The Study of Luminescence Efficiency by change of OLED's Hole Transport Layer

  • Lee, Jung-Ho (Department of Electronic Engineering, Hongik University)
  • Published : 2006.04.29


The OLEDs(Organic Light-Emitting Diodes) structure organizes the bottom layer using glass, ITO(indium thin oxide), hole injection layer, hole transport layer, emitting material layer, electron transport layer, electron injection layer and cathode using metal. OLED has various advantages. OLEDs research has been divided into structural side and emitting material side. The amount of emitting light and luminescence efficiency has been improved by continuing effort for emitting material layer. The emitting light mechanism of OLEDs consists of electrons and holes injected from cathode and anode recombination in emitting material layer. The mobilities of injected electrons and holes are different. The mobility of holes is faster than that of electrons. In order to get high luminescence efficiency by recombine electrons and holes, the balance of their mobility must be set. The more complex thin film structure of OLED becomes, the more understanding about physical phenomenon in each interface is needed. This paper observed what the thickness change of hole transport layer has an affection through the below experiments. Moreover, this paper uses numerical analysis about carrier transport layer thickness change on the basis of these experimental results that agree with simulation results.


  1. Martin, Simon J., Lupton, J. M., Samuel, I. D. W. and Walker, Alison B., 'Modeling temperature-dependent current-voltage characteristics of an MEH-PPV organic light emitting device,' J. Phys., Vol. 14, No. 42, pp.9925-9933, 2002
  2. Malliaras, G. G. and Scott, J. G., 'Roles of injection and mobility in organic light emitting diodes,' Appl. Phys., Vol. 83, No.10, pp.5399-5403, 1998
  3. Davids, P. S., Kogan, Sh. M., Parker, I. D. and Smith, D. L., 'Charge injection in organic light-emitting diodes: Tunneling into low mobility materials,' Appl. phys. Lett., Vol. 69, pp.2270-2272, 1996
  4. Kepler, R. G., Besson, P. M., Jacobs, S. J., Anderson, R. A., Sinclair, M. B., Valencia, V. S. and Cahill, P. A., 'Electron and hole mobility in tris(8-hydroxyquinolinolato-N1,O8) aluminum,' Appl. Phys. Lett., Vol. 66, pp.3618-3620, 1995
  5. Pay, D. M., 'Transient Photoconductivity in Poly(Nvinylcarbazole),' J. Chem, Phys., Vol. 52, pp.2285-2291, 1970
  6. Crone, B. K., Davids, P. S., Cambell, I. H. and Smith, D. L., 'Device model investigation of single layer organic light emitting diodes,' J. Appl. Phys., Vol. 87, No. 2, pp.833-842, 1998
  7. Blades, C. D. J. and Walker, Alison B., 'Simulation of organic light emitting diodes,'Synthetic Metals., Vol. 111-112, pp.335-340, 2002
  8. Conwell, E. M. and Wu., M. W., 'Contact injection into polymer light-emitting diodes,' Appl. phys. Lett., Vol. 70, pp.1867-1869, 1989