Facile Post Treatment of Ag Nanowire/Polymer Composites for Flexible Transparent Electrodes and Thin Film Heaters

Abstract

Typical polyol-based synthesis of silver nanowire employs insulating polymer as a surfactant for the silver nanowire growth, which limits direct contact between each nanowire and thus its optoelectronic properties. We herein demonstrate that a simple solvent treatment effectively removes the insulating polymer around Ag NWs, leading to significantly decreased sheet resistance (~12 Ω/sq) with an increased transmittance (81% @ T₅₅₀), as compared to other post-treatments. We successfully demonstrate the transparent film heaters using the solvent-treated Ag NWs network, which rapidly exhibited 150 °C under a bias of 5 V. Flexible film heaters on plastic substrate is also demonstrated, suggesting a great potential of the solvent treatment process of Ag NWs for flexible transparent electrode and film heater applications.

Keywords: film heaters; silver nanowires; transparent conductive electrode.

Figure 1

(a) SEM image of a thick Ag NWs network and (b) a thin Ag NWs network. Inset is a Ag NWs solution with thin and thick diameter.

Figure 2

(a) Optical transmittance and sheet resistance of thick Ag NWs network with various post treatment. Inset is a photograph of a thick Ag NWs network. (b–e) SEM images of a thick Ag NWs network followed by different post-treatment. (b) SEM images of the pristine thick Ag NWs network, (c) thick Ag NWs network after thermal annealing at 130 °C for 20 min, (d) thick Ag NWs network after solvent dipping, and (e) thick Ag NWs after N₂ gas-blowing.

Figure 3

(a) Optical transmittance and sheet resistance of a thin Ag NWs network with various post treatment. Inset is a photograph of the thin Ag NWs network. (b–e) SEM images of the thin Ag NWs network followed by different post-treatment. (b) SEM images of the pristine thin Ag NWs network, (c) thin Ag NWs network after thermal annealing at 130 °C for 20 min, (d) thin Ag NWs network after solvent dipping, and (e) thin Ag NWs after N₂ gas-blowing.

Figure 4

(a) Schematic illustration of layouts for a film heater with Ag NWs networks. (b,c) A photograph of Ag NWs of the thick and thin diameter-based film heaters (size = 20 × 20 mm²).

Figure 5

(a) Time-dependent temperature of thick Ag NWs network-based film heaters (20 × 20 mm²) under operation at different voltages. (b) Temperature evolution of thick Ag NWs network-based film heaters at stepwise voltage rise from 2 to 5V. (c) Temperature profiled of 20 × 20 mm² electrodes, measured using an IR camera. (scale bar = 6.5 mm).

Figure 6

(a) Time-dependent temperature of thin Ag NWs network-based film heaters (20 × 20 mm²) under operation at different voltages. (b) Temperature evolution of thin Ag NWs network-based film heaters at stepwise voltage rise from 2 to 5 V. (c) Temperature profiled of 20 × 20 mm² electrodes, measured using an IR camera (scalebar = 6.5 mm).

Figure 7

(a) The voltage-dependent temperature evolution, (b) sheet resistance variation, and (c) time-dependent temperature of Ag NWs network-based flexible film heaters at different voltages. The bending test was repeatedly performed to 7 mm bending radius.