mixture at 150 °C for 2 min and then Cs-oleate solution (0.4 mL in ODE) was quickly injected. After 5 s, the reaction mixture was cooled by the ice-water bath to room temperature.

The further practical applications of halide perovskite quantum dots (QDs) are blocked by problems of instability and nonradiative Auger recombination manifested as photoluminescence blinking. Here, single core/shell structured perovskite semiconductor QDs are successfully fabricated by capping CsPbBr3 QD core with CdS shell. It is demonstrated that CsPbBr3/CdS core/shell QDs exhibit ultrahigh chemical stability and nonblinking photoluminescence with high quantum yield due to the reduced electronic traps within the core/shell structure. Efficiency of amplified spontaneous emission exhibits obvious enhancement compared to that of pure CsPbBr3 QDs, originating from the mitigated competition between stimulated emission and suppressed nonradiative biexciton Auger recombination. Furthermore, low‐threshold whispering‐gallery‐mode lasing with a high‐quality factor is achieved by incorporating CsPbBr3/CdS QDs into microtubule resonators. Density functional theory (DFT)‐based first‐principles calculations are also performed to reveal the atomic interface structure, which supports the existence of CsPbBr3/CdS structure. An interesting feature of spatially separated charge density at CsPbBr3/CdS interface is found, which may greatly contribute to the suppressed Auger recombination. The results provide a practical approach to improve the stability and suppress the blinking of halide perovskite QDs, which may pave the way for future applications for various optoelectronic devices.

Recent years have witnessed a surge of research in all-inorganic perovskite nanomaterials for solar cells and light emitting diodes due to their higher chemical stability compared to their hybrid organic-inorganic counterparts. Herein, by combining material synthesis, characterization, optical measurement, and density functional theory based first principles calculation, a type of all-inorganic perovskite CsPb 2 Br 5 microplate with superior crystallinity, enhanced stability, and tunable optical properties is reported. With a robust band gap of ≈2.44 eV, CsPb 2 Br 5 microplate exhibits low-threshold amplified spontaneous emission under both one-and two-photon excitation, which is related to its unique spatially distinguished valence/conduction band edge states originating from the intrinsic sandwiched structure. These results are expected to shed new light on future design and development of novel perovskite nanomaterials for optoelectronic devices.

On-chip photonic information processing systems require great research efforts toward miniaturization of the optical components. However, when approaching the classical diffraction limit, conventional dielectric lasers with all dimensions in nanoscale are difficult to realize due to the ultimate miniaturization limit of the cavity length and the extremely high requirement of optical gain to overcome the cavity loss. Herein, we have succeeded in reducing the laser size to subwavelength scale in three dimensions using an individual CsPbBr perovskite nanocuboid. Even though the side length of the nanocuboid laser is only ∼400 nm, single-mode Fabry-Pérot lasing at room temperature with laser thresholds of 40.2 and 374 μJ/cm for one- and two-photon excitation has been achieved, respectively, with the corresponding quality factors of 2075 and 1859. In addition, temperature-insensitive properties from 180 to 380 K have been demonstrated. The physical volume of a CsPbBr nanocuboid laser is only ∼0.49λ (where λ is the lasing wavelength in air). Its three-dimensional subwavelength size, excellent stable lasing performance at room temperature, frequency up-conversion ability, and temperature-insensitive properties may lead to a miniaturized platform for nanolasers and integrated on-chip photonic devices in nanoscale.

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We report on near-GeV electron beam generation from an all-optical cascaded laser wakefield accelerator (LWFA). Electron injection and acceleration are successfully separated and controlled in different LWFA stages by employing two gas cells filled with a He/O2 mixture and pure He gas, respectively. Electrons with a Maxwellian spectrum, generated from the first LWFA assisted by ionization-induced injection, were seeded into the second LWFA with a 3-mm-thick gas cell and accelerated to be a 0.8-GeV quasimonoenergetic electron beam, corresponding to an acceleration gradient of 187  GV/m. The demonstrated scheme paves the way towards the multi-GeV laser accelerators.

IntroductionRecently, halide perovskite nanomaterials have been exploited as revolutionary materials in various research fields due to their low cost, long-range charge transport, high absorption coefficient, and photoluminescence quantum yield. [1][2][3][4][5][6][7][8][9][10][11] The exploration of these materials has been motivated by their potential applications not only in solar cells but also in wide-range tunable emission sources, such as perovskite-based light emitting devices (LEDs), photodetectors, and lasing devices. [5][6][7][8][9][10][11][12][13] Since the first preparation of all-inorganic CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) with tunable bandgaps, [9] CsPbX 3 NCs have been intensively investigated for potential applications in light displays and nanolasers. [7,[9][10][11] Although all-inorganic lead halide perovskite nanomaterials can exhibit outstanding optoelectronic performance, such materials still suffer from poor stability due to a high sensitivity to moisture in the ambient environment and fluctuation of the fluorescence (blinking property), which can hinder further commercial applications. [14][15][16][17] Therefore, improving stability in an air environment is one of the most critical factor that needs to be addressed for the realization of commercially available perovskite-based optoelectronic devices. In addition, blinking, which was first discovered in CdSe quantum dots (QDs) in 1996, [18] is another critical factor limiting the further practical application of 0 D QDs. In general, the blinking effect is the random switching between a bright emission status (neutral states) and dark status due to nonradiative Auger recombination (charged states) driven by charge transfer. [19,20] The blinking phenomenon reduces the practicability of the corresponding perovskite-based optoelectronic devices. Hence, effective suppression of the fluorescence fluctuation of perovskite QDs will advance progress in the lighting and display fields.It has been generally recognized that a coating method is an effective strategy for protecting colloidal nanoparticles from moisture and improving their photostabilities, such as CdSe/ ZnS, [21] CdSe/CdS, [21] and CdTe/ZnS QDs. [22] In addition, as an attractive transparent inorganic material, the silica coating is considered to be a simpler approach to isolate QDs from the air Perovskites have emerged as a class of cutting-edge photovoltaic and lightemitting materials. However, poor stability due to high moisture sensitivity and undesirable blinking severely limits their further application. Here, to solve these problems without destroying optoelectronic performance, a simple process for the fabrication of nonblinking CsPbBr 3 quantum dots (QDs) is investigated. By embedding CsPbBr 3 QDs into waterless silica spheres, the blinking of QDs can be strikingly suppressed, with an effective improvement of the moisture resistance and enhanced photostability. The silica sphere can also prevent anion exchange of different halide elements between perovskite QDs. Ultrasta...

All‐inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion‐exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO2 coated Mn2+ doped CsPbX3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well‐controlled within 2 nm, which gives the CsPbMnX3@SiO2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr3 QDs with green emission and CsPbMnX3@SiO2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light‐emitting diode (LED) is successfully prepared by the combination of a blue on‐chip LED device and the above perovskite mixture. The as‐prepared white LED displays a high luminous efficiency of 68.4 lm W−1 and a high color‐rendering index of Ra = 91, demonstrating their broad future applications in solid‐state lighting fields.