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Wide‐coverage near infrared (NIR) phosphor‐converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide‐coverage NIR phosphors. Here, we report the single‐component lanthanide (Ln3+) ions doped Cs2M(In0.95Sb0.05)Cl6 (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd‐Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs2M(In1−xSbx)Cl6 NCs can break the forbidden of f‐f transition of Ln3+, thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln3+. Finally, the wide‐coverage NIR LEDs based on Sm3+, Nd3+, Er3+‐tridoped Cs2K0.5Rb0.5(In0.95Sb0.05)Cl6 NCs are fabricated and employed in the multiplex gas sensing and night‐vision application. [ABSTRACT FROM AUTHOR]

Recently, metal halide perovskites have attracted extensive attentions owing to their superior optoelectronic properties in various device applications, such as solar cells, photodetectors, light‐emitting diodes, lasing, photocatalysis, etc. Up to now, the state‐of‐the‐art developments of perovskite‐based devices are most using the lead‐halide perovskite system. However, the presence of lead (Pb) in these devices, which is insidious bioaccumulative hazard to human bodies, and a poor stability against light, heat, and humidity hamper their practical applications and future commercialization. Therefore, the scientific community is searching for low‐toxicity and environmental‐friendly lead‐free perovskite‐type materials as a back‐up strategy. Among the possible Pb‐substitution strategies, the trivalent bismuth cation (Bi3+) possesses the same electronic configuration as Pb2+, and some emerging Bi‐based perovskites and derivatives are experimentally characterized, which exhibit comparable optoelectronic properties to the Pb‐based perovskites. In this review, a comprehensive overview of currently explored Bi‐based halide perovskites is reported, with an emphasis on their synthesis methods, structural diversity, photophysical properties, and their current and potential applications in various optoelectronic categories. Finally, this review is finished with a critical outlook into the current challenges and development prospects of Bi‐based halide perovskites toward the versatile optoelectronic applications. [ABSTRACT FROM AUTHOR]

Flexible perovskite light‐emitting diodes (LEDs) have been highly expected to realize advanced wearable optoelectronic applications due to the excellent optoelectronic properties of perovskites. However, the poor water and oxygen stability and limited flexibility of perovskites prevent their commercialization and applications in flexible LEDs. Herein, the low‐cost and green biomass materials‐ethyl cellulose (EC) is added in the CsPbI3 nanocrystals (NCs), acting as a cross‐linker between neighboring halide octahedra through hydrogen bonds and PbO coordination bonds. It reduces the defect densities of NCs, leading to improved photoluminescence quantum yield. Simultaneously, the synergistic effect of efficient defect passivation and hydrophobic ether groups of EC significantly improve the environment stability of NCs. Additionally, the favorable flexibility of EC and cross‐linking between EC and perovskite NCs improve the deformation resistance of the perovskite layer with stable photoluminescence and negligible cracks after repeated bending. Consequently, flexible LEDs based on the EC‐passivated CsPbI3 NCs achieved a record external quantum efficiency of 12.1% and significantly enhanced operational stability. Moreover, the flexible LEDs show small luminance degradation after bending for 1000 cycles at a radius of 3 mm, and still retain high performance even after repeatedly bending at an ultrasmall bending radius of 1 mm. [ABSTRACT FROM AUTHOR]

The corrosion tendency and fatigue behavior of a SM480C welded joint in a sea-crossing suspension bridge after twenty-year exposure to a marine environment was investigated in this work. It was found that the corrosion product on the whole surface of the welded joint is loose, with many holes and cracks, which allowing corrosive media enter and reach the surface of the substrate. Localized corrosion occurred in the weld zone (WZ) and the heat-affected zone (HAZ), the maximum depth of localized corrosion in the HAZ reached 1.8 mm, and the maximum local corrosion rate is 0.082 mm/y. By using Bimetallic Conjugation Theory calculations, the galvanic effect of the welded joint was qualified, indicates that HAZ was the most corrosion susceptible area in the welded joint. The galvanic corrosion current on HAZ reached approximately 2 μA, which is much higher than the corrosion of isolated HAZ by about 6.5 times. The corrosion has an obvious influence on the fatigue performance, the elongation of the bridge deck decreases by 40%~70%, and the tensile strength decreases by 4.5%~31.33%. In order to ensure the service safety and avoid premature failure, the average thickness of the corroded bridge deck should not be less than 10 mm under the stress amplitude of 115 MPa. [ABSTRACT FROM AUTHOR]

