Solid-state Lighting Applications Research Articles

Realization of orange-red emitting double perovskite structured Sm3+-doped Ba2ZnWO6 nanophosphors: A systematic study of structural, photoluminescence and photometric properties for solid-state lighting applications

Exploring luminescent materials that meet the necessary specifications which can beneficial for solid-state lighting applications has prompted extensive research. In this context, the present article deals with a successful exploration of orange-red emanating double perovskite structured Sm3+ (1–11 mol %) -doped Ba2ZnWO6 nanophosphors synthesized via a self-igniting solution combustion route. The crystallographic studies of the phosphors confirm the cubic phase having Fm̅3m space group. The morphological investigations exhibit non-uniform flaky-type particles with agglomeration. The average optical energy gap of the phosphors is found to be around 3.25 eV. The photoluminescence emission spectra enclosed three distinctive peaks located at around 564, 597, and 644 nm, which are attributed to 4G5/2→6HJ (J = 5/2, 7/2 and 9/2) transitions of Sm3+ ions, respectively. The estimated chroma coordinates (0.5385, 0.4527) are located in the orange-red region of the chromaticity diagram and achieve correlated color temperature values between 1865 and 2783 K with color purity in the range 94.7–98.7 %. The obtained results dominantly certified the suitability of the prepared nanophosphors as a favorable candidate for solid-state lighting applications.

Luminescence properties of ZrO2: Dy3+ phosphor for solid-state lighting applications

Herein, we report Dy3+-activated ZrO2 phosphors synthesized via the sol-gel technique. The structural, morphological, and optical properties of the synthesized powder samples annealed at 900 °C were investigated. The monoclinic phase of the synthesized phosphor was confirmed by recording the X-ray powder diffraction (XRPD) pattern. Ultraviolet–visible analysis was performed for the reflectance and bandgap measurements of the phosphors. Field emission scanning electron microscope and X-ray energy dispersive spectroscopy analyses were used to study the morphology and elemental composition of the phosphors, respectively. The distribution of ions in the undoped and Dy3+-doped samples was confirmed using time-of-flight secondary ion mass spectroscopy. The photoluminescence (PL) behavior of the synthesized phosphors was investigated by recording the excitation and emission spectra. When the synthesized phosphors were exposed to UV light at 353 nm, we observed characteristic blue and yellow Dy3+ PL emissions, corresponding to the transition 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. Additionally, we observed low-intensity red and brown-red emission peaks corresponding to 4F9/2 → 6H11/2 and 4F9/2 → 6H9/2. These observations indicate that the non-aqueous sol-gel route, coupled with the suitable post-synthesis heat treatment, resulted in the development of a monophase (monoclinic) zirconia. This makes it a strong candidate for phosphor applications due to its high room temperature stability and efficient characteristic features of the monoclinic phase. These findings strongly suggest that Dy3+-doped ZrO2 can serve as a superior phosphor material for white light-emitting diode applications.

Luminescence and optical thermometry strategy based on emission spectra of Li2Ba5W3O15:Pr3+ phosphors

In this study, a series of Pr3+ ions doped Lithium Barium Tungstate (Li2Ba5W3O15) was synthesized using the conventional high-temperature solid state method. The structure and phase of the phosphors were analysed using X-ray diffraction (XRD) patterns. Fourier Transform Infrared (FT-IR) spectroscopy was used to examine the different vibrational bands present. The optical band gap values of the optimized LBW phosphor and the undoped LBW sample were measured using diffuse reflectance spectra (DRS). Under 319 nm excitation, the photoluminescence (PL) spectra of the Pr3+-activated LBW phosphor exhibited strong visible blue and reddish emissions at 488 nm and 647 nm respectively corresponding to the 3P0 → 3H4 and 3F2 transitions of the Pr3+ ions. The evaluated CIE color chromaticity coordinates of the as-prepared LBW:Pr3+ phosphors lie within the white region. The temperature-dependent PL (TDPL) measurement demonstrated relatively good thermal stability for the synthesized phosphor. Moreover, the fluorescence intensity ratio (FIR) was used to analyze the optical sensing properties of the LBW:Pr1.0 phosphor. A maximum relative sensitivity (Sr) of 1.03 % K−1indicated the potential of these phosphors for optical thermometry applications. A double exponential trend with decreasing lifetime was observed in the PL decay data at 647 nm emission (λem) under 319 nm excitation (λex), with an increase in the Pr3+ ions concentration in the host matrix. In conclusion, the investigations conducted demonstrate that the Pr3+ ions doped LBW phosphors show great potential for applications in solid-state lighting and optical thermometry. Its emission characteristics, thermal stability, and optical sensing capabilities establish it as a suitable candidate for these applications.

