臺灣博碩士論文加值系統

摘要

本論文的實驗採取摻雜的方式以提高有機光伏電池的效能並探索其可能性。實驗使用共軛高分子聚-3-辛基塞吩（P3OT）作為光伏電池的主要材料，而採用的雜質成分來自單壁碳奈米管(SWNTs)、富樂烯碳六十(C60)以及向列型液晶E7。樣品包括五種組合，即ITO/(P3OT+SWNTs)/Al、ITO/(P3OT+C60)/Al、ITO/(P3OT+E7)/Al、ITO/(P3OT+(E7+SWNTs))/ Al、ITO/(P3OT+(E7+C60))/Al，摻雜濃度又分成1 wt%、3 wt%、5 wt%、10 wt%。實驗研究發現：摻雜奈米碳管的樣品其光電流表現並不理想，可能是碳管在材料中的分散能力不佳所致；碳六十摻雜物則如預期地能增加有機光伏電池的光電流；而摻雜液晶E7的樣品其對於光電流增益的表現最好。根據螢光光譜實驗結果推論，摻雜物E7在光導電高分子材料中的影響機制明顯與SWNTs或C60截然不同，我們推測液晶E7可以使聚合物高分子局部排列較為整齊，進而使電荷載子較易傳遞而提高了光電流值。

Abstract

In this thesis, we study the possibility of improvement of performance for organic photovoltaic cells by various dopants. The photovoltaic cell was primarily fabricated with conjugated polymer poly(3-octyl- thiophene) (P3OT), in conjunction with an additive based on singlewall carbon nanotubes (SWNTs), buckminsterfullerene (C60) or/and the nematic liquid-crystal E7. The samples include five constitutes: ITO/(P3OT+SWNTs)/Al, ITO/(P3OT+C60)/Al, ITO/(P3OT+E7)/Al, ITO/(P3OT+(E7+SWNTs))/Al and ITO/(P3OT+(E7+C60))/Al, and the doping concentration is chosen to be 1 wt%, 3 wt%, 5 wt% or 10 wt%. In view of photocurrent data, it is found that the samples doped with SWNTs perform poorly, likely due to the poor dispersion in the polymeric matrix. As anticipated, doping C60 can promote the photocurrent signal of the samples. The performance in photoconduction for the samples doped with E7 is the best among all samples investigated. From the experimental results of fluorescence spectra, we believe that the mechanism for the dopant E7 in the photoconducting polymer is different from that of carbon nanotubes or C60. We propose that the doapnt E7 may locally help polymeric molecules arrange more orderly and promote charge-carrier transport, leading to the higher photocurrent observed.

目錄

摘要............................................................1
Abstract........................................................2
第一章 緒論………………………………………………….............3
1.1 太陽能……………………………………………...............3
1.2 光伏電池……………………………………...................5
1.2.1 光伏電池之優勢……………………………...................5
1.2.2 有機光伏電池…………………………….....................6
1.2.3 導電高分子簡介…………………….......................…7
1.3 研究動機……………………………......................…9
第二章 有機光伏電池工作原理..................................12
2.1 共軛高分子材料導電原理...........................12
2.2 金半接觸.........................................19
2.3 光伏電池的能量轉換效率...........................23
第三章 實驗方法與測量.......................................27
3.1 吸收光譜.........................................27
3.2 螢光光譜.........................................28
3.3 元件製作與I-V測量................................29
3.3.1 元件製程演進................................29
3.3.2 元件的製作過程..............................33
3.3.3 暗電流與照光後電流之測量.....................37
第四章 結果與討論...........................................38
4.1 不同雜質與摻雜濃度之P3OT薄膜的吸收光譜比
較................................................38
4.2 不同雜質與摻雜濃度之P3OT氯仿溶液的螢光光譜比
較................................................43
4.3 不同摻雜的ITO/P3OT/Al光伏元件的I-V特性...........49
4.4 總結.............................................68
第五章 未來展望..............................................70
參考資料.......................................................71

