Crystal structure, tunable emission and applications of Ca1-xAl1-xSi1+xN3-xOx :RE (x=0-0.22, RE = Ce3+, Eu2+) solid solution phosphors for white light-emitting diodes

CaAlSiN3:Eu2+ is a very promising red phosphor for high color rendering white light-emitting diodes (wLEDs), but a large part of its emission covers wavelengths longer than 700 nm, which is not detectable by the human eye and thus wasted. Optimizing its luminescence properties will allow us to further enhance the overall optical properties of wLEDs. In this contribution, the luminescence spectra of Ce3+ or Eu2+-activated CaAlSiN3 were tuned and tailored by introducing isostructural Si2N2O to form solid solutions of Ca1-xAl1-xSi1+xN3-xOx (x = 0-0.22). The structural evolutions, microstructure, luminescence, thermal quenching and quantum efficiency of Ca1-xAl1-xSi1+xN3-xOx:RE (RE = Ce3+, Eu2+) were investigated and clarified by using various analytic techniques. Upon introducing Si2N2O into CaAISiN(3), the Ce3+-doped Ca1-xAl1-xSi1+xN3-xOx shifted its peak emission from 606 to 575 nm and retained the band width of 145 nm, whereas the Eu2+-doped one blue-shifted its emission from 650 to 638 nm and broadened its band width from 90 to 122 nm, owing to the structural distortion and disorder as well as the band gap broadening associated with the solid solution formation. By combining these phosphors with a blue LED, high color rendering (Ra) and luminous efficacy (eta) white LEDs were realized (Ra = 82.5 and eta = 104 lm W-1 for the Ce3+-doped phosphors, and Ra = 97 and eta = 101 lm W-1 for the Eu2+-doped phosphors).