Field Emission Display Research Articles

An efficient SiO2:Ce porous nanophosphor with high color purity to fulfil the cyan emission gap of field emission displays (FEDs)

An efficient SiO2:Ce porous nanophosphor with high color purity to fulfil the cyan emission gap of field emission displays (FEDs)

Enhanced Thermal Stability of Red‐Emitting Sr2Si5N8:Eu2+ Phosphors from Triggered Applicable Trap Level via Rare Earth Ions Co‐Doping

AbstractTo solve the problem of thermal stability of the red‐emitting phosphor Sr2Si5N8:Eu2+ with great valuable luminescence performance, trivalent rare earth ions Ln3+ (Ln = Dy, Ho, Er, Tm, Nd, and Pr) are co‐doped into Sr2Si5N8: Eu2+ lattice to form thermally robust phosphors Sr2Si5N8:Eu2+,xLn3+(Lnx‐258, 0 ≤ x ≤ 0.05). The successful incorporation of rare earth ions in the crystal structure and the regulation of luminescent properties are proven by a variety of material characterization techniques and analysis. Although the co‐doping of the selected rare earth ions reduces the luminescence intensity of the phosphor, the Dy0.01‐258 sample still has a high external quantum efficiency (EQE) of 78.6%. More importantly, the co‐doping of Dy3+ with x = 0.01 significantly improves the luminescent thermal stability of phosphors at high temperature and the luminescence intensity of Dy0.01‐258 samples at 200 °C can be maintained at 94.7% of room temperature. The thermoluminescence spectrum shows that the defects brought about by co‐doping of Dy3+ with x = 0.01 introduce trap energy levels, which can compensate for the Eu2+ luminescence at high temperature. At the same time, the cathodoluminescence mapping and spectra show that the phosphor has a high saturation current under high‐energy electron bombardment, which indicates that this nitride phosphor also has the potential to be used in field emission display (FEDs). Based on its extraordinary EQE and thermal stability data, this nitride phosphor is the first‐rate among the red phosphors for pc‐wLEDs, and has excellent application prospects in FEDs.

Electronic Properties of Functionalized Diamanes for Field-Emission Displays.

Ultrathin diamond films, or diamanes, are promising quasi-2D materials that are characterized by high stiffness, extreme wear resistance, high thermal conductivity, and chemical stability. Surface functionalization of multilayer graphene with different stackings of layers could be an interesting opportunity to induce proper electronic properties into diamanes. Combination of these electronic properties together with extraordinary mechanical ones will lead to their applications as field-emission displays substituting original devices with light-emitting diodes or organic light-emitting diodes. In the present study, we focus on the electronic properties of fluorinated and hydrogenated diamanes with (111), (110), (0001), (101̅0), and (2̅110) crystallographic orientations of surfaces of various thicknesses by using first-principles calculations and Bader analysis of electron density. We see that fluorine induces an occupied surface electronic state, while hydrogen modifies the occupied bulk state and also induces unoccupied surface states. Furthermore, a lower number of layers is necessary for hydrogenated diamanes to achieve the convergence of the work function in comparison with fluorinated diamanes, with the exception of fluorinated (110) and (2̅110) films that achieve rapid convergence and have the same behavior as other hydrogenated surfaces. This induces a modification of the work function with an increase of the number of layers that makes hydrogenated (2̅110) diamanes the most suitable surface for field-emission displays, better than the fluorinated counterparts. In addition, a quasi-quantitative descriptor of surface dipole moment based on the Tantardini-Oganov electronegativity scale is introduced as the average of bond dipole moments between the surface atoms. This new fundamental descriptor is capable of predicting a priori the bond dipole moment and may be considered as a new useful feature for crystal structure prediction based on artificial intelligence.

Electrical and magnetic performances of semiconductor based carbon nanoparticles

The temperature-dependent resistivity, room temperature electron field emission, and magnetic performance within the temperature range of 2–300 K of previously chemically synthesized pure carbon nanoparticles (CNPs) from candle soot having particle sizes of ≈2–6 nm have been studied. The highest saturation magnetization and coercivity of ≈8.9 × 10−2 emu/g and ≈130.8 Oe were obtained at 2 and 4 K, respectively. We also determined that the turn-on electric field is ≈27 V/μm with a current density of ≈0.8 × 10−8 A/cm2 @ 20 V/μm. The temperature vs electrical resistivity and applied high electric field (EA) vs electron emission show the tunneling from one conductive sp2 C=C cluster to another separated by an sp2 C=C cluster (and/or an insulating sp3 C–C cluster). The magnetic, as well as the electric, field emission results imply that CNPs could be useful for the fabrication of spintronic as well as field-emission display devices.

