Microstructure-Assisted Wafer-Scale Fabrication of Perovskite Microlaser Arrays.

All inorganic lead halide perovskites exhibit fascinating optical and optoelectronic characteristics for on-chip lasing, but the lack of precise control of wafer-scale fabrication for perovskite microstructure arrays restricts their potential applications in on-chip-integrated devices. In this work, a microstructure-template assisted crystallization method is demonstrated via a designed chemical vapor deposition process, achieving the controllable fabrication of homogeneous perovskite micro-hemispheroid (PeMH) arrays spanning the entire surface area of a 4-inch wafer. Benefiting from the low-loss whispering gallery resonance and plasmon-enhanced light-matter interactions in well-confined hybrid cavities, this CsPbX3/Ag (X = Cl, Br) plasmonic microlasers exhibit quite low thresholds below 10 µJ cm-2. Interestingly, these thresholds can be efficiently modulated through the manipulation of plasmonic resonance and electromagnetic field mode in PeMHs owning various diameters. This strategy not only provides a valuable methodology for the large-scale fabrication of perovskite microstructures but also endorses the potential of all-inorganic perovskite nanostructures as promising candidates for on-chip-integrated light sources.

Creating Unidirectional Fast Ion Diffusion Channels in G/NiS2 -MoS2 Heterostructures for High-Performance Sodium-Ion Batteries.

Exploring novel electrode composites and their unique interface physics plays a significant role in tuning electrochemical properties for boosting the performance of sodium-ion batteries (SIBs). Herein, mixed-dimensional G/NiS2 -MoS2 heterostructures are synthesized in a low-cost meteorological vulcanization process. The stable graphene supporting layer and nanowire heterostructure guarantee an outstanding structural stability to tolerate certain volume changes during the charge/discharge process. The rational construction of NiS2 -MoS2 heterostructures induces abundant interfaces and unique ion diffusion channels, which render fast electrochemical kinetics and superior reversible capacities for high-performance SIBs. Interestingly, theoretical studies reveal that the anisotropic diffusion barriers create unidirectional "high-speed" channels, which can lead to ordered and fast Na+ insertion/extraction in designed heterostructures. G/NiS2 -MoS2 anode exhibits a high capacity of 509.6 mA h g-1 after 500 cycles and a coulombic efficiency >99% at 0.5 A g-1 , which also displays excellent cycling performance with the capacity of 383.8 mA h g-1 after the 1000 cycles at 5 A g-1 . Furthermore, full cells are constructed exhibiting a high capacity of 70 mA h g-1 at 0.1 A g-1 after 150 cycles and applied to light LEDs. This study provides a feasible strategy of constructing mixed-dimensional heterostructures for SIBs with excellent performance and a long service lifetime.

Extrinsic photoluminescence properties of individual micro-particle of Cs4PbBr6 perovskite with "defect" structure.

Optical performance of the lead halide perovskites with zero-dimension (0D) structure has been in a hot debate for optoelectronic applications. Here, Cs4PbBr6 hexagonal micro-particles with a remarkable green emission are first fabricated via a low-temperature solution-process employed ethanol as solvent. Our results underline that the existence of bromine vacancies and the introduction of hydroxyl induce a narrowed band gap with the formation of a defect level, which contributes to the extrinsic photoluminescence (PL) properties synergistically. Thanks to the high exciton binding energy and the unique morphology with a regular geometric structure of the as-obtained micro-particles, two-photon pumped amplified spontaneous emission (ASE) and single mode lasing from an individual Cs4PbBr6 particle are realized. Our results not only provide an insight into the origin of optical emission from Cs4PbBr6, but also demonstrate that the versatile Cs4PbBr6 offers a new opportunity for novel nonlinear photonics applications as an up-conversion laser.

All-inorganic lead halide perovskite nanocrystals applied in advanced display devices.

Advanced display devices are in greater demand due to their large color gamut, high color purity, ultrahigh visual resolution, and small size pixels. All-inorganic lead halide perovskite (AILHP) nanocrystals (NCs) possess inherent advantages such as narrow emission width, saturated color, and flexible integration, and have been developed as functional films, light sources, backlight components, and display panels. However, some drawbacks still restrict the practical application of advanced display devices based on AILHP NCs, including working stability, large-scale synthesis, and cost. In this review, we focus on AILHP NCs, review the recent progress in materials synthesis, stability improvement, patterning techniques, and device application. We also highlight the important role of materials systems in creating advanced display devices, followed by the challenges and opportunities in industrial processes. This review provides beneficial inspiration for the future development of AILHP NCs in colorful and white backlight, as well as high resolution full-color displays.

Multifunctional Optoelectronic Synapses Based on Arrayed MoS2 Monolayers Emulating Human Association Memory.

