In Situ Growth of All-Inorganic Perovskite Single Crystal Arrays on Electron Transport Layer

Neuromorphic Computing with Emerging Antiferromagnetic Ordering in Spin-Orbit Torque Devices

Field-free switching (FFS) and spin-orbit torque (SOT)-based neuromorphic characteristics were realized in a W/Pt/Co/NiO/Pt heterostructure with a perpendicular exchange bias (HEB) for brain-inspired neuromorphic computing (NC). Experimental results using NiO-based SOT devices guided the development of fully spin-based artificial synapses and sigmoidal neurons for implementation in a three-layer artificial neural network. This system achieved impressive accuracies of 91-96% when applied to the Modified National Institute of Standards and Technology (MNIST) image data set and 78.85-81.25% when applied to Fashion MNIST images, due presumably to the emergence of robust NiO antiferromagnetic (AFM) ordering. The emergence of AFM ordering favored the FFS with an enhanced HEB, which suppressed the memristivity and reduced the recognition accuracy. This indicates a trade-off between the requirements for solid-state memory and those required for brain-inspired NC devices. Nonetheless, our findings revealed opportunities by which the two technologies could be aligned via controllable exchange coupling.

A low-toxic, robust, and sensitive colorimetric sensor for the peroxide value of edible oils with CsPbBr3 NCs in ethyl acetate

Sensitively, accurately, and rapidly evaluating edible oils' peroxide value (PV) is significant for safeguarding food quality and safety. However, the conventional detection methods are challenging to meet the above demands due to their complex operation, poor reproducibility, and professional personnel. The colorimetric method is an emerging technique to rapidly and on-site determine the PV of edible oils. CsPbBr3 NCs, as a novel fluorescent-sensing material, have been applied in the chemical colorimetric analysis. However, the heavy use of high-toxic solvents (toluene, chloroform) in the CsPbBr3 NCs colorimetric system significant-negatively influences the environment. This study evaluated the performances of CsPbBr3 NCs in nine low-toxic solvents and investigated the potential response mechanism to PV. The results presented that CsPbBr3 NCs in ethyl acetate displayed the highest photoluminescent intensity and the most uniform distribution. The results performed that the micro-morphology and crystal structure of CsPbBr3 NCs in ethyl acetate were similar to that in toluene, demonstrating the potential excellent performance. Under optimum conditions, three methods, including photoluminescence (PL)-decreased, wavelength-shifted, and phone-based colorimetric methods, were established to evaluate PV with the LOD of 0.0034 g/100 g. The PV recovery rates in Soybean oil, Camellia oil, Linseed oil, and Olive oil were from 75.0% to 100.0%, with a relative error below 25%. Furthermore, it was believed that the decreased PL and shifted wavelength originated from the halogen substitution with the crystal-structure destructions and the surface-defect formations. Thus, developing the low-toxic colorimetric CsPbBr3 NCs system with ethyl acetate could reduce the environmental influence and even enlighten the rise of other green detection methods for PV in edible oils.

All-Inorganic Perovskite Single Crystals for Optoelectronic Detection

Due to their many varieties of excellent optoelectric properties, perovskites have attracted large numbers of researchers in the past few years. For the hybrid perovskites, a long diffusion length, long carrier lifetime, and high μτ product are particularly noticeable. However, some disadvantages, including high toxicity and instability, restrict their further large-scale application. By contrast, all-inorganic perovskites not only have remarkable optoelectric properties but also feature high structure stability due to the lack of organic compositions. Benefiting from these, all-inorganic perovskites have been extensively explored and studied. Compared with the thin film type, all-inorganic perovskite single crystals (PSCs) with fewer grain boundaries and crystalline defects have better optoelectric properties. Nevertheless, it is important to note that only a few reports to date have presented a summary of all-inorganic PSCs. In this review, we firstly make a summary and propose a classification method according to the crystal structure. Then, based on the structure classification, we introduce several representative materials and focus on their corresponding growth methods. Finally, applications for detectors of all-inorganic PSCs are listed and summarized. At the end of the review, based on the current research situation and trends, some perspectives and advice are proposed.

