Recent Progress in Lanthanide-Activated Halo-Phosphors for White Light-Emitting Diodes and Photovoltaic Efficiency...

Lanthanide-activated down-conversion halo-phosphors have emerged as promising luminescent materials for advanced white light-emitting diodes (WLEDs) and photovoltaic applications due to their sharp emission lines, high color purity, and excellent thermal and chemical stability. This comprehensive review summarizes the fundamental aspects of luminescence, down-conversion mechanisms, and the role of key lanthanide ions such as Eu³⁺, Tb³⁺, Dy³⁺, and Sm³⁺ in achieving efficient red, green, blue, and color-tunable emissions. Strategies for spectral and color tuning through host lattice engineering, cationic/anionic substitution, and energy transfer processes are discussed, along with the importance of Judd-Ofelt theory in evaluating radiative properties. The advantages of halo-phosphor-based materials in enhancing color rendering index, correlated color temperature, and spectral stability are highlighted, and their potential in improving photovoltaic device performance via spectral conversion is briefly addressed.