High-performance low-cost silver-coated copper paste for silicon heterojunction solar cells

Abstract

The metallization process for silicon heterojunction solar cells usually requires the use of low-temperature curing paste. However, the high silver consumption in conventional silver paste has pushed up the cost of fabricating such solar cells. The silver-coated copper paste which uses copper as a partial replacement for silver has become a feasible solution. Currently, the preparation of high-performance silver-coated copper paste with reduced silver consumption still remains a challenge. This paper has compared several silver-coated copper pastes prepared with various combinations of conductive fillers, and investigated the effects of silver consumption, particle shape, silver content in silver-coated copper powder on the rheological, conductive and mechanical properties. The silver-coated copper paste with 70% silver consumption was able to achieve the volume resistivity of 5.9 μΩ cm, which was even lower than that obtained by pure silver paste. The study also found that the use of spherical shape rather than flake shape silver-coated copper powder would provide the paste with good performance. Furthermore, the silver-coated copper powder containing 20% silver would be the optimal choice for preparing silver-coated copper pastes with 30–50% silver consumption. Moreover, all these prepared silver-coated copper pastes exhibited good environmental stability. The low-temperature curing silver-coated copper paste will thus contribute to the cost reduction and efficiency improvement.