Self-powered temperature sensor based on thermoelectric effect and preparation method and application thereof

Abstract

The application discloses a self-powered temperature sensor based on thermoelectric effect and a preparation method and application thereof, and aims to provide a temperature sensor based on high-performance bismuth telluride-based thin film thermoelectric material, which has high sensitivity and strong flexibility, and a preparation method and application thereof in monitoring soil temperature of a greenhouse. The temperature sensor comprises a thermoelectric module, the thermoelectric module comprises a base plate, the base plate is provided with N-type bismuth telluride thin films and P-type antimony telluride thin films which are distributed in a scattering mode, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are arranged at intervals, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are integrated into multiple pairs of P-N junction thermoelectric legs by being connected in series through thin film electrodes, a center hollow hole is arranged on an inner ring formed by the thin film electrodes on the base plate, the hollow position at the center hollow hole and the thin film electrodes of the inner ring are encapsulated by high-thermal-conductivity material, and a thermal-conductivity encapsulation layer is formed in a middle region. The sensor has high sensitivity, strong flexibility and the ability of accurate monitoring.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of self-powered temperature sensors, and more particularly relates to a self-powered temperature sensor based on thermoelectric effect and a preparation method thereof, and application of the self-powered temperature sensor in monitoring soil temperature in an agricultural greenhouse. BACKGROUND

[0002] With the rapid development of smart agriculture, self-powered sensing technology that can provide sustainable and stable power is widely concerned by humans. In a greenhouse, both excessively high and low soil temperatures can affect the normal growth of crops. If the soil temperature in the greenhouse cannot be monitored in a timely manner, the crops may wither or yield too low, causing great losses to farmers. Therefore, effective monitoring of the soil temperature in the greenhouse is one of the important bases for determining the normal growth of crops.

[0003] At present, people manage the soil temperature in the greenhouse through experience. However, this method not only requires farmers to have strong perceptual judgment ability, but also is inaccurate in temperature control and wastes a lot of time, which indirectly causes economic losses in agriculture. In order to precisely control the soil temperature, a large number of temperature sensors have been studied. However, the temperature sensors reported at present need to be replaced with batteries regularly or be charged periodically, which brings inconvenience to the intelligent control of the agricultural greenhouse. Therefore, developing a self-powered temperature sensor for the greenhouse is the key to the further development of smart agriculture.

[0004] A thermoelectric device is integrated with a thermoelectric material and an electrode to convert heat energy in the environment into electrical energy through the thermoelectric effect of the material, so as to realize self-powered real-time monitoring of the soil temperature in the greenhouse. The advantage of this scheme is that the thermoelectric device prepared can utilize the temperature difference between the soil temperature and the environment temperature in the greenhouse to output a stable voltage, which is used to monitor the change of the soil temperature in real time, and is no longer limited to the charging and discharging of a battery, light or wind power generation. On the other hand, compared with a temperature sensor based on piezoelectric and friction type nanometer power supply, the sensor can be directly used as a self-powered power supply and a sensor in one, and does not need a voltage boosting device and an AC-DC conversion device to meet the demand for soil temperature testing.

[0005] However, the existing temperature sensor based on thermoelectric effect adopts an organic thermoelectric thin film material such as a polyaniline thin film, which has a relatively low thermoelectric performance, resulting in low sensitivity of the temperature sensor and far failing to meet the demand for monitoring the soil temperature in agriculture. In order to increase the performance of the thermoelectric material, a bismuth telluride-based thin film thermoelectric material with high room temperature performance has been studied a lot. Although the method and mechanism of improving the performance of the material have been explored a lot, the material is not patterned and integrated for design research, and cannot be applied to a soil temperature sensor based on thermoelectric effect. SUMMARY

[0006] The application aims at providing a self-powered temperature sensor with high sensitivity and flexibility based on high-performance bismuth telluride-based thin film thermoelectric material to solve the technical defects in the prior art.

[0007] Another object of the application is to provide a preparation method of the self-powered temperature sensor with high sensitivity and reliable structure.

[0008] Still another object of the application is to provide an application of the self-powered temperature sensor based on thermoelectric effect in monitoring soil temperature of agricultural greenhouse.

[0009] To achieve the objects of the application, the application adopts the technical scheme of:

[0010] A self-powered temperature sensor based on thermoelectric effect comprises a thermoelectric module, the thermoelectric module comprises a base plate, N-type bismuth telluride thin films and P-type antimony telluride thin films are arranged in a scattered manner on the base plate, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are arranged at intervals, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are integrated into multiple pairs of P-N junction thermoelectric legs in series through thin film electrodes, the N-type bismuth telluride thin films and the P-type antimony telluride thin films corresponding to negative electrode thin films and positive electrode thin films are connected with the negative electrode thin films and the positive electrode thin films respectively, a center hollow hole is arranged in an inner ring formed along the thin film electrodes on the base plate, the hollow position at the center hollow hole and the thin film electrodes in the inner ring are encapsulated by high-thermal-conductivity material to form a thermal-conductivity encapsulation layer in a middle region, the thickness of the thermal-conductivity encapsulation layer is greater than the thickness of the N-type bismuth telluride thin films, the P-type antimony telluride thin films and the thin film electrodes in an outer ring, so that a height difference is established between the thermal-conductivity encapsulation layer and the N-type bismuth telluride thin films, the P-type antimony telluride thin films and the thin film electrodes in the outer ring.

