Preparation method of metal chalcogenide flexible thermoelectric film and flexible thermoelectric film
By combining screen printing with hot pressing, the problem of loose bonding between flexible thermoelectric film and substrate is solved, improving thermoelectric performance and mechanical stability, simplifying the manufacturing process, and making it suitable for wearable electronic devices.
Patent Information
- Application Number
- CN202411295231.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-17
- Publication Date
- 2026-03-17
AI Technical Summary
In existing technologies, the bonding between flexible thermoelectric films and flexible substrates is not tight, which limits the stability of thermoelectric performance and makes the fabrication process complex, making it difficult to apply in wearable electronic devices.
By employing a combination of screen printing and hot pressing, the bonding strength between the thermoelectric material and the substrate is enhanced through surface roughening and hot pressing of the polyimide substrate, and the thermoelectric performance is improved by removing organic matter.
This method achieves a tight bond between the thermoelectric film and the substrate, improves thermoelectric performance and mechanical stability, simplifies the fabrication process, and is suitable for wearable electronic devices.
Smart Images
Figure CN121692980A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of thermoelectric energy conversion materials, specifically relating to a method for preparing a flexible thermoelectric film of a metal chalcogenide compound. Background Technology
[0002] With the advent of the Internet of Things (IoT) era, more and more researchers are focusing on wearable electronic devices. Flexible thermoelectric materials can convert the temperature difference between human skin and the external environment into electrical energy, making them one of the effective ways to achieve self-powered wearable electronic devices. In recent years, flexible thermoelectric materials have received widespread attention. Due to their excellent flexibility and lightweight characteristics, flexible thermoelectric films can be easily bonded to surfaces of various shapes, making them a material form with significant application potential in the field of flexible thermoelectric materials. The dimensionless thermoelectric figure of merit (zT) is typically used to evaluate the thermoelectric performance of materials, zT = S 2 σT / κ, where T is the absolute temperature, σ is the conductivity, and S is the Seebeck coefficient. 2 σ is the power factor, and κ is the thermal conductivity. Since the thermal conductivity within the surface of a flexible thermoelectric film is difficult to measure accurately, the power factor (σ) is typically used. 2 σ) Evaluate the thermoelectric properties of the thermoelectric film. Flexible thermoelectric films can generally be divided into self-supporting films and films combined with flexible substrates. The former is usually prepared based on conductive polymers and conductive polymer-based composites, but conductive polymers inherently have low S or S 2 The presence of σ limits its application. While combining it with inorganic thermoelectric materials with excellent thermoelectric properties can improve thermoelectric performance, these materials are typically brittle, and combining them may compromise flexibility, making it difficult to find a good balance between thermoelectric performance and flexibility. In contrast, inorganic thermoelectric films bonded to flexible substrates can combine the high thermoelectric performance of inorganic thermoelectric materials with the excellent flexibility of the substrate. Metal chalcogenides, in particular, with their excellent thermoelectric properties, have significant application potential in this type of thermoelectric film. Currently, the fabrication processes for such thermoelectric films are often quite complex. Therefore, finding a simpler fabrication process to prepare metal chalcogenide thermoelectric films bonded to flexible substrates is a crucial problem that urgently needs to be solved.
[0003] Screen printing is a low-cost, simple, and highly flexible film material preparation process that has been widely applied in many fields such as solar cells, electrodes, and electrochemical sensors. Therefore, using screen printing to prepare flexible thermoelectric films simplifies the preparation process and allows for optimization of film performance through flexible adjustment of process parameters. However, thermoelectric films prepared using screen printing often have weak adhesion to the substrate, and repeated bending may cause separation between the thermoelectric material and the substrate. Thus, the stability of the thermoelectric film's performance is limited by the degree of adhesion between the material and the flexible substrate. To enhance the adhesion between the thermoelectric film and the flexible substrate, researchers often add organic binders (e.g., polystyrene) when preparing the thermoelectric material ink. However, these organic binders have extremely poor conductivity, significantly degrading the thermoelectric performance of the film. Therefore, improving the adhesion strength between screen-printed thermoelectric films and flexible substrates while maintaining good thermoelectric performance and without using organic binders is a pressing problem to be solved. Summary of the Invention
[0004] In view of the above-mentioned problems in the existing technology, the present invention aims to solve the problem of poor bonding between the adhesive-free screen-printed metal chalcogenide thermoelectric film and the flexible substrate.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a flexible thermoelectric film of a metal chalcogenide compound, comprising the following steps:
[0006] S1: Obtain Ag2Se, Bi2Te3, SnTe, Ag2Te and AgSbTe2 thermoelectric material powders, which can be synthesized by solution synthesis or ball milling.
