For inorganic luminescent materials
with activators, the energy
yield is usually observed to decrease with an increase in activator
concentration, which is known as the concentration quenching effect.
To inhibit this phenomenon, a common strategy is to increase the distance
between activators. Most previous reports have focused on the three-dimensional
crystal lattice, and there have been few reports about two-dimensional
layered structure. Herein, we synthesized a novel Cr3+-activated
near-infrared (NIR) phosphor Li2Sr2Al(PO4)3 (LSAPO) with layered structure, and in such
a two-dimensional structure, we proved experimentally that the concentration
quenching was suppressed. Under 460 nm excitation, LSAPO:Cr3+ gave a broad NIR emission band (700–1200 nm) centered at
823 nm with a full width at half-maximum (fwhm) of 178 nm and a broad
absorption band, indicating its potential application in NIR spectroscopy.
Moreover, by codoping Cr3+ and Yb3+ ions, we
further widened the emission bandwidth to ∼230 nm of fwhm,
the internal quantum efficiency increased from 54% to 61%, and the
thermal stability was improved. The fabricated NIR device with a LSAPO:Cr3+,Yb3+ phosphor coupled with blue chips can be
applied in night-vision technologies and medical fields.