Journal of Computational Electronics

, Volume 13, Issue 4, pp 933–942 | Cite as

Optoelectronic simulation and thickness optimization of energetically disordered organic solar cells

  • A. H. FallahpourEmail author
  • A. Gagliardi
  • D. Gentilini
  • A. Zampetti
  • F. Santoni
  • M. Auf der Maur
  • A. Di Carlo


In this work a complete semi-classical model of an organic solar cell is presented. The different aspects of conversion of light to electricity are taken into account. Correct models for density of state and organic-metal interface are considered in order to include the effect of energetically disorder material properties. Most of the parameters for the model are taken from literature while some were fixed by fitting with several experimental current-voltage characteristics. The comparison between modeling results and experimental data shows consistency and are in good agreement. Finally the model is used to investigate the optimization of hole transport (PEDOT) and active (P3HT:PCBM) layer thicknesses in order to maximize the cell efficiency. The simulation of the efficiency of the cell with varying thickness shows a fine tuning between the exciton generation and the charge recombination, giving clear indications on the optimization of cell performance.


Computational modeling Organic photovoltaic Energetic disordered Optoelectronic device 



We acknowledge the “Polo Solare Organico—Regione Lazio”, MIUR PRIN “DSSCX”, projects for financial support.


  1. 1.
    He, Z., et al.: Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure. Nat. Photonics 6(9), 593–597 (2012)CrossRefGoogle Scholar
  2. 2.
    Li, G., Zhu, R., Yang, Y.: Polymer solar cells. Nat. Photonics 6(3), 153–161 (2012)zbMATHCrossRefGoogle Scholar
  3. 3.
    Dou, L., et al.: Tandem polymer solar cells featuring a spectrally matched low-bandgap polymer. Nat. Photonics 6(3), 180–185 (2012)CrossRefGoogle Scholar
  4. 4.
    Li, N., et al.: Towards 15 % energy conversion efficiency: A systematic study of the solution-processed organic tandem solar cells based on commercially available materials. Energy & Environmental Science (2013)Google Scholar
  5. 5.
    Pettersson, L.A.A., Roman, L.S., Inganas, O.: Modeling photocurrent action spectra of photovoltaic devices based on organic thin films. J. Appl. Phys. 86(1), 487–496 (1999)CrossRefGoogle Scholar
  6. 6.
    Peumans, P., Yakimov, A., Forrest, S.R.: Small molecular weight organic thin-film photodetectors and solar cells. J. Appl. Phys. 93(7), 3693–3723 (2003)CrossRefGoogle Scholar
  7. 7.
    Dennler, G., et al.: Angle dependence of external and internal quantum efficiencies in bulk-heterojunction organic solar cells. J. Appl. Phys. 102(5), 054516 (2007)CrossRefGoogle Scholar
  8. 8.
    Hausermann, R., et al.: Coupled optoelectronic simulation of organic bulk-heterojunction solar cells: parameter extraction and sensitivity analysis. J. Appl. Phys. 106(10), 104507 (2009)CrossRefGoogle Scholar
  9. 9.
    Mihailetchi, V.D., et al.: Photocurrent generation in polymer-fullerene bulk heterojunctions. Phys. Rev. Lett. 93(21), 216601 (2004)CrossRefGoogle Scholar
  10. 10.
    Gavin, A.B., Nigel, C.: Computer simulation of polymer solar cells. Modell. Simul. Mater. Sci. Eng. 15(2), 13 (2007)CrossRefGoogle Scholar
  11. 11.
    Hwang, I., Greenham, N.C.: Modeling photocurrent transients in organic solar cells. Nanotechnology 19(42), 424012 (2008)CrossRefGoogle Scholar
  12. 12.
    Tress, W., Leo, K., Riede, M.: Optimum mobility, contact properties, and open-circuit voltage of organic solar cells: a drift-diffusion simulation study. Phys. Rev. B 85(15), 155201 (2012)CrossRefGoogle Scholar
  13. 13.
