A new charge separation mechanism arising from interfacial dipolar fields at interfaces of organic photovoltaic materials has been identified using ultrafast infrared spectroscopy. This mechanism, termed electric field-assisted charge separation, is in part responsible for the surprisingly rapid and efficient charge separation that is observed in OPV materials. The dynamics of interfacial electron transfer and free carrier formation are examined through the carbonyl stretch of an electron accepting functionalized fullerene in a blend with an electron donating conjugated polymer. Free carrier formation following photoexcitation occurs on the 1-10 ps time scale, which suggests that the Coulombic binding energy is considerably smaller than the value predicted from the dielectric properties of the materials. The electric field that assists the separation of the charge carriers arises from interfacial dipoles that form due to spontaneous partial charge transfer from the polymer to the fullerene.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)