Optimal Doping Concentration Research Articles

Regarding the structural, thermodynamic, mechanical, thermoelectric, and optoelectronic properties of anti-perovskite Mg3XN (X = As, Sb, and Bi) through a DFT approach

In this work, we comprehensively analyzed the structure, thermodynamics, mechanical, thermoelectric, and photoelectric properties of antiperovskite Mg3XN (X = As, Sb, and Bi) using first-principles calculations and semi-classical Boltzmann transport theory. Our calculations of phonon spectra and elastic constants suggest that Mg3XN (X = As, Sb, and Bi) exhibit excellent dynamic and mechanical stability, characterized as brittle materials with Vickers hardness (HV) values exceeding 10 GPa. Electronic structure analysis reveals that Mg3AsN is a direct bandgap semiconductor with a 2.25 eV gap, whereas Mg3SbN and Mg3BiN are indirect bandgap semiconductors with gaps of 1.58 eV and 1.41 eV, respectively. At room temperature, the lattice thermal conductivities (κL) for Mg3AsN, Mg3SbN, and Mg3BiN are 13.63, 9.93, and 7.26 Wm−1K−1, respectively, with ZT values of 0.32, 0.08, and 0.10 at optimal doping concentrations. At 1000 K, κL values decrease to 3.19, 2.29, and 1.65 Wm−1K−1, respectively, with ZT values reaching 2.12, 0.98, and 0.92. Our analysis of optical properties demonstrates that these materials exhibit absorbance in the visible and ultraviolet spectra, with negligible energy loss in the respective energy ranges, thereby rendering them suitable for photovoltaic applications.

Temperature sensing of novel Tb3+/Ho3+/Bi3+ co-doped lead-free double perovskite Cs2AgInCl6 nanocrystals

Up to now, the research field of application of lanthanide ions doped lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) was relatively limited, even less in temperature sensing. Here, Tb3+/Ho3+/Bi3+ ions were successfully doped into Cs2AgInCl6 NCs by hot-injection. The temperature sensing performance of co-doped NCs by using the fluorescence intensity ratio (FIR) was studied through the temperature-dependent emission spectra. By analyzing the influence of ions' doping concentration on temperature sensing performance, the optimal doping concentration of co-doped Cs2AgInCl6 NCs was determined to be 7 % Tb3+, 20 % Ho3+ and 1 % Bi3+. The highest absolute and relative sensitivities reach 1.48 K−1 and 2.48 %/K, respectively. We provide a new doping scheme of lead-free double perovskite NCs which have good temperature sensing performance. This co-doped NCs have great potential application value in non-contact temperature sensing in nanoscale.

Lattice distortion effects induced by Li+ co-doping on ZnO:Tb3+ phosphors: Photoluminescence and unusual hypersensitive ⁵D₄ → ⁷F₀ transition

A series of Tb3+, Li+ co-doped ZnO phosphors were prepared using a precipitation method. X-ray diffraction (XRD) analysis indicated the successful incorporation of Tb3+ into the ZnO lattice. The influence of Tb3+ doping content and Li+ charge compensator on the photoluminescence (PL) properties of ZnO:Tb3+ was investigated. Under UV excitation, emissions corresponding to electron transitions 5D4→7FJ (J = 0,1,2,3,4,5,6) were observed from Tb3+ ions, including an unusual emission transition at 673 nm, which significantly enriches our understanding of Tb3+ luminescence. The critical concentration quenching of Tb3+ in ZnO:Tb3+ occurs at 7 mol%, as explained by the Van Uitert equation, which attributes this phenomenon to dipole-dipole interactions. Surprisingly, incorporating Li+ for charge balancing led to a reduction in the luminescence intensity of ZnO:7 mol%Tb3+, x%Li+ phosphors (x = 0.01 and 0.07) at 544 nm. This reduction highlights an increased degree of lattice distortion due to Li⁺ inclusion. Furthermore, CIE chromaticity analysis showed that the optimal doping concentration of 0.07 Tb³⁺ shifted the color coordinates towards vivid green, with a color temperature of approximately 6241 K, indicating of neutral white light.

