High-Performance Organic Devices based on Crystalline Stacks

The research on organic electronics is driven by new applications using properties like flexibility, easy manufacturing, biocompatibility, etc. While OLED displays and organic solar cells are commercially successful, organic electronic circuits have not yet reached broad application, mainly since device performance is lacking. In this talk, I will discuss highly ordered organic multilayer structures which have the potential to increase device performance by orders of magnitude. For the highly ordered layers, rubrene crystals are created by heating of amorphous layers and can be electrically doped during the epitaxial growth process to achieve hole or electron conduction. Analysis of the space charge limited current in these films reveals record vertical mobilities of 10 cm2/Vs. Furthermore, these structures allow comparatively long minority carrier diffusion lengths, allowing to realize the first organic bipolar transistors. OLED from highly ordered layers show high current densities and excellent emission homogeneity. Furthermore, I will address highly ordered organic thin-film blends with a similar chemical structure and show the effect of band structure engineering by spectroscopic methods. In contrast to previous studies where the experimental results can be described by quadrupole effects, delocalization is a significant effect for the crystalline layers.