Optoelectronic synaptic devices integrating light-perception and signal-storage functions hold great potential in neuromorphic computing for visual information processing, as well as complex brain-like learning, memorizing, and reasoning. Herein, the successful growth of MoS2 monolayer arrays assisted by gold nanorods guided precursor nucleation is demonstrated. Optical, spectral, and morphology characterizations of MoS2 prove that arrayed flakes are homogeneous monolayers, and they are further fabricated as optoelectronic devices showing featured photocurrent loops and stable optical responses. Typical synaptic behaviors of photo-induced short-term potentiation, long-term potentiation, and paired pulse facilitation are recorded under different light stimulations of 450, 532, and 633 nm lasers at various excitation powers. A visual sensing system consisting of 5 × 6 pixels is constructed to simulate the light-sensing image mapped by forgetting curves in real time. Moreover, the system presents the ability of utilizing associated images to restore vague and incomplete memories, which successfully mimics human intelligent behaviors of association memory and logical reasoning. The work emulates the brain-like artificial intelligence using arrayed 2D semiconductors, which paves an avenue to achieve smart retina and complex brain-like system.

Giant Enhancement of Second-Harmonic Generation in Hybrid Metasurface Coupled MoS2 with Fano-Resonance Effect.

Plasmonic nanostructures have been regarded as potential candidates for boosting the nonlinear up-conversion rate at the nanoscale level due to their strong near-field enhancement and inherent high design freedom. Here, we design a hybrid metasurface to realize the moderate interaction of Fano resonance and create the dual-resonant mode-matching condition to facilitate the nonlinear process of second harmonic generation (SHG). The hybrid metasurface presents dipolar and octupolar plasmonic modes near the fundamental and doubled-frequency wavelengths, respectively, further utilized to enhance the SHG of low-dimensional MoS2 semiconductors. The maximum intensity of SHG in hybrid metasurface coupled MoS2 is more than ten thousand times larger than that of other structure-units coupled MoS2. The conversion efficiency is reported to be as high as 3.27 × 10-7. This work paves the way to optimize nonlinear light-matter interactions in low-dimensional structures coupled with semiconductors.

High-Stable X-ray Imaging from All-Inorganic Perovskite Nanocrystals under a High Dose Radiation.

All-inorganic perovskites of CsPbBr3 nanocrystals (NCs) exhibit strong X-ray absorption and have been demonstrated to be highly efficient scintillators for X-ray detection and imaging. However, the long-term stability of the perovskite remains a major hurdle in practical applications, especially under a commercial dose of X-ray irradiation (0.5-5.5 mGy·s-1). Herein, with a solution-protected annealing approach reconstructing the CsPbBr3 NCs free from undesired defects, the perovskite scintillators provide a long-term (∼3600 s) stable visualization tool for X-ray radiography (1.44 × 106 captured images for the exposure time of 2.5 ms per image) under the irradiation dose of 1 mGy·s-1. This work opens a window for the stability of perovskite scintillators and demonstrates their robust and long-term efficient radioluminescence (RL) for low-cost radiography and X-ray imaging application.

Ultrahigh photo-stable all-inorganic perovskite nanocrystals and their robust random lasing.

Photo-instability has prevented further commercialization of all-inorganic perovskite nanocrystals (NCs) in the field of high-power optoelectronics. Here, an accelerated transformation process from non-luminescent Cs4PbBr6 to CsPbBr3 NCs with bright green emission is explored with irradiation at 365 nm during water-triggered structural transformation. The photoelectric field provided by the photon energy of 365 nm promotes the rapid stripping of CsBr and atomic reconstruction, contributing to the production of ultrahigh photo-stable defect-free CsPbBr3 NCs. The robust emission output of the as-obtained CsPbBr3 NCs is well preserved even when recorded after 160 min. Moreover, a long-term stable random lasing could be achieved when excited using an ∼800 nm femtosecond laser for at least 8.6 × 107 laser shots. Our results not only elucidate the photo-induced accelerated phase transformation process of the all-inorganic perovskites, but also open up opportunities to synthesize highly stable CsPbBr3 NCs for their practical application in photovoltaics and optoelectronics.

Atomic-Scale Insights into the Dynamics of Growth and Degradation of All-Inorganic Perovskite Nanocrystals.

An understanding of growth and degradation pathways is significant to solve the problem of the structural instability of all-inorganic perovskite nanocrystals (NCs). However, it is still a great challenge to directly record such dynamic processes with high spatial resolution owing to the existence of complex internal factors even using in situ transmission electron microscopy observation. Here, we employ a glassy matrix to produce CsPbBr3 NCs to ensure that the growth and degradation processes of CsPbBr3 NCs are recorded in the vacuum chamber, which could avoid the influence of the external factors, under electron beam (E-beam) irradiation. In addition, two stages of degradation pathways induced by the E-beam are observed sequentially: (1) a layer-by-layer decomposition and (2) instantaneous vanishing once the radius reaches the critical radius (∼2.3 nm). Indeed, we demonstrated that defects serve as a key flash point that could trigger the structural collapse of CsPbBr3 NCs. Our findings provide critical insights into the general instability issue of all-inorganic perovskite NCs in practical applications.