Ultrafast relaxation of free excitons in quasi-1D organic molecular crystals

Summary form only given. Recently, there has been large interest in organic materials due to promising device applications. Particular attractive are organic molecules which form quasi-1D crystals, with close stacking in one direction: The resulting strong inter-molecular interaction favors generation and transport of free carriers. The optical properties of such organic semiconducting materials, which are dominated by excitonic excitations, are much less understood than those of their inorganic counterparts. Therefore, a detailed investigation of the initial exciton relaxation and of the exciton-phonon coupling is needed. Here, we use pump-probe spectroscopy to study the energy relaxation of free excitons in the model 1D-system MePTCDI (N-N´-dimethylperylene-3,4,9,10-dicarboximide). The linear absorption spectrum of the crystalline layer is given.