Photoluminescence and afterglow of Tb3+ doped BaAl2O4

Tb3+ doped BaAl2O4 phosphors (0–9.0 mol%) were prepared through sol–gel combustion method. The crystal structure, morphology, chemical composition, photoluminescence (PL), afterglow and thermoluminescence (TL) glow curve of Tb3+ doped BaAl2O4 were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, PL spectroscopy, afterglow spectroscopy, and TL dosimetry. Characterizations of the PL and afterglow spectra indicate that both Tb3+ doping species and oxygen vacancies act as the luminescence center of PL whereas only Tb3+ dopant works as the luminescence center of afterglow for Tb3+ doped BaAl2O4. The green afterglow of Tb3+ doped BaAl2O4 lasts for about 214 min at the optimal doping concentration of about 1.0 mol%. The profile of TL glow curve of Tb3+ doped BaAl2O4 heavily depends on the doping concentration, and the evolution of the TL glow curve with doping concentration reveals that doping BaAl2O4 with Tb3+ can significantly modify the distribution of carrier traps in the phosphor. The effects of Tb3+ doping on the PL, afterglow, and TL glow curve of Tb3+ doped BaAl2O4 are discussed in terms of the creation, recombination, and neutralization of defects in BaAl2O4. This work proves that doing with Tb3+ species is a general and robust strategy for endowing BaAl2O4 with highly efficient green afterglow. This “defect engineering” approach enables ultra-long afterglow for Tb3+ doped BaAl2O4 when defect centers in the phosphors are optimized.

Analysis of CdS/CdTe Thin Film Solar Cells as a Function of CdS Doping Concentration: A Numerical Simulation Perspective

Cadmium Telluride (CdTe) photovoltaics, incorporating a thin film of Cadmium Sulfide (CdS), present a costeffective yet less efficient solar cell technology. Improving CdS/CdTe solar cell efficiency involves optimizing parameters like doping concentration and CdS layer thickness. However, limited research on cell defects necessitates a comprehensive analysis, including the often-overlooked impact of temperature. This study aims to analyze defect-free and defective CdS/CdTe solar cells, exploring the effects of doping concentration and other parameters. Using the SCAPS-1D simulator, design parameter variations will be investigated, and key metrics— open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and efficiency (η)—will be extracted. Simulation results indicate minimal efficiency impact from increased doping concentration in the ntype CdS layer for defect-free devices. The optimal doping concentration for CdS is 5 × 10<sup>18</sup> cm<sup>-3</sup>, with an optimum electron affinity of 4.0 eV. CdS thickness shows no significant efficiency impact, with the chosen optimum at 10 nm. In the defect-free CdS/CdTe solar cell, key metrics were Voc: 1.06 V, Jsc: 24.60 mA cm<sup>-2<sup>, FF: 87.89%, and η: 23.01%. Analysis of defects revealed single acceptor defects significantly impacting solar cell performance in both interfacial and bulk defects. Defect structure simulations demonstrated that increasing doping concentration, decreasing electron affinity, and thickness enhance efficiency. New optimum values for these parameters—1 × 10<sup>18</sup> cm<sup>-3</sup>, 4.0 eV, and 10 nm—yielded Voc: 1.03 V, Jsc: 23.88 mA cm<sup>-2</sup>, FF: 87.15%, and η: 21.40%. Additionally, a temperature decrease was associated with increased efficiency.

Luminescence properties and energy transfer of broadband NIR phosphor Li2MgZrO4: 1.0%Cr3+, y%Yb3+

The discovery of high thermal stability, broad-band near-infrared (NIR) fluorescent phosphors holds significant potential in applications such as non-destructive testing, promoting plant growth, and night vision devices. In this study, a novel broad-band NIR phosphors Li2MgZrO4 (LMZ): 1.0 %Cr3+, y%Yb3+ were synthesized via a high-temperature solid-state reaction method, with the optimal doping concentration found to be y = 1.5. These phosphors exhibited broad NIR emission in the range of 700–1050 nm by effective energy transfer from Cr3+ to Yb3+. The maximum full width at half maximum (FWHM) of the Cr3+/Yb3+ co-doped LMZ phosphor is 270 nm. The thermal stability of the phosphors was improved with Yb3+ co-doping. Additionally, energy transfer from Cr3+ to Yb3+ was confirmed through luminescence spectra and lifetime analysis. Finally, NIR pc-LED devices composed of a 460 nm ultraviolet chip and LMZ: 1.0 %Cr3+, 1.5 %Yb3+ phosphors were fabricated, offering a highly promising source of invisible light. These results demonstrate the wide-ranging potential applications of this novel, high thermal stability, and ultra-broad NIR emitting fluorescent phosphor.