[0011] The N-type bismuth telluride thin films and the P-type antimony telluride thin films are any one of isosceles trapezoid, rectangle and sector, the thin film electrodes are any one of isosceles trapezoid, rectangle and sector, the material of the thin film electrodes is any one of copper, silver, nickel and titanium, the base plate is square or rectangular, the material of the base plate is any one of polyimide, aluminum nitride and silicon wafer, and the high-thermal-conductivity encapsulation material is silicone grease, boron nitride insulation composite material or aluminum nitride insulation composite material.

[0012] The N-type bismuth telluride film and the P-type antimony telluride film are isosceles trapezoids, the upper base width of the isosceles trapezoid structure of the N-type bismuth telluride film and the P-type antimony telluride film is 0.20-0.5 mm, the lower base width is 0.5-0.9 mm, and the waist is 7-8 mm; the film electrode is an isosceles trapezoid; the film electrode is a copper material; the upper base width of the isosceles trapezoid structure of the inner ring of the film electrode is 0.5-2 mm, the lower base width is 1-2 mm, and the waist is 2-3 mm; the upper base width of the isosceles trapezoid structure of the outer ring of the film electrode is 1-2 mm, the lower base width is 1-3 mm, the waist is 1-2 mm, and the thickness is 2-4 μm; the radius of the inner ring circle formed by the film electrode is 5.5-7.5 mm; the thickness of the N-type bismuth telluride film and the P-type antimony telluride film is 3-15 μm, the thickness of the base plate is 0.3-1 mm, and the thickness of the heat-conducting packaging layer is 2-6 mm.

[0013] A preparation method of a self-powered temperature sensor based on thermoelectric effect, including a preparation method of a thermoelectric module, the preparation of the thermoelectric module includes the following steps:

[0014] (1) The N-type bismuth telluride film is patterned and deposited on the pretreated base plate in a scattered distribution by a magnetron sputtering method, then the P-type antimony telluride film is patterned and deposited between the two adjacent N-type bismuth telluride films by a magnetron sputtering method, and then the film electrode, the negative electrode film and the positive electrode film are deposited by a magnetron sputtering method to integrate multiple pairs of P-N junction thermoelectric legs in series;

[0015] (2) Hollow processing is performed on the inner ring of the film electrode on the base plate to form the center hollow hole, and then a high-thermal-conductivity material is used to package the hollow position of the center hollow hole and the film electrode of the inner ring to form a heat-conducting packaging layer in the middle area; a thermoelectric module of a self-powered temperature sensor is obtained.

[0016] Before patterned deposition, a model of the thermoelectric module is established by a finite element simulation software to obtain the thickness of the base plate of the thermoelectric module and the radius of the circle formed by the electrode film of the inner ring.

[0017] The magnetron sputtering temperature of the N-type bismuth telluride film is 350℃, the magnetron sputtering time is 3.5 hours, the gas pressure is 2 Pa, the sputtering power is 20 W, and the Te power is 16 W; the magnetron sputtering temperature of the P-type bismuth telluride film is 350℃, the magnetron sputtering time is 3.5 hours, the gas pressure is 2 Pa, the sputtering power is 20 W, and the Te power is 28 W; the magnetron sputtering temperature of the film electrode is 200℃, the magnetron sputtering time is 2 hours, the gas pressure is 1.6 Pa, and the sputtering power is 25 W.

[0018] The pretreatment method of the base plate comprises the following steps: sequentially immersing the base plate in detergent water, deionized water, acetone and ethanol for ultrasonic treatment, and then drying to obtain a pretreated base plate.

[0019] Application of a self-powered temperature sensor based on thermoelectric effect in monitoring soil temperature of an agricultural greenhouse.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] 1. The thermoelectric module in the self-powered temperature sensor based on thermoelectric effect comprises N-type bismuth telluride films and P-type antimony telluride films which are distributed in a scattering shape, are connected in series through thin film electrodes to form multiple pairs of P-N junction thermoelectric legs, and are designed to be hollow in the central region and are encapsulated by a high-thermal-conductivity material to form a thermal-conductivity encapsulation layer, so that the self-powered temperature sensor based on thermoelectric effect has high sensitivity and flexibility and can realize accurate monitoring.

[0022] 2. The outer electrode of the self-powered temperature sensor has a dispersed structure, so that the outer end can dissipate heat quickly and a stable temperature difference can be established more easily, thereby obtaining a sensing signal with high stability.

