In situ Studies of Morphology Formation in Solution-Processed Polymer–Fullerene Blends

  • Esther BarrenaEmail author
  • Felix Buss
  • Ana Perez-Rodriguez
  • Monamie Sanyal
  • Benjamin Schmidt-Hansberg
  • Michael F. G. Klein
  • Philip Scharfer
  • Wilhelm Schabel
  • Uli Lemmer
Part of the Advances in Polymer Science book series (POLYMER, volume 272)


Control of the blend nanomorphology in bulk heterojunctions (BHJs) is still a challenge that demands more fundamental knowledge of the mechanism of phase separation and crystallization during solvent drying. In this review we show that in situ studies using combined laser reflectometry and grazing-incidence wide-angle X-ray scattering provide a fundamental understanding on how the nanomorphology develops dynamically during film drying. We identify influencing parameters for controlled film formation in order to obtain optimized solar cell performance. We review here our results on BHJs of poly(3-hexylthiophene)–[6,6]-phenyl-C61-butyric acid methyl ester and poly{[4,40-bis(2-ethylhexyl)dithieno(3,2-b;20,30-d)silole]-2,6-diyl-alt-(2,1,3 benzothidiazole)-4,7-diyl} with [6,6]-phenyl-C71-butyric acid methyl ester.


Bulk heterojunction Crystallization Drying kinetics GIWAXS P3HT PCBM PSBTBT Real-time studies Solution processing 


  1. 1.
    Liao H-C et al (2013) Additives for morphology control in high-efficiency organic solar cells. Mater Today 16(9):326–336CrossRefGoogle Scholar
  2. 2.
    Liu F et al (2013) Characterization of the morphology of solution-processed bulk heterojunction organic photovoltaics. Prog Polym Sci 38(12):1990–2052CrossRefGoogle Scholar
  3. 3.
    Treat ND, Chabinyc ML (2014) Phase separation in bulk heterojunctions of semiconducting polymers and fullerenes for photovoltaics. Annu Rev Phys Chem 65:59–81CrossRefGoogle Scholar
  4. 4.
    Clarke TM et al (2008) Free energy control of charge photogeneration in polythiophene/fullerene solar cells: the influence of thermal annealing on P3HT/PCBM blends. Adv Funct Mater 18(24):4029–4035CrossRefGoogle Scholar
  5. 5.
    Chen F-C et al (2010) Morphological study of P3HT:PCBM blend films prepared through solvent annealing for solar cell applications. Sol Energy Mater Sol Cells 94(12):2426–2430CrossRefGoogle Scholar
  6. 6.
    Liu X et al (2012) Solvent additive control of morphology and crystallization in semiconducting polymer blends. Adv Mater 24(5):669–674CrossRefGoogle Scholar
  7. 7.
    Schmidt-Hansberg B et al (2011) Moving through the phase diagram: morphology formation in solution cast polymer-fullerene-blend films for organic solar cells. ACS Nano 5(11):8579–8590CrossRefGoogle Scholar
  8. 8.
    Schmidt-Hansberg B et al (2009) In situ monitoring the drying kinetics of knife coated polymer-fullerene films for organic solar cells. J Appl Phys 106(12):124501CrossRefGoogle Scholar
  9. 9.
    Sanyal M et al (2011) In situ X-ray study of drying-temperature influence on the structural evolution of bulk-heterojunction polymer-fullerene solar cells processed by doctor-blading. Adv Energy Mater 1(3):363–367CrossRefGoogle Scholar
  10. 10.
    Sanyal M et al (2011) Effect of photovoltaic polymer/fullerene blend composition ratio on microstructure evolution during film solidification investigated in real time by X-ray diffraction. Macromolecules 44(10):3795–3800CrossRefGoogle Scholar
  11. 11.
