Enhanced open-circuit voltages of trifluoromethylated quinoxaline-based polymer solar cells

Abstract

Abstract Three quinoxaline-based conjugated polymers with donor-π-acceptor configurations have been synthesized by Stille coupling reaction. The electron-donating 2,3-dioctylthienyl- substituted benzodithiophene (BDT) unit was linked to the electron-accepting 2,3-diphenylquinoxaline (DPQ) group through a thiophene bridge, to produce a reference polymer PTBDT-Qx. Furthermore, the strong electron-withdrawing trifluoromethyl moieties were introduced at the para-position of the phenyl groups in the 2,3-positions of DPQ and 6,7-difluorinated DPQ, to afford PTBDT-QxCF3 and PTBDT-FQxCF3, respectively. Owing to the continuous reduction in their HOMO energy levels with increasing number of electron-withdrawing groups, the open-circuit voltage (Voc) in polymer solar cells (PSCs) shows a gradual improvement in the order of PTBDT-Qx