Interstitial Li⁺ Occupancy Enabling Radiative/Nonradiative Transition Control toward Highly Efficient Cr³⁺-Based Near-Infrared Luminescence

Abstract

Highly efficient and stable broadband near-infrared (NIR) emission phosphors are crucial for the construction of next-generation smart lighting sources; however, the discovery of target phosphors remains a great challenge. Benefiting from the interstitial Li+ occupancy-induced relatively large distorted octahedral environment for Cr3+ and suppressed nonradiative relaxation of the emission centers, an NIR emission fluoride phosphor Na3GaF6:Cr3+,Li+ peaking at 758 nm with a high internal quantum efficiency of 95.8% and an external quantum efficiency of 38.3% is demonstrated. Moreover, it exhibits a good thermal stability (84.9%@150 °C of the integrated emission intensity at 25 °C) and excellent moisture resistance as well. A high-power light-emitting diode (LED) with a record watt-level NIR output (974.12 mW) and a photoelectric conversion efficiency of 20.9% is demonstrated by combining Na3GaF6:Cr3+,Li+ and a blue InGaN chip, and a special information encryption/decryption technology suitable for rapid and long-distance identification of machines is further presented based on this device. This study not only advances the development of efficient NIR emission phosphors for broadband NIR LEDs but also for NIR-related emerging applications and devices.

Blue-light-excitable pure and efficient short-wave infrared luminescenceviaCr3+→ Yb3+energy transfer in a KYbP2O7:Cr3+phosphor

“…The distorted lattice causes an uneven symmetric field, which promotes the deviation from inversion symmetry in the octahedral site occupied by Cr 3+ , helping in breaking the parity-forbidden transition of Cr 3+ . [42][43][44][45][46] XRD patterns of KYbP 2 O 7 :xCr 3+ (x = 0-0.10) are depicted in Fig. 1b, and are mainly consistent with the standard XRD data of the potassium ytterbium diphosphate phase (COD No.…”

“…The distorted lattice causes an uneven symmetric field, which promotes the deviation from inversion symmetry in the octahedral site occupied by Cr 3+ , helping in breaking the parity-forbidden transition of Cr 3+ . 42–46…”

Recent Advances in Chromium‐Doped Near‐Infrared Luminescent Materials: Fundamentals, Optimization Strategies, and Applications

“…Recently, Zhang's group codoped Li + ions into NIR emitting Na 3 GaF 6 :Cr 3+ phosphor. [ 114 ] Benefiting from the large distorted octahedral environment for Cr 3+ induced by the interstitial Li + occupancy, an NIR emission peaking at 758 nm with a high IQE of ≈96% and a good thermal stability (≈85%@150 °C) is achieved. The PL property of Na 3 GaF 6 :Cr 3+ ,Li + is improved compared to that of the Li + ‐free sample.…”

“…The above cases indicate that the Cr 3+ ‐activated NIR‐emitting phosphors are potential luminescent materials for information encryption and anti‐counterfeiting. Recently, many bulk and nano Cr 3+ ‐activated NIR luminescent materials such as Na 3 GaF 6 :Cr 3+ ,Li + , [ 114 ] La(Zn/Mg)(Ga,Al) 11 O 19 :Cr 3+ , [ 161 ] and ZnAl 1.4 Ge 0.3 O 3.7 :Cr 3+[ 162 ] have shown potential for information encryption and anti‐counterfeiting.…”

Thermally stable and tunable broadband near-infrared emission from NIR-I to NIR-II in Bi-doped germanate glass for smart light sources

“…Recently, inspired by converter technology in phosphorconverted (pc) white LEDs, [14][15][16] broadband NIR pc-LEDs formed by encapsulating NIR phosphors on the surface of the commercial blue LED chip with epoxy resin or silicone have been emerging as low-cost and high-performance miniature solid-state NIR light sources, 6,8,17 yet some issues still need to be resolved. Cr 3+ ions within phosphors have been proven to be favorable NIR active centers and have shown their superiority to other activator ions in emission bandwidth (4150 nm), high internal quantum efficiency (IQE 4 90%), and effective blue light excitation.…”