基于P3HT:PCBM聚合物太阳电池的研究
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摘要
近年来,由于有机太阳电池具有质量轻、柔性好、成本低、可大面积制备等优点,引起了人们广泛的关注。2011年4月,日本三菱化学报道了有机太阳电池光电转换效率的最新世界纪录9.2%,该效率突破了电池商业化门槛,点燃了人们的希望。作为该领域的重要分支,聚合物太阳电池的研究也进行得如火如荼,取得了许多重要成果。但是,与无机硅太阳电池接近25%的效率相比,有机太阳电池尤其是聚合物太阳电池的效率还比较低,亟待我们更多的研究。
在本文中,我们选取了目前研究的主流——聚合物/富勒烯体系的体异质结太阳电池,通过研究分析聚合物太阳电池的光电转换过程和损耗机制,发现光敏层薄膜在纳米尺度内的形貌是影响聚合物太阳电池中载流子传输的关键因素之一。因此,我们将本文的研究方向集中在光敏层的形貌控制。通过选用不同溶剂来溶解聚合物材料及在器件成膜过程中进行溶剂处理或热退火处理等手段,优化了聚合物太阳电池光敏层薄膜的形貌,提高了器件的光电转换效率,得到的主要结论如下：
①当光敏层材料选用P3HT:PCBM时,以氯苯为溶剂制备的器件性能要优于以甲苯或邻二氯苯为溶剂制备的器件,AFM图显示以氯苯为溶剂时P3HT和PCBM有最好的相分离。
②对器件进行后处理如溶剂处理或热退火处理,可以改善光敏层形貌,提高器件的光电特性。因为适当的后处理促使P3HT分子进行自组装,形成互穿网络结构,有利于光生载流子的传输和收集。
③为了拓展器件对太阳光中可见光及红外光波段的响应,增强光的吸收以提高器件短路电流,我们设计了一种光谱互补型多层结构的聚合物太阳电池,其结构为：ITO/PEDOT:PSS/PbPc/P3HT:PCBM/Al。实验中观察到,加入酞菁铅(PbPc)层后,器件对650 nm-800 nm范围内光波的响应有微弱增强,但对350 nm-600 nm范围内光波的响应下降显著,因此这种结构还需进一步优化。
Recent years, organic solar cells have attracted much attention due to its unique advantages such as flexible, lightweight, low cost and large-area devices. In early April, 2011, Mitsubishi Chemical and university of Tokyo reportedly set a new efficiency record, producing organic solar cells with a 9.2% power conversion efficiency (PCE) that broke the limit of commercialization, which brought hope to the people. As an important branch in the field of organic solar cells, polymer solar cells are developing quickly, and have achieved many important results. However, compared to inorganic solar cells with PCE close to 25%, the PCE of organic solar cells, especially polymer solar cells is relatively low, more researches are expected.
Polymer/fullerene bulk heterojunction solar cells were investigated as the main subject of this thesis. Researching and analysing of the photoelectric conversion process and the loss mechanism of polymer solar cells, we found that one of the key factors influences on the carrier transport in polymer solar cells is the nano-scale morphology of thin film. Therefore, Our work was focused on the photosensitive layer morphology control. We not only investigated the effect of some effective approaches, such as the selection of solvents, solvent vapour treatment and thermal treat, on the morphology of polymer solar cells, but also optimized the morphology of the photosensitive layer in polymer solar cells and improved the photoelectric conversion efficiency of the devices. We got the main conclusions as follows:
①For P3HT:PCBM as the photosensitive layer, the devices prepared with chlorobenzene as the solvent were superior to that prepared with toluene or o-dichlorobenzene as the solvent. AFM diagrams showed that P3HT and PCBM in chlorobenzene as solvent had a suitable phase separation.
②It was demonstrated that optimized post-treatment, such as solvent vapour treat or thermal annealing, forces the P3HT molecules to self-assemble, which induces continuity and correct interpenetrating networks being favorable for electrons and holes transporting and enhancing the power conversion efficiency of the devices.
