Down-conversion Photoluminescence Research Articles

Multicolor and multimode luminescent lanthanide-doped Cs2NaInCl6:Sb3+ from visible to near infrared for versatile applications

Double halide perovskites have shown admirable potential in promising optoelectronic applications due to simple synthesis, good stability and high structural tolerance. However, the poor optical properties caused by the parity-forbidden transitions posts a stringent limitation on their potential applications. Herein, we dope the lanthanide (Ln3+) ions with abundant energy levels into the Cs2NaInCl6:Sb3+ single crystals, which not only achieve multicolor visible emissions spectra from blue to red light, but also expand to the near infrared region from 800 to 1900 nm. In addition, the phosphors enable the multimode emissions with the up-conversion and down-conversion photoluminescence. Intriguingly, the excitation source, and the excitation light intensity also endow the multicolor emissions. Thus, combining with the multicolor and multimode luminescent properties, Cs2NaInCl6:Sb3+/Ln3+ could be applied to night vision imaging, substance detection, optical thermometry, white-light-emitting diodes (WLEDs) and anti-counterfeiting. The maximum value of relative temperature sensitivity reaches as high as 1.207 % K−1, which is relatively higher than those of most metal halide perovskites. Moreover, the single-source WLED displays Commission Internationale de L'Eclairage color coordinates (0.32, 0.31), a correlated color temperature of 6673 K, and color rendering index of 81.7. These results demonstrate the potential applications in the multifunctional photoelectric applications.

Highly efficiency up and down -conversion photoluminescence in Er/Tm/Yb co-doped lutecia-stabilized zirconia single crystals

High-quality transparent cubic lutecia-stabilized zirconia and LSZ:Yb1Er0.05Tm0.5 single crystals were grown by the optical floating zone method for the first time. For comparison, YSZ and YSZ:Yb1Er0.05Tm0.5 single crystals were also grown. No absorption peaks were observed in the 200 ∼1100 nm range in the transmission and absorption spectra of LSZ and YSZ, indicating that both crystals are excellent matrix crystals. The absorption spectra of LSZ:Yb1Er0.05Tm0.5 and YSZ:Yb1Er0.05Tm0.5 crystals exhibit several absorption peaks at 377, 408, 462, 488, 516, 679, 785 nm and a strong broad absorption band in the 836 ∼ 1050 nm range. The up-conversion photoluminescence of the LSZ:Yb1Er0.05Tm0.5 crystal excited by a 980 nm laser exhibited several distinct emission peaks at 300, 372, 476, 531, 548, 642 and 798 nm; similar emission peaks were observed in the up-conversion photoluminescence spectrum of the YSZ:Yb1Er0.05Tm0.5 crystal, except for the absence of the 300 nm peak. The intensity of the emission peaks of the former was higher than that of the corresponding peaks of the latter. Power curves indicated that the 300 nm emission is a four-photon up-conversion process, the 372 nm and 476 nm emissions are three-photon processes, and the 548 nm and 642 nm emissions are two-photon processes. Under excitation at 379 nm, the down-conversion photoluminescence spectra of the LSZ:Yb1Er0.05Tm0.5 and YSZ:Yb1Er0.05Tm0.5 crystals showed emission peaks at 450, 457, 511, 531 and 637 nm, the peak intensities of the former are higher than those of the latter, which is due to the former with higher density and lower phonon energy as compare to the latter. These results indicate that LSZ:Yb1Er0.05Tm0.5 single crystal has advantages over YSZ:Yb1Er0.05Tm0.5 single crystal for luminescence in photonic devices.

Upconversion luminescence of pyrochlore structured (A2B2O7) phosphors

The pyrochlore-structured (A2B2O7) compounds have emerged as a focal point in contemporary research and materials science, captivating attention for their intriguing properties such as photoluminescence, superconductivity, ionic mobility, and potential applications in high-temperature barrier coatings. Their potential application in up- or down-conversion photoluminescence further positions them for integration into a myriad of optoelectronic and sensing devices. Building on extensive prior research, this review delves into the upconversion (UC) luminescence properties of numerous pyrochlore-structured host materials (titanates, zirconates, hafnates, and ytterbium pyrochlores), specifically those doped with rare earth ions. While these materials may share similar chemical and structural characteristics, their luminescent capabilities exhibit significant variation upon rare earth ion doping. The phase transitions of various pyrochlore-structured compounds with respect to cation ratio, the relationship between crystal structure, doping concentrations, and UC luminescent properties in pyrochlore-structured compounds are summarized in detail. Through controlled doping strategies and structural adjustments, researchers have been able to tailor the luminescence properties of pyrochlore structured compounds to meet specific application requirements. The intricate exploration of the UC luminescence properties of pyrochlore-structured compounds, especially when doped with rare earth ions, showcases the rich potential for these materials in a wide array of applications across various fields, from advanced sensing technologies to innovative optoelectronic devices, paving the way for exciting advancements in materials science and beyond.

