Interface engineering is an efficient method for improving the performance of inverted planar heterojunction perovskite solar cells (PSCs). In this paper, the PSCs were modified by introducing mild argon plasma post-treatment on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The power conversion efficiency (PCE) was enhanced up to 12.17%, compared with 9.55% of the reference device without interlayer modification. We found that argon plasma treatment on the PEDOT:PSS layer effectively increases its conductivity due to the modification of the PSS ratio in the film. The argon plasma treatment time directly affects the surface morphologies and contact angles of the PEDOT:PSS layer and therefore optimises the uniformity of the PEDOT:PSS layer on the nanometer-scale. The improvement in the chemical compositions and film morphologies of PEDOT:PSS could be beneficial to enhancing the wettability and retarding the carrier recombination. The open-circuit voltage (Voc) and short circuit current density (Jsc) of PSCs based on the treated PEDOT:PSS were both improved, resulting in the enhancement of PCE.

AbstractDue to the predicted excellent electronic properties superior to group VIB (Mo and W) transition metal dichalcogenides (TMDs), group IVB TMDs have enormous potential in nanoelectronics. Here, the synthesis of ultrathin HfS2 flakes via space-confined chemical vapor deposition, realized by an inner quartz tube, is demonstrated. Moreover, the effect of key growth parameters including the dimensions of confined space and deposition temperature on the growth behavior of products is systematically studied. Typical as-synthesized HfS2 is a hexagonal-like flake with a smallest thickness of ≈1.2 nm (bilayer) and an edge size of ≈5 µm. The photodetector based on as-synthesized HfS2 flakes demonstrates excellent optoelectronic performance with a fast photoresponse time (55 ms), which is attributed to the high-quality crystal structure obtained at a high deposition temperature and the ultraclean interface between HfS2 and the mica substrate. With such properties HfS2 holds great potential for optoelectronics applications.

CuO and Cu2O are non-noble transition metal oxide supercapacitive materials with high theoretical specific capacitances above 1800 F g−1. In this work, by adjusting organic additives of a colloidal system, Cu, Cu2O, and CuO are grown in situ on nickel foam. CuO exhibits a specific capacitance of 1355 F g−1 at 2 A g−1 in 3 m KOH, a value well above those of Cu and Cu2O (<500 F g−1), and is superior to other known CuO electrodes. The CuO electrode exhibits 70% of its initial capacity, and the Columbic efficiency remains ≈100% after 7000 cycles at 4 A g−1. Cu2O exhibits the worst electrochemical performance, mainly due to the inactive barrier layer forming on the surface. This work provides an efficient synthetic platform for both comparable supercapacitive studies and cost-effective electrochemical energy storage applications.

AbstractWith the continuous exploration of 2D transition metal dichalcogenides (TMDs), novel high-performance devices based on the remarkable electronic and optoelectronic natures of 2D TMDs are increasingly emerging. As fresh blood of 2D TMD family, anisotropic MTe2 and ReX2 (M = Mo, W, and X = S, Se) have drawn increasing attention owing to their low-symmetry structures and charming properties of mechanics, electronics, and optoelectronics, which are suitable for the applications of field-effect transistors (FETs), photodetectors, thermoelectric and piezoelectric applications, especially catering to anisotropic devices. Herein, a comprehensive review is introduced, concentrating on their recent progresses and various applications in recent years. First, the crystalline structure and the origin of the strong anisotropy characterized by various techniques are discussed. Specifically, the preparation of these 2D materials is presented and various growth methods are summarized. Then, high-performance applications of these anisotropic TMDs, including FETs, photodetectors, and thermoelectric and piezoelectric applications are discussed. Finally, the conclusion and outlook of these applications are proposed.

2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small bandgap (<2 eV), the application of traditional TMDs into solar-blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS3 nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific Ag modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few-layered 2D NiPS3 nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 1012 Jones, outperforming some traditional wide-bandgap UV detectors. The wavelength-dependent photoresponsivity measurement allows the direct observation of an admirable cut-off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection.