①In addition, for enhancing overlap of the absorption spectra of photosensitive layer with the solar spectrum, we designed a type of polymer solar cells with a structure of ITO/PEDOT:PSS/PbPc/P3HT:PCBM/Al. Lead phthalocyanine (PbPc), which is a p type small molecule material, has a broad and strong absorption in the range from 600 nm to 800 nm, which is complementary with the absorption spectrum of P3HT (400 nm-650 nm). In this thesis, The polymer solar cells with PbPc expended the absorption spectra of devices, but they still need further optimization.
在本文中,我们选取了目前研究的主流——聚合物/富勒烯体系的体异质结太阳电池,通过研究分析聚合物太阳电池的光电转换过程和损耗机制,发现光敏层薄膜在纳米尺度内的形貌是影响聚合物太阳电池中载流子传输的关键因素之一。因此,我们将本文的研究方向集中在光敏层的形貌控制。通过选用不同溶剂来溶解聚合物材料及在器件成膜过程中进行溶剂处理或热退火处理等手段,优化了聚合物太阳电池光敏层薄膜的形貌,提高了器件的光电转换效率,得到的主要结论如下：
①当光敏层材料选用P3HT:PCBM时,以氯苯为溶剂制备的器件性能要优于以甲苯或邻二氯苯为溶剂制备的器件,AFM图显示以氯苯为溶剂时P3HT和PCBM有最好的相分离。
②对器件进行后处理如溶剂处理或热退火处理,可以改善光敏层形貌,提高器件的光电特性。因为适当的后处理促使P3HT分子进行自组装,形成互穿网络结构,有利于光生载流子的传输和收集。
③为了拓展器件对太阳光中可见光及红外光波段的响应,增强光的吸收以提高器件短路电流,我们设计了一种光谱互补型多层结构的聚合物太阳电池,其结构为：ITO/PEDOT:PSS/PbPc/P3HT:PCBM/Al。实验中观察到,加入酞菁铅(PbPc)层后,器件对650 nm-800 nm范围内光波的响应有微弱增强,但对350 nm-600 nm范围内光波的响应下降显著,因此这种结构还需进一步优化。
Recent years, organic solar cells have attracted much attention due to its unique advantages such as flexible, lightweight, low cost and large-area devices. In early April, 2011, Mitsubishi Chemical and university of Tokyo reportedly set a new efficiency record, producing organic solar cells with a 9.2% power conversion efficiency (PCE) that broke the limit of commercialization, which brought hope to the people. As an important branch in the field of organic solar cells, polymer solar cells are developing quickly, and have achieved many important results. However, compared to inorganic solar cells with PCE close to 25%, the PCE of organic solar cells, especially polymer solar cells is relatively low, more researches are expected.
Polymer/fullerene bulk heterojunction solar cells were investigated as the main subject of this thesis. Researching and analysing of the photoelectric conversion process and the loss mechanism of polymer solar cells, we found that one of the key factors influences on the carrier transport in polymer solar cells is the nano-scale morphology of thin film. Therefore, Our work was focused on the photosensitive layer morphology control. We not only investigated the effect of some effective approaches, such as the selection of solvents, solvent vapour treatment and thermal treat, on the morphology of polymer solar cells, but also optimized the morphology of the photosensitive layer in polymer solar cells and improved the photoelectric conversion efficiency of the devices. We got the main conclusions as follows:
①For P3HT:PCBM as the photosensitive layer, the devices prepared with chlorobenzene as the solvent were superior to that prepared with toluene or o-dichlorobenzene as the solvent. AFM diagrams showed that P3HT and PCBM in chlorobenzene as solvent had a suitable phase separation.
②It was demonstrated that optimized post-treatment, such as solvent vapour treat or thermal annealing, forces the P3HT molecules to self-assemble, which induces continuity and correct interpenetrating networks being favorable for electrons and holes transporting and enhancing the power conversion efficiency of the devices.
