Challenges for the interconnection of crystalline silicon heterojunction solar cells

Thumbnail for Challenges for the interconnection of crystalline silicon heterojunction solar cells

Crystalline silicon heterojunction (HJT) solar cells and modules based on amorphous silicon on monocrystalline wafers offer advantages over established wafer-based technologies in terms of efficiency potential, complexity of the manufacturing process, and energy yield of the modules. The temperature sensitivity of these solar cells, however, poses considerable challenges for their integration in modules. Currently, there exist three approaches for the interconnection of HJT solar cells, each with its own strengths and weaknesses:

  • ribbon soldering with low-meltingpoint alloys
  • gluing of ribbons by using electrically conductive adhesives (ECAs)
  • SmartWire Connection Technology (SWCT).

This paper provides an overview of the different approaches and focuses on ribbon-based interconnection technologies. Soldering at process temperatures below 200°C enables standard stringing equipment to be used, but this method is known to result in weak adhesion of the low-temperature metallization pastes on the cell surface. This study focuses on the microstructure of the solder joints for such pastes, and an indication of the origin of the associated low peel strength is given. The dependence of the quality of ECA-based interconnections on curing conditions is analysed with regard to printability, electrical properties and peel strength. Recent results for different ECAs processed using a mass-production stringer are presented, and a 60-cell HJT module exceeding 320Wp is demonstrated.

First published in Photovoltaics International - Volume 40