    Barker, J.A., Ramsdale, C.M., Greenham, N.C.: Modeling the current-voltage characteristics of bilayer polymer photovoltaic devices. Phys. Rev. B 67(7), 075205 (2003)CrossRefGoogle Scholar
  14. 14.
    Haerter, J.O., et al.: Numerical simulations of layered and blended organic photovoltaic cells. Appl. Phys. Lett. 86(16), 164101 (2005)Google Scholar
  15. 15.
    Petersen, A., Kirchartz, T., Wagner, T.A.: Charge extraction and photocurrent in organic bulk heterojunction solar cells. Phys. Rev. B 85(4), 045208 (2012)CrossRefGoogle Scholar
  16. 16.
    Shieh, J.-T., et al.: The effect of carrier mobility in organic solar cells. J. Appl. Phys. 107(8), 084503 (2010)MathSciNetCrossRefGoogle Scholar
  17. 17.
    Lacic, S., Inganas, O.: Modeling electrical transport in blend heterojunction organic solar cells. J. Appl. Phys. 97(12), 124901 (2005)CrossRefGoogle Scholar
  18. 18.
    Monestier, F., et al.: Modeling the short-circuit current density of polymer solar cells based on P3HT:PCBM blend. Solar Energy Mater. Solar Cells 91(5), 405–410 (2007)CrossRefGoogle Scholar
  19. 19.
    Lin, A.S., Phillips, J.D.: Drift-diffusion modeling for impurity photovoltaic devices. IEEE Trans. Electron Devices 56(12), 3168–3174 (2009)CrossRefGoogle Scholar
  20. 20.
    Wee Shing, K.: Three-dimensional optoelectronic model for organic bulk heterojunction solar cells. IEEE J. Photovoltaics 1(1), 84–92 (2011)CrossRefGoogle Scholar
  21. 21.
    Christ, N.S., et al.: Nanosecond response of organic solar cells and photodetectors. J. Appl. Phys. 105(10), 104513 (2009)CrossRefGoogle Scholar
  22. 22.
    Kotlarski, J.D., et al.: Combined optical and electrical modeling of polymer: fullerene bulk heterojunction solar cells. J. Appl. Phys. 103(8), 084502 (2008)CrossRefGoogle Scholar
  23. 23.
    Kirchartz, T., et al.: Electro-optical modeling of bulk heterojunction solar cells. J. Appl. Phys. 104(9), 094513 (2008)Google Scholar
  24. 24.
    Vervisch, W., et al.: Optical-electrical simulation of organic solar cells: excitonic modeling parameter influence on electrical characteristics. Appl. Phys. Lett. 98(25), 253306 (2011)CrossRefGoogle Scholar
  25. 25.
    Koster, L.J.A., et al.: Device model for the operation of polymer/fullerene bulk heterojunction solar cells. Phys. Rev. B 72(8), 085205 (2005)CrossRefGoogle Scholar
  26. 26.
    Rauh, D., Deibel, C., Dyakonov, V.: Charge density dependent nongeminate recombination in organic bulk heterojunction solar cells. Adv. Funct. Mater. 22(16), 3371–3377 (2012)CrossRefGoogle Scholar
  27. 27.
    Bässler, H.: Charge transport in disordered organic photoconductors a Monte Carlo simulation study. Physica Status Solidi (b) 175(1), 15–56 (1993)CrossRefGoogle Scholar
  28. 28.
    MacKenzie, R.C.I., et al.: Modeling nongeminate recombination in P3HT:PCBM solar cells. J. Phys. Chem. C 115(19), 9806–9813 (2011)CrossRefGoogle Scholar
  29. 29.
    Moehl, T., et al.: Relaxation of photogenerated carriers in P3HT:PCBM organic blends. ChemSusChem 2(4), 314–320 (2009)CrossRefGoogle Scholar
  30. 30.
    Garcia-Belmonte, G.: Temperature dependence of open-circuit voltage in organic solar cells from generation-recombination kinetic balance. Solar Energy Mater. Solar Cells 94(12), 2166–2169 (2010)CrossRefGoogle Scholar
  31. 31.
