PHOTOLUMINESCENCE OF C60 SINGLE-CRYSTALS

The photoluminescence (PL) spectra of C60 single crystals grown under double temperature gradient (DTG) and single temperature gradient (STG ) techniques were investigated at room temperature. The results show t hat the PL emission intensity increases first and then decreases with increasing illuminated power density for the C60 single crystals grown by both DTG and STG techniques. Furthermore, one main peak with a sho ulder peak can be clearly distinguished at low illumination, while onl y one main peak without the shoulder peak can be seen at high illumina tion. The main peak undergoes a continuous blue shift and broadening w ith the increase of illuminated power density. The difference of PL em ission energy at the same illumination density of DTG and STG samples may correlated with the degree of both the orientational disorder of C 60 molecule and lattice perfectness. The Laue diffraction patterns sho w that the DTG sample has stronger strains and poorer crystalline qual ity than the STG sample.