Chemical Solution Method Research Articles

Achievement of highly conductive p-type transparent NdCuOS film with Cu deficiency and effective doping

Future advanced invisible or transparent electronics necessitate the need to overcome the well-known challenge in achieving high-performance p-type transparent semiconducting oxides (TSOs). Here, we report our success in achieving an outstanding p-type TSO thin film NdCuOS, which is the best performing p-type TSO reported to date based on the figure of merit (FoM) according to the best of our knowledge. In this work, we designed a novel chemical solution method to prepare the highly performing NdCuOS films with different doping elements. Our success in using a chemical solution method to grow semiconducting NdCuOS demonstrates that highly conductive oxychalcogenide films are possible to be prepared by a solution method. Such a solution method is facile, economically efficient, and scalable. Among our NdCuOS films with different dopants, we find that Mg-doped NdCuOS film demonstrates a very high p-type conductivity of 52.1 S cm−1 and optical transmittance of 54.3% with a huge FoM value of 1706 μS. This surpassed all the other p-type films reported so far in terms of FoM. Strong photoluminescence peaks at 3.0 eV are observed for our films, indicating their great potential applications for UV or blue light LED and other devices. The science behind such a successful achievement of high-performance p-type NdCuOS film is analyzed and discussed. A transparent p-n diode with very low leakage current (9.12 μA at −3 V) and turn-on voltage (1.1 V) is successfully fabricated, and it demonstrates a good device performance.

Elaboration of ZnO nanowires by solution based method, characterization and solar cell applications

ZnO nanowires (NWs) layers have been synthesized using a two-step chemical solution method on ITO glass substrates coated with ZnO seeds at different immersing times. The structures, morphology and optical properties of the synthesized ZnO NWs have been investigated. The prepared ZnO NWs have an obvious polycrystalline hexangular wurtzite structure and are preferentially oriented along the c-axis (002). FESEM micrographs showed that the prepared ZnO NWs are close to being vertically grown and more densely at higher immersing times. Poly [2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene], MEH-PPV, was used as an active layer to prepare three samples of MEH-PPV/ZnO solar cell based on ZnO NWs that were prepared at different immersing times. A maximum power conversion efficiency of 0.812% was achieved for MEH-PPV/ZnO solar cell prepared at a higher immersing time. The improved efficiency may be attributed to the enhancement of both open-circuit voltage and fill factor.

Temperature-induced fabrication of 1D mesoporous Co3O4 for high performance Li-ion batteries

In present work, 1D cobalt(II) complexes were fabricated by a novel temperature-induced approach. The morphology of the cobalt(II) complex can convert from 3D microsphere to 1D nanowire via controlling the reaction temperature (≥90 °C) without any surfactant with a mild chemical solution method. By calcining the 1D Cobalt complex, the mesoporous Co3O4 nanowires can be obtained. The 1D mesoporous Co3O4 exhibits superior reversible capacity of 933 mA h g−1 remained after 200 cycles at a high current density of 1.0 A g−1.

Influences of Al dopant atoms to the structure and morphology of Al doped ZnO nanorod thin film

We report our work about dependency of Al dopant atoms to the growth process of Al doped ZnO (AZO) nanorod structure. ZnO is one of type metal oxide, which is classified as semiconducting material with direct wide band gap (∼ 3.4 eV). This metal oxide is widely used in optoelectronic devices, such as solar cell, gas sensing, and photocatalyst. To produce effective photoelectrode in solar cell devices and high sensitive sensor in gas sensing application, many researchers have been modifying the nanostructure, such as inserting dopant ions, variation in deposition technique and surface modifications. By inserting some dopant ions/atoms, the structure and morphology of ZnO nanorod can be controlled. Nucleation process of nanorod structure which is growth by chemical solution method, are depend on seed layer morphology. We have prepared ZnO nanorod thin film (growth by self-assembly method) with inserting aluminum as dopant atom both in seed layer and nanorod growth solution. The morphology of ZnO nanostructured significantly changes as the existence of aluminum atoms. Based on X-ray diffraction pattern, the wurtzite structures of AZO nanorod still possessed and only affect to the small shift of lattice crystal. A high surface roughness of seed layer can produce wide radius of nanorod, since the nucleation process initiated by seed layer particle size as a template of nanorod arrangement.

