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

Abstract

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 π–π 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.

Synthesis, Photophysical Characterization, and Self‐Assembly of Hexa‐peri‐hexabenzocoronene/Benzothiadiazole Donor–Acceptor Structure

“…In particular, the introduction of π‐conjugated electron‐withdrawing groups onto the electron‐rich HBC disk has been demonstrated to be an effective strategy to tune the energy levels of the molecular orbitals and broaden the absorption spectra. This is essential for applications in organic field‐effect transistors (OFETs) and organic photovoltaics (OPVs) ,,,. Nevertheless, there have been few reports on HBC‐based donor–acceptor (D–A) systems –,…”

Organic Photovoltaic Materials—Design, Synthesis and Scale‐Up

“…This led to OPV devices with a PCE of 1.5% despite the less than ideal spectral coverage of the FHBC material 13 . Attempts to improve the performance of FHBC materials were made by adding a variety of chromophores to enhance light absorption . Up to 3% PCE was observed but there was a trade‐off between the spectral coverage of the material and its semiconducting properties.…”

Efficient synthesis of 3,6,13,16-tetrasubstituted-tetrabenzo[a,d,j,m]coronenes by selective C–H/C–O arylations of anthraquinone derivatives

“…Coronene derivatives such as hexabenzocoronenes and ovalenes have been extensively studied because of their optoelectronic and self-assembling properties [34][35][36][37][38][39][40][41][42][43][44]. Various synthetic methods have been developed for coronene derivatives in general [34][35][36][37], however, only a few strategies have been reported for the syntheses of tetrabenzo[a,d,j,m]coronenes [43,44].…”