[0007] S2: Use 800-5000 grit sandpaper to roughen the surface of the polyimide substrate. This treatment helps to increase the bonding strength between the subsequent thermoelectric material and the substrate, and avoids the material being transferred to the mold surface during hot pressing.
[0008] S3: Clean the substrate and stencil: Sonicate the substrate with alcohol for 10–60 minutes to ensure the substrate surface is clean and free of stains. Rinse and clean the aluminum frame stencil with a mesh size of 100–300 and a specific printing shape using alcohol. Then dry the substrate and stencil.
[0009] S4: Weigh the thermoelectric material powder and grind it thoroughly in an agate mortar to refine and homogenize the powder particle size. Use a pipette to transfer terpineol and dispersant DISPERBYK-100 into the mortar, then mix the thermoelectric material ink by grinding for 0.5–2 hours. The thermoelectric material powder can be selected from metal chalcogenide thermoelectric material powders such as Ag2Se, Bi2Te3, SnTe, Ag2Te, or AgSbTe2. The mass of the thermoelectric material powder is 50–1000 parts, the volume of terpineol is 5–600 parts, and the volume of the dispersant is 5–600 parts. The mass unit of the thermoelectric material powder is mg, and the volume unit of terpineol and dispersant is μL. Terpineol, as a solvent in the ink, fully dissolves the metal chalcogenide thermoelectric material powder in the ink, and the viscosity of the ink can be adjusted by the amount of terpineol used. The addition of dispersants improves the separation of thermoelectric material particles by forming electrostatics or barriers on the particle surface, thereby achieving an optimal level of interaction between adjacent particles and reducing ink viscosity. Both dispersants and dispersants work together to optimize ink viscosity, thus improving the printing quality of subsequent thermoelectric films.
[0010] S5: Fix the screen and place the substrate treated in S3 as the printing material under the screen. Apply the ink obtained in S4 to the screen to obtain the printed film.
[0011] S6: Place the printed film in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40-70℃, and the drying time is 10-60 minutes.
[0012] S7: Transfer the membrane from S6 to a tube furnace and anneal at 300–450°C for 0.5–2 hours. After cooling to room temperature in the furnace, remove the membrane. The purpose of annealing is to remove organic matter such as terpineol and dispersants from the membrane to prevent them from reducing the thermoelectric properties of the membrane.
[0013] S8: The annealed film is hot-pressed at a temperature of 300–450℃ and a pressure of 15–30 MPa for 10–60 minutes. Hot pressing can effectively improve the density of the thermoelectric film and strengthen the bonding between the substrate and the material.
[0014] Compared with the prior art, the present invention has at least the following advantages:
[0015] 1. Roughening the surface of the polyimide substrate improves the bonding strength between the substrate and the thermoelectric material, preventing the thermoelectric material from transferring to the mold surface during hot pressing and ensuring the integrity of the thermoelectric film's shape and surface flatness. Specifically, a simple sanding method introduces an interlaced channel structure on the polyimide surface. When screen-printing metal chalcogenide ink onto the substrate, the ink can embed into the channels of the roughened polyimide surface, increasing the contact and bonding area, thereby enhancing the bonding strength. Further, annealing removes organic matter, and hot pressing (heat treatment under high uniaxial pressure) promotes the contact of the metal chalcogenide powder, thus densifying it. This allows the metal chalcogenide to be tightly embedded in the surface channels of the polyimide, forming an "anchoring" structure, increasing mechanical "interlocking," and significantly increasing the bonding strength between the substrate and the thermoelectric film. By changing the grit of the sandpaper used for polishing, the morphology of the channels on the polyimide surface (e.g., channel density, width, and depth) can be altered, effectively adjusting the surface roughness of the substrate and thus optimizing the bonding between the polyimide substrate and thermoelectric materials of different particle sizes. In contrast, smooth polyimide substrates are difficult to bond well with thermoelectric materials. After hot pressing, the thermoelectric material often transfers to the mold, resulting in an incomplete thermoelectric film shape and an uneven surface. Furthermore, after cyclic bending, the thermoelectric film detaches from the substrate, causing the composite thermoelectric film to fail.
