在本論文中，我們製作高開路電壓與高效率之有機層疊結構太陽能電池(cascade devices)，分為三個部分逐步分析討論。第一部分，我們仿效Kjell Cnops et al.的高效率fullerene-free cascade devices，但是我們使用MoO3作為我們的電洞傳輸層，其結構為ITO/MoO3/α-sexithiophene (α-6T)/subnaphthalocyanine chloride (SubNc)/ subphthalocyanine chloride (SubPc)/bathocuproine (BCP)/Ag，並且對元件做光場分佈和電性的最佳化，展現整個cascade devices結構最佳化的過程。
第二部分，嘗試將此cascade devices之材料替換，嘗試使用diindenoperylene (DIP)取代α-6T，因DIP之HOMO較α-6T高，故可提高元件開路電壓，並利用電激發光和外部量子效率頻譜做DIP和α-6T與SubNc的接面分析，證明了DIP的能量損失較α-6T少，因此可以提高VOC。另一方面，SubPc的放光與ClAlPc的吸收頻譜重疊，有利能量轉換，因此嘗試將ClAlPc取代SubNc。並利用電激發光和外部量子效率頻譜對SubNc與SubPc和ClAlPc的接面分析，證明SubNc與SubPc的reorganization energy較小，因此彼此的相容性較高，能量也較容易轉移。
第三部分，將DIP插入此cascade devices之α-6T/SubNc接面之中，一方面可以藉由DIP和SubNc的接面可以提升VOC，另一方面，可以藉由α-6T，穿過DIP和SubNc與SubPc接觸，保持α-6T所貢獻的效率，展現VOC較原結構元件高出10 %，且效率還有7 %的cascade元件。

In this thesis, we have demonstrated an organic photovoltaic (OPV) device with high open-circuit voltage (VOC) and power conversion efficiency (PCE). This thesis is divided into three parts. In the first part, we fabricate a series of high-performance fullerene-free cascade OPV devices with a structure of indium-tin-oxide (ITO)/MoO3/α-sexithiophene (α-6T)/ chloroboron subnaphthalocynine (SubNc)/chloroboron subphthalocyanine (SubPc)/bathocuproine (BCP)/Ag. The optical and electrical properties for optimizing the device structure is thoroughly discussed using optical-field simulation and space-charge limited current model. The second part studies the effects of replacing α-6T with a material, diindenoperylene (DIP), which has a higher highest occupied molecular orbital (HOMO) level than α-6T; the higher the HOMO is the larger the VOC will be obtained. The interface analysis at α-6T or DIP/SubNc indicates that the energy losses can be substantially reduced when SubNc is adjacent to DIP and therefore the VOC is improved considerably. On the frame work of Förster energy transfer, exciton energy transfer rate can be increased by the spectral overlap between emission of the energy donor and absorption of the energy acceptor (i.e. emission of SubNc overlaps with absorption of α-6T or DIP more the energy transfer rate will be larger). Therefore, the attempt to replacing SubNc with chloloroaluminum phthalocyanine (ClAlPc) that has a broad spectral overlap withα-6T or DIP is made. However, the device performance is substantially decreased when SubNc is replaced with ClAlPc, independent ofα-6T or DIP. The charge-transfer analysis shows that the reorganization energy between SubNc and SubPc is much lower than the reorganization energy between SubNc and ClAlPc. This result indicates that the exciton transfer rate can be influenced not only by the Förster energy transfer but also the reorganization energy between materials. Therefore, choosing materials should take both the energy-level alignment and reorganization energy between materials into account in cascade OPV devices. In the third part we insert a thin layer of DIP between the α-6T/SubNc interface for increasing both the VOC and short-circuit current density (JSC). The contribution of high VOC and JSC is originated from the interfacial contact at the DIP/SubNc and α-6T/SubNc interface, respectively. The OPV device with α-6T/DIP/SubNc/SubPc cascade structure exhibits a 10% enhancement in VOC and a PCE exceeding 7%.

[1] S. G. Benka, “Special Issue The Energy Challenge,” Phys. Today, 55, 38 (2002).
