Search

Tin(IV) oxide (SnO2) nanostructures, which possess larger surface areas for transporting electron carriers, have been used as an electron transport layer (ETL) in perovskite solar cells (PSCs). However, the reported power conversion efficiencies (PCEs) of this type of PSCs show a large variation. One of the possible reasons for this phenomenon is the low reproducibility of SnO2 nanostructures if they are prepared by different research groups using various growth methods. This work focuses on the morphological study of SnO2 nanostructures grown by a solvothermal method. The growth parameters including growth pressure, substrate orientation, DI water-to-ethanol ratios, types of seed layer, amount of acetic acid, and growth time have been systematically varied. The SnO2 nanomorphology exhibits a different degree of sensitivity and trends towards each growth factor. A surface treatment is also required for solvothermally grown SnO2 nanomaterials for improving photovoltaic performance of PSCs. The obtained results in this work provide the research community with an insight into the general trend of morphological changes in SnO2 nanostructures influenced by different solvothermal growth parameters. This information can guide the researchers to prepare more reproducible solvothermally grown SnO2 nanomaterials for future application in devices. [ABSTRACT FROM AUTHOR]

Weak‐light photodetection shows considerable potential in both theoretical and technical aspects while it would be a key issue to explore new candidate materials for practical application in view of high reliability and durability of the devices under ambient conditions. In this work, Ag2HgS2 single crystal rods (SCRs) with length up to 1.2 cm and width ranging from 10 to 200 µm are successfully fabricated in pure phase via facile solvothermal process at 200 °C for 24 h for the first time. The Ag2HgS2 SCRs are technically investigated, and the study reveals that they are in high quality via the determination of their crystal structure, morphology, and optical properties. Density functional theory (DFT) calculations are carried out to explore more reliably details on the band structure of bulk Ag2HgS2. Meanwhile, a series of photodetectors based on the individual Ag2HgS2 SCRs are fabricated, and they convey sensitive responses to a 0.170 µW cm−2 weak light and unanimous responses to incident light with different wavelengths from 254 to 980 nm. In addition, the devices show excellent detecting performances without any obvious slump after the Ag2HgS2 SCRs exposed in air over 18 months. [ABSTRACT FROM AUTHOR]

The effect of microbe combination with TiO2 on photocatalytic degradation of Rhodamine B was investigated. The self-assembled TiO2 spheres were synthesized by the solvothermal method for preparation of hybrid TiO2/Paint Sludge Extracted Microbe (PSEM) composite. The structure of as-synthesized TiO2 was analyzed by the powder X-ray diffraction method, and phase purity was verified with Raman analysis. Spherical morphology and self-assembled nature of TiO2 was confirmed by field emission scanning electron microscopy (FE-SEM). PSEM extracted from Paint sludge and was used to synthesize TiO2/PSEM hybrid composite. The dispersion of TiO2 self-assembled spheres on the walls of PSEM was confirmed with FE-SEM micrographs. TiO2/PSEM composite (94%) showed enhanced photocatalytic dye degradation when compared with as-synthesized TiO2 (85%). [ABSTRACT FROM AUTHOR]

Abstract While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO 2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO 2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA 0.83 MA 0.17 Pb(Br 0.17 I 0.83) 3 with optimized composition is used as the active layer. The excellent refractive index matching between the perovskite and TiO 2 , coupled with strong Mie scattering in the nanorod geometry results in broadband near-zero backscattering and high forward scattering, upon coating of HATNRs with perovskite. The maximum suppression of backscattering is found at ∼600 nm. The HATNRs ETL also improves the extraction of electrons from the perovskite layer and results in superior blocking of carrier recombination at the perovskite layer/FTO interface. Graphical abstract Image 1 Highlights • Perovskite-coated horizontal TiO2 nanorods ↓ backscattering & ↑ forward scattering. • Experiments and FDTD simulations confirmed nanophotonic enhancement. • Mixed phase ETL improves electron extraction from perovskite active layer. • Comprehensive optoelectronic characterization by TRPL, KPFM, EIS, IMPS and IMVS. • Comprehensive material characterization using TEM, EDS, XPS and UPS. [ABSTRACT FROM AUTHOR]

