Preparation method of N-type bismuth telluride-based thermoelectric thin film

Abstract

The invention discloses a preparation method of an N-type bismuth telluride-based thermoelectric thin film. The preparation method comprises the following steps: obtaining a bismuth raw material, a tellurium raw material and a selenium raw material; the preparation method comprises the following steps: smelting, grinding and sintering a bismuth raw material, a tellurium raw material and a selenium raw material to obtain an N-type bismuth-tellurium-selenium-based block target material; the N-type bismuth-tellurium-selenium-based block target material is deposited on a substrate through magnetron sputtering equipment, so that a bismuth-tellurium-selenium-based thin film is obtained; the N-type bismuth-tellurium-selenium-based block target material is deposited on a substrate through high-vacuum thermal evaporation equipment, so that a homogeneous-layer bismuth-tellurium-selenium-based thin film is obtained; according to the preparation method, the homogeneous layer bismuth-tellurium-selenium-based thin film is subjected to annealing treatment to obtain the N-type bismuth telluride-based thermoelectric thin film, and due to the fact that the method for preparing the bismuth-tellurium-selenium-based thin film through magnetron sputtering equipment and the method for preparing the bismuth-tellurium-selenium-based thin film through high-vacuum thermal evaporation equipment are combined, the high-performance N-type bismuth telluride-based thermoelectric thin film is obtained.

Description

Technical Field

[0001] This application relates to the field of thermoelectric technology, and more specifically, to a method for preparing an N-type bismuth telluride-based thermoelectric thin film. Background Technology

[0002] Among related technologies, bismuth telluride van der Waals (VdW) semiconductors have become the most commercially available thermoelectric materials at room temperature due to their unparalleled performance. In related technologies, physical vapor deposition (PVD) technology (Adv. Mater. 35, 2304751, 2023) and plastic engineering (Science. 386, 1112–1117, 2024) can generally be used to optimize P-type Bi2Te3-based thin films. However, the research and optimization of N-type Bi2Te3-based thin films are still insufficient. Finding a method to effectively improve the thermoelectric performance of prepared N-type bismuth telluride alloys is an urgent problem to be solved in this field. Summary of the Invention

[0003] This application provides a method for preparing an N-type bismuth telluride-based thermoelectric thin film, which can solve at least one of the above-mentioned technical problems.

[0004] One embodiment of this application discloses a method for preparing an N-type bismuth telluride-based thermoelectric thin film, comprising: obtaining bismuth raw materials, tellurium raw materials, and selenium raw materials; melting, grinding, and sintering the bismuth raw materials, tellurium raw materials, and selenium raw materials to obtain an N-type bismuth-telluride-selenium-based bulk target; depositing the N-type bismuth-telluride-selenium-based bulk target on a substrate using a magnetron sputtering apparatus to obtain a bismuth-telluride-selenium-based thin film; depositing the N-type bismuth-telluride-selenium-based bulk target on a substrate using a high-vacuum thermal evaporation apparatus to obtain a homogeneous bismuth-telluride-selenium-based thin film; and annealing the homogeneous bismuth-telluride-selenium-based thin film to obtain an N-type bismuth telluride-based thermoelectric thin film.

[0005] The method for preparing an N-type bismuth telluride-based thermoelectric thin film according to embodiments of this application involves obtaining bismuth, tellurium, and selenium raw materials; melting, grinding, and sintering the bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-selenium-based bulk target; depositing the N-type bismuth-tellurium-based bulk target on a substrate using magnetron sputtering to obtain a bismuth-tellurium-based thin film; depositing the N-type bismuth-tellurium-based bulk target on a substrate using high-vacuum thermal evaporation to obtain a homogeneous bismuth-tellurium-based thin film; and finally annealing the homogeneous bismuth-tellurium-based thin film to obtain an N-type bismuth telluride-based thermoelectric thin film. This method utilizes magnetron sputtering to prepare the bismuth-tellurium-based thin film and employs high-vacuum thermal evaporation. This paper combines methods for preparing bismuth-tellurium-selenium (BTS) based thin films using air-thermal evaporation equipment. After annealing, a single-layer N-type bismuth telluride (BTS) based thermoelectric thin film is obtained by fusing two homogeneous bismuth-tellurium (BTS) based thin films. This process combines the advantages of the Seebeck coefficient and carrier concentration of films deposited using both methods. In this process, carrier transport behavior is optimized, and the carrier concentration in the BTS film is precisely controlled within a reasonable range. Furthermore, the high-density interlaced layer structure formed by this process increases the effective mass of carriers. The combined effect of these factors results in the prepared N-type bismuth telluride (BTS) based thermoelectric thin film achieving both high Seebeck coefficient and conductivity, ultimately reaching up to 30 μW / cm². -1 K -2 In addition, the uniformly distributed pore structure and high-density interlaced layer structure inside the film can further improve the thermoelectric performance and flexibility of the film. The preparation method has good repeatability, high practicality, significant effect and simple control, and can effectively produce high-performance N-type bismuth telluride-based thermoelectric films.

