Thermal Quenching Mechanism of Mn in NaSiF, NaKSiF, and KSiF Phosphors: Insights from the First-Principles Analysis.

This study aims to identify the key factors governing the thermal quenching of Mn ion luminescence in fluoride-based phosphor materials used as red emitters in modern-day phosphor-converted LED devices. Here, we employ first-principles calculations for Mn-doped NaSiF, NaKSiF, and KSiF hosts to explore how host properties and local coordination environments influence thermal quenching behavior. The ΔSCF method was used to model the geometric structures of the MnA (ground) and E, T (excited) states and the energies of the optical transitions between these states.

Enhancement of NIR-II Emission of Er by Doping Fe in Double Perovskites: Multimode Luminescence for Versatile Optoelectronic Applications.

Erbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near-infrared range. However, achieving high-efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f-4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near-infrared region (NIR-II) emission in CsNaBiCl by incorporating Fe ions.

Excitation-wavelength-dependent persistent luminescence from single-component nonstoichiometric CaGaO:Bi for dynamic anti-counterfeiting.

Materials capable of dynamic persistent luminescence (PersL) within the visible spectrum are highly sought after for applications in display, biosensing, and information security. However, PersL materials with eye-detectable and excitation-wavelength-dependent characteristics are rarely achieved. Herein, a nonstoichiometric compound CaGaO:Bi (x < 2) is present, which demonstrates ultra-long, color-tunable PersL.

Dual-Emission Origins in Bi-Doped O Sesquioxides ( = Sc, Y, Gd and Lu): A First-Principles Study.

Bi-doped sesquioxides exhibit dual emissions, marked by distinct Stokes shift and bandwidth, meaning unraveling their underlying origins is particularly intriguing. In this study, we employ first-principles calculations to investigate the luminescence mechanisms within the O:Bi ( = Sc, Y, Gd, Lu) series, with the goal of addressing the posed inquiry. Our investigation commences with the analysis of the site occupancy and charge state of bismuth ions in the two cationic sites through formation energy calculations.

Unraveling Broadband Near-Infrared Luminescence in Cr-Doped CaYGeO Garnets: Insights from First-Principles Analysis.

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr-doped CaYGeO garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr activator ions, which revealed a pronounced preference for the Y sites over the Ca and Ge sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states E and T, along with their optical transition energies relative to the ground state A in CaYGeO:Cr, were successfully modeled using the ΔSCF method.

Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn Luminescence in the Double Perovskites, BaTaO ( = Y, Lu, Sc).

The spectroscopic properties of the Mn ion are investigated in the series of isostructural double perovskite compounds, BaTaO ( = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B-Ta cations on the energy and intensity of the MnE → A emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy.

Deep-blue narrow-band emissive cesium europium bromide perovskite nanocrystals with record high emission efficiency for wide-color-gamut backlight displays.

Lead halide perovskite nanocrystals (NCs) are highly promising for backlighting display applications due to their high photoluminescence quantum yields (PLQYs) and wide color gamut values. However, the practical applications of blue emitters are limited due to the toxicity of lead, unstable structure, and unsatisfactory PLQY. Herein, we report the successful synthesis of divalent europium-based perovskite CsEuBr NCs using a modified hot injection method.

Aqueous-Based Inorganic Colloidal Halide Perovskites Customizing Liquid Scintillators.

Compared to solid scintillators and organic liquid scintillators, aqueous-based liquid scintillators (AbLS) have more superiority in highly flexible scalability, yet are now limited by their low light yield (≈100 photons MeV ). Here, aqueous-based inorganic colloidal halide perovskites with high photoluminescence quantum yield (PLQY) of three primary color luminescence up to 88.1% (red), 96% (green), and 81.

Intervalence charge transfer of Cr-Cr aggregation for NIR-II luminescence.

The increasing demand for high-contrast biological imaging, non-destructive testing, and infrared night vision can be addressed by the development of high-performance NIR light-emitting materials. Unlike lanthanide (Ln) with sharp-line multiplets and isolated Cr with NIR-I emission, this study reports the first-ever NIR-II broadband luminescence based on the intervalence charge transfer (IVCT) of Cr-Cr aggregation in gallate magentoplumbite. In particular, LaMgGaO:0.

