Fullerene films with suppressed polymerizing ability

Illumination of fullerene with visible light in the presence of oxygen leads to a transition of oxygen from triplet (ground) to singlet (excited) state where singlet oxygen is a long-lived reactive oxygen species. The effectiveness of fullerene as a singlet oxygen generator drastically decreases when fullerenes are condensed into a bulk material, mainly due to the polymerization ability. The ability of fullerene films to polymerize was studied for the C$_{60}$ fullerene films intercalated with tetraphenylporphyrine (TPP), CdS, CdTe, HNO$_{3}$ as well as the hydrogen plasma treated films. Raman spectroscopy was used for monitoring the polymerization process. The ability to polymerize was found to be tightly connected to the formation of charge-transfer (Wannier-Mott) excitons which are revealed in the absorption spectra and measured with the help of spectroscopic ellipsometry.