Controlled self-aggregation of perylene bisimide and its application in thick photoconductive interlayers for high performance polymer solar cells
Highly conductive cathode interlayers that can work efficiently when the film is thick, are essentially important for polymer solar cells since this would facilitate their mass production in the future. Herein, an asymmetric organic dye molecule, perylene bisimide (PBI) 3, is synthesized as a photosensitizer for zinc oxide (ZnO) to achieve a photoconductive hybrid material. The self-aggregation of PBI3 was efficiently restricted by the introduction of an alkyl group at one of the imide positions in the structure of the molecule, whereas the formation of Zn–N chemical bonding between ZnO and PBI3 ensures the formation of a robust hybrid thin film. The photoconductive hybrid thin film shows highly enhanced conductivity under white light irradiation. Inverted polymer solar cells (PSCs) based on the photoconductive cathode interlayers (ZnO:PBI3 (3 wt%)) show a very high power conversion efficiency (PCE) of 8.79% when the thickness of the interlayer is 100 nm, which is three times higher than that of the ZnO cathode interlayer-based device.