Organic Electronics-Microfluidics/Lab on a Chip Integration in Analytical Applications.

Organic electronics (OE) technology has matured in displays and is advancing in solid-state lighting applications. Other promising and growing uses of this technology are in (bio)chemical sensing, imaging, in vitro cell monitoring, and other biomedical diagnostics that can benefit from low-cost, efficient small devices, including wearable designs that can be fabricated on glass or flexible plastic. OE devices such as organic LEDs, organic and hybrid perovskite-based photodetectors, and organic thin-film transistors, notably organic electrochemical transistors, are utilized in such sensing and (bio)medical applications. The integration of compact and sensitive OE devices with microfluidic channels and lab-on-a-chip (LOC) structures is very promising. This survey focuses on studies that utilize this integration for a variety of OE tools. It is not intended to encompass all studies in the area, but to present examples of the advances and the potential of such OE technology, with a focus on microfluidics/LOC integration for efficient wide-ranging sensing and biomedical applications.

Solution-Obtained (NH4)3In0.95Sb0.05Cl6 with High External Photoluminescence Quantum Yield and Excellent Antiquenching Properties.

The efficient broad-band emission from low-dimensional metal halides has garnered significant interest. However, most of these materials exhibit poor stability at the operating temperature of light-emitting diodes. In this study, using the solution method (temperature lower than 90 °C), a new compound (NH4)3In0.95Sb0.05Cl6 was obtained with the structure in the Pnma space group featuring unit-cell parameters of a = 12.3871(4) Å, b = 24.9895(9) Å, and c = 7.7844(3) Å. (NH4)3In0.95Sb0.05Cl6 can be prepared by doping (NH4)2InCl5·H2O when the Sb3+ feeding ratio is in the range of 30-80%. Thermal analysis reveals that (NH4)3In0.95Sb0.05Cl6 is stable up to 320 °C. (NH4)3In0.95Sb0.05Cl6 exhibits broad-band yellow-white emission with extremely high internal and external photoluminescence quantum yields of 93 and 77%, respectively. Interestingly, (NH4)3In0.95Sb0.05Cl6 displays remarkable resistance to thermal quenching, retaining 83% of its initial photoluminescence intensity at 80 °C. A white light-emitting diode is fabricated by combining (NH4)3In0.95Sb0.05Cl6 with a commercial phosphor, and a high color rendering of 92.8 was obtained. This work presents an environmentally friendly, efficient, stable UV-excited broad-band emission material for potential solid-state lighting applications.

High-quality reddish-orange-emitting Sr6Y2Al4O15:Eu3+ phosphors for solid-state lighting and anti-counterfeiting applications

The reddish-orange emitting Sr6Y2Al4O15:Eu3+ phosphors were synthesized via a high-temperature solid-state reaction technique, and their luminescent properties were systematically studied. The dominant emission peak assigned to the electric dipole transition (5D0 → 7F2) was recorded at 612 nm owing to the non-inversion symmetry of the substituted sites of Eu3+ ions under the excitation of charge transfer band (∼261 nm). The emission of Sr6Y2Al4O15:Eu3+ revealed a Commission Internationale de l'Eclairage (CIE) chromaticity coordinate of (0.571, 0.368) and a color purity of 93.6 %. The thermal stability and photoluminescence quantum yield (PLQY) of Sr6Y2Al4O15: Eu3+ were analyzed, exhibiting a high thermal stability of 88.24 % at 423K and a good external PLQY of 36.24 %. Furthermore, the solid-state lighting (SSL) and flexible anti-counterfeiting applications of Sr6Y2Al4O15:Eu3+ were demonstrated. The red light-emitting diode (LED) was packaged with ∼260 nm ultraviolet LED chip, representing a CIE chromaticity coordinate of (0.5955, 0.3592) and a color purity of 86.53 %. The flexible anti-counterfeiting film was fabricated with polydimethylsiloxane polymer, and it showed tunable emission under different excitations. Moreover, the anti-counterfeiting ink was prepared and printed on various substrates. Consequently, the reddish-orange emitting Sr6Y2Al4O15: Eu3+ phosphors with high color purity, good thermal stability, and high quantum efficiency were introduced and potentially used in SSL and flexible anti-counterfeiting applications.

