Jie Xing

Fast and enhanced broadband photoresponse of a ZnO nanowire array/reduced graphene oxide film hybrid photodetector from the visible to the near-infrared range.

In the present work, a ZnO nanowire array/reduced graphene oxide film hybrid nanostructure was realized, and the photovoltaic responses from the visible to the near-infrared range were investigated. Compared with the pure ZnO nanowire array and rGO thin film, the hybrid composite exhibited a fast and greatly enhanced broadband photovoltaic response that resulted from the formation of interfacial Schottky junctions between ZnO and rGO.

Photoelectric effects of ultraviolet fast response and high sensitivity in LiNbO3 single crystal

The photoelectric effects in LiNbO3 (LNO) single crystal have been systematically studied with the two kinds of LNO wafers of tilt of 10° and untilted at the ambient temperature. The ultrafast response photoelectric effect of 120 ps rise time was observed in 10° tilted LNO single crystal with a 266 nm laser pulse of 25 ps duration. The photocurrent responsivity of untilted LNO with an interdigitated electrode of 10 μm finger width and 10 μm interspacing is 17.1 mA/W under the irradiation of 300 nm wavelength UV light at 10 V bias. The noise current under sunlight is only 73 pA at 10 V bias. The experimental results suggest that the LNO single crystal is one of the promising materials for photodetectors working in UV region.

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.

High-Performance Ultraviolet Photodetector Based on Polycrystalline

SrTiO3 (STO) thin film has been fabricated on fused-quartz wafer by radio-frequency magnetron sputtering. The Ag interdigited electrodes were then evaporated on STO thin film in order to form the metal-insulator-metal photoconductive detector. Our photodetector exhibits a high photoresponse in the range of 225-340 nm with an ultraviolet-visible rejection ratio (R310 nm/R400 nm) of two orders of magnitude, indicating an intrinsic characteristic of visible-blindness. The maximum photocurrent responsivity is about 105 mA/W measured at 310 nm and the corresponding quantum efficiency is 42.1%. The dark current is only 0.4 nA at 50 V bias. Furthermore, the STO thin film detector presents a transient photovoltaic signal with a rise time of ~330 ps and a fall time of ~480 ps under the excitation of a 355-nm-pulsed laser, suggesting an ultrafast response characteristic of our STO thin film detector.

{\rm SrTiO}_{3}

The defect chemistry of perovskite oxides involves the cause to most of their abundant functional properties, including interface magnetism, charge transport, ionic exchange, and catalytic activity. The possibility to achieve dynamic control over oxygen anion vacancies offers a unique opportunity for the development of appealing switchable devices, which at present are commonly based on ferroelectric materials. Herein, we report the discovery of a switchable photovoltaic effect, that the sign of the open voltage and the short circuit current can be reversed by inverting the polarity of the applied field, upon electrically tailoring the distribution of oxygen vacancies in perovskite oxide films. This phenomenon is demonstrated in lateral photovoltaic devices based on both ferroelectric BiFeO3 and paraelectric SrTiO3 films, under a reversed applied field whose magnitude is much smaller than the coercivity value of BiFeO3. The migration of oxygen vacancies was directly observed by employing an advanced annular bright-field scanning transmission electron microscopy technique with in situ biasing equipment. We conclude that the band bending induced by the motion of oxygen vacancies is the driving force for the reversible switching between two photovoltaic states. The present work can provide an active path for the design of novel switchable photovoltaic devices with a wide range of transition metal oxides in terms of the ionic degrees of freedom.

Thin Film

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.

Toward Switchable Photovoltaic Effect via Tailoring Mobile Oxygen Vacancies in Perovskite Oxide Films

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.

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

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.

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

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.

Synthesis of ZnO Nanocrystals and Application in Inverted Polymer Solar Cells

A solar-blind ultraviolet photodetector based on perovskite (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) single crystal has been fabricated. The Deep Ultra Violet (DUV)/Ultra Violet (UV) (200 versus 290 nm) ratio is more than three orders of magnitude under the applied bias voltage 200 V. Under illumination at 200 nm, the responsivity of this ultraviolet photodetector reaches 4 mA/W at 200 V bias. The corresponding quantum efficiency and detectivity are 2.76% and 1×1011 cm⋅Hz0.5/W, respectively. The ultrafast response with a rise time of 563 ps and full width half maximum (FWHM) of 1.085 ns is obtained. The high sensitivity, ultrafast response speed, and good signal-to-noise ratio demonstrate that the LSAT photodetector could be a promising candidate as the solar-blind ultraviolet photodetector.