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Issue 12 ， 2021
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Crystal Site Engineering in Sr2LiSiO4F Enabling Mixed-valent Europium Toward Ratiometric Temperature Sensing Enhanced Publication
Abstract：Eu-doped Sr1.95+xLi1-xSi1-xAlxO4F(0≤x≤0.25) phosphors were prepared by solid-state method. The Sr polyhedron sites occupied by Eu2+ in the Sr2LiSiO4F matrix lattice were adjusted via crystal site engineering method which is implemented by replacing Si4+-Li+ with Al3+-Sr2+ ion pairs. The co-existence of Eu2+ and Eu3+ in single-phase Sr1.95+xLi1-xSi1-xAlxO4F∶0.05Eu(0≤x≤ 0.25) phosphors was achieved, and the luminescence was tuned from green to red light. The temperature-dependent spectra(25-300 ℃) of Eu2+ and Eu3+ ions in Sr1.95+xLi1-xSi1-x-AlxO4F∶0.05Eu were studied. It was found that Eu2+ and Eu3+ have different temperature sensitivities. The absolute sensitivity and relative sensitivity of temperature sensing of the Sr1.95+xLi1-xSi1-x-AlxO4F∶0.05Eu phosphor reach 2.83%·K-1 and 0.66%·K-1, respectively, which further confirms the application potential of the prepared phosphors in temperature sensing.Keywords：crystal site engineering;mixed-valent europium;ratiometric temperature sensing- 481
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Published：2021-12-17
Cover Story
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Preparation, Optical Control and Application of Red/Near Infrared Emitting Carbon Dots Enhanced Publication
Abstract：Red/near-infrared emitting carbon dots(marked as R/NIR-CDs) have the advantages of good biocompatibility and high spatial resolution, which had attracted the attention of researchers. However, the currently reported red carbon dots often have the defects of low fluorescence quantum efficiency, wide full width at half-maximum and excitation wavelength dependence, which limit their application in the biomedical field. Therefore, it is of great significance to synthesize carbon dots with high photoluminescence quantum yield(PLQY), narrow half-width and excitation-independent red/near-infrared emission. This article first describes several representative typical precursors and their synthesized carbon dots in recent years, and then summarizes several efficient regulation methods for the optical properties of CDs such as size effect, heteroatom doping, surface state, etc, and briefly introduces the application of red/near infrared emitting carbon dots in bioimaging, disease treatment and white light emitting diodes. Finally, the problems and challenges faced in the luminescence mechanism and the preparation method of red/near-infrared emitting carbon dots are prospected.Keywords：carbon dots;red/NIR emission;optical control;bioimaging;LED- 1026
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Published：2021-12-17
Invited Review
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Growth and Properties of Novel Mid-infrared Laser Crystal Er3+ /Ho3+/Eu3+∶PbF2 Enhanced Publication
Abstract：In this work, Er3+/Ho3+/Eu3+ tri-doped PbF2 mid-infrared laser crystal was successfully grown using the vertical Bridgman method. As far as we know, it is the first time to obtain a broadband mid-infrared luminescence extending from 2 600 nm to 3 200 nm with a full width at half maximum (FWHM) of 300 nm under 980 nm pump, which is the result of the superposition of the 2.7 μm emission peak of Er3+(2 600-2 950 nm) and 2.9 μm emission peak of Ho3+(2 800-3 200 nm). What's more, the introduction of deactivation ions Eu3+ can conquer self-termination bottleneck of both Er3+ and Ho3+ ions effectively. It is found that, compared with the Er3+/Ho3+∶PbF2 crystal, the Er3+/Ho3+/Eu3+∶PbF2 crystal has higher fluorescence branching ratio 18.7% of Er3+:4I11/2→ 4I13/2 transition and 18.0% of Ho3+:5I6→5I7 transition, and larger emission cross section 0.621×10-20 cm2 at 2 745 nm and 0.728×10-20 cm2 at 2 905 nm. These advantageous spectroscopic characteristics suggest that the Er3+/Ho3+/Eu3+∶PbF2 crystal may be a promising material for 2.6-3.2 μm mid-infrared lasers under the pump of a commercial 980 nm laser diodes (LDs).Keywords：PbF2 crystal;Er3+/Ho3+/Eu3+;Mid-infrared luminescence;Deactivation- 343
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Preparation and Stability of CsPbBr3 Perovskite Quantum Dots Glass for White LED Enhanced Publication