Metal Oxide Nanomaterial Network for Lithium-Ion Battery Anodes and Cathodes

Lithium-ion batteries have been investigated for their promising applications in hybrid electric vehicles. A great effort has been made to synthesize a variety of electrode materials to improve the energy density, rate capability, and cycling stability. Nanostructured materials have received much attention as anodes and cathodes due to the short ion transport length, higher electrolyte- electrode contact area and better accommodation of the strain of lithium insertion/extraction. Here we report a facile polymer-assisted chemical solution method to synthesize metal oxides nanoparticle network for lithium-ion battery anodes, such as cobalt oxide, nickel oxide, bismuth oxide, and cathode materials, such as vanadium oxide and lithium manganese oxide. The carbon left from the decomposition of polymers is an effective binder between metal oxides and the current collector. The one step binder-free anodes show much better lithium storage properties with high capacities, stable cyclability, and rate capability, as compared with the electrodes from the conventional slurry-paste way by mixing the active material, polymer binder and carbon black. The good performances of these electrodes could be attributed to intimate contact between the active material and the nickel foam, the porosity of the current collector, and the network structure of the active materials.

Formation of an active part of inertial mass based piezoelectric nanogenerator

Zinc oxide piezoelectric nanorstructured coatings were formed on tantalum and aluminum substrates by the chemical solution methods. The methods mentioned above are suitable for formation of active parts of inertial mass based piezoelectric nanogenerator (PENG). This PENGs design using leads to an enhanced output due to the increased effective active parts area. Obtained nanostructured ZnO coatings were investigated by scanning electron microscopy and atomic force microscopy.

Non-vacuum Preparation of wse2 Thin Films via the Selenization of Hydrated Tungsten Oxide Prepared using Chemical Solution Methods

ABSTRACTIt is known that tungsten oxide may be reacted with selenium sources to form WSe2 but literature reports include processing steps that involve high temperatures, reducing atmospheres, and/or oxidative pre-treatments of tungsten oxide. In this work, we report a non-vacuum process for the fabrication of compositionally high quality WSe2 thin films via the selenization of tungsten oxide under milder conditions. Tungsten source materials were various hydrated WO3 and WO2.9 compounds that were prepared using chemical solution techniques. Resulting films were selenized using a two-stage heating profile (250 °C for 15 minutes and 550 °C for 30 minutes) under a static argon atmosphere. Effects of the starting tungsten oxide phase on WSe2 formation after single and double selenization cycles were investigated using Raman spectroscopy and X-ray diffraction (XRD). After two selenization cycles, hydrated WO3 was converted to (002)-oriented WSe2 that exhibits well-resolved peaks for E12g and A1g phonon modes. Only a single selenization cycle was required to convert amorphous WO2.9 to WSe2. All selenizations in this work were achieved in non-reducing atmospheres and at lower temperatures and shorter times than any non-laser-assisted processes reported for WO3-to-WSe2 conversions.

Perovskite Oxide Nanoparticles As High Performance Bifunctional Catalyst

Developing efficient electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are vital to the new generation of electrochemical storage and conversion devices such as electrolyzer, metal-air batteries, and fuel cells. For the demand of reversible fuel cells and rechargeable metal-air batteries, the bifunctional catalyst that can be used for both ORR and OER is gathering attention. In order to address the longstanding problems with high cost and poor stability of noble metal electrocatalysts, perovskite (ABO3 formula, where A is rare-earth or alkaline metal and B is transition metal) with low cost, high versatility in structure and potential as bifunctional catalyst is of special interest. Applying our successful and novel polymer-assisted chemical solution (PACS) method, we will present the controlled synthesis of (La0.8Sr0.2)x(Mn1-yBy)O3 (B: Ir and Co, x=0-0.1, y=0-0.2) nanoparticles with different particle sizes, A-site nonstoichiometry, B-site doping, and oxygen vacancy, and epitaxial thin films with different crystal orientations. Stuctural characterizations and electrochemical analysis are utilized to investigate the correlation between their compositions, structures, and electrochemical properties.

