Inorganic Phosphors Research Articles

TiO2 and down-conversion phosphors to enhance UV protection of solar cells

In recent years, demand for solar generators for LEO (Low Earth Orbit) applications has been growing, and much research has focused on the use of less expensive and thinner (<90 μm). silicon-based solar cells that can be integrated on flexible Photovoltaic Assemblies (PVAs). These solar cells must be protected from space UV radiations and also withstand more than 50,000 thermal cycles in LEO. The solution advocated here involves the incorporation of UV-absorbing particles into a spatial polymer, combined with lanthanide ions based inorganic phosphors (Y2O3:Eu3+ and Y2O2S:Eu3+) to achieve the down-conversion process. Embedded into a silicone-based polymer matrix with a thickness close to 100 μm, these particles are then deposited on 180 μm thick Ga-doped heterojunction silicon cells (30x30 mm2). UV tests are carried out on ONERA's SEMIRAMIS platform at two doses: 425 esh and 1005 esh. A series of 1000 thermal cycles is carried out at the CEA. The first spatial UV analysis revealed a maximum loss of almost 5 % in short-circuit current (Isc) for PV devices after 1005 esh. Comparing results in open circuit voltage (Voc), the bare cell degrades as the dose increases (−2 % at 425 esh and −5 % at 1005 esh). One positive point is that the addition of TiO2 particles protects the solar cell. These initial results point out that it is possible to produce a protective coating to limit the effects of degradation of Silicon cells under space UV flux, with a focus on producing flexible PVAs.

Multiple stimuli-responsive double perovskite structured Ca2MgWO6: x % Eu3+ (x = 1–11 mol) red-emitting luminescent systems to combat counterfeiting

The rapid escalation of counterfeiting activities in recent years has posed significant challenges across diverse fields, such as pharmaceuticals, currency, luxury goods, and electronics. In response, inorganic phosphors have emerged as promising tools to combat counterfeiting due to their inherent durability and stability. The present work focuses on the synthesis of Ca2MgWO6:x % Eu3+ (x = 1–11 mol) luminescent systems via a gel-combustion route. The structural analysis of the synthesized luminescent systems confirmed a monoclinic crystal phase with a P21/n space group. The morphological study of the luminescent system revealed a network-like structure comprising interconnected particles. Photoluminescence emission spectra show a prominent red emission peak at 616 nm, corresponding to the 5D0→7F2 4f–4f electronic transition of Eu3+ ions in the host matrix. The emitted red light demonstrates a color purity and quantum efficiency of 93.1 % and 77.41 %, respectively. The anti-counterfeiting security patterns were developed using the Ca2MgWO6:x % Eu3+ (x = 9 mol) luminescent system showcase virtually invisible under normal light. However, developed patterns exhibit vivid red luminescence when exposed to multiple stimuli UV light at 365 and 395 nm, which envisages the versatility of the systems for enhancing product authentication and protecting against fraudulent activities across multiple industries. The aforementioned results demonstrated the efficacy of Ca2MgWO6: Eu3+ luminescent systems for integration into advanced security measures.

Opal‐Inspired SiO2‐Mediated Carbon Dot Doping Enables the Synthesis of Monodisperse Multifunctional Afterglow Nanocomposites for Advanced Information Encryption

AbstractDespite recent advancements in inorganic and organic phosphors, creating monodisperse afterglow nanocomposites (NCs) remains challenging due to the complexities of wet chemistry synthesis. Inspired by nanoinclusions in opal, we introduce a novel SiO2‐mediated carbon dot (CD) doping method for fabricating monodisperse, multifunctional afterglow NCs. This method involves growing a SiO2 shell matrix on monodisperse nanoparticles (NPs) and doping CDs into the SiO2 shell under hydrothermal conditions. Our approach preserves the monodispersity of the parent NP@SiO2 NCs while activating a green afterglow in the doped CDs with an impressive lifetime of 1.26 s. Additionally, this method is highly versatile, allowing for various core and dopant combinations to finely tune the afterglow through core‐to‐CD or CD‐to‐dye energy transfer. Our findings significantly enhance the potential of SiO2 coatings, transforming them from merely enhancing the biocompatibility of NCs to serving as a versatile matrix for emitters, facilitating afterglow generation and paving the way for new applications.