Strong f–f excitation in hafnium germanate: Near‐UV LED and cathode beam–pumped red phosphor with thermal robustness

AbstractDeveloping narrowband red phosphors has always been a frontier topic in the phosphor community. In this study, a novel hafnium germanate red phosphor, BaHfGe3O9:Eu3+, was successfully synthesized by solid‐state reaction method. The phase and crystal structure of BaHfGe3O9 were investigated by the Rietveld refinement of powder X‐ray powder diffraction. The band structure was analyzed by density functional theory calculations. Most importantly, the luminescence behavior of phosphors under near‐ultraviolet (n‐UV) light and cathode rays sources was studied in detail to explore the possibility of their applications in white light‐emitting diodes and field emission display. The BaHfGe3O9:Eu3+ phosphor exhibits strong f–f excitation and excellent thermal robustness due to Eu3+ localization in the rigid lattice and asymmetric Ba2+ sites. Under cathode rays and n‐UV light excitation, BaHfGe3O9:Eu3+ exhibits narrowband red light emission peaked at 610 nm. Moreover, BaHfGe3O9:Eu3+ shows excellent saturation resistance and aging resistance. The performance of the LED lamp encapsulated by the BaHfGe3O9:Eu3+ phosphor was studied. The results show that BaHfGe3O9:Eu3+ is a potential red phosphor for multifunctional applications.

Effect of VO2+ ions incorporation on paramagnetic behavior of Calcium Borophosphate (CaBP) nanophosphors: A detailed study of structural and EPR properties

Novel phosphor luminous materials have attracted much interest due to their prevalent use in light emitting diodes (LEDs), Field-emission display (FED), Plasma display panel (PDP), and fluorescent markers in biomedicine. Vanadium steel is utilised for crankshafts, bicycle frames, gears, and other things. Solid-state technique is used to produce samples of Calcium Borophosphate (CaBP) Nanophosphors that incorporate VO2+ ions. At various VO2+ concentrations, the structural and EPR features have been investigated. The powder XRD patterns and predicted lattice cell properties allow us to determine that the generated phosphors belong to the triclinic crystal system. Crystallite sizes for VO2+ doped CaBP nanophosphors are typically in the range of 29 nm. The octahedral coordination of VO2+ with tetragonal compression is shown in the EPR data. An increase in the bonding parameters is observed with an icnrease in VO2+ concentration. The Tetragonal and Spin Hamiltonian values and the calculated crystal field support the same.

Alq3-Graphene Bi-Functional Nanocomposite for Cold Cathodes and Luminescent Anodes in Field Emission Display Applications

Alq3-Graphene Bi-Functional Nanocomposite for Cold Cathodes and Luminescent Anodes in Field Emission Display Applications

Bright blue emissions on UV-excitation of LaBO3 (B=In, Ga, Al) perovskite structured phosphors for commercial solid-state lighting applications

Bright blue photoluminescence (PL) was obtained from Bi3+-activated LaBO3 (B = In, Ga, Al) perovskite nanophosphors. A cost-effective and low-temperature chemical route was employed for preparing Bi3+ doped LaBO3 (B=In, Ga, Al) which were then annealed at 1000 °C. The phase formation, morphological studies and luminescent properties of the as-prepared samples were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence and optical absorption spectroscopy. Comparison of emission intensities, lifetime studies, energy band gaps and color purity of all samples (pure and Bi3+ doped) were investigated for promising applications in UV light-emitting diodes, variable frequency drive (VFD), field emission display (FED), and other photoelectric fields.

Achieving Bright Reddish-Orange Luminescence in CaSnO3 Ceramics through Doping Manipulation

The reddish-orange phosphors of rare-earth activator have attracted intense interest due to their applications in lighting and display devices, including plasma display panel, field emission display and white light diode. In this work, Eu-doped CaSnO3 phosphor materials were prepared and examined. Their X-ray diffraction patterns were used for lattice parameters calculations and show that there was no phase transformation in all doping conditions. XANES studies suggest the stabilization of Sn and Eu ions in 4+ and 3+ oxidation states in the prepared phosphors, respectively. A broad emission band, with a major peak at 614 nm upon excitation wavelength of 395 nm, was observed in the range of 550 to 730 nm at room temperature due to 5D0 → 7FJ transition of Eu3+ ions. The luminescent spectra of the samples showed the intense light emission in the red-orange light region.