Abstract Cu 2 ZnSnSe 4 (CZTSe) nanocrystals were prepared by a solvo-thermal method using elemental copper, zinc, tin and selenium powders as precursors and ethylenediamine as a stabilizer and chelating medium. The particles were synthesized at 180 °C after which they were annealed at 300 °C and 400 °C for 1 h. The influence of annealing the nanocrystals, on the crystal structure, particle size, morphology, composition and optical properties has been investigated. As-grown particles were found to contain secondary phases, which subsequently transformed into CZTSe nanocrystals upon annealing. XRD and Raman results confirmed that the samples recrystallized into kesterite CZTSe on annealing at 400 °C. SEM studies show that the as-grown material has a platelet like morphology, and after annealing at 400 °C, freshly formed nanosized particles (10–20 nm) appear. TEM studies reveal that the grain size of CZTSe nanoparticles is about 5–10 nm. Optical studies show that the band gap energy exhibits a blue shift in the range 1.3–1.6 eV, indicative of quantum confinement of electrons. Highlights • Single step nanocrystalline growth of Cu 2 ZnSnSe 4 nanoparticles by solvothermal method. • XRD and Raman studies reveal single phase growth of CZTSe. • Stochiometric growth of material confirmed by EDAX analysis. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM) is a widely used tool to characterize materials. The required samples need to be electron transparent which should be achieved without changing the microstructure. This work describes different TEM sample preparation techniques of nanostructured CuInS 2 thin films on fluorine-doped tin oxide substrates, synthesized solvothermally using l ‐cysteine as sulfur source. Focused ion beam lamellae, conventional cross section samples and scratch samples have been prepared and investigated. It was possible to prepare appropriate samples with each technique, however, each technique brings with it certain advantages and disadvantages. FIB preparation of solvothermally synthesized CuInS 2 suffers from two main drawbacks. First, the whole CuInS 2 layer displays a strongly increased Cu content caused by Cu migration and preferential removal of In. Further, electron diffraction shows the formation of an additional CuS phase after Ga + bombardment. Second, diffraction analysis is complicated by a strong contribution of crystalline Pt introduced during the FIB preparation and penetrating into the porous film surface. The conventional cross sectional CuInS 2 sample also shows a Cu signal enhancement which is caused by contribution of the brass tube material used for embedding. Additionally, Cu particles have been observed inside the CuInS 2 which have been sputtered on the film during preparation. Only the scratch samples allow an almost artefact-free and reliable elemental quantification using energy-dispersive X-ray spectroscopy. However, scratch samples suffer from the drawback that it is not possible to determine the layer thickness, which is possible for both cross sectional preparation techniques. Consequently, it is concluded that the type of sample preparation should be chosen dependent on the required information. A full characterization can only be achieved when the different techniques are combined. [ABSTRACT FROM AUTHOR]

In this work a new method for the growth of thick silver nanowires (AgNWs) is presented. With this method, AgNWs are obtained in a first step by a modified polyol method and used, in a second step, as seeds for further growth in a solvothermal process. The variation of structure, morphology and dimensions of the obtained silver nanostructures was studied. It was found that the composition of solvent (ethylene glycol and isopropyl alcohol) used in the solvothermal process greatly influences the composition, morphology and dimensions of the final product. Several times longer and thicker silver nanowires, compared with the initial seeds, having diameters between 200 and 250 nm and lengths between 10 and 25 μm, can be obtained by controlling the solvent composition. [ABSTRACT FROM AUTHOR]

Significantly enhanced H2/CH4 (ca. 80) selectivity was realized by effective suppression of the framework flexibility of a prepared ZIF-8 membrane. Initially a ZnO buffer layer consisting of 20 nm-sized ZnO-nanoparticle aggregates was fabricated by controlled calcination of a ZnAl-NO3 layered double hydroxide membrane. Owing to its high chemical reactivity, the ZnO buffer layer was partially converted into a well-intergrown ZIF-8 membrane with a certain penetration depth upon solvothermal treatment with ligands. Our method may represent a new concept for the design of advanced MOF membranes with high selectivity. [ABSTRACT FROM AUTHOR]

Uniform zirconium-based porphyrin metal–organic framework (MOF-525) thin films are grown on conducting glass substrates by using a solvothermal approach. The obtained MOF-525 thin film is electrochemically addressable in aqueous solution and shows electrocatalytic activity for nitrite oxidation. The mechanism for the electrocatalytic oxidation of nitrite at the MOF-525 thin film is investigated by cyclic voltammetry. The redox mechanism of the MOF-525 thin film in the KCl aqueous solution is studied by amperometry. The MOF-525 thin film is deployed as an amperometric nitrite sensor. The linear range, sensitivity, and limit of detection are 20–800 μM, 95 μA/mM-cm 2 , and 2.1 μM, respectively. [ABSTRACT FROM AUTHOR]

