Direct observation of the potential distribution within organic light emitting diodes under operation

• Verfasst von: Weigel, Christian [VerfasserIn]
• Verfasst von: Kowalsky, Wolfgang [VerfasserIn]
• Verfasst von: Saive, Rebecca [VerfasserIn]
• Titel: Direct observation of the potential distribution within organic light emitting diodes under operation
• Verf.angabe: Christian S. Weigel, Wolfgang Kowalsky, and Rebecca Saive
• E-Jahr: 2015
• Jahr: 6 August 2015
• Umfang: 5 S.
• Fussnoten: Gesehen am 29.06.2020
• Titel Quelle: Enthalten in: Physica status solidi / Rapid research letters
• Ort Quelle: Weinheim : Wiley-VCH, 2007
• Jahr Quelle: 2015
• Band/Heft Quelle: 9(2015), 8, Seite 475-479
• ISSN Quelle: 1862-6270
• DOI: doi:10.1002/pssr.201510223
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: charge transport
• Sach-SW: organic light emitting diodes
• Sach-SW: potential distribution
• Sach-SW: scanning Kelvin probe microscopy
• K10plus-PPN: 1702874230

Abstract

We show the first direct measurement of the potential distribution within organic light emitting diodes (OLEDs) under operation and hereby confirm existing hypotheses about charge transport and accumulation in the layer stack. Using a focused ion beam to mill holes in the diodes we gain access to the cross section of the devices and explore the spatially resolved potential distribution in situ by scanning Kelvin probe microscopy under different bias conditions. In bilayer OLEDs consisting of tris(hydroxyquinolinato) aluminum (Alq3)/N, N ′-bis(naphthalene-1-yl)-N,N ′-bis(phenyl) benzidine (NPB) the potential exclusively drops across the Alq3 layer for applied bias between onset voltage and a given transition voltage. These findings are consistent with previously performed capacitance-voltage measurements. The behavior can be attributed to charge accumulation at the interface between the different organic materials. Furthermore, we show the potential distribution of devices with different cathode structures and degraded devices to identify the cathode interface as main culprit for decreased performance. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)