A simple, low-cost blade-coating method is developed for the large-area fabrication of single-crystalline aligned CH3NH3PbI3 microwire (MW) arrays. The solution-coating method is applicable to flexible substrates, enabling the fabrication of MW-array-based photodetectors with excellent long-term stability, flexibility, and bending durability. Integrated devices from such photodetectors demonstrate high performance for high-resolution, flexible image sensors.

If a small fraction of Fast Radio Bursts (FRBs) are associated with Gamma-Ray Bursts (GRBs), as recently suggested by Zhang, the combination of redshift measurements of GRBs and dispersion measure (DM) measurements of FRBs opens a new window to study cosmology. At z < 2 where the universe is essentially fully ionized, detections of FRB/GRB pairs can give an independent measurement of the intergalactic medium portion of the baryon mass fraction, Ω b f IGM , of the universe. If a good sample of FRB/GRB associations are discovered at higher redshifts, the free electron column density history can be mapped, which can be used to probe the reionization history of both hydrogen and helium in the universe. We apply our formulation to GRBs 101011A and 100704A that each might have an associated FRB, and constrained Ω b f IGM to be consistent with the value derived from other methods. The methodology developed here is also applicable, if the redshifts of FRBs not associated with GRBs can be measured by other means.

Compared with polycrystalline films, single-crystalline methylammonium lead halide (MAPbX, X = halogen) perovskite nanowires (NWs) with well-defined structure possess superior optoelectronic properties for optoelectronic applications. However, most of the prepared perovskite NWs exhibit properties below expectations due to poor crystalline quality and rough surfaces. It also remains a challenge to achieve aligned growth of single-crystalline perovskite NWs for integrated device applications. Here, we report a facile fluid-guided antisolvent vapor-assisted crystallization (FGAVC) method for large-scale fabrication of high-quality single-crystalline MAPb(IBr) (x = 0, 0.1, 0.2, 0.3, 0.4) NW arrays. The resultant perovskite NWs showed smooth surfaces due to slow crystallization process and moisture-isolated growth environment. Significantly, photodetectors made from the NW arrays exhibited outstanding performance in respect of ultrahigh responsivity of 12 500 A W, broad linear dynamic rang (LDR) of 150 dB, and robust stability. The responsivity represents the best value ever reported for perovskite-based photodetectors. Moreover, the spectral response of the MAPb(IBr) NW arrays could be sequentially tuned by varying the content of x = 0-0.4. On the basis of this feature, the NW arrays were monolithically integrated to form a unique system for directly measuring light wavelength. Our work would open a new avenue for the fabrication of high-performance, integrated optoelectronic devices from the perovskite NW arrays.

Fast-response and high-sensitivity deep-ultraviolet (DUV) photodetectors with detection wavelength shorter than 320 nm are in high demand due to their potential applications in diverse fields. However, the fabrication processes of DUV detectors based on traditional semiconductor thin films are complicated and costly. Here we report a high-performance DUV photodetector based on graphene quantum dots (GQDs) fabricated via a facile solution process. The devices are capable of detecting DUV light with wavelength as short as 254 nm. With the aid of an asymmetric electrode structure, the device performance could be significantly improved. An on/off ratio of ∼6000 under 254 nm illumination at a relatively weak light intensity of 42 μW cm(-2) is achieved. The devices also exhibit excellent stability and reproducibility with a fast response speed. Given the solution-processing capability of the devices and extraordinary properties of GQDs, the use of GQDs will open up unique opportunities for future high-performance, low-cost DUV photodetectors.

