Photophysical properties of solid films of fullerene, C₆₀

Abstract

The authors report results on photophysical properties of solid films at C60, including optical absorption, photoluminescence, electroabsorption, photoconductivity, and photoinduced absorption. They observe photoconductivity for excitation energies from the UV to the near IR and find that the excitation spectrum follows the optical absorption. The electroabsorption response varies quadratically with electric field, shows oscillations at the band edge, and has an anisotropy of slightly less than three with respect to the light polarization and the direction of the applied electric field. Photoluminescence from excited states shows vibrational fine structure, a strong temperature dependence, and some variation with excitation energy. They see photoinduced absorption attributed to triplet-triplet transitions at 1.7 eV and also a band peaking at 1.3 eV. A further band at 2.33 eV is seen in C60/C70 mixtures (10% C70) and also in degraded C60 samples. They consider that these bands may arise from extrinsic stabilization of photoseparated charges.