Accessing High-Power Near-Infrared Spectroscopy Using Cr³⁺-Substituted Metal Phosphate Phosphors

Abstract

Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) technology has attracted considerable interest as a next-generation light source for emerging NIR spectroscopic applications. However, discovering efficient broadband NIR phosphors necessary to access the desired long-wavelength (λem ≥ 800 nm) energy window remains a challenge. Here, a new phosphate phosphor, KGaP2O7:Cr3+, emerged from a fundamental study of the AMP2O7 (A = Li, Na, K; M = Al, Ga, Sc, In) family. This material combines all of the requisite properties for the efficient generation of NIR photons, including limited defect formation, minimal electron–phonon coupling, a subtle octahedral site distortion, and well-separated transition metal substitution sites. Photoluminescence spectroscopy indicates that this material emits from 700 to 1100 nm (λmax = 815 nm) with a full width at half-maximum (fwhm) of 127 nm or 1874 cm–1. Exciting the material with a blue LED reveals a quantum yield of 74.4% with an absorption efficiency of 44.8%, resulting in an excellent external quantum efficiency as high as 33.3% from the as-prepared sample. A prototype NIR pc-LED device generated an output power of 473.8 mW and a high photoelectric conversion efficiency (10.7% under 500 mA), demonstrating the potential of applying this phosphor in blue LED-based NIR spectroscopy.

Highly Efficient Broadband Near-Infrared Luminescence with Zero-Thermal-Quenching in Garnet Y3In2Ga3O12:Cr3+ Phosphors

“…The IQE value is much higher than that of most broadband NIR materials, such as ScF 3 :Cr 3+ (IQE = 45%, λ em = 853 nm), La 2 MgZrO 6 :Cr 3+ (IQE = 58%, λ em = 825 nm), Ca 2 LuZr 2 Al 3 O 12 :Cr 3+ (IQE = 69.1%, λ em = 750 nm), KGaP 2 O 7 :Cr 3+ (IQE = 74.4%, λ em = 815 nm), and LaMgGa 11 O 19 :Cr 3+ (83.8%, λ em = 715 nm); and the AE value is the highest in Cr 3+ -activated garnet materials (Table ). ,,− The ultrahigh IQE and AE of this material generate a high EQE of 42.7%, which is the highest among Cr 3+ activated garnet materials …”

“…The FWHM of emission spectra broadens from 125 to 140 nm, ascribing to the increasing number of vibrational energy levels with increasing temper- ature. 60 It is notable that when the temperature heated up to 423 K, the integrated emission intensity maintains 100% of the initial intensity at 298 K (Figure 5b), demonstrating a rare zero-thermal quenching property of this material. Generally, zero-thermal quenching of phosphor is closely related to the release of electrons from defect-induced trap states at increased temperature.…”

Green HF-Free Synthetic Route to the High-Efficiency K2NaGaF6:Cr3+ Phosphor and Its NIR-LED Application toward Veins Imaging

“…12 In addition, their preferable excitation by blue light could perfectly fit the commercial blue LED chips. 13 Enormous case studies were performed in search of suitable host matrices for Cr 3+ . 14 Plenty of Cr 3+ -activated NIR emitters were researched, such as oxide-based Gd 3 Sc 2 Ga 3 O 12 :Cr 3+ , Lu 2 CaMg 2 Si 3 O 12 :Cr 3+ , ScBO 3 :Cr 3+ , LiScP 2 O 7 :Cr 3+ , and fluoride-based K 3 AlF 6 :Cr 3+ , K 3 GaF 6 :Cr 3+ .…”

“…To date, NIR emissions were realized in Eu 2+ -, Cr 3+ -, and/or Mn 2+ -doped systems. − In particular, the Cr 3+ ones have shown broadband NIR emission originated from their unique d 3 electronic configuration when it situated in the weak crystal field environment . In addition, their preferable excitation by blue light could perfectly fit the commercial blue LED chips . Enormous case studies were performed in search of suitable host matrices for Cr 3+ .…”

Luminescence properties and energy transfer of the near-infrared phosphor Ca3In2Ge3O12:Cr3+,Nd3+

“…19 KGaP 2 O 7 exhibits a broadband NIR emission peak at 815 nm when Cr 3+ is added in a weak crystal eld environment. 20 In addition, the garnetstructured Gd 3 Y 0.5 In 0.5 Ga 4 O 12 phosphor displayed a broadband NIR emission peak at 760 nm, and broadband emission at 650-1050 nm was achieved by adjusting the six-coordinated crystal eld environment occupied by Cr 3+ with an IQE of 81.8%. 21 Although these materials are suitable for the NIR region, they are not well suited to the application requirements.…”