Dresden 2017 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 29: Organic Thin Films I
DS 29.10: Vortrag
Mittwoch, 22. März 2017, 12:00–12:15, CHE 91
Evaluation of in-operando potential distributions in OLEDs combining experimental and drift-diffusion studies — •Maybritt Kühn1,2, Christof Pflumm3, Wolfram Jaegermann1,2, and Eric Mankel1,2 — 1Technische Universität Darmstadt, Institute of Materials Science — 2InnovationLab GmbH, Heidelberg — 3Merck KGaA, department OLED-Physics, Darmstadt
Nowadays organic light-emitting diodes are widely used as displays in smart phones. As these devices consist of several functional layers it is not only important to know the driving voltage of the whole device but also the potential distributions within the single layers. Therefore we present a combined experimental and drift-diffusion study to determine in operando transport properties of the single layers. Two types of OLEDs that only differ in the emission layer but obviously exhibit different potential distributions are investigated. If the emission layer consists of TH-A a shift of the onset voltage in case of layer thickness variation can be observed while using TH-B, an isomer to TH-A, the onset voltage remains unchanged. The voltage development per layer is determined from IV curves of a set of devices with varying layer thickness. Empirically the voltage development can be described with a power law. Using the drift-diffusion model the current density dependent development of the coefficient and the exponent of the power law can be well described. With the model the mobility, the carrier injection mechanism into the respective layer and the barrier height are determined. Furthermore we are able to show that an electric field at or close to the contact is necessary to describe the TH-A behaviour.