Percolation‐Controlled Metal/Polyelectrolyte Complexed Films for All‐Solution‐Processable Electrical Conductors

The use of solution‐processable electrically conducting films is imperative for realizing next‐generation flexible and wearable devices in a large‐scale and economically viable way. However, the conventional approach of simply complexing metallic nanoparticles with a polymeric medium leads to a tradeoff between electrical conductivity and material properties. To address this issue, in this study, a novel strategy is presented for fabricating all‐solution‐processable conducting films by means of metal/polyelectrolyte complexation to achieve controlled electrical percolation; this simultaneously imparts superior electrical conductivity and good mechanical properties. A polymeric matrix comprised of polyelectrolyte multilayers is first formed using layer‐by‐layer assembly, and then Ag nanoparticles are gradually synthesized and gradationally distributed inside the polymeric matrix by means of a subsequent procedure of repeated cationic exchange and reduction. During this process, electrical percolation between Ag nanoparticles and networking of electrical pathways is facilitated in the surface region of the complexed film, providing outstanding electrical conductivity only one order of magnitude less than that of metallic Ag. At the same time, the polymer‐rich underlying region imparts strong, yet compliant, binding characteristics to the upper Ag‐containing conducting region while allowing highly flexible mechanical deformations of bending and folding, which consequently makes the system outperform existing materials.