CN116364791A - Solar cell and preparation method thereof - Google Patents

Abstract

The invention provides a solar cell and a preparation method thereof. The solar cell includes a silicon base, an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an ITO thin film, and a metal electrode located on one side of the silicon base in sequence. The ITO thin film includes at least two ITO films, and different ITO films have different grain sizes. Compared with the prior art, the ITO thin film of the present invention includes at least two film layers with different grain sizes, so that the IV performance of the solar cell is better, and the product reliability is further guaranteed.

Description

Solar cell and its preparation method

technical field

The invention relates to the field of photovoltaics, in particular to a solar cell and a preparation method thereof.

Background technique

Tin-doped indium oxide film (IndiumTinOxide, referred to as ITO film) is a commonly used transparent conductive film, which has the advantages of high conductivity, good light transmission, high mechanical hardness and good stability. Preferred electrode materials for screens, liquid crystal displays, etc.

Although the current ITO coating has excellent electrical and optical properties and a moderate degree of matching with the adjacent film layer, it is not optimized enough, which has a certain impact on the performance of the device. Taking the use of ITO film as the transparent conductive film of solar cells as an example, it cannot take into account light transmittance, carrier mobility, contact resistance with adjacent film layers, etc., which affects the conversion efficiency of the battery.

In view of this, it is necessary to provide a solar cell and a preparation method thereof to solve the above technical problems.

Contents of the invention

The object of the present invention is to provide a solar cell and a preparation method thereof.

In order to solve one of the above-mentioned technical problems, the present invention adopts the following technical solutions:

A solar cell, comprising a silicon base, an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an ITO film, and a metal electrode located on one side of the silicon base in sequence, and the ITO film includes at least two layers of ITO films, different The grain sizes of the ITO films are different.

Further, among the two adjacent ITO films, the film layer close to the metal electrode has larger crystal grains.

Further, the grain size of the ITO film in contact with the doped amorphous silicon layer is 1nm-20nm.

Further, the grain size of the ITO film in contact with the metal electrode is 20nm-500nm.

Further, the crystal form of the ITO film in contact with the doped amorphous silicon layer is columnar crystal, and the crystal form of the ITO film in contact with the metal electrode is equiaxed crystal.

Further, the ITO thin film includes a small-grain ITO film in contact with the doped amorphous silicon layer, a large-grain ITO film in contact with the metal electrode, and the thickness of the large-grain ITO film is greater than that of the Thickness of small grain ITO film.

Further, the thickness of the ITO thin film is 50nm-120nm, and the thickness of the large-grain ITO film is 40nm-90nm.

A method for preparing a solar cell, comprising: sequentially forming an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an ITO thin film, and a metal electrode on one side of a silicon base; forming the ITO thin film includes: forming at least two layers of ITO film, different ITO films have different grain sizes.

Further, the process of forming the small-grain ITO film in contact with the doped amorphous silicon layer is as follows: the coating pressure is 0.7-1.5 Pa, and the power density is 2-8 kW/m.

Further, the process of forming the large-grain ITO film in contact with the metal electrode is as follows: the coating pressure is 0.3Pa-0.7Pa, and the power density is 5-15kW/m.

Further, forming the ITO thin film includes: forming a small-grain ITO film in contact with the doped amorphous silicon layer, forming a large-grain ITO film in contact with the metal electrode, and the grain size of the small-grain ITO film The grain size of the large grain ITO film is 20 nm to 500 nm.

Further, the grain size of the small-grain ITO film is 1-20 nm, and the thickness of the small-grain ITO film is 10 nm-30 nm.

Further, the grain size of the large-grain ITO film is 15-500 nm, and the thickness of the large-grain ITO film is 40 nm-90 nm.

The beneficial effects of the present invention are: compared with the prior art, the ITO thin film of the present invention includes at least two film layers with different crystal grain sizes, so that the IV performance of the solar cell is better, and the product reliability is further guaranteed.

Description of drawings

1 is a schematic structural view of a solar cell according to an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a solar cell according to another embodiment of the present invention.

Among them, 1 solar cell, 1-silicon base, 2-the first intrinsic amorphous silicon layer, 3-the first doped amorphous silicon layer, 4-the first ITO film, 41-small grain ITO film, 42- Large-grain ITO film, 5-first metal electrode, 6-second intrinsic amorphous silicon layer, 7-second doped amorphous silicon layer, 8-second ITO thin film, 9-second metal electrode.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, method, or functional changes made by those skilled in the art according to these embodiments are included in the protection scope of the present invention.

