Inverse thermal quenching effect in lanthanide-doped upconversion nanocrystals for anti-counterfeiting

2018 ◽  
Vol 6 (20) ◽  
pp. 5427-5433 ◽  
Author(s):  
Lei Lei ◽  
Daqin Chen ◽  
Can Li ◽  
Feng Huang ◽  
Junjie Zhang ◽  
...  
Keyword(s):  
Energy Level ◽  
Thermal Quenching ◽  
Defect State ◽  
Quenching Effect ◽  
High Security ◽  
Upconversion Nanocrystals

An inverse thermal quenching effect is actualized in uniform lanthanide-doped Na3ZrF7 by artificially introducing defect state with an appropriate energy level. These kinds of systems are very suitable for anti-counterfeiting with high security.

Enhancing negative thermal quenching effect via low-valence doping in two-dimensional confined core–shell upconversion nanocrystals

2018 ◽  
Vol 6 (43) ◽  
pp. 11587-11592 ◽  
Author(s):  
Lei Lei ◽  
Jienan Xia ◽  
Yao Cheng ◽  
Yuansheng Wang ◽  
Gongxun Bai ◽  
...  
Keyword(s):  
Emission Intensity ◽  
Thermal Quenching ◽  
Core Shell ◽  
Two Dimensional ◽  
Quenching Effect ◽  
Upconversion Nanocrystals

Doping low-valence ions in core–shell NC is applied to improve negative thermal quenching effect. With the increase in temperature from 293 to 413 K, the UC emission intensity of 20Yb/2Er : NaGdF4 (12 nm) increases by 2.2 times, whereas that of NaGdF4@20Ca/20Yb/2Er: NaGdF4 (11 nm) increases by 10.9 times.

Thermoluminescence study on TlGaSSe layered single crystals

2014 ◽  
Vol 28 (16) ◽  
pp. 1450133 ◽  
Author(s):  
Serdar Delice ◽  
Nizami M. Gasanly
Keyword(s):  
Single Crystals ◽  
Heating Rate ◽  
Thermal Quenching ◽  
Activation Energies ◽  
Temperature Peak ◽  
Heating Rates ◽  
Quenching Effect ◽  
Defect Centers ◽  
General Order ◽  
Maximum Temperatures

The defect centers in TlGaSSe single crystals have been investigated by performing thermoluminescence (TL) measurements with various heating rates between 0.5 K/s and 1.0 K/s in the temperature range of 10–180 K. The TL spectra, with peak maximum temperatures at 39 K and 131 K, revealed the existences of two defect levels. Curve fitting, initial rise and peak shape methods were used to determine the activation energies of two defect centers. The experimental results also showed that the trapping process was dominated by second-order kinetics for the trap related with low temperature peak while the general order (mixed order) kinetics was dominant for the trap donated to high temperature peak. Furthermore, heating rate dependences and traps distributions were studied for two defect centers separately. Thermal quenching effect dominates the behavior of these defects as the heating rate is increased. Also, quasi-continuous distributions were established with the increase of the activation energies from 16 meV to 27 meV and from 97 meV to 146 meV for the traps associated with the peaks observed at low and high temperatures, respectively.

scholarly journals Photoluminescent Properties of Hydrogenated Amorphous Silicon Oxide Powders

2002 ◽  
Vol 17 (5) ◽  
pp. 977-980 ◽  
Author(s):  
Wei-Fang Su ◽  
Hong-Ru Guo
Keyword(s):  
Amorphous Silicon ◽  
Silicon Oxide ◽  
Hydrogenated Amorphous Silicon ◽  
Thermal Quenching ◽  
Amorphous Semiconductors ◽  
Electronic Density ◽  
Quenching Effect ◽  
Oxide Powders ◽  
Amorphous Silicon Oxide ◽  
Hydrogenated Amorphous

