Advertisement

Electronic Properties of Interfaces with Oligo- and Polythiophenes

  • Petra Tegeder
Chapter
Part of the Advances in Polymer Science book series (POLYMER, volume 272)

Abstract

Using energy- and femtosecond time-resolved two-photon photoemission spectroscopy and second harmonic generation to investigate interfaces with oligo- and polythiophenes provides important parameters such as energetic positions of transport levels , lifetimes of excitonic states , and charge-transfer times across donor–acceptor interfaces. They are essential for designing organic material–based optoelectronic devices.

Keywords

Exciton binding energies Exciton dynamics Second harmonic generation Transport levels Two photon photoemission 

Notes

Acknowledgments

It is a pleasure to thank all coworkers who made this work possible and carried out the experiments, especially Lea Bogner, Michael Schulze, and Erwan Varene. I am grateful for the fruitful collaboration with Peter Bäuerle, Katharina J. Franke, Dieter Neher, Nacho Pascual, Yan Pennec, and their coworkers. Funding by the Deutsche Forschungsgemeinschaft through the priority program SPP 1355 (project: TE 479/1) has been essential for this work.

References

  1. 1.
    Katz HE, Huang J (2009) Thin-film organic electronic devices. Annu Rev Mater Res 39:1–92CrossRefGoogle Scholar
  2. 2.
    Koch N (2007) Organic electronic devices and their functional interfaces. ChemPhysChem 8:1438–1455CrossRefGoogle Scholar
  3. 3.
    Günes S, Neugebauer H, Sariciftci NS (2007) Conjugated polymer-based organic solar cells. Chem Rev 107:1324–1338CrossRefGoogle Scholar
  4. 4.
    Walzer K, Maennig B, Pfeiffer M, Leo K (2007) Organic devices based on electrically doped transport layers. Chem Rev 107:1233–1271CrossRefGoogle Scholar
  5. 5.
    Ishii H, Sugiyama K, Ito E, Seki K (1999) Energy level alignment and interfacial electronic structures at organic/metal and organic/organic interfaces. Adv Mater 11:605–625CrossRefGoogle Scholar
  6. 6.
    Braun S, Salaneck, WR, Fahlman M (2009) Energy-level alignment at organic/metal and organic/organic interfaces. Adv Mater 21:1450–1472CrossRefGoogle Scholar
  7. 7.
    Oehzelt M, Koch N, Heimel G (2014) Organic semiconductor density of states controls the energy level alignment at electrode interfaces. Nat Comm 5:4174CrossRefGoogle Scholar
  8. 8.
    Umbach E, Sokolowski M, Fink R (1996) Substrate-interaction, long-range order, and epitaxy of large organic adsorbates. Appl Phys A Mater Sci Process 63:565–576CrossRefGoogle Scholar
  9. 9.
    Schreiber F (2000) Structure and growth of self-assembling monolayers. Prog Surf Sci 65:151–257CrossRefGoogle Scholar
  10. 10.
    Witte G, Wöll C (2004) Growth of aromatic molecules on solid substrates for applications in organic electronics. J Mater Res 19:1889–1916CrossRefGoogle Scholar
  11. 11.
    Love JC, Estroff LA, Kriebel JK, Nuzzo RG, Whitesides GM (2005) Self-assembled monolayers of thiolates on metals as a form of nanotechnology. Chem Rev 105:1103–1169CrossRefGoogle Scholar
  12. 12.
    Barth JV (2007) Molecular architectonic on metal surfaces. Annu Rev Phys Chem 58:375–407CrossRefGoogle Scholar
  13. 13.
    Heath JR (2009) Molecular electronics. Annu Rev Mater Res 39:1–23CrossRefGoogle Scholar
  14. 14.
