Quantifying the interfacial triboelectricity in inorganic-organic composite mechanoluminescent materials

Mechanoluminescence (ML) sensing technologies open up new opportunities for intelligent sensors, self-powered displays and wearable devices. However, the emission efficiency of ML materials reported so far still fails to meet the growing application requirements due to the insufficiently understood mechano-to-photon conversion mechanism. Herein, we propose to quantify the ability of different phases to gain or lose electrons under friction (defined as triboelectric series), and reveal that the inorganic-organic interfacial triboelectricity is a key factor in determining the ML in inorganic-organic composites. A positive correlation between the difference in triboelectric series and the ML intensity is established in a series of composites, and a 20-fold increase in ML intensity is finally obtained by selecting an appropriate inorganic-organic combination. The interfacial triboelectricity-regulated ML is further demonstrated in multi-interface systems that include an inorganic phosphor-organic matrix and organic matrix-force applicator interfaces, and again confirmed by self-oxidization and reduction of emission centers under continuous mechanical stimulus. This work not only gives direct experimental evidences for the underlying mechanism of ML, but also provides guidelines for rationally designing high-efficiency ML materials.

Tunable Emission of Low-Dimensional Organic Metal Halides by Stoichiometric Ratio and Metal Center

Low-dimensional (LD) organic metal halides (OMHs) have a bright future due to their excellent photoelectric characteristics and unique structure. However, the synthesis and emission control of LD-OMHs are still unclear. Herein, the different dimensional (zero-dimensional (0D), one-dimensional (1D), and three-dimensional (3D)) of OMHs were obtained by the reaction of 1,4-diazabicyclo (2.2.2) octane with PbBr2 in different stoichiometric ratios. This discovery shows that the structure and properties of OMHs can be regulated while maintaining the functional organic cations of OMHs, which broadens the path for the development of functional LD-OMHs. Among them, 0D-OMH 1 and 1D-OMH 3 have narrow-band (full width at half-maximum (fwhm) = 74 nm) and broad-band (fwhm = 201 nm) emission, respectively. We found that when organic cations have no contribution to the formation of conduction band minimum and valence band maximum, and the distances between polyhedrons are larger than the van der Waals diameter of the halogen atom, the effect of phonons on exciton transitions can be reduced to achieve a narrow-band emission. Further, Cu(I)- and Mn (II)-based 0D-OMHs were synthesized, which have high photoluminescence quantum yield (PLQY) (33.97 and 47.33%, respectively). When the emitting of 0D-OMHs produced by the interaction of the metal-center and halogens, the asymmetric planar metal-halogen structure will result in a higher PLQY.

Water-Soluble Quantum Dots for Inkjet Printing Color Conversion Films with Simultaneous High Efficiency and Stability

Water-soluble quantum dots (QDs) are necessary to prepare patterned pixels or films for high-resolution displays with less environmental burden but are very limited by the trade-off between photoluminescence and stability of QDs. In this work, we proposed synthesizing water-soluble QDs with simultaneous excellent luminescence properties and high stability by coating the amphiphilic poly(maleic anhydride-alt-1-octadecene)-ethanol amine (PMAO-EA) polymer on the surface of silane-treated QDs. These coated QDs show a photoluminescence quantum yield (PLQY) as high as 94%, and they have good photoluminescence stability against light irradiation and thermal attacks, owing to the suppression of the nonradiative recombination by the polymer layer and the isolation of oxygen and water by the silica layer. The water-soluble QDs, mixed with ethylene glycol, enable inkjet printing of QD color conversion films (QD-CCFs) with an average diameter of 68 μm for each pixel and a high PLQY of 91%. The QD-CCFs are demonstrated to fabricate red-emitting mini-LEDs by combining with blue mini-LED chips, which have an external quantum efficiency as high as 25.86% and a luminance of 2.44 × 107 cd/m2. We believe that the proposed strategy is applicable to other water-soluble QDs and paves an avenue for inkjet printing environmentally friendly QD-CCFs for mini/micro-LED displays.

Ligand Engineering Enables Efficient Pure Red Tin-Based Perovskite Light-Emitting Diodes

With increasing ecological and environmental concerns, tin (Sn)-based perovskite light-emitting diodes (PeLEDs) are competitive candidates for future displays because of their environmental friendliness, excellent photoelectric properties, and low-cost solution-processed fabrication. Nonetheless, their electroluminescence (EL) performance still lags behind that of lead (Pb)-based PeLEDs due to the fast crystallization rate of Sn-based perovskite films and undesired oxidation from Sn2+ to Sn4+ , leading to poor film morphology and coverage, as well as high density defects. Here, we propose a ligand engineering strategy to construct high-quality phenethylammonium tin iodide (PEA2 SnI4 ) perovskite films by using L-glutathione reduced (GSH) as surface ligands toward efficient pure red PEA2 SnI4 -based PeLEDs. We show that the hydrogen-bond and coordinate interactions between GSH and PEA2 SnI4 effectively reduce the crystallization rate of the perovskites and suppress the oxidation of Sn2+ and formation of defects. The improved pure red perovskite films not only show excellent uniformity, density, and coverage but also exhibit enhanced optical properties and stability. Finally, state-of-the-art pure red PeLEDs achieve a record external quantum efficiency of 9.32 % in the field of PEA2 SnI4 -based devices. This work demonstrates that ligand engineering represents a feasible route to enhance the EL performance of Sn-based PeLEDs.

Correction: A super-high brightness and excellent colour quality laser-driven white light source enables miniaturized endoscopy

Correction for 'A super-high brightness and excellent colour quality laser-driven white light source enables miniaturized endoscopy' by Shuxing Li et al., Mater. Horiz., 2023, 10, 4581-4588, https://doi.org/10.1039/D3MH01170D.

A super-high brightness and excellent colour quality laser-driven white light source enables miniaturized endoscopy

A laser-driven white light source promises intrinsic advantages for miniaturized endoscopic illumination. However, it remains a great challenge to simultaneously achieve high brightness and excellent colour rendition due to the shortage of highly efficient and thermally robust red-emitting laser phosphor converters. Here, we designed CaAlSiN3:Eu@Al (CASN@Al) converters with neglectable efficiency loss by tightly bonding all-inorganic phosphor films on an aluminium substrate. A layer-by-layer phosphor converter (LuAG/CASN@Al), i.e., stacking a green-emitting Lu3Al5O12:Ce (LuAG) layer on CASN@Al, was constructed to enhance light conversion efficiency and reduce reabsorption loss under blue laser excitation, which thus produces an excellent white light source with a luminous efficacy of 258 lm W-1 and a colour rendering index of 91. A miniaturized endoscopy with a coupling efficiency twice that of the commercial white LEDs was demonstrated by using the laser-driven white light and showed a central illuminance as high as 52 730 lx, more vivid images and long-term reliability.

