Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-28T19:33:31.613Z Has data issue: false hasContentIssue false
  • English
  • Français

The essence and efficiency limits of bulk-heterostructure organic solar cells: A polymer-to-panel perspective

Published online by Cambridge University Press:  07 February 2013

Muhammad A. Alam ,
Biwajit Ray ,
Mohammad Ryyan Khan  and
Sourabh Dongaonkar
Muhammad A. Alam*
Affiliation:
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906
Biwajit Ray
Affiliation:
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906
Mohammad Ryyan Khan
Affiliation:
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906
Sourabh Dongaonkar
Affiliation:
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906
*
a)Address all correspondence to this author. e-mail: alam@purdue.edu
Get access

Abstract

Bulk-heterojunction organic photovoltaic (BHJ-OPV) technology promises high efficiency at ultralow cost and weight, with potential for nontraditional applications such as building-integrated photovoltaic (PV). There is a widespread presumption that the complexity of morphology makes carrier transport in OPV irreducibly complicated and, possibly, beyond predictive modeling. However, understanding the complex morphology is important because it not only dictates cell efficiency but also the panel performance and the operating lifetime. In this paper, we derive the fundamental thermodynamic as well as morphology-specific practical limits of BHJ-OPV efficiency and lifetime. We find that performance improvement relies not only on morphology engineering but also on increasing the effective mobility–lifetime (μτ) product, the cross-gap between donor/acceptors, and reducing the series resistance. Even if the OPV fails to achieve the highest efficiency anticipated by the thermodynamic limit, its novel form factor, lightweight, and transparency can make it a commercially viable option for many applications.

Type
Invited Feature Paper
Information
Journal of Materials Research , Volume 28 , Issue 4 , 28 February 2013 , pp. 541 - 557
Copyright
Copyright © Materials Research Society 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1.Yu, G., Gao, J., Hummelen, J.C., Wudl, F., and Heeger, A.J.: Polymer photovoltaic cells: Enhanced efficiencies via a network of internal donor-acceptor heterojunctions. Science 270, 1789–1791 (1995).CrossRefGoogle Scholar
2.Forrest, S.R.: The limits to organic photovoltaic cell efficiency. MRS Bull. 30, 28–32 (2005).CrossRefGoogle Scholar
3.Krebs, F.C., Gevorgyan, S.A., and Alstrup, J.: A roll-to-roll process to flexible polymer solar cells: Model studies, manufacture and operational stability studies. J. Mater. Chem. 19, 5442–5451 (2009).CrossRefGoogle Scholar
4.Brabec, C.J., Gowrisanker, S., Halls, J.J.M., Laird, D., Jia, S., and Williams, S.P.: Polymer–fullerene bulk‐heterojunction solar cells. Adv. Mater. 22, 3839–3856 (2010).CrossRefGoogle ScholarPubMed
5.Nelson, J.: Polymer: Fullerene bulk heterojunction solar cells. Mater. Today 14, 462 (2011).CrossRefGoogle Scholar
6.Liang, Y. and Yu, L.: A new class of semiconducting polymers for bulk heterojunction solar cells with exceptionally high performance. Acc. Chem. Res. 43, 1227–1236 (2010).CrossRefGoogle ScholarPubMed
7.Park, S.H., Roy, A., Beaupre, S., Cho, S., Coates, N., Moon, J.S., Moses, D., Leclerc, M., Lee, K., and Heeger, A.J.: Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nat. Photonics 3, 297–302 (2009).CrossRefGoogle Scholar