    Garcia-Belmonte, G., Bisquert, J.: Open-circuit voltage limit caused by recombination through tail states in bulk heterojunction polymer-fullerene solar cells. Appl. Phys. Lett. 96(11), 113301 (2010)CrossRefGoogle Scholar
  32. 32.
    Deibel, C., Wagenpfahl, A., Dyakonov, V.: Influence of charge carrier mobility on the performance of organic solar cells. Physica Status Solidi (RRL) - Rapid Res. Lett. 2(4), 175–177 (2008)CrossRefGoogle Scholar
  33. 33.
    Kirchartz, T., et al.: Mobility dependent efficiencies of organic bulk heterojunction solar cells: surface recombination and charge transfer state distribution. Phys. Rev. B 80(3), 035334 (2009)CrossRefGoogle Scholar
  34. 34. Accessed 3 Feb 2014
  35. 35.
    Li, G., et al.: Investigation of annealing effects and film thickness dependence of polymer solar cells based on poly (3-hexylthiophene). J. Appl. Phys. 98(4), 043704–043705 (2005)CrossRefGoogle Scholar
  36. 36.
    Persson, N.K., Schubert, M., Inganäs, O.: Optical modelling of a layered photovoltaic device with a polyfluorene derivative/fullerene as the active layer. Solar Energy Mater. Solar Cells 83(2–3), 169–186 (2004)CrossRefGoogle Scholar
  37. 37.
    Burkhard, G.F., Hoke, E.T., McGehee, M.D.: Accounting for interference, scattering, and electrode absorption to make accurate internal quantum efficiency measurements in organic and other thin solar cells. Adv. Mater. 22(30), 3293–3297 (2010)CrossRefGoogle Scholar
  38. 38.
    Braun, C.L.: Electric field assisted dissociation of charge transfer states as a mechanism of photocarrier production. J. Chem. Phys. 80(9), 4157–4161 (1984)CrossRefGoogle Scholar
  39. 39.
    Zhu, X.Y., Yang, Q., Muntwiler, M.: Charge-transfer excitons at organic semiconductor surfaces and interfaces. Acc. Chem. Res. 42(11), 1779–1787 (2009)CrossRefGoogle Scholar
  40. 40.
    Deibel, C., Strobel, T., Dyakonov, V.: Role of the charge transfer state in organic donor-acceptor solar cells. Adv. Mater. 22(37), 4097–4111 (2010)CrossRefGoogle Scholar
  41. 41.
    Nenashev, A.V., et al.: Theory of exciton dissociation at the interface between a conjugated polymer and an electron acceptor. Phys. Rev. B 84(3), 035210 (2011)CrossRefGoogle Scholar
  42. 42.
    Pivrikas, A., et al.: Bimolecular recombination coefficient as a sensitive testing parameter for low-mobility solar-cell materials. Phys. Rev. Lett. 94(17), 176806 (2005)CrossRefGoogle Scholar
  43. 43.
    Koster, L.J.A., Mihailetchi, V.D., Blom, P.W.M.: Bimolecular recombination in polymer/fullerene bulk heterojunction solar cells. Appl. Phys. Lett. 88(5), 052104 (2006)CrossRefGoogle Scholar
  44. 44.
    Pivrikas, A., et al.: A review of charge transport and recombination in polymer/fullerene organic solar cells. Progress Photovoltaics: Res. Appl. 15(8), 677–696 (2007)CrossRefGoogle Scholar
  45. 45.
    Deibel, C.: Charge carrier dissociation and recombination in polymer solar cells. Physica Status Solidi (a) 206(12), 2731–2736 (2009)CrossRefGoogle Scholar
  46. 46.
    Miller, A., Abrahams, E.: Impurity conduction at low concentrations. Phys. Rev. 120(3), 745–755 (1960)zbMATHCrossRefGoogle Scholar
  47. 47.
    Pasveer, W.F., et al.: Unified description of charge-carrier mobilities in disordered semiconducting polymers. Phys. Rev. Lett. 94(20), 206601 (2005)CrossRefGoogle Scholar
  48. 48.
    Coehoorn, R., et al.: Charge-carrier concentration dependence of the hopping mobility in organic materials with Gaussian disorder. Phys. Rev. B 72(15), 155206 (2005)CrossRefGoogle Scholar
  49. 49.
