Tetravalent manganese-doped lithium meta-silicate red-emitting phosphors for LED applications: structural and luminescence properties

Abstract

In this paper, different concentrations of tetravalent manganese-activated lithium meta-silicate red-emitting phosphors, namely Li2SiO3:xMn4+ (x = 0.01, 0.02, 0.03, 0.04 and 0.05 mol), have been prepared by the solid-state reaction method at 950 °C. The structural, thermal, morphological, and optical properties of the sintered phosphors were characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), raman, UV-Visible and photoluminescence (PL) spectra. Excitation and emission spectra are used to study optical characteristics, which match well with the commercially visible region. The red emission bands for Li2SiO3:0.02Mn4+ peak at approximately 642 nm (λex = 425 nm) and 717 nm (λex = 475 nm), respectively due to the spin-forbidden 2E → 4A2 transition. The doping concentrations of xMn4+ in the Li2SiO3 host were investigated, and the correlations between Mn4+ doping concentration and luminescence intensity were examined. The Commission Internationale de l'Eclairage (CIE) chromatic coordinate graph confirmed the emission color observation in the red region, showed an excellent color purity (CP). In addition, the quantum efficiency (QE) of Li2SiO3:Mn4+ phosphors reached up to 70.51%. The investigation shows that synthesized Li2SiO3:Mn4+ phosphors are beneficial for red Light-Emitting Diodes (LEDs) used in solid-state lighting.