Toward Less Than 10 mg/Wp Silver Consumption in HJT Modules With ECA Based Interconnection

The interconnection technology for solar cells using electrically conductive adhesives (ECA) is a promising low-temperature, low-stress, and lead- and bismuth-free solution. The ECA ensures the bonding between either ribbons/wires and solar cells or cell tiles for shingle configurations providing excellent reliability during accelerated ageing tests and in outdoor conditions. The use of ECA has proven its value in recent years, particularly for interconnecting temperature-sensitive heterojunction (HJT) cells. Consequently, interest in the ECA interconnection process is expected to grow in the coming years, especially due to its compatibility with new Si/Perovskite tandem cells. For this technology, solder pads and even busbars are not necessary, allowing for a significant reduction in the amount of paste deposited at the cell level. However, the quantity of ECA used for interconnection remains substantial, and it is at this level that research must focus to reduce silver consumption. It has been shown that lowering the quantity of ECA deposited on the cell can hinder module reliability. Thus, the preferred approach to reduce silver in the interconnection process without affecting reliability is to use uncoated copper ribbons and to reduce the silver content within the ECAs. To achieve this, we used commercial ECAs with low silver content and also developed ECAs based on copper particles coated with a thin layer of silver to prevent oxidation. With the introduction of full copper metallization on the backside of HJT cells, the total amount of silver in the module can be lowered to 7 mg/Wp. This article presents the latest results obtained on the interconnection of HJT solar cells with ECA bonding material, focusing on reducing silver consumption by using low-silver ECAs combined with pure copper ribbons, Cu-Ag and full Cu pastes for cell metallization.