    Schmidt-Hansberg B et al (2012) Investigation of non-halogenated solvent mixtures for high throughput fabrication of polymer–fullerene solar cells. Sol Energy Mater Sol Cells 96:195–201CrossRefGoogle Scholar
  12. 12.
    Schmidt-Hansberg B et al (2011) Spatially resolved drying kinetics of multi-component solution cast films for organic electronics. Chem Eng Process Process Intensif 50(5–6):509–515CrossRefGoogle Scholar
  13. 13.
    Bergqvist J et al (2013) In situ reflectance imaging of organic thin film formation from solution deposition. Sol Energy Mater Sol Cells 114:89–98CrossRefGoogle Scholar
  14. 14.
    Heriot SY, Jones RA (2005) An interfacial instability in a transient wetting layer leads to lateral phase separation in thin spin-cast polymer-blend films. Nat Mater 4(10):782–786CrossRefGoogle Scholar
  15. 15.
    Schmidt-Hansberg B (2012) Process-structure-property relationship of polymer-fullerene bulk heterojunction films for organic solar cells: drying process, film structure and optoelectronic properties. Cuvillier, GöttingenGoogle Scholar
  16. 16.
    Wang T et al (2010) The development of nanoscale morphology in polymer:fullerene photovoltaic blends during solvent casting. Soft Matter 6(17):4128–4134CrossRefGoogle Scholar
  17. 17.
    Vogt BD et al (2005) Moisture absorption into ultrathin hydrophilic polymer films on different substrate surfaces. Polymer 46(5):1635–1642CrossRefGoogle Scholar
  18. 18.
    Eastman SA et al (2012) Effect of confinement on structure, water solubility, and water transport in Nafion thin films. Macromolecules 45(19):7920–7930CrossRefGoogle Scholar
  19. 19.
    Baker JL et al (2010) Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector. Langmuir 26(11):9146–9151CrossRefGoogle Scholar
  20. 20.
    Muller-Buschbaum P (2014) The active layer morphology of organic solar cells probed with grazing incidence scattering techniques. Adv Mater 26(46):7692–7709CrossRefGoogle Scholar
  21. 21.
    Rivnay J et al (2012) Quantitative determination of organic semiconductor microstructure from the molecular to device scale. Chem Rev 112(10):5488–5519CrossRefGoogle Scholar
  22. 22.
    van Krevelen DW (1990) Properties of polymers: their correlation with chemical structure: their numerical estimation and prediction from additive group contributions. Elsevier, AmsterdamGoogle Scholar
  23. 23.
    Yang X et al (2004) Crystalline organization of a methanofullerene as used for plastic solar-cell applications. Adv Mater 16(9–10):802–806CrossRefGoogle Scholar
  24. 24.
    Yao Y et al (2008) Effects of solvent mixtures on the nanoscale phase separation in polymer solar cells. Adv Funct Mater 18(12):1783–1789CrossRefGoogle Scholar
  25. 25.
    Westacott P et al (2013) On the role of intermixed phases in organic photovoltaic blends. Energy Environ Sci 6(9):2756CrossRefGoogle Scholar
  26. 26.
    Collins BA, Tumbleston JR, Ade H (2011) Miscibility, crystallinity, and phase development in P3HT/PCBM solar cells: toward an enlightened understanding of device morphology and stability. J Phys Chem Lett 2(24):3135–3145CrossRefGoogle Scholar
  27. 27.
    DeLongchamp DM et al (2011) Molecular characterization of organic electronic films. Adv Mater 23(3):319–337CrossRefGoogle Scholar
  28. 28.
    Richter LJ et al (2015) In situ morphology studies of the mechanism for solution additive effects on the formation of bulk heterojunction films. Adv Energy Mater 5(3):1400975CrossRefGoogle Scholar
  29. 29.
    Dennler G, Scharber MC, Brabec CJ (2009) Polymer-fullerene bulk-heterojunction solar cells. Adv Mater 21(13):1323–1338CrossRefGoogle Scholar
  30. 30.
