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Owing to the excellent optical properties, white light‐emitting diodes (WLEDs) based on metal halide perovskites have attracted great attention as promising light source for solid‐state lighting and wireless visible light communication (VLC). However, the instability and toxicity of classic hybrid lead halides hinder their practical applications. Here, a pressure‐assisted cooling method is developed to grow lead‐free Cs3Cu2I5 and CsCu2I3 single crystals, which exhibit more excellent stability, larger size and uniform orientations in comparison with pressure‐free cooling method. Then, both single crystals are used as the emitters of WLEDs without encapsulation, exhibiting a high Color Rendering Index of 91, a decent Commission Internationale de l'Eclairage coordinate of (0.33, 0.33), a proper Correlated Color Temperature of 5436 K, as well as an excellent 1350‐h operating stability at atmosphere. Furthermore, the prepared WLEDs are utilized in wireless VLC, which possesses a −3 dB bandwidth of 10.1 MHz. The pressure‐assisted cooling method is developed to grow lead‐free Cs3Cu2I5 and CsCu2I3 single crystals, which exhibit more excellent stability, larger size and uniform orientations. This work can promote the development of copper halides and extend their practical applications in solid‐state lighting and wireless visible light communication.

In this work, Ba[sub.2]MgWO[sub.6]: Eu[sup.3+] (BMW: Eu[sup.3+]) ceramic materials with a double perovskite structure were sintered using the High-Pressure Low-Temperature sintering (HPLT) technique. As part of the research, the influence of pressure (CP), sintering temperature (CT), and sintering time (CTS) on the structure and luminescence of the doped BMW were determined. Structural analysis via XRD and SEM + EDS and spectroscopic analysis via emission and excitation spectra, decay time, and absorption spectra of the obtained ceramics were performed. Dense double perovskite ceramics were obtained with a cubic structure with optimal sintering parameters: T = 500 °C, p = 8 GPa, and t = 1 min. The increase in temperature caused an increased extinction of the luminescence due to the diffusion of carbon into the ceramics. The increase in pressure led to the formation of the amorphous phase, which increased the speed of non-radiative transitions and also led to the extinction of the luminescence. The increase in sintering time from 1 to 3 min enhanced the luminescence output, but when the ceramic was sintered for 5 min, the luminescence was quenched, most likely by increasing the rate of the non-radiative process, as evidenced by reduced decay time.

A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method. The effects of various Mn 2+ –Si 4+ pair doping levels on the structure, transmittance, and luminescence properties were systematically investigated. These transparent ceramics have average grain sizes of 10–16 μm, clean grain boundaries, and excellent transmittance up to 83.4% at 800 nm. Under the excitation of 460 nm, three obvious emission peaks appear at 533, 590, and 745 nm, which can be assigned to the transition 5d→4f of Ce 3+ and 4 T 1 → 6 A 1 of Mn 2+ . Thus, the Mn 2+ –Si 4+ pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light. After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode (LED) chips, correlated color temperature (CCT) as low as 3723 K and luminous efficiency (LE) as high as 96.54 lm/W were achieved, implying a very promising candidate for application in white light-emitting diodes (WLEDs) industry.

Sunlight has participated in the development of all life forms on Earth. The micro-world and the daily rhythms of plants and animals are strongly regulated by the light–dark rhythm. Human beings have followed this pattern for thousands of years. The discovery and development of artificial light sources eliminated the workings of this physiological clock. The world’s current external environment is full of light pollution. In many electrical light bulbs used today and considered “environmentally friendly,” such as LED devices, electrical energy is converted into short-wavelength illumination that we have not experienced in the past. Such illumination effectively becomes “biological light pollution” and disrupts our pineal melatonin production. The suppression of melatonin at night alters our circadian rhythms (biological rhythms with a periodicity of 24 h). This alteration is known as chronodisruption and is associated with numerous diseases. In this article, we present a blue-free WLED (white light-emitting diode) that can avoid chronodisruption and preserve circadian rhythms. This WLED also maintains the spectral quality of light measured through parameters such as CRI (color reproduction index).

As the world evolves, the demand for efficient lighting sources is rising rapidly, and to cater to the burgeoning demand for swift expansion, technological advancement in white light-emitting diodes (WLEDs) and lighting materials is crucial. In this work, the photoluminescence of La 2 O 3 single-doped (Tm, Ho, Eu), double-doped and triple-doped phosphors prepared by combustion synthesis was studied. XRD confirms hexagonal phase (-P6c2c) with lattice contraction on doping, supported by Rietveld refinement, while SEM shows agglomerated particles (~ 12 µm) and FTIR confirms La–O bonding. Under UV excitation, Tm 3 ⁺, Ho 3 ⁺ , and Eu 3 ⁺ give blue, green, and orange-red emission, respectively; in Ho 3 ⁺ doped samples, the small 5 F₄– 5 S 2 gap (~ 200 cm⁻ 1 ) compared to host phonon energy (~ 400 cm⁻ 1 ) leads to merged emission. Efficient energy transfer (Tm → Ho, Ho → Eu, Tm → Eu) is observed in co-doped and tri-doped systems, with La 2 O 3 :Tm/Ho/Eu phosphor showing a strong red component. These results suggest La 2 O 3 —based phosphors are promising candidates for WLEDs, barcode security, and multicolour LED applications.

