Silver selenide / single-walled carbon nanotube flexible composite film and its preparation method and application

Abstract

The present invention relates to a silver selenide / single-walled carbon nanotube flexible composite film, its preparation method, and application, belonging to the technical field of flexible thermoelectric material preparation. The preparation method comprises preparing a dispersion of single-walled carbon nanotubes, adding a selenium source, a surface morphogen, and a reducing agent to the dispersion, and uniformly mixing to synthesize a selenium nanowire / single-walled carbon nanotube composite. Using the selenium nanowires in the composite as a template, silver nitrate is added to an ethylene glycol solution to react and obtain a silver selenide / single-walled carbon nanotube composite. The resulting product is dispersed in anhydrous ethanol, filtered using a porous filter membrane as a substrate, and vacuum dried. Finally, the composite film is cold-pressed and heat-treated to obtain the composite film. This maximizes the power factor of the silver selenide / single-walled carbon nanotube flexible composite film, compensates for the loss in Seebeck coefficient after direct composite of p-type single-walled carbon nanotubes and n-type silver selenide, and simultaneously improves the thermoelectric performance and bending resistance of the silver selenide / single-walled carbon nanotube composite film.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible thermoelectric material preparation, and in particular relates to a silver selenide / single-walled carbon nanotube flexible composite film, a preparation method thereof, and applications thereof. Background Art

[0002] In recent years, portable wearable electronic devices have entered a period of rapid development, but energy supply is the main obstacle to their continued development. Thermoelectric materials can achieve direct conversion of thermal energy into electrical energy. According to statistics, a 68 kg adult can generate more than 100W of electricity through daily activities such as breathing, typing, and generating heat. Only 1% of energy conversion is needed to drive most portable electronic products such as smart watches and pacemakers. Flexible thermoelectric films can better fit wearable electronic devices and directly charge them by collecting waste heat from the human body. Wearable electronic devices are mainly used in room temperature scenarios, so materials that combine flexibility and high room temperature thermoelectric properties have broad application prospects.

[0003] Silver selenide is a phase change material that changes from a tetragonal phase to a cubic phase at 407K. Silver selenide in the low-temperature tetragonal phase is an n-type semiconductor. Too high or too low a carrier concentration will lead to a decrease in its thermoelectric performance. However, the intrinsic carrier concentration of silver selenide is just in the appropriate range, and its carrier mobility is at a high level, which makes silver selenide exhibit high thermoelectric performance near room temperature (S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity). So far, the highest S of silver selenide at room temperature 2 σ is 35.2 μW cm -1 K -2 , close to the room temperature S of commercial Bi2Te3 2 σ~45μW cm -1 K -2 , which proves that silver selenide has excellent room-temperature thermoelectric properties.

[0004] However, silver selenide exhibits inherent brittleness and cannot be directly applied to flexible wearable devices. Therefore, in the prior art, silver selenide is usually grown on a flexible substrate to prepare a silver selenide film to meet the needs of flexible wearables. Specifically, a solution method is used to synthesize a one-dimensional silver selenide nanostructure with a large aspect ratio. Then, through vacuum filtration and hot pressing sintering, the large aspect ratio silver selenide nanostructure is tightly interwoven with the porous flexible nylon substrate to prepare a flexible silver selenide film with high thermoelectric performance. In existing research, the prepared silver selenide flexible film S 2 σ can be as high as 18.82 μW cm at 300 K -1 K -2, after the film was bent 1,000 times, the film's conductivity dropped by 9.3%. It is reported that some organic thermoelectric films have excellent bending resistance, with the conductivity dropping by only 1% to 5% after repeated bending 1,000 times. In actual applications, bending resistance determines whether the thermoelectric film can stably and continuously generate electricity in curved application scenarios. Therefore, the bending resistance of silver selenide flexible films needs to be further improved.

