Photoluminescence Excitation Research Articles

Near-infrared downshifting luminescence of Ca2LaTaO6:Nd3+/Yb3+/K+ phosphors and their applications: solar cells and anti-counterfeiting.

A series of Nd3+/Yb3+ co-doped Ca2LaTaO6 (CLTO) phosphors are synthesized by a high temperature solid phase method. Structural characterization confirms the successful incorporation of Nd3+ and Yb3+ ions into the CLTO host lattice. The photoluminescence excitation (PLE) spectra and photoluminescence (PL) spectra of CLTO:Nd3+ and CLTO:Nd3+/Yb3+ are investigated in detail. Under the excitation of ultraviolet (UV) and visible (VIS) light, the CLTO:Nd3+/Yb3+ phosphor emits broadband near infrared (NIR) luminescence. In particular, the luminescence intensity of the Yb3+ ion is increased through an energy transfer (ET) process from Nd3+ to Yb3+. The luminescence mechanism of the CLTO:Nd3+/Yb3+ sample is analyzed based on the decay lifetime and PL spectra. In addition, the NIR emission intensity of Yb3+ ions is also enhanced by doping K+ ions. The broadband luminescence (850-1050 nm) of the CLTO:Nd3+/Yb3+/K+ phosphor has good application in solar cells and anti-counterfeiting.

The Impact of Silver Codoping on Tb3+ Luminescence in Lithium Tetraborate Glasses.

Spectroscopic properties of Tb-doped and Tb-Ag codoped lithium tetraborate (LTB) glasses with Li2B4O7 (or Li2O-2B2O3) composition are investigated and analysed using electron paramagnetic resonance (EPR), optical absorption, photoluminescence (PL) and photoluminescence excitation (PLE) spectra, PL decay kinetics and absolute quantum yield (QY) measurements. PL spectra of the investigated glasses show numerous narrow emission bands corresponding to the 5D4 → 7FJ (J = 6-0) and 5D3 → 7FJ (J = 5-3) transitions of Tb3+ (4f8) ions. The most intense PL band of Tb3+ ions at 541 nm (5D4 → 7F5 transition) is characterised by a lifetime slightly exceeding 2.6 ms. PL spectra of the Ag-containing glass show two broad weakly resolved emission bands in the violet-green spectral range attributed to Ag+ ions and nonplasmonic Ag nanoclusters. Decay kinetics of these bands are nonmonoexponential, characterised by an average lifetime in the microsecond range. A significant enhancement of the PL intensity and PL QY of Tb3+ ions was observed in Tb-Ag codoped LTB glass in comparison with Tb-doped LTB glass. The excitation energy transfer (EET) mechanisms from Ag+ ions and Ag nanoclusters to Tb3+ ions were explored.

Development of High-Efficiency BaSrCaWO6:Mn4+ Red-Emitting Phosphors via La3+ Addition Strategy.

In this paper, a series of BaSrCaWO6:x%Mn4+, y%La3+ (x = 0.1, 0.5, 0.6, 1.5; y = 0, 5, 10, 15, 20) red-emitting phosphors were synthesized by the high-temperature solid-state method. The structure and optical properties of the samples were systematically studied by the characterizations of x-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis spectra, photoluminescence (PL) spectra, photoluminescence excitation (PLE) spectra, and quantum efficiency (QE). It was found that the addition of La3+ ions plays significant roles on the luminous performance of phosphors as compared with the nonluminous BaSrCaWO6:Mn (BSCW:Mn), which can be attributed to the Mn2+ → Mn4+ oxidation process induced by La3+ doping. The BSCW:0.5%Mn, 15%La3+ phosphor exhibited a strong emission peak at 685 nm with a CIE chromaticity coordinate at (0.720, 0.279), which is suitable for application in indoor plant cultivations. The BSCW:0.5%Mn, 15%La3+ phosphor exhibited an IQE of 47.8% and a high absorption efficiency of 72.8% with the EQE of 34.8%. Besides, the phosphor also showed the thermal stability with the emission intensity at 423 K being 48% of the emission intensity at 298 K. These results indicate that the synthesized BSCW:0.5%Mn, 15%La3+ phosphor could be a potential phosphor to be applied in plant growth LEDs.

