An Ultra‐Broadband Yellow‐Emitting Phosphor KRbCa_0.8Mg_0.2PO₄F:Eu²⁺ for White Light‐Emitting Diodes with High Color Rendering Index

Abstract Phosphor‐converted white light‐emitting diodes (pc–WLEDs) realized by combining near‐ultraviolet (NUV) chips and multi‐color phosphors are found to be an effective solution to make up the shortcomings of the poor color rendering index and high correlated color temperature of the combination of blue InGaN chips with YAG:Ce³⁺ yellow phosphor. However, the NUV excited phosphors suffer from deficiencies such as reabsorption and dissonance deterioration rates. To surmount the drawback above, the ion substitution engineering was carried out to the (Rb,K)₂CaPO₄F:Eu²⁺ phosphors, and an NUV excited ultra‐broadband yellow‐emitting phosphor was obtained in this work. With the substitution of Mg²⁺ for Ca²⁺, the emission intensities of (Rb,K)₂CaPO₄F:Eu²⁺ phosphors are significantly improved as well as the thermal stability. Under the excitation of 380 nm, the yellow phosphor KRbCa_0.78Mg_0.2PO₄F:0.02Eu²⁺ exhibits an ultra‐broad emission band covering the range from 450 to 800 nm with an amazing FWHM of 181 nm. White light with a super‐high color rendering index (Ra = 92.3), appropriate correlated color temperature (5644 K), as well as stable CIE chromaticity coordinates are achieved by the white light‐emitting diodes device fabricated with this yellow phosphor. These excellent performances indicate that KRbCa_0.78Mg_0.2PO₄F:0.02Eu²⁺ has great potential to be applicated in the NUV excited white LEDs.