To date, rare earth oxides (REOs) have proven to be key components in generating sustainable energy solutions, ensuring environmental safety and economic progress due to their diverse attributes. REOs' exceptional optical, thermodynamic, and chemical properties have made them indispensable in a variety of sophisticated technologies, including electric vehicle magnets, portable energy devices, fuel cell catalysts, radiation shielding, dosimetry, and many others. Therefore, the successful incorporation of rare earth elements (REEs) into host materials in controlled concentrations offers competitive advantages to fabricate portable energy devices, radiation sensors, and radiation shielding glasses, as well as to improve the performance of existing photovoltaic cells, which is of great interest to both researchers and industry. As the global demand for REEs grows rapidly, it is critical to comprehend the underlying physics as well as the wider consequences of REEs on sustainable energy and nuclear technologies, both in the near and long term. However, despite their relevance, a focused review on the applications, prospects, and challenges of REOs in photovoltaics, nuclear, and energy devices is still unavailable. To this effort, this review succinctly reports recent experimental studies on eight REOs (R 2 O 3 , R = Yb, Er, Sm, Eu, Y, Gd, Dy, and Ce) and their specific applications and industrial aspects. While several subdomains are reported, the applications of REOs in next-generation solar cells and photovoltaic devices for promoting zero-emission clean energy and rechargeable batteries for electric vehicles (EVs) are the most pioneering ones. Furthermore, REOs' chemical stability and compositional versatility allow them to be used in a variety of high-efficiency energy converters, including solid oxide fuel cells (SOFCs). From the perspective of thermodynamic and structural stability, the gamma and neutron absorptivity of REO-doped (such as Dy 3+ , Eu 3+ , Sm 3+ , Nd 3+ , etc.) glasses shows improved shielding performance in radiation domains. Aside from the applications, the prospects of REOs presented in this article are likely to encourage current and future scholars to pursue a wide range of important studies in the fields of energy and nuclear systems. This review also reports the key challenges (i.e., material degradation, phase transformation, magnetic entropy shift, etc.) associated with REOs in a standalone section. These challenges demand the immediate attention of scientists and engineers for efficient, costeffective, and environmentally sustainable solutions. At the end, future advancement pathways for REO applications are also suggested.
