Solid-state Lighting Applications Research Articles

Investigation on effect of Ca2+ ions in SrLa2O4:Dy3+ phosphors for solid state lighting application

White light emitting SrLa2−xO4:Dy3+/0.05 Ca2+phosphors are prepared by solid state reaction technique at 1200◦C.X-ray diffraction method interprets the phase structure of the material while the luminescence properties of the co-doped SrLa2O4 phosphors and energy transfer mechanism are scrutinized by photoluminescence spectra analysis. Two main emission peaks are attributed at 484 nm and 571 nm due to the Dy3+ions under 324 nm excitation wavelength. The resultant output is in consonance with the synthesis white-light emitting phosphors can be obtained from the single host material at x = 0.06 doping concentration Dy3+ ions. The phosphors reveal a strong absorption band obtained in UV region and the observed white-light emission with chromaticity co-ordinates read x = 0.326, y = 0.362. The inference illustrates the synthesis material prospective candidate for white LED applications.

Rare-earth-free Mn4+ ions activated Ba2YSbO6 phosphors for solid-state lighting, flexible display, and anti-counterfeiting applications

Recenlty, rare-earth (RE)-free ions (Mn4+) activated phosphor materials are becoming an alternative source while replacing Eu2+ ions activated metal oxide, phosphate, and nitride phosphors for multi-functional applications. In this report, we prepared novel RE-free Mn4+ (mol%) ions activated double perovskite-type Ba2YSbO6 (BYSO:Mn4+) phosphor materials by a solid-state reaction method in an ambient condition. The physicochemical properties such as phase purity, elemental composition, and morphology of the materials were systematically investigated. The temperature-dependent photoluminescence (PL) properties of the BYSO:8 mol% Mn4+ (i.e., BYSO:8Mn4+) phosphor samples were studied. The PL excitation of the phosphors showed a broadband spectrum in the near-ultraviolet region from 300 to 450 nm with a maximum intensity at 353 nm. Under 353 nm excitation, the Mn4+ ions activated phosphors showed a broadband far-red emission in the region of 650–750 nm with a maximum intensity at 694 nm due to the 2Eg→4A2g electronic configuration. The BYSO:8Mn4+ phosphors also showed a lower intensity band at 667 nm and the corresponding Commission Internationale de l’Eclairage chromaticity coordinate for the optimized phosphor was (0.653, 0.274) which is more beneficial, especially for the growth process in plants. Additionally, the optimized BYSO:8Mn4+ phosphor maintained good thermal PL behavior and its related binding energy value was 0.29 eV. Considering these good benefits from the BYSO:8Mn4+ phosphor, we further fabricated a red light-emitting device to demonstrate its potential applicability in solid-state lighting. Also, the as-prepared polydimethylsiloxane composite films demonstrated their suitability for flexible display and anti-counterfeiting applications in harsh environmental conditions.

Nickel-doped carbon dots with enhanced and tunable multicolor fluorescence emission for multicolor light-emitting diodes

Carbon dots (CDs) are a new type of carbon-based fluorescent nanomaterials, which have received a lot of interest because of their excellent properties, simple synthesis and wide applications. However, facial and fast synthesis of CDs with tunable multicolor emission that can be used for lighting still remains a challenge. Here, through a simple one-step solvothermal method, nickel-doped CDs with tunable fluorescence emission are successfully prepared. By optimizing the experimental conditions, fluorescence emission of the as-prepared CDs can be adjusted within a certain wavelength range (513 nm–612 nm), that is, from green to red. The particle size of the CDs also increases from 2 nm to 8 nm. The introduction of Ni can successfully enhance the fluorescence intensity and cause an obvious redshift. In addition, by mixing polyvinylpyrrolidone (PVP) with the multicolor nickel-doped CDs (Ni-MCDs), the self-quenching effect of solid-state fluorescence can be effectively avoided. Based on this, green, yellow and red light-emitting diodes (LEDs) with high performance can be constructed by integrating CDs/PVP composites with different colors on top of the UV chip, demonstrating their superior potential for solid-state lighting applications.

