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Published Online: 09 April 2014
Accepted: March 2014
Journal of Applied Physics 115, 144502 (2014); https://doi.org/10.1063/1.4870805
The slow decay of charge carriers in polymer–fullerene blends measured in transient studies has raised a number of questions about the mechanisms of nongeminate recombination in these systems. In an attempt to understand this behavior, we have applied a combination of steady-state and transient photoinduced absorption measurements to compare nongeminate recombination behavior in films of neat poly(3-hexyl thiophene) (P3HT) and P3HT blended with [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). Transient measurements show that carrier recombination in the neat P3HT film exhibits second-order decay with a recombination rate coefficient that is similar to that predicted by Langevin theory. In addition, temperature dependent measurements indicate that neat films exhibit recombination behavior consistent with the Gaussian disorder model. In contrast, the P3HT:PCBM blend films are characterized by a strongly reduced recombination rate and an apparent recombination order greater than two. We then assess a number of previously proposed explanations for this behavior including phase separation, carrier concentration dependent mobility, non-encounter limited recombination, and interfacial states. In the end, we propose a model in which pure domains with a Gaussian density of states are separated by a mixed phase with an exponential density of states. We find that such a model can explain both the reduced magnitude of the recombination rate and the high order recombination kinetics and, based on the current state of knowledge, is the most consistent with experimental observations.
The current work was supported by the Bundesministerium für Bildung und Forschung in the framework of the GREKOS Project (Contract No. 03SF0356B) and the European Commission through the Human Potential Program (Marie-Curie RTN SolarNType Contract No. MRTN-CT-2006-035533) and the Deutsche Forschungsgemeinschaft, DFG under the Contract INST 93/623-1 FUGG. C.D. gratefully acknowledges the support of the Bavarian Academy of Sciences and Humanities.
  1. 1. M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D. Dunlop, Prog. Photovoltaics 20, 12 (2012). https://doi.org/10.1002/pip.2163 , Google ScholarCrossref
  2. 2. A. Pivrikas, G. Juška, A. J. Mozer, M. Scharber, K. Arlauskas, N. S. Sariciftci, H. Stubb, and R. Österbacka, Phys. Rev. Lett. 94, 176806 (2005). https://doi.org/10.1103/PhysRevLett.94.176806 , Google ScholarCrossref
  3. 3. P. Parkinson, J. Lloyd-Hughes, M. B. Johnston, and L. M. Herz, Phys. Rev. B 78, 115321 (2008). https://doi.org/10.1103/PhysRevB.78.115321 , Google ScholarCrossref
  4. 4. T. M. Clarke, D. B. Rodovsky, A. A. Herzing, J. Peet, G. Dennler, D. DeLongchamp, C. Lungenschmied, and A. J. Mozer, Adv. Energy Mater. 1, 1062 (2011). https://doi.org/10.1002/aenm.201100390 , Google ScholarCrossref
  5. 5. A. Zusan, B. Gieseking, J. Rauh, A. Baumann, K. Tvingstedt, B. Mueller, M. Gluecker, V. Dyakonov, and C. Deibel, “ Being trapped on acceptor islands-influence of structural changes on the nongeminate recombination in PTB7:PC70BM solar cells” (unpublished). Google Scholar