Temperature Dependent Photoluminescence Properties of a Y2Ge2O7:Tb3+ phosphors. A dual band ratiometric luminescent thermometer

A series of green light emitting Y2Ge2O7:xTb3+ phosphors (x = 0.2, 0.5, 1.0, 2.0 and 4.0mol%) were obtained via the solid-state reaction method. The single phase was confirmed by XRD technique. The photoluminescence (PL) excitation spectrum, emission spectra at room and as a function of temperature, decay curves of phosphors were studied in detail. The emission spectra show typical emissions of Tb3+ ions, whose relative intensities change with the ion concentration or UV excitation. A shift of the CIE chromaticity coordinates from blueish to green region was observed. The emission decay curves are compatible with a single type of Tb3+ activator. The obtained internal Quantum Yield (iQY) increase with the terbium concentration, up to 10.0% for sample with 4.0mol%. In addition, the relative sensitivity values (Sr) for samples with 1.0 and 2.0mol% reached 0.97 and 2.02%K-1, respectively. These high thermal sensitivities obtained, in comparison with other Tb3+ based optical temperature sensors, in biophysical temperature range (30–45 °C), illustrates the potential use of Y2Ge2O7:xTb3+ phosphors in the design of efficient FIR luminescent thermometers for biological systems or other industrial applications.

Record-high hyperpolarizabilities in atomically precise single metal-doped silver nanoclusters.

Recent developments in optical imaging techniques, particularly multi-photon excitation microscopy that allows studies of biological interactions at a deep cellular level, have motivated intensive research in developing multi-photon absorption fluorophores. Biological tissues are optically transparent in the near-infrared region. Therefore, fluorophores that can absorb light in the near-infrared (NIR) region by multi-photon absorption are particularly useful in bio-imaging. For instance, photoluminescence from ligand-protected gold nanoclusters has drawn extensive research interest in the past decade due to their bright, non-blinking, stable emission and tunability from the blue to the NIR emission. In this work, using the control of single metal doping on silver nanoclusters (Ag25 protected by thiolate SR = 2,4-dimethylbenzenethiol (DMBT) ligand), we aim to explore the effects of metal doping on the (photo)stability and nonlinear optical response of liganded nanoclusters. We study two-photon excited photoluminescence and the second harmonic response upon excitation in the NIR (780-950 nm) range. Particular emphasis is placed on the effect of metal doping on the second-order nonlinear optical scattering properties (first hyperpolarizability, β(2ω)) of Ag25 nanoclusters. In addition, β(2ω) values are one order higher than the one reported for Au25 nanoclusters and represent the largest values ever reported for ligand-protected nanoclusters. Such enhanced hyperpolarizability leads to a strong second harmonic response and renders them attractive targets in bioimaging.

Investigation of Spectroscopic Parameters and Trap Parameters of Eu3+-Activated Y2SiO5 Phosphors for Display and Dosimetry Applications.

Using the solid-state reaction technique, varied Y2SiO5 phosphors activated by europium (Eu3+) ions at varied concentrations were made at calcination temperatures of 1000 °C and 1250 °C during sintering in an air environment. The XRD technique identified the monoclinic structure, and the FTIR technique was used to analyze the generated phosphors. Photoluminescence emission and excitation patterns were measured using varying concentrations of Eu3+ ions. The optimal strength was observed at a 2.0 mol% concentration. Emission peaks were detected at 582 nm and 589 nm for the 5D0→7F1 transition and at 601 nm, 613 nm, and 632 nm for the 5D0→7F2 transition under 263 nm excitation. Because Eu3+ is naturally bright, these emission peaks show how ions change from one excited state to another. This makes them useful for making phosphors that emit red light for use in optoelectronics and flexible displays. Based on the computed (1931 CIE) chromaticity coordinates for the photoluminescence emission spectra, it was determined that the produced phosphor may be used in light-emitting diodes. The TL glow curve was examined for various doping ion concentrations and durations of UV exposure levels, revealing a broad peak at 183 °C. Using computerized glow curve deconvolution (CGCD), we calculated the kinetic parameters.

