Photoinduced Electron Transfer in Li+@C60

Abstract

Lithium-ion-containing [60]fullerene, Li+@C60, has excellent electron-accepting properties with a low-lying LUMO level because of the positively charged inner lithium ion. The singlet and triplet excited state energies of Li+@C60 (1.94 and 1.53 eV, respectively) were characterized from emission spectra. The triplet state lifetime of Li+@C60 was determined to be 49 µs by transient absorption measurements. Photoinduced electron transfer reduction of Li+@C60 with various electron donors was examined to determine the electron transfer rate constants and the thermodynamic driving force. Utilizing the cationic nature of Li+@C60, supramolecular complexes with anionic electron donors were constructed and investigated to elucidate a long-live supramolecular charge-separated state. The addition of ions, such as chloride, was used to control electron transfer in the supramolecular charge-separation systems. Photovoltaic devices were fabricated using anionic porphyrin derivatives as electron donors and Li+@C60 as an electron acceptor. The devices gave a decent power conversion efficiency of 2.1%.