①In addition, for enhancing overlap of the absorption spectra of photosensitive layer with the solar spectrum, we designed a type of polymer solar cells with a structure of ITO/PEDOT:PSS/PbPc/P3HT:PCBM/Al. Lead phthalocyanine (PbPc), which is a p type small molecule material, has a broad and strong absorption in the range from 600 nm to 800 nm, which is complementary with the absorption spectrum of P3HT (400 nm-650 nm). In this thesis, The polymer solar cells with PbPc expended the absorption spectra of devices, but they still need further optimization.
引文
[1]Becquerel A. E. Compt. Rend. Acad. Science.1839.9(145).561
[2]Peter Wurfel菩.陈红雨,匡代彬,郭长娟译Physics of Solar Cells From Principles to New Concepts第1版.北京.化学工业出版社.2009.163
[3]李甫,徐建梅等.有机太阳电池研究现状与进展.能源与环境.2007.4.52-54
[4]Robert F.Outlook Brightens for Plastic Solar Cells.Science.2011.332(6027).293-293
[5]Guangjin Zhao, Youjun He, Yongfang Li.6.5% Efficiency of Polymer Solar Cellsworth Based on poly (3-hexylthiophene) and Indene-C60 Bisadduct by Device Optimization.Adv. Mater.2010.10.1-4
[6]Wanzhu Cai, Xiong Gongoing, Yongoing Cao.Polymer solar cells:Recent development and possible routes for improvement in the performance.Sol.Energy Mater.Sol.Cells.2010.94.114-127
[7]Tang C.W.Two-layer organic photovoltaic cell.Appl.Phys.Lett.1986.48.183
[8]吴世康,汪鹏飞.有机电子学概论.第1版.北京.化学工业出版社.2010.209-210
[9]Sariciftci N S, Smilowitz L, Heeger A J, et al.Photoinduced electron-transfer from conducting polymer to buckminsterfullerene.Science.1992.258.1474-1476
[10]YuG, Gao J, Hummelen J C, et al.Polymer photovoltaic cells-enhanced efficiencies via a network of internal donor-acceptor heterjunctions.Science.1995.270.1789-1791
[11]Brabec C J.Organic photovoltaics:technology and market. Sol.Energy Mater.Sol.Cells. 2004.83.273-292
[12]Wanli Ma, Cuiying Yang, Alan J.Heeger, et al.Thermally Stable,Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology.Adv.Funct.Mater. 2005.15.1617-1622
[13]Kim J Y, Lee K, Coates N E, et al.Efficient tandem polymer solar cells fabricated by all-solution processing.Science.2007.317.222-225
[14]Li Y F, Zou Y P.Conjugated polymer photovoltaic materials with broad absorption band and high charge carrier mobility.Adv.Mater.2008.20.2952-2958
[15]Wang E G, Wang L, LanLF, et al.High-performance polymer heterojunction solar cells of a polysilafluorene derivative.Appl.Phys.Lett..2008.92.033307
[16]熊绍珍,朱美芳.太阳电池基础与应用.第1版.北京.科学出版社.2009.92
[17]於黄忠,彭俊彪.共混型聚合物太阳电池原理及研究进展.化学进展.2007.19(11).1689-1694
[18]於黄忠,彭俊彪.影响共混结构聚合物光电性能的因素.高分子材料科学与工程.2008.24(9).23-31
[19]A.Yakimov,S.R.Forrest.High photovoltage multiple-heterojunction organic solar cells incorporating interfacial metallic nanoclusters.Appl.Phys.Lett.2002.806 (9).1667-1669
[20]胡涛.提高体异质结有机太阳电池特性的研究[学位论文].北京..北京交通大学.2009.3
[21]雷德生.C60和PCBM公掺P3HT体异质结太阳电池的研究[学位论文].北京.北京交通大学.2009.13
[22]宗骐,谢续明,王秀风.高分子共混物薄膜表面形貌形成过程中的溶剂效应.高等学校 化学学报,2004.25(12)：2363-2366
[23]李卫民.聚合物太阳电池机理及实验研究[学位论文].武汉.华中科技大学.2009.79-80
[24]Youngkyoo Kim, Stelios A. Choulis, Jenny Nelson, and Donal D.C.Brad.Device annealing effect in organic solar cells with blends of regioregular poly(3-hexylthiophene) and soluble fullerene. Appl.Phys.Lett.2005.86(063502)
[25]Bogyu Lim,Jang Jo,Seok-In Na,Juhwan Kim,Seok-Soon Kim and Dong-Yu Kim.A morphology controller for high-efficiency bulk-heterojunction polymer solar cells. J.Mater.Chem.2010.20.10919-10923
[26]Gang Li,Yan Yao,Hoichang Yang, et al."Solvent Annealing" Effect in Polymer Solar Cells Based on Poly(3-hexylthiophene) and Methanofullerenes.Adv.funct.Mater.,2007.17.1636-1644.
