功能性碳六十衍生物與聚硫族吩高分子其合成、分子性質與固態薄膜堆疊於光電元件之影響

Abstract

我們根據接觸介面、小分子與高分子三個面向，分別研究其性質與堆疊形貌上對於光電元件上所造成的影響；首先於第一部分合成出新型交聯性碳六十衍生化合物bis(2-(trichlorosilyl)propyl)-malonate C60 (TSMC)，在鈀金屬的催化下對烯烃官能基團進行矽氫化反應，並在富勒烯分子上修飾雙取代之三氯矽烷。有別於以往的元件製成，交聯薄膜的形成通常需要伴隨著照光或是後加熱處理，而憑藉著三氯矽烷的高度反應性，TSMC分子能夠藉由旋轉塗佈輕易地在氧化鈦表面進行水解並形成自組裝交聯薄層，此薄層不僅可以有效地鈍化氧化鈦表面的羥基，更重要的是，由TSMC分子所形成堅固的網狀交聯奈米結構，大幅度地提供了額外的激子拆解截面以及電子傳遞路徑，這使得以此材料製作的高分子太陽能元件(ITO/TiOx/SA-C-TSMC/P3HT:PC61BM (1:1, w/w)/PEDOT:PSS/Ag)，其效率可以達到3.9 %，相較於沒有此材料的元件效率有了大幅度地提升。同時我們也測試以poly(diindenothiophene-alt-dithienylbenzothiadizole) (PDITTDTBT) 為主動層材料組成之太陽能元件(ITO/TiOx/PDITTDTBT:PC71BM (1:4, w/w) /MoOx/Ag) ，其效率不僅達到了5.8 %，相對於缺少此材料之元件更是有了35 %的效率增長。此新一代以三氯矽烷為主要官能基之碳六十衍生物，為製作高效率且符合經濟成本之反式太陽能電池提供了一項既簡便又快速的技術。 在第二部分，我們探討小分子的排列堆疊，而成功將無序性奈米角錐型三苯胺分子、結晶性奈米球型碳六十分子進行結合，並生成新式雙岐型大分子8-(4-(triphenylamino)-1H-1,2,3-triazol-1-yl)octyl acetate C60 (TPA-C60)。有鑑於TPA-C60的雙單元特性，相對於組合前的單分子，此舉不只提高了分子的複雜度，同時角錐形狀之三苯胺，其不易結晶的特性，致使TPA-C60分子在排列時的主作用力由碳球之間所引導，並且在加熱熔化後難以再度形成規則晶體排列；另一方面，這樣的角錐併球型雙岐性分子能夠在溶劑的誘導下，自組裝形成三苯胺與碳六十各自分離且規則的奈米平面堆疊，而在結構解析的研究中，利用聚二甲基矽氧烷輔助長晶法，所獲得具方向性的TPA-C60晶體，能夠在有機場效應電晶體元件測試中，獲得均衡的電子遷移率2.11 × 10-4 cm2 V-1 s-1 與電洞遷移率 3.37 × 10-4 cm2 V-1 s-1 之雙載子特性效率，最後TPA-C60分子的晶格結構、排列方向以及雙載子通道在不同方位上的傳遞差異，更進一步使用電子繞射圖譜來分析與說明，成功將分子堆疊與元件輸出特性進行連結。 在最後，我們探討重原子取代於高分子薄層堆疊之影響，成功利用Kumada聚合反應，合成出一系列硫族吩之交替共聚物 P-SeS、P-TeS與P-TeSe，並與三個硫族吩同聚物P-SS、P-SeSe與P-TeTe進行綜合比較。隨著硫族元素替換重原子的比例更換，高分子之各項性質也隨之變動；在吸收光譜研究中，此六種高分子呈現出漸進式且寬廣之光吸收波長，並涵蓋整個可見光與少部分遠紅外光區範圍之吸收。此外，我們建立二十單元硫族吩共聚物模型進行理論計算，進而說明利用交替硫族吩單元組成之策略，能夠有效地改變分子構型並降低高分子規則度，最後達到控制溶解度的目的。隨後在X射線繞射光譜解析中，也觀察到當硫族元素替換至較高原子序時，其硫族原子尺寸變大與偏極化能力的增加所衍生出的分子間作用力，也主導著高分子成膜時的初始堆疊型態，並且在熱能量供給時，持續影響高分子排列上所做的移動與微調，最後於基板上的分子堆疊也由原來的各向同性趨向為各向異性，而造成薄層中堆疊的差異。因此，選擇性替換聚硫族吩之硫族原子的策略，可以針對光吸收波長、溶解度與高分子薄層堆疊進行三方面之微調，最終期許能在各式光電元件應用上嶄露頭角。

