Ozone-Mediated Polymerization of Fullerene and Fluorofullerene Thin Films

Films of an oxygen-linked fullerene polymer were synthesized by exposing about 15-nm-thick fullerite layers to ozone at room temperature. Moderate ozone exposure was found to lead to a polyoxifulleride that was stable in a vacuum up to at least 800 K. The oxidation and polymerization process was monitored by core-level and valence-band photoelectron spectroscopy, which Suggested that the bonding between fullerenes was by furan-like oxygen bridges and that the resulting polymer was three-dimensionally linked. The redox potential of the film was Unaffected by this kind of polymerization, as witnessed by the Unimpaired fullerene-induced Surface conductivity of diamond. Hence, in addition to stabilization of the diamond Surface conductivity, the polymerization is expected to be of considerable importance for C-60-based bulk heterojunction organic solar cells, as well as for C-60-based field-effect transistors. Similar albeit less effective thermal stabilization was also achieved for the fluorofullerene C60F48.