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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications
SYSA 5: Poster Session SYSA
SYSA 5.21: Poster
Dienstag, 26. Februar 2008, 14:30–20:00, Poster A
Surface modification for improved charge injection in copper electrode/ organic semiconductor interfaces of p-type OFET applications — •Johannes Frisch1, Norbert Koch1, and Silvia Janietz2 — 1Humboldt-Universität zu Berlin, Department of Physics, Newtonstrasse 15, D-12489 Berlin, Germany — 2Fraunhofer-Institute of Applied Polymer Research, Department Polymer Elektronics, Geiselbergstr. 69 D-14476 Potsdam, Germany
Very important for the development of practical applications in organic field effect transistors (OFETs) are high On-current and ON/Off ratio. The On-current in p-type OFET devices is limited by the hole injection density. One way to modify charge injection properties is to introduce a monolayer of the strong electron acceptor tetrafluorotetracyanoquinodimathane (F4-TCNQ) at the Cu-electrode/ organic hole transport layer (OHTL) interface. The adsorbed monolayer of F4-TCNQ results in an increase in work function and consequently in a reduction of the hole injection barrier. XPS analysis showed a significant difference between untreated and modified surfaces. Top gate structure OFETs with bottom contact and flexible substrates were produced to evaluate the influence of the modified Cu-electrode/ OHTL interface. The OFET-performance was evaluated in comparison to the conventional device structure without F4-TCNQ. The results of the Transfer-measurements and Output-characteristics corroborate the advantages of the modification with respect to high On-current, lower threshold voltage and operational stability.