6,6'-Dibromo-N,N'-(2-octyldodecanyl)isoindigo was coupled to either 4-(N-carbazolyl)phenyl boronic acid or 9-phenyl-9H-carbazole-3-boronic acid to give two different conjugated molecules of P-II-P and C-II-C, respectively. The optical band gap/HOMO levels of P-II-P and C-II-C were 1.90/-5.60 eV and 1.85/-5.39 eV, respectively. Based on the experimental and calculation data, C-II-C is more highly conjugated than P-II-P. The performances of C-II-C-based photovoltaic devices were better than those of P-II-P-based devices, with the best power conversion efficiency of 0.44%. (C) 2016 Elsevier B.V. All rights reserved.