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Alexei CHEPELIANSKII - Université Paris-Sud Orsay

Low-temperature transport properties of long lived photo-excitations in organic materials

In organic semi-conductors long lived photo-induced excitations can
take the form of electron-hole pairs and triplet excitons which are respectively protected by charge and spin conservation. We determined the localization length of the photo-induced charges in a photovoltaic donor-acceptor blend at low temperatures by comparing their dielectric and electron spin-resonance susceptibilities.

We then investigated spin dependent recombination pathways for triplet
excitons generated by singlet fission using optically detected magnetic
resonance. We showed that geminate recombination between a pair of triplets generated by the same photon and non-geminate triplet-triplet annihilation are characterized by distinct magnetic resonance line-shapes at low temperatures.