The film growth of the zeolitic imidazolate framework-8 on a copper-based substrate is reported for the first time in the literature. The growth mechanism on copper foils is analyzed, and it is demonstrated that during synthesis the development of the metal-organic framework (MOF) film is sensitive to the interactions produced between the support surface, the solvent and the reactants. In order to compare the surface interactions during synthesis, Fecralloy foils, porous alumina disks and macroporous cordierite monoliths are also analyzed. The physicochemical properties of the materials are evaluated by XRD, SEM, EPMA, AAS, DRIFT and XPS. In dimethylformamide-based media, no ZIF-8 film develops on the copper surface due to unfavorable interactions that make its growth non selective. At the same time, the formation of a dense ZnO layer is favored, this layer being promoted by decomposition products of the solvent and the zinc reagent. When water-based media are used, those interactions are modified thus avoiding the formation of oxide, but the growth kinetics of the ZIF-8 film is still low. On the other hand, when using mixtures based on methanol with the addition of acetate, continuous, uniform, and adherent ZIF-8 films can be obtained. Such films develop preferential crystallographic orientations in planes {200} and {110}, have thicknesses between 5 and 10 microns and good mechanical and thermal stability. The results obtained provide a platform for the obtention of ZIF-8 films on copper structures, which is relevant for the development of new structured catalysts based on MOFs. [ABSTRACT FROM AUTHOR]

Separation methods based on 2D interlayer galleries are currently gaining widespread attention. The potential of such galleries as high-performance gas-separation membranes is however still rarely explored. Besides, it is well recognized that gas permeance and separation factor are often inversely correlated in membrane-based gas separation. Therefore, breaking this trade-off becomes highly desirable. Here, the gas-separation performance of a 2D laminated membrane was improved by its partial self-conversion to metal-organic frameworks. A ZIF-8-ZnAl-NO3 layered double hydroxide (LDH) composite membrane was thus successfully prepared in one step by partial conversion of the ZnAl-NO3 LDH membrane, ultimately leading to a remarkably enhanced H2/CH4 separation factor and H2 permeance. [ABSTRACT FROM AUTHOR]

Monocrystalline n‐TiO2 nanowires of the rutile phase (Rtl‐NWs) grown by a scalable hydrothermal method constitute a functional oxide nanomaterial with potential applications in photovoltaics, photocatalysts, field emitters and electrochemical battery anodes. Carrier transport in Rtl‐NWs is of fundamental importance but has hitherto been inferred indirectly via impedance and intensity‐modulated spectroscopic techniques. We report an effective electron drift mobility of 1.95 × 10–5 cm2 V–1 s–1 in rutile nanowire arrays directly measured using the time‐of‐flight (TOF) and space charge limited current techniques. In addition, we measure an equilibrium free electron concentration of ∼1014 cm–3 and a trap density of 3.5 × 1016 cm–3 in rutile nanowires. These results point to the importance of reducing traps to improve charge transport in rutile nanowires. Transient photocurrents in rutile nanowires. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) Part of Focus Issue on “Functional Oxides” (Eds.: T. Frauenheim, J. M. Knaup, P. Broqvist, S. Ramanathan) Vertically oriented, monocrystalline, rutile‐phase TiO2 nanowire arrays are synthesizable by a simple, inexpensive and scalable hydrothermal process but their electronic properties for photovoltaic, photocatalytic and other applications are not well understood. This Letter presents the first direct measurements of electron mobility in TiO2 nanowire arrays using a combination of time‐of‐flight and space‐charge limited current techniques, and finds electron mobility to be limited by fast capture of electrons into deep traps. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous anatase TiO2 nanospheres are successfully synthesized via a simple solvothermal method without the aid of templates. The effects of systematic growth periods on the morphological, structural and optical properties of the mesoporous TiO2 nanospheres are investigated. It was found that the samples prepared with a 25 h growth period yielded good interparticle connection with a well-defined sphere-like morphology when compared with the samples with the 15 and 20 h growth periods. High surface area of 188 m2 g−1 is obtained from the BET analysis for the 25 h grown TiO2 mesoporous nanospheres. Mesoporous TiO2 nanospheres with different growth periods are used to prepare a photoanode layer by spray pyrolysis deposition for dye-sensitized solar cell (DSSC) fabrication. The ruthenium dye (N719) and indoline dye (D205) are used as sensitizers in the devices. The effect of the photoanode active layer thickness on the DSSC conversion efficiency is investigated. It is found that the maximum efficiency (η) of 7.02 (N719) and 6.97% (D205) are achieved for a layer thickness of 16 μm.TiO2 mesoporous nanospheres is used as a scattering layer for standard P25 titania coated DSSC and the enhanced efficiency of 5.92 (N719) and 5.12% (D205) are obtained. [Copyright &y& Elsevier]

