Broad Blue Emission Research Articles

Investigating the influence of carbon dots on β-Ca2SiO4:Ce3+ phosphors derived from agro-waste for diverse applications

A series of blue-emitting composite based on 3 wt% carbon dots in β-Ca2SiO4:Ce3+ (3 wt% CDs@β-CSO:Ce3+) was synthesized through a hydrothermal method, aiming to enhance applications in latent fingerprint (LFP) detection, anti-counterfeiting (AC) measures, and optical thermometry. The X-ray diffraction (XRD) analysis confirmed that these phosphors possess a monoclinic crystal structure. Under 356 nm excitation, the Ce3+ doped β-Ca2SiO4 phosphors (β-CSO:Ce3+) display a broad blue emission peak at 431 nm, attributed to the 5d → 4f electric dipole transition of Ce3+, while the inclusion of Carbon dots (CDs) shifts this emission to 442 nm. This shift and the improved photoluminescence (PL) intensity are thought to result from the Fӧrster Resonance Energy Transfer (FRET) mechanism. The optimal concentration of Ce3+ ions was determined to be 5 mol%, as higher concentrations led to a decrease in emission intensity due to concentration quenching (CQ). Additionally, a fabricated white light diode using these phosphors achieved chromaticity coordinates of (0.344, 0.330) according to the Commission International de L'Eclairage (CIE), with the CIE, correlated colour temperature (CCT), and colour purity (CP) metrics indicating a bright green output with values of (0.1486, 0.0433), 1759 K, and 96.4%, respectively. The optimized 3 wt% CDs@β-CSO:5Ce3+ composite demonstrated a remarkable CP of 99.9%. Notably, the phosphors maintained 85.77% of their emission intensity at 423 K, showcasing exceptional thermal stability. A novel approach utilizing sketch pen and brush mode was developed to apply the optimized AC security ink, allowing for the creation of various intricate patterns. The resulting AC tags featured high resolution and durability. These findings underscore the 3wt%CDs@β-CSO:5Ce3+ composite as superior luminescent materials for use in fields requiring LFP, AC strategies, and optical thermometry.

Dual-modal optical temperature sensing based on Sb3+/Mn2+ co-doped Cs2NaYCl6 double perovskites

Optical temperature sensing based on luminescence intensity ratio shows significant potential in achieving accurate temperature detection. In this work, Sb3+/Mn2+ co-doped Cs2NaYCl6 double perovskites were synthesised via a hydrothermal method. Introducing Sb3+ ions to the host significantly enhances the radiative recombination of self-trapped excitons (STEs), resulting in a broad blue emission. The co-doping of Mn2+ ions to the composition leads to a tunable dual-emission in the spectra, originating from the energy transfer between the STEs and Mn2+ ions. The dependence of the dual-emission on temperature is employed for optical temperature sensing. The maximum relative sensitivity, optimal thermal resolution, and optimal thermal repeatability are determined as 1.40 % K−1, 0.002 K and 99.3% at 250 K, respectively. The results indicate that the synthesised Cs2NaYCl6: Sb3+/Mn2+ double perovskites are promising candidates for high-sensitivity optical thermometers.

Structural and optical properties of arsenic-oxide microcrystals on GaAs substrate for photonic applications

Nano and microstructure semiconductor heterostructures are employed for a wide variety of sensor and photonics applications. The present paper discusses the synthesis of arsenic-oxide microcrystals by using electroless chemical etching of GaAs (100) substrate surface using aqueous nitric acid for 1–5 min at room temperature. The structural and morphological analyses reveal that the density of the polycrystalline octahedron microcrystals (15–20 μm size) of arsenic-oxide increased with the etching duration. The sample surfaces are engulfed by the arsenic-oxide microcrystals after 2 min of etching. The chemical analysis of the samples established the arsenic-oxide phases formed due to the surface oxidation during the etching process. The samples showed no distinctive Ga3d chemical state etched for more than 2 min. The crystallite size (55.70–86.68 nm), strain (2.93–13.7 × 10−4), and dislocation density (1.331– 3.22 × 1010 cm−2) in the microcrystals are estimated from the x-ray diffraction analysis. The Raman spectra of the micro-crystalline arsenic-oxides showed a 6-7 cm−1 red shift from its respective reference peak due to the presence of tensile residual stress. The samples exhibited photoluminescence (PL) in the UV and blue wavelength ranges due to the near band-edge transition (298.5 nm) in the arsenic-oxide microcrystals and defects transitions (310 nm, 405 nm, 430 nm) in oxide species. The peak intensity of the broad blue emission increases with the etching time. The time-resolved PL (TRPL) results showed the exciton average lifetime of the crystals is less than 1 ns which predicts their possible use in fast optical sensing, flashes, and fast switching applications.