Perovskite Light-Emitting Diodes with an External Quantum Efficiency Exceeding 30

Perovskite light-emitting diodes (PeLEDs) are strong candidates for next-generation display and lighting technologies due to their high color purity and low-cost solution-processed fabrication. However, PeLEDs are not superior to commercial organic light-emitting diodes (OLEDs) in efficiency, as some key parameters affecting their efficiency, such as the charge carrier transport and light outcoupling efficiency, are usually overlooked and not well optimized. Here, ultrahigh-efficiency green PeLEDs are reported with quantum efficiencies surpassing a milestone of 30% by regulating the charge carrier transport and near-field light distribution to reduce electron leakage and achieve a high light outcoupling efficiency of 41.82%. Ni0.9 Mg0.1 Ox films are applied with a high refractive index and increased hole carrier mobility as the hole injection layer to balance the charge carrier injection and insert the polyethylene glycol layer between the hole transport layer and the perovskite emissive layer to block the electron leakage and reduce the photon loss. Therefore, with the modified structure, the state-of-the-art green PeLEDs achieve a world record external quantum efficiency of 30.84% (average =  29.05 ± 0.77%) at a luminance of 6514 cd m-2 . This study provides an interesting idea to construct super high-efficiency PeLEDs by balancing the electron-hole recombination and enhancing the light outcoupling.

Constructing Perovskite/Polymer Core/Shell Nanocrystals with Simultaneous High Efficiency and Stability for Mini-LED Backlights

Lead halide perovskite nanocrystals (NCs) have been the star material in lighting and displays owing to their excellent photoelectrical properties, but they have not simultaneously realized high photoluminescence quantum yield (PLQY) and high stability. To solve this problem, we propose a perovskite/linear low-density polyethylene (perovskite/LLDPE) core/shell NC by the synergistic role of the pressure effect and steric effect. Green CsPbBr₃/LLDPE core/shell NCs with near-unity PLQY and nonblinking behavior were synthesized through an in situ hot-injection process. The mechanism of the improved photoluminescence (PL) properties is the enhanced pressure effect resulting in increased radiative recombination and interaction between the ligand and perovskite crystals, as confirmed by the PL spectra and finite element calculations. Meanwhile, the NCs show high stability under ambient conditions (with a PLQY of 92.5% after 166 days) and against 365 nm UV light (maintaining 61.74% of the initial PL intensity after continuous radiation for 1000 min). This strategy also works well in the blue and red perovskite/LLDPE NCs and red InP/ZnSeS/ZnS/LLDPE NCs. Finally, white-emitting Mini-LEDs were fabricated by combining the green CsPbBr₃/LLDPE and red CsPbBr_1.2I_1.8/LLDPE core/shell NCs with blue Mini-LED chips. The white-emitting Mini-LEDs exhibit super wide color gamut (∼129% of the National Television Standards Committee or 97% of the Rec. 2020 standards).

Visualizing Dynamic Mechanical Actions with High Sensitivity and High Resolution by Near-Distance Mechanoluminescence Imaging

Proportionally converting the applied mechanical energy into photons by individual mechanoluminescent (ML) micrometer-sized particles opens a new way to develop intelligent electronic skins as it promises high-resolution stress distribution visualization and fast response. However, a big challenge for ML sensing technology is its low sensitivity in detecting stress. In this work, a novel stress distribution sensor with the detection sensitivity enhanced by two orders of magnitude is developed by combining a proposed near-distance ML imaging scheme with an improved mechano-to-photon convertor. The enhanced sensitivity is the main contributor to the realization of a maximum photon harvesting rate of ≈80% in the near-distance ML imaging scheme. The developed near-distance ML sensor shows a high sensitivity with a detection limit down to ≈kPa level, high spatial resolution of 254 dpi, and fast response with an interval of 3.3 ms, which allows for high-resolution and real-time visualization of complex mechanical actions such as irregular solid contacts or fluid impacts, and thus enables use in intelligent electronic skin, structural health monitoring, and human-computer interaction.

Time-Gated Imaging of Latent Fingerprints with Level 3 Details Achieved by Persistent Luminescent Fluoride Nanoparticles

The discovery of X-ray-charged persistent luminescence (PersL) in fluoride nanoparticles enables these materials to emit photons without real-time excitation, which provides a great possibility for the development of new luminescent nanotechnologies. In this work, we developed NaLuF₄:Mn nanoparticles with intense green PersL and functionalized surfaces and accordingly achieved time-gated imaging of latent fingerprints (LFPs) with Level 3 details. These surface-modified NaLuF₄:Mn nanoparticles exhibited near-spherical morphology, long-lasting emission for several hours, appropriate trap depth distribution, and tight chemical bonding with amino acids from fingerprints, thus greatly improving the accuracy of LFP imaging in a variety of environments. The developed NaLuF₄:Mn PersL nanoparticles are expected to find broad applications in the fields of LFP imaging and in vivo biological imaging.

Passivation Layer of Potassium Iodide Yielding High Efficiency and Stable Deep Red Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) are promising candidates used for superthin emissive displays with high resolution, high brightness, and wide color gamut, but the CsPbI₃ nanocrystal (NC) based ones usually have an external quantum efficiency (EQE) of less than 20%, which needs further enhancement to minimize the gap between their counterparts. Herein, we propose to improve optical properties of the CsPbI₃:Sr emissive layer (EML) by inserting an additional potassium iodide (KI) passivation layer between the hole transport layer and EML to increase the film quality, photoluminescence quantum yield, and thermal stability of the EML. The KI layer can also increase the carrier mobility to balance the charge injection in PeLEDs, leading to a reduction in Auger recombination and Joule heating. An interesting deep-red-emitting PeLED (λ_em = 687 nm) with a record EQE of 21.8% and a lifetime T₅₀ of 69 min is obtained by applying the additional KI passivation layer. Moreover, a flexible PeLED consisting of the KI layer is also demonstrated to have a record EQE of 12.7%. These results indicate that the use of a functional KI layer is a feasible way to develop high-performance electroluminescent devices.

