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

Abstract

We demonstrate continuous fabrication of flexible transducer devices consisting of interdigitated (IDT) Ag microelectrodes interconnected by ZnO nanowires (ZNWs), created via serially connected solution-processable micro- and nanofabrication processes. On an Ag layer obtainable from the mild thermal reduction of an ionic Ag ink coating, the roll-to-roll-driven photolithography process [termed photo roll lithography (PRL)] followed by wet-etching can be applied to continuously define the IDT microelectrode structure. Conformal ZNWs can then be grown selectively on the Ag electrodes to interconnect them via an Ag-mediated hydrothermal ZNW growth that does not require high-temperature seed sintering. Given that all of these constitutive processes are vacuum-free and solution-processable at a low temperature, and are compatible with continuous processing onto flexible substrates, they can be eventually configured into the roll-to-roll-processable progressive assembly. Through parametric optimizations of processes consisting of the roll-to-roll-configurable, solution-based progressive assembly of nanostructures (ROLSPAN), a flexible transducer consisting of ZNW-interconnected, PRL-ed IDT Ag electrodes can be developed. This flexible architecture faithfully performs UV sensing as well as optoelectronic transduction. The ROLSPAN concept along with its specific applicability to flexible devices may inspire many diverse functional systems requiring high-throughput low-temperature fabrication over large-area flexible substrates.

All-Solution-Based, Low-to-Room-Temperature Fabrication of Position-Controlled Metal-Nanodot-Decorated Semiconductor Nanorods for Enhanced Optoelectronic Transducers

“…Notably, the Ag-ZNR device could produce a considerable current without any external bias, and the no-Ag-ZNR device could also generate a measurable current, be it subtle (Figure a). This reveals that the Ag-decorated ZnO/Ag system is energetically favorable, as previously confirmed by the study on its energy band structure . As we increase the bias from 0 to 3 V and then to 5 V, the UV-induced photocurrent increases with a more distinct margin between the Ag-ZNR and no-Ag-ZNR devices (Figure b,c).…”

“…This reveals that the Ag-decorated ZnO/Ag system is energetically favorable, as previously confirmed by the study on its energy band structure. 20 As we increase the bias from 0 to 3 V and then to 5 V, the UV-induced photocurrent increases with a more distinct margin between the Ag-ZNR and no-Ag-ZNR devices (Figure 6b,c). It could be confirmed that the Ag nanodots effectively and vividly enhance the sensitivity and responsivity for incident UV light.…”

“…This ionic Ag solution was spin-coated (2000 rpm, 20 s) onto the substrate, in this case polyethylene terephthalate (PET, typically 1.5 × 1.5 cm), followed by thermal annealing at 90 °C for 1 min (and hard-baking (120 °C, 5 min) as needed to expedite solvent removal) to complete the ∼50 nm thick nanoporous Ag thin films (see Figure a) . For the fabrication of the interdigitated Ag electrode, a PRL process was applied to the Ag thin film using a custom-built roll-type photolithography system (NcoreTechnology, Inc.), the detailed procedure of which can be found in the literature. , Briefly, a hollow quartz roll inside which a downward-collimated UV light source is mounted is covered with a flexible photomask film (see Figure b) and rolls over the photoresist (PR)-coated substrate to realize continuous UV exposure, followed by developing wet Ag etching and PR stripping processes (see the second scheme (simplified) in Figure ). The line width, spacing, and overall interdigitated area of the PRL-fabricated interdigitated electrodes typically used in this study are 10 μm, 10 μm, and 2 × 5 mm, respectively (see Figure a,c).…”