Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling


Carbon-based semiconductors such as conjugated organic polymers are of potential use in the development of spintronic devices and spin-based information processing. In particular, these materials offer a low spin–orbit coupling strength due to their relatively light constituent chemical elements, which should, in principle, favour long spin diffusion lengths. However, organic polymers are relatively disordered materials and typically have a carrier mobility that is orders of magnitude lower than crystalline inorganic materials. As a result, small spin diffusion lengths of around 50 nm have typically been measured using vertical organic spin valves. Here, we report measuring spin diffusion lengths in doped conjugated polymers using a lateral spin transport device architecture, which is based on spin pumping injection and inverse spin Hall detection. The approach suggests that long spin diffusion lengths of more than 1 μm and fast spin transit times of around 10 ns are possible in conjugated polymer systems when they have a sufficiently high spin density (around 1020 cm−3). We explain these results in terms of an exchange-based spin diffusion regime in which the exchange interactions decouple spin and charge transport.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Lateral spin pumping device architecture and measurement scheme.
Fig. 2: Observation of long-range spin transport in F4TCNQ-doped PBTTT.
Fig. 3: Carrier density dependence of spin current transport.
Fig. 4: Angular dependence of the ISHE signal.
Fig. 5: Theoretical modelling of spin transport in an exchange-mediated regime.

Data availability

The authors declare that all relevant data are included in the paper and in the accompanying Supplementary Information. Additional data are available from the corresponding authors upon reasonable request.

Change history

  • 16 May 2019

    Owing to a technical error, the ‘Published online’ date of this Article originally mistakenly appeared as ‘15 March 2019’, but should have been ‘18 March 2019’.


  1. 1.

    Cinchetti, M., Dediu, V. & Hueso, L. Activating the molecular spinterface. Nat. Mater. 16, 507–515 (2017).

    Article  Google Scholar 

  2. 2.

    Warner, M. et al. Potential for spin-based information processing in a thin-film molecular semiconductor. Nature 503, 504–508 (2013).

    Article  Google Scholar 

  3. 3.

    Dediu, V., Hueso, L., Bergenti, I. & Taliani, C. Spin routes in organic semiconductors. Nat. Mater. 8, 707–716 (2009).

    Article  Google Scholar 

  4. 4.

    Yu, Z. G. Spin–orbit coupling, spin relaxation, and spin diffusion in organic solids. Phys. Rev. Lett. 106, 106602 (2011).

    Article  Google Scholar 

  5. 5.

    Sinova, J., Valenzuela, S. O., Wunderlich, J., Back, C. H. & Jungwirth, T. Spin Hall effects. Rev. Mod. Phys. 87, 1213 (2015).

    Article  Google Scholar 

  6. 6.

    Yu, Z. G. Spin transport and the Hanle effect in organic spintronics. De Gruyter Open: Nanoelectronics and Spintronics 1, 1–18 (2015).

    Google Scholar 

  7. 7.

    Yu, Z. G. Impurity-band transport in organic spin valves. Nat. Commun. 5, 4842 (2014).

    Article  Google Scholar 

  8. 8.

    Yu, Z. G. Suppression of the Hanle effect in organic spintronic devices. Phys. Rev. Lett. 111, 016601 (2013).

    Article  Google Scholar 

  9. 9.

    Lou, X. et al. Electrical detection of spin transport in lateral ferromagnet–semiconductor devices. Nat. Phys. 3, 197–202 (2007).

    Article  Google Scholar 

  10. 10.

    Sirringhaus, H. 25th Anniversary article: Organic field-effect transistors: The path beyond amorphous silicon. Adv. Mater. 26, 1319–1335 (2014).

    Article  Google Scholar 

  11. 11.

    Xiong, Z. H., Wu, D., Vardeny, Z. V. & Shi, J. Giant magnetoresistance in organic spin-valves. Nature 427, 821–824 (2004).

    Article  Google Scholar 

  12. 12.

    Nguyen, T. D. et al. Isotope effect in spin response of π-conjugated polymer films and devices. Nat. Mater. 9, 345–352 (2010).

    Article  Google Scholar 

  13. 13.

    Zhang, X. et al. Observation of a large spin-dependent transport length in organic spin valves at room temperature. Nat. Commun. 4, 1392 (2013).

    Article  Google Scholar 

  14. 14.

    Mooser, S., Cooper, J. F. K., Banger, K. K., Wunderlich, J. & Sirringhaus, H. Spin injection and transport in a solution-processed organic semiconductor at room temperature. Phys. Rev. B 85, 235202 (2012).

    Article  Google Scholar 

  15. 15.

    Majumdar, S. & Majumdar, H. S. Decay in spin diffusion length with temperature in organic semiconductors—An insight of possible mechanisms. Org. Electron. 173, 26–30 (2013).