[0006] Additional aspects and advantages of embodiments of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of this application. Attached Figure Description

[0007] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0008] Figure 1 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0009] Figure 2 This is a schematic diagram of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0010] Figure 3 This is a schematic diagram of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0011] Figure 4 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0012] Figure 5 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0013] Figure 6 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0014] Figure 7 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0015] Figure 8 This is a schematic flowchart of a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application;

[0016] Figure 9 This is a schematic diagram illustrating a method for preparing an N-type bismuth telluride-based thermoelectric thin film according to certain embodiments of this application. Detailed Implementation

[0017] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of this application, and should not be construed as limiting the embodiments of this application.

[0018] To facilitate understanding of this application, the following explanations are provided for the terms and background information used in this application:

[0019] Thermoelectric (TE) technology enables direct energy conversion between heat and electricity, providing broad possibilities for waste heat recovery and on-demand cooling, while minimizing environmental impact during climate transition.

[0020] However, flexible thermoelectric materials are limited by low power factor (PF), brittleness, and scalability (especially in room temperature applications and under small temperature difference conditions). Meanwhile, considering heat harvesting or cooling on non-planar or curved surfaces, minimizing heat loss between heterogeneous interfaces requires a balance between high thermoelectric performance and flexibility.

[0021] Therefore, how to transform the inherent rigidity and brittleness of inorganic materials with high thermoelectric properties into highly flexible thin films with scalable manufacturing potential is a problem that urgently needs to be solved by those skilled in the art.

[0022] Currently, bismuth telluride van der Waals (VdW) semiconductors have become the most commercially available thermoelectric materials at room temperature due to their unparalleled performance. Among related technologies, physical vapor deposition (PVD) technology (Adv. Mater. 35, 2304751, 2023) and plastic engineering (Science. 386, 1112–1117, 2024) can generally be used to optimize P-type Bi2Te3-based thin films, but research and optimization of N-type Bi2Te3-based thin films are still insufficient.

[0023] The inherent structure of the VdW layer is prone to sliding and deformation along the (00l) crystal plane under external stress and / or heat treatment. Therefore, carrier and phonon transport performance and flexibility can be improved by mechanically controlling atomic rearrangement (Nat. Nanotechnol. 18, 1281-1288, 2023). Furthermore, although significant progress has been made through doping and texture control in PVD processes (Nat. Sustain. 6, 180-191, 2023; Nat. Mater. 18, 62-68, 2019) and the application of wet chemically prepared nano-binders in screen printing (Science. 386, 1265-1271, 2024), achieving 20 μW / cm² thickness at room temperature in N-type Bi₂Te₃ films via a single synthetic route remains a challenge. -1 K -2 Achieving a power factor threshold of (microwatts per centimeter per Kelvin squared) and having the capability for large-scale manufacturing remains challenging.

[0024] Therefore, finding a method to effectively improve the thermoelectric properties of the prepared N-type bismuth telluride alloy is a problem that urgently needs to be solved in this field.

[0025] In view of this, this application proposes a method for preparing N-type bismuth telluride-based thermoelectric thin films. The N-type bismuth telluride-based thermoelectric thin films prepared by this method have a power factor of 30 microwatts per centimeter (μW / cm²) at room temperature. -1 K -2 At 350 Kelvin (K), the thermoelectric figure of merit (ZT value) reached 1.1.

