Organic Thin Films
- Fig. 1: Surface of an organic thin film detected with an AFM (Atomic Force Microscope).
Our group is concerned with thin organic films (10-1000nm), that serve as active layers in both electrical (e.g. transistors) and optical (e.g. light emitting diodes) devices.
In the field of organic transistors (OTFT – Organic Thin-Film Transistors), especially crystalline materials such as Pentacene and Perylene are of importance. They grow as polycrystalline islands (fig. 1). Such transistors can be employed as control elements for organic displays. The important advantages of organic over anorganic transistors (e.g. based on silicon or germanium) are the ability of low-cost production and the prospect of using flexible substrates. This facilitates the development of elastic displays.
In contrast to the crystalline materials employed for OTFTs, amorphous organic films are used for organic light emitting diodes (OLEDs). Already today, OLEDs can be found in many products such as cell phones and digital cameras due to the high level of efficiency and the brilliant colors. Moreover, organic displays do not exhibt color shifting upon variation of the angel of vision. In addition to displays also their use as illuminants is of interest (fig. 2). Some of our investigated materials, e.g. ALq3 and alpha-NPD, are suitable candidates for these applications.
- Abb. 2: Vergleich zwischen herkömmlichen Leuchtmitteln und organischen Leuchtdioden (OLED).
For the deposition of organic thin film, our group investiagates evaporation techniques such as Vapour Thermal Evaporation (VTE) and Organic Vapur Phase Deposition (OVPD). In combination with our experimental lineup, comprising x-ray-diffraction and -reflectometry, atomic-force microscopy, ellipsometry and electrical characterization methods, we are able to produce multi-layer samples (e.g. OTFTs as shown in fig. 3) and characterize them with respect to their optical, structural, morphological and electrical properties.
- Fig. 3: Schematic design of an organic transistor (OTFT) and experimental realization.
The results of our young group can be found in our list of publications. If you are interested in working in this field, pleae consult our open positions.