# Research Progress of Zero-Busbar Technology Based on Heterojunction Photovoltaic Modules
## 4 Conclusions  
In this study, two HJT-0 BB technologies (soldering- and IFC-based 0 BB technologies) were systematically examined. Firstly, the contact resistance of the two 0 BB technologies was tested, revealing that the IFC-based 0 BB technology has a lower contact resistance. Both theoretical calculations and module power testing results indicate that the IFC-based 0 BB technology offers a higher \(FF\) and \(P_{max}\). Next, material selection was performed. For solder selection, based on the solder peeling force, solder spreading areas on silver paste, and the stability of small samples after TC200, Bi14 was identified as being suitable for the soldering-0 BB based technology. For the IFC-based 0 BB technology, Bi26 solder was selected based on baking experiments of small modules and their stability after TC200. Additionally, paste selection was conducted. Results from the TC200 and HF20 tests show that, for the soldering-based 0 BB technology, using silver paste in SRCAs ensures the reliability of the module by preventing significant de-soldering. For the IFC-based 0 BB technology, using Ag@Cu paste for the fingers in SRCAs can also provide a reliable connection, as proven by the results of the TC200 and DH1000 tests. Finally, modules of both 0 BB technologies with favorable materials passed the hot-spot tests, as well as more rigorous T-DML and T-SML tests, indicating that both 0 BB technologies have promising application potential. This work provides several strategies for research on HJT 0 BB technologies and ideas for the design and manufacture of photovoltaic modules at a low cost and with a high power output and reliability. In the future, more advanced characterization methods will be used to verify if other factors affect contact resistance, or to understand the specific impact of incomplete contact. Moreover, a micro-characterization of the solder joints will be conducted to explore the underlying mechanism of T-DML degradation.  
Conceptualization, S.Z., Y.C. and J.G.; methodology, S.Z., X.C. and H.C.; formal analysis, S.Z., X.C., H.C. and X.G.; investigation, X.G., Y.X., X.F., R.L. and J.Z.; resources, S.Z., Y.C. and J.G.; data curation, X.G., Y.X., X.F. and R.L.; writing--original draft preparation, X.G., R.L., J.Z., J.Y. and J.T.; writing--review and editing, S.Z., X.C., H.C. and J.T.; supervision, S.Z., X.C., H.C., Y.C. and J.G.; project administration, S.Z., X.C. and H.C.; funding acquisition, Y.C. and J.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Special Fund for Science and Technology Innovation of Jiangsu Province (Grant No. BE2022022-5).  
Not applicable.  
The data presented in this work are available upon request from the corresponding author. The data are not publicly available due to privacy.  
Authors [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company Trina Solar. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.