A method for preparing a stretchable flexible thermoelectric generator

Abstract

The application discloses a preparation method of a stretchable flexible thermoelectric generator, and the preparation comprises the following steps: preparing a metal mask plate a and a stretchable polyimide substrate; using a magnetron sputtering method, tungsten and Bi 0.5 Sb 1.5 Te3 are simultaneously deposited on the polyimide substrate covered by the metal mask plate a, the tungsten target is connected to a radio frequency power supply, the power is 10 W, the Bi 0.5 Sb 1.5 Te3 target is connected to a direct current power supply, the power is 32 W, the cavity pressure of the magnetron sputtering device is lower than 5*10 ‑4 Pa, the doping temperature is 250 DEG C; the obtained thin film is used as a substrate b, a magnetron sputtering method is used, Bi2Te 2.7 Se 0.3 is deposited on the substrate b covered by the metal mask plate b, the Bi2Te 2.7 Se 0.3 target is connected to a direct current power supply, the power is 35 W, the cavity pressure of the magnetron sputtering device is lower than 2*10 ‑4 Pa, the sputtering temperature is 70 DEG C; the obtained thin film is used as a substrate c, a magnetron sputtering method is used, Au is deposited on the substrate c covered by the metal mask plate c in an Ar atmosphere, and finally the stretchable flexible thermoelectric generator is obtained.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials and relates to a method for preparing a stretchable flexible thermoelectric generator. Background Technology

[0002] With the increasing demand for wearable electronic devices, thermoelectric materials have entered a golden age of rapid development. Thermoelectric materials can directly convert heat energy into electrical energy. Human skin is a stable heat source, capable of generating heat at a rate of 50–150 W / m². 2 Thermoelectric devices continuously release heat into the environment. Based on thermoelectric materials, thermoelectric devices can continuously power wearable electronic devices using the heat emitted by the human body. The advantages of wearable electronic devices lie in their miniaturization, flexibility, and lightweight nature; they can be applied to the skin or assembled onto clothing to perform various functions. This requires thermoelectric devices to be elastic, able to conform well to the curves of the skin, survive frequent bending, and efficiently convert the temperature difference between the human body (typically 37°C) and the ambient temperature into electrical energy. This makes the development of high-performance flexible thermoelectric devices a very challenging task.

[0003] Compared to bulk thermoelectric generators, thin-film thermoelectric generators offer advantages such as flexibility, thinness, and light weight. Compared to fabric-based thermoelectric generators, they offer advantages such as stable output and better performance. However, thin-film thermoelectric generators can only bend in one direction and primarily absorb energy in a planar direction, making them unsuitable for collecting heat from curved human surfaces. Therefore, how to enable thin-film structures to capture temperature changes in the vertical direction and output higher voltages are key issues currently being researched.

[0004] At room temperature, bismuth telluride-based materials exhibit good thermoelectric properties as thermoelectric arm materials, making them a preferred material for wearable devices. However, among bismuth telluride-based thermoelectric materials, the P-type material exhibits significantly better thermoelectric performance than the N-type material. But a practical thermoelectric device is assembled from both P-type and N-type thermoelectric materials, and they need to have as similar properties as possible. However, the weak thermoelectric properties of N-type bismuth telluride material make it unsuitable for assembling thermoelectric devices, hindering the application of bismuth telluride-based thermoelectric generators. Summary of the Invention

[0005] In view of this, the present invention provides a method for manufacturing a stretchable flexible thermoelectric generator. Specifically, the present invention provides the following technical solution:

[0006] A method for fabricating a stretchable flexible thermoelectric generator.

[0007] 1) Fabrication of metal mask a, metal mask b, metal mask c, and stretchable polyimide substrate a;

[0008] 2) Using magnetron sputtering under an Ar atmosphere, tungsten and Bi are... 0.5 Sb 1.5 Te3 is simultaneously deposited on a stretchable polyimide substrate a covered by a metal mask a. A tungsten target is connected to an RF power supply with a power of 10W. Bi 0.5 Sb 1.5 The Te3 target is connected to a 32W DC power supply, and the cavity pressure of the magnetron sputtering device is below 5×10⁻⁶. -4 Pa, with a doping temperature of 250℃;

[0009] 3) Using the thin film obtained in step 2) as substrate b, Bi₂Te is sputtered in an Ar atmosphere at room temperature. 2.7 Se 0.3 Bi2Te is deposited on substrate b covered by a metal mask b. 2.7 Se 0.3 The target is connected to a DC power supply with a power of 35W, and the cavity pressure of the magnetron sputtering device is less than 2×10⁻⁶. -4 Pa, sputtering temperature is 70℃;

[0010] 4) Using the thin film obtained in step 3) as substrate c, Au is deposited on the substrate c covered by the metal mask c using magnetron sputtering under an Ar atmosphere.

