Improvement of Photovoltaic Performance of Octahexylphthalocyanine-Based Bulk-Heterojunction Solar Cells Using Various Fullerene Derivatives

The improvement of the photovoltaic performance of 1,4,8,11,15,18,22,25-octahexyl-phthalocyanine (C6PcH2)-based bulk-heterojunction solar cells using various fullerene derivatives was studied. By using asymmetric fullerene derivatives, the external quantum efficiency of the solar cells at around 500 nm was improved from 8% to 24%, and the short-circuit current density increased from 8.09 to 10.17 mA・cm-2. An open-circuit voltage of 0.96 V was achieved by a using fullerene derivative with a high lowest unoccupied molecular orbital. The photovoltaic properties were also discussed, taking into consideration the effects of adding the fullerene on the crystallization of C6PcH2 molecules in the hexagonal structure and the optical properties.