The effect of three Isonicotinate derivatives as additives in iodide/triiodide redox electrolyte are investigated on the performance of 3-(4-carbazole-9-yl-phenyl)-2-cyano-acrylic acid (TC301) and 2-cyano-3-(4-(3,6-di-tert-butyl-9H-carbazole-9-yl) phenyl) acrylic acid (TC302) dye-sensitized TiO2 solar cell. Addition of 0.5 M additive into the electrolyte, leads to an increase of the open-circuit potential (V-oc) and short current density (J(sc)), consequently improving the energy conversion efficiency (h). Using these additives in the electrolyte shift the TiO2 band edge toward negative potentials. The electrochemical impedance spectroscopy (EIS) shows when an additive is added to electrolyte solution in comparison to an electrolyte without additive, a low recombination rate constant (k(eff)), a higher recombination resistance (R-ct) and a high effective electron-diffusion length (L-n) in TiO2 films are observed. In addition, cyclic voltammetry (CV) confirms the impedance results. Finally, we found that Isonicotinate derivatives are promising additives which can be used for high efficient and low cost dyesensitized solar cells. (C) 2015 Elsevier Ltd. All rights reserved.