Upconversion (UC) luminescent materials have emerged as captivating contenders in revolutionizing both photovoltaic (PV) solar cell efficiency and biological capabilities. Their unique ability to convert low-energy infrared light into high-energy visible or ultraviolet (UV) photons unlocks untapped resources in the solar spectrum and allows for deeper tissue penetration in biological imaging. By bridging the gap between recent advancements and remaining hurdles, we aim to inspire further research and accelerate the translation of these materials into practical and impactful applications for both energy and healthcare. This review delves into the recent trends propelling these materials forward. We explore advancements in UC efficiency through optimized material design, novel synthesis routes, and synergistic integration with existing technologies. In the domain of PVs, we shed light on strategies utilizing UC to address spectral mismatch and enhance light harvesting, paving the way for higher power conversion efficiencies. For biological applications, we illuminate the development of biocompatible and targeted UC probes, enabling deep tissue penetration, multimodality imaging, and theranostic potential. We critically analyze the current limitations and future directions of these materials, highlighting the challenges of toxicity, quenching, and scalability that remain to be tackled. By providing a comprehensive overview of the exciting progress and persistent hurdles in UC research, this review aims to guide future explorations and catalyze the widespread adoption of these materials in sustainable energy generation and advanced medical diagnostics.