[0016] 2. This invention simplifies a series of thermoelectric film preparation processes. Although screen printing has been used for the preparation of some thermoelectric films, reported work often focuses on the preparation of a few thermoelectric films using this process. Other thermoelectric materials (e.g., AgSbTe2, SnTe) have not yet been able to produce thermoelectric films with complete shapes and uniform thickness using this process. This invention develops a screen printing-hot pressing process and innovatively utilizes polyimide with a rough surface as a flexible substrate, achieving simplified preparation of a series of metal chalcogenide thermoelectric films (e.g., Ag2Se, Bi2Te3, SnTe, Ag2Te, AgSbTe2).
[0017] 3. This invention improves the density of the material through hot pressing, further enhancing the thermoelectric performance of the thermoelectric film. In previously reported work, cold pressing combined with annealing (compacting the thermoelectric powder at room temperature, followed by annealing to sinter the powder) is a commonly used method for densifying thermoelectric films; however, this method does not achieve a very good degree of densification (or relative density). This invention densifies the thermoelectric film through hot pressing, i.e., heating the powder under pressure to sinter and densify it, which effectively reduces the voids between thermoelectric particles and significantly improves the density of the thermoelectric film. The lower the density of the thermoelectric film, the more scattering the charge carriers experience during transport, which is detrimental to obtaining excellent charge carrier mobility; the thermoelectric film obtained through hot pressing has a high degree of density, and the charge carriers experience less scattering during transport, making it easier to obtain excellent charge carrier mobility and thermoelectric power factor. For example, in this invention, compared with Ag2Se films prepared by screen printing and cold pressing-annealing, Ag2Se films prepared by screen printing and hot pressing have more than doubled carrier mobility and power factor.
[0018] 4. This invention clarifies the effect of removing organic matter from the surface of solution-synthesized metal chalcogenide particles on improving thermoelectric performance. For example, Bi₂Te₃ can be synthesized via solution chemistry, and organic surfactants are often used in the preparation process to adjust the morphology of the product. However, these non-conductive organic substances often remain on the product surface, significantly reducing the electrical transport performance of the corresponding thermoelectric film. This invention significantly removes organic matter from the particle surface of solution-synthesized Bi₂Te₃ by heat-treating it at 500–550°C, thereby achieving a significant improvement in thermoelectric performance (e.g., ...). Figure 4 The thermoelectric film obtained by this invention exhibits a high power factor and superior flexibility. The Bi₂Te₃ film achieves a maximum power factor of 1186.3 μW / m at 427 K. -1 K -2 Furthermore, after 1000 bending cycles with a radius of 10 mm, the resistance increased by approximately 11%; while the conductivity of the Ag2Se film decreased by approximately 16% after 1000 bending cycles with a smaller radius of 4 mm. Attached Figure Description
[0019] Figure 1 Images of actual Bi2Te3 and Ag2Se thermoelectric films.
[0020] Figure 2 The resistance change of the Bi2Te3 film after 1000 bending cycles with a radius of 10 mm is shown.
[0021] Figure 3 The conductivity of the Ag2Se membrane changes after 1000 bending cycles with a radius of 4 mm.
[0022] Figure 4The thermoelectric power factor of Bi2Te3 films prepared after powder heat treatment at different temperatures.
[0023] Figure 5 This is a simplified flowchart of the method of the present invention. Detailed Implementation
[0024] The present invention will now be described in further detail.
[0025] The fabrication processes for thermoelectric films bonded to substrates are typically complex and costly, limiting their practical application potential. Screen printing, as a simple and low-cost process, effectively overcomes these challenges, making the practical application of thermoelectric films more feasible. Furthermore, hot-pressing the thermoelectric film improves its density, enhancing its thermoelectric performance, and also strengthens the bond between the substrate and the material. It is particularly noteworthy that using a flexible polyimide substrate with a rough surface enhances the bonding strength between the substrate and the thermoelectric material, ensuring the final thermoelectric film maintains its shape and uniform thickness. This invention enables the simple fabrication of a series of flexible metal chalcogenide thermoelectric films.
[0026] The following details the process of preparing various flexible thermoelectric films of metal chalcogenides based on screen printing technology:
[0027] A method for preparing a flexible thermoelectric film of a metal chalcogenide compound, which belongs to the screen printing combined with hot pressing process, includes the following steps:
[0028] Step S1: Synthetic electric material powders of Ag2Se, Bi2Te3, SnTe, Ag2Te and AgSbTe2 are synthesized by solution synthesis or ball milling.
