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.     

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.     

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.     

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.     

X-ray excited CsPb(Cl,Br)3 perovskite quantum dots-glass composite with long-lifetime

CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (QDs) have emerged as a kind of brand-new X-ray scintillator with high performance. Herein, following the phase transformation from amorphous to crystalline, CsPb(Cl,Br)₃ QDs are in-situ precipitated from a borate glass matrix. It is demonstrated for the first time that the perovskite QDs-glass composite yields radioluminescence (RL), showing X-ray excited RL ∼1/18 to that of commercial Bi₄Ge₃O₁₂ (BGO) single crystal. The color of RL is adjustable, dependent on the anionic species. Evidently, the high power X-ray induced damage in material is recoverable just by re-heating it at glass transition temperature. This work highlights the partial settlement of tough issues in perovskite QDs as scintillators, such as, physical stability, service lifetime, Pb-toxicity, and production scale.     

All-inorganic perovskite Cs4PbBr6 thin films in optoelectronic resistive switching memory devices with a logic application

Perovskite-based Cs₄PbBr₆ has potential applications in optoelectronic devices, such as photodetectors, electroluminescence devices and color converters. All-inorganic perovskite Cs₄PbBr₆ thin films were successfully prepared by a simple low-temperature synthesis method and were first implemented as an insulating layer in Au/Cs₄PbBr₆/PEDOT:PSS/Pt devices. The memory devices possess reproducible bipolar resistive switching behavior, low operating voltages, good endurance, and long retention times. Furthermore, the novel sandwich architecture enables the application of the Cs₄PbBr₆ films as memristors and photoresponsive behaviors. Considering the distinct photoresponses of the resistance state as a nonvolatile memory, the devices can be used as a logical "OR" gate by applying bias voltages and light illumination as input signals. The formation and annihilation of Br^- ion vacancy filaments induced by the external bias and light illumination can result in pronounced resistive switching performance. It is believed that solution-processed Cs₄PbBr₆-based devices have great potential for technological deployment at the forefront as a photonic nonvolatile memory as well as integrated modulating and arithmetic functions.     

Lattice relaxation effect in CsxMA(1-x)PbBr3 single crystal to enhance optoelectronic performance of perovskite photodetectors

Single crystal (SC) MAPbBr₃ perovskite is regarded as a promising material to fabricate high-performance photodetectors (PDs) due to its impressive optoelectronic properties and good chemical stability. Cs⁺ doping has been proved to be an effective method to significantly improve the optoelectronic properties of MAPbBr₃ SC. However, the intrinsic effect of Cs⁺ on the crystal structure is still unclear. Herein, we grew a series Cs_xMA_(1-x)PbBr₃ SCs. X-ray rocking curves (XRC) of Cs_xMA_(1-x)PbBr₃ SCs prove that appropriate Cs-doping concentration could reduce defect density effectively. X-ray photoelectron spectroscopy (XPS) measurements indicate that Cs-doping enhances the atoms interaction in Cs_xMA_(1-x)PbBr₃ lattice due to isoelectronic impurity effect. Single-crystal PDs were fabricated to compare the optoelectronic properties of MAPbBr₃ SCs with different Cs-doping concentration, and the 2% Cs-doped Cs_xMA_(1-x)PbBr₃ PD shows the optimum performance. Density functional theory (DFT) calculations demonstrate that Cs-doping leads to lattice relaxation effect which is benefit to reduce trap density of Cs_xMA_(1-x)PbBr₃ SCs. The Pb-6p level of Cs_xMA_(1-x)PbBr₃ slightly shifts to lower energy region compared with MAPbBr₃, resulting in the decrease of band gap of Cs_xMA_(1-x)PbBr₃.     

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.     

The phosphorescence emission in undoped lead-halide Cs4PbBr6 single crystals at low temperature

Recently, all-inorganic cesium lead-halide perovskites have shown their promise for light emission applications, due to the excellent optical performance. Herein, we report that the initially nonphosphorescent undoped lead-halide Cs₄PbBr₆ single crystals (SCs) exhibit an ultralong phosphorescence emission under X-ray excitation at low temperatures. It is shown that the dramatic change has been taken place in radioluminescence spectra and the broad-band emission gradually appeared with the decrease of temperature. Below 210 K, the radioluminescence spectra can be deconvoluted into one narrow peak located at 530 nm and two broad peaks centered at 595 nm and 672 nm respectively. Subsequently, the time-dependent radioluminescence spectra in undoped lead-halide Cs₄PbBr₆ SCs were investigated. The ultralong phosphorescence emission can persist over 120 min at 70 K. We consider that ultralong phosphorescence originates from defect-related emission. To the best of our knowledge, our finding is the first time that undoped Cs₄PbBr₆ SCs exhibit the phosphorescence emission, which will offer a paradigm to motivate revolutionary applications on perovskite.     

Effects of ion-exchange and post-thermal annealing on the precipitation of cesium lead halide nanocrystals in glasses

Ion-exchange has been widely employed to modify the composition and structure of glasses. In this work, Cs–K ion-exchange was carried out to facilitate the precipitation of cesium lead halide perovskite nanocrystals in the surface layer of glasses. Both Cs₄PbBr₆ and CsPbBr₃ perovskite nanocrystals and KBr nanocrystals can be precipitated through ion-exchange in nitrate salt. Content of Cs₄PbBr₆ and CsPbBr₃ perovskite nanocrystals is strongly dependent on the composition of nitrate salt, ion-exchange conditions, and post-thermal annealing. High concentration of Cs in nitrate salt, long ion-exchange duration, and post-thermal annealing are effective to promote the formation of CsPbBr₃ perovskite nanocrystals. Results reported is valuable for the developing of cesium lead halide perovskite nanocrystals embedded glass for light converters.     

