Complexation of pyrrolidinofullerenes and zinc-phthalocyanine in a bilayer organic solar cell structure

Bilayer organic solar cells were prepared using zinc-phthalocyanine (ZnPc) and a novel, highly soluble pyrollidinofullerene bearing three chelating pyridyl groups (PyF). The formation of supramolecular complexes between the two compounds is indicated by a significantly increased solubility of ZnPc in dichloromethane upon addition of the PyF. Spin-coating a film of PyF on a vacuum-evaporated film of ZnPc results in a solar cell yielding short circuit current (I-sc) densities of 3 mA/cm(2) and open-circuit voltages (V-oc) of about 0.4 V under 100 mW/cm(2) simulated AM1.5 illumination. Solar cells prepared by substituting the PyF with a fullerene derivative forming no complexes with ZnPc show significantly lower photovoltaic conversion efficiencies.