In each drawing of the present invention, for convenience of illustration, some dimensions of structures or parts are exaggerated relative to other structures or parts, and therefore, are only used to illustrate the basic structure of the subject matter of the present invention.

Please refer to FIG. 2, which is a solar cell 100 according to a preferred embodiment of the present invention, which includes a silicon base 1, an intrinsic amorphous silicon layer 2, 6, and a doped amorphous silicon layer located on one side of the silicon base in turn. 3,7, ITO thin films4,8, metal electrodes5,9.

When the solar cell 100 is a double-sided heterojunction cell, it includes a silicon base 1, a first intrinsic amorphous silicon layer 2 located on the first side of the silicon base 1, a first doped amorphous silicon layer, layer 3, the first ITO thin film 4, the first metal electrode 5, the second intrinsic amorphous silicon layer 6, the second doped amorphous silicon layer 7, the second ITO Thin film 8, second metal electrode 9.

The silicon base 1 is formed by textured silicon wafers. In one embodiment, an N-type silicon wafer is selected, the resistivity is 0.5Ω.cm˜3Ω.cm, the thickness is 150 μm˜200 μm, and the size is 156.75 cm. The silicon wafer is textured with an alkaline solution to form a pyramid structure to improve the capture of sunlight.

The first intrinsic crystalline silicon layer 2 and the second intrinsic crystalline silicon layer 6 are collectively referred to as the intrinsic amorphous silicon layers 2 and 6 , which passivate the silicon base 1 .

The first doped amorphous silicon layer 3 and the second doped amorphous silicon layer 7 are collectively referred to as doped amorphous silicon layers 3 and 7 , and the doping types of the two are opposite. In one embodiment, the first doped amorphous silicon layer 3 is an N-type doped amorphous silicon layer, such as a phosphorus-doped amorphous silicon layer; the second doped amorphous silicon layer 5 is a P-type doped amorphous silicon layer. A heterogeneous amorphous silicon layer, such as a boron-doped amorphous silicon layer. Of course, the doping types of the first doped amorphous silicon layer 3 and the second doped amorphous silicon layer 5 can also be interchanged.

The first ITO thin film 4 and the second ITO thin film 8 are collectively referred to as ITO thin films 4 and 8 . As transparent conductive films, their conductivity, light transmittance, and stability have a great influence on the performance of the solar cell 100 .

The first metal electrode 5 and the second metal electrode 9 are collectively referred to as metal electrodes 5, 9, including a main grid and a fine grid, for collecting and outputting electric energy.

The focus of the present invention is to improve the ITO thin films 4, 8 and their preparation process to improve the performance of solar cells. The inventors found that the small-grain ITO film has a relatively high carrier concentration, but because there are many grain boundaries and increased grain boundary scattering, the carrier mobility is low, so the optical absorption of the small-grain ITO film layer Seriously, the battery Isc will be reduced; and some metal ions migrate more easily in the film layer, and there is a certain risk in device reliability (such as PID, DH, etc.). However, the large-grain ITO film has relatively low carrier concentration and high mobility, and the contact loss with the amorphous silicon layer will be large, and the battery FF will decrease.

In view of this, the ITO thin film 4,8 of the present invention includes at least two layers of ITO films, and the grain sizes of different ITO films are different, which can balance and take into account the conductivity, light transmittance and stability of the entire ITO thin film 4,8 To improve its optical and electrical matching with other adjacent film layers, and improve the performance of solar cells.

Preferably, among the two adjacent ITO films, the ITO film near the metal electrodes 5 and 9 has larger crystal grains. The small-grain ITO film 41 with high carrier concentration and low mobility is located inside, and the contact resistance with the doped amorphous silicon layer 3, 7 is small, which can improve the FF of the battery; there are few grain boundaries, high stability, The large-grain ITO film 42 with high mobility is located on the outside, which improves the stability of the entire ITO film 4 , 8 , reduces the probability of short-circuit diffusion, and is beneficial to improve the stability of the solar cell 100 .

Further, when the ITO film 4,8 includes at least three layers of ITO film, along the direction from the doped amorphous silicon layer 3,7 to the metal electrode 5,9, the at least three layers of the ITO Gradually increasing the grain size of the film can further improve the performance of the solar cell 100 .

