在體異質有機太陽能電池(bulk heterojunction photovoltaic)當中，有機層的內部形貌嚴重影響激子(exciton)產生的效率。本研究利用紫外光可見光光譜(UV-vis spectroscopy)，以選擇性溶解法探討Cyanine染料(本研究中以S2109代稱)和PCBM組成的有機薄膜之內部形貌，再配合原子力顯微鏡(atomic force microscopy, AFM)的表面形貌，探討有機層內部3D結構。由於厚度是有機層薄膜結構的一個影響因子，因此本研究討論旋轉塗佈的轉速及有機溶液的濃度與有機層厚度的關係，實驗結果發現有機層膜厚與轉速成指數遞減而與有機溶液的濃度成正比。
將厚度的結果與選擇性溶解法做比較，發現當薄膜厚度較小時，薄膜中可生成島狀的獨立狀結構，有機膜厚度增加時，有機層的內部形貌會因組成的不同而變化，此時內部形貌與膜厚無關。當PCBM含量變大時，PCBM的結構會由分散狀的結構轉變成連續相，進一步加大含量至PCBM與S2109的莫耳比為1比1時，有機層會形成雙層狀的交織型結構。

1. http://www.wikinvest.com/industry/Solar_Power
2. http://www.epia.org/index.php?id=18
3. M. A. Green, K. Emery, Y. Hishikawa and W. Warta, "Solar cell efficiency tables (version 35)," Progress in Photovoltaics 18(2), 144-150 (2010)
4. D. M. Chapin, C. S. Fuller and G. L. Pearson, "A new silicon p-n junction photocell for converting solar radiation into electrical power," J. Appl. Phys. 25(5), 676-677 (1954)
5. R. Tipnis, J. Bernkopf, S. J. Jia, J. Krieg, S. Li, M. Storch and D. Laird, "Large-area organic photovoltaic module-Fabrication and performance," Solar Energy Materials and Solar Cells 93(4), 442-446 (2009)
6. M. Niggemann, B. Zimmermann, J. Haschke, M. Glatthaar and A. Gombert, "Organic solar cell modules for specific applications - From energy autonomous systems to large area photovoltaics," Thin Solid Films 516(20), 7181-7187 (2008)
7. F. C. Krebs, S. A. Gevorgyan and J. Alstrup, "A roll-to-roll process to flexible polymer solar cells: model studies, manufacture and operational stability studies," J. Mater. Chem. 19(30), 5442-5451 (2009)
8. K. M. Coakley and M. D. McGehee, "Conjugated polymer photovoltaic cells," Chemistry of Materials 16(23), 4533-4542 (2004)
9. M. C. Scharber, D. Wuhlbacher, M. Koppe, P. Denk, C. Waldauf, A. J. Heeger and C. L. Brabec, "Design rules for donors in bulk-heterojunction solar cells - Towards 10 % energy-conversion efficiency," Adv. Mater. 18(6), 789-794 (2006)
10. L. J. A. Koster, V. D. Mihailetchi and P. W. M. Blom, "Ultimate efficiency of polymer/fullerene bulk heterojunction solar cells," Appl. Phys. Lett. 88(9), 093511 (2006)
11. D. Kearns and M. Calvin, "Photovoltaic Effect and Photoconductivity in Laminated Organic Systems," Journal of Chemical Physics 29(4), 950-951 (1958)
12. R. N. Marks, J. J. M. Halls, D. D. C. Bradley, R. H. Friend and A. B. Holmes, "The photovoltaic response in poly(p-phenylene vinylene) thin-film devices," J. Phys.-Condes. Matter 6(7), 1379-1394 (1994)
13. C. W. Tang, "Two-layer organic photovoltaic cell," Appl. Phys. Lett. 48(2), 183-185 (1986)
14. S. R. Scully and M. D. McGehee, "Effects of optical interference and energy transfer on exciton diffusion length measurements in organic semiconductors," J. Appl. Phys. 100(3), 034907 (2006)
15. D. E. Markov, J. C. Hummelen, P. W. M. Blom and A. B. Sieval, "Dynamics of exciton diffusion in poly(p-phenylene vinylene)/fullerene heterostructures," Physical Review B 72(4), 045216 (2005)
16. P. Peumans, A. Yakimov and S. R. Forrest, "Small molecular weight organic thin-film photodetectors and solar cells," J. Appl. Phys. 93(7), 3693-3723 (2003)
17. Y. M. Nam, J. Huh and W. H. Jo, "Optimization of thickness and morphology of active layer for high performance of bulk-heterojunction organic solar cells," Solar Energy Materials and Solar Cells 94(6), 1118-1124 (2010)
