Doping manganese into CsPb(Cl/Br)3 quantum dots glasses: Dual-color emission and super thermal stability

CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (QDs) represent bright and tunable photoluminescence, it is regrettable that the air instability and poor water resistant properties prevent their application in optoelectronic devices. At the same time, the toxicity of lead is also a major factor restricting its development. As a consequence, we demonstrate the partial replacement of Pb with Mn through conventional melt-quenching and heat-treatment method preparation of Mn-doped CsPb(Cl/Br)₃ QD glass. Mn-doped CsPb(Cl/Br)₃ QD glass exhibits high luminescent intensity like QDs. It is important that Mn-doped CsPb(Cl/Br)₃ QD glass with Dual-Color maintained the same lattice structure like Mn-doped CsPb(Cl/Br)₃ QDs, and highly homogeneous spectral characteristics of Mn luminescence. The intensity and position of this Mn-related emission are also tunable by altering the experimental parameters, such as the Pb-to-Mn feed ratio, annealing temperature. More importantly, the as-prepared orange Mn-doped CsPb(Cl/Br)₃ QD glass was employed to fabricate white LEDs combined with a commercial Ce³⁺:Y₃Al₅O₁₂ phosphor-in-glass (Ce-PiG) on top of a InGaN blue chip. And the constructed WLEDs generate a warm white with an optimal luminous efficacy (LE) of 67.00 lm/W, a high CRI of 81.4, and a low CCT of 4902 K.     

Controlled growth and spectroscopy characterization of blue violet perovskite quantum dots in borate glasses

Blue violet light emitting CsPb(Cl/Br)₃ perovskite quantum dots glasses (QDGs) have been successfully fabricated in multi-component borate glass matrix by melt quenching and heat treatment. The spectral characteristics have been evaluated by photoluminescence (PL), PL excitation (PLE), PL decay and absorption spectra. The recipe and preparation conditions have been optimized for controlled growth of QDs. By using raw materials of NH₄Br/NH₄Cl/PbO and crucible cover, optimizing composition of Na₂O/K₂O in matrix, melting temperature and time, heat treatment temperature and time, and NH₄Cl and NH₄Br contents, we have finally realized blue violet exciton emission in target range of 405–440 nm. The PL wavelength adjustment is comprehensive effect of the abovementioned influence factors. The emission in short wavelength of 405–440 nm is due to controlled growth of the QDs. In final CsPb(Cl/Br)₃ QDs, the contents of Cl and Br are suitable and the Cl/Br ratios are large. A little Br is necessary for growth of CsPb(Cl/Br)₃ QDs and then the Br is partially replaced by Cl at suitable treatment condition. Unsymmetrical PL spectrum profile of some samples is explained as reabsorption effect by monitoring PL spectral profile and PL decay. The temperature characteristics of PL spectra show good recoverability after a temperature cycle.     

Effect of phase transition on SiO2-coated CsPbBr3/Cs4PbBr6 quantum dots: Air-stability and quantum efficiency improvement

To develop white light-emitting diodes (WLEDs) with wide color gamut for displays, compared with nitride-based phosphors and traditional core-shell quantum dots (QDs) such as CdSe, InP, CuInS₂, all-inorganic perovskite QDs CsPbX₃ (X = Cl, Br, I) were more promising luminescent materials due to tunable wavelength, narrow emission spectrum and high quantum efficiency. However, when QDs were made into solid form (powders or films), poor air-stability and drastic decrease of quantum efficiency would be observed in CsPbBr₃. These drawbacks would restrict their practical applications. To resolve these issues, in this paper, we proposed a new concept that zero-dimensional perovskite QDs powders Cs₄PbBr₆ with outstanding quantum efficiency and long lifetime up to three months could be successfully prepared via silica-coated method and crystal phase transition in low-temperature synthesis. This phenomenon of phase transition would be discussed in detail and the quantum efficiency could be improved from 31.41% to 45.87%. Moreover, green LEDs with high color purity of 92% and luminous efficiency of 88.59 lm/W could also be achieved by using this material. Therefore, our proposed perovskite QDs powders Cs₄PbBr₆ had extreme potential for displays applications.     

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.     

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.     