    Bombis C, Weigelt S, Knudsen MM, Nørgaard M, Busse C, Lægsgaard E, Besenbacher F, Gothelf KV, Linderoth TR (2010) Steering organizational and conformational surface chirality by controlling molecular chemical functionality. ACS Nano 4:297–311CrossRefGoogle Scholar
  15. 15.
    Gooding JJ, Ciampi S (2011) The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies. Chem Soc Rev 40:2704–2718CrossRefGoogle Scholar
  16. 16.
    Otero R, Gallego JM, Vázquez de Parga AL, Martín N, Miranda R (2011) Molecular self-assembly at solid surfaces. Adv Mat 23:5148–5176CrossRefGoogle Scholar
  17. 17.
    Hill IG, Kahn A, Soosb ZG, Pascal RA Jr (2000) Charge-separation energy in films of π-conjugated organic molecules. Chem Phys Lett 327:181–188CrossRefGoogle Scholar
  18. 18.
    Krause S, Casu MB, Schöll A, Umbach E (2008) Determination of transport levels of organic semiconductors by UPS and IPS. New J Phys 10:085001–16CrossRefGoogle Scholar
  19. 19.
    Zhu X-Y (2004) Electronic structure and electron dynamics at molecule-metal interfaces: implications for molecule-based electronics. Surf Sci Rep 56:1–83CrossRefGoogle Scholar
  20. 20.
    Lindstrom CD, Zhu X-Y (2006) Photoinduced electron transfer at molecule-metal interfaces. Chem Rev 106:4281–4300CrossRefGoogle Scholar
  21. 21.
    Tegeder P, Hagen S, Leyssner F, Peters MV, Hecht S, Klamroth T, Saalfrank P, Wolf M (2007) Electronic structure of the molecular switch tetra-tert-butyl-azobenzene adsorbed on Ag(111). Appl Phys A 88:465–472CrossRefGoogle Scholar
  22. 22.
    Blumenfeld ML, Steele MP, Monti OLA (2010) Near- and far-field effects on molecular energy level alignment at an organic/elecrode interface. J Phys Chem Lett 1:145–148CrossRefGoogle Scholar
  23. 23.
    Hagen S, Luo Y, Haag R, Wolf M, Tegeder P (2010) Electronic structure and electron dynamics at an organic molecule/metal interface: interface states of tetra-tert-butyl-imine/Au(111). New J Phys 12:125022 (17pp)CrossRefGoogle Scholar
  24. 24.
    Leyssner F, Hagen S, Óvári L, Dokić J, Peters MV, Hecht S, Saalfrank P, Klamroth T, Tegeder P (2010) Photoisomerization ability of molecular switches adsorbed on Au(111): comparison between azobenzene and stilbene derivatives. J Phys Chem C 114:1231–1239CrossRefGoogle Scholar
  25. 25.
    Bronner C, Schulze G, Franke KJ, Pascual JI, Tegeder P (2011) Switching ability of nitro-spiropyran on Au(111): electronic structure changes as a sensitive probe during a ring-opening reaction. J Phys Condens Matter 23:484005CrossRefGoogle Scholar
  26. 26.
    Bronner C, Schulze M, Hagen S, Tegeder P (2012) The influence of the electronic structure of adsorbate-substrate complexes on the photoisomerization ability. New J Phys 14:043032CrossRefGoogle Scholar
  27. 27.
    Bronner C, Leyssner F, Stremlau S, Utecht M, Saalfrank P, Klamroth T, Tegeder P (2012) Electronic structure of a sub-nanometer wide bottom-up fabricated graphene nanoribbon: end states, band gap and dispersion. Phys Rev B 86:085444CrossRefGoogle Scholar
  28. 28.
    Bronner C, Utecht M, Haase A, Saalfrank P, Klamroth T, Tegeder P (2014) Electronic structure changes during the surface-assisted formation of a graphene nanoribbon. J Chem Phys 140:024701CrossRefGoogle Scholar
  29. 29.
