Evolution of lighting technologies: The central role of rare-earth-doped materials in advancing modern illumination

This review presents an integrated perspective on the evolution of lighting technologies, with emphasis on the transition from conventional illumination systems to solid-state lighting based on light-emitting diodes (LEDs). Attention is devoted to the central role of rare-earth-doped materials in enabling efficient white-light generation through their unique electronic structures, narrow emission profiles, high photostability, and tunable photophysical properties. The main strategies for white-light production are discussed, including phosphor-converted LEDs based on blue or near-ultraviolet excitation, multichip RGB architectures, and energy conversion processes involving upconversion, downconversion, and downshifting mechanisms. The review highlights the relationship between host-lattice chemistry, dopant environment, energy-transfer processes, and emission performance, focusing on recent advances in rare-earth-based phosphors for solid-state lighting. Emerging developments such as single-phase white emitters, high-CRI and tunable correlated color temperature (CCT) phosphors, thermal-quenching suppression strategies, and multifunctional luminescent systems are critically examined in the context of next-generation lighting technologies. Beyond conventional illumination, the impact of spectral composition on circadian regulation, mediated by melanopsin activation and melatonin suppression, is discussed within the framework of human-centric lighting. Finally, emerging directions in the design of rare-earth-based phosphors and sustainable synthesis strategies are discussed, highlighting their importance for the development of next-generation lighting technologies.