The exploration of localized surface plasmon resonance (LSPR) beyond the usual visible waveband, for example within the ultraviolet (UV) or deep-ultraviolet (D-UV) regions, is of great significance due to its unique applications in secret communications and optics. However, it is still challenging to universally synthesize the corresponding metal nanostructures due to their high activity. Herein, we report a universal, eco-friendly, facile and rapid synthesis of various nano-metals encapsulated by ultrathin carbon shells, significantly with a remarkable deep-UV LSPR characteristic, via a liquid-phase laser fabrication method. Firstly, a new generation of the laser ablation in liquid (LAL) method has been developed with an emphasis on the elaborate selection of solvents to generate ultrathin carbon shells, and hence to stabilize the formed metal nanocrystals. As a result, a series of metal@carbon nanoparticles (NPs), including Cr@C, Ti@C, Fe@C, V@C, Al@C, Sn@C, Mn@C and Pd@C, can be fabricated by this modified LAL method. Interestingly, these NPs exhibit LSPR peaks in the range of 200–330 nm, which are very rare for localized surface plasmon resonance. Consequently, the UV plasmonic effects of these metal@carbon NPs were demonstrated both by the observed enhancement in UV photoluminescence (PL) from the carbon nanoshells and by the improvement of the photo-responsivity of UV GaN photodetectors. This work could provide a universal method for carbon shelled metal NPs and expand plasmonics into the D-UV waveband.

Two-dimensional materials (2DMs) are competitive candidates in replacing or supplementing conventional semiconductors owing to their atomically uniform thickness. However, current conventional micro/nanofabrication technologies realize hardly ultrashort channel and integration, especially for sub-10 nm. Meanwhile, experimental device performance associated with the scaling of dimension needs to be investigated, due to the short channel effects. Here, we show a novel and universal technological method to fabricate sub-10 nm gaps with sharp edges and steep sidewalls. The realization of sub-10 nm gaps derives from a corrosion crack along the cleavage plane of Bi2O3. By this method, ultrathin body field-effect transistors (FETs), consisting of 8.2 nm channel length, 6 nm high-k dielectric, and 0.7 nm monolayer MoS2, exhibit no obvious short channel effects. The corresponding current on/off ratio and subthreshold swing reaches to 106 and 140 mV/dec, respectively. Moreover, integrated circuits with sub-10 nm channel are capable of operating as digital inverters with high voltage gain. The results suggest our technological method can be used to fabricate the ultrashort channel nanopatterns, build the experimental groundwork for 2DMs FETs with sub-10 nm channel length and 2DMs integrated circuits, and offer new potential opportunities for large-scale device constructions and applications.Keywords: 2D materials; field-effect transistors; nanopatterns; Sub-10 nm; very-large-scale integration;

High-performance electrocatalysts for water splitting at all pH values have attracted considerable interest in the field of sustainable hydrogen evolution. Herein, we report an efficient electrocatalyst with a nanocrystalline cobalt phosphide (CoP) network for water splitting in the pH range of 0–14. The novel flexible electrocatalyst is derived from a desirable nanocrystalline CoP network grown on a conductive Hastelloy belt. This kind of self-supported CoP network is directly used as an electrocatalytic cathode for hydrogen evolution. The nanocrystalline network structure results in superior performance with a low onset overpotential of ~45 mV over a broad pH range of 0 to 14 and affords a catalytic current density of 100 mA·cm−2 even in neutral media. The CoP network exhibits excellent catalytic properties not only at extreme pH values (0 and 14) but also in neutral media (pH = 7), which is comparable to the behavior of state-of-the-art platinum-based metals. The system exhibits an excellent flexible property and maintains remarkable catalytic stability during continuous 100-h-long electrolysis even after 100 cycles of bending/extending from 100° to 250°.

In order to realize the promising potential of MoS2 as the alternative channel material, it is essential to achieve high-performance top-gated MoS2 field-effect transistors (FETs), especially since the back-gated counterparts cannot control the device individually. Although uniform high-k dielectric films, such as HfO2, can be obtained through the introduction of artificial nucleation sites on the MoS2 channel to fabricate top-gated FETs, this would inevitably degrade their channel/dielectric interface quality, induce significant charged impurity scattering and lower carrier mobility. In this work, MoS2 FETs are fabricated using a self-aligned nanowire top-gate, which can effectively reduce the charged impurity scattering on the surface of MoS2. Specifically, the fabricated short-channel devices exhibit impressive electrical performances, such as the high on/off current ratio, low interface trap density, and near-ideal subthreshold slope at room temperature. In addition, the short channel effect is systematically analyzed, which indicates that the phonon scattering can be the dominant scattering mechanism in the devices when the amount of charged impurities is effectively reduced with the self-aligned nanowire gate. All these provide an enhanced fabrication scheme to attain top-gated short-channel devices with the optimized interface and potentially to explore their corresponding performance limits.

•N-doped graphitic C-Co scaffold (C-Co-N) derived from MOF is synthesized.•Se is immobilized with C-Co-N via physical/chemical molecular interaction.•In-situ Raman spectroscopy and density functional theory simulation are employed.•C-Co-N/Se cathode with 76.5 wt% Se delivers superior electrochemical performances.Three-dimensional, porous graphitic carbon co-doped with cobalt and nitrogen (C-Co-N) is prepared with metal-organic framework (MOF) and employed as Lewis base matrix to host selenium. Owing to the unique structure with abundant micro/meso-pores, the highly-conductive C-Co-N matrix provides highly-efficient channels for electron transfer and ionic diffusion, and sufficient surface area for loading of selenium nanoparticles while mitigating dissolution of polyselenides and suppressing volume expansion. The homogenous distribution of cobalt nanoparticles and nitrogen-group in C-Co-N composite immobilize polyselenides through strong chemical interaction in the operation of Li-Se batteries. With a very high Se loading of 76.5 wt%, the C-Co-N/Se cathode delivers superior electrochemical performance with an ultrahigh reversible capacity of 672.3 mAh g−1 (99.6% of the theoretical value) and a capacity of 574.2 mAh g−1 after 200 cycles, giving a capacity fading of only 0.07% per cycle and a nearly 100% Columbic efficiency. In-situ Raman spectroscopy and density functional theory simulations are employed to investigate the Se (de)lithiation mechanism at the electrolyte/cathode interface, and confirm that the structure and composition of C-Co-N scaffold give rise to efficient cathode host for high-performance Se-based cathodes with dramatically reduced capacity fading.

A facile route for the fabrication of a novel ZnS shell/Cu–Zn–In–S nanosheets/TiO2 nanorods heterojunction was reported in this work. Especially, the quaternary Cu–Zn–In–S nanosheets were synthesized creatively from the ternary ZnIn2S4 nanosheets by partial exchange reaction, leading to substantial enhancement on the light absorbance. Such heterojunction could increase the surface area and accelerate the charge transfer resulting from its hierarchical 2D/1D structure and favorable energy bands. Moreover, the ZnS coating acted as a passivation layer as well as a potential barrier, significantly suppressing the interface recombination. The above synergistic effects resulted in the largely increased photocurrent density from 0.34 mA cm–2 for the pristine TiO2 to 0.81 mA cm–2 for the heterojunction at 0.8 V vs RHE.Keywords: Cu−Zn−In−S; heterostructure; ion exchange; nanosheets; photoelectrochemical; TiO2; water splitting; ZnIn2S4

In this study, we systematically investigated the composition dependence of the phase structure, microstructure, and electrical properties of (Ba0.94Ca0.06)(Ti1–xMx)O3 (M = Sn, Hf, Zr) ceramics synthesised by the conventional solid-state reaction method. The phase boundary type strongly depends on the composition, and then different electrical properties were exhibited. The addition of Hf and Zr can more quickly shift phase transition temperatures (TR–O and TO–T) to a higher temperature with respect to Sn, leading to the formation of different phase boundaries. In addition, different phase boundaries can also be affected by their doped contents. The R–O and O–T phase boundaries can be shown in the Sn-doped ceramics with x = 0.10, and the R–O phase boundary can exist in the Hf (x = 0.07) or Zr (x = 0.075)-doped ceramics. A high piezoelectric property of d33 = 600 pC N−1 can be achieved in the Sn-doped ceramics due to the involvement of converging R–O/O–T phase boundaries, an enhanced ferroelectric performance with Pr = 14.54 μC cm−2 and Ec = 1.82 kV cm−1 can be attained in the Zr-doped ceramics, and Hf would benefit from obtaining a large strain behaviour (∼0.20%). We believe that the electrical properties and the related physical mechanisms of BaTiO3-based ceramics can be well unveiled by studying their chemical modification behavior.

•Simplified buffer structure for YBCO coated conductors.•Growth of biaxially textured MgO films on flexible amorphous substrates.•Studying the influence of film deposition rate, ion energy and ion beam flux on the development of biaxial texture.•Demonstrating highly oriented YBCO films with a critical current density of 2.4 MA/cm2 at self-field and 77 K.A much simplified buffer structure, including a three-layer stack of LaMnO3/MgO/composite Y2O3–Al2O3, was proposed for high performance YBa2Cu3O7-δ (YBCO) coated conductors. In this structure, biaxially textured MgO films were prepared on solution deposition planarized amorphous substrate through ion-beam-assisted deposition (IBAD) technology. By the use of in situ reflection high-energy electron diffraction monitor, X-ray diffraction and atomic force microscope, the influence of deposition parameters, such as film deposition rate, ion penetrate energy and ion beam flux, on crystalline orientation, texture, lattice parameter and surface morphology was systematically investigated. Moreover, stopping and range of ion in mater simulation was performed to study the effects of ion bombardment on MgO films. By optimizing IBAD process parameters, the best biaxial texture showed ω-scan of (002) MgO and Φ-scan of (220) MgO yield full width at half maximum values of 2.4° and 3.7°, indicating excellent biaxial texture. Subsequently, LaMnO3 films were directly deposited on the IBAD-MgO template to improve the lattice mismatch between MgO and YBCO. Finally, YBCO films grown on this simplified buffer template exhibited a critical current density of 2.4 MA/cm2 at 77 K and self-field, demonstrating the feasibility of this buffer structure.

•A new nano-structured optical hetero-coating for ultraviolet protection.•GZO films were firstly prepared by metal organic deposition (MOD).•Modulating the reflectivity of Ge/GZO system by changing Ge thickness.•Strong interference effect and absorption resonance result in coloring effect.A new nano-structured optical hetero-coating, i.e., combination of absorptive Ge and transparent conductive oxide Ga-doped zinc oxide (GZO) film has been developed for ultraviolet (UV) protection. GZO (3% Ga) film spin-coated by metal organic deposition (MOD) acts as a UV light absorber because of its large band gap, while Ge film deposited by electron-beam evaporation is used as visible light absorber. Modulating the nanometer-level Ge thickness causes the prominent variations of transmittance and reflectivity, therefore coloring Ge/GZO system, ascribed to strong interference effect and therefore absorption resonance.

LaMnO3 (LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y2O3/Hastelloy tape. The effects of the surface roughness of LMO on the crystallization, texture and superconducting properties of YBa2Cu3O7−δ (YBCO) films were systematically investigated. The crystallization and epitaxial texture of resulting YBCO film are significantly improved with the surface roughness of LMO decreasing from 7.0 to 1.3 nm. High-performance YBCO-coated conductors could be achieved if surface roughness of LMO cap layer is well controlled.

We have successfully employed metal-organic chemical vapor deposition (MOCVD) technique to simultaneously deposit double-sided YBa2Cu3O7−δ (YBCO) films on both sides of Y2O3/yttria-stabilized zirconia (YSZ)/CeO2 (YYC) buffered biaxially textured Ni-5 at.% W substrates, which is of great prospect to cut the production cost of YBCO coated conductors. X-ray diffraction analysis revealed that both sides of YBCO film were purely c-axis oriented and highly textured. The ω-scan of (005) YBCO and ϕ-scan of (103) YBCO yielded full width at half maximum (FWHM) values of 4.9° and 6.6° for one side of double-sided YBCO film, respectively, as well as 4.4° and 6.4° for the other side. The current transportation measurements performed on such double-sided 500 nm-thickness YBCO films showed the self-field critical current density (Jc) at 77 K of 0.6 MA/cm2 and 1.2 MA/cm2, respectively. Further research is in the process of exploring new solution to improve the Jc in practice.

Metal–organic chemical vapor deposition was applied to fabricate YBa2Cu3O7−δ (YBCO) films on single-crystal LaAlO3 (001) substrates for its high deposition rate, easy adjustment on film composition, and low requirement on vacuum apparatus. The effects of Cu(tmhd)2 concentration in the precursor on the properties of YBCO films were systematically investigated. X-ray diffraction (XRD) reveals that the mole ratio of Cu/Ba in the precursor from 0.77 to 0.97 is helpful to improve the crystallization and out-of-plane orientation of YBCO films; however, it hardly affects the in-plane texture. Scanning electron microscope (SEM) shows the dense, crack-free but rough surface, on which there are Cu–O and Ba–Cu–O outgrowths identified by energy-dispersive spectrometer (EDS). As the mole ratio of Cu/Ba increasing, the average size of Ba–Cu–O precipitates keeps increasing and the film composition becomes inhomogeneous at the mole ratio of Cu/Ba of 0.97. The 250 nm thick YBCO film prepared at the mole ratio of Cu/Ba of 0.91 shows the critical current density (Jc) of 4.0 MA·cm−2 (77 K, 0 T).

The biaxially textured ion beam-assisted deposited (IBAD)-MgO templates were successfully prepared on polycrystalline Hastelloy metal substrate with reel-to-reel system for YB2Cu3O7−δ (YBCO)-coated conductors. By the solution deposition planarization technique, amorphous Y2O3 films were coated on untreated Hastelloy substrate as the bed layer to obtain smooth, dense, and crack-free surface for subsequent IBAD-MgO deposition. The 50 m long IBAD-MgO and homo-epitaxial (epi)-MgO buffer layers deposited on Y2O3 films exhibit excellent crystallographic consistency along the scope with full width half maximum (FWHM) values of (110) ΔΦ and (200) Δω in the range of 5.5°–6.0° and 3.0°–3.5°, respectively. To match the lattice constant of YBCO material, LaMnO3 cap layer was fabricated on IBAD-MgO templates by radio frequency (rf) magnetron sputtering with the FWHM values of in-plane and out-of-plane of 6.8° and 3.7°, respectively, indicating excellent biaxial texture.

•We reported a promising all-mod-derived buffer template for YBCO coated conductors.•The crystallinity of LZO was tailored by selective MOD-seed and annealing condition.•A LZO/CeO2 buffer layer allows us to grow epitaxial YBCO films with high Jc.•This buffer template could potentially decrease the manufacturing cost.Well-textured metal-organic-deposited (MOD) Lanthanum Zirconate (La2Zr2O7, LZO) films were spin-coated on biaxially textured Ni–5 at.%W substrates for low cost production of YBa2Cu3O7−δ (YBCO) coated conductors. Control of the crystallographic orientation of LZO buffers is of significance to achieve YBCO films with high current carrying capability by means of the selective MOD-seed layer and annealing conditions. X-ray diffraction analysis indicated that the three-layer LZO films on MOD-seed layer, especially MOD–CeO2, showed a significant improvement in out-of-plane and in-plane textures. The surface analysis revealed a typical dense, cracks-free, and homogenous morphology. 500 nm-thick YBCO films epitaxially grown on three-layer LZO buffer layers without seed layer, on seed MOD-Y2O3 and MOD-CeO2 by direct-current sputtering, yielded critical current density (Jc) at 77 K of 0.6 MA/cm2, 1.2 MA/cm2 and 1.4 MA/cm2, respectively, exhibiting that the superconducting properties were governed by the crystallographic texture of the underlying buffer layer.

•Mid-frequency AC sputtering provides significant advantages.•Double-sided Y2O3 seed layers are prepared with high speed of 35 m/h.•Sputtering voltage control was used to deposited epitaxial high quality films.•Coherent textures and surfaces of both sides of CeO2/YSZ/Y2O3 are achieved.A reel-to-reel magnetron sputtering system with mid-frequency alternating current (AC) power supply was used to deposit double-sided Y2O3 seed layer on biaxially textured Ni–5 at.%W tape for YBa2Cu3O7−δ coated conductors. A reactive sputtering process was carried out using two opposite symmetrical sputtering guns with metallic yttrium targets and water vapor for oxidizing the sputtered metallic atoms. The voltage control mode of the power supply was used and the influence of the cathode voltage and ArH2 pressure were systematically investigated. Subsequently yttrium-stabilized zirconia (YSZ) barrier and CeO2 cap layers were deposited on the Y2O3 buffered substrates in sequence, indicating high quality and uniform double-sided structure and surface morphology of such the architecture.

•Solution-derived amorphous films were first applied to yield flux pinning.•Acting as the effective blocking layer, and resulting in the defects propagation.•Surface roughness was modulated with the concentrations properly chosen.•The relationship between dislocation density and α was systematically investigated.•A promising future for cost-effective coated conductors on practical applications.Solution deposition planarisation (SDP), a novel surface modification method, was applied for the enhancement of flux pinning in superconducting thin films for the first time. Solution-derived amorphous Y2O3 films were spin-coated on LaAlO3 (LAO) substrates to modify substrates’ surface before sputtering YBa2Cu3O7−δ (YBCO) films. The effect of the concentration of the precursor solution on the surface roughness and superconducting properties of the YBCO films was studied. It is found that the crystallinity and self-field properties of the YBCO films were improved because of the resulting reduction in roughness when the concentration of the precursor solution was properly chosen. As increasing the precursor concentrations, self-field critical current densities (Jc) were deteriorated and the superconducting properties in magnetic fields were improved. In addition, dislocation densities in YBCO films induced by amorphous Y2O3 were measured and quantitatively calculated. The relationship between the dislocation density and power-law exponent α (proportional factor of Jc ∼ H−α) was systematically investigated. The surface planarisation and defect-induced flux pinning behaviour of amorphous Y2O3 films led to potential applications in low cost YBCO coated conductors.

In this study, we systematically investigated the composition dependence of the phase structure, microstructure, and electrical properties of (Ba0.94Ca0.06)(Ti1–xMx)O3 (M = Sn, Hf, Zr) ceramics synthesised by the conventional solid-state reaction method. The phase boundary type strongly depends on the composition, and then different electrical properties were exhibited. The addition of Hf and Zr can more quickly shift phase transition temperatures (TR–O and TO–T) to a higher temperature with respect to Sn, leading to the formation of different phase boundaries. In addition, different phase boundaries can also be affected by their doped contents. The R–O and O–T phase boundaries can be shown in the Sn-doped ceramics with x = 0.10, and the R–O phase boundary can exist in the Hf (x = 0.07) or Zr (x = 0.075)-doped ceramics. A high piezoelectric property of d33 = 600 pC N−1 can be achieved in the Sn-doped ceramics due to the involvement of converging R–O/O–T phase boundaries, an enhanced ferroelectric performance with Pr = 14.54 μC cm−2 and Ec = 1.82 kV cm−1 can be attained in the Zr-doped ceramics, and Hf would benefit from obtaining a large strain behaviour (∼0.20%). We believe that the electrical properties and the related physical mechanisms of BaTiO3-based ceramics can be well unveiled by studying their chemical modification behavior.