Publications

Abstract In addition to electrical, optical, and magnetic fields, mechanical forces have demonstrated a strong ability to modulate semiconductor devices. With the rapid development of piezotronics and flexotronics, force regulation has been widely used in field‐effect transistors (FETs), human–machine interfaces, light‐emitting diodes (LEDs), solar cells, etc. Here, a large mechanical modulation of electronic properties by nano‐Newton force in semiconductor materials with a large Young's modulus‐based force FET is reported. More importantly, this FET has ultralow switching energy dissipation (7 aJ per decuple current gain) and nearly zero leakage power; these values are even better than those of electronic FETs. This finding paves the way for practical applications of nanoforce modulation devices at high power efficiency.

A theoretical model for contact-mode TENGs was constructed in this paper. Based on the theoretical model, its real-time output characteristics and the relationship between the optimum resistance and TENG parameters were derived. The theory presented here is the first in-depth interpretation of the contact-mode TENG, which can serve as important guidance for rational design of the TENG structure in specific applications.

Abstract The triboelectric nanogenerator (TENG) is a promising technology with unique advantages for harvesting environmental high‐entropy energy like wind power. However, inefficient wind energy harvest devices have limited the operating wind speed and practical application of TENGs. In this work, a bionic blade lift‐drag hybrid turbine‐driven triboelectric‐electromagnetic hybrid generator (HT‐TEHG) is designed for broadband wind energy harvesting. The lift‐drag hybrid turbine combines the benefits of drag‐type blades enabling low wind speed start‐up and bionic lift‐type blades generating high torque, achieving an 11% increase in performance. The TENGs are designed with appropriate dielectric layer gaps to balance the output performance and friction torque and are independently driven by two types of blades to achieve self‐adaptive graded power generation at different wind speeds. The starting wind speed of the HT‐TEHG is 2 m s −1 and achieves a peak power of 202.4 mW with an energy conversion efficiency of 9.1% at a wind speed of 4 m s −1 . The durability of the TENG is verified by continuous operation for 1 × 10 5 cycles with almost no performance degradation. Moreover, the HT‐TEHG can power a wireless weather station using natural wind. The study introduces a valuable approach to harvest broadband wind energy and enable distributed power for Internet of Things devices.

Wind‐driven triboelectric nanogenerators (TENGs) play an important role in harvesting energy from ambient environments. Compared to single‐side‐fixed triboelectric nanogenerator (STENG) arrays for harvesting single‐pathway wind energy, double‐side‐fixed triboelectric nanogenerator (DTENG) arrays are developed to harvest bidirectional wind energy. Electrical performances of the STENG and DTENG can be improved due to sticky, abrasive, and electrical properties of the Ti buffer layers among Al, polytetrafluoroethylene (PTFE), and polyimide (Kapton), configuring in triboelectric PTFE/Ti/Al and Al/Ti/Kapton/Ti/Al thin films. Short‐circuit current ( I SC ), open‐circuit voltage ( V OC ), and frequencies of the STENG and DTENG increase with increasing wind velocity ranging from 9.2 to 18.4 m s 21 , revealing that the moderate I SC , V OC , frequencies, and output powers of the STENG and DTENG reach 67 μA, 57 μA, 334 V, 296 V, 173 Hz, 162 Hz, 5.5 mW and 3.4 mW with a matched load of 4 MΩ at airflow rate of 15.9 m s 21 , respectively. Compared with counterparts of the single‐pathway‐harvested STENG arrays, the I SC , durability, and stability of the bidirectional‐harvested DTENG can be dramatically improved by a 4 3 1 array connected in parallel because of the improved device configuration, stickiness, and abrasion by adhering Ti buffer layers. The durable DTENG arrays present a step toward practical applications in harvesting bidirectional wind energy for self‐powered systems and wireless sensors.

A plasma-induced p-type MoS2 flake and n-type ZnO film diode, which exhibits an excellent rectification ratio, is demonstrated. Under 365 nm optical irradiation, this p-n diode shows a strong photoresponse with an external quantum efficiency of 52.7% and a response time of 66 ms. By increasing the pressure on the junction to 23 MPa, the photocurrent can be enhanced by a factor of four through the piezophototronic effect.

