A yttria-stabilized zirconia (YSZ) cathode functional layer (CFL) was fabricated using a co-sputtering process to improve the oxygen reduction reaction (ORR) in solid oxide fuel cells (SOFCs). To optimize the yttria molar percentage and achieve a nano-granular structure with enhanced grain boundary density, the DC sputtering power for the metallic yttrium target was varied at 10, 30, and 50 W. Structural and compositional analyses were performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD). The results indicated that a DC power of 30 W resulted in a well-developed grain structure with high grain boundary density and an yttria composition close to the optimal molar percentage of 8-10 mol %. Under these optimized conditions, the SOFC with the co-sputtered YSZ CFL achieved a maximum power output of 9.22 mW/cm² at 450^oC, representing approximately a 43% enhancement compared to the reference cell. This highlights the significant potential of co-sputtering for future low-temperature SOFC applications.