A study of optical properties and site preference of Bi3+/Eu3+ co-doped CaLa4Si3O13 red-emitting phosphors for w-LED applications

Abstract

Eu3+ ions are commonly employed as emitting centres for red phosphors, which suffer from the small absorption cross-sections. In this work, Bi3+ ions are used to sensitize Eu3+ ions in CaLa4Si3O13 host as an attempt to enhance the Eu3+ emission. The site preference of Bi3+ ions is investigated in detail. The emission peak at 400 and 430 nm can be ascribed to the Bi3+ in La2 and La1 sites, respectively. The reduction of emission intensity and the shortened lifetime of Bi3+ ions suggest that efficient energy transfer from Bi3+ to Eu3+ ions. Moreover, the Bi3+ ions in the La1 sites are confirmed to be more efficient sensitizers for Eu3+ ions owing to the more significant spectral overlap than the Bi3+ ions in the La2 sites. The thermal stability of the synthesized phosphors is superior or comparable with other reported Bi3+/Eu3+ co-doped phosphors, which is not affected by the site preference of Bi3+ ions. The results suggest that Bi3+ ions are efficient sensitizers for Eu3+ ions and the prepared phosphors can be potentially employed as red-emitting component for w-LED applications.