Negative thermal quenching CsPbBr3 glass-ceramic based on intrinsic radiation and vacancy defect co-induced dual-emission

Halide perovskite glass-ceramic has recently moved into the center of the attention of perovskite research due to their potential for temperature sensing. However, quantum dots glass-ceramic with excellent luminescence performance still needs to be combined with rare-earth (RE) ions to accurately measure temperature. In this work, a novel non-RE doped dual-emission (460 nm and 512 nm) CsPbBr₃ quantum dots was obtained in telluride glass via the friction crystallization method, where 512 nm was derived from intrinsic luminescence of quantum dots, and 460 nm was originated from thermally induced bromine vacancy, which can be used for temperature sensing. Fluorescence intensity ratio results indicate that the relative sensitivity of dual-emission could reach 5.6 % K^?1 at 323 K. The discovery of non-RE doped CsPbBr₃ QDs glass-ceramic with negative thermal quenching uncovers a new optional sensing glass material that surpass traditional RE-doped QDs glass by their tunability and sensitivity.     

Double nanocrystalline engineering for effective enhanced photoluminescence of Tb3+ in glass ceramic

Despite possessing good feature for optical thermometry, the rare (RE) ions-based temperature sensing (TS) has innate shortcoming of thermally coupled levels (TCLs) energy gap overlap, which reduces the sensitivity. In this work, a dual-luminous centers TS based on Tb³⁺ doped Cs₄PbBr₆ quantum dots (QDs) glass ceramic is fabricated. By locating in low phonon energy crystal field environment of Cs₂ZnSi₅O₁₂ nanocrystalline (NS) and Cs₄PbBr₆ QDs, the emission intensity of Tb³⁺ can be enhanced by 14 times. The large exciton binding energy (420 meV) indicates that the prepared QDs glass ceramic has a good thermal stability and the PL intensity of Cs₄PbBr₆ QDs and Tb³⁺ can be well-maintained above 70% and 89% after 8 thermal cycles between 323K and 373K. Furthermore, the obtained maximum absolute sensitivity (S_a) and relative sensitivity (S_r) is as high as 0.2541 K^-1 and 2.68% K^?1, respectively. It is expected that the finding of this work can offer a help in exploring novel QDs/RE ions-based TS and further optimize their practical applications.     

Eu3+‐doped CsPbBr1.5I1.5 quantum dots glasses: A strong competitor among red fluorescence solid materials

CsPbBr_1.5I_1.5 quantum dots (QDs) glasses are synthesized by traditional melting and thermal treated method, CsPbBr_1.5I_1.5 QDs glasses show vast potential as red fluorescence component in warm WLED applications due to their moderate emission wavelength as well as good opacity property. However, the quantum yield of QDs glasses is still low, therefore, Eu³⁺ ions is chosen to introduce into CsPbBr_1.5I_1.5 QDs, the quantum yield is enhanced to 64.7%. After a sequence of testing operations, we find that 6.5%CsPbBr_1.5I_1.5:0.28%Eu³⁺ QDs glasses is a strong competitor among red fluorescence solid materials.     

Structure and luminescence of Eu doped glass ceramics embedding ZnO quantum dots

Eu³⁺ doped glass ceramics embedding ZnO quantum dots (QDs) were successfully prepared by a sol–gel method. High-resolution transmission electron microscopy (HRTEM) observations revealed that ZnO QDs with size of 3–6 nm precipitated homogeneously among the SiO₂ glassy matrix after thermal treatment of the precursor sample. Such glass ceramics show a high transparency in the visible-infrared range due to the much smaller size of the ZnO QDs than the wavelength of the visible light. The emission and excitation spectra of the samples with various ZnO contents were studied. Based on Judd–Ofelt theory, the intensity parameter Ω₂ was evaluated to investigate the change of the environment around Eu³⁺ in samples with and without QDs.     

Engineering the crystallization behavior of CsPbBr3 quantum dots in borosilicate glass through modulating the glass network modifiers for wide-color-gamut displays

The in-situ growth of CsPbBr₃ perovskite quantum dots (QDs) inside glass has been regarded as an alternative approach to improve their stability. Alkaline-earth metal oxides has multiple effects on the structure of the glass network. Herein, four types of alkaline-earth metal oxides are introduced into borosilicate glasses to modulate glass network structure, which has quite different effects on the crystallization behavior of CsPbBr₃ QDs. The reason can be ascribed to the different impacts of alkaline-earth metal on phase separation, nucleation, and growth procedure. Moreover, CsPbBr₃ QDs embedded in glass (CsPbBr₃ QD@glass) exhibit superior thermostability and photostability compared with CsPbBr₃ QDs powder. Finally, a white light-emitting diode achieving 124% of National Television System Committee (NTSC) gamut is fabricated using the CsPbBr₃ QD@glass, K₂SiF₆:Mn⁴⁺ phosphor film, and blue chip-on-board. This work provides a reference for modulating the glass network modifiers to regulate the crystallization behavior of perovskite QDs.     

