Battery piece passivation method

Abstract

According to the battery piece passivation method provided by the invention, the passivation film deposition and the annealing treatment are integrated in the same deposition chamber, so that the deposition and the annealing are integrated on the same machine and can be completed at the same time by one process, the time of the technological process is shortened, the use of annealing equipment is reduced, and meanwhile, the requirements of cost reduction and efficiency improvement are met.

Description

Technical Field

[0001] The invention relates to the technical field of silicon solar cells, and in particular to a cell passivation method. Background Art

[0002] With the development of silicon solar cell technology, the size of photovoltaic silicon wafers has been increasing, from 125mm to 156mm, 166mm, 182mm, and even 210mm. The power of photovoltaic modules has also increased rapidly with the increase of silicon wafer size, and the cost has been continuously reduced. However, as the size of silicon wafers increases, the current of single-cell batteries continues to increase, and the loss of single-string modules is also increasing. Now, modules often cut large-size cells into two, three, or even six pieces, that is, module half-cut technology, to reduce module current, reduce module internal losses, and thus increase module power.

[0003] The current half-cell technology requires the entire cell to be cut into half slices by slicing. The slicing process will damage the edge of the cell, resulting in increased edge recombination, affecting the cell opening voltage Voc and filling FF, and thus causing a decrease in efficiency. Edge recombination refers to the recombination of carriers at the edge of the solar cell where they are not processed or not completely processed, resulting in a decrease in the efficiency of the cell. With the development of silicon solar cell technology, especially when approaching the theoretical efficiency limit, the impact of edge recombination on solar cell performance is becoming more and more significant.

[0004] Two types of scribing processes are commonly used: the traditional laser scribing-mechanical breaking process or the thermal laser scribing process. After scribing with both processes, the cell efficiency dropped by 0.3% to 1.2%. The process limitations in the production process make the edge recombination problem become non-negligible. In addition, the separation processes commonly used in current industrial production, such as thermal laser separation, such as laser scribing and thermal cutting edges, will introduce edge recombination. New damage recombination centers appear on the cut surface of the cell after scribing, causing edge recombination and resulting in reduced cell efficiency, which is mainly manifested as the loss of opening voltage Voc and filling FF. In order to improve the efficiency of solar cells, it becomes important to passivate the edges of the cell.

[0005] CN111430506A discloses a crystalline silicon solar cell and its edge passivation method, which places the sliced ​​solar cells horizontally and stacks them neatly so that the slice sections of each solar cell are in the same plane, and then puts them into a sheet box, which is put into an alumina deposition device together with the solar cells, and a layer of alumina film is plated on the edge of the slice section of the solar cell, and then puts them into an electric injection annealing furnace for annealing. This method can reduce the carrier recombination rate of the laser cut surface of the cell to a certain extent, but the uniformity of the alumina film is poor, resulting in limited ability to repair damage to the solar cell after cutting; moreover, this method adopts the method of annealing in an electric injection annealing furnace after passivation. Since the electric injection annealing time is 5-180min, not only is the annealing time too long, but the possibility of defects is also increased.

[0006] In summary, a cell passivation method needs to be developed. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for passivating a battery cell, which integrates the passivation film deposition and annealing treatment in the same deposition chamber, so that the deposition and annealing are integrated into the same machine, and the process can be completed simultaneously in one go, which not only reduces the process time, but also reduces the use of annealing equipment, while meeting the needs of reducing costs and increasing efficiency.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The object of the present invention is to provide a cell passivation method, comprising the following contents: depositing a passivation film on the cell in a deposition chamber, and after the deposition is completed, performing an annealing treatment in the same deposition chamber.

[0010] As a preferred technical solution of the present invention, the deposition includes atomic layer deposition or chemical vapor deposition.

[0011] As a preferred technical solution of the present invention, the passivation film includes any one of a silicon oxide film, an aluminum oxide film, a silicon nitride film or a silicon oxynitride film, or a combination of at least two of them.

[0012] As a preferred technical solution of the present invention, the temperature difference between the deposition and the annealing treatment is ≤100°C.

[0013] As a preferred technical solution of the present invention, the reaction temperature of the deposition is ≤350°C.

[0014] As a preferred technical solution of the present invention, the reaction temperature of the deposition is 120°C to 350°C, for example, 120°C, 150°C, 180°C, 200°C, 230°C, 250°C, 270°C, 300°C, 330°C or 350°C.

[0015] As a preferred technical solution of the present invention, after the deposition is completed, a source-carrying carrier gas is used to return to normal pressure and constant temperature, and then an annealing treatment is performed in the same deposition chamber.

[0016] As a preferred technical solution of the present invention, the heating time of the constant temperature treatment is 1 to 30 minutes, for example, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0017] As a preferred technical solution of the present invention, the target temperature of the constant temperature treatment is 150-450°C, for example, 150°C, 180°C, 200°C, 230°C, 250°C, 270°C, 300°C, 330°C, 350°C, 380°C, 400°C or 450°C, etc.

