Method for limiting winding plating depth of semi-slice passive film of photovoltaic cell by using plasma
By setting up a plasma component with a grid line hollow structure in the ALD chamber and using a CO2 oxygen source and hydrogen discharge, the plating problem in the passivation process of photovoltaic cell slices was solved, the efficiency and yield of the cell components were improved, and the efficient deposition of the aluminum oxide film layer was achieved.
Patent Information
- Application Number
- CN202510704325.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-29
- Publication Date
- 2025-09-26
AI Technical Summary
During the passivation process of photovoltaic cell slices, the wrap-around plating phenomenon caused by conventional ALD technology affects the light absorption efficiency of the cell and the welding effect of the module, resulting in poor efficiency improvement of the cell module and yield loss.
A plasma assembly is set up in the ALD chamber and the lower electrode plate is designed as a grid line hollow structure. The half-slice of the photovoltaic cell is placed on the back of the plasma lower electrode plate. CO2 is used as an oxygen source and hydrogen discharge is performed in each cycle. The distance between the photovoltaic cell half-slice and the plasma lower electrode plate is controlled to reduce wrap-around plating.
It effectively reduces the plating width, improves the passivation effect of the passivation film, and increases the power and yield of battery components. The equipment has a simple structure and the gas is easy to industrialize and promote.
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Figure CN120700474A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of photovoltaic cells, and in particular to a method for limiting the coating depth of a passivation film on a half-slice of a photovoltaic cell by utilizing plasma. Background Art
[0002] Against the backdrop of overcapacity in the photovoltaic industry, internal competition has intensified, and companies are increasingly demanding cost reduction and efficiency improvement, leading to the emergence of slicing passivation technology. On the photovoltaic cell and silicon wafer side, in order to reduce the production cost per watt, the cell size has gradually increased, from 156mm*156mm to 182mm*182mm, 210mm*210mm, and may even increase to 230mm*230mm in the future. However, on the downstream component side, large-size cells will affect their fragmentation rate, airborne, power loss, etc. Therefore, a complete cell is usually cut into two or three pieces by laser. After slicing, a large number of recombination centers will be generated on the cut surface, which will seriously affect the cell efficiency and component power. In order to compensate for the efficiency loss of the cut surface, one or more layers of passivation film are usually coated on the cut surface to reduce minority carrier recombination, provide a field passivation effect, and reduce reflectivity. This technology is called half-slice passivation technology, or simply half-slice passivation technology.
[0003] Atomic layer deposition (ALD) technology, due to its superior film uniformity and three-dimensional coverage, is considered the preferred solution for silicon surface passivation. ALD technology is based on the principle of alternating, self-limiting surface reactions. By sequentially pulsed vapor precursors into the reaction chamber, they chemically adsorb onto the substrate surface and grow thin films layer by layer. For example, the ALD deposition process for aluminum oxide (Al2O3) typically involves four cyclic steps: trimethylaluminum (TMA) vapor injection → inert gas purge → water vapor (H2O) injection → a second purge. TMA molecules undergo a coordination reaction on the silicon surface to form a monolayer of Al-CH3 groups. The subsequent introduction of H2O generates an Al-O-Al bonded network through hydroxyl substitution, ultimately building a dense passivation film. Thanks to ALD's layer-by-layer growth characteristics, film thickness can be precisely controlled at the atomic scale and conformal deposition can be achieved on vertical channels or complex trenches. This property is particularly important for passivating surfaces with high aspect ratios. However, when using ALD technology to apply a passivation film to a half-cut silicon wafer, gases inevitably disperse into the gaps between the solar cells, causing severe wraparound plating on the half-cut solar cells. This affects the half-cut solar cells' light absorption, resulting in poor efficiency gains for the solar cell modules. Furthermore, wraparound plating can affect the soldering of solar cell modules, resulting in yield losses. Summary of the Invention
[0004] In response to the above-mentioned problems, the purpose of the present invention is to provide a method for limiting the depth of the passivation film winding of a photovoltaic cell half-slice by using plasma. The method comprises setting a plasma in an ALD chamber, setting the lower electrode of the plasma as a grid line hollow structure, placing the photovoltaic cell half-slice section on the back of the lower electrode, and using the plasma area on the back of the lower electrode to deposit a passivation film on the photovoltaic cell half-slice section. The method can effectively reduce the occurrence of "winding plating" and reduce the winding plating width by controlling the distance between the photovoltaic cell half-slice section and the plasma lower electrode. In addition, the present invention uses carbon dioxide as an oxygen source to further reduce the winding plating width, and uses hydrogen discharge to replenish hydrogen in each cycle of passivation film preparation to improve the passivation effect of the film layer.
