Critical work of adhesion for economical patterning of silver nanowire-based transparent electrodes
The lithographic process for flexible transparent electrodes is essential for constructing wearable optoelectronic devices with a well-defined active area. Although photolithography is a well-established patterning process, and can generate small features, it involves toxic materials and high processing cost. Herein, we introduce a novel lithographic process for both silver nanowire (AgNW)-embedded and AgNW-exposed flexible transparent electrodes. We selectively control the adhesion between AgNWs and the substrate via a local surface treatment with ultraviolet/ozone (UV/ozone), oxygen plasma, and atmosphere plasma. Since strong adhesion leads to retention of AgNWs on the substrate during embedding of AgNWs in a UV-curable polymer, selective control of adhesion induces selective embedding of AgNWs, generating AgNW-embedded and AgNW-exposed transparent electrodes with desirable patterns. Additionally, this process is versatile enough to be applicable to various substrates including poly(methyl methacrylate) (PMMA)-coated surfaces, poly(ethylene terephthalate) (PET) films, and acrylic substrates, and various AgNWs with different surface energies. The critical work of adhesion to successfully pattern AgNW-based transparent electrodes is experimentally obtained. Conclusively, we demonstrate that patterning of AgNW-based electrodes by controlling the work of adhesion is economical and eco-friendly, and can be successfully applied for designing various optoelectronic devices such as organic photovoltaic cells and liquid crystal cells.