18. P. Peumans and S. R. Forrest, "Very-high-efficiency double- heterostructure copper phthalocyanine/C-60 photovoltaic cells," Appl. Phys. Lett. 79(1), 126-128 (2001)
19. M. Hiramoto, H. Fujiwara and M. Yokoyama, "Three-layered organic solar cell with a photoactive interlayer of codeposited pigments," Appl. Phys. Lett. 58(10), 1062-1064 (1991)
20. G. Yu, K. Pakbaz and A. J. Heeger, "Semiconducting polymer diodes: Large size, low cost photodetectors with excellent visible-ultraviolet sensitivity," Appl. Phys. Lett. 64(25), 3422-3424 (1994)
21. K. Kim, J. Liu, M. A. G. Namboothiry and D. L. Carroll, "Roles of donor and acceptor nanodomains in 6% efficient thermally annealed polymer photovoltaics," Appl. Phys. Lett. 90(16), 163511 (2007)
22. M. Reyes-Reyes, K. Kim and D. L. Carroll, "High-efficiency photovoltaic devices based on annealed poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C-61 blends," Appl. Phys. Lett. 87(8), 083506 (2005)
23. H. Hoppe and N. S. Sariciftci, "Organic solar cells: An overview," J. Mater. Res. 19(7), 1924-1945 (2004)
24. 林思佑, 周維揚, "五環素/駢苯衍生物有機太陽能電池之研究," 國立成功大學光電科學與工程研究所碩士論文 (2007)
25. A. Yakimov and S. R. Forrest, "High photovoltage multiple-heterojunction organic solar cells incorporating interfacial metallic nanoclusters," Appl. Phys. Lett. 80(9), 1667-1669 (2002)
26. S. E. Shaheen, C. J. Brabec, N. S. Sariciftci, F. Padinger, T. Fromherz and J. C. Hummelen, "2.5% efficient organic plastic solar cells," Appl. Phys. Lett. 78(6), 841-843 (2001)
27. V. P. Singh, R. S. Singh, B. Parthasarathy, A. Aguilera, J. Anthony and M. Payne, "Copper-phthalocyanine-based organic solar cells with high open-circuit voltage," Appl. Phys. Lett. 86(8), 082106 (2005)
28. T. Mori and Y. Masumoto, "Effect of organic alloy for suppression of polycrystallization in BCP thin film," J. Photopolym Sci. Technol. 19(2), 209-214 (2006)
29. V. Tripathi, D. Datta, G. S. Somali, A. Awasthi and S. Kumar, "Role of exciton blocking layers in improving efficiency of copper phthalocyanine based organic solar cells," J. Non-Cryst. Solids 354(19), 2901-2904 (2008)
30. D. M. deLeeuw, M. M. J. Simenon, A. R. Brown and R. E. F. Einerhand, "Stability of n-type doped conducting polymers and consequences for polymeric microelectronic devices," Synth. Met. 87(1), 53-59 (1997)
31. L. J. A. Koster, V. D. Mihailetchi and P. W. M. Blom, "Bimolecular recombination in polymer/fullerene bulk heterojunction solar cells," Appl. Phys. Lett. 88(5), 052104 (2006)
32. M. Helgesen, R. Sondergaard and F. C. Krebs, "Advanced materials and processes for polymer solar cell devices," J. Mater. Chem. 20(1), 36-60 (2010)
33. A. B. Tamayo, B. Walker and T. Q. Nguyen, "A low band gap, solution processable oligothiophene with a diketopyrrolopyrrole core for use in organic solar cells," J. Phys. Chem. C 112(30), 11545-11551 (2008)
34. A. B. Tamayo, X. D. Dang, B. Walker, J. Seo, T. Kent and T. Q. Nguyen, "A low band gap, solution processable oligothiophene with a dialkylated diketopyrrolopyrrole chromophore for use in bulk heterojunction solar cells," Appl. Phys. Lett. 94(10), 103301 (2009)