[2] M. I. Hoffert, K. Caldeira, G. Benford, D. R. Criswell, C. Green, H. Herzog, A. K. Jain, H. S. Kheshgi, K. S. Lackner, J. S. Lewis, H. D. Lightfoot, W. Manheimer, J. C. Mankins, M. E. Mauel, L. J. Perkins, M. E. Schlesinger, T. Volk, and T. M. L. Wigley, “Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet,” Science, 298, 981 (2002).
[3] http://www.mainframegroup.net.
[4] http://static.ddmcdn.com/gif/blogs.
[5] https://ichemepresident.files.wordpress.com.
[6] http://img.zwbk.org/baike/bpic.
[7] https://upload.wikimedia.org/wikipedia/commons.
[8] http://images.epochweekly.com.
[9] M. A. Green, “Third generation photovoltaics: Ultra-high conversion efficiency at low cost,” Prog. Photovoltaics, 9, 123 (2001).
[10] N. S. Lewis, “Toward Cost-Effective Solar Energy Use,” Science, 315, 798 (2007).
[11] C. W. Tang and S. A. Vanslyke, “Organic Electroluminescent Diodes,” Appl. Phys. Lett., 51, 913 (1987).
[12] M. A. Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, and S. R. Forrest, “Highly efficient phosphorescent emission from organic electroluminescent devices,” Nature, 395, 151 (1998).
[13] C. Adachi, M. A. Baldo, S. R. Forrest, and M. E. Thompson, “High-efficiency organic electrophosphorescent devices with tris(2-phenylpyridine)iridium doped into electron-transporting materials,” Appl. Phys. Lett., 77, 904 (2000).
[14] G. Horowitz, “Field-effect transistors based on short organic molecules,” J. Mater. Chem., 9, 2021 (1999).
[15] A. Tsumura, H. Koezuka, and T. Ando, “Macromolecular electronic device: Field‐effect transistor with a polythiophene thin film,” Appl. Phys. Lett, 49, 1210 (1986).
[16] S. R. Forrest, “Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques,” Chem. Rev., 97, 1793 (1997).
[17] 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, 841 (2001).
[18] S. M. Sze, Physics of Semiconductor Devices, 2nd ed. (Wiley, New York, 1981).
[19] M. Riede, T. Mueller, W. Tress, R. Schueppel, and K. Leo, “Small-molecule solar cells - status and perspectives,” Nanotechnology, 19 (2008).
[20] P. Miranda, D. Moses, and A. Heeger, “Ultrafast photogeneration of charged polarons in conjugated polymers,” Phys. Rev. B, 64 (2001).
[21] X. Gong, J. C. Ostrowski, G. C. Bazan, D. Moses, and A. J. Heeger, “Red electrophosphorescence from polymer doped with iridium complex,” Appl. Phys. Lett., 81, 3711 (2002).
[22] B. A. Gregg and M. C. Hanna, “Comparing organic to inorganic photovoltaic cells: Theory, experiment, and simulation,” J. Appl. Phys., 93, 3605 (2003).
[23] Y. P. Yi, V. Coropceanu, and J. L. Bredas, “Exciton-Dissociation and Charge-Recombination Processes in Pentacene/C-60 Solar Cells: Theoretical Insight into the Impact of Interface Geometry,” J. Am. Chem. Soc., 131, 15777 (2009).
[24] R. Sokel and R. C. Hughes, “Numerical analysis of transient photoconductivity in insulators,” J. Appl. Phys., 53, 7414 (1982).
[25] L. D. Pulfry, Photovoltaic Power Generation. (Van Nostrand Reinhold Co., New York, 1978).
[26] http://www.g-watt.com.tw/solar.
[27] http://news.newmaker.com.
[28] http://www.vttresearch.com/media/news.
[29] J. Tsukamoto, H. Ohigashi, K. Matsumura, and A. Takahashi, “A Schottky barrier type solar cell using polyacetylene,” Jpn. J. Appl. Phys., 20, L127 (1981).
[30] D. Kearns and M. Calvin, “Photovoltaic Effect and Photoconductivity in Laminated Organic Systems,” J. Chem. Phys., 29, 950 (1958).
[31] G. Chamberlain, “Organic solar cells: a review,” Sol. Cells, 8, 47 (1983).
[32] H. Hoppe and N. S. Sariciftci, “Organic solar cells: An overview,” J. Mater. Res., 19, 1924 (2004).
