Explore the vast range of titles available.

A neuromorphic visual system integrating optoelectronic synapses to perform the in‐sensor computing is triggering a revolution due to the reduction of latency and energy consumption. Here it is demonstrated that the dwell time of photon‐generated carriers in the space‐charge region can be effectively extended by embedding a potential well on the shoulder of Schottky energy barrier. It permits the nonlinear interaction of photocurrents stimulated by spatiotemporal optical signals, which is necessary for in‐sensor reservoir computing (RC). The machine vision with the sensor reservoir constituted by designed self‐powered Au/P(VDF‐TrFE)/Cs2AgBiBr6/ITO devices is competent for both static and dynamic vision tasks. It shows an accuracy of 99.97% for face classification and 100% for dynamic vehicle flow recognition. The in‐sensor RC system takes advantage of near‐zero energy consumption in the reservoir, resulting in decades‐time lower training costs than a conventional neural network. This work paves the way for ultralow‐power machine vision using photonic devices. In this work, photovoltaic devices are innovatively used as self‐powered reservoirs. Ultralow‐power machine vision is achieved by the self‐powered sensor reservoir with Cs2AgBiBr6 photonic devices. Both image processing and dynamic video analysis are energy‐efficiently achieved in this in‐sensor reservoir computing system. The accuracy is 99.67% for face classification and 100% for dynamic vehicle flow recognition.

Double perovskite La2NiMnO6 (LNMO) nanoparticles and nanorods were synthesized via a hydrothermal process, where only aqueous inorganic solvents are used to regulate the microscopic morphology of the products without using any organic template. They crystallized in a monoclinic (P21/n) double perovskite crystal structure. The LNMO nanoparticles exhibited spherical morphology with an average particle size of 260 ± 60 nm, and the LNMO nanorods had diameters of 430 ± 120 nm and length about 2.05 ± 0.65 μm. Dual chemical oxidation states of the Ni and Mn ions were confirmed in the LNMO samples by X-ray photoelectron spectroscopy. Strong frequency dispersion dielectric behavior observed in the LNMO ceramics, is attributed to the space charge polarization and the oxygen vacancy induced dielectric relaxation. A ferroelectric—paraelectric phase transition appearing near 262 K (or 260 K) in the LNMO ceramics prepared from nanoparticles (or nanorods) was identified to be a second-order phase transition. The LNMO samples are ferromagnetic at 5 K but paramagnetic at 300 K. The LNMO nanoparticles had larger saturation magnetization (MS = 6.20 μB/f.u. @ 5 K) than the LNMO nanorods (MS = 5.68 μB/f.u.) due to a lower structural disorder in the LNMO nanorods. The semiconducting nature of the nanostructured LNMO with an optical band gap of 0.99 eV was revealed by the UV–visible absorption spectra. The present results enable the nanostructured LNMO to be a promising candidate for practical spintronic devices.

Lead‐free halide double perovskite (HDP) nanocrystals are considered as one of the most promising alternatives to the lead halide perovskite nanocrystals due to their unique characteristics of nontoxicity, robust intrinsic thermodynamic stability, rich and tunable optoelectronic properties. Although lead‐free HDP variants with highly efficient emission are synthesized and characterized, the photoluminescent (PL) properties of colloidal HDP nanocrystals still have enormous challenges for application in light‐emitting diode (LED) devices due to their intrinsic and surface defects, indirect band, and disallowable optical transitions. Herein, recent progress on the synthetic strategies, ligands passivation, and metal doping/alloying for boosting efficiency and stability of HDP nanocrystals is comprehensive summarized. It begins by introducing the crystalline structure, electronic structure, and PL mechanism of lead‐free HDPs. Next, the limiting factors on PL properties and origins of instability are analyzed, followed by highlighting the effects of synthesis strategies, ligands passivation, and metal doping/alloying on the PL properties and stability of the HDPs. Then, their preliminary applications for LED devices are emphasized. Finally, the challenges and prospects concerning the development of highly efficient and stable HDP nanocrystals‐based LED devices in the future are proposed. A review of lead‐free halide double perovskite (HDP) nanocrystals is presented to introduce the crystal and electronic structure, and highlight the recent progress on the synthetic strategies, ligands passivation, and metal doping/alloying for boosting their efficiency and stability. The outlook on developing high‐performance lead‐free HDP nanocrystals toward light emitting diodes are conceived and expected to be of great significance for guiding future research.