The one-pot fabrication of green-emitting composites based on PMMA

Photoluminescent composites consisting of a photoluminescent material dispersed in a suitable matrix have been applied in many applications, such as light-emitting diodes, solar concentrators, and anti-counterfeiting inks. The traditional method for the fabrication of composites by blending an as-synthesized photoluminescent material and a matrix is very challenging as it is difficult to obtain homogeneous composites. In this study, we have demonstrated a one-step method to prepare homogeneous composites by inducing the formation of in-situ photoluminescent centers in a stable matrix. Poly(methyl methacrylate) (PMMA) coated with o-phenylenediamine (oPD) was thermally annealed at 165oC for a duration of 5 minutes in an extruder to obtain green-emitting composites. The composites exhibited a broad absorption peak at 425 nm and an absorption shoulder at 495 nm. The emission spectrum of the composite was broad, ranging from 400 nm to 700 nm, and reached the maximum at 525 nm. The photoluminescent maximum position was independent of the excitation wavelength. The photoluminescent excitation spectrum of the composite resembled the absorption near 425 nm. Time-dependent density functional theory (TD-DFT) calculations suggested that 2,3-diaminophenazine and 3-amino-2-hydroxyphenazine are the main molecular fluorophores accounting for the optical properties of the composites. The synthetic method demonstrated in this study is transferable for preparing numerous photoluminescent thermoplastics.

Erbium doped P2O5-BiF3-MgO-ZnO-KF glasses for green laser applications

Abstract A series of oxyfluorophosphate glasses with the composition (60-x) P2O5 + 10 BiF3 +10 MgO + 10 ZnO + 10 KF + xEr2O3 (0 ≤ x ≥ 2.0 mol%) were prepared using conventional melt quenching method. The amorphous phase of studied glass samples was examined through powder x-ray diffraction. The optical properties were determined using UV–vis-NIR absorption, photoluminescence excitation and emission spectra. The radiative properties were determined using Judd–Ofelt and Fuchtbauer-Ladenburg theories. The optimal Er3+ doping concentration for efficient emission was determined by analysing the emission spectra under 377 nm excitation. The emission spectra of studied glasses exhibited characteristic emission bands of Er3+ ions corresponding to the 2H11/2 → 4I15/2 (529 nm), 4S3/2 → 4I15/2 (545 nm) and 4F9/2 → 4I15/2 (684 nm) transitions. At higher Er3+ doping levels, the emission bands shift towards longer wavelengths showing a red shift. Upon 980 nm excitation for upconversion, the Er3+ ions emitted intense green luminescence through the 4S3/2 → 4I15/2 (545 nm) transition. The applicability of studied glasses for the fabrication of green laser sources was discussed. The glass system containing 0.5 mol% of Er3+ ions was identified to be the optimal choice for designing green laser sources.

Organic Crystal with Anti‐Stokes Photoluminescent Excitation and Thermally Activated Delayed Fluorescence Features