[0029] Step S2: Use 800-5000 grit sandpaper to roughen the surface of the substrate. The specific grit of sandpaper can be selected as 800 grit, 1000 grit, 1500 grit, 2000 grit, 3000 grit, 4000 grit or 5000 grit to obtain substrates with different roughness.
[0030] Step S3: Clean the substrate and stencil: Sonicate the substrate with alcohol for 10–60 minutes to ensure the substrate surface is free of stains and clean. Rinse the stencil with alcohol and then dry the substrate and stencil. The specific ultrasonic treatment time can be selected as 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min.
[0031] Step S4: Weigh the thermoelectric material powder and grind it thoroughly. Then, grind the thermoelectric material powder, terpineol, and dispersant DISPERBYK-100 in a mortar for 0.5–2 hours to ensure thorough and uniform mixing. The mass fraction of the thermoelectric material powder is 50–1000 parts, and the amounts of terpineol and dispersant DISPERBYK-100 are adjusted within a volume range of 5–600 parts. Specifically, the amount of thermoelectric material powder can be 50, 100, 200, 350, 500, 600, 800, or 1000 parts, and the amounts of terpineol and dispersant DISPERBYK-100 can be 5, 25, 35, 50, 100, 200, 400, or 600 parts. The mass unit of the thermoelectric material powder is mg, and the volume unit of terpineol and dispersant DISPERBYK-100 is μL.
[0032] Step S5: Fix the screen and place the substrate treated in S3 below the screen as the printing material; apply the ink obtained in S4 to the screen to obtain the printed film.
[0033] Step S6: Place the printed film in a vacuum drying oven for drying. The temperature of the vacuum drying oven is set to 40-70℃, and the drying time is 10-60 minutes. Specifically, the drying temperature can be 40℃, 50℃, 60℃, or 70℃; the drying time can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.
[0034] Step S7: Transfer the dried printed film from step S5 to a tube furnace and anneal at 300–450°C for 0.5–2 hours. After cooling to room temperature in the furnace, remove the film. Specifically, the annealing time can be 0.5 hours, 1 hour, 1.5 hours, or 2 hours; the annealing temperature can be 300°C, 325°C, 350°C, 375°C, 400°C, 425°C, or 450°C.
[0035] Step S8: The annealed film is hot-pressed at a temperature of 300–450℃ and a pressure of 15–30 MPa for 10–60 minutes. Specifically, the hot-pressing temperature can be 300℃, 325℃, 350℃, 375℃, 400℃, 425℃, or 450℃; the pressure can be 15 MPa, 20 MPa, 25 MPa, or 30 MPa; and the hot-pressing time can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.
[0036] Example 1: Preparation process of Bi2Te3 thermoelectric film:
[0037] Bi₂Te₃ powder was synthesized via solution synthesis. The powder heat treatment temperature was 550℃, and the film hot pressing temperature was 400℃ (corresponding to...). Figure 1 a and Figure 4 Bi2Te3@PI R -823K HT-673 K HP).
[0038] 1) The steps for the solution synthesis of Bi₂Te₃ are as follows: 90 mL of ethylene glycol was added to a 250 mL three-necked flask, along with 1.4364 g of TeO₂, 0.4500 g of polyvinylpyrrolidone (PVP), and 2.2442 g of KOH. After stirring at room temperature for 30 min, a suspension A of TeO₂ was obtained. Simultaneously, 2.9398 g of Bi(NO₃)₃·5H₂O was added to 30 mL of ethylene glycol, and the mixture was stirred thoroughly until the solution became transparent, yielding solution B. Suspension A was heated to 130 °C. After the solution turned into a clear yellow solution, hydrazine hydrate solution was rapidly injected into it. The mixture was kept at this temperature for 30 min under a nitrogen atmosphere and then cooled to 120 °C to obtain suspension C. Solution B was then injected into suspension C, and the reaction was carried out at 120 °C for 2 h. After the reaction was complete, the mixture was washed several times by centrifugation with water and alcohol, and finally dried and collected as Bi₂Te₃ powder. The powder was then heat-treated at 550°C for 1 hour to remove residual organic matter from the powder surface, resulting in the final Bi2Te3 powder for use.
[0039] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0040] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0041] 4) Weigh 100mg of Bi2Te3 powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 30μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Bi2Te3 ink by hand grinding for 0.5h.
[0042] 5) Fix the stencil and place the prepared substrate under the stencil as the printing material; use a scraper to scrape Bi2Te3 ink and apply it to the stencil to initially obtain a Bi2Te3 film.