  6. 6. P. Langevin, Ann. Chim. Phys. 28, 433 (1903). Google Scholar
  7. 7. J. Guo, H. Ohkita, S. Yokoya, H. Benten, and S. Ito, J. Am. Chem. Soc. 132, 9631 (2010). https://doi.org/10.1021/ja9108787 , Google ScholarCrossref
  8. 8. C. Deibel and V. Dyakonov, Rep. Prog. Phys. 73, 096401 (2010). https://doi.org/10.1088/0034-4885/73/9/096401 , Google ScholarCrossref
  9. 9. C. Deibel, A. Wagenpfahl, and V. Dyakonov, Phys. Rev. B 80, 075203 (2009). https://doi.org/10.1103/PhysRevB.80.075203 , Google ScholarCrossref
  10. 10. C. Deibel, A. Baumann, and V. Dyakonov, Appl. Phys. Lett. 93, 163303 (2008). https://doi.org/10.1063/1.3005593 , Google ScholarScitation
  11. 11. J. Nelson, Phys. Rev. B 67, 155209 (2003). https://doi.org/10.1103/PhysRevB.67.155209 , Google ScholarCrossref
  12. 12. A. Foertig, A. Baumann, D. Rauh, V. Dyakonov, and C. Deibel, Appl. Phys. Lett. 95, 052104 (2009). https://doi.org/10.1063/1.3202389 , Google ScholarScitation
  13. 13. C. G. Shuttle, R. Hamilton, J. Nelson, B. C. O'Regan, and J. R. Durrant, Adv. Funct. Mater. 20, 698 (2010). https://doi.org/10.1002/adfm.200901734 , Google ScholarCrossref
  14. 14. J. Kniepert, M. Schubert, J. C. Blakesley, and D. Neher, J. Phys. Chem. Lett. 2, 700 (2011). https://doi.org/10.1021/jz200155b , Google ScholarCrossref
  15. 15. M. Mingebach, S. Walter, V. Dyakonov, and C. Deibel, Appl. Phys. Lett. 100, 193302 (2012). https://doi.org/10.1063/1.4711849 , Google ScholarScitation
  16. 16. G. -J. A. H. Wetzelaer, N. J. Van der Kaap, L. J. A. Koster, and P. W. M. Blom, Adv. Energy Mater. 3, 1130 (2013). https://doi.org/10.1002/aenm.201300251 , Google ScholarCrossref
  17. 17. J. Piris, T. Dykstra, A. Bakulin, P. van Loosdrecht, W. Knulst, M. T. Trinh, J. Schins, and L. Siebbeles, J. Phys. Chem. C 113, 14500 (2009). https://doi.org/10.1021/jp904229q , Google ScholarCrossref
  18. 18. W. J. Grzegorczyk, T. J. Savenije, T. E. Dykstra, J. Piris, J. M. Schins, and L. D. Siebbeles, J. Phys. Chem. C 114, 5182 (2010). https://doi.org/10.1021/jp9119364 , Google ScholarCrossref
  19. 19. I. A. Howard, R. Mauer, M. Meister, and F. Laquai, J. Am. Chem. Soc. 132, 14866 (2010). https://doi.org/10.1021/ja105260d , Google ScholarCrossref
  20. 20. 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, J. Am. Chem. Soc. 130, 3030 (2008). https://doi.org/10.1021/ja076568q , Google ScholarCrossref
  21. 21. J. L. Delgado, E. Espildora, M. Liedtke, A. Sperlich, D. Rauh, A. Baumann, C. Deibel, V. Dyakonov, and N. Martín, Chem. Eur. J. 15, 13474 (2009). https://doi.org/10.1002/chem.200902039 , Google ScholarCrossref
  22. 22. J. Schafferhans, A. Baumann, A. Wagenpfahl, C. Deibel, and V. Dyakonov, Org. Electron. 11, 1693 (2010). https://doi.org/10.1016/j.orgel.2010.07.016 , Google ScholarCrossref
  23. 23. J. E. Kroeze, T. J. Savenije, and J. Warman, J. Am. Chem. Soc. 126, 7608 (2004). https://doi.org/10.1021/ja039303u , Google ScholarCrossref
  24. 24. A. Baumann, J. Lorrmann, D. Rauh, C. Deibel, and V. Dyakonov, Adv. Mater. 24, 4381 (2012). https://doi.org/10.1002/adma.201200874 , Google ScholarCrossref
  25. 25. C. Deibel, D. Mack, J. Gorenflot, A. Schöll, S. Krause, F. Reinert, D. Rauh, and V. Dyakonov, Phys. Rev. B 81, 085202 (2010). https://doi.org/10.1103/PhysRevB.81.085202 , Google ScholarCrossref
