Tetradecahedral Cu@Ag core-shell powder with high solid-state dewetting and oxidation resistance for low-temperature conductive paste

The high cost of metallization using low-temperature cured Ag paste is one of the factors limiting the industrial deployment of silicon heterojunction (SHJ) solar cells, which can be mitigated by developing Ag-coated Cu (Cu@Ag) core-shell powders to replace Ag powders. Yet, a large number of grain boundaries in the Ag shell induce solid-state dewetting of the Ag shell and provide oxygen channels to the Cu core, thus adversely affecting the long-term stability and efficient operation of SHJ modules. Here, a novel tetradecahedral Cu@Ag core-shell powder with large Ag shell grains, meaning low grain boundary density, was fabricated by electroless plating, and the formation mechanism of Ag shells with large grains and smooth surfaces was revealed. The tetradecahedral Cu@Ag powder resists dewetting even after heat treatment at 250 °C for 30 min in air and survives oxidization at room temperature for at least 3 months in air, showing better dewetting and oxidation resistance. Experiments and simulations show that the electrode prepared with tetradecahedral Cu@Ag powder has higher electrical conductivity than that prepared with conventional spherical Cu@Ag powder. This study represents a promising strategy for improving the reliability and conductivity of Cu@Ag powder used for the metallization of SHJ solar cells. We demonstrate a novel tetradecahedral Cu@Ag core-shell powder with large Ag shell grains, which has better solid-state dewetting resistance, oxidation resistance and conductivity compared to conventional spherical Cu@Ag core-shell powder.