Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Organic Electronics and Photovoltaics V (CPP jointly with DS, HL, O)
O 54.5: Vortrag
Mittwoch, 2. April 2014, 16:00–16:15, ZEU 260
Towards fully printed organic light-emitting diodes: investigation of solution processed electron injection layers — •Sebastian Stolz1,4, Gerardo Hernandez-Sosa1,4, Michael Scherer2,4, Eric Mankel3,4, Robert Lovrinčić2,4, Janusz Schinke2,4, Uli Lemmer1,4, and Norman Mechau1,4 — 1Karlsruhe Institute of Technology, Light Technology Institute — 2Technische Universität Braunschweig, Institut für Hochfrequenztechnik — 3Technische Universität Darmstadt, Materials Science Institute, Surface Science Division — 4InnovationLab GmbH, Heidelberg
The fabrication of organic light-emitting diodes (OLEDs) by high throughput printing techniques requires the development of solution processable electron injection layers. Today, either alkali salts or low work-function alkaline earth metals are used as cathode layers in OLEDs. As these materials are highly reactive, they cannot be easily solution processed. In this work, we present blue fluorescent light-emitting diodes which use silver in combination with Polyethylenimine (PEI) and Polyethylenimine-ethoxylated (PEIE) as cathode layer. We demonstrate that both materials can be effectively used as electron injection layers in OLEDs and correlate the performance of the devices to the characteristics of the PEI(E) layers. Photoelectron spectroscopy is used to estimate the polymer thickness and the corresponding change in cathode work-function while the homogeneity of the layers is evaluated by AFM measurements. We show that OLEDs using PEI/PEIE and silver as cathode layer yield an improved performance and shelf lifetime compared to reference devices that use calcium, instead.