[PDF]  https://doi.org/10.3952/physics.v60i1.4160

Open access article / Atviros prieigos straipsnis
Lith. J. Phys. 60, 1–25 (2020)
 
Review

CHARGE CARRIER MOBILITY DYNAMICS IN ORGANIC SEMICONDUCTORS AND SOLAR CELLS
 
Vidmantas Gulbinas
  Center for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
Email: vidmantas.gulbinas@ftmc.lt

Received 18 December 2019; accepted 20 December 2019

Charge carrier mobility in organic semiconductors is not a constant value unambigously characterizing some particular material, but depends on the electric field, temperature and even on time after it was generated or injected. The time dependence is particularly important for the thin-film devices where charge carriers pass the organic layer before mobility reaching its stationary value. Here we give a review of experimental techniques with ultrafast time-resolution enabling one to address the mobility kinetics and analyse properties of the time-dependent mobility in conjugated polymers and organic solar cells. We analyse kinetics during the charge carrier generation and extraction of free charge carriers. The mobility typically decreases by several orders of magnitude on a picosecond-nanosecond time scale; however, its kinetics also depends on the investigation technique. The mobility kinetics in blends for bulk heterojunction solar cells strongly depends on the stoichiometric ratio of donor and acceptor materials.
Keywords: charge carrier, mobility, kinetics, ultrafast
PACS: 06.60.Jn, 72.20.Jv, 73.63.–b

Apžvalga

KRŪVININKŲ JUDRIS ORGANINIUOSE PUSLAIDININKIUOSE IR SAULĖS ELEMENTUOSE
Vidmantas Gulbinas

Fizinių ir technologijos mokslų centras, Vilnius, Lietuva

Krūvininkų judrio vertė organiniuose puslaidininkiuose nėra pastovi, vienareikšmiškai apibūdinanti medžiagos savybes, tačiau priklauso nuo elektrinio lauko, temperatūros ir netgi po generacijos ar injektavimo bėgant laikui kinta. Judrio laikinė priklausomybė ypač svarbi plonasluoksniams prietaisams, kuriuose krūvininkai pereina organinį sluoksnį greičiau nei nusistovi pusiausviro judrio vertė. Šioje publikacijoje apžvelgiami eksperimentiniai aukštos laikinės skyros krūvininkų judrio tyrimo metodai ir analizuojama judrio kinetika konjuguotuosiuose polimeruose ar organiniuose saulės elementuose krūvininkų generacijos ir ištraukimo metu. Krūvininkų judris kinta keliomis eilėmis pikosekundinėje-nanosekundinėje laiko skalėje, tačiau jo dinamika taip pat priklauso ir nuo tyrimo metodo. Krūvininkų judrio kinetika organiniuose tūrinės heterosandūros saulės elementuose priklauso nuo donorinės ir akceptorinės medžiagų santykio.
 
References / Nuorodos

[1] Organic Electronics, Nat. Mater., Focus Issue: Vol. 12, No. 7 (2013),
https://www.nature.com/collections/lxgzgbqbcg
[2] H. Koezuka, A. Tsumura, and T. Ando, Field-effect transistor with polythiophene thin film, Synth. Met. 18, 699 (1987),
https://doi.org/10.1016/0379-6779(87)90964-7
[3] I.D.W. Samuel and G.A. Turnbull, Organic semiconductor lasers, Chem. Rev. 107, 1272 (2007),
https://doi.org/10.1021/cr050152i
[4] J. Kniepert, M. Schubert, J.C. Blakesley, and D. Neher, Photogeneration and recombination in P3HT/PCBM solar cells probed by time-delayed collection field experiments, J. Phys. Chem. Lett. 2, 700–705 (2011),
https://doi.org/10.1021/jz200155b
[5] D.H.K. Murthy, A. Melianas, Z. Tang, G. Juška, K. Arlauskas, F. Zhang, L.D.A. Siebbeles, O. Inganäs, and T.J. Savenije, Origin of reduced bimolecular recombination in blends of conjugated polymers and fullerenes, Adv. Func. Mat. 23, 4262 (2013),
https://doi.org/10.1002/adfm.201203852
[6] C. Deibel and V. Dyakonov, Polymer–fullerene bulk heterojunction solar cells, Rep. Prog. Phys. 73, 096401 (2010),
https://doi.org/10.1088/0034-4885/73/9/096401
[7] D. Amarasinghe Vithanage, A. Devižis, V. Abramavičius, Y. Infahsaeng, D. Abramavičius, R.C.I. MacKenzie, P.E. Keivanidis, A. Yartsev, D. Hertel, J. Nelson, V. Sundström, and V. Gulbinas, Visualizing charge separation in bulk heterojunction organic solar cells, Nat. Commun. 4, 2334 (2013),