Abstract：CsPbBr3 perovskite quantum dots(PQDs)will degrade in different degrees in light, heat and air, which limits their application in optoelectronic devices. In this paper, the CsPbBr3 PQDs@glass was successfully prepared by traditional melting quenching and heat treatment methods, in which CsPbBr3 PQDs and zinc borosilicate glass were composited. The results show that the CsPbBr3 PQDs@glass is a kind of green emission material peaked at 520 nm with a half peak width (FWHM) of 20 nm. At the same time, the material has good light and water stability. After continuous irradiation under blue light for 30 d, the emission intensity is only reduced by about 4%. After soaking in water for 30 d, the emission intensity can still maintain 95% of its initial intensity. In addition, the white LED device is successfully encapsulated by the composite, which shows that the material has potential application in the field of lighting and display.Keywords：CsPbBr3;perovskite quantum dots;Zinc Borosilicate glass;white LED- 448
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Published：2021-12-17 -
Temperature Sensing Characteristics of Up-conversion Luminescence in Tm3+/Yb3+ Co-doped LuYO3 Phosphor Enhanced Publication
Abstract：LuYO3∶Tm3+(0.3%)-Yb3+(5%) phosphor was prepared by CO2 laser zone melting method. Under the excitation of 980 nm laser, the sample exhibits up-conversion luminescence(UCL) corresponding to 1G4→3H6, 1G4→3F4, 3F2,3→3H6, 3H4→3H6 transition in the visible light region, among which obvious Stark splits of luminescence are observed in the blue UCL corresponding to 1G4→3H6 transition. The temperature sensing characteristics of 1G4(a), 1G4(b) and 3F2,3, 3H4 thermally coupled levels(TCLs) are investigated by fluorescence intensity ratio(FIR) method. The results show that the temperature measurement range of the two pairs of TCLs is 223~723 K. The Stark sub-levels 1G4(a) and 1G4(b) have higher sensitivity at low temperatures with maximum absolute sensitivity 5.62×10-3 K-1 and maximum relative sensitivity 28.2×10-3 K-1 at 223 K, the 3F2,3 and 3H4 TCLs are more suitable for high temperature measurement with maximum absolute sensitivity 1.44×10-3 K-1(723 K) and maximum relative sensitivity 4.61×10-3 K-1(516.3 K), indicating that the prepared fluorescent material is very suitable for fluorescent temperature sensing.Keywords：Tm3+/Yb3+∶LuYO3;upconversion luminescence;fluorescence intensity ratio(FIR);optical temperature sensing- 231
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Preparation and Optical Properties of β-NaGdF4∶Yb3+,Er3+/Cellulose Nanocrystalline Cholesteric Composite Films Enhanced Publication
Abstract：β-NaGdF4∶Yb3+,Er3+ upconversion fluorescent nanoparticles with the particle size of 4.4 nm were synthesized by solvothermal method using rare earth chlorides as raw material and oleic acid and octadecene as solvent. And then β-NaGdF4∶Yb3+,Er3+/CNC cholesteric composite films were prepared by evaporation-induced self-assembly of cellulose nanocrystalline(CNC) suspension with β-NaGdF4∶Yb3+,Er3+ nanocrystals. The structure, morphology and properties of the prepared samples were analyzed by X-ray diffraction(XRD), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FT-IR) and fluorescence spectroscopy. The results show that the prepared NaGdF4∶Yb3+,Er3+ upconversion material with a spherical morphology has a pure hexagonal phase and good dispersivity. And the solution can emit the bright green light under the excitation of a 980 nm laser. β-NaGdF4∶Yb3+,Er3+/CNC cholesteric composite films with both upconversion luminescence and structural colors were obtained after self-assembly with nanocellulose solution. The structure of the cholesteric liquid crystal of the nanocellulose was not changed with adding a small amount of β-NaGdF4∶Yb3+,Er3+ nanoparticles. Meanwhile, it was found that the assembled chiral film, as a one-dimensional photonic crystal, could regulate the optical properties of β-NaGdF4∶Yb3+,Er3+to some extent, and the fluorescence intensity at the bandgap edge of the nanocellulose was enhanced by 2.7 times.Keywords：cellulose nanocrystalline;self assembly;cholesteric liquid crystal;upconversion fluorescence- 206
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Fabrication and Photoluminescence Properties of Eu3+ Doped Y2O3 Ceramic Fiber with High Aspect Ratio Enhanced Publication
Abstract：Eu3+ doped Y2O3 ceramic fiber phosphor with high aspect ratio was successfully fabricated by using direct ink writing(DIW) extrusion process combined with high temperature solid-state reaction method. The rheological properties of ceramic paste, phase structure and luminescence kinetic of ceramic fiber, as well as the temperature dependent photoluminescence(PL) spectra were successively investigated. The obtained results indicated that the optimal solid content was 55% for the ceramic paste with HPMC hydrogels as the additive. Pure ceramic phase could be achieved at the sintering temperature of >1 200 ℃. With increasing the temperature to 1 500 ℃, no significant change was observed for the phase structure. From the steady-state and transient PL spectra, the optimum luminescence performance was observed for the sample sintered at 1 300 ℃ with the luminescence lifetime of 1.12 ms. Finally, the temperature dependence of PL spectra was carefully studied, and the luminescence properties were not deteriorated with increasing temperature from 100 K to 500 K. Such a result may indicate an excellent luminescence thermal stability for our ceramic fiber.Keywords：ceramic fiber phosphor;(Y0.85La0.10Eu0.05)2O3;rheological properties;photoluminescence;luminescence lifetime- 262