Substitutional effects of the anionic group systems [BO33−], [PO43− ], and [SO42−] on the down-conversion photoluminescence properties of Y2O3:Er3+ nanophosphors

A series of Y2O3, Y2O3: Er3+ (1 %) and Y2O3-AG: Er3+ (1 %) (where AG = BO33−, PO43−, and SO42−) nanophosphors were prepared via a chemical combustion technique. The primary X-ray powder diffraction results showed that the Y2O3:Er3+ phosphor materials crystallized into a cubic standard structure, while the Y2O3-AG: Er3+ phosphor materials transformed to hexagonal and tetragonal structures for the [PO43−] and [BO33−]-based phosphors, respectively. However, no changes were observed for the [SO42−]-based phosphor materials. The scanning electron microscope micrographs revealed that the particles were formed in the nanometre range with different sizes and shapes. The fourier-transformed infrared spectra showed the presence of various structural groups in the pure Y2O3 and Y2O3-AG: Er3+ phosphors. In addition to that, the optical bandgap energy values were obtained using the diffuse reflection spectra (DRS) spectra and Kubelka-Munk function theory. Under UV-379 nm excitation for the Y2O3-AG: Er3+ phosphors, the Y2O3–SO4: Er3+ emitted the most intense green light at 563 nm wavelength. The Commission Internationale de l'Elcairage colour coordinates and correlated color temperature values indicated that the Y2O3:Er3+, Y2O3-PO4:Er3+, and Y2O3–SO4:Er3+ phosphor materials are potential candidates for producing enhanced green color components in white light-emitting diode (w-LED) applications.

Enhancing the blue and NIR emissions of NaBiF4:Er3+,Yb3+ phosphors by co-doping with Mg2+ or Mn2+

This work reports the morphological, structural, and photoluminescent properties of NaBiF4:Er3+/Yb3+ phosphors with and without Mg2+ or Mn2+ co-dopants. The XRD patterns showed that NaBiF4 (NBF) host and NaBiF4:Er3+/Yb3+ phosphors have a mixture of hexagonal and cubic phases, while the phosphors co-doped with Mg2+ or Mn2+ ions only presented a cubic phase. The analysis by microscopy revealed that the NaBiF4:Er3+/Yb3+ phosphors are composed of particles with quasi-spherical morphology, and adding the Mg or Mn co-dopants increased the particle size from 218-397 nm to 346–447 nm. The downconversion (DC) photoluminescence (PL) spectrum (λexc = 240 or 305 nm) of the undoped NBF host showed intense green emission (at 507 nm). After doping with the NBF host with Er3+/Yb3+ ions, violet-blue (403–472 nm) and NIR (804–852 nm) emissions were observed under UV excitation. Later, Mg2+ and Mn2+ co-dopants were incorporated into the NaBiF4:Er3+/Yb3+ system and enhanced the intensity of the NIR emission by 3–4.1 times. Furthermore, the NaBiF4:Er3+/Yb3+ phosphor doped with 5 mol% Yb3+ was annealed at 600 °C and excited with NIR light (980 nm). Such phosphor exhibited intense green (545 nm) and red (658 nm) upconversion (UC) emissions, which were not observed in the phosphors synthesized without annealing treatment. According to the CIE maps, the phosphors excited with UV and NIR light had their color coordinates in the blue and yellow regions, respectively. Overall, the phosphors studied here are promising lighting sources for biomedical applications such as bioimaging or biomarkers due to their intense NIR emission at 852 nm (not previously reported in the literature for the NaBiF4:Er3+/Yb3+ system).