https://doi.org/10.1038/ncomms3334
[8] A. Devižis, A. Serbenta, K. Meerholz, D. Hertel, and V. Gulbinas, Ultrafast dynamics of carrier mobility in a conjugated polymer probed at molecular and microscopic length scales, Phys. Rev. Lett. 103, 027404 (2009),
https://doi.org/10.1103/PhysRevLett.103.027404
[9] D. Moses, J. Wang, G. Yu, and A.J. Heeger, Temperature-independent photoconductivity in thin films of semiconducting polymers: photocarrier sweep-out prior to deep trapping, Phys. Rev. Lett. 80, 2685 (1998),
https://doi.org/10.1103/PhysRevLett.80.2685
[10] N. Stutzmann, R.H. Friend, and H. Sirringhaus, Self-aligned, vertical-channel, polymer field-effect transistors, Science 299, 1881 (2003),
https://doi.org/10.1126/science.1081279
[11] A. Melianas, F. Etzold, T.J. Savenije, F. Laquai, O. Inganäs, and M. Kemerink, Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells, Nat. Commun. 6, 8778 (2015),
https://doi.org/10.1038/ncomms9778
[12] A. Melianas, V. Pranculis, A. Devižis, V. Gulbinas, O. Inganäs, and M. Kemerink, Dispersion‐dominated photocurrent in polymer: fullerene solar cells, Adv. Func. Mat. 24, 4507 (2014),
https://doi.org/10.1002/adfm.201400404
[13] A. Einstein, Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen, Ann. Phys. 322, 549–560 (1905) [in German],
https://doi.org/10.1002/andp.200590005
[14] M. von Smoluchowski, Zur kinetischen Theorie der Brownschen Molekularbewegung und der Suspensionen, Ann. Phys. 326, 756–780 (1906) [in German],
https://doi.org/10.1002/andp.19063261405
[15] Y. Roichman and N. Tessler, Generalized Einstein relation for disordered semiconductors – implications for device performance, Appl. Phys. Lett. 80, 1948 (2002),
https://doi.org/10.1063/1.1461419
[16] G.A.H. Wetzelaer, L.J. Koster, and P.W. Blom, Validity of the Einstein relation in disordered organic semiconductors, Phys. Rev. Lett. 107, 066605 (2011),
https://doi.org/10.1103/PhysRevLett.107.066605
[17] P.W. Anderson, Absence of diffusion in certain random lattices, Phys. Rev. 109, 1492 (1958),
https://doi.org/10.1103/PhysRev.109.1492
[18] J. Frenkel, On pre-breakdown phenomena in insulators and electronic semi-conductors, Phys. Rev. 54, 647–648 (1938),
https://doi.org/10.1103/PhysRev.54.647
[19] P. Rottländer, M. Hehn, and A. Schuhl, Determining the interfacial barrier height and its relation to tunnel magnetoresistance, Phys. Rev. B 65(5), 054422 (2002),
https://doi.org/10.1103/PhysRevB.65.054422
[20] H. Bässler, Charge transport in disordered organic photoconductors – A Monte Carlo simulation study, Phys. Status Solidi B 175, 15 (1993),
https://doi.org/10.1002/pssb.2221750102
[21] P.M. Borsenberger, E.H. Magin, and J.J. Fitzgerald, Hole transport in 1,1-bis((di-4-tolylamino)phenyl) cyclohexane (TAPC) doped poly(styrene)s, J. Phys. Chem. 97, 8250 (1993),
https://doi.org/10.1021/j100133a022
[22] W.F. Laquai, G. Wegner, C. Im, H. Bässler, and S. Heun, Comparative study of hole transport in polyspirobifluorene polymers measured by the charge-generation layer time-of-flight technique, J. Appl. Phys. 99, 023712 (2006),
https://doi.org/10.1063/1.2165413
[23] A. Miller, Transient grating studies of carrier diffusion and mobility in semiconductors, in: Nonlinear Optics in Semiconductors II, Semiconductors and Semimetals Ser., Vol. 59 (Academic Press, 1998) pp. 287–312,
https://doi.org/10.1016/S0080-8784(08)62734-9
[24] D. Moses, M. Sinclair, and A.J. Heeger, Carrier photogeneration and mobility in polydiacetylene: Fast transient photoconductivity, Phys. Rev. Lett. 58, 2710 (1987),
https://doi.org/10.1103/PhysRevLett.58.2710
[25] O. Esenturk, J.S. Melinger, and E.J. Heilweil, Terahertz mobility measurements on poly-3-hexylthiophene films: Device comparison, molecular weight, and film processing effects, J. Appl. Phys. 103, 023102 (2008),
https://doi.org/10.1063/1.2828028
[26] P. Parkinson, J. Lloyd-Hughes, M.B. Johnston, and L.M. Herz, Efficient generation of charges via below-gap photoexcitation of polymer-fullerene blend films investigated by terahertz spectroscopy, Phys. Rev. B 78, 115321 (2008),
