Exploring the degradation of silver nanowire networks under thermal stress by coupling in situ X-ray diffraction and electrical resistance measurements.

The thermal instability of silver nanowires (AgNWs) leads to a significant increase of the electrical resistance of AgNW networks. A better understanding of the relationship between the structural and electrical properties of AgNW networks is primordial for their efficient integration as transparent electrodes (TEs) for next-generation flexible optoelectronics. Herein, we investigate the in situ evolution of the main crystallographic parameters (i.e. integrated intensity, interplanar spacing and peak broadening) of two Ag-specific Bragg peaks, (111) and (200), during a thermal ramp up to 400 °C through in situ X-ray diffraction (XRD) measurements, coupled with in situ electrical resistance measurements on the same AgNW network. First, we assign the (111) and (200) peaks of χ-scans to each five crystallites within AgNWs using a rotation matrix model. Then, we show that the thermal transition of bare AgNW networks occurs within a temperature range of about 25 °C for the electrical properties, while the structural transition spans over 200 °C. The effect of a protective tin oxide coating (SnO2) on AgNW networks is also investigated through this original in situ coupling approach. For SnO2-coated AgNW networks, the key XRD signatures from AgNWs remain constant, since the SnO2 coating prevents Ag atomic surface diffusion, and thus morphological instability (i.e. spheroidization). Moreover, the SnO2 coating does not affect the strain of both (111) and (200) planes. The thermal expansion for bare and SnO2-coated AgNW networks appears very similar to the thermal expansion of bulk Ag. Our findings provide insights into the underlying failure mechanisms of AgNW networks subjected to thermal stress, helping researchers to develop more robust and durable TEs based on metallic nanowire networks.

Enhancing the Properties of Photo-Generated Metallized Nanocomposite Coatings through Thermal Annealing.

In this work, the effect of thermal annealing on silver nanoparticles@polymer (AgNPs@polymer) nanocomposite coatings was investigated. These photo-generated metallized coatings have a spatial distribution of metal nanoparticles, with a depth-wise decrease in their concentration. During annealing, both structural and morphological variations, as well as a spatial reorganization of AgNPs, were observed, both at the surface and in the core of the AgNPs@polymer coating. Owing to their increased mobility, the polymer chains reorganize spontaneously, and, at the same time, a hopping diffusion process, caused by the minimization of the surface energy, promotes the migration and coalescence of the silver nanoparticles towards the surface. The layer of discrete nanoparticles gradually transforms from a weakly percolative assembly to a denser and more networked structure. Consequently, the surface of the coatings becomes significantly more electrically conductive, hydrophobic, and reflective. The general trend is that the thinner the nanohybrid coating, the more pronounced the effect of thermal annealing on its spatial reorganization and properties. These results open up interesting prospects in the field of metallized coating technology and pave the way for integration into a wide variety of devices, e.g., efficient and inexpensive reflectors for energy-saving applications, electrically conductive microdevices, and printed electronic microcircuits.

Silver Nanowire-Based Transparent Electrodes for V2O5 Thin Films with Electrochromic Properties.

The development of electrochromic systems, known for the modulation of their optical properties under an applied voltage, depends on the replacement of the state-of-the-art ITO (In2O3:Sn) transparent electrode (TE) as well as the improvement of electrochromic films. This study presents an innovative ITO-free electrochromic film architecture utilizing oxide-coated silver nanowire (AgNW) networks as a TE and V2O5 as an electrochromic oxide layer. The TE was prepared by simple spray deposition of AgNWs that allowed for tuning different densities of the network and hence the resistance and transparency of the film. The conformal oxide coating (SnO2 or ZnO) on AgNWs was deposited by atmospheric-pressure spatial atomic layer deposition, an open-air fast and scalable process yielding a highly stable electrode. V2O5 thin films were then deposited by radio frequency magnetron sputtering on the AgNW-based TE. Independent of the oxide's nature, a 20 nm protective layer thickness was insufficient to prevent the deterioration of the AgNW network during V2O5 deposition. On the contrary, crystalline V2O5 films were grown on 30 nm thick ZnO or SnO2-coated AgNWs, exhibiting a typical orange color. Electrochromic characterization demonstrated that only V2O5 films deposited on 30 nm thick SnO2-coated AgNW showed characteristic oxidation-reduction peaks in the Li+-based liquid electrolyte associated with a reversible orange-to-blue color switch for at least 500 cycles. The electrochromic key properties of AgNW/SnO2 (30 nm)/V2O5 films are discussed in terms of structural and morphological changes due to the AgNW network and the nature and thickness of the two protective oxide coatings.

Nanocomposites based on Cu2O coated silver nanowire networks for high-performance oxygen evolution reaction.

The development of highly active, low-cost, and robust electrocatalysts for the oxygen evolution reaction (OER) is a crucial endeavor for the clean and economically viable production of hydrogen via electrochemical water splitting. Herein, cuprous oxide (Cu2O) thin films are deposited on silver nanowire (AgNW) networks by atmospheric-pressure spatial atomic layer deposition (AP-SALD). AgNW@Cu2O nanocomposites supported on conductive copper electrodes exhibited superior OER activity as compared to bare copper substrate and bare AgNWs. Moreover, a relationship between Cu2O thickness and OER activity was established. Notably, the most effective catalyst (AgNW@50nm-thick Cu2O) demonstrated very high OER activity with a low overpotential of 409 mV to deliver a current density of 10 mA cm-2 (η 10), a Tafel slope of 47 mV dec-1, a turnover frequency (TOF) of 4.2 s-1 at 350 mV, and good durability in alkaline media (1 M KOH). This highlights the potential of AgNWs as a powerful platform for the formation of highly efficient copper oxide catalysts towards OER. This work provides a foundation for the development of nanostructured Cu-based electrocatalysts for future clean energy conversion and storage systems.