp measured at SolarWorld's Module Testing Lab. "Despite the final thickness of the wafers of only 100 μm, these cells could be run through SolarWorld's fully automated standard module mass production," said Johannes Kirchner, project manager at SolarWorld and department manager of the PV-Module Testing Lab. Joachim John, R&D PV project manager at Imec, stated: "We are delighted with this achievement as it is yet another demonstration of the industrial relevance of Imec's PERC technology. The low breakage rate in the i-PERC production and in the fully automated module fabrication, together with the narrow processing distribution of the cell results, demonstrate that a serious reduction of silicon material is feasible in highly efficient PERC solar cell production." IMEC SolarWorld Solvay