Lead (Pb) halide perovskites have witnessed highly promising achievements for high-efficiency solar cells, light-emitting diodes (LEDs), and photo/radiation detectors due to their exceptional optoelectronic properties. However, compound stability and Pb toxicity are still two main obstacles towards the commercialization of halide perovskite-based devices. Therefore, it is of substantial interest to search for non-toxic candidates with comparable photophysical characteristics. Metal-halide double perovskites (MHDPs), A BBʹX , are recently booming as promising alternatives for Pb-based halide-perovskites for their non-toxicity and significantly enhanced chemical and thermodynamic stability. Moreover, this family exhibits rich combinatorial chemistry with tuneable optoelectronic properties and thus a great potential for a broad range of optoelectronic/electronic applications. Herein, we present a comprehensive review of the MHDPs synthesized so far, and classified by their optical and electronic properties. We systematically generalize their electronic structure by both theoretical and experimental efforts to prospect the relevant optoelectronic properties required by different applications. The progress of the materials in various applications is explicated in view of the material structure-function relationship. Finally, a perspective outlook to improve the physical and optoelectronic properties of the materials is proposed aiming at fostering their future development and applications.

Lead‐free halide perovskites possess excellent photoelectric properties, making them widely used in the photoelectric fields. Herein, lead‐free double perovskite crystals (PCs) doped with manganese (Cs2NaInCl6:Mn2+) are successfully prepared by the more energy‐efficient crystallization method. The crystals emit bright orange‐red light under the ultraviolet (UV) lamp, showing unique optical properties. They have the highest photoluminescence quantum yield of 42.91%. The white light‐emitting diodes (LEDs) are fabricated using these perovskite crystals, which show a color rendering index of 92 and external quantum efficiency (EQE) as high as 16.3%. Furtherly, perovskite‐modified fiber paper made of aramid chopped fibers (ACFs) and polyphenylene sulfide (PPS) exhibited fluorescent properties under different conditions. This paper combines fiber composite technology with PPS fiber filter bags, which are widely used in environmental protection, for the first time and demonstrates functional fiber filter bags with fluorescent characteristics. This filter bag provides an idea for the automatic detection of industrial filtration. Meanwhile, after being exposed to industrial waste gas for 60 h, the filter bag can maintain superior fluorescence performance. In this study, lead‐free double perovskites are synthesized using an efficient method for preparing high‐performance LEDs and high‐stability fluorescent fibers. Concurrently, the application of perovskites in environmental protection is expanded. Manganese‐doped halide perovskites with high photoluminescent quantum yield can be used to prepare LEDs and fluorescent composite fibers with high external quantum efficiency. The fluorescent fiber filter bag is developed based on fluorescent composite fiber, which provides a new idea for detecting filter bag damage in industrial waste gas filtration systems.

Double perovskite materials have emerged as key players in the realm of advanced materials due to their unique structural and functional properties. This research mainly focuses on the synthesis and comprehensive characterization of Ba2CoWO6 double perovskite nanopowders utilizing a high-temperature conventional solid-state reaction technique. The successful formation of Ba2CoWO6 powders was confirmed through detailed analysis employing advanced characterization techniques. Rietveld refinement of X-ray diffraction (XRD) and Raman data established that Ba2CoWO6 crystallizes in a cubic crystal structure with the space group Fm-3m, indicative of a highly ordered perovskite lattice. The typical crystallite size, approximately 65 nm, highlights the nanocrystalline nature of the material. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) discovered a distinctive morphology characterized by spherical shaped particles, suggesting a complex particle formation process influenced by synthesis conditions. To probe the electronic structure, X-ray Photoelectron Spectroscopy (XPS) identified cobalt and tungsten valence states, critical for understanding dielectric properties associated with localized charge carriers. The semiconducting character of the synthesized Ba2CoWO6 nanocrystalline material was confirmed through UV-Visible analysis, which revealed an energy bandgap value of 3.3 eV, which aligns well with the theoretical predictions, indicating the accuracy and reliability of the experimental results. The photoluminescence spectrum exhibited two distinct emissions in the blue-green region. These emissions were attributed to the transitions 3P0→3H4, 3P0→3H5, and 3P0→3H6, primarily resulting from the contributions of Ba2+ ions. The dielectric characteristics of the compound were analyzed across a different range of frequencies, spanning from 1 kHz to 1 MHz. Magnetic characterization using Vibrating Sample Magnetometry (VSM) revealed antiferromagnetic behavior of Ba2CoWO6 ceramics at room temperature, attributed to super-exchange interactions between Co3+ and W5+ ions mediated by oxygen ions in the perovskite lattice. Additionally, first-principles calculations based on the Generalized Gradient Approximation (GGA+U) with a modified Becke–Johnson (mBJ) potential were employed to gain a deeper understanding of the structural and electronic properties of the materials. This approach involved systematically varying the Hubbard U parameter to optimize the description of electron correlation effects. These results deliver an extensive understanding of the structural, optical, morphological, electronic, and magnetic properties of Ba2CoWO6 ceramics, underscoring their potential for electronic and magnetic device applications.

