有機半導體薄膜內的分子若能以較有序的排列方式，形成大面積連續的區域，將比較有利於載子的傳輸。在這篇研究中使用示差掃描量熱儀（Differential Scanning Calorimeter，DSC）以及等溫X光繞射(In-situ X-Ray Diffractometer)，來分析三種設計之寡聚噻吩衍生物自溶液析出形成的結晶結構，以及結構隨著溫度的變化。並觀察樣品以溶液析出成膜(solution casting)的方式，形成之薄膜或析出物的形態。
NTETB是有一個有液晶相的分子。它很容易藉由溶液析出形成有大面積結晶區域的薄膜，薄膜內的分子長軸垂直於基板，以交錯排列的方式形成二維堆疊。在液晶相溫度時，晶面能夠沿著b軸滑移。在溶液析出的薄膜中，這種滑移在冷卻轉變為結晶時，形成許多方向一致的裂痕，而導致結晶區域的連續性較剛由溶液析出的薄膜差。然而，氣相蒸鍍的薄膜由任意分布的小晶區與液晶相組成。在升溫時，層列型液晶相區域的融合，使得較大而且有方向性的帶狀區域形成。在對於NTETB的研究中發現，液晶相的存在對於薄膜形態同時有正面與負面的影響。液晶相的流動性與分子的再排列，能使薄膜內的區域變大。然而液晶相內的晶面滑移，導致降溫結晶後結晶區域的不連續。
將NTETB兩側噻吩單元換為苯環的NTEBP，是一個沒有液晶相的分子，其溶解度以及成膜性皆不如NTETB。實驗發現在160 oC溶液析出能夠形成表面有纖維的薄膜，而且纖維會隨著時間轉變為薄膜。
在NTEBP中央噻吩單元β位置接著取代基的DBTTEBP，亦沒有出現液晶相，但其結晶結構不同於前兩種樣品。雖然有著遠超於前兩種樣品的溶解度，但是在溶液析出時僅能形成纖維狀組織。顯示這種分子結構可能導致成膜性不佳。

For newly synthesized organic semiconductor, NTETB, this research has identified polymorphous ordering behavior including the growth of orthorhombic crystalline phase at low temperature, and a highly ordered smectic phase above 120 oC, which exhibits a mosaic texture under PLM. The involved structural evolution and corresponding morphological changes has been found fundamental for elucidating thin film morphology and the continuity of crystalline packing, which are critical for the transportation of charge carrier within thin film.
For this calamitic oligothiophene derivative, the crystallization process through slow solvent evaporation is able to result in large crystalline domains with homeotropic molecular alignment. Upon crystallization directly from dissolution state, the crystal packing is established on the scheme of layer stacking, which can be efficiently extended two-dimensionally. This established layer stacking within crystalline phase involves the interdigited packing of studied oligothiophene along the layer normal, yielding a larger stacking periodicity than the molecular length.
While the method of vapor deposition being adopted for thin film fabrication, fast nucleation process during molecular deposition resulted in random stacking of small crystals. Upon the transformation from crystals to smectic phase during heating, the thermally activated coalescence of smectic domains caused significant morphological evolution, which consequently results in large ribbon-like crystals during subsequent cooling process. Therefore, based on this coalescence process of smectic phase, the morphological evolution involved during heating was recognized to favor the formation of continuous crystalline domains within thin film.
However, the slippage of packing plane along the b-axis was recognized to occur frequently within smectic phase, resulting in parallel crystallographic cracks along the b-axis. The following crystallization from prior coalescent smectic domains thus unavoidable includes discontinuities of molecular packing within crystalline domains. Therefore, in spite of lessening boundary effect upon domain coalescence, this crystallization route from prior smectic phase results in missed registries of molecular packing along the a-axis, and thus yields hindered transportation of charge carrier within thin film. Direct crystal growth from dissolution state can be a better option to develop continuous regular lattice packing. In summary, for oligothiophene derivatives to be used as organic semiconductor, this research illustrates both the positive and negative impacts of prior liquid crystalline phase to the formation of crystalline domains within thin film, and thus to semiconducting performance.

1. H. Koezuka, A. Tsumura, T. Ando, Synth. Met., 1987, 18, 699.
2. C. W. Tang, S. A. VanSlyke, Appl. Phys. Lett., 1987, 51, 21.
3. J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Burns, A. B. Holmes, Nature, 1990, 347, 539.
4. W. Rieβ, S. Karg, V. Dyakonov, M. Meier, M. Schwoerer, J. Lumin., 1994, 60, 906.
5. C. J. Drury, C. M. J. Mutsaers, C. M. Hart, M. Matters, D. M. de Leeuw, Appl. Phys. Lett., 1998, 73, 1.
6. H. E. A. Huitema, G. H. Gelinck, J. B. P. H. van der Putten, K. E. Kuijk, C. M. Hart, E. Cantatore, P. T. Herwig, A. J. J. M. van Breemen, D. M. de Leeuw, Nature, 2001, 414, 599.
