A method for preparing heterojunction TCO thin film

Abstract

The present invention relates to the technical field of heterojunction batteries, and in particular to a method for preparing a heterojunction TCO film. A method for preparing a heterojunction TCO film of the present invention comprises the following steps: a silicon wafer is sequentially deposited on the first surface of the silicon wafer through at least three target groups; a silicon wafer is sequentially deposited on the second surface of the silicon wafer through at least three target groups; along the movement direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group decreases successively, and the vertical distance between the second surface of the silicon wafer and the target group decreases successively; along the movement direction of the silicon wafer, the magnetic field strength of the target group deposited on the first surface of the silicon wafer decreases successively, and the magnetic field strength of the target group deposited on the second surface of the silicon wafer decreases successively. The preparation method of the present invention can improve the sputtering rate, reduce the preparation time, and improve the performance of the prepared TCO film.

Description

Technical Field

[0001] The present invention relates to the technical field of heterojunction batteries, and in particular to a method for preparing a heterojunction TCO film. Background Art

[0002] Transparent conductive film (TCO) is a functional thin film material that has both conductive properties and high transparency. It has a large bandgap, is transparent in the visible light region, and has low resistivity. It is mainly used in thin-film solar cells, flat panel displays, gas sensors, etc. Among them, transparent conductive film plays two main roles in thin-film solar cells. First, as a transparent electrode, this requires the transparent conductive oxide film to have both excellent conductivity and very good optical transmittance; second, as a light trapping structure of thin-film solar cells, it increases the optical path of incident light in the photoelectric conversion layer of the solar cell and improves the conversion efficiency of the solar cell.

[0003] In the prior art, the methods for preparing transparent conductive films include chemical methods and physical methods; among them, chemical methods include sol-gel, spray thermal decomposition and various chemical vapor deposition methods; physical methods include vacuum evaporation coating and sputtering coating technology. Sputtering coating refers to filling a high vacuum with an inert gas, ionizing the gas under a high-frequency and high-voltage electric field to produce a glow discharge, forming a high-energy ion flow to bombard the target electrode, so that the target electrode material is deposited on the substrate to form a thin film.

[0004] In the sputtering coating method, the distance between the target material and the silicon wafer is fixed, and the magnetic field strength in each target material is selected to be consistent. Although there are differences in power and gas flow, too much sputtering power will cause losses to amorphous silicon on the silicon wafer. The sputtering power cannot be set too high, and the overall performance of the transparent conductive film produced needs to be improved.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a heterojunction TCO thin film, which improves the sputtering rate and reduces the preparation time by optimizing the distance between the target material and the silicon wafer, the magnetic field strength and the sputtering power, and can produce a heterojunction TCO thin film with high transmittance, low resistivity, high electron mobility, low carrier concentration and low minority carrier lifetime degradation value, thereby facilitating improving the battery conversion efficiency.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The present invention provides a method for preparing a heterojunction TCO thin film, comprising the following steps:

[0009] The silicon wafer is sequentially passed through at least three target groups to deposit on the first surface of the silicon wafer; the silicon wafer is sequentially passed through at least three target groups to deposit on the second surface of the silicon wafer;

[0010] Along the moving direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group decreases successively, and the vertical distance between the second surface of the silicon wafer and the target group decreases successively;

[0011] Along the moving direction of the silicon wafer, the magnetic field strength of the target group depositing on the first surface of the silicon wafer decreases successively, and the magnetic field strength of the target group depositing on the second surface of the silicon wafer decreases successively.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The preparation method of the heterojunction TCO film of the present invention adopts a magnetron sputtering vacuum coating method. By optimizing the distance between the target material and the silicon wafer and the magnetic field strength during the vacuum coating process, the target-base distance and the magnetic field strength are both set in a gradient, and the sputtering power is regulated to match the target-base distance and the magnetic field strength, thereby improving the sputtering rate and reducing the preparation time. There is no sputtering damage to the silicon wafer such as the amorphous silicon layer, and a heterojunction TCO film with high density, high transmittance, high electron mobility, low carrier concentration, low resistivity, and low minority carrier lifetime reduction value can be prepared. The heterojunction TCO film used in a thin-film solar cell is beneficial to improving the conversion efficiency of the battery.