Tunability of the photoelectric properties of CdSe thin films through doping with manganese toward photovoltaic applications

Tandem solar cells have been demonstrated to surpass the Shockley-Queisser limit, promising the transition to third-generation solar cell technology. Tandem solar cells comprise thin film layers of various band gap semiconductors, and CdSe is a promising candidate for the top cell. In this study, we explore the properties of thermally evaporated CdSe thin films doped with 0 to 5 wt% Mn and report a significant five-fold increase in carrier concentration. Furthermore, our optoelectrical studies indicate a band gap energy of 1.681eV, experiencing up to a 28 meV shift with 5 wt% Mn doping and identifies 1 wt% as the optimal doping concentration, offering the best electrical properties and photo-response while maintaining a stable band gap.

Ultra-bright green emitting Sr2MgSi2O7:Tb3+ nanophosphors: unveiling multi-security applications in anti-counterfeiting, flexible films, optical thermometry and latent fingerprint visualization

In this study, we synthesized facile green-emitting Sr2MgSi2O7:Tb3+ (1–11 mol %) nanophosphors (SMSO:Tb3+ NPs) using a solid-state reaction method. Characterization through X-ray diffraction (XRD) revealed a tetragonal crystal structure in the as-synthesized SMSO:Tb3+ NPs. Crystallographic data obtained from Rietveld refinements identified the specific sites of Tb3+ ions in the host material. Chemical and photo-luminescent properties are explored using X-ray photo-electron spectroscopy (XPS) and Photoluminescence (PL) spectroscopy, respectively. The NPs exhibited vibrant green emission at 547 nm, attributed to the Tb3+ ions' 5D4→7F5 transition, with a high quantum yield of 63.10 %. Optimal doping concentration is determined as 7 mol % (SMSO:7 Tb3+), overcoming concentration quenching primarily due to dipole-dipole (d-d) interaction. Impressively, SMSO:7 Tb3+ NPs demonstrated a correlated colour temperature (CCT) of 5549 K, colour purity (CP) of 91.60 %, and excellent colour stability. These phosphors are effectively applied in latent fingerprints (LFPs) development, revealing distinct ridge features useful for personal identification. Additionally, SMSO:7 Tb3+ NPs, combined with soluble PVA, are used to create a transparent anti-counterfeiting (AC) film, exhibiting intense green emission under UV 365 nm light. Notably, the film flexibility, durability, and foldability enhance its applicability in AC techniques. This study showcases SMSO:Tb3+ NPs as versatile luminous platforms with applications in flexible displays, high-colour quality lighting, fingerprint (FP) visualization, and anti-counterfeiting.

Thermogravimetric and temperature-dependent electrical investigations of Pr3+ doped multi-component silicate glasses for microelectronic technology

Multi-component silicate glasses doped with 0, 0.5, 1, and 1.5 mol% of praseodymium (Pr3+) were synthesized by the sol–gel method. Thermal analysis of the glasses, evinced a high working temperature of 351 °C and Hruby coefficient, K H = 1.415 in the highly doped system, corroborating the effective role of Pr3+ ions in endowing superior thermal stability to the glass. Broadband dielectric spectroscopy was applied to study the temperature-dependent electrical behavior of the glasses for their suitability as electrodes and solid electrolyte materials in batteries. A high dielectric constant of 4797 was evidenced at 1 kHz when recorded at 473 K. The AC conductivity of the glass doped with 1 mol% was observed to be the highest with 94.8 × 10−5 S cm−1 at 10 MHz and 473 K. Jonscher’s power law exponent decreased with temperature, attributing the conducting mechanism to the Correlated Barrier Hopping (CBH) model. The Nyquist impedance spectra demonstrated a depressed semicircle with a spur at the low-frequency end, validating the non-Debye relaxation in the glasses. The equivalent circuitry of the plot predicted parallel combinations of resistor and constant phase elements which reflects a Warburg diffusion and capacitive approach. Bode’s phasor diagram confirmed the capacitive nature by a phase angle of −90° in all the glasses. While a uniform increase in dielectric constant and conductivity was observed up to 1 mol% of Pr3+, a sharp decline in the electrical phenomenon was observed with 1.5 mol% of Pr3+, due to the possible blockade of the hopping of charge carriers by the largely quantified dopant ions. Extracting a high dielectric constant, and ionic conductivity at high frequencies, with an optimal dopant concentration of 1 mol% Pr3+, the composite glasses could be considered for their potential use in integrated microcomponent storage devices as cathode and solid electrolyte materials.

