The effect of Li ion on the light-harvesting and electron injection efficiencies of D149-sensitized nanocrystalline TiO2 films was studied. Absorption spectra shifted toward the long-wavelength region when films were immersed in a Li ion solution, indicating that Li ion enhanced light-harvesting efficiency. We also found that electron injection efficiency was dramatically enhanced by Li ion. These observations indicate that it is essential to incorporate Li ion in the electrolyte of D149-sensitized solar cell devices to improve their performance. (C) 2015 Elsevier B.V. All rights reserved.