本研究嘗試以製程簡易且成本便宜之碳材料製作對電極催化層，應用於[Cu(II/I)(dmby)2]TFSI2/1錯合物電解質之染料敏化太陽能電池（Dye-Sensitized Solar Cell，DSSC）。使用包含鉛筆塗層、蒸鍍石墨基材、石墨烯與多壁式奈米碳管等碳材，探討催化層特性對於光電轉換效率之關鍵影響參數，同時比較不同光照強度下，催化層之阻抗特性對於整體光電轉換效率影響之差異。
本研究以拉曼光譜儀分析不同碳材料的結構，以掃描式電子顯微鏡（SEM）觀察催化層於FTO導電玻璃的覆蓋與分佈情形，以電化學阻抗分析（EIS）分析催化層之異質傳輸阻抗與介面間之串聯電阻，結合其組成DSSC之光伏參數，進行統整性比較。歸納結果發現，在低光時，催化層擁有較高的串聯電阻(RS)與較低的異質傳輸阻抗(RCT)較為理想，因為在低光下的漏電與再結合行為嚴重，對光伏數據有很大的負面影響，若催化層有較高的RS，則可以防止電荷回流至對電極，有助於提升電池性能，另方面RCT直接關係到催化效率，當RCT越低則電荷傳輸效率越佳。本研究測試之材料中，多壁式奈米碳管由於其高比表面積與微結構具有高比例的懸鍵(dangling bond)，而dangling bond又是與電解質鍵結並傳遞電子的關鍵結構，因此奈米碳管系列樣品具有較多的催化位址，其RCT值也是所有樣品中最低，在本研究測試之碳材料中具有最佳催化效率，在200 Lux光強下的光電轉換效率可達20.2 %，高於傳統Pt對電極催化層（16.6 %）。然而在光通量提高時，電子再結合作用與漏電的負面影響比例逐漸降低，此時RCT成為主導電池的光伏數據表現的關鍵因素。

Copper-complex redox couple is known as efficient electro-transfer mediator that exhibit low driving force for dye regeneration. Even though [Cu(II/I)(dmby)2]TFSI2/1 complex coupling with Y123 dye demonstrates a highest theoretical photovoltage over 1.0 V in liquid-electrolyte based DSSCs, the rapid electron self-exchange rate of copper-complexes requires a higher efficient catalytic counter-electrode. In this work, two carbon-based materials, graphite and multi-wall carbon nanotubes (MWCNTs), were respectively used as catalyst layer onto the FTO glass serving as counter-electrode and their electro-catalytic activities were carefully examined. The charge transfer resistance (RCT) at the electrolyte/electrode interface and the serial resistance (RS) of counter-electrode were investigated by Electrochemical Impedance Spectroscopy (EIS). The results showed that MWCNTs exhibits a lowest RCT, that allow a highest electron transfer rate, in comparison with the other carbon materials used in the present work. Briefly, the DSSC composed of MWCNTs as catalytic counter electrode demonstrated a high photovoltage up to 0.8 V and an overall high PCE at 20.2% under dim light condition (200 Lux).

[1] H. J. Kim, et al., “A Study of the Photo-Electric Efficiency of Dye-Sensitized Solar Cells Under Lower Light Intensity,” J. Electr. Eng. Technol., pp. 513-517, 2007.
[2] A. Yella, et al., “orphyrin-Sensitized Solar Cells with Cobalt (II/III)–Based Redox Electrolyte Exceed 12 Percent Efficiency,” Science, 334, pp. 629-634, 2011.
[3] Y. Bai, et al., “High-efficiency organic dye-sensitized mesoscopic solar cells with a copper redox shuttle,” Chem. Commun., 47, pp. 4376-4378, 2011.
[4] T. W. Hamann, et al., “Dye-sensitized solar cell redox shuttles,” Energy Environ. Sci., 4, pp. 370-381, 2011.
[5] N. Koumura, et al., “Alkyl-Functionalized Organic Dyes for Efficient Molecular Photovoltaics,” J. Am. Chem. Soc., 128, pp. 14256-14257, 2006.
[6] J. H. Yum, et al., “A cobalt complex redox shuttle for dye-sensitized solar cells with high open-circuit potentials,” Nat. Commun., 3, pp. 631-638, 2012.
