NUV-pumped red-emitting CaMnK(PO) phosphor: energy transfer and charge compensation

The development of novel Mn-based phosphor hosts has received increasing interest in the search for highly efficient red emitting phosphors for white LED applications. In this study, CaMnK(PO), a compound with the β-Ca(PO)-type structure, was successfully synthesized by a high-temperature solid-state reaction process. The Eu-doped CaMnK(PO) phosphor exhibits a broadband red emission peaking at 650 nm. The optimal excitation wavelength is 395 nm, which matches that of commercial ultraviolet (NUV) chips. Codoping Ce ions into the CaMnK(PO):Eu phosphor efficiently improves Mn luminescence. Here, Ce acts as a charge compensator rather than a sensitizer and substantially increases the effective number of Eu and finally improves the red emission of Mn. The charge compensation mechanism is also verified by codoping some optically inert rare earth ions (Ln) including Y, La and Gd. The results demonstrate that these developed CaMnK(PO):Eu, Ln phosphors have great potential for application in NUV-based white LEDs. The energy transfer approach combined with the charge compensation technique is valuable for improving the performance of the red-emitting CaMnK(PO):Eu phosphor, which can further be used in developing other Mn-based phosphors.