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  • 學位論文

聚(3-己烷基噻吩)之分子組裝行為及其內電荷移轉機制的理論研究

A Theoretical Study of the Molecular Organization Behavior and the Charge Transfer Mechanisms of Poly-3-hexylthiophene

指導教授 : 黃慶怡

摘要


高規整度的聚(3-己烷基噻吩)(P3HT)由於其應用在有機場效電晶體時,具有可達0.1 cm2/Vsec的高載子遷移率而受到廣泛的注意及研究。本研究希望以理論模擬的角度對P3HT系統內的電荷傳遞機制進行探討,並嘗試計算其系統之電洞遷移率。研究藉由跳躍模型為基礎,針對P3HT系統內的延鏈上及延鏈間維度,分別改變相鄰兩片段間的旋鈕角及片段間距,以量子計算(QM)進行延鏈上及延鏈間兩不同維度之電荷傳遞速率及遷移率之計算。另外並藉由分子動力模擬(MD)技術計算各個不同溫度及規整度環境下的P3HT系統,以得到其分子結構的細部資訊。 結合QM及MD的結果顯示在規整排列區的延鏈上傳遞速率會大於延鏈間傳遞約百倍,鏈上傳遞應是規則區內的主要傳遞路徑。計算結果並顯示延鏈間方向的電洞遷移率為10-2 cm2/Vs,此結果與P3HT的單纖維束實驗結果一致,顯示此方法在共軛高分子遷移率計算上的適用性。此外,對於紊亂區間我們提出交點/橋接鏈模型,此模型可以正確解釋對於P3HT遷移率與分子量以及聚集區塊尺寸間相關變化的實驗結果。最後,在平均遷移率的估算顯示紊亂區由於其較慢的遷移率會限制/拖慢整個系統的遷移率。因此對於提升紊亂區間的遷移率會是提升整體遷移率所必須考慮的一個方向。

並列摘要


The regioregular poly-3-hexylthiophene (rr-P3HT) system can reach mobility as high as 0.1 cm2/Vsec all around the polymer based organic field effect transistors (OFETs). Thus, to clarify the factors that affect the charge mobility and the transport mechanisms of the P3HT based OFET systems are of great importance. We use quantum mechanical (QM) methods to interpret the charge mobility and the transport properties of the P3HT molecules along the intrachain and interchain directions. Our approach is illustrated by a hopping transport model, in which we examine the variation of the charge mobility with the torsional angle and the inter-molecular distance between two adjacent thiophene segments. We also simulate the packed and vacuum state P3HT structures via the molecular dynamics (MD) simulations to obtain the detail chain conformation. The QM and MD results indicate that the main charge transfer route within the P3HT ordered domains is along the intrachains instead of the interchains. The calculation results of the interchain hole mobility is around 10-2 cm2/Vs, which is consistent with the excremental data from the P3HT single fibril. Besides, we proposed a crossing-point/bridging-chain model to illustrate the chain conformation in the disordered regions. This model can explain the mobility evolutions as a function of Mw/nanofibril-width very well. Finally, the average charge mobility approximation suggested that the disordered region is the mobility limitation zone of the whole systems since the large difference of mobility between the ordered and disordered state. One should consider the contributions of the disordered region in improving the total charge mobility in the OFETs system.

並列關鍵字

Charge Transfer Charge mobility Transfer Integral P3HT OFETs

參考文獻


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