Proliferation in the photo-response characteristics of MDC thin films for optoelectronic applications through NSP technique

Nebulizer spray pyrolysis (NSP), a simple thin-film deposition method, was used to fabricate p-Si/n-manganese-doped cerium oxide (MDC)/Al photodiodes. The structure, morphology, optics, composition, electrical and rectifying properties of the prepared materials were analyzed. UV-Vis analysis demonstrates a prominent and acute absorption edge at 425 nm in the visible region. As more Mn impurities are incorporated into CeO2 crystallites, the band gap decreases as the doping level increases, leading to the formation of new recombination sites with low energy emissions. Electrons in outer orbits operate in energy bands, moving to higher energy levels. At higher Mn doping, some NBE emissions and green emission peaks disappear. The emission spectrum confirmed that strong and broad blue emission peak occurred for the diode containing the 15% Manganese Diode Cerium film. XRD peak shows the mono-phase polycrystalline cubic fluorite structure with the main orientation in the 200 directions. The broad lines (CeO) symmetry at 695,659,538 and 517 cm−1 observed in the Fourier Transform -Infrared spectrum are due to the phonons of the cerium oxide (Ce-O) network caused by asymmetric tip stretching and fastening vibration. Satellite peaks arise due to the transition from ligand (O 2p) to metal (Ce 4f) achieved during the primary and main photo-ionization process. This suggests that the valence states of Ce3+ and Ce4+ provide access to the CeO2 lattice sites. The I-V properties of p-Si/n-MDC/Al devices show behavior limited by the properties of the inorganic semiconductor substrate and the size of the hetero-interface energy barrier. The switching voltage of the hetero-junction was found to be approximately 2.4 V.

In-situ fabrication of N-doped carbon dots on novel blue-emitting Y2TiWO8: Ce3+ nanophosphor for thermal sensing and fingerprint detection applications

A series of N-doped Carbon Dots @ Ce3+-doped Y2TiWO8 blue-emitting nanophosphors were obtained by the sol-gel assisted hydrothermal route for exploring the optical thermometry and latent fingerprint visualisation. X-Ray Diffraction, morphology, and PL spectra analysed the synthesised nanophosphors. Excited by 355 nm, the Ce3+-doped Y2TiWO8 nanophosphor shows a broad blue emission band at 424 nm, resulting from the electric dipole transition 5d → 4f of Ce3+ and the N-doped Carbon Dots @ Ce3+-doped Y2TiWO8 nanophosphor shows the blue emission band at 431 nm. A dramatic increase by a factor of 342.82 was observed in PL intensity when nitrogen doped carbon dots were embedded in the Ce3+-doped Y2TiWO8 nanophosphor. The enhanced PL intensity can be attributed to the FRET mechanism. Compared to its emission intensity at room temperature, the nanophosphor maintains 85 % of its intensity even at 400 K, demonstrating outstanding thermal stability. The N-doped Carbon Dots@ Ce3+-doped Y2TiWO8 exhibit high colour purity of 93.25 %. Further, the nanophosphor can be potentially used for optical thermometry with a wide temperature range from 300 K to 460 K. The latent fingerprint developed by N-doped Carbon Dots@ Ce3+-doped Y2TiWO8 nanophosphor presents excellent selectivity and high contrast. Under UV irradiation, latent fingerprints' level 1–3 structural features may be easily recognised.