https://doi.org/10.1103/PhysRevB.78.115321
[27] V. Gulbinas, R. Kananavičius, L. Valkunas, and H. Bässler, Dynamic Stark effect as a probe of the evolution of geminate electron-hole pairs in a conjugated polymer, Phys. Rev. B 66, 233203 (2002),
https://doi.org/10.1103/PhysRevB.66.233203
[28] J. Cabanillas-Gonzalez, T. Virgili, A. Gambetta, G. Lanzani, T.D. Anthopoulos, and D.M. de Leeuw, Photoinduced transient stark spectroscopy in organic semiconductors: A method for charge mobility determination in the picosecond regime, Phys. Rev. Lett. 96, 106601 (2006),
https://doi.org/10.1103/PhysRevLett.96.106601
[29] C.H. Lee, J.Y. Park, Y.W. Park, D. Moses, A.J. Heeger, T. Noguchi, and T. Ohnishi, Polarization dependence of the photoconductivity of stretch-oriented poly(p-phenylenevinylene) films, Synth. Met. 101, 444–445 (1999),
https://doi.org/10.1016/S0379-6779(98)01139-4
[30] D. Moses, H. Okumoto, C.H. Lee, A.J. Heeger, T. Ohnishi, and T. Noguchi, Mechanism of carrier generation in poly(phenylene vinylene): Transient photoconductivity and photoluminescence at high electric fields, Phys. Rev. B 54, 4748–4754 (1996),
https://doi.org/10.1103/PhysRevB.54.4748
[31] C.A. Schmuttenmaer, Exploring dynamics in the far-infrared with terahertz spectroscopy, Chem. Rev. 104, 1759–1779 (2004),
https://doi.org/10.1021/cr020685g
[32] M.C. Beard, G.M. Turner, and C.A. Schmuttenmaer, Subpicosecond carrier dynamics in low-temperature grown GaAs as measured by time-resolved terahertz spectroscopy, J. Appl. Phys. 90, 5915 (2001),
https://doi.org/10.1063/1.1416140
[33] E. Hendry, M. Koeberg, J.M. Schins, H.K. Nienhuys, V. Sundström, L.D.A. Siebbeles, and M. Bonn, Interchain effects in the ultrafast photophysics of a semiconducting polymer: THz time-domain spectroscopy of thin films and isolated chains in solution, Phys. Rev. B 71, 5201 (2005),
https://doi.org/10.1103/PhysRevB.71.125201
[34] A.E. Jailaubekov, A.P. Willard, J.R. Tritsch, W.-L. Chan, N. Sai, R. Gearba, L.G. Kaake, K.J. Williams, K. Leung, P.J. Rossky, and X-Y. Zhu, Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics, Nature Mater. 12, 66 (2013),
https://doi.org/10.1038/nmat3500
[35] X. Wu, H. Park, X.-Y. Zhu, Probing transient electric fields in photoexcited organic semiconductor thin films and interfaces by time-resolved second harmonic generation, J. Phys. Chem. C 118, 10670 (2014),
https://doi.org/10.1021/jp502381j
[36] D. Taguchi, M. Weis, T. Manaka, and M. Iwamoto, Probing of carrier behavior in organic electroluminescent diode using electric field induced optical second-harmonic generation measurement, Appl. Phys. Lett. 95, 263310 (2009),
https://doi.org/10.1063/1.3277155
[37] S. Gélinas, A. Rao, A. Kumar, S.L. Smith, A.W. Chin, J. Clark, T.S. van der Poll, G.C. Bazan, and R.H. Friend, Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes, Science 343, 512–516 (2014),
https://doi.org/10.1126/science.1246249
[38] E.A. Silinsh and V. Capek, Organic Molecular Crystals: Interaction, Localization and Transport Phenomena (AIP Press, New York, 1994)
[39] N.E. Geacintov and M.J. Pope, Generation of charge carriers in anthracene with polarized light, Chem. Phys. 47, 1194 (1965),
https://doi.org/10.1063/1.1712044
[40] L. Onsager, Initial recombination of ions, Phys. Rev. 54, 554 (1938),
https://doi.org/10.1103/PhysRev.54.554
[41] J. Noolandi and K.M. Hong, Theory of photogeneration and fluorescence quenching, J. Chem. Phys. 70, 3230 (1979),
https://doi.org/10.1063/1.437912
[42] Z. Popovic, A study of carrier generation mechanism in x‐metal‐free phthalocyanine, J. Chem. Phys. 78, 1552 (1983),
https://doi.org/10.1063/1.444846
[43] T. Saito, W. Sisk, T. Kobayashi, S. Suzuki, and T. Iwayanagi, Photocarrier generation processes of phthalocyanines studied by photocurrent and electroabsorption measurements, J. Phys. Chem. 97, 8026 (1993),
https://doi.org/10.1021/j100132a036