圖索引

圖1-3-1 聚-3-烷基塞吩的分子結構，其中P3OT中的R為C8H17。.....10
圖1-3-2 E7為四種純液晶的混合。...........................................................11
圖1-3-3 樣品結構簡圖。...........................................................11
圖2-1-1 簡易能帶示意圖。...........................................................13
圖2-1-2 基態具有簡併性的反式-聚乙炔的結構。....................14
圖2-1-3 在能隙中感應出孤波子態的示意圖。.......................14
圖2-1-4 偏極子。...............................................15
圖2-1-5 雙偏極子。.............................................15
圖2-1-6 兩種形式因為能階的不同故不能彼此轉換。.................15
圖 2-1-7 偏極子無法產生共振結構所以在塞吩環之間電荷無法傳遞。...........................................................16
圖2-1-8　雙偏極子的共振結構使得電荷可以在口塞 吩環之間傳遞。
...............................................................17
圖2-1-9 (a) 當聚-3-烷基塞吩處於基態時導電度很差。(b) 受到光激發之後失去一個電子時會在能隙間感應出偏極子能階。(c) 當高分子再失去一個電子時會在能隙間感應出雙偏極子能階。(d) 當有很多雙極子態的高分子聚在一起後，能隙間的雙極子能階會「堆出」能帶出來，使得電子的躍遷更為容易。...........................................................18
圖2-2-1 (a) 未達熱平衡時單一金屬與單一n型半導體接觸時的能帶圖；(b) 達到熱平衡之後金半接觸的接面會因為費米能階必須相同而使得半導體的能帶產生變化。...........................................................19
圖2-2-2 金屬/半導體接面在不同偏壓下的能帶示意圖。(a) 熱平衡；(b) 順向偏壓；(c) 逆向偏壓。.....................................................21
圖2-3-1 (a) 照光下的光伏電池能帶示意圖；(b) 光伏電池的等效電路。...........................................................23
圖2-3-2 光伏元件在太陽照下的I-V特性圖。........................24
圖3-3-1-1使用氯仿溶劑製作出P3OT薄膜在顯微鏡下的外觀。..........30
圖3-3-1-2 利用氯仿+環己酮（2:1）作為溶劑的P3OT溶液製成的薄膜，在顯微鏡下的外觀。...........................................................31
圖3-3-1-3 早期樣品的外觀。....................................32
圖3-3-1-4 樣品鍍鋁區域示意圖。................................32
圖3-3-2-1 溫度約45°C時為透明橙色的液體。......................34
圖3-3-2-2 剛降到室溫時溶液變成棕色半透明且有點黏稠狀的液體。...........................................................34
圖3-3-2-3 降到室溫一小時後溶液開始凝結。......................35
圖3-3-2-4 在室溫下放過久溶液已經凝結成紫色「果凍」。..........35
圖3-3-2-5 鍍鋁時所使用的系統簡圖。............................36
圖3-3-2-6 樣品的外觀。........................................36
圖3-3-1 測量I-V特性時的裝置示意圖。...................... ..37
圖4-1-1 純P3OT薄膜與不同的摻雜條件下 (a) SWNTs；(b) C60；(c) E7；(d) E7+SWNTs (1:1)；(e) E7+C60 (1:1)的樣品之吸收光譜比較。..................39
圖4-1-2 未摻雜之P3OT氯仿溶液的吸收光譜。.......................42
圖4-2-1 吸收光譜與螢光光譜對照圖。...........................................................43
圖4-2-2 純P3OT樣品與摻雜SWNTs後的螢光光譜之比較。..............45
圖4-2-3 純P3OT樣品與摻雜C60後的螢光光譜之比較。................45
圖4-2-4 純P3OT樣品與摻雜E7後的螢光光譜之比較。.................46
圖4-2-5 純P3OT樣品與摻雜E7+SWNTs後的螢光光譜之比較。...........47
圖4-2-6 純P3OT樣品與摻雜E7+C60後的螢光光譜之比較。.............48
圖4-3-1 本研究早期樣品的I-V曲線圖 (a) 是純P3OT樣品；(b) 是摻了1 wt%碳管的樣品。...........................................................50
圖4-3-2 (a) 純P3OT元件0-2 V的I-V圖；(b) 純P3OT元件的最大輸出功率示意圖。...........................................................53
圖4-3-3光伏元件摻雜 (a) 1 wt%；(b) 3 wt%；(c) 5 wt%SWNTs之I-V圖與最大輸出功率密度示意圖。.....................................................54
圖4-3-4光伏元件摻雜(a) 1 wt%；(b) 3 wt%；(c) 5 wt%；(d) 10 wt%C60之I-V。............................................................57
圖4-3-5 摻雜 (a) 0.5 wt%；(b) 1 wt%；(c) 3 wt%；(d) 5 wt%；(e) 10 wt%
E7之光伏元件I-V圖。............................................60
圖4-3-7 摻雜 (a) 1 wt%；(b) 3 wt%E7+SWNTs之光伏元件I-V圖。.....63
圖4-3-8 摻雜 (a) 1 wt%；(b) 3 wt%；(c) 5 wt%；(d) 10 wt%E7+C60之光伏元件I-V圖。...........................................................65

