Optimized electrical and optical properties of Ag micro-meshes by self-generated cracks for transparent electrodes†

Transparent conductive electrodes (TCEs) are essential components in the development of various transparent devices. In this study, a Ag micro-mesh network was investigated as an indium-free, non-rigid TCE for applications in flexible devices or solar cells. Instead of a complex and expensive process, such as photolithography with a shadow mask to fabricate a micro-grid, the Ag micro-mesh electrode was fabricated using self-generated cracked templates. The structure of the metallic network was controlled by varying the spin-coating speed and silica solution concentration so that a highly interconnected metallic network can be obtained. Using these techniques, various widths and densities of cracks were obtained and analyzed to compare their optical and electrical properties. Finally, the figure of merit (FoM) for the transparent electrode was calculated based on the measurement results, which revealed that the Ag micro-mesh electrode exhibited the highest performance when the crack widths were mostly distributed in the range of 1–2 μm, regardless of the fabrication conditions. The optimum Ag micro-mesh electrode achieved 88% transmittance at 550 nm wavelength and exhibited 20 Ω sq⁻¹ sheet resistance. These optical and electrical properties are comparable to those of indium-doped tin oxide (ITO) and/or aluminum-doped zinc oxide (AZO) that are used as TCE materials.