Jingjing Dong

Controllable synthesis of ZnO nanostructures on the Si substrate by a hydrothermal route

In this paper, controllable synthesis of various ZnO nanostructures was achieved via a simple and cost-effective hydrothermal process on the Si substrate. The morphology evolution of the ZnO nanostructures was well monitored by tuning hydrothermal growth parameters, such as the seed layer, solution concentration, reaction temperature, and surfactant. X-ray diffraction and photoluminescence measurements reveal that crystal quality and optical properties crucially depend on the morphology of the ZnO nanostructures. The ease of synthesis and convenience to tune morphology and optical properties bring this approach great potential for nanoscale applications.

The effect of solvents and surfactants on morphology and visible-light photocatalytic activity of BiFeO3 microcrystals

BiFeO3 microcrystals were prepared by hydrothermal method using different surfactants and solvents. The samples were examined by using X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The measurements showed that BiFeO3 microcrystals had solvent-dependent morphologies and crystal structure. The visible-light photocatalytic activity of BiFeO3 microcrystals was evaluated by degradating rhodamine B on a UV–Vis absorption spectrophotometer. These results showed that the kind of surfactants and solvents played a key role in the photocatalytic activity of BiFeO3 microcrystals.

High-sensitive switchable photodetector based on BiFeO3 film with in-plane polarization

A high-sensitive and fast-response photodetector based on BiFeO3 (BFO) ferroelectric thin film is fabricated using coplanar electrode configuration. A large photocurrent/dark current ratio is found up to two orders of magnitude at 1 V bias. Enhanced photocurrent and rectification behavior of the photodetector are observed after applying high voltage pulses to the BFO film. The short-circuit current varies systematically with the poling process and increases linearly with the light density. On the contrary, the open-circuit voltage keeps as a constant during the measurements. We attribute these behaviors to the depolarization field and the interfacial fields at the film-electrode interfaces. The BFO device presents a peak response of 0.15 mA/W at 365 nm and the response speed is on the order of tens of nanoseconds. Our work highlights the potential application of photodetector based on the ferroelectric materials.

Enhanced photocatalytic capability of zinc ferrite nanotube arrays decorated with gold nanoparticles for visible light-driven photodegradation of rhodamine B

One-dimensional nanostructures grown on substrates are favored for photocatalytic reactions because of their large specific surface areas and well-defined transport paths for charge carriers. In the present paper, zinc ferrite nanotube arrays are synthesized on indium-tin-oxide–glass substrates, and their photocatalytic capabilities are evaluated by degrading an aqueous solution of rhodamine B (RhB) under visible light irradiation. The photocatalytic performance of pure zinc ferrite nanotube arrays is unsatisfactory. To improve their photocatalytic abilities, the surfaces of zinc ferrite nanotube arrays are decorated with Au nanoparticles, significantly enhancing their photocatalytic capabilities for RhB degradation. The drastic improvement in the photocatalytic degradation ability is attributed to the effective separation of photogenerated electron–hole pairs in the Au-decorated zinc ferrite hybrid nanostructure, which facilitates the generation of oxidizing free radicals (i.e., O2• − and OH·) for RhB degradation.

Highly sensitive and ultrafast deep UV photodetector based on a .BETA.-Ga2O3 nanowire network grown by CVD

We investigated a high-performance deep ultraviolet photodetector based on a β-gallium oxide (β-Ga2O3) nanowire network. β-Ga2O3 nanowires were grown at different temperatures by a chemical vapor deposition method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrum analysis were utilized to characterize the structure and morphology. With increasing the temperature, the nanowires became thicker and their surface appeared more rough with many kinks and branch-like shapes. It is proposed that the growth mechanism is dominated by a combination of vapor–liquid–solid and vapor–solid growth. A photodetector based on the best quality β-Ga2O3 nanowire network was fabricated by a simple and cheap mask method, which exhibited excellent photoelectric performance. The responsive spectrum presented a peak response located at 231 nm with a sharp cutoff at 270 nm. The response rejection ratio of I 231 nm/I 290 nm is more than three orders of magnitude, demonstrating an intrinsic solar-blindness. The full width at half maximum of the response curve is only 1.2 ns under pulsed laser irradiation. The high sensitivity, superior selectivity, ultrafast response speed and simple fabrication technology show that the β-Ga2O3 nanowire network has promising application in solar-blind photodetectors.

Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on.PACS78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn

Highly ordered ZnO nanostructure arrays: Preparation and light-emitting diode application

In this paper, ordered arrays of various ZnO nanostructures were fabricated on both Si and p-GaN substrates via a hydrothermal process by the self-assembled nanosphere lithography (NSL). The morphology and orientation evolution of ZnO nanostructures were well-monitored by varying seed-layer-thickness, solution concentration, and underlying substrate. On this basis, the heterojunction light emitting diode (LED) based on the highly oriented ZnO nanocone array on the p-GaN substrate was fabricated and studied in detail. It is found that the ZnO nanostructure-based LED exhibits a much stronger ultraviolet (UV) emission peaked at 388 nm compared with its counterparts based on ZnO film, which is attributed to the low density of interfacial defects, improved carrier injection efficiency through the nano-sized junction, and excellent waveguiding property of the ZnO nanostructure array.

Synthesis of ZnO Nanocrystals and Application in Inverted Polymer Solar Cells

Controllable synthesis of various ZnO nanocrystals was achieved via a simple and cost-effective hydrothermal process. The morphology evolution of the ZnO nanostructures was well monitored by tuning hydrothermal growth parameters, such as solution concentration, reaction temperature, and surfactant. As-obtained ZnO nanocrystals with different morphologies, e.g., ZnO nanorods, nanotetrapods, nanoflowers, and nanocubes, were further introduced into the organic bulk heterojunction solar cells as the electron transport channel. It was found that the device performance was closely related to the morphology of the ZnO nanocrystals.

Flexible and high capacity lithium-ion battery anode based on a carbon nanotube/electrodeposited nickel sulfide paper-like composite

The integration of flexible carbon-based materials and high capacity anode materials is an effective route to obtain superior flexible electrode materials. In this work, nickel sulfide nanoparticles were electrodeposited on a CNT thin film to form a paper-like composite (NS@CNT). As a binder-free flexible Li-ion battery anode, a record specific capacity to date of ∼845 mA h g−1 at a current density of 60 mA g−1 in terms of the mass of the composite has been achieved. The high capacities were mainly attributed to reversible conversion reactions of nickel sulfide and the capacitance effect of the nanostructured composite.

Fabrication of Efficient Organic-Inorganic Perovskite Solar Cells in Ambient Air

Although many groups have been trying to prepare perovskite solar cells (PSCs) in ambient air, the power conversion efficiency (PCE) is still low. Besides, the effect of moisture on the formation of perovskite films is still controversial. In this paper, we studied the effect of moisture on the formation of perovskite films in detail, and found that moisture can speed up the crystallizing process of PbI2 films to form poor-quality films with large grain size and surface roughness, while, for the conversion of PbI2 to perovskite films, a small amount of moisture is not adverse, and even beneficial. On this basis, we report the successful fabrication of efficient mesoporous PSCs with PCE of 16.00% under ambient air conditions at 25% relative humidity by adding a small amount of n-butyl amine into the solution of PbI2 to enhance the quality of PbI2 films and thus to achieve high-quality perovskite films with smooth surface, large crystal grains, and high crystal quality.