[0023] 3. The self-powered temperature sensor is prepared by using bismuth telluride-based thermoelectric materials to form a circular thermoelectric device, the middle temperature-sensitive region is encapsulated by a thermal-conductivity material to establish a height difference with the sensing material and the electrode, when the temperature-sensitive region is attached to the soil region, a temperature difference with the surrounding environment can be established, and self-powered monitoring of the soil temperature can be realized, which is conducive to promoting the rapid development of smart agriculture.

[0024] 4. The self-powered temperature sensor utilizes the thermoelectric effect of bismuth telluride-based thin film materials to convert temperature changes into voltage signals, and can directly realize signal conversion or amplification in a digital circuit, which is conducive to promoting the development of wireless transmission and artificial intelligence. In addition, no external power supply is needed, and it is suitable for long-term unattended monitoring.

[0025] 5. The preparation method of the self-powered temperature sensor comprises the following steps: patterning deposition of N-type bismuth telluride thin films, patterning deposition of P-type antimony telluride thin films, and finally patterning deposition of copper thin film electrodes, which can ensure firm combination of the N-type bismuth telluride thin films, the P-type antimony telluride thin films and the copper thin film electrodes with the substrate, prevent falling off, and thus ensure the performance of the thermoelectric module.

[0026] 6. The preparation method of the self-powered temperature sensor optimizes the design and reasonably configures various process parameters, so that the obtained temperature sensor has high sensitivity, strong flexibility and the ability of accurate monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Fig. 1 shows a structural schematic diagram of a thermoelectric module of a self-powered temperature sensor based on thermoelectric effect of the present application before packaging;

[0028] Figure 2 Fig. 2 shows a structural schematic diagram of a thermoelectric module of a self-powered temperature sensor based on thermoelectric effect of the present application after packaging;

[0029] Figure 3 Fig. 3 shows a flow chart of a preparation method of a thermoelectric module;

[0030] Figure 4 Fig. 4 shows a temperature distribution nephogram of a soil temperature sensor with different base plate structures of the present application;

[0031] Figure 5 Fig. 5 shows a surface area section SEM image of a deposited bismuth telluride and antimony telluride film obtained by deposition when preparing a temperature sensor in Example 1 of the present application;

[0032] Figure 6 Fig. 6 shows a temperature distribution nephogram of a soil temperature sensor with different base thicknesses of the present application;

[0033] Figure 7 Fig. 7 shows a temperature and open circuit voltage distribution nephogram of a soil temperature sensor with different inner diameters of a hot end electrode of the present application;

[0034] Figure 8 Fig. 8 shows a schematic diagram of a thermoelectric performance test result of a thin film material of a self-powered temperature sensor of the present application with temperature change;

[0035] Figure 9 Fig. 9 shows a schematic diagram of a test result of an open circuit voltage of a self-powered temperature sensor based on thermoelectric effect of the present application under different temperature differences;

[0036] Figure 10 Fig. 10 shows a test result diagram of a sensitivity of a self-powered temperature sensor based on thermoelectric effect of the present application;

[0037] Figure 11 Fig. 11 shows a test result diagram of a sensing signal stability of a self-powered temperature sensor based on thermoelectric effect of the present application. DETAILED DESCRIPTION

[0038] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0039] The self-powered temperature sensor based on thermoelectric effect of the present application comprises a thermoelectric module, a structural schematic diagram of which is shown in Figures 1-2As shown, it comprises a base plate 7, on which N-type bismuth telluride thin film 1 and P-type antimony telluride thin film 2 are arranged in a scattering manner, the N-type bismuth telluride thin film 1 and P-type antimony telluride thin film 2 are arranged in intervals, and the N-type bismuth telluride thin film 1 and P-type antimony telluride thin film 2 are integrated into multiple pairs of P-N junction thermoelectric legs in series through thin film electrode 3. The N-type bismuth telluride thin film and P-type antimony telluride thin film corresponding to the negative electrode thin film and the positive electrode thin film are connected with negative electrode thin film 5 and positive electrode thin film 4 respectively. The inner circle of the base plate 7 along the thin film electrode 3 is provided with a center hollow hole 6, and the hollow position at the center hollow hole 6 and the thin film electrode 3 of the inner circle are packaged by high thermal conductive material to form a thermal conductive packaging layer 8 in the middle area. The thickness of the thermal conductive packaging layer 8 is greater than the thickness of the N-type bismuth telluride thin film 1, P-type antimony telluride thin film 2 and thin film electrode 3 of the outer circle, so that a height difference is established between the thermal conductive packaging layer and the N-type bismuth telluride thin film, P-type antimony telluride thin film and thin film electrode of the outer circle, the middle temperature can be highly concentrated, it is easier to establish a larger temperature difference between the two electrodes, so as to realize a larger output voltage, and improve the accuracy of the self-powered temperature sensor.

