Energy harvester

Abstract

The present invention relates to an energy generating device, and more specifically, to an energy generating device that induces hygroscopic electrical characteristics into triboelectric characteristics in a non-moisture environment and improves the characteristics of conventional triboelectricity that degrade in a moisture environment.

Description

Technology Field

[0001] The present invention relates to an energy generating device, and more specifically, to an energy generating device that induces hygroscopic electrical characteristics into triboelectric characteristics in a non-moisture environment and improves the characteristics of conventional triboelectricity that degrade in a moisture environment. Background Technology

[0002] In the information society, numerous energy harvesting technologies are being developed to supply energy suitable for Internet of Things (IoT) devices. Energy harvesting technology has grown with a focus on continuously supplying electrical energy regardless of environment, location, or time. In particular, mechanical energy harvesting technologies based on piezoelectric, electromagnetic, and triboelectric effects are continuously being researched to overcome these limitations while being less constrained by environmental factors. Specifically, triboelectric nanogenerators (TENGs), based on the mechanical friction between insulators and organic materials, have been the subject of research for the past decade as they can exhibit ultra-high output performance even with a simple structure. Recently, based on the elucidation of the tribovoltaic effect, ideas are expanding to various liquids as well as semiconductor materials.

[0003] The direct current (DC) output of triboelectric devices facilitates applications without the need for additional rectification circuits. Various studies have been conducted on DC triboelectric nanogenerators (DC-TENGs) utilizing various interlayer junctions and tribokinetic effects, including tunneling based on metal-insulator-semiconductor structures, mobile Schottky diodes based on metal-semiconductor configurations, triboelectric cells based on semiconductor pn junction structures, and other mobile heterojunction nanogenerators. However, despite their high utility, triboelectric nanogenerators suffer from performance degradation in high-humidity environments, which limits the continuous production of energy in diverse environments. To address this issue, triboelectric nanogenerators with improved performance in high-humidity environments based on materials stable in humid conditions have been demonstrated; however, most triboelectric nanogenerators operating in high-humidity environments adopt strategies that stabilize surface conditions rather than fully utilizing the electrical properties of water molecules.

[0004] Meanwhile, recent studies have confirmed that contact charging (CE) can occur not only at solid / solid interfaces but also at solid / liquid interfaces. Contact charging between solids and liquids introduces the mechanism of moisture-enabled electricity generators (MEGs), which utilize the potential difference induced by the concentration gradient of water molecules within hygroscopic materials.

[0005] Ionic concentration gradients arise from potential differences resulting from the spontaneous dissociation of water molecules or contact charging between solids and liquids. Specifically, the potential in regions where water molecules are abundant is positive (+), while regions with a relatively low concentration of water molecules possess a negative (-) potential. Recent studies have shown that some materials containing small water channels, such as graphene oxide (GO), protein nanofibers, and cellulose nanofibers, spontaneously form water molecule concentration gradients.

[0006] Layered double hydroxide (LDH) is an anionic material composed of an intermediate layer of negatively charged anions and water molecules and a layer of positively charged brucite-type metal hydroxide. Due to strong hydrogen bonding interactions, this material exhibits a highly hydrophilic surface and induces significant moisture adsorption. However, no studies have yet been found that demonstrate the simultaneous triboelectric and hygroscopic effects using the LDH structure. Prior art literature

[65535] Republic of Korea Published Patent Application No. 10-2022-0023408 The problem to be solved

[0007] The technical problem that the present invention aims to solve is to provide an energy generating device that solves the problem of the energy generation performance of conventional energy generating devices deteriorating in a wet environment.

[0008] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0009] One embodiment of the present invention provides an energy generating element comprising: a first electrode; a semiconductor layer attached on one surface of the first electrode; a layered-double hydrxide (LDH) layer attached on the semiconductor layer; and a second electrode disposed on the LDH layer, wherein the LDH layer stores a frictional charge generated by friction with the second electrode and a wet charge generated under a wet environment and generates a voltage in the form of a direct current. Effects of the invention

[0010] An energy generating element according to one embodiment of the present invention can improve energy generation efficiency and storage efficiency by applying friction to an LDH layer in a humid environment.