Specifically, the ITO film in contact with the doped amorphous silicon layer 3, 7 is a small-grain ITO film 41 with a grain size of 1 nm to 20 nm, which is beneficial for the ITO film 4, 8 to be in contact with the doped amorphous silicon layer. The contact of layers 3 and 7 has a small contact resistance, which can improve the FF of the battery.

The ITO film in contact with the metal electrodes 5 and 9 is a large-grain ITO film 42 with a grain size of 20nm-500nm; less grain boundaries and high stability, which is beneficial to the improvement of optical performance and reliability.

Preferably, the crystal forms of the ITO films of different layers are different.

Preferably, the crystal form of the ITO film in contact with the doped amorphous silicon layer 3, 7 is columnar crystal, and the columnar crystal grows along the vertical direction, and its lateral dimension is small, but the vertical length can be very long, which is conducive to the doping of the inner side Carriers in the amorphous silicon layer 3,7 are transported longitudinally to the outer metal electrodes 5,9.

The crystal form of the ITO film in contact with the metal electrodes 5, 9 is equiaxed, and the carrier transfer performance is excellent in both the horizontal and vertical directions, which is beneficial to the transfer of carriers from the doped amorphous silicon layer 3, 7 , The ITO film on the inner side is transmitted vertically and outwardly to the metal electrodes 5 and 9 layers, which is also conducive to the lateral migration of carriers along the ITO film and being collected by the fine grid.

In addition, the ITO films 4, 8 include a small-grain ITO film 41 in contact with the intrinsic amorphous silicon layer, a large-grain ITO film 42 in contact with the metal electrodes 5, 9, the large-grain The thickness of the ITO film 42 is greater than the thickness of the small-grain ITO film 41, through a thin layer of small-grain ITO film 41 in contact with the doped amorphous silicon layer 3,7 to reduce the contact resistance, and then thicken as much as possible The thickness of the large-grain ITO film 42 can make the performance of the entire ITO thin film 4, 8 tend to be that of the large-grain ITO film 42, improving its stability and optical performance.

For example, the thickness of the ITO films 4 and 8 is 50nm-120nm, the thickness of the large-grain ITO film 42 is 40nm-90nm, and the balance is the thickness of the small-grain ITO film 41 .

In a specific embodiment, the ITO film 4,8 includes two layers: a small-grain ITO film 41 in contact with the doped amorphous silicon layer 3,7, and a large-grain ITO film in contact with the metal electrodes 5,9. Grain ITO film42. The grain size of the small-grain ITO film 41 is 1nm-20nm, the crystal form is columnar crystal, and the thickness is 10nm-30nm; the grain size of the large-grain ITO film 42 is 20nm-500nm, the crystal form is etc. Axial crystals with a thickness of 40nm to 90nm.

Preferably, the structures of the ITO thin films 4 and 8 located on both sides of the silicon base 1 are arranged symmetrically, that is, the inner film layer and the outer film layer on both sides are respectively the same.

The present invention also provides a method for preparing a solar cell, comprising: sequentially forming the intrinsic amorphous silicon layers 2, 6, the doped amorphous silicon layers 3, 7, the The ITO thin films 4,8, the metal electrodes 5,9.

The present invention improves the preparation process of the ITO thin films 4 and 8 to improve the performance of the solar cell, and the process of other film layers refers to the prior art and will not be repeated here.

Specifically, forming the ITO thin films 4, 8 includes: forming at least two layers of ITO films, different ITO films have different grain sizes, which can balance and take into account the electrical conductivity, light transmittance and Stability, improve its optical and electrical matching with other adjacent film layers, and improve the performance of solar cells.

The process of forming the small-grain ITO film 41 in contact with the doped amorphous silicon layer is as follows: the coating pressure is 0.7-1.5 Pa, and the power density is 2-8 kW/m. The ITO film with small crystal grains is in contact with the doped amorphous silicon layer, and the contact resistance is small.

The process of forming the large-grain ITO film 42 in contact with the metal electrode is as follows: the coating pressure is 0.3Pa-0.7Pa, and the power density is 5-15kW/m. The large-grain ITO film 42 with few grain boundaries, high stability, and mobility is located on the outside, which improves the stability of the entire ITO film 4 and 8 and is beneficial to improve the stability of the solar cell 100 .

Usually, the ITO thin film includes two layers of ITO films. , the grain size of the at least three layers of the ITO film gradually increases, which can further improve the performance of the solar cell 100 .

