Abstract:The near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have great potential in food industry and medical fields. For applications based on NIR spectroscopy, the next generation of NIR pc-LEDs is in a high demand of a spectrum with a much broader full width at halfmaximum (fwhm), which triggers the discovery of novel broadband NIR phosphors. In this work, the Cr 3+ -doped La 2 MgZrO 6 (LMZ) was successfully synthesized by a conventional solid-state method in a reducing atmosphere, and the doub… Show more
“…The total radiant flux of the IR part of the emission amounts to 38 mW. This value surpasses the current Cr 3+ -based state-of-the-art, having IR radiant fluxes in the range of 20–25 mW 4 – 6 , 8 – 10 , by 50%. Fig.…”
Section: Resultsmentioning
confidence: 76%
“…The broadband IR MMCT emission is now applied to construct an IR pc-LED that can directly be used for the numerous above-mentioned spectroscopic applications. Because of the high absorption strength of the parity-allowed 4 f −5 d transitions of Eu 2+ , higher external quantum efficiencies can be achieved than with the current state-of-the-art, Cr 3+ -based phosphors 4 – 6 , 8 – 10 . Furthermore, the extremely broad MMCT emission extends the covered spectral range by several hundreds of nanometers to the IR compared to red/near-IR single Eu 2+ 5 d −4 f emission 11 .…”
Efficient broadband infrared (IR) light-emitting diodes (LEDs) are needed for emerging applications that exploit near-IR spectroscopy, ranging from hand-held electronics to medicine. Here we report broadband IR luminescence, cooperatively originating from Eu
2+
and Tb
3+
dopants in CaS. This peculiar emission overlaps with the red Eu
2+
emission, ranges up to 1200 nm (full-width-at-half-maximum of 195 nm) and is efficiently excited with visible light. Experimental evidence for metal-to-metal charge transfer (MMCT) luminescence is collected, comprising data from luminescence spectroscopy, microscopy and X-ray spectroscopy. State-of-the-art multiconfigurational ab initio calculations attribute the IR emission to the radiative decay of a metastable MMCT state of a Eu
2+
-Tb
3+
pair. The calculations explain why no MMCT emission is found in the similar compound SrS:Eu,Tb and are used to anticipate how to fine-tune the characteristics of the MMCT luminescence. Finally, a near-IR LED for versatile spectroscopic use is manufactured based on the MMCT emission.
“…The total radiant flux of the IR part of the emission amounts to 38 mW. This value surpasses the current Cr 3+ -based state-of-the-art, having IR radiant fluxes in the range of 20–25 mW 4 – 6 , 8 – 10 , by 50%. Fig.…”
Section: Resultsmentioning
confidence: 76%
“…The broadband IR MMCT emission is now applied to construct an IR pc-LED that can directly be used for the numerous above-mentioned spectroscopic applications. Because of the high absorption strength of the parity-allowed 4 f −5 d transitions of Eu 2+ , higher external quantum efficiencies can be achieved than with the current state-of-the-art, Cr 3+ -based phosphors 4 – 6 , 8 – 10 . Furthermore, the extremely broad MMCT emission extends the covered spectral range by several hundreds of nanometers to the IR compared to red/near-IR single Eu 2+ 5 d −4 f emission 11 .…”
Efficient broadband infrared (IR) light-emitting diodes (LEDs) are needed for emerging applications that exploit near-IR spectroscopy, ranging from hand-held electronics to medicine. Here we report broadband IR luminescence, cooperatively originating from Eu
2+
and Tb
3+
dopants in CaS. This peculiar emission overlaps with the red Eu
2+
emission, ranges up to 1200 nm (full-width-at-half-maximum of 195 nm) and is efficiently excited with visible light. Experimental evidence for metal-to-metal charge transfer (MMCT) luminescence is collected, comprising data from luminescence spectroscopy, microscopy and X-ray spectroscopy. State-of-the-art multiconfigurational ab initio calculations attribute the IR emission to the radiative decay of a metastable MMCT state of a Eu
2+
-Tb
3+
pair. The calculations explain why no MMCT emission is found in the similar compound SrS:Eu,Tb and are used to anticipate how to fine-tune the characteristics of the MMCT luminescence. Finally, a near-IR LED for versatile spectroscopic use is manufactured based on the MMCT emission.
“…The transition metal ion Cr 3+ can serve as a good NIR luminescence center due to its broad NIR emission when it locates in the weak octahedral crystal field. [ 5 ] Liu et al first realized the NIR LED with broad emission band (600–1200 nm, full width at half maximum [FWHM] = 330 nm) and 18.4 mW lumen efficiency based on La 3 Ga 5 GeO 14 :Cr 3+ phosphor. [ 6 ] Recently, via the chemical unit cosubstitution, Zhang et al obtained an NIR emission source with a lumen efficiency of 54.29 mW through the combination of Ca 3‐ x Lu x Hf 2 Al 2+ x Si 1− x O 12 :Cr 3+ garnet phosphor and blue LED chip.…”
High‐radiance near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are demanded for wearable biosensing devices and the properties of these pc‐LEDs are highly dependent on the performance of the NIR phosphor. An ultraviolet–visible and NIR‐responded broadband NIR NaScGe2O6:Cr3+ phosphor is reported. Under 490 nm excitation, NaScGe2O6:Cr3+ shows broad emission band from 700 to 1250 nm, which covers the first and second NIR windows. An NIR pc‐LED with radiant flux of 12.07 mW@350 mA is realized based on NaScGe2O6:Cr3+ and 450 nm blue LED chip. The ability of high‐power NIR light of the NIR pc‐LED to penetrate human tissues is observed successfully. Additionally, in NaScGe2O6:Cr3+, the luminescence performance of Cr3+ under 808 nm laser excitation is achieved for the first time.
“…In recent years, many researches have been focused on the development of the broadband NIR phosphors . OSRAM has demonstrated the prospect of NIR phosphors for endoscopy applications that facilitates mobile phones for analyzing the food composition .…”
Super broadband near‐infrared (NIR) phosphor converted light‐emitting diodes (pc‐LEDs) are future light sources in NIR spectroscopy applications such as food testing. At present, a few blue LED excitable super broadband NIR phosphors (bandwidth > 300 nm) have been developed producing the NIR output powers below 26 mW at 100 mA input current after LED packaging. Here, an efficient super broadband NIR phosphor achieved by doping Yb3+ is reported in the NIR Ca2LuZr2Al3O12:Cr3+ (CLZA:Cr3+) garnet phosphor developed previously. Benefited from the superposition of Cr3+ emission and highly efficient Yb3+ emission excited by energy transfer from Cr3+, the codoped CLZA:Cr3+,Yb3+ phosphor shows a bandwidth of 320 nm and an internal quantum efficiency of 77.2% both higher than that (150 nm and 69.1%) of singly doped CLZA:Cr3+ phosphor. The codoped phosphor converts LED produced 41.8 mW NIR output at 100 mA input current. The pc‐LED as a light source is also well applied to the NIR transmission spectra measurement of water. The results indicate the great potential of CLZA:Cr3+,Yb3+ phosphor in super broadband NIR pc‐LED applications.
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