Preparation of novel color tunable Na2Ca(PO4)F:Eu2+,Mn2+ phosphors for sunlike LED applications
A series of color-tunable Na 2 Ca(PO 4 )F:Eu 2+ , Mn 2+ phosphors were prepared by solid state reaction. The structure, as well as the photoluminescent properties of the as-prepared phosphor were investigated. The energy transfer process between Eu 2+ -Mn 2+ was also discussed. The phosphor demonstrates luminescence in the range of 420 nm–750 nm under UV excitation. Specifically, the emission spectra comprise green light (420–550 nm) attributed to the 4f-5d transition of Eu 2+ ions, and orange red light (550–750 nm) resulting from the 6 A 1 → 4 A 1 ( 4 G), 4 E( 4 G) transitions of Mn 2+ ions. An effective dipole-dipole energy transfer has been confirmed to occur between the co-doped Eu 2+ and Mn 2+ ions. The luminescent color of the as-prepared phosphors can change from blue to yellow, and finally to orange red by adjusting the doping amount of the co-doped ions. The optimal sample's EQE reached 20.59% due to the high absorption efficiency. Finally, a 400 nm violet light chip excited white LED with a high color rendering index (CRI) of Ra = 98 was fabricated by using the as-prepared Na 2 Ca(PO 4 )F:0.02Eu 2+ ,0.04Mn 2+ phosphor in combination with the commercial blue Sr 5 (PO 4 ) 3 Cl:Eu 2+ phosphor and red CaAlSiN 3 :Eu 2+ phosphor. The results indicated that the developed phosphor holds notable potential for application in in the field of sunlike healthy lighting.
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