Robust color purity of reddish-orange emission from Sm3+-activated La10W22O81 biocompatible microphosphors for solid state lighting and anticancer applications

We synthesized reddish-orange luminescent La10W22O81 (LWO):Sm3+ microphosphors by hydrothermal-assisted solid-state reaction. X-ray diffraction analysis reveals that all the studied phosphors crystallize in an orthorhombic structure in the Pbcn space group (60). Field emission scanning electron microscopy indicates that the LWO:1.5 mol% Sm3+ phosphor displays a smooth-surfaced hexagonal rod-like shape, with a closed shape at both ends, and high-resolution transmission electron microscopy demonstrates a robust crystalline structure. The chemical composition and valence states of the phosphor were investigated using X-ray photoelectron spectroscopy. At 403 nm excitation, LWO:1.5 mol% Sm3+ exhibits maximum intensity with the strongest band at 596 nm (4G5/2 → 6H7/2) in the reddish-orange region. The intensity of Sm3+ emission decreases beyond 1.5 mol% owing to concentration quenching regulated by dipole–quadrupole interaction between Sm3+ ions. The optimized microphosphor LWO:1.5 mol% Sm3+ exhibits color coordinates (0.5760, 0.4207), which is close to that of the Amber LED-NSPAR 70 BS (0.570, 0.420), displaying the highest color purity of 99.2% and correlated color temperature of 1694 K. In addition, both breast cancer cells MCF-7 and normal lung fibroblasts WI-38 were tested for toxicity with the optimized microphosphor. It is found that the LWO:1.5 Sm3+ microphosphor is extremely toxic to cancer cells, but not to normal cells. Based on these results, LWO:Sm3+ microphosphor can serve as a biomedical candidate for the treatment of cancer, as well as a potential multicolor emitting material for w-LEDs.

Luminescence properties of multicolor emitting La4GeO8:Tb3+,Eu3+ phosphors

Tb3+ and Eu3+ doped La4GeO8 multicolor emitting phosphors were synthesized. A systematic investigation was done into the photoluminescence properties of La4GeO8:Tb3+,Eu3+. Energy transfer from trivalent terbium to europium ions in La4GeO8 results from quadrupole-quadrupole interaction. The variable temperature emission spectra ranging from 303 to 513 K were used to demonstrate the thermal stability of La4GeO8:0.07Tb3+,0.01Eu3+ phosphor. The obtained activation energies for trivalent terbium and europium ions were 0.186 eV and 0.187 eV, separately. By altering the content ratio of Eu3+ to Tb3+, the La4GeO8:Tb3+,Eu3+ phosphors can achieve multicolor luminescence and tunable chromaticity from green (0.3416, 0.5423) to red (0.6479, 0.349) under 265 nm light excitation. The findings suggest that La4GeO8:Tb3+,Eu3+ are promising phosphors for solid-state lighting application.

White Light-Emitting Diodes Based on One-Dimensional Organic-Inorganic Hybrid Metal Chloride with Dual Emission.

White-light emissive organic-inorganic hybrid metal halides (MHs) have shown promising potential applications in solid-state lighting. As one-dimensional (1D) MHs for white-light emission remain rare and the key role of halogen regulation in 1D hybrid MHs for broadband emission (BE) has not been well established yet, herein, we report a family of 1D hybrid MHs TMGPbX3 (TMG = 1,1,3,3-tetramethylguanidine, X = Cl-, Br-, or I-) to systematically explore the influence of halogen on crystal structures and photoluminescence (PL) properties in 1D organic-inorganic hybrid MHs. Under ultraviolet excitation, TMGPbBr3 and TMGPbI3 exhibit BE originating from self-trapped excitons (STEs), while TMGPbCl3 manifests the special blue-white dual emission, which is contributed by STEs in inorganic frameworks and free excitons (FEs) in the organic component. Different emission mechanisms of three 1D MHs are well demonstrated and compared. With a PL quantum yield (PLQY) up to 11.67%, a white light-emitting diode (WLED) based on TMGPbCl3 was fabricated to show its valuable application in solid-state lighting.