[33] C. W. Tang, “Two-layer photovoltaic cell,” Appl. Phys. Lett., 48, 183 (1986).
[34] N. S. Sariciftci, L. Smilowitz, A. J. Heeger, and F. Wudl, “Photoinduced electron transfer from a conducting polymer to buckminsterfullerene,” Science, 258, 1474 (1992).
[35] H. Kurczewska and H. Bässler, “Energy transfer across an anthracene-gold interface,” J. Lumin., 15, 261 (1977).
[36] V. Choong, Y. Park, Y. Gao, T. Wehrmeister, K. Mullen, B. R. Hsieh, and C. W. Tang, “Dramatic photoluminescence quenching of phenylene vinylene oligomer thin films upon submonolayer Ca deposition,” Appl. Phys. Lett., 69, 1492 (1996).
[37] V.-E. Choong, Y. Park, Y. Gao, B. R. Hsieh, and C. W. Tang, “Metal induced photoluminescence quenching of a phenylene vinylene oligomer and its recovery,” Macromol. Symp., 125, 83 (1997).
[38] K. Kuhnke, R. Becker, M. Epple, and K. Kern, “C60 exciton quenching near metal surfaces,” Phys. Rev. Lett., 79, 3246 (1997).
[39] K. Petritsch and R. H. Friend, “Ultrathin organic photovoltaic devices,” Synth. Met., 102, 976 (1999).
[40] D. F. O'Brien, M. A. Baldo, M. E. Thompson, and S. R. Forrest, “Improved energy transfer in electrophosphorescent devices,” Appl. Phys. Lett., 74, 442 (1999).
[41] P. Peumans, V. Bulovic, and S. R. Forrest, “Efficient photon harvesting at high optical intensities in ultrathin organic double-heterostructure photovoltaic diodes,” Appl. Phys. Lett., 76, 2650 (2000).
[42] M. Y. Chan, S. L. Lai, K. M. Lau, C. S. Lee, and S. T. Lee, “Application of metal-doped organic layer both as exciton blocker and optical spacer for organic photovoltaic devices,” Appl. Phys. Lett., 89, 163515 (2006).
[43] Z. R. Hong, Z. H. Huang, and X. T. Zeng, “Investigation into effects of electron transporting materials on organic solar cells with copper phthalocyanine/C60 heterojunctions,” Chem. Phys. Lett., 425, 62 (2006).
[44] S.-W. Liu, C.-C. Lee, C.-F. Lin, J.-C. Huang, C.-T. Chen, and J.-H. Lee, “4-Hydroxy-8-methyl-1,5-naphthyridine aluminium chelate: a morphologically stable and efficient exciton-blocking material for organic photovoltaics with prolonged lifetime,” J. Mater. Chem., 20, 7800 (2010).
[45] J. Huang, J. Yu, H. Lin, and Y. Jiang, “Detailed analysis of bathocuproine layer for organic solar cells based on copper phthalocyanine and C60,” J. Appl. Phys., 105, 073105 (2009).
[46] M. Vogel, S. Doka, C. Breyer, M. C. Lux-Steiner, and K. Fostiropoulos, “On the function of a bathocuproine buffer layer in organic photovoltaic cells,” Appl. Phys. Lett., 89, 163501 (2006).
[47] H. Gommans, B. Verreet, B. P. Rand, R. Muller, J. Poortmans, P. Heremans, and J. Genoe, “On the Role of Bathocuproine in Organic Photovoltaic Cells,” Adv. Funct. Mater., 18, 3686 (2008).
[48] J. Yu, N. Wang, Y. Zang, and Y. Jiang, “Organic photovoltaic cells based on TPBi as a cathode buffer layer,” Sol. Energy Mater. Sol. Cells, 95, 664 (2011).
[49] J. Y. Kim, S. H. Kim, H. H. Lee, K. Lee, W. Ma, X. Gong, and A. J. Heeger, “New Architecture for High-Efficiency Polymer Photovoltaic Cells Using Solution-Based Titanium Oxide as an Optical Spacer,” Adv. Mater., 18, 572 (2006).
[50] J. Gilot, I. Barbu, M. M. Wienk, and R. A. J. Janssen, “The use of ZnO as optical spacer in polymer solar cells: Theoretical and experimental study,” Appl. Phys. Lett., 91, 113520 (2007).