The photoluminescence properties of hydrogenated amorphous silicon oxide powder SiO0.92H0.53 were investigated. The powder was prepared by reacting lithium with trichlorosilane in tetrahydrofuran. The luminescence peak energy was located between 1.0 and 1.61 eV. The samples were treated under different conditions such as annealing, hydrolysis, and hydrolysis plus HF etching. The changes of the photoluminescent intensity and location on the treated powders can be explained by the electronic density of state model of amorphous semiconductors. The temperature dependence of luminescence properties of the powders can be described by the relationship of thermal quenching effect: ln[Io/I(T) – 1] = ED/Eo = T/To at temperatures between 100 and 300 K.

scholarly journals (Ce, Gd):YAG-Al2O3 composite ceramics for high-brightness yellow light-emitting diode applications

2021 ◽  
Author(s):  
Xiaoyun Li ◽  
Jian Chen ◽  
Zhuguang Liu ◽  
Zhonghua Deng ◽  
Qiufeng Huang ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Thermal Quenching ◽  
Second Phase ◽  
Composite Ceramics ◽  
Vacuum Sintering ◽  
Phosphor Material ◽  
High Brightness ◽  
Light Emitting ◽  
Quenching Effect ◽  
Noticeable Improvement

Abstract Gd3+ ions were doped in Ce:YAG ceramics as the phosphor material for the high-brightness yellow LED (565-590 nm). Besides the role of spectral modulation, the introduction of Gd3+ ions also exacerbates the thermal quenching effect. To increase its thermal performance, Al2O3 were introduced as the second phase and (Ce0.6%Y69.4%Gd30%)3Al5O12-z% Al2O3 (z=0, 10, 20, 30, 40) composite ceramics were fabricated by vacuum sintering. Their composite microstructures and phase structures were characterized. As the amount of Al2O3 increases from 0 wt% to 40 wt%, there is a noticeable improvement on the thermal conductivity. The thermal stability also increases and the operating temperature of ceramics reduced from 141.1 °C to 132.2 °C. Collaborating composite ceramics with InGaN blue chips, the steady-state luminous efficiency of 40 wt%-Al2O3 yellow LED reaches the highest value of 109.49 lm/W, which is 8.54 % higher than that of Al2O3-free sample. Additionally, scattering behavior and conversion efficiency of composite ceramics with different thicknesses were investigated.

scholarly journals Fractional Contributions of Defect-Originated Photoluminescence from CuInS2/ZnS Coreshells for Hybrid White LEDs

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Quinton Rice ◽  
Sangram Raut ◽  
Rahul Chib ◽  
Zygmunt Gryczynski ◽  
Ignacy Gryczynski ◽  
...  
Keyword(s):  
Thermal Quenching ◽  
Defect State ◽  
White Led ◽  
Time Resolved ◽  
Light Emitting ◽  
White Leds ◽  
Slow Decay ◽  
Interface Defect ◽  
Donor Acceptor ◽  
White Light Emitting Diodes

The wide optical tunability and broad spectral distribution of CuInS2/ZnS (CIS/ZnS) coreshells are key elements for developing the hybrid white light emitting diodes where the nanoparticles are stacked on the blue LEDs. TwoCIS/ZnS555 nmandCIS/ZnS665 nmcoreshells are utilized for the hybrid white LED development. The time-resolved spectroscopy ofCIS/ZnS555 nmandCIS/ZnS665 nmreveals the correlation between the fast, intermediate, and slow decay components and the interface-trapped state and shallow- and deep-trapped states, although the fractional amplitudes of photoluminescence (PL) decay components are widely distributed throughout the entire spectra. The temperature-resolved spectroscopy explains that the PL from deep-trapped donor-acceptor (DA) state has relatively large thermal quenching, due to the relative Coulomb interaction of DA pairs, compared to the thermal quenching of PL from interface defect state and shallow-trapped DA state. A good spectral coupling between the blue diode excitation and the PL from CIS/ZnS leads to the realization of hybrid white LEDs.