[0014] The sputtering power in the method for preparing the heterojunction TCO thin film of the present invention can adopt a high sputtering power, and the process has a wide adjustable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 Schematic diagram of the method for preparing the heterojunction TCO thin film according to Example 1 of the present invention. DETAILED DESCRIPTION

[0017] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0018] A method for preparing a heterojunction TCO thin film according to an embodiment of the present invention is described in detail below.

[0019] In some embodiments of the present invention, a method for preparing a heterojunction TCO thin film is provided, comprising the following steps:

[0020] The silicon wafer is sequentially passed through at least three target groups to deposit on the first surface of the silicon wafer; the silicon wafer is sequentially passed through at least three target groups to deposit on the second surface of the silicon wafer;

[0021] Along the moving direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group decreases successively, and the vertical distance between the second surface of the silicon wafer and the target group decreases successively;

[0022] Along the moving direction of the silicon wafer, the magnetic field strength of the target group depositing on the first surface of the silicon wafer decreases successively, and the magnetic field strength of the target group depositing on the second surface of the silicon wafer decreases successively.

[0023] The preparation method of the heterojunction TCO film of the present invention adopts a magnetron sputtering vacuum coating method. By optimizing the distance between the target material and the silicon wafer and the magnetic field strength during the vacuum coating process, the target-base distance is set in a gradient, the magnetic field strength of each target material is matched with the target-base distance gradient, and the sputtering power is regulated to match the above two, thereby improving the performance of the film and reducing the preparation time. A heterojunction TCO film with high density, high transmittance, high electron mobility, low carrier concentration, low resistivity, and low minority carrier lifetime reduction value can be prepared. Using the heterojunction TCO film in a thin-film solar cell is beneficial to improving the conversion efficiency of the battery.

[0024] The preparation method of the invention improves the sputtering rate, shortens the preparation time, and does not cause sputtering damage to silicon wafers such as amorphous silicon layers of silicon wafers; the process operation is simple and suitable for industrial production.

[0025] In some embodiments of the present invention, along the movement direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group gradually decreases from 90 to 110 mm to 50 to 70 mm, and the vertical distance between the second surface of the silicon wafer and the target group gradually decreases from 90 to 110 mm to 50 to 70 mm; preferably, the difference in the vertical distances between adjacent target groups and the first surface of the silicon wafer is 10 to 30 mm, preferably 15 to 25 mm; the difference in the vertical distances between adjacent target groups and the second surface of the silicon wafer is 10 to 30 mm, preferably 15 to 25 mm.

[0026] In some embodiments of the present invention, along the movement direction of the silicon wafer, the magnetic field strength of the target group for deposition on the first surface of the silicon wafer decreases from 1200-1400GS to 800-1000GS, and the magnetic field strength of the target group for deposition on the second surface of the silicon wafer decreases from 1200-1400GS to 800-1000GS; preferably, the difference in magnetic field strength between adjacent target groups for deposition on the first surface of the silicon wafer is 100-300GS; preferably, 150-250GS; the difference in magnetic field strength between adjacent target groups for deposition on the second surface of the silicon wafer is 100-300GS; preferably, 150-250GS.

[0027] In some embodiments of the present invention, the sputtering power of the target group for depositing on the first surface of the silicon wafer is 0.9-1.9 kw, and the sputtering power of the target group for depositing on the second surface of the silicon wafer is 0.9-1.9 kw.

[0028] The sputtering power used in the preparation method of the present invention is higher than the sputtering power of conventional processes, and the process has a wide adjustable range.

[0029] In some embodiments of the present invention, the first surface of the silicon wafer is deposited sequentially through the first target group, the second target group and the third target group; the second surface of the silicon wafer is deposited sequentially through the fourth target group, the fifth target group and the sixth target group.

