Atomic layer deposition in advanced display technologies:from photoluminescence to encapsulation

Driven by the growing demand for next-generation displays,the development of advanced luminescent materials with exceptional photoelectric properties is rapidly accelerating,with such materials including quantum dots and phosphors,etc.Nevertheless,the primary challenge preventing the practical application of these luminescent materials lies in meeting the required durability standards.Atomic layer deposition(ALD)has,therefore,been employed to stabilize luminescent materials,and as a result,flexible display devices have been fabricated through material modification,surface and interface engineering,encapsulation,cross-scale manufacturing,and simulations.In addition,the appropriate equipment has been developed for both spatial ALD and fluidized ALD to satisfy the low-cost,high-efficiency,and high-reliability manufacturing requirements.This strategic approach establishes the groundwork for the development of ultra-stable luminescent materials,highly efficient light-emitting diodes(LEDs),and thin-film packaging.Ultimately,this significantly enhances their potential applicability in LED illumination and backlighted displays,marking a notable advancement in the display industry.

In situ luminescence measurements of GaN/Al_(2)O_(3) film under different energy proton irradiations

Ion beam-induced luminescence(IBIL) experiments were performed to investigate the in situ luminescence of GaN/Al_(2)O_(3) at varying ion energies,which allowed for the measurement of defects at different depths within the material.The energies of H^(+)were set to 500 keV,640 keV and 2 MeV,the Bragg peaks of which correspond to the GaN film,GaN/Al_(2)O_(3) heterojunction and Al_(2)O_(3) substrate,respectively.A photoluminescence measurement at 250 K was also performed for comparison,during which only near band edge(NBE) and yellow band luminescence in the GaN film were observed.The evolution of the luminescence of the NBE and yellow band in the GaN film was discussed,and both exhibited a decrease with the fluence of H^(+).Additionally,the luminescence of F centers,induced by oxygen vacancies,and Cr^(3+),resulting from the ^(2)E →^(4)A_(2) radiative transition in Al_(2)O_(3),were measured using 2 MeV H^(+).The luminescence intensity of F centers increases gradually with the fluence of H^(+).The luminescence evolution of Cr^(3+)is consistent with a yellow band center,attributed to its weak intensity,and it is situated within the emission band of the yellow band in the GaN film.Our results show that IBIL measurement can effectively detect the luminescence behavior of multilayer films by adjusting the ion energy.Luminescence measurement can be excited by various techniques,but IBIL can satisfy in situ luminescence measurement,and multilayer structural materials of tens of micrometers can be measured through IBIL by adjusting the energy of the inducing ions.The evolution of defects at different layers with ion fluence can be obtained.

Synthesis and upconversion luminescence of Lu_2O_3:Yb^(3+),Tm^(3+) nanocrystals

Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.

Effect of Lattice Mismatch on Luminescence of ZnO/Si Hetero-Structure

The photoluminescence （PL） and Raman spectra of undoped ZnO films deposited directly on Si substrate （sample A）,on Si substrate through a SiC buffer layer （sample B）,and on a ZnO crystal wafer （sample C） are investigated. There are emission peaks centered at 3.18eV （ultraviolet,UV） and 2.38eV （green） in these sampies. Comparing the Raman spectra and the variation of the PL peak intensities with annealing atmosphere, we conclude that the luminescence of the samples is related to the tensile strain in the ZnO film due to the lattice mismatch between the film and the substrate. In particular, the tensile strain reduces the formation energy of OZn antisite oxygen defects,which generate the green emission center. After annealing in oxygen-rich atmosphere, many OZn defects are generated. Thus, the intensity of green emission in ZnO/Si hetero-structure materials increases due to tensile strain in ZnO films.

Effects of Magnetic Stress on the Delayed Luminescence of Mung Bean Leaves

[Objective] The research aimed to study the effects of magnetic stress on the delayed luminescence of mung bean leaves.[Method]With mung bean leaves as the experimental materials,the delayed luminescence curve of mung bean leaves under the same magnetic field intensity at different processing time was measured by using BPCL-type weak luminescence measuring instrument.[Result] The absorption of the magnetic field stimulation within the leaves had its own rules.A certain magnetic field intensity and a certain...

