Back contact (BC) cells benefit significantly from ZBB designs, which improve current collection, reduce series resistance, and mitigate edge stress
BC module assembly eliminates the need for Z-shaped soldering, replacing it with linear soldering, which simplifies production and reduces soldering-induced microcracks
The architecture’s unique rear-contact layout enables tighter cell spacing and supports modern full-screen module formats
While all solar cell technologies require some level of optimization at the module stage, back contact (BC) cells demand specific adjustments due to their rear-contact architecture. These differences influence interconnection methods, module layout, and material choices to ensure reliable performance and efficiency.
One common topic in module making is ZBB. This approach has several other benefits in addition to savings on silver. By eliminating the busbars in BC solar cells, the carrier transport path is significantly shortened, which in turn helps reduce series resistance. This design shift also addresses a specific issue in BC architecture known as the electrical shading problem. The adoption of a ZBB layout allows for longer fingers and a larger collection area, which improves current collection and minimizes losses caused by shading. Additionally, this design helps alleviate edge stress, thereby reducing the risk of microcracks and enhancing the overall mechanical reliability of the cell.
Along with the changes they bring at the cell level, BC cells also have specific requirements and advantages in module design and assembly. While many materials and processes overlap with those used for conventional cell architectures like TOPCon, BC’s rear-contact design results in notable differences, particularly in interconnection, layout, and certain BOM components.
One of the most apparent differences is in the cell interconnection process. The absence of frontside electrodes in BC cells allows manufacturers to eliminate the Z-shaped soldering used in standard architectures like TOPCon, which must connect front and rear sides. Instead, BC modules use linear soldering, which not only streamlines the assembly but also helps reduce edge stress by up to 50%, lowering the risk of soldering-related microcracks, according to LONGi. In addition, this configuration supports narrower cell spacing, making BC an ideal candidate for full-screen module designs, according to AIKO.
This text is an excerpt from the TaiyangNews Cell & Module Technology Trends 2025 report, which can be downloaded for free here.