[0040] Preferably, the N-type bismuth telluride thin film and P-type antimony telluride thin film are in any one of isosceles trapezoid, rectangle and sector, and preferably in isosceles trapezoid shape. The thin film electrode is in any one of isosceles trapezoid, rectangle and sector, and preferably in isosceles trapezoid shape. The material of the thin film electrode is any one of copper, silver, nickel and titanium, and preferably copper material. The base plate is square or rectangular, and the material of the base plate is any one of polyimide, aluminum nitride and silicon wafer, and preferably polyimide. The packaging material is silicone grease, boron nitride insulation composite material or aluminum nitride insulation composite material, and preferably thermal conductive silicone grease.

[0041] In the embodiment, the thickness of the N-type bismuth telluride thin film 1 and P-type antimony telluride thin film 2 is 3-15 μm, and the thickness of the base plate 7 is 0.3-1 mm.

[0042] When the N-type bismuth telluride thin film 1 and P-type antimony telluride thin film 2 are both isosceles trapezoids, the upper base width of the N-type bismuth telluride thin film and P-type antimony telluride thin film in isosceles trapezoid structure is 0.20-0.5 mm, the lower base width is 0.5-0.9 mm, and the waist is 7-8 mm.

[0043] When the thin film electrode 3 is isosceles trapezoid, and the thin film electrode is copper material, the upper base width of the thin film electrode in the inner circle of the isosceles trapezoid structure is 0.5-2mm, the lower base width is 1-2mm, and the waist is 2-3mm; the upper base width of the thin film electrode in the outer circle of the isosceles trapezoid structure is 1-2mm, the lower base width is 1-3mm, and the waist is 1-2mm, and the thickness is 2-4μm; the radius of the circle formed by the inner circle of the copper thin film electrode is 5.5-7.5mm.

[0044] The thickness of the heat-conducting packaging layer is 2-6mm.

[0045] The preparation method of the self-powered temperature sensor based on the thermoelectric effect of the application comprises a preparation method of a thermoelectric module, and a flow chart of the preparation method of the thermoelectric module is as shown in the figure, comprising the following steps: Figure 3

[0046] (1) obtaining the optimal optimization process parameters of the core-thermoelectric module of the self-powered temperature sensor:

[0047] The optimal process parameters of the thermoelectric module can be obtained by the method of ANSYS finite element simulation software, and the optimal process parameters of the thermoelectric module can also be obtained by other finite element methods such as comsol. The application preferably adopts the obtaining method of ANSYS finite element simulation software.

[0048] A model of the thermoelectric module based on the thermoelectric effect is established by ANSYS finite element simulation software, and in the simulation process, the conductivity, thermal conductivity and Seebeck coefficient of bismuth telluride, antimony telluride, copper and the base plate are set, the structure design of the base plate, the thickness of the base plate and the inner circle radius of the copper electrode are solved, the steady-state heat transfer equation is calculated, and the temperature and open-circuit voltage distribution diagram of the temperature sensor are obtained.

[0049] (2) base plate pretreatment:

[0050] The pretreatment method of the base plate comprises the following steps: the base plate is sequentially soaked in detergent water, deionized water, acetone and ethanol for ultrasonic treatment, and then dried to obtain the pretreated base plate.

[0051] (3) preparation of the thermoelectric module:

[0052] ​The N-type bismuth telluride film 1 is patterned and deposited on the pretreated base plate 7 in a scattered distribution, then the P-type antimony telluride film 2 is patterned and deposited between two adjacent N-type bismuth telluride films 1, and then the thin film electrode 3, the negative electrode thin film 5 and the positive electrode thin film 4 are deposited to integrate multiple pairs of P-N junction thermoelectric legs in series. The inner circle of the thin film electrode formed on the base plate 7 is hollowed out to form the central hollow hole 6, and then the hollow position of the central hollow hole and the thin film electrode of the inner circle are encapsulated by using a high-thermal-conductivity material to form a thermal-conductivity encapsulation layer 8 in the central area, thereby obtaining a thermoelectric module for a self-powered temperature sensor. The thermoelectric module is assembled into a self-powered temperature sensor according to different structures of the self-powered temperature sensor by using a conventional method.

[0053] The method for patterned deposition is magnetron sputtering or vacuum coating, preferably magnetron sputtering. The magnetron sputtering temperature of the N-type bismuth telluride film is 350 DEG C, the magnetron sputtering time is 3.5 hours, the air pressure is 2 Pa, the sputtering power is 20 W, and the Te power is 16 W. The magnetron sputtering temperature of the P-type bismuth telluride film is 350 DEG C, the magnetron sputtering time is 3.5 hours, the air pressure is 2 Pa, the sputtering power is 20 W, and the Te power is 28 W. The magnetron sputtering temperature of the thin film electrode is 200 DEG C, the magnetron sputtering time is 2 hours, the air pressure is 1.6 Pa, and the sputtering power is 25 W.