[0030] In some embodiments of the present invention, the vertical distance d1 between the first target group and the first surface of the silicon wafer and the vertical distance d4 between the fourth target group and the second surface of the silicon wafer are each independently 90 to 110 mm; typically but not limiting, for example, d1 and d4 can each independently be 90 mm, 95 mm, 100 mm, 105 mm, 110 mm or a range consisting of any two of them.

[0031] In some embodiments of the present invention, the vertical distance d2 between the second target group and the first surface of the silicon wafer and the vertical distance d5 between the fifth target group and the second surface of the silicon wafer are each independently 70 to 90 mm; typically but not limitatively, for example, d2 and d5 can each independently be 70 mm, 75 mm, 80 mm, 85 mm, 90 mm or a range consisting of any two of them.

[0032] In some embodiments of the present invention, the vertical distance d3 between the third target group and the first surface of the silicon wafer and the vertical distance d6 between the sixth target group and the second surface of the silicon wafer are each independently 50 to 70 mm; typically but not limitatively, for example, d3 and d6 can each independently be 50 mm, 55 mm, 60 mm, 65 mm, 70 mm or a range consisting of any two of them.

[0033] In some embodiments of the present invention, the magnetic field strength of the first target group and the fourth target group are each independently 1200-1400GS; typically but not restrictively, for example, the magnetic field strength of the target magnetic rods of the first target group and the magnetic field strength of the target magnetic rods of the fourth target group can each independently be 1200GS, 1250GS, 1300GS, 1350GS, 1400GS or a range consisting of any two of them.

[0034] In some embodiments of the present invention, the magnetic field strength of the second target group and the fifth target group are each independently 1000-1200GS; typically but not limitatively, for example, the magnetic field strength of the target magnetic rods of the second target group and the magnetic field strength of the target magnetic rods of the fifth target group can each independently be 1000GS, 1050GS, 1100GS, 1150GS, 1200GS or a range consisting of any two of them.

[0035] In some embodiments of the present invention, the magnetic field strength of the third target group and the sixth target group are each independently 800-1000GS; typically but not limiting, for example, the magnetic field strength of the target magnetic rods of the third target group and the magnetic field strength of the target magnetic rods of the sixth target group can each independently be 800GS, 850GS, 900GS, 950GS, 1000GS or a range consisting of any two of them.

[0036] In some embodiments of the present invention, the sputtering power of the first target group and the fourth target group is independently 0.9 to 1.3 kw; typically but not limiting, for example, it can be 0.9 kw, 1 kw, 1.1 kw, 1.2 kw, 1.3 kw or a range consisting of any two of them.

[0037] In some embodiments of the present invention, the sputtering power of the second target group and the fifth target group is independently 1.2 to 1.6 kw; typically but not limiting, for example, it can be 1.2 kw, 1.3 kw, 1.4 kw, 1.5 kw, 1.6 kw or a range consisting of any two of them.

[0038] In some embodiments of the present invention, the sputtering power of the third target group and the sixth target group is independently 1.5 to 1.9 kw; typically but not limiting, for example, it can be 1.5 kw, 1.6 kw, 1.7 kw, 1.8 kw, 1.9 kw or a range consisting of any two of them.

[0039] In some embodiments of the present invention, depositing includes using a PVD coating device.

[0040] In some embodiments of the present invention, the pressure of the vacuum chamber of the PVD coating equipment is 0.1-1Pa, the volume content of oxygen is 1%-10%, and the volume content of hydrogen is ≤4%; typically but not limitatively, for example, the pressure of the vacuum chamber is 0.1Pa, 0.2Pa, 0.3Pa, 0.4Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, 0.9Pa, 1Pa or a range consisting of any two thereof; the volume content of oxygen in the vacuum chamber is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two thereof.

[0041] In some embodiments of the present invention, the temperature of the silicon wafer is 100-250° C.; typically but not limiting, for example, the temperature of the silicon wafer is 100° C., 150° C., 200° C., 250° C. or a range consisting of any two thereof.

