| By TD-DFT we studied the electronic structure of neutral and charged species of a conjugated oligomer related to PPV. Thereby it turns out that for the same nuclear structure the energy differences between the neutral and the charged species imply a trapping energy for both types of charge carriers (electron and holes) of about 0.5 eV. Up to now this trapping, which experimental evidences exist for, has been attributed to the nuclear relaxation in terms of polaron formation. However, we calculated the energy gain by nuclear relaxation to only 0.7 eV. Thus the possibility is to be discussed that instead of the electron-phonon coupling the electron-correlation is responsible for the charge carrier trapping in conjugated polymers. |
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