[44] Z.D. Popovic, M.I. Khan, S.J. Atherton, A.-M. Hor, and J.L. Goodman, Study of carrier generation in titanyl phthalocyanine (TiOPc) by electric-field-induced quenching of integrated and time-resolved fluorescence, J. Phys. Chem. B 102, 657–663 (1998),
https://doi.org/10.1021/jp973188q
[45] V. Gulbinas, R. Jakubenas, S. Pakalnis, and A. Undzenas, Dynamics of charge carrier precursor photogeneration in titanyl phthalocyanine, J. Chem. Phys. 107, 4927–4933 (1997),
https://doi.org/10.1063/1.474856
[46] L. Robins, J. Orenstein, and R. Superfine, Observation of the triplet excited state of a conjugated-polymer crystal, Phys. Rev. Lett. 56, 1850 (1986),
https://doi.org/10.1103/PhysRevLett.56.1850
[47] C.H. Lee, G. Yu, D. Moses, and A.J. Heeger, Picosecond transient photoconductivity in poly(p-phenylenevinylene), Phys. Rev. B 49, 2396–2407 (1994),
https://doi.org/10.1103/PhysRevB.49.2396
[48] Primary Photoexcitations in Conjugated Polymers: Molecular Exciton Versus Semiconductor Band Model, ed. N.S. Sariciftci (World Scientific, Singapore, 1998),
https://doi.org/10.1142/3299
[49] M. Yan, L.J. Rothberg, F. Papadimitrakopoulos, M.E. Galvin, and T.M. Miller, Spatially indirect excitons as primary photoexcitations in conjugated polymers, Phys. Rev. Lett. 72, 1104 (1994),
https://doi.org/10.1103/PhysRevLett.72.1104
[50] U. Scherf, A. Bohnen, and K. Mullen, Polyarylenes and poly(arylenevinylene)s, 9. The oxidized states of a (1,4‐phenylene) ladder polymer, Makromol. Chem. 193, 1127 (1992),
https://doi.org/10.1002/macp.1992.021930511
[51] E.L. Frankevich, A.A. Lymarev, I. Sokolik, F.E. Karasz, S. Blumstengel, R.H. Baughman, and H.H. Hörhold, Polaron-pair generation in poly(phenylene vinylenes), Phys. Rev. B 46, 9320 (1992),
https://doi.org/10.1103/PhysRevB.46.9320
[52] W. Graupner, G. Cerullo, G. Lanzani, M. Nisoli, E.W. List, G. Leising, and S. De Silvestri, Direct observation of ultrafast field-induced charge generation in ladder-type poly(para-phenylene), Phys. Rev. Lett. 81, 3259 (1998),
https://doi.org/10.1103/PhysRevLett.81.3259
[53] Y. Zaushitsyn, V. Gulbinas, D. Zigmantas, F. Zhang, O. Inganäs, V. Sundström, and A. Yartsev, Ultrafast light-induced charge pair formation dynamics in poly[3-(2’-methoxy-5’-octylphenyl) thiophene], Phys. Rev. B 70, 075202 (2004),
https://doi.org/10.1103/PhysRevB.70.075202
[54] V. Gulbinas, Y. Zaushitsyn, V. Sundström, D. Hertel, H. Bässler, and A. Yartsev, Dynamics of the electric field-assisted charge carrier photogeneration in ladder-type poly(para-phenylene) at a low excitation intensity, Phys. Rev. Lett. 89, 107401 (2002),
https://doi.org/10.1103/PhysRevLett.89.107401
[55] I.G. Scheblykin, A. Yartsev, T. Pullerits, V. Gulbinas, and V. Sundström, Excited state and charge photogeneration dynamics in conjugated polymers, J. Phys. Chem. B 111, 6303–6321 (2007),
https://doi.org/10.1021/jp068864f
[56] V. Gulbinas, R. Kananavičius, L. Valkūnas, H. Bässler, and V. Sundström, Charge carrier photogeneration in conjugated polymer, Mater. Sci. Forum 384–385, 279–286, (2002),
https://doi.org/10.4028/www.scientific.net/MSF.384-385.279
[57] M. Weiter, H.B. Bässler, V. Gulbinas, and U. Scherf, Transient photoconductivity in a film of ladder-type poly-phenylene: Failure of the Onsager approach, Chem. Phys. Lett. 379, 177–182 (2003),
https://doi.org/10.1016/j.cplett.2003.08.043
[58] V. Gulbinas, Y. Zaushitsyn, H. Bässler, A. Yartsev, and V. Sundström, Dynamics of charge pair generation in ladder type poly(para-phenylene) at different excitation photon energies, Phys. Rev. B 70, 035215 (2004),
https://doi.org/10.1103/PhysRevB.70.035215
[59] W. Graupner, S. Eder, M. Mauri, G. Leising, and U. Scherf, Excited states in PPP-type ladderpolymers probed by photoinduced absorption, Synth. Met. 69, 419 (1995),
https://doi.org/10.1016/0379-6779(94)02511-V
[60] W. Graupner, T. Jost, K. Petritsch, S. Tasch, F. Meghdadi, G. Leising, M. Graupner, and A. Hermetter, Optoelectronic properties of polyphenyls, Annu. Tech. Conf. Soc. Plast. Eng. 43, 1339–1343 (1997)
