Materials

Organic semiconductors are promising materials for future optoelectronic devices and can be divided into two general classes: small molecules and polymers.

We study the optical properties and the photophysics of these materials, prepared with molecular beam deposition, using time-resolved ultrafast optical spectroscopy (transient absorption spectroscopy, time-resolved photoluminescence spectroscopy, time-correlated single photon counting), spectroscopic ellipsometry, temperature dependent NIR-vis-UV spectroscopy and temperature dependent photoluminescence spectroscopy.

The main focus of our research is on singlet fission, a multi-exciton generation process converting on excited singlet state into two triplets, which we study in blends of small molecules prepared by coevaporation.

The main focus of our research is on the effects of intermolecular interactions and charge transfer on the optical properties and photophysics of blends of organic semiconductors.

By mixing compounds which differ in their sterical properties and chemical composition we selectively modify the strength of intermolecular interactions and study how this chances the shape of the absorption spectrum (Davydov-splitting), the temperature dependence and shape of the photoluminesence spectrum (emission from charge transfer states), the lifetime of excited states and the time-constants of photophysical processes.

We are interested in two effects:

1. The targeted modification of intermolecular interactions in chemically identical molecules
2. The modification and optimization of charge transfer in donor/acceptor systems