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Aluminum (Al)‐ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium. Nonetheless, given the nascent stage of advancement in Al‐ion batteries (AIBs), attaining electrode materials that can leverage both intercalation capacity and structural stability remains challenging. Herein, we demonstrate a C3N4‐derived layered N,S heteroatom−doped carbon, obtained at different pyrolysis temperatures, as a cathode material for AIBs, encompassing the diffusion−controlled intercalation and surface‐induced capacity with ultrahigh reversibility. The developed layered N,S‐doped corbon (N,S‐C) cathode, synthesized at 900 °C, delivers a specific capacity of 330 mAh g−1 with a relatively high coulombic efficiency of ~85% after 500 cycles under a current density of 0.5 A g−1. Owing to its reinforced adsorption capability and enlarged interlayer spacing by doping N and S heteroatoms, the N,S‐C900 cathode demonstrates outstanding energy storage capacity with excellent rate performance (61 mAh g−1 at 20 A g−1) and ultrahigh reversibility (90 mAh g−1 at 5 A g−1 after 10 000 cycles). [ABSTRACT FROM AUTHOR]

In spite of the flexoelectric effect being a universal phenomenon in the ferroelectric perovskites, the current understanding of flexoelectric aging in ferroelectrics is, actually, rather incomplete. In this paper, we have fabricated a series of Mn-doped BaTiO3 perovskite ceramics (BaTi1–xMnxO3, x = 0.1% and 1%, BTMO) to systematically investigate the corresponding flexoelectric aging behavior by controlling the concentration of Mn. We found that the variation of Mn dopant significantly effects the Curie temperature, dielectric constant, flexoelectric aging, and flexoelectric coefficient of the BTMO ceramics. Especially for the BTMO (0.1%) ceramics, obvious ferroelectric aging and flexoelectric aging phenomenon are observed at room temperature. The main reason for aging of BTMO ceramics is that the doping of Mn introduces oxygen vacancies, which tend to be stable under the action of strain gradient and electric field. Therefore, the results presented in this paper verify that the flexoelectric aging in Mn-doped BTO ceramics is closely related to ferroelectric fatigue. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) are drawing significant attention due to their intriguing photoelectric properties, and these interesting properties are closely related to the number of layers. Obtaining layer-controlled and high-quality TMD is still a challenge. In this context, we use the salt-assisted chemical vapor deposition to grow multilayered MoSe2 flake and characterize it by Raman spectroscopy, second harmonic generation, and photon luminescence. Spectroscopic analysis is an effective way to characterize the stacking order and optoelectronic properties of two-dimensional materials. Notably, the corresponding mapping reflects the film quality and homogeneity. We found that the grown continuous monolayer, bilayer, and trilayer of MoSe2 sheets with different stacking orders exhibit distinctive features. For bilayer MoSe2, the most stable stacking configurations are the AA' and AB order. And the uniformity of the spectroscopy maps demonstrates the high quality of the stacked MoSe2 sheets. [ABSTRACT FROM AUTHOR]

Hydrogen‐doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light‐emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency‐limiting mechanism, hard X‐ray photoelectron spectroscopy is employed to in‐situ monitor annealing‐induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex‐situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag‐ and In‐related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often‐reported deterioration. [ABSTRACT FROM AUTHOR]

2D layered materials with low crystal symmetries exhibit unique anisotropic physical properties. Here the systematic studies on the optical modulation effects of such anisotropic 2D materials to isotropic 2D materials in their stacked van der Waals (vdW) heterostructures are reported. By applying angle‐resolved polarization spectroscopic characterizations on the MoS2/ZrS3 vdW heterostructure, periodic intensity variations of the Raman scattering and photoluminescence (PL) emission modes of monolayer MoS2 are observed, which are closely correlated to the anisotropic optical properties of the underlying ZrS3 layers. Such anisotropic optical modulation effects can be identified with the thickness of ZrS3 reduced to few layers (≈6 nm), and are attributed to the strong birefringence and dichroism effects in ZrS3 that cause reflection difference between its crystal axis, thus modulating the Raman/PL intensities of MoS2 via Fabry–Pérot interference effect. Furthermore, the polarized photocurrent response of the heterostructure is also demonstrated, where its major contribution originates from MoS2. This work develops a new methodology to tune the light–matter interactions and properties of isotropic 2D materials by the combination with anisotropic 2D materials, which substantially broadens the application of low symmetry layered materials in polarization sensitive optoelectronic devices. [ABSTRACT FROM AUTHOR]