[7] S. Shalini, et al., “Status and outlook of sensitizers/dyes used in dye sensitized solar cells (DSSC): a review,” Int. J. Energy Res., 40, 2016.
[8] J. Gong, et al., “Review on dye-sensitized solar cells (DSSCs): Advanced techniques and,” Renew. Sust. Energ. Rev., 68, pp. 234-246, 2017.
[9] S. M. Feldt, et al., “Design of Organic Dyes and Cobalt Polypyridine Redox Mediators for High-Efficiency Dye-Sensitized Solar Cells,” J. Am. Chem. Soc., 132, p. 16714–16724, 2010.
[10] S. W. Lee, et al., “Effects of TiCl4 Treatment of Nanoporous TiO2 Films on Morphology,” J. Phys. Chem. C, 116, p. 21285−21290, 2012.
[11] P. M. Sommeling, et al., “Influence of a TiCl4 Post-Treatment on Nanocrystalline TiO2 Films in Dye-Sensitized Solar Cells,” J. Phys. Chem. B, 110, pp. 19191-19197, 2006.
[12] B. C. O’Regan, et al., “Influence of the TiCl4 Treatment on Nanocrystalline TiO2 Films in Dye-Sensitized Solar Cells. 2. Charge Density, Band Edge Shifts, and Quantification of Recombination Losses at Short Circuit,” J. Phys. Chem. C, 111, pp. 14001-14010, 2007.
[13] H. P. Wu, et al., “Hybrid Titania Photoanodes with a Nanostructured Multi-Layer Configuration for Highly Efficient Dye-Sensitized Solar Cells,” J. Phys. Chem. Lett., 4, pp. 1570-1577, 2013.
[14] M. Grätzel, “Photoelectrochemical cells,” Nature, 414, pp. 338-344, 2001.
[15] U. Diebold, “The surface science of titanium dioxide,” Surf. Sci. Rep., 48, pp. 53-229, 2003.
[16] S. Kambe, et al., “Effects of crystal structure, size, shape and surface structural differences on photo-induced electron transport in TiO2 mesoporous electrodes,” J. Mater. Chem., 12, pp. 723-728, 2002.
[17] D. L. Andrews, “Biological Energy 5: Electron transfer theory,” Biologicalphysics.iop.org., 2013.
[18] T. Daeneke, et al., “Dye Regeneration Kinetics in Dye-Sensitized Solar Cells,” J. Am. Chem. Soc., 134, pp. 16925-16928, 2012.
[19] Y. Saygili, et al., “Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage,” J. Am. Chem. Soc., 138, pp. 15087-15096, 2016.
[20] M. K. Nazeeruddin, et al., “Conversion of Light to Electricity by c/j-X2Bis(2,2'-bipyridyl-4,4/-dicarboxylate)ruthenium(II) Charge-Transfer Sensitizers (X = Cl", Br", I", CN", and SCN~) on Nanocrystalline TiO2 Electrodes,” J. Am. Chem. Soc., 115, pp. 6382-6390, 1993.
[21] K. Kakiage, et al., “An achievement of over 12 percent efficiency in an organic dye-sensitized solar cell,” Chem. Commun., 50, pp. 6379-6381, 2014.
[22] P. Wang, et al., “Molecular‐Scale Interface Engineering of TiO2 Nanocrystals: Improve the Efficiency and Stability of Dye‐Sensitized Solar Cells,” Adv. Mater., 15, pp. 2101-2104, 2003.
[23] N. Sridhar, et al., “A study of dye sensitized solar cells under indoor and low level outdoor lighting: comparison to organic and inorganic thin film solar cells and methods to address maximum power point tracking,” 26th European photovoltaic solar energy conference and exhibition., 2011.
[24] A. Listorti, et al., “The mechanism behind the beneficial effect of light soaking on injection efficiency and photocurrent in dye sensitized solar cells,” Energy Environ. Sci., 4, pp. 3494-3501, 2011.
[25] S. Hattori, et al., “Blue Copper Model Complexes with Distorted Tetragonal Geometry Acting as Effective Electron-Transfer Mediators in Dye-Sensitized Solar Cells,” J. Am. Chem. Soc., 127, pp. 9648-9654, 2005.
[26] 郭昱伶, “混和型二氧化鈦光電極於染料敏化太陽能電池在太陽光和室內光下之光伏效能表現差異,” 國立成功大學碩士論文, 2017.