Amphi-Luminescent MoS2 nanostructure for photocatalytic splitting of water and removal of Methylene Blue

Chemical dyes used in the textile industries are one of the major pollutants in water. Methylene blue (MB) is a commonly seen dye that creates hazardous health problems. In this article the photocatalytic degradation of MB by the nanocatalyst MoS2 (Nano-MoS2) and carbon dot (C Dots) incorporated MoS2 (Nano-CD-MoS2) is reported. The photocatalytic degradation of MB is analyzed based on the electron-hole recombination rate of the catalyst. Photoluminescence emission exhibited by the catalyst is used as a key indicator to probe the electron-hole recombination rate. Nano-MoS2 was synthesized hydrothermally at 180 0C for 8 h from ammonium tetra thiomolybdate (ATTM). C Dot was prepared following a green root from ash guard extract which later mixed with Nano-MoS2 and kept in an autoclave at a temperature 140 °C for 4 h to get Nano-CD-MoS2. The photoluminescence (PL) and photocatalytic behavior of Nano-MoS2 and Nano-CD-MoS2 and their application for water splitting and water purification are reported. The incorporation of graphene and artificial C Dot into MoS2 nanostructures are reported to increase the conductivity and active edge sites of MoS2 that enhances the photocatalytic action. Since green C Dots are eco-friendly and easily synthesizable than artificial C Dots, as a novel study, this article investigated the influence of green C Dots on the PL and photocatalytic performance of nanosized MoS2. Nano-MoS2 and Nano-CD-MoS2 exhibited both upconversion and downconversion PL; accordingly the nanostructures were termed as amphi-luminescent. The amphi-luminescence property widens the photon absorption range and hence enhances the catalytic degradation of dyes. Nano-MoS2 which exhibited lesser intensity of amphi-luminescence emission compared to Nano-CD-MoS2 showed better results in degradation of MB. C Dots may bind with the valence band electrons of MoS2, resulting in the reduction of dangling bonds. Dangling bonds can trap photo-induced excitons to hinder the rate of electron-hole recombination. So, fast electron-hole recombination occurs in Nano-CD-MoS2 than Nano-MoS2. Fast electron-hole recombination supports radiative electron-hole recombination while suppresses the non-radiative energy transfer of electrons and causes high PL intensity. However, according to the energy level diagram, Nano-MoS2 with minimal electron-hole recombination rate is more favorable for O2/O2–,.OH/ OH– and.OH/H2O reactions that facilitate MB degradation. Photocatalytic activity of catalysts were confirmed by measuring the photocurrent from a simple custom-made two-electrode water photolysis cell where the nanocatalysts were dispersed in electrolyte. Lead and steel rods were used as electrodes. Multimeter was used to measure current. Nano-MoS2 exhibited better performance with a maximum photocurrent of 141 µA. Influence of green C Dots in energy levels, PL and photocatalysis of MoS2 and mechanisms of PL and degradation of MB are thoroughly investigated in this article.

Unveiling the Radiative Electron-Hole Recombination of MoS2 Nanostructures at Extreme pH Conditions.

Nanostructures of MoS2 are in wide research for optoelectronic, energy and biological applications. Opto-electronic and biological applications requires the tuning of photoluminescence properties of MoS2 nanostructures. In this article, nanosized MoS2 is hydrothermally synthesized, and photoluminescence at extreme pH conditions (pH 1 and 13) is examined. As the photoluminescence gives a key to probe the radiative electron-hole recombination, here, photoluminescence emissions are used as an indicator to suggest the pattern of electron-hole recombination in the material at extreme pH conditions. Raman spectroscopy, dynamic light scattering, Scanning electron microscopic image and energy dispersive x-ray analysis are done for material confirmation. At pH 1 and 13 as-synthesized nanostructured MoS2 exhibited both upconversion and downconversion photoluminescence. The intensity of photoluminescence is varied with respect to pH. Excitation-dependent photoluminescence mechanisms and preliminary understanding on the ratio of quantum yields and life span of excited state of as-synthesized nanostructured MoS2 are unveiled here.

Up- and down-conversion photoluminescence properties of Ho2O3 doped YbAG single crystals prepared by optical floating zone method

