Metal-Insulator Phase Transition in Quasi-One-Dimensional VO₂Structures

The metal-insulator transition (MIT) in strongly correlated oxides has attracted considerable attention from both theoretical and experimental researchers. Among the strongly correlated oxides, vanadium dioxide (VO2) has been extensively studied in the last decade because of a sharp, reversible change in its optical, electrical, and magnetic properties at approximately 341 K, which would be possible and promising to develop functional devices with advanced technology by utilizing MITs. However, taking the step towards successful commercialization requires the comprehensive understanding of MIT mechanisms, enabling us to manipulate the nature of transitions. In this regard, recently, quasi-one-dimensional (quasi-1D) VO2structures have been intensively investigated due to their attractive geometry and unique physical properties to observe new aspects of transitions compared with their bulk counterparts. Thus, in this review, we will address recent research progress in the development of various approaches for the modification of MITs in quasi-1D VO2structures. Furthermore, we will review recent studies on realizing novel functional devices based on quasi-1D VO2structures for a wide range of applications, such as a gas sensor, a flexible strain sensor, an electrical switch, a thermal memory, and a nonvolatile electrical memory with multiple resistance.</jats:p

Field effect transistors and phototransistors based upon p-type solution-processed PbS nanowires.

We demonstrate the fabrication of solution processed highly crystalline p-type PbS nanowires via the oriented attachment of nanoparticles. The analysis of single nanowire field effect transistor (FET) devices revealed a hole conduction behaviour with average mobilities greater than 30 cm2 V-1 s-1, which is an order of magnitude higher than that reported to date for p-type PbS colloidal nanowires. We have investigated the response of the FETs to near-infrared light excitation and show herein that the nanowires exhibited gate-dependent photo-conductivities, enabling us to tune the device performances. The responsivity was found to be greater than 104 A W-1 together with a detectivity of 1013 Jones, which benefits from a photogating effect occurring at negative gate voltages. These encouraging detection parameters are accompanied by relatively short switching times of 15 ms at positive gate voltages, resulting from a combination of the standard photoconduction and the high crystallinity of the nanowires. Collectively, these results indicate that solution-processed PbS nanowires are promising nanomaterials for infrared photodetectors as well as p-type nanowire FETs

Emerging Applications of Liquid Crystals Based on Nanotechnology.

Diverse functionalities of liquid crystals (LCs) offer enormous opportunities for their potential use in advanced mobile and smart displays, as well as novel non-display applications. Here, we present snapshots of the research carried out on emerging applications of LCs ranging from electronics to holography and self-powered systems. In addition, we will show our recent results focused on the development of new LC applications, such as programmable transistors, a transparent and active-type two-dimensional optical array and self-powered display systems based on LCs, and will briefly discuss their novel concepts and basic operating principles. Our research will give insights not only into comprehensively understanding technical and scientific applications of LCs, but also developing new discoveries of other LC-based devices

Colloidal quantum dot hybrids: an emerging class of materials for ambient lighting

The rapid growth of the global economy and urbanization have resulted in major worldwide issues such as greenhouse gas emission, air pollution and the energy crisis. Artificial ambient light is one of the greatest inventions in human history, but it is also one of the primary energy consumption constituents and a focus of the global grand energy challenge. Therefore, low cost and low energy consumption lighting technology is in high demand. In this review, we will summarise and discuss one of the emerging lighting technologies – white electroluminescence light-emitting diodes enabled by hybrid colloidal quantum dots (WQLEDs), which have attracted intense attention because of promising potential in both flat-panel backlighting and solid-state lighting. WQLEDs have unique high luminescence efficiency, broad colour tunability and solution processability. Over the past few decades, the development of colloidal quantum dot synthesis, material engineering and device architecture has highlighted the tremendous improvements in WQLED formation. As WQLED efficiencies approach those of molecular organic LEDs, we identify the critical scientific and technological challenges and provide an outlook for ongoing strategies to overcome these challenges

Wireless thin film transistor based on micro magnetic induction coupling antenna

A wireless thin film transistor (TFT) structure in which a source/drain or a gate is connected directly to a micro antenna to receive or transmit signals or power can be an important building block, acting as an electrical switch, a rectifier or an amplifier, for various electronics as well as microelectronics, since it allows simple connection with other devices, unlike conventional wire connections. An amorphous indium gallium zinc oxide (α-IGZO) TFT with magnetic antenna structure was fabricated and studied for this purpose. To enhance the induction coupling efficiency while maintaining the same small antenna size, a magnetic core structure consisting of Ni and nanowires was formed under the antenna. With the micro-antenna connected to a source/drain or a gate of the TFT, working electrical signals were well controlled. The results demonstrated the device as an alternative solution to existing wire connections which cause a number of problems in various fields such as flexible/wearable devices, body implanted devices, micro/nano robots, and sensors for the &apos;internet of things&apos; (IoT).1

Highly Monodispersed PbS Quantum Dots for Outstanding Cascaded-Junction Solar Cells.

High-performance cascaded-junction quantum dot solar cells (CJQDSCs) are fabricated from as-prepared highly monodispersed lead sulfide QDs. The cells have a high power conversion of 9.05% and a short-circuit current density of 32.51 mA cm-2. A reliable and effective stratagem for fabricating high-quality lead sulfide quantum dots (QD) is explored through a "monomer" concentration-controlled experiment. Robust QDSC performances with different band gaps are demonstrated from the as-proposed synthesis and processing stratagems. Various potential CJQDSCs can be envisioned from the band edge evolution of the QDs as a function of size and ligands reported here

Colour-encoded electroluminescent white light-emitting diode Eenabled by Perovskite-Cu-In-S quantum composites

Solution-processed quantum dot (QD) white light-emitting diodes (WLEDs) have received much attention as a viable light source in the next-generation large-area ambient lighting, flexible photonics and full-colour display backlighting technologies. Attributable to their solution processibility, tunable colour temperature, high quantum efficiency and high photostability, considerable research efforts have been spent on accumulating new insights into the materials and device architecture design for high-performance QD WLEDs. At present, prevalent research on WLEDs focuses on using QDs as a photoluminescence colour converter or using purely narrow linewidth QD LEDs to complement white colour spectra, which is not energy efficient as well as challenging to achieve Eye Comfort ambient colour coding. Herein, a quantum composite made from hybridising perovskite (CsPbBr3 and CsPb(Br1-xClx)3) and CuInS2 (CIS) QDs is proposed as a colour-encoded electroluminescence layer, which underpins good white colour temperature and bias stability for ambient lighting. Instead of using solely sharp emission QDs to match the white light spectra, broad light emission spectrum CIS QDs are used for colour temperature toning. In addition, the mixed-halide perovskite CsPb(Br1-xClx)3 QDs are successfully synthesised through a noninvasive halide ion exchange method associated with trimethylsilyl chloride additives, which provide a good colour purity in blue and green electroluminescence region. This rational-designed QD composites enable the as-prepared WLED electroluminescence spectra to match the ideal ambient light Commission International de l’Éclairage 1931 (CIE) colour coordinates with a mean value of 0.33, 0.34. Moreover, as-prepared WLEDs show a turn-on voltage of 4 V with negligibly small leakage current, good colour stability and electrical bias tolerance even under a broad range of driving voltages. Our results herald the advent of molecular level hybridisation of different quantum materials for high-performance electroluminescence white colour toning