Soluble fluorene–benzothiadiazole polymer-grafted graphene for photovoltaic devices

Abstract

Herein, a polymer based on fluorene and benzothiadiazole (PFBT) was covalently grafted on brominated graphene (G-PFBT) sheets via Suzuki coupling reaction and characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis), fluorescence emission (FL), and ¹H-NMR spectroscopy. The obtained composite shows good solubility in organic solvents such as THF, DMF, and toluene, which is beneficial for the solution casting of device fabrication. In addition, photoinduced charge transfer was observed between the conjugated polymer donor and graphene acceptor, which was also an advantage of using G-PFBT in solar cells. The open-circuit voltage, short-circuit current density, and fill factor of a photovoltaic device based on G-PFBT are 0.22 V, 1.42 mA cm⁻², and 0.26, respectively.