    Google Scholar 

  16. 16.

    Li, F., Li, T., Chen, F. & Zhang, F. Excellent spin transport in spin valves based on the conjugated polymer with high carrier mobility. Sci. Rep. 5, 9355 (2015).

    Article  Google Scholar 

  17. 17.

    Sasaki, T. et al. Temperature dependence of spin diffusion length in silicon by Hanle-type spin precession. Appl. Phys. Lett. 96, 122101 (2010).

    Article  Google Scholar 

  18. 18.

    Jain, A. et al. Crossover from spin accumulation into interface states to spin injection in the germanium conduction band. Phys. Rev. Lett. 109, 106603 (2012).

    Article  Google Scholar 

  19. 19.

    Drögeler, M. et al. Spin lifetimes exceeding 12 ns in graphene nonlocal spin valve devices. Nano Lett. 16, 3533–3539 (2016).

    Article  Google Scholar 

  20. 20.

    Yan, W. et al. Long spin diffusion length in few-layer graphene flakes. Phys. Rev. Lett. 117, 147201 (2016).

    Article  Google Scholar 

  21. 21.

    Szulczewski, G., Sanvito, S. & Coey, M. A spin of their own. Nat. Mater. 8, 693–695 (2009).

    Article  Google Scholar 

  22. 22.

    Grünewald, M. et al. Tunneling anisotropic magnetoresistance in organic spin valves. Phys. Rev. B 84, 125208 (2011).

    Article  Google Scholar 

  23. 23.

    Grünewald, M. et al. Vertical organic spin valves in perpendicular magnetic fields. Phys. Rev. B 88, 085319 (2013).

    Article  Google Scholar 

  24. 24.

    Jedema, F. J., Heersche, H. B., Filip, A. T., Baselmans, J. J. A. & van Wees, B. J. Electrical detection of spin precession in a metallic mesoscopic spin valve. Nature 416, 713–716 (2002).

    Article  Google Scholar 

  25. 25.

    Olejnik, K. et al. Detection of electrically modulated inverse spin Hall effect in an Fe/GaAs microdevice. Phys. Rev. Lett. 109, 076601 (2012).

    Article  Google Scholar 

  26. 26.

    Avsar, A. et al. Toward wafer scale fabrication of graphene based spin valve devices. Nano Lett. 11, 2363–2368 (2011).

    Article  Google Scholar 

  27. 27.

    Zhou, Y. et al. Electrical spin injection and transport in germanium. Phys. Rev. B 84, 125323 (2011).

    Article  Google Scholar 

  28. 28.

    Salis, G., Fuhrer, A., Schlittler, R., Gross, L. & Alvarado, S. Temperature dependence of the nonlocal voltage in an Fe/GaAs electrical spin-injection device. Phys. Rev. B 81, 205323 (2010).

    Article  Google Scholar 

  29. 29.

    Fujiwara, K. et al. 5d iridium oxide as a material for spin-current detection. Nat. Commun. 4, 2893 (2013).

    Article  Google Scholar 

  30. 30.

    Kamiya, T., Kawasugi, Y., Ara, M. & Tada, H., Nonlocal magnetoresistance measurements of the organic zero-gap conductor α−(BEDT−TTF)2I3. Phys. Rev. B 95, 085307 (2017).

  31. 31.

    Tombros, N., Jozsa, C., Popinciuc, M., Jonkman, H. T. & van Wees, B. J. Electronic spin transport and spin precession in single graphene layers at room temperature. Nature 448, 571–574 (2007).

    Article  Google Scholar 

  32. 32.

    Schmidt, G., Ferrand, D., Molenkamp, L. W., Filip, A. T. & van Wees, B. J. Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor. Phys. Rev. B 62, R4790 (2000).

    Article  Google Scholar 

  33. 33.

    Martin, S. et al. Flicker noise properties of organic thin-film transistors. J. Appl. Phys. 87, 3381–3385 (2000).

    Article  Google Scholar 

  34. 34.

    Jang, H.-J. & Richter, C. A. Organic spin-valves and beyond: spin injection and transport in organic semiconductors and the effect of interfacial engineering. Adv. Mater. 29, 1602739 (2017).

    Article  Google Scholar 

  35. 35.

    de Oliveira, T. V. A. G., Gobbi, M., Porro, J. M., Hueso, L. E. & Bittner, A. E. Charge and spin transport in PEDOT:PSS nanoscale lateral devices. Nanotechnology 24, 475201 (2013).

    Article  Google Scholar 

  36. 36.

    Tserkovnyak, Y., Brataas, A. & Bauer, G. E. W. Enhanced Gilbert damping in thin ferromagnetic films. Phys. Rev. Lett. 88, 117601 (2002).

