含胺基團之改質石墨烯與聚苯乙烯/銀核殼型複合材料之合成及其應用

Synthesis, Characteristics and Applications of Novel Functionalized Graphene and Polystyrene-Silver Core-Shell Type Composites Based on Incorparation of Amino Groups

許經德(Ching-Te Hsu)

指導教授 ： 謝國煌

國立臺灣大學/工學院/化學工程學研究所/博士(2016年)

https://doi.org/10.6342/NTU201603345

摘要

本研究利用不同的研究方針並引入胺基官能基，以開發具高導電性之改質石墨烯複合材料薄膜、聚苯胺改質石墨烯之電子受體、核殼型複合顆粒及導電膠，且將分為三部分進行討論。
第一部分研究為天然石墨先經由化學氧化及高溫還原過程，得到奈米片狀氧化-還原石墨烯，接著以(1)硫醇基改質，(2)磺酸鈉基或胺基改質，分別得到RGO-SO3和RGO-NH2後，可大幅提升氧化-還原石墨烯在水相中之分散穩定性。藉由原位還原法，將奈米銀粒子裝飾於RGO-SO3和RGO-NH2的表面，而後與聚(3,4-乙烯二氧噻吩)-聚(苯乙烯磺酸)進行混摻並旋轉塗佈於玻璃基板表面，可能成功製備高透明導電複合薄膜。利用電子能譜儀測量氧化還原前後片狀石墨烯之元素成分及比例，掃描式電子顯微鏡觀測銀金屬粒子裝飾於氧化-還原石墨烯表面之大小及分布情形；透明導電複合薄膜則藉由四點探針、表面輪廓儀、紫外光-可見光光譜儀及原子力顯微鏡進行表面電阻、膜厚、穿透度及表面型態。結果顯示，由以上實驗方法所製備之複合薄膜展現極佳的透明度、導電度，並可提升環境耐久性，期望未來可進一步應用至光電元件領域。
第二部分，製備高分子有機太陽能電池並以聚苯胺改質之石墨烯為電子受體(p-rGO)的三相態塊材異質接面結構(ternary-blend bulk heterojunction)。利用與第一部分實驗相同之改質方式，氧化-還原石墨烯經由重氮化反應先改質上胺基官能基，再進行化學氧化聚合法接枝上聚苯胺，做為具有弱電荷轉移之電子受體。為了增進聚(3-己基噻吩) (P3HT)電子施體與p-rGO電子受體間之電子傳導，藉由設計以噻吩-苯并噻二唑為主體，具雙極性且不同封端拉電子官能基之兩種施體-受體(donor-acceptor type)共軛小分子為橋樑分子，(1)以羧酸封端之Tac及(2)以α-氰基丙烯酸封端之Taccn。與傳統兩相塊材異質接面結構之太陽能元件相比，在引入Tac後，由於電子傳導的改善使元件效率有顯著提升；對Taccn系列元件而言，能量轉換效率(PCE)可進一步至2.03 %，可歸因於具有比Tac更廣的吸光範圍。上述研究對於以石墨烯為電子受體之高分子有機太陽能電池的發展有顯著的重要性，且三相態塊材異質接面結構可作為一實際有效之製程用於製備具有良好電子傳導之太陽能電池。
本研究第三部分為，藉由引入聚苯胺高分子作為活化劑(activator)並設計合成方式以製備具有良好電子傳導能力之有機/無機核殼型導電複合顆粒及其高分子複合導電膠。首先，以分散聚合法製備高交聯之聚苯乙烯乳膠顆粒，並利用化學氧化聚合法將聚苯胺覆蓋於聚苯乙烯乳膠顆粒之外層，作為可螯合銀離子之活化劑。接著，以改良之無電電鍍法並設計一系列合成參數，製備聚苯乙烯-聚苯胺-銀核殼型導電複合顆粒(PS-PANI-Ag)且進而提升PS-PANI-Ag導電複合顆粒之電子傳導能力。上述實驗方法使奈米銀殼層展現不同的表面型態，並可完整包覆於PS-PANI複合核顆粒表面使其具有極佳的導電通路。此外，PS-PANI-Ag導電複合顆粒進一步與環保型分散劑-水性聚胺酯進行混摻形成導電膠體，並於聚對苯二甲酸(PET)基材上成功製備出環保型導電膜。此合成方法顯示所製備之殼層的表面型態與導電度有顯著之關係，而其環保型導電膠具有可應用於電子材料領域之潛力。