Polymer-assisted chemical solution synthesis of La0.8Sr0.2MnO3-based perovskite with A-site deficiency and cobalt-doping for bifunctional oxygen catalyst in alkaline media

The polymer-assisted chemical solution (PACS) method was used for the synthesis of La0.8Sr0.2MnO3 (LSM)-based perovskite catalyst network with nanoparticle size of 30–80 nm to enhance oxygen evolution reaction (OER) activity and maintain highly active oxygen reduction reaction (ORR). Samples investigated include the A-site cation deficient (La0.8Sr0.2)0.95MnO3-δ (ALSM) and the A-site cation deficient with the B-site cobalt-doped (La0.8Sr0.2)1-xMn1-xCoxO3-δ (x = 0.05 and 0.1 for LSMC5 and LSMC10, respectively). X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) aided in physical characterizations. Electrochemical properties were tested in 0.1 M KOH solution by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Our results indicate as compared to LSM, the lattice-shrunk ALSM with high oxygen vacancy displays enhanced OER performance, but its inferior ORR activity could be caused by reduced crystallinity. LSMC5 and LSMC10 show lowest total overpotential (0.93 and 0.91 V vs. Ag/AgCl (3.5 M)) with slightly less efficient ORR, despite their superior specific kinetic current density. Oxygen vacancy induces Fermi level upshift and reduced resistivity, while Co-doping increases orbital hybridization and enhances charge transfer. Understanding how the A-site non-stoichiometry and the B-site doping influence the BO covalence is the key to the rational design of perovskite bifunctional oxygen catalysts.

Plasmonic Ag nanoparticles decorated NaNbO3 nanorods for efficient photoelectrochemical water splitting

In the present work, photoanodes comprising of NaNbO3 nanorods and Ag nanoparticles decorated NaNbO3 nanorods have been fabricated by using hydrothermal and chemical solution method respectively. Photoelectrochemical water splitting performance of the fabricated photoanodes have been measured and it is found that Ag decorated NaNbO3 nanorods exhibit ∼4 fold enhancement in photocurrent as compared to bare NaNbO3 nanorods. The enhancement in the photoelectrochemical water splitting activity of Ag decorated NaNbO3 nanorods is attributed to efficient charge carrier separation and visible light sensitization due to Ag nanoparticles on NaNbO3 nanorods.

Large energy storage density, low energy loss and highly stable (Pb0.97La0.02)(Zr0.66Sn0.23Ti0.11)O3 antiferroelectric thin-film capacitors

In this work, high performance (Pb0.97La0.02)(Zr0.66Sn0.23Ti0.11)O3 polycrystalline antiferroelectric thin-film was successfully fabricated on (La0.7Sr0.3)MnO3/Al2O3(0001) substrate via a cost-effectively chemical solution method. A large recoverable energy storage density (Wre) of 46.3 J/cm3 and high efficiency (η) of 84% were realized simultaneously under an electric field of 4 MV/cm by taking full advantage of the linear dielectric response after the electric field induced antiferroelectric-ferroelectric transition. Moreover, the PLZST thin-film displayed high temperature stability. With increasing temperature from 300 K to 380 K, the Wre decreased only 1.3%. The film also exhibited good fatigue endurance up to 1 × 105 cycling under an electric field of 2.2 MV/cm. Our work underlines the importance of the interface quality between the film and the substrate and the important role of linear dielectric answer after saturation in the improvement of the energy storage density and efficiency of antiferroelectric materials.