Suppressed concentration quenching and tunable photoluminescence in Eu2+-activated Rb3Y(PO4)2 phosphors for full-spectrum lighting

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources, and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield (PLQY). However, the constraint of concentration quenching poses a great challenge for improving the PLQY. Herein, we propose a fundamental design principle by separating activators and prolonging their distance in Eu2+-activated Rb3Y(PO4)2 phosphors to inhibit concentration quenching, in which different quenching rates are controlled by the Eu distribution at various crystallographic sites. The blue-violet-emitting Rb3Y(PO4)2:xEu (x = 0.1%–15%) phosphors, with the occupation of Rb1, Rb2 and Y sites by Eu2+, exhibit rapid luminescence quenching with optimum external PLQY of 10% due to multi-channel energy migration. Interestingly, as the Eu concentration increases above 20%, Eu2+ prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances, resulting in green emission with suppressed concentration quenching, achieving an improved external PLQY of 41%. Our study provides a unique design perspective for elevating the efficiency of Eu2+-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

Opal-Inspired SiO2-Mediated Carbon Dot Doping Enables the Synthesis of Monodisperse Multifunctional Afterglow Nanocomposites for Advanced Information Encryption.

Despite recent advancements in inorganic and organic phosphors, creating monodisperse afterglow nanocomposites (NCs) remains challenging due to the complexities of wet chemistry synthesis. Inspired by nanoinclusions in opal, we introduce a novel SiO2-mediated carbon dot (CD) doping method for fabricating monodisperse, multifunctional afterglow NCs. This method involves growing a SiO2 shell matrix on monodisperse nanoparticles (NPs) and doping CDs into the SiO2 shell under hydrothermal conditions. Our approach preserves the monodispersity of the parent NP@SiO2 NCs while activating a green afterglow in the doped CDs with an impressive lifetime of 1.26 s. Additionally, this method is highly versatile, allowing for various core and dopant combinations to finely tune the afterglow through core-to-CD or CD-to-dye energy transfer. Our findings significantly enhance the potential of SiO2 coatings, transforming them from merely enhancing the biocompatibility of NCs to serving as a versatile matrix for emitters, facilitating afterglow generation and paving the way for new applications.

Realizing Bright-Dark Dual-Field Multimode Optical Signals in Photochromic Apatite Phosphors for Security Identification.

Regulating defect distribution in inorganic phosphors is paramount for realizing multimode dual-field optical signals for high security level identification but remains an ongoing challenge. Here, we propose a strategy of equivalent anion doping and nonequivalent cation doping to successfully regulate the trap distribution and density in Ba5(PO4)3Cl:F-,Eu2+,Ce3+ (BPCF-AG) phosphors. Due to the coexistence of shallow and deep traps for different photon processes, the BPCF-AG exhibits simultaneous photochromism in a bright field and tetramode luminescence (photoluminescence, afterglow, 980 nm photostimulated luminescence, and 650/532 nm photostimulated afterglow) in a dark field. The trap roles responsible for versatile optical behaviors are investigated by thermoluminescence curves, and a reasonable mechanism is proposed. In addition, we design a series of demonstrations for security identification and information encryption based on the dual-field multimode optical signals of BPCF-AG to illustrate its potential application scenarios.

Development of Mg2TiO4:Mn4+ phosphors for enhanced red LED emission and forensic fingerprint analysis

The advancement in the development of inorganic phosphors marks a significant milestone in the fields of LED technology and forensic science. Herein, Mg2TiO4:Mn4+ (MTO:Mn4+) novel red-emitting phosphors are synthesized through a solvothermal method, which demonstrates a promising approach for enhancing latent fingerprint detection capabilities and improving the performance of red LEDs. The confirmation of the cubic structure post-annealing and the nano-nature as revealed by TEM analysis underpin the MTO:Mn4+ phosphors suitability for these applications. The broad excitation spectra and the sharp red emission at 659 nm, coupled with the optimal doping concentration, showcase the MTO:Mn4+ phosphor's efficient luminescence properties. Moreover, the calculated critical distance between Mn4+ ions (32.906 Å) elucidates the concentration quenching mechanism, which is pivotal for optimizing the performance. The high purity of the emitted red light (97.2 %) and the precise CIE coordinates (0.5969, 0.2926) of the MTO:Mn4+ phosphor suggest its potential for producing high-quality red LEDs. Additionally, the capability of MTO:Mn4+ phosphors to reveal detailed and high-resolution latent fingerprints offers a more reliable and efficient method for processing and analyzing crucial evidence. These findings not only contribute to the scientific understanding of MTO:Mn4+ phosphor materials but also pave the way for their practical application in cutting-edge technologies.