8.Shaheen, S.E., Brabec, C.J., Sariciftci, N.S., Padinger, F., Fromherz, T., and Hummelen, J.C.: 2.5% efficient organic plastic solar cells. Appl. Phys. Lett. 78, 841–843 (2001).CrossRefGoogle Scholar
9.Padinger, F., Rittberger, R.S., and Sariciftci, N.S.: Effects of postproduction treatment on plastic solar cells. Adv. Funct. Mater. 13, 85–88 (2003).CrossRefGoogle Scholar
10.Li, G., Shrotriya, V., Huang, J.S., Yao, Y., Moriarty, T., Emery, K., and Yang, Y.: High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends. Nat. Mater. 4, 864–868 (2005).CrossRefGoogle Scholar
11.Ma, W., Yang, C., Gong, X., Lee, K., and Heeger, A.J.: Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology. Adv. Funct. Mater. 15, 1617–1622 (2005).CrossRefGoogle Scholar
12.Blom, P.W.M., Mihailetchi, V.D., Koster, L.J.A., and Markov, D.E.: Device physics of polymer: Fullerene bulk heterojunction solar cells. Adv. Mater. 19, 1551–1566 (2007).CrossRefGoogle Scholar
13.Deibel, C. and Dyakonov, V.: Polymer-fullerene bulk heterojunction solar cells. Rep. Prog. Phys. 73, 096401 (2010).CrossRefGoogle Scholar
14.Gregg, B.A.: Excitonic solar cells. J. Phys. Chem. B 107, 4688–4698 (2003).CrossRefGoogle Scholar
15.Kirchartz, T., Taretto, K., and Rau, U.: Efficiency limits of organic bulk heterojunction solar cells. J. Phys. Chem. C 113, 17958–17966 (2009).CrossRefGoogle Scholar
16.Mayer, A.C., Toney, M.F., Scully, S.R., Rivnay, J., Brabec, C.J., Scharber, M., Koppe, M., Heeney, M., McCulloch, I., and McGehee, M.D.: Bimolecular crystals of fullerenes in conjugated polymers and the implications of molecular mixing for solar cells. Adv. Funct. Mater. 19, 1173–1179 (2009).CrossRefGoogle Scholar
17.Ray, B., Nair, P.R., and Alam, M.A.: Annealing dependent performance of organic bulk-heterojunction solar cells: A theoretical perspective. Solar Energy Mater. Solar Cells 95, 3287–3294 (2011).CrossRefGoogle Scholar
18.Sze, S.M.: Physics of Semiconductor Devices (John Wiley & Sons, New York, NY, 1981).Google Scholar
19.Giebink, N.C., Wiederrecht, G.P., Wasielewski, M.R., and Forrest, S.R.: Thermodynamic efficiency limit of excitonic solar cells. Phys. Rev. B 83, 195326 (2011).CrossRefGoogle Scholar
20.Pensack, R.D. and Asbury, J.B.: Beyond the adiabatic limit: Charge photogeneration in organic photovoltaic materials. J. Phys. Chem. Lett. 1, 2255–2263 (2010).CrossRefGoogle Scholar
21.Servaites, J.D., Ratner, M.A., and Marks, T.J.: Practical efficiency limits in organic photovoltaic cells: Functional dependence of fill factor and external quantum efficiency. Appl. Phys. Lett. 95, 163302-3 (2009).CrossRefGoogle Scholar
22.Li, J., Ray, B., Alam, M.A., and Östling, M.: Threshold of hierarchical percolating systems. Phys. Rev. E 85, 021109 (2012).CrossRefGoogle ScholarPubMed
23.Lifshitz, I.M. and Slyozov, V.V.: The kinetics of precipitation from supersaturated solid solutions. J. Phys. Chem. Solids 19, 35–50 (1961).CrossRefGoogle Scholar
24.Ray, B. and Alam, M.A.: A compact physical model for morphology induced intrinsic degradation of organic bulk heterojunction solar cell. Appl. Phys. Lett. 99, 033303-3 (2011).CrossRefGoogle Scholar
25.Ray, B., Lundstrom, M.S., and Alam, M.A.: Can morphology tailoring improve the open circuit voltage of organic solar cells? Appl. Phys. Lett. 100, 013307–013307-3 (2012).CrossRefGoogle Scholar
26.Ray, B. and Alam, M.A.: Random vs regularized OPV: Limits of performance gain of organic bulk heterojunction solar cells by morphology engineering. Solar Energy Mater. Solar Cells 99, 204–212 (2012).CrossRefGoogle Scholar
