Abstract
Central to the operation of organic electronic and optoelectronic devices is the transport of charge and energy in the organic semiconductor, and to understand the nature and dynamics of charge carriers is at the focus of intense research efforts. As a basic transport property of solids, the Seebeck coefficient S provides deep insight as it is given by the entropy transported by thermally excited charge carriers and involves in the simplest case only electronic contributions where the transported entropy is determined by details of the band structure and scattering events. We have succeeded for the first time to measure the temperature- and carrier-density-dependent thermopower in single crystals and thin films of two prototypical organic semiconductors by a controlled modulation of the chemical potential in a field-effect geometry. Surprisingly, we find the Seebeck coefficient to be well within the range of the electronic contribution in conventional inorganic semiconductors, highlighting the similarity of transport mechanisms in organic and inorganic semiconductors. Charge and entropy transport is best described as band-like transport of quasiparticles that are subjected to scattering, with exponentially distributed in-gap trap states, and without further contributions to S.
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References
Siegrist, T., Kloc, C., Laudise, R. A., Katz, H. E. & Haddon, R. C. Crystal growth, structure, and electronic band structure of α-4T polymorphs. Adv. Mater. 10, 379–382 (1998).
Hummer, K. & Ambrosch-Draxl, C. Electronic properties of oligoacenes from first principles. Phys. Rev. B 72, 205205 (2005).
da Silva Filho, D., Kim, E.-G. & Brédas, J.-L. Transport properties in the rubrene crystal: Electronic coupling and vibrational reorganization energy. Adv. Mater. 17, 1072–1076 (2005).
Ortmann, F., Hannewald, K. & Bechstedt, F. Ab initio studies of structural, vibrational, and electronic properties of durene crystals and molecules. Phys. Rev. B 75, 195219 (2007).
Hannewald, K. et al. Theory of polaron bandwidth narrowing in organic molecular crystals. Phys. Rev. B 69, 075211 (2004).
Troisi, A. & Orlandi, G. Charge-transport regime of crystalline organic semiconductors: Diffusion limited by thermal off-diagonal electronic disorder. Phys. Rev. Lett. 96, 086601 (2006).
Silinsh, E. A. & Čápek, V. Organic Molecular Crystals: Interaction, Localization, and Transport Phenomena (AIP Press, New York, 1994).
Hannewald, K. & Bobbert, P. A. Anisotropy effects in phonon-assisted charge-carrier transport in organic molecular crystals. Phys. Rev. B 69, 075212 (2004).
Hulea, I. N. et al. Tunable Fröhlich polarons in organic single-crystal transistors. Nature Mater. 5, 982–986 (2006).
Devreese, J. T. Polarons. Encyclopedia Appl. Phys. 14, 383–409 (1996).
Emin, D. Enhanced Seebeck coefficient from carrier-induced vibrational softening. Phys. Rev. B 59, 6205–6210 (1999).
von Mühlenen, A., Errien, N., Schaer, M., Bussac, M.-N. & Zuppiroli, L. Thermopower measurements on pentacene transistors. Phys. Rev. B 75, 115338 (2007).
Geballe, T. H. & Hull, G. W. Seebeck effect in germanium. Phys. Rev. 94, 1134–1140 (1954).
Brandt, M. S., Herbst, P., Angerer, H., Ambacher, O. & Stutzmann, M. Thermopower investigation of n- and p-type GaN. Phys. Rev. B 58, 7786–7791 (1998).
Zuzok, R., Kaiser, A. B., Pukacki, W. & Roth, S. Thermoelectric power and conductivity of iodine-doped “new” polyacetylene. J. Chem. Phys. 95, 1270–1275 (1991).
Meyer, J. P., Schlettwein, D., Wöhrle, D. & Jaeger, N. I. Charge transport in thin films of molecular semiconductors as investigated by measurements of thermoelectric power and electrical conductivity. Thin Solid Films 258, 317–324 (1995).
Böhm, W., Fritz, T. & Leo, K. Charge transport in thin organic semiconducting films: Seebeck and field effect studies. Phys. Status Solidi A 160, 81–87 (1997).
Pfeiffer, M., Beyer, A., Fritz, T. & Leo, K. Controlled doping of phthalocyanine layers by cosublimation with acceptor molecules: A systematic Seebeck and conductivity study. Appl. Phys. Lett. 73, 3202–3204 (1998).
Maennig, B. et al. Controlled p-type doping of polycrystalline and amorphous organic layers: Self-consistent description of conductivity and field-effect mobility by a microscopic percolation model. Phys. Rev. B 64, 195208 (2001).
El-Nahass, M., Bahabri, F. S., Ghamdi, A. A. & Al-Harbi, S. R. Structural and transport properties of copper phthalocyanine (CuPc) thin films. Egypt. J. Solids 25, 307–321 (2002).
Pfeiffer, M. et al. Doped organic semiconductors: Physics and application in light emitting diodes. Org. Electron. 4, 89–103 (2003).