  26. 26. X. Jiang, R. Österbacka, O. Korovyanko, C. P. An, B. Horovitz, R. A. J. Janssen, and Z. V. Vardeny, Adv. Funct. Mater. 12, 587 (2002). https://doi.org/10.1002/1616-3028(20020916)12:9<587::AID-ADFM587>3.0.CO;2-T , Google ScholarCrossref
  27. 27. P. A. van Hal, M. P. T. Christiaans, M. M. Wienk, J. M. Kroon, and R. A. J. Janssen, J. Phys. Chem. B 103, 4352 (1999). https://doi.org/10.1021/jp9901803 , Google ScholarCrossref
  28. 28. C. J. Brabec, A. Cravino, D. Meissner, N. S. Sariciftci, T. Fromherz, M. T. Rispens, L. Sanchez, and J. C. Hummelen, Adv. Funct. Mater. 11, 374 (2001). https://doi.org/10.1002/1616-3028(200110)11:5<374::AID-ADFM374>3.0.CO;2-W , Google ScholarCrossref
  29. 29. P. J. Brown, H. Sirringhaus, M. Harrison, M. Shkunov, and R. H. Friend, Phys. Rev. B 63, 125204 (2001). https://doi.org/10.1103/PhysRevB.63.125204 , Google ScholarCrossref
  30. 30. A. J. Ferguson, N. Kopidakis, S. E. Shaheen, and G. Rumbles, J. Phys. Chem. C 115, 23134 (2011). https://doi.org/10.1021/jp208014v , Google ScholarCrossref
  31. 31. T. Leijtens, J. Lim, J. Teuscher, T. Park, and H. J. Snaith, Adv. Mater. 25, 3227 (2013). https://doi.org/10.1002/adma.201300947 , Google ScholarCrossref
  32. 32. R. D. Pensack and J. B. Asbury, J. Am. Chem. Soc. 131, 15986 (2009). https://doi.org/10.1021/ja906293q , Google ScholarCrossref
  33. 33. R. A. Street, S. Cowan, and A. J. Heeger, Phys. Rev. B 82, 121301 (2010). https://doi.org/10.1103/PhysRevB.82.121301 , Google ScholarCrossref
  34. 34. A. J. Mozer, N. S. Sariciftci, A. Pivrikas, R. Österbacka, G. G. Juška, L. Brassat, and H. Bässler, Phys. Rev. B 71, 035214 (2005). https://doi.org/10.1103/PhysRevB.71.035214 , Google ScholarCrossref
  35. 35. R. Mauer, M. Kastler, and F. Laquai, Adv. Funct. Mater. 20, 2085 (2010). https://doi.org/10.1002/adfm.201000320 , Google ScholarCrossref
  36. 36. J. Schafferhans, A. Baumann, C. Deibel, and V. Dyakonov, Appl. Phys. Lett. 93, 093303 (2008). https://doi.org/10.1063/1.2978237 , Google ScholarScitation, ISI
  37. 37. F. W. Schmidlin, Phys. Rev. B 16, 2362 (1977). https://doi.org/10.1103/PhysRevB.16.2362 , Google ScholarCrossref
  38. 38. J. Noolandi, Phys. Rev. B 16, 4466 (1977). https://doi.org/10.1103/PhysRevB.16.4466 , Google ScholarCrossref
  39. 39. J. O. Oelerich, D. Huemmer, and S. D. Baranovskii, Phys. Rev. Lett. 108, 226403 (2012). https://doi.org/10.1103/PhysRevLett.108.226403 , Google ScholarCrossref
  40. 40. T. Kirchartz, B. E. Pieters, J. Kirkpatrick, U. Rau, and J. Nelson, Phys. Rev. B 83, 115209 (2011). https://doi.org/10.1103/PhysRevB.83.115209 , Google ScholarCrossref
  41. 41. A. Foertig, J. Rauh, V. Dyakonov, and C. Deibel, Phys. Rev. B 86, 115302 (2012). https://doi.org/10.1103/PhysRevB.86.115302 , Google ScholarCrossref
  42. 42. C. Deibel, D. Rauh, and A. Foertig, Appl. Phys. Lett. 103, 043307 (2013). https://doi.org/10.1063/1.4816720 , Google ScholarScitation
  43. 43. H. Bässler, Phys. Status Solidi B 175, 15 (1993). https://doi.org/10.1002/pssb.2221750102 , Google ScholarCrossref
  44. 44. W. F. Pasveer, J. Cottaar, C. Tanase, R. Coehoorn, P. A. Bobbert, P. W. M. Blom, D. M. de Leeuw, and M. A. J. Michels, Phys. Rev. Lett. 94, 206601 (2005). https://doi.org/10.1103/PhysRevLett.94.206601 , Google ScholarCrossref
