Publications

Piezotronic and piezo-phototronic devices based on the third generation semiconductors

<p indent=0mm>Compared with the first-generation semiconductors (such as silicon, germanium) and the second-generation semiconductors (such as gallium arsenide, indium antimonide), the third-generation semiconductor materials represented by silicon carbide (SiC), zinc oxide (ZnO), gallium nitride (GaN) and cadmium sulfide (CdS) usually possess wider band gap, higher thermal conductivity, bigger electron saturation rate and better radiation resistance properties, and thus draw intensive attentions in high temperature and high frequency applications in recent years. Most of the third-generation semiconductors are wurtzite structures, which have piezoelectric effects due to their lack of symmetry in certain directions. This feature serves as a good bridge of transferring mechanical stress signals between the flexible semiconductor electronic devices and the surrounding environment or the host (e.g., the human body). Conventional piezoelectric effects are mainly found in barium titanate and lead zirconate titanate type perovskite materials, but such materials do not have semiconductor properties, thus limiting their use in electronics and optoelectronic devices. Our group has pioneered a new research field, i.e., piezoelectric nanogenerator, by utilizing third-generation semiconductor nanowires (such as ZnO nanowires) under a dynamic force. The piezoelectric potential generated by the dynamic strain on the nanowire can drive electrons to flow in the external load circuit, which is the basic principle of the piezoelectric nanogenerator. Piezoelectric nanogenerator based on ZnO nanowires was firstly proposed in 2006. When a uniform strain is applied on a non-centrosymmetric semiconductor, a piezo-potential will be induced in the semiconductor, accompanied with static piezoelectric charges distributed on the surfaces. This piezoelectric effect is commonly existed in the third generation semiconductors. The strain-induced piezo-potential and piezoelectric polarization charges can also statically and/or dynamically tune the transportation and photoelectric processes of carriers at the interfaces or junctions. The three ways coupling among piezoelectric, photoexcitation and semiconducting properties coined two new research fields, that is, the piezotronics and piezo-phototronics. In order to systematically explain the coupling properties of piezoelectric and semiconductor transport properties in such materials, our group first coined the term piezotronics in a paper published in 2007. The piezotronics is about the modulation of the metal-semiconductor interface barrier via piezoelectric potential acting as a “gate” voltage, which has been used to explain the transistor behavior observed in metal-ZnO-metal structures and the strain-gated diode effect of metal-ZnO structures. The basic core of piezo-phototronics is to regulate the generation, separation, transport and/or recombination of photogenerated carriers at interfaces or heterojunctions by piezoelectric polarization charges, which was first proposed by our group in 2010. The performance of many optoelectronic devices can be effectively enhanced by piezo-phototronic effect. Over the past decade, these two areas have received extensive attentions and made great progresses in basic science and device applications. The combinations of piezotronics and piezo-phototronics with the current popular electronics, optoelectronics and spintronics have great significances, which will bring in revolutionized impacts for future sensor networks, artificial intelligence, micro-nano energy and human-machine interaction applications. This paper gives a brief review of the experimental progress in device application in these two fields in recent years, and looks forward to the future development of these two subjects.

Piezoelectric Nanogenerators for Self-Powered Nanosystems and Nanosensors

Abstract : In this project, intensive research effort has been invested in the development of self-powered MNSs, and various prototypes have been built up. Flexible piezotronic device based on RF-sputtered piezoelectric ZnO thin film is a great UV sensor. A nanogenerator based on the hydrothermal growth of a ZnO nanowire film on a spring shows a stable output and both the output voltage and current, displaying a linear relationship with the weight loaded on the spring. Thus, the nanogenerator can be utilized as an active mechanical sensor for measuring the weight applied onto the spring. A flexible thermoelectric nanogenerator (TENG) can be used as a wearable energy harvester by using human body temperature as the energy source. At the same time, the TENG can work as a self-powered temperature sensor with a response time of 17 s and a reset time of 9 s. The detection sensitivity of the sensor can reach 0.15 K in ambient atmosphere. The single output peak from a pyroelectric nanogenerator (PENG) based on a lead zirconate titanate (PZT) film can be used to directly drive a LCD. Further, a homemade Li-ion battery can be charged by the PENG under different working frequencies from 0.005 to 0.02 Hz, which can be used to drive a green LED. An integrated module in the form of a combination of a nanoparticle-WO3 film electrochromic device and a nanogenerator demonstrates the potential of monochrome self-powered displays. This self-powered electrochromic device showed desirable electrochromic response times and high coloration efficiency values. A transparent flexible nanogenerators made by growing ZnO nanowires on flexible polydimethylsiloxane (PDMS) substrate is a self-powered sensor for monitoring vehicle speed and detecting vehicle weight. Using two kinds of piezoelectric material, ZnO and poly-(vinylidene fluoride) (PVDF), we fabricate a composite structure for a nanogenerator (NG) or active-sensor for mechanical energy harvesting and vortex-based gas/liquid flow measurements.

