Blue Light Emission Research Articles

Exploring the Multifunctional Properties of Tm‐Doped AlxGa1−xN Alloys: From Potoluminescence to Spintronics

ABSTRACTThis study delves into the electronic, magnetic, and optical properties of Tm‐doped wurtzite AlxGa1−xN alloys, utilizing first‐principles density functional theory (DFT) calculations. By applying the LSDA+U approach to capture the strong correlation effects of 4f‐Tm electrons, our findings reveal that Tm‐doped AlxGa1−xN exhibits semiconducting behavior with inherent ferromagnetic order. Remarkably, the bandgap of Tm‐doped AlxGa1−xN transitions from indirect to direct at an Al content (x) of 0.25, highlighting its potential for dual electrical and magnetic functionalities. The magnetic moments are highly localized at Tm sites, suggesting the feasibility of Tm as a dopant for developing AlGaN‐based diluted magnetic semiconductors. Moreover, the observed spin‐dependent characteristics and magnetic interactions in Tm‐doped AlxGa1−xN underscore its applicability in spintronic devices, including spin transistors and spin logic circuits, which could significantly advance next‐generation electronic systems. Additionally, the study predicts a blue shift in luminescence for Tm‐doped AlxGa1−xN, which is attributed to the interplay between Tm dopant energy levels, Al composition, and the host alloy's band structure, as well as energy transfer and quantum confinement effects. This positions Tm‐doped AlxGa1−xN as a promising material for applications in solid‐state lighting, displays, lasers, and other optoelectronic devices requiring blue light emission.

Development of highly thermal-stable blue emitting Y4Al2O9:Bi3+ phosphors for w-LEDs, fingerprint and data security applications

A new blue-emitting Y4Al2O9:Bi3+ (YAO:Bi3+) phosphor is synthesized using the solution combustion method with mushroom extract as a binder. Its structural properties, concentration effects, temperature-dependent luminescence, and performance in LED devices are thoroughly investigated. Upon excitation at 367 nm, a strong blue light emission at 423 nm is observed, attributed to the 3P1→1S0 transition of Bi3+. The quantum efficiency reached approximately 63.5 %. The CIE diagram shows that the emission colour falls within the intense blue region, achieving a colour purity (CP) of 94 %. YAO:Bi3+ exhibits strong absorption in the near-ultraviolet range (330–400 nm), making it suitable for LEDs powered by near-ultraviolet chips. A thermal quenching experiment revealed an activation energy (Ea) of 0.323 eV, indicating that this YAO:Bi3+ phosphor possesses good thermal stability. This study showcases the use of YAO:Bi3+ phosphor in encapsulated LED devices. The device’s Commission Internationale de l’Éclairage (CIE) coordinates are (0.325, 0.310), with a high colour rendering index (CRI) of 94.70 and a low correlated colour temperature (CCT) of 5915 K at a current of 120 mA. These properties indicate that this phosphor is suitable for developing white LED devices powered by near-ultraviolet chips. The optimized YAO:Bi3+ phosphor is employed to enhance the detection of Level I-III fingerprint (FP) details with high resolution and contrast, showing effective visualization of latent fingerprints (LFPs) on various substrates. Furthermore, it is used as a model for developing fluorescent ink, which is applied to different media. The results suggest that YAO:Bi3+ phosphor has significant potential for applications in w-LEDs, advanced forensics, and anti-counterfeiting ink technologies.

Replication of Leaf Surface Structures on Flat Phosphor-Converted LEDs for Enhanced Angular Color Uniformity.

We explored the use of biomimetic structures, including those that mimic leaf structures, to enhance the angular color uniformity of flat phosphor-converted light-emitting diodes (pcLEDs). The distinct microstructures found on natural leaf surfaces, such as micro-scale bumps, ridges, and hierarchical patterns, have inspired the design of artificial microstructures that can improve light extraction, scattering, and overall optical performance in LED applications. The effects of these leaf surface microstructures on the phosphor layer of flat pcLEDs were evaluated. An imprinting technique was employed to directly replicate the surface morphology structures from fresh plant leaves. The results indicated that this method provided excellent scattering capability and reduced the disparity in light output between blue and yellow light emissions from flat pcLEDs at various angles. Subsequently, uniform correlated color temperature in the flat pcLEDs was achieved, reducing the yellow ring effect. Furthermore, the availability of diverse wrinkle and surface patterns from a wide range of natural prototypes could reduce design costs compared with traditional mold fabrication, making the method suitable for application in mass production.

