Back contact battery and preparation method thereof

Abstract

The invention belongs to the technical field of solar cells, and provides a back contact cell and a preparation method thereof, and the method comprises the following steps: depositing Al2O3 layers on the front and back surfaces of a semi-finished cell to obtain an intermediate; sequentially depositing passivation anti-reflection films on the front surface and the back surface of the intermediate, and annealing to obtain a passivation battery; and printing an electrode on the passivated cell, and sintering to obtain the back contact cell. According to the preparation method, an intermediate with an Al2O3 layer is obtained in a deposition mode, corresponding annealing and sintering are carried out after the intermediate is subjected to deposition and passivation of an anti-reflection film, and preparation is completed. The annealing process is correspondingly added in the passivation process, better passivation control is provided for the chemical passivation effect and field effect passivation of aluminum oxide, replaceable interface passivation is achieved, and a debugging and cooling window can be better provided for the printing temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back contact cell and a preparation method thereof. Background Art

[0002] With the over-exploitation and depletion of traditional energy sources, scientists have focused on finding new green and sustainable energy types. The most common of these is solar energy, which has been used on a large scale as an inexhaustible energy source. Solar cells are the key device for converting light energy into electrical energy. BC cells, which refer to back contact cells, are an advanced design for improving the efficiency of solar cells. The core design concept is to place all the metal electrodes of the cell on the back of the cell to ensure that the front of the cell is not blocked by any metal grid lines, thereby maximizing the area of ​​the cell that absorbs sunlight, reducing optical losses, and improving photoelectric conversion efficiency. However, the basic structural framework of the technical route of the cell is now mature, and the complexity of the process will be emphasized in the actual research and development to mass production stage, which greatly increases the cost. Therefore, it is particularly important to reduce the production process of back contact cells. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects in the prior art and provide a back contact battery and a preparation method thereof.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a back contact battery, comprising the following steps:

[0006] (1) depositing Al2O3 layers on the front and back surfaces of the semi-finished battery to obtain an intermediate;

[0007] (2) sequentially depositing a passivation anti-reflection film on the front and back surfaces of the intermediate, and annealing to obtain a passivated cell;

[0008] (3) After printing the electrodes of the passivated battery, sintering is performed to obtain the back contact battery.

[0009] Preferably, the thickness of the Al2O3 layer in step (1) is independently 3 to 10 nm, the aluminum source of the Al2O3 layer is trimethylaluminum, and the oxygen source of the Al2O3 layer is water or ozone.

[0010] Preferably, the deposition temperature in step (1) is 200-230°C, the single aluminum source flow rate of the deposition is 1000-4000sccm, the single aluminum source time of the deposition is 3-7s, the single oxygen source flow rate of the deposition is 2000-5000sccm, the single oxygen source time of the deposition is 3-7s, and the number of deposition cycles is 20-40 times.

[0011] Preferably, the material of the passivation anti-reflection film in step (2) is independently one or more of silicon nitride, silicon oxide and silicon oxynitride.

[0012] Preferably, the thickness of the passivation anti-reflection film in step (2) is independently 70 to 110 nm, and the refractive index is independently 2 to 2.4%.

[0013] Preferably, in step (2), the deposition temperature of the front side deposition is 400-550°C, and the deposition temperature of the back side deposition is 400-550°C.

[0014] Preferably, the annealing temperature in step (2) is 550-700° C., the pressure is 1500-1800 MPa, and the time is 100-500 s.

[0015] Preferably, the sintering temperature in step (3) is 700-900° C. and the sintering time is 40-70 seconds.

[0016] The present invention also provides a back-contact battery prepared by the preparation method of the back-contact battery.