[0011] Further, in step 1), the metal mask a is composed of 19 rectangles of 0.84mm*2.61mm and 36 irregular patterns with a center width of 0.98mm and a height of 2.9mm arranged periodically; the metal mask b is composed of 54 irregular patterns with a center width of 0.98mm and a height of 2.9mm arranged periodically; the metal mask c is composed of 108 irregular patterns with a center width of 0.98mm and a height of 2.9mm and 36 irregular patterns with a center width of 0.98mm and a height of 1.5mm arranged periodically; the length of the cutting stripes on the stretchable polyimide substrate a is 6mm, the longitudinal spacing of the stripes is 3mm, and the transverse spacing is 1.5mm.

[0012] Furthermore, the Bi described in steps 2) to 4) 0.5 Sb 1.5 Te3 hits the target, Bi 0.5 Sb 1.5 The purity of Te3 is 99.999%; the purity of tungsten in the tungsten target is 99.94%; Bi2Te 2.7 Se 0.3 In the target, Bi2Te 2.7 Se 0.3 The purity of Au is 99.999%; the purity of Au in the Au target is 99.99%.

[0013] Furthermore, the workbench pressure in steps 2) to 4) is 0.5-3 Pa, and the Ar flow rate is 20-80 Sccm.

[0014] The beneficial effects of this invention are as follows: This invention uses a high-vacuum magnetron sputtering device to deposit a film, thus fabricating a stretchable flexible thermoelectric generator with high output voltage. The open-circuit voltage at a temperature difference of 60°C can reach 124mV, which is 553% higher than that of a conventional thermoelectric generator (open-circuit voltage of 19mV at a temperature difference of 60°C). Attached Figure Description

[0015] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided:

[0016] Figure 1 The mask and stretchable polyimide substrate required for fabricating a flexible thermoelectric generator.

[0017] Figure 2 The open-circuit voltage test results for different flexible wearable thermoelectric generators.

[0018] Figure 3 The results show the tensile properties of a stretchable, flexible wearable thermoelectric generator.

[0019] Figure 4 Bi2Te prepared at different temperatures 2.7 Se 0.3 Test results of open-circuit voltage of thermoelectric devices.

[0020] Figure 5 Bi2Te prepared under different chamber pressures 2.7 Se 0.3 Test results of open-circuit voltage of thermoelectric devices. Detailed Implementation

[0021] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] Example 1

[0023] Fabrication of a stretchable PN-type flexible thermoelectric generator. Specific steps are as follows:

[0024] Preparation such as Figure 1 The metal photomasks shown in (a), (b), and (c) and the polyimide substrate shown in (d) are illustrated. Draw them using CAD. Figure 1 Patterns shown in (a), (b), and (c) were then custom-made by Shenzhen MicroNano Electronics Technology Co., Ltd.; the patterns were then drawn using CAD. Figure 1 The pattern shown in (d) is then used, and the polyimide is cut into the pattern shown. Subsequent steps are as follows:

[0025] 1) Using magnetron sputtering under an Ar atmosphere, tungsten-doped Bi 0.5 Sb 1.5 Te3 film deposition in Figure 1 (a) shows the mask covering the polyimide (PI) substrate a. The specific method is as follows:

[0026] Bi 0.5 Sb 1.5 The Te3 (99.999%) target and the W (99.94%) target are connected to the DC power supply and the RF power supply, respectively. The cavity pressure of the magnetron sputtering device is below 5 × 10⁻⁶. -4 The working stage pressure is 1.8 Pa, the doping temperature is 250℃, and the Ar flow rate is 30 Sccm. The tungsten target is connected to an RF power supply with a power of 10W, and Bi... 0.5 Sb 1.5 The Te3 target is connected to a DC power supply with a power of 32W.