[51] J. J. M. Halls, C. A. Walsh, N. C. Greenham, E. A. Marseglia, R. H. Friend, S. C. Moratti, and A. B. Holmes, “Efficient photodiodes from interpenetrating polymer networks,” Nature, 376, 498 (1995).
[52] T. Tsuzuki, Y. Shirota, J. Rostalski, and D. Meissner, “The effect of fullerene doping on photoelectric conversion using titanyl phthalocyanine and a perylene pigment,” Sol. Energy Mater. Sol. Cells, 61, 1 (2000).
[53] S. Uchida, J. Xue, B. P. Rand, and S. R. Forrest, “Organic small molecule solar cells with a homogeneously mixed copper phthalocyanine: C60 active layer,” Appl. Phys. Lett., 84, 4218 (2004).
[54] P. Peumans, S. Uchida, and S. R. Forrest, “Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films,” Nature, 425, 158 (2003).
[55] K. Pankaj and et al., “A model for the current–voltage characteristics of organic bulk heterojunction solar cells,” J. Phys. Appl. Phys., 42, 055102 (2009).
[56] D. Wynands, B. Mannig, M. Riede, K. Leo, E. Brier, E. Reinold, and P. Bauerle, “Organic thin film photovoltaic cells based on planar and mixed heterojunctions between fullerene and a low bandgap oligothiophene,” J. Appl. Phys., 106 (2009).
[57] J. Xue, B. P. Rand, S. Uchida, and S. R. Forrest, “A hybrid planar-mixed molecular heterojunction photovoltaic cell,” Adv. Mater., 17, 66 (2005).
[58] M. Hiramoto, H. Fujiwara, and M. Yokoyama, “Three-layered organic solar cell with a photoactive interlayer of codeposited pigments,” Appl. Phys. Lett., 58, 1062 (1991).
[59] M. Hiramoto, H. Fujiwara, and M. Yokoyama, “p-i-n like behavior in three-layered organic solar cells having a co-deposited interlayer of pigments,” J. Appl. Phys., 72, 3781 (1992).
[60] M. Hiramoto, M. Suezaki, and M. Yokoyama, “Effect of thin gold interstitial-layer on the photovoltaic properties of tandem organic solar cell,” Chem. Lett., 19, 327 (1990).
[61] X. Che, X. Xiao, J. D. Zimmerman, D. Fan, and S. R. Forrest, “High-Efficiency, Vacuum-Deposited, Small-Molecule Organic Tandem and Triple-Junction Photovoltaic Cells,” Advanced Energy Materials, 4, n/a (2014).
[62] S. M. Menke and R. J. Holmes, “Exciton diffusion in organic photovoltaic cells,” Energy Environ. Sci., 7, 499 (2014).
[63] T. Ameri, P. Khoram, J. Min, and C. J. Brabec, “Organic ternary solar cells: a review,” Adv. Mater., 25, 4245 (2013).
[64] B. P. Rand, J. Xue, F. Yang, and S. R. Forrest, “Organic solar cells with sensitivity extending into the near infrared,” Appl. Phys. Lett., 87, 233508 (2005).
[65] S. L. Lai, M. F. Lo, M. Y. Chan, C. S. Lee, and S. T. Lee, “Impact of dye interlayer on the performance of organic photovoltaic devices,” Appl. Phys. Lett., 95, 153303 (2009).
[66] T. Goh, J.-S. Huang, E. A. Bielinski, B. A. Thompson, S. Tomasulo, M. L. Lee, M. Y. Sfeir, N. Hazari, and A. D. Taylor, “Coevaporated Bisquaraine Inverted Solar Cells: Enhancement Due to Energy Transfer and Open Circuit Voltage Control,” ACS Photonics, 2, 86 (2015).
[67] H. Cha, D. S. Chung, S. Y. Bae, M.-J. Lee, T. K. An, J. Hwang, K. H. Kim, Y.-H. Kim, D. H. Choi, and C. E. Park, “Complementary Absorbing Star-Shaped Small Molecules for the Preparation of Ternary Cascade Energy Structures in Organic Photovoltaic Cells,” Adv. Funct. Mater., 23, 1556 (2013).