7. T. Sekitani, H. Nakajima, H. Maeda, T. Fukushima, T. Aida, K. Hata, T. Someya, Nat. Mater., 2009, 8, 494..
8. http://college.itri.org.tw/default.aspx
9. T. W. Kelley, D. V. Muyres, P. F. Baude, T. P. Smith, T. D. Jones, Mater. Res. Soc. Proc., 2003, 771, 169.
10. A. Afzali, C. D. Dimitrakopoulos, J. Am. Chem. Soc., 2002, 124, 30, 8812.
11. G. Barhardla, M. Zumhianchi, A. Bongini, L. Antolini, Adv. Mater., 1993, 5, 834.
12. M. Melucci, M. Gazzano, G. Barbarella, M. Cavallini, F. Biscarini, P. Maccagnani, P. Ostoja, J. Am. Chem. Soc., 2003, 125, 10266.
13. A. R. Murphy, J. M. J. Fre´chet, Chem. Rev., 2007, 107, 1066.
14. C. D. Dimitrakopoulos, A. Afzali-Ardakani, B. Furman, J. Kymissis, S. Purushothaman, Synth. Met., 1997, 89, 193.
15. C. D. Dimitrakopoulos, P. R. L. Malenfant, Adv. Mater., 2002, 14, 99.
16. H. Klauk, U. Zschieschang, J. Pflaum, M. Halik, Nature, 2007, 445, 745.
17. Y. Inoue, Y. Sakamoto, T. Suzuki, M. Kobayashi, Y. Gao, S. Tokito, Jpn. J. Appl. Phys. Part 1, 2005, 44, 3663.
18. A. Facchetti, M. Mushrush, M. H. Yoon, G. R. Hutchison, M. A. Ratner, T. J. Marks, J. Am. Chem. Soc., 2004, 126, 13859.
19. G. Horowitz, Adv. Mater., 1998, 10, 5.
20. G. Horowitz, B. Bachet, A. Yassar, P. Lang, F. Demanze, J. L. Fave, F. Garnier, Chem. Mater., 1996, 7, 1337.
21. A. J. Lovinger, H. E. Katz, A. Dodabalapur, Chem. Mater., 1998, 10, 3275.
22. F. Garnier, A. Yassar, R. Hajlaoui, G. Horowitz, F. Deloffre, B. Servet, S. Ries, P. Alnot, J. Am. Chem. Soc., 1993, 115, 8716.
23. T. M. Kelley, C. D. Frisbie, J. Phys. Chem. B, 2001, 105, 4538.
24. M. O’Neill, S. M. Kelly, Adv. Mater., 2003, 15, 1135.
25. M. Funahashi, J. Hanna, Phys. Rev. Lett., 1997 ,78 , ,2184.
26. M. Funahashi, J. Hanna, Appl. Phys. Lett., 2000,76, 2574.
27. H. Maeda, M. Funahashi, J. Hanna, Mol. Cryst. Liq. Cryst., 2000, 346 183.
28. A. J. J. M. van Breemen, P. T. Herwig, C. H. T. Chlon, J. Sweelssen, H. F. M. Schoo, S. Setayesh, W. M. Hardeman, C. A. Martin, D. M. de Leeuw, J. J. P. Valeton, C. W. M. Bastiaansen, D. J. Broer, A. R. Popa-Merticaru, S. C. J. Meskers, J. Am. Chem. Soc., 2006, 128, 2336.
29. 蔡易展, “以液相製程製備液晶性半導體寡聚噻吩分子之場效電晶體其相變化及薄膜性質”, 國立暨南國際大學應用化學研究所碩士論文, 2010.
30. M. Halik, H. Klauk, U. Zschieschang, G. Schmid, S. Ponomarenko, S. Kirchmeyer, W. Weber, Adv. Mater., 2003, 15, 11.
31. M. M. Ling, Z. Bao, Chem. Mater., 2004, 16, 4824.
32. http://www.smartcoater.com/spin-coating-theory.html
33. L. Torsi, A. Dodabalapur, A. J. Lovinger, H. E. Katz, R. Ruel, D. D. Davis, K. W. Baldwin, Chem. Mater., 1995, 7, 2247.