[0042] In some embodiments of the present invention, the PVD coating equipment includes a vacuum chamber, the vacuum chamber includes a first vacuum chamber and a second vacuum chamber; the first vacuum chamber includes at least 3 target groups; the second vacuum chamber includes at least 3 target groups.

[0043] In some embodiments of the present invention, the first vacuum chamber includes a first target group, a second target group, and a third target group arranged in sequence; the second vacuum chamber includes a first target group, a second target group, and a third target group arranged in sequence.

[0044] In some embodiments of the present invention, the passing rate is 10 to 100 mm / s; typically but not limitatively, for example, the passing rate is 10 mm / s, 20 mm / s, 30 mm / s, 40 mm / s, 50 mm / s, 60 mm / s, 70 mm / s, 80 mm / s, 90 mm / s, 100 mm / s or a range consisting of any two of them; preferably, the passing rate is 60 to 80 mm / s.

[0045] In some embodiments of the present invention, the target material of the target group for depositing on the first surface of the silicon wafer includes at least one of an ITO target, an AZO target, an MZO target and an IWO target; the target material of the target group for depositing on the second surface of the silicon wafer includes at least one of an ITO target, an AZO target, an MZO target and an IWO target.

[0046] In some specific embodiments of the present invention, the target material of the target group for depositing on the first surface of the silicon wafer includes an ITO target material or an AZO target material; preferably, in the ITO target material, the mass ratio of Sn2O3 to In2O3 is 90:10; in the AZO target material, the mass ratio of ZnO to Al2O3 is 99:1.

[0047] In some embodiments of the present invention, the target material of the target group for depositing on the second surface of the silicon wafer includes an ITO target material; preferably, in the ITO target material, the mass ratio of Sn2O3 to In2O3 is 97:3. The use of the above-mentioned ITO target material has a low tin content, which is conducive to improving the battery conversion efficiency.

[0048] In some embodiments of the present invention, the electron mobility of the TCO film prepared by the above-mentioned heterojunction TCO film preparation method is greater than 80 cm 2 / V·s, carrier concentration<4.5×10 20 cm -3 The square resistance of TCO film is less than 48ohm / sq, and the minority carrier lifetime decrease value is less than 210μs.

[0049] Example 1

[0050] See also Figure 1 The method for preparing the heterojunction TCO thin film provided in this embodiment comprises the following steps:

[0051] In the PVD coating equipment, the silicon wafer enters the first vacuum chamber, and passes through the first target group, the second target group and the third target group at a rate of 75 mm / s to deposit on the first surface of the silicon wafer; then enters the second vacuum chamber, and passes through the fourth target group, the fifth target group and the sixth target group at a rate of 75 mm / s to deposit on the second surface of the silicon wafer.

[0052] The pressure of the first vacuum chamber and the second vacuum chamber are both 0.6 Pa, the volume content of oxygen is 8%, and the volume content of hydrogen is 3%;

[0053] The targets of the first, second and third target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 90:10), and the targets of the fourth, fifth and sixth target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 97:3); the temperature of the silicon wafer is 200°C;

[0054] The vertical distances d1 and d4 between the first target group and the fourth target group and the silicon wafer are both 100 mm, the magnetic field strength of the target magnetic bars of the first target group and the fourth target group is both 1300 GS, and the sputtering power is both 1.1 kW;

[0055] The vertical distances d2 and d5 between the second target group and the fifth target group and the silicon wafer are both 80 mm, the magnetic field strength of the target magnetic bars of the second target group and the fifth target group is both 1100 GS, and the sputtering power is both 1.4 kW;

[0056] The vertical distances d3 and d6 between the third target group and the sixth target group and the silicon wafer are both 60 mm, the magnetic field strengths of the target magnetic bars of the third target group and the sixth target group are both 900 GS, and the sputtering powers are both 1.7 kW.