[27] 洪肇崑, “以微波溶熱法合成超小奈米顆粒之二氧化鈦於染料敏化太陽能電池之應用,” 國立成功大學碩士論文, 2015.
[28] M. H. Yeh, et al., “Size effects of platinum nanoparticles on the electrocatalytic ability of the counter electrode in dye-sensitized solar cells,” Nano energy, 17, pp. 241-253, 2015.
[29] C.H. Yoon, et al., “Enhanced performance of a dye-sensitized solar cell with an electrodeposited-platinum counter electrode,” Electrochim. Acta, 53, pp. 2890-2896, 2008.
[30] L. Kavan, et al., “Novel highly active Pt/graphene catalyst for cathodes of Cu (II/I)-mediated dye-sensitized solar cells,” Electrochim. Acta., 251, pp. 167-175, 2017.
[31] W. L. Hoffeditz, et al., “One electron changes everything. A multispecies copper redox shuttle for dye-sensitized solar cells,” J. Phys. Chem., 120, pp. 3731-3740, 2016.
[32] L. Kavan, et al., “Electrochemical properties of Cu (II/I)-based redox mediators for dye-sensitized solar cells,” Electrochim. Acta, 227, pp. 194-202, 2017.
[33] G. Boschloo, et al., “Quantification of the Effect of 4-tert-Butylpyridine Addition to I-/I3 Redox Electrolytes in Dye-Sensitized Nanostructured TiO2 Solar Cells,” J. Phys. Chem. B, 110, pp. 13144-13150, 2006.
[34] F. Jonas, et al., “Conductive modifications of polymers with polypyrroles and polythiophenes,” Synth. Met., 41, pp. 831-836, 1991.
[35] S. Yasuteru, et al., “Application of Poly(3,4-ethylenedioxythiophene) to Counter Electrode in Dye-Sensitized Solar Cells,” Chem. Lett., 31, pp. 1060-1061, 2002.
[36] T. Yohanne, et al., “Photoelectrochemical studies of the junction between poly[3-(4-octylphenyl)thiophene] and a redox polymer electrolyte,” Sol. Energy Mater Sol. Cells, 51, pp. 193-202, 1998.
[37] R. Han, et al., “Influence of monomer concentration during polymerization on performance and catalytic mechanism of resultant poly(3,4-ethylenedioxythiophene) counter electrodes for dye-sensitized solar cells,” Electrochim. Acta, 173, pp. 796-803, 2015.
[38] J. G. Chen, et al., “Using modified poly(3,4-ethylene dioxythiophene): Poly(styrene sulfonate) film as a counter electrode in dye-sensitized solar cells,” Sol. Energy Mater Sol. Cells, 91, pp. 1472-1477, 2007.
[39] W. Wei, et al., “A review on PEDOT-based counter electrodes for dye-sensitized solar cells,” Int. J. Energy Res., 38, pp. 1099-1111, 2014.
[40] L. Kavan, et al., “Optically Transparent Cathode for Dye-Sensitized Solar Cells Based on Graphene Nanoplatelets,” J. Am. Chem. Soc., 5, pp. 165-172, 2011.
[41] J. D. Roy-Mayhew, et al., ACS Appl. Mater. Interfaces, 8, pp. 9134-9141, 2016.
[42] A. Hauch, et al., “Diffusion in the electrolyte and charge-transfer reaction at the platinum electrode in dye-sensitized solar cells,” Electrochim. Acta, 46, p. 3457–3466, 2001.
[43] M. Freitag, et al., “Dye-sensitized solar cells for efficient power generation under ambient lighting,” Nat. Photonics, 11, pp. 372-378, 2017.
[44] G. Veerappan, et al., “Sub-micrometer-sized Graphite As a Conducting and Catalytic Counter Electrode for Dye-sensitized Solar Cells,” Appl. Mater. Interfaces, 3, pp. 857-862, 2011.
[45] K. S. Novoselov, et al., “Electric field effect in atomically thin carbon films,” Science, pp. 666-669, 2004.
[46] J. Hodkiewicz, “Characterizing Carbon Materials with Raman Spectroscopy,” Thermo Fisher Scientific, 2010.