[0027] 2) Using the thin film obtained in step 1) as substrate b, Bi2Te is sputtered in an Ar atmosphere using magnetron sputtering. 2.7 Se 0.3 (99.999%) deposited in Figure 1 (b) On substrate b covered by the mask. Bi2Te 2.7 Se 0.3 (99.999%) The target is connected to a DC power supply. The cavity pressure of the magnetron sputtering device is below 2 × 10⁻⁶. -4 The pressure on the worktable is 0.8 Pa, the temperature is 70°C, and the Ar flow rate is 30 Sccm. (For details on the temperature and pressure in this step, please refer to Examples 2 and 3.)

[0028] 3) Using the thin film obtained in step 2) as substrate c, Au (99.99%) is deposited on it using magnetron sputtering in an Ar atmosphere. Figure 1 (c) On the substrate c covered by the mask plate. An Au (99.99%) target is connected to a DC power supply to obtain a stretchable PN-type flexible wearable thermoelectric generator 1.

[0029] Figure 2 Open-circuit voltage test results for different flexible wearable thermoelectric generators. From Figure 2 It can be seen that the open-circuit voltage of the stretchable flexible wearable thermoelectric generator 1 (Example 1) can reach 124mV when the temperature difference is 60℃.

[0030] Figure 3 The results show the tensile properties of a stretchable, flexible wearable thermoelectric generator 1. Figure 3It can be seen that when the tensile strain of the stretchable flexible wearable thermoelectric generator 1 reaches 50%, the device breaks. Therefore, the maximum tensile strain of the device is 45%.

[0031] Example 2

[0032] This embodiment investigates the optimal sputtering temperature in step 2) of Embodiment 1. Test conditions are determined by measuring the open-circuit voltage. The specific steps are as follows:

[0033] 1) Using magnetron sputtering, Bi₂Te was sputtered in Ar atmospheres at 300℃ and 70℃ respectively. 2.7 Se 0.3 The film was deposited on a polyimide (PI) substrate to form discrete rectangles of 4×5mm×15mm. Bi2Te 2.7 Se 0.3 (99.999%) The target is connected to a DC power supply.

[0034] 2) Using the thin film obtained in step 1) as a new substrate, Au is deposited on the new substrate by magnetron sputtering in an Ar atmosphere at room temperature, so that the four discrete rectangles form a series circuit. The Au (99.99%) target is connected to a DC power supply.

[0035] Figure 4 The open-circuit voltage test results of the flexible thermoelectric generator prepared at 300℃ and 70℃ are from... Figure 4 As can be seen, the fabrication temperature has a significant impact on the open-circuit voltage of the device. An appropriate deposition temperature can improve crystallinity, but excessively high temperatures will cause Te and Se to volatilize, severely affecting the device's output performance. From... Figure 4 The Bi2Te prepared at 300℃ can be seen 2.7 Se 0.3 The open-circuit voltage of the flexible thermoelectric device is much lower than that prepared at 70℃, therefore 70℃ was chosen as the temperature for step 2) of Example 1 to dope Bi2Te. 2.7 Se 0.3 The preparation temperature.

[0036] Example 3

[0037] This embodiment investigates the optimal chamber pressure in step 2) of Embodiment 1. Test conditions are determined by measuring the open-circuit voltage. The specific steps are as follows:

[0038] 1) Using magnetron sputtering, Bi₂Te₂ was sputtered in an Ar atmosphere at 70°C. 2.7 Se 0.3 The film was deposited on a polyimide (PI) substrate to form discrete rectangles of 4×5mm×15mm. Bi2Te 2.7 Se 0.3(99.999%) The target is connected to a DC power supply. The cavity pressure of the magnetron sputtering device is below 2 × 10⁻⁶. -4 Pa and below 8×10 -5 Pa. A higher vacuum level means fewer impurity atoms in the cavity, resulting in a coating composition closer to the desired ratio and better crystallinity. However, a higher vacuum level requires a longer evacuation time.