[0054] The self-powered temperature sensor based on the thermoelectric effect can be mainly applied to monitoring the soil temperature of a greenhouse, and can also be applied to monitoring the body temperature of a human or an animal in a greenhouse.

[0055] The self-powered temperature sensor based on the thermoelectric effect can be mainly applied to monitoring the soil temperature of a greenhouse, and can also be applied to monitoring the body temperature of a human or an animal in a greenhouse.

[0056] Embodiment 1

[0057] The self-powered temperature sensor based on the thermoelectric effect can be mainly applied to monitoring the soil temperature of a greenhouse, and can also be applied to monitoring the body temperature of a human or an animal in a greenhouse.

[0058] (1) Through ANSYS finite element simulation software simulation, the size of the thermoelectric arm, thickness, material properties and the size of the base are set to optimize the thickness of the thermoelectric effect-based temperature sensor base and the size of the inner ring electrode, and the optimal base thickness and inner ring electrode size of the self-powered temperature sensor based on bismuth telluride-based thermoelectric material are obtained.

[0059] In this embodiment, the thermoelectric module in ansys19.2 workbench is selected, and the bismuth telluride and antimony telluride thermoelectric arms of isosceles trapezoidal shape are first drawn in the geometric interface, and then the circular center array is performed to realize the model establishment of 36 thermoelectric arms; then the model establishment of the inner ring copper electrode on the upper surface of the thermoelectric arm is performed, and 36 isosceles trapezoidal copper thin film electrodes are drawn to be sequentially connected to the bottom P-N thermoelectric arm; then the model establishment of the outer ring copper electrode is performed, and 36 isosceles trapezoidal copper thin film electrodes are drawn to be sequentially connected to the lower bottom P-N thermoelectric arm; finally, the base model is established on the upper surface of the thermoelectric arm. The specific method is as follows:

[0060] The thermoelectric module in Ansysy19.2 Workbench is selected, and a two-dimensional thermoelectric arm of isosceles trapezoidal structure is set, the upper bottom width is 0.35mm, the lower bottom width is 0.70mm, and the waist is 7.3mm. The stretching height is 10μm, and then the circular array is set, and the array number is set to 36; a new flat plate is established on the upper surface of the stretched thermoelectric arm, and the two-dimensional inner ring copper electrode of isosceles trapezoidal structure connecting two thermoelectric arms is set on the upper bottom of the thermoelectric arm, the upper bottom width is 1.04mm, the lower bottom width is 1.34mm, and the waist is 2.2mm. The stretching height is 10μm, and then the circular array is set, and the array number is set to 36; the two-dimensional outer ring copper electrode of isosceles trapezoidal structure is set on the lower bottom of the thermoelectric arm, the upper bottom width is 1.8mm, the lower bottom width is 2.0mm, and the waist is 1.4mm. The stretching height is 10μm, and then the circular array is set, and the array number is set to 36.

[0061] A new flat plate is established on the lower surface of the stretched thermoelectric arm, and a rectangular base plate with a width of 36mm, a length of 38mm and a thick bottom of 0.3mm is set.

[0062] The middle of the base plate is hollowed out and cut by Boolean operation.

[0063] The related physical property parameter conditions used in the finite element simulation simulation are set in the engineering data interface, as shown in Table 1.

[0064] Table 1-Related physical property parameters used in finite element simulation

[0065] Material properties Seebeck coefficient (V / K) Electrical resistivity (Ωm) Thermal conductivity (W / mK) Bi2Te3 -140e -6 ]] 1.1e -5 ]]> 1 [Sb2Te3] 160e -6 ]] 1.1e -5 ]]> 1 Cu - 1.6e -8 ]]> 400 Base plate - - 0.3

[0066] In the calculation interface, each model in the geometry is assigned a corresponding material, the air temperature control is set to 300K, the heat source density is 1000W K -2 , the heat flux is 0, and the temperature distribution diagrams of thermoelectric modules under different base structure designs are calculated respectively, as shown in Figure 4 , Figure 4 , where a is the temperature distribution nephogram of the soil temperature sensor with a non-hollow base design, and b is the temperature distribution nephogram of the soil temperature sensor with a hollow base design. As can be seen from Figure 4 , the temperature difference between the inner and outer circles of the hollow design thermoelectric module reaches 71K, which is much larger than the temperature difference of 14.4K of the non-hollow design, so the hollow design can establish a larger temperature difference, thereby improving the accuracy.