Polychromatic tunable luminescence of Eu3+ doped CsPbBr3 quantum dot glass ceramic induced by mechanical crystallization

Nowadays, inorganic perovskite quantum dots (QDs) glass has become a hot topic in the field of new optical materials. In this work, the Eu³⁺ doped CsPbBr₃ QDs phosphate glass has been successfully prepared. Different from the traditional heat treatment method, the CsPbBr₃ QDs were prepared by mechanical crystallization. When the QDs glass was ground at different times, due to the synergistic effect of red emission (Eu³⁺) and green emission (CsPbBr₃ QDs), the prepared QDs glass can produce the red-yellow-green polychromatic luminescence phenomenon. Benefit from the dual-emission centers of CsPbBr₃ QDs and Eu³⁺ which do not interfere with each other, the relative sensitivity of the temperature sensing is up to 2.11% K^-1, proving that the prepared Eu³⁺ doped QDs glass has practical application in the field of temperature sensing. The glass material obtained in this way not only has tunability and favorable sensitivity but also provides an effective way for the preparation of QDs.     

Lead oxide enables lead volatilization pollution inhibition and phase purity modulation in perovskite quantum dots embedded borosilicate glass

Embedding all-inorganic cesium lead halide CsPbX₃ (X=Cl, Br, I) perovskite quantum dots (PQDs) PQDs into glass is one of the most effective strategies to improve their optical, thermal and chemical stabilities. Herein, by using PbO instead of PbBr₂ as the lead source, it is effective to lower the melting temperature and reduce the volatilization pollution from lead halide raw materials. Thus, a high-purity CsPbBr₃ PQDs embedded glass with 71.5 % PLQY was successfully prepared. The thermal stability, and photo-aging properties were also improved. By simply changing the halogen element, the red and blue CsPbX₃ PQDs embedded glasses were successfully prepared. The white LED fabricated by coating obtained green/red CsPbX₃ PQDs embedded glass on a blue chip displays high color gamut of 121.9 % NTSC standard and >91.1 % Rec. 2020 standard, which embodies the great potential of PQDs embedded glass in lighting and display fields.     

Synthesis and optical properties of novel mixed-metal cation CsPb1−xTixBr3-based perovskite glasses for W-LED

In this report, a mixed-metal cation-based halide perovskite (HP) CsPb_1−xTi_xBr₃ quantum dots (QDs) were first embedded in the B–Si–Zn glasses using a traditional approach of melt quenching and heat treating. A battery of test results such as photoluminescence, X-ray diffraction, and time-resolved attenuation prove that Ti ions do not destroy the properties of CsPbBr₃, and they are successfully doped into CsPbBr₃. At the same time, the doping of Ti ions also reduces the toxicity of lead. By altering the ratio of Pb/Ti, we determined the optimum ratio of CsPb_0.7Ti_0.3Br₃ QDs through experimental data. Due to the excellent optical properties and stability of CsPb_0.7Ti_0.3Br₃ QDs glass, it was designed to construct the white-light emitting diode device with tunable color coordinate, color rendering index, correlated color temperature, and a high luminous efficiency compared with CsPbBr₃ QDs glass, which may be a promising candidate for the field of lighting and displays.     

Environmentally friendly CsPbBr3 QDs multicomponent glass with super-stability for optoelectronic devices and up-converted lasing

Ultra-stable CsPbBr₃ perovskite quantum dots (QDs) multicomponent glass with high transmittance was prepared by melt-quenching heat treatment. The average diameter of the CsPbBr₃ QDs was ∼1.96 nm. The resulting glass displayed a high exciton binding energy of 362 ± 18 meV. Notably, these glass-encapsulated materials exhibited excellent resistance to heat, light, and water, superior to that of previously reported perovskite-based materials, and underwent an extremely low rate of Pb leaching during water immersion. Based on the glass, a high-performance white light-emitting diode (WLED) device was fabricated with Commission Internationale de L’Eclairage (CIE) coordinates of (0.3156, 0.3326) and color gamut of ∼113 % National Television Standards Committee (NTSC). The CsPbBr₃ QDs glass without rare earth elements further acted as an optical gain medium, realizing up-conversion lasing with 980-nm laser excitation for the first time. The reversible linear fluorescence response indicates that the glass could be a potential candidate for temperature sensors.     