[0057] Example 2

[0058] The method for preparing the heterojunction TCO thin film provided in this embodiment refers to Example 1, except that the vertical distances d1 and d4 between the first target group and the fourth target group and the silicon wafer are both 90 mm, the magnetic field strength of the target magnetic bars of the first target group and the fourth target group are both 1200 GS, and the sputtering power is both 0.9 kW;

[0059] The vertical distances d2 and d5 between the second target group and the fifth target group and the silicon wafer are both 70 mm, the magnetic field strength of the target magnetic bars of the second target group and the fifth target group is both 1000 GS, and the sputtering power is both 1.2 kW;

[0060] The vertical distances d3 and d6 between the third target group and the sixth target group and the silicon wafer are both 50 mm, the magnetic field strengths of the target magnetic bars of the third target group and the sixth target group are both 800 GS, and the sputtering powers are both 1.5 kW.

[0061] Example 3

[0062] The method for preparing the heterojunction TCO thin film provided in this embodiment refers to Example 1, except that the vertical distances d1 and d4 between the first target group and the fourth target group and the silicon wafer are both 110 mm, the magnetic field strength of the target magnetic bars of the first target group and the fourth target group are both 1400 GS, and the sputtering power is both 1.3 kW;

[0063] The vertical distances d2 and d5 between the second target group and the fifth target group and the silicon wafer are both 90 mm, the magnetic field strength of the target magnetic bars of the second target group and the fifth target group is both 1200 GS, and the sputtering power is both 1.6 kW;

[0064] The vertical distances d3 and d6 between the third target group and the sixth target group and the silicon wafer are both 70 mm, the magnetic field strengths of the target magnetic bars of the third target group and the sixth target group are both 1000 GS, and the sputtering powers are both 1.9 kW.

[0065] Comparative Example 1

[0066] The method for preparing the heterojunction TCO thin film provided in this comparative example comprises the following steps:

[0067] In the PVD coating equipment, the silicon wafer enters the first vacuum chamber, and passes through the first target group, the second target group, and the third target group at a rate of 65 mm / s to deposit on the first surface of the silicon wafer; then enters the second vacuum chamber, and passes through the fourth target group, the fifth target group, and the sixth target group at a rate of 65 mm / s to deposit on the second surface of the silicon wafer.

[0068] The pressure of the first vacuum chamber and the second vacuum chamber are both 0.6 Pa, the volume content of oxygen is 8%, and the volume content of hydrogen is 3%;

[0069] The targets of the first, second and third target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 90:10), and the targets of the fourth, fifth and sixth target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 97:3); the temperature of the silicon wafer is 200°C;

[0070] The vertical distance between the first target group, the second target group, the third target group, the fourth target group, the fifth target group, and the sixth target group and the silicon wafer is 70 mm, the magnetic field strength of the corresponding target magnet rods is 1000 GS, and the sputtering power is 1.3 kW.

[0071] Comparative Example 2

[0072] The method for preparing the heterojunction TCO thin film provided in this comparative example comprises the following steps:

[0073] In the PVD coating equipment, the silicon wafer enters the first vacuum chamber, and passes through the first target group, the second target group, and the third target group at a rate of 65 mm / s to deposit on the first surface of the silicon wafer; then enters the second vacuum chamber, and passes through the fourth target group, the fifth target group, and the sixth target group at a rate of 65 mm / s to deposit on the second surface of the silicon wafer.

[0074] The pressure of the first vacuum chamber and the second vacuum chamber are both 0.6 Pa, the volume content of oxygen is 8%, and the volume content of hydrogen is 3%;

[0075] The targets of the first, second and third target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 90:10), and the targets of the fourth, fifth and sixth target groups are all ITO targets (the mass ratio of Sn2O3 to In2O3 is 97:3); the temperature of the silicon wafer is 200°C;

[0076] The vertical distance between the first target group, the second target group, the third target group, the fourth target group, the fifth target group, and the sixth target group and the silicon wafer is 90 mm, the magnetic field strength of the corresponding target magnets is 1200 GS, and the sputtering power is 1.5 kW.

[0077] Test Example 1

[0078] Examples The coating rate (silicon wafer passing rate), sputtering rate and thickness of the heterojunction TCO film of Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 1.

[0079] Table 1

[0080] Coating rate (mm / s) Sputtering rate (w / cm) Thickness(nm) Example 1 75 85.54 98.0 Example 2 75 85.46 97.4 Example 3 75 83.39 97.8 Comparative Example 1 65 80.1 97.9 Comparative Example 2 65 79.3 97.6

[0081] It can be seen from Table 1 that, to prepare the target film thickness, the coating rate and sputtering rate required for Examples 1-3 are faster than those for Comparative Examples 1-2.

[0082] The performance of the heterojunction TCO films prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] It can be seen from Table 2 that the performance parameters of the thin films prepared in Examples 1 to 3 are better than those in Comparative Examples 1 to 2, and have the advantages of high electron mobility, low carrier concentration, low resistivity, high transmittance, and low decrease in minority carrier lifetime.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heterojunction TCO thin film, characterized in that: The steps include: The silicon wafer is sequentially passed through three target groups to deposit on the first surface of the silicon wafer; the silicon wafer is sequentially passed through three target groups to deposit on the second surface of the silicon wafer; The silicon wafer is deposited on the first surface of the silicon wafer by sequentially passing through the first target group, the second target group and the third target group; the silicon wafer is deposited on the second surface of the silicon wafer by sequentially passing through the fourth target group, the fifth target group and the sixth target group; Along the moving direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group decreases successively, and the vertical distance between the second surface of the silicon wafer and the target group decreases successively; Along the moving direction of the silicon wafer, the magnetic field strength of the target group depositing on the first surface of the silicon wafer decreases successively, and the magnetic field strength of the target group depositing on the second surface of the silicon wafer decreases successively; The sputtering power of the first target group and the fourth target group is independently 0.9 to 1.3 kw; The sputtering powers of the second target group and the fifth target group are independently 1.2 to 1.6 kw; The sputtering powers of the third target group and the sixth target group are each independently 1.5 to 1.9 kw.

2. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: Along the moving direction of the silicon wafer, the vertical distance between the first surface of the silicon wafer and the target group gradually decreases from 90 to 110 mm to 50 to 70 mm, and the vertical distance between the second surface of the silicon wafer and the target group gradually decreases from 90 to 110 mm to 50 to 70 mm.

3. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: Along the moving direction of the silicon wafer, the magnetic field strength of the target group for deposition on the first surface of the silicon wafer gradually decreases from 1200-1400GS to 800-1000GS, and the magnetic field strength of the target group for deposition on the second surface of the silicon wafer gradually decreases from 1200-1400GS to 800-1000GS.

4. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: The vertical distance between the first target group and the first surface of the silicon wafer and the vertical distance between the fourth target group and the second surface of the silicon wafer are each independently 90 to 110 mm; The vertical distance between the second target group and the first surface of the silicon wafer and the vertical distance between the fifth target group and the second surface of the silicon wafer are each independently 70 to 90 mm; A vertical distance between the third target group and the first surface of the silicon wafer and a vertical distance between the sixth target group and the second surface of the silicon wafer are each independently 50 to 70 mm.

5. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: The magnetic field strength of the first target group and the fourth target group are independently 1200-1400 GS; The magnetic field strength of the second target group and the fifth target group is independently 1000-1200 GS; The magnetic field strengths of the third target group and the sixth target group are independently 800-1000 GS.

6. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: The deposition includes using PVD coating equipment.

7. The method for preparing a heterojunction TCO thin film according to claim 6, characterized in that: The pressure of the vacuum chamber of the PVD coating equipment is 0.1-1 Pa, the volume content of oxygen is 1%-10%, and the volume content of hydrogen is ≤4%; the temperature of the silicon wafer is 100-250°C.

8. The method for preparing a heterojunction TCO thin film according to claim 1, characterized in that: The target material of the target group for depositing on the first surface of the silicon wafer includes at least one of an ITO target material, an AZO target material, an MZO target material and an IWO target material; the target material of the target group for depositing on the second surface of the silicon wafer includes at least one of an ITO target material, an AZO target material, an MZO target material and an IWO target material.

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