本論文製作低電壓驅動之有機薄膜電晶體並以有機高分子p型半導體Poly(2,5-bis(3-alkylthiophen-2- yl)thieno[3,2-b]thiophene) (PBTTT-C14)作為主動層，透過兩種不同的主動層製程方法改變薄膜結構，如:熱梯度結晶製程及旋轉塗佈製程，探討主動層結構變化對元件電性的影響。
本研究分為兩部分，第一部分有機半導體層採用熱梯度結晶製程，首先將PBTTT-C14與HMB混合溶液之試片於溫度梯度系統上透過推進平台儀器依穩定的速度移動試片，製作有結晶化的PBTTT-C14薄膜，其推進平台儀器速度為0.2 mm/s 至0.5 mm/s，測試何者推進平台儀器速度可得到最佳結晶化有機半導體薄膜，實驗結果顯示以0.4 mm/s的速度所製作的結晶化有機半導體薄膜，其元件有較佳的電性表現。再其，將分為兩種滴入PBTTT-C14溶液的方式於試片中，垂直滴入和水平滴入製作主動層。若PBTTT-C14溶液垂直滴入試片所製作的有機半導體薄膜結晶方向與電極通道垂直，使載子傳輸不易，導致元件電特性差。反之，PBTTT-C14溶液水平滴入試片所製作的有機半導體薄膜結晶則可得到有序排列並與電極通道平行，使載子傳輸較快，搭配後退火處理的元件，其載子遷移率可達0.06 cm2/Vs。
熱梯度結晶製程所製作有機半導體薄膜與旋轉塗佈製程所製作有機半導體薄膜皆做成元件比較電性，可以得知熱梯度結晶製程所製作有機元件在電性上有較佳表現，之後會以原子力顯微鏡、吸收光譜、光激發螢光光譜、低掠角X光繞射儀及拉曼光譜分析有機半導體薄膜結晶，觀察出有機半導體層若以熱梯度結晶製程有較好的結晶性與方向排列，使元件的載子傳輸較快，驗證其有較佳電性。第二部分為測量PBTTT-C14薄膜電晶體元件置於大氣環境下的電特性。因水氣滲入介電層間而導致漏電流上升，但通道電流也提升，推測水氣進入介電層間產生偶極(dipole)形成場的效應。因此，相較於旋轉塗佈製程，以熱梯度結晶製程製作的薄膜元件，其電流隨時間變化的穩定性較佳。

In this study, we investigated the influence of crystalline properties of polymeric semiconductoring thin films on the charge transport of organic thin-film transistors (OTFTs). P-type low operating voltage OTFTs were fabricated using poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b] thiophene) (PBTTT-C14) as the active layer. Thermal gradient method was used to guide the molecular orientation of PBTTT-C14 thin films, resulting in an ordered PBTTT-C14 crystallization. In the thermal gradient process, different sample moving speeds and solution dropping methods were used to change the crystal growth of thin films. Compared with spin-coating process, the carrier mobility of OTFTs made by thermal gradient process was better. Through atomic force microscope, grazing incident X-ray diffractometer, ultraviolet/visible spectrophotometer, and Raman spectrometer, we observed that the thin films from thermal gradient process had better crystallinity than those from spin-coating process. In addition, the thermal-gradient-processed thin films showed an ordered linear crystallization, leading to better electrical performance of OTFTs. The PBTTT-C14-based OTFT devices made by thermal gradient process also performed better electrical stability than by spin-coating process in the atmospheric environment.

[1] M. Pope, H. P. Kallmann, P. Magnante, “Electroluminescence in organic crystal”, Journal of Chemical Physics, 38, 1963.

[2] C. K. Chiang, C. R. Fincher, Y. W. Park, A. J. Heeger, H. Shirakawa, E.J. Louis, S. C. Gau, A. G. Macdiarmid, “Electrical conductivity in dopedpolyacetylene”, Physical Review Letters, 39, 1098, 1977.

[3] F. Ebisawa, T. Kurokawa, S. Nara, “Electrical Properties of Polyacetylene Polysiloxane Interface”, Journal of Applied Physics, 54, 3255-3259, 1983.

[4] G. Horowitz, “Organic field-effect transistors”, Advanced Material, 10, 365, 1998.

[5] J. Collet, O. Tharaud, A. Chapoton, D. Vuillaume, “Low-Voltage, 30 nm channel length, organic transistors with a self-assembled monolayer as gate insulating films”, Applied Physics Letters, 76, 1941, 2000.

