Cosensitization is a highly effective technique to enhance the photovoltaic performance of a dye-sensitized solar cell. The main objective of this work is to improve the performance of dye-sensitized solar cell using cosensitization approach and investigation of the effect of the organic cosensitizer concentration on the power conversion efficiency of the fabricated solar cell devices. In this work, Z907, a ruthenium dye, has been cosensitized with SQ2, an organic sensitizer, and an overall efficiency of 7.83% has been achieved. The fabricated solar cells were evaluated using UV-Vis spectroscopy, current-voltage (I-V) characteristics, and electrochemical impedance spectroscopy analysis. Our results clearly indicate that the concentration of organic cosensitizer strongly affects the photovoltaic performance of fabricated solar cells. Upon optimization, the cell fabricated with 0.3 mM Z907 + 0.2 mM SQ2 dye solution demonstrated Jsc (mA/cm2) = 21.38, Voc (mV) = 698.37, FF (%) = 52.46, and power conversion efficiency of. (%) = 7.83 under standard AM1.5G 1 sun illumination (100 mW/cm2). It was observed that the efficiency of cosensitized solar cells is significantly superior than that of individual sensitized solar cells (Z907 [. = 5.08%] and SQ2 [. = 1.39%]). This enhancement in efficiency could be attributed to the lower electron-hole recombination rate, decrease in competitive absorption of I-/I-3, and less dye aggregation because of the synergistic effect in cosensitized solar cells.