Study of blue-light emission properties of WO3:Eu microstructures

Structural, surface morphological, optical absorption and emission properties of 0–5% Eu doped WO3 samples are studied. The samples are synthesised by acidic precipitation method. The structural analysis reveals that the sample has ‘room-temperature monoclinic’ structure. The average crystallite size of the undoped sample is ∼58.57 nm and it decreases to 34.72 nm after doping of Eu at 5%. The undoped sample has hexagonal disc-like grain structures with average diameter of ∼0.84 μm. All the samples show a sharp absorption edge above 350 nm. The transmittance of the samples increases above 400 nm and reaches its maximum at ∼490 nm. The extinction coefficient of the undoped sample is minimum at 390 nm and it has a relatively smaller value than that of the doped samples. The optical bandgap of the undoped sample is found to be 3.56 eV and it decreases to 3.28 eV with the increase of concentration of Eu to 5%. Analyses of PL spectra show that the undoped sample under 355 nm UV excitation produces a broad blue emission band with five maxima at ∼403, 414, 435, 473 and 495 nm due to band-to-band transitions and transitions involving intrinsic defects. A blue emission band centred at ∼435 nm is increased by two-fold after doping of Eu at 1%. In addition, a secondary emission band is found at ∼505 nm due to formation of an aggregate defect (F2 centre). When the doping concentration is increased to 5%, another secondary band is observed at 610 nm due to interstitial Eu3+ centre. The enhancement of the blue emission band is attributed to formation of oxygen vacancies due to substitution of W6+ ions by Eu3+ ions. The enhanced blue light in the sample doped with 1% of Eu has potential application in WLED as well as other light emitting applications.

Full-visible-spectrum LED lighting by using a near-UV-excitable broadband blue-emitting Ca2LuHf2GaAl2O12:Ce3+ garnet phosphor

Highly efficient broadband blue-emitting phosphors are urgently needed for full-visible-spectrum white light-emitting diodes (WLEDs). Herein, we report a new highly luminescent garnet-type Ca2LuHf2GaAl2O12:Ce3+ (abbreviated as: CLHGAO:Ce3+) blue phosphor enabling full-visible-spectrum LED lighting. These CLHGAO:Ce3+ phosphors doped with different Ce3+ concentrations have been prepared by using a high-temperature solid-state reaction approach, and their phase purity, crystal structure, luminescent properties, CIE color coordinates, and quantum efficiency have been systematically studied. Importantly, CLHGAO:Ce3+ blue phosphors show a broadband excitation spectrum in the 300–450 nm spectral range peaking around 398 nm, matching well with the emission wavelengths of commercial near-ultraviolet LED chips (380–420 nm). Upon 398 nm excitation, the optimal CLHGAO:2%Ce3+ phosphor sample generates a bright broad blue emission band (emission peak: 472 nm; bandwidth: 84 nm) with high internal quantum efficiency of 79.2% and external quantum efficiency of 55.3%. Notably, the emission intensity of CLHGAO:2%Ce3+ phosphor is about 1.87 times higher compared to the commercial BaMgAl10O17:Eu2+ blue phosphor (emission peak: 451 nm; bandwidth: 53 nm). Finally, a white LED device is fabricated with a 395 nm near-UV LED chip with CLHGAO:2%Ce3+ blue phosphor and commercial (Ba,Sr)2SiO4:Eu2+ green phosphor as well as commercial CaAlSiN3:Eu2+ red phosphor, and the device demonstrates bright warm-white emission with an ultrahigh color rendering index (Ra = 95.1, R9 = 97.8, R12 = 88.4) and low correlated color temperature of 3540 K. These results show that as-developed blue-emitting CLHGAO:Ce3+ garnet phosphors with superior photoluminescence properties can potentially be used in phosphor-converted full-visible-spectrum WLEDs.

Colloidal synthesis and optical properties of Cs2ZnBr4 and Cs3ZnBr5 nanocrystals

A framework to understand the effects of an oxide-ligand environment on the photoluminescence (PL) of rare-earth-element-doped oxynitride compounds is well established, whereas the effects of halide coordination on crystal field splitting and the associated PL emission are rarely studied. In this paper, we report a synthetic route to alkali metal halide NCs of Cs2ZnBr4 and Cs3ZnBr5 with a broad blue PL emission and large Stokes shift. In particular, the zero-dimensional Cs3ZnBr5 phase, in which the isolated [ZnBr]42− units were completely separated by surrounding Cs+ cations, exhibited a strong blue PL emission at 437 nm with a PL quantum yield of 8.92 %. The formation of additional trap states or defects in the Cs3ZnBr5 crystalline lattice can be associated with a relatively considerable bands at 345 and 400 nm of the optical band edge, resulting in singlet-to-singlet transition of localized excitons with a short lifetime of 3.74 ns. Therefore, herein we demonstrate that tunable alkali metal halide NCs have considerable potential for optoelectronic applications.