35. L. L. Xue, J. T. He, X. Gu, Z. F. Yang, B. Xu and W. J. Tian, "Efficient Bulk-Heterojunction Solar Cells Based on a Symmetrical D-pi-A-pi-D Organic Dye Molecule," J. Phys. Chem. C 113(29), 12911-12917 (2009)
36. F. Silvestri, M. D. Irwin, L. Beverina, A. Facchetti, G. A. Pagani and T. J. Marks, "Efficient Squaraine-Based Solution Processable Bulk-Heterojunction Solar Cells," J. Am. Chem. Soc. 130(52), 17640-17641 (2008)
37. Y. W. Li, Q. Guo, Z. F. Li, J. N. Pei and W. J. Tian, "Solution processable D-A small molecules for bulk-heterojunction solar cells," Energy & Environmental Science 3(10), 1427-1436 (2010)
38. H. H. Liao, L. M. Chen, Z. Xu, G. Li and Y. Yang, "Highly efficient inverted polymer solar cell by low temperature annealing of Cs2CO3 interlayer," Appl. Phys. Lett. 92(17), 173303 (2008)
39. O. Inganas, M. Svensson, F. Zhang, A. Gadisa, N. K. Persson, X. Wang and M. R. Andersson, "Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells," Appl. Phys. A-Mater. Sci. Process. 79(1), 31-35 (2004)
40. C. P. Chen, S. H. Chan, T. C. Chao, C. Ting and B. T. Ko, "Low-bandgap poly(thiophene-phenylene-thiophene) derivatives with broaden absorption spectra for use in high-performance bulk-heterojunction polymer solar cells," J. Am. Chem. Soc. 130(38), 12828-12833 (2008)
41. G. Dennler, M. C. Scharber and C. J. Brabec, "Polymer-Fullerene Bulk-Heterojunction Solar Cells," Adv. Mater. 21(13), 1323-1338 (2009)
42. B. C. Thompson, Y. G. Kim and J. R. Reynolds, "Spectral broadening in MEH-PPV : PCBM-based photovoltaic devices via blending with a narrow band gap cyanovinylene-dioxythiophene polymer," Macromolecules 38(13), 5359-5362 (2005)
43. F. Padinger, T. Fromherz, P. Denk, C. J. Brabec, J. Zettner, T. Hierl and N. S. Sariciftci, "Degradation of bulk heterojunction solar cells operated in an inert gas atmosphere: a systematic study," Synth. Met. 121(1-3), 1605-1606 (2001)
44. J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger and G. C. Bazan, "Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols," Nat. Mater. 6(7), 497-500 (2007)
45. S. Cook, H. Ohkita, Y. Kim, J. J. Benson-Smith, D. D. C. Bradley and J. R. Durrant, "A photophysical study of PCBM thin films," Chem. Phys. Lett. 445(4-6), 276-280 (2007)
46. T. Geiger, H. Benmansour, B. Fan, R. Hany and F. Nuesch, "Low-band gap polymeric cyanine dyes absorbing in the NIR region," Macromolecular Rapid Communications 29(8), 651-658 (2008)
47. F. A. Castro, A. Faes, T. Geiger, C. F. O. Graeff, M. Nagel, F. Nuesch and R. Hany, "On the use of cyanine dyes as low-bandgap materials in bulk heterojunction photovoltaic devices," Synth. Met. 156(14-15), 973-978 (2006)
48. B. Fan, F. A. de Castro, J. Heier, R. Hany and F. Nuesch, "High performing doped cyanine bilayer solar cell," Organic Electronics 11(4), 583-588 (2010)
49. J. Nelson, "Organic photovoltaic films," Current Opinion in Solid State & Materials Science 6(1), 87-95 (2002)
50. N. S. Sariciftci, L. Smilowitz, A. J. Heeger and F. Wudl, "Photoinduced Electron Transfer from a Conducting Polymer to Buckminsterfullerene," Science 258(5087), 1474-1476 (1992)