AbstractThermal activation process utilizes environmental thermal energy to help supplement energy for the nonspontaneous energy‐consuming upconversion physical transitions with positive free energy change (ΔG>0). Reverse intersystem crossing (rISC) and hot band absorption are two kinds of thermal activation transitions. Thermally activated delayed fluorescence (TADF) materials with rISC have significantly propelled advancements in organic semiconductors. Hot band absorption, enables anti‐Stokes photoluminescence, offering a promising route for efficient photon upconversion. In this work, we constructed a crystal consisting of a donor‐acceptor type TADF molecule, DPQ‐DPAC, demonstrating dual thermal activation properties of hot band absorption with a notable 0.1 eV anti‐Stokes shift emission and proficient TADF performance. Only in the crystal TADF efficiency facilitates and the photoluminescence quantum yield elevates to an impressive 90.8 %. Combining the extended absorption spectrum, these enhancements collectively realize anti‐Stokes photoluminescence in crystal. Experimental and theoretical results on the DPQ‐DPAC crystal indicate optimizations in its conformational and vibrational modes, resulting in enhancements to its properties. This finding provides insight into crafting organic materials with thermally activated functionalities and contributes to fully exploiting the potential of organic materials, further advancing versatile materials applications.

Photoluminescent Device for Monitoring Fusarium Infection in Seeds

Plant diseases reduce crop yields and can significantly undermine the sustainability of the agricultural sector. Early detection is crucial for effective disease control and management. An analysis of optical methods and devices for diagnosing plant infestations was carried out. (Research purpose) To develop a device for optical photoluminescence diagnostics of Fusarium infestation in cereal seeds. (Materials and methods) Fusarium-infected seeds of Irishka 172 winter wheat and Moskovsky 86 barley were studied. (Results and discussion) A universal device for measuring wheat and barley infestation must be equipped with three radiation sources, operating at wavelengths of 362, 424, and 485 nanometers. The VLMU3510-365-130 LED is most suitable for exciting luminescence at 362 nanometers, the CREELED424 LED is optimal for 424 nanometers, and the XPEBBL-L1 LED is ideal for 485 nanometers. The VEMD5510 photodiode was chosen to detect seed luminescence in the ranges of 390-550 and 510-670 nanometers, while the BPW21R photodiode was selected for the range of 450-600 nanometers. Additionally, a microcontroller, operational amplifier, display, keyboard and other components were also selected. A block diagram was developed that includes incorporating light-optical and electronic units, along with a power supply. During laboratory tests of the LUM VIM-1 device prototype, photosignal responses were observed at 362, 424 and 485 nanometers for wheat and barley seeds with varying infestation levels. The method for determining Fusarium infection includes sample preparation, excitation and detection of photoluminescence, amplification of the photoluminescence signal ratio, and calculation of infection levels using calibration equations. (Conclusions) Based on the energy efficiency criterion, radiation sources and receivers were selected for the device used in the express monitoring of Fusarium infection levels in wheat and barley seeds. During laboratory tests, previously obtained dependencies of seed photoluminescence fluxes on infection levels were confirmed, and the calibration characteristics of the developed device were refined.

Enhancement of Sm3+ Luminescence in Sol-Gel Silica Matrix: Effect of Ligands Phenyl Phosphinic Acid and Trioctylphosphine Oxide.

Sol-gel silica matrices singly doped with Sm3+ and co-doped with ligands phenyl phosphinic acid (PPIA) and trioctylphosphine oxide (TOPO) were fabricated and studied for their structural and spectroscopic behaviour. Structural studies were done by x-ray diffraction (XRD) and Fourier transform infra-red (FTIR) absorption analysis whereas spectroscopic behaviour was studied by ultraviolet - visible (UV-Vis) absorption, photoluminescence (PL) excitation, emission and time-correlated decay analyses. XRD studies exhibit the amorphous nature of the samples and FTIR studies corroborate the presence of the ligands in the silica matrix. UV-Vis absorption and PL studies show significant enhancement in the radiative parameters in ligand co-doped samples compared to singly doped Sm3+ sample. Judd Ofelt parameters estimated from the absorption spectra possess higher values compared to popular hosts; revealing higher asymmetry and covalency around the active Sm3+ ions. An enhancement in PL intensity by 50.38 times and yield by 52.57 times with the co-doping of the ligands PPIA and TOPO is reported. These enhancement in the radiative output in ligand co-doped samples is attributed to the modification of the silica network with the incorporation of the ligands, energy transfer from ligands to nearby Sm3+ ions as well as due to the shielding of Sm3+ ions from the OH quenchers in the silica matrix. The improved PL behaviour especially corresponding to 4G5∕2→6H9∕2 transitions occurring at 643nm suggests the potential of PPIA and TOPO co-doped Sm3+ silica matrix for diverge optical applications.

