Penetrating Biological Tissue Using Light-Emitting Diodes with a Highly Efficient Near-Infrared ScBO₃:Cr³⁺ Phosphor

Abstract

Recently, infrared (IR) light-emitting diodes (LEDs) have attracted considerable interest in the research field worldwide. IR phosphors, the basic materials utilized in LEDs, have become a research hotspot as well. Here, we introduce the high-quantum-efficiency IR ScBO 3 :Cr 3+ phosphor, which provides a spectral range of emission from 700 to 1000 nm with a peak maximum at 800 nm. Electron paramagnetic resonance spectroscopy, with high element selectivity, was used to elucidate the unusual small peak in the photoluminescence spectrum. Phonon structure and electron−lattice interaction were well observed and discussed via temperature-dependent measurements. Moreover, the high quantum efficiency of 72.8% was achieved. To evaluate their potential practical application, phosphor-converted LED packages were designed, which revealed high stability and high output power of 39.11 mW. Furthermore, the fabricated IR LED demonstrated a remarkable ability to penetrate biological tissues. This study provides insights into the luminescent properties and the practical applications of IR LEDs.

Broadband deep‐red‐to‐near‐infrared emission from Mn2+ in strong crystal‐field of nitride MgAlSiN3

“…21 While an accurate energy level should be provided by zero-phonon line, it can be estimated by the intersection of excitation and emission spectra. As shown by the overlap in Figure 3, the obtained zero-phonon line is 628 nm (1.97 eV) for 6 A 1g → 4 T 1g level. For other transitions, we cannot estimate the zero-line level by intersection approach.…”

“…On account of strong concentration-dependence for the absorption/excitation intensity and position of the first peak as shown in diffuse reflection spectra ( Figure S2) and excitation spectra ( Figure 5A), the broadband peaking at ~300 nm may be a mixture of charge transfer (CT) transition from Mn 2+ to conduction band and 6 A 1g ( 6 S) → 4 E g ( 4 D) transition. These bands peaking at 343, 389/417, 457/478 and 573 nm in Figure 3, are attributed to 6 A 1g ( 6 S) → 4 T 2g ( 4 D), 6 A 1g ( 6 S) → 4 A 1g / 4 E g ( 4 G), 6 A 1g ( 6 S) → 4 T 2g ( 4 G), 6 A 1g ( 6 S) → 4 T 1g ( 4 G) transitions of shows broadband NIR emission peaking at ~825 nm, which originates from Mn 2+ -Mn 2+ pairs. 33 Since the tetrahedrally coordinated Mn 2+ usually gives green emission by forming a weak crystal field, 34 it is reasonable to predict that Mn 2+ does not occupy the crystallographic position of Al 3+ which is tetrahedral coordination.…”

“…Near‐infrared (NIR) light source has received increasing attention for application in night‐vision imaging, medical fields, the food processing industry, etc 1‐5 . Especially, spectral region at 700‐1100 nm shows excellent tissue penetration, which enables it advantageous for imaging blood vein distribution in vivo 6,7 . There is great commercial demand for optical devices and consumer electronics equipped with small‐size, high efficiency and broadband emission NIR light source.…”

Light-emitting diodes: brighter NIR-emitting phosphor making light sources smarter

“…Near-infrared (NIR) spectroscopy is an emerging and powerful technology for studying organic matter, such as food and biological tissues. It can be used to quickly and nondestructively detect organic components by taking advantage of the characteristic absorption signals of C-H, O-H, and N-H in the spectral range of 700-1100 nm 1,2 . This technology plays key roles in quality monitoring for foods and medicines, bioimaging, and night vision.…”

“…The transition metal Cr 3+ is an ideal NIR emitter, and several Cr 3+ -activated NIR phosphors have been developed for smart LEDs 1 , 5 – 9 . Among these, garnet-type phosphors have been intensively investigated due to their unique capability of luminescence regulation 5 – 9 .…”