Synthesis and characterizations of carbazole–isoindigo–carbazole oligomers for photovoltaic application

Abstract 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%.