Organic Crystal with Anti-Stokes Photoluminescent Excitation and Thermally Activated Delayed Fluorescence Features.

Thermal activation process utilizes environmental thermal energy to help supplement energy for the nonspontaneous energy-consuming upconversion physical transitions with positive free energy change (ΔG>0). Reverse intersystem crossing (rISC) and hot band absorption are two kinds of thermal activation transitions. Thermally activated delayed fluorescence (TADF) materials with rISC have significantly propelled advancements in organic semiconductors. Hot band absorption, enables anti-Stokes photoluminescence, offering a promising route for efficient photon upconversion. In this work, we constructed a crystal consisting of a donor-acceptor type TADF molecule, DPQ-DPAC, demonstrating dual thermal activation properties of hot band absorption with a notable 0.1 eV anti-Stokes shift emission and proficient TADF performance. Only in the crystal TADF efficiency facilitates and the photoluminescence quantum yield elevates to an impressive 90.8 %. Combining the extended absorption spectrum, these enhancements collectively realize anti-Stokes photoluminescence in crystal. Experimental and theoretical results on the DPQ-DPAC crystal indicate optimizations in its conformational and vibrational modes, resulting in enhancements to its properties. This finding provides insight into crafting organic materials with thermally activated functionalities and contributes to fully exploiting the potential of organic materials, further advancing versatile materials applications.

Synthesis and Photoluminescent Study of Dy Doped Ca3Gd2(BO3)4 Phosphors

The synthesis and photoluminescence study of Dysprosium (Dy) doped Calcium Gadolinium Borate Ca3Gd2(BO3)4:Dy3+ are presented in this research. The aim of this study was to investigate the optical properties and potential applications of Dy-doped Calcium Gadolinium Borate as a luminescent material. The samples with Dy+3 doping have been synthesized by the solid state reaction method at varying concentration of Dy+3 ions. The phase purity of the synthesized samples was confirmed from the X-ray diffraction where single phase orthorhombic structure was obtained. The UV excitation photoluminescence spectra of synthesized samples and emission peaks referring to the energy transition of Dy+3 ions are identified. Here, different emission intensities and the shift in the peaks position with reference to change in the Dy+3 concentration were analyzed, and the maximum luminescence intensity was observed at the best dopant concentration. This is made evident from this concentration-dependent behavior which suggests that energy transfer from the host lattice to Dy+3 ions is highly efficient. Therefore, the present work is a successful path towards Dy-doped Calcium Gadolinium Borate as a luminescent material. Due to its property this material seems to have good application potential in solid-state lighting, display and opto-sensing.

The Study of Tunable Excitation Independent and Dependent Photoluminescence Behaviour of P-Functionalized Carbon Dots

In this article, excitation independent and dependent fluorescence properties of surface functionalized carbon dots were studied. The samples were synthesized using a biomass derived Indian gooseberry as carbon precursor via microwave irradiation technique. Concentrated phosphonic acid is utilized as a surface passivator for carbon dots. The formation of spherical carbon dots in the size range of 6 to 12 nm was shown by transmission electron microscopy images. Raman and Fourier transform IR spectroscopies suggest the creation of highly disordered sp3carbon atoms including presence of surface functional groups and interaction of phosphorus with surface of carbon core. From the UV-visible absorption study, absorbance bands at 231 nm and 283 nm attributed to π-π* molecular transitions from carbon core are found. From the photoluminescence measurements, both excitation independent and excitation dependent tunable fluorescence is obtained from ultraviolet to visible (yellow) region of light respectively. The involvement of carbon core electronic states and surface modifier states are responsible for the origin of luminescence and their distinguished nature. The mechanism is discussed and emitted colour are confirmed by CIE plot. The relative quantum yield of the P-functionalized carbon dots is found to be 18.9% with reference to quinine sulfate. The fluorescence in ultra-violet and visible regions is applicable for bioimaging and potential antimicrobial activities.