[0017] The present invention provides a method for preparing a back-contact battery, comprising the following steps: depositing Al2O3 layers on the front and back surfaces of a semi-finished battery to obtain an intermediate; sequentially depositing a passivation anti-reflection film on the front and back surfaces of the intermediate, and annealing to obtain a passivated battery; printing electrodes on the passivated battery and then sintering it to obtain the back-contact battery. In the present invention, an intermediate with an Al2O3 layer is obtained by deposition, and a passivation anti-reflection film is deposited on the intermediate, followed by corresponding annealing and sintering to complete the preparation. The present invention adds an annealing process to the passivation process to provide better passivation control for the chemical passivation effect and field effect passivation of aluminum oxide, thereby achieving a replaceable interface passivation, and can better provide a debugging cooling window for the printing temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of a back contact battery of the present invention;

[0019] Among them, 1 is a semi-finished battery, 2 is the front Al2O3 layer, 3 is the back Al2O3 layer, 4 is the front passivation anti-reflection film, 5 is the back passivation anti-reflection film, 6 is the front annealing layer, and 7 is the back annealing layer. DETAILED DESCRIPTION

[0020] The present invention provides a method for preparing a back contact battery, comprising the following steps:

[0021] (1) depositing Al2O3 layers on the front and back surfaces of the semi-finished battery to obtain an intermediate;

[0022] (2) sequentially depositing a passivation anti-reflection film on the front and back surfaces of the intermediate, and annealing to obtain a passivated cell;

[0023] (3) After printing the electrodes of the passivated battery, sintering is performed to obtain the back contact battery.

[0024] In the present invention, the semi-finished battery is a battery that has completed all the manufacturing processes before depositing aluminum oxide, and is prepared using an N-type crystalline silicon substrate according to a method known to those skilled in the art.

[0025] In the present invention, the thickness of the Al2O3 layer in step (1) is preferably independently 3 to 10 nm, further independently 4 to 9 nm, and even more independently 5 to 8 nm; the aluminum source of the Al2O3 layer is trimethylaluminum, and the oxygen source of the Al2O3 layer is water or ozone.

[0026] In the present invention, the deposition temperature in step (1) is preferably 200-230°C, more preferably 205-225°C, and even more preferably 210-220°C.

[0027] In the present invention, during deposition, an aluminum source is first introduced and maintained for a certain period of time, and then an oxygen source is introduced and maintained for a certain period of time to complete a cycle.

[0028] In the present invention, the single aluminum source flow rate of deposition is preferably 1000-4000sccm, more preferably 1500-3500sccm, more preferably 2000-3000sccm, the single aluminum source time of deposition is preferably 3-7s, more preferably 4-6s, more preferably 5s; the single oxygen source flow rate of deposition is preferably 2000-5000sccm, more preferably 2500-4500sccm, more preferably 3000-4000sccm; the single oxygen source time of deposition is preferably 3-7s, more preferably 4-6s, more preferably 5s.

[0029] In the present invention, the number of deposition cycles is preferably 20 to 40 times, more preferably 25 to 35 times.

[0030] In the present invention, the material of the passivation anti-reflection film in step (2) is independently one or more of silicon nitride, silicon oxide and silicon oxynitride.

[0031] In the present invention, the thickness of the passivation anti-reflection film in step (2) is preferably independently 70 to 110 nm, further independently 80 to 100 nm, and more independently 85 to 95 nm; the refractive index is preferably independently 2 to 2.4%, further independently 2.1 to 2.3%, and more independently 2.15 to 2.2%.

[0032] In the present invention, the deposition temperature of the front deposition in step (2) is preferably 400-550°C, further preferably 450-500°C, and more preferably 460-480°C; the deposition temperature of the back deposition is preferably 400-550°C, further preferably 450-500°C, and more preferably 460-480°C.

[0033] In the present invention, the annealing temperature in step (2) is preferably 550-700°C, more preferably 600-650°C, and more preferably 620-630°C; the pressure is preferably 1500-1800 MPa, more preferably 1600-1700 MPa, and more preferably 1650 MPa; and the time is preferably 100-500 s, more preferably 200-400 s, and more preferably 240-260 s.