Self-crystallized Ba2LaF7:Nd3+/Eu3+ glass ceramics for optical thermometry

Eu³⁺/Nd³⁺-codoped Ba₂LaF₇ transparent bulk glass ceramics were successfully fabricated by glass self-crystallization. The structure and morphology of the sample were investigated by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction. The fluorescence intensity ratios of Nd³⁺ emission at 800 nm to the Eu³⁺ emission at 699 nm (⁵D₀ → ⁷F₄) were measured under 578.3 nm laser excitation in a wide temperature range from 290 to 740 K. A relatively good temperature sensing performance was obtained with a maximum relative sensitivity of 1.02% K⁻¹ at 420 K. Both the emission peaks for temperature sensing were located in the optical window of biological tissue, which is favorable for biomedical applications. The results indicate that Ba₂LaF₇:Nd³⁺/Eu³⁺ glass ceramics have a potential application as temperature probes.     

Perovskite quantum dots growth in situ in transparent medium for short wavelength shielding

High energy ultraviolet (UV) and blue light (short wavelength) radiation is proved to be harmful to human eyes, skin, and biological genomes. However, developing effective shielding materials providing protect from short wavelength is still a great challenge. Here, Eu³⁺-doped CsPbBr₃ embedded in a transparent glass medium is proved to shield the short wavelength from 200 to 475 nm with high performance, which is prepared by a facile and efficient melting-quenching technique. The uniform distribution of the CsPbBr₃ quantum dots (QDs) growth in situ from the transparent glass matrix ensures the high transmittance (>90%) at the long wavelength (520-800 nm). In addition, the excellent short wavelength shielding ability of the Eu³⁺-doped CsPbBr₃ glass ceramics (EGC) is demonstrated even suffered with accelerated weathering tests as long as 480 hours. Moreover the cell viability of A549 cells is well preserved thanks to the completely blocked blue light by the as-obtained EGC, which unambiguously demonstrates the promising application of EGC as short wavelength shielding materials.     

Investigation of optical properties: Eu with Al codoping in aluminum silicate glasses and glass‐ceramics

Eu‐doped transparent oxyfluoride aluminosilicate glass was prepared by controlling with Al codoping of melt‐quenched glass fabricated under air atmosphere. In the presence of Al input, the photoluminescence emission spectra under 393 nm excitation shows a blue shift by adjusting the ratio of Eu³⁺ and Eu²⁺. After heat treatment of glass, the ratio of Eu³⁺ and Eu²⁺ of luminescence emission were changed by controlling treatment temperature. The PL intensity of Eu³⁺ and Eu²⁺ ions in the glass‐ceramics (GC) was much stronger than in the precursor glass (PG). The possible mechanism responsible for color tuneability of the ratio of Eu³⁺ and Eu²⁺ doped was discussed.     

Homogeneous Precipitation Synthesis and Low‐Voltage Cathodoluminescence of SnO2:Eu3+ Phosphors for Field Emission Displays

A reddish‐orange‐emitting SnO₂:Eu³⁺ phosphor for field emission displays (FEDs) was successfully synthesized via a homogeneous precipitation route using urea as a precipitant. The influences of the dopant concentration of Eu³⁺ and calcination temperature on optical properties were investigated. The low‐voltage field emission properties of the FED device prepared using the synthesized SnO₂:Eu³⁺ phosphors were reported. Under the UV light, SnO₂:Eu³⁺ phosphors display the strong orange–red emission peaked at 587, 591, and 597 nm due to the ⁵D₀→⁷F₁ magnetic dipole transition of Eu³⁺. The phosphor doped with 1.0 mol% Eu³⁺ possesses the highest photoluminescent (PL) intensity. Under the low‐voltage excitation of 300 V, the fabricated FED device exhibits the bright orange–red emission, high‐voltage brightness saturation, and high color purity, which has a potential application in low‐voltage full color FEDs.     