A samarium (Ⅲ)-activated tantalum-based double perovskite phosphor with high thermostability

Inorganic double perovskite phosphor materials have received much attention in solid-state lighting domain due to efficient and versatile luminescence colors. This study employs a high-temperature solid-phase method to synthesize a series of Sm3+-activated Sr2YTaO6 (SYTO):Sm3+ phosphors with double perovskite structure. The structure, morphology, and content/temperature-dependent orange-red emissions are thoroughly elucidated. For SYTO:3 mol%Sm3+, the luminescence intensity at 423 K remains 95 % of that at 298 K, verifying high thermostability. Meanwhile, the phosphor exhibits good resistance to color shifting. A high Sm3+ content induces luminescence quenching due to dipole–dipole interaction. Finally, the synthesized material is utilized to fabricate a satisfactory and warm white light-emitting diode.

Circularly Polarized Phosphorescence Energy Transfer Combined with Chirality‐Selective Absorption for Modulating Full‐Color and White Circularly Polarized Long Afterglow

AbstractCircularly polarized long afterglow (CPLA) attracts great interests in multi‐disciplinary fields with significant potentials in optical multiplexing applications, but achieving full‐color and white CPLA is still challenging. The present contribution reports the first success in utilizing circularly polarized phosphorescence energy transfer (CPP‐ET) combined with chirality‐selective absorption (CSA) to construct full‐color and white CPLA materials. Blue CPLA with luminescence dissymmetry factor (glum) of 3×10−2 is firstly obtained via the CSA effect of chiral helical polyacetylene and blue ultralong afterglow of inorganic phosphor BP. Significantly, full‐color and white CPLA films are prepared by simply blending different fluorophores into the blue‐CPLA films via CPP‐ET. Benefited from the persistent luminescence of BP, the lifetimes of the fluorophores increase from nanoseconds to minutes, and ultralong full‐color CPLA emissions lasting for more than 20 min are realized with glum of 10−3. Also noticeably, chiral optoelectronic devices, multi‐dimension information encryption and chiral logic gate are developed based on the full‐color tunable CPLA‐active materials. The established strategy provides a universal platform for future development of CPLA‐active materials with great applications.

Circularly Polarized Phosphorescence Energy Transfer Combined with Chirality-Selective Absorption for Modulating Full-Color and White Circularly Polarized Long Afterglow.

Circularly polarized long afterglow (CPLA) attracts great interests in multi-disciplinary fields with significant potentials in optical multiplexing applications, but achieving full-color and white CPLA is still challenging. The present contribution reports the first success in utilizing circularly polarized phosphorescence energy transfer (CPP-ET) combined with chirality-selective absorption (CSA) to construct full-color and white CPLA materials. Blue CPLA with luminescence dissymmetry factor (glum) of 3×10-2 is firstly obtained via the CSA effect of chiral helical polyacetylene and blue ultralong afterglow of inorganic phosphor BP. Significantly, full-color and white CPLA films are prepared by simply blending different fluorophores into the blue-CPLA films via CPP-ET. Benefited from the persistent luminescence of BP, the lifetimes of the fluorophores increase from nanoseconds to minutes, and ultralong full-color CPLA emissions lasting for more than 20 min are realized with glum of 10-3. Also noticeably, chiral optoelectronic devices, multi-dimension information encryption and chiral logic gate are developed based on the full-color tunable CPLA-active materials. The established strategy provides a universal platform for future development of CPLA-active materials with great applications.

Analyzing the photoluminescence and energy transfer in Sr3Gd(BO3)3:inorganic borate-based phosphor Eu3+, Tb3+ and Ce3+

Analyzing the photoluminescence and energy transfer in Sr3Gd(BO3)3:inorganic borate-based phosphor Eu3+, Tb3+ and Ce3+

Exploring inorganic phosphors: basics, types, fabrications and their luminescence properties for LED/WLED/displays

Abstract The utilization of phosphors in lighting and display applications has garnered significant attention due to their unique luminescent properties and versatile crystal structures. This review article comprehensively examines recent advances in the synthesis, characterization, and applications of nitride and sulfide phosphors. This article addresses various phosphor crystal structures, including perovskite, garnet, nitride sulfide, fabrications strategies, and their impact on the optical and electronic properties. Furthermore, the review highlights the role of doping and activator ions in tailoring the emission characteristics of nitride and sulfide phosphors, enabling precise control over color rendering and efficiency. Additionally, the article also discusses emerging trends in phosphor technology, such as the development of novel synthesis methods and the integration of phosphors into next-generation lighting and display devices. The basic properties of phosphor materials like CRI, CIE chromaticity coordinates, quantum efficiencies are well discussed. Overall, this article provides valuable insights into the current state of research and future directions in the field of phosphors offering potential avenues for further advancements in lighting and display technologies.

