The polymer solar cells were fabricated by a novel solution coating process; the roller painting. The roller painted film composed of poly(3-hexylthiophene) (P3HT) and [6;6]-phenyl-C61-butyric acid methyl ester (PCBM) has smoother surface than the spin coated film. Since the roller painting is accompanied with shear and normal stresses and is also a slow drying process; the process induces effectively crystallization of P3HT and PCBM. Both crystalline P3HT and PCBM in the roller painted active layer contribute to enhanced and balanced charge carrier mobility. Consequently; the roller painting process results in higher power conversion efficiency (PCE) of 4.6% as compared to that of the spin coating (3.9%). Furthermore; the annealing-free polymer solar cell (PSC) with high PCE were fabricated by the roller painting process with addition of a small amount of 1;8-octanedithiol. Since the addition of 1;8-octanedithiol induces phase separation between P3HT and PCBM and the roller painting process induces crystallization of P3HT and PCBM; the PCE of roller painted PSC is achieved up to 3.8% without post-annealing.
[1] C. J. Brabec; N. S. Sariciftci; J. C. Hummelen; Plastic Solar Cells; Adv. Funct. Mater. 11; 2001; pp. 15-26.
doi: 10.1002/1616-3028(200102)11:1<15::AID-ADFM15>3.0.CO;2-A.
[2] G. Yu; A. J. Heeger; Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions; J. Appl. Phys. 78; 1995; pp. 4510-4515.
doi: 10.1063/1.359792.
[3] P. Schilinsky; U. Asawapirom; U. Scherf; M. Biele; C. J. Brabec; Influence of the Molecular Weight of Poly(3-hexylthiophene) on the Performance of Bulk Heterojunction Solar Cells; Chem. Mater. 17; 2005; pp. 2175-2180.
doi: 10.1021/cm047811c.
[4] Y. K. Kim; S. Cook; S. M. Tuladhar; S. A. Choulis; J. Nelson; J. R. Durrant; D. D. C. Bradley; M. Giles; I. McCulloch; C. S. Ha; M. H. Ree; A strong regioregularity effect in self-organizing conjugated polymer films and high-efficiency polythiophene:fullerene solar cells; Nat. Mater. 5; 2006; pp. 197-203.
doi: 10.1038/nmat1574.
[5] P. W. M. Blom; V. D. Mihailetchi; L. J. A. Koster; D. E. Markov; Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells; Adv. Mater. 19; 2007; pp. 1551-1566.
doi: 10.1002/adma.200601093.
[6] G. Dennler; M. C. Scharber; C. J. Brabec; Polymer-Fullerene Bulk-Heterojunction Solar Cells; Adv. Mater. 21; 2009; pp. 1323-1338.
doi: 10.1002/adma.200801283.
[7] J. W. Jung; J. U. Lee; W. H. Jo; High-Efficiency Polymer Solar Cells with Water-Soluble and Self-Doped Conducting Polyaniline Graft Copolymer as Hole Transport Layer; J. Phys. Chem. C 114; 2010; pp. 633-637.
doi: 10.1021/jp9083844.
[8] G. Li; V. Shrotriya; J. Huang; Y. Yao; T. Moriarty; K. Emery; Y. Yang; . High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends; Nat. Mater. 4; 2005; pp. 864-868.
doi: 10.1038/nmat1500.
[9] Ma; C. Yang; X. Gong; K. Lee; A. J. Heeger; Thermally Stable; Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology; Adv. Funct. Mater. 15; 2005; pp. 1617-1622.
doi: 10.1002/adfm.200500211.
[10] M. Campoy-Quiles; T. Ferenczi; T. Agostinelli; P. G. Etchegoin;Y. Kim; T. D. Anthopoulos; P. N. Stavrinou; D. D. C. Bradley; J. Nelson; Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends; Nat. Mater. 7; 2008; pp. 158-164.
doi: 10.1038/nmat2102.
[11] F. C. Krebs; Processing and preparation of polymer and organic solar cells; Sol. Energy Mater. Sol. Cells 93; 2009; pp. 394-412.
doi: 10.1016/j.solmat.2008.10.004.
[12] F. C. Krebs; Roll-to-roll fabrication of monolithic large-area polymer solar cells free from indium-tin-oxide; Sol. Energy Mater. Sol. Cells 93; 2009; pp. 1636-1641.
doi: 10.1016/j.solmat.2009.04.020.
