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Solution Processable Monosubstituted Hexa-Peri-Hexabenzocoronene Self-Assembling Dyes



Molecular organization behavior and visible light absorption ability are important factors for organic materials to be used in efficient bulk heterojunction solar cells applications. In this context, a series of monosubstituted fluorenyl hexa-peri-hexabenzocoronene (FHBC) are synthesized with the aim to combine the self-association property of the FHBC unit with broadened light absorption of a small molecule organic dye, bisthienylbenzothiadiazole (TBT). Optical and electrochemical properties of the FHBC compounds vary according to their structures. Introduction of a TBT unit into the FHBC system broadens the absorption. All of the FHBC compounds show strong ππ intermolecular association in solution. X-ray scattering measurements on thermally extruded filaments and thin films showed ordered alignment of these compounds in the solid state. In atomic force microscopy experiments, nanoscale phase separation is observed in thin films of FHBC and fullerene derivative blends. Solar cell devices with these compounds as donors are fabricated. FHBC compounds with the TBT unit show higher short circuit current while the high open circuit voltages are maintained. With C60 derivative as acceptor, power conversion efficiency of 1.12% is achieved in the unoptimized solar cell devices under simulated solar irradiation. The efficiency was further improved to 1.64% when C70 derivative was used as the acceptor.

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