Fully Solution-Based AgNW/AlO_x Nanocomposites for Stable Transparent Heaters

Abstract

Transparent heaters (TH) have a lot of potential in flexible and wearable applications. Consequently, interest in using nanomaterials, such as metallic networks, grids, and meshes, has expanded as an alternative to conventional transparent conductive oxides like indium tin oxide. In particular, silver nanowire (AgNW) networks are very promising transparent and flexible electrodes thanks to their optimum physical properties and the possibility to obtain them by low-cost fabrication techniques. However, AgNW networks suffer from instabilities that affect their electrical performance at high operating voltages or over time and thus require a protective layer, often deposited by vacuum-based techniques. In this work, we implemented a low-cost solutionbased aluminum oxide (AlO x ) coating produced by combustion synthesis to encapsulate spray-coated AgNW networks. The TH with an AlO x coating obtained from a 0.4 M precursor solution concentration presents the best compromise between optical transmittance and electrical resistance. Besides this, such a coating provides a robust protection against corrosion under accelerated environmental stress (relative humidity = 80%; temperature = 70 °C) up to 7 days. As a proof-of-concept, a 50 × 50 mm 2 TH was fabricated and tested as a defroster (down to −21 °C) showing a highly reproducible heating performance (up to 90 °C at 6 V) and stability for 12 h. In addition, different morphologies of the AlO x thin film, namely smooth or porous, can be obtained when either conventional thermal annealing or Joule heating of AgNWs is used, respectively, to carry out the combustion reaction. This offers a promising tunability for different final applications.

Silver Nanowire Networks Coated with a Few Nanometer Thick Aluminum Nitride Films for Ultra-Transparent and Robust Heating Applications

“…The normalized electrical resistance evolution is presented in Figure a, with initial values being 19 and 18 Ω for bare and nanocomposite networks, respectively. As it was expected and reported in several previous studies, ,, the electrical resistance of the AgNW started to increase after 11 V and completely degraded before reaching 13 V. However, in the case of the nanocomposites with AlN, the samples exhibited full stability until more than 20 V. It should be noted that the measurement was automatically stopped at 21 V as the current compliance of the instrument was reached. Furthermore, the insets of Figure a are IR images at the moment of failure of bare AgNW and at the maximum applied voltage (21 V) for the AgNW/AlN nanocomposite.…”

“…The oxide coatings failed to fully protect the nanowires at high temperatures. In other recent studies, AlO x coatings deposited on AgNW networks by ALD or solution-based techniques were integrated successfully as passivation layers against humidity while still degradation occurred at high applied voltages. , On the contrary, the nitride-coated networks demonstrated superior stability until 400 °C and once back to room temperature they had similar or even lower final electrical resistance; for the AlN-6.2 nm, the resistance increased 15%, while for the AlN-8.8 nm, AlN-13.3 nm, and AlN-19.6 nm, the resistance decreased by −6.2, −10.5, and −6.5% after annealing. In conclusion, the encapsulation of AgNW networks is necessary to develop transparent electrodes and the comparison between Al-based nanocomposites; the nitride coatings show a superior efficiency as compared to the oxide coatings.…”

Flexible and Transparent Leaf-vein Electrodes Fabricated by Liquid Film Rupture Self-Assembly AgNWs for Application of Heaters and Pressure Sensors

“…As the voltage increased, more and more joule heat was generated and a high temperature of 104 o C was achieved at a low voltage of 2 V (Fig. 5 (b)), which is superior to previously reported heaters [9,13,15,28] . Particularly, the heaters can reach the saturated temperature (90% of the maximum temperature) within 10 seconds after turning on and cool down to the room temperature within 15 seconds after turn off, as shown in Fig.…”

“…There are several ways to prepare flexible conductors: 1) Metal thin films deposited on the flexible substrates [4,5] . 2) Nanomaterials coating the flexible substrates [6][7][8][9] . Among them, nanomaterials have been widely investigated, such as carbon-based nanomaterials, conductive polymers, metal nanoparticles and metal nanowires (NWs), due to their transparency, flexibility and low resistance.…”

Metal–Organic Framework-Modified Silver Nanowire Transparent Film with Enhanced Conductivity and Stability for Efficient Organic Light-Emitting Diodes

“…In recent years, transparent conductive films (TCFs) have garnered a great deal of attention for their functionality as vital components in optoelectronic devices, such as smart windows, 1 organic light-emitting diodes (OLEDs), 2 organic solar cells, 3 and transparent heaters. 4 TCFs are necessarily expected to possess high transparency and conductivity, such as indium tin oxide (ITO), which has been the predominant TCF used in all kinds of applications over the past few decades. 5 However, inherent brittleness and limited reserves of indium have retarded ITO electrodes from taking a further step into novel applications that demand high flexibility and cost-effectiveness.…”