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Degradation Mechanisms in Organic Light-Emitting Diodes with Polyethylenimine as a Solution-Processed Electron Injection Layer

Stolz, Sebastian 1; Zhang, Yingjie; Lemmer, Uli 1,2; Hernandez-Sosa, Gerardo ORCID iD icon 1; Aziz, Hany
1 Lichttechnisches Institut (LTI), Karlsruher Institut für Technologie (KIT)
2 Institut für Mikrostrukturtechnik (IMT), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

In this work, we investigate the performance and operational stability of solution-processed organic light-emitting diodes (OLEDs), which comprise polyethylenimine (PEI) as an electron injection layer (EIL). We show that the primary degradation mechanism in these OLEDs depends on the cathode metal that is used in contact with the EIL. In the case of Al, the deterioration in OLED performance during electrical driving is mainly caused by excitons which reach and subsequently degrade the emitter/PEI interface. In contrast, in the case of Ag, device performance degradation occurs due to an additional mechanism: hole accumulation at the emitter/PEI interface and a consequent drop in the emitter quantum yield. As a result, the operational lifetime of OLEDs that use PEI as EIL can vary significantly with the cathode material, and at a current density of 20 mA cm–2, LT50 lifetimes of ∼200 h and <10 h are obtained for Al and Ag, respectively. Finally, we show that the first degradation mechanism can be significantly slowed by using a mixture of PEI and ZnO nanoparticles as EIL. As a result, the operational lifetime of OLEDs with an Al cathode is increased to more than 1000 h, without adversely affecting device performance. ... mehr

DOI: 10.1021/acsami.6b15062
Zitationen: 40
Web of Science
Zitationen: 36
Zitationen: 39
Zugehörige Institution(en) am KIT Institut für Mikrostrukturtechnik (IMT)
Lichttechnisches Institut (LTI)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2017
Sprache Englisch
Identifikator ISSN: 1944-8244, 1944-8252
KITopen-ID: 1000065501
HGF-Programm 43.22.03 (POF III, LK 01) Printed Materials and Systems
Erschienen in ACS applied materials & interfaces
Verlag American Chemical Society (ACS)
Band 9
Heft 3
Seiten 2776–2785
Schlagwörter Electron injection layers; Lifetime; OLEDs; Polyethylenimine; Solution-processing
Nachgewiesen in Dimensions
Web of Science
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