Synthesis and photovoltaic properties of new conjugated polymers based on two angular-shaped naphthodifuran isomers and isoindigo

New polymers based on two different angular-shaped naphthodifurans (NDFs) have been synthesized. The optical, electrochemical and photovoltaic properties of the new polymers were investigated. The UV–vis absorption spectra of polymer PIDNDF1 recorded in dilute solution and as thin-film were both red-shifted compared with those of polymer PIDNDF2. The HOMO energy levels of PIDNDF1 and PIDNDF2 were similar at −5.40 eV. There was slight difference in the LUMO energy levels of these two polymers. The maximum power conversion efficiency (PCE) of PIDNDF1 based solar cell devices was 1.83%, which was more than twice that of PIDNDF2 based device. The difference on the device performance resulted from the shapes of NDF repeating units and backbone geometries of polymers.