Monolayer transition metal dichalcogenides (TMDs) have become essential two-dimensional materials for their perspectives in engineering next-generation electronics. For related applications, the controlled growth of large-area uniform monolayer TMDs is crucial, while it remains challenging. Herein, we report the direct synthesis of 6-inch uniform monolayer molybdenum disulfide on the solid soda-lime glass, through a designed face-to-face metal-precursor supply route in a facile chemical vapor deposition process. We find that the highly uniform monolayer film, with the composite domains possessing an edge length larger than 400 µm, can be achieved within a quite short time of 8 min. This highly efficient growth is proven to be facilitated by sodium catalysts that are homogenously distributed in glass, according to our experimental facts and density functional theory calculations. This work provides insights into the batch production of highly uniform TMD films on the functional glass substrate with the advantages of low cost, easily transferrable, and compatible with direct applications.

storage, sodium-ion batteries (NIBs) are attracting more attention because of the abundant sodium resource. [7][8][9] In comparison to the natural abundance of lithium (20 ppm) in the Earth's crust, the abundances of Na (23 000 ppm) and K (17 000 ppm) seem infinite. [10][11][12] Unlike NIBs, really few researches are focused on potassium-ion batteries (KIBs) in a long-trem period. Till last two years, the new concept of KIBs has begun to gain much more attention. [13][14][15][16][17] The advantages of KIBs are obvious: the abundant resource and the closer redox potential of K/K + (−2.93 V vs standard hydrogen electrode) to that of Li/Li + (−3.04 V) than that of Na/Na + (−2.71 V), implying their higher voltage plateau and energy density.Different K ion anode materials such as graphite, [13,18,19] nitrogen-doped graphene, [14,20] Prussian Blue, [21][22][23] and transition metal compound [24,25] have been

www.advancedsciencenews.com www.small-methods.com an inorganic or organic cation (Cs + , CH 3 NH 3 + , NH 2 CHNH 2 + , etc.), M is a divalent metallic cation (Pb 2+ , Sn 2+ , Mn 2+ , Fe 2+ , etc.), and X is halogen anion (I − , Br − , Cl − ). [28][29][30] Since 2009, perovskites have gained worldwide attention due to their unprecedented success in photovoltaics. [31][32][33][34][35][36] The power conversion of solution-processed CH 3 NH 3 PbX 3 (MAPbX 3 ) perovskite solar cells has increased from 3.8% to 22.1% within a few years. [37][38][39][40][41][42] Although there is still some debate, it is widely accepted that the high power conversion efficiency of MAPbX 3 is attributed to the high absorption coefficient (≈10 4 cm −1 ), balanced and long diffusion length (≈100 nm to 100 µm), low density of defect states (10 9 -10 10 cm −3 ) and bipolar carrier-transport property. [31,33,34] As a direct-bandgap semiconductor, perovskites also show wide-band tunable emission color and high quantum yield, holding important potential applications in light sources, for example. [40,[43][44][45] Prior to the rapidly developing studies in solar cells, perovskites have been studied as light-emittingdiode (LED) devices for a long time. [46][47][48] In particular, recent studies on photophysical properties, structure engineering, and device development have led to the rapid progress of coherent and incoherent perovskite photonic sources. [44,[49][50][51][52][53][54][55] For example, several groups have demonstrated perovskite LEDs with external quantum efficiency of ≈8-12% using solutionprocessed and thermally evaporated quasi-two-dimensional perovskite thin films, etc. [44,51] Furthermore, perovskite nanostructures including NWs, NPs, and quantum dots (QDs) are also attracting more and more attention for exploring nanophotonic and quantum devices, including single-photon sources, optical detectors, transistors, optical sensors, etc. [56][57][58][59] In a nutshell, despite the Pb toxicity and poor stability, perovskites have been attracting more and more attention in divergent research areas. These fundamental studies on and applications of perovskite photonic sources could extensively push forward our present energy and communication technology.With high absorption coefficient and low density of defects, perovskites are excellent gain materials for the development of high-performance lasing devices. More interestingly, thanks to the long-distance ambipolar carrier-transport properties, perovskites could greatly raise the possibility of realizing electrically driven microlasers and nanolasers. In 2014, Xing et al. demonstrated the first amplification of spontaneous emission (ASE) of CH 3 NH 3 PbX 3 perovskite thin film, which had been solution processed at low temperature. [60] Through embedding CH 3 NH 3 PbI 3−x Cl x perovskite thin films into a distributed Bragg reflector Fabry-Pérot (F-P) cavity, Deschler et al. demonstrated room-temperature perovskite lasing. [49] Beyond these thin films, perovskite nanostructures including NP...

