- 學位論文
鐵氰化鉬薄膜電極製備分析與其電致色變性能研究
On the Fabrication and Analysis of the Molybdenum Hexacyanoferrate Thin Film Electrode and Its Electrochromic Performance
摘要
無機電致色變材料在顏色的選擇上常受限於類紅色罕見的問題，因而侷限了其應用發展。因此本研究旨在開發一可於紅棕與透明黃間進行可逆顏色變化之普魯士藍類似物電致色變材料-鐵氰化鉬，並由兩大部分分別進行單膜與複合膜之分析研究。於第一部分單膜探討中，將對其製備環境及操作條件進行最適化研究。結果顯示以循環伏安法在鍍液鹽酸濃度為0.5 M環境下析鍍80圈之薄膜展現附著力優良、電化學活性高且光學密度變化(ΔOD)達0.6 (@ 480 nm)之電致色變薄膜。且此薄膜在經過100℃烘烤1小時之處理後展現了500圈以上之操作壽命，相較於未烘烤時俱有約30倍左右之提升。於操作條件最適化方面，研究以不同操作電位窗對薄膜進行反覆氧化還原反應，結果顯示在氧化電位為2.4 V、還原電位為0 V (vs. Ag/Ag+)的情況下，鐵氰化鉬薄膜分別展現光學穿透率調幅約48% (@ 480 nm)、響應時間約2.1秒及操作壽命>500圈之理想表現，並且隨著電位窗範圍更改，其光譜響應均呈現相對不穩定的情況。研究接著進行薄膜之物理化學特性分析，針對鐵氰化鉬之組成成分、表面微結構、光電特性及連續操作穩定性進行探討。發現此薄膜由Mo、Fe、C、N等元素組成，顯示其為普魯士藍類似物之可能。表面結構觀察發現此薄膜由許多徑粒9-27 nm不等之細粒所組成，且表面呈現分布均勻無裂痕之形態，而在經過電化學處理過後發生表面重組現象，造成薄膜特性改變。另外循環伏安響應顯示此材料之標準電極電位約為0.84 V (vs. Ag/Ag+)，在480 nm波長光線之著色效率為46.93 cm2/C，氧化還原反應可逆度為0.92。於第二部分複合膜探討中，研究將單壁奈米碳管(SWCNTs)與聚乙二醇(PEG)利用旋轉塗佈法以雙層結構的方式進行複合膜電極修飾。SEM結果顯示SWCNTs成功的被固定於ITO電極表面，且以「被包埋」的形式複合於鐵氰化鉬薄膜中。循環伏安及平衡光譜響應顯示經過SWCNTs/PEG修飾之電極展現較小之峰值分離現象約876 mV及較大之著色效率約51.71 cm2/C，並且藉由SWCNTs優良之機械性與導電性，成功的將鐵氰化鉬析鍍量增加，光學密度變化由未修飾時的0.6 ± 0.02上升至修飾後之0.9 ± 0.12，且此時薄膜外觀呈現更趨於紅色之色澤。歸納而言，本研究利用市售可得之材料製備出具備紅棕色澤之普魯士藍類似物電致色變材料，並經由修飾電極技術使其外表更趨於紅色，提供未來電致色材料應用於顯示的一項選擇。
並列摘要
The development of inorganic electrochromic materials is restricted by the limitation of red-like colors. Therefore, this research aims at the fabrication and analysis of a new Prussian blue analogue- molybdenum hexacyanoferrate (MoHCF), which shows a color change reversibly between brownish-red and transparent-yellow. This study is divided into two parts. In the first part, the fabrication and analysis of MoHCF film are discussed, and the results showed that a MoHCF thin film with good adhesion, high electrochemical activity and high optical density modulation ca. 0.6 (@ 480 nm) was prepared successfully by cyclic voltametric deposition with a presence of 0.5 M HCl in the plating solution. And the stability of the film, which was baked at 100 ℃ for 1 hr., was improved about 30 times larger than the unbaked one. Different operating potentials were applied to optimize the transmittance modulation, response time and cycling stability of the film, and it was found that in the range of 0 V to 2.4 V the film had a maximum transmittance modulation value ca. 48%, fast response time 2.1 s and good cycling stability > 500 cycles. In comparison, the film became unstable when the operating potentials were out of the above range. The XPS result showed that the MoHCF film was composed of Mo, N, C and Fe, which corresponds to the compositions of a Prussian blue analogue. The SEM result showed that this film was constructed by nano-sized granules which were 9 ~ 27 nm in diameter, and the morphology of the surface was extremely uniform without any cracks, however, the surface was reformed after electrochemical operating. And the formal potential of MoHCF was determined to be 0.84 V (vs. Ag/Ag+) by CV response, and the coloration efficiency was ca. 46.93 cm2/C, the transmittance modulation (ΔT) reached ca. 48% (@ 480 nm), and the redox reversibility factor was ca. 0.92. In the second part, a composite, MoHCF/SWCNTs/PEG was made by applying spin coating, and the SEM result confirmed the successful immobilization of SWCNTs which was entrapped by the MoHCF film. The composite film showed lower peak separation and higher coloration efficiency of 51.71 cm2/C. Due to good mechanism and conductance of SWCNTs, the depositing quantity of the MoHCF granules was larger. As a result, the optical density modulation (ΔOD) was enhanced from 0.6 ± 0.02 to 0.9 ± 0.12, and the appearance of which was also improved. To sum up, this study used the commercial materials to prepare a red-like electrochromic film, which may become a candidate for the application in display in the near future.