Controlling Ink's Spreadability to Reduce Its Disorderly Flow for Promoting the Uniformity of Silver Nanowire Transparent Electrode

Abstract

In wet-process film preparation, much surfactant is conventionally incorporated into the ink because traditional viewpoint believes more surfactant can bring about higher film uniformity. In this work, we discover this popular viewpoint is not completely correct and may hinder the preparation of uniform film instead. In fact, with the increase of surfactant dosage, the silver-nanowire-film uniformity increases at low surfactant concentration first but then decreases at other wide concentration. Further studies reveal the reason: (1) appropriate ink’s spreading distance is critical for obtaining uniform film and both insufficient and excess spreading distance will bring about disorderly ink flow to lower the film uniformity; (2) at low concentration, the increase of surfactant dosage promotes the ink’s wettability and spreadability simultaneously from insufficient level to suitable level, hence the film uniformity increases; (3) at other wide concentration, the increase of surfactant dosage almost doesn’t further improve the ink’s wettability obviously but brings about excess spreadability instead to make the ink disorderly flow, so the film uniformity decreases. Based on above theoretical results, we reduce FS-3100 surfactant concentration from 0.10% to 0.022%. The sheet-resistance variation coefficient of film decreases from 47.56% to 9.80%, indicating that the film uniformity is greatly improved. Meanwhile, no ink overflow from the substrate is observed at 0.022% FS-3100 and ink-waste problem in industry is solved. Above theoretical results correct traditional viewpoint and above film-uniformity promotion method can be widely used by science and industry.