[0005] In order to improve the bending resistance of silver selenide films, materials with high adhesion, high flexibility and network structure building capabilities are usually selected to be compounded with silver selenide. Commonly used composite materials include: polyvinylidene fluoride, polyvinyl pyrrolidone, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid, and single-walled carbon nanotubes. Among them, single-walled carbon nanotubes are directly compounded with silver selenide. After bending 1000 times, the conductivity of the prepared flexible film decreased by 6%. Compared with the previous silver selenide flexible film, although the bending resistance has been significantly improved, the direct compounding of carbon nanotubes as a p-type material with n-type silver selenide will weaken the n-type characteristics of the silver selenide film, which is specifically manifested in the reduction of the Seebeck coefficient. In addition, because the thermoelectric performance S 2 σ is determined by the square of the Seebeck coefficient multiplied by the conductivity, so the reduction of the Seebeck coefficient will seriously affect the final S of silver selenide. 2 σ, resulting in the existing silver selenide / single-walled carbon nanotubes showing a lower S 2 σ~10.30μW cm -1 K -2 . Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a silver selenide / single-walled carbon nanotube flexible composite film and a preparation method thereof. The preparation method of the present invention adds single-walled carbon nanotubes with excellent mechanical and electrical properties during the growth process of selenium nanowires, greatly improving the electrical conductivity of the silver selenide / single-walled carbon nanotube flexible composite film to compensate for the loss of Seebeck coefficient after direct compounding of p-type single-walled carbon nanotubes and n-type silver selenide, and ultimately achieving the simultaneous improvement of the thermoelectric properties and bending resistance of the silver selenide / single-walled carbon nanotube composite film.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing a silver selenide / single-walled carbon nanotube flexible composite film, which is characterized by comprising the following steps:

[0009] S1: preparing a dispersion of single-walled carbon nanotubes, adding a selenium source, a surface morphology agent, and a reducing agent to the dispersion, and mixing them evenly to synthesize a selenium nanowire / single-walled carbon nanotube composite;

[0010] S2: using the selenium nanowires in the selenium nanowire / single-walled carbon nanotube composite as a template, dispersing the selenium nanowire / single-walled carbon nanotube composite in an ethylene glycol solution, and then adding silver nitrate to react to obtain a silver selenide / single-walled carbon nanotube composite;

[0011] S3: The silver selenide / single-walled carbon nanotube composite is dispersed in anhydrous ethanol, filtered using a porous filter membrane as a substrate, and vacuum dried to obtain a film; then cold pressing and heat treatment are performed to obtain a silver selenide / single-walled carbon nanotube flexible composite film.

[0012] The present invention further adopts that in said S1, the dispersion liquid of the single-walled carbon nanotubes uses anhydrous ethanol as a dispersant; and the concentration of the dispersion liquid of the single-walled carbon nanotubes is 0.0125 to 0.05 mol / L.

[0013] The present invention further comprises: in S1, the selenium source is selenium dioxide; the surface morphogen is cyclodextrin; the reducing agent is any one of sodium hydroxide, sodium borohydride, sodium bicarbonate, sodium sulfite, hydrazine and L-ascorbic acid; the reducing agent is configured into a reducing agent solution, and the concentration of the reducing agent solution is 0.05 to 0.1 mol / L.

[0014] The present invention further states that in S1, the uniform mixing process is stirring at room temperature for 5 to 6 hours.

[0015] The present invention further states that in S2, the molar ratio of the selenium nanowires to silver nitrate is (2-6):1.

[0016] The present invention further states that in S2, the reaction temperature of the selenium nanowires and silver nitrate is 40° C., and the reaction time is 4 to 6 hours.

[0017] The present invention further states that in S3, a porous filter membrane with a pore size of 0.22 μm is selected for filtration, and the porous filter membrane is any one of nylon, polytetrafluoroethylene, polyethersulfone, and polyvinylidene fluoride.

[0018] The present invention further states that in S3, the vacuum drying temperature is 50 to 80° C., and the vacuum drying time is 10 to 15 hours.

[0019] The present invention further states that in S3, the cold pressing pressure is 5-30 MPa, and the cold pressing holding time is 10-30 min; the heat treatment temperature is 200-220° C., and the heat treatment time is 30 min.

