Gravure-Printed Sol–Gels on Flexible Glass: A Scalable Route to Additively Patterned Transparent Conductors

Abstract

Gravure printing is an attractive technique for patterning high-resolution features (<5 μm) at high speeds (>1 m/s), but its electronic applications have largely been limited to depositing nanoparticle inks and polymer solutions on plastic. Here, we extend the scope of gravure to a new class of materials and on to new substrates by developing viscous sol-gel precursors for printing fine lines and films of leading transparent conducting oxides (TCOs) on flexible glass. We explore two strategies for controlling sol-gel rheology: tuning the precursor concentration and tuning the content of viscous stabilizing agents. The sol-gel chemistries studied yield printable inks with viscosities of 20-160 cP. The morphology of printed lines of antimony-doped tin oxide (ATO) and tin-doped indium oxide (ITO) is studied as a function of ink formulation for lines as narrow as 35 μm, showing that concentrated inks form thicker lines with smoother edge morphologies. The electrical and optical properties of printed TCOs are characterized as a function of ink formulation and printed film thickness. XRD studies were also performed to understand the dependence of electrical performance on ink composition. Printed ITO lines and films achieve sheet resistance (Rs) as low as 200 and 100 Ω/□, respectively (ρ≈2×10(-3) Ω-cm) for single layers. Similarly, ATO lines and films have Rs as low as 700 and 400 Ω/□ with ρ≈7×10(-3) Ω-cm. High visible range transparency is observed for ITO (86-88%) and ATO (86-89%). Finally, the influence of moderate bending stress on ATO films is investigated, showing the potential for this work to scale to roll-to-roll (R2R) systems.

Printing Conductive Nanomaterials for Flexible and Stretchable Electronics: A Review of Materials, Processes, and Applications

“…At low Ca , pattern fidelity is deteriorated by ink drag‐out from the cells, while at high Ca , inefficient doctoring leaves inks in nonpatterned area. Optimal printing can be achieved by adjusting printing speed and ink parameters to make Ca ≈ 1 …”

Crystal structure of bis[tetrakis(triphenylphosphane-κP)silver(I)] (nitrilotriacetato-κ4N,O,O′,O′′)(triphenylphosphane-κP)argentate(I) with an unknown amount of methanol as solvate

“…Metal nanoparticles are well known in the literature for their use in various applications, e.g., in joining processes (Hausner et al, 2014), catalysis (Steffan et al, 2009;Zhang et al, 2015) and electronics (Gilles et al, 2013;Scheideler et al, 2015). This is caused by the size and shape-dependent properties of the nanoparticles (Wilcoxon & Abrams, 2006).…”

Gravure Printing of Water-based Silver Nanowire ink on Plastic Substrate for Flexible Electronics

“…Printed electronics has drawn tremendous interest in the past few decades 1 – 6 , as it offers an attractive alternative to conventional silicon-based fabrication technologies by enabling low-cost, large-area, flexible devices for many applications such as energy storage 7 , thin film transistor 8 , light-emitting diodes 9 and wearable sensors for health monitoring 10 . Central to this technology are high-performance functional inks and high-throughput printing methods, such as screen 11 – 15 , inkjet 16 – 18 , gravure 19 , 20 and flexographic printing 21 . Among the existing printing methods, gravure printing, which utilizes direct transfer of functional inks through physical contact of engraved structures with a substrate, is a promising option for large-scale applications due to its high-speed, high-resolution deposition of functional materials and compatibility with roll-to-roll processes.…”