Comparative studies on solar cell structures using zinc phthalocyanine and fullerenes

We compare different structures of organic solar cells based on zinc phthalocyanine (ZnPc) and fullerene derivatives as electron donor and acceptor materials, respectively. Bilayer devices are fabricated and characterized by current-voltage and spectrally resolved photocurrent measurements. In a novel approach, the ZnPc was combined with soluble fullerene derivatives. With a pyrrolidinofullerene bearing chelating pyrridyl-groups we observed a complexation between donor and acceptor molecules. Due to a favorable structuring of the donor-acceptor interface this leads to a significant enhancement of the solar cell performance compared to similar devices where no complexation takes place. Coevaporated bulk heterojunction mixed-layers are introduced between the pristine layers. In these optimized structures short circuit currents up to 13 mA/cm2 are observed. We investigate the voltage dependence of the spectrally resolved photocurrent of ZnPc / Buckminsterfullerene bilayer solar cells and interpret the results in terms of the Gartner model.