The synthesis of monodisperse, surfactant-free, Ni-substituted ZnO nanocrystallites (ZnO:Ni) by the mild solvolysis of heterobimetallic Ni4− xZn xO4 cubane-like precursors ( x=1-3) in benzylamine is reported. Ni4− xZn xO4 was grafted by electrophoretic deposition onto fluorine-doped tin oxide glass substrates and used as an active and stable working electrode for water oxidation. Upon the application of a voltage at the electrodes, the ZnO:Ni precatalyst leads to an active composite material that can oxidize water (>15 h) with an increasing catalytic current. In contrast, the performance of homometallic NiO reference materials decreases rapidly over time and is surpassed by the composite from the ZnO:Ni precatalyst in terms of both stability and activity. Extensive characterization of the as-prepared and activated ZnO:Ni precatalyst by using hard X-ray photoelectron spectroscopy revealed that the excellent performance of the electrode material is because of the formation of a unique self-supported turbostratically disordered mixture of γ-NiOOH/α-Ni(OH)2-like phases from the rapid dissolution of ZnII in the ZnO:Ni precatalyst into the electrolyte during activation. [ABSTRACT FROM AUTHOR]

Crystalline Indan-C60 and its photovoltaic application were studied. Microsheets and aloe-like micro-nano superstructures can be assembled from Indan-C60. Indan-PC61BM derived from Indan-C60 was further investigated as an acceptor for OPV devices, which shows a higher Voc, FF, and PCE than those obtained using PC61BM. [ABSTRACT FROM AUTHOR]

Exploring high-κ gate dielectrics is crucial for the achievement of high-performance field-effect transistors (FETs). Here, we report the synthesis of a few-layer wide bandgap semiconductor gallium thiophosphate (GaPS 4 ), which can be easily mechanically exfoliated from a bulk material. The few-layered GaPS 4 flakes exhibit a relative dielectric constant of approximately 5.3. Two-dimensional (2D) van der Waals heterostructure FETs utilizing atomically smooth GaPS 4 flakes as the top-gate dielectric layer and MoS 2 as the channel material were fabricated, showing a high on-off ratio exceeding 10 7 with a subthreshold swing as low as 80 mV per decade. Our findings indicate that few-layer GaPS 4 is a high-performance dielectric candidate for two-dimensional transistors, which enrich the high-κ 2D community and pave the way for fabricating modern electronic devices.

Phase transitions play an important role in tuning the physical properties of two-dimensional (2D) materials as well as developing their high-performance device applications. Here, we reported the observation of a phase transition in few-layered MoTe 2 flakes by the irradiation of gallium (Ga + ) ions using a focused ion beam (FIB) system. The semiconducting 2H phase of MoTe 2 can be controllably converted to the metallic 1T'-like phase via Te defect engineering during irradiations. By taking advantage of the nanometer-sized Ga + ion probe proved by FIB, in-plane 1T'-2H homojunctions of MoTe 2 at submicrometer scale can be fabricated. Furthermore, we demonstrate the improvement of device performance (on-state current over 2 orders of magnitude higher) in MoTe 2 transistors using the patterned 1T'-like phase regions as contact electrodes. Our study provides a new strategy to drive the phase transitions in MoTe 2 , tune their properties, and develop high-performance devices, which also extends the applications of FIB technology in 2D materials and their devices.