[0005] To achieve the above objectives, the present invention first provides a method for limiting the depth of passivation film coating on a photovoltaic cell half-slice by using plasma, comprising the following steps:
[0006] (1) Add a plasma component to the ALD chamber and set the lower electrode of the plasma into a grid line hollow structure;
[0007] (2) Place the photovoltaic cell half slice with the cut surface facing upwards under the plasma lower plate;
[0008] (3) The ALD chamber is evacuated, leak tested, heated, and kept at a constant temperature. TMA, N2, an oxygen source, N2, H2, and N2 are then introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the cross-section of the photovoltaic cell half slice.
[0009] In one embodiment of the present invention, in step (1), the width of the grid lines in the grid line hollow structure is 1-5 mm, and the distance between each grid line is 5-10 mm.
[0010] In one embodiment of the present invention, in step (1), the edges of the grid lines are arc-shaped structures, which can effectively reduce the generation of tip discharge and make the glow discharge more stable.
[0011] In one embodiment of the present invention, in step (2), the distance between the cut surface of the photovoltaic cell half slice and the plasma bottom plate is 1-10 mm.
[0012] In one embodiment of the present invention, in step (3), after evacuation, the vacuum degree is 0-10 Pa.
[0013] In one embodiment of the present invention, in step (3), the constant temperature is 80-250°C.
[0014] In one embodiment of the present invention, in step (3), nitrogen gas carrying TMA is introduced when TMA is introduced, the flow rate of the nitrogen gas carrying TMA is 1000-10000 sccm, and the time for introducing TMA is 3-20 s.
[0015] In one embodiment of the present invention, in step (3), dilution nitrogen is also introduced when TMA is introduced, and the flow rate of the dilution nitrogen is 0-20000 sccm.
[0016] In one embodiment of the present invention, in step (3), the flow rate of N2 is 5000-30000 sccm for 5-20 seconds. The purpose of introducing N2 during this process is to purge the TMA present in the cross section and gap of the photovoltaic cell half-slice.
[0017] In one embodiment of the present invention, in step (3), the oxygen source introduced is CO2.
[0018] In one embodiment of the present invention, in step (3), argon is also introduced when CO2 is introduced, the flow rate of CO2 is 1000-10000 sccm, and the flow rate of argon is 1000-20000 sccm.
[0019] In one embodiment of the present invention, in step (3), plasma discharge is performed when CO2 is introduced, the discharge power is 3000-9000W, and the discharge time is 3-20s.
[0020] In one embodiment of the present invention, in step (3), the nitrogen flow rate of the secondary introduction of N2 is 5000-30000 sccm, and the time is 5-20 s. The purpose of the secondary introduction of N2 is to purge the CO2 present in the half-slice section and the gap of the photovoltaic cell.
[0021] In one embodiment of the present invention, in step (3), the flow rate of hydrogen when H2 is introduced is 5000-30000 sccm, and plasma discharge is performed when hydrogen is introduced, with a discharge power of 3000-9000 W and a time of 3 to 20 s.