[68] G. Zhang, W. Li, B. Chu, L. Chen, F. Yan, J. Zhu, Y. Chen, and C. S. Lee, “Cascade-energy-level alignment based organic photovoltaic cells by utilizing copper phthalocyanine as bipolar carrier transporting layer,” Appl. Phys. Lett., 94, 143302 (2009).
[69] Y. Zhou, T. Taima, T. Kuwabara, and K. Takahashi, “Efficient small-molecule photovoltaic cells using a crystalline diindenoperylene film as a nanostructured template,” Adv Mater, 25, 6069 (2013).
[70] B. Verreet, K. Cnops, D. Cheyns, P. Heremans, A. Stesmans, G. Zango, C. G. Claessens, T. Torres, and B. P. Rand, “Decreased Recombination Through the Use of a Non-Fullerene Acceptor in a 6.4% Efficient Organic Planar Heterojunction Solar Cell,” Advanced Energy Materials, 4, 1301413 (2014).
[71] O. L. Griffith and S. R. Forrest, “Exciton management in organic photovoltaic multidonor energy cascades,” Nano Lett, 14, 2353 (2014).
[72] K. Cnops, B. P. Rand, D. Cheyns, B. Verreet, M. A. Empl, and P. Heremans, “8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer,” Nature communications, 5, 3406 (2014).
[73] S. M. Menke and R. J. Holmes, “Energy-cascade organic photovoltaic devices incorporating a host-guest architecture,” ACS applied materials & interfaces, 7, 2912 (2015).
[74] W. A. Luhman and R. J. Holmes, “Investigation of Energy Transfer in Organic Photovoltaic Cells and Impact on Exciton Diffusion Length Measurements,” Adv. Funct. Mater., 21, 764 (2011).
[75] R. Flamini, A. Marrocchi, and A. Spalletti, “Quantitative cascade energy transfer in semiconductor thin films,” Photochemical & Photobiological Sciences, 13, 1031 (2014).
[76] J. Wagner, M. Gruber, A. Hinderhofer, A. Wilke, B. Bröker, J. Frisch, P. Amsalem, A. Vollmer, A. Opitz, N. Koch, F. Schreiber, and W. Brütting, “High Fill Factor and Open Circuit Voltage in Organic Photovoltaic Cells with Diindenoperylene as Donor Material,” Adv. Funct. Mater., 20, 4295 (2010).
[77] U. Hörmann, C. Lorch, A. Hinderhofer, A. Gerlach, M. Gruber, J. Kraus, B. Sykora, S. Grob, T. Linderl, A. Wilke, A. Opitz, R. Hansson, A. S. Anselmo, Y. Ozawa, Y. Nakayama, H. Ishii, N. Koch, E. Moons, F. Schreiber, and W. Brütting, “Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells,” The Journal of Physical Chemistry C, 118, 26462 (2014).
[78] C. Lungenschmied, G. Dennler, H. Neugebauer, S. N. Sariciftci, M. Glatthaar, T. Meyer, and A. Meyer, “Flexible, long-lived, large-area, organic solar cells,” Sol. Energy Mater. Sol. Cells, 91, 379 (2007).
[79] S. B. Rim, R. F. Fink, J. C. Schoneboom, P. Erk, and P. Peumans, “Effect of molecular packing on the exciton diffusion length in organic solar cells,” Appl. Phys. Lett., 91, 173504 (2007).
[80] B. Leckner, “The spectral distribution of solar radiation at the earth's surface--elements of a model,” Sol. Energy, 20, 143 (1978).
[81] P. Peumans, A. Yakimov, and S. R. Forrest, “Small molecular weight organic thin-film photodetectors and solar cells,” J. Appl. Phys., 93, 3693 (2003).
[82] P. W. M. Blom, V. D. Mihailetchi, L. J. A. Koster, and D. E. Markov, “Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells,” Adv. Mater., 19, 1551 (2007).
[83] H. Ohkita, S. Cook, Y. Astuti, W. Duffy, S. Tierney, W. Zhang, M. Heeney, I. McCulloch, J. Nelson, D. D. C. Bradley, and J. R. Durrant, “Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy,” J. Am. Chem. Soc., 130, 3030 (2008).