4797wileyonlinelibrary.com photoluminescence quantum yields (PLQY). Organometal halide perovskite quantum dots (OHP-QDs) have recently emerged as bright emitters with narrow-band colors and high PLQY (up to ≈90%). [11][12][13][14] Furthermore, tuning the size or halide compositions of OHP-QDs has enabled fi ne adjustment of their emitting colors across the entire visible spectrum. [ 12,13 ] These attractive characteristics highlight the enormous potential of OHP-QDs as light-emitting materials in electroluminescence (EL) devices.However, OHP-QDs-based LEDs (OQ-LEDs) have been rarely reported, primarily due to the diffi culties in the fabrication of dense fi lms of OHP-QDs for effi cient emitting layers. OHP-QDs are usually prepared by solvent exchange or hot injection methods, but the concentration of the resultant OHP-QDs suspension is low (≈0.5 mg mL −1 ). [ 12,13 ] The subsequent enrichment of the OHP-QDs suspension is diffi cult due to easy aggregation and/or potential damage of OHP-QDs during the concentration process via evaporation. [ 15 ] As a result, it is hard to form a continuous fi lm of OHP-QDs from dilute suspensions using a common spin-coating or printing method. The lack of effi cient fabrications of dense and uniform fi lms of OHP-QDs has greatly hampered their use in high-performance EL devices.In this work, we report one-step fabrication of high-quality uniform fi lms of OHP-QDs by using a simple dip-coating method. By varying the halide composition (X = Br, Cl, and I) or tuning the size of OHP-QDs, we can readily produce uniform fi lms of OHP-QDs emitting with tunable colors from blue to green and red. Based on the OHP-QDs fi lms, we fabricated multicolor higheffi ciency OQ-LEDs with sharp emissions (FWHM smaller than 30 nm). The packaged OQ-LEDs showed robust stability in air of ≈50% humidity for at least 7 d. The remarkable performance characteristics of OQ-LEDs demonstrate the high potential of OHP-QDs as effi cient and color-tunable light emitters for lowcost display, lighting, and optical communication applications.Organometal halide perovskites quantum dots (OHP-QDs) with bright, colortunable, and narrow-band photoluminescence have signifi cant advantages in display, lighting, and laser applications. Due to sparse concentrations and diffi culties in the enrichment of OHP-QDs, production of large-area uniform fi lms of OHP-QDs is a challenging task, which largely impedes their use in electroluminescence devices. Here, a simple dip-coating method has been reported to effectively fabricate large-area uniform fi lms of OHP-QDs. Using this technique, multicolor OHP-QDs light-emitting diodes (OQ-LEDs) emitting in blue, blue-green, green, orange, and red color have been successfully produced by simply tuning the halide composition or size of QDs. The blue, green, and red OQ-LEDs exhibited, respectively, a maximum luminance of 2673, 2398, and 986 cd m −2 at a current effi ciency of 4.01, 3.72, and 1.52 cd A −1 , and an external quantum effi ciency of 1.38%, 1.06%, and 0.53%, which are much bette...

Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux dominated flows. In this letter, we investigate nonthermal particle acceleration during magnetic reconnection in a magnetically-dominated ion-electron plasma using fully kinetic simulations. For an ion-electron plasma with the total magnetization σ 0 = B 2 /(4πn(m i + m e )c 2 ), the magnetization for each species is σ i ∼ σ 0 and σ e ∼ (m i /m e )σ 0 , respectively. We have studied the magnetically dominated regime by varying σ e = 10 3 − 10 5 with initial ion and electron temperatures T i = T e = 5 − 20m e c 2 and mass ratio m i /m e = 1 − 1836. The results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2 − 3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is 1 < s < 2 for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be γ be ∼ σ e and γ bi ∼ σ i , respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices s p are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. We discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds especially the applications for explaining the nonthermal high-energy emissions.

Recent observations by the Fermi satellite suggest that a photosphere emission component is contributing to the observed spectrum of many GRBs. One important question is whether the photosphere component can interpret the typical "Band" function of GRBs with a typical low energy photon spectral index α ∼ −1. We perform a detailed study of the photosphere emission spectrum by progressively introducing several physical ingredients previously not fully incorporated, including the probability distribution of the location of a dynamically evolving photosphere, superposition of emission from an equal-arrival-time "volume" in a continuous wind, the evolution of optical depth of a wind with finite but evolving outer boundary, as well as the effect of different top-hat wind luminosity (L w ) profiles. By assuming a co-moving blackbody spectrum emerging from the photosphere, we find that for an outflow with a constant or increasing L w , the low-energy spectrum below the peak energy (E p ), can be modified to F ν ∼ ν 1.5 (α ∼ +0.5). A softer (−1 < α < +0.5) or flat (α = −1) spectrum can be obtained during the L w decreasing phase or high-latitude-emission-dominated phase. We also study the evolution of E p as a function of wind and photosphere luminosity in this photosphere model. An E p − L tracking pattern can be reproduced if a certain positive dependence between the dimensionless entropy η and L w is introduced. However, the hard-to-soft evolution pattern cannot be reproduced unless a contrived condition is invoked. In order to interpret the Band spectrum, a more complicated photosphere model or a different energy dissipation and radiation mechanism are needed.

Large-area alignment and patterning of small-molecule organic semiconductor micro-/nanocrystals (SMOSNs) at desired locations is a prerequisite for their practical device applications. Recent strategies for alignment and patterning of ordered SMOSNs and their corresponding device applications are highlighted.