In a specific embodiment, forming the ITO films 4 and 8 includes: forming a small-grain ITO film 41 in contact with the intrinsic amorphous silicon layer, and forming a large-grain ITO film 42 in contact with the metal electrode.

The grain size and thickness of the small-grain ITO film 41 and the large-grain ITO film 42 are as described above, and will not be repeated here.

Hereinafter, a method for preparing a solar cell is provided, comprising the steps of:

S1 silicon wafer: choose N-type silicon wafer, the resistivity is 0.5~3Ω.cm, the thickness is 150~200μm, and the size is 156.75cm;

S2 Cleaning and Texturing: Use HF solution with a volume fraction of 5% to remove the surface oxide layer, use KOH, or NaOH, or tetramethyl ammonium hydroxide (TMAH) to add alcohol, and use the anisotropic etching of single crystal silicon, A shallow pyramidal structure is formed on the surface of the silicon wafer.

S3 forming the intrinsic amorphous silicon layers 2, 6 and the doped amorphous silicon layers 3, 7:

Silane (SiH ₄ ) gas was introduced into a vacuum chamber, and the first intrinsic amorphous silicon layer 2 was formed on the entire area of the first surface of the silicon base 1 by plasma CVD. Then SiH ₄ gas, H ₂ gas and PH ₃ gas are introduced into the vacuum chamber, and an N-type amorphous silicon layer 3 is formed on the first intrinsic amorphous silicon layer 2 by a plasma CVD method:

Next turn over, change the tray, then introduce SiH ₄ gas into the vacuum chamber, and form the second intrinsic amorphous silicon layer 6 on the entire area of the second surface of the silicon base 1 by plasma CVD. Then SiH ₄ gas, H ₂ gas and B ₂ H ₆ (diborane) gas are introduced into the vacuum chamber, and a p-type amorphous silicon layer is formed on the second intrinsic amorphous silicon layer 6 by a plasma CVD method 7.

S4 deposits ITO thin films4,8:

On the doped amorphous silicon layers 3 and 7 on the front and back, use reactive plasma deposition (RPD) or magnetron sputtering to perform ITO coating; wherein the back is shielded by the edge of the carrier plate, that is, through a mask Blocking, the specific blocking area around it is 0.8mm, which plays a role in preventing winding during the deposition process.

During ITO film coating, ITO films with different crystal grains are sequentially deposited on the first side and the second side of the substrate after depositing the doped amorphous silicon layers 3 and 7 .

The specific method is: there are at least 4 coating target positions that are not polluting each other in the PVD mass production equipment, and different targets are installed on the target positions; the substrate is loaded on the carrier plate, and the coating is sequentially processed through different target positions to obtain the required film layer design. . Adjust the _O2 atmosphere at different target positions to adjust the work function and carrier concentration of the TCO film to the required concentration range.

After CVD, the silicon wafer is carried on the carrier. The carrier is designed as a hollow plate. There is a convex edge of about 0.6-0.8mm on the edge of the hollow to support the silicon wafer, and at the same time expose the coating area on the front and back. The specific coating process adopts the method of physical vapor deposition, using a certain energy to bombard the phase in the target material, and at the same time injecting the corresponding gas to form a certain atmosphere environment, usually 90% to 99% Ar, 1% to 6 % of O ₂ ; 0% to 4% of H ₂ . Different flow ratios of Ar, O ₂ , and H ₂ are used for different work functions. The specific process selection is described in different embodiments.

S5 Printed electrodes: Print a layer of low-temperature conductive silver paste on the front and back ITO films 4 and 8 by screen printing, and then sinter at a low temperature of 150°C to 300°C to form a good ohmic contact.

Hereinafter, the present invention will be illustrated by specific examples and comparative examples.

Comparative Example 1: Please refer to the solar cell structure shown in FIG. 1 .

The first ITO film 4 on the front side is a single-layer film, the ratio of indium oxide to tin oxide is 97:3, and the film thickness is 70nm-75nm. The preparation process is as follows: Ar, O ₂ , H ₂ gases with a certain gas flow ratio are introduced to obtain an ITO film with a ratio of indium oxide to tin oxide of 97:3, and the coating process pressure in the process chamber is 0.7Pa～1.0 Pa, the grain size of the obtained first ITO thin film 4 is in the range of 1-10 nm.