[0011] The effects of the present invention are not limited to those described above, and unmentioned effects will be clearly understood by those skilled in the art from the present specification and the accompanying drawings. Brief explanation of the drawing

[0012] FIG. 1 is a schematic diagram of an energy band showing the triboelectric characteristics of an energy generating element according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the triboelectric and hygroscopic electrical characteristics of an energy generating element according to one embodiment of the present invention. FIG. 3 is a schematic diagram showing the manufacturing process of the Al / Si / LDH layer structure of Example 1 and Example 2 of the present invention. Figure 4 is an SEM image showing a cross- section of an LDH layer on a Si wafer formed in Examples 1-1 and 1-2 of the present invention. Figure 5 is an XRD graph (a) of the ZnAl-LDH layer and Si wafer of Example 1-1 of the present invention and an FT-IR spectrum (b) of the ZnAl-LDH layer. FIG. 6 is a graph of the current-voltage (IV) curve of the Al / ZnAl-LDH / n-Si / Al energy generating device of Example 3-2 of the present invention. Figure 7 is a potential graph according to the change in humidity of the energy generating element of Example 3-2 of the present invention. FIG. 8 is a graph of voltage and current output generated by hygroscopic electricity at RH 60% according to the LDH layer thickness of the energy generating element of Comparative Example 1 and Examples 2-1 and 2-2 of the present invention (a), a graph of output voltage and current according to the load resistance of the energy generating element of Example 2-1 (b), and a graph of power density according to the load resistance of the energy generating element of Example 2-1 (c). FIG. 9 is a graph of output voltage and current according to the width of the second electrode of the energy generating element of Examples 2-1, 3-1 and 4 of the present invention. FIG. 10 is a schematic diagram of the reciprocating motion on the surface of the LDH layer of the second electrode of Example 2-1 of the present invention and a graph of the open circuit voltage according to the time taken for one reciprocating friction. FIG. 11 is a graph of output voltage and current according to the width of the second electrode due to the reciprocating friction of the second electrode of the energy generating element of Example 2-1, Example 3-1, and Example 4 of the present invention. FIG. 12 is a graph of output voltage (a) and current (b) according to the reciprocating friction of the second electrode of the energy generating element of Example 2-1, Example 2-2 and Comparative Example 1 of the present invention. FIG. 13 is a graph of the output voltage (a, b) and the rate of change of output voltage (c) according to the reciprocating motion speed of the second electrode before and after 5,000 cycles of driving of the energy generating element of Example 2-1 of the present invention. FIG. 14 is a graph of the voltage output generated by the frictional effect of the air brushing mode by pulsed air flow at relative humidity 20% and pressure 30 mmHg of the energy generating element of Example 3-1 of the present invention. FIG. 15 is an FT-IR spectrum of the H2O adsorption process before and after interfacial friction between the second electrode and the LDH layer through an air brushing mode by pulsed air flow at relative humidity 20% and pressure 30 mmHg of the energy generating element of Example 3-1 of the present invention. FIG. 16 is a graph of voltage (a) and current (b) according to the frictional effect of the air brushing mode by pulsed air flow with different pressures at a relative humidity of 20% of the energy generating element of Example 3-1 of the present invention. FIG. 17 is a voltage graph (a) and a current graph (b) measured in an air brushing mode of air jets repeated 10 times at a pressure of 5 mmHg and a relative humidity of 20% at the energy generating element of Example 3-1 of the present invention. FIG. 18 is a voltage graph of the energy generating element of Example 2-1 of the present invention when friction and moisture supply by air injection are repeated at a pressure of 5 mmHg and a relative humidity of 20%. FIG. 19 is a graph of voltage and current of a generator using an energy generating element according to Example 2-1 of the present invention in series and parallel circuits. Specific details for implementing the invention

[0013] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0014] Throughout this specification, when a component is described as being located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0015] Throughout the entire specification, the unit "parts by weight" may refer to the ratio of weight between each component.

[0016] Throughout this specification, "A and / or B" means "A and B, or A or B".

[0017] Throughout this specification, the “weight-average molecular weight” and “number-average molecular weight” of a compound can be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, a sample with a compound concentration of 1 wt% is prepared by placing tetrahydrofuran (THF) and the compound in a 1 ml glass vial. After filtering the standard sample (polystyrene) and the sample through a filter (pore size 0.45 μm), the sample is injected into a GPC injector, and the molecular weight and molecular weight distribution of the compound can be obtained by comparing the elution time of the sample with the calibration curve of the standard sample. At this time, an Infinity II 1260 (Agilient) can be used as the measuring instrument, and the flow rate can be set to 1.00 mL / min and the column temperature to 40.0 °C.

[0018] Throughout the entire specification, the “glass transition temperature (Tg)” can be measured using Differential Scanning Analysis (DSC). Specifically, using a Differential Scanning Calorimeter (DSC-STAR3, METTLER TOLEDO), the sample is heated at a rate of 5 ℃ / min within a temperature range of -60 ℃ to 150 ℃, and two cycles of the experiment are conducted in the above range. The glass transition temperature can then be obtained by measuring the midpoint of the DSC curve created at the point where the amount of heat change is present.

[0020] The present invention will be described in more detail below.

[0022] One embodiment of the present invention provides an energy generating element comprising: a first electrode; a semiconductor layer attached on one surface of the first electrode; a layered-double hydrxide (LDH) layer attached on the semiconductor layer; and a second electrode disposed on the LDH layer, wherein the LDH layer stores a frictional charge generated by friction with the second electrode and a wet charge generated under a wet environment and generates a voltage in the form of a direct current.

