Flexible InP based quantum dot light-emitting diodes using Ag nanowire-colorless polyimide composite electrode

A smooth, flexible, and transparent electrode was fabricated by embedding a percolated network of Ag nanowires (AgNWs) at a surface of colorless polyimide utilizing an inverted layer film-processing approach. The electrode with buried AgNWs showed excellent physical characteristics: a smooth surface roughness (less than 1 nm in root-mean-square roughness), high flexibility (resisted cyclic bend testing with a curvature radius of 500 μm for 1000 iterations), high transparency (higher than 84% at a wavelength of 550 nm), and good conductivity (12.38 Ω/sq for sheet resistance). One demerit that remained for this electrode was a limited surface coverage of conductive pathways for electric carrier transference, originated from the fully embedded structural configuration. Here, the authors could successfully deal with this issue by an Ar plasma treatment in order to partially excavate the embedded AgNWs without a significant increase in surface roughness. Green quantum-dot light-emitting diodes (QLEDs) using InP based quantum dots were fabricated using these composites as a bottom electrode. Hole-injection was poor for an electrode without the plasma treatment since the AgNWs were fully buried beneath the composite's surface. As a result of the plasma treatment, however, the authors could obtain much improved electroluminescence properties of the flexible QLEDs due to the enlarged conductive pathways. The fabricated flexible devices showed durable performance even under a bending with a curvature radius of 5 mm.