Ultra-narrow-band luminescence with spectral width down to 32 nm in bismuth-activated phosphate phosphors with superior thermal stability

Abstract

Bismuth-activated phosphors have become popular as a replacement for phosphors based on intensively studied lanthanide ions because of their low spectral reabsorption and sustainable utilization. However, it is of a great challenge to yield narrow-band emission from Bi3+ since its ns2-nsp electron transition lacks the shielding of outer electron orbitals. Herein, we report a new ultra-narrow band Bi3+-activated blue-violet phosphor Ca6BaP4O17 (Ca6BaP4O17:Bi3+). Impressively, its emission band width is down to ∼32 nm, which is less than that of all the reported Bi3+-activated ones. Experimental and theoretical calculation results corroborate that such unusual narrow-band emission originates from Bi3+ ions occupying two cation sites, Ca1 and Ca2, in the Ca6BaP4O17 compound. At 423 K, Ca6BaP4O17:0.5%Bi3+ shows a robust thermal quenching resistance with an integrated emission intensity loss of merely 1%. This is attributable to rare structural advantages of the host such as a high Debye temperature (Θ = 632 K) and large bandgap (∼6.1 eV), which could minimize thermally non-radiative relaxation pathways. We fabricate a blue-violet LED prototype by using the resulting phosphors and ultraviolet LED chip, and demonstrate its potential application in porrets growth. These findings provide in-depth insights the on site occupancy of Bi3+ ions and may simulate more research studies on Bi3+-activated phosphors.