Flexible 3D Nanonetworked Silica Film as a Polymer-Free Drug-Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110 µm) by only 0.4 percent (110.45 µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p < 0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

MAPbBr3nanocrystals from aqueous solution for poly(methyl methacrylate)-MAPbBr3nanocrystal films with compression-resistant photoluminescence

In this work, we develop an environmental-friendly approach to produce organic-inorganic hybrid MAPbBr₃(MA = CH₃NH₃) perovskite nanocrystals (PeNCs) and PMMA-MAPbBr₃NC films with excellent compression-resistant PL characteristics. Deionized water is used as the solvent to synthesize MAPbBr₃powder instead of conventionally-used hazardous organic solvents. The MAPbBr₃PeNCs derived from the MAPbBr₃powder exhibit a high photoluminescence quantum yield (PLQY) of 93.86%. Poly(methyl methacrylate) (PMMA)-MAPbBr₃NC films made from the MAPbBr₃PeNCs retain ∼97% and ∼91% of initial PL intensity after 720 h aging in ambient environment at 50 °C and 70 °C, respectively. The PMMA-MAPbBr₃NC films also exhibit compression-resistant photoluminescent characteristics in contrast to the PMMA-CsPbBr₃NC films under a compressive stress of 1.6 MPa. The PMMA-MAPbBr₃NC film integrated with a red emissive film and a blue light emitting source achieves an LCD backlight of ∼114% color gamut of National Television System Committee (NTSC) 1953 standard.

In Situ Low-Temperature Growth and Superior Luminescent Property of Well-Aligned, High-Quality Cubic CsPbBr3 Micrometer-Scale Single Crystal Arrays on Transparent Conductive Substrates

Direct assembly of high-quality single-crystal perovskite microarrays on transparent conductive substrates and carrier injection layers is vital to realize high-performance optoelectronic devices. Although cubic-phase CsPbBr₃ is considered to have a higher structural and optical quality than the orthorhombic one, obtaining a well-aligned assembly directly on the aforementioned substrates is still challenging. Here we developed a solvent-assisted crystallization strategy with the assistance of surface modifiers, through which the in situ low-temperature growth of well-aligned cubic single-crystal CsPbBr₃ microarray with a preferential out-of-plane [100] orientation is achieved for the first time on commercial transparent conductive substrates. As compared with the control orthorhombic samples, the cubic CsPbBr₃ single crystals possess superior properties including a higher photoluminescence internal quantum efficiency, fewer defect states, a weaker scattering by phonons, and an appearance of lasing. The results presented here can pave the way for future design and applications of optoelectronic devices based on perovskite microarrays.

Interfaces and Interfacial Layers in Inorganic Perovskite Solar Cells

Owing to their superior thermal stability, metal halide inorganic perovskite materials continue to attract interest for photovoltaics applications. The highest reported power conversion efficiency (PCE) for solar cells based on inorganic perovskites is over 20 %. As this PCE corresponds to 73 % of the theoretical limit, there remains more room for further improving the device PCEs than for improving organic-inorganic hybrid perovskite solar cells (PSCs). The main loss is in the photovoltage, which is limited by interfaces in terms of non-radiative recombination caused by traps and energy-level mismatch. Furthermore, inefficient charge extraction at interfacial contacts reduces the photocurrent and fill factor. This Minireview summarizes the recent developments in the fundamental understanding of how the interfaces and interfacial layers influence the performance of solar cells based on inorganic perovskite absorbers. An outlook for the development of highly efficient and stable inorganic PSCs from the interface point of view is also given.

Oriented Halide Perovskite Nanostructures and Thin Films for Optoelectronics

Oriented semiconductor nanostructures and thin films exhibit many advantageous properties, such as directional exciton transport, efficient charge transfer and separation, and optical anisotropy, and hence these nanostructures are highly promising for use in optoelectronics and photonics. The controlled growth of these structures can facilitate device integration to improve optoelectronic performance and benefit in-depth fundamental studies of the physical properties of these materials. Halide perovskites have emerged as a new family of promising and cost-effective semiconductor materials for next-generation high-power conversion efficiency photovoltaics and for versatile high-performance optoelectronics, such as light-emitting diodes, lasers, photodetectors, and high-energy radiation imaging and detectors. In this Review, we summarize the advances in the fabrication of halide perovskite nanostructures and thin films with controlled dimensionality and crystallographic orientation, along with their applications and performance characteristics in optoelectronics. We examine the growth methods, mechanisms, and fabrication strategies for several technologically relevant structures, including nanowires, nanoplates, nanostructure arrays, single-crystal thin films, and highly oriented thin films. We highlight and discuss the advantageous photophysical properties and remarkable performance characteristics of oriented nanostructures and thin films for optoelectronics. Finally, we survey the remaining challenges and provide a perspective regarding the opportunities for further progress in this field.