PANI或PANI/SiO2與PMeT或PProDOT-Et2搭配之互補式電致色變元件：最適化與穩定性

Complementary Electrochromic Devices Based on PANI or PANI/SiO2 and PMeT or PProDOT-Et2：Optimization and Stability

陳威凱(Wei-Kai Chen)

指導教授 ： 何國川

國立臺灣大學/工學院/化學工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01781

摘要

近年來，有機導電高分子在電致色變應用上逐漸受到重視，並朝著節能智慧窗、提升行車安全的防眩光裝置、顯示器等應用發展。特別是在現今提倡綠色能源的時代，互補式有機薄膜電致色變元件具有高著色效率與記憶效應，只要給予微小的能源就能達到持續的節能效果。因此，本研究採用陽極著色的PANI、PANI/SiO2、兩極著色的PMeT以及陰極著色的PProDOT-Et2四種材料相互搭配並組合成四種互補式有機薄膜電致色變元件，同時進行一系列薄膜與元件的最適化與穩定性之比較探討，以期獲得較佳的元件效能與穩定性。

在PANI與PANI/SiO2薄膜方面，首先利用同步電沉積法析鍍PANI/SiO2複合膜，並探討其不同SiO2含量下對於其電致色變性質與穩定性之影響，同時也與PANI進行一系列比較性的研究。由結果顯示，PANI/SiO2具有較高的表面積、較大的氧化還原電量以及較高的摻雜程度。因此，在其著色效率幾乎與PANI一樣的情況下提高其光學對比。從光學對比的觀點來看：此複合膜最佳製備條件為42 mg SiO2分散於50 ml電鍍液中，使SiO2在電鍍過程中被包覆於PANI中。所得到的PANI/SiO2膜當操作在-0.5到0 V (vs. Ag/Ag+)之間，於波長700 nm下穿透度變化可從10.7%提升至16.4%。其安全操作電位窗範圍為-0.5至0.3 V (vs. Ag/Ag+)之間，顏色變化可由-0.5 V的透明黃色變化至0.3 V的綠色。另外，XPS光譜顯示，SiO2亦能抑制過度氧化態PANI的生成，因此PANI/SiO2複合膜具有較佳的穩定性。此外，本研究也利用EQCM方法提出此PANI/SiO2複合膜的形成機制。

在PT的衍生物PMeT與PProDOT-Et2薄膜方面，同樣以定電位法析鍍薄膜並探討其電致色變性質。PMeT薄膜安全操作電位窗範圍為-0.4至0.6 V (vs. Ag/Ag+)之間，可由-0.4 V的紅色變化至0.6 V的藍色；PProDOT-Et2薄膜安全操作電位窗範圍為-0.9至0.3 V (vs. Ag/Ag+)之間，可由-0.9 V的深藍色變化至0.3 V的淡藍色。

在元件設計上，從薄膜安全操作電位窗與光學性質的角度搭配元件設計方程式，針對PANI、PANI/SiO2、PMeT以及PProDOT-Et2薄膜作初步的最適化，並比較探討PANI-PMeT、PANI/SiO2-PMeT、PANI-PProDOT-Et2以及PANI/SiO2-PProDOT-Et2四種系統。由初步最適化結果得知，PANI-PProDOT-Et2及PANI/SiO2-PProDOT-Et2系統具有較優越的表現。因此，進一步從元件兩極電量比與操作電壓窗的角度，對這兩種元件進行一系列最適化與穩定性的比較。結果顯示，PANI-PProDOT-Et2及PANI/SiO2-PProDOT-Et2元件皆具有高光學對比、高著色效率、毫秒等級的反應時間以及良好的開環(記憶效應)與靜態穩定性。在25 ℃下操作穩定性方面，PANI-PProDOT-Et2元件在操作28,775圈後光學對比開始有明顯的衰退現象發生，若由第1圈操作至第45,000圈，光學對比將從58.1%衰退至30.2%；PANI/SiO2-PProDOT-Et2元件，則由第1圈的光學對比為56.5%衰退至第45,000圈的50.0%。此外，在 70 ℃下操作穩定性方面，PANI-PProDOT-Et2元件在操作24,795圈後光學對比開始有明顯的衰退現象發生，若由第1圈操作至第53,000圈，光學對比將從58.5%衰退至3.0%；PANI/SiO2-PProDOT-Et2元件，則由第1圈的光學對比為59.9%衰退至第53,000圈的43.0%。因此，相較於PANI-PProDOT-Et2元件，PANI/SiO2-PProDOT-Et2不論在室溫或高溫下皆有良好的長期操作穩定性。