Triboelectric potential gated transistors have inspired various applications toward mechanical behavior controlled logic circuits, multifunctional sensors, artificial sensory neurons, etc. Their rapid development urgently calls for high-performance devices and corresponding figure of merits to standardize the tribotronic gating properties. Organic semiconductors paired with solution processability promise low-cost manufacture of high-performance tribotronic transistor devices/arrays. Here, we demonstrate a record high-performance tribotronic transistor array composed of an integrated triboelectric nanogenerator (TENG) and a large-area device array of C8-BTBT-PS transistors. The working mechanism of effective triboelectric potential gating is elaborately explained from the aspect of conjugated energy bands of the contact-electrification mediums and organic semiconductors. Driven by the triboelectric potential, the tribotronic transistor shows superior properties of record high current on/off ratios (>108), a steep subthreshold swing (29.89 μm/dec), high stability, and excellent reproducibility. Moreover, tribotronic logic devices modulated by mechanical displacement have also been demonstrated with good stability and a high gain of 1260 V/mm. The demonstrated large-area tribotronic transistor array of organic semiconductor exhibits record high performance and offers an effective R&D platform for mechano-driven electronic terminals, interactive intelligent system, artificial robotic skin, etc.

It is well known that the photovoltaic effect produces a direct current (DC) under solar illumination owing to the directional separation of light-excited charge carriers at the p-n junction, with holes flowing to the p-side and electrons flowing to the n-side. Here, it is found that apart from the DC generated by the conventional p-n photovoltaic effect, there is another new type of photovoltaic effect that generates alternating current (AC) in the nonequilibrium states when the illumination light periodically shines at the junction/interface of materials. The peak current of AC at high switching frequency can be much higher than that from DC. The AC cannot be explained by the established mechanisms for conventional photovoltaics; instead, it is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions, which results in electron flow in the external circuit back and forth to balance the potential difference between two electrodes. By virtue of this effect, the device can work as a high-performance broadband photodetector with extremely high sensitivity under zero bias; it can also work as a remote power source providing extra power output in addition to the conventional photovoltaic effect.

The piezotronic effect is applied to modulate the physical properties of heterojunction electron gas and thus tune the electric transport in AlGaN/AlN/GaN heterostructure microwires. At room temperature, the conductance is increased by 165% under −1.78% compressive strains, and reduced by 48% under 1.78% tensile strains; at 77 K, this modulating effect is further improved by 890% and 940% under compressive and tensile strains, respectively. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to 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.

Recent progress in triboelectric nanogenerators (TENGs) has demonstrated their promising potential as a high‐efficiency mechanical energy harvesting technology, and plenty of effort has been devoted to improving the power output by maximizing the triboelectric surface charge density. However, due to high‐voltage air breakdown, most of the enhanced surface charge density brought by material/surface optimization or external ion injection is not retainable or usable for electricity generation during the operation of contact‐separation‐triggered TENGs. Here, the existence of the air breakdown effect in a contact‐separation mode TENG with a low threshold surface charge density of ≈40–50 µC m −2 is first validated under the high impedance external load, and then followed by the theoretical study of the maximized effective energy output as limited by air breakdown for contact‐separation‐triggered TENGs. The effects of air pressure and gas composition are also studied and propose promising solutions for reducing the air breakdown effect. This research provides a crucial fundamental study for TENG technology and its further development and applications.

The relatively low sensitivity of flexible piezoelectric nanogenerators (PENG) is the most urgent problem to be solved for their applications in internet of things and artificial intelligences. To improve the piezoelectricity of polymeric fibers without discount of flexibility, BaTiO 3 nanowire (BTNW) with high aspect ratio is introduced into the piezoelectric P(VDF-TrFE) (denoted as PT) electrospun fibers to form coaxial composite nanofibers for improving the sensitivity towards external mechanical loads. To reinforce the organic-inorganic interfacial interaction for the improvement of the piezoelectric response, a nanolayer of polydopamine (PDA) is uniformly coated on the surface of BTNW (denoted as pBTNW) to form PT/pBTNW nanofibers. The introduction of 7 wt% pBTNW into the fibers significantly improves the polymeric β-phase conformation and mechanical properties, simultaneously, resulting in an optimal piezoelectric output of 18.2 V under an impact force of 5 N with excellent sensitivity of 4.3 V N -1 . Through both theoretical simulation and experimental characterization, the PT/pBTNW-based PENG exhibits a higher electrical output than the equivalent nanoparticle-based PENG. The optimized PENG sensor can be used for self-powered and sensitive biomonitoring of physiological movements, finger identification and voice recognition. Overall, this work offers a reliable method for enhancing piezoelectricity of flexible polymeric nanofiber and designing high-performance PENG for wearable fabric-based sensors.