Metallic nanowire networks: effects of thermal annealing on electrical resistance

Abstract

a Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing.Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 Ω sq −1. Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays.

On “resistance overpotential” caused by a potential drop along the ultrathin high aspect ratio gold nanowire electrodes in cyclic voltammetry

“…Some studies demonstrated the modification of electrode materials with ultrathin metal nanowires matrix [12][13][14]. However, highly reproducible devices with regard to the number of NWs crossing the contact electrode gap and contact areas between the NWs and contact electrodes [6,15] have not been practicable thus far. There are reports on low sensitivity, poor performance, and deviations in the cyclic voltammetry (CV) of low-dimensional electrodes [16,17], where the electrode dimension approaches the mean free pathway of the electron in the metal, approx.…”

“…However, our case appears significantly different because the uncompensated nanowire resistance in the present study resulted in the gradient of the potential along the NW. Consequently, it is difficult to introduce a defined value of this parameter over the length of the nanowire network electrode, because it depends on the distance from the contact point to the NWs from the external circuitry and on a percolation pathway [15], so that various points on the NW network Therefore, we would like to emphasize here that a more detailed study, e.g., with the variation of scan rate or concentration of the redox probes for quantitative interpretation of the data is hardly possible in this case. Furthermore, actual magnitudes are given rather for qualitative estimation, because the networks are unstable even in a narrow potential window and are intrinsically not reproducible.…”

Comprehensive Synthesis Study of Well-Dispersed and Solution-Processed Metal Nanowires for Transparent Heaters

“…The immersion treatment in water leads to an efficient dissolution of the insulating capping agent PVP and thus results in a decrease in resistance, in accordance with the literature. Subsequent annealing at 150 ∘ C, the commonly reported glass transition temperature of PVP, aids to lower the resistance further by melting residual PVP and sintering the wire-to-wire junctions, which in turn increases the cross section of the wire-to-wire contact areas [55]. The effect of the water treatment is further studied by FTIR measurements, as shown in Figure 6(d) that depicts the spectra before and after immersion in water.…”

“…Due to the electrically insulating capping agent and solvent, that is, EG and PVP, the as-synthesized nanowires show a high resistance and cannot be used for most applications. Thus, a pre-or postdeposition treatment has to be applied [55]. As a predeposition treatment, the as-synthesized wires are usually centrifuged 1-3 times in acetone and subsequently in either ethanol or water to remove EG and PVP [6,33,42].…”

Deformable and Transparent Ionic and Electronic Conductors for Soft Energy Devices

“…[120] Moreover, the percolated network structures maintain their conductive path by structural reconfiguration during mechanical deformation. Low fabrication cost is another advantage due to a solution-based processing that is compatible with roll to roll slot-die coating.…”