A broadband yellow Yb2+-doped oxynitride phosphor for high-performance white light-emitting diodes

A broadband, efficient and stable yellow (Ba,Sr)Si3Al3O4N5:Yb2+ phosphor shows promising applications in single-phosphor-converted warm w-LEDs.

Mechanoluminescence Rebrightening the Prospects of Stress Sensing: A Review

The emergence of new applications, such as in artificial intelligence, the internet of things, and biotechnology, has driven the evolution of stress sensing technology. For these emerging applications, stretchability, remoteness, stress distribution, a multimodal nature, and biocompatibility are important performance characteristics of stress sensors. Mechanoluminescence (ML)-based stress sensing has attracted widespread attention because of its characteristics of remoteness and having a distributed response to mechanical stimuli as well as its great potential for stretchability, biocompatibility, and self-powering. In the past few decades, great progress has been made in the discovery of ML materials, analysis of mechanisms, design of devices, and exploration of applications. One can find that with this progress, the focus of ML research has shifted from the phenomenon in the earliest stage to materials and recently toward devices. At the present stage, while showing great prospects for advanced stress sensing applications, ML-based sensing still faces major challenges in material optimization, device design, and system integration.

X-ray-charged bright persistent luminescence in NaYF4:Ln3+@NaYF4 nanoparticles for multidimensional optical information storage

NaYF4:Ln3+, due to its outstanding upconversion characteristics, has become one of the most important luminescent nanomaterials in biological imaging, optical information storage, and anticounterfeiting applications. However, the large specific surface area of NaYF4:Ln3+ nanoparticles generally leads to serious nonradiative transitions, which may greatly hinder the discovery of new optical functionality with promising applications. In this paper, we report that monodispersed nanoscale NaYF4:Ln3+, unexpectedly, can also be an excellent persistent luminescent (PersL) material. The NaYF4:Ln3+ nanoparticles with surface-passivated core-shell structures exhibit intense X-ray-charged PersL and narrow-band emissions tunable from 480 to 1060 nm. A mechanism for PersL in NaYF4:Ln3+ is proposed by means of thermoluminescence measurements and host-referred binding energy (HRBE) scheme, which suggests that some lanthanide ions (such as Tb) may also act as effective electron traps to achieve intense PersL. The uniform and spherical NaYF4:Ln3+ nanoparticles are dispersible in solvents, thus enabling many applications that are not accessible for traditional PersL phosphors. A new 3-dimensional (2 dimensions of planar space and 1 dimension of wavelength) optical information-storage application is demonstrated by inkjet-printing multicolor PersL nanoparticles. The multicolor persistent luminescence, as an emerging and promising emissive mode in NaYF4:Ln3+, will provide great opportunities for nanomaterials to be applied to a wider range of fields.

Phosphorus-Doped Metal-Organic Framework-Derived CoS2 Nanoboxes with Improved Adsorption-Catalysis Effect for Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising next-generation battery technologies owing to their ultrahigh energy density up to 2600 W h kg^-1 and low cost. However, major challenges still remain in the application of Li-S batteries, such as shuttle effect and sluggish redox kinetics. Herein, it is demonstrated that phosphorus doping can not only significantly improve the polysulfide adsorption but also enhance the catalysis effects of metal-organic framework-derived CoS₂ nanoboxes in Li-S batteries. Consequently, a modified separator integrated with P-CoS₂ and carbon nanotubes effectively suppresses the polysulfide shuttle and propels the redox kinetics of polysulfides, thus promising higher specific discharge capacity, better rate, and stable cycle performance. Even under the high sulfur loading condition (4.8 mg cm^-2), the areal discharge capacity of the cell with the functional separator can still remain at 4.5 mA h cm^-2 after 100 cycles at 0.2 C. More importantly, this work may encourage more effort on anion doping for engineering the polar surface of transition-metal compounds to further mediate the interfacial redox chemistry between transition-metal compounds and polysulfides in Li-S batteries.

In Situ Inkjet Printing Patterned Lead Halide Perovskite Quantum Dot Color Conversion Films by Using Cheap and Eco-Friendly Aqueous Inks

Inkjet-printed perovskite quantum dot (PQD) color conversion films (CCFs) have great potentials for mini/micro-LED displays because of their ultrahigh color purity, tunable emissions, high efficiency, and high-resolution. However, current PQD inks mainly use expensive, toxic, and flammable organic substances as solvents. In this work, water is proposed to be used as the solvent for inkjet printing PQD/polymer CCFs. The green-emitting patterned MAPbBr₃ /polyvinyl alcohol (PVA) films are in situ prepared by using halides and the PVA-based aqueous ink. The as-printed CCFs exhibit a high-resolution dot matrix of 90 µm with a bright green emission (λ_em  = 526 nm), a high photoluminescence quantum yield of 85%, and a narrow full width at half maximum of 22 nm. They have both air- and photo-stabilities under ambient conditions, and each pixel of CCFs is relatively uniform in morphology and fluorescence when the substrate temperature is 80 °C. The patterned blue-emitting MAPbCl_x Br_3-x /PVA and red-emitting Cs_0.3 MA_0.7 PbBr_x I_3-x /PVA can also be printed by aqueous inks. These results indicate that the designed aqueous inks are promising for in situ inkjet printing high resolution and reliability PQD CCFs for mini/micro-LED displays.

In situ TEM study of edge reconstruction and evolution in monolayer black phosphorus

As symmetry-breaking interfaces, edges inevitably influence material properties, particularly for low-dimensional materials such as two-dimensional (2D) graphene and black phosphorus (BP). Hence, exploiting pristine edge structures and the associated edge reconstruction is important. In this study, we revealed edge reconstruction and evolution in monolayer BP (ML-BP) via in situ high-resolution transmission electron microscopy. Under our typical experimental conditions, spontaneous edge reconstruction occurred in all types of as-prepared edges that include zigzag, Klein zigzag, diagonal, and Klein diagonal edges. Reconstruction induces a periodic variation of the bond length and bond angles of edge atoms: an out-of-plane bending for zigzag and diagonal edge atoms and a dimerization for two neighboring edge atoms on the Klein edge, respectively. Surface atom diffusion can also induce edge structural evolution as evidenced by the atomic scale dynamics captured for the zigzag edge. Experimentally resolved edge configurations and reconstruction were further corroborated by ab initio first-principles calculations. This study explores the understanding of the edge stability in 2D BP materials and may provide routes for precisely controlled edge structure engineering.

