Non-Stoichiometric Calcium Addition in Red-Emitting CaSc2O4:Eu2+ Phosphor Toward Enhanced Photoluminescence Quantum Efficiency for LED Applications

The rapid advancements in solid-state lighting have underscored the need for efficient and thermally stable phosphors for light-emitting diode (LED) applications. Herein, a red phosphor CaSc₂O₄:Eu²⁺ (λ_ex = 450 nm, λ_em = 650 nm) is synthesized employing a non-stoichiometric strategy to increase photoluminescence quantum efficiency (PLQY). Spectroscopic and crystallographic properties analysis confirm that the red emission band originates from Eu²⁺ ions occupying a single Ca²⁺ site with significant nephelauxetic effects and crystal field splitting. Excessive CaCO₃ additions promote the reduction of Eu³⁺ and an increase of trap concentration, enhancing the PLQY from 24% to 61% and improving the emission intensities at 150 °C from 8% to 41% of that at room temperature. Versatile LED light sources, including high-quality white LED, red LED in plant growth, and the integrated pixelated intelligent LED matrices have been explored for the practical applications. This study proposes an optimized strategy to enhance the efficiency and thermal stability of Eu²⁺-doped oxide-based red phosphors for multifunctional lighting applications.