Ya Yang

A One-Structure-Based Hybridized Nanogenerator for Scavenging Mechanical and Thermal Energies by Triboelectric–Piezoelectric–Pyroelectric Effects

A hybridized nanogenerator is demonstrated, which has the structure of PVDF nanowires-PDMS composite film/indium tin oxide (ITO) electrode/polarized PVDF film/ITO electrode, and which can individually/simultaneously scavenge mechanical and thermal energies using piezoelectric, triboelectric, and pyroelectric effects. As compared with the individual energy harvesting unit, the hybridized nanogenerator has a much better charging performance. This work may push forward a significant step toward multienergy harvesting technology.

Flow-driven triboelectric generator for directly powering a wireless sensor node.

A triboelectric generator (TEG) for scavenging flow-driven mechanical -energy to directly power a wireless sensor node is demonstrated for the first time. The output performances of TEGs with different dimensions are systematically investigated, indicating that a largest output power of about 3.7 mW for one TEG can be achieved under an external load of 3 MΩ.

Hybrid energy cell for simultaneously harvesting wind, solar, and chemical energies

AbstractWe report a hybrid energy cell that can simultaneously or individually harvest wind, solar, and chemical energies to power some electronic devices. By utilizing the wind driven relative rotations between a polytetrafluoroethylene film and an etched Al film attached on two acrylic tubes, the fabricated triboelectric nanogenerator (TENG) can deliver an open-circuit voltage of about 90 V, a short-circuit current density of about 0.5 mA/m2, and a maximum power density of 16 mW/m2, which is capable of directly lighting up 20 blue light-emitting-diodes (LEDs). By integrating a TENG, a solar cell, and an electrochemical cell, a hybrid energy cell has been fabricated to simultaneously scavenge three different types of energies. As compared with the individual energy units, the hybrid energy cell exhibited much better performance in charging a capacitor. Moreover, we also demonstrated that the hybrid energies generated can be stored in a Li-ion battery for powering a commercial wind speed sensor and a temperature sensor. This work represents significant progress toward practical applications of hybrid energy cells, providing potential solutions for simultaneously scavenging wind, solar, and chemical energies.n

Hybrid electromagnetic–triboelectric nanogenerator for harvesting vibration energy

We report a hybrid nanogenerator that includes a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) for scavenging mechanical energy. This nanogenerator operates in a hybrid mode using both the triboelectric and electromagnetic induction effects. Under a vibration frequency of 14 Hz, the fabricated TENG can deliver an open-circuit voltage of about 84 V, a short-circuit current of 43 µA, and a maximum power of 1.2 mW (the corresponding power per unit mass and volume are 1.82 mW/g and 3.4 W/m3, respectively) under a loading resistance of 2 MΩ, whereas the fabricated EMG can produce an opencircuit voltage of about 9.9 V, a short-circuit current of 7 mA, and a maximum power of 17.4 mW (the corresponding power per unit mass and volume are 0.53 mW/g and 3.7 W/m3, respectively) under a loading resistance of 2 kΩ. Impedance matching between the TENG and EMG can be achieved using a transformer to decrease the impedance of the TENG. Moreover, the energy produced by the hybrid nanogenerator can be stored in a home-made Li-ion battery. This research represents important progress toward practical applications of vibration energy generation for realizing self-charging power cells.

Photovoltaic–Pyroelectric Coupled Effect Induced Electricity for Self-Powered Photodetector System

Ferroelectric materials have demonstrated novel photovoltaic effect to scavenge solar energy. However, most of the ferroelectric materials with wide bandgaps (2.7-4 eV) suffer from low power conversion efficiency of less than 0.5% due to absorbing only 8-20% of solar spectrum. Instead of harvesting solar energy, these ferroelectric materials can be well suited for photodetector applications, especially for sensing near-UV irradiations. Here, a ferroelectric BaTiO3 film-based photodetector is demonstrated that can be operated without using any external power source and a fast sensing of 405 nm light illumination is enabled. As compared with photovoltaic effect, both the responsivity and the specific detectivity of the photodetector can be dramatically enhanced by larger than 260% due to the light-induced photovoltaic-pyroelectric coupled effect. A self-powered photodetector array system can be utilized to achieve spatially resolved light intensity detection by recording the output voltage signals as a mapping figure.

