Space charge effect in organic light-emitting devices (OLEDs)

Harry L. Kwok

doi:10.1117/12.505781

9 July 2003 Space charge effect in organic light-emitting devices (OLEDs)

Harry L. Kwok

Proceedings Volume 5218, Complex Mediums IV: Beyond Linear Isotropic Dielectrics; (2003) https://doi.org/10.1117/12.505781
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

Space charge is known to affect current transport in organic light emitting devices (OLEDs). This normally occurs at low bias when current density varies quadratically with the bias voltage. A transition exists when current flow changes from space-charge limited to “recombination” limited. In order to further investigate this transition, we extended our model on exciton formation based on bimolecular recombination [7] to include the existence of space charge. In examining the model characteristics, we found that where the transition occurs depends on the density of the space charge in the active layer and the fraction of it associated with "recombination". This also relates to a parameter a₀ defining the optimal charge separation for "recombination" to take place. Our results indicated that the transition would vary for different organic semiconductors and would be an important factor affecting the device performance. In comparing our model with experimental data, we are of the opinion that space charge effect may be responsible for the occasional occurrence of an "anomalous" current reported in the J-V characteristics of OLEDs.

Citation Download Citation

Harry L. Kwok "Space charge effect in organic light-emitting devices (OLEDs)", Proc. SPIE 5218, Complex Mediums IV: Beyond Linear Isotropic Dielectrics, (9 July 2003); https://doi.org/10.1117/12.505781

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