27.Dongaonkar, S., Servaites, J.D., Ford, G.M., Loser, S., Moore, J., Gelfand, R.M., Mohseni, H., Hillhouse, H.W., Agrawal, R., Ratner, M.A., Marks, T.J., Lundstrom, M.S., and Alam, M.A.: Universality of non-ohmic shunt leakage in thin-film solar cells. J. Appl. Phys. 108, 124509 (2010).CrossRefGoogle Scholar
28.Shockley, W. and Queisser, H.J.: Detailed balance limit of efficiency of p-n junction solar cells. J. Appl. Phys. 32, 510–519 (1961).CrossRefGoogle Scholar
29.Polman, A. and Atwater, H.A.: Photonic design principles for ultrahigh-efficiency photovoltaics. Nat. Mater. 11, 174–177 (2012).CrossRefGoogle ScholarPubMed
30.Khan, M.R. and Alam, M.A.: Fundamentals of PV efficiency interpreted by a two-level model. Am. J. Phys. (2012, accepted).Google Scholar
31.Hirst, L.C. and Ekins‐Daukes, N.J.: Fundamental losses in solar cells. Prog. Photovoltaics Res. Appl. 19, 286–293 (2011).CrossRefGoogle Scholar
32.Green, M.A.: Analytical treatment of Trivich–Flinn and Shockley–Queisser photovoltaic efficiency limits using polylogarithms. Prog. Photovoltaics Res. Appl. 20, 127–134 (2012).CrossRefGoogle Scholar
33.Tress, W., Petrich, A., Hummert, M., Hein, M., Leo, K., and Riede, M.: Imbalanced mobilities causing S-shaped IV curves in planar heterojunction organic solar cells. Appl. Phys. Lett. 98, 063301–063301-3 (2011).CrossRefGoogle Scholar
34.Rand, B.P., Burk, D.P., and Forrest, S.R.: Offset energies at organic semiconductor heterojunctions and their influence on the open-circuit voltage of thin-film solar cells. Phys. Rev. B 75, 115327 (2007).CrossRefGoogle Scholar
35.Scharber, M.C., Mühlbacher, D., Koppe, M., Denk, P., Waldauf, C., Heeger, A.J., and Brabec, C.J.: Design rules for donors in bulk-heterojunction solar cells—towards 10 % energy-conversion efficiency. Adv. Mater. 18, 789–794 (2006).CrossRefGoogle Scholar
36.Koster, L.J.A., Smits, E.C.P., Mihailetchi, V.D., and Blom, P.W.M.: Device model for the operation of polymer/fullerene bulk heterojunction solar cells. Phys. Rev. B 72, 085205 (2005).CrossRefGoogle Scholar
37.Clarke, T.M. and Durrant, J.R.: Charge photogeneration in organic solar cells. Chem. Rev. 110, 6736–6767 (2010).CrossRefGoogle ScholarPubMed
38.Sylvester-Hvid, K.O., Rettrup, S., and Ratner, M.A.: Two-dimensional model for polymer-based photovoltaic cells: Numerical simulations of morphology effects. J. Phys. Chem. B 108, 4296–4307 (2004).CrossRefGoogle Scholar
39.Giebink, N.C., Wiederrecht, G.P., Wasielewski, M.R., and Forrest, S.R.: Ideal diode equation for organic heterojunctions. I. Derivation and application. Phys. Rev. B 82, 155305 (2010).CrossRefGoogle Scholar
40.Zhu, X. and Kahn, A.: Electronic structure and dynamics at organic donor/acceptor interfaces. MRS Bull. 35, 443–448 (2010).CrossRefGoogle Scholar
41.van Bavel, S.S., Sourty, E., de With, G., and Loos, J.: Three-dimensional nanoscale organization of bulk heterojunction polymer solar cells. Nano Lett. 19, 507–513 (2009).CrossRefGoogle Scholar
42.Andersson, B.V., Herland, A., Masich, S., and Inganäs, O.: Imaging of the 3D nanostructure of a polymer solar cell by electron tomography. Nano Lett. 9, 853–855 (2009).CrossRefGoogle ScholarPubMed
43.Chen, W., Xu, T., He, F., Wang, W., Wang, C., Strzalka, J., Liu, Y., Wen, J., Miller, D.J., Chen, J., Hong, K., Yu, L., and Darling, S.B.: Hierarchical nanomorphologies promote exciton dissociation in polymer/fullerene bulk heterojunction solar cells. Nano Lett. 11, 3707–3713 (2011).CrossRefGoogle ScholarPubMed