    Bronner C, Haase A, Tegeder P (2015) Image potential states at chevron-shaped graphene nanoribbons/Au(111) interfaces. Phys Rev B 91:045428CrossRefGoogle Scholar
  30. 30.
    Dutton G, Quinn DP, Lindstrom CD, Zhu X-Y (2005) Exciton dynamics at molecule-metal interfaces: C60 /Au(111). Phys Rev B 72:045441CrossRefGoogle Scholar
  31. 31.
    Chan W-L, Ligges M, Jailaubekov A, Kaake L, Miaja-Avila L, Zhu X-Y (2011) Observing the multiexciton state in singlet fission and ensuing ultrafast multielectron transfer. Science 334:1541–1545CrossRefGoogle Scholar
  32. 32.
    Marks M, Sachs S, Schwalb CH, Schöll A, Höfer U (2013) Electronic structure and excited state dynamics in optically excited PTCDA films investigated with two-photon photoemission. J Chem Phys 139:124701CrossRefGoogle Scholar
  33. 33.
    Muntwiler M, Yang Q, Tisdale WA, Zhu X-Y (2008) Coulomb barrier for charge separation at an organic semionductor interface. Phys Rev Lett 101:196403CrossRefGoogle Scholar
  34. 34.
    Zhu X-Y, Yang Q, Muntwiler M (2009) Charge-transfer excitons at organic semiconductor surfaces and interfaces. Acc Chem Res 42:1779–1787CrossRefGoogle Scholar
  35. 35.
    Katz HE (1997) Organic molecular solids as thin film transistor semiconductors. J Mater Chem 7:369–376CrossRefGoogle Scholar
  36. 36.
    Fichou D (2000) Structural order in conjugated oligothiophenes and its implications on opto-electronic devices. J Mater Chem 10:571–588CrossRefGoogle Scholar
  37. 37.
    Sakai J, Taima T, Saito K (2008) Efficient oligothiophene: fullerene bulk heterojunction organic photovoltaic cells. Org Electron 9:582–590CrossRefGoogle Scholar
  38. 38.
    Kiguchi M, Entani S, Saiki K, Yoshikawa G (2004) One-dimensional ordered structure of α-sexithienyl on Cu(110). Appl Phys Lett 84:3444–3446CrossRefGoogle Scholar
  39. 39.
    Koch N, Heimel G, Wu J, Zojer E, Johnson RL, Brédas J-L, Müllen K, Rabe JP (2005) Influence of molecular conformation on organic/metal interface energetics. Chem Phys Lett 413:390–395CrossRefGoogle Scholar
  40. 40.
    Kiel M, Duncker K, Hagendorf C, Widdra W (2007) Molecular structure and chiral separation in α-sexithiophene ultrathin films on Au(111): low-energy electron diffraction and scanning tunneling microscopy. Phys Rev B 75:195439CrossRefGoogle Scholar
  41. 41.
    Grobosch M, Knupfer M (2007) Charge-injection barriers at realistic metal/organic interfaces: metals become faceless. Adv Mater 19:754CrossRefGoogle Scholar
  42. 42.
    Yokoyama T, Kurata S, Tanaka S (2006) Direct identification of conformational isomers of adsorbed oligothiophene on Cu(100). J Phys Chem B 110:18130CrossRefGoogle Scholar
  43. 43.
    Kakudate T, Tsukamoto S, Nakaya M, Nakayama T (2006) Initial stage of adsorption of octithiophene molecules on Cu(111). Surf Sci 605:1021–1026CrossRefGoogle Scholar
  44. 44.
    Mishra A, Uhrich C, Reinold E, Pfeiffer M, Bäuerle P (2011) Synthesis and characterization of acceptor-substituted oligothiophenes for solar cell applications. Adv Energy Mater 1:265–273CrossRefGoogle Scholar
  45. 45.