Small Stokes shift and high thermostability in Ce3+ doped K2BaPO4F phosphors

Novel K2BaPO4F:Ce3+ phosphors with strong violet-emission and high thermostability were synthesized by a traditional high-temperature solid-state reaction method. The phase composition and crystal structure were investigated in detail by XRD refinement. DFT calculations based on refined crystal structure were performed. A bright emission in the range of 340–390 nm with a small Stokes shift has been observed when excited at about 323 nm in K2BaPO4F:Ce3+ phosphors. The temperature-dependent PL spectra from 80 to 500 K were investigated systematically. The best doping concentration of K2BaPO4F:xCe3+ phosphors was verified and the concentration quenching mechanism was also confirmed. When the temperature increased from 80 K to 500 K, the emission intensity still remains 53 %. The thermal quenching mechanism was explained using the crystal structure investigation and DFT calculation. The strong near-ultraviolet emission intensity and ultra-high thermal stability indicating that the prepared K2BaPO4F:Ce3+ phosphors have potential applications in anti-counterfeiting and solid-state lighting.

Kilogram-scale synthesis of carbon dots with high-efficiency full-color solid-state fluorescence using an aggregation-induced emission strategy

Carbon dots (CDs), one of the most promising luminescent nanomaterials, have attracted widespread concern due to their unique optoelectronic properties and widespread application. However, mass production of solid-state CDs with highly efficient full-color emission has rarely been reported, severely limiting their practical application in solid-state lighting and displays. Here, using an aggregation-induced emission (AIE) strategy, full-color solid-state fluorescent (SSF) CDs with quantum yields (QYs) of up to 55.3–27.9% have been prepared on a kilogram scale through one-step microwave-assisted pyrolysis of the same precursors. Detailed structure–property studies demonstrate that the SSF of CDs is derived from the suppression of surface carboxyl group motions and the decrease of the non-radiative rate in their aggregated state, and that their tunable emission is attributed to the excessive fluorescence resonance energy transfer (FRET) induced by the increasing number of aromatic rings on CD surfaces. Therefore, these CDs exhibit both the AIE enhancement and red shift throughout the entire visible spectrum in the solid state. Finally, because of their excellent AIE properties, these highly efficient SSF CDs have been applied to pattern encryption, large-area luminescent fibrous membranes (LFMs), light-emitting diodes (LEDs), and fingerprint detection.

Synthesis, optical properties and Judd-Ofelt analysis of Eu3+ doped Ca2KMg2V3O12

The synthesis of undoped and the Eu3+ doped garnet-type vanadate Ca2KMg2V3O12 (CKMV) was achieved using a solid-state reaction method. The phase formation of the samples was confirmed through powder XRD analysis. The morphological properties of the material were examined using SEM, and elemental mapping through EDAX provided information about the elements present in the samples. The band gap energy of CKMV and CKMV:0.05Eu3+ was determined using DRS measurements. Photoluminescence properties of CKMV and CKMV: xEu3+ (x = 0.01–0.09) were investigated under excitation at 370 nm, with emission at 612 nm. Additionally, the dominant characteristic peak of Eu3+ was studied through photoluminescence emission under excitation at 472 nm. Lifetime decay analysis and CIE color coordinates were obtained. Judd-Ofelt intensity parameters were calculated based on the emission spectra, elucidating the radiative properties of CKMV:0.05Eu3+. Temperature-dependent photoluminescence demonstrated the good thermal stability of the optimized sample. From the temperature dependent life time analysis, the sensitivity of the material has been calculated. These findings suggest that this phosphor is well-suited for use in solid-state lighting applications.