Color tunability and NIR luminescence in Cr3+/Li+ co-doped ZnGa2O4 phosphor for solid state lighting and NIR LEDs

In this work, we report the color tunable photoluminescence in the Cr3+/Li+ doped and co-doped ZnGa2O4 (ZGO) phosphors synthesized by solid state reaction method. The phase and surface morphology of ZGO phosphor were examined by XRD and SEM measurements, respectively. The EDS spectra revealed the presence of Zn, Ga, Cr and O elements in the phosphor. The vibrational structure of the phosphor materials has been analyzed by FTIR measurements. The Cr3+ doped phosphor shows electronic absorption bands at 302, 408 and 544 nm alongwith the host CTB at 260 nm. The optical band gap of the phosphor decreases via doping of Cr3+ and Cr3+/Li+ ions. The ZGO is a self-activated host and emits broad blue emission with maximum at 434 nm upon excitation at 260 nm. The Cr3+ doped phosphors show emission bands due to spin-allowed as well as spin-forbidden transitions due to Cr3+ ion in the blue, green and NIR regions on excitation with 260, 302, 408 and 544 nm wavelengths. The emission intensity is optimum for 0.5 mol% concentration of Cr3+ ion. The emission intensity of Cr3+ doped ZGO phosphor increases via doping of Li+ ion. The color tunability has been observed in the phosphor upon 260 and 302 nm excitations. The lifetimes of 4T2 (4F) and 2E states of Cr3+ ion have been measured and it is found that it decreases with increasing concentrations of Cr3+ and Cr3+/Li+ ions. The Cr3+/Li+ doped and co-doped ZGO phosphors may be suitable candidates for display devices, solid state lighting and NIR LEDs.

Trap engineering in ZnGa2O4:Tb3+ through Bi3+ doping for multi-modal luminescence and advanced anti-counterfeiting strategy

Optical information encryption based on luminescence materials have received much attention recently. However, the single luminescence mode of the luminescence materials greatly limits its anti-counterfeiting application with high safety level. Here, a series of luminescence materials of Tb3+ and Bi3+ co-doped ZnGa2O4 phosphors with great correspondence in photoluminescence (PL), persistent luminescence (PersL), and thermoluminescence (TL) modes was synthesized by the conventional solid-phase method for the application in multi-modal anti-counterfeiting fields. Under the excitation of 254 nm, ZnGa1.99O4:0.01 Tb3+, yBi3+ (y = 0.001,0.002) sample exhibited a broad blue emission band (the transition from [GaO6]) at 440 nm and the characteristic emission peaks of Tb3+ at 495 nm, 550 nm, 591 nm and 625 nm, corresponding to the transitions of 5D4-7Fn (n = 6, 5, 4, 3), respectively. Interestingly, the co-doping of Bi3+ ions improve the crystallinity and particle size of the phosphor, subsequently enhanced the PL intensity of Tb3+ to 6 times that of Tb3+ singly doped ZnGa2O4 phosphor. Further, the flexible films with multi-modal luminescence properties have been fabricated through the unique TL and PersL characteristics of ZnGa2O4: Tb3+, Bi3+ phosphors, including “Optical information storage film”, “snowflake and characters” and “QR code”. Moreover, a set of optical information encryption is obtained by combining ZnGa2O4:Tb3+, Bi3+ phosphor and red emitting phosphor. The results indicate that ZnGa2O4:Tb3+, Bi3+ phosphor with multi-modal stimulus response can be expected to be potentially used in the applications of optical information storage and anti-counterfeiting fields.

Local structure, spectroscopy and luminescence of the Li2B4O7:Cu,Eu glass

The Li2B4O7:Cu,Eu glass containing 1.0 mol.% CuO and Eu2O3 impurities was obtained and studied by XRD, EPR, optical absorption, and photoluminescence techniques. Parameters of local structure (interatomic distances and coordination numbers) were derived from XRD data analysis. The EPR and optical absorption, emission, photoluminescence excitation show that the Cu impurity is incorporated into the Li2B4O7 glass as Cu2+ (3d9) and Cu+ (3d10) ions. The Cu2+ ions in Li2B4O7:Cu,Eu glass show characteristic EPR and optical absorption spectra. Spin Hamiltonian parameters of the Cu2+ EPR spectrum were determined. Optical absorption spectrum of the Li2B4O7:Cu,Eu glass was analysed and interpreted. Optical band gap and Urbach energy of the Li2B4O7:Cu,Eu glass were evaluated. Photoluminescence spectra of the Li2B4O7:Cu,Eu glass reveal broad blue emission band of Cu+ (3d94s1 → 3d10 transition) and narrow emission bands of Eu3+ (4f6) ions belonging to the 5D0 → 7FJ (J = 0 – 4) transitions with characteristic decay kinetics.

