電致色變現象(electrochromism)泛指當材料被施加不同直流電壓或電流時，該材料會可逆地改變對光線的吸收度進而呈現不同的顏色變化。氧化鎳在做為電致色變元件的主要變色層(primary electrochrome)時，其光學對比度高，材料本身也較低廉且易取得；另一方面，氧化鎳也具備做為次要變色層(secondary electrochrome)的能力，它與目前實際應用程度最高的氧化鎢，組成互補式電致色變元件，為一極佳的選擇。
目前無機電致色變元件中的電致色變材料大部份都是以薄膜的型態存在。但由於電致色變材料是藉由外加電子與電解質中的離子擴散進出薄膜來進行氧化還原反應，所以此種薄膜結構不利於離子的擴散與電子的傳遞，使得相關電致色變技術長久以來存在著反應速度緩慢與循環壽命不佳的問題。因此，本研究探討奈米結構電致色變材料的基礎性質與其應用性，利用隨機排列的導電奈米顆粒做為一多孔隙的導電介質，再以不同的製程方法將氧化鎳電致色變材料包覆在導電奈米顆粒上。此新結構具有多孔隙及奈米複合材料的特性，可使電解質滲入整個結構中來增加彼此的接觸面積，進而提升氧化還原反應速度及改善循環壽命。
本研究主要分為二個部份：
第一部份為利用噴霧熱分解法(spray pyrolysis technique, SPT)在多孔性的ITO奈米顆粒導電層上形成奈米結構型氧化鎳層(nano-structured nickel oxide layer, NSNO)。此新型結構在光譜對比及反應速度均有改善，但並不顯著。主要是以噴霧熱分解法所製備的工作電極，氧化鎳電致色變材料只有覆蓋在多孔隙導電層的表層，其反應面積增加有限。但從循環伏安圖及光譜圖可知，新型的奈米結構使得氧化鎳薄膜的循環壽命大幅改善。經過2000次循環後，其穿透率對比只衰退5 %，而一般薄膜則衰退了37 %。顯示在長時間的循環下，奈米結構型氧化鎳層的循環壽命優於一般氧化鎳薄膜。
第二部份為利用電鍍法(electro-deposition method)，以0.2 M硝酸鎳水溶液為電鍍液，在多孔性的ITO奈米顆粒導電層上製備工作電極，熱處理後可得到新穎的奈米複合型氧化鎳層(nano-composite nickel oxide layer, NNO)。由TEM及SEM/EDX elemental maps 分析可知，所製備的奈米複合型氧化鎳層是NiO/ITO的core-shell結構。新型的奈米複合型氧化鎳層在552 nm有最大的穿透率對比(66.3 %)，一般氧化鎳薄膜只有55.7 %，兩者的差異超過10 %。且奈米複合型氧化鎳層的著去色反應速度是一般氧化鎳薄膜的2.3倍。顯示此新型結構有效改善薄膜的光譜特性及反應速度。此外與第一部份相同，此奈米複合結構亦大幅改善薄膜的循環壽命，試片至2000次循環的穿透率對比仍維持不變；而一般氧化鎳薄膜則已衰退了67 %。
本研究成功發展出新穎的奈米結構型氧化鎳層與奈米複合型氧化鎳層，此兩種結構皆具有優異的循環壽命，同時奈米複合型氧化鎳層更具有良好的電致色變性質，能更符合商業化應用之期待。而本研究的製程簡單，亦有利於在工業上的應用。

Electrochromic (EC) materials, which are able to change their optical properties reversibly upon charge insertion/extraction, have received high attention due to their unique characteristics in the past decades. Among inorganic EC materials, nickel oxide is considered to be a good anodic candidate because it has low material cost and an excellent contrast. Usually, nickel oxide is used as a counter-electrode in complementary EC devices assembled with a cathodic EC electrode, such as tungsten oxide.
Coloration of inorganic EC devices depends upon ion-intercalation into the transition metal oxide film. Therefore, the switching speeds of coloring/bleaching are limited by ion transporting into a solid metal oxide film. To obtain sufficient optical contrast, large charge (ion/electron) insertion and extraction must extend to the bulk of the EC film. Consequently, the switching time of such devices is typically in the order of tens seconds to minutes, even for small area devices. On the contrary, a fast-switching device may result in insufficient optical contrast because of less ion-intercalation.
In this study, transparent ITO nano-particles are sprayed on ITO coated glass substrates to form a porous conducting network. And then nickel oxide films are deposited onto this substrate by two methods. The porous structure provides large active surface area for charge insertion and extraction. This nano-structure leads to large surface area for depositing EC materials. Electrolyte can penetrate through the porous nano-structured film. When an electrochemical redox reaction carried out, ion intercalation and charge compensation could happen rapidly at or near the electrode/electrolyte interface.

This dissertation contents two parts:
Part I: A nano-structured nickel oxide (NSNO) based EC electrode was successfully produced by a spray pyrolysis technique (SPT) onto the porous ITO nano-particle layer. In this case, the improvements in the switching speed and transmittance contrast were not obvious. It is because the NSNO film prepared by SPT only covers the top surface of the ITO nano-particle layer. With this porous structure, however, the NSNO based EC electrodes showed great improvement in the cycling durability.
Part II: In the present work, the nickel oxide film is prepared using an electro-deposition method followed by a thermal oxidation process. It is intended to form a nano-composite nickel oxide (NNO) layer. From the elemental maps and TEM images, we ensure that the nickel oxide completely covers the whole surface of ITO nano-particle layer and forms the core-shell structure with ITO nano-particles instead of just covering top surface of the ITO nano-particle layer. High porosity in the NNO layer offers large active surface area for redox reaction. Electrochromic electrodes fabricated with the NNO layers produce high transmittance variation (66.3% at a wavelength of 552 nm), fast switching speed (coloring: 3.8 sec, bleaching: 3.0 sec) and good durability (over 2000 cycles without degradation), which are much better than those of ones made with the traditional nickel oxide films. These good EC properties promote the potential application of the NNO structure for EC devices.

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