Sm2+-doped CsEuI3 crystals with highly efficient near-infrared emission and X-ray radioluminescence

Cationic tuning for lanthanide (Ce3+/Pr3+)-activated inorganic phosphors with stable, efficient, and fast-decay 5d-4f emissions has emerged as an important strategy toward the continuing pursuit of superior scintillators. The in-depth understanding of the cationic effects on photo- and radioluminescence of lanthanides Ce3+ and Pr3+ centers is requisite for the rational cationic tuning. Here, we perform a systematic study on the structure and photo- and X-ray radioluminescence properties of K3RE(PO4)2:Ce3+/Pr3+ (RE = La, Gd, and Y) phosphors to elucidate the underlying cationic effects on their 4f-5d luminescence. By using the Rietveld refinements, low-temperature synchrotron-radiation vacuum ultraviolet-ultraviolet spectra, vibronic coupling analyses, and vacuum-referred binding energy schemes, the origins of lattice parameter evolutions, 5d excitation energies, 5d emission energies, and Stokes shifts as well as good emission thermal stabilities of K3RE(PO4)2:Ce3+ systems are revealed. In addition, the correlations of Pr3+ luminescence to Ce3+ in the same sites are also discussed. Finally, the X-ray excited luminescence manifests that the K3Gd(PO4)2:1%Ce3+ sample possesses a light yield of ∼10,217 photons/MeV, indicating its potentiality toward X-ray detection application. These results deepen the understanding of cationic effects on Ce3+ and Pr3+ 4f-5d luminescence and inspire the inorganic scintillator development.

Long-lasting persistent luminescent nanoparticles (PLNPs) with efficient near-infrared (NIR) emission have emerged as a new generation of probes for in vivo optical bioimaging owing to their advantages of zero-autofluorescence benefited from the self-sustained emission after excitation, deep penetration depth, and a high signal-to-noise ratio. However, most of the PLNPs are charged by ultraviolet (UV) or visible light, remarkably limiting their applications for in vivo long-term bioimaging. Here we demonstrate 980 nm laser activated upconversion-PLNPs (UC-PLNPs) with efficient NIR emission. The NIR-emitting UC-PLNPs (Zn3Ga2GeO8:Yb/Er/Cr) were synthesized by a sol-gel method with subsequent calcination. Owing to the efficient energy-transfer between Er and Cr ions, these UC-PLNPs present long-lasting up to 15 h NIR emission at 700 nm after the excitation of a 980 nm laser; in which both excitation and emission bands fall within the biological transparent window. The results of in vitro/in vivo toxicity assessments indicate that UC-PLNPs after surface modification present low biotoxicity and side effects in living animals. More importantly, the synthesized UC-PLNPs can be effectively recharged by 980 nm laser to restore in vivo persistent bioimaging signals and can also be employed as nanoprobes for in vivo UC optical bioimaging. This is the first demonstration of rechargeable UC-PLNPs for NIR-to-NIR in vivo bioimaging. We believe that the synthesized UC-PLNPs by combining UC and persistent luminescence properties into a single host may have potential applications in the bioimaging area and pave the way for widely using PLNPs for in vivo renewable long-lasting bioimaging.

Luminescent metal halides have attracted increasing attention because of their tunable emission and superior photoelectric properties. However, it is still challenging to achieve near‐infrared (NIR) emission from metal halides, which is important in applications such as food quality analysis and night vision. In this work, the broadband NIR emission is achieved by alloying Sn2+ into zero‐dimensional (0D) Cs2ZnBr4. The incorporating of Sn2+ cations enables the originally weakly luminescent Cs2ZnBr4 to exhibit an efficient broadband NIR emission. Upon photoexication, the optimized Sn2+ alloyed Cs2ZnBr4 (Cs2Zn0.875Sn0.125Br4) exhibits a highly efficient broadband NIR emission peaked around 700 nm, with a large Stokes shift of 323 nm, a full width at maximum of 177 nm, and a high quantum efficiency of around 41%. Spectroscopic and theoretical calculations unveil that the efficient NIR emission originates from the self‐trapping emission introduced by the Sn alloying. In addition to the high efficient broadband emission, the Sn2+ alloyed Cs2ZnBr4 also exhibits high thermal stability, retaining 78% of its initial intensity at 150 °C. The night vision application is demonstrated by using a light source fabricated by combining Sn2+ alloyed Cs2ZnBr4 phosphor with a 365 nm LED chip in the dark.