Site regulation and luminescence properties of Eu3+, Eu2+ in (La, Mg):SrAl12O19 matrix

The partially and equivalent substitution of La + Mg → Sr + Al in SrAl12O19 lattice is an effective strategy to provide trivalent sites, reduce the site occupation splitting of Al and stabilize the entire lattice. When excited by 397 nm, the Eu3+ activated La, Mg:SrAl12O19 (ASL) phosphor shows intense linear emission through the 5D0→7F4 transition at 707 nm when compared with SrAl12O19:Eu3+. Especially, the Eu, Mg co-doped Sr1-xLaxMgxAl12-xO19 with certain amount of x = 1/3 exhibits the significant intense photoluminescence, which was demonstrated through a lattice evolutional model. Eu2+ in the host with 1/3 ratio of (La, Mg) substitution shows broad blue emission and as short fluorescence lifetime as 248 ns. The temperature-depended fluorescence quenching behavior confirms the essence of strong electric-phonon coupling originated from distorted and polarized crystal field around Eu2+/Sr2+ site. Basing on site regulation of SrAl12O19 matrix, our study provides a reference for exploration on efficient rare earth ions activated luminescent laser or scintillation materials.

Modulating Nonluminous 0D (NH4)2SnCl6 Perovskites by Metal Ion Doping

Metal halide perovskite materials have highly attracted wide attention for lighting applications because of their unique optoelectronic properties. However, the complex preparation processes and the toxicity of lead have limited their practical applications. There are few reports on zero-dimensional (0D) organic/inorganic tin-based perovskites with both good stability and a high photoluminescence quantum yield (PLQY). Here, Sb3+ doping and Bi3+ doping of 0D (NH4)2SnCl6 perovskite powders are reported. Sb3+ doping of 0D (NH4)2SnCl6 perovskites shows wide emission peaks at 530 and 640 nm with a PLQY of up to 17.03%, while Bi3+ doping of 0D (NH4)2SnCl6 perovskites exhibits a broad blue emission at 460 nm with a PLQY of 4.40%. Combining experimental results and theoretical calculations, we propose that the mechanism of Sb3+ ion doping of 0D (NH4)2SnCl6 perovskites is a P1 → 1S0 transition (singlet) at 530 nm and a 3P1 → 1S0 transition (triplet) at 640 nm. However, the mechanism of Bi3+ ion doping of 0D (NH4)2SnCl6 perovskites is a 3P1 → 1S0 transition at 460 nm. In addition, both metal ion dopings of 0D (NH4)2SnCl6 perovskites have good air and thermal stability. We demonstrate that the Sb3+ doping and Bi3+ doping of 0D (NH4)2SnCl6 perovskite phosphors have great potential for solid-state lighting.

Morphology control and blue luminescent performance of one dimensional Si3N4 via Nano-SiO2 assisted pyrolysis of polyvinylsilazane

One-dimensional Si3N4 wires and belts have been successfully synthesized via pyrolysis of polyvinylsilazane (PVSZ) with nano-SiO2 powders as the additive. The morphology of white Si3N4 was tailored from wire-like morphology to belt-like morphology by controlling pyrolysis temperature. The maxlength of Si3N4 wires and belts is up to 550 μm. The diameter of Si3N4 wires is 200–300 nm and the width and thickness of belts are 1–2.5 μm and 130–250 nm respectively. Nano SiO2 powders induced the formation of SiO2 phase in the substrate and promoted the growth of α-Si3N4 belts. Vapor-solid is the growth mechanism for Si3N4 microwires and micorbelts. Si3N4 wires and belts have broad blue emission ranging from 410 nm to 550 nm.