Isomorphism of Sr[Li3AlO4] and Sr[Li3GaO4] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li3AlO4], Sr[Li3GaO4], and five substitutional derivates of Sr[Li3(Al1-x Ga x )O4] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li3(Al1-x Ga x )O4] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li3GaO4] and the known oxolithoaluminate Sr[Li3AlO4] in an ordered variant of the U[Cr4C4] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu2+-activated Sr[Li3(Al1-x Ga x )O4] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λem = 572 nm (fwhm equals 47 nm, 1446 cm-1, 0.18 eV) for yellow-emitting Sr[Li3AlO4]:Eu2+ and at λem = 554 nm (fwhm equals 49 nm, 1589 cm-1, 0.20 eV) for green-emitting Sr[Li3GaO4]:Eu2+. Sr[Li3AlO4]:Eu2+ has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.

Highly Efficient Broadband Near‐Infrared Emission in Cr3+‐Activated Organic Hafnium Chlorine for Multi‐Optoelectronic Applications

AbstractCr3+ ions doped broadband emission near‐infrared (NIR) phosphors are pertinent to widespread emerging applications and get rapid developed. However, it remains a challenge to simultaneously achieve highly efficient and broadband near‐infrared emission in Cr3+ ions doped phosphors. Herein, the Cr3+ ions firstly doped into organic–inorganic hafnium chlorine TEA2HfCl6 (TEA = Tetraethylammonium, C8H20N), which show broadband emission at a range of 700–1300 nm, a full width at half maximum (FWHM) of 164 nm, and a high photoluminescence quantum yield (PLQY) of 60%. The organic–inorganic metal halides show huge advantages than traditional inorganic phosphors, like high luminescence efficiency, low temperature solution synthesis progress, and low cost, which provide an efficiency strategy for lighting industry. Based on these advantages, a high power NIR light emitting diode (LED) is fabricated by TEA2HfCl6:Cr3+ with a high‐power 530 nm chip, which is used in food analysis, night vision, and biomedical imaging as a demonstration. This work indicates the feasibility of organic–inorganic metal halides as host materials for developing Cr3+ ions emitting phosphor toward multi‐optoelectronic applications.

Negative Thermal Expansion Materials as Anti-Thermal-Quenching Phosphor Matrixes: Status, Opportunities, and Challenges.

Inorganic phosphor materials often face the common phenomenon of luminescence thermal quenching (TQ), which deteriorates their device performance and consequently limits their applicability for broad applications. Thus, exploring thermally stable and even anti-TQ phosphors is viable to meet the urgent requirements of lighting technology and many other luminescence-based applications. One of the emerging approaches devoted to solving the TQ issue of phosphors, especially at elevated temperatures, is to employ negative thermal expansion (NTE) properties occurring in some unique inorganic materials. The present Review focuses on the progress of exploring NTE-based inorganic phosphor materials that have demonstrated unusual negative TQ with enhancing upconversion and downshift luminescence upon elevating temperature. We have also provided a brief history of exploring NTE phosphors for thermally stable and enhanced emission along with the investigation methods and proposed mechanisms of these unusual phenomena. To summarize, we have further discussed some opportunities and challenges that NTE materials face as host matrixes for anti-TQ phosphors. Overall, the aim of this Review is to stimulate the exploration of new NTE-based inorganic phosphors, the correlation of their fundamental structural changes with varying temperature, and the investigation of their potential for broad applications.

Optical property dataset of inorganic phosphor

Developing inorganic phosphor with desired properties for light-emitting diode application has traditionally relied on time-consuming and labor-intensive material development processes. Moreover, the results of material development research depend significantly on individual researchers’ intuition and experience. Thus, to improve the efficiency and reliability of materials discovery, machine learning has been widely applied to various materials science applications in recent years. However, the prediction capabilities of machine learning methods fundamentally depend on the quality of the training datasets. In this work, we constructed a high-quality and reliable dataset that contains experimentally validated inorganic phosphors and their optical properties, sourced from the literature on inorganic phosphors. Our dataset includes 3952 combinations of 21 dopant elements in 2238 host materials from 553 articles. The dataset provides material information, optical properties, measurement conditions for inorganic phosphors, and meta-information. Among the preliminary machine learning results, the essential properties of inorganic phosphors, such as maximum Photoluminescence (PL) emission wavelength and PL decay time, show overall satisfactory prediction performance with coefficient of determination (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R^2$$\\end{document}) scores of 0.7 or more. We also confirmed that the measurement conditions significantly improved prediction performance.

Robust, Narrow-Band Nanorods LEDs with Luminous Efficacy > 200lm/W: Next-Generation of Efficient Solid-State Lighting.

