Regulating Eu²⁺ Multisite Occupation through Structural Disorder toward Broadband Near-Infrared Emission

Abstract

To promote the development of near-infrared (NIR) light sources in optoelectronic and biomedical applications, the discovery of NIR-emitting phosphor materials and their design principles are essential. Herein, we report a novel Eu 2+ -activated broadband NIR-emitting phosphor, BaSrGa 4 O 8 :Eu 2+ , which features multisite occupation due to Ba/Sr and oxygen site occupancy disorder. With an increase in the Ba/Sr atomic ratio from 1:1 to 1.7:0.3, the Eu 2+ emission band maximum red-shifts from 670 to 775 nm, along with an enlargement of the full width at half-maximum (FWHM) from 140 to 230 nm. The underlying mechanism for the structure−property relationship is elucidated using density functional theory calculations. The application of the NIR phosphor-converted light-emitting diodes (pc-LEDs) is demonstrated, showing their potential in night-vision technology. Our results can initiate further exploitation of the host structural disorder toward Eu 2+ broadband NIR luminescence for applications in pc-LEDs.

8-Phenylquinoline-Based Tetradentate 6/6/6 Platinum(II) Complexes for Near-Infrared Emitters

“…Finally, we adopted Pd(PPh 3 ) 4 -catalyzed Suzuki coupling of the corresponding borate ester with Cz-Br to give ligands L1H2, L2H2, and L3H2 in 60−90% yields; then the ligands directly metalized with K 2 PtCl 4 in acetic acid at 120 °C to obtain Pt(II) complexes PtYL1−PtYL3 in high yields of 60−90% (Figure 3, Scheme 4). The chemical structures of the Pt(II) complexes were confirmed by 1 H, 13 C nuclear magnetic resonance (NMR) spectra, and high-resolution mass spectrometry (HRMS).…”

“…Near-infrared (NIR) emitters with emission peaks beyond 700 nm have great potential applications in photodynamic therapy, − in vivo bioimaging, − optical signal processing, and night-vision technologies. − However, because the main nonradiative deactivation pathway induces the quenching of NIR emission, which is known as the “energy gap law”, the photoluminescence quantum efficiencies (PLQEs, Φ) of most NIR emitters are low, typically less than 1%, such as phosphorescent d 6 , d 8 , and d 10 transition-metal complexes. − Therefore, the design and development of highly efficient NIR emitters remains a great challenge. In the past decades, Pt­(II) complexes had been demonstrated to act as efficient phosphorescent blue-to-red emitters because of the heavy-atom effect-induced strong spin-orbit coupling, which enabled efficient intersystem crossing (IC) from the lowest singlet (S 1 ) to triplet state (T 1 ) and then radiative decay to the ground state (S 0 ). − Recently, great progress had been made for thermally activated delayed fluorescence (TADF) NIR emitters and Pt­(II)-based NIR emitters through rational molecular design (Figure ).…”

Unraveling Luminescent Energy Transfer Pathways: Futuristic Approach of Miniature Shortwave Infrared Light-Emitting Diode Design

“…A shortwave infrared light (SWIR, 900–1700 nm) source in a compact size and operable with battery power is a critical need for delivering exciting answers to a wide range of spectroscopy, night surveillance, anticounterfeiting, solar cells, and bioimaging applications. − The phosphor-converted light-emitting diode (pc-LED) based on energy downshifting converter technology has been pursued as a promising energy device for infrared light and also an alternative to the well-known conventional SWIR light devices. , For example, pc-white LEDs have already revolutionized lighting and backlighting technologies by saving energy and trimming the device size, , and pc-LED devices based on Cr 3+ - and Eu 2+ -activated inorganic phosphors can emit near-infrared light around 600–1100 nm. − Obtaining emissions beyond 1100 nm using Cr 3+ , Bi 3+ , or Eu 2+ is difficult, while La 3 Ga 5 GeO 14 :Cr 3+ is the only reported super broadband (650–1200 nm) near-infrared phosphor, and its practical applications are limited. ,,, Thus, the development of SWIR-emitting luminous inorganic phosphors is a vital and urgent task.…”

“…12−14 Obtaining emissions beyond 1100 nm using Cr 3+ , Bi 3+ , or Eu 2+ is difficult, while La 3 Ga 5 GeO 14 :Cr 3+ is the only reported super broadband (650−1200 nm) 15 near-infrared phosphor, and its practical applications are limited. 12,13,16,17 Thus, the development of SWIR-emitting luminous inorganic phosphors is a vital and urgent task.…”

Color-tunable emissions realized by Tb3+ to Eu3+ energy transfer in ZnGdB5O10 under near-UV excitation

“…1–4 Common strategies to realize color-tunable emissions include the modification of the local coordination environment of activators by lattice substitutions (such as in the cases of (Y, Lu, Sc)VO 4 :Bi 3+ and Ba 1+ y Sr 1− y Ga 4 O 8 :Eu 2+ ), and adjusting the excitation wavelengths, which is applicable in those hosts containing more than one crystallographic site for activators. 5–7 In addition, photoluminescent energy transfer can also be also utilized to manipulate the emission color by changing the relative ratio between the sensitizer and activator cations. Such cases can be found in LiCa 3 MgV 3 O 12 :Bi 3+ ,Eu 3+ and Y 2 Mg 2 Al 2 Si 2 O 12 :Eu 2+ ,Ce 3+ .…”