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Preparation of Graphene Quantum Dots by Laser-induced Polydimethylsiloxane Enhanced Publication
Abstract：Using simple, green and low-cost methods to synthesize graphene quantum dots(GQDs) has always been a hot topic pursued and explored by researchers. In this paper, a simple and low-cost laser-induced polydimethylsiloxane(PDMS) method was used to successfully prepare the defective graphene with few layers. Then, using the prepared graphene as carbon source, the GQDs with good dispersion, transverse average size of about 6.67 nm and stable blue fluorescence GQDs solution were successfully prepared by one-step hydrothermal method. The morphology and blue fluorescence characteristics of GQDs were characterized by transmission electron microscopy(TEM), Raman spectroscopy, UV absorption spectroscopy and fluorescence spectroscopy. Taking quinine sulfate as the standard reference, the calculated fluorescence quantum yield of GQDs is about 6.3%. The method of preparing GQDs proposed in this study has the advantages of simplicity, low cost and low pollution. It provides a new way and new reference for the preparation of GQDs, and also provides potential for the large-scale commercial preparation of GQDs.Keywords：laser induced;graphene;graphene quantum dots;hydrothermal method;fluorescence properties- 168
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Published：2021-12-17
Synthesis and Properties of Materials
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Highly Efficient Near Ultraviolet Organic Light-emitting Device Based on WCl6 Doped PEDOT∶PSS as Hole Injection Layer Enhanced Publication
Abstract：Wide bandgap of emissive molecule in ultraviolet organic light-emitting device(UV-OLED) restricts hole injection, which results in inefficient carrier recombination and counteracts performance promotion. Solution-processed techniques with low cost, fine tunability and high throughout production meet the current requirement of manufacture. Herein, solution-processed WCl6 and its doping composite of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT∶PSS)+WCl6 are employed for tailoring hole injection of near UV-OLED, and thus achieving high efficiency. X-ray photoelectron spectroscopy and UV-visible absorption analysis show that WCl6 and PEDOT∶PSS+WCl6 films behave exceptional electronic properties and superior optical transmittance. Current-voltage characteristics and impedance spectroscopy analysis confirm that the hole injection ability is enhanced in the order of WCl6, PEDOT∶PSS and PEDOT∶PSS+WCl6. Using PEDOT∶PSS+WCl6 as hole injection tailoring and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole(PBD) as emissive layer, the near UV-OLED reaches maximum external quantum efficiency of 2.6%, radiance of 8.05 mW/cm2, full width at half maximum of 45 nm and electroluminescent peak of 405 nm. Device aging tests indicate that WCl6 doped PEDOT∶PSS considerably enhances the stability of near UV-OLED. Our results expand the application of WCl6 and efficient stable near UV-OLED.Keywords：Ultraviolet organic light-emitting device;WCl6;solution process;hole injection;impedance spectroscopy- 176
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Effect of Hybrid Nucleation Layer on Internal Quantum Efficiency of InGaN-based Yellow LEDs Enhanced Publication
Abstract：A hybrid nucleation layer consisting of sputtered AlN component and mid-temperature GaN component was developed to improve the internal quantum efficiency of yellow LED. Transmission electron microscopy, X-ray diffraction, and Raman spectra were used to characterize the crystal quality of InGaN-based yellow LEDs. The optical properties of InGaN-based yellow LEDs were investigated by temperature-dependent photoluminescence spectra and electroluminescence spectra. It is found that stacking faults are formed using the hybrid nucleation layer, which can effectively reduce the dislocation density and residual stress in the epitaxial layer. The dislocation density of yellow LED epitaxial layer grown on the sputtered AlN nucleation layer and hybrid nucleation layer is 5.04×108 cm-2 and 3.98×108 cm-2. The in-plane compressive stress of yellow LED grown on the sputtered AlN nucleation layer and hybrid nucleation layer is 482.71 MPa and 266.38 MPa. By replacing the conventional sputtered AlN nucleation layer with hybrid nucleation layer, the internal quantum efficiency of yellow LEDs is increased from 12.5% to 29.8% at room temperature of 295 K.Keywords：yellow light-emitting diodes;nucleation layers;internal quantum efficiency;stacking faults;piezoelectric polarization- 185
