目前有機太陽能電池常使用混合式異質接面結構(Bulk Heterojunction)，主動層(active layer)為予體與受體材料相混合，較常採用的材料為poly(3-hexylthiophene)(P3HT)與C60衍生物PCBM。然而P3HT的能隙偏大，較不利於吸收太陽光的能量，且其能階與PCBM不甚匹配，因此需設計新型的共軛聚合物材料，藉由推拉電子效應，以降低能隙並調整能階。然而，設計與合成材料的過程耗時且繁複，因此若能以電腦先進行模擬，並使用分子動力學(Molecular Dynamics)的方式，觀測分子在週期時間內的軌跡、分子間的交互作用力，並分析材料的物理特性，勢必能縮短找到適當的新型予體材料的時間。
因此，本研究設計三種聚噻吩衍生物的予體材料，並與P3HT相互比較。材料以thiophene為主鏈，並在長鏈中加入拉電子基benzimidazole或是共平面性良好的benzo[1,2-b:4,5-b’]-dithiophene (BDT)基團，藉由模擬的方式分析四種共軛聚合物溶於chloroform時分子的共平面性、排列秩序性，並探討其作為主動層材料的優劣。藉由分子內與分子間的徑向分布函數、二面角、迴轉半徑與末端距等的分析，發現若將BDT接於主鏈，可有效增進分子的共平面性，此可提升載子遷移率與延長吸收波段，較適合做為取代P3HT的予體材料。
第二部分分析主動層電子予、受體材料與溶劑chloroform作用下的混和情形，在電子予、受體以1:1混合時，由RDF的結果發現PCBM與迴轉半徑、末端距較小的高分子會各自聚集，相分離較嚴重，而若為支鏈間距較大的高分子，則可使PCBM嵌入支鏈之間，並沿著主鏈分布，因而有較好的相分離。電子予、受體以1:2混合時，PCBM仍會嵌入支鏈間距較大的材料，此時因提升PCBM的比例，而可形成PCBM的傳輸通道，達成微相分離，而若與其他材料混合時則會使PCBM嚴重聚集。

The most widely used structures in organic photovoltaic cell are bulk-heterojunction, which blend electron-donor and electron-acceptor materials together in an active layer. Poly(3-hexylthiophene)(P3HT) and PCBM, a C60 derivative, are the most often used materials as donor and acceptor materials, respectively. However, the band gap of P3HT is too large to absorb sunlight energy efficiently, and the HOMO-LUMO energy levels of P3HT and PCBM do not match well. As a result, the most critical thing is to design and synthesize an ideal p-type material, a conjugated polymer, which possesses smaller band gap and suitable energy level by donor-acceptor push-pull effects. Synthesizing a new conjugated polymer is time-consuming, for this reason, we would try to use computer to simulate some new conjugated polymers by molecular dynamics, and investigate the trajectory of molecules in a period of time, the interaction of molecules ,and analyze the properties of polymer blended with PCBM. In this way, the time to find a suitable p-type material would be shortened.
In this study, we designed three polythiophene derivatives as p-type materials, and compared their properties with P3HT. The structures of the p-type materials are consisted of thiophene as donor moiety, benzimidazole or benzo[1,2-b:4,5-b’]-dithiophene (BDT) as acceptor moiety, which has good coplanarity. We analyzed the coplanarity and the degree of order in arrangement of the conjugated polymers by radial distribution function, torsion angel, radius of gyration and end-to-end distance to investigate the properties when they dissolve in chloroform. We found that the structure which consists BDT in the main chain would not only improve coplanarity of the polymer but also hole mobility and absorption ability in long-wavelength, which would be the most suitable p-type material.
Second, we mixed donor and acceptor materials together to investigate the properties of active layer. When the ratio of donor and acceptor was 1:1, we found that the radius of gyration and end-to-end distance of the polymers was small; they would aggregate separately and became severely phase separation. However, when the free space of the polymer side chains was larger enough for PCBM intercalation, PCBM would have strong interaction with polymer. If the component of PCBM increase to 50% in active layer, the polymer side chains were large enough for PCBM intercalation and would form a proper phase separation, which was good for transporting electron and hole by PCBM and polymer respectively and improve the efficiency of exciton dissociation.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 vi
圖目錄 ix
表目錄 xiii
第壹章 緒論 1
1-1 太陽能電池的定義 1
1-2 有機與無機太陽能電池的分別與介紹 2
1-3 有機太陽能電池結構介紹與工作原理 4
1-3-1 單層結構有機太陽能電池 4
1-3-2 雙層異質接面結構有機太陽能電池 4
1-3-3 混合層異質接面結構有機太陽能電池 5
1-3-4 光電轉換原理 7
1-4 材料發展與材料特性模擬回顧 10
1-4-1 聚合物能隙與能階的調變 10
1-4-2 主動層材料特性模擬之文獻回顧 13
1-5 研究動機 16
第貳章 理論基礎 17
2-1 分子動力模擬(Molecular Dynamics Simulation) 17
2-1-1 簡介 17
2-1-2 分子動力學基本架構 18
2-2 系統作用力場 21
2-3 數值方法 22
2-3-1 Verlet’s Algorithm 23
2-3-2 Leap-Frog Algorithm 24
2-3-3 Velocity Verlet Algorithm 25
2-3-4 Beeman’s Algorithm 25
2-3-5 Gear’s Predictor-Corrector Algorithm 26
2-4 模擬系統的設定 29
2-5 週期性邊界條件 31
2-6 Rescaling 溫度修正 35
2-7 分子動力學模擬的流程 36
第參章 系統建構方法及參數設定 37
3-1 系統建構 37
3-1-1 電子予體材料 37
3-1-2 分子個數設定 39
3-2 模擬系統平台 43
3-3 參數設定 44
3-3-1 結構最佳化參數設定 45
3-3-2 分子動力模擬參數設定 45
第肆章 結果與討論 46
4-1 分析方法 46
4-1-1 徑向分布函數（Radial Distribution Function，RDF） 46
4-1-2 配位數（Coordination number） 47
4-1-3 迴轉半徑（Radius of gyration） 47
4-1-4 末端距（End-to-end Distance） 48
4-1-5 均方位移（Mean Square Displacement，MSD） 48
4-2 電子予體材料在溶劑中之特性分析 49
4-2-1 溶解度 49
4-2-2 氫鍵作用力 51
4-2-3 長鏈的共平面性 52
4-2-4 支鏈間的作用力 56
4-2-5 聚合物整體長鏈的分布情形 59
4-2-6 初步結論 61
4-3 電子予/受體材料在溶劑中之特性分析 62
4-3-1 電子予體、受體材料以1:1混合時之特性分析 62
4-3-2 電子予體、受體材料以1:2混合時之特性分析 69
第伍章 總結與未來工作 76
參考文獻 78

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