[61] V. Gulbinas, D. Hertel, A. Yartsev, and V. Sundström, Charge carrier photogeneration and recombination in ladder-type poly(paraphenylene): Interplay between impurities and external electric field, Phys. Rev. B 76, 235203 (2007),
https://doi.org/10.1002/masy.200450802
[62] V. Arkhipov, H. Bässler, E. Emelyanova, D. Hertel, V. Gulbinas, and L. Rothberg, Exciton dissociations in conjugated polymers, Macromol. Symp. 212, 13–24 (2004),
https://doi.org/10.1002/masy.200450802
[63] J. Hou, O. Inganas, R.H. Friend, and F. Gao, Organic solar cells based on non-fullerene acceptors, Nat. Mater. 17, 119119 (2018),
https://doi.org/10.1038/nmat5063
[64] S. Gunes, H. Neugebauer, and N.S. Sariciftci, Conjugated polymer-based organic solar cells, Chem. Rev. 107, 1324–1338 (2007),
https://doi.org/10.1021/cr050149z
[65] H. Bässler and A. Köhler, ‘Hot or cold’: How do charge transfer states at the donor–acceptor interface of an organic solar dissociate?, Phys. Chem. Chem. Phys. 17, 28451 (2015),
https://doi.org/10.1039/c5cp04110d
[66] C.S. Ponseca Jr., P. Chábera, J. Uhlig, P. Persson, and V. Sundström, Ultrafast electron dynamics in solar energy conversion, Chem. Rev. 117, 10940−11024 (2017),
https://doi.org/10.1021/acs.chemrev.6b00807
[67] C.J. Brabec, G. Zerza, G. Cerullo, S. De Silvestri, S. Luzzati, J.C. Hummelen, and S. Sariciftci, Tracing photoinduced electron transfer process in conjugated polymer/fullerene bulk heterojunctions in real time, Chem. Phys. Lett. 340, 232 (2001),
https://doi.org/10.1016/S0009-2614(01)00431-6
[68] F.L. Zhang, K.G. Jespersen, C. Björström, M. Svensson, M.R. Andersson, V. Sundström, K. Magnusson, E. Moons, A. Yartsev, and O. Inganas, Copolymer/fullerene blends, Adv. Funct. Mater. 16, 667 (2006),
https://doi.org/10.1002/adfm.200500339
[69] R. Hidayat, Y. Nishihara, A. Fujii, M. Ozaki, K. Yoshino, and E. Frankevich, Time-resolved optical and electrical study of second-order processes responsible for the formation of free polarons in conjugated polymers, Phys. Rev. B 66, 075214 (2002),
https://doi.org/10.1103/PhysRevB.66.075214
[70] S.D. Dimitrov, A.A. Bakulin, C.B. Nielsen, B.C. Schroeder, J.P. Du, H. Bronstein, I. McCulloch, R.H. Friend, and J.R. Durrant, On the energetic dependence of charge separation in low-band-gap polymer/fullerene blends, J. Am. Chem. Soc. 134, 18189–18192 (2012),
https://doi.org/10.1021/ja308177d
[71] G. Grancini, M. Maiuri, D. Fazzi, A. Petrozza, H.-J. Egelhaaf, D. Brida, G. Cerullo, and G. Lanzani, Hot exciton dissociation in polymer solar cells, Nat. Mater. 12, 29–33 (2013),
https://doi.org/10.1038/nmat3502
[72] K. Chen, A.J. Barker, M.E. Reish, K.C. Gordon, and J.M. Hodgkiss, Broadband ultrafast photoluminescence spectroscopy resolves charge photogeneration via delocalized hot excitons in polymer-fullerene photovoltaic blends, J. Am. Chem. Soc. 135, 18502–18512 (2013),
https://doi.org/10.1021/ja408235h
[73] H. Ohkita, S. Cook, Y. Astuti, W. Duffy, S. Tierney, W.M. Zhang, M. Heeney, I. McCulloch, J. Nelson, D.D.C. Bradley, and J.R. Durrant, Charge carrier formation in polythiophene/fullerene blend films studied by transient absorption spectroscopy, J. Am. Chem. Soc. 130, 3030–3042 (2008),
https://doi.org/10.1021/ja076568q
[74] V. Abramavičius, D. Amarasinghe Vithanage, A. Devižis, Y. Infahsaeng, A. Bruno, S. Foster, P.E. Keivanidis, D. Abramavičius, J. Nelson, A. Yartsev, V. Sundström, and V. Gulbinas, Carrier motion in as-spun and annealed P3HT:PCBM blends revealed by ultrafast optical electric field probing and Monte Carlo simulations, Phys. Chem. Chem. Phys. 16, 2686–2692 (2014),
https://doi.org/10.1039/C3CP54605E
[75] K. Vandewal, S. Albrecht, E.T. Hoke, K.R. Graham, J. Widmer, J.D. Douglas, M. Schubert, W.R. Mateker, J.T. Bloking, G.F. Burkhard, et al., Efficient charge generation by relaxed charge-transfer states at organic interfaces, Nat. Mater. 13, 63–68 (2014),
https://doi.org/10.1038/nmat3807
[76] A. Armin, M. Velusamy, P. Wolfer, Y.L. Zhang, P.L. Burn, P. Meredith, and A. Pivrikas, Quantum efficiency of organic solar cells: Electro-optical cavity considerations, ACS Photonics 1, 173–181 (2014),