Realizing Tunable White Light Emission in Lead-Free Indium(III) Bromine Hybrid Single Crystals through Antimony(III) Cation Doping

Low-dimensional metal halide hybrids (OIMHs) have recently been explored as single-component white-light emitters for use in solid-state lighting. However, it still remains challenging to realize tunable white-light emission in lead-free zero-dimensional (0D) hybrid system. Here, a combination strategy has been proposed through doping Sb³⁺ enabling and balancing multiple emission centers toward the multiband warm white light. We first synthesized a new lead-free 0D (C₈NH₁₂)₆InBr₉·H₂O single crystal, in which isolated [InBr₆]^3- octahedral units are separated by large organic cations [C₈NH₁₂]⁺. (C₈NH₁₂)₆InBr₉·H₂O exhibits dual-band emissions with one intense cyan emission and a weak red emission tail. The low-energy ultrabroadband red emission tail can be greatly enhanced by the Sb³⁺ doping. Experimental data and first-principles calculations reveal that the original dominant cyan emission is originated from the organic cations [C₈NH₁₂]⁺ and that the broadband red emission is ascribed to self-trapped excitons in [In(Sb)Br₆]^3-. When the Sb concentration is 0.1%, a single-component warm white-light emission with a photoluminescence quantum efficiency of 23.36%, correlated color temperature of 3347 K, and a color rendering index up to 84 can be achieved. This work represents a significant step toward the realization of single-component white-light emissions in environmental-friendly, high-performance 0D metal halide light-emitting materials.

Force-induced charge carrier storage: a new route for stress recording

Stress sensing is the basis of human-machine interface, biomedical engineering, and mechanical structure detection systems. Stress sensing based on mechanoluminescence (ML) shows significant advantages of distributed detection and remote response to mechanical stimuli and is thus expected to be a key technology of next-generation tactile sensors and stress recorders. However, the instantaneous photon emission in ML materials generally requires real-time recording with a photodetector, thus limiting their application fields to real-time stress sensing. In this paper, we report a force-induced charge carrier storage (FICS) effect in deep-trap ML materials, which enables storage of the applied mechanical energy in deep traps and then release of the stored energy as photon emission under thermal stimulation. The FICS effect was confirmed in five ML materials with piezoelectric structures, efficient emission centres and deep trap distributions, and its mechanism was investigated through detailed spectroscopic characterizations. Furthermore, we demonstrated three applications of the FICS effect in electronic signature recording, falling point monitoring and vehicle collision recording, which exhibited outstanding advantages of distributed recording, long-term storage, and no need for a continuous power supply. The FICS effect reported in this paper provides not only a breakthrough for ML materials in the field of stress recording but also a new idea for developing mechanical energy storage and conversion systems.

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

A brighter near-infrared (NIR) phosphor is achieved by inhibiting the oxidation of Cr3+ and reducing the surface defects of phosphor particles, enabling the realization of smarter and more sensitive light sources for night vision.

Inkjet-Printed Quantum Dot Color Conversion Films for High-Resolution and Full-Color Micro Light-Emitting Diode Displays

Micro light-emitting diodes (μLEDs) have been considered an excellent candidate for next-generation display technology because of their promising optical properties, outstanding power efficiency, fast response time, high reliability, etc. However, the μLED displays based on individual red-green-blue (RGB) primary chips suffer from severe issues in mass production, such as difficulty in mass transfer, high cost, and low reproducibility. To overcome these issues, an alternative approach has been proposed to achieve full-color μLEDs by assembling ultraviolet- or blue-μLEDs with QD color conversion films (CCFs). In this Perspective, we give a general introduction of QD-based μLEDs and provide an overview of the preparation of fine patterned QD CCFs by inkjet printing. We then discuss advances in II-VI core/shell QD-based μLEDs. This is followed by representative progress on preliminary exploration of lead halide perovskite QD CCFs, which have great potential for use in high-resolution and full-color μLEDs displays. Finally, we address the remaining challenges for further improvement of QD-based μLEDs.

Blue-emitting and self-assembled thinner perovskite CsPbBr3 nanoplates: synthesis and formation mechanism

Low dimensional semiconductor nanomaterials show great promise for a variety of applications due to their size-dependent and excellent optoelectronic properties. In this work, we developed a strategy to synthesize uniform and very thin CsPbBr₃ perovskite nanoplates (NPls) by introducing additional metal bromides. The CsPbBr₃ NPls, self-assembled into a face-to-face stacked state, had a thickness of 4.4 nm (equal to only 2 monolayers, 2 MLs) and showed a maximum emission at 437 nm and a narrow FWHM of 14 nm. The formation mechanism of the CsPbBr₃ NPls by adding FeBr₃ was ascribed to the constrained growth of CsPbBr₃ nanocubes when the surface Cs⁺ ions were substituted by the protonated oleylammonium from the byproduct OLA-HBr.

A selective and sensitive fluorescent probe for bilirubin in human serum based on europium(III) post-functionalized Zr(IV)-Based MOFs

In the present study, a kind of Eu(III) post-functionalized Zr(IV)-based metal-organic framework (UiO-66(COOH)₂, Zr-MOF: Eu³⁺) was synthesized and utilized as an independently luminescent probe for sensing bilirubin (BR) in human serum, a biomarker of jaundice hepatitis. It can be served as a turn-off fluorescent switch for BR because its red emission from Eu³⁺ can be easily quenched by BR through a fluorescent resonant energy transfer (FRET) process between BR and its ligands, and as a result, BR is recognized successfully. Particularly, Zr-MOF: Eu³⁺ has shown many appealing properties, such as high sensitivity, quick response (less than 1 min), broad response window (0-15 μM), and excellent selectivity. Most importantly, a kind of portable test paper based on Zr-MOF: Eu³⁺ probe has been developed for directly assessing the level of BR in real human serum and further diagnosing bilirubin-related diseases via visually observing the luminescent color variation.

Novel Mn4+ doped red phosphors composed of MgAl2O4 and CaAl12O19 phases for light-emitting diodes

The EL spectra and photographs of the as-obtained plant growth LED and white LED by using CMA:Mn⁴⁺ red phosphors.