Novel Zn2SiO4: Nb phosphor for light emitting applications

The researchers have focussed on finding new novel phosphors with enhanced emissions under UV/near UV excitation in a suitable host due to the limitation of commercial phosphors. In this study, niobium (Nb) doped zinc silicate (Zn2SiO4) by varying different wt. % of Nb was synthesized through the sol-gel method at 1200 °C under normal atmospheric conditions. The incorporation of Nb in the Zn2SiO4 host lattice significantly modifies their crystallinity, morphology, optical, and photoluminescent behaviours. In the PL study, Zn2SiO4: Nb phosphor shows a broad blue emission peak at 460 nm under 315 nm excitation. The highest PL emission intensity at 460 nm is obtained in 4 wt % of Nb-doped Zn2SiO4 materials among the prepared materials. The highest quantum yield and average lifetime were achieved for 4 wt % Nb-doped Zn2SiO4 materials which enunciates that the 4 wt % Nb-doped Zn2SiO4 is a potential candidate for light-emitting applications.

Defects and Persistent Luminescence in Eu -Doped SrAl 2 O 4

We investigate native point defects and rare-earth (co)dopants in SrAl$_2$O$_4$ using hybrid density-functional defect calculations. Europium (Eu) and dysprosium (Dy) are found to be mixed valence and energetically most favorable at the Sr lattice sites. However, unlike Eu where both Eu$^{2+}$ and Eu$^{3+}$ can be realized in synthesis, Dy is stable predominantly as Dy$^{3+}$, and the divalent Dy$^{2+}$ may only be photogenerated under irradiation. On the basis of an analysis of Eu-related band-defect (including charge-transfer) and interconfigurational $5d$-$4f$ optical transitions, we assign the characteristic broad blue (445 nm) and green (520 nm) emission bands in Eu$^{2+}$-doped SrAl$_2$O$_4$ to the $4f^65d^1$ $\rightarrow$ $4f^7$ transition in Eu$^{2+}$ incorporated at the Sr1 and Sr2 sites, respectively. Strontium interstitials (not oxygen vacancies, in contrast to what is commonly believed) and Dy$_{\rm Sr}$ can act as efficient electron traps for room-temperature persistent luminescence. This work calls for a re-assessment of certain assumptions regarding specific carrier trapping centers made in all mechanisms previously proposed for the persistent luminescence in Eu- and (Eu,Dy)-doped SrAl$_2$O$_4$. It also serves as a methodological template for the understanding and design of rare-earth doped phosphors.

Tunable red/ blue emitting of Ca5(PO4)3F: Eu2+, Eu3+ and remote-excited color convertor for NUV-WLED

Eu2+/Eu3+ co-doped Ca5(PO4)3F (FAP) phosphors with tunable color of red/blue (R/B) emission were successfully synthesized by the two-step method for potential applications in light-emitting diodes (LED). Eu2+ (or Eu3+) single-doped and Eu2+/Eu3+ co-doped FAP all showed pure hexagonal FAP crystal with space group P63/m, indicating the occupation of Ca sites by Eu2+ and Eu3+ ions. Typically, Ca5(PO4)3F: Eu2+ phosphors exhibited a broad blue emission band at 451 nm under 293 nm excitation and Ca5(PO4)3F: Eu3+ samples emitted strong orange-red light at 596 nm, 615 nm and 620 nm under 394 nm excitation. Further, Eu2+/Eu3+ co-doped FAP phosphors obtained by the two-step method depicted the blue emission at 451 nm (Eu2+ ions) and the orange-red emission (Eu3+ ions) at 596 nm, 615 nm and 620 nm with an excitation wavelength of 365 nm (NUV). The tunable R/B ratio from 0.079 to 7.035 with various CIE chromaticity coordinate can be achieved by adjusting the recalcined temperature in the second step. Ca5(PO4)3F: Eu2+, Eu3+ sample can be packaged with green Lu3Al5O12 (LuAG) phosphors by 365 nm chip (1 W) and the cold white light with CIE chromaticity coordinate (0.2815, 0.3485) (CRI: 73, CCT: 7973 K) is achieving. Based on Ca5(PO4)3F: Eu2+, Eu3+ and 25B2O3-10SiO2-35ZnO-6Li2O-12La2O3-12WO3 (BS-glass) (in mol%) with strong mechanical strength as a great binder, the remote-excited color convertor (PiG: phosphor in glass) has been fabricated by screen printing technology for NUV-WLED application. Finally, by comparing the working temperature of PiG and pc-WLED at the same operating time, the working temperature of PiG was stable at 32 °C when remote excitation lighting was applied, which greatly avoided the phenomenon of “thermal quenching” for phosphors caused by high temperature under the operating of WLED. Thus, it was demonstrated that Eu2+ and Eu3+ co-doped Ca5(PO4)3F phosphors with tunable red/blue emitting would be a highly potential candidate for NUV-WLED.