Preliminary Studies on High-performance Liquid Chro-matography Chemiluminescence Determination of theSaturated Fatty Acids(C_(16) C_(18))in Human Serum

The peroxyoxalate chemiluminescence(CL)detection of fatty acids in human se- rum combined with high-performance liquid chromatography (HPLC)is described.Some fatty acids in serum were extracted with a 1 :1(v/v)mixture of chloroform-n-heptane.2-(4-Hydrazinocarbonyl- phenyl)-4,5-diphenylimidazole (HCPI) was used as a fluorescent labelling reagent of the fatty acids. The labelling reaction was carried out at 30℃ for 1 h at pH 6.5 and the resulting reaction mixture was sudjected to HPLC. The labelled fatty acid C_(17)(P-C_(17))was used as the internal standard. The la- belled fatty acids C_(16) and C_(18) were separated within 18 min on an ODS-8OTM column (150 mm× 6 mm ID,5μm,Tosoh Japan).The calibrlation curves of fatty acids from the spiked control serum were Y_1=-0.003 7 + 0.0028X_1,r=0.994 for FA C_( 16) and Y_2=0.00 1 2 + 0.00098X_2,r=0.999 for FA C_( 18),respectively.The average recoveries of facids from the spiked contrl serum were 107.2%(n=8,RSD=4.3%)for FA C_(16) and 97.35%(n=8, RSD=4.0%)for FA C_(18),respectively.The lower detection limits of fatty acids after reaction were 12μmol per 20μl injection for FA C_(16) and 18 μmol per 20μl injection for FA C_(18),respectively(signal to noise ratio, S/N=2).The HPLC/CL method was applied to the determination of FA C_(16) and FA C_(18) in normal human serum and the results showed that the concentrations of fatty acids in normal human serum were 0.134 ± 0.009 μ mol/ml serum(n=5) for FA C_(16) and 0.052±0.028 μmol/ml serum(n=5)for FA C_(18),respectively.

New Opportunities for Lanthanide Luminescence

Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence： materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris（8-hydroxyquinolinate） displayed a bright green emission suitable for organic light emitting diodes （OLEDs） was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such as YbⅢ is now being tested because of deeper penetration in biological tissues.

Recent Advances of Persistent Luminescence Nanoparticles in Bioapplications

Persistent luminescence phosphors are a novel group of promising luminescent materials with afterglow properties after the stoppage of excitation.In the past decade,persistent luminescence nanoparticles(PLNPs)with intriguing optical properties have attracted a wide range of attention in various areas.Especially in recent years,the development and applications in biomedical fields have been widely explored.Owing to the efficient elimination of the autofluorescence interferences from biotissues and the ultra-long near-infrared afterglow emission,many researches have focused on the manipulation of PLNPs in biosensing,cell tracking,bioimaging and cancer therapy.These achievements stimulated the growing interest in designing new types of PLNPs with desired superior characteristics and multiple functions.In this review,we summarize the works on synthesis methods,bioapplications,biomembrane modification and biosafety of PLNPs and highlight the recent advances in biosensing,imaging and imaging-guided therapy.We further discuss the new types of PLNPs as a newly emerged class of functional biomaterials for multiple applications.Finally,the remaining problems and challenges are discussed with suggestions and prospects for potential future directions in the biomedical applications.