Li2CaSi2N4:Sm3+: A nitride-based red phosphor with excellent temperature sensitivity and cathodoluminescence for temperature sensor and FED

Temperature sensor and field emission displays (FED) are the intensive topics for Sm3+ activated red phosphor. In this study, a novel lithium nitride red phosphor Li2CaSi2N4:Sm3+ was successfully prepared by solid phase method. The photoluminescence and cathodoluminescence performances were systematically studied to explore the possibility in FED and temperature sensor applications. The results indicate that the Li2CaSi2N4:Sm3+ phosphor features intense red emission under the UV light and cathode ray excitations. The phosphor also has a long red afterglow with an afterglow time of 12.7 min. Most importantly, Li2CaSi2N4:Sm3+ exhibits excellent temperature sensitivity with the relative sensitivity of 4.8% K−1 @473 K, which is higher than other temperature sensor materials. The thermal quenching mechanism was proposed based on a configurational-coordinate model. Moreover, excellent cathode ray saturation and aging resistance were observed in Li2CaSi2N4:Sm3+. The results indicate that Li2CaSi2N4:Sm3+ is a potential temperature sensor and FED materials.

Investigations on the Carbon Nanotube Paste Made by the Optimized Ball-Milling Method and Its Applications for the e-Beam Source

The carbon nanotube (CNT) has the outstanding mechanical/chemical properties, which makes it a promising electron source for various applications such as the field emission display (FED), the microcolumn, and the X-ray tube. In this work, we have developed the CNT paste by applying the noble ball-milling method to the paste mixer. The newly developed CNT paste was used to fabricate the CNT field emitter whose electric characteristics were evaluated by observing the I–V curve and long-term stability of the emitter. The new CNT paste showed much better electrical characteristics than those of the conventional CNT paste. We also used the CNT tip as a source of the electron beam (e-beam) of the microcolumn and found that the operating range of the e-beam was enhanced by 100% compared to that of the conventional microcolumn where the tungsten tip was used as the e-beam source. By replacing the tungsten tip with the CNT tip, we could not only obtain more flexibility in design of the microcolumn but also remove the alignment problem between the emitter tip and the source lens.

Cyan Broad-Band Emission Phosphor with Scandium Silicon Multiple-Ring Structure for White Light-Emitting Diodes and Field Emission Displays.

Silicate phosphor KBaScSi2O7:Ce3+ (KBSS:Ce3+), as a novel material, has been prepared by the solid-state method in this study. The crystal structure, luminescent properties, thermal stability, and cathodoluminescence (CL) properties of this material were analyzed systematically. It concludes that the phosphor can emit cyan light with emission peak at 509 nm under n-UV light excitation (300-400 nm). By coating KBSS:Ce3+ with a red-emitting CaAlSiN3:Eu2+ on a n-UV (365 nm) light-emitting diode (LED) chip, the intense warm white light with high RA (83.4) and low CCT (3652) can be produced under a 350 mA forward bias current.In addition, the CL performance shows that KBSS:0.10Ce3+ has high saturation current and voltage and good color stability under low voltage conditions. All these results indicate that KBSS:Ce3+ phosphor will be very promising in LED and field emission display applications.

Scintillating zinc oxide ensconced in a carbon nanotube forest engineered by laser micro-welding

Herein, we report defect-introduction via focused-laser-beam (FLB) modification to introduce carbon defects into zinc oxide (ZnO) thin film. The approach begins with a carbon nanotube (CNT) array covered by a thin layer of sputtered Zn on top of the array. When FLB irradiates the covered CNT array under ambient conditions, effective laser energy absorption by CNT results in ZnOCNT nanohybrid formation, it also enables site-selective transformation to be achieved. By adjusting the laser power, the degree of carbon incorporation into the pristine Zn system can be tuned and this exerts some degree of control over the fluorescent properties of the nanohybrid. Generating a higher defect density increases the intensity and changes the wavelength of the fluorescence emitted by ZnO under ultraviolet (UV) excitation and enhances its field emission properties. In particular, the turn-on electric field (ETO) of the nanohybrid decreases. A lower ETO reduces the probability of arc formation, a significant problem currently undermining the industrial feasibility of field emission displays (FED). Electron emission from these samples can be enhanced by exciting the laser-treated sample with an external laser source. The normalised current produced increases by as much as 6µA/(mW/mm2) when the sample is excited by a 405 nm monochromatic laser.

