Efficient and Tunable Luminescence in Ga_2–xIn_xO₃:Cr³⁺ for Near-Infrared Imaging

Abstract

Broadband near-infrared (NIR) emitting materials are in great demand as next-generation smart NIR light sources. In this work, a Cr3+-substituted phosphor capable of efficiently converting visible to NIR light is developed through the solid solution, Ga2–x In x O3:Cr3+ (0 ≤ x ≤ 0.5). The compounds were prepared using high-temperature solid-state synthesis, and the crystal and electronic structure, morphology, site preference, and photoluminescence properties are studied. The photoluminescence results demonstrate a high quantum yield (88%) and impressive absorption efficiency (50%) when x = 0.4. The NIR emission is tunable across a wide range (713–820 nm) depending on the value of x. Moreover, fabricating a prototype of a phosphor-converted NIR light-emitting diode (LED) device using 450 nm LED and the [(Ga1.57Cr0.03)­In0.4]­O3 phosphor showed an output power that reached 40.4 mW with a photoelectric conversion efficiency of 25% driven by a current of 60 mA, while the resulting device was able to identify damaged produce that was undetectable using visible light. These results demonstrate the outstanding potential of this phosphor for NIR LED imaging applications.

Glass‐Crystallized Luminescence Translucent Ceramics toward High‐Performance Broadband NIR LEDs

“…[ 12 ] Nevertheless, the fundamental problem for Cr 3+ activated phosphors is the small absorption cross‐section (10 −19 –10 −20 cm 2 ) of Cr 3+ as a result of the parity‐forbidden nature of intraconfigurational d–d transitions ( 4 A 2 → 4 T 1 / 4 T 2 ). [ 13 ] Increasing the doping concentration, [ 11,14 ] and introducing the odd‐parity crystal field by lattice distortion, [ 15 ] can expectedly improve the light absorption efficiency (AE), but inevitably impose serious adverse effects on IQE and thermal stability because of the enhanced (thermally activated) concentration quenching and/or the reduced structural rigidity. [ 16 ] Another knotty problem for traditional NIR pc‐LEDs with phosphor powders embedded in organic resin is the massive heat accumulation resulting from large quantum defect (>40%) in down‐converting blue light into NIR one and the very low thermal conductivity (≈0.2 W m −1 K −1 ) of organic binders, which fundamentally limit the performance of the pc‐LED devices.…”

Crystal-field induced tuning of luminescence properties of Na3GaxAl1−xF6:Cr3+ phosphors with good thermal stability for NIR LEDs

“…16 The tuning of NIR emission peaks of Ga 2− x In x O 3 :Cr 3+ can be achieved in a broad region (713–820 nm) due to a weakening crystal field strength with increasing x values. 17 The above results prove that it is a promising way to tune the NIR emission of Cr 3+ through crystal field engineering to meet the requirements of various applications and detectors.…”

“…2C) because of the enhanced EPC effect. 17 The emission peak position can be tuned from 13 440.9 cm −1 in Na 3 AlF 6 :0.05Cr 3+ to 13 192.6 cm −1 in Na 3 GaF 6 :0.05Cr 3+ (Fig. 2D and Fig.…”

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

“…xenon lamps) have not met the current work requirements due to their large size and high operating temperatures. [8][9][10] NIR phosphor-converted light-emitting diodes (pc-LEDs) activated by commercial blue chips are one of the ideal light sources because of their low cost, small size, high energy efficiency, and environmental friendliness. [11][12][13][14][15][16] A large number of NIR phosphors doped with rare-earth ions (Eu 2+ , Pr 3+ , Nd 3+ , etc.)…”

“…[ 1–7 ] With the rise of these new applications, NIR light sources with excellent luminescence properties are heavily relied upon, and traditional NIR light sources (halogen and xenon lamps) have not met the current work requirements due to their large size and high operating temperatures. [ 8–10 ] NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) activated by commercial blue chips are one of the ideal light sources because of their low cost, small size, high energy efficiency, and environmental friendliness. [ 11–16 ] A large number of NIR phosphors doped with rare‐earth ions (Eu 2+ , Pr 3+ , Nd 3+ , etc.)…”