| 摘要: | 軟性電子擁有可彎曲和捲曲的特性，具有極大的發展潛力與更多的創新應用，而有機半導體材料 具有良好的可撓性，已成為製造軟性電子元件的關鍵材料，例如有機薄膜電晶體（OTFT)、有機太陽 能電池（OPV)與有機發光二極體（OLED)，都是軟性電子技術發展的重點元件與材料。在這些可撓 式有機光電元件的結構組成中，高透明性、高導電性之導電薄膜電極以及高阻絕水氣能力之封裝薄膜 阻絕層，扮演相當重要的角色，也是軟性電子元件材料技術發展的重要一環。這些軟性電子元件，未 來應用時，因應場景需求，有可能製作成具有撓曲外型的裝置，長期承受靜態撓曲變形作用，或會具 有反覆撓曲作動的功能，甚至也有可能承受固定與反覆撓曲變形交互作用。當受到長期固定或反覆撓 曲作用時，其變形所衍生的損傷（如微裂缝或介面脫層），會提高導電薄膜的電阻，降低導電性，也 會成為水氣滲透的管道，降低封裝薄膜阻絕水氣能力。因此，在開發軟性電子關鍵元件材料時，除了 其相關功能性（如電性、光學性質或阻水氣性質）需滿足特定應用場景之要求外，同時也要求在受到 長期固定與反覆撓曲變形作用時，仍能維持此良好的功能性質，方能確保可撓式軟性電子元件的耐久 使用壽命。 為了深入且有系統地探討撓曲疲勞與潛變對軟性電子關鍵元件功能性質之影響，本三年期研究計 晝將對使用不同有機聚合物軟性基板（聚對苯二曱酸乙二酯[PET]及聚萘二曱酸乙二醇酯[PEN])之銦 錫氧化物（ITO)透明導電薄膜，進行長時間固定撓曲潛變負載、不同應變速率之撓曲疲勞負載、不 同持時長短之潛變一疲勞交互負載等負載模式的機械試驗，並於機械試驗進行中，同步量測其電阻變 化，結合力學行為分析與微結構、損傷觀察，評估不同撓曲負載損傷機制對ITO/PET及ITO/PEN導 電膜之導電性質的影響，並建立機械行為、破損機制與導電性能三者間的關係。除此之外，亦將對不 同阻絕結構設計之封裝薄膜，同樣進行長時間固定撓曲潛變負載、不同應變速率之撓曲疲勞負載、不 同持時長短之潛變一疲勞交互負載等負載模式的機械試驗，並於機械試驗後，利用鈣潮解法量測其水 氣滲透率（WVTR)之變化，從而建立WVTR值隨潛變作用時間或疲勞週期數變化之關係，同時結合 力學行為分析與微結構、損傷觀察，評估不同封裝薄膜結構設計抵抗長期固定與反覆撓曲變形之能 力；並嘗試利用有限元素法分析含有缺陷或微裂紋之封裝薄膜的水氣滲透速率，以期能建立封裝薄膜 WVTR值的預測模型。預期本三年期計晝所衍生的研究成果，將有助於瞭解軟性電子關鍵元件在承受 長久固定撓曲及反覆撓曲變形作用下的破損機制，以及這些變形、損傷對其功能性影響的關連性，從 而尋求防制及改善機制，回饋給國内產業及學界作為改善材料與製程設計之參考，對提升軟性電子元 件的使用壽命及精進國内軟性電子技術開發能量能有所貢獻。 ;Flexible electronic devices have great potential for widely novel applications as they can conform to a desired shape, or flex during its use. As organic semiconducting materials have the ability to flex such that they are the key materials in flexible electronic devices such as organic light-emitting diode (OLED), organic photovoltaic (OPV), and organic thin-film transistor (OTFT). In a typical flexible electronic assembly, transparent conductive thin-film electrode and encapsulation thin-film barrier are two of the major components, e.g. in OLED and OPV. A highly transparent, conductive electrode is needed for light transmitting and an effective encapsulation barrier is needed to protect the device from exposure to the environment. In practical applications of such flexible electronic devices, they might be subjected to long-term static and/or cyclic flexural deformation which may cause damages in their components and degrade their performance. In particular, flexural-deformation induced damages (microcracking and/or delamination) would reduce the electronic conductance of transparent conductive thin-film electrode and increase exposure to water vapor and oxygen leading to adverse oxidation of functional layers. In this regard, structural reliability is one of the greatest challenges which must be addressed prior to wide spread commercial application of flexible organic devices. For this reason, it is necessary to investigate the mechanical behavior of transparent conductive thin film and encapsulation thin film for use in flexible electronic devices and how their functional properties are affected, when subjected to long-term static and/or cyclic flexural deformation. The aim of this three-year study is thus to systematically characterize the effects of long-term static and/or cyclic flexural deformation on the electric conductance of transparent conductive thin films as well as on the water vapor transportation resistance of encapsulation thin films used in flexible electronic devices. Flexural fatigue, creep and fatigue-creep combined tests are to be conducted on indium-tin-oxide (ITO) thin film on two types of polymeric substrate, namely polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). The change of electrical resistance will be monitored simultaneously during mechanical testing so as to investigate the effects of flexural deformation on electrically conductive properties of the ITO film under applied loadings. A finite element method (FEM) modeling is to be developed to simulate the mechanical behavior and offer more understanding of the failure mechanism that governs the change in electrical conductivity of ITO thin film. Similarly, static, cyclic, and cyclic-static combined bending tests will be conducted on two encapsulation thin films of different barrier structures to investigate the effects of long-term flexural deformation on their water vapor transportation rate (WVTR). Calcium corrosion test is to be employed to measure the WVTR for the given encapsulation thin films after each given flexural loading. Moreover, an FEM model is to be established to simulate the moisture permeation mechanism in a damaged encapsulation thin film so as to predict the WVTR. It is hoped that results of this study could provide useful information for flexible electronics developers and users to prevent failure of ITO thin film on polymeric substrate and of encapsulation thin film, to find methodologies for improving their performance and mechanical integrity, and to reach competitive cost and engineering requirements. |