Linear-grating hybridized electromagnetic-triboelectric nanogenerator for sustainably powering portable electronics

Utilizing a nanogenerator to scavenge mechanical energy from our living environment is an effective method to solve the power source issue of portable electronics. We report a linear-grating hybridized electromagnetic-triboelectric nanogenerator for scavenging the mechanical energy generated from sliding motions to sustainably power certain portable electronics. The hybridized nanogenerator consists of a slider and a stator in the structural design, and possesses a 66-segment triboelectric nanogenerator (TENG) and a 9-segment electromagnetic generator (EMG) in the functional design. At a sliding acceleration of 20 m/s2, the hybridized nanogenerator can deliver maximum powers of 102.8 mW for the TENG at a loading resistance of 0.4 MΩ and 103.3 mW for the EMG at a loading resistance of 6 kΩ. With an optimal hybridized combination of the TENG with a transformer and the EMG with a power management circuit, a 10 mF capacitor can be easily charged to 2.8 V in 20 s. A packaged hybridized nanogenerator with a light weight of 140 g and small dimensions of 12 cm × 4 cm × 1.6 cm excels in scavenging low-frequency sliding energy to sustainably power portable electronics.

Triboelectric nanogenerators as flexible power sources

The triboelectric nanogenerator (TENG) as a new power-generation technology was reported by Wang and co-workers in 2012. Because of its great potential for scavenging mechanical energy from living environment and sustainably driving portable devices, many researchers have developed various methods to improve output performances of TENG. In this paper, we review the progress in TENG made as flexible power sources by integrating flexible materials and stretching structures, especially for the applications of flexible electronics. For optimizing performances of TENG, the structural designs, material selections, and hybrid energy cells are presented. The reported TENG as flexible power sources has the potential applications in lighting up light emitting diodes (LEDs), powering sensors, and monitoring biomechanical motions.

Ag Nanoparticles-Based Triboelectric Nanogenerator to Scavenge Wind Energy for a Self-Charging Power Unit

Li-ion batteries are a green energy storage technology with advantages of high energy density, long lifetime, and sustainability, but they cannot generate electric energy by themselves. As a novel energy-harvesting technology, triboelectric nanogenerators (TENGs) are a promising power source for supplying electronic devices, however it is difficult to directly use their high output voltage and low output current. Here, we designed a Ag nanoparticle-based TENG for scavenging wind energy. After including a transformer and a power management circuit into the system, constant output voltages such as 3.6 V and a pulsed current of about 100 mA can be obtained, which can be used to directly light up a light-emitting diode. Furthermore, the produced electric energy can be effectively stored in a WO3/LiMn2O4 electrode based Li-ion battery. Our present work provides a new approach to effectively scavenge wind energy and store the obtained electric energy, which is significant for exploring self-charging power units.

Enhancing Photocurrent of Radially Polarized Ferroelectric BaTiO3 Materials by Ferro-Pyro-Phototronic Effect

Summary The pyro-phototronic effect has been utilized to modulate photoexcited carriers, to enhance the photocurrent in semiconducting nanomaterials. However, most of these materials have low pyroelectric performances. Using radially polarized ferroelectric BaTiO3 materials with a pyroelectric coefficient of about 16 nC/cm2K, we report a dramatic photocurrent enhancement due to ferro-pyro-phototronic effect. The fabricated device enables a fast sensing of 365-nm light illumination with a response time of 0.5 s at the rising edge, where the output current-time curve displays a sharp peak followed by a stable plateau. By applying a heating temperature variation, the output current peak can be enhanced by more than 30 times under a light intensity of 0.6 mW/cm2. Moreover, the stable current plateau can be enhanced by 23% after utilizing a cooling temperature variation, which can be well explained by ferro-pyro-phototronic-effect-induced energy band bending.

Photocurrent Polarity Controlled by Light Wavelength in Self-Powered ZnO Nanowires/SnS Photodetector System

Summary Self-powered photodetectors are expected to play a crucial role in future nano-optoelectronic devices owing to their independent and sustainable operation. Based on the heterojunction between ZnO nanowires (NWs) and shuttle-like SnS, we design a self-powered photodetector exhibiting wide-range photoresponse and tunable spectral selectivity. Differently from conventional devices, a wavelength-induced photocurrent polarity is observed in the ZnO NWs/SnS photodetector, which enables the device to distinguish between photons in the UV and visible (VIS) regions. This is due to switching of the interfacial modulation by the pyroelectric-polarization potential (pyro-potential) inside ZnO NWs and thermoelectric-polarization potential (thermo-potential) inside SnS. A photocurrent enhancement of 125% and improved responsivity of 364 μA/W are obtained under the pyro-potential upon 690 nm light illumination, whereas reversed responsivity of −155 μA/W is obtained under the thermo-potential upon 365 nm light illumination. We believe the photocurrent polarity could be useful for improving resolution of dynamic light sensing/imaging.