[0023] An energy generating element according to one embodiment of the present invention can improve energy generation efficiency and storage efficiency by applying friction to an LDH layer in a humid environment.

[0024] An energy generating element according to one embodiment of the present invention can generate triboelectricity. Specifically, triboelectric charge can be generated because electrons and holes on the surface of the LDH layer are excited and charge carriers move during the friction process with the LDH layer of the second metal.

[0025] [Equation 1]

[0026] Pf = μsF v

[0027] In Equation 1 above, Pf is the frictional force, μs is the brush friction coefficient independent of the apparent contact area and brush speed, F is the normal force, and v is the frictional speed of the second electrode. Referring to Equation 1 above, the normal force of the energy generating element according to one embodiment of the present invention is very small, so the frictional force is very low.

[0028] FIG. 1 is a schematic diagram of an energy band showing the triboelectric characteristics of an energy generating element according to one embodiment of the present invention.

[0029] Referring to Figure 1 above, the triboelectric output performance is determined by the charge density resulting from surface friction, which is influenced by the difference in charge retention and work function (WF) between the two friction materials. ZnAl-LDH(W LDH ) and Al(W Al) are 3.64 and 4.28 eV, respectively, i.e., with a difference of 0.64 eV, W Al Eun W LDH Since it is 0.64 eV greater, electrons move from ZnAl-LDH to Al, and equilibrium is reached. Referring to Fig. 1(a), when the LDH layer and the second electrode come into contact, the energy band bends upward, and a thin space charge region (SCR) is formed between the LDH layers, causing the internal electric field (E) to spread from the LDH to Al. At this time, water molecules spontaneously dissociate within the LDH layer. Referring to Fig. 1(b), when friction occurs due to the movement of the second electrode, electron-hole pairs are formed at the interface due to the triboelectric effect, and non-equilibrium charge carriers form a potential energy difference (|qΔVs|). This causes electrons to move from the valence band to the conduction band, from the valence band to the surface state, or from the surface state. In the narrow space charge region, the OH of the LDH layer - Ions combine with holes to reduce the electron-hole pair recombination rate and improve charge separation efficiency; therefore, due to the built-in potential, electrons and holes are separated in opposite directions, ultimately generating a DC output.

[0031] FIG. 2 is a schematic diagram showing the triboelectric and hygroscopic electrical characteristics of an energy generating element according to one embodiment of the present invention.

[0032] Referring to Figure 2 above, Stage 1 is a state of dynamic equilibrium where the number of water molecules at the bottom and top of the LDH layer is equal. Specifically, in Stage 1, water molecules on the surface (top) of the LDH layer are in dynamic equilibrium with the vapor pressure of the external air and the number of water molecules, while the bottom of the LDH layer maintains this dynamic equilibrium by spontaneously diffusing water molecules from the top. In Stage 2, a frictional mechanism effect occurs due to friction of the metal brush on the LDH surface caused by the airflow, thereby generating electron-hole pairs. The holes are OH in the LDH layer. -It recombines with ions to form hydroxyl radicals. Therefore, the triboelectric effect of the LDH layer reduces the number of water molecules within the LDH layer. In step 3, water molecules from the air are adsorbed onto the LDH layer, and water molecules supplied from the air diffuse from the top to the bottom of the LDH layer due to the hygroscopicity of the LDH layer. Even without a change in relative humidity, a concentration gradient of water molecules occurs due to the hygroscopic electric effect of the LDH layer, and a potential difference can be generated. Through the diffusion of water molecules, the potential decreases until the LDH layer reaches equilibrium (step 1). Since the hygroscopic properties of water molecules from the air originate from the interface of the material, controlling the thickness of the LDH layer allows for the control of the generation of a potential difference via hygroscopic electrics and the control of the water molecule concentration gradient between the top and bottom.

[0034] According to one embodiment of the present invention, the semiconductor layer is made of Si, InAs, GaAs, AlAs, InN, GaN, AlN, SiC, SnO 2, It may include one or more of Ga2O3 and ZnO. Specifically, it is preferable that the semiconductor layer includes Si. By selecting the type of semiconductor layer as described above, mass production can be facilitated and high energy efficiency and durability can be achieved.

[0036] According to one embodiment of the present invention, the LDH layer may be an M(II)M(III)-LDH layer formed by growing a reaction product of a divalent metal (M(II)) hydroxide precursor and a trivalent metal (M(III)) hydroxide precursor on top of the semiconductor layer.

