Electroluminescent device with reversible switching between red and green emission


Research on new materials for organic electroluminescence has recently focused strongly on phosphorescent emitters1,2,3, with the aim of increasing the emission efficiency and stability. Here we report the fabrication of a simple electroluminescent device, based on a semiconducting polymer combined with a phosphorescent complex, that shows fully reversible voltage-dependent switching between green and red light emission. The active material is made of a polyphenylenevinylene (PPV) derivative molecularly doped with a homogeneously dispersed dinuclear ruthenium complex, which fulfils the dual roles of triplet emitter and electron transfer mediator. At forward bias (+4 V), the excited state of the ruthenium compound is populated, and the characteristic red emission of the complex is observed. On reversing the bias (-4 V), the lowest excited singlet state of the polymer host is populated, with subsequent emission of green light. The mechanism for the formation of the excited state of the PPV derivative involves the ruthenium dinuclear complex in a stepwise electron transfer process that finally leads to efficient charge recombination reaction on the polymer.

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Figure 1: Electroluminescence spectra at forward bias (right) and reverse bias (left) of a light-emitting cell comprising a dinuclear Ru complex, [Ru(ph4)Ru]4+, mixed in a PPV host matrix as the emissive layer.
Figure 2: Schematic representation of the device structure (top), and plots of the current density (left) and photocurrent (right) versus voltage for the light-emitting cell described in Fig. 1.
Figure 3: Proposed mechanism for the emission of green light at reverse bias.


  1. 1

    Baldo, M. A. et al. Highly efficient phosphorescent emission from organic electroluminescent devices. Nature 395, 151–154 (1998)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Buda, M., Kalyuzhny, G. & Bard, A. J. Thin-film solid-state electroluminescent devices based on tris(2,2′-bipyridine)ruthenium(II) complexes. J. Am. Chem. Soc. 124, 6090–6098 (2002)

    CAS  Article  Google Scholar 

  3. 3

    Wu, A., Yoo, D., Lee, J.-K. & Rubner, M. F. Solid-state light emitting devices based on the tris-chelated ruthenium(II) complex. 3. High efficiency devices via a layer-by-layer molecular-level blending approach. J. Am. Chem. Soc. 121, 4883–4891 (1999)

    CAS  Article  Google Scholar 

  4. 4

    Faulkner, L. R. & Bard, A. J. Electroanalytical Chemistry (ed. Bard, A. J.) 1–95 (Marcel Dekker, New York, 1977)

    Google Scholar 

  5. 5

    Rudmann, H., Shimada, S. & Rubner, M. F. Solid-state light emitting devices based on the tris-chelated ruthenium(II) complex. 4. High-efficiency light-emitting devices based on derivatives of the tris(2,2′-bipyridyl) ruthenium(II) complex. J. Am. Chem. Soc. 124, 4918–4921 (2002)

    CAS  Article  Google Scholar 

  6. 6

    Handy, E. S., Pal, A. J. & Rubner, M. F. Solid-state light emitting devices based on the tris-chelated ruthenium(II) complex. 2. Tris(bipyridyl)ruthenium(II) as a high-brightness emitter. J. Am. Chem. Soc. 121, 3525–3528 (1999)

    CAS  Article  Google Scholar 

  7. 7

    Elliott, C. M., Pichot, F., Bloom, C. J. & Rider, L. S. Highly efficient solid-state electrochemically generated chemiluminescence from ester-substituted trisbipyridineruthenium(II)-based polymers. J. Am. Chem. Soc. 120, 6781–6784 (1998)

    CAS  Article  Google Scholar 

  8. 8

    Juris, A. et al. Ru(II) polypyridine complexes: photophysics, photochemistry, and chemiluminescence. Coord. Chem. Rev. 84, 85–277 (1988)

    CAS  Article  Google Scholar 

  9. 9

    Pei, Q., Yu, G., Yang, Y. & Heeger, A. J. Polymer light-emitting electrochemical cells. Science 269, 1086–1088 (1995)

    ADS  CAS  Article  Google Scholar 

  10. 10

    De Cola, L. & Belser, P. Photoinduced energy and electron transfer processes in rigidly bridged dinuclear Ru/Os complexes. Coord. Chem. Rev. 177, 301–346 (1998)

    CAS  Article  Google Scholar 

  11. 11

    Maness, K. M., Terrill, R. H., Meyer, T. J., Murray, R. W. & Wightman, R. M. Solid-state diode-like chemiluminescence based on serial, immobilized concentration gradients in mixed-valent poly[Ru(vbpy)3](PF6)2 films. J. Am. Chem. Soc. 118, 10609–10616 (1996)

    CAS  Article  Google Scholar 

  12. 12

    Luttmer, J. D. & Bard, A. J. Electrogenerated chemiluminescence. 38. Emission intensity-time transients in the tris(2,2′-bipyridine)ruthenium(II) system. J. Phys. Chem. 85, 1155–1159 (1981)

    CAS  Article  Google Scholar 

  13. 13

    deMello, J. C., Tessler, N., Graham, S. C. & Friend, R. H. Ionic space-charge effects in polymer light-emitting diodes. Phys. Rev. B 57, 12951–12963 (1998)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Brédas, J. L., Chance, R. R. & Silbey, R. Comparative theoretical study of the doping of conjugated polymers: polarons in polyacetylene and polyparaphenylene. Phys. Rev. B 26, 5843–5854 (1982)

    ADS  Article  Google Scholar 

  15. 15

    Berggren, M. et al. Light-emitting diodes with variable colours from polymer blends. Nature 372, 444–446 (1994)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Yang, Y. & Pei, Q. Voltage controlled two colour light-emitting electrochemical cells. Appl. Phys. Lett. 68, 2708–2710 (1996)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Hamaguchi, M. & Yoshino, K. Color-variable electroluminescence from multilayer polymer films. Appl. Phys. Lett. 69, 143–145 (1996)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Tasch, S. & Brandstätter, C. Red-green-blue light emission from a thin film electroluminescence device based on parahexaphenyl. Adv. Mater. 9, 33–36 (1997)

    CAS  Article  Google Scholar 

  19. 19

    DeCola, L. & Belser, P. Electron Transfer in Chemistry (ed. Balzani, V.) 97–136 (Wiley-VCH, Weinheim, 2001)

    Google Scholar 

  20. 20

    Yaliraki, S. N., Kemp, M. & Ratner, M. A. Conductance of molecular wires: influence of molecule-electrode binding. J. Am. Chem. Soc. 121, 3428–3434 (1999)

    CAS  Article  Google Scholar 

  21. 21

    Pourtois, G., Beljonne, D., Cornil, J., Ratner, M. A. & Brédas, J. L. Photoinduced electron-transfer processes along molecular wires based on phenylenevinylene oligomers: a quantum-chemical insight. J. Am. Chem. Soc. 124, 4436–4447 (2002)

    CAS  Article  Google Scholar 

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Correspondence to K. Brunner or L. De Cola.

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Welter, S., Brunner, K., Hofstraat, J. et al. Electroluminescent device with reversible switching between red and green emission. Nature 421, 54–57 (2003). https://doi.org/10.1038/nature01309

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