Fabrication of Up-Conversion Phosphor Films on Flexible Substrates Using a Nanostructured Organo-Silicon.

Up-conversion phosphors have attracted considerable attention because of their applications in solid-state lasers, optical communications, flat-panel displays, photovoltaic cells, and biological labels. Among them, NaYF4 is reported as one of the most efficient hosts for infrared to visible photon up-conversion of Yb3+ and Er3+ ions. However, a low-temperature method is required for industrial scale fabrication of photonic and optoelectronic devices on flexible organic substrates. In this study, hexagonal β-NaYF4: 3 mol% Yb3+, 3 mol% Er3+ up-conversion phosphor using Ca2+ was prepared by chemical solution method. Then, we synthesized a nanostructured organo-silicon compound from methyl tri-methoxysilane and 3-glycidoxy-propyl-trimethoxy-silane. The transmittance of the organo-silicon compound was found to be over 90% in the wavelength range of 400~1500 nm. Then we prepared a fluoride-based phosphor paste by mixing the organo-silicon compound with Na(Ca)YF4:Yb3+, Er3+. Subsequently, this paste was coated on polyethylene terephthalate, followed by heat-treatment at 120 °C. The visible emission of the infrared detection card was found to be at 655 nm and 661 nm an excitation wavelength of 980 nm.

Synthesis of nanostructure manganese doped zinc oxide/polystyrene thin films with excellent stability, transparency and super-hydrophobicity

Superhydrophobic transparent thin films using Mn doped zinc oxide (Mn/ZnO) and polystyrene (PS) composites have been synthesized successfully by chemical solution method. The nanocomposites thin films were fabricated by using Mn/ZnO and PS mixture in toluene, followed by film casting on glass substrate. For a comparison ZnO nanoparticles thin film was also prepared with PS. Mn/ZnO nanostructures have been synthesized by hydrothermal method using hexamethylenetetramine (HMTA) as a capping agent. The XRD analysis shown that the development of hexagonal wurtzite structure of Mn/ZnO with preferred (101) orientation. SEM analysis shown that Mn/ZnO nanorods have been uniformly dispersed in the PS matrix. Water contact angle (WCA) was found as 107° and 151° for the ZnO@PS and Mn doped ZnO@PS thin film, respectively. The transparency of the Mn doped ZnO@PS films are also large (∼90%) as compared to ZnO@PS film (∼80%) which is attributed to enhanced energy band gap of ZnO after Mn doping. The larger contact angle (WCA ∼151°) in the Mn/ZnO@PS thin film has been recognized to the rough surface of PS thin film due to the presence of Mn/ZnO nanorods. The present process is very simple and embrace ability for extensive applications for making super hydrophobic transparent surfaces.

Solution-Processed Nb-Substituted BaBiO3 Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Photoelectrochemical (PEC) water reduction is a long-term strategical technology for hydrogen production. In this work, we synthesize a series of compact and nano/mesoporous Nb-substituted BaBiO3 [i.e., Ba2Bi(Bi1–xNbx)O6, 0 ≤ x ≤ 0.93, BBNO] thin films using cost-effective chemical solution methods. The synthesized BBNO alloy based thin films demonstrate tunable bandgaps from 1.41 eV (x = 0) to 1.89 eV (x = 0.93) to efficiently absorb the solar spectrum and p-type conductivities suitable for hydrogen production. The photoelectrodes with a configuration fluorine-doped SnO2/BBNO (0 ≤ x ≤ 0.93)/Pt produce cathodic photocurrents of 0.05–1 mA·cm–2 at 0 VRHE (volt versus reversible hydrogen electrode) measured in a neutral (pH = 7.2) phosphate buffer and under simulated AM 1.5G illumination (100 mW·cm–2). The BaBiO3 without Nb alloying based electrode delivers the best photocurrent of 1 mA·cm–2 at 0 VRHE but is subjected to severe corrosions during the PEC related tests. Alloying Nb has an obvious influence on enhancing the material stability against corrosion. With Nb alloying, the screen-printed nanoporous BBNO (x = 0.6, bandgap = 1.62 eV) based photoelectrode generates a better photocurrent of 0.2 mA·cm–2 at 0 VRHE with a highly positive onset at 1.5 VRHE enabling unbiased water reduction.