    Ziehlke H, Fitzner R, Körner C, Gresser R, Reinold E, Bäuerle P, Leo K, Riede M (2011) Side chain variations on a series of dicyanovinyl-terthiophenes: a photoinduced absorption study. J Phys Chem A 115:8437–8446CrossRefGoogle Scholar
  46. 46.
    Fitzner R, Reinold E, Mishra A, Mena-Osteritz E, Ziehlke H, Körner C, Leo K, Riede M, Weil M, Tsaryova O, Weiß A, Uhrich C, Pfeiffer M, Bäuerle P (2011) Dicyanovinyl-substituted oligothiophenes: structure-property relationships and application in vacuum-processed small-molecule organic solar cells. Adv Funct Mater 21:897–910CrossRefGoogle Scholar
  47. 47.
    Fitzner R, Mena-Osteritz E, Mishra A, Schulz G, Reinold E, Weil M, Körner C, Ziehlke H, Elschner C, Leo K, Riede M, Pfeiffer M, Uhrich C, Bäuerle P (2012) Correlation of π-conjugated oligomer structure with film morphology and organic solar cell performance. J Am Chem Soc 134:11064–11067CrossRefGoogle Scholar
  48. 48.
    Meerheim R, Körner C, Leo K (2014) Highly efficient organic multi-junction solar cells with a thiophene based donor material. Appl Phys Lett 105:063306CrossRefGoogle Scholar
  49. 49.
    Ludwigs S (ed) (2014) P3HT revisited—from molecular scale to solar cell devices. Advances in polymer science, vol 265. Springer, Berlin, HeidelbergGoogle Scholar
  50. 50.
    Shen YR (1984) The principles of nonlinear optics. Wiley, New YorkGoogle Scholar
  51. 51.
    Shen YR (1989) Surface properties probed by second-harmonic and sum-frequency generation. Nature 337:519–525CrossRefGoogle Scholar
  52. 52.
    Heinz TF (1991) Second-order nonlinear optical effects at surfaces and interfaces. Elsevier, AmsterdamCrossRefGoogle Scholar
  53. 53.
    McGilp JF (1996) A review of optical second-harmonic and sum- frequency generation at surfaces and interfaces. J Phys D Appl Phys 29:1812–1821CrossRefGoogle Scholar
  54. 54.
    Varene E, Martin I, Tegeder P (2011) Optically induced inter- and intrafacial electron transfer probed by two-photon photoemission: electronic states of sexithiophene on Au(111). J Phys Chem Lett 2:252–256CrossRefGoogle Scholar
  55. 55.
    Tegeder P (2012) Optically and thermally induced molecular switching processes at metal surfaces. J Phys Condens Matter 24:394001 (34pp)CrossRefGoogle Scholar
  56. 56.
    Knupfer M, Liu X (2006) Interface electronic properties of oligothiophenes: the effect of chain length and chemical substituents. Surf Sci 600:3978–2981CrossRefGoogle Scholar
  57. 57.
    Dutton G, Zhu X-Y (2002) Unoccupied states in C60 thin films probed by two-photon photoemission. J Phys Chem B 106:5975–6981CrossRefGoogle Scholar
  58. 58.
    Oeter D, Egelhaaf HJ, Ziegler Ch, Oelkrug D, Göpel W (1994) Electronic transitions in α-oligothiophene thin films. comparison of ultraviolet/visible absorption spectroscopy and high resolution electron energy loss spectroscopy investigations. J Chem Phys 101:6344– 6352CrossRefGoogle Scholar
  59. 59.
    Egelhaaf HJ, Oelkrug D, Oeter D, Ziegler Ch, Göpel W (1995) HREELS and UV/VIS spectroscopic studies on the electronic structure of oligothiophene thin films. J Mol Struct 384:405–408CrossRefGoogle Scholar
  60. 60.
    Varene E, Bogner L, Meyer S, Pennec Y, Tegeder P (2012) Coverage-dependent adsorption geometry of octithiophene on Au(111). Phys Chem Chem Phys 14:691–696CrossRefGoogle Scholar
  61. 61.
