Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - SFB 951 - HIOS

Eigenschaften und Synthesen großer Heteroacene werden vorgestellt. Ausgehend von kleinen Kohlenstoffreichen Molekülen hat sich unsere Forschung in den letzten Jahren in Richtung größerer N-Heteroacene entwickelt. Diese Materialien sind kaum bekannt aber möglicherweise attraktiv als elektronentransportierende Versionen von Pentacen.

Hybrids of inorganic and organic semiconductors may exhibit electronic and excitonic properties that may go beyond a linear combination of the material’s properties with each other. At the interface, new states may form through hybridization of molecular orbitals with substrate states. We investigate the occupied and unoccupied electronic band structure and the ultrafast electron dynamics using femtosecond time-resolved two-photon photoemission (2PPE) spectroscopy. Characterization of the pristine, ZnO(10-10) surface yields the absolute measurement of the valence and conduction band (CB) edge energies and significant surface band bending upon hydrogen termination leading to the formation of a metallic surface state. We furthermore directly monitor the hot electron relaxation in the bulk ZnO CB on femtosecond timescales and electron capture at the semiconductor surface (>100 ps). Adsorption of pyridine (C5H5N) leads to a massive reduction of the work function of the sample up to ΔΦ = - 2.7 eV which strongly affects the energy level alignment at the inorganic/organic interface.

Acknowledgement: This work was funded by the DFG through SFB 951.