Linear and non-linear photoluminescence studies of Ho3+/Yb3+ co-doped titanate phosphors for photonic applications

This work presents the morphological and photoluminescence (PL) studies of the single ion Ho3+ doped and Ho3+/Yb3+ co-doped Ba3−x-yMoTiO8:xHo3+/yYb3+ phosphors synthesized by conventional solid-state reaction method. Phase confirmation of all the as-prepared samples was done by X-Ray Diffraction (XRD) patterns. The morphological behavior and vibrational frequency bands were studied by Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR) techniques respectively. Diffuse Reflectance Spectra (DRS) has been recorded for the singly doped and co-doped samples to find out the optical bandgap. The linear and non-linear emission spectral studies under 448 and 980 nm excitation wavelengths respectively showed three bands in the green, red, and blue regions. A relatively more intense band observed in the green region under 980 nm excitation shows promising usage of the titled phosphor for non-linear applications. A plot drawn between non-linear luminescence emission intensity Vs pump power reveals the information pertaining to the number of photons involved in the process. In addition, Commission Internationale de I′Eclairage (CIE) coordinates calculated from the emission spectral features lie in the green region. All the studies show the broad application of the as-prepared phosphors in linear and non-linear luminescence process-based green emitting diodes, display devices, security inks, phototherapy, and solid-state lighting (SSL) applications.

Ligand Engineering Triggered Efficiency Tunable Emission in Zero-Dimensional Manganese Hybrids for White Light-Emitting Diodes.

Zero-dimensional (0D) hybrid manganese halides have emerged as promising platforms for the white light-emitting diodes (w-LEDs) owing to their excellent optical properties. Necessary for researching on the structure-activity relationship of photoluminescence (PL), the novel manganese bromides (C13H14N)2MnBr4 and (C13H26N)2MnBr4 are reported by screening two ligands with similar atomic arrangements but various steric configurations. It is found that (C13H14N)2MnBr4 with planar configuration tends to promote a stronger electron-phonon coupling, crystal filed effect and concentration-quenching effect than (C13H26N)2MnBr4 with chair configuration, resulting in the broadband emission (FWHM = 63 nm) to peak at 539 nm with a large Stokes shift (70 nm) and a relatively low photoluminescence quantum yield (PLQY) (46.23%), which makes for the potential application (LED-1, Ra = 82.1) in solid-state lighting. In contrast, (C13H26N)2MnBr4 exhibits a narrowband emission (FWHM = 44 nm) which peaked at 515 nm with a small Stokes shift (47 nm) and a high PLQY of 64.60%, and the as-fabricated white LED-2 reaches a wide colour gamut of 107.8% National Television Standards Committee (NTSC), thus highlighting the immeasurable application prospects in solid-state display. This work clarifies the significance of the spatial configuration of organic cations in hybrids perovskites and enriches the design ideas for function-oriented low-dimensional emitters.

Thermometric and luminescence studies of Eu3+ activated CaSr2(PO4)2 phosphor for non-contact optical thermometry and solid state lighting applications

Using a low-cost solution combustion method, CaSr2(PO4)2 orthophosphate phosphors doped with Eu3+ were prepared and examined as non-contact optical thermometers and solid state lighting sources. The synthesized phosphors were characterized via X-ray diffraction (XRD), photoluminescence spectroscopy (PL), Fourier transform infrared spectroscopy (FTIR) and temperature-dependent photoluminescence spectroscopy. The results of XRD and FTIR spectroscopy confirms the creation of a single-phase CaSr2(PO4)2 phosphors with the presence of orthophosphate anion (PO4)3-. Near-ultraviolet stimulation at 395 nm produced intense, orange and red emission bands centered at 592 nm and 615 nm for CaSr2(PO4)2:Eu3+ phosphors, matching the typical 5D0→7F1 and 5D0→7F2 transition states of Eu3+ ions. CIE chromaticity coordinates (0.65, 0.35) in the color gamut confirm the red emission. To accomplish optical thermometry, the fluorescence intensity ratio (FIR) approach was applied, which employed the thermally coupled emission levels 5D1 and 5D0 of Eu3+. With a maximal sensitivity of about 0.0023 K−1 at 323 K, the prepared phosphors are most sensitive at low temperatures. Based on the results obtained, the synthesized phosphor CaSr2(PO4)2:Eu3+ can be exploited in non-contact optical thermometry and solid-state lighting applications.