Aggregation-Induced Emission Gold Clustoluminogens for Enhanced Low-Dose X-ray-Induced Photodynamic Therapy

The use of gold nanoparticles as radiosensitizers is an effective way to boost the killing efficacy of radiotherapy while drastically limiting the received dose and reducing the possible damage to normal tissues. Herein, we designed aggregation-induced emission gold clustoluminogens (AIE-Au) to achieve efficient low-dose X-ray-induced photodynamic therapy (X-PDT) with negligible side effects. The aggregates of glutathione-protected gold clusters (GCs) assembled through a cationic polymer enhanced the X-ray-excited luminescence by 5.2-fold. Under low-dose X-ray irradiation, AIE-Au strongly absorbed X-rays and efficiently generated hydroxyl radicals, which enhanced the radiotherapy effect. Additionally, X-ray-induced luminescence excited the conjugated photosensitizers, resulting in a PDT effect. The in vitro and in vivo experiments demonstrated that AIE-Au effectively triggered the generation of reactive oxygen species with an order-of-magnitude reduction in the X-ray dose, enabling highly effective cancer treatment.

New Deep-Blue-Emitting Ce-Doped A4-mBnC19+2mX29+m (A = Sr, La; B = Li; C = Si, Al; X = O, N; 0 ≤ m ≤ 1; 0 ≤ n ≤ 1) Phosphors for High-Color-Rendering Warm White Light-Emitting Diodes

A new sialon Eu_3.60LiSi_13.78Al_6.03O_6.82N_22.59 has been discovered via the single-particle diagnosis approach. Its crystal structure (space group P3m1) was solved and refined from single-crystal X-ray diffraction data. It has the interesting feature of two types of disorder at the Eu2 site: positional disorder (Eu2a/Eu2b) and substitutional disorder with (Si/Al)₂(O/N). The structure is generalized to the formula A_4-mB_nC_19+2mX_29+m (A = Sr, La, Eu, Ce; B = Li; C = Si, Al; X = O, N; 0 ≤ m ≤ 1; 0 ≤ n ≤ 1), of which Sr_3.61LiSi_14.27Al_5.61O_6.19N_23.25 (Sr-sialon, m = 0.41, n = 1) and La_2.85Sr_0.76LiSi_14.86Al_4.93O_2.89N_26.51 (LaSr-sialon, m = 0.40, n = 1) are two examples that have been obtained as a single-phase powder. Sr-sialon:Eu and LaSr-sialon:Eu both show blue to yellow emission, depending on the Eu concentration, whereas Sr-sialon:1% Ce shows a deep-blue emission band centered at 422 nm with a full width at half-maximum of 80 nm and an internal quantum efficiency of 80% (λ_ex = 355 nm). The latter phosphor has very good thermal stability of both emission intensity and color. A white light-emitting diode (LED) containing the newly discovered Sr-sialon:5% Ce as the blue phosphor component shows excellent color-rendering indices (R_a = 96 and R₁₂ = 97) with a correlated color temperature of 4255 K. This indicates that Sr-sialon:Ce is a highly promising deep-blue phosphor for illumination grade white LEDs.

Transparent Ceramics Enabling High Luminous Flux and Efficacy for the Next-Generation High-Power LED Light

By designing novel chemical compositions and controlling precursor powders, perfect transparent ceramics (TCs) of Gd₃Al₄GaO₁₂:2%Ce³⁺ garnets (GAGG:2%Ce³⁺) were achieved for the first time. Ce³⁺ distributions in ceramics were revealed by micromorphology and micro-cathodoluminescence. Benefiting from the components that are rich in red emission, warm light with a correlated color temperature of about 2800 K was generated when TC was used in high-power (hp) blue light emitting diodes (LEDs) (∼450 nm, ∼34 W driven at 1 A). The hp LED device shows high brightness with a luminous flux nearly 2100 lm. The luminous efficacy even reaches 388 lm/W, which is the highest value reported till now, indicating that the use of GAGG:2%Ce³⁺ TCs promises energy saving. We believe that this work will open a new perspective to develop TCs for next-generation hp LED lighting to substitute traditional hp xenon lamps and high-pressure sodium lamps.

Blue, green, and red full-color ultralong afterglow in nitrogen-doped carbon dots

Carbon dots (CDs) with tunable emission colors and multiple emission modes are highly desirable in advanced optical anti-counterfeiting. Some pioneering efforts to trigger additional long-lived emission modes, nevertheless, did not perfectly solve the issue of printability and color-tunability in practical applications. Herein, we developed an encapsulating-dissolving-recrystallization route for the synthesis of CD-based anti-counterfeiting inks, and accordingly realized blue, green, and red full-color afterglow emissions from these CD-based inks when printed on paper. The printed inks simultaneously possessed triple emission modes including fluorescence (FL), delayed fluorescence (DF), and room-temperature phosphorescence (RTP), among which the long-lived emissions (DF and RTP) could be selectively activated by using different excitation wavelengths. We believe that the proposed synthetic route in this work may promote the development of multicolor-encoded and multiple-mode-integrated optical anti-counterfeiting systems, and will expand the application of CD-based materials to the fields of sensing, photodynamic therapy and bio-imaging.

[Interventional effect of bicyclol on isoniazid-induced liver injury in rats and the expression of glucose-regulated protein 78, and growth arrest and DNA-damage-inducible gene 153]

Objective: To investigate the interventional effect of bicyclol on isoniazid-induced liver injury in rats and the expression of endoplasmic reticulum stress (ERS) protein, glucose regulatory protein 78 (GRP78), and growth arrest and DNA-damage-inducible gene 153(CHOP). Methods: Eighty Wistar rats were randomly divided into control group (8 rats) and model group (72 rats). After 10 days of intragastric administration of isoniazid, the model group rats were randomly divided into treatment group (A), natural recovery group (B), etiological persistence group (C) and etiological persistence plus treatment group (D). Sixteen rats from each group were sacrificed after 1 and 2 weeks of intervention with different methods. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected. Liver pathological morphology was observed. Apoptotic cells were detected by TUNEL assay. ERS protein expression was detected by Western blot. A t-test or randomized block analysis of variance, K-S test and Levene's test were used to analyze the normality and homogeneity of variance. Kruskal-Wallis rank sum test was used for data that did not suit the conditions of t-test and variance analysis. Results: ALT and AST were elevated in the model group, and liver pathological examination showed liver tissue damage. Apoptotic index was higher than control group (7.13% ± 1.55% vs. 0.75% ± 0.71%, Z = -3.411, P < 0.01), and the expression value of ERS protein in model group was significantly higher than control group (GRP78: 1.16 ± 0.30 vs. 0.23 ± 0.05, t = -6.008, P < 0.01; CHOP: 0.98±0.23 vs. 0.20 ± 0.10, t = -6.378, P < 0.01). Serum enzymes, apoptotic index and ERS protein expressions of rats were decreased after treatment with bicyclol, and the pathological damage was eased. Rats in natural recovery group recovered less than the treatment group. Conclusion: Isoniazid-induced liver injury is associated to ERS-related excessive apoptosis and the therapeutic effect of bicyclol on drug-induced liver injury may minimize ERS-induced apoptosis.