[84] J. L. Bredas, J. E. Norton, J. Cornil, and V. Coropceanu, “Molecular Understanding of Organic Solar Cells: The Challenges,” Accounts Chem. Res., 42, 1691 (2009).
[85] A. Jannat, M. F. Rahman, and M. S. H. khan, “A Review Study of Organic Photovoltaic Cell ” Int. J. Sci. Eng. Res., 4, 1 (2013).
[86] B. P. Rand, J. Genoe, P. Heremans, and J. Poortmans, “Solar cells utilizing small molecular weight organic semiconductors,” Prog. Photovoltaics, 15, 659 (2007).
[87] C. Kulshreshtha, J. W. Choi, J.-k. Kim, W. S. Jeon, M. C. Suh, Y. Park, and J. H. Kwon, “Open-circuit voltage dependency on hole-extraction layers in planar heterojunction organic solar cells,” Appl. Phys. Lett., 99, 023308 (2011).
[88] B. Rand, D. Burk, and S. Forrest, “Offset energies at organic semiconductor heterojunctions and their influence on the open-circuit voltage of thin-film solar cells,” Phys. Rev. B, 75, 113527 (2007).
[89] J. Nelson, “Organic photovoltaic films,” Current Opinion in Solid State and Materials Science, 6, 87 (2002).
[90] D. Gupta, S. Mukhopadhyay, and K. S. Narayan, “Fill factor in organic solar cells,” Sol. Energy Mater. Sol. Cells, 94, 1309 (2010).
[91] R. Marcus, “Relation between charge transfer absorption and fluorescence spectra and the inverted region,” The Journal of Physical Chemistry, 93, 3078 (1989).
[92] R. A. Marcus, “Electron transfer reactions in chemistry. Theory and experiment,” Reviews of Modern Physics, 65, 599 (1993).
[93] T. Ishwara, D. D. C. Bradley, J. Nelson, P. Ravirajan, I. Vanseveren, T. Cleij, D. Vanderzande, L. Lutsen, S. Tierney, M. Heeney, and I. McCulloch, “Influence of polymer ionization potential on the open-circuit voltage of hybrid polymer/TiO[sub 2] solar cells,” Appl. Phys. Lett., 92, 053308 (2008).
[94] S. Gélinas, O. Paré-Labrosse, C.-N. Brosseau, S. Albert-Seifried, C. R. McNeill, K. R. Kirov, I. A. Howard, R. Leonelli, R. H. Friend, and C. Silva, “The Binding Energy of Charge-Transfer Excitons Localized at Polymeric Semiconductor Heterojunctions,” The Journal of Physical Chemistry C, 115, 7114 (2011).
[95] M. J. Kendrick, A. Neunzert, M. M. Payne, B. Purushothaman, B. D. Rose, J. E. Anthony, M. M. Haley, and O. Ostroverkhova, “Formation of the Donor–Acceptor Charge-Transfer Exciton and Its Contribution to Charge Photogeneration and Recombination in Small-Molecule Bulk Heterojunctions,” The Journal of Physical Chemistry C, 116, 18108 (2012).
[96] A. Najari, P. Berrouard, C. Ottone, M. Boivin, Y. Zou, D. Gendron, W.-O. Caron, P. Legros, C. N. Allen, S. Sadki, and M. Leclerc, “High Open-Circuit Voltage Solar Cells Based on New Thieno[3,4-c]pyrrole-4,6-dione and 2,7-Carbazole Copolymers,” Macromolecules, 45, 1833 (2012).
[97] H. van Eersel, R. A. J. Janssen, and M. Kemerink, “Mechanism for Efficient Photoinduced Charge Separation at Disordered Organic Heterointerfaces,” Adv. Funct. Mater., 22, 2700 (2012).
[98] K. Vandewal, Z. Ma, J. Bergqvist, Z. Tang, E. Wang, P. Henriksson, K. Tvingstedt, M. R. Andersson, F. Zhang, and O. Inganäs, “Quantification of Quantum Efficiency and Energy Losses in Low Bandgap Polymer:Fullerene Solar Cells with High Open-Circuit Voltage,” Adv. Funct. Mater., 22, 3480 (2012).
[99] A. E. Jailaubekov, A. P. Willard, J. R. Tritsch, W. L. Chan, N. Sai, R. Gearba, L. G. Kaake, K. J. Williams, K. Leung, P. J. Rossky, and X. Y. Zhu, “Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics,” Nat Mater, 12, 66 (2013).
