OSA's Digital Library

Optical Materials Express

Optical Materials Express

  • Editor: David Hagan
  • Vol. 4, Iss. 4 — Apr. 1, 2014
  • pp: 798–809

Dependence of the dynamics of exciton transport, energy relaxation, and localization on dopant concentration in disordered C545T-doped Alq3 organic semiconductors

Shih-Wei Feng  »View Author Affiliations

Optical Materials Express, Vol. 4, Issue 4, pp. 798-809 (2014)

View Full Text Article

Enhanced HTML    Acrobat PDF (2056 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



The dynamics of exciton transport, energy relaxation, and localization in disordered Tris(8-quinolinolato)-aluminum (Alq3) organic semiconductors with different 10-(2-benzothiazolyl)-1, 1, 7, 7-tetramethyl-2, 3, 6, 7-tetrahydro-lH, 5H, 11H-benzo[l] pyrano[6, 7, 8-і ј] quinolizin-11-one (C545T) dopant concentrations were reported. The increasing trend of the Stokes Shift (737~764 meV) with increasing dopant concentrations is consistent with the degree of disorder and a more effective Förster energy transfer from Alq3 to C545T. In addition, a dynamic scenario representing possible paths of the exciton transport (hopping) among host molecules and the competition of the exciton transport from host molecules into the deep site traps (localized states) and aggregations was proposed to elucidate the recombination dynamics in disordered C545T-doped Alq3 organic semiconductors. The early-stage decay times, decreasing with increasing emission photon energy, show the characteristic of the exciton hopping and energy relaxation processes within the inhomogeneously broadened density-of-states in organic semiconductors. Because the current-voltage (J-V) characteristics of the C545T-doped organic light emitting diode (OLED) fitted well with the power law J~Vm (m>2), the carrier transport behaviours can be described by the trapped-control mode and the tail state distribution can be approximated by the exponential trap distribution. With the approximation of an exponential distribution for the tail states, the characteristic energy (Em), radiative recombination lifetime (τrad), and localization depth (E0) associated with the dynamics of exciton energy relaxation and localization can be quantitatively determined. The much larger E0 (40~120 meV), increasing with the dopant concentration, than other disordered semiconductors (2~34 meV) indicates a strong localization effect in such doped organic semiconductors. Also, the strong dependence of Em on the dopant concentration shows that a relatively small dopant concentration can enhance the degree of disorder and greatly affect the recombination dynamics. Furthermore, the observed optical properties and dynamic scenario of C545T-doped Alq3 films are found to be consistent with the carrier transport and recombination dynamics of C545T-doped Alq3 OLEDs.

© 2014 Optical Society of America

OCIS Codes
(160.4890) Materials : Organic materials
(300.6500) Spectroscopy : Spectroscopy, time-resolved
(320.7150) Ultrafast optics : Ultrafast spectroscopy

ToC Category:
Organics Compounds for OLEDs

Original Manuscript: February 18, 2014
Revised Manuscript: March 18, 2014
Manuscript Accepted: March 18, 2014
Published: March 26, 2014

Virtual Issues
Optical Materials for Flat Panel Displays (2013) Optical Materials Express

Shih-Wei Feng, "Dependence of the dynamics of exciton transport, energy relaxation, and localization on dopant concentration in disordered C545T-doped Alq3 organic semiconductors," Opt. Mater. Express 4, 798-809 (2014)