為了改善元件因電解質漏液與封裝上的問題所造成的元件安全性與穩定性不佳，本研究也利用surlyn封裝技術進行元件組裝，並嘗試以離子液體與PVDF-HFP膠態電解質取代液態電解質。結果顯示，利用surlyn封裝可有效改善元件組裝效果。然而，若使用離子液體取代液態電解質，將會導致元件表現不佳；相反的，若以膠態電解質取代液態電解質，除了元件保有良好的靜態穩定性，還可提升於室溫下的長期穩定性。PANI-PProDOT-Et2元件在操作119,905圈後光學對比開始有明顯的衰退現象發生，若由第1圈操作至第200,205圈，光學對比將從55.3%衰退至0.3%；PANI/SiO2-PProDOT-Et2元件，則由第1圈的光學對比為52.4%，操作至134,460圈後開始衰退，直至第200,235圈的39.7%。因此，PANI/SiO2-PProDOT-Et2元件於室溫下具有較佳的長期操作穩定性。但是，在高溫時，以膠態電解質取代液態電解質，則會使這兩個系統的光學對比提前衰退。

關鍵字

著色效率 ； diethyl substituted poly(3,4-propylenedioxythiophene) (PProDOT-Et2) ； 電致色變 ； 聚苯胺 ； 聚苯胺/二氧化矽 ； 聚(3-甲基噻吩) ； 穩定性

並列摘要

Recently, organic conducting polymers have gained increasingly attention for electrochromic (EC) applications, such as smart windows for energy saving, anti-glare mirrors for driving safety, displays and so on. Especially in this era of green energy, the complementary electrochromic devices (ECDs) based on organic thin films, possessing high coloration efficiency and memory effect, has the function of energy saving permanently upon the application of low power. In this study, four EC materials, polyaniline (PANI), PANI/silica (SiO2), poly(3-methylthiophene) (PMeT) and diethyl substituted poly(3,4-propylenedioxythiophene) (PProDOT-Et2) were used to construct four ECDs, in which PANI and PANI/SiO2 served as the anodically coloring materials, PMeT served as the anodically and cathodically coloring material and PProDOT-Et2 served as the cathodically coloring material. In the meantime, the optimization and the stability of these EC films and the assembled ECDs were also discussed toward getting an ECD with excellent performance.

For PANI and PANI/SiO2 thin films, PANI/SiO2 composite films have been potentiaostatically prepared by an in-situ electrodeposition method in the presence of different contents of SiO2 nanoparticles and its electrochromic properties were studied. A PANI thin film was also prepared for comparison. When PANI was electrodeposited in the presence of SiO2 particles, the resulting PANI/SiO2 composite films possessed higher surface areas, larger redox charge capacities, and higher doping levels, and thus enhanced optical contrasts under the same coloration efficiency of PANI and PANI/SiO2 films. From the viewpoint of optical contrast, the optimal SiO2 content in 50 ml of the electrodeposition bath was 42 mg for electrodeposition. By incorporating SiO2 particles into the PANI film, the transmittance change at 700 nm from 10.7% to 16.4%, or an enhancement of ca. 50%, was achieved when operating between -0.5 and 0 V (vs. Ag/Ag+). The safe operating potential window was between -0.5 and 0.3 V (vs. Ag/Ag+). In addition, X-Ray photoelectron spectroscopy (XPS) study indicated that the presence of SiO2 might have retarded the formation of the highly oxidized PANI and hence improved the stability. Furthermore, the growth mechanism of the PANI/SiO2 composite film was proposed based on electrochemical quartz crystal microbalance (EQCM) technique.
For the polythiophene (PT) derivatives, PMeT and PProDOT-Et2 thin films, both thin films were potentiostatically electrodeposited and their electrochromic properties were also studied. The safe operating potential window of PMeT thin films was between -0.4 and 0.6 V (vs. Ag/Ag+). The PMeT thin film showed red and blue by applying -0.4 and 0.6 V, respectively. The safe operating potential window of PProDOT-Et2 thin films was between -0.9 and 0.3 V (vs. Ag/Ag+). The PProDOT-Et2 thin film showed deep blue and light blue by applying -0.9 and 0.3 V, respectively.

