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

We investigate structure and photo-excitation in C 60 –zinc tetraphenylporphyrin (ZnTPP) and C 60 F 48 -ZnTPP complexes, which are promising candidates for organic photovoltaic devices. The C 60 -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 C 60 cage leads to decrease in ZnTPP binding, due to reduced π-π stacking interaction. C 60 -ZnTPP photo-excitation results largely from internal ZnTPP π → π* transitions, although delocalised ZnTPP π → C 60 π* transitions are also observed below 300 nm. The more intense photo-excitations of C 60 F 48 -ZnTPP arise solely from localised ZnTPP π → π* transitions.