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Ultraviolet (UV/Vis) and Electroabsorption (EA) spectroscopy is used to examine and differentiate between intermolecular and intra molecular excited state species in fullerene films. Charge Transfer (CT) states are identified at 2.4 eV and 2.7 eV and dipole moments are calculated. Thermal annealing of C60 films is monitored in situ using absorption spectroscopy and electroabsorption spectroscopy. Recorded spectra display both some temperature dependent and partially irreversible effects, indicating the occurrence of an annealing process. EA shows that the CT states associated with the transferring an electron from the HOMO of one molecule located at the (0,0,0) position to the LUMO of its nearest neighbour in the (½,½,0) have been modified as a result of the annealing process. Confirmation of this structural change due to the annealing process is provided by previously reported X-Ray crystallographic work.
Farrell, G., Chambers, G., Byrne, H.: Electroabsorption studies of structurally modified fullerene thin films. Proceedings of Opto Ireland 2005. SPIE vol.5826, 232, 2005.