Effect of B-site substitution on the luminescence,thermal stability and temperature sensitivity of Ba2NaNb5O15:Eu3+/Er3+ glass ceramics

Transparent glass ceramic with Ba₂NaNb₅O₁₅ as the main crystal phase was prepared, and the appropriate heat treatment condition was selected as 710 °C/150 min through various characterizations. The luminous intensity and thermal stability were enhanced significantly when the glass ceramic was used as the luminous matrix. After introducing Ti⁴⁺ ions as charge compensators, the luminescence performance and thermal stability were further improved, and the reasons for this were analyzed. At 458 K, the luminous intensity of 0.5%Eu³⁺ doped glass ceramic containing 0.5%Ti⁴⁺ can maintain about 65% of room temperature with a chromaticity shift of 5.16 × 10⁻². The relative and absolute sensitivities of 0.7%Er³⁺ doped glass ceramic were 4.04 × 10⁻³ K⁻¹ and 1.31% K⁻¹. Introducing Ti⁴⁺ ions would weaken the population redistribution ability of ²H_11/2 and ⁴S_3/2 levels and reduce the temperature sensitivity. However, the sample containing Ti⁴⁺ shows good thermal stability, its green emission at 458 K has a small chromaticity shift of 6.45 × 10⁻³. The research shows that the glass ceramic can be used as a good luminescent host material, and Eu³⁺/Er³⁺ doped glass ceramic can be used in the fields of LEDs or temperature sensing.     

Preparation and photoluminescence properties of perovskite Cs4PbBr6/CsPbBr3 quantum dots integrated into lithium-borosilicate glass

Quantum dots (QDs), like all inorganic perovskite cesium lead bromide Cs₄PbBr₆ and CsPbBr_3, have shown potential as multifunctional optoelectronic materials. However, their lack of stability precludes any further practical uses from being developed. Glass as a carrier can effectively resolve these problems while retaining excellent luminescent properties. Herein, a novel perovskite Cs₄PbBr₆/CsPbBr₃ QDs embedded in lithium borosilicate glass was prepared. The phase transition mechanism of Cs₄PbBr₆/CsPbBr₃-based QDs in lithium-borosilicate glass with varying concentrations of Li₂O was investigated. Increases in the size and quantity of QDs with increasing contents of Li₂O were analyzed using transmission electron microscopy (TEM). A narrow photoluminescence (PL) emission band was observed, with a substantial emission intensity shift and a red-shifted luminescence peak. After 30 days of immersion in water, the QDs maintained approximately 84% of their luminescence intensity. According to the results, the perovskite Cs₄PbBr₆/CsPbBr₃ QDs embedded into lithium borosilicate glass have promising future applications in display technology.     

Molecular‐Like Ag Clusters and Eu3+ Co‐Sensitized Efficient Broadband Spectral Modification with Enhanced Yb3+ Emission

AgNO₃/EuF₃/YbF₃ tri‐doped oxyfluoride glass was prepared by a melt‐quenching method, in which a high‐efficient broadband spectral modification can be realized due to the simultaneous energy‐transfer processes of Eu³⁺→Yb³⁺, molecular‐like Ag (ML‐Ag) clusters→Yb³⁺, and ML‐Ag clusters→Eu³⁺→Yb³⁺. The spectral measurements indicated that besides the F‐center brought by the fluorides, the formation of the ML‐Ag clusters and the evolution of silver species within the glass matrix were also closely related to the introduction of Eu³⁺ and Yb³⁺ ions and which in return greatly affected the luminescence properties of these rare‐earth ions. As the UV‐visible irradiation in the wavelength region of 250–600 nm can be efficiently converted into near‐infrared emission around 1000 nm in the AgNO₃/EuF₃/YbF₃ tri‐doped glass, which thus has promising application in enhancing the photovoltaic conversion efficiency of the silicon solar cell.     

Photoluminescence and temperature sensing of lanthanide Eu3+ and transition metal Mn4+ dual-doped antimoniate phosphor through site-beneficial occupation

For a long time, rare-earth ion-doped phosphors have been widely used in temperature sensing because of their excellent light-emitting properties. However, most of the rare earth elements are relatively rare and expensive, so the transition group elements that are economical and easy to obtain have been favored by researchers. This paper presents a new type of phosphor doped with rare earth ion and transition metal for optical temperature measurement. In recent years, Mn⁴⁺-doped phosphors have attracted wide attention because of their strong deep red light-emitting properties. La₂LiSbO₆ provides a good host environment for Mn⁴⁺ and Eu³⁺ due to its unique crystal structure. In this paper, a series of La₂LiSbO₆ phosphors singly doped with Mn⁴⁺ and Eu³⁺, and co-doped with Eu³⁺/Mn⁴⁺ were synthesized. The crystal phases and optical properties of these materials were characterized and analyzed in detail. We specifically studied the temperature dependence of the fluorescence intensity of the optimized La₂LiSbO₆: Eu³⁺, Mn⁴⁺ phosphors at 303K–523K. The experimental results prove that the thermal responses of Mn⁴⁺ and Eu³⁺ are different. With increasing temperature, the thermal quenching of the Mn⁴⁺ fluorescence intensity is much faster than that of Eu³⁺, so the temperature characteristics can be explored by the fluorescence intensity ratio (FIR) of Eu³⁺ to Mn⁴⁺. At 523 K, its maximum relative sensitivity and maximum absolute sensitivity can reach 0.891% K⁻¹ and 0.000264 K^-1, respectively. Our experimental analysis shows that La₂LiSbO₆:Eu³⁺/Mn⁴⁺ phosphors have relatively high temperature sensitivity and have potential application prospects in the field of high temperature sensing.     