Warm White Light with a High Color-Rendering Index from a Single Gd3Al4GaO12:Ce3+ Transparent Ceramic for High-Power LEDs and LDs

Transparent ceramics (TCs) are promising for high-power (hp) white light-emitting diode (WLED) and laser diode (LD) lighting. However, comfortable warm white light has not been achieved only using a single TC in hp-WLEDs/LDs. Herein, highly transparent Gd₃Al₄GaO₁₂:Ce³⁺ (GAGG:Ce³⁺) TCs (transmittance, T = 55.9-80.2%) were prepared via a solid-state reaction. Ce³⁺ as a doped activator center in grains plays a positive role in luminescence based on the microstructural investigations by scanning electron microscopy and the cathodoluminescence system. T decreases upon increasing the Ce³⁺ concentration and/or the ceramic thickness, whereas the luminous efficacy of hp-WLEDs/LDs goes up. For blue hp-LEDs driven at 350 mA or LDs of 2 W, warm white light with a low correlated-color temperature of ∼3000 K was achieved by a single GAGG:Ce³⁺ TC, benefiting from its broad emission band (full width at half maximum, FWHM = 133-137 nm) and abundant red components (peaking at about 568-574 nm). The color-rendering index of hp-WLEDs reaches 78.9. These results are much better than the performance of the traditional Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) TC, indicating that GAGG:Ce³⁺ TCs are promising color converters for hp-WLEDs/LDs with a comfortable warm white light.

Chromium-Doped Zinc Gallogermanate@Zeolitic Imidazolate Framework-8: A Multifunctional Nanoplatform for Rechargeable In Vivo Persistent Luminescence Imaging and pH-Responsive Drug Release

Multifunctional theranostic nanoplatforms greatly improve the accuracy and effectiveness in tumor treatments. Much effort has been made in developing advanced optical imaging-based tumor theranostic nanoplatforms. However, autofluorescence and irradiation damage of the conventional fluorescence imaging technologies as well as unsatisfied curative effects of the nanoplatforms remain great challenges against their wide applications. Herein, we constructed a novel core-shell multifunctional nanoplatform, that is, chromium-doped zinc gallogermanate (ZGGO) near-infrared (NIR) persistent luminescent nanoparticles (PLNPs) as a core and zeolitic imidazolate framework-8 (ZIF-8) as a shell (namely ZGGO@ZIF-8). The ZGGO@ZIF-8 nanoplatform possessed dual functionalities of the autofluorescence-free NIR PersL imaging as well as the pH-responsive drug delivery, thus it has high potential in tumor theranostics. Notably, the loading content of doxorubicin (DOX) in ZGGO@ZIF-8 (LC = 93.2%) was quite high, and the drug release of DOX-loaded ZGGO@ZIF-8 was accelerated in an acidic microenvironment such as tumor cells. The ZGGO@ZIF-8 opens up a new material system in the combination of PLNPs with metal-organic frameworks and may offer new opportunities for the development of advanced multifunctional nanoplatforms for tumor theranostics, chemical sensing, and optical information storage.

Improved stability of CsPbBr3 perovskite quantum dots achieved by suppressing interligand proton transfer and applying a polystyrene coating

All-inorganic lead halide perovskite quantum dots (PQDs) have shown great promise for optoelectronic applications due to their unique optical and electrical properties. However, their poor stability against moisture, UV light or thermal attacks greatly hinders their practical applications. One of the reasons for this instability is the proton transfer between oleic acid (OA) and oleylamine (OLA), which induces serious ligand loss. The idea of this work is to prevent the interligand proton transfer by replacing OLA with cetyl trimethylammonium bromide (CTAB) that cannot be protonated. The synthesized CsPbBr₃ PQDs in solution show high photoluminescence quantum yields up to 71% and also exhibit higher stability against acetone than the counterparts synthesized using oleylammonium bromide (OLABr). Subsequently, CsPbBr₃ PQDs with a peak wavelength of 515 nm (g-CsPbBr₃) synthesized using CTAB are further composited with a polymer of carboxyl-functionalized polystyrene (cPS). The composite shows enhanced thermal and moisture stability. It is demonstrated that this green-emitting composite can produce high color gamut (130%) white light-emitting diodes when combined with the K₂SiF₆:Mn⁴⁺ phosphor and a blue InGaN chip, enabling its use in display backlights.

Synthesis of Eu2+/Eu3+ Co-Doped Gallium oxide nanocrystals as a full colour converter for white light emitting diodes

Eu²⁺ and Eu³⁺ co-doped Ga₂O₃ nanocrystals (Ga₂O₃:Eu NCs) were synthesized in an organic phase at a low reaction temperature of 300 °C. The surface of Ga₂O₃:Eu NCs was passivated by oleylamine (OAm) and acetylacetone (acac). The coexistence of Eu²⁺ and Eu³⁺ as well as passivation by acac and OAm enable Ga₂O₃ to be excited in the broad spectral range of 200-500 nm. The broadened absorption band is attributed to the strong acac → Ln(III) ligand to the metal charge transfer transition at ∼370 nm, Eu(III) f-f allowed ⁷F₀ → ⁵L₆ transition at 395 nm, and ⁷F₀ → ⁵D₂ transition at 465 nm, as well as the efficient electronic transition of Eu(II) 4f → 5d at ∼400 nm. Under near-ultraviolet excitation, white light emission can be achieved by combining orange-red light from f-f electronic transition of Eu(III) with blue-green-yellow light from Ga₂O₃ oxygen defects levels. Furthermore, the resultant Ga₂O₃:Eu NCs with optimized quantum yield of 14.5% were coated onto 395 nm near-ultraviolet chips to fabricate a white light emitting diode. It exhibits a luminous efficiency of 34 lm/W, CIE colour coordinate of (0.2964, 0.2831) and high colour rendering index of 80.