[0037] According to one embodiment of the present invention, the divalent metal precursor and the trivalent metal precursor may comprise at least one divalent metal cation among Zn, Mg, Co, Cd, Ni, V, Fe, Ca, Mn, and Cu, or at least one trivalent metal cation among Al, Ti, Fe, Cr, and Co; and at least one anion among OH-, NO3-, CO32-, Cl-, and CH3COO-. Specifically, it may be preferable to select the divalent metal cation as a Zn cation, the trivalent metal cation as an Al cation, and the anion as NO3-. By selecting the divalent metal precursor and the trivalent metal precursor comprising the divalent metal cation, the trivalent metal cation, and the anion as described above, the adsorption capacity of LDH can be improved.

[0038] According to one embodiment of the present invention, the thickness of the LDH layer may be 0.5 μm to 5 μm. Specifically, the thickness of the LDH layer is preferably 1.0 μm to 1.5 μm. By controlling the thickness of the LDH layer within the above-described range, the amount of absorbed water molecules and the concentration gradient can be controlled.

[0039] According to one embodiment of the present invention, the first electrode may comprise one or more of Al, Au, Pt, Pd, Ni, Ru, Ag, Cu, Zn, Ti, phosphorus tin oxide (ITO), fluorine-containing tin oxide (FTO), gallium zinc oxide (GZO), carbon nanotubes (CNT), and graphene.

[0040] According to one embodiment of the present invention, the second electrode may comprise one or more of Al, Au, Pt, Pd, Ni, Ru, Ag, Cu, Zn, Ti, phosphorus tin oxide (ITO), fluorine-containing tin oxide (FTO), gallium zinc oxide (GZO), carbon nanotubes (CNT), and graphene. Specifically, it is preferable that the second electrode be Al. By selecting the type of the second electrode as described above, a Schottky contact can be formed between the interface with the LDH layer.

[0041] According to one embodiment of the present invention, the thickness of the first electrode may be 50 nm to 100 nm. Specifically, it is preferable that the thickness of the first electrode be 50 nm to 100 nm. By controlling the thickness of the first electrode within the above-described range, the thickness of the LDH layer can be controlled, and the amount of absorbed water molecules and the concentration gradient within the LDH layer can be controlled.

[0042] According to one embodiment of the present invention, the second electrode may be in the form of a brush. By selecting the shape of the second electrode as described above, a frictional charge can be generated with less force.

[0043] According to one embodiment of the present invention, the friction speed of the second electrode with the LDH layer may be 0.02 m / s or more and 0.24 m / s or less. By adjusting the friction speed between the second electrode and the LDH layer within the above-described range, the output voltage and current can be increased.

[0045] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0047] Al / Si / ZnAl-LDH structure fabrication

[0048] FIG. 3 is a schematic diagram showing the manufacturing process of the Al / Si / LDH layer structure of Example 1 and Example 2 of the present invention.

[0049] Example 1-1

[0050] First, hexamethylenetetramine (HMTA; C6H 12 3.364 g of N4 (99.9%) (Purchased from: Sigma Aldrich) and 7.139 g of Zn(NO3)2·6H2O (98%) (Purchased from: Sigma Aldrich) were added to 200 ml of distilled water and stirred at 90 ℃ for 30 minutes to completely dissolve them, thereby preparing a precursor solution for forming an LDH layer.

[0051] Subsequently, a Si wafer (Purchased from: Silicon Materials inc.) with an electrical resistivity of 1 to 5 Ωcm and a thickness of 500 μm was washed sequentially with acetone, methanol, buffer oxide etching solution, and distilled water, then placed in the vacuum chamber of a thermal evaporation apparatus (Manufacturer: Vectron Co., Ltd., Model: UVS-295), and then aluminum was deposited to a thickness of 100 nm by depositing at a deposition rate of 200 angstrom / min for 5 minutes under an applied voltage of 0.07 V and a current of about 0.1 A.

[0052] Then, the aluminum-deposited Si wafer was immersed in the precursor solution at 90°C for 60 minutes to grow a 1.5 μm thick ZnAl-LDH on the opposite side of the aluminum-deposited Si wafer, and the residue on the surface was removed by washing in an ultrasonic bath using distilled water for 5 minutes.

[0054] Examples 1-2

[0055] A Zn-Al LDH layer with a thickness of 1.0 μm was formed on one side and the opposite side of the Si wafer on which aluminum was deposited, in the same manner as in Example 1-1, except that aluminum was deposited on the Si wafer for 2.5 minutes to a thickness of 50 nm.

[0057] Figure 4 is an SEM image showing a cross- section of an LDH layer on a Si wafer formed in Examples 1-1 and 1-2 of the present invention.

[0058] Referring to Figures 4(a) and 4(b), it can be seen that as the thickness of the deposited aluminum layer increases from 50 nm to 100 nm, the thickness of the formed LDH layer increases from 1.0 μm to 1.5 μm. Figure 4(c) shows an SEM image of the surface of the LDH layer of Example 1-1, confirming that the ZnAl-LDH nanostructure has grown uniformly on the Si wafer.

