Research Progress of Zero-Busbar Technology Based on Heterojunction Photovoltaic Modules

In order to reduce manufacturing costs, the design of silicon-based solar modules is changing from a super-multi-busbar design to a zero-busbar (0BB) design. In this study, two different 0BB technologies based on heterojunction with intrinsic thin-layer solar cells—conventional soldering, and Integrated Film Covering (IFC)—were investigated. IFC-based 0BB technology was found to have a lower contact resistance, which well matches the theoretical calculations and module power testing results. To further measure module reliability, a series of tests on solders and silver pastes were carried out. The results show that Sn43Pb43Bi14 solder is more suitable for soldering-based 0BB technology, whereas Sn32Pb42Bi26 solder is more suitable for IFC-based technology. Additionally, silver paste, which is used for solder ribbon contact areas (SRCAs), is suitable for soldering-based 0BB technology. When Ag@Cu paste is used in SRCAs with IFC-based 0BB technology, a reliable connection can also be achieved. After optimization, modules using both techniques were subjected to and passed lifetime tests, including the thermal cycling, humidity freeze, and hot-spot tests required in IEC standards, as well as more rigorous tests such as thermal–dynamic and thermal–static mechanical loading. The results show that the two technologies have great potential for future mass production.