Karlsruher Institut für Technologie (TFT)

Beschichtung von homogenen, großflächigen Schichten

Für die organische Elektronik werden sehr homogene Schichten benötigt. Durch die Optimierung der Beschichtungsbedingungen wollen wir die Defektmechanismen während der Filmabscheidung zur Beseitigung von weiteren Defekten verstehen. Deshalb untersuchen wir:

• Den Einfluss der Fließeigenschaften auf die Beschichtungsstabilität und -qualität
• Prozessfenster zur Erhltung stabiler Beschichtungsbedingungen
• Warum sich Kanteneffekte bilden und wie sie reduziert werden können
• Möglichkeiten für eine Ausweitung des Prozesses auf den industriellen Maßstab

Trocknung homogener großflächiger Schichten

Auf den Beschichtungsschritt folgt immer ein Trocknungsschritt zum Entfernen des Lösungsmittels. Während des Trocknens entwickeln sich die Eigenschaften des Funktionsfilms. Durch die Steuerung des Trocknungsprozesses kann die gewünschte Filmmorphologie eingestellt werden. Durch Messung von Phasengleichgewichten und Trocknungskinetiken können Modelle für den Trocknungsprozess entwickelt werden. Der Fokus liegt auf:

• The control of drying kinetics and drying times (as these are very cost-intensive).
• Realization of the homogenous drying of the films.
• How can film morphology be controlled by drying conditions?
• Residual solvent contents in thin films.

Development of multilayer concepts

Besides the investigation of single layers, the development of multilayer deposition concepts is very crucial for organic electronics. The results from single layer experiments are transferred to multilayer experiments to investigate the simultaneous application of several layers in one step. The challenges are:

• Can intermixing between the layers be prohibited?
• How can layers be applied simultaneously?
• Which concepts can be transferred to the industrial scale?

Coating lines: High precision slot die coater (S2S) and R2R pilot plant

At InnovationLab we run a sheet-to-sheet (S2S) table slot die coater which was built in cooperation with TSE Troller AG (Switzerland). It offers the possibility to coat on a table as well as on a roll. Besides single layer experiments, two layers can be coated in one step with a dual-layer slot die. An in-house developed dryer was installed to ensure homogenous coating conditions after the deposition step. Continuous coatings on a roll-to-roll (R2R) are possible in our coating lab at KIT. The first promising results state that slot die coating is applicable for the high-throughput fabrication of highly efficient OLEDs.

Simulation

Our research is based on calculations and simulations on the one hand and their experimental verification on the other hand. With the help of CFD programs we improve the fluid flow in our coating apparatus and our drying equipment. During the past years, several models were developed and are continuously improved to predict the relevant coating and drying steps. With the help of the established routines, plants at an industrial scale can be designed. The required material properties have to be measured in advance in our characterization lab.

Magnetic sorption balance

For the determination of thermodynamic phase equilibria, we use a magnetic sorption balance. The knowledge of phase equilibria is essential for all models and predictions of drying times and diffusion. With the help of a magnetic sorption balance, sorption and desorption experiments are performed to investigate diffusion in thin films. Currently, the influence of the substrate on the diffusion of solvent in thin polymeric films is investigated.

Raman spectroscopy

With Raman spectroscopy, the local composition of films in the micrometer-range can be measured in-situ during drying experiments. This allows us to determine diffusion coefficients in binary and multilayer systems. Interdiffusion of polymeric films can be measured as well. It is a powerful tool for verifying our models and simulations.