[0022] In one embodiment of the present invention, in step (3), the nitrogen flow rate of the three times of N2 introduction is 5000-30000 sccm, and the time is 5-20 s. The purpose of the three times of introduction of N2 is to purge the H2 present in the cross section and gap of the photovoltaic cell half-slice.
[0023] In one embodiment of the present invention, the number of cycles in step (3) is 100-500 cycles, and the thickness of the aluminum oxide film layer grown on the cross section is 12-65 nm.
[0024] Beneficial effects:
[0025] (1) The prior art uses a conventional deposition process to deposit an aluminum oxide film layer on the cross-sectional surface of stacked solar cell slices. Although the solar cells are tightly stacked, there are still certain gaps between adjacent solar cells. The applicant found in previous research that during the deposition process, the gas source used to deposit the aluminum oxide film layer, such as TMA and water vapor, will diffuse into these gaps, resulting in wrap-around plating. The present invention, however, places a plasma component in an ALD chamber, sets the lower electrode plate of the plasma component as a grid line hollow structure, and places the photovoltaic cell half-slice section at a certain distance from the back of the plasma lower electrode plate. The limited plasma area on the back of the lower electrode plate is used to deposit a passivation film on the photovoltaic cell half-slice section. This method can effectively reduce the occurrence of "wrapping plating" and reduce the wrap-around plating width by controlling the distance between the photovoltaic cell half-slice section and the plasma lower electrode plate.
[0026] (2) The present invention sets the edge of the plasma lower electrode plate to an arc structure, which can reduce the generation of tip discharge and make the glow discharge more stable.
[0027] (3) Conventional ALD deposition of aluminum oxide passivation film usually uses H2O, O2 or O3 as the oxygen source to prepare the aluminum oxide passivation film. These oxygen sources are highly active and easily diffuse into the gaps between half-cut cells during the deposition of the aluminum oxide film, resulting in wrap-around plating. The present invention uses CO2 as the oxygen source. CO2 has low activity and it is generally difficult to use the oxygen in it as an oxygen source to generate aluminum oxide through ALD technology. The present invention uses plasma to ionize it. In the area where plasma exists, a reaction can occur to generate aluminum oxide, and no reaction will occur in the area without plasma. This can effectively prevent the occurrence of extra wrap-around plating.
[0028] (4) The present invention uses hydrogen discharge to replenish hydrogen in each cycle of depositing the aluminum oxide film, thereby improving the passivation effect of the aluminum oxide film layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 Schematic diagram of the positional relationship between a photovoltaic cell half-slice and a plasma assembly during preparation of a passivation film on a photovoltaic cell half-slice according to the present invention;
[0030] Figure 2 1. The top view and side view of the plasma lower electrode plate of the present invention;
[0031] Figure 3 This is an appearance diagram of the photovoltaic cell after the passivation film is prepared in Example 2;
[0032] Figure 4 This is an appearance diagram of the photovoltaic cell after the passivation film is prepared in Comparative Example 2;
[0033] Figure 5 This is an appearance diagram of the photovoltaic cell after the passivation film is prepared in Example 3;
[0034] Figure 6 This is an appearance diagram of the photovoltaic cell after the passivation film is prepared in Comparative Example 3;
[0035] Figure 7 This is an appearance diagram of the photovoltaic cell after the passivation film is prepared in Comparative Example 5. DETAILED DESCRIPTION
[0036] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.
[0037] Example 1
[0038] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0039] (1) A plasma assembly is set in the ALD chamber, and the lower plate of the plasma assembly is set to a grid line hollow structure, such as Figure 2 As shown, the width of the grid lines is 2 mm and the distance between the grid lines is 5 mm;
[0040] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0041] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0042] ① TMA introduction: 5000 sccm of TMA-carrying nitrogen and 10000 sccm of dilution nitrogen were introduced for 10 s;
[0043] ② Once N2 is introduced: 15000 sccm nitrogen is introduced for 10 s to purge the cell surface and gap TMA;
[0044] ③Introduce CO2: introduce 5000sccmCO2 and 10000sccmArgon, discharge power 6000W, time 10s;
[0045] ④ Secondary N2 injection: 15000 sccm nitrogen gas is introduced for 10 seconds to purge CO2 from the cell surface and gaps;
[0046] ⑤Introduce H2: introduce 15000 sccm of hydrogen, discharge power 6000 W, time 10 s;
[0047] ⑥ Introduce N2 three times: Introduce 15000 sccm nitrogen for 10 seconds to purge H2 from the cell surface and gaps.
