Effective red compensation of Sr ₂SiO ₄: Dy ³⁺ Phosphor by Codoping Mn ²⁺ ions and its energy transfer

Mn ²⁺ ions codoped Sr ₂SiO ₄: Dy ³⁺ phosphors were prepared by the solid-state reaction method using NH ₄Cl as the flux. Their phase compositions, photoluminescence properties, and the energy transfer process were systematically investigated. All Mn/Dy codoped powders were α ′-Sr ₂SiO ₄. The codoping concentration range of Mn ²⁺ was ≤ 4.0 mol to keep the structure undamaged. The broad red emission of Mn ²⁺ centered at 647 nm in Sr ₂SiO ₄: Mn, Dy powders, which effectively compensated the red emission of Sr ₂SiO ₄: Dy ³⁺ phosphor. The CIE chromaticity coordinates dramatically changed from (0.310, 0.340) to (0.332, 0.326) due to the red enhancement via the energy transfer from Dy ³⁺ to Mn ²⁺. This energy transfer is realized by the exchange interaction. But the luminescence quenching of Sr ₂SiO ₄: Dy, Mn phosphor was mainly caused by the electric multipoles interaction. The concentration optimized (Sr _0.96, Mn _0.02, Dy _0.02) ₂SiO ₄ phosphor with high and almost pure white emission has great potential to act as a single-matrix white phosphor for white LEDs.