Single crystals of garnets with composition Yb2.96-xYxHo0.04Al5O12 (x = 0, 2.92, 2.96) were grown by optical floating zone method, and shown by XRD measurements to be in the cubic phase. EDS spectra show that Ho3+ and Yb3+ were homogenously distributed in the structure. As shown by the transmission and absorption spectra, the Yb2.96-xYxHo0.04Al5O12 crystals are highly transparent and can function as excellent optical crystals. Compared to the Y2.96Ho0.04Al5O12 crystal, the Yb2.96Ho0.04Al5O12 crystal has an additional strong broad absorption in the 836–1070 nm range, which increases its absorption of 980 nm photons. The optical band gaps of the Yb2.96-xYxHo0.04Al5O12 crystals decrease with increasing Yb2O3 concentration. Furthermore, differences with Yb2O3 concentrations in the Yb2.96-xYxHo0.04Al5O12 crystals were observed for the first time in the up- and down-conversion photoluminescence. Under excitation with a 980 nm laser, the up-conversion PL spectra of the Yb2.96-xYxHo0.04Al5O12 crystals show several emission peaks at 548 nm, 665 nm and 775 nm, and their intensities increase with Yb2O3 concentrations. In the Yb2.96Ho0.04Al5O12 crystal, Yb3+ not only is a component of the garnet structure, but it also acts as a sensitizer. In regards of down-conversion, under excitation at 454 nm, the down-conversion PL spectra of the Yb2.96-xYxHo0.04Al5O12 crystals show strong emission peaks at 550 nm, and their intensities decrease with increasing Yb2O3 concentrations, which is considered to be the consequence of increasing matrix density.

A green light emissive LaSr2AlO5:Er3+ nanocrystalline material for solid state lighting: crystal phase refinement and down-conversion photoluminescence with high thermal stability.

The present study reveals the structural and optoelectronic characteristics of a down-converted (DC) green luminous Er3+ doped LaSr2AlO5 phosphor that was produced by employing an efficient and reliable gel-combustion process assisted with urea as a fuel. Using Rietveld refinement of diffraction data, the crystal structure and phase formation were examined. The surface morphology and elemental configuration of the phosphor were analyzed via TEM and EDX spectroscopy, respectively. The band gap of LaSr2AlO5 (5.97 eV) and optimized La0.96Sr2AlO5:4 mol% Er3+ (5.51 eV) classify the optimized sample as a direct band-gap material. The PL peaks located in the visible range corresponding to transitions 2H9/2 → 4I15/2 (406 nm), 2H11/2 → 4I15/2 (520 nm), 4S3/2 → 4I15/2 (550 nm), and 4F9/ 2 → 4I15/2 (665 nm) were revealed by photoluminescence spectroscopy under 377 nm excitation. Above 4 mol% Er3+ doping, concentration quenching was observed, which was controlled by the quadrupole-quadrupole interaction. Based on the findings of the double exponential fitting of lifetime curves acquired from the emission spectra at λex = 377 nm and λem = 550 nm, the average lifetime of the excited levels of considered nanomaterials was estimated. The temperature-dependent emission spectra of the La0.96Sr2AlO5:4 mol% Er3+ sample were collected in the range 298-498 K. The considered phosphor was found to have a high thermal stability as evidenced by the luminous intensity being sustained at 74.29% at 498 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.1453 eV. The calculated color purity and superb chromaticity coordinates indicates that the phosphors have a high degree of color purity, which further supports its applicability as a green component in solid-state lighting.

An in-depth photoluminescence investigation of charge carrier transport in ZrO2|V2O5 type I junction: Probing the production of hydroxyl radicals

The determination of the band edge positions turns out to be of particular importance in different fields. We present a comparison of different approaches for the determination of the band edge alignment. For this purpose, we suggested studying the ZrO2|V2O5 heterojunction. The structural properties investigated by means of X-ray diffraction (XRD) revealed the formation of pure V2O5 with an orthorhombic structure. The resulting ZrO2, however, exhibits two different phases (monoclinic and tetragonal). Based on the absorption spectra, the near-band edges for V2O5, ZrO2, and ZrO2|V2O5 were found to be 2.07, 4.9, and 2.12 eV, respectively. The corresponding band gap values determined by the Tauc method were found to be 2.32, 5.16, and 2.35 eV, respectively. The down-conversion photoluminescence (PL) spectra of pure and junctioned materials are discussed in detail. The up-conversion in ZrO2 revealed its band gap value (∼5.14 eV), which is very close to the one obtained by the Tauc method (∼5.16 eV). The band gap alignment of the ZrO2|V2O5 heterojunction was determined using Sanderson method and experimentally using X-ray photoelectron spectroscopy (XPS). In this work, we propose an In-depth photoluminescence study for the confirmation of the type of heterojunction by probing the hydroxyl radical (HO•) production.

