| dc.description.abstract | Indium tin oxide (ITO) is an excellent transparent electrode material, but it has some disadvantages, such as it is rare in nature, its fabrication process is material wasting and poor in flexibility, and it is not applicable to wearable electronics. Recently, many studies have shown that metal mesh electrodes are quite excellent in light transmittance and conductivity, and are fairly potential ITO replacement electrodes. The main purpose of this research is to develop a new approach for rapidly fabricating metal mesh transparent electrodes using the technique of laser direct writing in the ambient environment. In this study, we first synthesize a new type of metal ink based on silver oxalate and propylenediamine. It is then subjected to the method of laser direct write to fabricate into a silver-based metal mesh electrode. Finally, the conductivity, transparency and mechanical properties of the electrode are examined.
For metal ink configurations, the advantage of using silver oxalate as a precursor is its high silver content and which can be directly thermally decomposed into metallic silver and carbon dioxide without other by-products. In this study, we combine both ethanol and water as the solvent to synthesize inks, and the effects of the weight ratios between water and ethanol on the surface morphology and electrical properties of the resulting mesh were studied. The proposed ink has good stability and is stable in colorless and transparent state after being left in the ambient for 7 days. By a fixing set of laser writing parameters, the results indicate that the higher the content of ethanol in the solvent, the better surface morphology as well as higher conductivity on the resulting silver metal mesh. As the average thickness of the written meshes is of 800 nm and the transmittance of the electrode is up to 86% (@550 nm), the electrode’s resistivity is only 1.8 times that of the block silver.
The second part of this study is to examine the electrode’s flexibility. The originally fabricated silver electrode on a glass substrate is embedded into a flexible PI (liquid polyimide) thin film to make the electrode flexible. Its flexibility is examined by a cyclely bending test which is executed 5000 cycles with a radius of bending curvature of 5 mm. The increase of relative resistance (ΔR/R0) was less than 40% of its original one and that was still within the allowable range. | en_US |