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.     

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.     

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.     

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.     

Ultrafine Cu2ZnSnS4 quantum dots functionalized TiO2 nanotube arrays for potential optoelectronic applications

Tremendous progress has been made in power conversion efficiency (PCE) of thin-film photovoltaics over the past few years, yet most current high-efficient photoactive layer usually contains rare or toxic elements accompanied by expensive and complicated vacuum processes, which increases the cost and limits the scope of the applications in the long run. Here we present a synergistic effect of quantum effect of an earth-abundant and low toxic ultrafine Cu₂ZnSnS₄ (CZTS) quantum dots (QDs) and low charge recombination in one dimensional TiO₂ nanotube arrays for optoelectronic devices. By ligands exchange, the as-obtained ultrafine CZTS QDs have been robustly anchored to a highly ordered TiO₂ nanotube arrays (TNAs) to be served as a function layer in a simple QDs sensitized solar cells. Such ultrafine CZTS QDs based solar cells exhibit significant enhancement up to 457% in PCE compared to that of CZTS QDs with larger size. The CZTS QDs functionalized TNAs has also shown excellent charge transport capability with lower recombination rate than QDs sensitized TiO₂ nanoparticles and it is expected to be used as a low-cost environment-friendly function layer for various potential optoelectronic applications.     

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.     

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.     

The thermal stability and consolidation of perovskite variant Cs2SnCl6 using spark plasma sintering

Defect perovskites, a category of air and moisture stable perovskite molecular salts, have gained attention for photovoltaics in the search of alternatives to the organic lead‐based photovoltaics which show exceptional photovoltaic performance but suffer significant environmental instability and toxicity of Pb. Defect perovskites also have exceptional structural flexibility and diverse crystal chemistry, and thus, display potentials as host phases for incorporating high amounts of halides such as iodine and chorine. In this study, pure Cs₂SnCl₆, a lead‐free defect perovskite variant, was synthesized through a solution‐based route that produced particles ranging from 200 to 500 nm. The thermal stability of the as‐synthesized Cs₂SnCl₆ powders was investigated using thermogravimetric analysis (TGA), demonstrating stability up to 615°C, above which a phase decomposition occurs leading to the loss of constituent component of SnCl₄. Consolidation of Cs₂SnCl₆ into dense pellets (≥94% theoretical density) was achieved via spark plasma sintering (SPS) at a low sintering temperature of 350°C. X‐ray diffraction confirms no phase decomposition in the SPS‐densified perovskite pellets as a result of rapid consolidation of the SPS sintering at a short duration and lower temperature, and the TGA analysis suggest a comparable thermal stability up to 627°C for the densified pellet, slightly better than the as‐synthesized powders. The thermal diffusivity of Cs₂SnCl₆ at room temperature was determined as 0.388 mm²·s^?1 by laser flash measurement. This work further discussed the potential applications of the SPS‐densified Cs₂SnCl₆ beyond perovskite photovoltaics, introducing potential nuclear separations and waste forms for chlorine.     

Cs4PbBr6 QDs silicate glass-ceramic: A potential anode material for LIBs

Lithium-ion batteries (LIBs) have attracted special attention in the new energy field, while halide perovskites are potential materials in the field of energy. In this work, Cs₄PbBr₆ quantum dots silicate glass-ceramic is synthesized by melt-quenching methods and examined as LIBs anode materials. The half-battery provides a high initial discharge specific capacity of about 1986.9 mAh g^?1 and a remarkably high reversible capacity of 426.7 mAh g^?1. Also, the present glass material shows good rate performance. Between the perovskite quantum dots and the silicate glass exists an interesting synergistic effect, and the observed prominent electrochemical performance proves that the quantum dots glass-ceramic materials are viable for lithium-ion batteries application.     

Enhanced photoluminescence quantum yield of red-emitting CdTe:Gd3+ QDs for WLEDs applications

In order to improve the quantum yield of red-emitting CdTe quantum dots (QDs), CdTe:Gd³⁺ QDs were synthesized by a facile one-step aqueous method. The composition, morphology, and photoluminescence property of CdTe:Gd³⁺ QDs were characterized. The results show that the doping of Gd³⁺ not only leads to a red-shift in the emission wavelength but also improves the photoluminescence quantum yield (PL QY) of CdTe QDs up to 85.74%. Doping of Gd element causes the Te dangling bond on the surface of CdTe QDs to be destroyed, thus reducing the nonradiative surface recombination, which is considered to be the reason of the increase in PL QY of CdTe QDs. Finally, high color rendition white light was generated from the CdTe:Gd³⁺ QDs-assisted phosphor-converted white light-emitting diode (WLED). Under operation of 50 mA forward bias current, the fabricated WLED emitted bright warm white light with a high color rendering index of 86, a low correlated color temperature (CCT) of 4020 K, a suitable Commission Internationale de l’Eclairage color coordinates of (0.3651, 0.3223), and an enhanced luminous efficiency of 68.52 lm/W.