Flexible Embedded Metal Meshes by Nanosphere Lithography for Very Low Sheet Resistance Transparent Electrodes, Joule Heating, and Electromagnetic Interference Shielding.

Abstract

We demonstrate the highest transparent electrode performance among metal meshes fabricated via nanosphere lithography (NSL), achieving an order-of-magnitude improvement in the figure of merit FoM (σ _<i>DC</i> /σ _<i>OP</i> ). Additionally, we present, for the first time, the application of metal meshes fabricated by NSL for transparent electromagnetic interference (EMI) shielding, enabled by exceptional improvements in sheet resistance. Our NSL method produces substrate-embedded metal meshes in PET and glass by etching trenches, yielding high-aspect-ratio features with low sheet resistance. Embedded structures also exhibit superior robustness during bending and tape tests compared to sputtered metallic films on the surface. As a transparent electrode, the flexible Ag meshes exhibit a sheet resistance of 1.52 Ω/sq and transparency of 73.1% as well as a sheet resistance of 0.22 Ω/sq and transparency of 58.1%, corresponding to FoMs of 737 and 2736, respectively. For transparent EMI shielding, the flexible metal meshes achieve a shielding efficiency (SE) of 34.5 dB with 73.1% visible transmission and an EMI SE of 52.8 dB with 58.1% visible transmission. As a flexible heater, the metal meshes can reach a saturation temperature exceeding 70^◦C within 60 s under an applied voltage of 1.2 V. These embedded metal meshes hold promise for applications requiring ultralow sheet resistance, including heated windows and defrosting systems, large-area organic light-emitting diode (OLED) lighting and displays, solar cells, and EMI shielding.