Storage of charge carriers on emitter molecules in organic light-emitting diodes
Name
Weichsel-2012-Storage of charge carriers on emitter molecules in organic light-emitting diodes.pdf
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4.54 MB
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Author(s)
Reineke, Sebastian
Weichsel, Caroline
Burtone, Lorenzo
Hintschich, Susanne I.
Gather, Malte C.
Leo, Karl
Lüssem, Björn
Date Issued
August 2012
Journal
Physical Review B
Publisher
American Physical Society
Citation
Weichsel, Caroline et al. “Storage of Charge Carriers on Emitter Molecules in Organic Light-emitting Diodes.” Physical Review B 86.7 (2012). ©2012 American Physical Society
Version
Final published version
Abstract
Organic light-emitting diodes (OLEDs) using the red phosphorescent emitter iridium(III)bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) [Ir(MDQ)[subscript 2](acac)] are studied by time-resolved electroluminescence measurements. A transient overshoot after voltage turn-off is found, which is attributed to electron accumulation on Ir(MDQ)[subscript 2](acac) molecules. The mechanism is verified via impedance spectroscopy and by application of positive and negative off-voltages. We calculate the density of accumulated electrons and find that it scales linearly with the doping concentration of the emitter. Using thin quenching layers, we locate the position of the emission zone during normal OLED operation and after voltage turn-off. In addition, the transient overshoot is also observed in three-color white-emitting OLEDs. By time- and spectrally resolved measurements using a streak camera, we directly attribute the overshoot to electron accumulation on Ir(MDQ)[subscript 2](acac). We propose that similar processes are present in many state-of-the-art OLEDs and believe that the quantification of charge carrier storage will help to improve the efficiency of OLEDs.
MIT Department
Massachusetts Institute of Technology. Research Laboratory of Electronics
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.86.075204
