Highly Conductive, Transparent, and Antireflective PEDOT:PSS/ITO/Ag/ITO on Parylene-C with Tunable Peak Transmittance

Transparent and flexible conductive thin films are critical components in optoelectronics, such as wearable electronics, biosensors, and displays. Traditional transparent electrodes made of a single layer of indium-tin-oxide (ITO), ultrathin metal, graphene or poly-(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT: PSS) hardly possess the desired combination of high transmittance, low electrical resistivity, mechanical flexibility, and biocompatibility. Although ITO/Ag/ITO multilayer thin films have been studied for solar cell applications, the deposition of high-quality ITO usually requires high-temperature processes incompatible with polymers. In this work, we successfully fabricated an ultra-flexible, conductive, transparent thin film using a PEDOT:PSS/ITO/Ag/ITO multilayer structure on Parylene C at room temperature. Compared to single-layer ITO of an equivalent thickness, the multilayer film exhibited significantly enhanced sheet conductivity, reduced electrochemical impedance, remarkable transmittance, excellent adhesion, and flexibility. The peak transmittance of the combined films can be tailored to a specific wavelength for particular applications, such as optogenetics. Besides Parylene C, our high-quality ITO/Ag films can be deposited on a wide variety of heat-sensitive substrates over large scales.