A Review on Polymeric Photoluminiscent Nanofibers: Inorganic, Organic and Perovskites Additives for Solid-State Lighting Application

A Review on Polymeric Photoluminiscent Nanofibers: Inorganic, Organic and Perovskites Additives for Solid-State Lighting Application

Lead-Free Potassium Alloyed Cs2AgBiBr6: Tunable Optoelectronic Properties and Carrier-Lattice Interaction

The role of the carrier-lattice interaction and associated self-trapped excitons (STEs) in broadband white-light emission in perovskite halides is one of the key aspects when aiming to develop next generation semiconductors for lighting applications. Herein, we provide microscopic insight on optoelectronic properties and electron–phonon interactions in potassium (K+) alloyed Cs2AgBiBr6, while evaluating its potential as a single material tunable light emitter. While K+ partially occupying the Cs+ site leads to blue-light emission at low K+ ion concentrations, a sudden photoluminescence broadening and white-light emission occur at relatively higher alloying concentrations where K+ starts to occupy Ag+ sites. Simulation reveals an anomalous increase in carrier lattice coupling strength (via the Fröhlich mechanism) when K+ replaces Ag+. This along with the increased density of STEs (aided by strong electron–phonon coupling and more octahedral distortion) and induced free exciton (FE) emission is proposed to play a major role behind the observed photoluminescence (PL) broadening and white-light emission. This study should stimulate further research on single material based white-light emitters for next generation solid-state lighting applications.

Investigation on luminescence properties and energy transfer of Gd3+ and Sm3+-doped phosphate glass for solid-state lighting

The physical and optical properties of glasses for solid-state lighting applications are being investigated. The melt quenching procedure at 1200 °C was used to create the Gd3+ and Sm3+ ions using doped phosphate-based glasses. Gd2O3 and Sm2O3 concentrations increased density, according to the findings. For the alteration in the glass, the intensity of molar volume rose, indicating the establishment of a non-bridging oxygen (NBO) network. The absorption spectra migrated from 6H5/2, the ground state, to different states with wavelengths ranging from 300 to 1700 nm. When the energy transfer from the IH model is at its greatest at 11 mol% Gd3+ concentration, photoluminescence spectra exhibit four emission peaks ranging from 4G9/2 to 6H5/2, 6H7/2, 6H9/2, and 6H11/2, respectively. The maximum photoluminescence spectra intensity was 1 mol% of Sm2O3, which was compared to bismuth germanium oxide (Bi4Ge3O12; BGO) crystal at 10.33% by x-ray excitation. The color of orange emission is determined by the CIE 1931. The Judd-Ofelt (JO) parameter (Ωλ (λ = 2, 4, 6)) have been used by evaluated Judd-Ofelt theory and trend were Ω4 > Ω6 > Ω2. As a result, doped phosphate base glasses with Gd3+ and Sm3+ ions have property requirements, and cost-cutting production is the best option for solid-state lighting applications.

Bright white light emission from blue emitting carbon dot-coated Dy3+-doped luminescent glasses

Dy3+-doped luminescent glasses have received great attention due to their ability to emit white light at a suitable yellow-to-blue intensity ratio. However, achieving bright white light using single Dy3+-doped glasses remains a challenge due to the hypersensitivity of the emission band at 575 nm — usually resulting in intense yellow emission. In this work, we present a novel approach for compensating for the blue emission deficiency of Dy3+ to produce resin-free white light-emitting diodes (WLEDs) by synthesizing two series of Dy3+-doped glasses from tellurite and silicate systems on which blue-emitting carbon dots (BCDs) are spin-coated. The structural, chemical, optical, and luminescence properties of tellurite and silicate glasses are compared and discussed in detail. White light emissions are obtained upon 365-nm excitation for BCD-coated Dy3+-doped tellurite and silicate glasses with color coordinates of (x = 0.31, y = 0.33) and (x = 0.31, y = 0.34) and correlated color temperatures (CCT) of 5518 K and 5316 K, respectively. BCDs coating increases photoluminescence quantum yield (PLQY) values from 3.10 % to 5.62 % and from 20.81 % to 31.49 % for tellurite and silicate glasses, respectively. Ultimately, the findings in this work show the potential of BCD-coated luminescent glasses with excellent luminescent properties to be considered in solid-state lighting applications.