approach to realize new functionalities through facile van der Waals coupled 2D layers. [6] Owing to the large dielectric mismatch between the inorganic and organic layers, the quasi-2D RPPs naturally form quantum well structures, in which, the inorganic and organic layers serve as potential wells and barriers, respectively. [7] Moreover, these quantum confined structures impart the appealing characteristics of improved environmental stability and enhanced exciton confinement. [2] These make the quasi-2D RPPs promising for solar cell and light-emitting diode (LED) applications. [5,[8][9][10] Recently, the amplified spontaneous emission (ASE) and lasing behaviors of 2D RPPs have been demonstrated. [11][12][13][14][15][16][17] However, the lasing is mostly obtained from solution-processed spin-coated thin films, in which multiple RPP components inevitably form with different bandgaps that drive cascade carrier transfer and may reshape the build-up of population inversion. [11,14,15,18] Also, the development of continuous-wave or electrically driven RPP lasers central for practical applications is still challenging. The exploitation of homologous RPP lasers is of great importance to gain further insights into the intrinsic lasing mechanisms of these quantum well-like structures as well as the design of low-threshold 2D 2D Ruddlesden-Popper perovskites (RPPs) have aroused growing attention in light harvesting and emission applications owing to their high environmental stability. Recently, coherent light emission of RPPs was reported, however mostly from inhomologous thin films that involve cascade intercompositional energy transfer. Lasing and fundamental understanding of intrinsic laser dynamics in homologous RPPs free from intercompositional energy transfer is still inadequate. Herein, the lasing and loss mechanisms of homologous 2D (BA) 2 (MA) n −1 Pb n I 3n+1 RPP thin flakes mechanically exfoliated from the bulk crystal are reported. Multicolor lasing is achieved from the large-n RPPs (n ≥ 3) in the spectral range of 620-680 nm but not from small-n RPPs (n ≤ 2) even down to 78 K. With decreasing n, the lasing threshold increases significantly and the characteristic temperature decreases as 49, 25, and 20 K for n = 5, 4, and 3, respectively. The n-engineered lasing behaviors are attributed to the stronger Auger recombination and exciton-phonon interaction as a result of the enhanced quantum confinement in the smaller-n perovskites. These results not only advance the fundamental understanding of loss mechanisms in both inhomologous and homologous RPP lasers but also provide insights into developing low-threshold, substrate-free, and multicolor 2D semiconductor microlasers.2D Ruddlesden-Popper perovskites (RPPs), with the general chemical formula of L 2 (MA) n−1 M n X 3n+1 , are composed of welldefined inorganic layers with corner connected [MX 6 ] 4− octahedra and long organic chains (L + ) intercalated between these inorganic fragments. [1][2][3][4][5] This structure promises a viable

Lead halide perovskites have emerged as excellent optical gain materials for solution-processable and flexible lasers. Recently, continuous-wave (CW) optically driven lasing was established in perovskite crystals; however, the mechanism of low-threshold operation is still disputed. In this study, CW-pumped lasing from one-dimensional CsPbBr3 nanoribbons (NBs) with a threshold of ∼130 W cm–2 is demonstrated, which can be ascribed to the large refractive index induced by the exciton–polariton (EP) effect. Increasing the temperature reduces the exciton fraction of EPs, which decreases the group and phase refractive indices and inhibits lasing above 100 K. Thermal management, including reducing the NB height to ∼120 ± 60 nm and adopting a high-thermal-conductivity sink, e.g., sapphire, is critical for CW-driven lasing, even at cryogenic temperatures. These results reveal the nature of ultralow-threshold lasing with CsPbBr3 and provide insights into the construction of room-temperature CW and electrically driven perovskite macro/microlasers.

1D nanowires of all-inorganic lead halide perovskites represent a good architecture for the development of polarization-sensitive optoelectronic devices due to their high absorption efficient, emission yield, and dielectric constants. However, among as-fabricated perovskite nanowires with the lateral dimensions of hundreds nanometers so far, the optical anisotropy is hindered and rarely explored owing to the invalidating of electrostatic dielectric mismatch in the physical dimensions. Here, well-aligned CsPbBr and CsPbCl nanowires with thickness T down to 15 and 7 nm, respectively, are synthesized using a vapor phase van der Waals epitaxial method. Strong emission anisotropy with polarization ratio up to ≈0.78 is demonstrated in the nanowires with T < 40 nm due to the electrostatic dielectric confinement. With the increasing of thickness, the polarization ratio remarkably reduces monotonously to ≈0.17 until T ≈140 nm; and further oscillates in a small amplitude owing to the wave characteristic of light. These findings not only represent a demonstration of perovskite-based polarization-sensitive light sources, but also advance fundamental understanding of their polarization properties of perovskite nanowires.

2D metallic TaS is acting as an ideal platform for exploring fundamental physical issues (superconductivity, charge-density wave, etc.) and for engineering novel applications in energy-related fields. The batch synthesis of high-quality TaS nanosheets with a specific phase is crucial for such issues. Herein, the successful synthesis of novel vertically oriented 1T-TaS nanosheets on nanoporous gold substrates is reported, via a facile chemical vapor deposition route. By virtue of the abundant edge sites and excellent electrical transport property, such vertical 1T-TaS is employed as high-efficiency electrocatalysts in the hydrogen evolution reaction, featured with rather low Tafel slopes ≈67-82 mV dec and an ultrahigh exchange current density ≈67.61 µA cm . The influence of phase states of 1T- and 2H-TaS on the catalytic activity is also discussed with the combination of density functional theory calculations. This work hereby provides fundamental insights into the controllable syntheses and electrocatalytic applications of vertical 1T-TaS nanosheets achieved through the substrate engineering.

Two-dimensional (2D) metal−semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal−semiconductor TMDC vertical stacks (VSe 2 /MX 2 , M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe 2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX 2 underlayer to form VSe 2 /MX 2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe 2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe 2 and p-type WSe 2 or n-type MoSe 2 , respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and potential applications of such 2D metal−semiconductor stacks in next-generation electronics, optoelectronic devices, and energy-related fields.