[0048] The above steps were repeated for 500 cycles, and an aluminum oxide film layer with a thickness of 62 nm was grown on the cross section.
[0049] Example 2
[0050] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0051] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0052] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0053] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0054] ① TMA introduction: 10,000 sccm of TMA-carrying nitrogen and 20,000 sccm of dilution nitrogen were introduced for 20 s;
[0055] ② Once N2 is introduced: 30,000 sccm of nitrogen is introduced for 20 seconds to purge the TMA on the cell surface and gap;
[0056] ③Introduce CO2: introduce 10000sccmCO2 and 20000sccmArgon, discharge power 9000W, time 20s;
[0057] ④ Secondary N2 injection: 30,000 sccm nitrogen is introduced for 20 seconds to purge CO2 from the cell surface and gaps;
[0058] ⑤Introduce H2: introduce 30000 sccm of hydrogen, discharge power 9000 W, time 20 s;
[0059] ⑥ Inject N2 three times: Inject 30,000 sccm nitrogen for 20 seconds to purge H2 from the cell surface and gaps.
[0060] The above steps were repeated for 500 cycles, and an aluminum oxide film layer with a thickness of 62 nm was grown on the cross section.
[0061] Example 3
[0062] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0063] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0064] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0065] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0066] ① TMA introduction: 1000 sccm of TMA-carrying nitrogen and 0 sccm of dilution nitrogen were introduced for 3 seconds;
[0067] ② Once N2 is introduced: 5000 sccm nitrogen is introduced for 5 seconds to purge the cell surface and gap TMA;
[0068] ③Introduce CO2: introduce 1000sccmCO2 and 1000sccmArgon, discharge power 3000W, time 3s;
[0069] ④ Secondary N2 injection: 5000 sccm nitrogen gas is introduced for 5 seconds to purge CO2 from the cell surface and gaps;
[0070] ⑤Introduce H2: introduce 5000 sccm of hydrogen, discharge power 3000 W, time 3s;
[0071] ⑥ Introduce N2 three times: Introduce 5000 sccm nitrogen for 5 seconds to purge H2 from the cell surface and gaps.
[0072] The above steps were repeated for 100 cycles, and an aluminum oxide film layer with a thickness of 13 nm was grown on the cross section.
[0073] Example 4
[0074] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0075] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0076] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0077] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0078] ① TMA introduction: 5000 sccm of TMA-carrying nitrogen and 15000 sccm of dilution nitrogen were introduced for 10 s;
[0079] ② Once N2 is introduced: 20,000 sccm of nitrogen is introduced for 10 seconds to purge the cell surface and gap TMA;
[0080] ③Introduce CO2: introduce 5000sccmCO2 and 15000sccmArgon, discharge power 5000W, time 10s;
[0081] ④ Secondary N2 injection: 20,000 sccm nitrogen gas is introduced for 10 seconds to purge CO2 from the cell surface and gaps;
[0082] ⑤Introduce H2: introduce 20000sccm of hydrogen, discharge power 5000W, time 10s;
[0083] ⑥ Inject N2 three times: inject 20,000 sccm nitrogen for 10 seconds to purge H2 from the cell surface and gaps.
[0084] The above steps were repeated for 400 cycles, and an aluminum oxide film layer with a thickness of 50 nm was grown on the cross section.