We based on three aspects in interfaces, small molecules and polymers to investigate the influences between molecular morphology and device performance. First of all, a new cross-linkable fullerene material, bis(2-(trichlorosilyl)propyl)-malonate C60 (TSMC), functionalized with two trichlorosilane groups, was easily synthesized by Pt-catalyzed olefin hydrosilylation. By making use of facile hydrolysis of the trichlorosilyl moieties, TSMC can be spontaneously self-assembled and cross-linked on the TiOx surface by a simple spin-coating processing without the aid of photoirradiation or post-thermal treatments. The rapid formation of self-assembled and crosslinked TSMC (SA-C-TSMC) effectively passivates the residual hydroxyl groups on the TiOx surface. More significantly, the solvent-resistant TSMC network features a nanostructured surface to provide extra charge-generating interfacial area and straight electron transport pathways. The device (ITO/TiOx/SA-C-TSMC/P3HT:PC61BM (1:1, w/w)/PEDOT:PSS/Ag) with this C60 interlayer exhibited an efficiency of 3.9 % which greatly outperformed the device without this layer. Furthermore, the strategy can also be effectively applied to the device (ITO/TiOx/PDITTDTBT:PC71BM (1:4, w/w) /MoOx/Ag) incorporating a conjugated polymer, poly(diindenothiophene-alt-dithienylbenzothiadizole) copolymer (PDITTDTBT). This device delivered a high efficiency of 5.8 % which represents a 35 % enhancement over the device without SA-C-TSMC. This new generation of trichlorosilane-based fullerene offers an easy and accelerated processing technique to produce efficient and cost-effective inverted solar cells. On the other hand, we shift discussions to small molecules. A giant amphiphile, which is constructed with an amorphous nano-pyramid (triphenylamine, TPA) and a crystalline nano-sphere (C60), was synthesized. Structural characterization indicates that this pyramid-sphere-shaped amphiphile (TPA-C60) forms a solvent-induced ordered phase, in which the two constituent units self-assemble into alternating stacks of two-dimensional (2D) TPA and C60 nano-sheets. Due to the complexity of the molecular structure and the amorphous nature of the nano-pyramid, phase formation was driven by intermolecular C60-C60 interactions and the ordered phase could not be reformed from the TPA-C60 melt. Oriented crystal arrays of TPA-C60, which contain flat-on TPA/C60 nano-stacks, can be obtained via a PDMS-assisted crystallization (PAC) technique. The flat-on dual-channel supramolecular structure of TPA-C60 delivered ambipolar and balanced charge-transport characteristics with an average μe of 2.11 × 10−4 cm2 V−1 s−1 and μh of 3.37 × 10−4 cm2 V−1s−1. The anisotropic charge-transport ability of the pyramid-sphere-shaped amphiphile was further understood based on the lattice structure and the lattice orientation of TPA-C60 revealed from electron diffraction analyses. Thus, it shows high correlation between crystal structure and electronic characteristics For polymer section, a series of polychalcogenophenes have been successfully tailored and synthesized by Kumada polymerization. In comparison with three alternating polymers P-SeS, P-TeS, P-TeSe and three different homopolymers P-SS, P-SeSe, P-TeTe, we found that polymeric properties were dramatically influenced by heavy-atom substitutions within chalcogenophene units. In Uv-Vis spectrum analysis, six polychalcogenophenes further exhibited stepwise and extensive absorptions, which cover the whole visible light and part of infrared area. Besides, we built up optimized geometries to elucidate the strategy for turning homo-units into alternatings could effectively reduce molecular regularity and control solubility. Furthermore, GIXRD characterizations revealed that heavy-atom substitution could possibly produce additional driving force to dominate polymeric packing in thin film, which tended to form anisotropic XRD pattern eventually. Therefore, heavy-atom substitution in polychalcogenophenes could fine-tune their light harvesting, solubility and molecular packing abilities, showing great promise for applications in optoelectronics.