本論文揭露並探討共軛高分子(MEH-PPV)在溶劑退火並同時以光罩照光時，所造成物理性質的改變及其因亂度與自由能驅使下形成可控制之分子流動現象。
共軛高分子因其π-電子軌域能階轉換在可見光附近，能與可見光進行光電反應而發光或發電，是一種深具未來發展潛力、低碳足跡的光電材料。基本上，當共軛高分子被光照射時，電子吸收光子由基態躍遷至激發態，產生電子-電洞對(exciton)，而其分子軌域在受激態時，主鏈結構將轉為相較於照光之前更為平面化(planar)與剛直(stiff)，而使得該分子之亂度下降。
因此，共軛高分子(如MEH-PPV)與一般飽和高分子(如聚苯乙烯, polystyrene)混摻後，施以溶劑(如,甲苯)退火，並同時透過光罩照光時，受到光照而轉剛直化的MEH-PPV分子，其亂度(entropy)下降，因而驅使聚苯乙烯從非照光區擴散至照光區，以提高局部亂度來降低整體系統的自由能。並也因共軛高分子剛直化的亂度效應，促進在退火環境中甲苯溶劑分子對照光區之擴散，而產生局部的額外退火效應。以上的交互作用，催生出由暗區到照光區之分子流動。另一方面，由於照光剛直化的共軛高分子，乃處於較高之分子能態，因此，在持續照光之下，會有一驅動力推動剛直化的共軛高分子逃逸到未照光之暗區，形成另一反向的分子流。但是因為剛直化的高分子之運動能力大幅下降，因此由照光區到暗區之由共軛高分子所主導之分子流，相較於之前飽和高分子所主導，由暗區到照光區之分子流，其流通量較小。同時，很明顯地，共軛高分子在此混摻系統中的濃度，會強烈影響此兩種分子流的驅動力。
我們以厚度在10-30nm區間內之MEH-PPV/PS混摻薄膜，在光學顯微鏡下，以不同間隙尺度(間距5-100μm)的線性圖樣光罩進行光照，並同時施以甲苯溶劑之退火實驗。在此實驗中，我們觀察到此奈米薄膜的局部厚度，會因光罩上的圖像而進行改變。在低MEH-PPV濃度薄膜中，局部厚度的變化主要乃因由暗區到照光區之分子流動所引起。然當薄膜之MEH-PPV濃度提高至80%或甚至100%時，我們發現薄膜局部厚度的變化是由從照光區膜旅行到暗區的分子流動所主宰。MEH-PPV因照光後的剛直化限制了流動，此時其遷移率約較低濃度以聚苯乙烯為主之分子流通量小了三個數量級，因此高濃度MEH-PPV薄膜因照光造成的局部膜厚變化，在實驗觀察中，亦遠較低濃度情況小得多。因此，我們可以利用光罩控制照光範圍，藉由照光與非照光區間物理性質與亂度上的差異形成特定圖樣。
此外，在低濃度MEH-PPV薄膜中，照光區邊界上因亂度差異驅使的分子劇烈流動使得高分子鏈上存在著應力，由先前實驗結果已知，高分子鏈上應力的存在會大幅增加螢光發光效益，本實驗中亦觀察到此一現象。
最後，我們利用光照差異影響高分子薄膜在除潤時的行為。實驗觀察中，溶劑除潤現象在經由光照後明顯加快，由此速度上的差異及藉由光罩控制光照範圍，我們可於特定區域進行除潤並產生特定圖樣。

This report discloses and explores the changes of the physical properties of the conjugated polymer MEH-PPV upon light exposure through an optical mask under a “solvent annealing” condition, including the induced molecular flows driven by local entropy and free energy that are controllable through various material and light exposure parameters.
Conjugated polymers, owing to their delocalized π electrons capable to undergo state transition in the optical range, react to light to generate luminescence or charge currents, thus highly promising for low carbon-footprint optoelectronic applications. Generally, upon excitation to create electron-hole pairs under light illumination, the molecular backbone of the conjugated polymer becomes straightened and rigidified, producing an entropy reduction of the molecule.
Hence, in a blend with a saturated polymer (such as polystyrene) that is illuminated through an optical mask under the annealing condition in solvent vapor, polymer molecules will migrate from the dark region to the light region in order to compensate local entropy reduction, while the solvent molecules preferentially diffuse into the dark region bringing about additional local heating. Consequently, a molecular flow arises from the dark region to the lighted region. Conversely, owing to the higher energy states in the lighted region, the conjugated polymer will be prompted to move from the lighted region to the dark, forming the opposite molecular flow. However, due to the decline of molecular mobility arising from restricted molecular conformations of the straightened backbones, the MEH-PPV flow from the lighted to the dark region is smaller than the PS-dominated flow from the dark region to the lighted region. Obviously, the driving forces for these molecular flows are highly sensitive to the concentration of the conjugated polymer in the blend.
We conducted experiments using ultrathin (10-30 nm) MEH-PPV/PS films illuminated through an optical mask in an optical microscope while annealed in toluene vapor. The optical mask has line patterns of fixed spacing ranging from 5 to 100 μm. We observed the ultrathin films underwent local thickness changes in accordance to the patterns in the optical mask. For low MEH-PPV concentrations, the local thickness changes were mainly resulted from the molecular flows from the dark region to the lighted regions. As the concentration increased to 80% or even 100%, we found that the local thickness changes were dominated by MEH-PPV migration from the lighted area to the dark. The flows reigned by the rigidified MEH-PPV, however, were much slower compared to those dominated by PS as observed in the low MEH-PPV concentrations by approximately 3 orders of magnitude. So were the light-induced thickness changes as compared to those in the low concentrations. Therefore, we can use optical mask to define specific lighted patterns to result desired local thickness changes via the light-induced local variances of physical properties including entropy.
In addition, in the films of low MEH-PPV concentrations, the robust molecular flows may create molecular stretching to impart local mechanical stress increase to enhance the optoelectronic efficiencies, in good agreement with published prior experimental results.
Finally, we was able to demonstrate a controlled dewetting process of the ultrathin films by using the masked light in the solvent annealing condition where the dewetting velocity was accelerated in the lighted regions to produce the local thickness variations copied from the optical mask.

摘要 I
Abstract IV
致謝 VII
目錄 VIII
圖目錄 X
第一章 簡介 1
第二章 文獻回顧 4
2-1 旋轉塗佈 4
2-2 超薄膜的殘留應力 5
2-3 高分子薄膜的除潤現象(dewetting) 9
2-4 共軛高分子MEH-PPV 10
2-4-1 MEH-PPV分子鏈構型的性質 11
2-4-2 Exciton、Excimer、Exciplexes和Polaron pair 14
2-4-3 MEH-PPV共軛高分子的摻雜 16
2-4-4 MEH-PPV共軛高分子的溶劑退火 17
2-4-5 MEH-PPV共軛高分子的除潤現象 19
2-5 殘留應力與光電效率 22
第三章 實驗設置 24
3-1 實驗材料 24
3-2 實驗方法 25
3-3 實驗器材 26
第四章 結果與討論 30
4-1 溶劑退火及除潤現象 30
4-2 照光影響 32
4-3 光罩 36
4-3-1 光罩-50μm 39
4-3-2 SIMS分析 43
4-3-3 光罩-5μm 44
4-4 光譜 46
4-4-1 光譜-no mask 46
4-4-2 光譜-mask-covered 50
4-4-3 Intrachain Peak Analysis 52
4-5 低濃度與純MEH-PPV薄膜 56
4-6 光控除潤 59
第五章 結論 63
第六章 參考文獻 65

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