Two-dimensional (2D) layered materials with low crystal symmetries have exhibited unique anisotropic physical properties. Here, we report systematic studies on the photoresponse of field effect transistors (FETs) fabricated using quasi-one-dimensional ZrS 3 nanoflakes. The as-fabricated phototransistors exhibit a broadband photocurrent response from ultraviolet to visible regions, where the responsivity and detectivity can be enhanced via additional gate voltages. Furthermore, benefiting from the strong in-plane anisotropy of ZrS 3 , we observe a gate-voltage and illumination wavelength-dependent polarized photocurrent response, while its sub-millisecond-time response speed is also polarization-dependent. Our results demonstrate the flexible tunability of photodetectors based on anisotropic layered semiconductors, which substantially broadens the application of low symmetry layered materials in polarization-sensitive optoelectronic devices.

The gate dielectric layer is an important component in building a field-effect transistor. Here, we report the synthesis of a layered rhombohedral-structured MnAl 2 S 4 crystal, which can be mechanically exfoliated down to the monolayer limit. The dielectric properties of few-layered MnAl 2 S 4 flakes are systematically investigated, whereby they exhibit a relative dielectric constant of over 6 and an electric breakdown field of around 3.9 MV/cm. The atomically smooth thin MnAl 2 S 4 flakes are then applied as a dielectric top gate layer to realize a two-dimensional van der Waals stacked field-effect transistor, which uses MoS 2 as a channel material. The fabricated transistor can be operated at a small drain-source voltage of 0.1 V and gate voltages within ranges of ±2 V, which exhibit a large on-off ratio over 10 7 at 0.5 V and a low subthreshold swing value of 80 mV/dec. Our work demonstrates that the few-layered MnAl 2 S 4 can work as a dielectric layer to realize high-performance two-dimensional transistors, and thus broadens the research on high-κ 2D materials and may provide new opportunities in developing low-dimensional electronic devices with a low power consumption in the future.

The limited long-term stability of metal halide perovskite-based solar cells is a bottleneck in their drive toward widespread commercial adaptation. The organic hole-transport materials (HTMs) have been implicated in the degradation, and metal oxide layers are proposed as alternatives. One of the most prominent metal oxide HTM in organic photovoltaics is MoO 3 . However, the use of MoO 3 as HTM in metal halide perovskite-based devices causes a severe solar cell deterioration. Thus, the formation of the MoO 3 /CH 3 NH 3 PbI 3- x Cl x (MAPbI 3- x Cl x ) heterojunction is systematically studied by synchrotron-based hard X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. Upon MoO 3 deposition, significant chemical interaction is induced at the MoO 3 /MAPbI 3- x Cl x interface: substoichiometric molybdenum oxide is present, and the perovskite decomposes in the proximity of the interface, leading to accumulation of PbI 2 on the MoO 3 cover layer. Furthermore, we find evidence for the formation of new compounds such as PbMoO 4 , PbN 2 O 2 , and PbO as a result of the MAPbI 3- x Cl x decomposition and suggest chemical reaction pathways to describe the underlying mechanism. These findings suggest that the (direct) MoO 3 /MAPbI 3- x Cl x interface may be inherently unstable. It provides an explanation for the low power conversion efficiencies of metal halide perovskite solar cells that use MoO 3 as a hole-transport material and in which there is a direct contact between MoO 3 and perovskite.

The chemical and electronic structure of MoO 3 thin films is monitored by synchrotron-based hard X-ray photoelectron spectroscopy while annealing from room temperature to 310 °C. Color-coded 2D intensity maps of the Mo 3d and O 1s and valence band maximum (VBM) spectra show the evolution of the annealing-induced changes. Broadening of the Mo 3d and O 1s spectra indicate the reduction of MoO 3 . At moderate temperatures (120-200 °C), we find spectral evidence for the formation of Mo 5+ and at higher temperatures (>165 °C) also of Mo 4+ states. These states can be related to the spectral intensity above the VBM attributed to O vacancy induced gap states caused by partial filling of initially unoccupied Mo 4d-derived states. A clear relation between annealing temperature and the induced changes in the chemical and electronic structure suggests this approach as a route for deliberate tuning of MoO 3 thin-film properties., Competing Interests: The authors declare no competing financial interest.