Novel high-efficiency and superior thermal stability red-emitting phosphors for WLEDs

The development of near-ultraviolet (n-UV) light-excited phosphors is crucial for light-emitting diode (LED) lighting. In this work, we used LMSA as the matrix material and utilized the energy transfer between Eu²⁺ and Mn²⁺ to design a broadband red phosphor that can be efficiently excited by near-ultraviolet light. In this matrix, the Mg²⁺ and Sr²⁺ sites were occupied by Mn²⁺ and Eu²⁺, respectively, generating a broadband red light with a peak at 664 nm and a blue-violet light with a peak at 395 nm. Based on the energy transfer between Eu²⁺ and Mn²⁺, the novel Li₅MgSrAlB₁₂O₂₄:Eu²⁺,Mn²⁺ (LMSAB:Eu²⁺,Mn²⁺) was successfully obtained. The material can be excited by n-UV light yielding a bright, broadband red emission. Furthermore, LMSAB:Eu²⁺,Mn²⁺ exhibits high quantum efficiency (IQE = 91%, EQE = 71.4%) and excellent thermal stability (<i>I</i>_{423 K}/<i>I</i>_{298 K} = 86.7%). Finally, WLEDs (white light-emitting diodes) containing a 365 nm LED, LMSAB:Eu²⁺,Mn²⁺, blue and green phosphors yield warm white light with a color rendering index (<i>R</i>_a) of 92.7 and a high luminous efficiency of 57.59 lm W^-1. These results showed the potential of LMSAB:Eu²⁺,Mn²⁺ for applications in WLEDs.