Precursor Reactivity‐Controlled Synthesis of ZnSeTe Spherical Quantum Wells with Narrow and Symmetric Photoluminescence

AbstractEnvironment‐friendly ZnSeTe quantum dots (QDs) are considered as potential blue light emitters. However, due to the large reaction activity difference between Se and Te precursors, ZnSeTe QDs usually can not uniformly alloyed and generate lattice distortion, reducing the color purity or photoluminescence quantum yield (PLQY). A ZnSe/ZnSeTe/ZnSe spherical quantum well (SQW) structure with quasi type‐II energy band arrangement is designed. To promote the uniform growth and even alloying of ternary ZnSeTe, weakly active biphenyltellurium (Ph2Te2) is applied as a new Te source for balancing the reactivity between Te and Se. Epitaxial growth of high crystallinity ZnSeTe with greatly reduced defects is obtained. After ZnS outer layer passivation, the obtained ZnSe/ZnSeTe/ZnSe/ZnS QDs exhibit a high PLQY (≈84%) and a narrow full width at half maxima (19 nm) without asymmetric broaden at 455 nm, contributing to an ultrahigh color purity, which is among the best photoluminescence performance for blue emitting ZnSeTe based QDs. This work provides a new balance strategy of precursor reactivity for synthesizing high color purity and heavy metal free blue ZnSeTe QDs.

A Paradox of LED Road Lighting: Reducing Light Pollution Is Not Always Linked to Energy Savings

A variety of LED types can be employed for street and road lighting purposes. White phosphor-converted LEDs represent the most widely used option. However, amber LEDs are increasingly being used to reduce some negative effects associated with light pollution. These LEDs can be manufactured using both phosphor-converted and monochromatic direct chip technologies. This paper addresses the link between the reduction in short-wavelength light emissions which contribute to sky glow and the energy efficiency of LED-based road lighting. This paper focuses on an example illustrating the common misconception that reducing light pollution also means saving energy. Through the consideration of how spectral power distribution influences both mesopic vision and the amount of emitted blue light, it has been concluded that while monochromatic direct amber LEDs consume more energy than their white or amber phosphor-converted counterparts, their use in outdoor lighting is justifiable due to their potential effects of reducing sky brightness.

Long-Lived Room-Temperature Phosphorescence from Silica Nanoparticles with In Situ Generated Carbonaceous Defects for Blue Organic Light-Emitting Diodes.

In this study, in situ formed silica nanoparticles (SNPs) emitting second-level phosphorescence at room temperature without a phosphorescent dopant have been achieved for the first time. This phosphorescence is achieved through the simple in situ formation of carbonaceous defects (CDs) within the SNPs, followed by passivation of the CDs by a robust silica matrix. The CD in the SNPs, termed CD@SNPs, are synthesized by cross-linking tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES), and these cross-linked components create a porous structure within the silica matrix. Upon calcination, the carbon-related structures within the pores deform, leading to the formation of CDs. Confined within a robust silica matrix, the molecular motion of the CD is restricted, facilitating the generation of a stable triplet state and suppressing nonradiative decay. Moreover, the robust silica matrix passivates the CD confined in the SNPs at a nanoscale. These comprehensive effects enable prolonged phosphorescence emission from the SNPs. In addition, these phosphorescence-emitting SNPs have been applied as dopants in the emissive layer of organic light-emitting diodes to realize blue light emission. This feature suggests the possibility of utilizing luminescent SNPs as light emitters in display technologies.

Design and Synthesis of Aggregation‐Caused Quenching Hydroxy‐Phenanthroimidazole Derivatives for Probing of Fe3+ Ions and as Potential Blue Light Emitters

AbstractFluorescence aggregated molecules tend to employ versatile opportunities in metal ion probe sensors and fluorescent lighting. To achieve this dual challenging task, currently synthesized three phenanthroimidazole‐naphthalene‐based compounds Pq‐tBu‐OH, Pq‐mF‐OH, and Pq‐pF‐OH are derived based on substitution at N1 position for better photophysical and electrochemical properties. Compared experimental and theoretical calculations define the highest bandgap to be 2.75 eV of Pq‐pF‐OH, and the same molecule expressed a higher (348 °C) thermal decomposition. The calculated singlet and triplet energies found in the range of 3.24–3.67 and 2.70–2.72 eV indicate well energy transfer from S1→S0 (quantum yield of 23.36 %, lifetime is 4.05 ns). Among the numerous morphologies, the solid form exhibited improved intensive deep blue emission (x=0.159, y=0.051), and its InGaN LED results demonstrated a strong deep blue emission at 418 nm. Moreover, the fluorophores were experimentally visualizing the aggregation‐caused quenching (ACQ) which enables the probing of Fe3+ ion. However, for the first time, the ACQ‐assisted concept is applied through synthesized molecules for Fe3+ ion probing via fluorescence spectra, Job's plot calculation, and 1H NMR results. In addition, the probe works excellently at a detection limit of 10 μM and it could also act as a potential competitor for lighting applications.