    Zade SS, Bendikov M (2006) From oligomers to polymer: convergence in the HOMO-LUMO gaps of conjugated oligomers. Org Lett 8:5243–5246CrossRefGoogle Scholar
  62. 62.
    Bogner L, Yang Z, Corso M, Fitzner R, Bäuerle P, Franke KJ, Pascual JI, Tegeder P (2015) Electronic structure and excited states dynamics in a dicyanovinyl-substituted oligothiophene on Au(111). Phys Chem Chem Phys 17:27118–27126CrossRefGoogle Scholar
  63. 63.
    Bogner L, Yang Z, Corso M, Fitzner R, Bäuerle P, Franke KJ, Pascual JI, Tegeder P (2016, in preparation) Electronic structure and exciton dynamics in optically excited dicyanovinyl-sexithiophene on Au(111)Google Scholar
  64. 64.
    Fernández Torrente I, Franke KJ,Pascual JI (2008) Spectroscopy of C60 single molecules: the role of screening on energy level alignment. J Phys Condens Matter 20:184001CrossRefGoogle Scholar
  65. 65.
    Schwalb CH, Sachs S, Marks M, Schöll A, Reinert F, Umbach E, Höfer U (2008) Electron lifetime in a Shockley-type metal-organic interface state. Phys Rev Lett 101:146801CrossRefGoogle Scholar
  66. 66.
    Galbraith MCE, Marks M, Tonner R, Höfer U (2014) Formation of an organic/metal interface state from a shockley resonance. J Phys Chem Lett 5:50–55CrossRefGoogle Scholar
  67. 67.
    Marks M, Schöll A, Höfer U (2014) Formation of metal-organic interface states studied with 2PPE. J Electron Spectrosc Relat Phenom 195:263–271CrossRefGoogle Scholar
  68. 68.
    Weinelt M, Kutschera M, Fauster T, Rohlfing M (2004) Dynamics of exciton formation at the Si(100) c(4×2) surface. Phys Rev Lett 92:126801.CrossRefGoogle Scholar
  69. 69.
    Varene E, Pennec Y, Tegeder P (2011) Assembly and electronic structure of octithiophene on Au(111). Chem Phys Lett 515:141–145CrossRefGoogle Scholar
  70. 70.
    Lanzani G, Frolov SV, Lane PA, Vardeny ZV, Nisoli M, De Sivestri S (1997) Transient spectroscopy of frenkel and charge transfer excitons in α-sexithienyl films. Phys Rev Lett 79:3066–3069CrossRefGoogle Scholar
  71. 71.
    Watanabe K, Asahi T, Fukumura H, Masuhara H, Hamano K, Kurata T (1997) Ultrafast decay dynamics of excited and charged states in α-sexithienyl film as revealed by femtosecond transient absorption and picosecond fluorescence spectroscopy. J Phys Chem B 101:1510–1519CrossRefGoogle Scholar
  72. 72.
    Urbasch G, Giessen H, Murgia M, Zamboni R, Mahrt RF (2000) Femtosecond differential transmission spectroscopy of α-sexithienyl thin film at low temperature. J Phys Chem B 104:6536–6540CrossRefGoogle Scholar
  73. 73.
    Yang A, Shipman ST, Garrett-Roe S, Johns J, Strader M, Szymanski P, Muller E, Harris CB (2008) Two-photon photoemission of ultrathin film ptcda morphologies on Ag(111). J Phys Chem C 112:2506CrossRefGoogle Scholar
  74. 74.
    Varene E, Bogner L, Bronner C, Tegeder P (2012) Ultrafast exciton population, relaxation, and decay dynamics in thin oligothiophene films. Phys Rev Lett 109:207601CrossRefGoogle Scholar
  75. 75.