[0067] The optimal process parameters are: the N-type bismuth telluride film and the P-type antimony telluride film are isosceles trapezoidal, and the film electrodes are isosceles trapezoidal; the upper base width of the N-type bismuth telluride film and the P-type antimony telluride film in the isosceles trapezoidal structure is 0.35mm, the lower base width is 0.70mm, the waist is 7.3mm, and the thickness is 4μm; the upper base width of the copper film electrode in the inner circle of the isosceles trapezoidal structure is 1.04mm, the lower base width is 1.34mm, the waist is 2.2mm, and the thickness is 4μm; the upper base width of the copper film electrode in the outer circle of the isosceles trapezoidal structure is 1.8mm, the lower base width is 2.0mm, the waist is 1.4mm, and the thickness is 4μm. The middle blank area is hollowed out to obtain a center hollow hole with a radius of 5.5mm, and the thickness of the heat-conducting silicone grease packaged in the sensitive area is 3mm. The thickness of the base plate is 3mm.

[0068] (2) Preparation of thermoelectric module for greenhouse self-powered temperature sensor

[0069] A polyimide base plate with a thickness of 0.3mm is sequentially soaked in detergent water, deionized water, acetone and ethanol for ultrasonic cleaning and then dried to obtain a pretreated base plate.

[0070] The 36 N-type bismuth telluride thin films of isosceles trapezoid structure are first deposited on the pretreated substrate by magnetron sputtering technology, and then the 36 P-type antimony telluride thin films of isosceles trapezoid structure are deposited after patterning: the upper base width is 0.35 mm, the lower base width is 0.70 mm, the waist is 7.3 mm, and the film thickness is 4 μm; then the inner circle copper thin film electrode of isosceles trapezoid structure is deposited: the upper base width is 1.04 mm, the lower base width is 1.34 mm, the waist is 2.2 mm, and the thickness is 4 μm, and the upper base P-N thermoelectric arm is sequentially connected by the inner circle copper thin film electrode; then the outer circle copper thin film electrode of isosceles trapezoid structure is deposited: the upper base width is 1.8 mm, the lower base width is 2.0 mm, the waist is 1.4 mm, and the thickness is 4 μm, and the lower base P-N thermoelectric arm is sequentially connected by the outer circle copper thin film electrode, so that the N-type bismuth telluride thin film and the P-type antimony telluride thin film are connected in series by the thin film electrode to integrate 36 pairs of P-N junction thermoelectric legs, and the radius of the circle formed by the inner circle copper thin film electrode is 5.5 mm.

[0071] The material-free part in the middle of the thermoelectric module is hollowed out to form a center hollow hole, the radius of the center hollow hole is 5.5 mm, and finally the inner circle thin film electrode and the hollow part are packaged with heat-conducting silicone grease to form a heat-conducting packaging layer, the thickness of the heat-conducting packaging layer is 3 mm, and a thermoelectric module of a self-powered temperature sensor based on thermoelectric effect is obtained.

[0072] Figure 5 Fig. a and Fig. b in the drawings show the surface and cross-section SEM images of the deposited bismuth telluride thin film deposited in the preparation of the thermoelectric module in Example 1, Figure 5 Fig. c and Fig. d in the drawings show the surface and cross-section SEM images of the deposited antimony telluride thin film deposited in the preparation of the thermoelectric module in Example 1, from which it can be seen that the sputtered bismuth telluride thin film is formed by multi-scale nanoparticles accumulation, and the particles are close and of uneven size; the antimony telluride thin film structure is a "ear-like" multi-stage particle accumulation, and the particle size is uniform, and the cross-sections of the two are columnar structures perpendicular to the substrate.

[0073] In the preparation of the thermoelectric module, the magnetron sputtering conditions for depositing different thin films are shown in Table 2;

[0074] Table 2 - Magnetron sputtering conditions for depositing different thin films

[0075]

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is only that the thickness of the substrate plate is different, and the thickness of the substrate plate is designed to be 0.5 mm and 1 mm, respectively.

[0078] Figure 6The soil temperature sensor temperature distribution cloud map for different substrate thicknesses shows that the thermoelectric module with a small substrate thickness can achieve a large temperature difference.

[0079] Example 3

[0080] Example 3 is different from Example 1 only in the radius of the circle formed by the inner ring copper thin film electrode, and the inner diameter of the circle formed by the inner ring copper thin film electrode is designed to be 7.5 mm and 6.5 mm, respectively.

[0081] Figure 7 The soil temperature sensor temperature and open circuit voltage distribution cloud map for different inner diameters of the hot end electrode shows that the larger the radius of the circle formed by the inner ring electrode, the larger the temperature difference and open circuit voltage of the temperature sensor based on the thermoelectric module.

[0082] To realize the intelligent application of the self-powered temperature sensor, the thermoelectric module prepared in the application can be used with a digital processor with a display screen, the voltage signal is converted into a temperature signal by using the relationship between the sensitivity of the thermoelectric module and the greenhouse room temperature, and the temperature of the sensitive area can be directly recorded in the display screen.