    Ma W et al (2005) Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology. Adv Funct Mater 15(10):1617–1622CrossRefGoogle Scholar
  31. 31.
    Li G et al (2005) High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends. Nat Mater 4(11):864–868CrossRefGoogle Scholar
  32. 32.
    Mihailetchi VD et al (2006) Origin of the enhanced performance in poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester solar cells upon slow drying of the active layer. Appl Phys Lett 89(1):012107CrossRefGoogle Scholar
  33. 33.
    Li G et al (2007) “Solvent annealing” effect in polymer solar cells based on poly(3-hexylthiophene) and methanofullerenes. Adv Funct Mater 17(10):1636–1644CrossRefGoogle Scholar
  34. 34.
    Shin M et al (2010) Abrupt morphology change upon thermal annealing in poly(3-hexylthiophene)/soluble fullerene blend films for polymer solar cells. Adv Funct Mater 20(5):748–754CrossRefGoogle Scholar
  35. 35.
    Campoy-Quiles M et al (2008) Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends. Nat Mater 7(2):158–164CrossRefGoogle Scholar
  36. 36.
    Schmidt-Hansberg B et al (2012) Structure formation in low-bandgap polymer:fullerene solar cell blends in the course of solvent evaporation. Macromolecules 45(19):7948–7955CrossRefGoogle Scholar
  37. 37.
    Brinkmann M et al. (2014) Understanding the structure and crystallization of regioregular poly (3-hexylthiophene) from the perspective of epitaxy, vol 265. Springer, Heidelberg, pp 83–106Google Scholar
  38. 38.
    Chu C-W et al (2008) Control of the nanoscale crystallinity and phase separation in polymer solar cells. Appl Phys Lett 92(10):103306CrossRefGoogle Scholar
  39. 39.
    Moulé AJ, Meerholz K (2008) Controlling morphology in polymer–fullerene mixtures. Adv Mater 20(2):240–245CrossRefGoogle Scholar
  40. 40.
    Dang MT, Hirsch L, Wantz G (2011) P3HT:PCBM, best seller in polymer photovoltaic research. Adv Mater 23(31):3579–3602CrossRefGoogle Scholar
  41. 41.
    Bundgaard E, Krebs FC (2007) Low band gap polymers for organic photovoltaics. Sol Energy Mater Sol Cells 91(11):954–985CrossRefGoogle Scholar
  42. 42.
    Scharber MC et al (2010) Influence of the bridging atom on the performance of a low-bandgap bulk heterojunction solar cell. Adv Mater 22(3):367–370CrossRefGoogle Scholar
  43. 43.
    Maurano A et al (2010) Recombination dynamics as a key determinant of open circuit voltage in organic bulk heterojunction solar cells: a comparison of four different donor polymers. Adv Mater 22(44):4987–4992CrossRefGoogle Scholar
  44. 44.
    Hou J et al (2008) Synthesis, characterization, and photovoltaic properties of a low band gap polymer based on silole-containing polythiophenes and 2,1,3-benzothiadiazole. J Am Chem Soc 130(48):16144–16145CrossRefGoogle Scholar
  45. 45.
    Chen HY et al (2010) Silicon atom substitution enhances interchain packing in a thiophene-based polymer system. Adv Mater 22(3):371–375CrossRefGoogle Scholar
  46. 46.
    Morana M et al (2010) Nanomorphology and charge generation in bulk heterojunctions based on low-bandgap dithiophene polymers with different bridging atoms. Adv Funct Mater 20(7):1180–1188CrossRefGoogle Scholar
  47. 47.
    Colsmann A et al (2011) Efficient semi-transparent organic solar cells with good transparency color perception and rendering properties. Adv Energy Mater 1(4):599–603CrossRefGoogle Scholar
  48. 48.
    Chou C-H et al (2011) A metal-oxide interconnection layer for polymer tandem solar cells with an inverted architecture. Adv Mater 23(10):1282–1286CrossRefGoogle Scholar
  49. 49.