https://doi.org/10.1021/ph400044k
[77] T.G.J. van der Hofstad, D.D. Nuzzo, M. van dez Berg, R.A.J. Janssen, and S.C.J. Meskers, Influence of photon excess energy on charge carrier dynamics in a polymer-fullerene solar cell, Adv. Energy. Mater. 2, 1095–1099 (2012),
https://doi.org/10.1002/aenm.201200030
[78] M.A. Loi, S. Toffanin, M. Muccini, M. Forster, U. Scherf, and M. Scharber, Charge transfer excitons in bulk heterojunctions of a polyfluorene copolymer and a fullerene derivative, Adv. Func. Mater. 17, 2111–2116 (2007),
https://doi.org/10.1002/adfm.200601098
[79] B. Bernardo, D. Cheyns, B. Verreet, R.D. Schaller, B.P. Rand, and N.C. Giebink, Delocalization and dielectric screening of charge transfer states in organic photovoltaic cells, Nat. Commun. 5, 3245 (2014),
https://doi.org/10.1038/ncomms4245
[80] F.-J. Kahle, C. Saller, S. Olthof, C. Li, J. Lebert, S. Weiß, E.M. Herzig, S. Hüttner, K. Meerholz, P. Strohriegl, and A. Köhler, Does electron delocalization influence charge separation at donor-acceptor interfaces in organic photovoltaic cells?, J. Phys. Chem. C 122, 21792–21802 (2018),
https://doi.org/10.1021/acs.jpcc.8b06429
[81] V.I. Arkhipov, P. Heremans, and H. Bässler, Why is exciton dissociation so efficient at the interface between a conjugated polymer and an electron acceptor?, Appl. Phys. Lett. 82, 4605–4607 (2003),
https://doi.org/10.1063/1.1586456
[82] T.M. Clarke and J.R. Durrant, Charge photogeneration in organic solar cells, Chem. Rev. 110, 6736−6767 (2010),
https://doi.org/10.1021/cr900271s
[83] B.A. Gregg, Entropy of charge separation in organic photovoltaic cells: the benefit of higher dimensionality, J. Phys. Chem. Lett. 2, 3013–3015 (2011),
https://doi.org/10.1021/jz2012403
[84] F. Laquai, G. Wegner, C. Im, H. Bässler, and S. Heun, Nondispersive hole transport in carbazole- and anthracene-containing polyspirobifluorene copolymers studied by the charge-generation layer time-of-flight technique, J. Appl. Phys. 99, 033710 (2006),
https://doi.org/10.1063/1.2168590
[85] D. Hertel and H. Bässler, Photoconduction in amorphous organic solids, Chem. Phys. Chem. 9, 2–26 (2008),
https://doi.org/10.1002/cphc.200700575
[86] G. Juska, K. Genevicius, R. Osterbacka, K. Arlauskas, T. Kreouzis, D.D.C. Bradley, and H. Stubb, Initial transport of photogenerated charge carriers in p-conjugated polymers, Phys. Rev. B 67, 081201 (2003),
https://doi.org/10.1103/PhysRevB.67.081201
[87] E. Hendry, J.M. Schins, L.P. Candeias, L.D.A. Siebbeles, and M. Bonn, Efficiency of exciton and charge carrier photogeneration in a semiconducting polymer, Phys. Rev. Lett. 92, 6601 (2004),
https://doi.org/10.1103/PhysRevLett.92.196601
[88] E. Hendry, M. Koeberg, J.M. Schins, H.K. Nienhuys, V. Sundström, L.D.A. Siebbeles, and M. Bonn, Interchain effects in the ultrafast photophysics of a semiconducting polymer: THz time-domain spectroscopy of thin films and isolated chains in solution, Phys. Rev. B 71, 5201 (2005),
https://doi.org/10.1103/PhysRevB.71.125201
[89] E. Hendry, M. Koeberg, J.M. Schins, L.D.A. Siebbeles, and M. Bonn, Free carrier photogeneration in polythiophene versus poly(phenylene vinylene) studied with THz spectroscopy, Chem. Phys. Lett. 432, 441–445 (2006),
https://doi.org/10.1016/j.cplett.2006.10.105
[90] J.M. Warman, G.H. Gelinck, and M.P.D. Haas, The mobility and relaxation kinetics of charge carriers in molecular materials studied by means of pulse-radiolysis time-resolved microwave conductivity: Dialkoxy-substituted phenylene-vinylene polymers, J. Phys. C 14, 9935 (2002),
https://doi.org/10.1088/0953-8984/14/42/308
[91] G. Dicker, M.P.D. Haas, J.M. Warman, D.M.D. Leeuw, and L.D.A. Siebbeles, The disperse charge-carrier kinetics in regioregular poly(3-hexylthiophene), J. Phys. Chem. B 108, 17818 (2004),
https://doi.org/10.1021/jp046853l
[92] P.D. Cunningham, L.M. Hayden, H.-L. Yip, and A.K.-Y. Jen, Charge carrier dynamics in metalated polymers investigated by optical-pump terahertz-probe spectroscopy, J. Phys. Chem. B 113, 15427–15432 (2009),