Enhanced UV Absorption By 2D MoS2 Nanoparticles

MoS2 is one of the promising 2D materials that caught the interest of many research fields[1], [2] due to their size-dependent tunable bandgap and attractive magnetic, optical, and electrical properties[3]. Furthermore, recently there has been a growing interest in utilizing MoS2 for solar cell applications that demonstrated measurable device enhancements[4]–[6]. Hence, there is a great interest in understanding its potential for solar energy harvesting. In this study, we show a simple method to deposit a 2D layer of MoS2 nanoparticles (NPs) on top of Aluminum-doped Zinc oxide (AZO) layer (transparent conductive oxide) and investigate its spectral response and potential for application in optoelectronic systems.A thin film of 80 nm AZO layer was grown on a 4-inch quartz wafer using thermal Atomic Layer Deposition (ALD) with a 1:19 ratio which has shown good electrical and optical qualities for solar cell applications[7]. We deposited the MoS2 by spin-coating it on the AZO/quartz wafers for 40 sec at 1000 rpm. Incremental coating is carried on by dispersing seven layers with 500 μL of MoS2 in each step using a precise pipet to a cumulative dispersion volume of 3500 μL. The prepared samples were characterized using a UV-Vis-NIR spectrometer (Perkin Elmer Lambda) across a wide range of wavelengths (250-1200 nm) by measuring both transmittance and reflectance and calculating absorbance. Furthermore, the base AZO/quartz and quartz background signal were measured before spin-coating as reference.The obtained data shows a high absorbance effect due to MoS2 NPs at low wavelengths (<400 nm), where it peaks around 340 nm with an approximate absorbance of ~6.7%. Upon further examination, we notice that this behavior is not linear across the whole spectrum and instead is a function of (i) wavelength and (ii) MoS2 quantity which could be partially due to the quantum confinement effect of several layers of stacked 3D MoS2 nanoparticles[8]. This phenomenon could open the possibility of utilizing this material for low-wavelength filters or UV sensing applications[9]. Also, it can potentially be utilized for quantum down-conversion[10] of high-energy photons to re-emit photons at lower energies in order to enhance solar cells’ efficiencies and reduce thermal burden; however, further investigation is needed.[1] P. Zhou, C. Chen, X. Wang, B. Hu, and H. San, “2-Dimentional photoconductive MoS2 nanosheets using in surface acoustic wave resonators for ultraviolet light sensing,” Sensors and Actuators A: Physical, vol. 271, pp. 389–397, Mar. 2018, doi: 10.1016/j.sna.2017.12.007.[2] H. Dong et al., “Fluorescent MoS 2 Quantum Dots: Ultrasonic Preparation, Up-Conversion and Down-Conversion Bioimaging, and Photodynamic Therapy,” ACS Appl. Mater. Interfaces, vol. 8, no. 5, pp. 3107–3114, Feb. 2016, doi: 10.1021/acsami.5b10459.[3] K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically Thin MoS 2 : A New Direct-Gap Semiconductor,” Phys. Rev. Lett., vol. 105, no. 13, p. 136805, Sep. 2010, doi: 10.1103/PhysRevLett.105.136805.[4] Y. Tsuboi et al., “Enhanced photovoltaic performances of graphene/Si solar cells by insertion of a MoS 2 thin film,” Nanoscale, vol. 7, no. 34, pp. 14476–14482, 2015, doi: 10.1039/C5NR03046C.[5] N. A. Abd Malek et al., “Ultra-thin MoS2 nanosheet for electron transport layer of perovskite solar cells,” Optical Materials, vol. 104, p. 109933, Jun. 2020, doi: 10.1016/j.optmat.2020.109933.[6] Y.-J. Huang, H.-C. Chen, H.-K. Lin, and K.-H. Wei, “Doping ZnO Electron Transport Layers with MoS 2 Nanosheets Enhances the Efficiency of Polymer Solar Cells,” ACS Appl. Mater. Interfaces, vol. 10, no. 23, pp. 20196–20204, Jun. 2018, doi: 10.1021/acsami.8b06413.[7] S. Abdul Hadi, G. Dushaq, and A. Nayfeh, “Effect of atomic layer deposited Al 2 O 3 :ZnO alloys on thin-film silicon photovoltaic devices,” Journal of Applied Physics, vol. 122, no. 24, p. 245103, Dec. 2017, doi: 10.1063/1.4990871.[8] T. Li and G. Galli, “Electronic Properties of MoS 2 Nanoparticles,” J. Phys. Chem. C, vol. 111, no. 44, pp. 16192–16196, Nov. 2007, doi: 10.1021/jp075424v.[9] Z. Lou et al., “High-performance MoS_2/Si heterojunction broadband photodetectors from deep ultraviolet to near infrared,” Opt. Lett., vol. 42, no. 17, p. 3335, Sep. 2017, doi: 10.1364/OL.42.003335.[10] A. P. Sunitha, P. Praveen, M. K. Jayaraj, and K. J. Saji, “Upconversion and downconversion photoluminescence and optical limiting in colloidal MoS2 nanostructures prepared by ultrasonication,” Optical Materials, vol. 85, pp. 61–70, Nov. 2018, doi: 10.1016/j.optmat.2018.08.038.[11] Y. Wu et al., “Monolithic integration of MoS 2 -based visible detectors and GaN-based UV detectors,” Photon. Res., vol. 7, no. 10, p. 1127, Oct. 2019, doi: 10.1364/PRJ.7.001127. Figure 1