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Grating Structure and Coupling Characteristics of Laterally-coupled Distributed Feedback Semiconductor Lasers Enhanced Publication
Abstract：Coupling coefficient is an important parameter for evaluating the grating performance of distributed feedback(DFB) semiconductor lasers. In this paper, based on the coupled-wave theory and combined with numerical simulation, the effect of the structural parameters of the laterally-coupled surface grating on their coupling characteristics is investigated. In contrast to the laterally-coupled ridge-waveguide structure of rectangular gratings, six special lateral microstructure gratings, namely, symmetric trapezoid, misaligned trapezoid, symmetric junction, misaligned junction, bisymmetric trapezoid and bisymmetric junction, have been studied to effectively achieve the coupling coefficient regulation of gratings by changing the longitudinal inclination angle of the grating sidewalls and adjusting the optical confinement factor of the grating. The effects of structural parameters such as duty cycle, ridge width and lateral width of the grating on the coupling coefficient of the special lateral microstructure grating of ridge-waveguide were simulated and analyzed, and it was found that reasonable structural parameters can effectively mitigate the fluctuation of the coupling coefficient and help reduce the effect of process errors on the coupling coefficient. The work in this paper provides a theoretical basis for the design and preparation of subsequent grating structures.Keywords：bragg grating;coupling coefficient;laterally-coupled;distributed feedback- 194
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Temperature Sensor Based on Chirped Fiber Bragg Grating Laser Enhanced Publication
Abstract：An annular cavity erbium-doped fiber laser is put forward and designed, and used in the temperature measurement. Using chirped fiber Bragg grating for optical filtering and unpumped erbium-doped fiber as saturable absorber to stabilize the frequency, the single-wavelength laser output of annular cavity erbium-doped fiber laser is realized. Through the temperature experiment, the single-wavelength laser output is realized for temperature sensing measurement. When the output power of the pump source is 219 mW, the single-wavelength laser output of 1 555.25 nm is realized, 3 dB linewidth is 0.06 nm, and the signal-to-noise ratio(SNR) is 47.05 dB. In the experiment, the stability of the single-wavelength laser of 1 555.25 nm is tested, and the output power change is 0.59 dB during 10 min. The temperature sensitivity is 12.59 pm/℃ and the linearity is 0.998 6. The temperature sensitivity of the cooling process is 12.58 pm/℃, and the linearity is 0.998 3. The laser stability was tested at different temperatures. During 10 min, the output powers of the laser at 50 ℃ and 300 ℃ are 0.27 dB and 0.09 dB, respectively.Keywords：fiber laser;Chirped fiber Bragg Grating;Saturable absorbers;temperature sensing- 283
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Influence of Zn Doped SnO2 Nanocrystals as Photoanode Materials on Photoelectric Performance of Dye-sensitized Solar Cells Enhanced Publication
Abstract：Zn-doped SnO2 nanocrystals under hydrothermal conditions were synthesized and subsequently the photoanodes were prepared via the screen printing technology for dye-sensitized solar cells. The effect of Zn-doped SnO2 on the performance of dye-sensitized solar cells was investigated. It is found that Zn doping into SnO2 can induce a negative shift in the flat-band potential and enhance the isoelectric point. As a result, the power conversion efficiency(PCE) of 4.2% was achieved for 2% Zn-doped SnO2 based dye-sensitized solar cell compared with undoped SnO2 based dye-sensitized solar cell. The enhancement in performance was ascribed to improve photogenerated electron lifetime(τe) and dye-uptake capabilities. Moreover, after the TiCl4 treatment of the photoanode, the 2% Zn-doped SnO2 based dye-sensitized solar cell exhibited an impressive power conversion efficiency of 7.7%.Keywords：dye-sensitized solar cell;SnO2;Zn doped;photoanode- 141
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Published：2021-12-17