[0039] 2) Using the thin film obtained in step 1) as a new substrate, Au is deposited on it using magnetron sputtering in an Ar atmosphere at room temperature. Figure 1 (b) On a new substrate covered by a mask. An Au (99.99%) target is connected to a DC power supply.

[0040] Figure 5 The open-circuit voltage test results of flexible thermoelectric generators prepared under different chamber pressures are as follows: Figure 5 As can be seen, the chamber pressure has a significant impact on the open-circuit voltage of the device. Higher vacuum levels result in better crystallinity, and therefore a higher open-circuit voltage. However, lower chamber pressures require a longer time to evacuate, typically below 8 × 10⁻⁶. -5 Pa ratio is less than 2×10 -4 The Pa experiment lasted 4 hours. To balance time constraints, a value lower than 2 × 10⁻⁶ was chosen. -4 Pa is used as the doped Bi2Te in step 2) of Example 1 2.7 Se 0.3 The pressure of the sputtering cavity.

[0041] Comparative Example 1

[0042] This embodiment describes the fabrication of a stretchable P-type flexible thermoelectric generator, without step 2) of Example 1. (Bi2Te) 2.7 Se 0.3 Sputtering steps.

[0043] Preparation such as Figure 1 The metal photomasks shown in (a), (b), and (c) and the polyimide substrate shown in (d) are illustrated. Draw them using CAD. Figure 1 Patterns shown in (a), (b), and (c) were then custom-made by Shenzhen MicroNano Electronics Technology Co., Ltd.; the patterns were then drawn using CAD. Figure 1 The pattern shown in (d) is then used, and the polyimide is cut into the pattern shown. Subsequent steps are as follows:

[0044] 1) Using magnetron sputtering under an Ar atmosphere, tungsten-doped Bi 0.5 Sb 1.5 Te3 film deposition in Figure 1 (a) shows the mask covering the polyimide (PI) substrate a. The specific method is as follows:

[0045] Bi 0.5 Sb 1.5 The Te3 (99.999%) target and the W (99.94%) target are connected to the DC power supply and the RF power supply, respectively. The cavity pressure of the magnetron sputtering device is below 5 × 10⁻⁶. -4 The working stage pressure is 1.8 Pa, the doping temperature is 250℃, and the Ar flow rate is 30 Sccm. The tungsten target is connected to an RF power supply with a power of 10W, and Bi... 0.5 Sb 1.5 The Te3 target is connected to a DC power supply with a power of 32W.

[0046] 2) Using the thin film obtained in step 1) as substrate b, Au (99.99%) is deposited on it using magnetron sputtering in an Ar atmosphere. Figure 1 (b) The substrate b is covered by a mask. An Au (99.99%) target is connected to a DC power supply.

[0047] 3) Using the thin film obtained in step 2) as substrate c, Au (99.99%) is deposited on it using magnetron sputtering in an Ar atmosphere. Figure 1 (c) On the substrate c covered by the mask plate. An Au (99.99%) target is connected to a DC power supply to obtain a stretchable P-type flexible wearable thermoelectric generator 2.

[0048] Figure 2 Open-circuit voltage test results for different flexible wearable thermoelectric generators. From Figure 2 It can be seen that the open-circuit voltage of the stretchable P-type flexible wearable thermoelectric generator 2 (Comparative Example 1) can reach 79mV at a temperature difference of 60℃. In the stretchable flexible wearable thermoelectric generator 1, the current generated by the P-type material flows from the high-temperature end to the low-temperature end, while the N-type material flows in the opposite direction. Au acts as a conductor to connect them in series. In addition, the stretchable thermoelectric generator and the heat source are spatially perpendicular. Therefore, compared to the stretchable PN-type thermoelectric generator (Example 1), the stretchable P-type flexible wearable thermoelectric generator 2 (Comparative Example 1) requires Au to fill the gaps in the N-type material. Therefore, the stretchable P-type flexible wearable thermoelectric generator 2 (Comparative Example 1) lacks the contribution of the N-type material to the output voltage compared to the stretchable PN-type thermoelectric generator 1 (Example 1), so its voltage output value is much lower than that of the stretchable PN-type thermoelectric generator 1 (Example 1).

[0049] Comparative Example 2

[0050] This embodiment describes the fabrication of a stretchable N-type flexible thermoelectric generator, without step 1)Bi of Embodiment 1. 0.5 Sb 1.5 Te3 and W sputtering steps.

