本論文研究塊材異質接面(bulk-heterojunction)有機高分子太陽能電池的光電轉換特性，主動層材料選用聚3-已基噻吩[Poly(3-hexylthiophene-2,5-diyl)，P3HT]為電子施體與[6,6]-苯基-C61-丁酸甲酯 [(6,6)-phenyl C61-butyric acid methyl ester，PCBM]為電子受體，聚二氧乙基塞吩:聚(磺酸苯烯)[poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)為電荷萃取層。利用奈米壓印技術，製作具奈米結構之P3HT:PCBM主動層，分析其結構特性，並於其上製作不同的電子萃取層，探討奈米結構是否能增益有機太陽能電池的光電轉換效率。
第一部分，利用奈米壓印技術製作具奈米溝槽之P3HT:PCBM主動層，研究奈米結構對有機太陽能電池電特性的影響。使用吸收光譜、X-ray繞射、與Raman光譜研究主動層之吸收與微結構特性，利用導電式原子力顯微鏡（C-AFM）搭配照射綠光雷射研究壓印形貌與萃取電流的相關性。具奈米壓印結構主動層所製備之元件之短路電流（JSC）可達7.06 mA/cm2，光電轉換效率（η）可高於2.30%，優於使用平面結構主動層之元件（JSC約為5.2 mA/cm2；η~1.99%），使用600與800奈米周期寬度結構製作之主動層，都可使元件性能有些微提升。吸收光譜分析指出具奈米壓印結構的主動層的吸收與平面結構的主動層幾乎一致，但C-AFM的結果則指出具奈米壓印結構的主動層有較高的電流輸出，與元件電性結果相符。進一步使用C-AFM分析奈米結構主動層於不同位置的電荷萃取特性，發現具壓印結構之主動層的溝槽處，相較於平面結構的主動層，於施加正偏壓時，具有較佳的電荷萃取效果，因此，總平均電流值皆上升；而壓印結構的隆起處，不論是電子流還是電洞流分佈都較溝槽處低。此外，照射綠光雷射於有壓壓印結構與平面結構的主動層，均造成C-AFM量測的電子流下降，但電洞流則無明顯變化。
第二部分，本研究發現在具奈米壓印結構之P3HT:PCBM主動層上，塗佈一高分子linear polyethylenimine（LPEI）作為電子萃取層，可增益元件的短路電流，使元件效能高於平面結構主動層的元件。C-AFM量測也指出具奈米壓印結構的主動層有較高的平均總電流，而外部量子效率的量測則發現奈米壓印結構雖然會降低可見光區的光電流轉換效率，但卻可有效增加紅光到紅外光區的光電流轉換效率。

In this thesis, we studied the photoelectric conversion (PEC) characteristics of conjugated polymer–fullerene-based bulk heterojunction organic polymer solar cells (OSCs). The polymer-based active layer (AL) consisted of poly(3-hexylthiophene) (P3HT) as the electron donor and [6,6]-pheny-C61-butyric acid methyl ester (PCBM) as the electron acceptor. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was used as the charge extraction layer.
The nanogroove-structured P3HT:PCBM-based ALs with various periodic gratings (widths: 600, 800, and 1200 nm) were fabricated using nano-imprint technology. The OSCs with a nanostructured AL exhibited a slight increase in PEC efficiency compared with the OSCs with a planar AL. Local conductive atomic force microscopy (c-AFM) was performed to measure charge transport/extraction efficiency at different locations within the nanogroove. c-AFM results showed that the maximum current appeared on the sidewall of the nanogroove of the AL. Incident photon-to-current efficiency measurement indicated that the OSCs with a nanostructured AL exhibited increased absorption in the near-infrared region, thereby providing potential applications for different products.

[1] D. M. Chapin, C. S. Fuller, G. L. Pearson, ”A new silicon p-n junction photocell for converting solar radiation into electrical power”, J. Appl. Phys., 25, 676–677, 1954.
[2] H. Kallmann and M. Pope, ”Photovoltaic Effect in Organic Crystals” J. Phys. Chem., 30, 585–586, 1959.
[3] C. W. Tang, ”Two-layer organic photovoltaic cell”, Appl. Phys. Lett., 48, 183–185, 1986.
[4] N. S. Sariciftci, D. Braun, C. Zhang, V. I. Srdanov, A. J. Heeger, G. Stucky, F. Wudl, ”Semiconducting polymer-buckminsterfullerene heterojunctions:diodes, photodiodes, and photovoltaic cells”, Appl. Phys. Lett., 62, 585–587, 1993.
[5] S. E. Shaheen, C. J. Brabec, N. S. Sariciftci, F. Padinger, T. Fromherz, J. C. Hummelen, ”2.5% efficient organic plastic solar cells”, Appl. Phys. Lett., 78, 841–843, 2001.
[6] C. J. Brabec, S. E. Shaheen, C. Winder, N. S. Sariciftci, P. Denk, ”Effect of LiF/metal electrodes on the perfoemance of plastic solar cells”, Appl. Phys. Lett., 80, 1288–1290, 2002.
[7] M. T. Dang, L. Hirsch, G. Wantz, ”P3HT:PCBM, best seller in polymer photovoltaic research”, Adv. Mater., 23, 3597–3602, 2011.
[8] F. C. Krebs, H. Spanggard, T. Kjar, M. Biancardo, J. Alstrup, ”Large area plastic solar cell modules”, Mater. Sci. Eng., B 138, 106–111, 2007.