[27]Jang Jo, Seok-In Na, Seok-Soon Kim, Tae-Woo Lee, Youngsu Chung, Seok-Ju Kang. Dong-Yu Kim.Three-Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar Cells.Adv.Funct.Mater.2009.19.2398-2406
[28]T.Erb, U.Zhokhavets, G.Gobsch, S.Raleva, B.Stuhn, et al.Correlation Between Structural and Optical Properties of Composite Polymer/Fullerene Films for Organic Solar Cells.Adv.Func.Mater.2005.15.1193-1196
[29]A.Zen,M.Saphiannikova,D.Nether,G.Wegner.Effect of Molecular Weight on the Structure and Crystallinity of Poly(3-hexylthiophene).Macromolecules.2006.39(6).2162-2171
[30]Liang Shen,Yang Xu,et al.Short-circuit current density improvement of inverted polymer solar cells using PbPc to enhance photon absorption over 600 nm. Sol. Energy Mater.Sol.Cells.2010.10.1016
[31]Chunfu Zhang,Shi Wun Tong,et al.Simple tandem organic photovoltaic cells for improved energy conversion efficiency.Appl.Phys.Lett.2005.92.083310
[2]Peter Wurfel菩.陈红雨,匡代彬,郭长娟译Physics of Solar Cells From Principles to New Concepts第1版.北京.化学工业出版社.2009.163
[3]李甫,徐建梅等.有机太阳电池研究现状与进展.能源与环境.2007.4.52-54
[4]Robert F.Outlook Brightens for Plastic Solar Cells.Science.2011.332(6027).293-293
[5]Guangjin Zhao, Youjun He, Yongfang Li.6.5% Efficiency of Polymer Solar Cellsworth Based on poly (3-hexylthiophene) and Indene-C60 Bisadduct by Device Optimization.Adv. Mater.2010.10.1-4
[6]Wanzhu Cai, Xiong Gongoing, Yongoing Cao.Polymer solar cells:Recent development and possible routes for improvement in the performance.Sol.Energy Mater.Sol.Cells.2010.94.114-127
[7]Tang C.W.Two-layer organic photovoltaic cell.Appl.Phys.Lett.1986.48.183
[8]吴世康,汪鹏飞.有机电子学概论.第1版.北京.化学工业出版社.2010.209-210
[9]Sariciftci N S, Smilowitz L, Heeger A J, et al.Photoinduced electron-transfer from conducting polymer to buckminsterfullerene.Science.1992.258.1474-1476
[10]YuG, Gao J, Hummelen J C, et al.Polymer photovoltaic cells-enhanced efficiencies via a network of internal donor-acceptor heterjunctions.Science.1995.270.1789-1791
[11]Brabec C J.Organic photovoltaics:technology and market. Sol.Energy Mater.Sol.Cells. 2004.83.273-292
[12]Wanli Ma, Cuiying Yang, Alan J.Heeger, et al.Thermally Stable,Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology.Adv.Funct.Mater. 2005.15.1617-1622
[13]Kim J Y, Lee K, Coates N E, et al.Efficient tandem polymer solar cells fabricated by all-solution processing.Science.2007.317.222-225
