13 September 2012 Quantification of charge carrier density in organic light-emitting diodes by time-resolved electroluminescence
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Abstract
Excessive charge carrier densities in the emission layer of organic light-emitting diodes (OLEDs) can lead to significant quenching by triplet-polaron-annihilation [1] or field-induced quenching [2]. Thus, to increase the efficiency of OLEDs further, a technique for the reliable determination of charge carrier densities in OLEDs is most desirable. Time-resolved spectroscopy is a powerful tool to investigate electronic and excitonic transfer processes [3]. By application of a voltage pulse to a phosphorescent state-of-the-art OLED we find a transient overshoot after voltage turn-off. This has primarily been found in phosphorescent OLEDs and has typically been attributed to delayed recombination of trapped charge carriers [4-7]. In this contribution we investigate charge carrier accumulation within the emission layer (EML) and provide a method to quantify the density of stored electrons.
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Caroline Weichsel, Sebastian Reineke, Malte C. Gather, Karl Leo, Björn Lüssem, "Quantification of charge carrier density in organic light-emitting diodes by time-resolved electroluminescence", Proc. SPIE 8476, Organic Light Emitting Materials and Devices XVI, 84761I (13 September 2012); doi: 10.1117/12.929586; https://doi.org/10.1117/12.929586
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