Femtosecond UV laser enhancement of silver nanowires based transparent conductive electrodes

Description

The investigation of metallic nanowires-based transparent conductive electrodes (TCEs) possesses great promise in several optoelectronic devices, like solar cells, touchscreens, flexible electronics, and organic light emitting diodes (OLEDs) [1]. Silver nanowires (AgNWs) mesh electrodes are especially promising candidates to replace indium-tin oxide (ITO) as the next-generation TCE. This is largely due to their facile and low-cost liquid phase processing in ambient conditions, low sheet resistance, flexibility, and high transparency owing to sub-optical wavelength size. However, there are a few challenges in using AgNWs as TCEs, which are high junction resistance between the adjacent nanowires due to a small contact area, and the presence of insulating organic ligands on their surface. Hence, post-treatment is required to enhance electrical performance of Ag nanowires grid. This can be done using thermal sintering, plasma treatment, and optical welding.

In this study, we present our findings on AgNWs plasmonic welding using a femtosecond supercontinuum pulsed laser with selected wavelength varied between UV-B and visible spectral range. The experimental sequence is shown in Figure 1. Femtosecond pulses enable highly localized heating due to a time scale shorter than the electron–phonon equilibrium time. Due to a significant electric field enhancement in the nanoscale gap between the adjacent nanowires, this can induce optical welding at a temperature below the conventional thermal melting point. This can effectively join AgNWs in a highly controlled and self-limiting mode [2]. As a result, this treatment increases nanowires contact area, reducing sheet resistance of the nanowires grid, while maintaining its high transmittance. Here, we will demonstrate TCEs based on optically welded silver nanowires, which exhibit both high transmittance of T > 85% and low sheet resistance Rs < 20 Ω/sq. Using conventional ITO and Al:ZnO (AZO) TCEs as our benchmarks, we will compare their electrical and transmittance performance to optically-welded Ag nanowires grid, and ZnO/AgNWs/ZnO hybrid electrodes.

Period	29 Sept 2024 → 4 Oct 2024
Event title	17th International Conference on Laser Ablation: COLA 2024
Event type	Conference
Location	Heraklion, GreeceShow on map
Degree of Recognition	International