Line‐Shaped Laser Lithography for Efficiently Fabricating Flexible Transparent Electrodes with Hierarchical Metal Grids across λ/10 to Microscale

Abstract

Hierarchical metal grids are proven to be a promising solution for achieving high‐performance flexible transparent electrodes (FTEs) due to their significantly enhanced conductivity without noticeably sacrificing transparency. This work develops a one‐step mask‐free line‐shaped laser lithography by separated pulse laser ablation to efficiently fabricate large‐area FTEs composed of hierarchical metal grids, namely microscale grids interconnected with aligned nanowire arrays. The linewidth of aligned wires is highly controllable from the nanometer scale far beyond the diffraction limit (<λ/10) to the micrometer scale. This work experimentally studies the overall performance of FTEs to provide a guideline for selecting the layout and feature sizes of hierarchical metal grids. Hierarchical metal grids with 50 nm nanowires aligned inside the microscale grids show outstanding optoelectronic properties and mechanical stability, with sheet resistance of 4.6 Ω sq−1, transmittance of 82.9%, and a tiny increase in sheet resistance less than 4% after 1000 cycles of bending tests. These results prove that the line‐shaped laser lithography technique is a facile, low‐cost, and high‐throughput fabrication method for high‐performance FTEs.

Metallic Micro‐Nano Network‐Based Soft Transparent Electrodes: Materials, Processes, and Applications

“…Reproduced with permission. [ 71 ] Copyright 2023, Wiley‐VCH GmbH. f) Schematic illustration of the metallic NP ink layer on a substrate before (top left) and after (top right) laser sintering; SEM (bottom left) and AFM (bottom right) images of the laser‐sintered Ag microstructure.…”

“…Recently, metallic grids with linewidth across nanometers to micrometers are realized by using a cylindrical lens to shape the laser spot into lines. [ 71 ] Laser sintering consumes much smaller power density by using the localized heat source to selectively convert the metal [ 98 , 99 , 100 ] or metal oxide [ 101 ] NPs into a continuous solid state. The residual NPs after sintering are then rinsed away, leaving MMNNs on the substrate.…”

Alternative Look at Calcium Digermanide CaGe2: A High-Performing Semimetal Transparent Conducting Material for Ge Optoelectronics

“…In addition, widely used band engineering and doping close to the solubility limit hardly can result in simultaneous low optical losses and high electrical conductivity due to free-carrier absorption and impurity-enhanced electron scattering, respectively . Owing to thickness reduction down to tens of nanometers, further accompanied by nanostructuring of all sorts, conventional thin metal films were granted a second chance. − Unfortunately, there is a significant conductivity drop partially associated with island-like growth, which assumes the needs for additional seeding layer deposition to improve electrical properties, nothing to say about electrical losses induced by different metal-film processing toward enhanced optical transparency resulted from defects introducing . Quite a different approach was introduced by Zhang et al with original materials screening based on high carrier effective mass rather than high concentration .…”