[100] Y. Yi, V. Coropceanu, and J.-L. Brédas, “Exciton-dissociation and charge-recombination processes in pentacene/C60 solar cells: theoretical insight into the impact of interface geometry,” J. Am. Chem. Soc., 131, 15777 (2009).
[101] D. Veldman, S. C. J. Meskers, and R. A. J. Janssen, “The Energy of Charge-Transfer States in Electron Donor-Acceptor Blends: Insight into the Energy Losses in Organic Solar Cells,” Adv. Funct. Mater., 19, 1939 (2009).
[102] D. Veldman, O. Ipek, S. C. Meskers, J. r. Sweelssen, M. M. Koetse, S. C. Veenstra, J. M. Kroon, S. S. v. Bavel, J. Loos, and R. A. Janssen, “Compositional and electric field dependence of the dissociation of charge transfer excitons in alternating polyfluorene copolymer/fullerene blends,” J. Am. Chem. Soc., 130, 7721 (2008).
[103] K. Tvingstedt, K. Vandewal, A. Gadisa, F. Zhang, J. Manca, and O. Inganas, “Electroluminescence from charge transfer states in polymer solar cells,” J. Am. Chem. Soc., 131, 11819 (2009).
[104] K. Vandewal, A. Gadisa, W. D. Oosterbaan, S. Bertho, F. Banishoeib, I. Van Severen, L. Lutsen, T. J. Cleij, D. Vanderzande, and J. V. Manca, “The Relation Between Open‐Circuit Voltage and the Onset of Photocurrent Generation by Charge‐Transfer Absorption in Polymer: Fullerene Bulk Heterojunction Solar Cells,” Adv. Funct. Mater., 18, 2064 (2008).
[105] K. Vandewal, K. Tvingstedt, A. Gadisa, O. Inganäs, and J. V. Manca, “On the origin of the open-circuit voltage of polymer–fullerene solar cells,” Nat. Mater., 8, 904 (2009).
[106] K. Vandewal, K. Tvingstedt, A. Gadisa, O. Inganäs, and J. V. Manca, “Relating the open-circuit voltage to interface molecular properties of donor:acceptor bulk heterojunction solar cells,” Phys. Rev. B, 81, 125204 (2010).
[107] X. Y. Zhu, Q. Yang, and M. Muntwiler, “Charge-Transfer Excitons at Organic Semiconductor Surfaces and Interfaces,” Accounts Chem. Res., 42, 1779 (2009).
[108] R. A. Marcus, “Electron transfer reactions in chemistry. Theory and experiment,” Reviews of Modern Physics, 65, 599 (1993).
[109] S. Fukuzumi, “Development of bioinspired artificial photosynthetic systems,” Physical Chemistry Chemical Physics, 10, 2283 (2008).
[110] U. Rau, “Reciprocity relation between photovoltaic quantum efficiency and electroluminescent emission of solar cells,” Phys. Rev. B, 76 (2007).
[111] N. Kaiser, “Review of the fundamentals of thin-film growth,” Applied optics, 41, 3053 (2002).
[112] P. Murgatroyd, “Theory of space-charge-limited current enhanced by Frenkel effect,” J. Phys. Appl. Phys., 3, 151 (1970).
[113] P. López Varo, J. A. Jiménez Tejada, J. A. López Villanueva, and M. J. Deen, “Space-charge and injection limited current in organic diodes: A unified model,” Org. Electron., 15, 2526 (2014).
[114] W. Brütting, S. Berleb, and A. G. Mückl, “Device physics of organic light-emitting diodes based on molecular materials,” Org. Electron., 2, 1 (2001).
[115] P. He, S. D. Wang, W. K. Wong, L. F. Cheng, C. S. Lee, S. T. Lee, and S. Y. Liu, “Vibrational analysis of oxygen-plasma treated indium tin oxide,” Chem. Phys. Lett., 370, 795 (2003).
[116] Y. Wang, S. W. Tong, X. F. Xu, B. Ozyilmaz, and K. P. Loh, “Interface engineering of layer-by-layer stacked graphene anodes for high-performance organic solar cells,” Adv Mater, 23, 1514 (2011).