Energy-efficient white light-emitting diodes (LEDs) are in high demand across the society. Despite the significant advancements in the modern lighting industry based on solid-state electronics and inorganic phosphor, solid-state lighting (SSL) continues to pursue improved efficiency, saturated color performance, and longer lifetime. Here in this article, robust, narrow emission band nanorods (NRs) are disclosed with tailored wavelengths, aiming to enhance the color rendering index (CRI) and luminous efficacy (LE). The fabricated lighting device consists of NRs of configuration CdSe/ZnxCd1-xS/ZnS, which can independently tune CRI R1-R9 values and maximize the luminous efficacy. For general lighting, NRs with quantum yield (QY) up to 96% and 99% are developed, resulting in ultra-efficient LEDs reaching a record high luminous efficacy of 214lmW-1 (certified by the National Accreditation Service). Furthermore, NRs are deployed onto mid-power (0.3 W@ 50mA) LEDs, showing significantly enhanced long-term stability (T95 = 400h @ 50mA). With these astonishing properties, the proposed NRs can pave the way for efficient lighting with desired optical spectrum.

A novel n-UV convertible colour-tunable emitting oxynitride phosphor: Realization based on Ce3+ -Tb3+ energy transfer.

In the present work, a novel n-UV convertible colour-tunable emitting phosphor was obtained based on the efficient Ce3+ -Tb3+ energy transfer in the Y10 Al2 Si3 O18 N4 host. By properly controlling the ratio of Ce3+ /Tb3+ , the colour hue of the obtained powder covered the blue and green regions, under excitation of 365 nm. The steady-state and dynamic-state luminescence measurement was performed to shed light on the related mechanism, which was justified by the electronic dipole-quadrupole dominating the related energy transfer process. Preliminary studies showed that Y10 Al2 Si3 O18 N4 :Ce3+ ,Tb3+ can be promising as an inorganic phosphor for white LED applications.

Development of reddish orange-emitting Y2Sn2O7:Eu3+phosphors for latent fingerprint detection and anti-counterfeit security ink

In forensic science, fingerprint detection and anti-counterfeiting technologies are crucial. Inorganic phosphors are potentially suitable materials for high-quality visualization and security. We synthesized novel Y2Sn2O7:Eu3+ (YSO:Eu3+) phosphors by a sol–gel method. They have a cubic structure and emit reddish orange emission from the Eu3+ ions electronic transition of 5D0→7F1. The optimal doping concentration of Eu3+ is 7 mol% and dipole-dipole interaction causes the quenching mechanism. The chromaticity coordinates of YSO:7Eu3+ phosphor are (0.6086, 0.3906). We used the optimized YSO:7Eu3+ phosphors for forensic applications, such as latent fingerprints and security ink. The latent fingerprints stained with YSO:7Eu3+ phosphors showed clear images and reliable level 1–3 characteristics. The security ink was visible on different surfaces. Our results indicate that the YSO:7Eu3+ phosphor can be used for visualizing latent fingerprints and anti-counterfeiting applications.

Synthesis, structural, photoluminescence, and EPR analysis of far red emitting Ca3La2W2O12:Mn4+ inorganic phosphor for applications in plant-growth LEDs

This study explores the structural and optical properties of Mn4+ doped Ca3La2W2O12 phosphor. It also investigates the incorporation of Mn4+ ions for deep red emission and electron paramagnetic resonance (EPR) analysis. The phosphors were synthesized using the sol-gel method, and their properties were thoroughly examined using a combination of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), photoluminescence (PL), and EPR technique. The XRD analysis provided insights into the phase purity, and constituents of the synthesized samples. Under 345 nm excitation, we observed far red emission at 705 nm, with the highest emission intensity occurring at a concentration of 0.0025 mol of Mn4+ metal ions in the host matrix. Concentration quenching was observed due to dipole-quadrupole interactions. The CIE chromaticity coordinates confirm far red region emission, and the estimated correlated color temperature (CCT) suggests that these phosphors can be used for bright illumination. Concurrently, the EPR examination also confirmed the presence of Mn4+ ions in the host matrix and showed the effect of variation on Mn4+ concentration in the EPR spectroscopy measurements. Furthermore, the electron paramagnetic resonance analysis demonstrated a distinctive six-line spectrum with a g-factor of approximately 1.98, indicating the presence of paramagnetic Mn4+ ions. This primary line was accompanied by a broader resonance with a linewidth of 950 Gauss, partially overlapping the six-line spectrum. The initial investigation indicates that this far red emitting phosphor can be applied to plant-growth LEDs.