Highly chromatic red light emitting Pr³⁺ doped CaZn₂(PO₄)₂ phosphors for bluechip excited WLEDs

The focus and attention on inorganic crystalline phosphor materials with enhanced chemical and physical properties have been of great interest due to their profuse scientific and technological applications in optoelectronic and display devices. A concentration dependent spectroscopic analysis of highly chromatic red emitting Ca_(1-x)Zn₂(PO₄)₂: xPr³⁺ (x= 0.02-0.08) phosphors synthesized by solid state reaction method have been performed. The obtained phosphors had a triclinic structure with P1 (2) space group. The optical properties including reflectance, excitation, emission and the color coordinates were investigated. The band gap of the phosphors was calculated from diffused reflectance spectra data using the Kubelka- Munk function. The photoluminescence (PL) excitation spectra showed the excitation peaks ranging from 430 to 490 nm. Under 444 nm blue photon excitation, the phosphors emit red light due to ¹D₂→³H₄ and ¹D₂→³H₅ transitions of Pr³⁺. The optimal concentration of Pr³⁺ was identified to be x = 0.04 after which concentration quenching occurs. The colorimetric results suggest the phosphor to be of high color purity 100% and could be an eventual choice as the red component in tricolor system used ∼ for solid state lighting. (author)