Study of the up/down-conversion green luminescence of BaWO4: Er3+ phosphors for non-contact temperature sensing and solid-state lighting applications

Study of the up/down-conversion green luminescence of BaWO4: Er3+ phosphors for non-contact temperature sensing and solid-state lighting applications

Eu3+ doped K2O-B2O3-Al2O3-SiO2 glass ceramics containing KAlSiO4 crystalline phase: Realizing red emission and high thermal stability

Eu3+ doped K2O-B2O3-Al2O3-SiO2 glass ceramics containing KAlSiO4 crystallite were synthesized by melt crystallization method. Differential scanning calorimetry (DSC) analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the optimal heat treatment conditions for glass ceramics, which were 560 °C/90 min. The light transmittance of the glass ceramics can reach up to 75% in the visible light range. The luminescence properties of glass ceramics were studied by fluorescence spectra, and the optimal doping concentration of Eu3+ was determined to be 0.7%. At this concentration, the fluorescence lifetime is 1.65 ms, the chromaticity coordinate (CIE) is (0.583, 0.4048). The luminescent properties of glass ceramics have high stability under the change of temperature (300–460 K). Eu3+ doped K2O-B2O3-Al2O3-SiO2 based glass ceramics have potential applications in solid-state lighting, red lasers.

Luminescence investigation of Sm3+ activated CaAl2(Sio4)2Cl2 chlorapatite phosphor for solid state lighting applications

Rare earth activated chloride based phosphors have attention in recent years in the field of solid state lighting. Sm 3+ activated was synthesized by a high-temperature solid-state reaction. Synthesized phosphors are characterized by XRD to confirm its phase purity and structural analysis. Vibrational features are confirmed by Fourier-transform infrared spectroscopy (FTIR). Photoluminescence spectra of Sm 3+ activated CaAl 2 (Sio 4 ) 2 Cl 2 chlorapatite phosphor emission ranges from 552 nm to 625 nm peaking at 564 nm due to 4 G 5/2 → 6 H 5/2 emitting in yellow region. While emission observed in orange region shows doublet at 601 nm and 607 nm are due to 4 G 5/2 → 6 H 7/2 and small hump observed at 648 nm is due to 4 G 5/2 → 6 H 9/2 transition. All the supported results of the present phosphor are proving its worth in the field of solid state lighting and WLEDs applications.

Luminescence properties of MgCaAl10 O17 :RE3+ (RE3+ = Sm3+ ,Dy3+ ) phosphor for eco-friendly solid-state lighting applications.

Different concentrations of rare earth Sm3+ - and Dy3+ -activated MgCaAl10 O17 phosphors were synthesized using the combustion route and their detailed luminescence investigations are reported in this paper. The photoluminescence excitation spectra of Sm3+ - and Dy3+ -activated MgCaAl10 O17 phosphor show multiple peaks in the ultraviolet light region of the electromagnetic spectrum. The characteristic emission spectra of the MgCaAl10 O17 :Sm3+ phosphor are located at 563 nm, 594 nm, and 644 nm, with the maximum emission intensity occurring at 594 nm. The emission spectra of the MgCaAl10 O17 :Dy3+ phosphor show two emission peaks, one at 476 nm wavelength in the blue light region and the other at 573 nm wavelength in the yellow region. The above results suggest that the prepared phosphor can be suitable for applications in eco-friendly solid-state lighting.

