The progressively decline problem of fuel sources underlines the pressing need for sustainable energy alternatives like thermoelectric materials. These materials possess the unique ability to convert temperature differences into electricity using the Seebeck effect. Herein, we investigate the effect of 0.1%, 0.2%, and 0.3% cobalt (Co) doping on the structural, optical, and thermoelectric properties of zinc oxide (ZnO) nanoparticles produced via the co-precipitation chemical method. X-ray diffraction analysis unequivocally gives the hexagonal wurtzite structure of ZnO. By introducing cobalt in the ZnO host, as depicted by shifts in the XRD patterns, the crystallite size of Co-doped ZnO nanoparticles is found to increase. Additionally, doping leads to increased optical absorption in the visible spectrum and a noticeable red shift in the absorption band edge. Notably, the optical band gap decreases from 3.34 eV to 3.05 eV as the Co doping level increases up to 0.3%. We also conducted measurements of electrical conductivity and the Seebeck coefficient. Our findings reveal that the incorporation of Co into ZnO leads to improvements in the Seebeck coefficient, which directly correlates with thermoelectric efficiency. These outcomes have broad-ranging applications and hold promise for advancing thermoelectric technology, thereby contributing to a more sustainable future in alignment with the Sustainable Development Goals established by the United Nations Organization.