Wuesten, J., Ziegler, C. & Ertl, T. Electron transport in pristine and alkali metal doped perylene-3,4,9,10-tetracarboxylicdianhydride (PTCDA) thin films. Phys. Rev. B 74, 125205 (2006).
Reddy, P., Jang, S.-Y., Segalman, R. A. & Majumdar, A. Thermoelectricity in molecular junctions. Science 315, 1568–1571 (2007).
Hiroshige, Y., Ookawa, M. & Toshima, N. Thermoelectric figure-of-merit of iodine-doped copolymer of phenylenevinylene with dialkoxyphenylenevinylene. Synth. Met. 157, 467–474 (2007).
Cai, J. & Mahan, G. D. Effective Seebeck coefficient for semiconductors. Phys. Rev. B 74, 075201 (2006).
Fritzsche, H. A general expression for the thermoelectric power. Solid State Commun. 9, 1813–1815 (1971).
Mott, N. F. & Davis, E. A. Electronic Processes in Non-Crystalline Materials (Clarendon, Oxford, 1971).
Herring, C. Theory of the thermoelectric power of semiconductors. Phys. Rev. 96, 1163–1187 (1954).
Seeger, K. Semiconductor Physics (Springer, Berlin, 1973).
Callaerts, R., Nagels, P. & Denayer, M. Thermopower in amorphous As2Se3 . Phys. Lett. A 38, 15–16 (1972).
Kalb, W. L., Mathis, T., Haas, S., Stassen, A. F. & Batlogg, B. Organic small molecule field-effect transistors with Cytop gate dielectric: Eliminating gate bias stress effects. Appl. Phys. Lett. 90, 092104 (2007).
Takeya, J. et al. Field-induced charge transport at the surface of pentacene single crystals: A method to study charge dynamics of two-dimensional electron systems in organic crystals. J. Appl. Phys. 94, 5800–5804 (2003).
de Boer, R. W. I., Klapwijk, T. M. & Morpurgo, A. F. Field-effect transistors on tetracene single crystals. Appl. Phys. Lett. 83, 4345–4347 (2003).
Oberhoff, D., Pernstich, K. P., Gundlach, D. J. & Batlogg, B. Arbitrary density of states in an organic thin-film field-effect transistor model and application to pentacene devices. IEEE Trans. Electron Devices 54, 17–25 (2007).
Schein, L. B. & McGhie, A. R. Band-hopping mobility transition in naphthalene and deuterated naphthalene. Phys. Rev. B 20, 1631–1639 (1979).
Warta, W. & Karl, N. Hot holes in naphthalene: High, electric-field-dependent mobilities. Phys. Rev. B 32, 1172–1182 (1985).
Podzorov, V., Menard, E., Rogers, J. A. & Gershenson, M. E. Hall effect in the accumulation layers on the surface of organic semiconductors. Phys. Rev. Lett. 95, 226601 (2005).
Ostroverkhova, O. et al. Bandlike transport in pentacene and functionalized pentacene thin films revealed by subpicosecond transient photoconductivity measurements. Phys. Rev. B 71, 035204 (2005).
Marumoto, K., Kuroda, S., Takenobu, T. & Iwasa, Y. Spatial extent of wave functions of gate-induced hole carriers in pentacene field-effect devices as investigated by electron spin resonance. Phys. Rev. Lett. 97, 256603 (2006).
Fischer, M., Dressel, M., Gompf, B., Tripathi, A. K. & Pflaum, J. Infrared spectroscopy on the charge accumulation layer in rubrene single crystals. Appl. Phys. Lett. 89, 182103 (2006).
Koller, G. et al. Intra- and intermolecular band dispersion in an organic crystal. Science 317, 351–355 (2007).
Takeya, J. et al. In-crystal and surface charge transport of electric-field-induced carriers in organic single-crystal semiconductors. Phys. Rev. Lett. 98, 196804 (2007).
Li, Z. Q. et al. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors. Phys. Rev. Lett. 99, 016403 (2007).
Casu, M. B. et al. Investigation of polarization effects in organic thin films by surface core-level shifts. Phys. Rev. B 76, 193311 (2007).
Horowitz, G. Semiconducting Polymers: Chemistry, Physics and Engineering Vol. 2 (Wiley-VCH, Weinheim, 2007).
Krellner, C. et al. Density of bulk trap states in organic semiconductor crystals: Discrete levels induced by oxygen in rubrene. Phys. Rev. B 75, 245115 (2007).
Acknowledgements
The authors would like to thank K. Mattenberger and H.-P. Staub for technical support and A. Stassen, R. Häusermann, S. Haas for crystal growth. Special thanks are given to T. Mathis for preparation and characterization of a Cytop layer and to W. Kalb for helpful discussions.
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Pernstich, K., Rössner, B. & Batlogg, B. Field-effect-modulated Seebeck coefficient in organic semiconductors. Nature Mater 7, 321–325 (2008). https://doi.org/10.1038/nmat2120
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DOI: https://doi.org/10.1038/nmat2120
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