Mechanistic insights for regulating the site occupancy, valence states and optical transitions of Mn ions in yttrium-aluminum garnets codoping.

The site-dependent photoluminescence of activators can be regulated by the sintering atmosphere, coexistence conditions, and especially cation codoping, which have been intensively studied for design and optimization of optical functional materials. Here, first-principles calculations are performed to determine the regulation of the site occupancy, valence states and optical transitions of Mn activators codoping in yttrium aluminum garnets (YAGs), which contain three different cation sites. Without any codopants, Mn dominates in defect concentration and photoluminescence, which can hardly be tuned by the sintering atmosphere or coexistence conditions of YAGs with other competing compounds.

Tb Ion Optical and Magneto-Optical Properties in the Cubic Crystals KTbF.

The optical and magneto-optical characteristics of KTb3F10 crystals in the transition region of 5D4 → 7F6 4f8 configurations of the Tb3+ ion at temperatures of 90 and 300 K were studied. The schemes of the optical transitions in the KTb3F10 crystals were constructed, and the energies of most of the Stark sublevels of the ground 7F6 and excited 5D4 multiplets of the Tb3+ ion split by the C4v symmetry crystal environment were determined. The presence of three- and two-doublet states in the energy spectra of the Tb3+ion multiplets 7F6 and 5D4, respectively, was established, which is in good agreement with theoretical predictions.

Mn-activated CaBa(PO)O near-infrared phosphor and its application in luminescence thermometry.

The near-infrared luminescence of CaBa(PO)O:Mn is demonstrated and explained. When excited into the broad and strong absorption band that spans the 500-1000 nm spectral range, this phosphor provides an ultranarrow (FWHM = 5 nm) emission centered at 1140 nm that originates from a spin-forbidden E → A transition with a 37.5% internal quantum efficiency and an excited-state lifetime of about 350 μs.

Angular Jahn-Teller Effect and Photoluminescence of the Tetrahedral Coordinated Mn Activators in Solids-A First-Principles Study.

First-principles calculations based on density functional theory have been performed to investigate the electronic structure, excited-state Jahn-Teller distortion, and photoluminescence of the multielectron system of the strongly covalent tetrahedral coordinated Mn activator in solids. The electronic structure of the T and A/E excited states is analyzed, and Slater's transition-state method and occupation matrix control methodology are applied to deal with the spin contamination in the lower-spin excited states, which is due to the mixing of the ground state of the same spin projection number. In a series of covalent tetrahedral coordinations, the A → T and A/E excitations and the T → A emission energies are obtained and compared to the reported experimental results.

Efficient Broadband Near-Infrared Emission from Lead-Free Halide Double Perovskite Single Crystal.

Ultra-broadband near-infrared (NIR) luminescent materials are the most important component of NIR light-emitting devices (LED) and are crucial for their performance in sensing applications. A major challenge is to design novel NIR luminescent materials to replace the traditional Cr -doped systems. We report an all-inorganic bismuth halide perovskite Cs AgBiCl single crystal that achieves efficient broadband NIR emission by introducing Na ions.

Solar-Driven Overproduction of Biofuels in Microorganisms.

Microbial cell factories reinvigorate current industries by producing complex fine chemicals at low costs. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is the main reducing power to drive the biosynthetic pathways in microorganisms. However, insufficient intrinsic NADPH limits the productivity of microorganisms.

The photoluminescence of isolated and paired Bi ions in layered LnOCl crystals: a first-principles study.

Luminescent s centers have shown great potential for applications as phosphors and scintillators. First-principles calculations based on density functional theory are performed to systematically analyze the luminescent centers of isolated and paired Bi(6s) ions in layered LnOCl (Ln = Y, Gd, La) crystals. The spin-orbit coupling and orbital hybridization both show important effects on the luminescence properties.

Experimental and Theoretical Studies of the Site Occupancy and Luminescence of Ce in LiSr(BO) for Potential X-ray Detecting Applications.

Ce-doped LiSr(BO) phosphors have been prepared by a high-temperature solid-state reaction method, and structural refinement of the host compound has been performed. The excitation and emission spectra in the vacuum ultraviolet-ultraviolet-visible range at cryogenic temperatures reveal that Ce ions preferentially occupy eight-coordinated Sr sites in LiSr(BO). Such experimental attribution is well corroborated by the calculated 4f-5d transition energies and defect formation energies of Ce ions at two distinct Sr sites in the first-principles framework.

