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

Broadband near-infrared (NIR) light source based on phosphor-converted light-emitting-diode (pc-LED) is crucial for applications in medical diagnosis, food quality analysis, and night vision fields, motivating the development of highly efficient and thermal robust NIR phosphor materials. Herein, a novel Cr3+-doped garnet phosphor Y3In2Ga3O12:Cr3+ emerges from a fundamental study of the Ln3In2Ga3O12 (Ln = La, Gd, Y, and Lu) family. Upon 450 nm excitation, this material presents a broadband NIR emission covering 650–1100 nm with a peak located at 760 nm and a full width at half maximum of 125 nm. This material also possesses an ultrahigh internal quantum efficiency (IQE = 91.6%) and absorption efficiency (AE = 46.6%), resulting in an external quantum efficiency as high as 42.7%. Moreover, the emission intensity of this material at 150 °C maintains 100% of the initial intensity, showing a rare zero-thermal-quenching property. Fabricating an NIR pc-LED device by using this material, an excellent NIR output power of 68.4 mW with a photoelectric efficiency of 15.9% under 150 mA driving current can be obtained, which exhibits much better performance than the devices fabricated by using some reported efficient NIR materials. Therefore, this work not only provides an ultraefficient and thermally robust broadband NIR material for spectroscopy application but also contributes to the foundation of design rules of NIR materials with high performance

Producing Tunable Broadband Near-Infrared Emission through Co-Substitution in (Ga_1–<i>x</i>Mg_<i>x</i>)(Ga_1–<i>x</i>Ge_<i>x</i>)O₃:Cr³⁺

Broadband near-infrared (NIR) phosphors are in high demand for creating “smart” NIR phosphor-converted light-emitting diode (pc-LED) sources. In this work, a series of Cr3+-substituted NIR-emitting materials with highly efficient, broad, tunable emission spectra are achieved by modifying the simple oxide Ga2O3 using [Mg2+-Ge4+] and [Ga3+-Ga3+] co-unit substitution. The results show that the emission peak can be shifted from 726 to 830 nm while maintaining a constant excitation peak in the blue light region, enabling extensive application. The optical properties stem from changes in the Cr3+ crystal field environment upon substitution. Intriguingly, the temperature-dependent photoluminescence emission peak position shows virtually no change in the [Mg2+-Ge4+] co-substituted materials. This abnormal phenomenon is found to be a comprehensive embodiment of a weakening crystal field environment (red-shift) as the temperature increases and reduced local structure distortion (blue-shift) with increasing temperature. The high quantum yield, NIR emission, and net-zero emission shift as a function of temperature make this phosphor class optimal for device incorporation. As a result, their performance was studied by coating the phosphor on a 450 nm emitting LED chip. The fabricated device demonstrates an excellent NIR output power and NIR photoelectric conversion efficiency. This study provides a series of efficient, tunable, broadband NIR materials for spectroscopy applications and contributes to the basic foundation of Cr3+-activated NIR phosphors

Synthesis, Crystal Structures, and Photoluminescence Properties of Ce³⁺-Doped Ca₂LaZr₂Ga₃O₁₂: New Garnet Green-Emitting Phosphors for White LEDs

A new family of garnet compounds, Ca₂LnZr₂Ga₃O₁₂ (Ln = La, Y, Lu, Gd) have been synthesized by high-temperature solid-state reaction method. The crystal structures were characterized by the X-ray diffraction (XRD) and refined by the Rietveld method. The photoluminescence properties, morphology, CIE value, quantum efficiency, and thermal stability of Ca₂LaZr₂Ga₃O₁₂:Ce³⁺ phosphors were investigated in detail to evaluate the use in w-LEDs. The photoluminescence results revealed that these phosphors have a broad excitation band in the blue region ranging from 400 to 470 nm and a broad green emission band centered at about 515 nm. The above results indicated that the phosphors could be effectively excited by blue light and may have the potential to serve as green-emitting phosphors for application in w-LEDs

Origin of Spectral Blue Shift of Lu³⁺-Codoped YAG:Ce³⁺ Phosphor: First-Principles Study

Lu³⁺, with the smallest ionic radii in lanthanide ions, is an important and beneficial cation for tuning spectrum shifting toward a longer wavelength by ion substitution in many phosphors for solid-state lighting. However, in the Lu³⁺-substituted garnet system, the phosphor always has smaller lattice parameters and exhibits a shorter emission wavelength than other garnet phosphors. The mechanism of such a spectral blue shift induced by the Lu³⁺-codoped garnet phosphor is still unclear. In this study, the local and electronic structures of Lu³⁺-codoped and Lu³⁺-undoped YAG:Ce³⁺ phosphor have been studied by first-principles calculation to reveal the origin of the spectral blue shift. Our results provide a full explanation of the experimental data and the methodology, which is useful to understand and design garnet phosphors with tunable emission characteristics

Identifying the Emission Centers and Probing the Mechanism for Highly Efficient and Thermally Stable Luminescence in the La₃Si₆N₁₁:Ce³⁺ Phosphor

Nitride La₃Si₆N₁₁:Ce³⁺ is an important commercial phosphor for high-power white light-emitting diodes due to its strong resistance toward thermal quenching and sufficient emission efficiency. However, the underlying mechanisms of this high performance is still a mystery. Also, the emission properties of Ce³⁺ in two kinds of crystallographic sites are currently in dispute. Here, we confirmed the yellow emission ascribed to Ce_La(2) luminescence center and proposed a blue emission owning to Ce_La(1) luminescence center through both theoretical and experimental methods. Particularly, we find an unusual efficient and fast energy transfer from Ce_La(1) to Ce_La(2) due to a large spectral overlap between the emission of Ce_La(1) and the absorption of Ce_La(2), and efficient electron transfer from defects to 5d orbital at high temperature, which shows high relevance to the highly efficient yellow emission and thermal stability of this material. This study presents a full and new understanding toward this special phosphor and provides useful insights into designing highly efficient and thermally stable luminescent materials for future lighting