關鍵字

改質石墨烯 ； 聚 (3,4 -乙烯二氧噻吩)-聚(苯乙烯磺酸) ； 奈米銀粒子 ； 石墨烯電子受體 ； 雙極性 ； 三相型高分子有機太陽能電池 ； 核殼型複合顆粒 ； 導電膠 ； 導電複合(薄)膜

並列摘要

In this dissertation, the develop of the electrically conductive particles, composite films and the graphene-based electron acceptor are studied in different strategies. This research is divided into three parts, and discussed separately.
In the first part, a solution-processed metal nanoparticle/graphene composite material is developed by the incorporation of functionalized reduced graphene oxide (RGO) nanosheets, which are synthesized via diaozotization process in the presence of –SH, –SO3Na or –NH2 functional groups. In the beginning, the RGO is prepared by the oxidation of natural graphite powder and the thermal reduction of graphene oxide (GO). Both of the functionalized RGO nanosheets (RGO-SO3 and RGO-NH2) show the improved dispersibility in aqueous phase with two different functional groups –SO3Na and –NH2, respectively. After a simple in-situ reduction method, Ag nanoparticls can be distributed uniformly on the surface of functionalized RGO and utilized as conductive spacers between the graphene nanosheets. The best electrical conductivity of around 2080 S/cm at a transmittance of 88 % (at λ=550 nm) is obtained with the well-dispersed Ag@RGO-SO3 in the PEDOT:PSS matrix. By making good use of the conducting network built up by the graphene, conductive spacers (Ag NPs) and conducting polymer, we demonstrate the promising application of these nanocomposite thin film as highly conductive and transparent electrodes for organic optoelectronic devices.
Second, the ternary-blend organic photovoltaic device based on an acceptor of polyaniline-functionalized graphene (p-rGO) is demonstrated. The solution-processed graphene acceptor is first functionalized via diaozotization procedure, followed by the polyaniline chain covalently grafted on the surface of graphene. To further improve the charge transport at the interface of poly (3-hexylthiophene) (P3HT) donor and p-rGO acceptor, two novel thiophene-benzothiadiazole based small molecules, Tac and Taccn, end-capped with electron-withdrawing functional groups, carboxylic acid and 2-cyanoacrylic acid, respectively, is designed. The utilization of p-rGO as the electron acceptor material in P3HT bulk heterojunction photovoltaic (BHJ) devices is first demonstrated. Afterwards, the device of ternary blend BHJ organic solar cells using Tac as bridging materials shows an improved power conversion efficiency (PCE). Moreover, in Taccn series devices, the best performance is PCE of 2.03% and a short-circuit current density of 6.14 mA/cm2. The presented graphene-based acceptor shows the significance of developments in organic solar cells, and the ternary-blend BHJ is expected to be a practical approach for the fabrication of solar cell devices.
In the last part, the core-shell type conductive particles based on the incorporation of polyaniline (PANI) as the activator are designed and fabricated to apply in electrically conductive adhesives. The polystyrene (PS) core particles with crosslinked structures are first prepared by dispersion polymerization to enhance the thermal stability, followed by the synthesis of PANI layer on the core surface via chemical oxidation polymerization. The modified electroless plating process is then utilized to fabricate the PS-PANI-Ag core-shell conductive particles. A series of reaction parameters, leading to various amounts of silver content and morphological effects, are investigated, including different ratios of aniline/PS and concentration of AgNO3. The prepared PS-PANI-Ag conductive particles have excellent electrical properties with Ag shells densely packed on the surface of PS-PANI cores. Moreover, the PS-PANI-Ag conductive particle are blended with environmentally friendly dispersions, water-borne polyurethane (WPU) to form electrically conductive films with a outstanding electrical property. The presented synthetic process exhibits a noteworthy relationship between the morphologies of core-shell particles and the electrical properties, and the environmentally friendly ECAs show the significant potential for the applications of electronic fields.

並列關鍵字

functionalized graphene ； PEDOT:PSS ； silver nanoparticles ； graphene-based acceptor ； ambipolarity ； ternary-blend polymer solar cell ； core-shell particles ； electrically conductive adhesives ； conductive composite films

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