Mesoscopic Donor−Acceptor Multilayer by Ultrahigh-Vacuum Codeposition of Zn-Tetraphenyl-Porphyrin and C₇₀

The peculiar electrochemical and photophysical properties of porphyrin and fullerene molecules make them promising candidates for the construction of two- and three-dimensional organic-based materials. An important question is how pristine fullerene and porphyrin will organize when deposited on surfaces via in vacuum molecular beam evaporation. Here we show that codeposition of C₇₀ and Zn-tetraphenyl-porphyrin (ZnTPP) induces the self-assembly of electron-rich flat aromatic molecules at the curved surface of C₇₀, thus enhancing the chromophore interaction and forming a supramolecular multilayer donor−acceptor structure. While the ground-state electronic spectra almost reflect a simple summation of ZnTPP and C₇₀ components, the excited-state electrons at the porphyrin macrocycle can rapidly delocalize to the fullerene. The excited charge transfer time scale is faster than 1−2 fs, as shown by resonant photoemission for the core-excited charges.