[47] L. Kavan, et al., “Graphene Nanoplatelets Outperforming Platinum as the Electrocatalyst in Co-Bipyridine-Mediated Dye-Sensitized Solar Cells,” Nano Lett., 11, pp. 5501-5506, 2011.
[48] S. Iijima, “Helical microtubules of graphitic carbon,” Nature, 354, pp. 56-58, 1991.
[49] S. U. Lee, et al., “A comparative study of dye-sensitized solar cells added carbon nanotubes to electrolyte and counterelectrodes,” Sol. Energy Mater Sol. Cells, 94, pp. 680-685, 2010.
[50] X. Mei, et al., “High-performance dye-sensitized solar cells with gel-coated binder-free carbon nanotube films as counter electrode,” Nanotechnology, 21, p. 395202, 2010.
[51] A. A. Arbab, et al., “Multiwalled carbon nanotube coated polyester fabric as textile based flexible counter electrode for dye sensitized solar cell,” Phys. Chem. Chem. Phys., 17, pp. 12957-12969, 2015.
[52] N. Pierard, et al., “Production of short carbon nanotubes with open tips by ball milling,” Chem. Phys. Lett., 335, pp. 1-8, 2001.
[53] Z. Kónya, et al., “Large scale production of short functionalized carbon nanotubes,” Chem. Phys. Lett., 5-6, pp. 429-435, 2002.
[54] L. Chen, et al., “Carbon nanotubes with hydrophilic surfaces produced by a wet-mechanochemical reaction with potassium hydroxide using ethanol as solvent,” Mater. Lett., 63, pp. 45-47, 2009.
[55] A. Ikeda, et al., “Solubilization and debundling of purified single-walled carbon nanotubes using solubilizing agents in an aqueous solution by high-speed vibration milling technique,” Chem. Commun., pp. 1334-1335, 2004.
[56] K. J. Ziegler, et al., “Controlled Oxidative Cutting of Single-Walled Carbon Nanotubes,” J. Am. Chem. Soc., 127, pp. 1541-1547, 2005.
[57] H. Yu, et al., “Kinetically Controlled Side-Wall Functionalization of Carbon Nanotubes by Nitric Acid Oxidation,” J. Phys. Chem. C, 112, p. 6758–6763, 2008.
[58] F. Harnisch, et al., “Comparative study on the performance of pyrolyzed and plasma-treated iron(II) phthalocyanine-based catalysts for oxygen reduction in pH neutral electrolyte solutions,” J. Power Sources, 193, pp. 86-92, 2009.
[59] A. Felten, et al., “Radio-frequency plasma functionalization of carbon nanotubes surface O2, NH3, and CF4 treatments,” J. Appl. Phys., 98, p. 074308, 2005.
[60] H. Tian, et al., “The Influence of Environmental Factors on DSSCs for BIPV,” Int. J. Electrochem. Sci., 7, pp. 4686 - 4691, 2012.
[61] F. De Rossi, et al., “Characterization of photovoltaic devices for indoor light harvesting and customization of flexible dye solar cells to deliver superior efficiency under artificial lighting,” Appl Energy., 156, pp. 413-422, 2015.
[62] M. C. Tsai, “A large, ultra-black, efficient and cost-effective dye-sensitized solar module approaching 12% overall efficiency under 1000 lux indoor light,” J. Mater. Chem. A, 6, pp. 1995-2003, 2018.
[63] Y. C. Wu, et al., “Clean and time-effective synthesis of anatase TiO2 nanocrystalline by microwave-assisted solvothermal method for dye-sensitized solar cell,” Journal of Power Sources, 247, pp. 444-451, 2014.
[64] H. Ellisa, et al., “PEDOT counter electrodes for dye-sensitized solar cells prepared byaqueous micellar electrodeposition,” Electrochim. Acta, 107, pp. 45-51, 2013.
[65] 林學溢, “丁腈電解液應用於染料敏化太陽能電池於低光之研究,” 國立成功大學碩士論文, 2017.
[66] “Beer–Lambert law,” Wikipedia, , 2019.
[67] M. Mizgeen, “Uv-Visible spectroscopy,” SlideShare, 2015.
[68] “What is Raman Spectroscopy,” Nanophoton Corporation, 2016.
[69] A. C. Ferrari, “Raman spectroscopy of graphene and graphite: Disorder, electron–phonon coupling, doping and nonadiabatic effects,” Solid State Commun., 143, pp. 47-57, 2007.