    Koch SW, Kira M, Khitrova G, Gibbs HM (2006) Semiconductor excitons in new light. Nat Mat 5:523–531CrossRefGoogle Scholar
  76. 76.
    Louarn G, Buisson JP, Lefrant S, Fichou D (1995) Vibrational studies of a series of α-oligothiophenes as model systems of polythiophene. J Phys Chem 99:11399–11404CrossRefGoogle Scholar
  77. 77.
    Johns JE, Muller EA, Frechet JMJ, Harris CB (2010) The origin of charge localization observed in organic photovoltaic materials. J Am Chem Soc 132:15720–15725CrossRefGoogle Scholar
  78. 78.
    Miller AD, Bezel I, Gaffney KJ, Garrett-Roe S, Liu SH, Szymanski P, Harris CB (2002) Electron solvation in two dimensions. Science 297:1163–1166CrossRefGoogle Scholar
  79. 79.
    Kaake LG, Barbara PF, Zhu X-Y (2010) Intrinsic charge trapping in organic and polymeric semiconductors: a physical chemistry perspective. J Phys Chem Lett 1:628–635CrossRefGoogle Scholar
  80. 80.
    Bovensiepen U, Stähler J, Gahl C, Bockstedte M, Meyer M, Baletto F, Scandolo S, Zhu X-Y, Rubio A, Wolf M (2009) A dynamic landscape from femtoseconds to minutes for excess electrons at ice-metal interfaces. J Phys Chem C 113:979–988CrossRefGoogle Scholar
  81. 81.
    Dang MT, Hirsch L, Wantz G (2011) P3HT:PCBM best seller in polymer photovoltaic research. Adv Mater 23:3597–3602CrossRefGoogle Scholar
  82. 82.
    Dennler G, Scharber MC, Brabec CJ (2009) Polymer-fullerene bulk-heterojunction solar cells. Adv Mater 21:1323–1338CrossRefGoogle Scholar
  83. 83.
    Green MA, Emery K, Hishikawa Y, Warta W, Dunlop ED (2012) Solar cell efficiency tables (version 39). Prog Photovolt Res Appl 20:12–20CrossRefGoogle Scholar
  84. 84.
    Chen K, Barker AJ, Reish ME, Gordon KC, Hodgkiss JM (2013) Broadband ultrafast photoluminescence spectroscopy resolves charge photogeneration via delocalized hot excitons in polymer: fullerene photovoltaic blends. J Am Chem Soc 135:18502–18512CrossRefGoogle Scholar
  85. 85.
    Jailaubekov AE, Willard AP, Tritsch JR, Chan W-L, Sai N, Gearba R, Kaake LG, Williams KJ, Leung K, Rossky PJ et al (2013) Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics. Nat Mater 12:66–73CrossRefGoogle Scholar
  86. 86.
    Grancini G, Maiuri M, Fazzi D, Petrozza A, Egelhaaf H-J, Brida D, Gerullo G, Lanzani G (2013) Hot exciton dissociation in polymer solar cells. Nat Mater 12:29–33CrossRefGoogle Scholar
  87. 87.
    Borges I Jr, Aquino AJA, Köhn A, Nieman R, Hase WWL, Chen LX, Lischka H (2013) Ab initio modeling of excitonic and charge-transfer states in organic semiconductors: the PTB1/PCBM low band gap system. J Am Chem Soc 135:18252–18255CrossRefGoogle Scholar
  88. 88.
    Gélinas S, Rao A, Kumar A, Smith SL, Chin AW, Clark J, van der Poll TS, Bazan GC, Friend RH (2014) Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes. Science 343:512–516CrossRefGoogle Scholar
  89. 89.
    Vandewal K, Albrecht S, Hoke ET, Graham KR, Widmer J, Douglas JD, Schubert M, Mateker WR, Bloking JT, Burkhard FG et al (2014) Efficient charge generation by relaxed charge-transfer states at organic interfaces. Nat Mater 13:63–68CrossRefGoogle Scholar
  90. 90.