[0020] A silver selenide / single-walled carbon nanotube flexible composite film with high thermoelectric performance, prepared by any one of the preparation methods described.

[0021] Application of the silver selenide / single-walled carbon nanotube flexible composite film prepared by any one of the preparation methods in semiconductor materials or electronic devices.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a method for preparing a highly flexible and thermoelectrically efficient silver selenide / single-walled carbon nanotube flexible composite film. Single-walled carbon nanotubes with excellent mechanical and electrical properties are added during the growth of selenium nanowires. The resulting selenium nanowires / carbon nanotubes are then chemically reacted with silver nitrate to significantly improve the electrical conductivity of the silver selenide / single-walled carbon nanotube flexible composite film, thereby compensating for the loss of the Seebeck coefficient after direct composite of p-type single-walled carbon nanotubes and n-type silver selenide. Ultimately, the thermoelectric performance and bending resistance of the silver selenide / single-walled carbon nanotube composite film are simultaneously improved. ; The present invention adopts a solution method to compound silver selenide with single-walled carbon nanotubes, and the composite process of silver selenide and single-walled carbon nanotubes affects the growth of silver selenide nanostructures. After adding single-walled carbon nanotubes, the carrier concentration of the material is increased, the electrical conductivity is increased, and the thermoelectric properties of the silver selenide-based film are significantly improved; the large aspect ratio of single-walled carbon nanotubes is utilized to exhibit excellent mechanical properties, further optimizing the bending resistance of the silver selenide-based composite film, which is more conducive to the application of wearable devices; the preparation process is simple and easy, and the process conditions are low temperature, energy-saving, and environmentally friendly.

[0024] The high thermoelectric performance silver selenide / single-walled carbon nanotube flexible composite film prepared by the preparation method described in the present invention can be used in the fields of semiconductor materials or devices, thermoelectric devices or other micro-nano devices; the single-walled carbon nanotube material with high adhesion, high flexibility and network structure building ability is composited with silver selenide, and the bending resistance is significantly improved. The film also has excellent thermoelectric properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 XRD comparison diagram of the silver selenide / single-walled carbon nanotube composite material and composite film prepared in the present invention;

[0026] Figure 2 Comparison of carrier concentrations between the silver selenide / single-walled carbon nanotube flexible composite film and the silver selenide flexible composite film prepared in the present invention;

[0027] Figure 3 The thermoelectric properties of the silver selenide / single-walled carbon nanotube flexible composite film and the silver selenide flexible composite film prepared by the present invention are compared;

[0028] Figure 4 The conductivity trend diagrams of the silver selenide / single-walled carbon nanotube flexible composite film and the silver selenide flexible composite film prepared in the present invention after being bent for different times with a bending radius of 5 mm are shown. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] The present invention is described in further detail below with reference to the accompanying drawings:

[0032] The present invention provides a high thermoelectric performance silver selenide / single-walled carbon nanotube flexible composite film and a preparation method thereof, comprising the following steps:

[0033] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as a dispersant, and having a concentration range of 0.0125 to 0.05 mol / L;

[0034] Among them, SWCNT powder is a commercial product with the specification of TNSAR type. The specific information is shown in Table 1:

[0035] Table 1 Product specifications of SWCNT powder

[0036]

[0037]

[0038] Step 2): Prepare a reducing agent of ascorbic acid solution with a concentration of 0.05 to 0.1 mol / L, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0039] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0040] Step 4): slowly adding solution B to solution A, magnetically stirring for 5 to 6 hours, then washing the sample four times with distilled water and anhydrous ethanol alternately to obtain a selenium / single-walled carbon nanotube composite; the reducing agent is any one of sodium hydroxide, sodium borohydride, sodium bicarbonate, sodium sulfite, hydrazine and L-ascorbic acid;