Self-assembly of α-6T Molecule on Ag（100） and Related STM Induced Luminescence

We have investigated the self-assembly and light emission properties of organic α- sexithiophene （α-6T） molecules on Ag（100） under different coverage by scanning tunneling microscopy （STM）. At very low coverage, the α-6T molecules form a unique enantiomer by grouping four molecules into a windmill supermolecular structure. As the coverage is increased,α-6T molecules tend to pack side by side into a denser stripe structure. Further increase of the coverage will lead to the layer-by-layer growth of molecules on Ag（100） with the lower-layer stripe pattern serving as a template. Molecular fluorescence for α-6T molecules on Ag（100） at a coverage of five monolayers has been detected by light excitations, which indicates a well decoupled electronic states for the top-layer α-6T molecules. However, the STM induced luminescent spectra for the same sample reveal only plasmonic-like emission. The absence of intramolecular fluorescence in this case suggests that the electronic decoupling is not a sufficient condition for generating photon emission from molecules. For intramolecular fluorescence to occur, the orientation of the dynamic dipole moment of molecules and the energy-level alignment at the molecule-metal interface are also important so that molecules can be effectively excited through efficient dipolar coupling with local plasmons and by injecting holes into the molecules.

Luminescence Properties of Green-Emitting Phosphor (Ba_(1-x),Sr_x_2SiO_4∶Eu^(2+) for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO_2 catalyst doped with upconversion luminescence agent

A new upconversion luminescence agent, 40CdF2·60BaF2·0.8ErO3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.

Electronic structure of the SrAl_2O_4:Eu^(2+) persistent luminescence material

The electronic structure of the strontium aluminate （SrAl2O4：Eu^2＋） materials was studied with a combined experimental and theo- retical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structure of the non-optimized and optimized crystal structure were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands as well as the band gap energy of the material together with the position of the Eu2＋ 4f7 85712 ground state were calculated. The calculated band gap energy （6.4 eV） agreed well with the experimental value of 6.6 eV. The valence band consisted mainly of oxygen states whereas the bottom of the conduction band of strontium states. In agreement with the experimental results, the calculated 4f7 8S7r2 ground state of Eu2＋ lies in the energy gap of the host. The position of the 4f7 ground state depended on the Coulomb repulsion strength. The position of the 4f7 ground state with respect to the valence and conduction bands was discussed using theoretical and experimental evidence available.

Relationship between Crystal Structure and Luminescence Properties of (Y_(0.96-x)Ln_xCe_(0.04))_3Al_5O_(12) (Ln=Gd, La, Lu) Phosphors

The doping effects of La^3＋, Gd^3＋ and Lu^3＋ on the crystal structure and luminescence properties of （Yo96-x LnxCe0.04）3Al5O12（Ln = Gd, La, Lu） phosphors were studied. The X-ray diffraction patterns presented that with the inerease of the doping concentrations of La^3＋ and Gd^3＋ ions, the d-value of （Y0.96-xLnxCe0.04）3Al5O12 （Ln = Gd, La） inereased and the larger the doping ion, the stronger the effect would be. The doping amount causing phase transition in （Y0.96-xLnxCe0.04）3Al5O12 decreased with the inerease of the ionic radii of the doping lanthanide ions （La^3＋： 0.106 nm, Gd^3＋： 0. 094 nm, Lu^3＋ ： 0.083 nm）. The bigger doping ion of Gd^3＋ made the emission of （Y0.96-xGdxCe0.04）3Al5O12 move to red spectral region, but the smaller one of Lu^3＋ made it blue.

Preparation and luminescence properties of the red-emitting phosphor(Sr_(1-x)Ca_x)_2Si_5N_8:Eu^(2+) with different Sr/Ca ratios

A series of Eu2＋-doped ternary nitride phosphors, with a formula of（Sr1-xCax）2Si5N8：Eu2＋, were synthesized by high-temperature solid-state method.The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes.The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of（Sr1-xCax）2Si5N8：Eu2＋ and coexisted in the range of 0.5≤x≤0.75.The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2＋ ions.The emission peak changed with the variations in Ca2＋ concentration.

Combustion synthesis and luminescence properties of LaPO4： Eu （5%）

Rare earth doped materials are an important type of phosphors due to their excellent performance such as stability at high temperature and light emission covering the entire visible domain. The combustion synthesis at acid pH of the monoclinic LaPO4： Eu（5%） powders was described. A mixture of La（NO3）3·6H2O, EuCly6H2O and （NH4）2HPO4 was used as anion precursor and glycin as fuel. The synthesis was followed by structure, morphology characterisation and luminescent properties of the obtained compound. The room temperature emission measurements under ultraviolet excitation at 254 nm were made for the emission transition ^5D0→^7FJ of this phosphor. The CIE （Commission Intemationale de L＇Eclairage） chromatic coordinates, dominant wavelength and colour purity were determined and compared to other luminescent materials obtained by other methods.

