The aim of this study was to modify the platinum particle size to observe the effects on the efficiency of a Dye Sensitized Solar Cell (DSCC). DSSC was prepared as follows: On the anode side, TiO2 was annealed on the transparent conducting oxide (TCO) which is SnO2:F coated and a cis-bis (isothiocyanato) bis (2,2&#039 / -bipyridyl-4,4&#039 / -dicarboxylato)&ndash / ruthenium(II) dye was adsorbed on the TiO2. On the cathode side, platinum was coated on TCO from an alcohol based solution of platinum (plasitol) by thermal decomposition method. Potassium iodide and iodine were dissolved in ethylene glycol to prepare the electrolyte. Four cathode surfaces were prepared by thermal decomposition method at 400 oC and 5 min. Cathode surface morphology was changed by changing the annealing conditions. Current-voltage measurements were performed for determining the cell efficiency. One cathode glass was used as such giving a cell efficiency of 2.36%. Three glasses were further thermally treated at 450 oC, 500 oC and 550 oC for 30 min. highest efficiency was measured with the counter electrode annealed at 550 oC for 30 min as 2.89%. SEM micrographs of the substrate which was SnO2:F coated TCO revealed a decrease in average surface particle size with an increase in annealing temperature. EDX mappings showed that as the annealing temperature increased, Pt particles segregated together to form porous patches. In this study, it was demonstrated that as the annealing temperature of cathode increased, DSSC efficiency increased. These results can be used to design cheaper DSSCs with higher efficiencies.