44.de Gennes, P.G.: Dynamics of fluctuations and spinodal decomposition in polymer blends. J. Chem. Phys. 72, 4756–4763 (1980).CrossRefGoogle Scholar
45.Balluffi, R.W., Allen, S.M., Carter, W.C., and Kemper, R.A.: Kinetics of Materials (Wiley-Interscience, Hoboken, NJ, 2005).CrossRefGoogle Scholar
46.Jones, R.A.L.: Soft Condensed Matter (Oxford University Press, Oxford, New York, 2002).CrossRefGoogle Scholar
47.Wodo, O. and Ganapathysubramanian, B.: Modeling morphology evolution during solvent-based fabrication of organic solar cells. Comput. Mater. Sci. 55, 113–126 (2012).CrossRefGoogle Scholar
48.Shang, Y., Kazmer, D., Wei, M., Mead, J., and Barry, C.: Numerical simulation of phase separation of immiscible polymer blends on a heterogeneously functionalized substrate. J. Chem. Phys. 128, 224909-7 (2008).CrossRefGoogle ScholarPubMed
49.Chen, D., Liu, F., Wang, C., Nakahara, A., and Russell, T.P.: Bulk heterojunction photovoltaic active layers via bilayer interdiffusion. Nano Lett. 11, 2071–2078 (2011).CrossRefGoogle ScholarPubMed
50.Peumans, P., Uchida, S., and Forrest, S.R.: Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films. Nature 425, 158–162 (2003).CrossRefGoogle ScholarPubMed
51.Collins, B.A., Cochran, J.E., Yan, H., Gann, E., Hub, C., Fink, R., Wang, C., Schuettfort, T., McNeill, C.R., Chabinyc, M.L., and Ade, H.: Polarized x-ray scattering reveals non-crystalline orientational ordering in organic films. Nat. Mater. 11, 536–543 (2012).CrossRefGoogle ScholarPubMed
52.Liu, F., Gu, Y., Jung, J.W., Jo, W.H., and Russell, T.P.: On the morphology of polymer‐based photovoltaics. J. Polym. Sci., Part B: Polym. Phys. 50, 1018–1044 (2012).CrossRefGoogle Scholar
53.Ruderer, M.A. and Müller-Buschbaum, P.: Morphology of polymer-based bulk heterojunction films for organic photovoltaics. Soft Matter. 7, 5482–5493 (2011).CrossRefGoogle Scholar
54.Hou, L., Wang, E., Bergqvist, J., Andersson, B.V., Wang, Z., Müller, C., Campoy‐Quiles, M., Andersson, M.R., Zhang, F., and Inganäs, O.: Lateral phase separation gradients in spin‐coated thin films of high‐performance polymer: Fullerene photovoltaic blends. Adv. Funct. Mater. 21, 3169–3175 (2011).CrossRefGoogle Scholar
55.Li, L., Hu, W., Fuchs, H., and Chi, L.: Controlling molecular packing for charge transport in organic thin films. Adv. Energy Mater. 1, 188–193 (2011).CrossRefGoogle Scholar
56.Schäfer, S., Petersen, A., Wagner, T.A., Kniprath, R., Lingenfelser, D., Zen, A., Kirchartz, T., Zimmermann, B., Würfel, U., Feng, X., and Mayer, T.: Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells. Phys. Rev. B 83, 165311 (2011).CrossRefGoogle Scholar
57.Voroshazi, E., Verreet, B., Aernouts, T., and Heremans, P.: Long-term operational lifetime and degradation analysis of P3HT: PCBM photovoltaic cells. Solar Energy Mater. Solar Cells 95, 1303–1307 (2011).CrossRefGoogle Scholar
58.Seemann, A., Egelhaaf, H.J., Brabec, C.J., and Hauch, J.A.: Influence of oxygen on semi-transparent organic solar cells with gas permeable electrodes. Org. Electron. 19, 1424–1428 (2009).CrossRefGoogle Scholar
59.Krebs, F.C.: Degradation and stability of polymer and organic solar cells. Solar Energy Mater. Solar Cells 92, 685 (2008).CrossRefGoogle Scholar
60.Bhattacharya, J., Mayer, R.W., Samiee, M., and Dalal, V.L.: Photo-induced changes in fundamental properties of organic solar cells. Appl. Phys. Lett. 100, 193501–193501-3 (2012).CrossRefGoogle Scholar