    Article  Google Scholar 

  37. 37.

    Silsbee, R. H., Janossy, A. & Monod, P. Coupling between ferromagnetic and conduction-spin-resonance modes at a ferromagnetic–normal-metal interface. Phys. Rev. B 19, 4382 (1979).

    Article  Google Scholar 

  38. 38.

    Watanabe, S. et al. Polaron spin current transport in organic semiconductors. Nat. Phys. 10, 308 (2014).

    Article  Google Scholar 

  39. 39.

    Jiang, S. W. et al. Exchange-dominated pure spin current transport in Alq3 molecules. Phys. Rev. Lett. 115, 086601 (2015).

    Article  Google Scholar 

  40. 40.

    Mendes, J. B. S. et al. Efficient spin transport through polyaniline. Phys. Rev. B 95, 014413 (2017).

    Article  Google Scholar 

  41. 41.

    Maekawa, S., Valenzuela, S. O., Saitoh, E. & Kimura, T. Spin Current (Oxford Univ. Press, Oxford, 2012).

    Google Scholar 

  42. 42.

    Shikoh, E. et al. Spin-pump-induced spin transport in p-type Si at room temperature. Phys. Rev. Lett. 110, 127201 (2013).

    Article  Google Scholar 

  43. 43.

    Yamamoto, A., Ando, Y., Shinjo, T., Uemura, T. & Shiraishi, M. Spin transport and spin conversion in compound semiconductor with non-negligible spin–orbit interaction. Phys. Rev. B 91, 024417 (2015).

    Article  Google Scholar 

  44. 44.

    Tang, Z. et al., Dynamically generated pure spin current in single-layer graphene. Phys. Rev. B 87, 140401(R) (2013).

  45. 45.

    Dushenko, S. et al. Experimental demonstration of room-temperature spin transport in n-type germanium epilayers. Phys. Rev. Lett. 114, 196602 (2015).

    Article  Google Scholar 

  46. 46.

    Yamamoto, T., Seki, T., Ono, S. & Takanashi, K.,Characterization of spin pumping effect in Permalloy/Cu/Pt microfabricated lateral devices. J. Appl. Phys. 115, 17C505 (2014).

  47. 47.

    Ohshima, R. et al. Strong evidence for d-electron spin transport at room temperature at a LaAlO3/SrTiO3 interface. Nat. Mater. 16, 609–614 (2017).

    Article  Google Scholar 

  48. 48.

    Tserkovnyak, Y., Brataas, A. & Bauer, G. E. W. Spin pumping and magnetization dynamics in metallic multilayers. Phys. Rev. B 66, 224403 (2002).

    Article  Google Scholar 

  49. 49.

    Brataas, A., Tserkovnyak, Y., Bauer, G. & Halperin, B. Spin battery operated by ferromagnetic resonance. Phys. Rev. B 66, 060404(R) (2002).

    Article  Google Scholar 

  50. 50.

    Ando, K. & Saitoh, E. Observation of the inverse spin Hall effect in silicon. Nat. Commun. 3, 629 (2012).

    Article  Google Scholar 

  51. 51.

    Saitoh, E., Ueda, M., Miyajima, H. & Tatara, G. Conversion of spin current into charge current at room temperature: Inverse spin-Hall effect. Appl. Phys. Lett. 88, 182509 (2006).

    Article  Google Scholar 

  52. 52.

    McCulloch, I. et al. Liquid-crystalline semiconducting polymers with high charge-carrier mobility. Nat. Mater. 5, 328–333 (2006).

    Article  Google Scholar 

  53. 53.

    Schuettfort, T. et al. Microstructure of polycrystalline PBTTT Films: domain mapping and structure formation. ACS Nano 6, 1849–1864 (2012).

    Article  Google Scholar 

  54. 54.

    Kang, K. et al. 2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion. Nat. Mater. 15, 896–902 (2016).

    Article  Google Scholar 

  55. 55.

    Alberga, D. et al. Morphological and charge transport properties of amorphous and crystalline P3HT and PBTTT: insights from theory. Phys. Chem. Chem. Phys. 17, 18742 (2015).

    Article  Google Scholar 

  56. 56.

    Tani, Y., Kondo, T., Teki, Y. & Shikoh, E. Spin current relaxation time in thermally evaporated pentacene films. Appl. Phys. Lett. 110, 032403 (2017).

    Article  Google Scholar 

  57. 57.

    Morita, T. Spin diffusion in the Heisenberg magnets at infinite temperature. Phys. Rev. B 6, 3385 (1972).

    Article  Google Scholar 

  58. 58.

    Herring, C. & Flicker, M. Asymptotic exchange coupling of two hydrogen atoms. Phys. Rev. 134, A362 (1964).

    Article  Google Scholar 

  59. 59.