Enhancing Strategy of the Small-Polaron Conductivity in LaCrO3: First-Principles Calculations and Experimental Validation.

LaCrO3 (LCO) has promising applications as a p-type conductive material in the fields of transparent conducting oxes, high-temperature sensors, and magnetohydrodynamic power generators. However, the easy volatility of the Cr element, along with the issues of low electrical conductivity caused by the small-polaron conduction mechanism and wide band gap, has hindered the widespread application of LCO. In this work, based on band engineering and defect engineering, we screened doping schemes through first-principles calculations that can reduce Cr volatility by enhancing the Cr-O bond energy. We also aimed to promote small-polaron hopping and improve the electrical conductivity by introducing impurity levels. Additionally, we conducted a thorough analysis of the small-polaron conductivity mechanism. Through the solid-state method, we successfully prepared codoped LCO with Ca and Zn. The Zn dopants effectively enhanced the Cr-O bond strength, suppressed the Cr volatility, and improved high-temperature stability. The Zn dopants introduced additional impurity energy levels within the band gap, significantly changing the mobility of small polarons. Through optimal doping concentration, the La0.7Ca0.3Cr0.95Zn0.05O3 sample demonstrated a significant enhancement in electrical conductivity compared to La0.7Ca0.3CrO3, increasing from 7 to 60 at 1000 K. Additionally, the impurity energy levels enhanced the asymmetry near the Fermi level, resulting in an increased Seebeck coefficient (S). This is beneficial for the production of high-temperature sensors. The output voltage of an LCO thermocouple module reaches up to 58 mV at 2170 K, indicating that the performance optimization strategy employed in this work has significant implications for the regulation and application of oxide electrical materials.

Graphdiyne particles as nano-floating gates for high-performance nonvolatile organic field-effect transistor memory

Graphdiyne particles (GDYP), newcomers of carbon family, were employed as nano-floating gates in organic field-effect transistor (OFET) memories. The charge-trapping layer was prepared by blending GDYP into a polystyrene (PS) matrix. The effect of GDYP doping ratio on memory performances was investigated, and the OFET memory with the optimal doping concentration of the GDYP (0.3 mg/mL) exhibits ambipolar memory behavior with a wide memory window as large as 86 V, excellent retention time over 104 s with a high ON/OFF current ratio of 7.5 × 105. This work demonstrates that graphdiyne is a promising charge-trapping material for high-performance nonvolatile OFET memory devices.

Effect of concentration of Er3+ on up-conversion luminescence in NaYF4 embedded oxy-fluoride glass-ceramics under 1550 nm excitation

Oxy-fluoride glass-ceramics (GC) has advantages such as low phonon energy of fluorides and the excellent physical and chemical properties of oxides. Here we report the synthesis of a series of transparent oxy-fluoride GCs with various doping contents of Er3+ (0.2 mol%-10 mol%) synthesized under different temperatures, and their UCL properties under the excitation of 1550 nm laser. We found that Er3+-doped glass matrix with NaYF4 fluoride nanocrystals demonstrated greatly enhanced UCL compared with as-prepared glass. The samples showed red light emission with 3 mol% Er3+ as the optimal doping content. The wavelength of UCL could be fine-tuned by the temperature of heat treatment, and 893 K seems to be the optimal temperature. We also studied the photoelectric conversion characteristics of the optimal Er3+ doped oxy-fluoride GCs with a polycrystalline silicon solar cell under the excitation of a 1550 nm laser as a possible strategy to effectively improve the photo-electric conversion efficiency of solar cells.