[0083] The thermoelectric performance of the bismuth telluride and antimony telluride thin film materials of the thermoelectric module obtained in Example 1 changes with temperature as shown in Figure 8 The Seebeck coefficient changes with temperature, and the Seebeck coefficients of the bismuth telluride and antimony telluride thin film materials increase with temperature, and the change of the antimony telluride thin film material is more obvious than that of the bismuth telluride, indicating that the performance of the antimony telluride thin film material is more affected by temperature than that of the bismuth telluride thin film material. However, the bismuth telluride and antimony telluride thin film materials are less affected by temperature in the range of 30℃ to 90℃. It shows that the Seebeck coefficients of the two materials are relatively stable in the low temperature region, and are suitable for accurate testing of soil temperature of planted crops. The power factor of the prepared antimony telluride thin film is higher than that of the bismuth telluride thin film, which is mainly because the size of the power factor is proportional to the square of the Seebeck coefficient, and the Seebeck coefficient of the antimony telluride thin film is higher than that of the bismuth telluride thin film, so the change trend of the power factor is similar to that of the Seebeck coefficient. The room temperature power factor of the bismuth telluride is 15.8 μW cm -1 K -2 The room temperature power factor of the antimony telluride is 28.4 μW cm -1 K -2 .

[0084] The self-powered temperature sensor based on the thermoelectric effect is tested by placing a heating sheet in the sensitive area of the thermoelectric module of the soil temperature sensor to heat, establishing different temperature differences between the hot end and the cold end of the thermoelectric module, and testing the output voltage of the thermoelectric module, as shown in Figure 9The open circuit voltage test of the self-powered temperature sensor based on thermoelectric effect according to Example 1 is shown, from which it can be seen that the I-V curves of the self-powered temperature sensor based on thermoelectric effect under different temperature differences are parallel to each other, indicating that the internal resistance of the sensor is stable and unchanged under different temperature differences, and the device exhibits good thermal stability. Figure 10 The open sensitivity test of the self-powered temperature sensor based on thermoelectric effect according to Example 1 is shown. The open circuit voltage of the sensor is proportional to the temperature difference of the thermoelectric module, satisfying the relationship V = 5.314ΔT. Then the temperature of the soil temperature sensor and the electrical signal can satisfy T = V / 5.317-T0, when the temperature in the greenhouse is known, the soil temperature can be measured by the temperature sensor based on thermoelectric effect.

[0085] The reliability of the self-powered temperature sensor based on thermoelectric effect according to Example 1 is tested, specifically: the sensitive area of the self-powered temperature sensor based on thermoelectric effect is contacted and away from the operation (air temperature is 25℃) by using a heating piece with a temperature of 26.5℃, as shown in Figure 11 (a), the sensor device sensing signal is stable. The positive and negative electrodes of the self-powered temperature sensor based on thermoelectric effect are reversed, and it is found that the sensing signal of the thermoelectric device is opposite to the previous one, but the sensing signal is still stable, as shown in Figure 11 (b), which shows that the sensitive area of the self-powered temperature sensor based on thermoelectric effect can be used as both cold end temperature and hot end temperature, and the self-powered temperature sensor based on thermoelectric effect can flexibly and accurately test the soil temperature.

[0086] When applied to measure the soil temperature in the greenhouse, the middle temperature sensitive area of the thermoelectric module of the self-powered temperature sensor is contacted with the soil, and since the temperature sensitive area has a certain height difference with the sensing material and the outer electrode, the outer electrode is suspended in the greenhouse environment, and when the soil temperature changes, the voltage of the thermoelectric module of the self-powered temperature sensor changes, and by using the relationship between the sensitivity and the temperature of the sensor, the voltage signal is converted into a temperature signal, and the corresponding soil temperature can be read out through the display screen of the self-powered temperature sensor.

[0087] The thermoelectric module in the self-powered temperature sensor based on thermoelectric effect of the application adopts N-type bismuth telluride film and P-type antimony telluride film distributed in a scattering shape, and a plurality of P-N junction thermoelectric legs are formed by connecting the thin film electrodes in series, and the central region is designed to be hollow, and a high-thermal-conductivity material with a certain height is used for packaging to form a thermal conduction packaging layer, so that the self-powered temperature sensor based on thermoelectric effect has high sensitivity and strong flexibility, and can realize accurate monitoring.

[0088] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A self-powered temperature sensor based on the thermoelectric effect, comprising a thermoelectric module, characterized in that, The thermoelectric module comprises a base plate, N-type bismuth telluride thin films and P-type antimony telluride thin films are arranged in a scattering manner on the base plate, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are arranged at intervals, the N-type bismuth telluride thin films and the P-type antimony telluride thin films are integrated into multiple pairs of P-N junction thermoelectric legs in series through thin film electrodes, the N-type bismuth telluride thin films and the P-type antimony telluride thin films corresponding to negative electrode thin films and positive electrode thin films are connected with the negative electrode thin films and the positive electrode thin films respectively; a center hollow hole is arranged at an inner circle formed by the thin film electrodes on the base plate, the hollow position at the center hollow hole and the thin film electrodes of the inner circle are encapsulated by high-thermal-conductivity materials to form a thermal-conductivity encapsulation layer in a middle region; the thickness of the thermal-conductivity encapsulation layer is greater than the thicknesses of the N-type bismuth telluride thin films, the P-type antimony telluride thin films and the thin film electrodes of an outer circle, the thicknesses of the N-type bismuth telluride thin films and the P-type antimony telluride thin films are 3-15 μm, the thickness of the thin film electrodes is 2-4 μm, and the thickness of the thermal-conductivity encapsulation layer is 2-6 mm, so that a height difference is established between the thermal-conductivity encapsulation layer and the N-type bismuth telluride thin films, the P-type antimony telluride thin films and the thin film electrodes of the outer circle, a middle temperature is highly concentrated, a greater temperature difference is established between two end electrodes, and a greater output voltage is achieved.