[9] J. S. Moon, J. Jo, A. J. Heeger, ”Nanomorphology of PCDTBT:PC70BM bulk heterojunction solar cells”, Adv. Energy Mater., 2, 304–308, 2012.
[10] L. Dou, C. -C. Chen, K. Yoshimura, K. Ohya, W. -H. Chang, J. Gao, Y. Liu,E. Richard, Y. Yang, ”Synthesis of 5H-dithieno[3,2-b:20,30-d]pyran as an electron-rich building block for donor–acceptor type lowbandgap polymers”, Macromolecules., 46, 3384–3390, 2013.
[11] Z. He, C. Zhong, S. Su, M. Xu, H. Wu, Y. Cao, ”Enhanced powerconversionefficiency in polymer solar cells using an inverted device structure”, Nat. Photon., 6, 591–595, 2012.
[12] J. D. Chen, C. Cui, Y. Q. Li, L. Zhou, Q. D. Ou, C. Li, Y. Li, J. X. Tang, ”Single-junction polymer solar cells exceeding 10% power conversion efficiency”, Adv. Mater., 27, 1035–1041, 2014.
[13] H. Zhou, Q. Chen, G. Li, S. Luo, T. B. Song, H. S. Duan, Z. Hong, J. You, Y. Liu, Y. Yang, ”Interface engineering of highly efficient perovskite solar cells” Science., 345, 542–546, 2014.
[14] FrontMaterials Co. Ltd., see for instance www.frontmaterials.com.
[15] Y. J. Cheng, S. H. Yang, C. S. Hsu, ”Synthesis of Conjugated Polymers for Organic Solar Cell Applications”, Chem. Rev., 109, 5868–5923, 2009.
[16] P. W. M. Blom, V. D. Mihailetchi, L. J. A. Kostr and D. E. Markov, ”Device physics of polymer:Fullerene bulk heterojunction solar cells”, Adv. Mater., 19, 1551–1566, 2007.
[17] Dipl. Ing. Klaus Petritsch, ”Organic solar cell architectures ”, PhD Thesis., 2000.
[18] V. D. Mihailetchi, P. W. M. Blom, J. C. Hummelen, M. T. Rispens, ”Cathode dependence of the open-circuit voltage of polymer: Fullerene bulk heterojunction solar cells ”, J Appl Phys., 94, 6849–6854, 2003.
[19] C. J. Barbec, A. Cravino, D. Meissner, N. S. Sariciftci, T. Frpmherz, M. T. Rispens, L. Sanchez, J. C. Hummelen, ”Origin of the open circuit voltage of plastic solar cells”, Adv. Fun. Mater., 11, 374–380, 2001.
[20] M. C. Scharber, D. Wuhlbacher, M. Koppe, P. Denk, C. Waldauf, A. J. Heeger, C. L. Brabec, ”Design rules for donors in bulk-heterojunction solar cells – towards 10% energy-conversion efficiency”, Adv Mater., 18, 789, 2006.
[21] G. Dennler, M. C. Scharber, C. J. Brabec, ”Polymer-Fullerene Bulk Heterojunction Solar Cells”, Adv Mater., 21, 1323–1338, 2009.
[22] P. Peumans, A. Yakimov, S. R. Forrest, ”Small molecular weight organic thin-film photodetector and solar cell ”, J Appl Phys., 93, 3693–3723, 2003.
[23] Jenny Nelson, The Physics Of Solar Cells. Imperial College Press, 2003.
[24] C. Deibel and V. Dyakonov, ”Polymer-Fullerene Bulk Heterojunction Solar Cells”, Rep. Prog. Phys., 73, 1–40, 2010.
[25] http://www.materialsnet.com.tw/DocView.aspx?id=7004
[26] M. Aryal, F. Buyukserin, K. Mielczarek, X. M. Zhao, J. M. Gao, A. Zakhidov, W. C. Hu, ” Imprinted large-scale high density polymer nanopillars for organic solar cells”, J. Vac. Sci. Technol. B., 26 , 2562–2566, 2008.
[27] M. Aryal, K. Trivedi, W. C. Hu, ”Nano-confinement induced chain alignment in ordered P3HT nanostructures defined by nanoimprint lithography”, ACS Nano., 3, 3085–3090, 2009.
[28] J. M. Nunzi, ”Organic photovoltaic materials and devices ”, C. R. Phys., 3(4), 523–542, 2002.
[29] Y. Kim, S. Cook, S. M. Tuladhar, S. A. Choulis, J. Nelson, J. R. Durrant, D. D. C. Bardley, M. Giles, I. Mcculloch, C.S. Ha, M. Ree, ”A strong regioregularity effect in self-organizing conjugated polymer films and high-efficiency polythiophene: fullerene solar cells”, Nat. Mater., 5, 197–203, 2006.
[30] R. Österbacka, C. P. An, X. M. Jiang Z. V. Vardeny, ”Two dimensional electronic excitations in self-assembled conjugated polymer nanocrystals”, Science., 287, 839–842, 2000.
[31] T. Erb, U. Zhokhavets, G. Gobsch, S. Raleva, B, Stühn, P. Schilinsky, C. Waldauf , C. J Barbec, ”Correlation between structural and optical properties of composite polymer/fullerene films for organic solar cells”, Adv. Fun. Mater., 15, 1193–1196, 2005.