scholarly journals Thermal-responsive multicolor emission of single NaGdF4:Yb/Ce/Ho upconversion nanocrystals for anticounterfeiting application

Nanophotonics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2879-2885 ◽  
Author(s):  
Yanqing Hu ◽  
Qiyue Shao ◽  
Xinyi Deng ◽  
Jianqing Jiang
Keyword(s):  
Critical Factor ◽  
Temperature Dependent ◽  
Recognition Method ◽  
Promising Candidate ◽  
Thermally Induced ◽  
Quenching Effect ◽  
Security Authentication ◽  
Upconversion Nanocrystals ◽  
Nonradiative Transitions ◽  
High Level

AbstractThis study presents a novel and high-level anticounterfeiting strategy based on Ce/Yb/Ho triply-doped NaGdF4 nanocrystals with temperature-responsive multicolor emission. A critical factor leading to the multicolor emission is confirmed by comparing the luminescence thermal behaviors of nanocrystals in various atmospheres. Through analyzing the temperature-dependent lifetimes of Yb3+ ions in air, we demonstrate that thermally-induced multicolor emission mainly originates from the gradually-attenuated H2O quenching effect. Because the cross-relaxations between Ce3+ and Ho3+ ions and the nonradiative transitions of Yb3+ ions create plenty of phonon heat, the multicolor emission of nanocrystals can be achieved under 975 nm excitation at a relatively low power density. This recognition method is efficient and convenient for security authentication. The as-synthesized core nanocrystals can be directly used to fabricate anticounterfeiting ink without further processing (e.g. core/shell or hybrid). Therefore, the small-sized β-NaGdF4:Yb/Ce/Ho nanocrystals are promising candidate for security application.

Thermal quenching effect of an infrared deep level in Mg-doped p-type GaN films

2002 ◽  
Vol 80 (10) ◽  
pp. 1767-1769 ◽  
Author(s):  
Keunjoo Kim ◽  
Sang Jo Chung
Keyword(s):  
Deep Level ◽  
Thermal Quenching ◽  
Quenching Effect ◽  
P Type ◽  
Mg Doped

scholarly journals The reduction of the thermal quenching effect in laser-excited phosphor converters using highly thermally conductive hBN particles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Akvilė Zabiliūtė-Karaliūnė ◽  
Justina Aglinskaitė ◽  
Prancis̆kus Vitta
Keyword(s):  
Hexagonal Boron Nitride ◽  
Imaging Techniques ◽  
Thermal Quenching ◽  
Optical Power ◽  
Excitation Power ◽  
Excitation Power Density ◽  
Quenching Effect ◽  
Wide Range ◽  
Thermally Conductive ◽  
Phosphor Thermometry

AbstractPhosphor converters for solid state lighting applications experience a strong thermal stress under high-excitation power densities. The recent interest in laser diode based lighting has made this issue even more severe. This research presents an effective approach to reduce the thermal quenching effect and damage of laser-excited phosphor-silicone converters using thermally conductive hexagonal boron nitride (hBN) particles. Herein, the samples are analyzed by employing phosphor thermometry based on the photoluminescence decay time, and thermo-imaging techniques. The study shows that hBN particle incorporation increases the thermal conductivity of a phosphor-silicone mixture up to 5 times. It turns out, that the addition of hBN to the Eu$$^{2+}$$ 2 + doped chalcogenide-silicone converters can increase the top-limit excitation power density from 60 to 180 W cm$$^{-2}$$ - 2 , thus reaching a 2.5 times higher output. Moreover, it is shown that the presence of hBN in Ce$$^{3+}$$ 3 + activated garnet phosphor converters, may increase the output power by up to 1.8 times and that such converters can withstand 218 W cm$$^{-2}$$ - 2 excitation. Besides, hBN particles are also found to enhance the stability of the converters chromaticity and luminous efficacy of radiation. This means that the addition of hBN particles into silicone-based phosphor converter media is applicable in a wide range of different areas, in particular, the ones requiring a high optical power output density.

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