Continuous indium metal-organic framework thin films of In12O(OH)12[(OH)4·(H2O)5)][BTC]6 (MIL-96(In)) (BTC=1,3,5-benzenetricarboxylate) were prepared on indium tin oxide glass by in situ solvothermal growth method. The structure of the films was confirmed by X-ray diffraction. The growth process and the possible growth mechanism of MIL-96(In) films were investigated by a scanning electron microscopy. Furthermore, the influence of the reaction conditions on the morphology and thickness of films was studied. The best crack-free, continuous film with thickness of approximate 6μm was obtained at the proper concentrations of InCl3 and H3BTC of 25.0mmol·l−1 at 100°C for 12h. [ABSTRACT FROM AUTHOR]

Bismuth Selenide (Bi2Se3) nanoplates have been synthesized via a facile solvothermal route using the mixed solvents of ethylenediamine (EN) and ethylene glycol (EG) with the assistant ofpolyvinylpyrrolidone(PVP). The X-ray diffraction and Transmission electron microscopy (TEM) indicate that the nanoplates are well-crystallized single crystals with rhombohedral phase. Scanning electron microscopy (SEM) observations show that the nanoplates have approximate hexagonal outer shape with lateral length of 200–600 nm and thickness of 80–160 nm. The influences of solvents and PVP on the growth of the nanoplates were checked and it is found that EN can facilitate the formation of plate-like morphology while EG and PVP can benefit the uniform hexagonal outer shape. The P-type conduction of the Bi2Se3nanoplates is revealed by Hall measurement. [ABSTRACT FROM AUTHOR]

Abstract: One-step synthesis of wurtzite-structured ZnS thin nanorods with mean diameters of about 6nm is achieved by a novel ethanol amine (EA)-assisted solvothermal approach adopting ZnO and Na2S2O3·5H2O as starting reagents. The as-prepared ZnS nanorods are well-crystallized single crystals with growth direction along [001]. The effects of solvents, sources of zinc and sulfur are investigated in details and it is found that EA solvent plays a key role to control both the phase and morphology of the ZnS nanorods. The possible growth mechanism involving EA-mediated nucleation and one-dimensional (1D) growth is discussed. The optical properties of the wurtzite ZnS thin nanorods are characterized by UV–Vis absorption and photoluminescence spectra. [Copyright &y& Elsevier]

Abstract: Tunable LiFePO4/C thin films demonstrating high power were fabricated by drop-casting a LiFePO4 nano-plate/sucrose suspension on titanium foil, followed by pyrolysis at 600°C for 3h in nitrogen. The thickness, carbon content, and morphology of the LiFePO4/C film cathode can be adjusted by changing the amount of drop-cast, sucrose solution concentration and LiFePO4 raw material. For this work, well-crystallized LiFePO4 nano-plates synthesized via solvothermal route were used to prepare high power LiFePO4/C thin films. The resultant binder-free films consisted of well-packed LiFePO4 nano-plates coated with nano-carbon, a result of sucrose pyrolysis, and were directly assembled into cells for testing. The LiFePO4/C nano-composite film cathode delivered a lithium ion intercalation capacity of 162mAhg−1 and 90mAhg−1 at current density of 170mAg−1 (1C) and 1.7Ag−1 (10C), respectively, while demonstrating excellent cyclic stability. [Copyright &y& Elsevier]

Abstract: Solvothermal growth of cuprous selenide films on copper substrate has been succeeded by treating copper foil in the mixture of selenium powder and amines or hydrazine. The films were characterized by methods of XRD, SEM, TEM and optical spectra (Cu2Se, JCPDS 47-1448). Films with hexagonal microcrystals can be obtained in hydrazine/water reaction system. When CTAB (CTAB=cetyltrimethylammonium bromide) is added to the system, the film is composed of thin leaf-like microcrystals. When ethylenediamine (en) is used as solvent, the leaf-like microcrystals are crimped. [Copyright &y& Elsevier]