Crystal structure, optical spectroscopy and energy transfer properties in NaZnPO:Ce, Tb phosphors for UV-based LEDs.

A new series of Ce, Tb singly doped and Ce/Tb co-doped NaZnPO (NZPO) phosphors have been synthesized a high-temperature solid-state reaction method at 800 °C. The crystal cell structure, luminescence proprieties, energy transfer, and chromaticity coordinates of the as-prepared phosphors were investigated in detail. The photoluminescence spectra of NZPO:Ce phosphors exhibited broad emission in the 300-380 nm range, while under UV excitation, the singly doped NZPO:Tb phosphor showed emission peaks at ∼485-690 nm among which the green emission peak appears at ∼543 nm. The Tb green emission was significantly enhanced almost 20 times energy transfer from Ce to Tb. The energy transfer (ET) mechanism from Ce to Tb in NZPO is identified to be a resonant type the dipole-dipole interaction mechanism with an ET efficiency of 91%. Intense green emission is obtained at very low Tb concentrations under 285 nm excitation, making NZPO:Ce/Tb an efficient UV-excited green phosphor. The NaZnPO:Ce/Tb phosphors are promising UV convertible materials of green light for UV -LEDs applications.