[0043] 6) Transfer the Bi2Te3 membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0044] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Bi2Te3 membrane is then removed after cooling to room temperature in the furnace.
[0045] 8) The annealed Bi2Te3 film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Bi2Te3 film.
[0046] Example 2: Preparation process of Bi2Te3 thermoelectric film:
[0047] Bi₂Te₃ powder was synthesized by solution synthesis or ball milling. The powder heat treatment temperature was 550℃, and the film hot pressing temperature was 350℃ (corresponding to...). Figure 4 Bi2Te3@PI R -823K HT-623K HP).
[0048] 1) The steps for the solution synthesis of Bi₂Te₃ are as follows: 90 mL of ethylene glycol was added to a 250 mL three-necked flask, along with 1.4364 g of TeO₂, 0.4500 g of polyvinylpyrrolidone (PVP), and 2.2442 g of KOH. After stirring at room temperature for 30 min, a suspension A of TeO₂ was obtained. Simultaneously, 2.9398 g of Bi(NO₃)₃·5H₂O was added to 30 mL of ethylene glycol, and the mixture was stirred thoroughly until the solution became transparent, yielding solution B. Suspension A was heated to 130 °C. After the solution turned into a clear yellow solution, hydrazine hydrate solution was rapidly injected into it. The mixture was kept at this temperature for 30 min under a nitrogen atmosphere and then cooled to 120 °C to obtain suspension C. Solution B was then injected into suspension C, and the reaction was carried out at 120 °C for 2 h. After the reaction was complete, the mixture was washed several times by centrifugation with water and alcohol, and finally dried and collected as Bi₂Te₃ powder. The powder was then heat-treated at 550°C for 1 hour to remove residual organic matter from the powder surface, resulting in the final Bi2Te3 powder for use.
[0049] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0050] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0051] 4) Weigh 100mg of Bi2Te3 powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 30μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Bi2Te3 ink by hand grinding for 0.5h.
[0052] 5) Fix the stencil and place the prepared substrate below the stencil as the printing medium. Use a squeegee to scrape Bi2Te3 ink onto the stencil to initially obtain a Bi2Te3 film.
[0053] 6) Transfer the Bi2Te3 membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0054] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Bi2Te3 membrane is then removed after cooling to room temperature in the furnace.
[0055] 8) The annealed Bi2Te3 film was subjected to hot pressing treatment at a temperature of 350℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Bi2Te3 film.
[0056] Example 3: Preparation process of Bi2Te3 thermoelectric film:
[0057] Bi₂Te₃ powder was synthesized by solution synthesis or ball milling. The powder was not heat-treated, and the film hot-pressing temperature was 350℃ (corresponding to...). Figure 4 Bi2Te3@PI R -UnHT-623K HP).
[0058] 1) The steps for the solution synthesis of Bi₂Te₃ are as follows: 90 mL of ethylene glycol was added to a 250 mL three-necked flask, along with 1.4364 g of TeO₂, 0.4500 g of polyvinylpyrrolidone (PVP), and 2.2442 g of KOH. After stirring at room temperature for 30 min, a suspension A of TeO₂ was obtained. Simultaneously, 2.9398 g of Bi(NO₃)₃·5H₂O was added to 30 mL of ethylene glycol, and the mixture was stirred thoroughly until the solution became transparent, yielding solution B. Suspension A was heated to 130 °C. After the solution turned into a clear yellow solution, hydrazine hydrate solution was rapidly injected into it. The mixture was kept at this temperature for 30 min under a nitrogen atmosphere and then cooled to 120 °C to obtain suspension C. Solution B was then injected into suspension C, and the reaction was carried out at 120 °C for 2 h. After the reaction was complete, the mixture was washed several times by centrifugation with water and alcohol, and finally dried and collected as Bi₂Te₃ powder.
[0059] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0060] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0061] 4) Weigh 100mg of Bi2Te3 powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 30μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Bi2Te3 ink by hand grinding for 0.5h.
[0062] 5) Fix the stencil and place the prepared substrate below the stencil as the printing medium. Use a squeegee to scrape Bi2Te3 ink onto the stencil to initially obtain a Bi2Te3 film.
[0063] 6) Transfer the Bi2Te3 membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0064] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Bi2Te3 membrane is then removed after cooling to room temperature in the furnace.
[0065] 8) The annealed Bi2Te3 film was subjected to hot pressing treatment at a temperature of 350℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Bi2Te3 film.