    Sista S et al (2010) Highly efficient tandem polymer photovoltaic cells. Adv Mater 22(3):380–383CrossRefGoogle Scholar
  50. 50.
    Ameri T et al (2013) Organic ternary solar cells: a review. Adv Mater 25(31):4245–4266CrossRefGoogle Scholar
  51. 51.
    Koppe M et al (2010) Near IR sensitization of organic bulk heterojunction solar cells: towards optimization of the spectral response of organic solar cells. Adv Funct Mater 20(2):338–346CrossRefGoogle Scholar
  52. 52.
    Ameri T et al (2012) Performance enhancement of the P3HT/PCBM solar cells through NIR sensitization using a small-bandgap polymer. Adv Energy Mater 2(10):1198–1202CrossRefGoogle Scholar
  53. 53.
    Pearson AJ et al (2014) Morphology development in amorphous polymer:fullerene photovoltaic blend films during solution casting. Adv Funct Mater 24(5):659–667CrossRefGoogle Scholar
  54. 54.
    Agostinelli T et al (2011) The role of alkane dithiols in controlling polymer crystallization in small band gap polymer:fullerene solar cells. J Polym Sci B 49(10):717–724CrossRefGoogle Scholar
  55. 55.
    Rogers JT et al (2011) Structural order in bulk heterojunction films prepared with solvent additives. Adv Mater 23(20):2284–2288CrossRefGoogle Scholar
  56. 56.
    Rogers JT et al (2012) Time-resolved structural evolution of additive-processed bulk heterojunction solar cells. J Am Chem Soc 134(6):2884–2887CrossRefGoogle Scholar
  57. 57.
    Pearson AJ, Wang T, Lidzey DG (2013) The role of dynamic measurements in correlating structure with optoelectronic properties in polymer:fullerene bulk-heterojunction solar cells. Rep Prog Phys 76(2):022501CrossRefGoogle Scholar
  58. 58.
    Engmann S et al (2015) Real-time X-ray scattering studies of film evolution in high performing small-molecule-fullerene organic solar cells. J Mater Chem A 3(16):8764–8771CrossRefGoogle Scholar
  59. 59.
    Chou KW et al (2013) Spin-cast bulk heterojunction solar cells: a dynamical investigation. Adv Mater 25(13):1923–1929CrossRefGoogle Scholar
  60. 60.
    Schmidt K et al (2014) A mechanistic understanding of processing additive-induced efficiency enhancement in bulk heterojunction organic solar cells. Adv Mater 26(2):300–305CrossRefGoogle Scholar
  61. 61.
    Smilgies D-M et al (2013) Look fast: crystallization of conjugated molecules during solution shearing probed in-situ and in real time by X-ray scattering. Phys Status Solidi RRL 7(3):177–179CrossRefGoogle Scholar
  62. 62.
    Wei Chou K et al (2014) Late stage crystallization and healing during spin-coating enhance carrier transport in small-molecule organic semiconductors. J Mater Chem C 2(28):5681–5689CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  • Esther Barrena
    • 1
    Email author
  • Felix Buss
    • 2
  • Ana Perez-Rodriguez
    • 1
  • Monamie Sanyal
    • 3
  • Benjamin Schmidt-Hansberg
    • 2
  • Michael F. G. Klein
    • 4
  • Philip Scharfer
    • 2
  • Wilhelm Schabel
    • 2
  • Uli Lemmer
    • 4
  1. 1.Instituto de Ciencia de Materiales de Barcelona (ICMAB CSIC)BarcelonaSpain
  2. 2.Institute of Thermal Process Engineering, Thin Film Technology, Karlsruhe Institute of TechnologyKarlsruheGermany
  3. 3.Max Planck Institut für MetallforschungStuttgartGermany
  4. 4.Light Technology Institute, Karlsruhe Institute of TechnologyKarlsruheGermany

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