61.Renz, J.A., Keller, T., Schneider, M., Shokhovets, S., Jandt, K.D., Gobsch, G., and Hoppe, H.: Multiparametric optimization of polymer solar cells: A route to reproducible high efficiency. Solar Energy Mater. Solar Cells 93, 508–513 (2009).CrossRefGoogle Scholar
62.Stauffer, D. and Aharony, A.: Introduction to Percolation Theory (CRC Press, Boca Raton, FL, 1994).Google Scholar
63.Mark, J.E.: Physical Properties of Polymers Handbook (Springer, New York, NY, 2006).Google Scholar
64.Chen, F-C., Ko, C-J., Wu, J-L., and Chen, W-C.: Morphological study of P3HT: PCBM blend films prepared through solvent annealing for solar cell applications. Solar Energy Mater. Solar Cells 94, 2426–2430 (2010).CrossRefGoogle Scholar
65.Martens, T., D’Haen, J., Munters, T., Beelen, Z., Goris, L., Manca, J., D’Olieslaeger, M., Vanderzande, D., De Schepper, L., and Andriessen, R.: Disclosure of the nanostructure of MDMO-PPV: PCBM bulk hetero-junction organic solar cells by a combination of SPM and TEM. Synth. Met. 138, 243–247 (2003).CrossRefGoogle Scholar
66.Miller, N.C., Sweetnam, S., Hoke, E.T., Gysel, R., Miller, C.E., Bartelt, J.A., Xie, X., Toney, M.F., and McGehee, M.D.: Molecular packing and solar cell performance in blends of polymers with a bisadduct fullerene. Nano Lett. 12, 1566–1570 (2012).Google Scholar
67.Zeng, L., Tang, C.W., and Chen, S.H.: Effects of active layer thickness and thermal annealing on polythiophene: Fullerene bulk heterojunction photovoltaic devices. Appl. Phys. Lett. 97, 053305-3 (2010).CrossRefGoogle Scholar
68.Meng, L., Shang, Y., Li, Q., Li, Y., Zhan, X., Shuai, Z., Kimber, R.G.E., and Walker, A.B.: Dynamic Monte Carlo simulation for highly efficient polymer blend photovoltaics. J. Phys. Chem. B 114, 36–41 (2010).CrossRefGoogle ScholarPubMed
69.Coffey, D.C., Ferguson, A.J., Kopidakis, N., and Rumbles, G.: Photovoltaic charge generation in organic semiconductors based on long-range energy transfer. ACS Nano 4, 5437–5445 (2010).CrossRefGoogle ScholarPubMed
70.Shuttle, C.G., Hamilton, R., O’Regan, B.C., Nelson, J., and Durrant, J.R.: Charge-density-based analysis of the current–voltage response of polythiophene/fullerene photovoltaic devices. Proc. Natl. Acad. Sci. U.S.A. 107, 16448–16452 (2010).CrossRefGoogle ScholarPubMed
71.Häusermann, R., Knapp, E., Moos, M., Reinke, N.A., Flatz, T., and Ruhstaller, B.: Coupled optoelectronic simulation of organic bulk-heterojunction solar cells: Parameter extraction and sensitivity analysis. J. Appl. Phys. 106, 104507–104507-9 (2009).CrossRefGoogle Scholar
72.Shah, M. and Ganesan, V.: Correlations between morphologies and photovoltaic properties of rod−coil block copolymersl. Macromolecules 43, 543–552 (2010).CrossRefGoogle Scholar
73.Buxton, G.A. and Clarke, N.: Predicting structure and property relations in polymeric photovoltaic devices. Phys. Rev. B 74, 085207 (2006).CrossRefGoogle Scholar
74.Dutta, P., Xie, Y., Kumar, M., Rathi, M., Ahrenkiel, P., Galipeau, D., Qiao, Q., and Bommisetty, V.: Connecting physical properties of spin-casting solvents with morphology, nanoscale charge transport, and device performance of poly(3-hexylthiophene): Phenyl-C61-butyric acid methyl ester bulk heterojunction solar cells. J. Photonics Energy 1, 011124–011124-17 (2011).CrossRefGoogle Scholar
75.Geens, W., Martens, T., Poortmans, J., Aernouts, T., Manca, J., Lutsen, L., Heremans, P., Borghs, S., Mertens, R., and Vanderzande, D.: Modelling the short-circuit current of polymer bulk heterojunction solar cells. Thin Solid Films 451–452, 498–502 (2004).CrossRefGoogle Scholar