Enhancing luminescence in bio-cellulose derived carbon microcoils through europium incorporation: A pathway to high-performance UV luminophores

Bio-cellulose derived carbon microcoils (BCMC) are renowned for their distinctive helical structure, sustainability, and renewability, making them highly versatile for applications such as microwave absorption, water purification, and energy storage. Despite extensive research on carbon microcoils or nanocoils, the luminescent properties of BCMC remain largely unexplored. This study delves into the luminescence characteristics of BCMC extracted from recycled tea leaves, revealing a broad spectrum of multicolor emissions including ultraviolet (355 nm, 396 nm), blue (467 nm), and near-infrared (764 nm). These emissions are attributed to BCMC's distinctive three-dimensional helical configuration and its rich array of oxygen-containing functional groups. Incorporating europium further tailors the photoluminescent properties of BCMC, significantly amplifying UV and blue light emissions. Additionally, annealing improves UV emission, showcasing the potential for enhanced luminescence performance. This research not only deepens our understanding of sustainable luminescent materials but also paves the way for developing advanced UV luminophores with diverse applications.

Simultaneous Improvement in Blue-Light Emission and Operational Stability of Nanometer-Thick Perovskite Light-Emitting Diodes by Incorporating Multiple Organic/Inorganic Chloride Salts

Simultaneous Improvement in Blue-Light Emission and Operational Stability of Nanometer-Thick Perovskite Light-Emitting Diodes by Incorporating Multiple Organic/Inorganic Chloride Salts

Sustained Regeneration of Hydrogen Peroxide at the Water-Gas Interface of Electrogenerated Microbubbles on an Electrode Surface.

Microbubbles, inside-out microdroplets, act as extraordinary microreactors to facilitate thermodynamically unfavorable reactions in bulk solutions of water. We explored the formation of hydrogen peroxide (H2O2) and its sustained regeneration at the interface of water-gas microbubbles. For this purpose, the chemiluminescence of luminol was recorded by a digital camera to map the intensity of blue light emission over the time of about 20 min. The formation and regeneration of hydrogen peroxide were also monitored by fluorescence microscopic imaging of a hydrogen peroxide probe. The microscopic images consistently show a stable glow around the microbubbles over time during which the formed hydrogen peroxide diffuses into the bulk solution. This observation confirms that the concentration of H2O2 at the interface is 30 times higher than that in the water solution bulk after several minutes, which can be attributed to its regeneration at the water-gas interface. These findings increase our understanding of why the chemistries of gas microbubbles in water and water microdroplets surrounded by gas are so distinct from those of bulk-phase water.

Transient Photocurrent Responses of Sr1-xCexTiO3 Perovskites Under Visible Light Illumination for Photovoltaic Applications.

The objective of this study was to synthesize strontium titanate (Sr1-xCexTiO3) doped with Ce3+ by solid state method.Its crystalline structure is Sr1-xCexTiO3, and its bandgap ranges from ~3.3 to ~2.7 eV. In the photoluminescence of samples excited at 288 nm, the maximum emission of blue light was observed at 380 and 390 nm. Photocatalytic results show that dye molecules have a high absorbance, whereas their surface area is large. According to a line sweep voltammetric plot (LSV), illumination increases the current density by 0.4 μA cm-2 compared with dark conditions. It was demonstrated that the material changed from n-type to p-type under doping. Chronoamperometry spectra were obtained for sample Sr1-xCexTiO3 (x = 0, 0.005, 0.01, 0.03, 0.05) when an electrical voltage of 0.8 V was applied versus NHE. The plots indicate an increase in the current density under "light ON" conditions and a decrease under "light OFF" conditions. As Ce3+ concentration increases, the photocurrent increases until about 3 mol%, after which it decreases abruptly.

