We examined the optimized conditions for preparing Pt/FTO glass counter electrodes (CEs) for the fabrication of highly efficient, bifacial, and quasi-solid-state dye-sensitized solar cells (QSS-DSSCs). The Pt/FTO glass CEs were prepared via thermal decomposition, and the molar concentration of the employed Pt precursor solution was controlled in the range of 5-40mM. Impedance analysis and Tafel polarization curves revealed that electrocatalytic activity was optimized at 20mM, whereas specular transmittance gradually decreased with increasing concentration of the precursor solution. When the CEs were applied to bifacial QSS-DSSCs employing a polymer gel electrolyte, the power conversion efficiency (PCE) was maximized at 20mM under front illumination because the condition resulted in the highest electrocatalytic activity. Meanwhile, PCE under back illumination was optimized at 10 mM because of the larger incident light loss by the CEs at higher concentrations. Because the influence of the inferior performance under back illumination was more dominant in bifacial operations, the average PCE under front and back illumination was optimized at 10 mM.