The second ITO film 8 on the back is a single-layer film, the ratio of indium oxide to tin oxide is 90:10, and the film thickness is 70nm-75nm. The preparation process is as follows: Ar, O ₂ , H ₂ gases with a certain gas flow ratio are introduced to obtain an ITO film with a ratio of indium oxide to tin oxide of 90:10, and the pressure of the coating process in the process chamber is 0.7Pa～1.0 Pa; the grain size of the obtained second ITO thin film 8 is in the range of 1-10 nm.

Embodiment 1: Please refer to the solar cell structure shown in FIG. 1 .

The first ITO film 4 on the front side is a single-layer film, the ratio of indium oxide to tin oxide is 97:3, and the film thickness is 70nm-75nm. The preparation process is as follows: Ar, O ₂ , H ₂ gases with a certain gas flow ratio are introduced to obtain an ITO film with a ratio of indium oxide to tin oxide of 97:3, and the coating process pressure in the process chamber is 0.5-0.7Pa ; The grain size of the obtained first ITO thin film 4 is in the range of 20nm-30nm.

The second ITO thin film 8 on the back has a single-layer structure, the ratio of indium oxide to tin oxide is 90:10, and the film thickness is 70nm-75nm. Introduce Ar, O ₂ , H ₂ gases with a certain gas flow ratio to obtain an ITO film with a ratio of indium oxide to tin oxide of 90:10, and the pressure of the coating process in the process chamber is 0.5-0.7Pa; the obtained The grain size of the second ITO thin film 8 is in the range of 20-30nm.

Embodiment 2: Please refer to the solar cell structure shown in FIG. 2 .

The first ITO thin film 4 on the front side is two layers of ITO films. Wherein, for the ITO film in contact with the first doped amorphous silicon layer 3, the ratio of indium oxide to tin oxide is 97:3, and the thickness of the film layer is 5nm-10nm; Ar, O ₂ , H ₂ gas, so that indium oxide: tin oxide is 97:3, the coating process pressure in the inner layer ITO film process chamber is 0.7Pa ~ 1.0Pa, and the grain size of the film layer is between 1nm ~ 10nm between. For the ITO film in contact with the first metal electrode 5, the ratio of indium oxide to tin oxide is 97:3, and the thickness of the film layer is 65nm-70nm; the preparation process is as follows: Ar, O ₂ , H ₂ gas with a certain gas flow ratio , so that the ratio of indium oxide: tin oxide is 97:3, the coating process pressure in the outer layer ITO film process chamber is 0.5Pa～0.7Pa; the grain size of the film layer is between 20nm～30nm.

The second ITO thin film 8 on the back is two layers of ITO films. Among them, the ITO film in contact with the second doped amorphous silicon layer 7 has a composition of indium oxide and tin oxide with a ratio of 90:10, a work function of 4.6-4.8eV, and a film thickness of 5nm-10nm; the preparation process It is: to feed Ar, O ₂ , H ₂ gases with a certain gas flow ratio, so that the ratio of indium oxide: tin oxide is 90:10, and the coating process pressure in the inner layer ITO film process chamber is 0.7Pa ~ 1.0Pa, the film layer The grain size is between 1nm and 10nm. The ITO film in contact with the second metal electrode 9 has a composition of indium oxide and tin oxide at a ratio of 90:10, and a film thickness of 65 nm to 70 nm. The preparation process is as follows: Ar, O ₂ , H ₂ gases with a certain gas flow ratio are introduced, so that the ratio of indium oxide: tin oxide is 90:10, and the coating process pressure in the outer ITO film process chamber is 0.5Pa ~ 0.7Pa; The grain size of the film layer is between 20nm and 30nm.

The performance of the solar cell 100 corresponding to the comparative example, Example 1, and Example 2 is shown in Table 1, wherein the data of Example 1 and Example 2 are the change values relative to the comparative example.

Table 1

group Eff(%) Voc(V) Isc(A) FF(%) comparative example 24.51 744.9 6.416 84.92 Example 1 +0.05 +0.1 +0.028 -0.2 Example 2 +0.10 +0.1 +0.025 +0.01

The ITO films on the front and back of the comparative example are small-grained films formed by high-voltage routes, with many grain boundaries and poor light transmission. They have advantages in electricity and high FF. The ITO films on the front and back of Example 1 are large-grain films formed by the low-voltage route, and the light transmission is good, but the electrical performance is slightly poor. Both the front and back ITO films of Example 2 use a combination of ITO films with different grain sizes, that is, the inner layer is a small-grain ITO film 41 formed by a high-voltage route, and the outer layer is a large-grain ITO film 42 formed by a low-pressure route.

