The optical and electrical properties of silver nanowire mesh films

We present experimental results for the transmission T, haze H, sheet resistance R-s, and its spatial fluctuations Delta R-s for silver nanowire films. Mie light scattering theory of nanowires is developed to predict both T and H as a function of diameter D of wires and the surface fraction phi(s) covered by the wires. Percolation theory is used to derive an equation for R-s in terms of D, the aspect ratio of wires D/L and phi(s). The critical exponent t for percolation of R-s is found to be 1.23 in close agreement with theoretical results for 2D random resistive networks (t = 1.3). These equations show the importance of both the distributions of diameter < D > and aspect ratio of wires < D > < L >/< L-2 > to predict the optical and electrical properties. Spatial fluctuations Delta R-s/R-s can also be significant in these films and be greater than 10% as phi(s) approaches the critical percolation concentration phi(c). We show that the calculated T versus R-s and H versus R-s curves are in good agreement with the experimental data. We propose figures of merit for percolating nanowire films in terms of high T, low H, and low R-s to order the quality of films for touch screen applications. The results show that D < 50 nm and L > 5 mu m are needed to achieve low haze H< 1%, high transmission T > 90%, together with low R-s similar to 100 Omega/sq for touch screen applications. Finally, we present experimental and theoretical results of the real and imaginary refractive indices of AgNW/polymer nanocomposites, and find that the Van De Hulst model is more accurate than the Maxwell Garnett models. (C) 2013 AIP Publishing LLC.