[0066] Example 4: Preparation process of Bi2Te3 thermoelectric film:
[0067] Bi2Te3 powder was synthesized by ball milling, and the film hot pressing temperature was 400℃.
[0068] 1) The steps for ball milling to synthesize Bi2Te3 are as follows: Weigh 5g of Bi powder and 5g of Te powder according to the stoichiometric ratio Bi:Te = 2:3. Place the powder into a ball mill jar and seal it (ball-to-powder ratio set to 4:1). Place it in a high-energy ball mill and ball mill for 8 hours. Then, the powder is annealed at 350-500℃ to ensure that the two powders react completely, and the final Bi2Te3 powder is obtained.
[0069] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0070] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0071] 4) Weigh 100mg of Bi2Te3 powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 30μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Bi2Te3 ink by hand grinding for 0.5h.
[0072] 5) Fix the stencil and place the prepared substrate below the stencil as the printing medium. Use a squeegee to scrape Bi2Te3 ink onto the stencil to initially obtain a Bi2Te3 film.
[0073] 6) Transfer the Bi2Te3 membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0074] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Bi2Te3 membrane is then removed after cooling to room temperature in the furnace.
[0075] 8) The annealed Bi2Te3 film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Bi2Te3 film.
[0076] Example 5: Preparation process of Ag2Se thermoelectric film:
[0077] Ag₂Se powder was synthesized by solution synthesis.
[0078] 1) The steps for the solution synthesis of Ag₂Se are as follows: 50 mL of deionized water and 20 mmol of AgNO₃ are added sequentially to a 200 mL two-necked flask, and stirred at room temperature to form an AgNO₃ aqueous solution. The solution is then heated to boiling in an oil bath under an Ar atmosphere. Simultaneously, 50 mL of deionized water, 10 mmol of Se powder, and 20 mmol of NaBH₄ are added sequentially to a single-necked flask, and the mixture is stirred at room temperature for 30 min to obtain a NaHSe aqueous solution. Subsequently, the NaHSe aqueous solution is rapidly injected into the boiling AgNO₃ aqueous solution, and the reaction is carried out at boiling for 2 h. After the reaction is complete and cooled to room temperature, the sample is washed several times by centrifugation with water and alcohol, and finally dried and the Ag₂Se powder is collected.
[0079] 2) Use 2000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0080] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0081] 4) Weigh 100mg of Ag2Se powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 18μL of terpineol and 50μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Ag2Se ink by hand grinding for 0.5h.
[0082] 5) Fix the stencil and place the prepared substrate below it as the printing medium. Use a squeegee to scrape Ag2Se ink onto the stencil to initially obtain an Ag2Se film.
[0083] 6) Transfer the Ag2Se membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0084] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Ag2Se membrane is then removed after cooling to room temperature in the furnace.
[0085] 8) The annealed Ag2Se film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Ag2Se film.
[0086] Example 6: Preparation process of Ag2Se thermoelectric film:
[0087] Ag₂Se powder was synthesized by ball milling.
[0088] 1) The steps for ball milling to synthesize Ag2Se are as follows: Weigh 5g of Ag powder and Se powder according to the stoichiometric ratio of Ag:Se = 2:1, put the powder into a ball mill jar and seal it (the ball-to-material ratio is set to 5:1), and place it in a high-energy ball mill for 2 hours to obtain Ag2Se powder.
[0089] 2) Use 2000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0090] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0091] 4) Weigh 100mg of Ag2Se powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 50μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Ag2Se ink by hand grinding for 0.5h.
[0092] 5) Fix the stencil and place the prepared substrate below it as the printing medium. Use a squeegee to scrape Ag2Se ink onto the stencil to initially obtain an Ag2Se film.
[0093] 6) Transfer the Ag2Se membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0094] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Ag2Se membrane is then removed after cooling to room temperature in the furnace.
[0095] 8) The annealed Ag2Se film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 20MPa, and a holding time of 30min to finally obtain a dense Ag2Se film.
[0096] Example 7: Preparation process of SnTe thermoelectric film:
[0097] SnTe powder was synthesized by solution synthesis.
[0098] 1) The steps for solution synthesis of SnTe are as follows: 2 mmol SnCl2·2H2O, 2 mmol Na2TeO3, 15 mmol NaOH, and 1 g PVP are sequentially added to 50 mL ethylene glycol. After stirring at room temperature for 30 min, the solution is transferred to a polytetrafluoroethylene reactor and heated at 220 °C for 4 h. After the reaction is complete, the reactor is cooled to room temperature. The precipitate is washed several times with water and alcohol, and the product is collected by centrifugation and then dried to obtain SnTe powder.