This study reports the synthesis and characterization of Na 2 Ca 4 (PO 4 ) 3 F phosphor doped with Dy 3+ , Tb 3+ , and Eu 3+ ions were synthesized using a conventional solid-state method. The phase formation was confirmed by X-ray diffraction (XRD). Functional group analysis through Fourier transforms infrared spectroscopy (FTIR) and morphological evaluation via scanning electron microscope (SEM) and EDS revealed good crystallinity and elemental distribution. The triple-doped phosphor exhibited color-tunable emissions under near-UV excitation, covering the blue, green, yellow, and red regions, resulting in efficient white light output. Photoluminescence (PL) studies indicated effective energy transfer among the dopant ions. Additionally, the phosphor was applied as a down-conversion layer on silicon solar cells using the doctor blade technique. The coated cells showed a 16.33% improvement in efficiency compared to uncoated cells. The combined optical and photovoltaic performance highlights the potential of Na 2 Ca 4 (PO 4 ) 3 F: Dy 3+ /Tb 3+ /Eu 3+ as a multifunctional material for white light-emitting diodes and solar energy devices.

Artificial lighting is ubiquitous in modern society, with detrimental effects on sleep and health. The reason for this is that light is responsible not only for vision but also for non-visual functions, such as the regulation of the circadian system. To avoid circadian disruption, artificial lighting should be dynamic, changing throughout the day in a manner comparable to natural light in terms of both light intensity and associated color temperature. This is one of the main goals of human-centric lighting. Regarding the type of materials, the majority of white light-emitting diodes (WLEDs) make use of rare-earth photoluminescent materials; therefore, WLED development is at serious risk due to the explosive growth in demand for these materials and a monopoly on sources of supply. Photoluminescent organic compounds are a considerable and promising alternative. In this article, we present several WLEDs that were manufactured using a blue LED chip as the excitation source and two photoluminescent organic dyes (Coumarin 6 and Nile Red) embedded in flexible layers, which function as spectral converters in a multilayer remote phosphor arrangement. The correlated color temperature (CCT) values range from 2975 K to 6261 K, while light quality is preserved with chromatic reproduction index (CRI) values superior to 80. Our findings illustrate for the first time the enormous potential of organic materials for supporting human-centric lighting.

The development of novel phosphor materials with excellent performance and modification of their photoluminescence to meet the higher requirements for applications are the essential research subjects for luminescent materials. Multi-site luminescent materials with crystallographic sites for the activator ions that broaden the tunable range of luminescent spectra and even enhance the luminescent performance have attracted significant attention in the pursuit of high-quality luminescence for white light-emitting diodes. Here, we summarize multi-site luminescence characteristics based on the different kinds of host and activator ions, introduce the identifications of multi-site activator ions via optical analysis, provide a structural analysis and theoretical calculation methods, and introduce the regulation strategies and advance applications of multi-site phosphors. The review reveals the relationship between crystal structure and luminescent properties and discusses future opportunities for multi-site phosphors. This will provide guidance for the design and development of luminescent materials or other materials science.

The preparation of high-efficiency phosphor is the key to the construction of white light-emitting diode (WLED) devices and their application in indoor photovoltaics. Compared with YVO 4 , InVO 4 is not suitable as the host material of lanthanide ions because of its strong self-luminescence. Here, the work focused on combining the broadband emission from InVO 4 and the red luminescence from YVO 4 :Eu 3+ to obtain enhanced and stable multicolor luminescence. The band structure, density of state, and optical properties were studied by density functional theory. The spectral configuration of YVO 4 :In 3+ /Eu 3+ with (112) surface appears to be broadening and redshifts with increasing layer number. When the In 3+ concentration is 3.5 mol%, the YVO 4 :30%Eu 3+ /In 3+ emits the strongest light. The Judd-Ofelt parameter Ω 2 of YVO 4 :In 3+ /Eu 3+ increases with increaing In 3+ concentration, indicating that the symmetry decreases. By adjusting In 3+ /Eu 3+ contents, the YVO 4 :In 3+ /Eu 3+ not only can emit white light with a color rendering index of 95, but also can be used as high-efficiency red phosphor to build WLED devices with blue emitting N/Tb codoped carbon quantum dots (CQDs-N:Tb 3+ ) and green emitting MOF:Tb 3+ (MOF = metal organic framework), for which the color rendering index can also reach 95 and the color temperature is 5549 K. The manufactured WLED devices were further used to excite the silicon solar cell and make it show good photoelectric characteristics.

The role of site symmetry is one of the important parameters in the emission spectrum of the phosphor. The emission from the phosphor can be tuned due to alteration in the site symmetry by selecting appropriate synthesis procedure. The spectral shift in the emission spectrum can be achieved by variation in the coordination number (CN) or by tuning symmetry in a coordination environment. Few reported phosphors such as Eu2+ doped Ca3Mg3(PO4)4, Ba2CaMg2Si6O17 and Ca3Al2O6 where the spectral shift is noted are used in this review for the analysis.