[117] S. Sutty, G. Williams, and H. Aziz, “New insights into charge extraction and formation of the band-bending region in Schottky junction organic solar cells,” Proc. SPIE 8830, Organic Photovoltaics XIV, 8830, 88300L (2013).
[118] W.-C. Su, C.-C. Lee, S.-W. Liu, C.-F. Lin, C.-C. Chou, B.-Y. Huang, and C.-W. Cheng, “Improving the performance of subphthalocyanine/C60planar heterojunction organic photovoltaic device through the insertion of molybdenum oxide anodic buffer,” Jpn. J. Appl. Phys., 53, 03CE02 (2014).
[119] F. Dinelli, M. Murgia, P. Levy, M. Cavallini, F. Biscarini, and D. M. de Leeuw, “Spatially Correlated Charge Transport in Organic Thin Film Transistors,” Phys. Rev. Lett., 92 (2004).
[120] B. O’Connor, K. H. An, K. P. Pipe, Y. Zhao, and M. Shtein, “Enhanced optical field intensity distribution in organic photovoltaic devices using external coatings,” Appl. Phys. Lett., 89, 233502 (2006).
[121] C.-C. Lee, W.-C. Su, Y.-S. Shu, W.-C. Chang, B.-Y. Huang, Y.-Z. Lee, T.-H. Su, K.-T. Chen, and S.-W. Liu, “Decoupling the optical and electrical properties of subphthalocyanine/C70bi-layer organic photovoltaic devices: improved photocurrent while maintaining a high open-circuit voltage and fill factor,” RSC Adv., 5, 5617 (2015).
[122] S. Yoo, W. Potscavagejr, B. Domercq, S. Han, T. Li, S. Jones, R. Szoszkiewicz, D. Levi, E. Riedo, and S. Marder, “Analysis of improved photovoltaic properties of pentacene/C60 organic solar cells: Effects of exciton blocking layer thickness and thermal annealing,” Solid-State Electron., 51, 1367 (2007).
[123] J. Wittmann, C. Straupe, S. Meyer, B. Lotz, P. Lang, G. Horowitz, and F. Garnier, “Sexithiophene thin films epitaxially oriented on polytetrafluoroethylene substrates: Structure and morphology,” Thin Solid Films, 311, 317 (1997).
[124] C. Lorch, R. Banerjee, C. Frank, J. Dieterle, A. Hinderhofer, A. Gerlach, and F. Schreiber, “Growth of Competing Crystal Phases of α-Sexithiophene Studied by Real-Timein SituX-ray Scattering,” The Journal of Physical Chemistry C, 119, 819 (2015).
[125] J. Wagner, M. Gruber, A. Wilke, Y. Tanaka, K. Topczak, A. Steindamm, U. Hörmann, A. Opitz, Y. Nakayama, H. Ishii, J. Pflaum, N. Koch, and W. Brütting, “Identification of different origins for s-shaped current voltage characteristics in planar heterojunction organic solar cells,” J. Appl. Phys., 111, 054509 (2012).
[126] S. Pfuetzner, J. Meiss, A. Petrich, M. Riede, and K. Leo, “Improved bulk heterojunction organic solar cells employing C70 fullerenes,” Appl. Phys. Lett., 94, 223307 (2009).
[127] J. Sakai, T. Taima, T. Yamanari, and K. Saito, “Annealing effect in the sexithiophene:C70 small molecule bulk heterojunction organic photovoltaic cells,” Sol. Energy Mater. Sol. Cells, 93, 1149 (2009).
[128] J. Nelson, J. Kirkpatrick, and P. Ravirajan, “Factors limiting the efficiency of molecular photovoltaic devices,” Phys. Rev. B, 69, 035337 (2004).
[129] J. C. Wang, X. C. Ren, S. Q. Shi, C. W. Leung, and P. K. L. Chan, “Charge accumulation induced S-shape J–V curves in bilayer heterojunction organic solar cells,” Org. Electron., 12, 880 (2011).
[130] W. Tress, A. Petrich, M. Hummert, M. Hein, K. Leo, and M. Riede, “Imbalanced mobilities causing S-shaped IV curves in planar heterojunction organic solar cells,” Appl. Phys. Lett., 98, 063301 (2011).