Line luminosities of Galactic and Magellanic Cloud Wolf–Rayet stars

ABSTRACT We provide line luminosities and spectroscopic templates of prominent optical emission lines of 133 Galactic Wolf–Rayet (WR) stars by exploiting Gaia DR3 parallaxes and optical spectrophotometry, and provide comparisons with 112 counterparts in the Magellanic Clouds. Average line luminosities of the broad blue (He ii λ4686, C iii λλ4647,51, N iii λλ4634,41, and N v λλ4603,20) and yellow (C iv λλ5801,12) emission features for WN, WN/C, WC, and WO stars have application in characterizing the WR populations of star-forming regions of distant, unresolved galaxies. Early-type WN stars reveal lower line luminosities in more metal-poor environments, but the situation is less clear for late-type WN stars. LMC WC4–5 line luminosities are higher than their Milky Way counterparts, with line luminosities of Magellanic Cloud WO stars higher than Galactic stars. We highlight other prominent optical emission lines, N iv λλ3478,85 for WN and WN/C stars, O iv λλ3403,13 for WC and WO stars, and O vi λλ3811,34 for WO stars. We apply our calibrations to representative metal-poor and metal-rich WR galaxies, IC 4870 and NGC 3049, respectively, with spectral templates also applied based on a realistic mix of subtypes. Finally, the global blue and C iv λλ5801,12 line luminosities of the Large Magellanic Clouds or LMCs (Small Magellanic Clouds) are 2.6 × 1038 erg s−1 (9 × 1036 erg s−1) and 8.8 × 1037 erg s−1 (4 × 1036 erg s−1), respectively, with the cumulative WR line luminosity of the Milky Way estimated to be an order of magnitude higher than the LMC.

Fabrication of organic-inorganic hybrid device for optoelectronic applications: Charge carriers dynamics and photoresponse assessment

In this study, we introduce the fabrication of an organic-inorganic hybrid architecture for photodetection applications that is constructed from Ethyl Nile Blue (ENB) and p-type silicon. The optical absorption and emission spectra of the deposited ENB films are investigated yielding high UV–visible absorption features with a broad blue and violet emission band. The developed Ag/ENB/p-Si/Al heterojunction's microelectronic characteristics are assessed under dark conditions and at various temperatures (303−353) K. The variation of the barrier height and ideality factor with temperature are interpreted in detail. Considering the barrier height inhomogeneity, the modified Richardson constant has been estimated and found to be 30 A/cm2 K2. Analysis and discussion have been conducted about the charge carrier dynamics scenario under forward and reverse bias settings. The implemented hybrid device's photoresponse is evaluated at various light intensities (20–100 mW/cm2). In comparison to other organic-inorganic hybrid photodetectors, the manufactured hybrid device demonstrated a promising, stable, and reliable performance. The manufactured photodetector exhibited R, D* , LDR, SNR, and (tr/tf) time at power density 100 mW/cm2 of about 1.85 mA/W, 8.5 × 108 Jones, 55.9 dB, 626, and (69.7 ms/52.6 ms), respectively.

Zero-dimensional rubidium zinc halide blue-emitting quantum dots for X-ray imaging

Low-dimensional-networked metal halide (MH) materials are emerged as a new class of semiconductors owing to their unique structure and outstanding photoelectric properties. Compared with the extensively studied three-dimensional (3D) MHs, the zero-dimensional (0D) MHs are of great interest to be widely studied. Here we report the successful colloidal synthesis of all-inorganic lead-free 0D MHs, including undoped and Cu-doped Rb2ZnCl4 quantum dots (QDs) with bright broad blue and cyan emissions, respectively. Combining the theoretical and experimental study, the band structures are well characterized and the originations of the blue and cyan emissions are attributed to the singlet and triplet self-trapped exciton (STE) emissions, respectively. Finally, owing to the bright radioluminescence (RL), the Cu-doped Rb2ZnCl4 QDs is prepared into a thin film to demonstrate the feasibility for X-ray imaging application. This work not only provides a cyan-emitting all-inorganic 0D MH QDs, but also exploits it as a scintillator for X-ray imaging.