Study on Luminescence Properties and Crystal-Lattice Environment of Eu^(2+) in Sr_(4-x)Mg_x Si_3O_8Cl_4∶Eu^(2+) Phosphor

According to the Van Uitert experimental equation, crystal-lattice environment of Eu^(2+) in the Sr_4Si_3O_8Cl_4 crystal was discussed. By adding Mg^(2+) to the host lattice, Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) was synthesized and the emission peak shifted from blue-green (488 nm) to blue-violet (411 nm) with the increase of amount of the magnesium which replaced the strontium. By analyzing the spectra of Sr_(4- x )Mg_ x Si_3O_8Cl_4∶Eu^(2+) the two Eu^(2+) emission centers were found because of the change of crystal-lattice environment in the host and the crystal structure was obtained by X-ray diffraction data.

Synthesis and luminescence properties of rare earth ternary complexes consisting of Tb(Ⅲ), β-diketones and 1,10-phenanthroline (phen)

In order to study the luminescent properties of ternary rare earth complexes with fl-diketone ligand, three new β-diketone ligands, 1-phenyl-3-（p-phenylethynylphenyl）-1,3-propanedione（HPPP）, 1-（2-thienyl）-3-（p-phenylethynylphenyl）-1,3-propanedione （HTPP） and 1-（2-furyl）-3-（p-phenylethynylphenyl）-1,3-propanedione （HFPP）, were synthesized by Sonogashira coupling reaction and Claisen condensation. Three new ternary rare earth complexes, TbL3phen （L = PPP, TPP, or FPP）, were synthesized by the reaction of rare earth chloride TbCl3,1,10-phenanthroline （phen） with HPPP, HTPP, or HFPP respectively, in alcohol solution. The compositions were characterized by means of elemental analysis, chemical analysis, and IR spectra. Luminescent properties of the three new complexes have been studied. The results show that the ternary Yb（Ⅲ） complexes only emit the weak fluorescence of the Tb（Ⅲ） ion, which reveals the triplet state energy of the ligands does not match well with the excited state vibrating energy of Tb^3＋ ion.

Ultraviolet Super-Radiation Luminescence of Sputtering ZnO Film Under Cathode-Ray Excitation at Room Temperature

We report the observation of the cathode-ray(CR)pumped ultraviolet(UV)super-radiation luminescence in ZnO thin film at room temperature(RT).The dependence of UV(peak at about 390nm)and green(peak at about 520nm)luminescent peaks in ZnO thin film under CR excitation on excitation electron beam current has been investigated.With the increase of the density of excitation electron beam current,green peak relatively decreases and UV peak increases,resulting in a change of the luminescent color from green to blue-purple.The green peak intensity increases sublinearly with the increase of the electron beam current density and saturates at a relatively low density of electron beam current.But the intensity of 390nm UV peak increases superlinearly with the increase of the electron beam current density.This is a UV super-radiation luminescence of exciton in ZnO under high density pump.In this paper,three-dimensional atomic force microscope images of the surface of unannealled and annealled ZnO films are given.

Upconversion luminescence of Y_2O_3:Er^(3+), Yb^(3+) nanoparticles prepared by a homogeneous precipitation method

Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.

Cathodoluminescence of ZnO Films

The cathodoluminescence of ZnO films deposited on Si substrates by reactive dc sputtering is investigated.Apart from the characteristic green emission band(522nm)of ZnO,an ultraviolet(392nm)band and a blue(430-460 nm)band have been observed.The x-ray diffraction and cathodoluminescent spectra reveal the dependences of the luminescence on the preparation conditions and crystallinity of the ZnO films.