    Albrecht S, Vandewal K, Tumbleston JR, Fischer FSU, Douglas JD, Fréchet JMJ, Ludwigs S, Ade H, Salleo A, Neher D (2014) On the efficiency of charge transfer state splitting in polymer:fullerene solar cells. Nat Mater 26:2533–2539, 2014.Google Scholar
  91. 91.
    Ma W, Yang C, X Gong X, Lee K, Heeger AJ (2005) Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology. Adv Funct Mater 15:1617–1622Google Scholar
  92. 92.
    Campoy-Quiles M, Ferenczi T, Agostinelli T, Etchegoin PG, Kim Y, Anthopoulos TD, Stavrinou PN, Bradley DDC, Nelson J (2008) Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends. Nat Mater 7:158–164CrossRefGoogle Scholar
  93. 93.
    Xu Z, Chen L-M, Chen M-H, Li G, Yang Y (2009) Energy level alignment of poly(3-hexylthiophene): [6,6]-phenyl c61 butyric acid methyl ester bulk heterojunction. Appl Phys Lett 95:013301CrossRefGoogle Scholar
  94. 94.
    Kim Y, Cook S, Tuladhar SM, Choulis SA, Nelson J, Durrant JR, Bradley DDC, Giles M, McCulloch I, Ha C-S et al (2006) Strong regioregularity effect in self-organizing conjugated polymer films and high-efficiency polythiophene:fullerene solar cells. Nat Mater 5:197–203CrossRefGoogle Scholar
  95. 95.
    Mauer R, Kastler M, Laquai F (2010) The impact of polymer regioregularity on charge transport and efficiency of P3HT:PCBM photovoltaic devices. Adv Funct Mater 20:2085–2092CrossRefGoogle Scholar
  96. 96.
    Agostinelli T, Lilliu S, Labram JC, Campoy-Quilles M, Hampton M, Pires Rawle EJ, Bikondoa O, Bradley DDC, Anthopoulos D (2011) Real-time investigation of crystallization and phase-segregation dynamics in P3HT:PCBM solar cells during thermal annealing. Adv Funct Mater 21:1701–1708CrossRefGoogle Scholar
  97. 97.
    Chirvase D, Parisi J, Hummelen JC, Dyakonov V (2004) Influence of nanomorphology on the photovoltaic action of polymer-fullerene composites. Nanotechnology 15:1317–1323CrossRefGoogle Scholar
  98. 98.
    Schulze M, Hänsel M, Tegeder P (2014) Hot excitons increase the donor/acceptor charge transfer yield. J Phys Chem C 118:28527–28534CrossRefGoogle Scholar
  99. 99.
    Bouhelier A, Beversluis M, Hartschuh A, Novotny L (2003) Field second-harmonic generation induced by local field enhancement. Phys Rev Lett 90:013903–1–013903–4, 2003.Google Scholar
  100. 100.
    Janner A-M, Eder R, Koopmans R, Jonkman HT, Sawatzky GA (1995) Excitons in C60 studied by temperature-dependent optical second-harmonic generation. Phys Rev B 52:17158–17164CrossRefGoogle Scholar
  101. 101.
    Guo J, Ohkita H, Benten H, Ito S (2010) Charge generation and recombination dynamics in poly(3-hexylthiophene)/fullerene blend films with different regioregularities and morphologies. J Am Chem Soc 132:6154–6164CrossRefGoogle Scholar
  102. 102.
    Herrmann D, Niesar S, Scharsich C, Köhler A, Stutzmann M, Riedle E (2011) Role of structural order and excess energy on ultrafast free charge generation in hybrid polythiophene/Si photovoltaics probed in real time by near-infrared broadband transient absorption. J Am Chem Soc 133:18220–18233CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.Physikalisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergHeidelbergGermany

Personalised recommendations