    Cottaar, J., Bobbert, P.A.: Calculating charge-carrier mobilities in disordered semiconducting polymers: mean field and beyond. Phys. Rev. B 74(11), 115204 (2006)CrossRefGoogle Scholar
  50. 50.
    Mozer, A.J., Sariciftci, N.S.: Conjugated polymer photovoltaic devices and materials. Comptes Rendus Chimie 9(5–6), 568–577 (2006)CrossRefGoogle Scholar
  51. 51.
    Boix, P.P., et al.: Determination of gap defect states in organic bulk heterojunction solar cells from capacitance measurements. Appl. Phys. Lett. 95(23), 233302 (2009)CrossRefGoogle Scholar
  52. 52.
    Garcia-Belmonte, G., et al.: Simultaneous determination of carrier lifetime and electron density-of-states in P3HT:PCBM organic solar cells under illumination by impedance spectroscopy. Solar Energy Mater. Solar Cells 94(2), 366–375 (2010)CrossRefGoogle Scholar
  53. 53.
    Cowley, A.M., Sze, S.M.: Surface states and barrier height of metal-semiconductor systems. J. Appl. Phys. 36(10), 3212–3220 (1965)Google Scholar
  54. 54.
    Hwang, J., Wan, A., Kahn, A.: Energetics of metal-organic interfaces: new experiments and assessment of the field. Mater. Sci. Eng.: R: Rep. 64(1–2), 1–31 (2009)CrossRefGoogle Scholar
  55. 55.
    Kampen, T., et al.: Barrier heights of organic modified Schottky contacts: theory and experiment. Appl. Surf. Sci. 234(1–4), 313–320 (2004)CrossRefGoogle Scholar
  56. 56.
    Crowell, C.R., Sze, S.M.: Current transport in metal-semiconductor barriers. Solid-State Electron. 9(11–12), 1035–1048 (1966)CrossRefGoogle Scholar
  57. 57.
    Scott, J.C., Malliaras, G.G.: Charge injection and recombination at the metal-organic interface. Chem. Phys.Lett. 299(2), 115–119 (1999)CrossRefGoogle Scholar
  58. 58.
    Dang, M.T., Hirsch, L., Wantz, G.: P3HT: PCBM, best seller in polymer photovoltaic research. Adv. Mater. 23(31), 3597–3602 (2011)CrossRefGoogle Scholar
  59. 59.
    Kyaw, A.K.K., et al.: Intensity dependence of current-voltage characteristics and recombination in high-efficiency solution-processed small-molecule solar cells. ACS Nano 7(5), 4569–4577 (2013)CrossRefGoogle Scholar
  60. 60.
    Street, R.A., et al.: Interface state recombination in organic solar cells. Phys. Rev. B 81(20), 205307 (2010)CrossRefGoogle Scholar
  61. 61.
    Brown, T.M., et al.: Time dependence and freezing-in of the electrode oxygen plasma-induced work function enhancement in polymer semiconductor heterostructures. Org. Electron. 12(4), 623–633 (2011)CrossRefGoogle Scholar
  62. 62.
    Brown, T.M., et al.: Built-in field electroabsorption spectroscopy of polymer light-emitting diodes incorporating a doped poly(3,4-ethylene dioxythiophene) hole injection layer. Appl. Phys. Lett. 75(12), 1679–1681 (1999)CrossRefGoogle Scholar
  63. 63.
    Scharber, M.C., et al.: Design rules for donors in bulk-heterojunction solar cells-towards 10% energy-conversion efficiency. Adv. Mater. 18(6), 789–794 (2006)CrossRefGoogle Scholar
  64. 64.
    Kim, J.Y., et al.: New architecture for high-efficiency polymer photovoltaic cells using solution-based titanium oxide as an optical spacer. Adv. Mater. 18(5), 572–576 (2006)CrossRefGoogle Scholar
  65. 65.
    Baek, W.-H., et al.: Effect of P3HT:PCBM concentration in solvent on performances of organic solar cells. Solar Energy Mater. Solar Cells 93(8), 1263–1267 (2009)MathSciNetCrossRefGoogle Scholar
  66. 66.