76.Wodo, O., Tirthapura, S., Chaudhary, S., and Ganapathysubramanian, B.: A graph-based formulation for computational characterization of bulk heterojunction morphology. Org. Electron. 13, 1105–1113 (2012).CrossRefGoogle Scholar
77.Lei, B., Yao, Y., Kumar, A., Yang, Y., and Ozolins, V.: Quantifying the relation between the morphology and performance of polymer solar cells using Monte Carlo simulations. J. Appl. Phys. 104, 024504-6 (2008).CrossRefGoogle Scholar
78.Monestier, F., Simon, J-J., Torchio, P., Escoubas, L., Flory, F., Bailly, S., de Bettignies, R., Guillerez, S., and Defranoux, C.: Modeling the short-circuit current density of polymer solar cells based on P3HT: PCBM blend. Solar Energy Mater. Solar Cells 91, 405–410 (2007).CrossRefGoogle Scholar
79.Maturovaá, K., van Bavel, S.S., Wienk, M.M., Janssen, R.A.J., and Kemerink, M.: Morphological device model for organic bulk heterojunction solar cells. Nano Lett. 9, 3032–3037 (2009).CrossRefGoogle Scholar
80.Jo, J., Kim, S-S., Na, S-I., Yu, B-K., and Kim, D-Y.: Time-dependent morphology evolution by annealing processes on polymer: Fullerene blend solar cells. Adv. Funct. Mater. 19, 866–874 (2009).CrossRefGoogle Scholar
81.Wodo, O. and Ganapathysubramanian, B.: Computationally efficient solution to the Cahn–Hilliard equation: Adaptive implicit time schemes, mesh sensitivity analysis and the 3D isoperimetric problem. J. Comput. Phys. 230, 6037–6060 (2011).CrossRefGoogle Scholar
82.Street, R.A., Schoendorf, M., Roy, A., and Lee, J.H.: Interface state recombination in organic solar cells. Phys. Rev. B 81, 205307 (2010).CrossRefGoogle Scholar
83.Ray, D., Burtone, L., Leo, K., and Riede, M.: Detection of trap charge in small molecular organic bulk heterojunction solar cells. Phys. Rev. B 82, 125204 (2010).CrossRefGoogle Scholar
84.Ray, D. and Narasimhan, K.L.: Measurement of deep states in hole doped organic semiconductors. J. Appl. Phys. 103, 093711–093711-6 (2008).CrossRefGoogle Scholar
85.Nalwa, K.S., Kodali, H.K., Ganapathysubramanian, B., and Chaudhary, S.: Dependence of recombination mechanisms and strength on processing conditions in polymer solar cells. Appl. Phys. Lett. 4, 279 (2011).Google Scholar
86.Ferenczi, T.A.M., Nelson, J., Belton, C., Ballantyne, A.M., Campoy-Quiles, M., Braun, F.M., and Bradley, D.D.C.: Planar heterojunction organic photovoltaic diodes via a novel stamp transfer process. J. Phys. Condens. Matter 20, 475203 (2008).CrossRefGoogle Scholar
87.Kim, H., Shin, M., Park, J., and Kim, Y.: Effect of long time annealing and incident light intensity on the performance of polymer: Fullerene solar cells. IEEE Trans. Nanotechnol. 9, 400–406 (2010).Google Scholar
88.Uhrich, C., Wynands, D., Olthof, S., Riede, M.K., Leo, K., Sonntag, S., Maennig, B., and Pfeiffer, M.: Origin of open circuit voltage in planar and bulk heterojunction organic thin-film photovoltaics depending on doped transport layers. J. Appl. Phys. 104, 043107-6 (2008).CrossRefGoogle Scholar
89.Andersson, L.M., Müller, C., Badada, B.H., Zhang, F., Würfel, U., and Inganäs, O.: Mobility and fill factor correlation in geminate recombination limited solar cells. J. Appl. Phys. 110, 024509 (2011).CrossRefGoogle Scholar
90.Mauer, R., Howard, I.A., and Laquai, F.: Effect of nongeminate recombination on fill factor in polythiophene/methanofullerene organic solar cells. J. Phys. Chem. Lett. 1, 3500–3505 (2010).CrossRefGoogle Scholar