[0018] As a preferred technical solution of the present invention, the annealing treatment time is 1 to 60 minutes, for example, 1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0019] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0020] The present invention provides a cell passivation method, which integrates the passivation film deposition and annealing treatment in the same deposition chamber, so that the deposition and annealing are integrated into the same machine and can be completed simultaneously in one process, which not only reduces the process time, but also reduces the use of annealing equipment, while meeting the needs of reducing costs and increasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the battery cell passivation method of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0023] The present invention provides a battery cell passivation method, such as Figure 1 As shown, it includes the following contents: a passivation film is deposited on the battery cell in a deposition chamber, after the deposition is completed, a source carrier gas is used to return to normal pressure and constant temperature treatment, and then an annealing treatment is performed in the same deposition chamber.

[0024] Specifically, the present invention provides a passivation method for the edge of a half-cell battery, comprising the following contents:

[0025] The finished battery cells are taken for dicing, and the obtained half-cell cells are neatly stacked and placed in a deposition chamber, where a passivation film is deposited on the edge of the battery cell to complete the passivation of the edge of the half-cell cell; a source-carrying carrier gas is used to return to normal pressure and constant temperature treatment, and then an annealing treatment is performed in the same deposition chamber.

[0026] Among them, regarding the deposition of the passivation film: it can be selected to set a first buffer and a second buffer between the deposition chamber where the battery cell is located and the first precursor and the second precursor respectively; firstly, the first buffer and the second buffer are respectively pressed once by carrying the source carrier gas with the first precursor and the second precursor, so that the first precursor and the second precursor required for a single cycle reaction cycle enter the first buffer and the second buffer respectively; then, the first buffer and the second buffer are respectively pressed twice by carrying the source carrier gas, so that the diluted first precursor and the second precursor required for the single cycle reaction cycle enter the deposition chamber where the battery cell is located, and the deposition is completed; it can also be selected to directly allow the first precursor and the second precursor to enter the deposition chamber where the battery cell is located respectively through the source carrier gas, and dilute them in the deposition chamber, and no buffer is set between the source bottle and the deposition chamber.

[0027] In some embodiments, the slicing in the passivation method of the present invention adopts laser scribing mechanical breaking or thermal laser slicing to cut the finished battery cells, which belongs to the prior art and will not be repeated here; moreover, the source carrier gas is N2 or Ar, the first precursor can be an aluminum source or a silicon source, and the second precursor can be an oxygen source or a nitrogen source.

[0028] In some embodiments, atomic layer deposition is performed on half a cell in an atomic layer deposition chamber to deposit an aluminum oxide passivation film, and the deposition includes 60 to 300 single-cycle reaction cycles, for example 60, 100, 150, 200, 250 or 300, etc., and the single-cycle reaction cycle is a 6-step method or a 4-step method.

[0029] In some embodiments, the reaction temperature of the deposition is ≤350°C, preferably 120-350°C, for example, 120°C, 150°C, 180°C, 200°C, 230°C, 250°C, 270°C, 300°C, 330°C or 350°C, etc.; the passivation method of the present invention is particularly suitable for atomic layer deposition on the edge of the battery cell in an atomic layer deposition chamber to generate an aluminum oxide film; the first precursor is an aluminum source, preferably trimethylaluminum (TMA for short), and the second precursor is an oxygen source, preferably water or O3.

[0030] It should be noted that, although the reaction temperature ≤ 350°C is a low temperature condition known in the industry, the reaction temperature of the atomic layer deposition described in the present invention is preferably 120-350°C, which is higher than the reaction temperature of the prior art, and can effectively improve the quality of the aluminum oxide film obtained by atomic layer deposition, and provide favorable conditions for integrating atomic layer deposition and annealing treatment in the same deposition chamber; moreover, the reaction temperature of the atomic layer deposition described in the present invention is ≤ 350°C, which results in fewer decomposition products of the reactants involved, reduces the CVD reaction, and improves the density of the aluminum oxide film.

[0031] In some embodiments, the passivation method of the present invention integrates the deposition and annealing of the aluminum oxide passivation film into the same machine for the edge of a half-cell, and can be completed simultaneously in one process, that is, the aluminum oxide film is first deposited using the ALD device, and then the ALD device is used for annealing, which not only reduces the process time, but also reduces the use of annealing equipment, while meeting the needs of cost reduction and efficiency improvement, and can also increase pFF by 0.1-0.4%, and the pEff of the cell by >0.05%

[0032] Example 1

[0033] This embodiment provides a passivation method for a half-cell battery, comprising the following steps:

[0034] (1) Take the finished battery cell and cut the battery cell by thermal laser scribing process;

[0035] (2) The ALD machine is heated to 250°C and kept at a constant temperature for 30 minutes, ensuring that the machine temperature difference is ±1°C. The obtained half-cells are neatly stacked and inserted into a special aluminum boat, which is then sent into the machine process chamber. The temperature is again kept constant for 15 minutes before the process begins.

