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Register a new userDirect-Current Generator Based on Dynamic Water-Semiconductor Junction with Polarized Water as Moving Dielectric Medium
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There is a rising prospective in harvesting energy from water droplets, as microscale energy is required for the distributed sensors in the interconnected human society. However, achieving a sustainable direct-current generating device from water flow is rarely reported, and the quantum polarization principle of the water molecular remains uncovered. Herein, we propose a dynamic water-semiconductor junction with moving water sandwiched between two semiconductors as a moving dielectric medium, which outputs a sustainable direct-current voltage of 0.3 V and current of 0.64 uA with low internal resistance of 390 kilohm. The sustainable direct-current electricity is originating from the dynamic water polarization process in water-semiconductor junction, in which water molecules are continuously polarized and depolarized driven by the mechanical force and Fermi level difference, during the movement of the water on silicon. We further demonstrated an encapsulated portable power-generating device with simple structure and continuous direct-current voltage, which exhibits its promising potential application in the field of wearable electronic generators.
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As the fast development of internet of things (IoTs), distributed sensors have been frequently used and the small and portable power sources are highly demanded. However, the present portable power source such as lithium battery has low capacity and need to be replaced or recharged frequently. A portable power source which can continuously generate electrical power in situ will be an idea solution. Herein, we demonstrate a wind driven semiconductor electricity generator based on a dynamic Schottky junction, which can output a continuous direct current with an average value of 4.4 mA (the maximum value of 8.4 mA) over 360 seconds. Compared with the previous metal/semiconductor generator, the output current is one thousand times higher. Furthermore, this wind driven generator has been explored to function as a turn counter due to its stable output and also to drive a graphene ultraviolet photodetector, which shows a responsivity of 35.8 A/W under the 365 nm ultraviolet light. Our research provides a feasible method to achieve wind power generation and power supply for distributed sensors in the future.
Liquid electricity generator and hydrovoltaic technology have received numerous attentions, which can be divided into horizontal movement generator and vertical movement generator. The horizontal movement generator is limited for powering the integrated and miniaturized energy chip as the current output direction is depending on the moving direction of the water droplet, which means a sustainable and continuous direct-current (DC) electricity output can be hardly achieved because of the film of limited length. On the other hand, the existing vertical movement generators include triboelectricity or humidity gradient-based liquid electricity generator, where the liquid or water resource must be sustainably supplied to ensure continuous current output. Herein, we have designed an integratable vertical generator by sandwiching water droplets with semiconductor and metal, such as graphene or aluminum. This generator, named as polarized liquid molecular generator (PLMG), directly converts the lateral kinetic energy of water droplet into vertical DC electricity with an output voltage of up to ~1.0 V from the dynamic water-semiconductor interface. The fundamental discovery of PLMG is related to the non-symmetric structure of liquid molecules, such as water and alcohols, which can be polarized under the guidance of built-in field caused by the Fermi level difference between metal and semiconductor, while the symmetric liquid molecules cannot produce any electricity on the opposite. Integratable PLMG with a large output power of ~90 nW and voltage of ~2.7 V has been demonstrated, meanwhile its small internal resistance of ~250 kilohm takes a huge advantage in resistance matching with the impedance of electron components. The PLMG shows potential application value in the Internet of Things (IoTs) after proper miniaturization and integration.
Traditionally, Schottky diodes are used statically in the electronic information industry but dynamic state Schottky diodes based applications have been rarely explored. Herein, a novel Schottky diode named moving Schottky diode generator has been designed, which can convert mechanical energy into electrical energy with voltage output as high as 0.6V, by means of lateral movement between graphene/metal film and semiconductor, where the semiconductor can be non-piezoelectric materials. The mechanism is based on the built-in electric field separation of drifting electrons in moving van der Waals Schottky diode. The power output can be further increased in future through optimizing the Schottky diode. The graphene film/silicon moving van der Waals Schottky diode based generator behaves better stability. This direct-current generator has the potential of converting mechanical efficiently and vibrational energy into electricity and enables many promising applications.
After the electromagnetic generator, searching for novel electric generators without strong magnetic field is highly demanded. The generator without strong magnetic field calls for a physical picture distinct from the traditional generators. As the counterpart of the static PN junction has been widely used in the integrated circuits, we develop an electric generator named dynamic PN generator with a high current density and voltage output, which converts mechanical energy into electricity by sliding two semiconductors with different Fermi level. A dynamic N-GaAs/SiO2/P-Si generator with the open-circuit voltage of 3.1 V and short-circuit density of 1.0 A/m2 have been achieved. The physical mechanism of the dynamic PN generator is proposed based on the built-in electric field bounding back diffusing carriers in dynamic PN junctions, which breaks the equilibrium between drift and diffusion current in the PN junction. Moreover, the dynamic MoS2/AlN/Si generator with the open-circuit voltage of 5.1 V and short-circuit density of 112 A/m2 (11.2 mA/cm2) have also been achieved, which can effectively output a direct-current and light up a blue light-emitting diode directly. This dynamic MoS2/AlN/Si generator can continuously work for hours without obvious degradation, demonstrating its unique mechanism and potential applications in many fields where the mechanical energy is available.
In this paper, a novel water-based reconfigurable frequency selective rasorber (FSR) at microwave band is proposed, which has a thermally tunable absorption band above the transmission band. The water-based FSR consists of a bandpass type frequency selective surface (FSS) and a 3D printing container. The water substrate is filled into the sealed space constructed by the above two structures. The numerical simulation results show that the FSR can achieve absorption with high absorptivity from 8.3 to 15.2 GHz, and obtain a transmission band of 5.2 to 7.0 GHz. The minimum insertion loss of the transmission band reaches 0.72 dB at 6.14 GHz. In addition, the FSR has the reconfigurable characteristics of absorbing or reflecting electromagnetic waves by filling with water or not. The proposed water-based FSR shows its good transmission/absorption performance under different polarizations and oblique incident angles. Due to the Debye model of water, the absorption band can be adjusted by water temperature, while the passband remains stable. At last, prototype of the FSR based on water has been fabricated, and the experimental results are presented to demonstrate the validity of the proposed structure.
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