Solution-Processable Ag-Mediated ZnO Nanowires for Scalable Low-Temperature Fabrication of Flexible Devices

Abstract

We present a scalable and vacuum-free hybrid nanoarchitecturing strategy demonstrated by the solution-processable Ag-mediated ZnO nanowire (termed "SPAZN") growth on transparent and flexible substrates at low temperature. The SPAZN protocol enables selective hydrothermal ZnO nanowire (ZNW) growth on a nanoporous Ag framework obtainable from mild annealing of ionic Ag ink coating. The ZNW morphology and density can be readily controlled by tuning the SPAZN processing parameters including Ag ink concentration, coating condition, and hydrothermal growth temperature based on the underpinnings of the Ag-morphology-mediated ZNW growth mechanism proposed. We exemplify a transparent plastic gas sensor as one of many promising applications.

Demonstration of a roll-to-roll-configurable, all-solution-based progressive assembly of flexible transducer devices consisting of functional nanowires on micropatterned electrodes

“…The typical diameter and length of the ZNWs grown in this experiment were 750-800 nm and 7-8 µm, respectively, as indicated in Fig. 3c; the diameter and aspect ratio of ZNWs can be tailored by controlling the SPAN morphology and hydrothermal growth temperature and time [23,27,28]. Given that the Agmediated hydrothermal ZNW growth process obviates the high-temperature seed preparation process (e.g., ZnO seed sintering at 350°C), ZNWs can be grown at a low temperature on diverse substrates, including a Si wafer, glass, and exible polymers such as PET, as exempli ed in Figs.…”

“…The full procedure of Ag-seeded hydrothermal ZNW growth can be found in the literature [23,27,28]. Brie y, the precursor solution was initially prepared by mixing 3.75 g of N 2 O 6 Zn•6H 2 O and 1.75 g of HMTA in a beaker containing 500 ml of DI water (i.e., resulting in a concentration of ~ 25 mM for both materials) on a 140°C hot plate for one hour under 200 rpm magnetic bar stirring.…”

“…To this end, we demonstrate a functional micro/nanoarchitecture consisting of solution-processed ZnO nanowire (NW) structures selectively grown on solution-processed Ag electrodes fabricated by continuous rollable photolithography for exible transducer devices such as UV sensors. More speci cally, initially we create Ag layers from the mild thermal reduction of an ionic Ag ink coating, which can be performed on any common -either rigid or exible -substrate, including glass and polymer lm [20][21][22][23]. The Ag layer can then be patterned into interdigitated (IDT) microelectrodes through continuous photo roll lithography (PRL) [24][25][26]; during the PRL process, a exible photomask-attached hollow quartz roll inside of which a UV exposure source is mounted rolls over the photoresist (PR)-coated substrate fed continuously underneath.…”

“…The Ag layer can then be patterned into interdigitated (IDT) microelectrodes through continuous photo roll lithography (PRL) [24][25][26]; during the PRL process, a exible photomask-attached hollow quartz roll inside of which a UV exposure source is mounted rolls over the photoresist (PR)-coated substrate fed continuously underneath. Finally, ZnO NWs (ZNWs) can be conformally grown on the PRL-processed IDT Ag electrodes to interconnect them via a low-temperature hydrothermal reaction, with the Ag surface providing favorable sites for ZnO crystal nucleation and growth [23,27,28], thereby obviating the high-temperature sintering of a textured ZnO seed layer. As brie y introduced above and as detailed later in this paper, all of these constitutive processes involve vacuum-free and solution-based steps and are compatible with continuous processing onto exible substrates.…”

Low-Temperature Hydrothermal Growth of ZnO Nanowires on AZO Substrates for FACsPb(IBr)3 Perovskite Solar Cells

“…The ETL also brings a specific processing step that has to be taken into account for large-scale developments. In the case of ZnO NWs, the hydrothermal growth required a starting ZnO seed layer, which can be formed by various techniques on different substrates, including conventional FTO-coated glass [41,[54][55][56]. However, zinc-oxide-based transparent electrodes such as AZO have been suggested to potentially act as efficient seed layers [48,57,58].…”