Trap Level Study of Alq3 for OLED with Debye Dielectric Relaxation

Debye 이론을 이용한 유기 EL용 Alq3계 재료의 Trap Level 측정

  • 정용석 (부경대학교 화상정보공학부) ;
  • 정연태 (부경대학교 화상정보공학) ;
  • 김종태 (부경대학교 화상정보공학부)
  • Published : 2004.06.01


Upon Debye's dielectric relaxation theory, we tried simple determination method of trap level in organic EL materials. From dielectric measurements in the 20 Hz - 1 MHz frequency range and in the 150 K - 320K temperature range, the depth of traps in Alq$_3$ filled with remaining electrons was determinated. Comparing to other determination techniques like TSL, or TL, the apparatus all we need is just simple LCR meter, thermometer and cooling method(liquid nitrogen). The mean activation energy is about 0.20 eV. It is in good agreement with previous determinations by other techniques like TSL. This results consolidate the validity of Burrow's transport mechanism model. Further intensified experiment with UV light on the dielectric absorption(Photodipolair effect) was nevertheless disturbed by the photoconductivity component.


  1. K. C. Kao, W. Hwang, 'Electrical transport in solids', Pergamon Press, 1981
  2. E. W. Forsythe E. W., Morton D. C., Tang C. W., and Gao Y., 'Trap states in $Alq_3$ using thermally stimulated luminescence', Proc. conf. SPIE, Vol 3476, p. 123, 1998
  3. M.Meier, S. Karg, K. Zuleeg, W. Brutting, and M. Schwoerer, 'Detemination of trapping parameters in PPV light-emitting devices using thermally stimulated currents', J. of Appl. Phys., 84(1), p. 87, 1998
  4. P. E. Burrows, Z. Shen, V. Bulovic, D. M. McCarty, S. R. Forrest, J. A. Cronin, and M. E. Thompson., 'Relationship between electroluminescence and current transport in organic heterojunction light-emitting devices', J. of Appl. Phys., 79, p. 7991, 1996
  5. A. Ioannidis., E. Forsythe, Y. Gao, M. W. Wu, and E. M. Conwell, 'Current-voltage characteristic of organic light emitting diodes', Appl. Phys. Lett., 72, p. 3038, 1998
  6. N. F. Mott, 'Conduction in non-crystalline materials', Clarendon Press, 1993
  7. A.K. Jonsher, 'Dielectric relaxation in solids', Chelsea Dielectric Press, 1983
  8. R. Freymann and M. Soutif, 'La spectroscpie hertzienne', Dunod, 1960
  9. R. Freymann, E. Grillot, M. Hagene, M. Le Page, 'Comptes Rendus Acad. Sci.', 243, p. 1522, 1956