參考資料

[1]莊嘉珅，《太陽能工程—太陽電池篇》，全華科技圖書股份有限公 司，台北，民國86年。
[2]D. Gebeyehu, C. J. Brabec, N. S. Sariciftic, D. Vangeneugden, R. Kiebooms, D. Vanderzande, F. Kienberger, and H. Schindler, “Hybrid solar cell based on dye-sensitized nanoporous TiO2 electrodes and conjugated polymers as hole transport materials,” Synthetic Metals 125, 279–287 (2002).
[3]S. Bhattacharyya, E. Kymakis, and G. A. J. Amaratunga, “Photovotaic properties of dye functionalized single-wall carbon nanotube /conjugated polymer devices,” Chemistry of Materials 16, 4819– 4823 (2004).
[4]D. Chirvae, Z. Chiguvare, M. Knipper, J. Parisi, V. Dyakonov, and J. C. Hummelen, “Temperature dependent characteristics of poly(3 hexylthiophene)-fullerene based heterojunction organic solar cells,” Journal of Applied Physics 93, 3376–3383 (2003).
[5]K. Tada, R. Hidayat, M. Hirohata, T. Kawai, S. B. Lee, I. U. Bakhadirov, A. A. Zakhidov, and K. Yoshino, “Conducting polymer-fullerene D-A photocell with decreased serial resistance: ITO/PAT(C60)y/C60/Al structure,” Synthetic Metals 85, 1349–1350 (1997).
[6]E. Kymakis and G. A. J. Amaratunga, “Single-wall carbon nanotube/ conjugated polymer photovoltaic devices,” Applied Physics Letters 80, 112–114 (2002).
[7]E. Kymakis, I. Alexandrou, and G. A. J. Amaratunga, “High open-circuit voltage photovoltaic device from carbon-nanotube- polymer composites,” Journal of Applied Physics 93, 1764–1768 (2003).
[8]S. Licht, O. Khaselev, P. A. Ramakrishnan, D. Faiman, E. A. Katz, A. Shames, and S. Goren, “Fullerene photoelectrochemical solar cells,” Solar Energy Mateials & Solar Cells 51, 1–19 (1998).
[9]L. Cao, H. Chen, M. Wang, J. Sun, and F. kong “Photoconductivity study of modified carbon nanotube/ oxotitanium phthalocyanine composites,” Journal of Physical Chemistry B106, 8971–8975 (2002).
[10]M. F. Islam, E. Rojas, D. M. Bergey, A. T. Johnson, and A. G. Yodh, “High weight fraction surfactant solubilization of single-wall carbon nanotubes in water,” Nano Letters 3, 269–273 (2003).
[11]Z. Bao, A. Dodabalapur, and A. Lovinger, “Soluble and processable reioregular poly(3-hexyl-thiophene) for thin film field-effect transistor applications with high mobility,” Applied Physics Letters 69, 4108–4110 (1996).
[12]J. Y. Kim, M. Kim, H. M. Kim, J. Joo, J. H. Choi, “Electrical and optical studies of organic light emitting devices using SWCNTs-polymer nanocomposites,” Optical Materials 21, 147–151 (2002).
[13]I. Alexandrou, E. Kymakis, and G. A. J. Amaratunga, “Polymer- nanotube composites: Burying nanotubes improves their field emission properties,” Applied Physics Letters 80, 1435–1437 (2002)
[14]K. Kaneto, K. Harada, W. Takashima, K. Endo, and M. Rikukawa, ”Scanning tunneling microscopy (STM) study on morphology of regioregular poly(3-alkylthiophene) deposited on A(111) surface,” Japanese Journal of Applied Physics 38, L1062–L1065 (1999).
[15]T. A. Chen, X. Wu, and R. D. Rieke, ”Regio-controlled synthesis of poly(3-alkylthiophenes) mediated by rieke zinc: Their characterization and solid-state properties,” Journal of the American Chemical Society 117, 233–244 (1995).
[16]謝文仁，《塞吩-烷基塞吩共聚物之合成與性質探討》，國立中央大學化學研究所碩士論文，民國88年。
[17]施敏原著，黃調元譯，《半導體元件物理與製作技術》，國立交通大學出版社，民國91年。
[18]K. Kaneyo, K. Hatae, S. Nagamatsu, W. Takashima, S. S. Pandey, K. Endo, and M. Rikukawa, “Photocarrier mobility in regioregular poly(3-hexylthiophene) studied by the time of flight method,” Japanese Journal of Applied Physics 38, L1188–L1190 (1999).
[19]S. S. Pandey, S. N. Nagamatsu, W. Takashima, and K. Kaneto, “Mechanism of photocarrier generation and transport in poly(3-alkylthiophene) films,” Japanese Journal of Applied Physics 39, 6309–6315 (2000).
[20]K. Kanemoto, M. Shishido, T. Sudo, I. Akai, H. Hashimoto, and T. Karasawa, “Concentration-dependence of photoluminescence properties in polythiophene diluted in an inactive polymer matrix,” Chemical Physics Letters 402, 549–553 (2005).
[21]陳惠玉，《液晶–多壁碳奈管膠態溶液之光譜分析》，碩士論文，私立中原大學，民國92年。