The keynote speaker on day 2 of the TaiyangNews High Efficiency Solar Technologies 2024 conference, Head of Silicon Heterojunction Solar Cell & Module Department at Forschungszentrum Jülich, Kaining Ding, presented an overview of the current trends in HJT production, including the urgency for manufacturers to shift to zero busbar (0BB) technology to further increase efficiency and reduce costs. At present, HJT manufacturers use the G12 half-cell format as well as G12R and G10. A wafer thickness of 110 µm is the industry standard, but some manufacturers have started to experiment with 90 µm wafers. Stencil printing with nickel or steel mask has significantly reduced metal consumption. Silver constitutes 40% to 50% of the silver-coated copper paste used, but the aim is to bring it down to 30%. The mass production cell efficiencies range from 25.4% to 25.5%. At the module level, the manufacturers prefer a bifacial dual-glass module, using reflective stripes on the rear glass. The front glass is textured and AR-coated. A PIB-based edge sealant is the most prevalent option. Commercial module efficiency for HJT modules is more than 23%. Due to its low-temperature processes, HJT cells can withstand the increased oxygen content due to the process of continuous feeding of polysilicon during ingot production as well as the ingot pullers fed with fluid bed reactor (FBR) silicon, both of which help lower costs. Manufacturers are increasingly looking at resolving what Ding referred to as dark degradation, which can cost a few watts. This refers to cells losing their efficiency when placed in the dark. It is an issue because the cell is in a dark environment after it is finished and waits to be used in the module. At this point, the module will be made with lower-efficiency cells. Keeping the cells in nitrogen seems to work as it slows down the degradation. This indicates that the degradation is related to environmental factors like moisture. Most recently, there have been reports of using nitrous oxide or N2O as the oxygen source for the nanocrystalline silicon growth instead of CO2 as a means for controlling dark degradation. At the module level, there is an urgency to shift to 0BB to further reduce the consumption cost of metallization and increase efficiency. Different concepts are being tested. For example, the most favorable solution now is either to use SmartWire technology by Meyer Burger, or Maxwell’s Integrated Film Covering (IFC) approach to position the wires. Contacting is the same, however, in both methods. In terms of the market, Chinese HJT manufacturers are willing to become a solution provider for HJT aspirants outside of China. Outside of China, Europe, the US, India, the Middle East, and Turkiye have emerged as the hotspots for HJT production. He summed up by saying that HJT is already a meaningful case for customers at the system level.
