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. Issue 47 (17th November 2016) - Li, Shuxing
Abstract : The designed Ca1− x Al1− x Si1+ x N3− x O x :Eu 2+ /Ce 3+ red or yellow phosphors by structure and bandgap engineering afford wLEDs with high color rendition and luminous efficacy. Abstract : CaAlSiN3 :Eu 2+ 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 Ce 3+ or Eu 2+ -activated CaAlSiN3 were tuned and tailored by introducing isostructural Si2 N2 O to form solid solutions of Ca1− x Al1− x Si1+ x N3− x O x ( x = 0–0.22). The structural evolutions, microstructure, luminescence, thermal quenching and quantum efficiency of Ca1− x Al1− x Si1+ x N3− x O x :RE (RE = Ce 3+, Eu 2+ ) were investigated and clarified by using various analytic techniques. Upon introducing Si2 N2 O into CaAlSiN3, the Ce 3+ -doped CaAl1− x Si1+ x N3− x O x shifted its peak emission from 606 to 575 nm and retained the band width of 145 nm, whereas the Eu 2+ -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 ( η ) white LEDs were realized (Ra = 82.5 and η = 104 lm W −1 for the Ce 3+ -doped phosphors, and Ra = 97 and η = 101 lm W −1 for the Eu 2+ -doped phosphors).