The stability of ECDs is of paramount importance for practical applications. In order to fabricate an ECD with good performance, the EC materials and the operating conditions for the ECD should be chosen carefully. Herein, four ECDs, PANI-PMeT, PANI/SiO2-PMeT, PANI-PProDOT-Et2 and PANI/SiO2-PProDOT-Et2, were assembled with the theoretical equations from the viewpoint of the safe operating potential window and the optical contrast of thin films for ECD design. Their electrochromic properties were also comparatively studied. Initial optimal results revealed that the PANI-PProDOT-Et2 and PANI/SiO2-PProDOT-Et2 ECDs showed better performance than that of the PANI-PMeT and PANI/SiO2-PMeT ECDs. Therefore, the PANI-PProDOT-Et2 and PANI/SiO2-PProDOT-Et2 ECDs were further optimized and their stability was comparatively discussed from the viewpoint of the charge capacity and the operating voltage of ECDs. Under suitable collocation, both ECDs showed light blue and deep blue by applying -0.8 and 0.9 V, respectively and possessed high optical contrast, coloration efficiency, ultrafast response and good open circuit (memory effect) and at-rest stabilities. In long-term cycling stability analysis at 25 ℃, the PANI-PProDOT-Et2 ECD showed obvious decay after 28,775 cycles. At 590 nm, the optical contrast of the PANI-PProDOT-Et2 ECD was ca. 58.1% at 1 cycle and ca. 30.2% at 45,000 cycles, whereas the optical contrast of the PANI/SiO2-PProDOT-Et2 ECD was ca. 56.5% at 1 cycle and ca. 50.0% at 45,000 cycles. In long-term cycling stability analysis at 70 ℃, the PANI-PProDOT-Et2 ECD showed obvious decay after 24,795 cycles. At 590 nm, the optical contrast of the PANI-PProDOT-Et2 ECD was ca. 58.5% at 1 cycle and ca. 3.0% at 53,000 cycles, whereas the optical contrast of the PANI/SiO2-PProDOT-Et2 ECD was ca. 59.9% at 1 cycle and ca. 43.0% at 53,000 cycles. Hence, the PANI/SiO2-PProDOT-Et2 ECD had good long-term cycling stability no matter at room or high temperature when compared to the PANI-PProDOT-Et2 ECD.

In oder to improve the poor safety and the poor stability of ECDs caused by electrolyte leakage and sealing problems, the ECDs were sealed by surlyn and tried to use ionic liquid and gel electrolytes instead of the liquid electrolyte. Results revealed that electrolyte leakage and sealing problems could be improved by using surlyn. Nevertheless, that using ionic liquids instead of the liquid electrolyte is unsuitable for both PANI-PProDOT-Et2 and PANI/SiO2-PProDOT-Et2 ECDs. On the contrary, both ECDs using a gel electrolyte instead of the liquid electrolyte could enhance the at-rest stability and the long-term cycling stability at 25 ℃. The PANI-PProDOT-Et2 ECD showed obvious decay after 119,905 cycles. At 590 nm, the optical contrast of the PANI-PProDOT-Et2 ECD was ca. 55.3% at 1 cycle and ca. 0.3% at 200,205 cycles, whereas the optical contrast of the PANI/SiO2-PProDOT-Et2 ECD was ca. 52.4% at 1 cycle and ca. 39.7% at 200,235 cycles. Consequently, the PANI/SiO2-PProDOT-Et2 ECD had good long-term cycling stability at room temperature when compared to the PANI-PProDOT-Et2 ECD. But at high temperature, that using gel electrolyte instead of the liquid electrolyte will accelerate the decay of the PANI-PProDOT-Et2 and PANI/SiO2-PProDOT-Et2 ECDs.

並列關鍵字

coloration efficiency ； diethyl substituted poly(3,4-propylenedioxythiophene) (PProDOT-Et2) ； electrochromism ； polyaniline (PANI) ； PANI/silica (SiO2) ； poly(3-methylthiophene) (PMeT) ； stability

參考文獻

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