Ligand-Engineered Cu@Ni Core-Shell Nanoparticles with Excellent Performance for Printed Electronics

Employing Cu nanoparticle (NP) inks to replace Ag inks for printing conductive patterns is a highly promising manufacturing technology in advanced electronics, due to the cost-effective characteristic and electrochemical migration resistance. However, the easy oxidation in air and high-temperature sintering conditions present significant challenges for the preparation of high-performance Cu NP inks and the fabrication of long-lasting printed electronic devices. To address this, based on the ligand exchange strategy, low-cost, uniformly sized, and stable Cu@Ni core-shell NPs are prepared via a one-pot in situ-reduced method. Then, the influences of varying Ni dosages on the surface ligand structures are investigated. Notably, the dense Ni shell passivates the Cu@Ni NPs, endowing them with excellent oxidation resistance, allowing storage in air for a month without deterioration. Through experiments and molecular dynamics (MD) simulations, the low-temperature sintering mechanisms of the Cu@Ni NPs are systematically elaborated. Compared with Cu NPs, the interfacial diffusion of Cu–Ni core-shell structures and ultrafine particles (UFPs) significantly promotes the sintering of NPs. A low resistivity (18.6 µΩ cm) of Cu–Ni thin films is further achieved via low-temperature sintering (200 °C) and UV nanosecond laser sintering. Finally, large-area and functionalized Cu–Ni conductive patterns are fabricated on flexible substrates, demonstrating great potential in advanced printed electronics.