https://doi.org/10.1021/jp906454g
[93] P.D. Cunningham and L.M. Hayden, Carrier dynamics resulting from above and below gap excitation of P3HT and P3HT/PCBM investigated by optical-pump terahertz-probe spectroscopy, J. Phys. Chem. C 112, 7928–7935 (2008),
https://doi.org/10.1021/jp711827g
[94] M.G. Harrison, S. Möller, G. Weiser, G. Urbasch, R.F. Mahrt, H. Bässler, and U. Scherf, Electrooptical studies of a soluble conjugated polymer with particularly low intrachain disorder, Phys. Rev. B 60, 8650 (1999),
https://doi.org/10.1103/PhysRevB.60.8650
[95] A. Devižis, A. Serbenta, D. Hertel, and V. Gulbinas, Exciton and polaron contributions to photocurrent in MeLPPP on a picosecond time scale, Mol. Cryst. Liq. Cryst. 496, 16–24 (2008),
https://doi.org/10.1080/15421400802451345
[96] P. Prins, F.C. Grozema, J.M. Schins, S. Patil, U. Scherf, and L.D.A. Siebbeles, High intrachain hole mobility on molecular wires of ladder-type poly(p-phenylenes), Phys. Rev. Lett. 96, 146601 (2006),
https://doi.org/10.1103/PhysRevLett.96.146601
[97] A. Devižis, K. Meerholz, D. Hertel, and V. Gulbinas, Hierarchical charge carrier motion in conjugated polymers, Chem. Phys. Lett. 498, 302–306 (2010),
https://doi.org/10.1016/j.cplett.2010.08.071
[98] C.H. Lee, G. Yu, and A.J. Heeger, Persistent photoconductivity in poly(p-phenylenevinylene): Spectral response and slow relaxation, Phys. Rev. B 47, 15543 (1993),
https://doi.org/10.1103/PhysRevB.47.15543
[99] A. Devizis, K. Meerholz, D. Hertel, and V. Gulbinas, Ultrafast charge carrier mobility dynamics in poly(spirobifluorene-co-benzothiadiazole): Influence of temperature on initial transport, Phys. Rev. B 82, 155204 (2010),
https://doi.org/10.1103/PhysRevB.82.155204
[100] R. Noriega, A. Salleo, and A.J. Spakowitz, Chain conformations dictate multiscale charge transport phenomena in disordered semiconducting polymers, PNAS 110, 16315–16320 (2013),
https://doi.org/10.1073/pnas.1307158110
[101] A. Devižis, D. Hertel, K. Meerholz, V. Gulbinas, and E. Moser, Time-independent, high electron mobility in thin PC61BM films: relevance to organic photovoltaics, Org. Electron. 15, 3729–3734 (2014),
https://doi.org/10.1016/j.orgel.2014.10.028
[102] L.J.A. Koster, Charge carrier mobility in disordered organic blends for photovoltaics, Phys. Rev. B 81, 205318 (2010),
https://doi.org/10.1103/PhysRevB.81.205318
[103] X. Ai, M.C. Beard, K.P. Knutsen, S.E. Shaheen, G. Rumbles, and R.J. Ellingson, Photoinduced charge carrier generation in a poly(3-hexylthiophene) and methanofullerene bulk heterojunction investigated by time-resolved terahertz spectroscopy, J. Phys. Chem. B 110, 25462−25471 (2006),
https://doi.org/10.1021/jp065212i
[104] P.D. Cunningham and L.M. Hayden, Carrier dynamics resulting from above and below gap excitation of P3HT and P3HT/PCBM investigated by optical-pump terahertz-probe spectroscopy, J. Phys. Chem. C 112, 7928–7935 (2008),
https://doi.org/10.1021/jp711827g
[105] C.S. Ponseca, A. Yartsev, E. Wang, M.R. Andersson, D. Vithanage, and V. Sundström, Ultrafast terahertz photoconductivity of bulk heterojunction materials reveals high carrier mobility up to nanosecond time scale, J. Am. Chem. Soc. 134, 11836–11839 (2012),
https://doi.org/10.1021/ja301757y
[106] D.G. Cooke, F.C. Krebs, and P.U. Jepsen, Direct observation of sub-100 fs mobile charge generation in a polymer-fullerene film, Phys. Rev. Lett. 108, 056603 (2012),
https://doi.org/10.1103/PhysRevLett.108.056603
[107] H. Němec, H.-K. Nienhuys, F. Zhang, O. Inganäs, A. Yartsev, and V. Sundström, Charge carrier dynamics in alternating polyfluorene copolymer: fullerene blends probed by terahertz spectroscopy, J. Phys. Chem. C 112, 6558–6563 (2008),
https://doi.org/10.1021/jp710184r
[108] R. Jasiūnas, A. Melianas, Y. Xia, N. Felekidis, V. Gulbinas, and M. Kemerink, Dead ends limit charge carrier extraction from all-polymer bulk heterojunction solar cells, Adv. Electron. Mater. 4, 1800144 (2018),
https://doi.org/10.1002/aelm.201800144