Down-conversion photoluminescence of Ta2O5:Ho3+ and up-conversion photoluminescence of Ta2O5:Ho3+/Yb3+ coatings formed by plasma electrolytic oxidation of tantalum

Down-conversion photoluminescence of Ta2O5:Ho3+ and up-conversion photoluminescence of Ta2O5:Ho3+/Yb3+ coatings formed by plasma electrolytic oxidation of tantalum

Crystallization and up-/down-conversion luminescence of size-dependent CdWO4:Yb3+,RE3+ (RE=Ho and Er)

Tartrate (Tar2−) was originally employed as a chelating/structure-directing agent for hydrothermal synthesis of CdWO4:Yb3+,RE3+ (RE = Ho and Er) micro/nanocrystallites, followed by calcination at 700 °C for 2 h. It was clearly demonstrated that Tar2− restricted the exposed ab planes and 3D self-assembly of microplates, resulting in ∼50 nm sized nanoparticles. Up-/down-conversion (UC/DC) photoluminescence were revealed to be strongly size dependent. Under 978 nm pump laser excitation, flower-like assembly was found to exhibit the stronger UC emissions of Ho3+ and Er3+, among which two CdWO4:Yb3+,Ho3+ phosphors generated orange-yellow fluorescence via three-photon processes, while CdWO4:Yb3+,Er3+ microflowers and nanoparticles showed yellowish-green and pale green colors, respectively. Moreover, nanoparticles intensified the dominant green DC emissions of Ho3+ and Er3+ by ∼3 and 2 times, implying the pivotal roles of morphology engineering in tunable photoluminescence. This research may provide insights into crystallite/architecture engineering and luminescence optimization for near-infrared response solar cells and solid-state lighting.

Up and down-conversion photoluminescence energy demonstration of Ho3+/Yb3+ co-doped double perovskites microcrystals

Recently, lanthanide-doped fluorescence materials with perovskite structures have attracted great attention due to their abundant 4f energy levels, of which up- and down-conversion photoluminescence (PL) usually can be achieved by energy-level transition of single or multiple rare-earth ions (REI). Here, we synthesized for the first time a series of holmium (Ho) and ytterbium (Yb) co-doped Cs2Ag0.4Na0.6In0.9Bi0.1Cl6 (CANIBC) microcrystals (MCs) by hydrothermal method and realized the synergistic effect of efficient dual-mode PL of host and REI. The CANIBC MCs show yellow-white light emission stimulated by a 405 nm laser, of which the down-conversion (DC) PL is superimposed by the self-trapped excitons (STEs) emission of [AgCl6]5- octahedral and the energy level leap emission of REI. While the green emission of Ho3+ can be observed on the up-conversion (UC) PL stimulated by a 980 nm laser. We systematically analyzed the effect of CANIBC MCs in the dual-mode PL by time-resolved spectroscopy and found the existence of energy transfer between the STEs to REI in the DC PL process. Whereas in UC PL there is only energy transfer between REI. The variable-temperature dual-mode PL, reflects good temperature measurement performance. Simultaneously, it is effectively processed into a powder and mixed with 415 nm chips to create warm white light-emitting diodes with a CIE of (0.34, 0.36).