Triboelectric nanogenerators as a new energy technology: From fundamentals, devices, to applications

Wafer‐Level Patterned and Aligned Polymer Nanowire/Micro‐ and Nanotube Arrays on any Substrate

A novel technique for fabrication of patterned and aligned polymer-nanowire/micro-and nanotube (PNW/PNT) arrays on a wafer-level substrate of any material is reported. By creating a designed pattern on a spin-coated polymer film using techniques, such as stamping or micro-tip writing, plasma etching results in the formation of aligned PNW arrays distributed according to the pattern. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Triboelectric Nanogenerator for Underwater Sensing

An Ultrarobust High-Performance Triboelectric Nanogenerator Based on Charge Replenishment

Harvesting ambient mechanical energy is a green route in obtaining clean and sustainable electric energy. Here, we report an ultrarobust high-performance triboelectric nanogenerator (TENG) on the basis of charge replenishment by creatively introducing a rod rolling friction in the structure design. With a grating number of 30 and a free-standing gap of 0.5 mm, the fabricated TENG can deliver an output power of 250 mW/m(2) at a rotating rate of 1000 r/min. And it is capable of charging a 200 μF commercial capacitor to 120 V in 170 s, lighting up a G16 globe light as well as 16 spot lights connected in parallel. Moreover, the reported TENG holds an unprecedented robustness in harvesting rotational kinetic energy. After a continuous rotation of more than 14.4 million cycles, there is no observable electric output degradation. Given the superior output performance together with the unprecedented device robustness resulting from distinctive mechanism and novel structure design, the reported TENG renders an effective and sustainable technology for ambient mechanical energy harvesting. This work is a solid step in the development toward TENG-based self-sustained electronics and systems.

Mechanical−Electrical Triggers and Sensors Using Piezoelectric Micowires/Nanowires

We demonstrate a mechanical−electrical trigger using a ZnO piezoelectric fine-wire (PFW) (microwire, nanowire). Once subjected to mechanical impact, a bent PFW creates a voltage drop across its width, with the tensile and compressive surfaces showing positive and negative voltages, respectively. The voltage and current created by the piezoelectric effect could trigger an external electronic system, thus, the impact force/pressure can be detected. The response time of the trigger/sensor is ∼10 ms. The piezoelectric potential across the PFW has a lifetime of ∼100 s, which is long enough for effectively "gating" the transport current along the wire; thus a piezoelectric field effect transistor is possible based on the piezotronic effect.

Neuromimetic circuits enabled by dynamic regulation of the electrical double layer

Abstract Iontronics presents a transformative paradigm for energy and information processing via ions as active charge carriers. Here, triboiontronics is introduced, a novel strategy leveraging contact electrification to achieve dynamic regulation of electrical double layers. Inspired by signaling mechanisms of biological neural systems, triboiontronics enables enhanced ionic-electronic coupling without external power input, offering a material-independent and self-powered pathway for programmable interfacial behavior, underscoring its promise for post-Moore, energy-autonomous information technologies.

Synthesis and microwave dielectric properties of 2ZnO⋅3B2O3-doped ZnAl2O4 low-permittivity ceramics

Size‐Dependent Chemical and Magnetic Ordering in L1₀‐FePt Nanoparticles.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Quantum Effects on Maxwell’s Equations

Discovery and Initial SAR of Arylsulfonylpiperazine Inhibitors of 11β-Hydroxysteroid Dehydrogenase Type 1 (11β-HSD1)

MOF-Based Supramolecule Helical Nanomaterials: Toward Highly Enantioselective Electrochemical Recognition of Penicillamine

For the first time, we report the formation of a chiral MOF-based helical nanomaterial (h-HDGA@ZIF-67) through arranging zeolitic imidazolate framework (ZIF-67) nanocrystals on helical l-glutamic acid terminated bolaamphiphile (h-HDGA) via a facile process at room temperature. The self-assembly leads to the chiral function of the ZIF-67 from an achiral ligand. The h-HDGA@ZIF-67 served as a new type of electrochemical sensing interface for recognizing and quantifying Pen enantiomers that realize significant enantioselectivity, satisfactory stability, and reproducibility. The synergetic effect from ZIF-67 nanocrystals on h-HDGA and stereoselectivity of h-HDGA@ZIF-67 lead to the excellent enantioselectivity. The present strategy showed the first example of a chiral MOF-based supramolecule helical nanomaterial, presenting high enantioselectivity for electrochemical enantiomeric determination.