Comparing the comparative example with Example 1, it can be seen that the optical properties of the front ITO thin film of Example 1 are improved, and the short-circuit current Isc is significantly increased by 28mA; but the contact becomes worse, FF decreases by 0.2, the open-circuit voltage Voc slightly increases by 0.1mV, and the efficiency gain is 0.05 %.

Comparing the comparative example with Example 2, it can be seen that the optical properties of the front ITO film are improved, the short-circuit current Isc is increased by 25mA, the contact is equivalent to the comparative example, the FF is unchanged, the open-circuit voltage Voc is slightly increased by 0.1mV, and the efficiency gain is 0.10%.

To sum up, compared with the prior art, the ITO thin film of the present invention includes at least two film layers with different grain sizes, so that the IV performance of the solar cell is better, and the product reliability is further guaranteed. The inner film adopts a small crystal grain, high carrier concentration, and ensures contact; the outer film adopts a multi-layer ITO film design with large grain, high mobility, and guaranteed light transmission.

It should be understood that although this description is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the description is only for clarity, and those skilled in the art should take the description as a whole, and each The technical solutions in the embodiments can also be properly combined to form other embodiments that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions for feasible implementations of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent implementation or implementation that does not depart from the technical spirit of the present invention All changes should be included within the protection scope of the present invention.

Claims (13)

1. A solar cell, comprising a silicon base, an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an ITO film, and a metal electrode positioned at one side of the silicon base successively, wherein the ITO film comprises at least Two layers of ITO films, different ITO films have different grain sizes. 2. The solar cell according to claim 1, characterized in that: among the two adjacent ITO films, the film layer closest to the metal electrode has larger crystal grains. 3. The solar cell according to claim 1, characterized in that: the grain size of the ITO film in contact with the doped amorphous silicon layer is 1nm-20nm. 4. The solar cell according to claim 1, characterized in that: the grain size of the ITO film in contact with the metal electrode is 20nm-500nm. 5. The solar cell according to claim 1, characterized in that: the crystal form of the ITO film in contact with the doped amorphous silicon layer is columnar crystal, and the crystal form of the ITO film in contact with the metal electrode is For equiaxed crystals. 6. The solar cell according to claim 1, wherein the ITO thin film comprises a small-grain ITO film in contact with the doped amorphous silicon layer, a large-grain ITO film in contact with the metal electrode , the thickness of the large-grain ITO film is greater than the thickness of the small-grain ITO film. 7 . The solar cell according to claim 6 , wherein the thickness of the ITO thin film is 50 nm to 120 nm, and the thickness of the large grain ITO film is 40 nm to 90 nm. 8. A method for preparing a solar cell, comprising: sequentially forming an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an ITO film, and a metal electrode on one side of a silicon base; it is characterized in that: forming the ITO film includes : At least two layers of ITO films are formed, and the grain sizes of different ITO films are different. 9. The method for preparing a solar cell according to claim 8, characterized in that: the process of forming the small-grain ITO film in contact with the doped amorphous silicon layer is as follows: the coating pressure is 0.7-1.5Pa, and the power density It is 2~8kW/m. 10. The method for preparing a solar cell according to claim 8, characterized in that: the process of forming a large-grain ITO film in contact with the metal electrode is as follows: the coating pressure is 0.3Pa～0.7Pa, and the power density is 5～ 15kW/m. 11. The method for preparing a solar cell according to claim 8, characterized in that: forming the ITO thin film comprises: forming a small-grain ITO film in contact with the doped amorphous silicon layer, forming an ITO film in contact with the metal electrode The large-grain ITO film, the grain size of the small-grain ITO film is 1nm-20nm, and the grain size of the large-grain ITO film is 20nm-500nm. 12 . The method for preparing a solar cell according to claim 9 or 11 , characterized in that: the grain size of the small-grain ITO film is 1-20 nm, and the thickness of the small-grain ITO film is 10 nm-30 nm. 13 . 13. The method for preparing a solar cell according to claim 10 or 11, characterized in that: the grain size of the large-grain ITO film is 15-500 nm, and the thickness of the large-grain ITO film is 40 nm-90 nm.

Images