Charge compensation and solid-state lighting application for dysprosium-activated Ba2TeP2O9 phosphor

In this study, trivalent dysprosium (Dy 3+ ) activators were doped into barium tellurooxyphosphate Ba 2 TeP 2 O 9 (BTP) by a solid-state sintering procedure, where alkali metal (A = Li, Na, and K) ions co-doped as charge compensator were aimed at improving the luminescent performance. To investigate optical absorption behavior, the electronic structure of the BTP host was realized via the density functional theory (DFT) method. The BTP:Dy 3+ phosphor excited by 349 nm shows bright yellow emission. When the concentration of the Dy 3+ activator is greater than 0.03 mol, concentration quenching occurs owing to dipole–dipole interaction. After doping 0.03 mol A + ions into the BTP:0.03Dy 3+ phosphor, the emission intensity of BTP:0.03Dy 3+ enhances by 1.18 (Li + ), 1.43 (Na + ), and 2.32 times (K + ). Additionally, the BTP:0.03Dy 3+ ,0.03 K + phosphor exhibits satisfactory thermal stability. A white light-emitting diode (w-LED) was successfully fabricated from the BTP:0.03Dy 3+ ,0.03 K + and commercial blue phosphors with a 365 nm LED chip. The study reveals that the BTP:0.03Dy 3+ ,0.03 K + phosphor is a prospective yellow-emitting candidate for w-LED. • Due to the asymmetric coordination of Dy 3+ , the yellow-emitting of BTP:Dy 3+ is stronger than its blue-emitting. • Co-doping K + into the host can both produce minimal lattice distortion and reduce the structural vacancy. • The thermostability of BTP:0.03Dy 3+ ,0.03 K + is competitive with that of the commercial yellow phosphor. • The concentration quenching mechanism is the dipole–dipole interaction.

Efficient Orange Emission in Mn2+-Doped Cs3Cd2Cl7 Perovskites with Excellent Stability.

Low-dimensional metal halides are attractive for applications in photodetectors, solid-state lighting, and solar cells, but poor stability is an obstacle that must be overcome in commercial applications. Herein, we successfully synthesized a Ruddlesden-Popper (RP)-phased perovskite Mn2+:Cs3Cd2Cl7 with high photoluminescence quantum yield (PLQY) and outstanding thermal and environmental stability by a solvothermal method. The pristine sample Cs3Cd2Cl7 exhibits a weak cyan broad emission centered at 510 nm with a low PLQY of ∼4%. Once Mn2+ ions are introduced into the host lattice, a bright orange emission peaking at 580 nm with a high PLQY of ∼74% was achieved, which is attributed to the efficient energy transfer from the host to Mn2+ ions and thus results in the 4T1 → 6A1 radiation transition of Mn2+ ions. The photoluminescence (PL) intensity and environmental stability of Mn2+:Cs3Cd2Cl7 can be further improved through A-site Rb alloying. Finally, an orange LED with outstanding color stability was fabricated on the basis of the Mn2+:Cs3Cd2Cl7. Our work successfully elucidates that dopant plays an integral role in tailoring optical properties.

Zero-dimensional Hybrid Antimony Halide with Intrinsic Cyan Light Emission.

Recently, zero-dimensional (0D) hybrid metal halides have attracted intensive attention with wide applications in solid-state lighting and display diodes. Herein, by using a facile wet-chemistry method, we prepared one new 0D hybrid antimony halide of [HMHQ]2 SbCl5 ⋅ 2H2 O (MHQ=2-methyl-8-hydroxyquinoline) based on the discrete [SbCl5 ]2- unit. Remarkably, the bulk crystals of [HMHQ]2 SbCl5 ⋅ 2H2 O exhibit strong cyan light emission with a promising photoluminescence quantum yield (PLQY) of 18.92%. Systematical studies disclose that the cyan emission is mainly derived from the radiative recombination within conjugated organic cation. Benefiting from the promising luminescent performance, this 0D antimony halide can be utilized as an excellent down-conversion light emitting luminescent material to assemble white light-emitting diodes with high color rendering index (CRI) of 90.2.