Semiconductor Contact‐Electrification‐Dominated Tribovoltaic Effect for Ultrahigh Power Generation

The semiconductor direct-current triboelectric nanogenerator (SDC-TENG) based on the tribovoltaic effect is promising for developing a new semiconductor energy technology with high power density. Here, the first SDC-TENG built using gallium nitride (GaN) and bismuth telluride (Bi2 Te3 ) for ultrahigh-power generation is reported. During the friction process, an additional interfacial electric field is formed by continuous contact electrification (CE), and abundant electron-hole pairs are excited and move directionally to form a junction current that is always internally from Bi2 Te3 to GaN, regardless of the semiconductor type. The peak open-circuit voltage can reach up to 40 V and the power density is 11.85 W m-2 (average value is 9.23 W m-2 ), which is approximately 200 times higher than that of previous centimeter-level SDC-TENGs. Moreover, compared to traditional polymer TENGs under the same conditions, the average power density is remarkably improved by over 40 times. This study provides the first evidence of CE on the tribovoltaic effect and sets the normalized power density record for TENGs, which demonstrates a great potential of the tribovoltaic effect for energy harvesting and sensing.

Fabrication of a High‐Brightness Blue‐Light‐Emitting Diode Using a ZnO‐Nanowire Array Grown on p‐GaN Thin Film

Bright n-ZnO nanowire/p-GaN film hybrid heterojunction light-emitting-diode (LED) devices are fabricated by directly growing n-type ZnO-nanowire arrays on p-GaN wafers. UV–blue electroluminescence emission was observed from the heterojunction diodes, and the heterojunction LED device exhibited a high sensitivity in responding to UV irradiation.

Optical Fiber/Nanowire Hybrid Structures for Efficient Three‐Dimensional Dye‐Sensitized Solar Cells

Effizienter als in zweidimensionalen Einheiten ist die Energieumwandlung in dreidimensionalen farbstoffsensibilisierten Solarzellen (DSSCs) in einer Hybridstruktur aus optischen Fasern und Nanodrähten. Axiale Bestrahlung von innen erhöht die Energieumwandlungseffizienz einer Hybridstruktur mit der Form einer rechteckigen Faser (siehe Bild) bis zum Sechsfachen gegenüber der Bestrahlung von außen senkrecht zur Faserachse. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Catalyst−Nanostructure Interfacial Lattice Mismatch in Determining the Shape of VLS Grown Nanowires and Nanobelts: A Case of Sn/ZnO

Vapor-liquid-solid (VLS) is a well-established process in catalyst-guided growth of nanowires. The catalyst particle is generally believed to be in liquid state during growth, and it is the site for adsorbing incoming molecules; the crystalline structure of the catalyst may not have any influence on the structure of the grown one-dimensional nanostructures. In this paper, using tin particle guided growth of ZnO nanostructures as a model system, we show that the interfacial region of the tin particle with the ZnO nanowire/nanobelt could be ordered (or partially crystalline) during the VLS growth, although the local growth temperature is much higher than the melting point of tin, and the crystallographic lattice structure at the interface is important in defining the structural characteristics of the grown nanowires and nanobelts. The interface prefers to take the least lattice mismatch; thus, the crystalline orientation of the tin particle may determine the growth direction and the side surfaces of the nanowires and nanobelts. This result may have important impact on the understanding of the physical chemical process in the VLS growth.

Self-Powered Smart Arm Training Band Sensor Based on Extremely Stretchable Hydrogel Conductors

The development of elastic electronic technology has promoted the application of triboelectric nanogenerators (TENGs) in flexible wearable electronics. However, most of the flexible electronics cannot achieve the requirements of being extremely stretchable, transparent, and highly conductive at the same time. Herein, we report a TENG constructed using a double-network polymer ionic conductor sodium alginate/zinc sulfate/poly acrylic-acrylamide (SA–Zn) hydrogel, which exhibited outstanding stretchability (>10,000%), high transparency (>95%), and good conductivity (0.34 S·m–1). The SA–Zn hydrogel TENG (SH-TENG) could harvest energy from typical human movements, such as bending, stretching, and twisting, which could light up 234 green commercial LEDs easily. Additionally, the SH-TENG can be used to prepare a self-powered smart training band sensor for monitoring arm stretching motion. This work may provide an innovative platform for accessing the next generation of sustainable wearable and sports monitoring electronics.