[0041] Step 5): The selenium / single-walled carbon nanotube composite prepared in step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, and the reaction time was 4-6 hours. The molar ratio of selenium to silver nitrate was (2-6):1. After the reaction, the sample was washed alternately with distilled water and anhydrous ethanol four times, and dried at 50-70°C for 10-12 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0042] Step 6): The silver selenide / single-walled carbon nanotube composite is dispersed in anhydrous ethanol and ultrasonically subjected to 2 hours. The composite is filtered using a nylon filter membrane as a substrate, and the obtained silver selenide / single-walled carbon nanotube composite film is placed in a vacuum environment and dried at a temperature of 50 to 80° C. for 10 to 15 hours. A porous filter membrane with a pore size of 0.22 μm is selected for the filtration, and the porous filter membrane is any one of nylon, polytetrafluoroethylene, polyethersulfone, and polyvinylidene fluoride.

[0043] Step 7): After taking out the membrane, cold pressing is performed on it, and the pressure is maintained at a pressure of 5 to 30 MPa for 10 to 30 minutes, and then the membrane is heat treated for 30 minutes at a temperature of 200 to 220°C.

[0044] The σ of the composite film prepared by the present invention is about 1666.9S cm -1 ,S is about 107.2μV K -1 , S 2 σ is approximately 1914.5 μW m -1 K -2 .

[0045] Figure 1 This is a comparison of the XRD patterns of silver selenide and a silver selenide / single-walled carbon nanotube composite. The characteristic peaks of both correspond to those of a standard silver selenide card. The XRD pattern of the silver selenide / single-walled carbon nanotube composite does not show the characteristics of single-walled carbon nanotubes. This is because the added content of single-walled carbon nanotubes is relatively low, and the XRD test process cannot capture trace components.

[0046] like Figure 2 As shown, the carrier concentration of the original silver selenide film is 2.06×10 18 cm -3After adding 0.025 mol / L of single-walled carbon nanotubes, the carrier concentration of the silver selenide / single-walled carbon nanotube composite film increased significantly to 13.2×10 18 cm -3 .

[0047] Figure 3 This is a comparison of the thermoelectric properties of the silver selenide film and the silver selenide / single-walled carbon nanotube composite film prepared in Example 1. Since the addition of a small amount of single-walled carbon nanotubes significantly increases the carrier concentration of the film, the conductivity of the composite film is as high as 1656.638 S cm -1 , which is 1.7 times the conductivity of the original silver selenide film, and the power factor of the film is increased from 16.293μWcm -1 K -2 Increased to 19.358 μW cm -1 K -2 .

[0048] Figure 4 : is a comparison chart of the bending resistance of the silver selenide film and the silver selenide / single-walled carbon nanotube composite film prepared in Example 1, as shown in FIG. Figure 4 As shown in the figure, after the silver selenide film was bent 1000 times with a bending radius of 5 mm, the conductivity decreased by 25.58%, while the conductivity of the silver selenide / single-walled carbon nanotube composite film only decreased by 5% under the same bending conditions. The comparison in the figure shows that the addition of single-walled carbon nanotubes can significantly improve the bending resistance of silver selenide-based flexible films.

[0049] Example 1

[0050] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.0125 mol / L;

[0051] Step 2): Prepare an ascorbic acid solution with a concentration of 0.057 mol / L, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0052] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0053] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0054] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 4:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 60°C for 12 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0055] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 60° C. for 12 hours.

[0056] Step 7): After removing the film, cold pressing was performed, maintaining the pressure at 20 MPa for 10 minutes, and then heat treating the film for 30 minutes at a temperature of 200° C. Thus, a silver selenide / single-walled carbon nanotube flexible composite film was obtained.

[0057] Example 2

[0058] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.0125 mol / L;

[0059] Step 2): Prepare a 0.05 mol / L ascorbic acid solution, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0060] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0061] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0062] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 2:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 50°C for 12 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0063] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 50° C. for 15 hours.

[0064] Step 7): After taking out the membrane, cold pressing is performed on it, and the pressure is maintained at 5 MPa for 10 minutes, and then the membrane is heat treated for 30 minutes at a temperature of 200°C.

