Structure-property relationships in silver nanowire coatings

• Main Author: Large, Matthew J.
• Other Authors: Dalton, Alan B.
• Published: University of Surrey 2016
• Subjects: 620.1
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690424

This report discusses new understanding of the fundamental links between the micro- and nano-structure of silver nanowire-based transparent conductive films and their resulting macroscopic electrical and optical properties. A new relationship between the optical transmittance and electrical sheet resistance is derived based on percolation theory. Application of this model to experimental data allows parameters of film micro-structure to be determined using macroscopic measurement techniques. Conversely, it is also possible to tailor the optoelectronic properties of a film by manipulation of the length distribution of the constituent nanowire material. Further, we examine the effect of geometrical confinement on silver nanowire networks. It is observed that as feature sizes decrease below some threshold value, there is a rapid increase of sheet resistance. This is understood in terms of finite-size scaling theory, and is linked to film parameters that can be measured from the transmittance-sheet resistance curve (T-R curve) of a given material. The effect is quantified using experimental and simulation data, and the implications for device structure and design are discussed. Expressions describing both the T-R and finite-size scaling responses of a material are derived in terms of length distribution statistics, which allows a deeper understanding of how materials may be tailored to meet application-specific requirements. Finally, a preliminary investigation of the formation of graphene-silver nanowire hybrid electrodes by mechanical transfer deposition of graphene is performed. The T-R model developed is applied to understand the change in film performance (in terms of the T-R response). It is hoped that further development of the work presented will lead to a coherent framework for quantifying and predicting a range of film properties for nanowire materials. This will facilitate material design and speed up optimisation of materials for specific applications, both in academic and industrial settings.