Vacancy induced enhanced photocatalytic activity of nitrogen doped CuO NPs synthesized by Co-precipitation method

The chemical co-precipitation method, an effective approach in the synthesis of nanomaterials, was used to synthesize CuO nanoparticles (NPs). Structural and morphological modification of undoped and nitrogen (N) doped CuO nanoparticles were studied thoroughly using X-ray diffraction (XRD), FT-IR and field emission scanning electron microscope (FE SEM). Doping effect on defects was investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL) spectroscopy. Thus, the effect of doping on crystallinity, crystallite size, strain induced in lattice, defects and electron-hole recombination rate were investigated. Optical band gap was calculated using Kubelka-Munk function from the diffuse reflectance spectra (DRS) obtained using ultraviolet visible (UV–Vis) spectroscopy. Finally, photocatalytic performance was studied from rhodamine B (Rh B) degradation and reaction kinetics were analyzed. Maximum degradation efficiency was obtained for 1.0 mol% N doped CuO NPs which also exhibited minimum band gap and lowest electron-hole recombination rate. For the optimum doping concentration, nitrogen was found to create oxygen vacancies while substituting oxygen in the lattice, and thus reduce electron-hole recombination rate and increase photocatalytic degradation rate effectively.

Temperature sensing performance of M2La8(SiO4)6O2:Ce3+(M=Ca, Sr, Ba) based on fluorescence intensity ratio of dual emission centers in different coordination environments

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M2La7.9Ce0.1(SiO4)6O2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba2La8(SiO4)6O2:xCe3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors.

Effect of Ti3C2Tx MXenes on the structure, morphology, fluorescence and temperature-sensitive properties of Eu3+-doped (YSZ)0.3-(YTaO4)0.7 rare-earth high-temperature ceramic powders

The rapid development of rare-earth fluorescent materials based on the fluorescence intensity ratio method allows the monitoring of internal temperature, stability and service life of thermal barrier coatings (TBCs). In this paper, Eu3+ doped (YSZ)0.3-(YTaO4)0.7 rare-earth ceramic materials was firstly prepared by chemical co-precipitation technique, and the doping content of Eu3+ was optimized by comparing its effect on morphology, luminescence and temperature sensitive performance of (YSZ)0.3-(YTaO4)0.7. Then the Ti3C2Tx MXene was subsequently blended into the optimal (YSZ)0.3-(YTaO4)0.7: Eu3+ powders by mechanical milling. The influence of Ti3C2Tx MXenes on the structure, morphology, fluorescence properties and temperature sensitivity of (YSZ)0.3-(YTaO4)0.7: Eu3+ powders was further investigated systematically. Results showed that (YSZ)0.3-(YTaO4)0.7: Eu3+ powders were compound of M′-YTaO4 and YSZ in tetragonal phase. The optimal doping content of Eu3+ is 1.5 mol%. The adding of Ti3C2Tx MXene did not affect the structure of (YSZ)0.3-(YTaO4)0.7:Eu3+ powders. After addition of Ti3C2Tx MXenes, part of (YSZ)0.3-(YTaO4)0.7:Eu3+ particles embedded in the middle of the accordion-shaped MXenes sheet, while the other part wrapped around MXenes. Ti3C2Tx MXenes could significantly improve the luminescence intensity, fluorescence lifetime and temperature-sensitive performance of (YSZ)0.3-(YTaO4)0.7: Eu3+powders. The optimal addition amount of Ti3C2Tx MXenes is 0.6 wt%. The absolute and relative sensitivities of MXene/(YSZ)0.3-(YTaO4)0.7:Eu3+ powders archived 2 times of (YSZ)0.3-(YTaO4)0.7: Eu3+ powders. Therefore, MXene/(YSZ)0.3-(YTaO4)0.7: Eu3+ could be used as temperature-indicating ceramic materials with highly efficient fluorescent properties for real-time monitoring of internal temperature of TBCs.

Structural engineering of vertically aligned nanocomposite films fabricated via magnetron and pulsed laser co-deposition for microwave application

Microwaves are often used in communication engineering, including in microwave relays as well as multichannel, mobile, and satellite communications. To meet the demand for a “small, light, thin, and precise” modern electronic machine, developing highly tunable microwave materials to manufacture miniaturized microwave devices has become a top priority. Ferroelectric materials are excellent microwave materials, showing outstanding dielectric properties and tunability. Introducing low dielectric loss oxides in the construction of vertical self-assembly nanocomposites (VSNs) effectively improves their tunability and reduces dielectric loss. However, the optimal doping content of simple VSN films limits further improvement of tunability. Herein, we propose a strategy-gradient VSN to achieve combined improvement in tunability and dielectric constant by designing a sputtering and pulsed laser co-deposition. The resulting VSN composite film has a dielectric constant of 428.08, a dielectric loss of 0.0212, and a tunability of 78.69%. Our results contribute to the development of filters and have broad application prospects in the microwave industry.