A single crystal of N,N'-bis(4-methoxybenzyl)perylene-3,4,9,10-bis(dicarboximide) (mb-PBI) that possesses novel magic-angle stacking (M-type stacking) and strong intermolecular π-π interaction is achieved by physical vapor transport (PVT), which shows attractive optoelectronic functions such as efficient NIR emission and high electron mobility. In this special M-type staking, the strong Frenkel/CT mixing state promotes fluorescence and, importantly, the elimination of long-distance Förster resonance energy transfer enables the minimization of the possible fluorescence quenching, which ensure the highly efficient emission. Moreover, the strong π-π interaction elongates the "supramolecular conjugation" to reduce the energy gap and also benefits the electron mobility of the crystal. The experimental results clearly indicate that M-type staking is a novel approach to optimize the optoelectronic functions of organic semiconducting materials.

Highly efficient and stable broadband near-infrared (NIR) emission phosphors are crucial for the construction of next-generation smart lighting sources; however, the discovery of target phosphors remains a great challenge. Benefiting from the interstitial Li+ occupancy-induced relatively large distorted octahedral environment for Cr3+ and suppressed nonradiative relaxation of the emission centers, an NIR emission fluoride phosphor Na3GaF6:Cr3+,Li+ peaking at 758 nm with a high internal quantum efficiency of 95.8% and an external quantum efficiency of 38.3% is demonstrated. Moreover, it exhibits a good thermal stability (84.9%@150 °C of the integrated emission intensity at 25 °C) and excellent moisture resistance as well. A high-power light-emitting diode (LED) with a record watt-level NIR output (974.12 mW) and a photoelectric conversion efficiency of 20.9% is demonstrated by combining Na3GaF6:Cr3+,Li+ and a blue InGaN chip, and a special information encryption/decryption technology suitable for rapid and long-distance identification of machines is further presented based on this device. This study not only advances the development of efficient NIR emission phosphors for broadband NIR LEDs but also for NIR-related emerging applications and devices.

Presently, a multitude of all-inorganic and lead-free metal halide perovskites are chosen as matrices for Cr3+ doping due to their favorable coordination environments, aiming to achieve a near-infrared (NIR) emission. Nonetheless, the acquisition of a more efficient NIR emission remains challenging. Herein, we successfully enhanced NIR luminescence within the Cs2ScCl5·H2O:Cr3+ by codoping Te4+ ions. The weak symmetry of Cs2ScCl5·H2O provides an appropriate crystal environment for the broadband near-infrared emission of Cr3+. The NIR emission from the 4T2 → 4A2 transition of Cr3+ is significantly enhanced due to the energy transfer by the emission of STEs, with a photoluminescence quantum yield (PLQY) of 11.02%. Compared to single doping with Cr3+, the emission intensity of Cs2ScCl5·H2O:Cr3+, Te4+ in the NIR region obtains a 3-fold enhancement, while a new yellow emission is simultaneously obtained. This discovery offers a viable method for achieving efficient NIR emission in lead-free metal halides via codoping with ns2 ions and Cr3+. Additionally, Cs2ScCl5·H2O:Cr3+, Te4+ sample was combined with a 380 nm violet light chip for encapsulation, demonstrating its potential applications in the fields of nondestructive material testing and night vision.