[0026] Please see Figure 1 The preparation method of the N-type bismuth telluride-based thermoelectric thin film of this application will be described in detail below. In this application, the order of execution of steps 013 and 014 is not limited:

[0027] Step 011: Obtain bismuth (Bi), tellurium (Te), and selenium (Se) raw materials, wherein the ratio of bismuth, tellurium, and selenium raw materials is 2:(3-m):m, where m>0;

[0028] Step 012: The bismuth raw material, tellurium raw material and selenium raw material are smelted, ground and sintered to obtain N-type bismuth-tellurium-selenium based bulk target material;

[0029] Step 013: Deposit an N-type bismuth-tellurium-selenium-based bulk target on a substrate using a magnetron sputtering device to obtain a bismuth-tellurium-based thin film;

[0030] Step 014: Deposit an N-type bismuth-tellurium-selenium-based bulk target on a substrate using a high-vacuum thermal evaporation device to obtain a homogeneous bismuth-tellurium-selenium-based thin film;

[0031] Step 015: Anneal the bismuth-tellurium-selenium-based thin film and the homogeneous bismuth-tellurium-selenium-based thin film together to obtain an N-type bismuth telluride-based thermoelectric thin film.

[0032] The substrate is a flexible substrate.

[0033] Optionally, the flexible substrate includes at least one of high-temperature resistant flexible films such as polyimide film (PI film), polytetrafluoroethylene film, carbon nanotube film, and ultrathin carbon paper. For ease of explanation, this application uses PI film as an example for illustration.

[0034] Optionally, an N-type bismuth-tellurium-selenium-based bulk target is deposited on a substrate using a magnetron sputtering device to obtain a bismuth-tellurium-based thin film, prior to the step of depositing an N-type bismuth-tellurium-based bulk target on a substrate using a high-vacuum thermal evaporation device to obtain a homogeneous bismuth-tellurium-based thin film.

[0035] Optionally, the thin film deposition rate of the magnetron sputtering equipment and the high-vacuum thermal evaporation equipment can be set within the range of [0.5 nm / min]. -1 12nm min -1 ].

[0036] Optionally, the thickness range of the bismuth-tellurium-selenium-based thin film and the homogeneous bismuth-tellurium-selenium-based thin film is [50 nm, 3000 nm], and / or the thickness range of the N-type bismuth telluride-based thermoelectric thin film is [100 nm, 6000 nm].

[0037] Considering the different thermal expansion coefficients of N-type bismuth telluride-based thermoelectric films of varying thicknesses compared to the substrate, the deposition rate range of the magnetron sputtering equipment and the high-vacuum thermal evaporation equipment can be set to [0.5 nm min]. -1 12nm min -1 To prepare bismuth-tellurium-selenium based thin films and homolayer bismuth-tellurium-selenium based thin films with a wavelength of [50 nm, 3000 nm], or N-type bismuth telluride-based thermoelectric thin films with a wavelength of [100 nm, 6000 nm].

[0038] Specifically, according to the chemical formula Bi2Te3-m Se m In this study, the stoichiometric ratios of each element were determined by weighing 2 parts Bi metal particles, (3-m) parts Te metal particles, and m parts Se particles as raw materials. Using Se as an N-type dopant not only suppressed lattice thermal conductivity and increased the ZT value, but also adjusted the carrier concentration and carrier mobility of the bismuth telluride-based material. In other words, by adding Se during the preparation of bismuth telluride materials, precise control of carrier concentration was achieved, balancing conductivity and the Seebeck coefficient, laying the foundation for the high thermoelectric performance of subsequent thin films.

[0039] By mixing Bi, Te and Se, and then melting the mixed raw materials (e.g., melting at high temperature (500℃~800℃) in a vacuum or inert atmosphere), grinding (e.g., ball milling), and sintering (e.g., hot pressing sintering), N-type bismuth-tellurium-selenium-based bulk targets are obtained, ensuring the structural uniformity and stability of the obtained targets.