[109] G.A.H. Wetzelaer, L.J.A. Koster, and P.W.M. Blom, Validity of the Einstein relation in disordered organic semiconductors, Phys. Rev. Lett. 107, 066605 (2011),
https://doi.org/10.1103/PhysRevLett.107.066605
[110] V. Abramavicius, V. Pranculis, A. Melianas, O. Inganäs, V. Gulbinas, and D. Abramavicius, Role of coherence and delocalization in photoinduced electron transfer at organic interfaces, Sci. Rep. 6, 32914 (2016),
https://doi.org/10.1038/srep32914
[111] V. Pranculis, Y. Infahsaeng, Z. Tang, A. Devižis, D.A. Vithanage, C.S. Ponseca Jr., O. Inganäs, A.P. Yartsev, V. Gulbinas, and V. Sundström, Charge carrier generation and transport in different stoichiometry APFO3:PC61BM solar cells, J. Am. Chem. Soc. 136, 11331–11338 (2014),
https://doi.org/10.1021/ja503301m
[112] M. Schubert, E. Preis, J. Blakesley, P. Pingel, U. Scherf, and D. Neher, Mobility relaxation and electron trapping in a donor/acceptor copolymer, Phys. Rev. B 87, 024203 (2013),
https://doi.org/10.1103/PhysRevB.87.024203
[113] S. De, T. Pascher, M. Maiti, K.G. Jespersen, T. Kesti, F. Zhang, O. Inganäs, A. Yartsev, and V. Sundström, Geminate charge recombination in alternating polyfluorene copolymer/fullerene blends, J. Am. Chem. Soc. 129, 8466 (2007),
https://doi.org/10.1021/ja068909q
[114] V. Pranculis, A. Ruseckas, D.A. Vithanage, G.J. Hedley, I.D.W. Samuel, and V. Gulbinas, Influence of blend ratio and processing additive on free carrier yield and mobility in PTB7:PC71BM photovoltaic solar cells, J. Phys. Chem. C 120, 9588–9594 (2016),
https://doi.org/10.1021/acs.jpcc.6b01548
[115] R. Augulis, A. Devižis, D. Peckus, V. Gulbinas, D. Hertel, and K. Meerholz, High electron mobility and its role in charge carrier generation in merocyanine/fullerene blend, J. Phys. Chem. C 119, 5761–5770 (2015),
https://doi.org/10.1021/jp5054698
[116] A. Devizis, D. Peckus, D. Hertel, K. Meerholz, and V. Gulbinas, Charge carrier generation and transport in a polyfluorene copolymer with electron donating side groups doped with PCBM, J. Phys. Chem. 117, 15871–15878 (2013),
https://doi.org/10.1021/jp4014256
[117] A. Devižis, J. De Jonghe-Risse, R. Hany, F. Nuesch, S. Jenatsch, V. Gulbinas, and J.- E. Moser, Dissociation of charge transfer states and carrier separation in bilayer organic solar cells: A time-resolved electroabsorption spectroscopy study, J. Am. Chem. Soc., 137, 8192–8198 (2015),
https://doi.org/10.1021/jacs.5b03682
[118] D.A. Vithanage, A.B. Matheson, V. Pranculis, G.J. Hedley, S.J. Pearson, V. Gulbinas, I.D.W. Samuel, and A. Ruseckas, Barrier-less slow dissociation of photogenerated charge pairs in high-performance polymer-fullerene solar cells, J. Phys. Chem. C 121, 14060–14065 (2017),
https://doi.org/10.1021/acs.jpcc.7b04868
[119] M.A. Baldo, R.J. Holmes, and S.R. Forrest, Prospects for electrically pumped organic lasers, Phys. Rev. B 66, 035321 (2002),
https://doi.org/10.1103/PhysRevB.66.035321
[120] A. Melianas, V. Pranculis, A. Devižis, V. Gulbinas, O. Inganäs, and M. Kemerink, Dispersion-dominated photocurrent in polymer:fullerene solar cells, Adv. Funct. Mater. 24, 4507–4514 (2014),
https://doi.org/10.1002/adfm.201400404
[121] A. Melianas, V. Pranculis, Y. Xia, N. Felekidis, O. Inganäs, V. Gulbinas, and M. Kemerink, Photogenerated carrier mobility significantly exceeds injected carrier mobility in organic solar cells, Adv. Energy Mater. 7, 160214 (2017),
https://doi.org/10.1002/aenm.201602143
[122] N.J. van der Kaap and L.J.A. Koster, Charge carrier thermalization in organic diodes, Sci. Rep. 6, 19794 (2016),
https://doi.org/10.1038/srep19794
[123] V.M. Le Corre, A.R. Chatri, N.Y. Doumon, and L.J.A. Koster, Charge carrier extraction in organic solar cells governed by steady-state mobilities, Adv. Energy Mater. 7, 1701138 (2017),
https://doi.org/10.1002/aenm.201701138
[124] S. Athanasopoulos, F. Schauer, V. Nádaždy, M. Weiß, F.J. Kahle, U. Scherf, H. Bässler, and A. Köhler, What is the Binding Energy of a Charge Transfer State in an Organic Solar Cell, Adv. Energy Mater. 9, 1900814 (2019),
https://doi.org/10.1002/aenm.201900814