A novel red-emitting Ca2GdHf2Al3O12:Eu3+ phosphor for light-emitting didoes and field emission display

In this work, a novel garnet-based Eu3+-doped Ca2GdHf2Al3O12 phosphor was synthesized through the traditional high temperature solid-state method. The phase purity, fundamental structure of the crystal, morphology, photoluminescence and cathodoluminescence properties have been investigated in detail. Along the temperature rises to 200 °C, the Ca2GdHf2Al3O12:0.08Eu3+ remains about 70.2% according to the initial emission intensity. Under the electron bombardment, the Ca2GdHf2Al3O12:0.08Eu3+ phosphor reveals a remarkably improved performance in the anti-degradation property. All results indicating that the Ca2GdHf2Al3O12:Eu3+ could be regarded as a valuable phosphor in the multiple industrial applications, such as WLEDs and FEDs.

Design of a Bismuth-Activated Narrow-Band Cyan Phosphor for Use in White Light Emitting Diodes and Field Emission Displays

To overcome the problem that Bi3+-activated phosphors suffer from, it is an urgent need to realize narrow-band light emission of Bi3+-activated phosphors, which not only improves their luminescence...

A promising red-emitting phosphor SrLiAl3N4:Eu2+ for field emission displays

Exploring efficient and stable phosphors have already attract highly public attentions and always been considered as a crucial issue in the development of field emission displays (FEDs). In order to discover the potential application for FEDs, the red phosphor, SrLiAl3N4:Eu2+, was synthesized by a simple preparation method at low temperature and the photoluminescence(PL) as well as cathodoluminescence (CL) performances were studied in our work. The SrLiAl3N4: Eu2+ phosphor exhibits irregular spherical morphology with a soft agglomeration and the mean particle size is 4.52 µm. When excited by a low-voltage electron beam, it shows a narrow band red emission in the 600–700 nm range with the 51 nm of full width at half maximum (FWHM) and the strongest emission peak is located at 647 nm, which is attributed to the 4f65d → 4f7 electron transition of Eu2+. The effects of different Eu2+ doping concentration and probe current, accelerating voltage, as well as electron bombardment time on the CL performance of SrLiAl3N4:Eu2+ were studied in detail and found that the optimal sample, SrLiAl3N4:0.5%Eu2+, exhibits no saturation effect and excellent degradation property compared with the commercial Y2O3:Eu3+ phosphor. In view of the prominent CL performance of SrLiAl3N4:Eu2+, it can be considered as candidate phosphor in full color FEDs.

A novel narrow-band blue-emitting phosphor of Bi3+-activated Sr3Lu2Ge3O12 based on a highly symmetrical crystal structure used for WLEDs and FEDs

Investigating highly efficient narrow-band emission phosphors that have strong excitation bands in the near-ultraviolet (NUV) region is the main goal of the present light-emitting diode (LED) research, especially for Bi3+-activated phosphors. The naked 6s and 6p electrons of Bi3+ are sensitive to the microenvironment, thus leading to broad emission bands, while most Bi3+-activated phosphors suffer from low absorption of NUV-LED chips. Here, we report on a narrow-band blue-emitting garnet-type phosphor of Sr3Lu2Ge3O12: Bi3+ that is available for NUV-LED chips; its full width of the half maximum (FWHM) is limited to 40 nm, which is comparative to rare earth-activated phosphors, such as commercial blue phosphor BaMgAl10O17: Eu2+ (FWHM ≈ 52 nm), and this phenomenon is extremely rare among most Bi3+-activated phosphors. The internal quantum efficiency (IQE) of Sr3Lu2Ge3O12: Bi3+ can reach 57%. Moreover, it is interesting to find that Sr3Lu2Ge3O12: Bi3+ also exhibits exalting cathodoluminescence properties and its narrow-band emission produces brilliant images with high color saturation. The significant luminescent properties of trivalent bismuth are ascribed to the compact and highly symmetrical crystal structure of Sr3Lu2Ge3O12; thus, the discussion of the structure-property relations for Bi3+-activated Sr3Lu2Ge3O12 is the most anticipated part of this work. The results pave the way for the design of better Bi3+-activated phosphors for use as white light emitting diodes (WLEDs) and field emission displays (FEDs).