[0060] Figure 5 shows the XRD graph (a) of the ZnAl-LDH layer and Si wafer and the FT-IR spectrum (b) of the ZnAl-LDH layer of Example 1-1 of the present invention. The equipment used was the Rigaku D / MAX 2500 and the Nicolet iS50 / Thermo Scientific, respectively.

[0061] Referring to Figure 5(a) above, it can be seen that ZnAl-LDH has crystallized due to the peaks of the (003) and (006) basal planes of the ZnAl-LDH layer.

[0062] Referring to Fig. 5(b) above, the 1,350 cm of ZnAl-LDH -1 The narrow absorption band of NO3 supplied by the zinc nitrate source - It corresponds to the asymmetric stretching mode where the ion is located, and is 3,200 to 3,600 cm -1 The broad absorption band corresponds to OH stretching vibrations caused by the hydroxyl groups of LDH and physically adsorbed water molecules. Therefore, ZnAl-LDH with a scroll structure consists of a positively charged brucite-type metal hydroxide layer and negatively charged NO3 - It was confirmed that it contains an intermediate layer of anions and water molecules.

[0064] Fabrication of Al / Si / ZnAl-LDH / Al energy generation devices

[0065] Example 2-1

[0066] A brush-shaped polyimide sheet coated with an aluminum thin film (Purchased from: Device Mart) was prepared with a thickness of 50 μm and a width of 1 cm. As the second electrode, the aluminum thin film-coated polyimide sheet was used to have an actual contact area of ​​10 with the ZnAl-LDH surface of the Al / Si / ZnAl-LDH structure prepared in Example 1-1. -4 cm 2 An energy generating device was manufactured by adjusting and arranging it to make contact.

[0068] Example 2-2

[0069] An energy generating device was manufactured in the same manner as in Example 2-1, except that the Al / Si / ZnAl-LDH structure prepared in Example 1-2 was used instead of the Al / Si / ZnAl-LDH structure prepared in Example 1-1.

[0071] Examples 3-1 and 3-2

[0072] Energy generating elements were manufactured in the same manner as in Examples 2-1 and 2-2, respectively, except that a brush-shaped polyimide sheet coated with an aluminum thin film was used, with a thickness of 50 μm and a width of 2 cm.

[0074] Example 4

[0075] An energy generating device was manufactured in the same manner as in Example 2-1, except that a brush-shaped polyimide sheet coated with an aluminum thin film was used, with a thickness of 50 μm and a width of 0.5 cm.

[0077] Comparative Example 1

[0078] A Si wafer (Purchased from: Silicon Materials inc.) with an electrical resistivity of 1 to 5 Ωcm and a thickness of 500 μm was washed in sequence with acetone, methanol, buffer oxide etching solution, and distilled water, then placed in the vacuum chamber of a thermal evaporation apparatus (Manufacturer: Vectron Co., Ltd., Model: UVS-295), and then aluminum was deposited to a thickness of 100 nm.

[0079] Then, a brush-shaped polyimide sheet coated with an aluminum thin film (purchased from Device Mart) was manufactured with a thickness of 50 μm and a width of 1 cm. An energy generating device was manufactured by placing the polyimide sheet coated with the aluminum thin film as a second electrode onto the aluminum-deposited Si wafer manufactured above.

[0081] Aluminum deposition thickness ZnAl-LDH thickness Polyimide sheet width Example 1-1 100 nm 1.5 μm - Examples 1-2 50 nm 1.0 μm - Example 2-1 100 nm 1.5 μm 1 cm Example 2-2 50 nm 1.0 μm 1 cm Example 3-1 100 nm 1.5 μm 2 cm Example 3-2 50 nm 1.0 μm 2 cm Example 4 100 nm 1.5 μm 0.5 cm Comparative Example 1 100 nm - 1 cm

[0083] Figure 6 is a graph of the current-voltage (IV) curve of the Al / ZnAl-LDH / n-Si / Al energy generation device of Example 3-2 of the present invention. It was confirmed that a Schottky contact is formed between these interfaces because the work function of aluminum (4.28 eV) corresponding to the second electrode is greater than the work function of ZnAl-LDH (3.64 eV).

[0085] Experimental Example 1: Charge Generation Using Moisture

[0086] The energy generating element prepared in Example 3-2 was placed at room temperature, and the charge generation performance was measured by increasing the relative humidity from 40% to 99.9%.

[0088] FIG. 7 is a potential graph according to changes in humidity of the energy generating element of Example 3-2 of the present invention. Specifically, FIG. 7 is a potential graph generated during a cycle in which relative humidity (RH) is increased from 40% to 99.9% and then returned to an initial state. The RH around the device was controlled using a commercial humidifier contained in a tightly sealed box. As the RH increased by turning on the humidifier, the voltage output of the energy generating element continuously increased from 0 to 125 mV. Even after turning off the humidifier, the voltage output was maintained for a while, and it was observed that the voltage output slowly decreased as the RH decreased.