Development of reddish orange-emitting Y2Sn2O7:Eu3+phosphors for latent fingerprint detection and anti-counterfeit security ink

In forensic science, fingerprint detection and anti-counterfeiting technologies are crucial. Inorganic phosphors are potentially suitable materials for high-quality visualization and security. We synthesized novel Y2Sn2O7:Eu3+ (YSO:Eu3+) phosphors by a sol–gel method. They have a cubic structure and emit reddish orange emission from the Eu3+ ions electronic transition of 5D0→7F1. The optimal doping concentration of Eu3+ is 7 mol% and dipole-dipole interaction causes the quenching mechanism. The chromaticity coordinates of YSO:7Eu3+ phosphor are (0.6086, 0.3906). We used the optimized YSO:7Eu3+ phosphors for forensic applications, such as latent fingerprints and security ink. The latent fingerprints stained with YSO:7Eu3+ phosphors showed clear images and reliable level 1–3 characteristics. The security ink was visible on different surfaces. Our results indicate that the YSO:7Eu3+ phosphor can be used for visualizing latent fingerprints and anti-counterfeiting applications.

Optimal Doping Concentrations of Nd3+ Ions in CYGA Laser Crystals

The kinetic process of the excited state population of Nd3+ ion in Nd: CaY0.9Gd0.1AlO4 (Nd: CYGA) crystal were studied in detail to estimate the optimal doping concentration, which maximize ~1 μm fluorescence emission from the 4F3/2 state to the 4I9/2 state of Nd3+. The analysis was accomplished by revealing the dependence of the excited state population on the doping concentration in a relatively convenient way in theory. After comparing the theoretical prediction results with the experimental findings and approximating the results obtained using the aforementioned method, the optimal relative doping concentration of Nd: CYGA was determined to be 2.1 at.%, which closely matched the 2.0 at.% obtained through experimental comparison. This verifies the effectiveness and accuracy of the proposed method. In particular, it is worth mentioning that in this method only one doping concentration of the crystal is required to obtain the optimal concentration, which may be used to guide the concentration optimization process for improving efficiency and saving resources.

Eu3+ doped (Y0.75Sc0.25)2O3 red-emitting ceramics with excellent photoluminescence properties for LEDs

Developing narrow-band red-emitting ceramic phosphors with high quantum yield and low thermal quenching is vital for mid to high powder solid state lighting. In this study, a series of (Y0.75Sc0.25)2O3:Eu3+ ceramics were fabricated and their photoluminescence properties were studied. The spectral measurement suggests that the optimal doping concentration of Eu3+ is as high as 14%. The heavily doped samples show strong absorption in the NUV-blue region (particularly 360–420 nm and 460–475 nm), bright red emission dominated by the sharp peak located at 611 nm, CIE chromaticity coordinates close to the NTSC standard value of red emission, and single exponential photoluminescence decay without afterglow. In particular, ((Y0.75Sc0.25)0.86Eu0.14)2O3 ceramic exhibits high QY of 86.9%, high color purity of 96.9%, and low thermal quenching loss of 16% as the temperature increases from 300 to 570 K. The excellent photoluminescence properties highlight the great potential of Eu3+ heavily doped (Y0.75Sc0.25)2O3 red-emitting ceramics as color converters for solid state lighting, which is demonstrated by the outstanding electroluminescence performance of the fabricated red and white LEDs.

Improvement of rewriting time of optically driven liquid crystal display by azo-dye doping

ABSTRACT Optically driving liquid crystal display (ODLCD) uses polarized light field to control the orientation of the liquid crystal, and the display content can be maintained without external electric field, with extremely low power consumption. However, it has a long rewriting time, which is difficult to achieve industrialization. In order to improve the rewriting performance, the influence of the rotational viscosity of the mixed system of azo-dyes (SD1, MR) and nematic liquid crystal (5CB) on the rewriting speed is investigated. The experimental results show that the electro-optical properties of SD1-5CB and MR-5CB have great changes after irradiation by polarized light, among which the SD1-5CB is the best to improve the performance. With the increase of SD1 concentration, the rotational viscosity of SD1-5CB decreases significantly due to the change of cis-trans isomerization of azo-dye, and the optimal doping concentration is 0.5 wt%. In this case, the rewriting time is shortened from 45 s to 11 s, which has the potential to broaden the application of ODLCD.