TRANSIENT SPECTROSCOPY OF EXCITONS AND POLARONS IN C-60 FILMS FROM FEMTOSECONDS TO MILLISECONDS

We have studied photoexcitations in C-60 films using transient photomo dulation and photoluminescence from 100 fs to 50 ms and absorption-det ected magnetic resonance (ADMR). We show that singlet Frenkel excitons are the primary photoexcitations; their recombination kinetics in the picosecond time domain are dispersive as a result of inhomogeneity. T he long-lived photoexcitations, however, are shown to be triplet excit ons and charged polarons (C-60(+/-)), identified by the correlation fo und between their associated optical transitions and ADMR signals with spin 1 and 1/2, respectively.