Carbon-modulated reduction synthesis of dual-valent Eu-doped La3Si2O8Cl phosphors: single-matrix white LEDs and high-resolution solar-blind UV detection†

Abstract

Developing single-component white-light phosphors remains challenging due to the difficulty in achieving dual emission from mixed-valent activators. Herein, we present a carbon-modulated reduction synthesis (CARS) method to fabricate Eu²⁺/Eu³⁺ co-doped La₃Si₂O₈Cl (LSOCl) phosphors without requiring hazardous reducing atmospheres. By modulating carbon content (Eu : C = 1 : 0–2.4), the Eu²⁺/Eu³⁺ ratio is effectively controlled, enabling tunable emission from pink to white and yellow under 365 nm UV excitation. The optimized LSOCl:7%Eu (Eu : C = 1 : 1.9) exhibits broadband emission (390–720 nm) with a high color rendering index (R_a = 85.05), cool white light (5489 K, CIE: 0.33, 0.38), and stable performance under varying currents. Additionally, LSOCl:7%Eu (Eu : C = 1 : 1.4) shows excitation-dependent chromaticity shifts: minimal changes under solar-blind UV (250–280 nm) but dramatic variations at 280–350 nm, facilitating rapid detection. A solar-blind UV detector was designed, demonstrating fast response, high resolution (50% CIE shift at 330 nm), and anti-interference capability. The CARS method offers an eco-friendly, scalable route for dual-emission phosphors, showcasing their dual utility in high-quality white LEDs and sensitive UV detection technologies.