[0099] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0100] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0101] 4) Weigh 100mg of SnTe powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 15μL of terpineol and 15μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the SnTe ink by hand grinding for 0.5h.
[0102] 5) Fix the stencil and place the prepared substrate below it as the printing medium. Use a squeegee to scrape SnTe ink onto the stencil to initially obtain the SnTe film.
[0103] 6) Transfer the SnTe membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0104] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The SnTe membrane is then removed after cooling to room temperature in the furnace.
[0105] 8) The annealed SnTe film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 25MPa, and a holding time of 30min to finally obtain a dense SnTe film.
[0106] Example 8: Preparation process of SnTe thermoelectric film:
[0107] SnTe powder was synthesized by ball milling.
[0108] 1) The steps for ball milling to synthesize SnTe are as follows: Weigh 5g of Sn powder and Te powder together according to the stoichiometric ratio Sn:Te = 1:1, put the powder into a ball mill jar and seal it (the ball-to-material ratio is set to 5:1), and place it in a high-energy ball mill for 2 hours to obtain SnTe powder.
[0109] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0110] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0111] 4) Weigh 100mg of SnTe powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 25μL of terpineol and 15μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the SnTe ink by hand grinding for 0.5h.
[0112] 5) Fix the stencil and place the prepared substrate below it as the printing medium. Use a squeegee to scrape SnTe ink onto the stencil to initially obtain the SnTe film.
[0113] 6) Transfer the SnTe membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0114] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The SnTe membrane is then removed after cooling to room temperature in the furnace.
[0115] 8) The annealed SnTe film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 25MPa, and a holding time of 30min to finally obtain a dense SnTe film.
[0116] Example 9: Preparation process of Ag2Te thermoelectric film:
[0117] Ag2Te powder was synthesized by ball milling.
[0118] 1) The steps for ball milling to synthesize Ag2Te are as follows: Weigh 5g of Ag powder and Te powder according to the stoichiometric ratio of Ag:Te = 2:1, put the powder into a ball mill jar and seal it (the ball-to-material ratio is set to 5:1), and place it in a high-energy ball mill for 2 hours to obtain Ag2Te powder.
[0119] 2) Use 1500-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0120] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0121] 4) Weigh 100mg of Ag2Te powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 15μL of terpineol and 15μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the Ag2Te ink by hand grinding for 0.5h.
[0122] 5) Fix the stencil and place the prepared substrate below it as the printing medium. Use a squeegee to scrape Ag2Te ink onto the stencil to initially obtain an Ag2Te film.
[0123] 6) Transfer the Ag2Te membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0124] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The Ag2Te membrane is then removed after cooling to room temperature in the furnace.
[0125] 8) The annealed Ag2Te film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 25MPa, and a holding time of 30min to finally obtain a dense Ag2Te film.
[0126] Example 10: Preparation process of AgSbTe2 thermoelectric film:
[0127] AgSbTe2 powder was synthesized by ball milling.
[0128] 1) Ball milling synthesis of AgSbTe2 powder. The steps for ball milling synthesis of AgSbTe2 are as follows: Weigh 5g of Ag powder, Sb powder and Te powder according to the stoichiometric ratio of Ag:Sb:Te = 1:1:2. Put the powder into a ball mill jar and seal it (the ball-to-material ratio is set to 5:1). Place it in a high-energy ball mill and ball mill for 4 hours to obtain AgSbTe2 powder.
[0129] 2) Use 3000-grit sandpaper to roughen the surface of the polyimide film used as the substrate material.
[0130] 3) Cleaning the substrate and stencil: Sonicate the polyimide substrate with alcohol for 30 minutes to ensure the substrate surface is free of stains and clean. Rinse and clean the aluminum frame stencil with 200 mesh openings and specific printing shapes using alcohol.
[0131] 4) Weigh 100mg of AgSbTe2 powder, pour it into an agate mortar and grind it thoroughly. Use a pipette to take 15μL of terpineol and 15μL of dispersant DISPERBYK-100 respectively, then transfer them into the mortar and mix the AgSbTe2 ink by hand grinding for 0.5h.
[0132] 5) Fix the stencil and place the prepared substrate below the stencil as the printing medium. Use a squeegee to scrape AgSbTe2 ink onto the stencil to initially obtain an AgSbTe2 film.
