Influence of shallow traps on the failure mechanism of aluminum (III) 8-hydroxyquinoline-based OLEDs

Keith A. Higginson; Mathew K. Mathai; Fotios Papadimitrakopoulos; Bing R. Hsieh

doi:10.1117/12.416900

2 February 2001 Influence of shallow traps on the failure mechanism of aluminum (III) 8-hydroxyquinoline-based OLEDs

Keith A. Higginson, Mathew K. Mathai, Fotios Papadimitrakopoulos, Bing R. Hsieh

Proceedings Volume 4105, Organic Light-Emitting Materials and Devices IV; (2001) https://doi.org/10.1117/12.416900
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

Abstract

Conduction in aluminum(III) 8-hydroxyquinoline (Alq₃)- based organic light-emitting diodes (OLEDs) was modeled based on trapped charge-limited conduction of electrons in the Alq₃ bulk. This model was chosen since it can easily incorporate an arbitrary trap distribution such as may arise during the material's degradation. The evolution of a narrow Gaussian distribution of localized trap states below the lowest unoccupied molecular orbital (LUMO) of Alq₃, lying against a natural exponential background, was used to explain changes in the current-voltage characteristic and external quantum efficiency with time observed by many researchers for organic light-emitting diodes. Based on the change of the shape of the DC current density vs. voltage (J-V) curve, the depth of the electron trap states that were formed during aging was about 0.25 eV below the LUMO of Alq₃. This value is consistent with electrochemical measurements of known chemical degradation products. The J-V characteristics show behavior which is suggestive of a trap- filled limit, and this is discussed along with the general appropriateness of the model used.

Citation Download Citation

Keith A. Higginson, Mathew K. Mathai, Fotios Papadimitrakopoulos, and Bing R. Hsieh "Influence of shallow traps on the failure mechanism of aluminum (III) 8-hydroxyquinoline-based OLEDs", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); https://doi.org/10.1117/12.416900

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