2. The self-powered temperature sensor based on the thermoelectric effect according to claim 1, characterized in that, The N-type bismuth telluride thin films and the P-type antimony telluride thin films are any one of isosceles trapezoids, rectangles and sectors, the thin film electrodes are any one of isosceles trapezoids, rectangles and sectors, and the material of the thin film electrodes is any one of copper, silver, nickel and titanium; the base plate is a square or a rectangle, and the material of the base plate is any one of polyimide, aluminum nitride and a silicon wafer; and the high-thermal-conductivity encapsulation material is silicone grease, boron nitride insulation composite material or aluminum nitride insulation composite material.

3. The self-powered temperature sensor based on the thermoelectric effect according to claim 2, characterized in that, The N-type bismuth telluride thin films and the P-type antimony telluride thin films are isosceles trapezoids, the upper base width of the N-type bismuth telluride thin films and the P-type antimony telluride thin films in isosceles trapezoidal structures is 0.20-0.5 mm, the lower base width is 0.5-0.9 mm, and the waist is 7-8 mm; the thin film electrodes are isosceles trapezoids; the material of the thin film electrodes is copper; the upper base width of the thin film electrodes of the inner circle in isosceles trapezoidal structures is 0.5-2 mm, the lower base width is 1-2 mm, and the waist is 2-3 mm; the upper base width of the thin film electrodes of the outer circle in isosceles trapezoidal structures is 1-2 mm, the lower base width is 1-3 mm, the waist is 1-2 mm, and the thickness is 2-4 μm; the radius of the inner circle of the thin film electrodes is 5.5-7.5 mm; and the thickness of the base plate is 0.3-1 mm.

4. A method for producing a self-powered temperature sensor based on the thermoelectric effect according to any one of claims 1 to 3, comprising a method for producing a thermoelectric module, characterized in that, The preparation of the thermoelectric module comprises the following steps: (1) the N-type bismuth telluride film is patterned and deposited in a scattered distribution on the pretreated base plate by a magnetron sputtering method, then the P-type antimony telluride film is patterned and deposited between two adjacent N-type bismuth telluride films by a magnetron sputtering method, and then the N-type bismuth telluride film and the P-type antimony telluride film are integrated into multiple pairs of P-N junction thermoelectric legs in series by depositing the thin film electrode, the negative electrode film and the positive electrode film by a magnetron sputtering method; (2) the inner circle formed by the thin film electrode on the base plate is hollowed out to form the central hollow hole, and then the hollow position of the central hollow hole and the thin film electrode of the inner circle are encapsulated by a high-thermal-conductivity material to form a thermal-conductivity encapsulation layer in the middle region; and a thermoelectric module of a self-powered temperature sensor is obtained.

5. The method for preparing a self-powered temperature sensor based on the thermoelectric effect according to claim 4, characterized in that, Before the patterned deposition, a model of the thermoelectric module is established by a finite element simulation software to obtain the thickness of the base plate of the thermoelectric module and the radius of the circle formed by the electrode film of the inner circle.

6. The method for preparing a self-powered temperature sensor based on the thermoelectric effect according to claim 5, characterized in that, The magnetron sputtering temperature of the N-type bismuth telluride film is 350℃, the magnetron sputtering time is 3.5 hours, the air pressure is 2Pa, the sputtering power is 20W, and the Te power is 16W; the magnetron sputtering temperature of the P-type antimony telluride film is 350℃, the magnetron sputtering time is 3.5 hours, the air pressure is 2Pa, the sputtering power is 20W, and the Te power is 28W; the magnetron sputtering temperature of the thin film electrode is 200℃, the magnetron sputtering time is 2 hours, the air pressure is 1.6Pa, and the sputtering power is 25W.

7. The method for preparing a self-powered temperature sensor based on the thermoelectric effect according to claim 6, characterized in that, The pretreatment method of the base plate comprises the following steps: the base plate is sequentially soaked in a detergent water, deionized water, acetone and ethanol for ultrasonic treatment, and then dried to obtain a pretreated base plate.

8. Application of the self-powered temperature sensor based on the thermoelectric effect in any one of claims 1-3 in monitoring the soil temperature of an agricultural greenhouse.

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