[0133] 6) Transfer the AgSbTe2 membrane to a vacuum drying oven and vacuum dry it at 60°C for 30 minutes.
[0134] 7) After drying, the membrane is transferred to a tube furnace, heated to 400°C under argon protection, and held at this temperature for 1 hour for annealing. The AgSbTe2 membrane is then removed after cooling to room temperature in the furnace.
[0135] 8) The annealed AgSbTe2 film was subjected to hot pressing treatment at a temperature of 400℃, a pressure of 25MPa, and a holding time of 30min to finally obtain a dense AgSbTe2 film.
[0136] Figure 1 a is a photograph of the Bi2Te3 thermoelectric film (Example 1). Figure 1 Figure b shows a photograph of the Ag2Se thermoelectric film (Example 5). It can be seen that both Bi2Te3 and Ag2Se can bond well with the substrate, and there is no separation between the substrate and the material when bending, indicating that the thermoelectric film prepared by this process can achieve good flexibility.
[0137] Figure 2 The resistance change of the Bi2Te3 film in Example 1 after 1000 bending cycles with a radius of 10 mm is shown. It can be seen that the resistance of the thermoelectric film gradually increases with the increase in the number of bends. In the bending test with a bending radius of 10 mm, the resistance of the Bi2Te3 thermoelectric film increased by only about 11% after 1000 bends. This result indicates that the Bi2Te3 thermoelectric film has good flexibility.
[0138] Figure 3 The conductivity retention of the Ag2Se film in Example 5 after 1000 bending cycles with a radius of 4 mm is shown. It can be seen that the conductivity of the thermoelectric film gradually decreases with increasing number of bending cycles. In the bending test with a bending radius of 4 mm, the conductivity decreased by approximately 16% after 1000 bending cycles. This result indicates that the Ag2Se thermoelectric film has good flexibility.
[0139] Figure 4 The electrical transport performance of the Bi2Te3 thermoelectric film was tested, demonstrating the influence of powder heat treatment temperature and film hot-pressing temperature on the power factor of the flexible thermoelectric film (corresponding to Examples 1-3). With increasing heat treatment temperature and film hot-pressing temperature, the power factor of the Bi2Te3 thermoelectric film gradually increased. This is because both powder heat treatment and increasing the film hot-pressing temperature contribute to improving the conductivity of the Bi2Te3 film: ① After appropriate heat treatment, non-conductive organic matter on the surface of the solution-synthesized Bi2Te3 powder is effectively removed; ② With increasing hot-pressing temperature, the density of the Bi2Te3 thermoelectric film increases, effectively reducing carrier scattering and significantly improving carrier mobility and conductivity.
[0140] In summary, the method of preparing flexible thermoelectric films using screen printing and hot pressing processes of the present invention has successfully achieved the preparation of a series of flexible films combining thermoelectric materials with substrates. Furthermore, the thermoelectric films have achieved good thermoelectric performance through parameter optimization and exhibit excellent flexibility.
[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method of fabricating a metal chalcogenide flexible thermoelectric film, characterized by: The method comprises the following steps: Step S1: roughen the surface of the substrate by polishing it with sandpaper with a mesh size of 800-5000. Step S2: clean the substrate and the screen: ultrasonically treat the substrate with alcohol for 10-60 min to make the surface of the substrate free of stains and clean; rinse the screen with alcohol and then dry the substrate and the screen. Step S3: weigh the thermoelectric material powder and grind it thoroughly, then grind the thermoelectric material powder, terpineol and dispersant DISPERBYK-100 in a mortar for 0.5-2 h to make them mix uniformly. The thermoelectric material powder is 50-1000 parts by mass; The terpineol is 5-600 parts by volume; The dispersant is 5-600 parts by volume; Step S4: fix the screen and place the substrate treated in step S2 as the printing material under the screen, then apply the ink obtained in step S3 on the screen by squeegee coating to obtain a printed film. Step S5: dry the printed film in a vacuum drying oven, with the temperature of the vacuum drying oven set to 40-70℃ and the drying time set to 10-60 min. Step S6: transfer the printed film dried in step S5 to a tube furnace and anneal it at 300-450℃ for 0.5-2 h, then take out the film after the furnace cools to room temperature. Step S7: heat-press the annealed printed film at a temperature of 300-450℃ and a pressure of 15-30 MPa for 10-60 min.
2. A flexible thermoelectric film, characterized by: The metal chalcogenide flexible thermoelectric film is prepared by the method of claim 1.