<p>The present study successfully synthesized a ZnO/Nd₂O₃/rGO ternary heterostructure for multifunctional photocatalytic and photovoltaic applications using a straightforward ultrasonication-assisted method. The structural, morphological, optical, and surface characteristics of the prepared samples were thoroughly examined using a variety of analytical techniques. UV–Visible diffuse reflectance analysis revealed a gradual reduction in the optical band gap from pristine ZnO to the ternary composite, with the ZnO/Nd₂O₃/rGO heterostructure exhibiting a band gap of 2.76&#xa0;eV, resulting in enhanced visible-light absorption. BET analysis demonstrated the formation of a mesoporous structure with a high specific surface area of 124&#xa0;m² g⁻¹, providing abundant active sites for photocatalytic reactions. Under natural sunlight irradiation, the ternary heterostructure achieved 98% degradation of Rhodamine B (RhB) within 75&#xa0;min and maintaining excellent recyclability and structural stability. In addition, the ZnO/Nd₂O₃/rGO photoanode delivered a power conversion efficiency of 9.15% in dye-sensitized solar cells. The enhanced multifunctional performance is attributed to the synergistic effects of ZnO/Nd₂O₃ heterojunction formation, oxygen-vacancy-induced defect states, efficient charge separation, rapid electron transport through the conductive rGO network, and improved visible-light utilization. This work demonstrates that integrating rare-earth oxides with graphene-based conductive materials is an effective strategy for designing multifunctional semiconductor heterostructures, offering promising potential for sustainable environmental remediation and solar-energy conversion. </p>