Anomalous excitation wavelength dependent photoluminescence of Sb3+/Bi3+ co-doped double perovskites

Lead-free double perovskites have recently attracted lots of research interest due to their enhanced structural stability and decreased toxicity compared to lead-halide perovskites. However, origins of the dual emissions observed in photoluminescence (PL) are still controversial. Herein, PL properties of Sb/Bi co-doped Cs2NaInCl6 microcrystals are investigated. When the excitation wavelength is about 320–360 nm, the emission peak mainly locates at 450 nm. While excited at 250 nm, the emission peak reversely increases to ∼580 nm. According to Stokes shift, bandwidth, PL excitation spectra, PL lifetime, and temperature dependent PL, the 450 and 580 nm emissions are attributed to recombination of free exciton (FE) and self-trapped exciton (STE), respectively. Only when the excitation photon energy is large enough to generate lattice distortion and create excitons simultaneously does the STE form, exhibiting emission at 580 nm. As excitation wavelength increases, the photon energy becomes insufficient for the formation of the STE but is able to create FEs. Thus, the emission is dominated by FE recombination. Therefore, the excitation wavelength dependent PL peak position is observed. Moreover, we demonstrate an anti-counterfeiting pattern with excitation wavelength dependent color, which cannot be imitated by other luminescent materials, implying an improved security.

Excitation-Dependent Anti-Thermal Quenching in Zero-Dimensional Manganese Bromides for Photoluminescence and X-Ray Scintillation.

One of the most significant challenges of luminescent materials is the thermal quenching (TQ) at high temperature. Understanding the correlation between crystal structure variation and photoluminescence (PL) quenching is significant to achieve anti-thermal quenching (anti-TQ) phosphors. Herein, we unveil a universal principle governing switchable TQ and anti-TQ behaviors in zero-dimensional (0D) organic-inorganic hybrid manganese bromides. We observed an abnormal anti-TQ phenomenon when phosphor is excited in the valley of PL excitation (PLE) spectrum (indirect excitation) while TQ phenomenon is observed when excited in the peak and shoulder positions of PLE. Our findings demonstrate that PL intensity is influenced by two variable parameters: the effective Mn-ligand distance and the shortest Mn-Mn distance. These excitation-dependent TQ and anti-TQ behaviors originate from the relative changes in these distances, which modulate the competition between radiative and nonradiative recombination rates, as evidenced at the molecular level by molecular dynamics simulation. X-ray activated radioluminescence (RL) also exhibits anti-TQ behavior, which is analogous to the indirect excitation of PL evolution when excited at PLE valley. These insights bridge the gap between PL and RL properties in 0D manganese halides and offer potential avenues for developing advanced anti-TQ phosphors, efficient LEDs, and high-performance scintillators.

Broadening mechanisms of donor-bound exciton photoluminescence in Ga-doped ZnO nanowires

Donor spins in ZnO NWs have promise for quantum information (QI) applications due to high crystalline quality, narrow excitonic luminescence linewidths, and a direct bandgap of this material. It is important to understand the processes that can lead to inhomogeneous broadening of the excitonic transitions for realization of QI devices. We investigate the effect of Ga dopant concentration on the low temperature photoluminescence (PL) of Ga-doped ZnO nanowires. Spectrometer-resolution-limited donor-bound exciton (D0X) PL lines are observed at low concentrations with linewidths of around 0.1 meV. A clear increase in the Ga D0X line is observed as trace amounts of Ga are added. Above a certain concentration threshold, we observe a strong increase in the lateral growth coupled with a significant tail on the low energy side of the D0X emission, which scales linearly with dopant precursor concentration. We have analyzed this behavior using different models, including a model based on a bound exciton wavefunction overlap with neigbhouring donors and a Stark effect model due to random charged impurities. We rule out both of these models based on PL excitation spectroscopy measurements and show that a simple exponential model of the Urbach form gives the best fit and points to disorder in the more heavily doped shells.

