Electronic Structure, Band Formation and Singlet Fission Dynamics at Metal/Organic Interfaces

Abstract

Charge carrier injection at the metal/organic interface is crucial for the performance of organic semiconductor based (opto)electronic devices. To achieve an efficient charge carrier injection a detailed knowledge of the electronic properties at the metal/organic interface is needed. In this thesis ultraviolet photoemission spectroscopy and (time-resolved, angle-resolved) two-photon photoemission spectroscopy were utilized to reveal occupied as well as unoccupied electronic states including excitonic states and transport levels. On the one hand the electronic structure and excited state dynamics of a pentacene derivative, in particular regarding the singlet fission dynamics with respect to the film thickness on an Au(111) surface, were examined. On the other hand the electronic structure at the interface between several promising Nheteropolycyclic semiconductors, including a porphyrin, a N-heteroacene and different N-heteroperopyrenes, and Au(111) was revealed. The investigations of the N-heteroperopyrenes stand out as the observation of band formation via hybridization between delocalized metal bands and localized molecular orbitals at the metal/organic interface should foster efficient charge injection.