Reactive Sintering of Copper Nanoparticles Using Intense Pulsed Light for Printed Electronics

Most commercial copper nanoparticles are covered with an oxide shell and cannot be sintered into conducting lines/films by conventional thermal sintering. To address this issue, past efforts have utilized complex reduction schemes and sophisticated chambers to prevent oxidation, thereby rendering the process cost ineffective. To alleviate these problems, we demonstrate a reactive sintering process using intense pulsed light (IPL) in the present study. The IPL process successfully removed the oxide shells of copper nanoparticles, leaving a conductive, pure copper film in a short period of time (2 ms) under ambient conditions. The in situ copper oxide reduction mechanism was studied using several different experiments and analyses. We observed instant copper oxide reduction and sintering through poly(N-vinylpyrrolidone) functionalization of copper nanoparticles, followed by IPL irradiation. This phenomenon may be explained by oxide reduction either via an intermediate acid created by ultraviolet (UV) light irradiation or by hydroxyl (-OH) end groups, which act like long-chain alcohol reductants.