[0036] (3) The total pressure of the TMA buffer is 300 Torr, and the pressure ratio of the total pressure of the TMA buffer to the total pressure of the H2O buffer is 1:0.6. The TMA source bottle and the H2O source bottle are respectively pressed once by using high-purity N2 to carry TMA / H2O, and the source flow rate is 8000 sccm, wherein the MFC range of N2 is 30 slm, the TMA one-time pressing value is 40% of the total pressure of the TMA buffer, and the H2O one-time pressing value is 60% of the total pressure of the H2O buffer, so that the aluminum source and oxygen source required for a single cycle reaction cycle enter the aluminum source buffer and the oxygen source buffer respectively; high-purity N2 is used to carry TMA / H2O. The TMA buffer and the H2O buffer were respectively subjected to secondary stamping, the N2 flow rate was 12000sccm, the MFC range of N2 was 30slm, and accordingly, the TMA secondary stamping value was 60% of the total pressure of the TMA buffer, and the H2O secondary stamping value was 40% of the total pressure of the H2O buffer, so that the aluminum source and oxygen source required for the diluted single-cycle reaction period respectively entered the deposition chamber where the battery cell was located, and entered from the top of the deposition chamber in a spray-type air intake mode to complete the deposition of the single-cycle reaction period; wherein, the process was cycled 200 times, and the aluminum oxide thickness of 40nm was deposited, and the time of a single cycle was as follows:

[0037] 6-step method:

[0038] Pass TMA (5s) → N2 purge (12s) → wait (10s) → pass H2O (5s) → N2 purge (10s) → evacuate (10s);

[0039] (4) After the aluminum oxide film is deposited, N2 is used to return to normal pressure and constant temperature treatment. The heating time of the constant temperature treatment is 10 minutes, the target temperature of the constant temperature treatment is 250°C, and the annealing treatment is performed for 30 minutes.

[0040] Comparative Example 1

[0041] This comparative example provides a passivation method for half-cell cells. Compared with Example 1, the only difference is that the annealing treatment in step (4) is no longer integrated with the deposition in the same deposition chamber. The specific contents are as follows: After the deposition of the aluminum oxide film is completed, N2 is used to return to normal pressure and naturally cool to room temperature, and then placed in an electric injection annealing furnace for annealing. The annealing temperature is 250°C and the annealing time is 30 minutes.

[0042] The solar cells obtained in the above-mentioned embodiment and comparative example were subjected to SunsVoc test respectively, and the test results are summarized in Table 1.

[0043] Table 1

[0044]

[0045] Comparing Example 1 with Comparative Example 1, it can be seen that Example 1 integrates the passivation film deposition and annealing treatment in the same deposition chamber, and can basically achieve the film thickness uniformity and SunsVoc test performance of Comparative Example 1. Example 1 not only reduces the time of the process, but also reduces the use of annealing equipment, while meeting the needs of cost reduction and efficiency improvement, and has more advantages for promotion.

[0046] In summary, the present invention provides a method for passivating a battery cell, which integrates the deposition of a passivation film and the annealing treatment in the same deposition chamber, so that the deposition and annealing are integrated into the same machine, and can be completed simultaneously in one process, which not only reduces the time of the process, but also reduces the use of annealing equipment, while meeting the needs of reducing costs and increasing efficiency. Through the field passivation and chemical passivation of the passivation film, the passivation film is activated by annealing at the same time, the passivation effect is enhanced, and the edge recombination effect after cutting is reduced, the pFF can be increased by 0.1-0.4%, and the pEff of the battery cell can be increased by >0.05%.

[0047] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0048] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0050] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A cell passivation method, characterized in that: It includes the following: A passivation film is deposited on the cell in a deposition chamber, and after the deposition is completed, an annealing process is performed in the same deposition chamber.

2. The cell passivation method according to claim 1, characterized in that: The deposition includes atomic layer deposition or chemical vapor deposition.

3. The cell passivation method according to claim 1, characterized in that: The passivation film includes any one of a silicon oxide film, an aluminum oxide film, a silicon nitride film, or a silicon oxynitride film, or a combination of at least two of them.

4. The cell passivation method according to claim 1, characterized in that: The temperature difference between the deposition and the annealing treatment is ≤100°C.

5. The cell passivation method according to claim 1, characterized in that: The reaction temperature of the deposition is ≤350°C.

6. The cell passivation method according to claim 5, characterized in that: The reaction temperature of the deposition is 120°C to 350°C.

7. The cell passivation method according to claim 1, characterized in that: After the deposition is completed, the source-carrying carrier gas is used to return to normal pressure and constant temperature, and then an annealing treatment is performed in the same deposition chamber.

8. The cell passivation method according to claim 7, characterized in that: The heating time of the constant temperature treatment is 1 to 30 minutes.

9. The cell passivation method according to claim 7, characterized in that: The target temperature of the constant temperature treatment is 150-450°C.

10. The battery cell passivation method according to claim 1 or 7, characterized in that: The annealing treatment time is 1 to 60 minutes.

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