In this study, a novel deep‐ultraviolet photodetector (DUVPD) based on the hybrids of solution‐processed CsPbX3 (X = Cl, Br):Ce3+ perovskite nanocrystals (PNCs) and plasmonic Al film is presented. The optical absorption strength of the CsPbX3:Ce3+ PNCs is improved by one order of magnitude in the solar‐blind DUV range (200–280 nm) compared with the undoped. First‐principles calculations and Dorenbos's 4f and 5d host referred binding energy (HRBE) models prove that such an improvement results from the 4f–5d transition of Ce3+. The presence of Al film further improves the optical absorption strength in this DUV range due to the plasmonic effect and the metal−perovskite junction between Al film and perovskite. Finally, the DUVPDs based on CsPbCl3:Ce3+/Al hybrids demonstrate extremely high detectivity of 4 × 1013 Jones. This work is the first approach to build up high‐performance DUVPDs based on the doped PNCs. [ABSTRACT FROM AUTHOR]

The performance of perovskite solar cells (PSCs) strongly depends on the electron transport layer (ETL), perovskite absorber, hole transport layer (HTL), and their interfaces. Herein, the first approach to utilize ultrathin 2D titanium‐carbide MXenes (Ti3C2Tx quantum dots, TQD) by engineering the perovskite/TiO2 ETL interface and perovskite absorber and introducing Cu1.8S nanocrystals to perfect the Spiro‐OMeTAD HTL is represented. A significant hysteresis‐free power conversion efficiency improvement from 18.31% to 21.64% of PSCs is achieved after modifications with the enhanced short‐circuit current density, open‐circuit voltages, and fill factor. Various advanced characterizations, including femtosecond transient absorption spectroscopy, electrochemical impedance spectroscopy, and ultraviolet photoelectron spectroscopy, elucidate that the TQD/Cu1.8S significantly contribute to the improved crystalline quality of the perovskite film with its large grain size and improved electron/holes extraction efficiencies at perovskite/ETL and perovskite/HTL interfaces. Furthermore, the long‐time ambient and light stability of PSCs are largely boosted through the TQD and/or Cu1.8S nanocrystals doping, originating from the better crystallization of perovskite, suppressing the film aggregation and crystallization of HTL, and inhibiting the ultraviolet‐induced photocatalysis of the ETL. The findings highlight the TQD and Cu1.8S can act as a superfast electrons and holes tunnel for the optoelectronic devices. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskite quantum dots (QDs) with high photoluminescence quantum yield, narrow spectral bandwidth, and broad spectral tunability have broad applications. However, perovskite QDs suffer from poor stability and the fast anion‐exchange reaction between different halide ions. Herein, we embedded green‐light‐emitting CsPbBr3 QDs and red‐light‐emitting CsPb(Br/I)3 QDs into carboxyl‐containing polymethyl methacrylate (PMMA) by the hot‐injection method. As a result, the as‐prepared perovskite@PMMA composites not only retain high luminescence but also exhibit good water resistance. Moreover, this treatment prevents anion exchange between different halide QD particles in the solid state. The applications in light‐emitting diodes and cellular labeling agents are also carried out to demonstrate their good stability. Waterproof particles: CsPbBr3 particles were successfully encapsulated into carboxyl‐containing PMMA and exhibited good stability in water. The water resistance of 500 nm CsPbBr3@PMMA composites was tested (figure shows photographs of the composites water solution under daylight and UV light). The relative PL emission intensity decreased very slowly over time, retaining 90% of its original value after 12 h exposure to water. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) characteristics of semiconductor CdSe quantum dots (QDs) aggregated on Cu nanowires (NWs) were studied in detail. The PL relaxation dynamic data show that Cu NWs improve the PL intensity of CdSe QDs by accelerating the emission relaxation rate. The temperature-dependent PL data and excitation intensity-dependent PL data suggest that the activation energy of CdSe QDs might decrease due to the excellent heat transfer properties and the plasmon effect of Cu NWs. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A seeded growth method to produce colloidal carbon dots (CDs) through controlling the number of seeds and reaction time, which is demonstrated to be an effective way to tune their optical properties, is developed. Color‐tunable fluorescence of CDs with blue, green, yellow, and orange emissions under UV excitation is achieved by increasing the size of the seed CDs, with the color depending on the size of the π‐conjugated domains. Strong multicolor photoluminescence of powdered samples enables realization of efficient down‐conversion white‐light‐emitting devices with correlated color temperature ranging from 9579 to 2752 K and luminous efficacy from 19 to 51 lm W−1. Moreover, color‐tunable room‐temperature phosphorescence of CD powders is demonstrated in the broad spectral range of 500–600 nm. It is related to the presence of the nitrogen‐containing groups at the surface of CDs, which form interparticle hydrogen bonds to protect the CD triplet states from quenching, and to the existence of the polyvinylpyrrolidone polymer chains at the surface of CDs. The color‐tunable room‐temperature phosphorescence from CDs demonstrated in this work exhibits potential for data encryption. [ABSTRACT FROM AUTHOR]