Tianjun Li

Indium-doped SnO2 nanobelts for high-performance transparent and flexible photosensors by a facile assembly

Flexible and transparent electronics is the emerging future technology for optoelectronic devices. Recently, it has attracted considerable attention from the research community due to its prodigious commercial applications. Herein, we report highly flexible and transparent ultraviolet photosensors based on indium-doped tin oxide nanobelts with enhanced simultaneous photosensitivity and recovery speed, compared to pure SnO2 nanobelts. Optoelectronic properties of the nanobelt photosensors have been found to be strongly related to the indium doping concentration and grain size of the nanobelts. A facile assembly method has been used to prepare the well-aligned nanobelt device for UV photosensors. Excellent flexible properties of the nanobelts have been explored, which show a superior response during bending tests and almost maintain their properties after 300 bending cycles. The enhanced photosensitivity of about 70 times that of undoped SnO2 nanobelts along with a highly enhanced recovery speed of less than 1.75 s have been achieved by the precise doping of In3+ into SnO2 lattice nanobelts. All these results show that our prepared photosensors demonstrate superior mechanical, electrical, and optical properties for their use in flexible and transparent electronics.

High photodetectivity of low-voltage flexible photodetectors assembled with hybrid aligned nanowire arrays

One-dimensional (1-D) hybrid nanostructures with high opto-electronic performance, flexible features, and a rationally designed device assembly have an exponentially growing demand for their use in transparent and flexible photodetectors. To meet these requirements, a cost effective and facile processing route is mandatory for their fabrication and integration into the device assembly. Herein, we have successfully assembled photodetectors from high quality well-oriented uniaxially aligned hybrid ZnO–ZnGa2O4 nanofibers. Our prepared flexible devices demonstrate outstanding performance in terms of large responsivity (1.73 × 102 A W−1), high photodetectivity (∼1.02 × 1012 Jones), and external quantum efficiency (7.10 × 104%) along with fast rise and recovery times of less than 400 and 500 ms, respectively. In addition, the prepared photodetectors have shown outstanding flexibility and stability with more than 70% retention in photosensitivity at a very small bending radius of 2 mm. The synthesized hybrid nanofibers have also shown more than 80% transparency in the visible range (400–700 nm). The assembled hybrid photodetectors indicate that ZnO–ZnGa2O4 nanofibers are highly valuable for optoelectronic devices. It is also worth emphasizing that our assembled flexible photodetectors based on hybrid nanofibers with high surface-to-volume ratio have promising applications in soft electronics and invisible optoelectronic devices.

Transparent Ultraviolet Photodetectors Based on Ga2O3 Electrospun Nanowires

Ultraviolet photodetectors (PDs) based on low-dimensional (LD) gallium oxide nanofibers were synthesized and assembled by a low cost and scalable electrospinning method. Highly uniaxially aligned nanofibers were used to assemble photodetectors. Photoconductive investigations indicate that the prepared photodetectors (PDs) are highly sensitive to ultraviolet (UV) light. The prepared photodetectors have shown a high photosensitivity (103), fast photoresponse, excellent stability, and reproducibility under the illumination of UV light 254 nm. These electrospun nanofibers have also shown a high transparency (<85%) in the visible light 400-700 nm range. The high transparency of these nanobelts demonstrates their use for invisible UV photosensors.

Enhanced Ionic Conductivity in Ce0.8Gd0.2O2-δ Nanofiber: Effect of the Crystallite Size

The relationship between the microstructure and the conductivity of nanocrystallized oxygen ionic electrolytes has been received great interest since it provides guidelines for designing electrolytes with high performances which might find applications in fuel cells and oxygen sensors. Here, we present a strategy for controlling the calcination temperature to tune the crystallite size and ionic transport properties of solid electrolyte. Different crystallite sizes of Ce0.8Gd0.2O2-δ (CGO) nanofiber electrolytes were prepared. As the average crystallite size decreased from 27 nm to 8 nm, the conductivity of the nanofibers increased by more than five times. An exceptionally high oxide ion conductivity of 0.023 S∙cm-1 for the nanofibers was observed at 550°C. These insights into the effect of the crystallite size on the structure and the conductivity allow a better control of the electrical properties of solid electrolytes, which might foster their applications in electrochemical devices operable at lower temperatures.

Synthesis of La2NiO4+δ Nanofibers by Electrospinning Method and their Application

La2NiO4+σ nanofibers exhibiting typical Ruddlesden–Popper structure (K2NiO4) were fabricated by a facile electrospinning method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the structure, morphology and crystal process of the La2NiO4+σ nanofibers. For electrical properties measurement, uniaxially aligned nanofibers were directly collected and assembled into electrode. In our research, La2NiO4+σ phase forms above 873K with no impurity phase emerges during the thermal treatments. The nanofibers are smooth and uniform throughout the entire length and the grain is growing as calcination temperature increases. Furthmore, the La2NiO4+σ nanofibers own high mixed conductivity at 773K, laying good foundation for intermediate temperature solid oxide fuel cells application.

Fabrication of YSZ/SNDC Bilayer Electrolytes by Spark Plasma Sintering

Doped ceria has been reported as a promising candidate of electrolyte applicable for solid oxide fuel cells (SOFCs) and oxygen sensors due to its high ionic conductivity at intermediate temperature. However, it suffers from certain limitations including the existence of electronic conductivity at reduced atmosphere, which would thus increase the leakage current in cells, and the low fracture strength. In this work, we fabricated a bilayer electrolyte with samarium and neodymium co-doped ceria (SNDC) and yttrium stabilized zirconia (YSZ) using spark plasma sintering (SPS) method, which possess the advantages of two layers, high conductivity of SNDC and good electron blocking ability of YSZ. Both layers of the specimen we obtained were dense and well crystallized according to the scanning electron microscope (SEM) and X-ray diffraction (XRD). The bilayer electrolyte exhibits improved ionic conductivity than YSZ with the value of 1.7 S/cm at 550.