Giant Red‐Shifted Emission in (Sr,Ba)Y₂O₄:Eu²⁺ Phosphor Toward Broadband Near‐Infrared Luminescence

Abstract

Near-infrared (NIR) light-emitting diodes (LEDs) light sources are desirable in photonic, optoelectronic, and biological applications. However, developing broadband red and NIR-emitting phosphors with good thermal stability is always a challenge. Herein, the synthesis of Eu 2+ -activated SrY 2 O 4 red phosphor with high photoluminescence quantum efficiency and broad emission band ranging from 540 to 770 nm and peaking at 620 nm under 450 nm excitation is designed. Sr/Ba substitution in SrY 2 O 4 :Eu 2+ has been further utilized to achieve tunable emission by modifying the local environment, which facilitates the giant redshifted emission from 620 to 773 nm while maintaining the outstanding thermal stability of SrY 2 O 4 :Eu 2+ . The NIR emission is attributed to the enhanced Stokes shift and crystal field strength originated from the local structural distortions of [Y1/Eu1O 6 ] and [Y2/Eu2O 6 ]. The investigation in charge distribution around Y/Eu provides additional insight into increasing covalency to tune the emission toward the NIR region. As-fabricated NIR phosphor-converted LEDs demonstration shows its potential in night-vision technologies. This study reveals the NIR luminescence mechanism of Eu 2+ in oxide-based hosts and provides a design principle for exploiting Eu 2+ -doped NIR phosphors with good thermal stability.

Competitive Site Occupation toward Improved Quantum Efficiency of SrLaScO4:Eu Red Phosphors for Warm White LEDs

“…As shown in Figure 1b, the cell volume V refined from the PXRD decreases with increasing x(Eu), which demonstrates the fact of Eu 2+ ↔ Sr 2+ ion replacements since the ionic radius of Eu 2+ is slightly smaller than that of Sr 2+ (IR (Eu 2+ , CN = 8) = 1.25 Å; IR (Sr 2+ , CN = 8) = 1.26 Å). [13] It is worth noting that there could be another reason for the decreased cell volume V after Eu doping, which is Eu 3+ ↔ La 3+ ion replacements (IR (Eu 3+ , CN = 8) = 1.066 Å; IR (La 3+ , CN = 8) = 1.16 Å). Moreover, the possibility that a few Eu 2+ occupy the La 3+ sites still needs to be investigated further.…”

Tunable concentration/excitation-dependent deep-red and white light emission in single-phase Eu2+-activated Sc-based oxide phosphors for blue/UV-LEDs

“…Eu 2+ in the Sc site produces near-infrared light emission due to large crystal field splitting (on account of the small CNs and short bond length), which is similar to the reported Eu 2+ occupying the trivalent rare earth ion sites to produce deep-red or near-infrared emission, such as K 3 ScSi 2 O 7 :Eu 2+ , K 3 LuSi 2 O 7 :Eu 2+ , SrY 2 O 4 :Eu 2+ and Sr 2 Sc 0.5 Ga 1.5 O 5 :Eu 2+ . 32,51–53 In addition, Eu 2+ ions undergo selective site occupation in the matrix with increasing doping concentration. Since small amounts of M–O bond breaking and Eu–O bond bonding are required to enter the 6-coordinated cation site, which means less energy is required, Eu 2+ ions preferentially occupy the 6-coordinated Sr and Sc sites.…”

“…1,28 The emission color can be tuned from ultraviolet to red or even near-infrared (NIR) by site-occupancy engineering, such as Ca 2 BN 2 Cl:Eu 2+ (cyan-emitting), 8 RbLi(Li 3 SiO 4 ) 2 : Eu 2+ (green-emitting), 29 Sr 8 ZnSc(PO 4 ) 7 :Eu 2+ (yellow-emitting), 30 Ca 2 SiO 4 :Eu 2+ (far-red-emitting), 31 and (Sr,Ba)Y 2 O 4 :Eu 2+ (nearinfrared-emitting). 32 It is noteworthy that Eu 2+ -activated oxide luminescent materials have been back in the spotlight in recent years due to the fact that it is easier to prepare them than nitrides and their long-wavelength luminescence in deep-red and NIR light regions. In short, the matrix compound offering abundant cationic sites to accommodate Eu 2+ can easily realize photoluminescence-tunable and a strong crystal field environment with a short bond length and a small coordination number can contribute to the FR/NIR light emission of Eu 2+ .…”

Optical fiber temperature sensor of Er3+/Yb3+ codoped LaGaO3 microcrystals with high reliability and stability

“…Temperature is a greatly basic physical parameter, as it plays a critical role in numerous areas such as solid lighting, industry, manufacturing, climatology, and scientific research. [1][2][3][4][5][6] For example, controlling the temperature can not only reduce energy consumption and increase productivity in industry, but also has a great impact on the life activities of cells in biomedicine. Nowadays, optical temperature sensing built with an emission intensity of two thermal coupling levels (TCLs) has attracted considerable attention from numerous researchers owing to its fast response and high sensitivity.…”