[0040] Next, N-type bismuth-tellurium-selenium-based bulk targets are deposited on the substrate using magnetron sputtering and high-vacuum thermal evaporation equipment, respectively. For example, a bismuth-tellurium-selenium-based thin film (named MS-BTS) can be deposited on a PI film using magnetron sputtering, and then a second deposition can be made on top of the bismuth-tellurium-selenium-based thin film using high-vacuum thermal evaporation equipment to obtain a homogeneous bismuth-tellurium-selenium-based thin film composed of two thin films (named VTE@MS-BTS). Finally, the homogeneous bismuth-tellurium-selenium-based thin film is annealed (e.g., annealing at 425°C with an annealing gradient of 25°C) to fuse the two thin films into one, thus obtaining an N-type bismuth telluride-based thermoelectric thin film. During the annealing process of the homogeneous bismuth-tellurium-selenium-based thin film composed of two thin films, such as... Figure 2 The van der Waals layer A shown will also interleave, forming something like... Figure 3 The high-density interlaced layer structure B is shown.

[0041] It is understandable that thin films deposited by magnetron sputtering and high-vacuum thermal evaporation equipment have different properties. For example, the Seebeck coefficient of thin films deposited by magnetron sputtering equipment is lower than that of thin films deposited by high-vacuum thermal evaporation equipment, while the carrier concentration is higher. The N-type bismuth telluride-based thermoelectric thin film obtained by annealing the thin films deposited by the two equipment can combine the advantages of the Seebeck coefficient and carrier concentration of both equipment. Furthermore, the high crystallinity of the film deposited by magnetron sputtering equipment leads to improved texture. By depositing an N-type bismuth-tellurium-selenium-based bulk target on a substrate using magnetron sputtering to obtain a bismuth-tellurium-based thin film, and then depositing the same N-type bismuth-tellurium-based bulk target on the substrate using high-vacuum thermal evaporation equipment to obtain a homogeneous bismuth-tellurium-based thin film, the N-type bismuth telluride-based thermoelectric thin film on the PI film can have good structure, further improving the performance of the N-type bismuth telluride-based thermoelectric thin film.

[0042] For example, with m = 0.15 and a film thickness of 1000 nm, the power factor (PF) of the N-type bismuth telluride-based thermoelectric film is as high as 30 μW / cm at 300 K. -1 K -2 The ZT value reached 1.1 at 350K.

[0043] Thus, by obtaining bismuth, tellurium, and selenium raw materials, wherein the ratio of bismuth, tellurium, and selenium raw materials is 2:(3-m):m, where m>0; smelting, grinding, and sintering the bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-selenium-based bulk target; then, depositing the N-type bismuth-tellurium-selenium-based bulk target on a substrate using magnetron sputtering to obtain a bismuth-tellurium-based thin film; then, depositing the N-type bismuth-tellurium-selenium-based bulk target on a substrate using high-vacuum thermal evaporation to obtain a homogeneous bismuth-tellurium-selenium-based thin film; finally, annealing the homogeneous bismuth-tellurium-selenium-based thin film to obtain an N-type bismuth telluride-based thermoelectric thin film. Because the bismuth-tellurium-selenium-based thin film is prepared using magnetron sputtering... A method for preparing bismuth-tellurium (BTS) films using tellurium-selenium (TGS) thin films and high-vacuum thermal evaporation equipment was combined to obtain high-performance homolayer bismuth-tellurium (BTS) films. After annealing, the two homolayer bismuth-tellurium (BTS) films were fused together to obtain a single-layer N-type bismuth telluride (BTS) thermoelectric film. During this process, carrier transport behavior was optimized, and the carrier concentration in the BTS film was precisely controlled within a reasonable range. Furthermore, the high-density interleaved layer structure formed by this process also increased the effective mass of carriers. The combined effect of these factors resulted in the prepared N-type bismuth telluride (BTS) thermoelectric film achieving both high Seebeck coefficient and conductivity, ultimately reaching up to 30 μW / cm². -1 K -2In addition, the uniformly distributed pore structure and high-density interlaced layer structure inside the film can further improve the thermoelectric performance and flexibility of the film. The preparation method has good repeatability, high practicality, significant effect and simple control, and can effectively produce high-performance N-type bismuth telluride-based thermoelectric films.

[0044] Please see Figure 4 Optionally, step 012: smelting, grinding, and sintering bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-selenium based bulk target, including:

[0045] Step 0121: The mixed bismuth, tellurium and selenium raw materials are smelted in a muffle furnace to obtain a master alloy.