Down-conversion and up-conversion photoluminescence studies of Er3+ doped calcium zinc borosilicate glass for optical fiber amplifiers

A series of Er3+ ion doped calcium zinc borosilicate (CZBS) glass with composition 15ZnO-(10-x)CaO-10SiO2-65B2O3-xEr2O3 (x = 0.1, 0.5, 1.0, 1.5, 2.0 mol%) has been synthesized using conventional melt quenching technique. The non-crystalline nature of the as-synthesized glass is established through X-Ray diffraction (XRD). Fourier Transform Infrared (FT-IR) spectral studies present a full picture of the functional groups present in the glass system. The absorption, up-conversion (UC) and down-conversion (DC) photoluminescence (PL) and corresponding PL decay dynamics, and laser power dependent PL are investigated to better understand the optical properties and energy transfer mechanism in the glass matrices. The radiative properties such as transition probability (AR), branching ratios (βR), radiative lifetimes (τR) and near infrared (NIR) emission quantum efficiency (η) are estimated. The absorption, emission cross-sections and optical gain coefficients reveal the potential applications as laser amplifiers. The results favorably suggest the potential utility of these Er3+ doped CZBS glasses in solid-state lighting and optical communication devices.

Phase Stability and Dual-Mode Photoluminescence Modulation in Er-Doped Lead Zirconate Titanate Antiferroelectrics.

The electric-field-modulation (E-modulation) of photoluminescence (PL) properties in bulk ceramics has attracted tremendous interest due to its potential application in optical data storage and communication devices. One promising approach of reversibly and largely modulating the PL intensity has been proposed in rare-earth Er3+-doped Pb0.96La0.04Zr0.9Ti0.1O3 (PLZT) antiferroelectrics (AFEs) based on the unique E-dependent antiferroelectric-ferroelectric (AFE-FE) phase transition. However, the AFE phase stability of PLZT doped with various Er contents and their E-modulated PL properties have not been systematically investigated. In this paper, the intrinsic AFE phase of PLZT-Er is found to be stabilized in the high-temperature and high-E regions with increasing Er3+ content. The enhanced AFE nature caused by increasing Er doping leads to a larger E-dependent PL tunability (∼35%). Moreover, the ceramics exhibit the characteristics of both upconversion and downconversion PL (UCPL and DCPL) effects. Based on the excellent E-dependent dual-mode PL tunability, an optoelectronic device named the optical latch is demonstrated, where an electric signal can be used to trigger a notable intensity change in both the UCPL and DCPL modes. This reversible E-dependent dual-mode capability in PLZT-Er sheds light on a feasible approach to optoelectronic applications.

Enhanced piezoelectricity and non-contact optical temperature sensing performance in Er3+ ion modified (K,Na)NbO3-based multifunctional ceramics

Rare earth ions doped ferroelectrics have attracted wide attentions due to their multifunction characteristics with both ferroelectric/piezoelectric properties and intriguing photoluminescence performance, which show great prospects for future multifunctional devices. In this work, a novel rare earth Er3+ ion modified potassium-sodium niobate (KNN) based ceramics were elaborately designed and prepared by the conventional solid-state reaction. The microstructure, phase structure, electric properties and photoluminescence performance of the Er3+ ion modified KNN-based ceramics were systematically investigated. Enhanced piezoelectricity (a considerable d33 of exceeding 300 pC/N and a large d33* up to 500 p.m./V) was realized through optimizing the substitution of BaZrO3 by (Er0.5,Na0.5)ZrO3. Both down-conversion and up-conversion photoluminescence emissions were detected in the optimal composition. The temperature-dependent upconversion emissions of the optimal Er3+ modified ceramic sample in the temperature range of 303–573K were verified to be applicable for non-contact optical temperature sensing with a maximum sensitivity Sa of 0.0028 K-1 and a peak relative sensitivity Sr of 0.96% K−1. Moreover, low-temperature sensing performance with a maximum Sr of 16.7% K−1 in the temperature range of 80–280K was also presented based on the temperature-dependent down-conversion emissions. With both decent electrical properties and intriguing photoluminescence performance, the Er3+-modified KNN-based ferroelectrics exhibit good application potential in the future multifunctional optoelectronic devices.

Magnetic and photoluminescence properties of rare-earth substituted quaternary spinel ferrite nanoparticles

Rare earth substituted quaternary spinel ferrites Ni0.5Zn0.5Fe1.95Eu0.05O4, Co0.5Zn0.5Fe1.95Dy0.05O4, and Cu0.5Zn0.5Fe1.95Tb0.05O4 were prepared by a low-temperature co-precipitation method without any post heat treatment. Structural confirmation of the prepared materials was done by XRD. Using TEM, their morphology was investigated. Magnetic studies were conducted using VSM. The prepared materials exhibit soft ferrimagnetic nature. The magnetization curves were further studied by applying the law of approach to saturation. Downconversion and upconversion photoluminescence properties of the prepared materials were investigated at different excitation wavelengths. No characteristic emission spectra of the rare-earths elements were observed. In the case of downconversion, a broad emission band formed by sub-bands and in the upconversion spectra, characteristic emission peaks were observed in all compositions. The observed emission spectra depict the presence of multiple energy levels within the band gap of spinel ferrites.

