and FARAMARZ FARAHI$

Photocarrier generation efficiency (PGE) and reverse saturable absorption (RSA) measure-ments have been conducted on fullerene (C,,)/polymethyl methacrylate (PMMA) thin films and C,,/toluene solutions. The photocarrier generation has been measured at 330 and 532 nm for various concentrations and electron donor/acceptor addition. The photocarrier generation yield for 330 nm traversed a maximum with increasing concentration which was not observed for 532nm excitation. This concentration dependence is explained via electron-hole pair dissociation. A large enhancement of photocarrier generation was observed in the case of triphenylamine addition to C,,. Fullerene solutions containing electron donors and acceptors demonstrated optical limiting with a vertical shift in the transmittance versus fluence optical limiting plots. This vertical shift could not account for the optical limiting profile of C,,/dimethylbenzoquinone samples. 1