Introduction

OFETs which are made of conjugated polymers present several potential advantages. First, the deposition techniques for semiconductor films allow large areas to be coated. Many conjugated polymers can be synthesized in a way that they are soluble in organic solvents, so that they can be processed by spin-coating, casting or by various printing methods. Second advantage is that polymers are mechanically tough and flexible, therefore compatible with plastic substrates. This offers the possibility to realize foldable, flexible products with extremely light-weight.

Goals

At the institute of OEM at TUHH the research conducted on OFETs can be classified in 4 sections:

1. Characterization of novel dielectric and semiconductor thin-films for OFETs

Various thermosetting and thermoplastic materials are used as dielectric. Compatibility of layers and the electronic properties of transistors are characterized. In cooperation with the company Elantas Beck new dielectric materials are being developed.

2. Influence of interfaces on OFET device properties and interface tuning

Dielectric/semiconductor interface plays a crucial role in OFET performance. Therefore a proper interface should be formed during the deposition of these layers. By means of experimental studies on interfaces, like usage of new solvents or surface modifications, it is tried to extract new information on physical properties of interfaces in OFETs. Charge carrier mobility and interface doping are the main investigated mechanisms.

3. OFET-sensors for light and chemical sensing

Chemical volatile sensing properties of OFETs are demonstrated. Selective volatile sensing by using organic transistor-sensors is aimed.

4. Ferroelectric OFETs for memory applications

Well known superb ferroelectric and dielectric properties of PVDF/TrFE copolymers were modified by blending barium titanate nanopowder and preparing thin nanocomposite films. The films have up to 50 volume % BT powder and exhibit dielectric constant values of up to 51.5 at 1 kHz. These films are introduced as gate insulator in OFETs where ferroelectric memory and low-voltage operation are demonstrated.

In 2009 we investigated UV crosslinking epoxies as dielectric materials for OFETs. Problems of wetting on P3HT were solved and the curing time was reduced to lower than 20 s. The interface between the organic semiconductor and the dielectric material was characterized using CV measurements. This technique allows us to determine the trap density at the interface semiconductor/insulator.

Wissenschaftliche Kontakte und Kooperationen

• Prof.Dr.-Ing. Wolfgang Krautschneider, Arbeitsbereich Mikroelektronik, Elektrotechnik V, TUHH
• Prof.Dr.-Ing. Holger Göbel, Fachbereich Elektrotechnik, Universität der Bundeswehr, Hamburg
• Elantas Beck  http://www.elantas.com/de/