One step preparation of copper–silver self-catalyzed hybrid conductive ink with reduced sintering temperature for flexible electronics

Abstract

Copper–silver hybrid conductive inks can combine the advantages of lower cost, better conductivity and long-term stability of the copper or silver ink, which have attracted wide research interest in the development of materials for flexible electronics. Although Cu–Ag nanoparticle based inks, such as Cu–Ag core–shell nanoparticle inks and Cu–Ag bimetallic nanoparticle inks, have already been developed and applied to produce conductive patterns using different deposition methods, they are still not ideal because of the complex and time-consuming synthetic process, low yield and high sintering temperature for good conductivity. In this paper, we report synthesis and characterization of novel self-catalyzed Cu–Ag organic complex inks with reduced sintering temperature via a simple one-step method. The effects of Cu–Ag ratio on the thermal property, stability and electrical performance of the formulated inks were investigated, where the Cu1–Ag1 ink was found to be ideal in terms of cost, conductivity and thermal behavior. The presence of silver oxalate in the copper complex ink was beneficial to the thermal decomposition of the Cu complex and able to decrease the sintering temperature by 30 °C due to the catalytic function of silver, making it more compatible with flexible polymer substrate materials. Meanwhile, the addition of a small amount of silver oxalate could improve the conductivity of the Cu ink. The sintered Cu–Ag films showed favorable conductivity which is comparable to the value of the reported Cu–Ag nano inks but with a lower sintering temperature. The Cu1–Ag1 hybrid ink with self-catalyzing capability is a balanced choice when considering the cost and conductivity.