The effects of the dye-adsorption solvent on the performances of the dye-sensitized solar cells (DSSCs) based on black dye have been investigated. The highest conversion efficiency (10.6 %) was obtained in the cases for which 1-PrOH and the mixed solvent of EtOH and tBuOH (3:1 v/v) were employed as dye-adsorption solvents. The optimized value for the dielectric constant of the dye-adsorption solvent was found to be around 20. The DSSCs that used MeOH as a dye-adsorption solvent showed inferior solar-cell performance relative to the DSSCs that used EtOH, 1-PrOH, 2-PrOH, and 1-BuOH. Photo- and electrochemical measurements of black dye both in solution and adsorbed onto the TiO2 surface revealed that black dye aggregates at the TiO2 surface during the adsorption process in the case for MeOH. Both the shorter electron lifetime in the TiO2 photoelectrode and the greater resistance in the TiO2–dye–elecrolyte interface, attributed to the dye aggregation at the TiO2 surface, cause the decrease in the solar-cell performance of the DSSC that used MeOH as a dye adsorption solvent.