Recent Progress on the Fabrication and Properties of Silver Nanowire-Based Transparent Electrodes

Abstract

Transparent electrodes (TEs) made of metallic nanowires, such as Ag, Au, Cu, and Ni, are attracting increasing attention for several reasons: (1) they can act as a substitute for tin oxide-based TEs such as indium-tin oxide (ITO) and fluorine-doped tin oxide (FTO); (2) various methods exist for fabricating such TEs such as filtration, spraying, and Meyer bar coating; (3) greater compatibility with different substrates can be achieved due to the variety of fabrication methods; and (4) extra functions in addition to serving as electrodes, such as catalytic abilities, can be obtained due to the metals of which the TEs are composed. There are a large number of applications for TEs, ranging from electronics and sensors to biomedical devices. This short review is a summary of recent progress, mainly over the past five years, on silver nanowire-based TEs. The focus of the review is on theory development, mechanical, chemical, and thermal stability as well as optical properties. The many applications of TEs are outside the scope of this review.

Keywords: chemical stabilities; mechanical stabilities; optical properties; silver nanowires; thermal stabilities; transparent electrodes.

Figure 1

Transmittance (550 nm) plotted as a function of sheet resistance for thin films prepared from four nanostructured materials: graphene, single-walled carbon nanotubes, silver nanowires, and silver flakes. The dashed lines represent fits to the bulk regime using Equation (5), while the solid lines represent fits to the percolative regime using Equation (9). Reprinted from [12], with permission from American Chemical Society, 2010.

Figure 2

Scattering geometry of nanowires in films. Reprinted from [19], with the permission from AIP Publishing, 2013.

Figure 3

Optical haze versus silver area coverage /s for nanowires S-1 (100 nm), S-3 (56 nm), and S-6 (153 nm). Calculated curves are shown as (_____, S-1), (- - - - , S-3) and (........., S-6). Reprinted from [19], with permission from AIP Publishing, 2013.

Figure 4

Scanning electron microscopy (SEM) images of transparent electrodes fabricated from (a,b) 100 nm, (c,d) 60 nm, and (e,f) 20 nm silver nanowires before and after chemical treatment. Reprinted from [31], with permission from John Wiley & Sons, Inc., 2015.

Figure 5

(a) Schematic diagram of an e-textile with a polyester/Ag nanowire (NW)/graphene core–shell structure. (b–d) SEM images of polyester/Ag NW/graphene samples with different numbers of graphene-coating cycles: (b) one cycle, (c) two cycles, and (d) three cycles. SEM images of the fiber cross-linked regions (e) before graphene coating and (f) after graphene coating. (g) Visible-light transmittance of the textile, the textile/Ag NW, and the textile/Ag NW/graphene samples; the insets are photographs. Reprinted from [50], with permission from American Chemical Society, 2016.

Figure 6

(a) Schematics showing the stretching directions of the uniaxial tensile strains for uniwavy NWs and biwavy NWs. Resistance changes as a function of the applied uniaxial tensile strain for (b) uniwavy NWs and (c) biwavy NWs. Resistance changes as a function of the uniaxial cyclic strain for (d) uniwavy NWs and (e) biwavy NWs. Electrodes were repeatedly stretched to 30% and released back to 0%. Reprinted from [55], with permission from American Chemical Society, 2017.

Figure 7

Scheme showing the fabrication of a heterogeneous Ag NW/polymer composite structure. Reprinted from [44], with permission from American Chemical Society, 2017.

Figure 8

Changes in (a) optical transmittance/haze and (b) sheet resistance of the Ag and Al₂O₃/Ag nanowire electrodes as a function of the annealing temperature. The annealing time is 20 min. Reprinted from [5], with permission from Springer Nature Limited, 2017.

Figure 9

Comparison of haze and transmittance for transparent films fabricated with bare Ag nanowires, Au-coated Ag nanowires made using HAuCl₄ exchange, and Au-coated Ag nanowires made using [Au(en)₂]Cl₃ exchange and NH₃ treatment. The sheet resistance for each sample is also stated. Reprinted from [77], with permission from American Chemical Society, 2014.

Figure 10

Schematic drawing of the basic factors for evaluating transparent electrodes.