| 摘要: | 銦錫氧化物(ITO)是透明電極最常使用的材料， 但其主要的缺點是易脆因而無法應用於軟性基板。金屬具有良好的導電性與優異的機械柔韌性，故本研究仍以靜電紡絲技術，將金屬材料圖案化形成一維金屬線，利用線與線之間的間格提供透光度，取代 ITO應用於可撓式金屬透明電極。本研究結合靜電紡絲、選擇性無電鍍沉積與翻膜等技術製作銅線網格可撓式透明電極，即先以靜電紡絲技術形成網絡基底，再透過選擇性無電鍍沉積技術，在纖維絲外側沉積均勻性金屬層，最後藉由溶液翻膜製程將金屬網絡嵌入至聚醯亞胺(Polyimide, PI)膜內形成可撓式透明電極。在此，我們提供一種佈置晶種的新方法來作為無電鍍的基底，僅藉由聚乙烯醇(Polyvinyl alcohol, PVA)螯合銀離子的機制，透過靜電紡絲技術形成 PVA/Ag 複合奈米纖維，隨後進行熱還原使銀原子在纖維絲表面析出，作為無電鍍銅沉積的晶種。此法直接在電紡奈米纖維上產生銀金屬顆粒作為晶種，能夠取代以往文獻報導在纖維上產生晶種
的繁瑣步驟。利用 TEM 觀察得知藉由螯合機制所佈置的銀顆粒可均勻地分散於奈米纖維表面，隨著加熱時間增加纖維克的銀顆粒向表面移動生成更大尺寸的銀顆粒團簇，故維持適當的加熱時間可避免過多的銀殘留在纖維內部浪費銀晶種，亦可降低硝酸銀用量，節省材料成本。本研究製成的 PVA@Cu 網絡透明電極，其透光度在波長 550 nm 為 94.3 %、片電阻為8.1 Ω/sq，其性能值(Figure of Merit, FoM)與文獻相較相對較佳。進一步，將此透明電極嵌入至 PI 基板製作成可撓式透明電極，能夠降低不同纖維互相交錯造成時所增加的高表面粗糙度。經撓曲測試、抗氧化測試，結果證明適用於可撓式透明電極。;In recent years, the indium tin oxide (ITO) has been the most commonly commercially available material for the transparent electrode. But due to its hard and brittle characteristics, ITO is not able to meat the requirement in flexibility for the emerging flexible electronics. On the other hand, metal has good electrical conductivity and excellent mechanical flexibility.
Therefore, in this study, we propose a new method, which combines both techniques of electrospinning and selective electroless deposition, for fabricating metal-web electrodes. A flexible transparent electrode is fabricated as follows. First, the network of web is formed by the electrospun fibers. Then, a uniform metal thin film is deposited on the fibers by the method of selective electroless deposition. Finally, the metal web is embedded into a polyimine (PI) substrate.
Through making a new electrospun solution, that combines both polyvinyl alcohol (PVA) and silver nitrate (AgNO3), we provide a new method of arranging uniform seed sites for selective electroless deposition. It is based on that silver ions in the PVA/AgNO3 solution are regularly chelated by the PVA. The metal ions in the electrospun fibers can be thermally reduced into atoms and precipitate on the fiber surfaces that serves as the seed sites for the subsequent selective electroless copper deposition. The seed metal particles are thus generated directly from the electrospun nanofibers, which can replace the complicated steps reported in the literature. The TEM pictures show that the silver particles are indeed uniformly dispersed on the surface of the nanofibers and they migrate toward the surface to form larger-sized clusters as the heating time is increased. Thus, appropriate heating arrangement during the thermal reduction process can avoid excessive silver particles residue in the fiber and save the material cost.
The fabricated PVA@Cu-web transparent electrode shows the characteristics of transmittance of 94.3 % (@550 nm) and sheet resistance of 8.1 Ω/sq that is very competitive because its performance value (Figure of Merit, FoM) is better than those reported the literature.
Further, after being embedded into an PI substrate, the flexible transparent electrode, in addition to reducing its surface roughness, shows good flexible and anti-oxidation capabilities and is applicable to flexible transparent electrodes. |
