Large area solution processed transparent conducting electrode based on highly interconnected Cu wire network

Abstract

Virtually unlimited and highly interconnected Cu wire networks have been fabricated on polyethylene terephthalate (PET) substrates with sheet resistance of <5 Omega square(-1) and transmittance of similar to 75%, as alternatives to the commonly used tin doped indium oxide (ITO) based electrodes. This is a four step process involving deposition of commercially available colloidal dispersions onto PET, drying to induce crackle network formation, nucleating Au or Pd seed nanoparticles inside the crackle regions, washing away the sacrificial layer and finally, depositing Cu electrolessly or by electroplating. The formed Cu wire network is continuous and seamless, and devoid of crossbar junctions, a property which brings high stability to the electrode towards oxidation in air even at 130 degrees C. The flexible property of the PET substrate is easily carried over to the TCE. The sheet resistance remained unaltered even after a thousand bending cycles. The as-prepared Cu wire network TCE is hydrophobic (contact angle, 80 degrees) which, upon UV-ozone treatment, turned to hydrophilic (similar to 40 degrees).