51. H. Benmansour, F. A. Castro, M. Nagel, J. Heier, R. Hany and F. Nuesch, "Ionic space charge driven organic photovoltaic devices," Chimia 61(12), 787-791 (2007)
52. L. A. A. Pettersson, L. S. Roman and O. Inganas, "Modeling photocurrent action spectra of photovoltaic devices based on organic thin films," J. Appl. Phys. 86(1), 487-496 (1999)
53. A. J. Moule and K. Meerholz, "Minimizing optical losses in bulk heterojunction polymer solar cells," Appl. Phys. B-Lasers Opt. 86(4), 721-727 (2007)
54. J. M. Nunzi, "Organic photovoltaic materials and devices," Comptes Rendus Physique 3(4), 523-542 (2002)
55. M. Lenes, L. J. A. Koster, V. D. Mihailetchi and P. W. M. Blom, "Thickness dependence of the efficiency of polymer : fullerene bulk heterojunction solar cells," Appl. Phys. Lett. 88(24), 243502 (2006)
56. C. C. Chang, C. L. Pai, W. C. Chen and S. A. Jenekhe, "Spin coating of conjugated polymers for electronic and optoelectronic applications," Thin Solid Films 479(1-2), 254-260 (2005)
57. P. C. Sukanek, "''Anomalous'' speed dependence in polyimide spin coating," Journal of the Electrochemical Society 144(11), 3959-3963 (1997)
58. P. C. Sukanek, "Dependence of Film Thickness on Speed in Spin Coating," Journal of the Electrochemical Society 138(6), 1712-1719 (1991)
59. M. A. Ruderer, E. Metwalli, W. N. Wang, G. Kaune, S. V. Roth and P. Muller-Buschbaum, "Thin Films of Photoactive Polymer Blends," Chemphyschem 10(4), 664-671 (2009)
60. W. L. Ma, C. Y. Yang and A. J. Heeger, "Spatial Fourier-transform analysis of the morphology of bulk heterojunction materials used in "plastic" solar cells," Adv. Mater. 19(10), 1387-1390 (2007)
61. X. N. Yang, J. Loos, S. C. Veenstra, W. J. H. Verhees, M. M. Wienk, J. M. Kroon, M. A. J. Michels and R. A. J. Janssen, "Nanoscale morphology of high-performance polymer solar cells," Nano Lett. 5(4), 579-583 (2005)
62. X. N. Yang, G. H. Lu, L. G. Li and E. L. Zhou, "Nanoscale phase-aggregation-induced performance improvement of polymer solar cells," Small 3(4), 611-615 (2007)
63. J. Heier, J. Groenewold, S. Huber, F. Nuesch and R. Hany, "Nanoscale structuring of semiconducting molecular blend films in the presence of mobile counterions," Langmuir 24(14), 7316-7322 (2008)
64. J. Jo, S. I. Na, S. S. Kim, T. W. Lee, Y. Chung, S. J. Kang, D. Vak and D. Y. Kim, "Three-Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar Cells," Adv. Funct. Mater. 19(15), 2398-2406 (2009)
65. M. Drees, R. M. Davis and J. R. Heflin, "Improved morphology of polymer-fullerene photovoltaic devices with thermally induced concentration gradients," J. Appl. Phys. 97(3), 036103 (2005)
66. C. M. Bjorstrom, A. Bernasik, J. Rysz, A. Budkowski, S. Nilsson, M. Svensson, M. R. Andersson, K. O. Magnusson and E. Moons, "Multilayer formation in spin-coated thin films of low-bandgap polyfluorene : PCBM blends," J. Phys.-Condes. Matter 17(50), L529-L534 (2005)
67. Y. Yao, J. H. Hou, Z. Xu, G. Li and Y. Yang, "Effect of solvent mixture on the nanoscale phase separation in polymer solar cells," Adv. Funct. Mater. 18(12), 1783-1789 (2008)
68. S. Y. Heriot and R. A. L. Jones, "An interfacial instability in a transient wetting layer leads to lateral phase separation in thin spin-cast polymer-blend films," Nat. Mater. 4(10), 782-786 (2005)