Highly transparent and conductive electrode based on aligned silver nanowires

Abstract

The wide attention paid to one-dimensional nanomaterials such as nanotubes, nanorods and nanowires has been fuelled by the anisotropic physical properties and the potential application of these nanomaterials in opto-electronic nanodevices. Among these one-dimensional nanomaterials, silver nanowires (AgNWs) are widely chosen for research due to their excellent intrinsic electrical conductivity and high aspect ratio, on top of the high optical transmittance and relatively simple synthesis process. However, current methods of depositing AgNWs, such as drop casting and electrostatic spraying, produce randomly-orientated AgNWs. Herein, stirring-assisted assembly of aligned AgNWs with high transparency and conductivity, is reported. The AgNW thin film is comprised of layers of aligned AgNWs and polyethlyenimine (PEI) on a polydimethylsiloxane (PDMS) substrate. The AgNWs are aligned using a facile stirring technique that produced an orientation factor of up to 0.846 and alignment within ±0.4° of the stirring direction. Moreover, the AgNW thin film with 90° cross alignment possessed significantly enhanced electrical and optical properties (i.e. sheet resistance, Rs = 3.7 W/sq and transmittance, T550nm = 85%), compared to that of randomly-orientated AgNWs (i.e. Rs = 179.7 W/sq). The influence of parameters, such as stirring speed and solvent, on the alignment of AgNWs were also explored and it was discovered that 500 rpm and glycerol are the ideal stirring speed and solvent, respectively. The usage of PEI improved the adhesion of AgNWs on the PDMS substrate where the coverage density of AgNWs increased with increasing stirring duration and layers (in multi-layered structures). Furthermore, the stirring technique is compatible with large-area assembly of AgNWs and the monolayers can be repeatedly aligned in a layer-by-layer (LbL) manner with different orientation modes for multi-layered structures. As a proof of concept, the function of the 90° cross-aligned AgNW thin film as a transparent electrode to illuminate an LED light is demonstrated.