  45. 45. G. Juška, K. Genevičius, N. Nekrašas, G. Sliaužys, and R. Österbacka, Appl. Phys. Lett. 95, 013303 (2009). https://doi.org/10.1063/1.3141513 , Google ScholarScitation, ISI
  46. 46. C. Groves and N. C. Greenham, Phys. Rev. B 78, 155205 (2008). https://doi.org/10.1103/PhysRevB.78.155205 , Google ScholarCrossref
  47. 47. T. Erb, U. Zhokhavets, U. Gobsch, S. Raleva, B. Stühn, P. Schilinsky, C. Waldauf, and C. Brabec, Adv. Funct. Mater. 15, 1193 (2005). https://doi.org/10.1002/adfm.200400521 , Google ScholarCrossref
  48. 48. L. J. A. Koster, V. D. Mihaletchi, and P. W. M. Blom, Appl. Phys. Lett. 88, 052104 (2006). https://doi.org/10.1063/1.2170424 , Google ScholarScitation, ISI
  49. 49. A. Baumann, T. J. Savenije, D. H. K. Murthy, M. Heeney, V. Dyakonov, and C. Deibel, Adv. Funct. Mater. 21, 1687–1692 (2011). https://doi.org/10.1002/adfm.201002358 , Google ScholarCrossref
  50. 50. S. S. van Bavel, E. Sourty, G. de With, and J. Loos, Nano Lett. 9, 507 (2009). https://doi.org/10.1021/nl8014022 , Google ScholarCrossref
  51. 51. M. Pfannmöller, H. Flügge, G. Benner, I. Wacker, C. Sommer, M. Hanselmann, S. Schmale, H. Schmidt, F. A. Hamprecht, T. Rabe, W. Kowalsky, and R. R. Schröder, Nano Lett. 11, 3099 (2011). https://doi.org/10.1021/nl201078t , Google ScholarCrossref
  52. 52. D. Rauh, C. Deibel, and V. Dyakonov, Adv. Funct. Mater. 22, 3371 (2012). https://doi.org/10.1002/adfm.201103118 , Google ScholarCrossref
  53. 53. T. J. Savenije, D. H. K. Murthy, M. Gunz, J. Gorenflot, L. D. A. Siebbeles, V. Dyakonov, and C. Deibel, J. Phys. Chem. Lett. 2, 1368 (2011). https://doi.org/10.1021/jz200569h , Google ScholarCrossref
  54. 54. V. D. Mihailetchi, J. K. J. van Duren, P. W. M. Blom, J. C. Hummelen, R. A. J. Janssen, J. M. Kroon, M. T. Rispens, W. J. H. Verhees, and M. M. Wienk, Adv. Funct. Mater. 13, 43 (2003). https://doi.org/10.1002/adfm.200390004 , Google ScholarCrossref
  55. 55. M. Hilczer and M. Tachiya, J. Phys. Chem. C 114, 6808 (2010). https://doi.org/10.1021/jp912262h , Google ScholarCrossref
  56. 56. B. A. Collins, E. Gann, L. Guignard, X. He, C. R. McNeill, and H. Ade, J. Phys. Chem. Lett. 1, 3160 (2010). https://doi.org/10.1021/jz101276h , Google ScholarCrossref
  57. 57. K. Vandewal, K. Tvingstedt, A. Gadisa, O. Inganäs, and J. V. Manca, Nature Mater. 8, 904 (2009). https://doi.org/10.1038/nmat2548 , Google ScholarCrossref
  58. 58. R. A. Street, M. Schoendorf, A. Roy, and J. H. Lee, Phys. Rev. B 81, 205307 (2010). https://doi.org/10.1103/PhysRevB.81.205307 , Google ScholarCrossref
  59. 59. C. Deibel and A. Wagenpfahl, Phys. Rev. B 82, 207301 (2010). https://doi.org/10.1103/PhysRevB.82.207301 , Google ScholarCrossref
  60. 60. R. A. Street, Phys. Rev. B 82, 207302 (2010). https://doi.org/10.1103/PhysRevB.82.207302 , Google ScholarCrossref
  61. 61. M. Presselt, F. Herrmann, S. Shokhovets, H. Hoppe, E. Runge, and G. Gobsch, Chem. Phys. Lett. 542, 70 (2012). https://doi.org/10.1016/j.cplett.2012.05.063 , Google ScholarCrossref
  62. 62. D. P. McMahon, D. L. Cheung, and A. Troisi, J. Phys. Chem. Lett. 2, 2737 (2011). https://doi.org/10.1021/jz201325g , Google ScholarCrossref
  63. 63. F. C. Jamieson, E. B. Domingo, T. McCarthy-Ward, M. Heeney, N. Stingelin, and J. R. Durrant, Chem. Sci. 3, 485 (2012). https://doi.org/10.1039/c1sc00674f , Google ScholarCrossref
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