Electron -: hole separation distance during the charge carrier photogeneration in conjugated polymer

Charge separation dynamics in a Ladder-Type Methyl substituted Poly(Para-Phenylene) (m-LPPP) was investigated by means of electric filed modulated femtosecond pump-probe absorption spectroscopy. The Stark shift of the absorption band modified by created excitons and electron-hole pairs provided information about the average intrapair charge separation distance. The electron and hole initially separated by ca. 7 Angstrom moved away from each other to more than 30 Angstrom during 600 ps and later the separation rate decreased. Neither the initial separation distance, nor that obtained at 600 ps were found to depend on the applied electric field, only the separation rate at stronger field was slightly faster.