    Garcia-Belmonte, G., et al.: Charge carrier mobility and lifetime of organic bulk heterojunctions analyzed by impedance spectroscopy. Org. Electron. 9(5), 847–851 (2008)CrossRefGoogle Scholar
  67. 67.
    Torricelli, F., Kovács-Vajna, Z.M., Colalongo, L.: The role of the density of states on the hole mobility of disordered organic semiconductors. Org. Electron. 10(5), 1037–1040 (2009)CrossRefGoogle Scholar
  68. 68.
    Tanase, C., et al.: Unification of the hole transport in polymeric field-effect transistors and light-emitting diodes. Phys. Rev. Lett. 91(21), 216601 (2003)CrossRefGoogle Scholar
  69. 69.
    Garcia-Belmonte, G., et al.: Influence of the intermediate density-of-states occupancy on open-circuit voltage of bulk heterojunction solar cells with different fullerene acceptors. J. Phys. Chem. Lett. 1(17), 2566–2571 (2010) Google Scholar
  70. 70.
    Dou, L., et al.: 25th Anniversary article: a decade of organic/polymeric photovoltaic research. Adv. Mater. 25(46), 6642–6671 (2013)Google Scholar
  71. 71.
    Moulé, A.J., Bonekamp, J.B., Meerholz, K.: The effect of active layer thickness and composition on the performance of bulk-heterojunction solar cells. J. Appl. Phys. 100(9), 094503(2006)Google Scholar
  72. 72.
    Sievers, D.W., Shrotriya, V., Yang, Y.: Modeling optical effects and thickness dependent current in polymer bulk-heterojunction solar cells. J. Appl. Phys. 100(11), 114509 (2006)Google Scholar
  73. 73.
    Paulus, G.L.C., Ham, M.-H., Strano, M.S.: Anomalous thickness-dependence of photocurrent explained for state-of-the-art planar nano-heterojunction organic solar cells. Nanotechnology 23(9), 095402 (2012)CrossRefGoogle Scholar
  74. 74.
    Li, Y., et al.: Spectral response of fiber-based organic photovoltaics. Solar Energy Mater. Solar Cells 98, 273–276 (2012)CrossRefGoogle Scholar
  75. 75.
    Jin, H., et al.: Thickness dependence and solution-degradation effect in poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester based solar cells. Solar Energy Mater. Solar Cells 94(3), 465–470 (2010)CrossRefGoogle Scholar
  76. 76.
    Zeng, L., Tang, C.W., Chen, S.H.: Effects of active layer thickness and thermal annealing on polythiophene: Fullerene bulk heterojunction photovoltaic devices. Appl. Phys. Lett. 97(5), 053305 (2010)Google Scholar
  77. 77.
    Peet, J., et al.: Bulk heterojunction solar cells with thick active layers and high fill factors enabled by a bithiophene-co-thiazolothiazole push-pull copolymer. Appl. Phys. Lett. 98(4), 043301(2011)Google Scholar
  78. 78.
    Kirchartz, T., et al.: Understanding the thickness-dependent performance of organic bulk heterojunction solar cells: the influence of mobility, lifetime, and space charge. J. Phys. Chem. Lett. 3(23), 3470–3475 (2012)CrossRefGoogle Scholar
  79. 79.
    Dang, M.T., Hirsch, L., Wantz, G.: P3HT:PCBM, best seller in polymer photovoltaic research. Adv. Mater. 23(31), 3597–3602 (2011)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • A. H. Fallahpour
    • 1
    Email author
  • A. Gagliardi
    • 2
  • D. Gentilini
    • 1
  • A. Zampetti
    • 1
  • F. Santoni
    • 1
  • M. Auf der Maur
    • 1
  • A. Di Carlo
    • 1
  1. 1.CHOSE (Center for Hybrid and Organic Solar Energy), Department of Electronic EngineeringUniversity of Rome “Tor Vergata”RomeItaly
  2. 2.Electrical Engineering and Information TechnologyTechnische Universität MünchenMünchenGermany

Personalised recommendations