Tailoring Trap Depth and Emission Wavelength in Y3Al5- xGa xO12:Ce3+,V3+ Phosphor-in-Glass Films for Optical Information Storage

Deep-trap persistent luminescent materials, due to their exceptional ability of energy storage and controllable photon release under external stimulation, have attracted considerable attention in the field of optical information storage. Currently, the lack of suitable materials is still the bottleneck that restrains their practical applications. Herein, we successfully synthesized a series of deep-trap persistent luminescent materials Y₃Al_{5- x}Ga _xO₁₂:Ce³⁺,V³⁺ ( x = 0-3) with a garnet structure and developed novel phosphor-in-glass (PiG) films containing these phosphors. The synthesized PiG films exhibited sufficiently deep traps, narrow trap depth distributions, high trap density, high quantum efficiency, and excellent chemical stability, which solved the problem of chemical stability at high temperatures in the reported phosphor-in-silicone films. Moreover, the trap depth in the phosphors and PiG films could be tailored from 1.2 to 1.6 eV, thanks to the bandgap engineering effect, and the emission color was simultaneously changed from green to yellow due to the variation of crystal field strength. Image information was recorded on the PiG films by using a 450 nm blue-light laser in a laser direct writing mode and the recorded information was retrieved under high-temperature thermal stimulation or photostimulation. The Y₃Al_{5- x}Ga _xO₁₂:Ce³⁺,V³⁺ PiG films as presented in this work are very promising in the applications of multidimensional and rewritable optical information storage.

Color-Tunable and High-Efficiency Dye-Encapsulated Metal-Organic Framework Composites Used for Smart White-Light-Emitting Diodes

Luminescent metal-organic frameworks (MOFs) (typically dye-encapsulated MOFs) are considered as one kind of interesting downconversion materials for white-light-emitting diodes (LEDs), but their quantum efficiency (QE) is not sufficient and thus needs to be significantly enhanced for practical applications. In this study, we successfully synthesized a series of Rh@bio-MOF-1 (Rh = rhodamine) with an internal QE as high as ∼79% via a solvothermal reaction followed by cation exchanges. The high efficiency of the Rh@bio-MOF-1 composites was attributable to the high intrinsic luminescent efficiency of the selected Rh dyes, the confinement effect in the bio-MOF-1 host, and the uniform particle morphology. The emission maximum could be continuously tuned from 550 to 610 nm by controlling the species and concentration of encapsulated dye molecules, showing great color tunability of the dye-encapsulated MOFs. The emission lifetime of ∼7 ns was 1 or 2 magnitude orders shorter than that of Ce³⁺- or Eu²⁺-doped inorganic phosphors, allowing for visible light communication (VLC). White LEDs, fabricated by using the synthesized Rh@bio-MOF-1 composite and inorganic phosphors of green (Ba,Sr)₂SiO₄:Eu²⁺ and red CaAlSiN₃:Eu²⁺, exhibited a high color rendering index of 80-94, a luminous efficacy of 94-156 lm/W, and an excellent stability in color point against drive current. The Rh@bio-MOF-1 composites with tunable colors, short emission lifetime, and high QE are expected to be used for smart white LEDs with multifunctions of both lighting and VLC.

Achieving deep-red-to-near-infrared emissions in Sn-doped Cu-In-S/ZnS quantum dots for red-enhanced white LEDs and near-infrared LEDs

Semiconductor quantum dots (QDs) are promising luminescent materials for use in lighting, display and bio-imaging, and the color tuning is a necessity for such applications. In this work, we report tunable colors and deep-red or near infrared (NIR) emissions in Cu-In-S and Cu-In-S/ZnS QDs by incorporating Sn. These QDs (with a size of 5 nm) with varying Sn concentrations and/or Cu/In ratios were synthesized by a non-injection method, and characterized by a variety of analytical techniques (i.e., XRD, TEM, XPS, absorption, photoluminescence, decay time, etc.). The Cu-Sn-In-S and Cu-Sn-In-S/ZnS QDs with Cu/In = 1/2 show the emission maximum in the ranges of 701-894 nm and 628-785 nm, respectively. The red-shift in emission is ascribed to the decrease of the band gap with the Sn doping. The highest quantum yield of 75% is achieved in Cu-Sn-In-S/ZnS with 0.1 mmol Sn and Cu/In = 1/2. Both the white and NIR LEDs were fabricated by using Cu-Sn-In-S/ZnS QDs and a 365 nm LED chip. The white LED exhibits superhigh color rendering indices of Ra = 97.2 and R9 = 91 and a warm color temperature of 2700 K. And the NIR LED shows an interesting broadband near-infrared emission centered at 741 nm, allowing for applications in optical communication, sensing and medical devices.

Unique Color Converter Architecture Enabling Phosphor-in-Glass (PiG) Films Suitable for High-Power and High-Luminance Laser-Driven White Lighting

As a next-generation high-power lighting technology, laser lighting has attracted great attention in high-luminance applications. However, thermally robust and highly efficient color converters suitable for high-quality laser lighting are scarce. Despite its versatility, the phosphor-in-glass (PiG) has been seldom applied in laser lighting because of its low thermal conductivity. In this work, we develop a unique architecture in which a phosphor-in-glass (PiG) film was directly sintered on a high thermally conductive sapphire substrate coated by one-dimensional photonic crystals. The designed color converter with the composite architecture exhibits a high internal quantum efficiency close to that of the original phosphor powders and an excellent packaging efficiency up to 90%. Furthermore, the PiG film can even be survived under the 11.2 W mm^-2 blue laser excitation. Combining blue laser diodes with the YAG-PiG-on-sapphire plate, a uniform white light with a high luminance of 845 Mcd m^-2(luminous flux: 1839 lm), luminous efficacy of 210 lm W^-1, and correlated color temperature of 6504 K was obtained. A high color rendering index of 74 was attained by adding a robust orange or red phosphor layer to the architecture. These outstanding properties meet the standards of vehicle regulations, enabling the PiG films with the composite architecture to be applied in automotive lighting or other high-power and high-luminance laser lighting.

Down-Conversion Nitride Materials for Solid State Lighting: Recent Advances and Perspectives

Advances in solid state white lighting technologies witness the explosive development of phosphor materials (down-conversion luminescent materials). A large amount of evidence has demonstrated the revolutionary role of the emerging nitride phosphors in producing superior white light-emitting diodes for lighting and display applications. The structural and compositional versatility together with the unique local coordination environments enable nitride materials to have compelling luminescent properties such as abundant emission colors, controllable photoluminescence spectra, high conversion efficiency, and small thermal quenching/degradation. Here, we summarize the state-of-art progress on this novel family of luminescent materials and discuss the topics of materials discovery, crystal chemistry, structure-related luminescence, temperature-dependent luminescence, and spectral tailoring. We also overview different types of nitride phosphors and their applications in solid state lighting, including general illumination, backlighting, and laser-driven lighting. Finally, the challenges and outlooks in this type of promising down-conversion materials are highlighted.