Luminescence and self-referenced optical temperature sensing performance in Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors

Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca₂YZr₂Al₃O₁₂:Bi³⁺ samples, energy transfer from Bi³⁺ to Eu³⁺, and the temperature sensing properties of Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples have been systematically researched. Under the excitation of ultraviolet light, Bi³⁺ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi³⁺ instead of Ca²⁺ and Y³⁺ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu³⁺ content in Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K^-1 and 0.664 %K^-1, respectively. All above results suggest that Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphor is a potential alternative for optical thermometer.     

Fabrication and Luminescence Properties of Transparent Glass‐Ceramics Containing Eu3+‐Doped TbPO4 Nanocrystals

Eu³⁺‐doped transparent phosphate precursor glasses and glass‐ceramics containing TbPO₄ nanocrystals were successfully fabricated by a conventional high‐temperature melt‐quenching technique for the first time. The formation of TbPO₄ nanocrystals was identified through X‐ray diffraction, transmission electron microscopy, high‐resolution transmission electron microscopy, selected‐area electron diffraction, and photoluminescence emission spectra. The obvious Stark splitting of ⁵D₀‐⁷F_J (J = 1, 2, 4) transitions of Eu³⁺and the increase of internal quantum efficiency indicate the incorporation of Eu³⁺ into TbPO₄ nanocrystals. Energy transfer from Tb³⁺ ions to Eu³⁺ ions was investigated using excitation and emission spectra at room temperature. The glass‐ceramics obtained have more efficient Tb³⁺ to Eu³⁺ energy transfer than the glass, and so serve as good hosts for luminescent materials.     

Enhanced luminescence properties and device applications of Tb3+-doped Cs4PbBr6 perovskite quantum dot glass

Cs₄PbBr₆ perovskite quantum dots (QDs) have unique optoelectronic properties and are expected to become a new generation of luminescent materials. However, poor stability, low photoluminescence quantum yield (PLQY), and poor understanding as to the origin of photoluminescence behavior limit its further application. In this study, a series of Tb³⁺-doped Cs₄PbBr₆ perovskite QD glasses with excellent stability were obtained through the optimization of Tb³⁺ doping concentration and in-situ crystallization temperature. Density functional theory calculations and experimental characterization showed that an appropriate amount of lattice-incorporated Tb³⁺ ions can reduce structural defects in QDs, improve the PLQY, and reduce the QD heavy-metal requirements. Notably, the maximum PLQY value reached 47%, which is near to the Cs₄PbBr₆ perovskite crystal. Furthermore, a high-performance white light-emitting diode (WLED) device was prepared. The device featured a color rendering index of 80 and luminous efficiency of 41 lm W^?1. Finally, a QD glass with double emission peaks was prepared by controlling the in-situ crystallization temperature (550 °C). The temperature sensitivity of the QD glass was then studied using the fluorescence intensity ratio method. The maximum relative temperature sensitivity (Sr) reached 2.03% K^?1, which is higher than the previously reported value. Thus, the method proposed in this study can greatly improve the photoluminescence properties of Cs₄PbBr₆ QD glass and expand its applications in WLED and visual temperature sensing.     