Polymer assisted deposition of epitaxial oxide thin films

Chemical solution methods for thin-film deposition constitute an affordable alternative to high-vacuum physical technologies, like Sputtering, Pulsed Laser Deposition (PLD) or Molecular Beam Epitaxy (MBE).

Low-temperature crystallization of solution-derived metal oxide thin films assisted by chemical processes.

Over the last few years the efforts devoted to the research on low-temperature processing of metal oxide thin films have increased notably. This has enabled the direct integration of metal oxide layers (amorphous semiconductors) on low-melting-point polymeric substrates for flexible electronic systems, which adds to the economic and environmental benefits of the use of these processes with reduced energy consumption. More challenging is the preparation of crystalline complex oxide films at temperatures compatible with their direct integration in flexible devices. However, the usually high crystallization temperatures (>600 °C) impede the development of devices that take full advantage of the large variety of oxide functionalities available. This tutorial review analyzes a number of strategies based on wet chemical methods for inducing the crystallization of metal oxide thin films at low temperatures. The key mechanisms are explained in relation to the specific step of the fabrication process reached in an earlier stage: the formation of a defect-free, highly densified amorphous metal-oxygen network or the actual crystallization of the metal oxide. The role of photochemistry, where light can be used as a complementary energy source to induce crystallization, is particularly highlighted. This requires the synthesis of novel photosensitive solutions (modified metal alkoxides, charge-transfer metal complexes or structurally designed molecular compounds) and a precise control over the reactions promoted by UV irradiation (photochemical cleavage, ozonolysis, condensation or photocatalysis). Relevant examples derived from the integration of crystalline metal oxide thin films on flexible substrates (≤350 °C) illustrate the most recent achievements in this field.

A facile route for fabrication of hierarchical porous Nb2O5/ZnO composites with enhanced photocatalytic degradation of palm oil mill effluent

A facile route was demonstrated for the synthesis of hierarchical porous ZnO microspheres based on a surfactant-free chemical solution method. The as-synthesized ZnO were assembled by large numbers of interleaving nanosheets and formed an open porous structure. Under UV irradiation, the as-synthesized ZnO exhibited photocatalytic property on the degradation of palm oil mill effluent (POME) solution. The Nb2O5 decorated ZnO photocatalysts (Nb2O5/ZnO) with enhanced photocatalytic performances were also synthesized via a facile and rapid route. Compared with ZnO, the Nb2O5(3 wt%)/ZnO exhibited the best POME degradation and colour removal efficiencies of 91.7% and 100%, respectively after 240 min irradiation. Phytotoxicity of the POME after Nb2O5/ZnO photocatalysis was significantly reduced via the measurement of radicle lengths of Vigna radiata. The observed results demonstrated the photocatalytic technology using hierarchical Nb2O5/ZnO composites had the potential to effectively purify wastewater.

Structural, multiferroic, dielectric and magnetoelectric properties of (1-x)Ba0.85Ca0.15Ti0.90Zr0.10O3-(x)CoFe2O4 lead-free composites