[0046] Specifically, 2 parts Bi metal particles, (3-m) parts Te metal particles and m parts Se particles can be mixed evenly first, and then put into a muffle furnace. The evenly mixed raw materials can be smelted in the muffle furnace to ensure that Bi, Te and Se can be fully mixed to form a master alloy with uniform composition (avoiding local segregation, etc.), which helps to optimize the mechanical and thermoelectric properties of the material.

[0047] Please see Figure 5 Optionally, step 0121: The mixed bismuth, tellurium, and selenium raw materials are smelted in a muffle furnace to obtain a master alloy, including:

[0048] Step 01211: Place the mixed bismuth raw material, tellurium raw material and selenium raw material into a muffle furnace, control the muffle furnace to heat to a preset temperature threshold at a preset heating rate, hold at the preset temperature threshold for a first preset time, and then cool naturally to room temperature to obtain the master alloy.

[0049] The preset heating rate is selected within the range of [1℃min]. -1 6℃min -1 The preset temperature threshold is selected within the range of [900℃, 1100℃], and the first preset duration is selected within the range of [2.8h, 3.2h].

[0050] It is understandable that Bi, Te, and Se have significantly different melting points. For example, Bi has a melting point of 271℃, Te has a melting point of 449℃, and Se has a melting point of 217℃. By setting [2℃min]... -1 5℃min -1The controlled heating rate can prevent localized thermal stress concentration that could lead to alloy ingot cracks. By setting the preset temperature threshold range to [950℃, 1050℃], it is ensured that all raw materials can be completely melted, guaranteeing the uniformity of the melt composition. Setting the time range to [2.8h, 3.2h] ensures complete reaction and guarantees the carrier mobility of the resulting master alloy.

[0051] Specifically, after the uniformly mixed Bi, Te, and Se are placed into a muffle furnace, the mixture can be heated in the muffle furnace at [2℃ min]. -1 5℃min -1 The temperature is raised to [950℃, 1050℃] at the preset heating rate and held for 2.8h to 3.2h, then naturally cooled to room temperature in the furnace to obtain the master alloy.

[0052] Please see Figure 6 In some embodiments, step 012, which involves melting, grinding, and sintering bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-based bulk target, further includes:

[0053] Step 0122: The master alloy is ground for a second preset time using a first grinding jar to obtain bismuth-tellurium-selenium-based particles;

[0054] Step 0123: The bismuth-tellurium-selenium-based particles are vacuum ball-milled in a vacuum ball mill to obtain nanoscale bismuth-tellurium-selenium-based powder.

[0055] The first grinding jar is an agate grinding jar. The second preset time may include 0.5 hours to 1 hour.

[0056] Please see Figure 7 Optionally, step 0123: Vacuum ball milling of bismuth-tellurium-selenium-based particles in a vacuum ball mill jar to obtain nanoscale bismuth-tellurium-selenium-based powder, including:

[0057] Step 01231: Place the bismuth-tellurium-selenium-based particles into a vacuum ball mill jar, control the vacuum ball mill jar to be evacuated to the first preset vacuum level, and fill it with inert gas to provide an atmosphere protection;

[0058] Step 01232: Control the vacuum ball mill jar to ball mill at a preset speed for a third preset time to obtain nanoscale bismuth-tellurium-selenium-based powder.

[0059] The first preset vacuum level is less than 6 Pa, and the preset ball milling speed is selected within the range of [350 r / min]. -1 500rmin -1 The third preset duration is selected within the range of [2h, 7h].

[0060] Specifically, the master alloy can be first ground in an agate grinding jar for 0.5-1 hour to obtain bismuth-tellurium-selenium-based particles. These particles are then placed in a vacuum ball mill jar, which is evacuated to below 6 Pa (e.g., 5 Pa). An inert gas (e.g., argon) is then introduced to provide a protective atmosphere to inhibit oxidation. Finally, the grinding is performed at 400 rpm. -1 up to 450r min -1 The mixture was ball-milled at a certain speed for 3 to 6 hours to obtain nanoscale bismuth-tellurium-selenium-based powder.

[0061] Please see Figure 8 In some embodiments, step 012, which involves melting, grinding, and sintering bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-based bulk target, further includes:

[0062] Step 0124: Based on the spark plasma sintering process, nanoscale bismuth-tellurium-selenium-based powder is sintered into N-type bismuth-tellurium-selenium-based bulk target material.