Influence of Isostatic Pressure on the Elastic and Electronic Properties of KSiF:Mn.

Isostatic pressure effects on the elastic and electronic properties of non-doped and Mn-doped KSiF (KSF) have been investigated by first-principles calculations within density functional theory (DFT). Bulk modulus was obtained by the Murnaghan's equation of states (EOS) using the relationship between volume and pressures at pressures between 0 and 40 GPa, and elastic constants were calculated by the stress-strain relationship giving small distortions at each pressure point. The other elastic parameters such as shear modulus, sound velocity and Debye temperature, which can be obtained from the elastic constants, were also estimated.

Self-Activated and Bismuth-Related Photoluminescence in Rare-Earth Vanadate, Niobate, and Tantalate Series-A First-Principles Study.

Rare-earth vanadates, niobates, and tantalates have shown self-activated and Bi-activated emissions. Their intrinsic emission has been attributed to self-trapped excitons (STEs), but the detailed information concerning the geometric and electronic structures of the excited states has remained unknown. Regarding the Bi dopants in these hosts, the luminescence has been attributed to two different mechanisms, .

First Principles Calculations of Atomic and Electronic Structure of TiAl3+- and TiAl2+-Doped YAlO.

In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti and Ti ions substituted for the host Al atom in orthorhombic bulk YAlO crystals. The disordered crystalline structure of YAlO was modelled in a large supercell containing 160 atoms, allowing simulation of a substitutional dopant with a concentration of about 3%. In the case of the Ti-doped YAlO, compensated -center (oxygen vacancy with two trapped electrons) is inserted close to the Ti to make the unit cell neutral.

Systematic Analysis of the Crystal Chemistry and Eu Spectroscopy along the Series of Double Perovskites CaLnSbO (Ln = La, Eu, Gd, Lu, and Y).

Eu (1 mol %)-doped CaLnSbO (replacing Ln; Ln = Lu, Y, Gd, and La) and CaEuSbO were synthesized and structurally characterized by means of X-ray powder diffraction. The Eu luminescence spectroscopy of the doped samples and of CaEuSbO has been carefully investigated upon collection of the excitation/emission spectra and luminescence decay curves of the main excited states. Surprisingly, apart from the dominant red emission from D, all the doped samples show an uncommon blue and green emission contribution from D ( = 1, 2, and 3).

Efficient Luminescence from CsPbBr Nanoparticles Embedded in CsPbBr.

CsPbBr is regarded as an outstanding luminescent material with good thermal stability and optical performance. However, the mechanism of green emission from CsPbBr has been controversial. Here we show that isolated CsPbBr nanoparticles embedded within a CsPbBr matrix give rise to a "normal" green luminescence while superfluorescence at longer wavelengths is suppressed.

Unraveling the Near-Unity Narrow-Band Green Emission in Zero-Dimensional Mn-Based Metal Halides: A Case Study of (CHN)ZnMnBr Solid Solutions.

Zero-dimensional (0D) Mn-based metal halides are potential candidates as narrow-band green emitters, and thus it is critical to provide a structural understanding of the photophysical process. Herein, we propose that a sufficiently long Mn-Mn distance in 0D metal halides enables all Mn centers to emit spontaneously, thereby leading to near-unity photoluminescence quantum yield. Taking lead-free (CHN)ZnMnBr ( = 0-1) solid solution as an example, the Zn/Mn alloying inhibits the concentration quenching that is caused by the energy transfer of Mn.

High-security-level multi-dimensional optical storage medium: nanostructured glass embedded with LiGaO: Mn with photostimulated luminescence.

The launch of the big data era puts forward challenges for information preservation technology, both in storage capacity and security. Herein, a brand new optical storage medium, transparent glass ceramic (TGC) embedded with photostimulated LiGaO: Mn nanocrystals, capable of achieving bit-by-bit optical data write-in and read-out in a photon trapping/detrapping mode, is developed. The highly ordered nanostructure enables light-matter interaction with high encoding/decoding resolution and low bit error rate.