Highly Conductive and Highly Dispersed Polythiophene Nanoparticles for Fabricating High-Performance Conductive Adhesives

The continuous advancement of modern electronic equipment requires increasing the conductivity of electrically conductive adhesives (ECAs), but the gap between discrete silver flakes in conventional ECAs considerably hinder electron transport. In this work, we demonstrated 1500-fold enhancement in electrical conductivity by adding a kind of polythiophene nanoparticle (PTh nanoparticles) in the polyurethane-based ECAs with an optimal value of 3.2 × 104 S/cm. These PTh nanoparticles have exceptionally high conductivity and are capable of forming a stable colloidal suspension in various kinds of organic solvents. These properties enable PTh nanoparticles to be well-distributed in the polymer matrix and enable gap-filling among Ag flakes to fabricate high-performance ECAs. In the presence of PTh nanoparticles, the resulting ECA has not only outstanding conductivity but also excellent electrical stability under high mechanical deformation. The electrical resistivity of the pattern made by the PTh nanoparticles-containing ECAs remained stable after being wrapped in a 6 mm bend radius for over 7500 cycles or pressed under 1000 kPa. In addition, when the ECAs were stored for 2 weeks at 80 °C and 60% relative humidity, no significant change in conductivity of the ECAs was observed. A flexible printed circuit was fabricated using the above-mentioned ECAs containing PTh nanoparticles, demonstrating their potential for advanced flexible electronic devices.