[0063] The sintering temperature range for the spark plasma sintering process is [300℃, 500℃], the pressure range is [60MPa, 80MPa], and the sintering time range is [6min, 8min].

[0064] Specifically, nanoscale bismuth-tellurium-selenium-based powder is sintered using spark plasma sintering (SPS) at temperatures of [450℃, 480℃] for 4-6 minutes (e.g., 5 minutes) to obtain N-type bismuth-tellurium-selenium-based bulk targets, ensuring the compositional stability of the N-type bismuth-tellurium-selenium-based bulk targets.

[0065] Please see Figure 9 , Figure 9 The Seebeck coefficient, conductivity, power factor, and ZT value of thin films A, B, C, and D are shown as a function of temperature. Among these, Bi, Te, and Se are used to simulate the chemical formula Bi₂Te. 2.85 Se 0.15 The target material prepared according to the specified ratio was deposited on a PI substrate to obtain a 1 μm BTS thin film (VTE-BTS) using a high-vacuum thermal evaporation device, wherein the thermal evaporation rate was 5 nm / min. -1 The cavity vacuum level is maintained below 3.0 × 10⁻⁶. -4 Pa, and VTE-BTS was annealed at 425℃ for 3h to obtain film A.

[0066] Using Bi, Te, and Se to irradiate the chemical formula Bi₂Te 2.85 Se 0.15The prepared target material was used to deposit a 1 μm BTS thin film (MS-BTS) on a PI substrate using magnetron sputtering equipment, wherein the magnetron sputtering rate was 5 nm / min. -1 The cavity vacuum level is maintained below 3.0 × 10⁻⁶. -4 Pa, and then the obtained MS-BTS film was annealed at 425℃ for 3h to obtain film B.

[0067] Using Bi, Te, and Se to irradiate the chemical formula Bi₂Te 2.85 Se 0.15 The prepared target material was first deposited on a PI substrate using magnetron sputtering to obtain a 500 nm BTS thin film (MS-BTS) (wherein, the magnetron sputtering rate was 5 nm / min). -1 The cavity vacuum level is maintained below 3.0 × 10⁻⁶. -4 Pa), and then a 500 nm thin film is deposited on the MS-BTS using a high vacuum thermal evaporation equipment to obtain a homogeneous layer film (VTE@MS-BTS) with a total thickness of 1 μm. Finally, the VTE@MS-BTS is annealed at 350 °C for 3 h to obtain film C.

[0068] Using Bi, Te, and Se to irradiate the chemical formula Bi₂Te 2.85 Se 0.15 The prepared target material was first deposited on a PI substrate using magnetron sputtering to obtain a 500 nm BTS thin film (MS-BTS) (wherein, the magnetron sputtering rate was 5 nm / min). -1 The cavity vacuum level is maintained below 3.0 × 10⁻⁶. -4 Pa), and then a 500 nm thin film is deposited on the MS-BTS using a high vacuum thermal evaporation equipment to obtain a homogeneous layer film (VTE@MS-BTS) with a total thickness of 1 μm. Finally, the VTE@MS-BTS is annealed at 425 °C for 3 h to obtain film D.

[0069] Based on Figures 1-2, it can be seen that the N-type bismuth telluride-based thermoelectric thin film prepared according to this application has excellent thermoelectric properties.

[0070] In the description of this specification, the references to terms such as "some embodiments," "in one example," "exemplarily," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0071] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0072] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing an N-type bismuth telluride-based thermoelectric thin film, characterized in that, include: Obtain bismuth, tellurium and selenium raw materials; The bismuth raw material, tellurium raw material and selenium raw material are smelted, ground and sintered to obtain N-type bismuth-tellurium-based bulk target material; The N-type bismuth-tellurium-selenium-based bulk target is deposited on a substrate using a magnetron sputtering device to obtain a bismuth-tellurium-based thin film. The N-type bismuth-tellurium-selenium-based bulk target is deposited on a substrate using a high-vacuum thermal evaporation device to obtain a homogeneous bismuth-tellurium-based thin film. The bismuth-tellurium-selenium-based thin film and the homogeneous bismuth-tellurium-selenium-based thin film are annealed together to obtain an N-type bismuth telluride-based thermoelectric thin film.

2. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The process of melting, grinding, and sintering the bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-based bulk target includes: The mixed bismuth, tellurium and selenium raw materials are smelted in a muffle furnace to obtain a master alloy.

3. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 2, characterized in that, The process of smelting the mixed bismuth, tellurium, and selenium raw materials in a muffle furnace to obtain a master alloy includes: The mixed bismuth, tellurium and selenium raw materials are placed in the muffle furnace, and the muffle furnace is heated to a preset temperature threshold at a preset heating rate. The temperature is then held at the preset temperature threshold for a first preset time, and then naturally cooled to room temperature to obtain the master alloy.

4. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 3, characterized in that, The preset heating rate is selected within the range of [1℃min]. -1 6℃min -1 The preset temperature threshold is selected within the range of [900℃, 1100℃], and the first preset duration is selected within the range of [2.8h, 3.2h].

5. The method for preparing an N-type bismuth telluride-based thermoelectric thin film according to any one of claims 2-4, characterized in that, The process of melting, grinding, and sintering the bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-based bulk target material further includes: The master alloy is ground for a second preset time using a first grinding jar to obtain bismuth-tellurium-selenium-based particles. The bismuth-tellurium-selenium-based particles were vacuum ball-milled in a vacuum ball mill to obtain nanoscale bismuth-tellurium-selenium-based powder.

6. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 5, characterized in that, The process of vacuum ball milling the bismuth-tellurium-selenium-based particles in a vacuum ball mill jar to obtain nanoscale bismuth-tellurium-selenium-based powder includes: The bismuth-tellurium-selenium-based particles are placed in the vacuum ball mill jar, the vacuum ball mill jar is evacuated to a first preset vacuum level, and an inert gas is introduced to provide an atmosphere for protection. The vacuum ball mill is controlled to ball mill at a preset speed for a third preset time to obtain the nanoscale bismuth-tellurium-selenium-based powder.

7. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 6, characterized in that, The first preset vacuum degree is less than 6 Pa, and the preset ball milling speed is selected within the range of [350 r / min]. -1 500r min -1 The selection range for the third preset duration is [2h, 7h].

8. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 6 or 7, characterized in that, The process of melting, grinding, and sintering the bismuth, tellurium, and selenium raw materials to obtain an N-type bismuth-tellurium-based bulk target material further includes: Based on the spark plasma sintering process, the nanoscale bismuth-tellurium-selenium-based powder is sintered into an N-type bismuth-tellurium-selenium-based bulk target.

9. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 8, characterized in that, The sintering temperature range of the spark plasma sintering process is [300℃, 500℃], the pressure range is [60MPa, 80MPa], and the sintering time range is [6min, 8min].

10. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The step of depositing the N-type bismuth-tellurium-selenium-based bulk target on the substrate using a magnetron sputtering device to obtain the bismuth-tellurium-based thin film is performed before the step of depositing the N-type bismuth-tellurium-based bulk target on the substrate using a high-vacuum thermal evaporation device to obtain a homogeneous bismuth-tellurium-based thin film.

11. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The annealing temperature range of the annealing process is [250℃, 500℃], and the annealing gradient range is [20℃, 30℃].

12. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The substrate is a flexible substrate.

13. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 12, characterized in that, The flexible substrate includes at least one of polyimide film, polytetrafluoroethylene film, carbon nanotube film, and ultrathin carbon paper.

14. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The ratio of bismuth raw material, tellurium raw material and selenium raw material is 2:(3-m):m, where m>0.

15. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1, characterized in that, The thin film deposition rate of the magnetron sputtering equipment and the high-vacuum thermal evaporation equipment is set within the range of [0.5 nm min]. -1 12nm min -1 ].

16. The method for preparing N-type bismuth telluride-based thermoelectric thin films according to claim 1 or 14, characterized in that, The thickness range of the bismuth-tellurium-selenium-based thin film and the homogeneous bismuth-tellurium-selenium-based thin film is [50nm, 3000nm], and / or the thickness range of the N-type bismuth telluride-based thermoelectric thin film is [100nm, 6000nm].

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