[0034] In the present invention, after the passivated battery is obtained after step (2), aluminum paste is printed on the P region to form a positive electrode through a metallization process, and silver paste is printed on the N region to form a negative electrode, and the conventional methods in the art are used for preparation.

[0035] In the present invention, the sintering temperature in step (3) is preferably 700-900°C, more preferably 750-850°C, more preferably 780-820°C; the sintering time is preferably 40-70s, more preferably 45-65s, more preferably 50-60s.

[0036] The present invention also provides a back-contact battery prepared by the preparation method of the back-contact battery.

[0037] The structural schematic diagram of the back contact battery of the present invention is as follows Figure 1 As shown;

[0038] Among them, 1 is a semi-finished battery, 2 is the front Al2O3 layer, 3 is the back Al2O3 layer, 4 is the front passivation anti-reflection film, 5 is the back passivation anti-reflection film, 6 is the front annealing layer, and 7 is the back annealing layer.

[0039] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] A 5nm Al2O3 layer is deposited on the front side of the semi-finished battery, and a 5nm Al2O3 layer is deposited on the back side. The aluminum source is trimethylaluminum and the oxygen source is ozone (the deposition temperature is 210°C, the flow rate of the aluminum source is 2000sccm, maintained for 5s, and then the flow rate of the oxygen source is 3000sccm, maintained for 5s; the above method is repeated 30 times to complete the deposition). After completion, it is placed in a PECVD device, and a 90nm thick, 2.2% refractive index silicon nitride passivation anti-reflection film is deposited on the front side (the deposition temperature is 500°C), and a 80nm thick, 2.1% refractive index silicon oxide passivation anti-reflection film is deposited on the back side (the deposition temperature is 550°C). After the deposition is completed, it is annealed at 600°C and 1700MPa for 300s; then it is transferred to printing, and finally aluminum paste is printed on the P area to form a positive electrode through a metallization process, and silver paste is printed on the N area to form a negative electrode, and sintered at 800°C for 60s to obtain a back contact battery.

[0042] Example 2: A 4nm Al2O3 layer is deposited on the front side of the semi-finished battery, and a 4nm Al2O3 layer is deposited on the back side. The aluminum source is trimethylaluminum, and the oxygen source is ozone (the deposition temperature is 200°C, the flow rate of the aluminum source is 1500sccm, maintained for 5s, and then the flow rate of the oxygen source is 4500sccm, maintained for 5s; the above method is repeated 25 times to complete the deposition). After completion, it is placed in a PECVD device, and a layer of silicon nitride passivation anti-reflection film with a thickness of 80nm and a refractive index of 2.1% is deposited on the front side (the deposition temperature is 550°C), and a layer of silicon oxide passivation anti-reflection film with a thickness of 85nm and a refractive index of 2.15% is deposited on the back side (the deposition temperature is 550°C). After the deposition is completed, it is annealed at 550°C and 1500MPa for 200s; then it is transferred to printing, and finally aluminum paste is printed on the P area to form a positive electrode through a metallization process, and silver paste is printed on the N area to form a negative electrode, and sintered at 800°C for 50s to obtain a back contact battery.

[0043] Example 3: A 7nm Al2O3 layer is deposited on the front side of the semi-finished battery, and a 7nm Al2O3 layer is deposited on the back side. The aluminum source is trimethylaluminum, and the oxygen source is ozone (the deposition temperature is 230°C, the flow rate of the aluminum source is 3500sccm, maintained for 5s, and then the flow rate of the oxygen source is 4500sccm, maintained for 5s; the above method is repeated 40 times to complete the deposition). After completion, it is placed in a PECVD device, and a layer of silicon nitride passivation anti-reflection film with a thickness of 75nm and a refractive index of 2.1% is deposited on the front side (the deposition temperature is 500°C), and a layer of silicon oxide passivation anti-reflection film with a thickness of 90nm and a refractive index of 2.10% is deposited on the back side (the deposition temperature is 500°C). After the deposition is completed, it is annealed at 650°C and 1800MPa for 400s, and then transferred to printing. Finally, aluminum paste is printed on the P area to form a positive electrode, and silver paste is printed on the N area to form a negative electrode through a metallization process. It is sintered at 800°C for 40s to obtain a back contact battery.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that deposition, passivation anti-reflection, annealing and sintering are not performed.

