Electrohydrodynamic NanoDrip Printing of High Aspect Ratio Metal Grid Transparent Electrodes

• Published in: Advanced functional materials Vol. 26; no. 6; pp. 833 - 840
• Main Authors: Schneider, Julian, Rohner, Patrik, Thureja, Deepankur, Schmid, Martin, Galliker, Patrick, Poulikakos, Dimos
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 09.02.2016
• Subjects: Additives; Electrodes; electrohydrodynamic nanodrip printing; Electrohydrodynamics; gold; metal grids; Nanostructure; Opacity; Printing; Resistivity; Silver; transparent electrodes
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201503705

The transparent conducting electrode is an essential component in many contemporary and future devices, ranging from displays to solar cells. Fabricating transparent electrodes requires a balancing act between sufficient electrical conductivity and high light transmittance, both affected by the involved materials, fabrication methodology, and design. While metal films possess the highest conductivity at room temperature, a decent optical transmittance can only be achieved with ultrathin films. Structuring the metal into optically invisible nanowires has been shown to be promising to complement or even substitute transparent conductive oxides as dominant transparent electrode material. Here the out‐of‐plane fabrication capability of the recently developed method of electrohydrodynamic NanoDrip printing to pattern gold and silver nanogrids with line widths from 80 to 500 nm is demonstrated. This fully additive process enables the printing of high aspect ratio nanowalls and by that significantly improves the electrical performance, while maintaining the optical transmittance at a high level. Metal grid transparent electrodes optimized for low sheet resistances (8 Ω sq−1 at a relative transmittance of 94%) as well as optimized for high transmittance (97% at a sheet resistance of 20 Ω sq−1) are reported, which can be tailored on demand for the use in various applications. Electrohydrodynamic NanoDrip printing is used to pattern gold and silver nanowalls into high performance metal grid transparent electrodes. The out‐of‐plane capability of this additive process enables the printing of nanowall aspect ratios up to 7, greatly improving the electrical performance, while maintaining the exceptional optical transmittance.