White light emitting devices with high color rendering index and electrically adjustable color temperature

Herein, we report a rare earth-free white light emitting composite for applications in solid-state lighting, which is made up of carbon nitride (CN) and Mn2+-doped perovskite quantum dots (PQDs). The correlated color temperature (CCT) is adjustable from 18 088 to 2926 K by varying the ratio of the two components. When the PQDs content is 2.88%, the white light emitting diode (W-LED) based on the CN/PQDs composite shows a competitive color rendering index of 88, a CCT of 5737 K, and a chromaticity coordinate of (0.327, 0.33), which is close to the standard white light. The light conversion efficiency of the composite is around 10%, which is attributed to the high photoluminescence efficiencies of the two components and weak photon reabsorption between them. Moreover, the CCT can be tuned from 4750 to 7315 K by changing the repetition frequency of the electrical input.

Enhanced Circular Dichroism and Polarized Emission in an Achiral, Low Band Gap Bismuth Iodide Perovskite Derivative.

Lead halide perovskites and related main-group halogenido metalates offer unique semiconductor properties and diverse applications in photovoltaics, solid-state lighting, and photocatalysis. Recent advances in incorporating chiral organic cations have led to the emergence of chiral metal-halide semiconductors with intriguing properties, such as chiroptical activity and chirality-induced spin selectivity, enabling the generation and detection of circularly polarized light and spin-polarized electrons for applications in spintronics and quantum information. However, understanding the structural origin of chiroptical activity remains challenging due to macroscopic factors and experimental limitations. In this work, we present an achiral perovskite derivative [Cu2(pyz)3(MeCN)2][Bi3I11] (CuBiI; pyz = pyrazine; MeCN = acetonitrile), which exhibits remarkable circular dichroism (CD) attributed to the material's noncentrosymmetric nature. CuBiI features a unique structure as a poly-threaded iodido bismuthate, with [Bi3I11]2- chains threaded through a cationic two-dimensional coordination polymer. The material possesses a low, direct optical band gap of 1.70 eV. Notably, single crystals display both linear and circular optical activity with a large anisotropy factor of up to 0.16. Surprisingly, despite the absence of chiral building blocks, CuBiI exhibits a significant degree of circularly polarized photoluminescence, reaching 4.9%. This value is comparable to the results achieved by incorporating chiral organic molecules into perovskites, typically ranging from 3-10% at zero magnetic field. Our findings provide insights into the macroscopic origin of CD and offer design guidelines for the development of materials with high chiroptical activity.

Photoluminescence study of Sr3Al32O51:Eu3+ phosphor for Solid state lighting applications

Sr3Al32O51:Eu3+ phosphor prepared successfully by simple combustion method. Prepared matrix synthesized for different percentage of composition for rare earth Eu3+ = (0.5, 1.0, 1.5, 2.0 and 2.5). Photoluminescence property was taken for the given doped phosphor which shows the excitation peak at 395 nm and 466 nm respectively. Emission peak observed at 593 nm and 613 nm for excitation wavelength 395 nm and same emission peak observed for excitation wavelength 466 nm comparatively less intense than 395 nm. The phase of the synthesized phosphor confirmed by X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Photoluminescence (Pl) property shows that the given matrix is the one of the potential material which can be used for solid state lightening.

White afterglow observed in Ce3+, Eu2+ and Dy3+ Co-activated Sr3Al2O5Cl2 phosphor

A white phosphor, Sr3Al2O5Cl2: Ce3+, Eu2+ and Dy3+, was synthesized successfully through high temperature solid state process. XRD refinement revealed that all the doping cations replaced the original Sr2+ site in the phosphor lattice. Upon ultraviolet excitation, the phosphor displayed a blue emission from the 5 d-4f Ce3+ transition centered at 441 nm, as well as a broad orange emission from the 5 d-4f Eu2+ transition centered at 636 nm. By adjusting the concentrations of Eu2+, a white emission was achieved with the formula Sr3Al2O5Cl2: 0.005Eu2+, 0.02Dy3+, 0.005Ce3+. After the removal of excitation, a persistent white afterglow was observed due to the presence of Dy3+ electron traps in the lattice with optimal trap depth. The mechanism proposed suggests that the recombination between thermally released electrons originating from the trap center and existing holes at the emission centers of Ce3+ and Eu2+ drives the observed white afterglow phenomenon. These findings highlight the potential of Sr3Al2O5Cl2: Ce3+, Eu2+ and Dy3+ phosphors in solid-state lighting applications.

