Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 27: INTERNAL SYMPOSIUM Optical Spectroscopy II

CPP 27.1: Invited Talk

Thursday, March 29, 2007, 14:30–15:00, H40

Controlling intermolecular interactions in organic semiconductors — •Laura Herz — University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU

Conjugated polymers and molecules have emerged over the last decade as cheap and flexible alternatives to existing inorganic semiconductor technology. Light-emitting displays based on these materials are now at commercial standards with several products on the market, with transistors and photovoltaics being at the research and development stage. This talk will summarize our recent research into the mechanisms governing the femtosecond dynamics of electronic processes at the interface formed between two organic semiconductor components. We have examined the Coulombic interactions at the interface in a blend of two copolymers with intramolecular charge-transfer character and optimized band offsets for photoinduced charge generation. Through a combination of both time-resolved measurements of photoluminescence, and quantum-chemical modeling of the heterojunction, we demonstrate that the relative molecular orientation at the heterojunction can lead to either a repulsive barrier or an attractive interaction. For the latter case, charge transfer across the heterojunction may occur, but is followed by rapid relaxation into a coulombically bound state (exciplex) across the interface. I will follow on to show that electronic delocalization across more than one conjugated polymer chain may be tailored effectively through supramolecular self-assembly strategies, as for example shielding of chains with insulating macrocycles, or complexation with inert macromolecules.