Sort:  Author  |  Year  |  Journal  |  Reset  


  1. S. W. Feng, M. C. Shih, C. J. Huang, and C. T. Chung, “Impacts of dopant concentration on the carrier transport and recombination dynamics in organic light emitting diodes,” Thin Solid Films517(8), 2719–2723 (2009). [CrossRef]
  2. G. P. Crawford, Flexible Flat Panel Display (John Wiley & Sons, Chichester, UK, 2005).
  3. M. Pagliaro, G. Palmisano, and R. Ciriminna, Flexible Solar Cells (Wiley-VCH, Weinheim, 2008).
  4. V. I. Arkhipov, P. Heremans, E. V. Emelianova, G. J. Adriaenssens, and H. Bässler, “Charge carrier mobility in doped semiconducting polymers,” Appl. Phys. Lett.82(19), 3245–3247 (2003). [CrossRef]
  5. V. I. Arkhipov, P. Heremans, E. V. Emelianova, G. J. Adriaenssens, and H. Bässler, “Charge carrier mobility in doped disordered organic semiconductors,” J. Non-Cryst. Solids338–340, 603–606 (2004). [CrossRef]
  6. V. I. Arkhipov, P. Heremans, E. V. Emelianova, and H. Bässler, “Effect of doping on the density-of-states distribution and carrier hopping in disordered organic semiconductors,” Phys. Rev. B71(4), 045214 (2005). [CrossRef]
  7. V. I. Arkhipov, E. V. Emelianova, P. Heremans, and H. Bässler, “Analytic model of carrier mobility in doped disordered organic semiconductors,” Phys. Rev. B72(23), 235202 (2005). [CrossRef]
  8. V. I. Arkhipov, P. Heremans, E. V. Emelianova, G. J. Adriaenssens, and H. Bässler, “Weak-field carrier hopping in disordered organic semiconductors: the effects of deep traps and partly filled density-of-states distribution,” J. Phys. Condens. Matter14(42), 9899–9911 (2002). [CrossRef]
  9. H. Bässler, “Charge transport in disordered organic photoconductors a Monte Carlo simulation study,” Phys. Status Solidi175(1), 15–56 (1993). [CrossRef]
  10. E. V. Emelianova and G. J. Adriaenssens, “Stochastic approach to hopping transport in disordered organic materials,” J. Optoelectron. Adv. Mater.6(4), 1105–1131 (2004).
  11. A. Dieckmann, H. Bässler, and P. M. Borsenberger, “An assessment of the role of dipoles on the density-of-states function of disordered molecular solids,” J. Chem. Phys.99(10), 8136–8141 (1993). [CrossRef]
  12. S. V. Novikov and A. V. Vannikov, “Cluster structure in the distribution of the electrostatic potential in a lattice of randomly oriented dipoles,” J. Phys. Chem.99(40), 14573–14576 (1995). [CrossRef]
  13. N. S. Sariciftci, Primary Photoexcitations in Conjugated Polymers: Molecular Exciton versus Semiconductor Band Model (World Scientific, 1998).
  14. A. B. Walker, A. Kambili, and S. J. Martin, “Electrical transport modelling in organic electroluminescent devices,” J. Phys. Condens. Matter14(42), 9825–9876 (2002). [CrossRef]
  15. H. Bässler, P. M. Borsenberger, and R. J. Perry, “Charge transport in poly(methylphenylsilane):The case for superimposed disorder and polaron effects,” J. Polym. Sci. B32(9), 1677–1685 (1994). [CrossRef]
  16. P. Mark and W. Helfrich, “Space‐charge‐limited currents in organic crystals,” J. Appl. Phys.33(1), 205–215 (1962). [CrossRef]
  17. V. Kumar, S. C. Jain, A. K. Kapoor, W. Geens, T. Aernauts, J. Poortmans, and R. Mertens, “Carrier transport in conducting polymers with field dependent trap occupancy,” J. Appl. Phys.92(12), 7325–7329 (2002). [CrossRef]
  18. V. Kumar, S. C. Jain, A. K. Kapoor, J. Poortmans, and R. Mertens, “Trap density in conducting organic semiconductors determined from temperature dependence of J-V characteristics,” J. Appl. Phys.94(2), 1283–1285 (2003). [CrossRef]
  19. Z. Chiguvare and V. Dyakonov, “Trap-limited hole mobility in semiconducting poly(3-hexylthiophene),” Phys. Rev. B70(23), 235207 (2004). [CrossRef]
  20. N. Huby, L. Hirsch, G. Wantz, L. Vignau, A. S. Barrière, J. P. Parneix, L. Aubouy, and P. Gerbier, “Injection and transport processes in organic light emitting diodes based on a silole derivative,” J. Appl. Phys.99(8), 084907 (2006). [CrossRef]
  21. G. Y. Zhong, Z. Xu, J. He, S. T. Zhang, Y. Q. Zhan, X. J. Wang, Z. H. Xiong, H. Z. Shi, X. M. Ding, W. Huang, and X. Y. Hou, “Aggregation and permeation of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran molecules in Alq,” Appl. Phys. Lett.81(6), 1122–1124 (2002). [CrossRef]
  22. H. Bässler and B. Schweitzer, “Site-selective fluorescence spectroscopy of conjugated polymers and oligomers,” Acc. Chem. Res.32(2), 173–182 (1999). [CrossRef]
  23. R. Richert and A. Blumen, Disordered Effect on Relaxational Processes (Springer-Verlag, Berlin, 1994).
  24. W. Brutting, Chapter 7 of Physics of Organic Semiconductors (Wiley-VCH, Weinheim, 2006).
  25. M. Scheidler, U. Lemmer, R. Kersting, S. Karg, W. Riess, B. Cleve, R. F. Mahrt, H. Kurz, H. Bässler, E. O. Göbel, and P. Thomas, “Monte Carlo study of picosecond exciton relaxation and dissociation in poly(phenylenevinylene),” Phys. Rev. B Condens. Matter54(8), 5536–5544 (1996). [CrossRef] [PubMed]
  26. R. Kersting, U. Lemmer, R. F. Mahrt, K. Leo, H. Kurz, H. Bässler, and E. O. Göbel, “Femtosecond energy relaxation in π -conjugated polymers,” Phys. Rev. Lett.70(24), 3820–3823 (1993). [CrossRef] [PubMed]
  27. S. Krause, M. B. Casu, A. Schöll, and E. Umbach, “Determination of transport levels of organic semiconductors by UPS and IPS,” New J. Phys.10(8), 085001 (2008). [CrossRef]
  28. A. J. Campbell, D. D. C. Bradley, and D. G. Lidzey, “Space-charge limited conduction with traps in poly(phenylene vinylene) light emitting diodes,” J. Appl. Phys.82(12), 6326–6342 (1997). [CrossRef]
  29. C. Gourdon and P. Lavallard, “Exciton transfer between localized states in CdS1–xSex alloys,” Phys. Status Solidi153(2), 641–652 (1989). [CrossRef]
  30. Y. Narukawa, S. Saijou, Y. Kawakami, S. Fujita, T. Mukai, and S. Nakamura, “Radiative and nonradiative recombination processes in ultraviolet light-emitting diode composed of an In0.02Ga0.98N active layer,” Appl. Phys. Lett.74(4), 558–560 (1999). [CrossRef]
  31. H. S. Kim, R. A. Mair, J. Li, J. Y. Lin, and H. X. Jiang, “Time-resolved photoluminescence studies of AlxGa1-xN alloys,” Appl. Phys. Lett.76(10), 1252–1254 (2000). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited