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Mechanoluminescent (ML) materials have become a novel and excellent fluorescent material in the field of luminescence for demonstrating potential applications in stress detection, biological imaging and optical displays. Through some trivial modifications between the constituent atoms and the crystal structures, these luminescent materials exhibit different ML performances for various applications. Herein, a series of novel red emitting Mn2+-activated (Ca, Sr)ZnOS shows strong fluorescence emission under the mechanical actions of compression or ultrasonic effect. The traps in (Ca, Sr)ZnOS:Mn2+ become deeper and the optical band gap decreases from 3.75 to 3.15 eV with the increase of the Sr2+ content. It is worth noting that the ML intensity of Ca0.7Sr0.3ZnOS:Mn2+ is about one order of magnitude stronger than that of CaZnOS:Mn2+ under the same conditions. The enhanced ML performance can be attributed to the fact that when the trap depths become deeper, the trap energy level greatly increases. In addition to conventional stress monitoring, (Ca, Sr)ZnOS:Mn2+ was successfully used for determining the ultrasonic intensity distribution through ML. The work not only provides a facile and effective method for facile synthesis of (Ca, Sr)ZnOS:Mn2+ solid solution, but also demonstrates its extraordinary ML properties and applications in the field of ultrasound monitoring.

A series of Bi3+ and Mn2+ co-doped CaZnOS phosphors with a tunable emission color have been synthesized by a high temperature solid-state reaction method. Their crystal structure, spectroscopic properties, energy transfer and thermal quenching have been investigated systematically. An intense blue-green emission band at 485 nm and a red emission band at 616 nm were observed at an excitation wavelength of 375 nm, owing to the 3P1,0 → 1S0 transition of Bi3+ and the 4T1(4G) → 6A1(6S) transition of Mn2+, respectively. The tunable color from blue-green, white light to red light can be obtained by varying the Mn2+ ion concentration from 0.005 to 0.015 in CaZnOS:Bi3+. The decay time decreased from 642 to 273 ns with the Mn2+ ion concentration x increasing from 0.005 to 0.015, and the energy transfer efficiency ηT can reach up to 65% in the CaZnOS:Bi3+,0.015Mn2+ phosphor. As the temperature increases from 300 to 420 K, the emission intensity is maintained at 67%, and the activation energy Ea is estimated to be 0.28 eV. An LED fabricated using CaZnOS:Bi3+,0.01Mn2+ exhibited the chromaticity coordinates and corrected color temperature (CCT) of (0.338, 0.364) and 4655 K, respectively. These results validate the promising applications of the CaZnOS:Bi3+,Mn2+ phosphor in UV white LEDs.

Mechanoluminescence materials that emit light under mechanical stimulation have attracted widespread attention in sensing, anti-counterfeiting and imaging applications. In this study, a series of novel Sr1-xBixZnSO (0.001≤x≤0.1) samples were synthesized by the method of high temperature solid-state reaction. It is worth noting that the distortion degree of SrO3S3 octahedron was increased with increasing Bi3+ concentration, and the color manipulated Sr1-xBixZnSO which can emit different photoluminescence (blue to dark blue and finally red) and mechanoluminescence (orange to red) colors are obtained. Moreover, the deep traps can stably store and provide electronic supplement to shallow traps released under mechanical stimulated. Therefore, devices made of SrZnSO: Bi3+ phosphor and polydimethylsiloxane (PDMS) can be used as thermo-mechano-opto three-mode anti-counterfeiting. The ML intensity is linear to the external load, can be utilized for stress sensing or imaging.

Recently, realizing artificial perception learning systems at the hardware level based on neuromorphic devices has become a new research branch in artificial intelligence technology. Here, we report multi-functional starch-based bio-polysaccharide electrolyte gated photoelectronic synergic coupled indium–gallium–zinc oxide (IGZO) neuromorphic transistors. Both light illumination and voltage biasing will modulate the channel conductance. Thanks to strong electrical-double-layer (EDL) coupling behaviors of the starch-based bio-polysaccharide electrolyte, the neuromorphic transistor can operate at low voltages. Interestingly, the neuromorphic transistor exhibits long-term memory response behaviors under light stimuli. Moreover, photoelectric synergic spatiotemporal integration behaviors are demonstrated by introducing a light spike stimulus and voltage spike stimulus in a temporal and spatial manner. Furthermore, connections between electric spikes and light spikes have been established, which results in the demonstration of the Pavlovian classical condition. The proposed photoelectric synergic neuromorphic transistors would have potential applications in brain-inspired multifunction intelligent perception system applications.

The influence factors on the defect types in vertical graphene nanosheets (VGNs) are widely researched while few systematic research has been reported on the growth temperature, which should play an important role in the transformation of defects types. In this work, VGNs were grown via plasma enhanced chemical vapor deposition (PECVD) method in the atmosphere of CH4, H2 and Ar. Based on SEM, Raman, XPS, NEXAFS and UPS spectrum analysis, we found that the types of defects in VGNs have clearly transformed from vacancy-like to boundary-like, corresponding to the rising growth temperature. Moreover, NEXAFS suggests that features near 7.7 eV are attributed to boundary-like defects, as well as −6.7 eV in UPS, providing an intuitive and half-quantitative direction to characterize boundary-like defects in VGNs. Additionally, the sheet resistance (from 1386 to 175 Ohm/Sq) and the wetting angle (from 148° to 121°) decrease as the temperature rises. It shows that changing the growth temperature, as the easy and effective method, is crucial of modulating the properties of VGNs owning to the transition of defects types from vacancy-like to boundary-like.

This work first reports the controllable preparation of rGO/VO2(B) intercalation films via a simple sol-gel method at relative low temperature (420 °C). The excellent conductance and thermal conductivity of rGO could significantly enhance the performance and sensitivity of VO2(B) films to be used for uncooled infrared detectors. Aluminum (Al) reduction is introduced to reduce the oxygen-containing functional groups of graphene oxide (GO) and V2O5 of GO/V2O5 intercalation films in a two-zone furnace. According to our results, the reduced-GO (rGO), as a fast channel for electron transport, was inserted into the VO2(B) film, and thus the electron transfer between rGO/VO2(B) intercalation films occurs much faster than in pure VO2(B) films. The film preparation processes were optimized through adjusting the doping concentration of rGO, and rGO/VO2(B) intercalation films with applicable temperature coefficient of resistance (TCR) (−2.78%/K) and square-resistance (21.22 kΩ) were achieved. Our work provided a promising and feasible technique to convict the cost and complexity of high vacuum method used to fabricate the VO2 thermal sensing thin films.

A comparative study of anti-reflection microstructures (ARMs) and ARMs with Al2O3 coatings (Al2O3/ARMs) on zinc selenide (ZnSe) has been carried out. The transmittance and electric field intensities were analyzed and presented using finite-difference time-domain (FDTD) simulations. ARMs were successfully fabricated on ZnSe surfaces by reactive ion etching and an Al2O3 layer was deposited onto the ARMs by an ion beam sputtering method. The theoretical analysis and experimental results showed that the transmittance of Al2O3/ARMs-treated ZnSe had a close relationship with the thickness of Al2O3 layer and was higher than that of ARMs-treated ZnSe in the 2–5 μm wavelength range, which was due to the fact that the Al2O3/ARMs had a better graded refractive index profile. The angle-dependent reflectance of ZnSe with Al2O3/ARMs was lower than that with ARMs. A difference of the spatial distribution of the electric field intensity between ARMs and Al2O3/ARMs was observed due to the surface Al2O3 coating, which predicted qualitative laser damage thresholds for both structures. The results of this study provide potential applications in high-efficiency IR optoelectronic devices and high power mid-infrared laser systems.

Endowing vanadium dioxide (VO2) thin films with excellent thermal sensitive performance is greatly desired for application in uncooled infrared (IR) detectors. Here, we demonstrate a strategy of co-doping by using a simple and feasible CVD method to synthesize Mo-Al-doped VO2(B) thin films with high temperature-coefficient-of-resistance (TCR, −3.6%/K) and favorable square resistances (16.2 kΩ). Both the TCR and resistance are superior to that of undoped and Al-doped VO2(B) thin film, and the TCR is larger than that of Mo-doped VO2(B) thin film. The underlying microscopic mechanism for the performance improvement might be that Mo-Al co-doping creates less lattice deformation, strain and inhomogeneity of carrier concentration due to dimension and charge compensation than that of single-doping and the partly release of 3d electrons around V4+-V4+ pairs in co-doping films. Besides, the special two-dimensional octahedral structure of monoclinic (C2/m) VO2(B) favors the strain control with doping. The films have been subjected to synchrotron radiation based X-ray photoelectron spectroscopy (SRPES) and X-ray absorption near edge structure (XANES) techniques to study the local atomic and electronic structure around V ions. The results indicated that the dopants of Mo and Al were incorporated into the VO2 lattice and occupied some of the V lattice sites, resulting in the formation of the V1-x-yMoxAlyO2 substitution solid solution. V L-edge and O K-edge XAS results identically verified that Mo-Al co-doping might create the least lattice deformation in films. Hence, the high performance of films proves that the co-doping strategy is suitable for uncooled infrared detector applications.

Eco-friendly “green” electronics are attracting increasing interests in recent years. Here, biodegradable organic/inorganic hybrid indium-tin-oxide electric double layer (EDL) transistors were fabricated on plastic substrates. Solution processed chitosan based polysaccharide films were used as gate dielectrics. Due to extremely high EDL capacitances of the chitosan-based electrolytes, the oxide EDL transistors exhibit good performances. Resistor loaded inverters were also built, exhibiting full-swing characteristics and high voltage gains at low operation voltages. Wave-type conversions were realized including conversions from sinusoid waves into rectangular waves and from noise signals into two-bit outputs. Furthermore, the organic/inorganic hybrid transistors can be dissolved in water easily. The proposed organic/inorganic hybrid oxide transistors may have potential applications in “green” portable devices.

To meet the increasing requirements of minimizing circuits, the development of novel device architectures that use ultra-thin two-dimensional materials is encouraged. Here, we demonstrate a non-volatile black phosphorus (BP) PNP junction in a BP/h-BN/graphene heterostructure in which BP acts as a transport channel layer, hexagonal boron nitride (h-BN) serves as a tunnel barrier layer and graphene is the charge-trapping layer. The device architecture is designed such that only the middle part of the BP is aligned over the graphene flake, enabling the flexible tuning of the charge carriers in the BP over the graphene charge-trapping layer. Thus, the device exhibits the ability to work in two different operating modes (PNP and PP+P). Each operating mode can be retained well and demonstrates non-volatile behavior, and each can be programmed by using the control-gate.

Due to the high lattice symmetry and special three-dimensional crystal channel, sulvanite Cu3VSe4 is predicted to be a new type of thermoelectric material with good performance. In this work, the energy band diagram and phonon spectrum of Cu3VSe4 with sulvanite structure were calculated using density functional theory, and Cu3VSe4 pure phase was experimentally synthesized through the combination of the elements using conventional solid-state reactions. Surprisingly, the thermoelectric characterization reveals that Cu3VSe4 is a semiconductor with electron-hole co-transport feature, which results in the poor thermoelectric performance due to the recombination of electrons and holes at low temperature. While holes gradually dominate with the increase of temperature and Cu3VSe4 possesses a high Seebeck coefficient of 558 μV/K at 571 K. Our results may serve as the groundwork for future research on the structure and thermoelectric properties of Cu3VSe4.

Batteries with fast recharge rates while maintaining sufficient capacity are highly attractive for applications such as electric transportation and electrical storage of renewable sources. Designing an electrode structure that enables facile transport of lithium ions and electrons is an effective way to enhance capacity retention at fast charge and discharge rates. Here, we report a LiFePO4 (LFP) cathode as the model electrode with directional microstructure using an in-house developed freeze tape casting (FTC) technique. The microstructure and electrochemical performance of the electrodes with different freeze velocity and solid content were investigated, and an optimized directional electrode microstructure was obtained. The optimized LFP electrode exhibited competitive discharge capacities of 123.8 and 40.7 mA h g−1 at 0.1 and 15 C respectively, where 15 C represents ~4 min charge or discharge. For comparison, the capacity of conventional LFP cathodes containing typical tortuous porous microstructures often drops to negligible levels at the fast charge and discharge rate of 15 C. A relatively large cathode (~10 cm × 5 cm) containing the directional microstructure was fabricated, demonstrating the scalability of the FTC technique.

To achieve a better material for uncooled infrared (IR) detector, polycrystalline VO2(B) thin films with layered W-doping were fabricated on Si substrates by magnetron sputtering, and the best temperature coefficient of resistance (TCR) value reached −4.1%/K. The film synthesis was in a two-step route, first deposition at room temperature and then post-deposition annealing at 450 °C, to better control the crystallization behavior. Various transmission electron microscopy (TEM) methods were employed to investigate three sets of multi-layered films with different deposition time, 10, 20, and 30 min, with especial emphasis on the effect of layered W-doping scheme on the formation of multiple VO2(B) layers. Spatial-resolved energy dispersive X-ray spectroscopy (EDS) revealed the alternative patterns of W-rich layers and W-poor layers, while the thinner films exhibited better crystallinity and texturing. By comparison with an as-deposited film, it was found that the inter-diffusion between the two types of layers was completed in the deposition step while both remained in amorphous structure. A stable W solution of about 8 cat% in VO2(B) layers measured from all these films indicated that the layered doping can tailor the multi-layered microstructure to optimize the performance of VO2(B) films.

This work reports a new method for low-temperature, cost-effective fabrication of VO2(B) thin films, which is assumed to be the preferred phase structure for the application in uncooled infrared detectors using chemical vapor deposition (CVD) in a three-zone furnace. While high-vacuum techniques are extensively used nowadays which together with high temperature post-annealing are very complicated in operation and expensive, our method successively achieves the facile and scalable synthesis of thermal sensitive VO2(B) thin films with high TCRs (from −2.4%/K to −2.89%/K) and favorable square resistances (10 kΩ–40 kΩ) at a growth temperature range of 375–450 °C. The output results are comparable to the reported values of the high-vacuum synthesized VO2(B) thin films, proved our method suitable for uncooled infrared detector applications.

Nanocomposites of (1-x)CuFe2O4/xNiO (x = 10% to 50 wt %) have been synthesized utilizing a chemical co-precipitation method. In order to obtain the required phase, the samples have been annealed at 600 °C for 6 h. The x-ray Diffraction (XRD) technique has been used for the crystallographic structure analysis which not only confirms the coexistent of both copper ferrite (CuFe2O4) and nickel oxide (NiO) phases in all samples but also verifies the absence of any impurity phases. The average crystallite size as estimated via XRD patterns show that the average size lies in the range of 22–36 nm which has also been confirmed by TEM. The FTIR absorbance spectra also show the characteristic vibration modes of cation at tetrahedral and octahedral sites. The electrical properties like A.C. conductivity, impedance, Dielectric constant, and Tangent loss has been measured by LCR meter. The results show that with the increase in NiO concentration, electrical conductivity increases for all concentration while dielectric constant decreases up to 30% NiO wt% and increases with further addition of NiO. The real and imaginary parts of impedance depict same dispersion i.e the impedance decreases at higher frequency due to increase in conductivity. Moreover the magnetic characterizations performed by VSM, reveal that the hysteresis loops exhibit normal behavior of ferromagnetic/ferrimagnetic materials for all compositions but the coercivity (Hc), and saturation magnetization (Ms) decreases with the increase in NiO contents that transform the material in to soft magnetic.

In this study, the influence of Si ions irradiations (12 MeV energetic) on structural and optical characteristics of InGaN/GaN thin film has been investigated. Irradiation was performed at different Si ions fluences in the range of 1×10 13 to 1×10 15 ions/cm 2 . X-ray diffraction (XRD) pattern of pristine film indicates only the (0 0 2) oriented crystallites of InGaN while the irradiated films patterns showed other phases (InN and GaN) as well. Ion irradiations at different dose rates have shown no or negligible effect on grain size of InGaN except a shift in the peak position which demonstrates the development of tensile stresses. The existence of other phases in the irradiated films patterns is the indication of InGaN phase separation. Defects produced due to irradiation were also confirmed from peak shifting and appearance of new peak at 669 cm −1 in Raman spectra. A decrease in optical bandgap with the increase of ion irradiation dose rate is being reported in this work.

The Nanocomposites of CuFe 2 O 4 /ZnO have been synthesized by two steps wet chemical coprecipitation method under optimum condition. The crystal structure, particle size, and morphology of the synthesized samples have been characterized by X-ray Diffraction (XRD) and electron microscopy techniques. The XRD measurements have depicted the formation of required phases of nanocomposites and no impurity phases are being observed. The FTIR analysis confirm the presence of vibration bands at the surface of synthesized materials. The magnetic properties have been measured by Vibrating Sample Magnetometer (VSM) under applied field of ±2 T, all the samples except pristine ZnO have shown superparamagnetic behaviour for all concentration with decreasing saturation magnetization. The electromagnetic wave (EMW) absorption properties have been studied by reflectometer under frequency range of 2–10 GHz. The maximum absorption of 42.35 dB has been achieved at frequency of 8.35 GHz with 30% ZnO. Moreover with concentration ≥40% of ZnO whole frequency band below −10 dB has been covered. The observed results show that these nanocomposites have excellent microwaves absorption properties due to the compatibility of dielectric and magnetic properties.

Novel WO3–CuFe2O4 nanocomposites with significantly higher electromagnetic wave absorption properties have been synthesized. The synthesized nanocomposites exhibit coexistence of both phases at higher WO3 concentrations without impurity phases as confirmed by XRD and FTIR studies. TEM micrographs demonstrate the formation of CuFe2O4 nanoparticles embedded in WO3 shells. FTIR results reveal the presence of characteristic stretching and vibration modes associated with WO3 and CuFe2O4. The magnetic measurements show the ferromagnetic behavior of all studied samples. However the saturation magnetization has shown a decreasing behavior while coercivity increases with the concentration of incorporated WO3. The WO3 concentration up to 30 wt% enhances the microwaves absorption properties (−26.32 dB at frequency 6.6 GHz) and shifts the absorption maximum curve to higher frequency.

The nanocomposites of (SnO 2 ) x (CuFe 2 O 4 ) (1−x) (where x=0–100 wt%) have been successfully synthesized via two steps chemical method. XRD pattern has revealed the formation of inverse spinal phases with tetragonal crystal structure without any impurity phases for CuFe 2 O 4 sample. The thermodynamic solubility limit of SnO 2 in CuFe 2 O 4 matrix has been found to be 30 wt% and above this percentage crystal phases related to SnO 2 started to appear. The average particle size and shape of CuFe 2 O 4 nanoparticles have been strongly influenced by addition of SnO 2 as depicted by TEM results. FTIR results have confirmed the existence of cation vibration bands at tetrahedral and octahedral sites along with Sn-O vibration band at higher concentrations, which also validates the formation of nanocomposites. Furthermore, the dielectric constant, tangent loss and conductivity of CuFe 2 O 4 nanoparticles have been found to increase up to 30 wt% addition of SnO 2 and then decreases with further increase which is attributed to variations in resistivity and space charge carriers. Magnetic measurements have shown that saturation magnetization decreases from 35.68 emu/gm to 10.26 emu/gm with the addition of SnO 2 content.

The nanocomposites of MgO/CuFe 2 O 4 has been prepared by two steps co-precipitation method at low temperature. The crystal structure, morphology and particle size have been characterized by X-ray Diffraction (XRD) and Transmission electron microscopy (TEM). The average crystallite size lies in the range of 20–32 nm and XRD pattern also confirms the coexistent of both phases without impurity related phases. The TEM images reveal that spherical CuFe 2 O 4 magnetic nanoparticles are embedded in MgO Matrix. The Fourier Transform Infrared Spectroscopy (FTIR) results show the stretching and bending vibrations of tetrahedral and octahedral sites of ferrites along with vibration mode of MgO. The magnetic characterization has been performed by Vibrating Sample Magnetometer (VSM) at room temperature under the applied field of ±2T. The M-H loop of MgO shows ferromagnetic behavior at low field value of ±0.5 T due to oxygen vacancies defects and diamagnetic behavior at higher field value. On the other hand, the CuFe 2 O 4 nanoparticles shows normal superparamagnetic behavior with 30.78emu/gm saturation magnetization. Morever with the increase in concentration of MgO, the coercivity remains same but saturation magnetization decreases due to decrease in volume percent of magnetic contents. The electromagnetic wave absorption properties has been measured by vector analyzer in the frequency range of 2–10 GHz and best absorption reach to −25.35 dB at frequency of 8.38 GHz. Furthermore at higher concentration of MgO ≥40%, it covers the whole frequency band below −10 dB. This excellence microwave absorption may be due to the effective complementarities between dielectric and magnetic loss in this novel MgO/CuFe 2 O 4 nanocomposites.

VO 2 (B) is currently a preferred phase structure for the application as bolometer material, which, however, suffers from low temperature-coefficient-of-resistance (TCR) values and large resistances. Here we present the combined experimental and first-principles calculations study on both doped and undoped VO 2 (B) thin films enabling us to attain high TCR (−3.9%/k) and suitable square-resistance (32.7 kΩ) by controlled W doping employing the widely used magnetron sputtering technique. The TCR value is 50% larger than reported ones at the similar resistance. The underlying microscopic mechanism for the performance improvement was studied and results indicated that the introduction of extra electrons and the variation in the band structure resulting from the incorporation of W 6+ ions in the VO 2 (B) crystal lattice contribute to the enhancement of the electronic conductivity. Moreover, the special two-dimensional octahedral structure of monoclinic ( C 2/m) B-phase VO 2 favors the strain control with W-doping for achieving a large TCR, which overcomes the analogous predicament between the high conductivity and large TCR generated by dopants in the M-phase VO 2 . The present findings provides a facile and simple pathway for the design and fabrication of high performance W-doped VO 2 (B) thin films rendering superior optical and electrical properties for its wide applications in thermo-opto-electro sensing devices.

Monoclinic vanadium dioxide is a thermochromic material for advanced applications to smart optoelectronic devices. However, the poor visible-light transmission and high phase transition temperature (Tc) of VO2 hinder its practical use. Our first-principles calculations show that group IV elements (Si, Ge, Sn, Pb) doping may be an efficient way to reduce the Tc of VO2, which is coupled with the changes in the geometry and electronic structures, i.e., the decrease in Tc is associated with the correlation between the volume and the β angle, and the variable band gaps between eg and t2g are narrowed by 0.05–0.37 eV after doping. In addition, group IV elements (Si, Ge, Sn, Pb) doping can improve the absorption and transmittance of light in the low energy region, favoring the efficient utilization of sunlight in the infrared region. Our findings would provide a useful guidance for fabrication of high quality VO2 based thermochromic materials.

VO2(B) is a candidate material for thermal sensors in uncooled infrared detectors; however, it suffers from low temperature coefficient of resistance (TCR) values and unfavorable square resistances. Here, we present an effective strategy to modify the electronic properties of VO2(B) by inducing elastic strain with an anatase TiO2(A) buffer layer. The combined experimental and first-principles computational study on TiO2(A)-induced VO2(B) thin films deposited by magnetron sputtering enables us to achieve high TCRs (−3.48% K−1) and favorable square resistances (18.97 kΩ). The underlying microscopic mechanism for the improvement in performance was studied, and the results indicate that the tensile strain contributes to a reduction in overlapping of V-3d orbitals and an increase in carrier concentrations along the c-axis in VO2(B), both of which result in an increase in the electrical conductivity and TCR values. These findings promote the design and fabrication of high-performance VO2(B) thin films by scaling the lattice strain along the c-axis with suitable buffer layers or substrates, and the simplicity of this method and the superior electrical properties of the films may enable its wide application in uncooled infrared detectors.

VO2(M) is of special interest as the material with the most potential for future application in smart windows and switching devices. However, a number of drawbacks need to be overcome, including the high processing temperature of current synthesis techniques and low thermochromic properties. This work reports the fabrication of high-performance thermochromic VO2 thin films at low temperatures below 400 °C based on a low-pressure chemical vapor deposition (LPCVD) with a vanadium(III) acetylacetonate precursor. Proper tuning of the process parameters is found to be critical in fabricating thickness-controllable highly-crystalline VO2 films. For an ∼62 nm thick VO2 film, visible transmittances of 52.3% (annealed at 400 °C) and 52.7% (annealed at 350 °C) were obtained. The corresponding solar energy modification abilities (ΔTsol) were 9.7% and 7.1%, and the transition temperatures were 45.1 °C and 50.9 °C. The underlying microscopic mechanism was studied by first-principles calculations and the results indicated that improved performances, including a low transition temperature, could be achieved by properly controlling the annealing temperature, ascribed to the combined effect of strain and oxygen vacancies. Moreover, the initial use of a pre-grown seed layer induced fast grain growth, which is favorable for further decreasing the deposition and annealing temperature to 325 °C.

Molybdenum (Mo) thin films, most commonly used as electrical back contacts in Cu(In,Ga)Se2 (CIGS) solar cells, are deposited by rf and dc magnetron sputtering in identical systems to study the discrepancy and growth mechanisms of the two sputtering techniques. The results reveal that though different techniques generally deposit films with different characteristic properties, Mo films with similar structural and physical properties can be obtained at respective suitable deposition conditions. Highly adhesive and conductive Mo films on soda lime glass are further optimized, and the as-fabricated solar cells reach efficiencies as high as 9.4% and 9.1% without an antireflective layer.

Vanadium dioxide (VO2) is one of the most promising thermochromic materials with a reversible metal–insulator transition (MIT) from a high-temperature rutile phase to a low-temperature monoclinic phase, although a high MIT temperature (Tc) of 340 K for bulk VO2 restricts its wide application. Our first-principles calculations show that the oxygen nonstoichiometry plays an important role in tuning the MIT behavior of VO2. The O-vacancy in bulk VO2 gives rise to an increase in electron concentration, which induces a decrease in Tc. On the other hand, O-vacancy and O-adsorption on VO2(R) (1 1 0) and VO2(M) (0 1 1) surfaces could alter their work functions and in turn regulate Tc. In addition, the formation and adsorption energies of O-adsorption on the two types of surfaces are negative, indicating that VO2 surfaces are prone to oxidation in ambient air. The present results contribute to both tuning phase transition behaviors experimentally and reducing hindrances for the advanced applications of VO2-based materials.

Introduction of broadband antireflection coatings (ARCs) is a promising method to enhance efficiency of solar cells. In this paper, the TiO 2 –SiO 2 stack coatings with refractive-index-grade structure are proposed and have been successfully fabricated via sol–gel dip-coating technique. The structure, morphology, optical properties and wettability of TiO 2 –SiO 2 stack coatings were systemically investigated. The broadband antireflection performance is improved over the solar spectrum with increase of solar transmittance by 7.80% and maximum transmittance of 99.16% at 550 nm on glass slide substrates. The responding reflectance is largely reduced and the minimum values in visible and near-infrared regions are 0.40% and 0.05%, respectively. By introducing broadband ARCs, the efficiency of Cu(In,Ga)Se 2 solar cells is increased from 11.20% to 12.15%, which reveals superiority and importance of TiO 2 –SiO 2 stack coating as an outstanding antireflection material, having high potential for practical applications.

Graphene/ceramic composites are proposed by directly depositing graphene on the insulating Al2O3 particles by chemical vapor deposition without any metal catalysts. Carbothermic reduction occurring at the Al2O3 surface is vital during the initial stage of graphene nucleation and the graphene sheet can connect with neighboring sheets to completely cover Al2O3 particles. The quality and layer number of graphene on Al2O3 can be finely tailored by changing the growth temperature and gas ratio. Graphene coated Al2O3 (G-Al2O3) composites are used as effective fillers of stearic acid (SA) to increase the thermal transport property. By the optimization of the layer number of graphene, size of Al2O3 particles and ratio of G-Al2O3/SA in a quantitative, their thermal conductivities significantly increase up to 11 folds from 0.15 to 1.65 W m−1 K−1. The great improvement is attributed to the high thermal transfer performance of graphene and excellent wettability between graphene and SA. When the G-Al2O3/SA composites with the graphene coated porous Al2O3 foam, the thermal conductivity further reaches to 2.39 W m−1 K−1, and the corresponding latent heat is 38 J g−1. It demonstrates the potential applications of graphene in thermal transport and thermal energy storage devices.

Direct growth of graphene on Al2O3 film is successfully achieved assisted with NiAl2O4 film on a SiO2 substrate by chemical vapor deposition at 800 °C. The Ni particles are first uniformly separated out on the substrate, and play an important role in capturing carbon atoms and accelerating the nucleation to grow high quality graphene rooting on insulating Al2O3 film. The thickness of graphene films can be tuned from two layers to few layers (

Modification of rutile titanium dioxide (TiO2) for hydrogen generation and water cleaning is a grand challenge due to the chemical inertness of rutile, while such inertness is a desired merit for its stability in photoelectrochemical applications. Herein, we report an innovative two-step method to prepare a core-shell nanostructured S-doped rutile TiO2 (R'-TiO2-S). This modified black rutile TiO2 sample exhibits remarkably enhanced absorption in visible and near-infrared regions and efficient charge separation and transport. As a result, the unique sulfide surface (TiO(2-x):S) boosts the photocatalytic water cleaning and water splitting with a steady solar hydrogen production rate of 0.258 mmol h(-1) g(-1). The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen conversion efficiency of 1.67%. The sulfided surface shell is proved to be an effective strategy for enhancing solar light absorption and photoelectric conversion.

A phase change material consisting of three-dimensional graphene aerogel (GA) and octadecanoic acid (OA) was produced. The GA was assembled from the sheets of graphene oxide in a hydrothermal reaction. The pore sizes of the network were several micrometers and the pore walls consisted of thin layers of stacked graphene sheets. OA was impregnated into GA by capillary forces, with the GA acting as the support. The GA/OA composite had a thermal conductivity about 2.635 W/m K at a GA loading fraction of ∼20 vol%, which was about 14 times that of the OA (0.184 W/m K). The transient heating and cooling responses of the material were investigated for thermal energy storage. The GA had a low bulk density so that the weight percent of the GA in the composite was only about 15%. The composite presents a high heat storage capacity of 181.8 J/g, which was very close to the value of the OA alone (186.1 J/g).

Black TiO2 attracts enormous attention due to its large solar absorption and induced excellent photocatalytic activity. Herein, a new approach assisted by hydrogen plasma to synthesize unique H-doped black titania with a core/shell structure (TiO2@TiO2-xHx) is presented, superior to the high H-2-pressure process (under 20 bar for five days). The black titania possesses the largest solar absorption (approximate to 83%), far more than any other reported black titania (the record (high-pressure): approximate to 30%). H doping is favorable to eliminate the recombination centers of light-induced electrons and holes. High absorption and low recombination ensure the excellent photocatalytic activity for the black titania in the photo-oxidation of organic molecules in water and the production of hydrogen. The H-doped amorphous shell is proposed to play the same role as Ag or Pt loading on TiO2 nanocrystals, which induces the localized surface plasma resonance and black coloration. Photocatalytic water splitting and cleaning using TiO2-xHx is believed to have a bright future for sustainable energy sources and cleaning environment.

A novel architecture of graphene paper is proposed to consist of “1D metallic nanowires/defect-free graphene sheets”. Highly conductive and flexible papers of 1D silver nanowires (Ag NWs) and chemical vapor deposition (CVD) graphene sheets as an example were fabricated by a simple filtration method. CVD graphene paper possesses much higher electrical conductivity of 1097 S/cm, compared with other reported carbon-related papers (graphene, carbon nanotube, etc.). With the addition of Ag NWs to form Ag NWs/graphene paper, the electrical conductivity is further improved up to 3189 S/cm, even higher than ∼2000 S/cm of bulk graphite. Ag NWs/graphene papers have very good flexibility with the only

We simulate a micromechanical exfoliation process to design a simple but effective and low-cost strategy for mass production of high-quality graphene sheets by planetary milling with oxalic acid. The selective carboxylation enables oxalic acid molecules to adhere to the edge and defects of graphite like a Scotch tape and plays a crucial role in the non-destructive exfoliation.

An oriented millerite nickel sulfide (NiS) nanorod array was successfully grown on bare glass substrate. Metallic conductivity and outstanding electrocatalytic activity make it possible to function as a new type of “two-in-one” counter electrode (CE) in dye-sensitized solar cells (DSCs) to replace both the transparent conductive oxide (TCO) and Pt electrocatalyst. When applied in DSCs, an impressive power conversion efficiency of 7.41% was achieved, comparable to that of TCO supported Pt CE (7.55%). The NiS nanoarray film could be a potential candidate to realize a “two-in-one” CE in DSCs, which is highly desirable to reduce the fabrication cost of DSCs while retaining a comparable conversion efficiency.

A novel uniform multi-level matrix of vertically erected graphene walls is directly grown on a dielectric substrate by plasma enhanced chemical vapor deposition (PECVD) at 900 °C without the presence of any catalyst and post-transfer treatment. Such a two-level structure is composed of continuous vertically erected graphene sheets (the second level) on a nanocrystalline graphene film (the first level). A nanocrystalline film is formed in the first stage (

For specific application to an uncooled infrared detector, VO2 thin films should have a series of characteristics including purposefully chosen polymorphs, accurate stoichiometry, phase stabilization, a high temperature-coefficient of resistance (TCR), and suitable square-resistance. This work reports controllable preparation of high-performance VO2 films via post annealing of a sandwich-structured V2O5/metal (V, W)/V2O5 multilayer precursor, which was deposited by RF magnetron sputtering. This sandwich structure can dynamically regulate oxygen contents and doping element levels in the films, enabling us to achieve accurate regulation of stoichiometry and polymorphs. The precursor films undergo a B to M phase transition depending on the quantity of the metal layers. At the thickness of the metal layer below a limitation, the resulting film after heat treatment was VO2 (B), and above the limitation, the product was VO2 (M). The optical modulation of the VO2 (M) in the near-infrared region can be tuned from 1.2 to 39.8% (ΔT2000 nm). TCR values can range from -1.89 to -4.29%/K and the square-resistances at room temperature (R0) from 69.68 to 12.63 kΩ. The simplicity in phase regulation of the present method and the superior optical and electrical properties of the films may allow its wide applications in thermo-opto-electro sensing devices.

A novel architecture of 3D graphene growth on porous Al2O3 ceramics is proposed for thermal management using ambient pressure chemical vapor deposition. The formation mechanism of graphene is attributed to the carbothermic reduction occurring at the Al2O3 surface to initialize the nucleation and growth of graphene. The graphene films are coated on insulating anodic aluminum oxide (AAO) templates and porous Al2O3 ceramic substrates. The graphene coated AAO possesses one-dimensional isolated graphene tubes, which can act as the media for directional thermal transport. The graphene/Al2O3 composite (G-Al2O3) contains an interconnected macroporous graphene framework with an extremely low sheet electrical resistance down to 0.11 Ω sq−1 and thermal conductivity with 8.28 W m−1 K−1. The G-Al2O3 provides enormous conductive pathways for electronic and heat transfer, suitable for application as heat sinks. Such a porous composite is also attractive as a highly thermally conductive reservoir to hold phase change materials (stearic acid) for thermal energy storage. This work displays the great potential of CVD direct growth of graphene on dielectric porous substrates for thermal conduction and electronic applications.

Low-temperature aluminum (Al) reduction is first introduced to reduce graphene oxide (GO) at 100-200 °C in a two-zone furnace. The melted Al metal exhibits an excellent deoxygen ability to produce well-crystallized reduced graphene oxide (RGO) papers with a low O/C ratio of 0.058 (Al-RGO), compared with 0.201 in the thermally reduced one (T-RGO). The Al-RGO papers possess outstanding mechanical flexibility and extremely high electrical conductivities (sheet resistance R(s) ~ 1.75 Ω/sq), compared with 20.12 Ω/sq of T-RGO. More interestingly, very nice hydrophobic nature (90.5°) was observed, significantly superior to the reported chemically or thermally reduced papers. These enhanced properties are attributed to the low oxygen content in the RGO papers. During the aluminum reduction, highly active H atoms from H(2)O reacted with melted Al promise an efficient oxygen removal. This method was also applicable to reduce graphene oxide foams, which were used in the GO/SA (stearic acid) composite as a highly thermally conductive reservoir to hold the phase change material for thermal energy storage. The Al-reduced RGO/SnS(2) composites were further used in an anode material of lithium ion batteries possessing a higher specific capacity. Overall, low-temperature Al reduction is an effective method to prepare highly conductive RGO papers and related composites for flexible energy conversion and storage device applications.

Tungsten bronze compounds M 2 KNb 5 O 15 ( M =Ca, Sr, Ba) were successfully synthesized, and the luminescence properties were investigated. Among the three compounds, Ca 2 KNb 5 O 15 showed an obviously broad band of host luminescence at 460 nm with exciting at 269 nm. By doping Eu 3+ into the M sites, Ca 2 KNb 5 O 15 :Eu 3+ displayed strong red emission from Eu 3+ ions characteristic transitions, nearly four times higher than Sr 2 KNb 5 O 15 :Eu 3+ and seven times higher than Ba 2 KNb 5 O 15 :Eu 3+ . Crystal packing factor (PF) was introduced to account for this luminescence difference, lower PF being correlated to higher luminescence intensity for perovskite-related structure. Both the as-prepared compounds and the literature examples were proved to fit this correlation. This can be explained through the influence of the structural packing on the environment distortion and crystal field splitting of the doping site.