Enhancing anti-counterfeiting strategies: Exploring defect excitation Mechanisms in Eu2+-Doped Na-β"-Al2O3 phosphors

To enhance the diverse application of rare-earth doped luminescent materials in the domain of fluorescent anti-counterfeiting, a set of Na-β"-Al2O3 phosphors doped with Eu2+ were synthesized. Initially, according to the lattice parameter variation rules and the local symmetry analysis results of Eu3+ ion “probe”, it was ascertained that the activator ion Eu2+ is situated at Na + sites within Na-β"-Al2O3 matrix. Furthermore, the inherent O vacancy defects present in Na-β"-Al2O3 have the capability to excite intrinsic blue light emission at a wavelength of 420 nm, and the emission intensity is impacted by the concentration of Eu2+ ions. The primary cause of the irregular changes in the intrinsic blue light emission intensity of the matrix is the synergistic energy transfer from Eu2+ → O vacancies (Vo) and from Eu2+ → Na vacancies (VNa′). Finally, by incorporating Na-β"-Al2O3:0.05Eu2+ cyan phosphor as the solid component in conjunction with commercial ink, a fluorescent anti-counterfeiting ink was formulated to address diverse anti-counterfeiting requirements. Typical examples demonstrate the adaptability of this ink to diverse printing methods and its ability to produce high-quality imaging results on a variety of paper types. This feature enables the quick deciphering of encrypted data, thereby elevating the security level of anti-counterfeiting.

Synthesis and structure of an aqueous stable Cu(II)-based coordination polymer with multifunctional fluorescence sensing property

Advanced methods for both biological and environmental hazardous pollutants are of sustained interest. Herein, a new coordination polymer, namely, [Cu2(OH)(1,2,4-bca)(bmoe)]·H2O (Cu-CP) has been hydrothermally constructed with a mix-ligand strategy, employing 1,2,4-benzenetricarboxylic acid (1,2,4-bca) and 1,1′-bis(1H-benzimidazolyl) oxydiethane (bmoe) as organic ligands. The intrinsic strong blue-light emission and the great stability in water solutions with the broad range of pH values (pH = 4 − 12) of Cu-CP provide a platform for practical fluorescence sensing application in water samples. Fluorescence measurements reveal that Cu-CP displays interesting multi-responsive dection activities toward toxic heavy-metal ions Cr2O72- / CrO42− / MnO4−, nitrofuran antibiotics nitrofurantoin (NFT) / nitrofurazone (NFZ) and acetylacetone (ACAC) in aqueous solutions achieving both high sensitivity and low detection limits (micromolar for Cr(VI) / Mn(VII) / ACAC and nanomolar for NFT / NFZ). Furthermore, the interference experiments have verified its excellent selectivity. A synergetic contribution of internal filtration effect (IFE) and Förster resonance energy transfer (FRET) between Cr2O72- / CrO42− / MnO4− and the framework of Cu-CP realize the fluorescence quenching behavior for Cr(VI) / Mn(VII) detection, while FRET, IFE and photoinduced electron transfer (PET) mechanisms are synergistically responsible in the case of NFT / NFZ, ACAC sensing supported by the molecular simulations and UV−vis spectral overlap experiments. This present work affords precious guidance for the effective and facile design and preparation of multifunctional luminescent coordination polymers with promising performance.

Innovative synthesis and forensic applications of bio-mediated SrO–MgO–In[formula omitted]O[formula omitted] nanocomposites with blue photoluminescence

The first of its kind Strontium oxide–Magnesium Oxide–Indium oxide (SMI) nanocomposites were synthesized utilizing a bio-mediated method with Euphorbiatirucalli latex as a reducing agent, followed by calcination. Synthesis of SMI NCs is confirmed by Bragg reflections of SrO, MgO, and In2O3, among them peaks belonging to In2O3 are observed to be prominent. The crystallite size, and other parameters like dislocation density, strain, structural factor, and crystallinity were estimated. Due to lower surface energy and the adhesion of particles with weak forces, morphology of the surface contains a larger degree of agglomeration. The direct energy band gap was determined to be 3.18 eV. Furthermore, the PL (photoluminescence) emission spectra, CIE, and CCT coordinates strongly indicate high-intensity emission in the region of blue color. Dusting of powder reveals latent fingerprints. Synthesized SMI nanocomposite exhibits highly-resolved patterns in the form of ridges used to analyze specific latent fingerprints with clarity. Thus, the recently synthesized nanocomposite may have been used in forensics, fluorescence labeling, and blue light emission.

Revealing the Role of Organic Ligands in Deep-Blue-Emitting Colloidal Europium Bromide Perovskite Nanocrystals.