Efficient near-infrared emission in Eu3+-Yb3+-Y3+ tri-doped cubic ZrO2 via down-conversion for silicon solar cells

Perovskite nanocrystals (PeNCs) have emerged as a promising class of luminescent materials offering size and composition-tunable luminescence with high efficiency and color purity in the visible range. PeNCs doped with Yb3+ ions, known for their near-infrared (NIR) emission properties, have gained significant attention due to their potential applications. However, these materials still face challenges with weak NIR electroluminescence (EL) emission and low external quantum efficiency (EQE), primarily due to undesired resonance energy transfer (RET) occurring between the host and Yb3+ ions, which adversely affects their emission efficiency and device performance. Herein, we report the synergistic enhancement of NIR emission in a CsPbCl3 host through co-doping with Yb3+/Nd3+ ions for perovskite LEDs (PeLEDs). The co-doping of Yb3+/Nd3+ ions in a CsPbCl3 host resulted in enhanced NIR emission above 1000 nm, which is highly desirable for NIR optoelectronic applications. This cooperative energy transfer between Yb3+ and Nd3+ can enhance the overall efficiency of energy conversion. Furthermore, the PeLEDs incorporating the co-doped CsPbCl3/Yb3+/Nd3+ PeNCs as an emitting layer exhibited significantly enhanced NIR EL compared to the single doped PeLEDs. The optimized co-doped PeLEDs showed improved device performance, including increased EQE of 6.2% at 1035 nm wavelength and low turn-on voltage. Our findings highlight the potential of co-doping with Yb3+ and Nd3+ ions as a strategy for achieving synergistic enhancement of NIR emission in CsPbCl3 perovskite materials, which could pave the way for the development of highly efficient perovskite LEDs for NIR optoelectronic applications.

Zero-dimensional metal halides with diverse structures and rich photophysical properties have been reported. However, achieving multimode dynamic luminescence and efficient near-infrared (NIR) emission under blue light excitation in a single system is a great challenge. Herein, Sb3+-doped hybrid Cd(II) halides were synthesized by a large scale synthesis process at room temperature. Compared with the poor emission of (C12H28N)2CdX4 (C12H28N = tetrapropylammonium; X = Cl and Br) and single steady-state visible light emission of (C12H28N)2SbX5, (C12H28N)2CdX4:Sb3+ exhibits efficient tunable emission from visible to NIR regions. More specifically, (C12H28N)2CdCl4:Sb3+ exhibits distinct excitation wavelength-dependent luminescence characteristics, which can change from green to white and orange emission. Parallelly, halogen substitution can regulate the optical properties of Sb3+-doped (C12H28N)2CdCl4-xBrx (x = 0-1), which enables the excitation and emission bands to exhibit a significant redshift. Thus, the efficient broad NIR emission upon 450 nm excitation was realized in (C12H28N)2CdBr4:Sb3+. In addition, we demonstrated the use of (C12H28N)2CdCl4:Sb3+ phosphors in solid state lighting, and an advanced NIR light source was fabricated by coating (C12H28N)2CdBr4:Sb3+ on a commercial blue chip (450 nm), which exhibits the most advanced photoelectric efficiency (14.67%) and output power (32.84 mW) in hybrid metal halides. Finally, we also demonstrated the use of Sb3+-activated phosphors in four-level fluorescence anti-counterfeiting and information encryption.

Co-doping of Stibium and rare earth (Nd, Yb) in lead-free double perovskite for efficient near-infrared emission

Portable X‐ray imaging technology plays a crucial role in enabling prompt diagnosis and treatment outdoors. Nevertheless, the persistent challenge of external optical signal crosstalk poses a significant bottleneck to its advancement. Herein, a solution utilizing near‐infrared (NIR) light to effectively mitigate optical crosstalk is proposed, thereby demonstrating the feasibility of portable X‐ray imaging even under ambient light. A series of rare earth ions doped Cs2AgxNa1‐xInyBi1‐yCl6 halide scintillators is reported, which possess bright broadband visible and NIR emissions. Taking Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm as an example, it shows decent thermal quenching resistance, high PLQY up to 76.3%, and compelling light yield up to 33500 photons MeV−1. The highly efficient NIR emission is attributed to the energy transfer from the optimized host to lanthanide ions. A flexible scintillation film is prepared by mixing poly(dimethyl‐siloxane) with Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm powder, realizing a low X‐ray detection limit of 55.2 nGyair/s and a high spatial resolution of 11.2 lp mm−1. Due to the efficient NIR emission, the scintillation film enables clear X‐ray imaging under bright LED illumination with the simple addition of filters, avoiding the necessity of a complex imaging apparatus. This work sheds light on NIR emissive scintillator for rapid outdoor response and portable X‐ray imaging.