[6] C. Rolin, K. Vasseur, S. Schols, M. Jouk, G. Duhoux, “High mobility electron-conducting thin-film transistor by organic vapor phase deposition”, Applied Physics Letters, 93, 033305, 2008.

[7] H.-G. Jeon, J. Hattori, S. Kato, “Thermal treatment effects on N-alkyl perylene diimide thin-film transistors with different alkyl chain”, Journal of Applied Physics, 108, 124512, 2010.

[8] G. Horowitz, “Organic Field-Effect Transistors”, Advanced Material, 10, 365, 1998.

[9] C. Rolin, K. Vasseur, S. Schols, M. Jouk, G. Duhoux, “High mobility electron-conducting thin-film transistor by organic vapor phase deposition”, Applied Physics Letters, 93, 033305, 2008.

[10] Leah A. Lucas, “Combinatorial screening of the effect of temperature on the microstructure and mobility of a high performance polythiophene semiconductor”, Applied Physics Letters, 90, 012112, 2007.

[11] Iain Mcculloch, Martin Heeney, Clare Bailey, “Liquid-crystalline semiconducting polymers with high charge-carrier mobility”, Nature, VOL 5 APRIL, 2006.

[12] Takuya Higashi, “Anisotropic Properties of Aligned π-Conjugated Polymer Films Fabricated by Capillary Action and Their Post-Annealing Effects”, Applied Physics Letters, 2011.

[13]W.C.Cheng, C.Y.Yang, B.Y.Kang, M.Y.Kuob, J.Ruan “Impact of undercooling on epitaxially oriented liquid crystalline organizations of poly (3-hexylthiophene) below the eutectic temperature”, Soft Matter, 9, 10822, 2013.

[14] Domenico Alberga, Aure´lie Perrier, Ilaria Ciofini, Giuseppe Felice Mangiatordi, Gianluca Lattanzi, Carlo Adamo, “Morphological and charge transport properties of amorphous and crystalline P3HT and PBTTT:insights from theory”, Physical Chemistry Chemical Physics, 17, 18742–18750.

[15] Gilles Horowitz, “Organic Field-Effect Transistors”, Advance Materials, 10, 5, 368-369, 1998.

[16] M. A. Lampert, “Simplified Theory of Space-Charge-Limited Currents in an Insulator with Traps”, Physical Review, 103, 1648, 1956.

[17] J. R. Ferraro, “Introductory raman spectroscopy”, Academic Press, 2, 15, 2002.

[18] Shuai Wang, Jie-Cong Tang, Li-Hong Zhao, Rui-Qi Png, Loke-Yuen Wong, Perq-Jon Chia, Hardy S. O. Chan, Peter K.-H. Ho, Lay-Lay Chua, “Solvent effects and multiple aggregate states in high-mobility organic field-effect transistors based on poly(bithiophene-alt-thienothiophene)”, Applied Physics Letters, 93, 162103, 2008.

[19] Manish Pandey, Shyam S. Pandey, “Solvent driven performance in thin floating-films of PBTTT for organic field effect transistor: Role of macroscopic orientation”, Organic Electronics, 43, 240-246, 2017.

[20] Yukio Furukawaa, Kotaro Akiyamaa, Ippei Enokidab, Jun Yamamotoa, “Raman spectra of carriers in ionic-liquid-gated transistors fabricated with poly (2, 5-bis (3-tetradecylthiophen-2- yl) thieno [3, 2- b] thiophene)”, Vibrational Spectroscopy, 29-34, 2016.

[21] C. Francis, D. Fazzi, S. B. Grimm, F Paulus, S. Beck, S. Hillebrandt, A. Pucci, J. Zaumseil, “Raman spectroscopy and microscopy of electrochemically and chemically doped high-mobility semiconducting polymers”, Journal of Materials Chemistry C, 5, 6176, 2017.

[22] 盧承昌, “聚(3-己基噻吩)結晶特性對薄膜電晶體電特性影響之研 究”, 國立成功大學碩士論文, 2015.

[23] 周柏安, “高分子poly(2,5-bis(3-alkylthiophen-2-yl)thieno〔3,2-b〕thiophene) (PBTTT)結晶特性對有機薄膜電晶體之電特性影響”, 國立成功大學碩士論文, 2018.

[24] 楊焙凱, “熵驅動之小分子嵌入與複合液晶相的成長”, 國立成功大學碩士論文, 2016.