Effect of Eu3+ on optical and energy bandgap of SrY2O4 nanophosphors for FED applications

The red colour emitting Eu3+ (0.01, 0.03, 0.05, 0.07, 0.09 and 0.11 at mol) doped SrY2O4 nanophosphors were prepared via a novel solution combustion synthesis route by taking glycine as a fuel. The prepared nanophosphors further annealed at 1300°C for three hour. The structural, morphological and spectroscopic properties of nanophosphors are characterized by means of XRD, FESEM, HR-TEM, PL, Ultra Violet-Visible DRS and FTIR spectroscopy. The XRD studies for all Eu3+ doped samples support crystallinity to the orthorhombic CaFe2O4 structure with Pnam space group and cell parameters, a=10.07 Å, b=11.91 Å, c=3.41 Å. Using Debye Scherrer formula, the particles size were estimated to be 92 nm, which agrees with HR-TEM studies. Nearly spherical and agglomeration of the particles were detected from the FE-SEM micrographs. A powerful red colour release was noticed with a powerful peak at 613 nm because of 5D0 → 7F2 transition at an excitation wavelength of 254 nm and it has been confirmed by CIE chromaticity graph. FTIR, UV–vis DRS indicate that the Sr2+ replacement by Eu3+ ions makes prompt structural defects in SrY2O4 lattice. Direct energy bandgap of nanophosphors estimated by the help of Kubelka–Munk's approximation thru UV–vis DRS, energy bandgap of the red nanophosphors is lesser (∼ 4.974 eV) compared to un-doped SrY2O4 (∼ 5.043 eV), corroborating that ions of Eu3+ shoot ups SrY2O4 structural deficiencies. These analyses reveal that SrY2O4:Eu3+ nanophosphors would be used as the red colour emitting nanophosphors for the improvement of W-LEDs and field emission displays (FED).

Cathodoluminescence degradation of Y2O3:Dy3+ nanophosphor for field emission displays

Cathodoluminescence (CL) degradation of Y2O3:Dy3+ nanophosphors prepared by the solution combustion method was explored for feasible applications in low voltage field emission displays (FEDs). Oxide materials are excellent candidates for FED fabrication due to their high melting points, chemical and radiation stability with long lifetimes, high color purity, and being environmentally friendly. Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) were used to monitor changes in the surface chemical composition and correlation fit with CL degradation. AES and CL spectroscopy (2 keV energy electrons and with a beam current of 15 μA) measurements were done in high vacuum (1.5 × 10−8 Torr) and oxygen pressures of 1 × 10−7 and 5 × 10−7 Torr. The Y2O3:Dy3+ nanophosphor showed strong yellow (572 nm) and relatively weaker blue (492 nm) CL emissions. These CL emissions increased as carbon (C) was depleted from the surface, and then it slightly decreased at a high electron dose in both the vacuum and oxygen atmospheres, for electron doses up to about 690 C/cm2. The C was depleted from the surface due to electron stimulated reactions. No significant change in the chemical state of Y 3d was observed with XPS high resolution spectra for the postirradiation sample. The change in the CL intensity was, therefore, attributed to the depletion of C from the surface.

Dual-functional of non-contact thermometry and field emission displays via efficient Bi3+ → Eu3+ energy transfer in emitting-color tunable GdNbO4 phosphors

Using solid-state reaction technique, we prepared a series of Bi3+/Eu3+-activated GdNbO4 phosphors. Under 308 nm excitation, the energy transfer from Bi3+ to Eu3+ ions, which belonged to the dipole-quadrupole interaction mechanism, allowed the GdNbO4:Bi3+,Eu3+ compounds to display tunable multi-color emissions. The temperature dependent photoluminescence emission and water resistance behaviors of the obtained samples were investigated in detail. Taking full advantage of the diverse thermal quenching performance between Bi3+ and Eu3+ ions along with their distinct characteristic color emission, we designed a highly sensitive non-invasion optical thermometer. The maximum absolute and relative sensor sensitivities of the final compounds were about 0.0367 K−1 and 3.81% K−1, respectively. Moreover, the as-prepared phosphors exhibited excellent cathode-luminescence properties. These above characteristics indicated that Bi3+/Eu3+-activated GdNbO4 phosphors can be used as potential luminescent materials for non-contact temperature measurement and field emission display.