[0089] FIG. 8 is a graph of voltage and current output generated by hygroscopic electricity at RH 60% according to the LDH layer thickness of the energy generating element of Comparative Example 1 and Examples 2-1 and 2-2 of the present invention (a), a graph of output voltage and current according to the load resistance of the energy generating element of Example 2-1 (b), and a graph of power density according to the load resistance of the energy generating element of Example 2-1 (c).

[0091] Referring to Figure 8(a) above, the voltage and current outputs on the Si surface without the LDH layer were 17.5 mV and 1.95 nA, respectively, and the voltage and current generated after coating with a 1 μm thick ZnAl-LDH were 81.8 mV and 4.92 nA, respectively, and it was confirmed that as the thickness of the LDH layer increased to 1.5 μm, the voltage and current increased to 157.4 mV and 14.37 nA, respectively.

[0092] Figure 8(b) is a graph of the output voltage and current of an energy generating device according to the load resistance by connecting a variable load resistance in the range of 10 kΩ to 1 GΩ. Referring to Figure 8(b), as the load resistance increased, the output voltage increased and the current decreased.

[0093] FIG. 8(c) is a graph of the power density of the energy generating device according to the load resistance, with variable load resistances ranging from 10 kΩ to 1 GΩ connected. The maximum power density was calculated by dividing the output power (P=IV) by the contact volume of ZnAl-LDH and the second electrode. Referring to FIG. 8(c), the maximum power density is 367 W / m² at an optimal load resistance of 1 MΩ. 3 Reached.

[0094] FIG. 9 is a graph of output voltage and current according to the width of the second electrode of the energy generating element of Examples 2-1, 3-1 and 4 of the present invention. Referring to FIG. 9, it can be seen that when humidity is provided, the output voltage and current increase as the width of the second electrode of the energy generating element increases from 0.5 cm to 2 cm.

[0096] Experimental Example 2: Charge generation using friction in mechanical brushing mode

[0097] Using a motor, the second electrode of Example 2-1 was subjected to one cycle of reciprocating friction back and forth on the ZnAl-LDH surface at a speed of 0.02 m / s.

[0098] FIG. 10 is a schematic diagram of the reciprocating motion on the surface of the LDH layer of the second electrode of Example 2-1 of the present invention and a graph of the open-circuit voltage according to the time taken for one reciprocating friction cycle. Referring to FIG. 10, the forward direction represents the movement of the crankshaft moving from top to bottom due to the rotation of the motor, and the reverse direction represents the movement of the crankshaft moving from bottom to top. During the 2.5-second reciprocating time of the second electrode, the open-circuit voltage (VOC) of the 1.5 μm thick LDH layer was continuously formed in the same direction regardless of the direction of movement of the second electrode. The noise signal was attributed to tension imbalance caused by the shaking of the brush. In addition, it was confirmed that more electrical energy is generated even when a much lower force (3.5 mN) is applied than that required for other conventional TVNGs, by removing holes from electron-hole pairs caused by the triboelectric effect of spontaneously dissociated water molecules.

[0100] FIG. 11 is a graph of output voltage and current according to the width of the second electrode due to reciprocating friction of the second electrode of the energy generating element of Examples 2-1, 3-1, and 4 of the present invention. Referring to FIG. 11, it can be seen that the output voltage and current increase as the width of the second electrode of the energy generating element increases from 0.5 cm to 2 cm when frictional force is provided.

[0102] FIG. 12 is a graph of output voltage (a) and current (b) according to the reciprocating friction of the second electrode of the energy generating element of Example 2-1, Example 2-2 and Comparative Example 1 of the present invention.

[0103] Referring to Figures 12 (a) and (b) above, when the second electrode reciprocates on the surface of a Si wafer without an LDH layer attached (Comparative Example 1), the output voltage and current were very low at 81.18 mV and 9.57 nA, respectively, due to the low frictional force. On the other hand, when the second electrode reciprocates on the surface of a Si wafer with a 1 μm thick LDH layer attached (Example 2-2), the output voltage and current were improved to 284.3 mV and 24.7 nA, respectively. When the second electrode reciprocates on the surface of a Si wafer with a 1.5 μm thick LDH layer attached (Example 2-1), the output voltage and current were improved to 482.94 mV and 53.87 nA, respectively, which was 5.9 times and 5.6 times higher than in the case of a Si wafer without an LDH layer attached.