Europium halide perovskites are promising candidates for environmentally benign blue-light emitters with their narrow emission line width. However, the development of high-photoluminescence quantum yield (PLQY) colloidal europium halide perovskite nanocrystals (PNCs) is hindered by limited synthetic methods and elusive reaction mechanisms. Here, we provide an effective synthetic route for achieving high-PLQY deep-blue-emitting colloidal CsEuBr3 PNCs. Using two Br-organic ligand precursors, oleylammonium bromide (OLAMHBr) and trioctylphosphine dibromide (TOPBr2), we identified distinct phase evolution routes involving Eu2+:CsBr, Cs4EuBr6, and CsEuBr3. The OLAMHBr precursor initially promotes the formation of the Eu2+:CsBr phase, which reorganizes into the CsEuBr3 perovskite phase via proton transfer. In contrast, the TOPBr2 precursor induces the formation of core/shell Cs4EuBr6/CsBr PNCs, which subsequently transform into CsEuBr3 through nucleophilic addition. The TOPBr2 route exhibited enhanced CsEuBr3 phase homogeneity, resulting in a significantly higher PLQY (40.5%; full width at half-maximum (fwhm) = 24 at 430 nm), compared to the OLAMHBr route (16.5% at 418 nm). Notably, the phase-pure CsEuBr3 PNCs demonstrated a world-record PLQY among the reported blue-emitting lead-free PNCs that exhibit a narrow emission line width (fwhm <25 nm). This work highlights the significant role of organic ligands in the colloidal synthesis of CsEuBr3 PNCs and their potential as nontoxic, solution-processable blue-light emitters.

The origin of broadband blue emission in zero-dimensional organic lead iodine perovskites: A first-principles study.

Broadband blue emission in zero-dimensional perovskites has received considerable attention, which is very important for the realization of stable blue-light emitters; however, the underlying formation mechanism remains unclear. Based on first-principles calculations, we have systematically studied the self-trapped excitons (STEs) behavior and luminescence properties in 0D-(DMA)4PbI6 perovskite. Our calculations show that there is a significant difference between the intrinsic STE luminescence mechanism (∼2.51eV) and experimental observations (∼2.70eV). In contrast, we found that the iodine vacancy (VI) is energetically accessible and exhibits a shallow charge transition level at ∼2.69eV (0/+1) above the valence band maximum, which provides the initial local well for the STEs formation. Moreover, the low electronic dimension synergistic Jahn-Teller distortion facilitates the formation of extrinsic excitons self-trapping. Further excited state electronic structure analysis and configuration coordinate diagram calculations confirmed that the broadband blue emission in 0D-(DMA)4PbI6 is the origin of VI-induced extrinsic STEs instead of intrinsic STEs. Therefore, our simulation results rationalize the experimental phenomena and provide important insights into the formation mechanism of STEs in low-dimensional perovskite systems.

Mg2+‐Doped Cesium Copper Halide for Bright Electroluminescent White Light‐Emitting Diodes

AbstractLead‐based perovskite nanocrystals (NCs) as one of the most promising materials in the fields of display and lighting, have outstanding optical performance and simple solution preparation process. However, the toxicity of lead and poor stability limit their commercialization. Meanwhile, as a key component of display and lighting, white light‐emitting diodes (WLEDs) still faces challenges such as low luminance and complex preparation process. A method is proposed for preparing nontoxic and stable Cs3Cu2I5 NCs by doping Mg2+ ions, achieved broadband blue light emission with a high PLQY of 96.2% and excellent thermal cycling stability and air stability. Then, the Mg2+ ions doped Cs3Cu2I5 NCs are used as emissive layer, while the 1,3,5‐Tri (m‐pyridine‐3‐ylphenyl) benzene (TmPyPb) is selected as electron transport layer to interact with Cs3Cu2I5 thin films for the formation of Cu‐I complex with broadband yellow light emission. This approach obviated the need for multi‐layer sedimentary emission layers, resulting in WLEDs featuring a high color rendering index (CRI) of 91, a peak external quantum efficiency (EQE) of 0.71% and maximum luminance of 2116 cd m−2 that is the highest values of lead‐free perovskite WLEDs at present. Therefore, Cs3Cu2I5 NCs have good application prospects in WLEDs.