This study investigates the structural, morphological, and photoluminescent properties of Yb³+ doped Y2O3 phosphors synthesized via the solution combustion method. The structural analysis confirmed the cubic phase of Y2O3, with high crystallinity and successful incorporation of Yb³+ ions, as evidenced by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed uniform morphology with nanoparticles averaging ∼50 nm. Photoluminescence (PL) studies highlighted strong near-infrared (NIR) emission at 980 nm, attributed to the 2F5/2 → 2F7/2 transition of Yb³+ under ultraviolet and visible excitation. The emission intensity exhibited a dependence on Yb³+ concentration, with a peak at 10 mol%, followed by quenching at higher concentrations. Energy transfer mechanisms, quantum yield, and the impact of host lattice properties on emission efficiency were analyzed in detail. The material demonstrates significant potential for enhancing the efficiency of silicon-based photovoltaic devices and for applications in bio-imaging due to its efficient NIR emission and compatibility with biological systems. This research establishes Yb³+ doped Y2O3 as a versatile phosphor for advanced optical applications.

Efficient tunable visible and near-infrared emission in Sb3+/Sm3+-codoped Cs2NaLuCl6 for near-infrared light-emitting diode, triple-mode fluorescence anti-counterfeiting and information encryption

Near-infrared (NIR) light is crucial for medical diagnostics, industrial inspection, and military applications, but achieving both broad-band and efficient NIR luminescence remains challenging. Here, we propose an energy transfer strategy in low-dimensional halides to enable efficient NIR emission, exemplified by zero-dimensional Cs4CaI6:Yb2+,Sm2+. The optimized Cs4CaI6:1%Yb,3%Sm single crystals exhibit high internal and external quantum efficiencies of 73.3% and 47.8% in the NIR region, respectively, resulting from effective Yb2+→Sm2+ energy transfer. When integrated with a commercial blue-light-emitting chip, a record NIR photoelectric conversion efficiency of 31.0% is achieved. Moreover, Cs4CaI6:1%Yb,3%Sm exhibits an exceptional scintillation efficiency of 52,000 photons/MeV, representing a state-of-the-art performance among NIR scintillators. Its bright NIR scintillation enables clear imaging with polydimethylsiloxane-based scintillation screens, even under ambient light conditions, paving the way for portable outdoor X-ray imaging. This work provides an effective approach to achieve NIR emission for light-emitting diodes and scintillation applications.

Abstract0D hybrid Sb(III) halides generally exhibit unique crystal structure and efficient emission. However, achieving efficient white light and blue light‐excited near‐infrared (NIR) emission remains an enormous challenge. Herein, a series of 0D hybrid Sb(III) halides of (18‐crown‐6@K)2SbX5 (X = Cl, Br) crystals with different Cl/Br rations are synthesized via supramolecular self‐assembly. All compounds show the broadband emission, which stems from the self‐trapped excitons in [SbX5]2− pseudo‐octahedral structure. Particularly, (18‐crown‐6@K)2SbCl5 crystal shows tunable emission under various excitation wavelengths, and the efficient white emission with an ultra‐high luminous efficiency of 92.3% is obtained under 310 nm excitation. As Br gradually replaces Cl, not only the excitation and emission bands show a red‐shift but also facilitate the intersystem crossing process from singlet to triplet excitons. Thus, an independent broadband NIR emission upon 450 nm excitation with an ultra‐high luminous efficiency of 58.2% is obtained in (18‐crown‐6@K)2SbBr5 crystals. Moreover, the high‐performance single‐component white light‐emitting diode (WLED) based on (18‐crown‐6@K)2SbCl5 and NIR LED based on (18‐crown‐6@K)2SbBr5 are fabricated, and white light and NIR image fusion is realized. Finally, combined with multiangle imaging under WLED and NIR LED irradiation, the 3D image reconstruction of a centrifuge tube wrapped in a capsule is successfully demonstrated.