Luminescence improvement via site environment adjustment and site occupancy regulation of Eu2+ in Ca8MgSi4O16Cl2

Phosphors emitting cyan-green light with a small Stokes shift under blue light excitation is crucial for addressing spectral deficiencies in phosphor-converted white light-emitting diodes (pc-wLEDs). In this work, a series of Mg²⁺ ion doped and Mg²⁺-Th³⁺ (ThGa,In) ion pair co-doped Ca₈MgSi₄O₁₆Cl₂: Eu²⁺ phosphors were synthesized using a high-temperature solid-phase reaction method. It is found that the doped Mg²⁺ ions can improve the local environment of Eu²⁺ ions thus enhance its luminescence, while the doped Th³⁺ (ThGa,In) can regulate the distribution of Eu²⁺ ions occupying hexa-coordinated and octa-coordinated Ca²⁺ sites. It is proven that co-doping Mg²⁺-Ga³⁺ ion pair facilitates more Eu²⁺ ions enter the octa-coordinated Ca²⁺ sites, which largely enhances the cyan-green emission intensity. A pc-wLEDs device with a color rendering index (CRI) of 97.2 and a correlated color temperature (CCT) of 3480K has been fabricated combining the present Ca₇Ga_0.9Mg_1.9Si_3.1O₁₆Cl₂:0.1Eu²⁺ phosphor, commercial yellow and red phosphors with blue LED chip. It is found that Ca₇Ga_0.9Mg_1.9Si_3.1O₁₆Cl₂:0.1Eu²⁺ phosphor can partially fill the cyan gap of the pc-wLEDs spectra, enhancing the emission quality of the pc-wLEDs device.