[0046] The back contact cells prepared in Examples 1 to 3 were subjected to performance tests, and the passivation and minority carrier lifetime tests were simulated by the testing machine WCT 120 / sinton instrument. The results are recorded in Table 1.

[0047] Table 1 Test results

[0048]

[0049]

[0050] It can be seen from Table 1 that the minority carrier lifetime, overall saturation current density, maximum open circuit voltage value and fill factor measured in Examples 1, 2 and 3 are all better than those in Comparative Example 1, indicating that the passivation characteristics of this process are more excellent and have an effect of improving the efficiency conversion of the battery cell.

[0051] It can be seen from the above embodiments that the present invention provides a method for preparing a back-contact battery, comprising the following steps: depositing Al2O3 layers on the front and back surfaces of a semi-finished battery to obtain an intermediate; sequentially depositing a passivation anti-reflection film on the front and back surfaces of the intermediate to obtain a passivated battery; printing electrodes on the passivated battery and then sintering it to obtain the back-contact battery. In the present invention, an intermediate with an Al2O3 layer is obtained by deposition, and a passivation anti-reflection film is deposited on the intermediate, followed by corresponding annealing and sintering to complete the preparation. The present invention adds an annealing process to the passivation process to provide better passivation control for the chemical passivation effect and field effect passivation of aluminum oxide, thereby achieving a replaceable interface passivation, and providing a better debugging and cooling window for the printing temperature.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a back contact battery, characterized in that: It includes the following steps: (1) depositing Al2O3 layers on the front and back surfaces of the semi-finished battery to obtain an intermediate; (2) sequentially depositing a passivation anti-reflection film on the front and back surfaces of the intermediate, and annealing to obtain a passivated cell; (3) After printing the electrodes of the passivated battery, sintering is performed to obtain the back contact battery.

2. The method for preparing a back contact battery according to claim 1, characterized in that: The thickness of the Al2O3 layer in step (1) is independently 3 to 10 nm, the aluminum source of the Al2O3 layer is trimethylaluminum, and the oxygen source of the Al2O3 layer is water or ozone.

3. The method for preparing a back contact battery according to claim 1 or 2, characterized in that: The deposition temperature in step (1) is 200-230° C., the single aluminum source flow rate of the deposition is 1000-4000 sccm, the single aluminum source time of the deposition is 3-7 s, the single oxygen source flow rate of the deposition is 2000-5000 sccm, the single oxygen source time of the deposition is 3-7 s, and the number of deposition cycles is 20-40 times.

4. The method for preparing a back contact battery according to claim 3, characterized in that: The material of the passivation anti-reflection film in step (2) is independently one or more of silicon nitride, silicon oxide and silicon oxynitride.

5. The method for preparing a back contact battery according to claim 1 or 4, characterized in that: The thickness of the passivation anti-reflection film in step (2) is independently 70 to 110 nm, and the refractive index is independently 2 to 2.4%.

6. The method for preparing a back contact battery according to claim 5, characterized in that: In step (2), the deposition temperature of the front side deposition is 400-550°C, and the deposition temperature of the back side deposition is 400-550°C.

7. The method for preparing a back contact battery according to claim 5, characterized in that: The annealing temperature in step (2) is 550-700° C., the pressure is 1500-1800 MPa, and the time is 100-500 s.

8. The method for preparing a back contact battery according to claim 1, 2, 4, 6 or 7, characterized in that: The sintering temperature in step (3) is 700-900° C. and the sintering time is 40-70 seconds.

9. A back-contact battery prepared by the method for preparing a back-contact battery according to any one of claims 1 to 8.

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