Efficient deep-red-emitting CaMg2La2W2O12:Mn4+, Nd3+ phosphor toward indoor plant cultivation LED lighting

Abstract

This study presents the synthesis and characterization of efficient deep-red-emitting CaMg₂La₂W₂O₁₂:Mn⁴⁺, Nd³⁺ (CMLW:Mn⁴⁺, Nd³⁺) phosphors for application in light-emitting diodes (LEDs) designed for indoor plant cultivation. The phosphors were prepared via a high-temperature solid-state reaction and exhibited an orthorhombic structure with optimal luminescence properties at Mn⁴⁺ (0.90 %) and Nd³⁺ (0.60 %) doping concentrations. The enhanced performance of CMLW:0.90 %Mn⁴⁺, 0.60 %Nd³⁺ over its Nd³⁺-free counterpart originates from three synergistic mechanisms: (1) Nd³⁺ substitution for larger La³⁺ induces lattice shrinkage, shortening the Mn⁴⁺-O^2- bond length and enhancing the crystal-field strength, thereby increasing the radiative transition probability of ²E_g→⁴A_2g emission at 708 nm; (2) Nd³⁺ co-doping suppresses concentration quenching by increasing the critical distance between Mn⁴⁺ ions, as evidenced by prolonged lifetime and higher optimal Mn⁴⁺ concentration; (3) The optimal Nd³⁺ concentration improves lattice rigidity while avoiding defect formation observed at higher doping levels. The resulting phosphor demonstrates intense deep-red emission matching the phytochrome P_FR absorption band, excellent thermal stability (73.66 % intensity at 453 K), and a high internal quantum efficiency (IQE) of 86.80 %. A prototype LED device exhibits stable deep-red emission and a luminous efficacy of 0.10 lm/W under 365 nm excitation. These results position CMLW:Mn⁴⁺, Nd³⁺ phosphor as a promising candidate for indoor plant cultivation LEDs.