Ultrafast charge transfer in conjugated polymer-fullerene composites

Phonon modes, which are strongly coupled to the electronic excitation of th e conjugated polymer are coherently excited by sub-10-femtosecond laser pul ses. Pump probe experiments show vibrational modulations as fast as 25 fsec . The Fourier transformed spectrum displays the non-resonant Raman spectrum . Addition of fullerenes into the conjugated polymer matrix quenches the vi brational coherence of the polymer due to a strong interaction of the excit ed polymer with the fullerene moeity. Charge separation times of less than 100 fsec are reported.