P7: Energy and charge transfer at surfaces

Supervision:Ulrich Kleinekathöfer, Thorsten Klüner, Thomas Frauenheim

Motivation and state of the art: Similar to (bacterio) chlorophylls in biological light-harvesting systems and reaction centres, porphyrins and other tetrapyrolles at surfaces can be used efficiently for light harvesting and charge transfer purposes. Porphyrins have been shown to be excellent photosensitizer for dye-sensitized solar cells. In this project we plan to enhance the description of the molecular flexibilities and (quantum) dynamics in dye-sensitized systems since these properties have not found proper attention so far.

Own work: So far, we have studied energy and charge transfer mainly in biological molecular systems using a combination of molecular dynamics, quantum chemistry and quantum dynamics. A focus has been onto exciton transfer in light-harvesting systems as well as charge transport through molecules such as DNA.

Aims and work plan: The aims of this project are twofold though both parts deal with porphyrins on surfaces. In the first application, we plan to study the 2D excitation energy transfer among porphyrins deposited on inorganic surfaces such as exfoliated sheets of clay. Different from biological systems one now has to develop an algorithm for excitation energy transfer in the (infinite) 2D plane due to the periodic boundary conditions. We want to highlight that due to the different time and length scale involved, a dynamical modelling of these systems is very challenging and methods combining molecular dynamics simulations, quantum chemistry and dynamics need to be extended. In the second application, the porphyrins will be attached to a TiO2 surface.