[0104] FIG. 12(c) is a graph of the output voltage according to the reciprocating speed of the second electrode of the energy generating element of Example 2-1, and FIG. 12(d) is a graph of the current according to the reciprocating friction speed of the second electrode of the energy generating element of Example 2-1. Referring to FIG. 12(c) and (d), as the friction speed of the second electrode increased from 0.02 m / s to 0.16 m / s, the output voltage and current increased from 378.81 mV to 567.375 mV and from 41.85 nA to 53.87 nA, respectively. The output voltage and current saturated at a friction speed of 0.16 m / s or higher. The increase in voltage and current at brushing speeds of 0.16 m / s or lower was attributed to more electron transitions induced at the friction surface. On the other hand, if the friction speed is excessively increased to more than 0.24 m / s, partial damage and heat generation occur at the friction interface, resulting in a decrease in output voltage and current performance.

[0105] FIG. 12(e) is a graph of output voltage according to relative humidity at a friction speed of 0.02 m / s for the second electrode of the energy generating element of Example 2-1, and FIG. 12(f) is a graph of current according to relative humidity at a friction speed of 0.02 m / s for the second electrode of the energy generating element of Example 2-1. Referring to FIG. 12(e) and (f), as the relative humidity increased from 20% to 80%, the output voltage and current continuously increased from 370.59 mV to 693.38 mV and from 31.37 nA to 65.48 nA, respectively. Actual contact area (10 -4 cm 2 The current density for ) is approximately 6.548 x 10 at 80% RH. -3 mA / cm 2 It was calculated as follows. Considering that the pressure applied by the second electrode manufactured in Example 2-1 is 3.5 mN, it can be seen that the current density is excellent, and therefore, high output can be achieved even with weak force in high humidity conditions, and in FIG. 8 (a), it can be seen that the current output using friction and moisture absorption is improved compared to the current by moisture absorption electricity at RH 60%.

[0107] FIG. 13 is a graph of the output voltage (a, b) and the rate of change of output voltage (c) according to the reciprocating motion speed of the second electrode before and after 5,000 cycles of driving of the energy generating element of Example 2-1 of the present invention.

[0108] Referring to Figure 13(c) above, it was confirmed that when the brushing speed is reduced to less than 0.08 m / s, the output performance is maintained even after 5,000 cycles of operation, and at a brush speed faster than 0.16 m / s, the output voltage decreases slightly after 5,000 cycles of operation. Therefore, it can be seen that the energy generating device manufactured in Example 2-1 does not undergo significant degradation due to the very low pressure of 3.5 mN, considering the microporous structure of the LDH.

[0110] Experimental Example 3: Charge generation using friction in airbrushing mode

[0111] Figure 14 is a graph of the voltage output generated by the frictional effect of the airbrushing mode by a pulsed air flow at a relative humidity of 20% and a pressure of 30 mmHg of the energy generating element of Example 3-1 of the present invention. Referring to Figure 14, it was confirmed that the output voltage rapidly increased and then decreased exponentially due to friction between the surface of the LDH layer and the second electrode caused by short airflow pulses. In particular, it was observed that the potential decreased over time and persisted for more than one minute. Through this, it can be seen that the energy generating element of the present invention can exhibit the characteristics of wet power generation through friction even in a non-wet state. That is, it can be seen that the energy generated by frictional power generation can be stored through the mechanism of wet power generation. Such behavior of potential change over time has not been observed in other conventional TVNG elements.

[0113] FIG. 15 is the FT-IR spectrum of the H2O adsorption process before and after interfacial friction between the second electrode and the LDH layer via an air brushing mode using pulsed air flow at a relative humidity of 20% and a pressure of 30 mmHg of the energy generating element of Example 3-1 of the present invention. 3,450 cm⁻¹ -1 and 1,630 cm -1The broad absorption band centered at corresponds to physically adsorbed water molecules on the LDH layer. The intensity of this absorption band decreased after friction with the second electrode for 5 minutes, indicating that a significant amount of water molecules bound to the surface were lost. After being held in the air for 5 minutes without friction, the peak intensity of the absorption band increased again because the moisture content was recovered through adsorption from the air. Therefore, the FT-IR spectrum confirmed that water molecules are consumed and recovered from the LDH layer during triboelectric generation in airbrushing mode. In other words, by analyzing the FT-IR results before and after friction, the holes generated during the triboelectric generation process and the spontaneously generated OH within the LDH - It was confirmed that the ions actually combined and the OH- decreased, and after some time had passed following friction, OH - Through the recovery, water molecules and OH depleted by the hygroscopic properties of LDH are restored. - It can be seen that recovery is possible.

[0115] FIG. 16 is a graph of voltage (a) and current (b) according to the frictional effect of the air brushing mode by pulsed air flow with different pressures at a relative humidity of 20% of the energy generating element of Example 3-1 of the present invention.