Novel low temperature synthesis of Y2-x 03 :Eux 3+ nanophosphor prepared by combustion with Thioglycerol as fuel for near UV light emitting diodes (n-UVLEDs).

Luminescent materials used in flat panel displays (FPD), compact fluorescent lamps (CFL), and light-emitting diodes (LEDs) require high purity, uniform particle size, clean surfaces, spherical shape, and dense morphology to ensure long-term stability. Y2 O3 :Eu3+ is a widely studied red phosphor known for its characteristic photoluminescence emission at 613 nm with near-UV excitation at 392 nm. Many synthesis methods have been explored to achieve Y2 O3 :Eu3+ nanoparticles with exceptional purity, consistent phases, and uniform particle sizes. The goal is to obtain particles with pristine surfaces, spherical shape, and compact morphology. This study focuses on the low-temperature synthesis and photoluminescence investigation of Y2-x O3 :Eux 3+ nanophosphors prepared using combustion with thioglycerol as a fuel. The results are compared with Y2-x O3 :Eux 3+ red nanophosphors synthesized using wet chemical and nitrate combustion methods. The photoluminescence characteristics of the Y2-x O3 :Eux 3+ nanophosphors were analyzed using PL emission spectroscopy, XRD, and scanning electron microscopy (SEM). These findings highlight the advantageous properties of the synthesized nanophosphors, such as their suitability for solid-state lighting applications in the lamp industry as highly efficient red phosphors. The combination of high purity, uniform particle size, clean surfaces, spherical shape, and dense morphology contributes to their potential for long-term stability and reliable performance in lighting devices.

An ab initio modelling for pristine and defect-induced emissions from NaCe(WO4)2: a potential material for solid-state lighting application

An ab initio modelling for pristine and defect-induced emissions from NaCe(WO4)2: a potential material for solid-state lighting application

High Emission Efficiency and Thermal Stability in Zero-Dimensional Hybrid Zinc Halide as a Blue Light Emitter.

Exploring highly efficient blue-emissive lead-free halide materials is a significant and challenging objective in the study of luminescent materials. This study reports the synthesis of a new zero-dimensional (0D) hybrid zinc halide of [CYP]ZnBr4 (CYP = 1-cyclohexylpiperazine) containing an isolated [ZnBr4]2- tetrahedron. [CYP]ZnBr4 exhibits strong blue light emission with a high photoluminescence quantum yield (PLQY) of 79.22%, surpassing all previously reported 0D zinc halide counterparts. According to the theoretical and experimental studies, the blue light emission is attributed to intrinsic self-trapped excitons resulting from strong electron-phonon coupling and structural deformation. Importantly, [CYP]ZnBr4 demonstrates excellent structural and luminescence stability toward high temperatures (180 °C) over at least half a month. High luminescence efficiency and stability enable [CYP]ZnBr4 to be an efficient blue phosphor to fabricate white light-emitting diodes (LEDs), which produces high-quality white light with a color rendering index (CRI) of 93.1 and a correlated color temperature (CCT) of 5304 K, closely resembling natural sunlight. This white LED also exhibits consistent performance and stability across different drive currents, suggesting the potential for high-power optoelectronic applications. Overall, this study paves the way for the utilization of 0D hybrid halides in advanced solid-state lighting applications.

Spectroscopic and energy transfer analysis in Dy3+/Eu3+ activated/co-activated LiNaSO4 phosphors: Structural and optical properties

Sulphate based phosphors shows great impact in the field of luminescence in recent times. In the present investigation, Dy3+, Eu3+ activated/co-activated LiNaSO4 phosphor prepared by simple combustion method using urea as a fuel. Phase identification and crystal structure of prepared phosphor is investigated by XRD and Reitveld refinement. Vibrational features of proposed phosphors were confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Morphological study of the proposed phosphor with elemental analysis of the sample is investigated by SEM analysis. Photoluminescence study of the proposed phosphor shows three simultaneous emission peaks in the visible range gives white light emission. These all results confirm that the proposed phosphor is potential candidate for WLEDs and solid state lighting applications.