[0065] Example 3

[0066] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.05 mol / L;

[0067] Step 2): Prepare a 0.1 mol / L ascorbic acid solution, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0068] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0069] Step 4): Solution B was slowly added to solution A, magnetically stirred for 6 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0070] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 6 hours, and the molar ratio of selenium to silver nitrate was 6:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 50°C for 12 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0071] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 50° C. for 12 hours.

[0072] Step 7): After taking out the membrane, cold press it and maintain the pressure at 30 MPa for 10 minutes, then heat treat the membrane for 30 minutes at a temperature of 200°C.

[0073] Example 4

[0074] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.0125 mol / L;

[0075] Step 2): Prepare a 0.05 mol / L ascorbic acid solution, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0076] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0077] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0078] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 6:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 70°C for 10 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0079] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 80° C. for 10 hours.

[0080] Step 7): After taking out the membrane, cold press it and maintain the pressure at 20 MPa for 10 minutes, then heat treat the membrane for 30 minutes at a temperature of 220°C.

[0081] Example 5

[0082] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.02 mol / L;

[0083] Step 2): Prepare a 0.05 mol / L ascorbic acid solution, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0084] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0085] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0086] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 5:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 70°C for 10 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0087] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 60° C. for 10 hours.

[0088] Step 7): After taking out the membrane, it was cold pressed and maintained at a pressure of 20 MPa for 10 minutes, and then the membrane was heat treated for 30 minutes at a temperature of 210°C.

[0089] Example 6

[0090] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.02 mol / L;

[0091] Step 2): Prepare a 0.05 mol / L ascorbic acid solution, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0092] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0093] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0094] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 4:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 70°C for 10 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0095] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 60° C. for 10 hours.

[0096] Step 7): After taking out the membrane, it was cold pressed and maintained at a pressure of 15 MPa for 30 minutes. The membrane was then heat treated for 30 minutes at a temperature of 205°C.

[0097] Example 7

[0098] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration of the dispersion is in the range of 0.025 mol / L;

[0099] Step 2): Prepare an ascorbic acid solution with a concentration of 0.057 mol / L, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0100] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0101] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0102] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 6:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 60°C for 10 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0103] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 60° C. for 10 hours.

[0104] Step 7): After taking out the membrane, cold pressing is performed on it, and the pressure is maintained at 20 MPa for 20 minutes, and then the membrane is heat treated for 30 minutes at a temperature of 200°C.

[0105] Example 8

[0106] Step 1): preparing a dispersion of single-walled carbon nanotubes, using anhydrous ethanol as the dispersant, and the concentration range of the dispersion is 0.0375 mol / L;

[0107] Step 2): Prepare an ascorbic acid solution with a concentration of 0.057 mol / L, stir until clear, and then add the single-walled carbon nanotube dispersion obtained in step 1 to prepare solution A;

[0108] Step 3): Add 1 g of selenium dioxide and 1 g of cyclodextrin to distilled water to prepare solution B;

[0109] Step 4): Solution B was slowly added to solution A, magnetically stirred for 5 h, and then the sample was washed alternately with distilled water and anhydrous ethanol 4 times to collect;

[0110] Step 5): The selenium / single-walled carbon nanotube composite prepared in Step 4 was dispersed in 200 mL of ethylene glycol solution, and then silver nitrate was added under magnetic stirring. The reaction temperature was 40°C, the reaction time was 4 hours, and the molar ratio of selenium to silver nitrate was 4:1. After the reaction, the sample was washed four times alternately with distilled water and anhydrous ethanol, and dried at 60°C for 12 hours to obtain a black silver selenide / single-walled carbon nanotube composite.

[0111] Step 6): The silver selenide / single-walled carbon nanotube composite was dispersed in anhydrous ethanol and ultrasonically filtered for 2 hours. The obtained silver selenide / single-walled carbon nanotube composite film was placed in a vacuum environment and dried at 60° C. for 12 hours.

