Study Hoped to Fasten Advent of IoT (Internet of Things) Era by Enabling Plastic Transparent Electrodes on Any Desired Surface via Simple Stamping

A Korean research team has developed a novel method of transfer-printing plastic transparent electrodes, which have both low cost and high performance, onto arbitrary surfaces via simple stamping. Through the versatile integration of high-performance flexible transparent electrodes (FTEs) with other device components, such as flexible devices and adhesive sensors, their research is expected to accelerate the arrival of the Internet of Things era.

The research was led by corresponding author Prof. Kwanghee Lee of GIST School of Materials Science and Engineering and by co-first authors Mrs. Nara Kim, a doctoral student at GIST School of Materials Science and Engineering, and Dr. Hongkyu Kang of the Research Institute for Solar and Sustainable Energies (RISE). This work was supported by a grant from the National Research Foundation of Korea, funded by the Ministry of Science, ICT and Future Planning. The result was published online on April 8, 2015 in Advanced Materials (Title: Highly Conductive All-Plastic Electrodes Fabricated Using a Novel Chemically Controlled Transfer-Printing Method).

Conducting plastics (CPs) have been considered a promising candidate for FTEs to replace conventional transparent electrodes based on brittle and expensive indium tin oxide, due to their mechanical flexibility and low-cost solution processability. However, the necessity of applying a harsh treatment using sulfuric acids to enhance the electrical conductivity of CPs up to that of ITO makes these cost-effective and high-performance FTEs unsuitable for application to most underlying layers, including typical plastic substrates, which would be destroyed by the requisite strong acid treatment.

The research team developed a facile method of transfer-printing the highly conductive plastic FTEs onto arbitrary surfaces, including typical plastic substrates, by controlling the adhesion between plastic films and substrates. While the conventional transfer-printing methods rely on etching the donor substrates for the detachment of the donor-film interface to “ink” an elastomeric stamp with the film, the novel transfer-printing method based on the chemically controlled adhesion at the donor-film interface enabled the simple process of bringing the stamp into contact with the highly conductive plastic films on the donor substrates and lifting  the stamp away to produce a stamp that is fully “inked” with the high-performance plastic FTEs, which is then readily available for transfer-printing onto arbitrary surfaces by using thin adhesive layers. The plastic FTEs transferred onto various surfaces exhibited a high visible-range transmittance of 90% and a low sheet resistance of 45 Ω/sq.

Prof. Lee said, “Our simple and low-cost manufacturing method for high-performance plastic electrodes on arbitrary surfaces is expected to expand the scope of applications of FTEs for the realization of next-generation ubiquitous electronic technologies, including wearable devices, transparent displays, adhesive sensors, and transparent antennas, in the coming era of the Internet of Things.”