Energy transfer,tunable emission and optical thermometry in Tb3+/Eu3+ co-doped transparent NaCaPO4 glass ceramics

Tb³⁺/Eu³⁺ co-doped glass ceramics containing NaCaPO₄ nanocrystals were successfully synthesized via traditional melt-quenching route with further heat-treatment and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence spectroscopy. The energy transfer process of Tb³⁺→Eu³⁺ was confirmed by excitation and emission spectra and luminescence decay curves, and the energy transfer efficiency was also estimated. The results indicated that the efficient emission of Eu³⁺ was sensitized by Tb³⁺ under the excitation of 378 nm, realizing tunable emission in the transparent bulk glass ceramics containing NaCaPO₄ nanocrystals. Furthermore, optical thermometry was achieved by the fluorescence intensity ratio between Tb³⁺:⁵D₄→⁷F₅ (~542 nm) and Eu³⁺:⁵D₀→⁷F₂ (~612 nm). The maximum absolute sensitivity of 4.55% K⁻¹ at 293 K and the maximal relative sensitivity of 0.66% K⁻¹ at T=573 K for Tb³⁺/Eu³⁺ co-doped transparent NaCaPO₄ glass ceramic are obtained. It is expected that the investigated transparent NaCaPO₄ glass ceramics doped with Tb³⁺/Eu³⁺ have prospective applications in display technology and optical thermometry.     

Dual-mode optical thermometry based on Bi3+/Eu3+ co-activated BaGd2O4 phosphor with high sensitivity and signal discriminability

A series of BaGd₂O₄:Bi³⁺,Eu³⁺ phosphors with dual-emitting centers were prepared by high-temperature solid-state method. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), fluorescence spectroscopy, lifetime decay curve and variable temperature emission spectroscopy were used to systematically study the structure, luminescence performance and temperature characteristics. Under ultraviolet (UV) excitation, the BaGd₂O₄:Bi³⁺,Eu³⁺ phosphor showed a broad-band emission in the blue region corresponding to transitions of Bi³⁺ ions and the sharp red light emission corresponding to Eu³⁺ ions. The Bi³⁺ and Eu³⁺ ion emission peaks were well-separated, which meets a prerequisite for efficient temperature signal resolution measurement. The fluorescence intensity ratio (FIR) technique was used to measure the different temperature response characteristics between Bi³⁺ blue emission and Eu³⁺ red emission. When the temperature varies from 293 K to 473 K, the relative temperature sensitivity (S_r) of BaGd₂O₄:Bi³⁺,Eu³⁺ phosphors is obtained, was determined as 1.0182%K⁻¹. In addition to calculating the relative sensitivity by FIR technology, we can also obtain the value of S_r through experiments and formulas related to the decay life, and found to be 1.0651%K⁻¹. Therefore, BaGd₂O₄: Bi³⁺,Eu³⁺ phosphor is an excellent non-contact optical temperature measurement material.     

Tunable colors and applications of Dy3+/Eu3+ co-doped CaO-B2O3-SiO2 glasses

A series of Dy³⁺/Eu³⁺ single- and co-doped calcium borosilicate luminescent glasses were prepared by the conventional high temperature melt-quenching method. A compact glass structure is obtained by the addition of Dy³⁺/Eu³⁺ ions, which is verified by the physical properties of synthetic glasses. As network modifiers, Dy³⁺/Eu³⁺ fill in the interspaces of glass network and contribute to the conversion of [BO₃] to [BO₄]. Dy³⁺/Eu³⁺ co-doped calcium borosilicate glasses can emit white light, which consists of blue, yellow, and red light under 387 nm excitation. The emission spectra and decay curves of the white-emitting glasses have proved the existence of energy transfer. The average lifetime of Dy³⁺ decreases from 0.251 to 0.165 ms with the increasing Eu³⁺ concentration. Changing rare earth ions concentration, CIE color coordinates of Dy³⁺/Eu³⁺ co-doped glass shifts from cyan to white with increasing excitation wavelength. A white-light emission is obtained when the concentration of Dy³⁺ and Eu³⁺ equals to 4% and 2%, respectively. Moreover, the Dy³⁺/Eu³⁺ co-doped calcium borosilicate glass shows high-thermal stability and it may be applicable for high-quality white LEDs based on high power near ultraviolet (n-UV) LED chip in the future.     

Linear and nonlinear optical characteristics of CsPbBr3 perovskite quantum dots-doped borosilicate glasses

CsPbBr₃ perovskite QDs are precipitated in a borosilicate glass matrix, while protects efficiently the QD from photo-induced and chemical degradation. We show that the CsPbBr₃ QD doped glasses exhibit strong visible photoluminescence (PL), which is dependence on the concentration that can be controlled by heat treatment conditions. Due to the stabilization by the glass matrix, we are able to determine the nonlinear optical (NLO) properties with a Z-scan technique. We observe a cross-over from saturated absorption (SA) to reverse saturated absorption (RSA) by either increase the pumping intensity or the QD size, reminiscent of quantum size effect in the NLO response. The RSA is associated with two-photon absorption (TPA) that induces strong upconversion luminescence of QD doped glass samples. Our results imply that the glasses containing CsPbBr₃ QDs may find potential applications from solid state lighting to ultrafast optical switches.