Vibronic Excitation Dynamics in Conjugated Polymers

Summary: We will study the interaction between the optical excited electronic state and the nuclear dynamics in conjugated polymers by advanced quantum chemical methods theoretically in order to analyze experimental results from time-resolved spectroscopy. Abstract: Conjugated polymers are new organic semiconducting materials, which promise numerous applications in opto-electronic devices, e.g. organic LEDs, transistors, computer displays, and solar cells. Nevertheless the theoretical description of their properties is still patchy. In particular the processes immediately after photo- excitation (localization of excitation energy, structural relaxation, charge separation) are still unclear, though they have intensively been studied experimentally, in particular, by time-resolved spectroscopic methods. In this project we will study these processes theoretically on a molecular and mesoscopic level. For this purpose we will utilize advanced ab initio and semi-empirical quantum-chemical methods and molecular dynamic programs, in order to establish a mesoscopic model for the relation between the polymer structure and its functional properties. This is an important prerequisite for the directed molecular design of specific opto-electronic devices. In the cooperation to be established by this project the theoretical work will be continuously compared with experimental data from femtosecond spectroscopy as provided by the co-applicant`s group.