Lecture Claudia Ambrosch-Draxl
|07 February 2011||FWN-Building 5116.0136, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Prof. Claudia Ambrosch-Draxl|
|Affiliation:||Chair Atomistic modelling and design of materials, University of Leoben, Austria|
|Title:||From molecular arrangements to opto-electronic properties of organic/inorganic interfaces: Challenges for first-principles approaches|
|Date:||Mon Feb 7, 2011|
|Telephone:||+31 50 363 4374|
Despite the weak intermolecular bonding and molecule-substrate interaction, the opto-electronic properties of organic semiconductors, crucially depend on alignment, conformation, and packing of the molecules as well as on details of the substrate. For example, surface corrugations and order/disorder affect the orientation of molecules within a monolayer or thin film. This, in turn, is correlated with charge transfer, band alignment at the interface, and electronic transport. The orientation together with the anisotropic nature of the molecules then determines whether the material indeed efficiently emits visible light. The packing, finally, governs the electron-hole interaction in excitation processes. All this is scientifically puzzling, but also decisive for the function of devices.
Insight from a theoretical viewpoint is a must for deeper understanding. Density functional theory, although tremendously successful for describing the properties of many materials, can badly fail here as non-local exchange and/or correlation effects are essential at all levels: in the bonding in terms of van der Waals interactions, in the electronic structure in terms of level alignment and band gaps, and in the optical spectra in terms of exciton formation.
Selected cases will illustrate what we can learn from first-principles studies about these challenging systems. I will address in particular the molecule-substrate interaction and their role in the opto-electronic properties. As a special example I will discuss the physics of recently synthesized nano-peapods which could be a future light source in organic devices.
|Last modified:||22 October 2012 2.30 p.m.|