Superluminescent variants of Gaussia luciferase in living animal deep-tissue imaging

Gaussia luciferase (Gluc) is widely recognized as a powerful bioluminescent tool for biosensing and molecular imaging. However, its utility in mammalian deep tissue imaging and high-throughput applications is hampered by two primary limitations: the emission of blue light and the transient nature of its bioluminescence reaction. In this study, we have engineered two novel luciferases, BeM and SuM, by incorporating known amino acid mutations that have demonstrated the ability to stabilize, enhance, or shift the wavelength of Gluc-catalyzed luminescence towards the red spectrum. The BeM and SuM-coelenterazine systems exhibited a more than 100-fold increase in bioluminescence intensity in vitro, and over a 10-fold enhancement in vivo, compared to the conventional firefly luciferase-D-luciferin system. This significant improvement enables the noninvasive deep tissue imaging of a small number of cells within living mice. BeM and SuM emerge as the most efficient Gaussia luciferase variants to date, showcasing their immense potential as bioengineered light sources. Their applications could span various fields, ranging from fundamental scientific research to clinical diagnostics and therapeutic interventions, marking a significant leap forward in bioluminescence technology.

Perylene-3,4,9,10-tetracarboxylic dianhydride dye intercalated liquid crystal molecules: Synthesis, spectroscopic characterizations and photoluminescence dynamics

The present research explores the interaction between perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)-dye (PD) and 3b {(E)-1-[3-fluoro-4-(pentyloxy)phenyl]-2-(4-methylphenyl)diazene} liquid crystal (LC) mesophase, 3c{(E)-1-[3-fluoro-4-(hexyloxy)phenyl]-2-(4-methylphenyl)diazene} nematic liquid crystal (NLC) molecule. Spectroscopic characterizations of 3b@PD LC mesophase and 3c@PD NLC molecule were carried out using scanning electron microscopy (SEM), polarizing optical microscope (POM), Raman, Fourier transform infrared spectroscopy (FT-IR), and UV–visible analytical methods. The UV–visible studies revealed a red shift in absorption bands (348.0 nm to 374 nm) with a decrease in optical band gap from 2.43 eV to 2.25 eV. Room temperature photoluminescence (RTPL) spectra of 3b@PD LC mesophase exhibited blue light emission characteristics centred at 453.1 nm and 3c @PD NLC molecule showed broad emission peaks located at 400.7 nm and 324.8 nm. Steady-state photoluminescence (SSPL) spectra showcased indigo-purple emission bands corresponding to the wavelengths 303–353 nm, 420.5 nm, 418 nm, 418.3 nm, and 347.0 nm, however, for the 3c@PD NLC molecule, emission intensity peaks appeared at 429.6 nm, 418.0 nm and 329.0 nm. The stoke’s shift for 3b@PD LC mesophase varied between 0.01 eV to 0.613 eV while for 3c@PD NLC molecule it was found in between 0.317 eV to 0.453 eV. POM analysis unveiled distinct fan-like textures with varied colour interfaces. Time-resolved photoluminescence (TRPL) decay studies unveiled average lifetime of 3b@PD LC mesophase was 1.80 ns, 0.98 ns, 0.308 ns and for 3c@PD NLC molecule, the average lifetime was found to be 0.98 ns, 0.82 ns, and 0.306 ns at various excitation wavelengths. However, phosphorescence decay studies showed faster decay characteristics for 3c@PD NLC molecule (1.40 ns to 4.00 ns) compared with 3b@PD LC mesophase (1.65 to 5.42 ns) when excited at various wavelengths. The interaction between LC molecules and PTCDA demonstrated a significant enhancement in RTPL, TRPL, and SSPL properties, suggesting promising applications in photonics and optoelectronics.

Efficient blue light emission induced by the Cu-doping in Cs2ZnI4 for white light-emitting diodes

Zinc halides have attracted much interest because of their unique structures, non-toxicity and low cost among lead-free halides. In this work, we studied the crystal structures and luminescence properties of Cu-doped Cs2ZnI4 (Cs2Zn1-xCuxI4-x, x = 0.01–0.15). The pristine Cs2ZnI4 has no luminescence properties under ultraviolet light irradiation, while the Cu-doped ones emit blue lights. With the increase of the doping level, the luminescence peak of as-fabricated samples gradually shifted from 476 nm to 450 nm. Detailed experimental characterization and theoretical calculations demonstrate that the emission of blue light originates from the mechanism of self-trapped exciton. A phosphor-converted white light-emitting diode fabricated with Cs2Zn0.9Cu0.1I3.9 exhibits a high color rendering index of 94.2 and remains stable when adjusting the operating current. This work reports Cs2ZnI4 as a new phosphor, demonstrating the potential application of the zinc family for the field of solid-state lighting.