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 KRbCa0.78Mg0.2PO4F: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 KRbCa0.78Mg0.2PO4F:0.02Eu2+ has great potential to be applicated in the NUV excited white LEDs.

Acid Post-Treatment Triggered High-Efficiency Blue-Emitting LiNa2Sr8B12O24F6Cl:Eu2+ Phosphors toward Multipurpose LED Applications

“…Significantly, the emission peaks exhibit a modest blue shift of 5 nm as the temperature increases, as illustrated in Figure c. Typically, this shift toward the blue region of the spectrum can be explained by the thermally activated phonon-assisted tunneling mechanism . Under the influence of phonons activated by thermal energy, electrons that overcome the specified energy barrier (Δ E ) transition from an initial low-energy state (E1) to a more elevated energy state (E2).…”

BaLiZn3(PO4)3:Eu2+: Ultranarrow-Band Violet Emission in a Highly Symmetric Crystal Structure

“…Although the fwhm increases with an increasing temperature, it is still an ultranarrow-band violet emission. Generally speaking, the broaden emission is closely related to the electron–phonon coupling interaction, and it could be evaluated by the following equation , FWHM = 2.36 S normalℏ ω coth ℏ ω 2 k T where S is the Huang–Rhys electron–phonon coupling factor, ℏω refers to the phonon energy, and k and T are the Boltzmann constant (8.617 × 10 –5 eV K –1 ) and Kelvin’s temperature, respectively.…”

“…Although the fwhm increases with an increasing temperature, it is still an ultranarrow-band violet emission. Generally speaking, the broaden emission is closely related to the electron−phonon coupling interaction, and it could be evaluated by the following equation 50,51…”

Crystal structure, Bi3+ yellow luminescence, and high quantum efficiency of Ba3SbAl3Ge2O14:Bi3+ phosphor for white light-emitting diodes

“…Similar to Ce 3+ or Eu 2+ ions, Bi 3+ ions are highly influenced by the crystal field environment in the host lattice, enabling them to emit light ranging from UV to red in various host compounds. 14–16 More importantly, Bi 3+ doped phosphors exhibit strong absorption in the NUV range and weak or no absorption in the visible range, effectively minimizing reabsorption among phosphors. Unfortunately, few Bi 3+ doped phosphors have high quantum efficiency.…”