Dresden 2014 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Organic Electronics and Photovoltaics (joint session with DS/HL/O) IV

CPP 34.5: Talk

Wednesday, April 2, 2014, 16:00–16:15, ZEU 260

Towards fully printed organic light-emitting diodes: investigation of solution processed electron injection layers — •Sebastian Stolz^1,4, Gerardo Hernandez-Sosa^1,4, Michael Scherer^2,4, Eric Mankel^3,4, Robert Lovrinčić^2,4, Janusz Schinke^2,4, Uli Lemmer^1,4, and Norman Mechau^1,4 — 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.