INVESTIGATION OF PHOTOEXCITATIONS OF CONJUGATED POLYMER FULLERENE COMPOSITES EMBEDDED IN CONVENTIONAL POLYMERS/

A promising approach to improve the processability of semiconducting p olymers is their incorporation into host matrices formed by convention al polymers such as polyethylene (PE) or polystyrene (PS). We:have cha racterized the Linear optical properties of several guest-host systems by absorption and luminescence measurements and probed the excited st ates by photoinduced absorption measurements (PIA) and light induced e lectron spin resonance (LESR). The:interesting photophysics of conjuga ted polymer/fullerene donor-acceptor system,showing an ultrafast photo induced electron transfer and a metastable charge separation in the pr istine state, has been investigated in such composites where the photo active components are further embedded into a conventional polymer mat rix. The composition of the blend and the relative concentration,of th e components are found to strongly influence the photoinduced interact ion between the conjugated polymer and the fullerenes (C-60 and functi onalized fullerenes). Photoinduced electron transfer between a soluble polyphenylenevinylene (PPV) derivative and C-60 is observed in a syst em with PS as host when the concentration of the both electroactive; c omponents is 33%. In, diluted-composites with PS as; matrix we find st rong luminescence quenching of the:PPV derivative but no electron tran sfer upon adding C-60. Dominant photoexcitations in these PS systems a re tripler states as follows from intensity dependencies and lifetime measurements. In diluted systems with PE as matrix neither charge tran sfer nor luminescence quenching has been observed. (C) 1998 American I nstitute of Physics.