[0051] Preparation such as Figure 1 The metal photomasks shown in (a), (b), and (c) and the polyimide substrate shown in (d) are illustrated. Draw them using CAD. Figure 1 Patterns shown in (a), (b), and (c) were then custom-made by Shenzhen MicroNano Electronics Technology Co., Ltd.; the patterns were then drawn using CAD. Figure 1 The pattern shown in (d) is then used, and the polyimide is cut into the pattern shown. Subsequent steps are as follows:

[0052] 1) Using magnetron sputtering, Au (99.99%) was deposited on an Ar atmosphere. Figure 1 (a) shows a polyimide (PI) substrate a covered by a mask. An Au (99.99%) target is connected to a DC power supply.

[0053] 2) Using the thin film obtained in step 1) as substrate b, Bi2Te is sputtered in an Ar atmosphere using magnetron sputtering. 2.7 Se 0.3 (99.999%) deposited in Figure 1 (b) On substrate b covered by the mask. Bi2Te 2.7 Se 0.3 (99.999%) The target is connected to a DC power supply. The cavity pressure of the magnetron sputtering device is below 2 × 10⁻⁶. -4 The pressure on the worktable is 0.8 Pa, the temperature is 70°C, and the Ar flow rate is 30 Sccm. (For details on the temperature and pressure in this step, please refer to Examples 2 and 3.)

[0054] 3) Using the thin film obtained in step 2) as substrate c, Au (99.99%) is deposited on it using magnetron sputtering in an Ar atmosphere. Figure 1 (c) On the substrate c covered by the mask plate. An Au (99.99%) target is connected to a DC power supply to obtain a stretchable N-type flexible wearable thermoelectric generator 3.

[0055] Figure 2 Open-circuit voltage test results for different flexible wearable thermoelectric generators. From Figure 2 It can be seen that the open-circuit voltage of the stretchable N-type flexible wearable thermoelectric generator 3 (Comparative Example 2) can reach 34mV at a temperature difference of 60℃. Compared with the stretchable PN-type (Example 1), the stretchable N-type flexible wearable thermoelectric generator 3 (Comparative Example 2) requires Au to fill the gaps in the P-type material. Therefore, the stretchable N-type flexible wearable thermoelectric generator 3 (Comparative Example 2) lacks the contribution of the P-type material to the output voltage compared with the stretchable PN-type thermoelectric generator 1 (Example 1), so its voltage output value is much lower than that of the stretchable PN-type thermoelectric generator 1 (Example 1).

[0056] Comparative Example 3

[0057] This embodiment is for the fabrication of a conventional PN-type flexible thermoelectric generator, without the polyimide cutting and sputtering special patterning steps of Example 1.

[0058] 1) Using magnetron sputtering, tungsten-doped Bi was sputtered in an Ar atmosphere at 250°C. 0.5 Sb 1.5 Te3 films were deposited on polyimide (PI) substrates to form discrete rectangles of 2×5mm×15mm. 0.5 Sb 1.5 The Te3 (99.999%) target and the W (99.94%) target are connected to the DC power supply and the RF power supply, respectively. The cavity pressure of the magnetron sputtering device is below 5 × 10⁻⁶. -4 The working stage pressure is 1.8 Pa, the doping temperature is 250℃, and the Ar flow rate is 30 Sccm. The tungsten target is connected to an RF power supply with a power of 10W, and Bi... 0.5 Sb 1.5 The Te3 target is connected to a DC power supply with a power of 32W.

[0059] 2) Using the thin film obtained in step 1) as substrate b, Bi2Te is sputtered in an Ar atmosphere using magnetron sputtering. 2.7 Se 0.3 (99.999%) Discrete rectangles of 2×5mm×15mm were formed on substrate b. Bi2Te 2.7 Se 0.3 (99.999%) The target is connected to a DC power supply. The cavity pressure of the magnetron sputtering device is below 2 × 10⁻⁶. -4 The pressure on the worktable is 0.8 Pa, the temperature is 70°C, and the Ar flow rate is 30 Sccm. (For details on the temperature and pressure in this step, please refer to Examples 2 and 3.)

