再生性高分子材料於有機光電元件應用

Abstract

隨著環保意識逐漸抬頭，再生性材料在生醫、能源、包裝、光電等領域的應用引起許多關注。另一方面，有機電子及光電元件由於其可撓性、可調控性、輕量化及低成本等，已被用來開發未來穿戴式裝置。相較於使用一般有機材料製備電子及光電元件，生質材料的利用對於整體製程與元件回收上具備了低汙染、低危害及環境友善的優勢，在穿戴式裝置的應用上可提供更佳的生物相容性。然而目前將生質材料導入軟性元件的應用仍有許多挑戰需要被克服。在本研究中探討以生質聚酯材料－聚乙烯呋喃酸酯(PEF)為基材，取代傳統以化石燃料為基礎之塑膠基材在軟性有機場效電晶體、太陽能電池以及記憶體元件方面的應用。其研究細節分述如下： 本研究第二章，成功以聚乙烯呋喃酸酯為原料，製備可與一般聚對苯二甲酸乙二酯(PET)以及聚對萘二甲酸乙二酯(PEN)薄膜相比之高透明度之薄膜基材，並進一步藉由溶液製程技術將奈米銀線沉積於聚乙烯呋喃酸酯基材上。由於聚乙烯呋喃酸酯結構中之呋喃環所帶的孤對電子，使奈米銀線均勻的吸附並與基材產生良好的附著力。為了製備高導電性薄膜，我們利用不同銀線溶液濃度並透過旋轉塗佈的方式對銀線密度與電阻之關係加以控制。此生質複合導電膜具備高透光性、高導電度以及優異之機械性質，使其在取代常用之化石燃料為基礎之塑膠基材與傳統金屬或透明導電氧化物之電極上更具有優勢。另一方面，進一步成功以此聚乙烯呋喃酸酯/奈米銀線生質複合導電膜應用於有機場效電晶體以及有機太陽能電池，這些軟性生質元件皆具備可與使用硬板基材製備之元件相比之性質。 本研究第三章，以生質聚乙烯呋喃酸酯為基材、導電性高分子為電極並導入生物材料如去氧核糖核酸、核糖核酸以及聚左旋脯氨酸，以全溶液製程成功製備軟性全高分子之再生性電阻式記憶元件。此元件為單次寫入多次讀取(WORM)記憶體，具備低操作電壓、高電流開關比、資料儲存能力佳等特點，即使於撓曲狀態下亦可進行操作，極具應用於下一世代穿戴式元件之潛力。 以上的研究顯示使用生質材料於軟性電子及光電元件之基材，能夠取代一般塑膠基材並達到接近硬板基材元件的表現。另一方面，實驗結果亦證明了將再生性材料導入元件結構中，並透過全溶液製程製備軟性電子元件的可行性。

Renewable materials have attracted extensive attentions for applications in numerous field such as biomedical, energy, packaging, and optoelectronics. On the other hand, organic electronic and optoelectronic devices could be applied in future wearable electronics. The utilization of renewable materials for organic electronics is environmentally friendly and could minimize the generation of pollution and hazardous substances in processing in comparison with those using petroleum-based organic materials. Also, it can provide the biocompatibility in wearable electronic applications. However, there are some challenges for introducing bio-based component into flexible device applications must be overcome, such as adhesion or compatibility with other layers, reduced performance, etc. In this study, 100% bio-based polyethylene furanoate (PEF) was employed as the substrate in replacement for petroleum-based plastics, and used to explore the properties and applications on flexible organic field-effect transistors (OFET), organic photovoltaics (OPV), and memory devices, as described in the following: In chapter 2, a highly transparent film was fabricated by PEF, with comparable performance to polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films. We further deposited silver nanowires (Ag NWs) on the PEF substrate by solution processing. PEF could adsorb the Ag NWs tightly due to the coordination-type bonding effect between the lone pair electrons in the furan unit of PEF and Ag NWs. In order to fabricate highly conductive films, various concentrations of Ag NW solutions were used for controlling the film resistance by the Ag NW density via spin coating. The bio-based PEF/Ag NW conductive film has great potential as an alternative of petroleum-based plastics and traditional metal or transparent conductive oxide (TCO) electrode by taking advantage of its high transparency, good conductivity, and excellent mechanical durability. It is demonstrated the conductive PEF/Ag NWs film could be used in fabricating efficient OTFT and OPV. The OPV device of PEF/Ag NWs/ZnO/PFN/PTB7-Th:PC71BM/MoO3/Ag achieved the power conversion efficiency of 6.7%, which was superior to the device based on ITO/PEN device, manifesting the promising merit of the bio-based PEF for flexible electronic applications. In chapter 3, we demonstrated the fully solution-processed all-polymer flexible resistive switching memory devices by incorporating bio-based materials including deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and polyamino acid (poly-L-proline, PLP) were successfully fabricated by using PEF as substrate and conductive polymer as electrodes. The devices demonstrated the write-once-read-many-times (WORM) memory behavior with a low threshold voltage ~ -2V, an on/off current ratio as high as 104, and a data retention time over 104 s, which can sustain after 1000 cycles of bending. The above studies demonstrate that the renewable materials based substrate for flexible organic electronic and optoelectronic devices is a possible replacement for petroleum-based plastics with comparable performance to rigid devices.