An N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof

Abstract

The present invention discloses an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof. The preparation method includes the steps of: preparing a Bi2Te y thin film by magnetron sputtering, wherein 2.5 ≤ y ≤ 3.5; preparing a Se thin film by thermal evaporation; laminating the Bi2Te y thin film and the Se thin film and performing heat treatment to sublime Se in the Se thin film and diffuse it into the Bi2Te y thin film to obtain an N-type Bi-Te-Se-based thermoelectric thin film. In the present invention, the Bi2Te y thin film prepared by magnetron sputtering has good quality and uniform composition. The Se thin film prepared by thermal evaporation has a lower density, which is more conducive to subsequent sublimation and diffusion. By using magnetron sputtering and thermal evaporation in combination, uniform doping of Se, Se doping and heat treatment are carried out simultaneously, avoiding the loss of Te and Se, and no defects are generated. An N-type Bi-Te-Se-based thermoelectric thin film with controllable and uniform composition and high electrical transport performance is prepared. The N-type Bi-Te-Se-based thermoelectric thin film in the present invention has high quality, good thermoelectric performance and good repeatability, and can be produced in large areas.

Description

Technical Field

[0001] The present invention relates to the field of thermoelectric materials, and particularly to an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof. Background Art

[0002] Thermoelectric materials can directly convert thermal energy and electrical energy into each other. Thermoelectric devices made of thermoelectric materials have the advantages of no pollution, long life, less maintenance, no noise, etc., and are widely used in fields such as thermoelectric power generation and thermoelectric refrigeration. Compared with bulk materials, low-dimensional thermoelectric thin films have more interfaces, which can enhance phonon scattering in the material to obtain low thermal conductivity and high thermoelectric figure of merit. As the thermoelectric material with the best room-temperature performance, the research on Bi 2 Te 3 -based thin films is a hot topic in the thermoelectric field. The performance of currently reported P-type bismuth telluride thin films has reached a relatively high level. There is an urgent need for high-performance N-type bismuth telluride-based thin films to match them and form corresponding thermoelectric devices to improve the energy conversion efficiency. However, in the existing technology, Te and Se are lost during the annealing process of Bi-Te-Se-based thin films, resulting in composition deviation, defects in the thin films, and affecting the thermoelectric performance of the materials.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above deficiencies of the existing technology, the purpose of the present invention is to provide an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof, aiming to solve the problem that Te and Se are lost during the annealing process of existing Bi-Te-Se-based thin films, resulting in composition deviation and thus affecting the thermoelectric performance of the materials.

[0005] The technical solution of the present invention is as follows:

[0006] In the first aspect of the present invention, a preparation method of an N-type Bi-Te-Se-based thermoelectric thin film is provided, which includes the steps of:

[0007] Preparing a Bi 2 Te y thin film by magnetron sputtering, where 2.5 ≤ y ≤ 3.5;

[0008] Preparing a Se thin film by thermal evaporation;

[0009] Laminating the Bi 2 Te y thin film and the Se thin film and performing heat treatment to sublime and diffuse Se in the Se thin film into the Bi 2 Te y thin film to obtain the N-type Bi-Te-Se-based thermoelectric thin film.

[0010] Optionally, the specific steps for preparing the Bi 2 Te y thin film by magnetron sputtering method include:

[0011] Provide a first substrate;

[0012] Put the first substrate into a magnetron sputtering device and perform magnetron sputtering with a Bi 2 Te y target to prepare a Bi 2 Te y thin film on the first substrate.

[0013] Optionally, the parameters of the magnetron sputtering are set as follows: the power is 10W - 40W.

[0014] Optionally, the specific steps for preparing the Se thin film by thermal evaporation method include:

[0015] Provide a second substrate;

[0016] Put the second substrate into a thermal evaporation device and perform thermal evaporation with Se powder as the Se source to prepare a Se thin film on the second substrate.

[0017] Optionally, the parameters of the thermal evaporation are set as follows: the evaporation current is 10A - 80A, and the mass of Se powder is 0.05g - 0.5g.

[0018] Optionally, the specific steps for laminating the Bi 2 Te y thin film and the Se thin film and performing heat treatment to sublime Se in the Se thin film and diffuse it into the Bi 2 Te y thin film to obtain the N-type Bi-Te-Se-based thermoelectric thin film include:

[0019] Laminating the Bi 2 Te y thin film on the first substrate and the Se thin film on the second substrate, and performing heat treatment at a temperature of 100 - 400°C for 0 - 300 min to sublime Se in the Se thin film and diffuse it into the Bi 2 Te y thin film to prepare the N-type Bi-Te-Se-based thermoelectric thin film on the first substrate.

[0020] Optionally, the thickness of the Se thin film is 40 - 250 nm.

[0021] Optionally, the Bi 2 Te yThe thickness of the thin film is 0.1 μm to 5 μm.

[0022] Optionally, the thickness of the Se thin film is 80 to 130 nm, and the 2 Te y thin film has a thickness of 900 nm.

[0023] In a second aspect of the present invention, an N-type Bi-Te-Se-based thermoelectric thin film is provided, which is prepared by using the preparation method as described above in the present invention. The molar ratio of Bi, Te, and Se in the N-type Bi-Te-Se-based thermoelectric thin film is 2:(2.5 to 3.5):(0.1 to 2.0).

[0024] Beneficial effects: The present invention provides an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof. In the present invention, the Bi 2 Te y thin film prepared by magnetron sputtering has good quality and uniform composition. The Se thin film with lower density is prepared by thermal evaporation method, which is more conducive to subsequent sublimation and diffusion. Then, the Bi 2 Te y thin film and the Se thin film are attached and heat-treated. The Se thin film serves as a selenium source, sublimes at high temperature and diffuses into the Bi 2 Te y thin film to prepare the N-type Bi-Te-Se-based thermoelectric thin film. In the present invention, an N-type Bi-Te-Se-based thermoelectric thin film with controllable and uniform composition and high electrical transport performance is prepared by the combined use of magnetron sputtering method and thermal evaporation method; and the uniform doping of Se is realized by the combined use of magnetron sputtering method and thermal evaporation method. The Se doping and heat treatment are carried out simultaneously, avoiding the loss of Te and Se, and no defects are generated in the thin film. The N-type Bi-Te-Se-based thermoelectric thin film prepared by the present invention has high quality, good thermoelectric performance and good repeatability, and can be produced in large areas. Description of the Drawings

[0025] Figure 1 It is a preparation flow chart of the N-type Bi-Te-Se-based thermoelectric thin film in the embodiment of the present invention.

[0026] Figure 2 It is a preparation schematic diagram of the N-type Bi-Te-Se-based thermoelectric thin film in another embodiment of the present invention. Among them, (a) is a preparation schematic diagram of the Bi 2 Te 3 thin film prepared by magnetron sputtering, (b) is a preparation schematic diagram of the Se thin film prepared by thermal evaporation method, (c) is a schematic diagram of heat treatment, and (d) is a schematic diagram of obtaining the N-type Bi-Te-Se-based thermoelectric thin film.

[0027] Figure 3XRD patterns of Examples 1-4 and Comparative Example 1 of the present invention.

[0028] Figure 4 Among them, (a) is the SEM image of BT in Comparative Example 1 of the present invention, (b) is the SEM image of BT-40Se in Example 1 of the present invention, (c) is the SEM image of BT-80Se in Example 2 of the present invention, (d) is the SEM image of BT-130Se in Example 3 of the present invention, (e) is the SEM image of BT-250Se in Example 4 of the present invention, and (f) is the energy spectrum image of BT-80Se in Example 2 of the present invention.

[0029] Figure 5 Among them, (a) is the conductivity test result graph of Examples 1-4 and Comparative Example 1 of the present invention; (b) is the Seebeck coefficient test result graph of Examples 1-4 and Comparative Example 1 of the present invention; (c) is the power factor test result graph of Examples 1-4 and Comparative Example 1 of the present invention; (d) is the Hall test result graph of Examples 1-4 and Comparative Example 1 of the present invention. Detailed implementation manners

[0030] The present invention provides an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof. To make the purpose, technical solution and effect of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] An embodiment of the present invention provides a preparation method of an N-type Bi-Te-Se-based thermoelectric thin film, and its preparation flow chart is as Figure 1 shown, wherein, it includes the steps:

[0032] Prepare a Bi 2 Te y thin film by magnetron sputtering method, wherein, 2.5 ≤ y ≤ 3.5;

[0033] Prepare a Se thin film by thermal evaporation method;

[0034] Bond the Bi 2 Te y thin film and the Se thin film and perform heat treatment, so that Se in the Se thin film sublimes and diffuses into the Bi 2 Te y thin film to obtain the N-type Bi-Te-Se-based thermoelectric thin film.

[0035] In this embodiment, the Bi 2 Te y thin film prepared by magnetron sputtering method has good quality and uniform composition. The Se thin film prepared by thermal evaporation method has a lower density, which is more conducive to subsequent sublimation and diffusion. Then, the Bi2 Te y The Te thin film and the Se thin film are laminated and heat-treated. The Se thin film serves as a selenium source, sublimes at high temperature and diffuses into the Bi 2 Te y thin film, and the N-type Bi-Te-Se-based thermoelectric thin film is prepared. In the present invention, the N-type Bi-Te-Se-based thermoelectric thin film with controllable composition, uniformity and high electrical transport performance is prepared by the combined use of magnetron sputtering method and thermal evaporation method; and the uniform doping of Se is realized by the combined use of magnetron sputtering method and thermal evaporation method. The Se doping and heat treatment are carried out simultaneously, avoiding the loss of Te and Se, and making the thin film defect-free. The N-type Bi-Te-Se-based thermoelectric thin film prepared by the present invention has high quality, good thermoelectric performance and good repeatability, and can be produced in large areas. Further, in this embodiment, the content of Te in the Bi 2 Te y thin film and the thickness of the Se thin film can be adjusted to optimize the process of the N-type Bi-Te-Se-based thermoelectric thin film.

[0036] In one embodiment, as shown in (a) of Figure 2 , the specific steps for preparing the Bi 2 Te y thin film by magnetron sputtering method include:

[0037] Provide a first substrate;

[0038] Put the first substrate into a magnetron sputtering device, and perform magnetron sputtering with a Bi 2 Te y target to prepare a Bi 2 Te y thin film on the first substrate.

[0039] In one embodiment, the parameters of the magnetron sputtering are set as: the power is 10W - 40W. These parameters can realize the preparation of a Bi 2 Te y thin film with high density and low density defects.

[0040] In one embodiment, as shown in (b) of Figure 2 , the specific steps for preparing the Se thin film by thermal evaporation method include:

[0041] Provide a second substrate;

[0042] Put the second substrate into a thermal evaporation device, and perform thermal evaporation with Se powder as the Se source to prepare a Se thin film on the second substrate.

[0043] In one embodiment, the parameters of the thermal evaporation are set as follows: the evaporation current is 10 A to 40 A, and the mass of the Se powder is 0.05 g to 0.5 g. These parameters can effectively achieve uniform film formation of the Se film and control of the film thickness.

[0044] In one embodiment, as Figure 2 shown in (c) and (d) therein, the step of laminating the Bi 2 Te y film and the Se film and performing heat treatment to sublime Se in the Se film and diffuse it into the Bi 2 Te y film to obtain the N-type Bi-Te-Se-based thermoelectric film specifically includes:

[0045] Laminating the Bi 2 Te y film on the first substrate and the Se film on the second substrate, and performing heat treatment at a temperature of 100 to 400 °C for 0 to 300 min to sublime Se in the Se film and diffuse it into the Bi 2 Te y film, and preparing the N-type Bi-Te-Se-based thermoelectric film on the first substrate.

[0046] In this embodiment, heat is transferred from the second substrate to the Se film, causing Se in the Se film to sublime and detach from the second substrate and diffuse into the Bi 2 Te y film, realizing doping of Bi 2 Te y to obtain the N-type Bi-Te-Se-based thermoelectric film. In this embodiment, in order to further avoid loss of Te and Se, after laminating the Bi 2 Te y film on the first substrate and the Se film on the second substrate, the first substrate and the second substrate are connected and fixed with glue, and then wrapped with aluminum foil paper, thereby realizing close-range diffusion of Se in a closed space. That is, sealant is poured into the corresponding positions of the first substrate and the second substrate without films to connect the first substrate and the second substrate, and then the composite film with the structure of the first substrate - Bi 2 Te y film - Se film - second substrate is wrapped with aluminum foil paper.

[0047] In one embodiment, the first substrate can be selected from a glass substrate, and the second substrate can also be selected from a glass substrate, but is not limited thereto.

[0048] In one embodiment, the thickness of the Se film is 40 to 250 nm.

[0049] In this embodiment, different Se doping amounts can be achieved by the thickness of the Se thin film.

[0050] In one embodiment, the thickness of the Bi 2 Te y thin film is 0.1 μm to 5 μm.

[0051] In one embodiment, the thickness of the Se thin film is 80 to 130 nm, and the thickness of the Bi 2 Te y thin film is 900 nm. In this embodiment, when the thickness of the Se thin film is 80 to 130 nm and the thickness of the Bi 2 Te y thin film is 900 nm, the prepared N-type Bi-Te-Se-based thermoelectric thin film has the optimal electrical transport performance.

[0052] In the second aspect of the present invention, an N-type Bi-Te-Se-based thermoelectric thin film is provided, which is prepared by the preparation method as described above in the present invention. The molar ratio of Bi, Te, and Se in the Bi-Te-Se-based thermoelectric thin film is 2:(2.5 - 3.5):(0.1 - 2.0).

[0053] The present invention will be further described below through specific examples.

[0054] Example 1

[0055] Using a 2 cm × 2 cm glass as the substrate, magnetron sputtering is carried out with a Bi 2 Te 3 target. The magnetron sputtering parameters are set as follows: the power is 30 W, and a Bi 2 Te 3 thin film with a thickness of 900 nm is prepared on the glass substrate.

[0056] Using a 2 cm × 2 cm glass as the substrate, thermal evaporation is carried out with Se powder as the Se source. The thermal evaporation parameters are set as follows: the evaporation current is 20 A, the mass of Se powder is 0.05 g, and a Se thin film with a thickness of 40 nm is prepared on the glass substrate.

[0057] The Bi 2 Te 3 thin film on the glass substrate and the Se thin film on the glass substrate are arranged face to face (the inner side is the Bi 2 Te 3 thin film and the Se thin film, and the outer side is two glass substrates, specifically as shown in Figure 2As shown in (c), after sealing the gap between the two outer glass substrates with sealant and wrapping them with aluminum foil, heat treatment is carried out at a temperature of 300 °C for 40 min to obtain an N-type Bi-Te-Se-based thermoelectric thin film, denoted as BT-40Se.

[0058] Example 2

[0059] Bi 2 Te 3 The preparation of the thin film is the same as that in Example 1.

[0060] Using a 2 cm × 2 cm glass as the substrate, Se powder is used as the Se source for thermal evaporation. The parameters of thermal evaporation are set as follows: the evaporation current is 20 A, the mass of Se powder is 0.1 g, and a Se thin film with a thickness of 80 nm is prepared on the glass substrate.

[0061] The Bi 2 Te 3 thin film on the glass substrate and the Se thin film on the glass substrate are arranged face-to-face (the inner side is the Bi 2 Te 3 thin film and the Se thin film, and the outer side is two glass substrates, specifically as shown in Figure 2 (c)), after sealing the gap between the two outer glass substrates with sealant and wrapping them with aluminum foil, heat treatment is carried out at a temperature of 325 °C for 40 min to obtain an N-type Bi-Te-Se-based thermoelectric thin film, denoted as BT-80Se.

[0062] Example 3

[0063] Bi 2 Te 3 The preparation of the thin film is the same as that in Example 1.

[0064] Using a 2 cm × 2 cm glass as the substrate, Se powder is used as the Se source for thermal evaporation. The parameters of the thermal evaporation current are set as follows: the evaporation current is 20 A, the mass of Se powder is 0.15 g, and a Se thin film with a thickness of 130 nm is prepared on the glass substrate.

[0065] The Bi 2 Te 3 thin film on the glass substrate and the Se thin film on the glass substrate are arranged face-to-face (the inner side is the Bi 2 Te 3 thin film and the Se thin film, and the outer side is two glass substrates, as shown in Figure 2 (c)), after sealing the gap between the two outer glass substrates with sealant and wrapping them with aluminum foil, heat treatment is carried out at a temperature of 325 °C for 40 min to obtain an N-type Bi-Te-Se-based thermoelectric thin film, denoted as BT-130Se.

[0066] Example 4

[0067] Bi 2 Te 3 The preparation of the thin film was the same as that in Example 1.

[0068] Using a 2 cm × 2 cm glass as the substrate, Se powder was used as the Se source for thermal evaporation. The parameters of thermal evaporation were set as follows: the evaporation current was 20 A, the mass of Se powder was 0.35 g, and a Se thin film with a thickness of 250 nm was prepared on the glass substrate.

[0069] The Bi 2 Te 3 thin film on the glass substrate was arranged face-to-face with the Se thin film on the glass substrate (the inner side was the Bi 2 Te 3 thin film and the Se thin film, and the outer side was two glass substrates, as specifically shown in Figure 2 (c)), and the gap between the two outer glass substrates was sealed with a sealant and then wrapped with aluminum foil paper. After heat treatment at a temperature of 325 °C for 40 min, an N-type Bi-Te-Se-based thermoelectric thin film was obtained, denoted as BT-250Se.

[0070] Comparative Example 1

[0071] Using a 2 cm × 2 cm glass as the substrate, magnetron sputtering was carried out with a Bi 2 Te 3 target and heat treatment was carried out at a temperature of 325 °C for 40 min. The parameters of magnetron sputtering were set as follows: the power was 30 W, and a Bi 2 Te 3 thin film with a thickness of 900 nm was prepared on the glass substrate. It was denoted as BT-A.

[0072] Comparative Example 2

[0073] Using a 2 cm × 2 cm glass as the substrate, magnetron sputtering was carried out with a Bi 2 Te 3 target. The parameters of magnetron sputtering were set as follows: the power was 30 W, and a Bi 2 Te 3 thin film with a thickness of 900 nm was prepared on the glass substrate, denoted as Bi 2 Te 3 .

[0074] XRD tests were carried out on the samples in Examples 1-4 and Comparative Example 1, and the results were as shown in Figure 3 . The main phase of each thin film was Bi 2 Te 3 . The peak shape was sharp, the crystal form was good, there were no impurity peaks, and the quality of the prepared thin film was good.

[0075] The samples in Examples 1-4 and Comparative Example 1 were subjected to SEM testing and energy spectrum testing, and the results are as Figure 4 shown. It can be seen that the morphology is good and the particle size is uniform. Among them, (f) is the energy spectrum diagram of BT-80Se in Example 2, and it can be seen that the elements are uniformly distributed in the thin film. Using energy spectrum testing, the molar ratios of various elements in different thin films (Examples 1-4 and Comparative Examples 1-2) are shown in Table 1 below.

[0076] Table 1. Molar ratios of various elements in different thin films

[0077]

[0078] The samples in Examples 1-4 and Comparative Example 1 were subjected to thermoelectric performance testing (electrical conductivity, Seebeck coefficient and power factor), and the results are as Figure 5 (a) to (c) in. It can be seen from the figure that all the samples are N-type. As the thickness of the Se thin film increases, the electrical conductivity σ gradually decreases. When the thickness of the Se thin film is 40 and 80 nm, it has a better Seebeck coefficient S, and the doping of Se can improve the 2 Te 3 Seebeck coefficient of. When the thickness of the Se thin film is 80 nm, it has the optimal power factor.

[0079] The samples in Examples 1-4 and Comparative Example 1 were subjected to Hall testing, and the results are as Figure 5 (d) in. When the thickness of the Se thin film is 80 nm, it has the optimal mobility μ.

[0080] In summary, the present invention provides an N-type Bi-Te-Se-based thermoelectric thin film and a preparation method thereof. In the present invention, the Bi 2 Te y thin film prepared by magnetron sputtering has good quality and uniform composition. The Se thin film with a lower density is prepared by thermal evaporation method, which is more conducive to subsequent sublimation and diffusion. Then, the Bi 2 Te y thin film and the Se thin film are attached and heat-treated. The Se thin film is used as a selenium source, which sublimes and diffuses into Bi 2 Te yIn the thin film, the N-type Bi-Te-Se-based thermoelectric thin film is prepared. In the present invention, by using magnetron sputtering method and thermal evaporation method in combination, an N-type Bi-Te-Se-based thermoelectric thin film with controllable composition, uniformity and high electrical transport performance is prepared; and uniform doping of Se is realized by using magnetron sputtering method and thermal evaporation method in combination. Se doping and heat treatment are carried out simultaneously, avoiding the loss of Te and Se, resulting in no defects in the thin film, and solving the problem that Te and Se are lost during the annealing process of Bi-Te-Se-based thin films in the prior art, causing composition deviation, resulting in defects in the thin film and affecting the thermoelectric performance of the material. The N-type Bi-Te-Se-based thermoelectric thin film prepared by the present invention has high quality, good thermoelectric performance and good repeatability, and can be produced in large areas.

[0081] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for preparing an N-type Bi-Te-Se-based thermoelectric thin film, characterized in that, it includes the steps of: Bi is prepared on a first substrate by magnetron sputtering method 2 Te y thin film, where 2.5 ≤ y ≤ 3.5; preparing a Se thin film on a second substrate by thermal evaporation; Attach the Bi 2 Te y thin film on the first substrate and the Se thin film on the second substrate, seal the gap between the first substrate and the second substrate with sealant, and then perform heat treatment at a temperature of 300-325 °C to sublime the Se in the Se thin film and diffuse it into the Bi 2 Te y thin film to obtain the N-type Bi-Te-Se-based thermoelectric thin film.

2. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 1, characterized in that, The specific steps of preparing the Bi 2 Te y thin film on the first substrate by magnetron sputtering method include: providing a first substrate; Place the first substrate into a magnetron sputtering device and perform magnetron sputtering using a Bi 2 Te y target to prepare a Bi 2 Te y thin film on the first substrate.

3. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 2, characterized in that, the parameters of the magnetron sputtering are set as follows: the power is 10W - 40W.

4. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 2, characterized in that, the specific steps of preparing the Se thin film on the second substrate by thermal evaporation include: providing a second substrate; putting the second substrate into a thermal evaporation device, using Se powder as the Se source for thermal evaporation, and preparing a Se thin film on the second substrate.

5. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 4, characterized in that, the parameters of the thermal evaporation are set as follows: the evaporation current is 10A - 80A, and the mass of the Se powder is 0.05g - 0.5g.

6. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 4, characterized in that, the heat treatment time is 0 - 300 min, and the heat treatment time does not take 0.

7. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 1, characterized in that, the thickness of the Se thin film is 40 - 250 nm.

8. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 1, characterized in that, The Bi 2 Te y thin film has a thickness of 0.1 μm to 5 μm.

9. The method for preparing an N-type Bi-Te-Se-based thermoelectric thin film according to claim 1, characterized in that, The thickness of the Se thin film is 80 to 130 nm, and the 2 Te y thin film has a thickness of 900 nm.

10. An N-type Bi-Te-Se-based thermoelectric thin film, characterized in that, it is prepared by using the preparation method described in any one of claims 1 - 9, and the molar ratio of Bi, Te, and Se in the N-type Bi-Te-Se-based thermoelectric thin film is 2:(2.5 - 3.5):(0.1 - 2.0).

Images