The authors successfully dope the magnetically silent double perovskite semiconductor Sr2GaSbO6 to induce ferromagnetism and tune its bandgap, with Ga3+ partially substituted by the magnetic trivalent cation Mn3+, in a rigid cation ordering with Sb5+. The new ferromagnetic semiconducting Sr2Ga1−xMnxSbO6 double perovskite, which crystallizes in tetragonal symmetry (space group I4/m) and has tunable ferromagnetic ordering temperature and bandgap, suggests that magnetic ion doping of double perovskites is a productive avenue toward obtaining materials for application in next‐generation oxide‐based spintronic devices. This study reports the successful doping of the magnetically silent double perovskite semiconductor Sr2GaSbO6 to induce ferromagnetism and tune its bandgap, with Ga3+ partially substituted by the magnetic trivalent cation Mn3+. Ferromagnetic semiconducting double perovskites with tunable properties are extremely rare and to the best of the authors’ knowledge this Sr2Ga1−xMnxSbO6 series is unique.

Lead‐free halide double perovskites (DPs) have attracted great attention due to their stability, nontoxicity, and good photophysical properties. Herein, environmentally friendly small‐bandgap Cs2CuSbCl6 and Cs4CuSb2Cl12 DPs microcrystals (MCs) are prepared via a solvent synthesis technique. This study also reports a bottom‐up synthetic protocol for obtaining evenly distributed Cs2CuSbCl6 and Cs4CuSb2Cl12 quantum dots (QDs) utilizing a modified hot injection approach. These MCs and QDs have strong absorption throughout the visible region, indicating that they could be promising light‐absorbing materials as sunlight‐driven photocatalysts. For the first time, the efficient sunlight‐driven photocatalytic CO2 reduction activity of these Pb‐free “green” MCs and QDs has been revealed, and a product yield of 307 μmol g−1 and an electron consumption of 1053 μmol g−1 are achieved by the Cs4CuSb2Cl12 QDs under 3 h irradiation. Our results highlight the potential of this family of materials for photocatalytic applications. Environmentally friendly small‐bandgap Cs2CuSbCl6 and Cs4CuSb2Cl12 halide double perovskites microcrystals and quantum dots (QDs) are fabricated successfully, and the Cs4CuSb2Cl12 QDs present an impressive electron consumption of 1053 µmol g−1 under 3 h illumination.

Double perovskite materials have gradually become widely studied due to their potential applications in solar cells and other optoelectronic devices. We take Cs2NaFeCl6 as an example to investigate the carrier mobility with respect to the acoustic phonon and the optical phonon scattering mechanisms. By considering the deformation potential, carrier effective mass, and bulk modulus, the longitudinal acoustic (LA) phonon-determined mobilities for electrons and holes in Cs2NaFeCl6 are found to be μe = 2886.08 cm2 v−1 s−1 and μh = 39.09 cm2 v−1 s−1, respectively. The optical scattering mechanism involves calculating the Fröhlich coupling constant, dielectric constant, and polaron mass to determine the multiple polar optical (PO) phonon-scattering-determined mobilities, resulting in μe = 279.25 cm2 v−1 s−1 and μh = 21.29 cm2 v−1 s−1, respectively. By combining both interactions, the total electron mobility and hole mobility are determined to be 254.61 cm2 v−1 s−1 and 13.78 cm2 v−1 s−1, respectively. The findings suggest that the polarization of both electrons and ions, small coupling constant, and bulk modulus in Cs2NaFeCl6’s lattice make PO scattering a significant contribution to carrier mobility in this specific double perovskite, highlighting the importance of considering this in enhancing the optoelectronic properties of Cs2NaFeCl6 and other double perovskites.

The magnetocaloric effect based Magnetic refrigeration (MR) was considered a novel energy-efficient and environmentally benign cooling method. However, the lack of suitable magnetic solids has slowed the development of its practical applications. We herein fabricated the RE ₂ NiTiO ₆ ( RE = Gd, Tb and Ho) double perovskite (DP) compounds and systematically determined their structural, magnetic and magnetocaloric properties by experimental determination and density functional theory calculations, in which the Gd ₂ NiTiO ₆ was realized to exhibit promising cryogenic magnetocaloric performances. The results indicated that all the RE ₂ NiTiO ₆ DP compounds crystallized in a distorted monoclinic structure with P 2 ₁ / n space group and underwent a second order type magnetic phase transition around 4.3, 4.5 and 3.9 K, for Gd ₂ NiTiO ₆ , Tb ₂ NiTiO ₆ and Ho ₂ NiTiO ₆ , respectively. The magnetocaloric performances were checked by the parameters of maximum magnetic entropy change and relative cooling power, which are 31.28 J·kg ⁻1 ·K ⁻1 and 242.11 J·kg ⁻1 for Gd ₂ NiTiO ₆ , 13.08 J·kg ⁻1 ·K ⁻1 and 213.41 J·kg ⁻1 for Tb ₂ NiTiO ₆ , 11.98 J·kg ⁻1 ·K ⁻1 and 221.73 J·kg ⁻1 for Ho ₂ NiTiO ₆ under the magnetic field change of 0–50 kOe, respectively. Evidently, the Gd ₂ NiTiO ₆ compound exhibit promising magnetocaloric performances and therefore is of potential for practical cryogenic MR applications.