[0116] Referring to Figures 16 (a) and (b) above, as the atmospheric pressure increased from 10 mmHg to 30 mmHg, the voltage and current increased from 336.25 mV to 486.72 mV and from 32.63 nA to 67.11 nA, respectively. Since the potential was generated by the triboelectric effect, it was confirmed that the holding time for maintaining the potential also increased as the atmospheric pressure increased. More holes generated by the increased frictional force further depleted the water molecules in the LDH layer. As the moisture content of the LDH layer decreased, the diffusion time for the equilibrium concentration gradient of water in the air and inside the LDH layer increased.

[0118] FIG. 17 shows a voltage graph (a) and a current graph (b) measured in the air brushing mode of 10 repeated air jets at a pressure of 5 mmHg and a relative humidity of 20% for the energy generating element of Example 3-1 of the present invention. As the air jets were repeated, the voltage and current continuously increased from 85.88 mV to 564.69 mV and from 23.66 nA to 75.15 nA, respectively. It can be seen that charging was successful during continuous triboelectric generation because the second electrode moved within a minimum range to minimize charge loss.

[0120] Figure 18 is a voltage graph of the energy generating element of Example 2-1 of the present invention when friction by air injection and moisture supply are repeated at a pressure of 5 mmHg and a relative humidity of 20%. Referring to Figure 18, moisture was initially supplied instantaneously by a humidifier to maintain the relative humidity at 90%. The voltage generated by moisture absorption during the first moisture supply was measured at 121.22 mV. As friction was repeated by air brushing, the voltage due to moisture absorption increased from 121.22 mV to 227.38 mV due to the first and second moisture supplies, and further increased from 227.38 mV to 269.47 mV due to the second and third moisture supplies. It was confirmed that when moisture in an equilibrium state was supplied from the surrounding air, the voltage changed within a small range, but when moisture was supplied after the water molecules of the LDH were depleted due to the friction mechanism effect, the voltage according to the change in humidity increased further. Therefore, a larger voltage and a larger concentration gradient of water molecules can be generated. In addition, it was confirmed that as water was repeatedly supplied, the output voltage due to the tribokinetic effect increased from 713.78 mV to 824.57 mV, and then increased again from 824.57 mV to 892.17 mV.

[0121] From this, it can be seen that the energy generating device of the present invention exhibits storage characteristics through frictional power generation as well as storage characteristics through wet power generation, and that a single device structure capable of both energy generation and storage can be realized through two power generation methods regarding friction and wetness.

[0123] Experimental Example 4: Generator using an energy generating element

[0124] FIG. 19 is a graph of voltage and current of a generator (Al / Si / ZnAl-LDH / Al) using energy generating elements according to Example 2-1 of the present invention in series and parallel circuits. In FIG. 19, 'series' means series and 'parallel' means parallel, and 1, 2, 3, and 4 represent the number of corresponding Al / Si / ZnAl-LDH / Al elements. Referring to FIG. 19, the voltage and current of the generator using the energy generating elements of Example 2-1 increased under both moisture absorption conditions and friction conditions, regardless of whether they were arranged in series circuits or parallel circuits, respectively.

[0126] Although the present invention has been described above by limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

Claim 1 An energy generating device comprising: a first electrode; a semiconductor layer attached to one surface of the first electrode; a layered-double hydrxide (LDH) layer attached to the semiconductor layer; and a second electrode disposed on the LDH layer, wherein the LDH layer stores a frictional charge generated by friction with the second electrode and a wet charge generated under a wet environment and generates a voltage in the form of a direct current. Claim 2 An energy generating device according to claim 1, wherein the LDH layer is an M(II)M(III)-LDH layer formed by growing a reaction product of a divalent metal (M(II)) hydroxide precursor and a trivalent metal (M(III)) hydroxide precursor on top of the semiconductor layer. Claim 3 In claim 1, the semiconductor layer is made of Si, Ge, InAs, GaAs, AlAs, InN, GaN, AlN, SiC, SnO 2, An energy generating device comprising one or more of Ga2O3 and ZnO. Claim 4 In paragraph 2, the divalent metal precursor and the trivalent metal precursor are at least one divalent metal cation selected from Zn, Mg, Co, Cd, Ni, V, Fe, Ca, Mn, and Cu, or at least one trivalent metal cation selected from Al, Ti, Fe, Cr, and Co; and OH - , NO3 - , CO3 2- , Cl - , and CH3COO - An energy generating device comprising at least one anion. Claim 5 An energy generating device according to claim 1, wherein the first electrode and the second electrode comprise one or more materials selected from Al, Au, Pt, Pd, Ni, Ru, Ag, Cu, Zn, Ti, phosphorus tin oxide (ITO), fluorine-containing tin oxide (FTO), gallium zinc oxide (GZO), carbon nanotubes (CNT), and graphene, and the materials of the first electrode and the second electrode are the same or different from each other.

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