    Yu, Z. G., Ding, F. & Wang, H. Hyperfine interaction and its effects on spin dynamics in organic solids. Phys. Rev. B 87, 205446 (2013).

    Article  Google Scholar 

  60. 60.

    Elliott, R. J. Theory of the effect of spin–orbit coupling on magnetic resonance in some semiconductors. Phys. Rev. 96, 266–279 (1954).

    Article  Google Scholar 

  61. 61.

    Yafet, Y. in Solid State Physics (eds Seitz, F. & Turnbull, D.) 1–98 (Academic, New York, 1963).

  62. 62.

    Yu, Z. G. Spin–orbit coupling and its effects in organic solids. Phys. Rev. B 85, 115201 (2012).

    Article  Google Scholar 

  63. 63.

    Boeckmann, M. et al. Structure of P3HT crystals, thin films, and solutions by UV/Vis spectral analysis. Phys. Chem. Chem. Phys. 17, 28616 (2015).

    Article  Google Scholar 

  64. 64.

    Luzny, W. X-ray diffraction and computer modelling study of the structure and conformation of poly(3-decylthiophene). Acta Crystallogr. B 51, 255–260 (1995).

    Article  Google Scholar 

  65. 65.

    O’Dea, A. R., Curtis, A. F., Green, N. J. B., Timmel, C. R. & Hore, P. J. Influence of dipolar interactions on radical pair recombination reactions subject to weak magnetic fields. J. Phys. Chem. A 109, 869–873 (2005).

    Article  Google Scholar 

  66. 66.

    Riminucci, A. et al. Hanle effect missing in a prototypical organic spintronic device. Appl. Phys. Lett. 102, 092407 (2013).

    Article  Google Scholar 

  67. 67.

    Sakimura, H., Matsumoto, T. & Ando, K. Spin rectification induced by dynamical Hanle effect. Appl. Phys. Lett. 103, 132402 (2013).

    Article  Google Scholar 

Download references


The authors wish to thank L. Vila and S. Auffret from SPINTEC in France for support with the fabrication of Co/Al2O3 films used in the organic nonlocal spin valves. We also thank C. H. W. Barnes and S. J. Brennan from the Thin Film Magnetism group of the Cavendish Laboratory for support with metal deposition, and J. A. Haigh of Hitachi Cambridge Laboratories for discussions on the measurements. K. Müllen of MPI Mainz supplied the polymer CDT-BTZ, for which the authors are grateful. The inputs of C. Chen and J. Armitage on the doping of organic semiconductors is also gratefully acknowledged. D.V. is grateful to X.-J. She for discussions on orthogonal resists. G.S. acknowledges postdoctoral fellowship support from the Wiener-Anspach Foundation and the Leverhulme Trust (Early Career Fellowship supported by the Isaac Newton Trust). I.E.J. acknowledges funding from the Royal Society through a Newton International Fellowship. Finally, the authors are very grateful for the excellent technical support offered by R. Chakalov and R. Beadle during the course of the ERC Synergy grant. Funding from the ERC Synergy Grant SC2 (grant no. 610115) is gratefully acknowledged.

Author information



Corresponding authors

Correspondence to Deepak Venkateshvaran or Henning Sirringhaus.

Ethics declarations

Author contributions

S.-J.W., D.V., H.S. and J.W. developed the idea of probing spin transport in organic semiconductors using lateral spin pumping architectures. S.-J.W. and D.V. nanofabricated the devices and performed lateral spin pumping measurements. M.R.M., U.C., E.R.M., S.A.E., S.M., S.S. and J.S. developed the supporting theory. R.D.P. and A.W. set up the experimental facilities required to do the experiments. R.D.P., J.W. and D.V. conceived the ideas for control experiments to remove spurious artefacts. S.-J.W., G.S., K.K. and I.E.J. developed the doping techniques used. R.C. and S.S. performed ESR measurements. D.P.G.H.W. and S.S. performed the supporting Hanle simulations. C.J., M.L., A.M. and I.M. synthesized and characterized the polymers used. M.C., J.N.M.S., T.J.W., O.Z. and P.S. provided technical help with measurements. D.V. nanofabricated and measured organic nonlocal spin valves. R.O.A. and A.I. assisted with thin film deposition of ferromagnets and tunnel barriers for organic nonlocal spin valves. D.V., S.-J.W., E.R.M. and H.S. wrote the manuscript with inputs from the other authors. All authors within the ERC Synergy SC2 grant made significant contributions to discussions throughout the progression of the project.

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Sections 1–7.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wang, S., Venkateshvaran, D., Mahani, M.R. et al. Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling. Nat Electron 2, 98–107 (2019). https://doi.org/10.1038/s41928-019-0222-5

Download citation

Further reading


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing