Cadmium telluride target material and preparation method thereof

Abstract

The invention belongs to the field of solar cells, and discloses a preparation method of a cadmium telluride target material, which comprises the following preparation steps: mixing cadmium telluride and cuprous telluride, then loading into a mold, and pre-pressing and vacuumizing a vacuum pipe to obtain a blank body; and then the blank is subjected to vacuum sintering, heat preservation, pressurization and cooling, and the cadmium telluride target material is obtained. According to the method, the cadmium telluride powder and the cuprous telluride which are distributed according to a certain proportion gradient are combined, so that the resistivity in the prepared cadmium telluride target material is reduced, and the conductivity of the cadmium telluride film in the subsequent use process is improved; in addition, the invention also discloses the cadmium telluride target material which is prepared by the method.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a cadmium telluride target material and a preparation method thereof. Background Art

[0002] In the field of new energy technology, solar cells are increasingly used, and the industry is constantly pursuing low-cost manufacturing of solar cells, so as to achieve large-scale and widespread application of solar cells. Among them, thin-film solar cells have good prospects in terms of low cost characteristics compared to single-crystal silicon or polycrystalline silicon solar cells. Therefore, thin-film solar cells are continuously studied and commercialized, among which cadmium telluride thin-film solar cells are widely used.

[0003] However, the relative density and other properties of the CdTe target will affect the contact resistance with other electrode materials, thereby affecting battery performance.

[0004] Chinese patent application 201610836897.0 discloses a cadmium zinc telluride target material and its preparation method and application. The preparation method comprises: uniformly mixing cadmium telluride powder, zinc telluride powder and cuprous telluride powder to obtain a mixed powder; and then vacuum hot pressing and sintering the mixed powder to obtain a cadmium zinc telluride target material with high density and good mechanical properties.

[0005] In this solution, the particle sizes of cadmium telluride powder and zinc telluride powder are both less than 100 mesh, the particle size of cuprous telluride powder is less than 325 mesh, and its content in the cadmium zinc telluride target is 250 mg / kg to 330 mg / kg.

[0006] Chinese patent application 202210584839.9 discloses a method for preparing a conductive cadmium telluride target material, and the preparation method is: first mix Cd powder and CdTe powder to obtain a mixed material; then load the mixed material into a graphite mold, and place it in a hot press furnace for pre-pressing; after the pre-pressing is completed, evacuate the mixture until the vacuum degree is <10pa, and then start heating and heating at a heating rate of 10-20℃ / min. After heating to 500-750℃, keep warm; after the insulation time is reached, pressurize the target material; after the pressurization treatment, cool it to room temperature, take it out of the furnace, demold it, and obtain a blank target material. The blank target material is processed by machine tools to obtain a conductive cadmium telluride target material.

[0007] In this scheme, free cadmium is doped to destroy the crystallization mode of cadmium telluride, reduce the resistivity of the cadmium telluride target, and improve the conductivity of the cadmium telluride film.

[0008] The problem that this proposal needs to solve: How to propose a method for preparing high-density cadmium telluride targets. Summary of the invention

[0009] The purpose of this application is to propose a cadmium telluride target material and a preparation method thereof, by adding a certain proportion of cadmium telluride and cuprous telluride for mixed sintering, thereby increasing the relative density of the cadmium telluride target material, thereby reducing the contact resistance between cadmium telluride and other electrode materials, and improving battery performance.

[0010] To achieve the above object, the present application discloses a method for preparing a cadmium telluride target, which comprises the following steps:

[0011] Step 1: mixing cadmium telluride and cuprous telluride to obtain a mixture;

[0012] Step 2: Load the mixed material into the mold, pre-press it, and evacuate it to obtain the embryo body;

[0013] Step 3: vacuum sintering the embryo, keeping the temperature under pressure, and cooling the embryo to obtain a cadmium telluride target;

[0014] Wherein, in step 1, the cadmium telluride is composed of powder 1 and powder 2;

[0015] The mesh number of the powder 1 is 150-200 meshes, and the mesh number of the powder 2 is greater than 200 meshes;

[0016] The mass ratio of the powder 1 to the powder 2 is 0.5-3:0.5-3;

[0017] The mass ratio of cadmium telluride to cuprous telluride is 95-98:2-5.

[0018] Further preferably, the mass ratio of powder one to powder two is 0.8-1.2:0.8-1.2, including but not limited to 0.8:0.8, 0.8:0.9, 0.8:1.0, 0.8:1.1, 0.8:1.2, 0.9:0.8, 0.9:0.9, 0.9:1.0, 0.9:1.1, 0.9:1.2, 1.0:0.8, 1.0:0.9, 1.0:1.0, 1.0:1.1, 1.0:1.2, 1.1:0.8, 1.1:0.9, 1.1:1.0, 1.1:1.1, 1.1:1.2, 1.2:0.8, 1.2:0.9, 1.2:1.0, 1.2:1.1, 1.2:1.2.

[0019] Preferably, the powder mesh size of cuprous telluride in step 1 is greater than 325 meshes.

[0020] Preferably, the vacuum degree of the vacuum environment in step 2 is below 10 Pa.

[0021] Preferably, in step 2, the pre-pressing pressure is 20 to 30T, and the pre-pressing time is 10 to 15 minutes.

[0022] Preferably, the vacuum sintering in step 3 is specifically as follows: heating the temperature to 650-750° C. at a heating rate of 5-10° C. / min, and then keeping the temperature for 55-65 min.

[0023] Preferably, the heat preservation and pressurization in step 3 are specifically as follows: after the sintering and heat preservation are completed, the pressure is increased to 60-70°C, the pressure is maintained for 20-30 minutes, and then the heat preservation and pressure are maintained for 50-60 minutes.

[0024] In addition, the present application also discloses a cadmium telluride target material, which is prepared by any of the above-mentioned methods for preparing the cadmium telluride target material.

[0025] The beneficial effects of this application are:

[0026] The present application provides a method for preparing a cadmium telluride target. By adding cadmium telluride composed of two powders with a mesh size of 150 to 200 and a mesh size greater than 200 in a certain mass ratio, and mixing and sintering with cuprous telluride, the particle size distribution will affect the migration of the grain boundaries. During the sintering process, the grain boundaries will migrate in the direction of low energy to reduce the total energy of the system. If the particle size distribution is uneven, the grain boundary migration may be hindered, resulting in insufficient sintering and reducing the target density. The appropriate particle size distribution can make the grain boundary migration smoother and promote the growth and fusion of grains. Therefore, the relative density of the cadmium telluride target can be increased by mixing with different mesh sizes, thereby reducing the contact resistance between cadmium telluride and other electrode materials and improving battery performance. DETAILED DESCRIPTION

[0027] In the description of this application, it should be noted that if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0028] Example 1

[0029] Step 1: mixing cadmium telluride and cuprous telluride in a mass ratio of 96.5:3.5 to obtain a mixture;

[0030] Step 2: Load the mixture into the mold, pre-press at 25T for 12 minutes, and evacuate to below 10Pa to obtain the embryo body;

[0031] Step 3: The embryo body is heated to 700°C at 8°C / min and kept at this temperature for 60 minutes for sintering, then pressurized to 65°C and kept at this temperature for 25 minutes, then kept at this temperature and pressure for another 55 minutes, and finally cooled to room temperature to obtain a cadmium telluride target;

[0032] Wherein, the cadmium telluride in step 1 is composed of powder 1 and powder 2, the average mesh number of powder 1 is 170 mesh, and the mesh number of powder 1 is within 150-200 mesh; the average mesh number of powder 2 is 250 mesh, and the mesh number of powder 2 is greater than 200 mesh;

[0033] The mass ratio of the powder 1 to the powder 2 is 1:1;

[0034] The mesh number of the cuprous telluride is 350 meshes.

[0035] Example 2

[0036] Step 1: mixing cadmium telluride and cuprous telluride in a mass ratio of 96.5:3.5 to obtain a mixture;

[0037] Step 2: put the mixed material into the mold, pre-press at 20T for 10 minutes, and evacuate to below 10Pa to obtain the embryo body;

[0038] Step 3: The embryo body is heated to 650°C at a rate of 5°C / min and kept at that temperature for 55 minutes for sintering, and then pressurized to 60°C and kept at that temperature for 20 minutes, and then kept at that temperature and pressure for another 50 minutes, and finally cooled to obtain a cadmium telluride target;

[0039] Wherein, the cadmium telluride in step 1 is composed of powder 1 and powder 2, the average mesh number of powder 1 is 170 mesh, and the mesh number of powder 1 is within 150-200 mesh; the average mesh number of powder 2 is 250 mesh, and the mesh number of powder 2 is greater than 200 mesh;

[0040] The mass ratio of the powder 1 to the powder 2 is 1:1;

[0041] The mesh number of the cuprous telluride is 350 meshes.

[0042] Example 3

[0043] Step 1: mixing cadmium telluride and cuprous telluride in a mass ratio of 96.5:3.5 to obtain a mixture;

[0044] Step 2: Load the mixture into the mold, pre-press at 30T for 15 minutes, and evacuate to below 10Pa to obtain the embryo body;

[0045] Step 3: The embryo body is sintered by heating the temperature to 750°C at a rate of 10°C / min and maintaining the temperature for 65 minutes, then pressurized to 70°C and maintained at the pressure for 30 minutes, then maintained at the temperature for another 60 minutes, and finally cooled to obtain a cadmium telluride target;

[0046] Wherein, the cadmium telluride in step 1 is composed of powder 1 and powder 2, the average mesh number of powder 1 is 170 mesh, and the mesh number of powder 1 is within 150-200 mesh; the average mesh number of powder 2 is 250 mesh, and the mesh number of powder 2 is greater than 200 mesh;

[0047] The mass ratio of the powder 1 to the powder 2 is 1:1;

[0048] The mesh number of the cuprous telluride is 350 meshes.

[0049] Example 4

[0050] The method is substantially the same as Example 1, except that in step 1, the mass ratio of cadmium telluride to cuprous telluride is 95:5.

[0051] Example 5

[0052] The method is substantially the same as Example 1, except that in step 1, the mass ratio of cadmium telluride to cuprous telluride is 98:2.

[0053] Example 6

[0054] The method is basically the same as Example 1, except that the mass ratio of powder 1 to powder 2 in cadmium telluride in step 1 is 0.8:1.2.

[0055] Example 7

[0056] The method is basically the same as Example 1, except that the mass ratio of powder 1 to powder 2 in cadmium telluride in step 1 is 1.2:0.8.

[0057] Example 8

[0058] The method is basically the same as Example 1, except that the mesh size of the cuprous telluride in step 1 is 300 meshes.

[0059] Comparative Example 1

[0060] The method is basically the same as Example 1, except that cuprous telluride is not added in step 1.

[0061] Comparative Example 2

[0062] The method is substantially the same as Example 1, except that in step 1, the mass ratio of cadmium telluride to cuprous telluride is 94:6.

[0063] Comparative Example 3

[0064] The method is substantially the same as Example 1, except that in step 1, the mass ratio of cadmium telluride to cuprous telluride is 98.5:1.5.

[0065] Comparative Example 4

[0066] It is basically the same as Example 1, except that the average mesh size of the cadmium telluride powder in step 1 is 210 meshes, and the mesh size of the cadmium telluride powder is greater than 150 meshes, without step distribution.

[0067] Comparative Example 5

[0068] The method is basically the same as Example 1, except that the average mesh size of the powder 1 in the cadmium telluride in step 1 is 170 meshes, and the powder 1 is composed of the following powders:

[0069] 99wt% of the powder has a mesh size of 150-200 mesh;

[0070] 1wt% of powder with mesh size of 120 to 150 mesh.

[0071] Comparative Example 6

[0072] It is basically the same as Example 1, except that in step 1, the cadmium telluride is entirely composed of powder 1, and the average mesh size of powder 1 is 170 meshes.

[0073] Comparative Example 7

[0074] The method is basically the same as Example 1, except that the cadmium telluride in step 1 is entirely composed of powder 2, and the average mesh size of powder 2 is 250 meshes.

[0075] Performance Testing

[0076] Density: The relative density of the cadmium telluride targets prepared in the examples and comparative examples was tested by the Archimedean drainage method.

[0077] Resistivity: The four-probe method is used to test the resistivity of the target materials of the embodiments and comparative examples. It is used to measure low-resistivity and high-resistivity materials. The measurement range is (0.0001-19000 ohm·cm) and it is relatively accurate. The resistivity is very good when it is <8000 ohm·cm, and the conductivity is relatively good.

[0078] The performance test results are shown in Table 1:

[0079] Table 1

[0080]

[0081]

[0082] Conclusion analysis:

[0083] 1. It can be seen from Example 1, Examples 4-5, and Comparative Examples 1-3 that in Example 1, the mass ratio of cadmium telluride to cuprous telluride is 96.5:3.5;

[0084] In Example 4, the mass ratio of cadmium telluride to cuprous telluride is 95:5;

[0085] In Example 5, the mass ratio of cadmium telluride to cuprous telluride is 98:2;

[0086] In Comparative Example 1, cuprous telluride was not added;

[0087] In Comparative Example 2, the mass ratio of cadmium telluride to cuprous telluride is 94:6;

[0088] In Comparative Example 3, the mass ratio of cadmium telluride to cuprous telluride is 98.5:1.5. From the data in Table 2, it can be seen that:

[0089] Table 2

[0090]

[0091]

[0092] It can be seen from the data that when the mass ratio of cadmium telluride to cuprous telluride is in the range of 95-98:2-5, the relative density of the cadmium telluride target and the resistance of the obtained cadmium telluride film can be maintained within 7000Ω.cm. However, when the mass ratio of cadmium telluride to cuprous telluride exceeds the range, the performance changes brought about are huge. When the cadmium telluride content increases, the relative density of the target decreases by 8.8%, and the resistance of the cadmium telluride film increases by 7650Ω.cm; when the cadmium telluride content decreases, the relative density of the target decreases by 9.8%, and the resistance of the cadmium telluride film increases by 6120Ω.cm; at the same time, when cuprous telluride is not added, the relative density of the target decreases by 14.8%, and the resistance of the cadmium telluride film exceeds the measurement range.

[0093] In combination with the data in Examples 2-3 and Table 1, it can be seen that changes in process parameters during the preparation process will also affect the performance of the target material, but the impact is relatively small.

[0094] 2. From Example 1 and Examples 6-7, combined with the data in Table 1, it can be seen that in cadmium telluride, the mass ratio of powder 1 to powder 2 has a relatively large impact on the target performance. Among them, when the mass of powder 1 increases, that is, Example 7, the relative density of the target decreases by 5.8%, and the resistance of the cadmium telluride film increases by 2800Ω.cm; when the mass of powder 1 decreases, that is, Example 6, the relative density of the target decreases by 5.9%.

[0095] 3. According to Example 1 and Comparative Examples 4-7, in the cadmium telluride of Example 1, the average mesh number of powder 1 is 170 mesh, and the mesh number of powder 1 is within 150-200 mesh; the average mesh number of powder 2 is 250 mesh, and the mesh number of powder 2 is less than 200 mesh;

[0096] In Comparative Example 4, the average mesh size of the cadmium telluride powder is 210 meshes, and the mesh sizes of the cadmium telluride powders are all less than 150 meshes, with no step distribution;

[0097] In Comparative Example 5, the average mesh number of the powder 1 in the cadmium telluride is 170 meshes, and the mesh number of the powder 1 is within the range of 120-200 meshes, and the powder 1 with a mesh number of 120-150 meshes must be contained. It can be seen from the data in Table 3 that:

[0098] Table 3

[0099]

[0100]

[0101] It can be seen from the data that in cadmium telluride, the mesh distribution of powder one and powder two has a great influence on the performance of the cadmium telluride target. Whether the cadmium telluride powder described in Comparative Example 4 has a mesh size greater than 150 but has no step distribution or the powder one described in Comparative Example 5 contains cadmium telluride powder with a mesh size of 120 to 150, the target performance will be deteriorated, the relative density will be reduced by 10.8% to 11.8%, and the cadmium telluride film resistance will increase by 9580 to 11521Ω.cm.

[0102] At the same time, relative to Example 1, the cadmium telluride in Comparative Example 6 is entirely composed of powder 1, and the cadmium telluride in Comparative Example 7 is entirely composed of powder 2. Although they are also improved compared with Comparative Examples 4-5, the improvement effect is not as good as the effect brought by the cadmium telluride powder with a step distribution in Example 1.

[0103] The above embodiments are preferred implementation modes of the present application, but the implementation modes of the present application are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A method for preparing a cadmium telluride target, characterized in that: The following steps are included: Step 1: mixing cadmium telluride and cuprous telluride to obtain a mixture; Step 2: Load the mixed material into the mold, pre-press it, and evacuate it to obtain the embryo body; Step 3: vacuum sintering the embryo, keeping the temperature under pressure, and cooling the embryo to obtain a cadmium telluride target; Wherein, in step 1, the cadmium telluride is composed of powder 1 and powder 2; The mesh number of the powder 1 is 150-200 meshes, and the mesh number of the powder 2 is greater than 200 meshes; The mass ratio of the powder 1 to the powder 2 is 0.5-3:0.5-3; The mass ratio of cadmium telluride to cuprous telluride is 95-98:2-5.

2. The method for preparing a cadmium telluride target according to claim 1, characterized in that: The mass ratio of the powder 1 to the powder 2 is 0.8-1.2:0.8-1.

2.

3. The method for preparing a cadmium telluride target according to claim 1, characterized in that: In the step 1, the powder mesh size of cuprous telluride is greater than 325 meshes.

4. The method for preparing a cadmium telluride target according to claim 1, characterized in that: The vacuum degree of the vacuum environment in step 2 is below 10Pa.

5. The method for preparing a cadmium telluride target according to claim 1, characterized in that: In step 2, the pre-pressing pressure is 20-30T, and the pre-pressing time is 10-15min.

6. The method for preparing a cadmium telluride target according to claim 1, characterized in that: The vacuum sintering in step 3 is specifically as follows: heating the temperature to 650-750° C. at a heating rate of 5-10° C. / min, and then keeping the temperature for 55-65 minutes.

7. The method for preparing a cadmium telluride target according to claim 1, characterized in that: The heat preservation and pressurization in step 3 are specifically as follows: after the sintering and heat preservation are completed, the pressure is increased to 60-70°C, the pressure is maintained for 20-30 minutes, and the heat preservation and pressure are maintained for 50-60 minutes.

8. A cadmium telluride target, characterized in that: The cadmium telluride target is prepared by the preparation method of any one of claims 1 to 7.

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