This study aimed to investigate the effect of pyridine in electrolyte on the photocurrent density-photovoltage (J-V) characteristics in dye-sensitized solar cells. When the concentration of pyridine (c(p)) in an electrolyte (0.1 M Lil and 0.05 MI2 in acetonitrile) is increased from 0 to 0.4 M, the open-circuit voltage (V-oc) increased by 0.14V, whereas the short-circuit photocurrent density (J(sc)) decreased by 3.0 mA cm(-2). The optimum c(p) for the maximum cell performance was around 0.1-0.2 M. The model calculation predicted that by increasing c(p) from 0 to 0.4 M, the electron diffusion coefficient (D) decreases by more than one order of magnitude and the lifetime of conduction band-free electrons (tau) increases by more than one order of magnitude, implying that the electron diffusion length (L = root D tau) increases by 31%, whereas the electron injection flux from dye molecules to TiO2 nanoporous films (Phi) decreases by 28%. (C) 2010 Elsevier Ltd. All rights reserved.