噴印銀墨與導電高分子透明網格狀電極之製程開發及其性質探討

Development and Characterization of Inkjet-Printed-Silver and Conducting Polymer Transparent Mesh-Type Electrodes

游博進(Po-Chin Yu)

指導教授 ： 劉通敏 ； 洪健中

國立清華大學/工學院/動力機械工程學系/碩士(2013年)

摘要

透明導電薄膜廣泛地應用於太陽電池、發光元件及消費性電子產品中，作為電流與光線通過的媒介，因此其導電性質與透光度直接地影響了元件的效率。近年來銦錫氧化物(ITO, Indium tin oxide)成為了透明電極的主流材料。但隨著需求量的劇增以及稀有金屬銦產量的限制下，ITO的價格亦隨之飆漲。尋找ITO替代材料議題便逐漸受到重視。其中關鍵技術在於以同樣的成本條件，製備導電性及透光度皆足以媲美ITO的透明導電薄膜。
本研究提出以材料利用率高的噴墨製程噴印銀網格電極，配合添加物修飾後的導電高分子材料(PEDOT)，合成複合式透明網狀電極。其中網狀電極的金屬線段寬度與線段間距決定了電極的透光度與導電性，故特別針對過去文獻不足之處首度建構數學理論模型，對於網格外觀尺寸與透明電極優值之關係進行分析，求得最佳線段寬距比為0.05，並以實驗方法驗證線段寬距比與透明電極優值之關係曲線的準確性。其次，為了進一步增加電極的導電性，以重複噴印的方式提高線段的深寬比，並研究噴印層數1至4層的線段形貌、導電性及透光度的變化，成功地在透光度維持90%以上的狀況下，使導電度提升至單層噴印50倍。另外，考慮到應用於元件時塗佈後續材料的可能性，本研究引進熱壓平坦化成功使平均厚度超過150 nm 的金屬線段降至10 nm以下，故電極表面具備高度平整性。整合上述製程製備透明網狀電極後，量測其片電阻值為7.2 Ω/□，透光度為84.03 %，計算可得透明電極優值為24.39×10-3 Ω-1。與過去同樣研究厚度為奈米等級之電極的文獻結果相比，較平均值(11.78×10-3 Ω-1 )與最佳值(22.13×10-3 Ω-1)分別提升了107%與10.2%。此外，為了驗證電極的可繞性與可靠度，本研究亦針對工業界需求進行導線的可繞性測試，在繞曲曲率半徑為11 mm的條件下，進行往返±135°的彎曲。在經過23000次的繞曲次數後，電極的電阻值上升幅度仍在10%以內，較過去文獻的最佳結果高出15000次。

關鍵字

噴墨技術 ； 透明電極 ； 金屬網格 ； 電極優值理論 ； 軟性電子

並列摘要

Transparent conductive films has been widely used in solar cells, LED and consumer electronics as a medium of electric current and light. Its conductivity and transmittance affect the efficiency of these devices. The mainstream material for transparent conductor is ITO (indium tin oxide) in recent years. However, the price of ITO has increased dramatically due to the huge demand and the strained supply of indium. Seeking the replacement materials for ITO becomes an important issue, and the way how to fabricate a transparent conductor with comparable conductivity and transmittance under the same cost is the only solution.
This study presents a transparent mesh-type electrode by integrating inkjet-printed-silver and modified conductive polymer (PEDOT). A mathematical model has been proposed for calculating the optimized grid pattern, and the optimized line width/line spacing ratio is 0.05 by this model. Furthermore, the theoretical relationship between line width/line spacing ratio and figure of merit has been verified by experimental results. For improving the conductivity of electrodes, the aspect ratio of lines has been raised by overprinting. The conductivity of four-layers printed electrodes is 50 times as high as the conductivity of monolayer printed electrode, and their transmittance are still higher than 90%. Moreover, planarization of transparent mesh-type electrodes by hot-pressing has been proposed and demonstrated. The thickness of grid lines decreases from 150 nm to 10 nm by this planarization. Integrating all of these processes, the sheet resistance of fabricated electrode is 7.2 Ω/□, the transmittance is 84.03 % and the figure of merit is 24.39×10-3 Ω-1 which is 2 times as high as the mean value of the literature before. After 23000 times of bendings to a 11 mm radius curvature, the resistance incensement of electrode developed by this study is still less than 10%.

並列關鍵字

Ink-jet Printing ； Transparent Electrodes ； Metal Grids ； Figure of Merit Fomula ； Flexible Electronics

參考文獻

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