[70] “PN Junction Diode,” ElectronicsTutorials, 2019.
[71] 陳恭世, “奈米顆粒敏化奈米晶體二氧化鈦之光電效應研究,” 國立台灣大學碩士論文, 2005.
[72] “DSSC: Dye Sensitized Solar Cells Basic Principles and Measurements,” Gamry Instruments, 2018.
[73] “Solar Cells: A Guide to Theory and Measurement,” Ossila, 2018.
[74] “Planning and Installing Photovoltaic Systems: A Guide for Installers, Architects and Engineers,” Deutsche Gesellschaft Für Sonnenenergie, 2008.
[75] “Standard Solar Spectra,” PVEducation, 2018.
[76] Q. Wang, et al., “Electrochemical Impedance Spectroscopic Analysis of Dye-Sensitized Solar Cells,” J. Phys. Chem. B, 109, pp. 14945-14953, 2005.
[77] M. E. Orazem, et al., “Electrochemical Impedance Spectroscopy,” John Wiley& Sons, Inc., p. 251, 2008.
[78] L. Kavan, et al., “Graphene-based cathodes for liquid-junction dye sensitized solar cells: Electrocatalytic and mass transport effects,” Electrochim. Acta, 128, pp. 349-359, 2014.
[79] 張育銘, “使用交流電阻抗法中傳輸線模組分析氧化鈮阻隔層對染料敏化太陽能電池陽極界面逆電流抑制之研究,” 國立清華大學碩士論文, 2014.
[80] 吳慧屏, “奈米管染料敏化太陽能電池的製備與鑑識及其交流阻抗圖譜的研究,” 國立交通大學碩士論文, 2010.
[81] J. Nielsen, et al., “Impedance of SOFC electrodes: A review and a comprehensive case study on the impedance of LSM:YSZ cathodes,” Electrochim. Acta, 115, pp. 31-45, 2014.
[82] E. Mosconi, et al., “Cobalt Electrolyte/Dye Interactions in Dye-Sensitized Solar Cells: A Combined Computational and Experimental Study,” J. Am. Chem. Soc., 134, p. 19438−19453, 2012.
[83] M. K. Kashif, et al., “A New Direction in Dye-Sensitized Solar Cells Redox Mediator Development: In Situ Fine-Tuning of the Cobalt(II)/(III) Redox Potential through Lewis Base Interactions,” J. Am. Chem. Soc, 134, p. 16646−16653, 2012.
[84] F. T. C. Moreira, et al., “Biomimetic materials assembled on a photovoltaic cell as a novel biosensing approach to cancer biomarker detection,” Sci. Rep., 8, p. 10205, 2018.
[85] J. E. Trancik, et al., “Transparent and catalytic carbon nanotube films,” Nano Lett., 8, pp. 982-987, 2008.
[86] J. D. Roy-Mayhew, et al., “Functionalized graphene as a catalytic counter electrode in dye-sensitized solar cells,” ACS nano, 4, pp. 6203-6211, 2010.
[87] L. Kavan, et al., “Optically Transparent Cathode for Co(III/II) Mediated Dye-Sensitized Solar Cells Based on Graphene Oxide,” Appl. Mater. Interfaces, 4, p. 6999−7006, 2012.
[88] S. C. S. Lai, et al., “Definitive evidence for fast electron transfer at pristine basal plane graphite from high‐resolution electrochemical imaging,” Angew. Chem. Int. Ed., 51, pp. 5405-5408, 2012.
[89] J. Velten, et al., “Carbon nanotube/graphene nanocomposite as efficient counter electrodes in dye-sensitized solar cells,” Nanotechnology, 23, p. 085201, 2012.
[90] A. C. Ferrari, et al., “Interpretation of Raman spectra of disordered and amorphous carbon,” Phys. Rev. B, 61, pp. 14095-14107, 2000.
[91] A. C. Ferrari, et al., “Raman Spectrum of Graphene and Graphene Layers,” Phys. Rev. Lett., 97, p. 187401, 2006.
[92] B. Park, et al., “Understanding Interfacial Charge Transfer between Metallic PEDOT Counter Electrodes and a Cobalt Redox Shuttle in Dye-Sensitized Solar Cells,” ACS Appl. Mater. Interfaces, 6, pp. 2074-2079, 2014.