Structure and absorption in C₆₀-zinc tetra-phenylporphyrin composite materials: a computational study

We investigate structure and photo-excitation in C₆₀-zinc tetraphenylporphyrin (ZnTPP) and C₆₀F₄₈-ZnTPP complexes, which are promising candidates for organic photovoltaic devices. The C₆₀-ZnTPP complex results from π-π stacking between the fullerene and porphyrin structures, and has a binding energy of 76.0 kJ/mol. Fluorination of the C₆₀ cage leads to decrease in ZnTPP binding, due to reduced π-π stacking interaction. C₆₀-ZnTPP photo-excitation results largely from internal ZnTPP π → π* transitions, although delocalised ZnTPP π → C₆₀ π* transitions are also observed below 300 nm. The more intense photo-excitations of C₆₀F₄₈-ZnTPP arise solely from localised ZnTPP π → π* transitions.