Device Fabrication and Physics
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Fluorescence Interaction Between Folate Molecules and CdTe and CdTe/CdS Quantum Dots Enhanced Publication
Abstract：Water soluble cysteine modified CdTe and CdTe/CdS core-shell quantum dots were prepared, which can realize the specific fluorescent labeling of folate molecules, and function as a fluorescent probe for detecting the concentration of folate. The experimental results showed that folate can cause obvious fluorescence quenching of CdTe quantum dots, but this quenching behavior was not observed in CdTe/CdS core-shell system. The fluorescence quenching mechanism was analyzed by Stern-Volmer equation, and the research showed that it was a static fluorescence quenching mechanism. The fluorescence emission spectrum had a blue shift of about 35 nm in the interaction between CdTe quantum dots and folate molecules. Thermodynamic calculation showed that a complex structure may be formed through electrostatic interaction between the quantum dots and folate molecules.Keywords：fluorescence;quantum dots;folate;quenching;CdTe;CdTe/CdS core-shell structure- 212
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Detection of Hydrogen Peroxide and Cholest-erol Based on Zinc Doped Quantum Dots and Fenton-like Reaction Fluorescent Probe Preparation Enhanced Publication
Abstract：Zinc doped carbon quantum dots (Zn-CQDs) with fluorescence quantum yield up to 34% were synthesized by one step hydrothermal method, and the structural properties of Zn-CQDs were analyzed. Based on the fact that hydrogen peroxide produced by Cu2+ and H2O2 can effectively quench Zn-CQDs, a Zn-CQDs-Cu2+ fluorescent probe was constructed to detect hydrogen peroxide and indirectly detect cholesterol concentration. The effects of buffer type, pH, reaction time and temperature on the determination of H2O2 and cholesterol were investigated. The results showed that (F0-F)/F0 of the system has good linear relationship with the concentration of H2O2 when incubated at 50 ℃ for 40 min in HEPES buffer solution with pH=7.06. The linear range was 1.0×10-5 ~1.0×10-6 mol/L. The detection limit was 7.2×10-7 mol/L. The (F0-F)/F0 of the system also has good linear relationship with concentration of cholesterol. The linear range was 3.0×10-5-9.0×10-7 mol/L, and the detection limit was 6.8×10-7 mol/L. The method was used for the determination of H2O2 in water samples and cholesterol content in milk,the detection recovery rate can reach 98.55%-105.4% and 98.00%-103.0% respectively, and the result was satisfactory. It can also provide effective detection ideas for the detection of other metabolites in the H2O2 reaction.Keywords：Zinc doped carbon quantum dots;hydrogen peroxide;cholesterol;fluorescence quenching- 178
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Published：2021-12-17
Luminescence Applications and Interdisciplinary Fields
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Photothermal Performance of Phosphor-in-glass Packaged Chip-scale White LED Enhanced Publication
Abstract：Chip-scale packaging(CSP) is an important way to realize a white LED with high optical density and reduce its package size. However, chip-scale white LED has the problems of the aging of phosphor layer and the thermal quenching of phosphor, which seriously affect the performance and reliability of white LED. Herein, combined with the technical advantages of PiG, we proposed a phosphor-in-glass(PiG) packaged chip-scale white LED, and analyzed the photothermal performance of white LED. The PiG layer was prepared on the surface of glass substrate with the process of screen printing and low-temperature sintering, and then the PiG was cut into the chip-scale PiG for white LED packaging. The microscopic morphology of PiG was analyzed. The phosphor particles were embedded in the glass matrix, and the film layer displays a dense structure with no obvious residual pores. The optical properties of white LED were optimized by adjusting the thickness of PiG layer. When the thickness of PiG layer is 120 μm, the related luminous efficiency(LE), correlated color temperature(CCT), and chromaticity coordinate are 111.8 lm/W, 6 876 K, and (0.307 4, 0.321 4), respectively. The effect of PiG packaging structure on the photothermal performance of white LED was analyzed. The PiG layer close to LED chip packaging has higher LE and lower CCT, while the surface temperature of white LED is lower.Keywords：white LED;Chip-scale packaging;phosphor-in-glass;Photothermal performance- 540
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Published：2021-12-17
Luminescence Industry and Technology Frontier
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