[13] Gunes; H. Neugebauer; N. S. Sariciftci; Conjugated Polymer-Based Organic Solar Cells Chem. Rev. 107; 2007; pp. 1324-1338.
doi: 10.1021/cr050149z.
[14] C. J. Brabec; F. Padinger; J. C. Hummelen; R. A. Janssen; N. S. Sariciftci; Realization of large area flexible fullerene - conjugated polymer photocells: A route to plastic solar cells; Synth. Met. 102; 1999; pp. 861-864.
doi: 10.1016/S0379-6779(98)00366-X.
[15] P. Schilinsky; C. Waldauf; C. J. Brabec; Performance Analysis of Printed Bulk Heterojunction Solar Cells; Adv. Funct. Mater. 16; 2006; pp. 1669-1672.
doi: 10.1002/adfm.200500581.
[16] C. N. Hoth; S. A. Choulis; P; Schilinsky; C. J. Brabec; . On the effect of poly(3-hexylthiophene) regioregularity on inkjet printed organic solar cells; J. Mater. Chem. 19; 2009; pp. 5398-5404.
doi: 10.1039/b823495g.
[17] D. Vak; S. Kim; J. Jo; S. Oh; S. Na; J. Kim; D. Kim; Fabrication of organic bulk heterojunction solar cells by a spray deposition method for low-cost power generation; Appl. Phys. Lett. 91; 2007; 081102.
doi: 10.1063/1.2772766.
[18] C. N. Hoth; R. Steim; P. Schilinsky; S. A Choulis; S. F. Tedde; O. Hayden; C. J. Brabec; Topographical and morphological aspects of spray coated organic photovoltaics ; Organ. Electron. 10; 2009; pp. 587-593.
doi: 10.1016/j.orgel.2009.02.010.
[19] R. Green; A. Morpha; A. J. Ferguson; N. Kopidakis; G. Rumbles; S. E. Shaheen; Performance of bulk heterojunction photovoltaic devices prepared by airbrush spray deposition; Appl. Phys. Lett. 92; 2008; 33301.
doi: 10.1063/1.2836267.
[20] K. X. Steirer; M. O. Reese; B. L. Rupert; N. Kopidakis; D. C. Olson; R. T. Collins; D. S. Ginley; Ultrasonic spray deposition for production of organic solar cells; Sol. Energy Mater. Sol. Cells 93; 2009; pp. 447-453.
doi: .
F. C. Krebs, M. Jorgensen, K. Norrman, O. Hagemann, J. Alstrup, T. D. Nielsen, J. Fyenbo, K. Larsen, J. Kristensen, A complete process for production of flexible large area polymer solar cells entirely using screen printing—First public demonstration, Sol. Energy Mater. Sol. Cells 93, 2009, pp. 422-441.
[22] S. Kim, S. Na, J. Jo, G. Tae, D. Kim, Efficient Polymer Solar Cells Fabricated by Simple Brush Painting, Adv.Mater. 19, 2007, pp. 4410-4415.
[23] J. W. Jung, W. H. Jo, . Annealing-Free High Efficiency and Large Area Polymer Solar Cells Fabricated by a Roller Painting Process, Adv. Funct. Mater. 20, 2010, pp. 2355-2363.
[24] G. Derue, S. Coppee, S. Gabriele, M. Surin, V. Geskin, F, Monteverde, P. Leclere, R. Lazzaroni, P. Damman, Nanorubbing of Polythiophene Surfaces, J. Am. Chem. Soc. 127, 2005, pp. 8018-8019.
[25] H. Sirringhaus, P. J. Brown, R. H. Friend, M. M. Nielsen, K. Bechgaard, B. M. W. Langeveld-Voss, A. J. H. Spiering, R. A. J. Janssen, E. W. Meijer, P. Herwig, D. M. De Leeuw, Two-dimensional charge transport in self-organized, high-mobility conjugated polymers, Nature 401, 1999, pp. 685-688.
[26] R. Osterbacka, C. P. An, X. M. Jiang, Z. V. Vardeny, Two-Dimensional Electronic Excitations in Self-Assembled Conjugated Polymer Nanocrystals, Science 287, 2000, pp. 839-842.
[27] M. Kim, B. Kim, J. Kim, Effective Variables To Control the Fill Factor of Organic Photovoltaic Cells, ACS Appl. Mater. & Interfaces 1, 2009, pp. 1264-1269.
[28] G. Lu, L. Li, X. Yang, Creating a Uniform Distribution of Fullerene C60 Nanorods in a Polymer Matrix and its Photovoltaic Applications, Small 4, 2008, pp. 601-606.