The role of the dopant in the electronic structure of erbium-doped TiO2 for quantum emitters

Erbium-doped TiO2 materials are promising candidates for advancing quantum technologies, necessitating a thorough understanding of their electronic and crystal structures to tailor their properties and enhance coherence times. This study explored epitaxial erbium-doped rutile TiO2 films deposited on r-sapphire substrates using molecular beam epitaxy. Photoluminescence excitation spectroscopy demonstrated decreasing photoluminescence lifetimes with erbium doping, indicating limited optical coherence times. Lattice distortions associated with Er3+ were probed by x-ray absorption spectroscopy, indicating that erbium primarily occupies Ti4+ sites and influences oxygen vacancies. Significant lattice distortions in the higher-order shells and apparent full coordination around erbium suggest that additional defects are likely prevalent in these regions. These findings indicate that defects contribute to limited coherence times by introducing alternative decay pathways, leading to shorter photoluminescence lifetimes.

Study of the microstructure and temperature dependent luminescence of Na- and Li-beta gallia rutile compounds

We present the structural, vibrational and luminescence properties of Na- and Li- stabilized gallium-titanium oxides studied by optical spectroscopy techniques. The microstructure and characteristic vibrational modes of this homologous series, which are not well known, have been determined with the aid of Raman spectroscopy and compared to density functional theory (DFT) calculations. On the other hand, intense cathodoluminescence bands in the visible and in the near-infrared are observed depending on the term of the series and related to native defects. Besides, the study of the temperature evolution of the photoluminescence and photoluminescence excitation spectra has allowed us to determine both the band gap energy temperature dependence as well as to get some insight into the luminescence mechanisms of the defect-related emissions in these compounds. The results pave the way to exploit the physical properties of these Na- and Li- gallium titanate series in functional optoelectronic devices to operate from the ultraviolet to the infrared range.

Synthesis and luminescence properties of Ca2AlNbO6:Fe3+ phosphor for plant growth lighting

With the development of plant growth lighting, more and more attention has been paid to red and far red luminescent materials. In this work, we synthesize successfully a non-rare earth and non-toxic Ca2AlNbO6:Fe3+ phosphor in air and investigate the crystal structure, morphology, and luminescence properties of Ca2AlNbO6:Fe3+ by using powder X-Ray Diffraction, the field emission scanning electron microscopy, and the Edinburgh steady-state FS5 spectrometer, respectively. The far-red emission with peak at 714 nm of Ca2AlNbO6:Fe3+ is due to the 4T1(4G) → 6A1(6S) transition of Fe3+ ion. Photoluminescence excitation (PLE) spectrum of Ca2AlNbO6:Fe3+ includes four PLE peaks, which are assigned to the O2− → Fe3+ charge transfer band (CTB) (309 nm), the 6A1(6S) → 4T1(4P) (364 nm), 6A1(6S) → 4E(4D) (395 nm), and 6A1(6S) → 4T2(4G) (532 nm) transitions of Fe3+, respectively. We further study the concentration/temperature dependent emission spectra and time-resolved emission spectra. The optimal Fe3+ doping concentration (0.6mol%) and the only luminous center (Fe3+) in Ca2AlNbO6:Fe3+ are confirmed. The decay curves of Ca2AlNbO6:xFe3+ (0.2 mol% ≤ x ≤ 1.2 mol%) are measured and their lifetimes decrease from 463.24 to 385.29 μs＀ The emission spectra under different temperatures prove that Ca2AlNbO6:Fe3+ has a good heat stability. We explain the luminous mechanism and concentration/thermal quenching mechanisms, and further research the application prospect of Ca2AlNbO6:Fe3+ in plant growth lighting.