Analysis of the Structure, Thermal, and Molecular Dynamics of Organic-Inorganic Hybrid Crystal at Phases IV, III, II, and I: [NH2(CH3)2]2CdBr4.

A comprehensive understanding of the physicochemical properties of organic-inorganic hybrids is essential for their solid-state lighting applications. Therefore, a single crystal of [NH2(CH3)2]2CdBr4 was grown; the crystal structure was monoclinic, and the phase transition temperatures for the four phases IV, III, II, and I were 383 K (TC1), 417 K (TC2), and 427 K (TC3). Furthermore, the chemical shifts caused by the local field around 1H, 13C, 14N, and 113Cd changed continuously with temperature, especially near TC1, indicating that the local environment changes with temperature. Owing to the large change in 113Cd chemical shifts, the coordination geometry of Br around Cd in the CdBr4 tetrahedra changes near TC1. Therefore, it is proposed that Br plays a significant role in the N-H···Br hydrogen bond. Finally, the spin-lattice relaxation time T1ρ, representing the energy transfer around the 1H and 13C atoms of the cation, changed significantly with temperature. The activation energies obtained from the T1ρ results were two times larger at high temperatures than at low temperatures. This study provides an understanding of the fundamental properties of organic-inorganic hybrid compounds to broaden their applications.

N-UV triggered green emitting Er3+ doped Zirconia: A bifunctional material for solid-state lighting and optical thermometry

In the current piece of work, we have synthesized the Er3+-activated ZrO2 and illustrated the bifunctional utility of this material for solid-state lighting and non-contact optical thermometry. The synthesized samples were characterized by XRD, XPS, and PL techniques for their structural, surface, and luminescence studies. Under the excitation of 377 nm, characteristic green emission corresponding to intra 4f-4f transitions of Er3+ is obtained. The concentration quenching effect was observed beyond 1.2 mol % concentration of doping. Using Dexter's theory, it was revealed that dipole-quadrupole interactions are predominantly responsible for concentration quenching. The Photometric study was performed using the PL data. For the most intense phosphor, a highly pure green color (color purity ∼ 97.6%) and CCT ∼ 5375 K is observed. Furthermore, the temperature-sensing capability of the most intense sample has also been explored by triggering the synthesized phosphor by n-UV light. The temperature sensing performance is checked by measuring variations in the fluorescence intensity ratio (FIR) of the thermally coupled levels of Er3+ with temperature. The synthesized phosphor gives high relative sensitivity (1.19% K−1 at 303 K)) and absolute sensitivity (11.39 × 10−4 at 603 K)) values. These results suggest that n-UV-triggered Er3+ doped ZrO2 can be a promising bifunctional material for applications in solid-state lighting and non-contact optical thermometry.

A novel yellow whitish Dy3+ activated [formula omitted] phosphor: Structural, spectral and optical investigations

This study details the effective solution combustion synthesis of novel Na1−xZr2Dyx(PO4)3(x=0.05−0.5) (hereby abbreviated as NaZrPO:Dy3+) phosphor. The structural investigation of synthesized phosphor employing X-ray diffraction and FTIR spectroscopy reveals the formation of single-phase phosphor and the presence of (PO4)3- group. The lattice parameters turned out to be a=b=8.798Å,c=22.794Å. The morphological and chemical analysis is characterized by FE-SEM and X-ray photoelectron spectroscopy, respectively. According to PL spectrum, three traditional emission bands of Dy3+ ions (482 nm, 574 nm, and 663 nm) are observed, and the concentration quenching of the Dy3+ ions in the phosphor occurred at 3 mol. % as a result of the dipole-dipole interaction. Photometric results reveal the emission of the synthesized phosphor in the yellow-whitish region with a color purity of ∼80%. The optical parameters obtained from diffuse-reflectance spectroscopy, such as refractive index, metallization criterion, and bandgap, for the optimal molar concentration (3 mol. %) are 2.109, 0.46, and 4.3 eV, respectively. According to these results, when stimulated by a source of n-UV (348 nm), the synthesized phosphor is a promising candidate for solid-state lighting applications and might be used to produce WLEDs.