Divergent Synthesis and Tuning of the Electronic Structures of Cobalt–Dithiolene–Fullerene Complexes for Organic Solar Cells

Abstract

A pentakis(aryl)[60]fullerene cobalt trisulfide complex (1a) was obtained from the reaction of a pentakis(aryl)[60]fullerene cobalt dicarbonyl complex (2a) with triphenylmethanethiol. This reaction proceeded smoothly even at ambient temperature to produce 1a in moderate to high yield. The series of pentakis(aryl)[60]fullerene cobalt dithiolene complexes 3–9 were also synthesized by the reaction of 1a with a variety of readily available disulfide compounds. The HOMO and LUMO levels of the complexes could be tuned by making changes to the substituents on the dithiolene ligands, with changes to the electronic structure of the compounds influencing their photovoltaic performance, especially in terms of their open-circuit voltage. Small-molecule organic solar cells constructed from the naphthalene dithiolene complex 9 and tetrabenzoporphyrin showed a power conversion efficiency of 0.59%.