91.Wagner, J., Gruber, M., Wilke, A., Tanaka, Y., Topczak, K., Steindamm, A., Hörmann, U., Opitz, A., Nakayama, Y., Ishii, H., Pflaum, J., Koch, N., and Brütting, W.: Identification of different origins for s-shaped current voltage characteristics in planar heterojunction organic solar cells. J. Appl. Phys. 111, 054509–054509-12 (2012).CrossRefGoogle Scholar
92.Cowan, S.R., Banerji, N., Leong, W.L., and Heeger, A.J.: Charge formation, recombination, and sweep‐out dynamics in organic solar cells. Adv. Funct. Mater. 22, 1116–1128 (2012).CrossRefGoogle Scholar
93.Bakulin, A.A., Rao, A., Pavelyev, V.G., van Loosdrecht, P.H.M., Pshenichnikov, M.S., Niedzialek, D., Cornil, J., Beljonne, D., and Friend, R.H.: The role of driving energy and delocalized states for charge separation in organic semiconductors. Science 335, 1340–1344 (2012).CrossRefGoogle ScholarPubMed
94.Gupta, D., Mukhopadhyay, S., and Narayan, K.S.: Fill factor in organic solar cells. Solar Energy Mater. Solar Cells 94, 1309–1313 (2010).CrossRefGoogle Scholar
95.Mihailetchi, V.D., Koster, L.J.A., Hummelen, J.C., and Blom, P.W.M.: Photocurrent generation in polymer-fullerene bulk heterojunctions. Phys. Rev. Lett. 93, 216601 (2004).CrossRefGoogle ScholarPubMed
96.Limpinsel, M., Wagenpfahl, A., Mingebach, M., Deibel, C., and Dyakonov, V.: Photocurrent in bulk heterojunction solar cells. Phys. Rev. B 81, 085203 (2010).CrossRefGoogle Scholar
97.Wehenkel, D.J., Koster, L.J.A., Wienk, M.M., and Janssen, R.A.J.: Influence of injected charge carriers on photocurrents in polymer solar cells. Phys. Rev. B 85, 125203 (2012).CrossRefGoogle Scholar
98.Petersen, A., Kirchartz, T., and Wagner, T.A.: Charge extraction and photocurrent in organic bulk heterojunction solar cells. Phys. Rev. B 85, 045208 (2012).CrossRefGoogle Scholar
99.Minemawari, H., Yamada, T., Matsui, H., Tsutsumi, J., Haas, S., Chiba, R., Kumai, R., and Hasegawa, T.: Inkjet printing of single-crystal films. Nature 475, 364–367 (2011).CrossRefGoogle ScholarPubMed
100.Northrup, J.E.: Two-dimensional deformation potential model of mobility in small molecule organic semiconductors. Appl. Phys. Lett. 99, 062111–062111-3 (2011).CrossRefGoogle Scholar
101.McGehee, M.D.: Nanostructured organic-inorganic hybrid solar cells. MRS Bull. 34, 95–100 (2009).CrossRefGoogle Scholar
102.Gorodetsky, A.A., Chiu, C-Y., Schiros, T., Palma, M., Cox, M., Jia, Z., Sattler, W., Kymissis, I., Steigerwald, M., and Nuckolls, C.: Reticulated heterojunctions for photovoltaic devices. Angew. Chem. Int. Ed. 49, 7909–7912 (2010).CrossRefGoogle ScholarPubMed
103.Berson, S., de Bettignies, R., Bailly, S., Guillerez, S., and Jousselme, B.: Elaboration of P3HT/CNT/PCBM composites for organic photovoltaic cells. Adv. Funct. Mater. 17, 3363–3370 (2007).CrossRefGoogle Scholar
104.Nam, C.: Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon nanotube dispersed polythiophene-fullerene blend devices. J. Appl. Phys. 110, 064307 (2011).CrossRefGoogle Scholar
105.Allen, J.E. and Black, C.T.: Improved power conversion efficiency in bulk heterojunction organic solar cells with radial electron contacts. ACS Nano 5, 7986–7991 (2011).CrossRefGoogle ScholarPubMed
106.Hsu, M-H., Yu, P., Huang, J-H., Chang, C-H., Wu, C-W., Cheng, Y-C., and Chu, C-W.: Balanced carrier transport in organic solar cells employing embedded indium-tin-oxide nanoelectrodes. Appl. Phys. Lett. 98, 073308-3 (2011).Google Scholar