[0112] Step 7): After taking out the membrane, it was cold pressed and maintained at a pressure of 20 MPa for 10 minutes, and then the membrane was heat treated for 30 minutes at a temperature of 210°C.

[0113] In summary, the present invention provides a silver selenide / single-walled carbon nanotube flexible composite film with high thermoelectric performance and a preparation method thereof. The preparation method of the present invention adopts a solution method to composite silver selenide with single-walled carbon nanotubes; the composite process of silver selenide and single-walled carbon nanotubes affects the growth of silver selenide nanostructures. After adding single-walled carbon nanotubes, the carrier concentration of the material is increased, the electrical conductivity is improved, and the thermoelectric performance of the silver selenide-based film is significantly improved; the σ of the prepared composite film is approximately 1666.9S cm -1 ,S is about 107.2μV K -1 , S 2 σ is approximately 1914.5 μW m -1 K -2 The present invention utilizes the large aspect ratio of single-walled carbon nanotubes to exhibit excellent mechanical properties, further optimizing the bending resistance of the silver selenide-based composite film, further facilitating its application in wearable devices. The high-thermoelectric performance silver selenide / single-walled carbon nanotube flexible composite film produced by the preparation method described herein can be used in fields such as semiconductor materials or devices, thermoelectric devices, and other micro-nano devices.

[0114] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a silver selenide / single-walled carbon nanotube flexible composite film, characterized in that: The following steps are involved: S1: preparing a dispersion of p-type single-walled carbon nanotubes, adding a selenium source, a surface morphology agent, and a reducing agent to the dispersion, and mixing them evenly to synthesize a selenium nanowire / p-type single-walled carbon nanotube composite; S2: using the selenium nanowires in the selenium nanowire / p-type single-walled carbon nanotube composite as a template, dispersing the selenium nanowire / p-type single-walled carbon nanotube composite in an ethylene glycol solution, and then adding silver nitrate to react to obtain an n-type silver selenide / p-type single-walled carbon nanotube composite; S3: dispersing the n-type silver selenide / p-type single-walled carbon nanotube composite in anhydrous ethanol, filtering with a porous filter membrane as a substrate, and vacuum drying to obtain a film; then cold pressing and heat treating to obtain an n-type silver selenide / p-type single-walled carbon nanotube flexible composite film; In S1, the dispersion of the single-walled carbon nanotubes uses anhydrous ethanol as a dispersant; the concentration of the dispersion of the single-walled carbon nanotubes is 0.0125-0.05 mol / L.

2. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S1, the selenium source is selenium dioxide; the surface morphogen is cyclodextrin; the reducing agent is any one of sodium hydroxide, sodium borohydride, sodium bicarbonate, sodium sulfite, hydrazine and L-ascorbic acid; the reducing agent is configured as a reducing agent solution, and the concentration of the reducing agent solution is 0.05~0.1 mol / L.

3. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S1, the uniform mixing process is stirring at room temperature for 5 to 6 hours.

4. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S2, the molar ratio of the selenium nanowires to silver nitrate is (2-6):1; in S2, the reaction temperature of the selenium nanowires and silver nitrate is 40°C, and the reaction time is 4-6 h.

5. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S3, a porous filter membrane with a pore size of 0.22 μm is selected for filtration, and the porous filter membrane is any one of nylon, polytetrafluoroethylene, polyethersulfone, and polyvinylidene fluoride.

6. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S3, the vacuum drying temperature is 50-80 ° C, and the vacuum drying time is 10-15 h.

7. The method for preparing a silver selenide / single-walled carbon nanotube flexible composite film according to claim 1, characterized in that: In S3, the cold pressing pressure is 5-30 MPa, and the cold pressing holding time is 10-30 min; the heat treatment temperature is 200-220 °C, and the heat treatment time is 30 min.

8. A silver selenide / single-walled carbon nanotube flexible composite film prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the silver selenide / single-walled carbon nanotube flexible composite film prepared by the preparation method according to any one of claims 1 to 7 in semiconductor materials and flexible electronic devices.

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