Design of a Broadband NIR Phosphor for Security-Monitoring LEDs: Tunable Photoluminescence Properties and Enhanced Thermal Stability

Abstract

Near-infrared (NIR) phosphors with capability for blue light to 850 nm broadband NIR emission conversion are highly desirable for security-monitoring LEDs. Targeted phosphor LaSc 2.93-y Ga y B 4 O 12 (LSGB): 0.07Cr 3+ (y = 0.6) is designed from the initial model of LaSc 2.93 B 4 O 12 (LSB): 0.07Cr 3+ by chemical composition modification. The correlations among crystal-field environment, structural evolution, and luminescence properties of LSGB: 0.07Cr 3+ (0 ≤ y ≤ 1.5) are elucidated by the Dq/B values, decay curves, and polyhedron distortion. The substitution of Sc 3+ by Ga 3+ in LSGB: Cr 3+ (0 ≤ y ≤ 1.5) leads to decreasing structural polyhedron distortion and strengthened crystal field, consequently resulting in the blue-shift of broadband emission and enhanced thermal stability of LSGB: 0.07Cr 3+ (y = 0.6) compared to that of LSB: 0.07Cr 3+ . The above results demonstrate that the superiority of blue-shift and enhanced thermal stability of LSGB: 0.07Cr 3+ (y = 0.6) make it more suitable for the blue-pumped securitymonitoring LEDs.

Simultaneous Broadening and Enhancement of Cr3+Photoluminescence in LiIn2SbO6by Chemical Unit Cosubstitution: Night‐Vision and Near‐Infrared Spectroscopy Detection Applications

“…[10] Given that the spin-allowed 4 T 2g ! 4 A 2g transition (d-d transition) of Cr 3+ is strongly influenced by the crystal field, [11] its PL tuning can also be expected by changing the local lattice environment through ac hemical unit cosubstitution strategy.…”

Efficient Broadband Near‐Infrared Emission in the GaTaO4:Cr3+ Phosphor

“…[12] Of the options available, Cr 3+ in a weak crystal field environment, with its unique 3d 3 electronic configuration, is considered the best option for broadband NIR emission. [13,14] Cr 3+ can be excited by blue light and emits between 700 and 1100 nm. This concept has led to the discovery of numerous Cr 3+ -substituted NIR phosphors.…”

Efficient near‐infrared pyroxene phosphor LiInGe2O6:Cr3+for NIR spectroscopy application

“…Notably, the emission spectra slightly shift to longer wavelength as the concentration of Cr 3+ increases. This phenomenon can also be found in many other materials, in which resorption, energy transfer and Stokes shift may play a part 18,32,33 . We can exclude the possibility of energy transfer because only one type of luminescent center exists in LiInGe 2 O 6 .…”