Enhancement of Near‐Infrared Phosphor Luminescence Properties via Construction of Stable and Compact Energy Transfer Paths

Abstract

The rapid development of near‐infrared (NIR) spectroscopy urgently requires the exploration of NIR‐emitting phosphors with excellent luminescence properties. Herein, GaTaO4:Cr3+,Yb3+ NIR phosphor with excellent luminescence properties is reported, which exhibits ultra‐broadband NIR emission with a full width at half maximum of 300 nm, good thermal stability of 90%@423 K, and most remarkably, high internal quantum efficiency of 95.5% and external quantum efficiency of 44.79%. Such outstanding luminescence properties mainly give the credit to the unique sandwiched structure of GaTaO4:Cr3+,Yb3+, in which layers of Yb3+ ions (activator) are sandwiched between layers of Cr3+ ions (sensitizer), and hence many stable and compact Cr–Yb pairs are formed, so that the energy can be rapidly transferred from Cr3+ to Yb3+, effectively activating the characteristic f–f transition of Yb3+ that is very stable and almost independent of the temperature, and at the same time, the non‐radiative transition of Cr3+ ions can be suppressed to a certain degree. The NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) are fabricated by combining GaTaO4:Cr3+,Yb3+ with blue LED chips, and the application potential is fully demonstrated by non‐destructive food detection, night vision, and vein display. The results provide novel prospects for the design of NIR‐emitting materials with desirable luminescent properties.

Improved Near-Infrared Luminescence Properties of LiScSi2O6:Cr3+,Yb3+ Phosphors via Efficient Energy Transfer

“…Yb 3+ has relatively weak NIR emission due to weak absorption in blue light. However, the Yb 3+ NIR emission can be greatly strengthened by the energy transfer (ET) from Cr 3+ to Yb 3+ due to the large absorption cross section of Cr 3+ in the blue light region. , Many studies have demonstrated that co-doping Yb 3+ into Cr 3+ not only effectively expands the NIR spectral band but also improves the thermal stability due to the ET from Cr 3+ to Yb 3+ . − …”

Manipulation of the ratio of Li+/Zn2+ on the structure and persistent luminescence property of Li2Zn0.9992Ge3O8:0.08%Cr3+

“…The global demand for energy consumption seems to be increasing due to the rapid growth of population and industrialization, forcing the desire to develop energy‐efficient and environment‐friendly materials 1–4 . Moreover, long persistent luminescence (LPL) materials, as a special energy storage material, can store energy well and achieve delayed luminescence times ranging from a few seconds to several days 5–9 .…”

“…The global demand for energy consumption seems to be increasing due to the rapid growth of population and industrialization, forcing the desire to develop energyefficient and environment-friendly materials. [1][2][3][4] Moreover, long persistent luminescence (LPL) materials, as a special energy storage material, can store energy well and achieve delayed luminescence times ranging from a few seconds to several days. [5][6][7][8][9] In particular, LPL materials have been shown to be superior to other labels for in vivo imaging applications because their emission times are long enough to allow delayed gated imaging.…”

Does Cr3+Occupy Tetrahedral Sites and Luminesce in Oxides? A First-Principles Exploration

“…Broadband near-infrared (NIR) light has drawn much attention in the application field of organic analysis. , Numerous studies have been reported on broadband NIR emission with high thermal stability and high quantum efficiency produced by transition-metal activators. − In particular, Cr 3+ ion is the most preferred activator among these transition metals due to the good performance in these related aspects. − For example, La 3 Ga 5 GeO 14 :Cr 3+ has a broadband NIR emission with a full width at half-maximum (FWHM) of 330 nm, and Gd 3 Sc 2 Ga 3 O 12 :Cr 3+ has a near-unity internal quantum efficiency . The codoping of Cr 3+ and some rare earth ions (Yb 3+ , Eu 2+ , and Ce 3+ ) could further improve the properties of the NIR phosphors . The NIR broadband emissions of Cr 3+ doped phosphors usually come from the 3d–3d transition ( 4 T 2 → 4 A 2 ) in the octahedral ligand field .…”

“…11 The codoping of Cr 3+ and some rare earth ions (Yb 3+ , Eu 2+ , and Ce 3+ ) could further improve the properties of the NIR phosphors. 12 The NIR broadband emissions of Cr 3+ doped phosphors usually come from the 3d−3d transition ( 4 T 2 → 4 A 2 ) in the octahedral ligand field. 13 The energy of the excited state 4 T 2 is dominated by the ligand field splitting of 3d orbitals of Cr 3+ with a local structure of CrL n (L being the ligand element and n its number), and the deviation from the regular octahedral ligand field splits the 4 T 2 levels and reduces the emission energy.…”