TEMPERATURE-DEPENDENT PHOTOLUMINESCENCE STUDY OF C-60 AND C-70

The photoluminescence (PL) spectra of C60 and C70 in toluene, as films on silicon and as KBr pellet, were obtained as a function of temperat ure. Different emission profiles are observed between the fullerenes i n solution and in the solid form. The PL spectra of the C60 solids are similar regardless of their substrates, while those of C70 show diffe rent emission profiles between the films on silicon and the pellet, wh ich is believed to be due to the substrate-dependent stacking disorder resulting from the nonspherical shape of the molecule. The changes in emission intensity and prof ile upon temperature are observed in the PL spectra of solid C60 and C70, suggesting the strong influence of ro tational diffusion. The vibrational mode progressions are identified f rom the low-temperature photoluminescence spectra of C60 and C70.