Effect of ZnO on the crystallization and photoluminescence of CsPbI3 perovskite quantum dots in borosilicate glasses

CsPbI₃ perovskite quantum dots (QDs) doped borosilicate glass was prepared by the process of melt-quenching and subsequent annealing. With the introduction of ZnO to the parent glass as the glass network intermediate, the optical properties of the resultant samples are dramatically enhanced. Both the photoluminescence (PL) intensity and photoluminescence quantum yield (PLQY) shows a strong dependence on ZnO concentration as ZnO is found to facilitate the precipitated of the QDs by reducing the connectivity of three-dimensional glass network built from SiO₄ tetrahedrons. The tunable visible-band PL emission of the CsPbI₃ QD-doped glass could find potential applications in white LEDs and lasers.     

Low toxicity antisolvent synthesis of composition-tunable luminescent all-inorganic perovskite nanocrystals

All-inorganic perovskite nanocrystals have held great promise as incredibly effective luminescent materials and also have been synthesized efficiently by room temperature approaches. Toluene, a high toxicity solvent, is often used as a valid antisolvent in ligand-assisted reprecipitation strategy, which badly restricts the commercial application of this convenient method. Here, aiming to address the toluene toxicity issue, the low toxic tetraethyl orthosilicate (TEOS) is employed as a new alternative antisolvent to achieve high uniform and composition dependent luminescent all-inorganic perovskite Cs₄PbX₆ (X?=?I, Br, Cl) combined with CsPbX₃ (X?=?I, Br, Cl) nanocrystals with tunable emission large-span wavelengths (626–437?nm) and remarkably narrow full width at half-maximum (FWHM) monochromaticity (down to 19?nm). Meanwhile, the ratio of CsBr to PbBr₂ is proved to be a critical factor to control the crystalline phase of the resulting perovskite nanocrystals. Additionally, one monochromatic light-emitting diode (LED) lamp with brightly pure green emission is fabricated based on bromine-based perovskite nanocrystals. This newly developed low toxicity antisolvent synthesis (LTaS) is suitable candidate for commercial production in an environmentally-friendly way, and the as-obtained perovskite materials with superior optical merits will be brought to the forefront of lighting and displays.     

Nanocrystallization and optical properties of CsPbBr3−xIx perovskites in chalcogenide glasses

The confinement of CsPbX₃ (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr_3?xI_x NCs with arbitrary I/Br ratio among an elaborately designed GeS₂–Sb₂S₃-based chalcogenide glass matrix. Spherical CsPbBr_3?xI_x NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr_3?xI_x NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX₃ NCs into glassy matrices, facilitating their future applications in photoelectronic fields.     

Silver nanoparticles enhanced luminescence and stability of CsPbBr3 perovskite quantum dots in borosilicate glass

Series of silver nanoparticles (NPs) embedded CsPbBr₃ quantum dots (QDs) glass was synthesized via the melt-quench method. Ag NPs and CsPbBr₃ QDs coexist in the TEM image of the Ag-doped glass sample. Photoluminescence (PL) spectra show that the 0.1 molar ratio Ag₂O-doped sample had a PL intensity 2.37 times than the undoped sample. This increase is generated by localized surface plasmon resonance coupling between the Ag NPs and CsPbBr₃ QDs. Excessive Ag doping weakens the PL intensity due to spectral self-absorption of the Ag NP surface plasmon resonance (SPR). Self-adsorption of SPR is detrimental to luminescence properties because it increases the amount of photogenerated charge carriers, which proceed through nonradiative relaxation pathways. In addition, stability results of Ag NP-doped-CsPbBr₃ QD glass show that they have excellent stability. This study on Ag NP-doped-CsPbBr₃ QD glass provides a new idea for the future development of perovskite QD optoelectronic devices.     

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.     

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.     

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.     

Rb+-doped CsPbBr3 quantum dots with multi-color stabilized in borosilicate glass via crystallization

All-inorganic lead halide quantum dots (QDs) have attracted immense interest because of their excellent photoelectric properties. By virtue of a similar ionic radius and the same valence state, Rb⁺/Cs⁺ mixed-cation have become a novel mechanism to adjust multi-color emission. However, their poor stability remains a serious problem that has not been solved satisfactorily. Interestingly, QDs glass shows good thermostability and moisture susceptibility. Herein, CsPbBr₃: xRb (x = 0, 0.4, 0.6, 0.8) QD glasses which yield tunable emission spectra (475–523 nm) were synthesized successfully via glass crystallization. Most importantly, the as-prepared QDs glasses exhibited ultrastability under various atmospheric, water and heat conditions. Thus, synthesis of a mixed-cation perovskite QDs glass is a new method to achieve stable multi-color emission. They are also expected to become a new generation of photoelectric materials and can be prospectively applied to light-emitting devices.     