107.Bhattacharya, J., Chakravarty, N., Pattnaik, S., Dennis Slafer, W., Biswas, R., and Dalal, V.L.: A photonic-plasmonic structure for enhancing light absorption in thin film solar cells. Appl. Phys. Lett. 99, 131114–131114-3 (2011).CrossRefGoogle Scholar
108.Tada, A., Geng, Y., Wei, Q., Hashimoto, K., and Tajima, K.: Tailoring organic heterojunction interfaces in bilayer polymer photovoltaic devices. Nat. Mater. 10, 450–455 (2011).CrossRefGoogle ScholarPubMed
109.Heidel, T.D., Hochbaum, D., Sussman, J.M., Singh, V., Bahlke, M.E., Hiromi, I., Lee, J., and Baldo, M.A.: Reducing recombination losses in planar organic photovoltaic cells using multiple step charge separation. J. Appl. Phys. 109, 104502-6 (2011).CrossRefGoogle Scholar
110.Yuan, Y., Reece, T.J., Sharma, P., Poddar, S., Ducharme, S., Gruverman, A., Yang, Y., and Huang, J.: Efficiency enhancement in organic solar cells with ferroelectric polymers. Nat. Mater. 10, 296–302 (2011).CrossRefGoogle ScholarPubMed
111.Ray, B. and Alam, M.: Achieving fill factor above 80% in organic solar cells by charged interface. IEEE J. Photovoltaics 3, 1–8 (2012).Google Scholar
112.Honda, S., Ohkita, H., Benten, H., and Ito, S.: Selective dye loading at the heterojunction in polymer/fullerene solar cells. Adv. Energy Mater. 1, 588–598 (2011).CrossRefGoogle Scholar
113.Jin, H., Tao, C., Velusamy, M., Aljada, M., Zhang, Y., Hambsch, M., Burn, P.L., and Meredith, P.: Efficient, large area ITO‐and‐PEDOT‐free organic solar cell sub‐modules. Adv. Mater. 24, 2571–2577 (2012).CrossRefGoogle ScholarPubMed
114.Medford, A.J., Lilliedal, M.R., Jørgensen, M., Aarø, D., Pakalski, H., Fyenbo, J., and Krebs, F.C.: Grid-connected polymer solar panels: Initial considerations of cost, lifetime, and practicality. Opt. Express 18, A272–A285 (2010).CrossRefGoogle ScholarPubMed
115.Krebs, F.C., Gevorgyan, S.A., Gholamkhass, B., Holdcroft, S., Schlenker, C., Thompson, M.E., Thompson, B.C., Olson, D., Ginley, D.S., Shaheen, S.E., Alshareef, H.N., Murphy, J.W., Youngblood, W.J., Heston, N.C., Reynolds, J.R., Jia, S., Laird, D., Tuladhar, S.M., Dane, J.G.A., Atienzar, P., Nelson, J., Kroon, J.M., Wienk, M.M., Janssen, R.A.J., Tvingstedt, K., Zhang, F., Andersson, M., Inganäs, O., Lira-Cantu, M., de Bettignies, R., Guillerez, S., Aernouts, T., Cheyns, D., Lutsen, L., Zimmermann, B., Würfel, U., Niggemann, M., Schleiermacher, H.-F., Liska, P., Grätzel, M., Lianos, P., Katz, E.A., Lohwasser, W., and Jannon, B.: A round robin study of flexible large-area roll-to-roll processed polymer solar cell modules. Solar Energy Mater. Solar Cells 93, 1968–1977 (2009).CrossRefGoogle Scholar
116.Dongaonkar, S., Karthik, Y., Mahapatra, S., and Alam, M.A.: Physics and statistics of non-ohmic shunt conduction and metastability in amorphous silicon p–i–n solar cells. IEEE J. Photovoltaics 1, 111–117 (2011).CrossRefGoogle Scholar
117.Dongaonkar, S. and Alam, M.: End-to-end modeling for variability and reliability analysis of thin film PV. IEEE Int. Rel. Phys. Symp. (IRPS), 2012 4A.4.1–4A.4.6.Google Scholar
118.Wolden, C.A., Kurtin, J., Baxter, J.B., Repins, I., Shaheen, S.E., Torvik, J.T., Rockett, A.A., Fthenakis, V.M., and Aydil, E.S.: Photovoltaic manufacturing: Present status, future prospects, and research needs. J. Vac. Sci. Technol., A 29, 030801 (2011).CrossRefGoogle Scholar
119.Kim, K., Liu, J., Namboothiry, M.A.G., and Carroll, D.L.: Roles of donor and acceptor nanodomains in 6% efficient thermally annealed polymer photovoltaics. Appl. Phys. Lett. 90, 163511-3 (2007).Google Scholar