High performance lead-free multiferroic composites with strong magnetoelectric coupling effect are desired to replace lead-based ceramics in multifunctional device applications due to increasing environmental issues. We report crystal structure, ferroelectric, magnetic, dielectric and magnetoelectric properties of (1-x)Ba0.85Ca0.15Ti0.90Zr0.10O3-(x)CoFe2O4 (BCTZ-CFO) lead-free composites with x = 0.1, 0.3, 0.5, 0.7 and 0.9 synthesized by chemical solution method. BCTZ power was synthesized by sol-gel method while CFO was prepared by metallo-organic decomposition (MOD) method. The XRD results confirm successful formation of the BCTZ-CFO composites without presence of any impurity phase. At room temperature, the BCTZ-CFO composites show multiferroic behavior characterized by ferroelectric and ferromagnetic hysteresis curves. The composite having 10 wt% of CFO exhibited maximum polarization, remnant polarization and coercive field of Ps ∼ 5.1 µC/cm2, Pr ∼ 1.4 µC/cm2 and Ec ∼ 11.6 kV/cm respectively. The BCTZ-CFO composite with 90 wt% of CFO incorporation exhibits improved ferromagnetic properties with Ms ∼ 32 emu/g, Mr ∼ 11.7 emu/g and Hc ∼ 504 Oe. Mӧssbauer spectra analysis show two sets of six-line hyperfine patterns for BCTZ-CFO composites, indicating the presence of Fe3+ ions in both A and B sites. Increasing BCTZ content was found to decrease the hyperfine field strength at both sites and is consistent with the decreasing magnetic moment observed for the samples. The maximum dielectric constant value ε′ ∼ 678 is obtained at 1 MHz for composite with 10 wt% of CFO phase. The results indicate that the BCTZ-CFO composites are potential lead-free room temperature multiferroic systems.

Kinetics study on the generation of hydrogen from an aluminum/water system using synthesized aluminum hydroxides

Kinetics study on the generation of hydrogen from an Al/water system is performed. The reaction is affected by three major factors such as the concentration of hydroxyl ions (pH values), catalysts, and temperature. However, these factors are interacted and sometimes difficult to separate. This study demonstrates how these factors affect the generation of hydrogen in an Al/water system. Aluminum hydroxide, Al(OH)3 (bayerite phase), synthesized using a chemical solution method, is proved to be a very effective catalyst for the reaction of Al and water. Approximately 95% yield (1300 mL) of hydrogen is produced from 1 g Al in 10 mL water using 3 g Al(OH)3 catalyst at room temperature within 1 minute. The generation rate of hydrogen is accelerated due to the catalyst Al(OH)3 and the exothermic heat. In this report, a ball-mixing process, the ratio of Al:Al(OH)3:H2O, and the reacting temperatures are investigated to clarify the effect of catalyst Al(OH)3. The synthesized Al(OH)3 catalyst is found to reduce the activation energy of Al/water reaction from 158 kJ/mol to 73.3~76.9 kJ/mol. The roles of hydroxyl ions (ie, pH values), temperature, and catalyst on this phenomenal reaction are explained using a kinetics study and the concept of Fick first law. The 3 factors all improve the flux of hydroxyl ions through the passive Al2O3 layer; therefore, the generation of hydrogen is enhanced.

Performance enhancement of quantum dot sensitized solar cells by treatment of ZnO nanorods by magnesium acetate

In this work, the performance of Quantum dot-sensitized solar cells (QDSSCs) is enhanced with the treatment of ZnO nanorods by magnesium acetate. A chemical solution method is used for decoration of magnesium acetate on the ZnO nanorods. Current density–voltage (J-V) results show short-circuit current density (J sc ), open circuit voltage (V oc ), and power conversion efficiency (PCE) are enhanced by treatment of the photoanode with magnesium acetate from 13.76 to 15.47 mAcm−2, 557 to 668 mV, and 2.64 to 5.47%, respectively. This performance improvement of the cell is attributed to the reduction of the surface density of defects at ZnO surface and consequently decreasing recombination of the photoelectrons with surface defects at ZnO surface with the treatment of ZnO nanorods by magnesium acetate. Electrochemical impedance spectroscopy (EIS) results indicate recombination resistance is increased with decoration magnesium acetate on the ZnO nanorods, which is caused fill factor (FF) raises from 0.35 to 0.53. Also, electron lifetime at the photoanode/electrolyte interface is improved.