Enhanced Luminescence Performance of Cr-Doped CaMgSi2O6 Phosphor via Alkali Metal Ion Codoping

Enhancing the luminous intensity of near-infrared (NIR) phosphors is critical for practical applications. This study demonstrates that codoping charge-compensating ions (Li+, Na+, and K+) significantly improves the fluorescence emission intensity and quantum efficiency of Cr3+-doped CaMgSi2O6 (CMSO:Cr) phosphors. Optimal enhancements were achieved with specific ion concentrations: the CMSO:0.01Cr phosphor codoped with 0.8 at. % Na2CO3 exhibited a 1.8-fold increase in emission intensity, while the CMSO:0.04Cr phosphor codoped with 1.5 at. % Li2CO3 demonstrated an 8-fold enhancement. Charge compensation also improved the internal quantum yield (IQY) and photoelectric conversion efficiency without compromising the thermal stability. Mechanistic insights from absorption/emission spectra, electron paramagnetic resonance (EPR), and fluorescence lifetime analyses revealed that alkali metal ions occupy defect sites, suppress nonradiative recombination, and simplify emission profiles by eliminating defect-induced luminescent centers.