[0060] 3) Using the thin film obtained in step 1) as substrate c, Au is deposited on substrate c by magnetron sputtering in an Ar atmosphere at room temperature, forming a series circuit of four discrete rectangles. An Au (99.99%) target is connected to a DC power supply. A conventional PN-type flexible thermoelectric generator 4 is thus fabricated.

[0061] Figure 2 Open-circuit voltage test results for different flexible wearable thermoelectric generators. From Figure 2It can be seen that the traditional PN-type thermoelectric generator 4 (Comparative Example 3) has a low output voltage, only 19mV at a temperature difference of 60℃. In contrast, the stretchable PN-type thermoelectric generator 1 prepared in Example 1 of this invention has an output voltage of 124mV at a temperature difference of 60℃. From the expression for open-circuit voltage ΔV=-S*ΔT, it can be seen that the magnitude of the open-circuit voltage is related not only to the Seebeck coefficient of the material but also to its heat capture capability. The stretchable structure (Example 1) has as many as 54 contact points with the heat source, while the traditional structure only has 4, thus significantly improving the open-circuit voltage.

Claims

1. A method for preparing a stretchable flexible thermoelectric generator, characterized in that: 1) Fabrication of metal mask a, metal mask b, metal mask c, and stretchable polyimide substrate; 2) Using magnetron sputtering under an Ar atmosphere, tungsten and Bi are... 0.5 Sb 1.5 Te3 was simultaneously deposited on a polyimide substrate covered by a metal mask a, and a tungsten target was connected to an RF power supply with a power of 10 W. Bi 0.5 Sb 1.5 The Te3 target is connected to a 32W DC power supply, and the cavity pressure of the magnetron sputtering device is below 5×10⁻⁶. -4 Pa, with a doping temperature of 250℃; 3) Using the thin film obtained in step 2) as substrate b, Bi₂Te is sputtered in an Ar atmosphere at room temperature using a magnetron sputtering method. 2.7 Se 0.3 Bi2Te is deposited on substrate b covered by a metal mask b. 2.7 Se 0.3 The target is connected to a DC power supply with a power of 35W, and the cavity pressure of the magnetron sputtering device is less than 2×10⁻⁶. -4 Pa, sputtering temperature is 70℃; 4) Using the thin film obtained in step 3) as substrate c, Au is deposited on the substrate c covered by the metal mask c using magnetron sputtering under an Ar atmosphere to obtain a stretchable flexible thermoelectric generator. The worktable pressure in step 2) is 0.5-3 Pa, and the Ar flow rate is 20-80 Sccm; The metal mask a mentioned in step 1) is composed of 19 rectangles of 0.84 mm * 2.61 mm and 36 irregular patterns with a center width of 0.98 mm and a height of 2.9 mm arranged periodically; the metal mask b is composed of 54 irregular patterns with a center width of 0.98 mm and a height of 2.9 mm arranged periodically; the metal mask c is composed of 108 irregular patterns with a center width of 0.98 mm and a height of 2.9 mm and 36 irregular patterns with a center width of 0.98 mm and a height of 1.5 mm arranged periodically; the dicing stripe length of the stretchable polyimide substrate a is 6 mm, the longitudinal spacing of the stripes is 3 mm, and the transverse spacing is 1.5 mm; The worktable pressure from step 2) to step 4) is 0.5-3 Pa, and the Ar flow rate is 20-80 Sccm.

2. The method for preparing a stretchable flexible thermoelectric generator according to claim 1, characterized in that: Step 2) Bi 0.5 Sb 1.5 Te3 hits the target, Bi 0.5 Sb 1.5 The purity of Te3 is 99.999%; in the tungsten target, the purity of tungsten is 99.94%, and in the Au target, the purity of Au is 99.99%.

3. The method for preparing a stretchable flexible thermoelectric generator according to claim 1, characterized in that: Steps 2) to 4) of Bi 0.5 Sb 1.5 Te3 hits the target, Bi 0.5 Sb 1.5 The purity of Te3 is 99.999%; the purity of tungsten in the tungsten target is 99.94%; Bi2Te 2.7 Se 0.3 In the target, Bi2Te 2.7 Se 0.3 The purity of Au is 99.999%; the purity of Au in the Au target is 99.99%.

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