Achieving Multicolor Long-Lived Luminescence in Dye-Encapsulated Metal-Organic Frameworks and Its Application to Anticounterfeiting Stamps

Long-lived luminescent metal-organic frameworks (MOFs) have attracted much attention due to their structural tunability and potential applications in sensing, biological imaging, security systems, and logical gates. Currently, the long-lived luminescence emission of such inorganic-organic hybrids is dominantly confined to short-wavelength regions. The long-wavelength long-lived luminescence emission, however, has been rarely reported for MOFs. In this work, a series of structurally stable long-wavelength long-lived luminescent MOFs have been successfully synthesized by encapsulating different dyes into the green phosphorescent MOFs Cd(m-BDC)(BIM). The multicolor long-wavelength long-lived luminescence emissions (ranging from green to red) in dye-encapsulated MOFs are achieved by the MOF-to-dye phosphorescence energy transfer. Furthermore, the promising optical properties of these novel long-lived luminescent MOFs allow them to be used as ink pads for advanced anticounterfeiting stamps. Therefore, this work not only offers a facile way to develop new types of multicolor long-lived luminescent materials but also provides a reference for the development of advanced long-lived luminescent anticounterfeiting materials.

Trap Depth Engineering of SrSi2O2N2:Ln2+,Ln3+ (Ln2+ = Yb, Eu; Ln3+ = Dy, Ho, Er) Persistent Luminescence Materials for Information Storage Applications

Deep-trap persistent luminescence materials exhibit unique properties of energy storage and controllable photon release under additional stimulation, allowing for both wavelength and intensity multiplexing to realize high-capacity storage in the next-generation information storage system. However, the lack of suitable persistent luminescence materials with deep traps is the bottleneck of such storage technologies. In this study, we successfully developed a series of novel deep-trap persistent luminescence materials in the Ln²⁺/Ln³⁺-doped SrSi₂O₂N₂ system (Ln²⁺ = Yb, Eu; Ln³⁺ = Dy, Ho, Er) by applying the strategy of trap depth engineering. Interestingly, the trap depth can be tailored by selecting different codopants, and it monotonically increases from 0.90 to 1.18 eV in the order of Er, Ho, and Dy. This is well explained by the energy levels indicated in the host-referred binding energy scheme. The orange-red-emitting SrSi₂O₂N₂:Yb,Dy and green-emitting SrSi₂O₂N₂:Eu,Dy phosphors are demonstrated to be good candidates of information storage materials, which are attributed to their deep traps, narrow thermoluminescence glow bands, high emission efficiency, and excellent chemical stability. This work not only validates the suitability of deep-trap persistent luminescence materials in the information storage applications, but also broadens the avenue to explore such kinds of new materials for applications in anticounterfeiting and advanced displays.

Significantly enhanced photoluminescence and thermal stability of La3Si8N11O4:Ce3+,Tb3+via the Ce3+ → Tb3+ energy transfer: a blue-green phosphor for ultraviolet LEDs

The peak emission intensity and thermal stability of Tb³⁺ in codoped La₃Si₈N₁₁O₄:Ce,Tb sample are strongly enhanced via Ce³⁺ to Tb³⁺ energy transfer.

Ce-Doped La3Si6.5Al1.5N9.5O5.5, a Rare Highly Efficient Blue-Emitting Phosphor at Short Wavelength toward High Color Rendering White LED Application

Phase pure nondoped and Ce doped La₃Si_6.5Al_1.5N_9.5O_5.5 (Al containing La N-phase) samples have been obtained by solid-state reaction synthesis for the first time. 1% Ce-doped La₃Si_6.5Al_1.5N_9.5O_5.5 phosphor displays a broad excitation band ranging from UV to 410 nm, with a maximum at 355 nm. UV light excitation results in a narrow Ce³⁺ 5d-4f emission band (fwhm = 68 nm) centered at 418 nm. The emission can be tuned from 417 nm at 0.5% Ce to 450 nm at 50% Ce. A high internal quantum efficiency up to 84% is achieved for a 1% Ce doped sample, which has CIE chromaticity coordinates of x = 0.157 and y = 0.069, close to the NTSC blue standard (x = 0.155; y = 0.070). Compared to La₃Si₈O₄N₁₁:Ce phosphor, the quantum efficiency and thermal stability have been enhanced for La₃Si_6.5Al_1.5N_9.5O_5.5:Ce phosphor without shifting the emission peak wavelength. La₃Si_6.5Al_1.5N_9.5O_5.5:Ce shows less thermal quenching than La₃Si₈O₄N₁₁:Ce and no shift or change in the shape of emission spectra with increasing the temperature from 4 to 573 K. These results show that La₃Si_6.5Al_1.5N_9.5O_5.5:Ce is more efficient than any other (oxy-)nitride phosphor with an emission in the short wavelength blue region (400-450 nm). A white LED was fabricated using the La₃Si_6.5Al_1.5N_9.5O_5.5:5%Ce as a blue phosphor. The high color rendering index (Ra = 93.2, R9 = 91.4, and R12 = 89.5) obtained shows that the phosphor is a very promising conversion phosphor for white LEDs.

Realizing superior white LEDs with both high R9 and luminous efficacy by using dual red phosphors

An unique spectral configuration was designed to improve both luminous efficacy and color rendering by using dual red phosphors.

Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and flexibility of their emission properties can be achieved by controlling their composition and dopants. However, a lot of work is still required to improve their properties and to reduce the production cost. A possible approach is to correlate the luminescence properties of the Sialon particles with their local structural and chemical environment in order to optimize their growth parameters and find novel phosphors. For such a purpose, the low-voltage cathodoluminescence (CL) microscopy is a powerful technique. The use of electron as an excitation source allows detecting most of the luminescence centers, revealing their luminescence distribution spatially and in depth, directly comparing CL results with the other electron-based techniques, and investigating the stability of their luminescence properties under stress. Such advantages for phosphors characterization will be highlighted through examples of investigation on several Sialon phosphors by low-energy CL.