Highly stretchable & flexible transparent metal conductor from ultra-long metallic nanowire network

Abstract

Ag nanowire is one of strong candidates for ITO substitutes for its high transparency, conductivity and flexibility. Longer nanowire is more beneficial for these properties. And we synthesized ultralong nanowire of ~500um length with multigrowth process which uses repetitive Ag ion reduction. Ultralong Ag nanowires mesh electrode fabricated with suggested vacuum transfer method shows competitive performance, transparency of 96.15%, 94.68%, 92.57%, 90.47% and 88.71% with the sheet resistance of 186 Ohm/sq, 69 Ohm/sq, 23 Ohm/sq, 19 Ohm/sq and 9 Ohm/sq. Suggested vacuum transfer process utilizes the uniform vacuum pressure for filtering, pressing for transfer and fixing a patterning film. This method has various merits. Vertical pressing with vacuum pressure and thin Teflon filter enable this process to transfer Ag nanowires on glass substrate without heat or transfer-assisting material. This process uses dry transfer method and does not involve common steps such as removing membrane filter and rinse. And it can form patterned electrode easily with the aid of patterning film. This process is economical in that Ag nanowires are deposited on the area where they are necessary and the membrane filter is reusable. Subsequent annealing process is important for the enhancement of conductivity. Thermal annealing improves the conductivity of the fabricated nanowires electrode. But process is time-consuming and not proper for flexible electronics. Laser annealing process suggested in this research is expeditious and proper for Ag nanowires annealing on flexible substrates. Laser enhances the field on the nanowires junction part and makes the local heating occur, which prevents the flexible substrate from deformation. The mesh structure of nanowires has advantage in flexible electronics field because of its strain-enduring characteristic. For practical application, design or positioning of electrical element is very important. In this research, bendable Ag nanowires elect...