[14]Li Y F, Zou Y P.Conjugated polymer photovoltaic materials with broad absorption band and high charge carrier mobility.Adv.Mater.2008.20.2952-2958
[15]Wang E G, Wang L, LanLF, et al.High-performance polymer heterojunction solar cells of a polysilafluorene derivative.Appl.Phys.Lett..2008.92.033307
[16]熊绍珍,朱美芳.太阳电池基础与应用.第1版.北京.科学出版社.2009.92
[17]於黄忠,彭俊彪.共混型聚合物太阳电池原理及研究进展.化学进展.2007.19(11).1689-1694
[18]於黄忠,彭俊彪.影响共混结构聚合物光电性能的因素.高分子材料科学与工程.2008.24(9).23-31
[19]A.Yakimov,S.R.Forrest.High photovoltage multiple-heterojunction organic solar cells incorporating interfacial metallic nanoclusters.Appl.Phys.Lett.2002.806 (9).1667-1669
[20]胡涛.提高体异质结有机太阳电池特性的研究[学位论文].北京..北京交通大学.2009.3
[21]雷德生.C60和PCBM公掺P3HT体异质结太阳电池的研究[学位论文].北京.北京交通大学.2009.13
[22]宗骐,谢续明,王秀风.高分子共混物薄膜表面形貌形成过程中的溶剂效应.高等学校 化学学报,2004.25(12)：2363-2366
[23]李卫民.聚合物太阳电池机理及实验研究[学位论文].武汉.华中科技大学.2009.79-80
[24]Youngkyoo Kim, Stelios A. Choulis, Jenny Nelson, and Donal D.C.Brad.Device annealing effect in organic solar cells with blends of regioregular poly(3-hexylthiophene) and soluble fullerene. Appl.Phys.Lett.2005.86(063502)
[25]Bogyu Lim,Jang Jo,Seok-In Na,Juhwan Kim,Seok-Soon Kim and Dong-Yu Kim.A morphology controller for high-efficiency bulk-heterojunction polymer solar cells. J.Mater.Chem.2010.20.10919-10923
[26]Gang Li,Yan Yao,Hoichang Yang, et al."Solvent Annealing" Effect in Polymer Solar Cells Based on Poly(3-hexylthiophene) and Methanofullerenes.Adv.funct.Mater.,2007.17.1636-1644.
[27]Jang Jo, Seok-In Na, Seok-Soon Kim, Tae-Woo Lee, Youngsu Chung, Seok-Ju Kang. Dong-Yu Kim.Three-Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar Cells.Adv.Funct.Mater.2009.19.2398-2406
[28]T.Erb, U.Zhokhavets, G.Gobsch, S.Raleva, B.Stuhn, et al.Correlation Between Structural and Optical Properties of Composite Polymer/Fullerene Films for Organic Solar Cells.Adv.Func.Mater.2005.15.1193-1196
[29]A.Zen,M.Saphiannikova,D.Nether,G.Wegner.Effect of Molecular Weight on the Structure and Crystallinity of Poly(3-hexylthiophene).Macromolecules.2006.39(6).2162-2171
[30]Liang Shen,Yang Xu,et al.Short-circuit current density improvement of inverted polymer solar cells using PbPc to enhance photon absorption over 600 nm. Sol. Energy Mater.Sol.Cells.2010.10.1016
[31]Chunfu Zhang,Shi Wun Tong,et al.Simple tandem organic photovoltaic cells for improved energy conversion efficiency.Appl.Phys.Lett.2005.92.083310