(INVITED)Judd-Ofelt analysis, visible to NIR photoluminescence emission under 450 nm and 976 nm excitations and energy transfer of barium fluorotellurite glasses doping with Ho3+, Yb3+, Ho3+:Yb3+

Barium fluorotellurite glasses doping with Ho3+, Yb3+, and Ho3+:Yb3 were fabricated using the conventional melt and quenching method, and their optical properties were studied using different optical spectroscopic techniques. The FITR absorption band at 3000 cm−1 was used to investigate OH- concentrations of the prepared glasses, which increased with Yb3+ content. However, it decreased by substituting a portion of BaF2 content with Ba2CO3 concentration. The electric dipole line strengths and Judd-Ofelt parameters were estimated using UV–visible near-infrared (NIR) optical absorption spectra to gain information on the rare earth ions doped glasses for laser applications. The various radiative parameters such as line strengths, optical intensity, and radiative rates from the higher energy levels, including 5F4+5S2, 5F5, 5I4,5I5,5I6 and 5I7, to the ground state, 5I8 have been reported and discussed. The influence of the Yb3+ and Ba2CO3 concentrations on the upconversion and downconversion photoluminescence emission intensities of the glasses prepared have been investigated by pumping with 450 nm and 976 nm excitation sources. Under 450 nm and 976 nm, the NIR photoluminescence emissions reveal a band ranging from 980 nm to 1220 nm attributing to an overlap between Yb3+ and Ho3+ transitions. The influence of Yb3+ concentration on photoluminescence lifetime at the 2F5/2→2F7/2, 5F4+5S2 →5I8 and 5I6 →5I8 transitions under 976 nm laser excitation has been studied and reported. The results indicate that lifetime decreases with increasing Yb3+ concentration attributing to an efficient energy transfer from Yb3+ to Ho3+ ions. The energy transfer efficiency from Yb3+ → Ho3+ has been examined, which rises from 30% to 47% upon increasing Yb3+ content. Nevertheless, it decreases with the mixing of BaF2 and Ba2CO3 lattice modifier contents. The results demonstrated that the 1200 nm (5I6 →5I8 transition) has remarkable potential for developing fiber lasers.

Influence of excitation wavelength on the down-conversion photoluminescence characteristics of Gd2O3:Er3+-Yb3+ phosphor

• The emission and excitation spectra of prepared phosphor samples were systematically recorded and they displayed intense emission in visible region. The excitation was observed at 613 nm and the peaks found at 254 and 278 nm. • Similar to that excitation with various emission peaks were also observed correspondingly at 466, 585 and 613 nm. This present study gives basic information about the transition of [Yb, Er] activated rare earth as well as the spectroscopic parameters of prepared phosphor samples. • The CIE (Commission Internationale de-l'Eclairage) coordinate for the prepared phosphor samples were calculated and the color rendering index [CRI] parameters were also calculated by using CIE. • The prepared phosphor samples are proposed to be very useful in numerous optoelectronic applications. Herein the synthesis, structural characterization and photoluminescence behavior of Er/Yb activated Gd 2 O 3 phosphor is presented. Yb and Er-doped Gd 2 O 3 phosphor samples were synthesized through the conventional solid-state-reaction (SSR) method and their structural aspects were examined by the X-ray diffraction (XRD) analysis. Morphology of the prepared phosphor samples was examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The emission and excitation spectra of the prepared phosphor samples were systematically recorded. They displayed intense emission in the visible region. The excitation spectra recorded at 613 nm emission showed two prominent excitation peaks at 254 and 278 nm. Similar to that excitation with various emission peaks were also observed correspondingly at 467, 545 and 613 nm. The present study gives basic information about the transition of (Yb, Er) activated rare earth as well as the spectroscopic parameters of the prepared phosphor samples. The CIE (Commission Internationale de-l'Eclairage) coordinate for the prepared phosphor samples was calculated and the color rendering index [CRI] parameters were also calculated using CIE. The prepared phosphor samples are proposed to be very useful in numerous optoelectronic applications.