Enhanced luminescence of self-crystallized Cs4PbBr6 quantum dots via regulating glass ceramic network structure

The most used method to obtain Cs₄PbBr₆ quantum dots (QDs) in glass is heat treatment, but the more energy-efficient method of self-crystallization is seldom explored. In this work, Cs₄PbBr₆ QDs are obtained in glass matrix through self-crystallization method. The results elucidate that with the increase of Na₂O, glass network structure transforms from three-dimensional (3D) framework structure to two dimensional (2D) layered structure and phase separation process of glass is aggravated. The looser network structure facilitates atoms rearrangement, and the presence of phase interface reduces activation energy of nucleation. Both of the two aspects can promote the self-crystallization of Cs₄PbBr₆ QDs. Importantly, the PLQY of PG3 is 81.24 %, which is much higher than the heat treated one (CG3:11.89 %). Finally, a green backlit light-emitting diode (LED) with high color purity of 96.1 % and white light-emitting diode (WLED) with color coordinate of (0.3212, 0.3315) are fabricated. Our work puts forward a new perspective to investigate QDs glass ceramic and brings QDs glass ceramic significant prospect in the optoelectronic applications.     

Removal of vapor-phase elemental mercury by N-doped CuCoO4 loaded on activated carbon

The adsorption ability for vapor-phase Hg° on commercially available granular activated carbon (AC) loaded with CuCoO₄ (AC–C), CuCoO₄ + NH₄Cl (AC–Cl), and CuCoO₄ + NH₄Br (AC–Br) were investigated in an attempt to produce more economic and effective sorbents for the control of Hg^o emission from combustion processes. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and mass balance analysis on mercury, we found that N-doped AC–C had bigger S_BET and the nitrogen doping greatly improved CuCoO₄ Hg^o oxidation ability. It was considered that nitrogen atoms in doped CuCoO₄ polycrystalline and anion Cl⁻/Br^- activated by AC and N-doped CuCoO₄ were responsible for the significant enhancement in Hg^o oxidation ability of AC–Cl and AC–Br. We explored the Hg^o oxidation ability of the three kinds of materials under various loading values and adsorption temperatures. We found that AC–Cl and AC–Br were more sensitive to loading value and had much higher Hg^o oxidation ability than AC–C over a wide range temperature. The longevities of AC–C, AC–Cl and AC–Br were all less than the corresponding Al₂O₃ carrier material due to CuCoO₄ decomposition effect on AC, which destroyed the porous structure of AC. The effect of 0.31 vol.% SO₂ on the Hg^o oxidation ability of AC–C, AC–Cl and AC–Br was insignificant which indicated that N-doping did not adversely affect Co³⁺ and Cu²⁺-octahedral structure.     

Improved photoluminescence quantum yield of CsPbBr3 quantum dots glass ceramics

We have fabricated CsPbBr₃ perovskite quantum dots (QDs) in a multi-component borate glass by melt-quenching technique. Transmission electron microscopy (TEM) reveals a cubic phase CsPbBr₃ crystal for QDs. As the treatment temperature or the treatment time duration increases, the photoluminescence (PL) peak shifts to long wavelength in the range of 510 to 525 nm, and the full width at half-maximum varies in the range of 24 to 18 nm. The absorption edge shifts to low energy side in the range of 2.54 to 2.41 eV. The different photoluminescence excitation spectra (PLE) reflect the change of microstructure for different samples. The PL peak wavelength and line-shape are independent of excitation wavelength. These results of spectra show typical exciton emission characteristics. As treatment conditions strengthens, photoluminescence quantum yield (PLQY) first increases and then decreases, having the best PLQY 86.9%. Bi-exponential fitting curves show that short lifetime τ₁ continuously decreases. Long lifetime τ₂, weight for long lifetime component, and average lifetime τ_avg first increase and then decrease. The PLQY values are affected by both τ₁ and τ₂, which are relative to the crystal quality in the interior and the surface of QDs, respectively. The high PLQY value corresponds to medium treatment condition, which is attributed to a balanced effect of crystal quality in interior and the surface of QDs.