[0085] Comparative Example 1
[0086] The difference between Comparative Example 1 and Example 1 is that the passivation film is not formed after the complete battery is sliced.
[0087] Comparative Example 2
[0088] The difference between Comparative Example 2 and Example 2 is that the distance between the cut surface of the photovoltaic cell half slice and the plasma lower plate is 5 mm.
[0089] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0090] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0091] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 5mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0092] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0093] ① TMA introduction: 10,000 sccm of TMA-carrying nitrogen and 20,000 sccm of dilution nitrogen were introduced for 20 s;
[0094] ② Once N2 is introduced: 30,000 sccm of nitrogen is introduced for 20 seconds to purge the TMA on the cell surface and gap;
[0095] ③Introduce CO2: introduce 10000sccmCO2 and 20000sccmArgon, discharge power 9000W, time 20s;
[0096] ④ Secondary N2 injection: 30,000 sccm nitrogen is introduced for 20 seconds to purge CO2 from the cell surface and gaps;
[0097] ⑤Introduce H2: introduce 30000 sccm of hydrogen, discharge power 9000 W, time 20 s;
[0098] ⑥ Inject N2 three times: Inject 30,000 sccm nitrogen for 20 seconds to purge H2 from the cell surface and gaps.
[0099] The above steps were repeated for 500 cycles, and an aluminum oxide film layer with a thickness of 62 nm was grown on the cross section.
[0100] Comparative Example 3
[0101] The difference between Comparative Example 3 and Example 3 is that the CO2 in the CO2-introducing step in step (3) is replaced by O2.
[0102] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0103] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0104] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0105] (3) TMA, N2, O2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0106] ① TMA introduction: 1000 sccm of TMA-carrying nitrogen and 0 sccm of dilution nitrogen were introduced for 3 seconds;
[0107] ② Once N2 is introduced: 5000 sccm nitrogen is introduced for 5 seconds to purge the cell surface and gap TMA;
[0108] ③Introduce O2: introduce 1000sccmO2 and 1000sccmArgon, discharge power 3000W, time 3s;
[0109] ④ Secondary N2 injection: 5000 sccm nitrogen gas is introduced for 5 seconds to purge O2 from the cell surface and gaps;
[0110] ⑤Introduce H2: introduce 5000 sccm of hydrogen, discharge power 3000 W, time 3s;
[0111] ⑥ Introduce N2 three times: Introduce 5000 sccm nitrogen for 5 seconds to purge H2 from the cell surface and gaps.
[0112] The above steps were repeated for 100 cycles, and an aluminum oxide film layer with a thickness of 13 nm was grown on the cross section.
[0113] Comparative Example 4
[0114] The difference between Comparative Example 4 and Example 4 is that steps ⑤ and ⑥ in step (3) are omitted.
[0115] A method for limiting the depth of passivation film coating on a half-cut photovoltaic cell by using plasma comprises the following steps:
[0116] (1) A plasma assembly is set in the ALD chamber, and the lower electrode plate of the plasma assembly is set to a grid line hollow structure;
[0117] (2) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and put them into the material box with the cut surface facing upwards. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upwards. Place the half-sliced photovoltaic cell slice with the cut surface facing upwards and place it below the plasma lower plate at a distance of 10 mm from the lower plate, as shown in the figure. Figure 1 As shown; and vacuuming, leak detection, heating, and constant temperature are carried out, the vacuum degree is 1Pa, and the constant temperature is 150℃;
[0118] (3) TMA, N2, CO2, N2, H2, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the half-cut photovoltaic cell.
[0119] ① TMA introduction: 5000 sccm of TMA-carrying nitrogen and 15000 sccm of dilution nitrogen were introduced for 10 s;
[0120] ② Once N2 is introduced: 20,000 sccm of nitrogen is introduced for 10 seconds to purge the cell surface and gap TMA;
[0121] ③Introduce CO2: introduce 5000sccmCO2 and 15000sccmArgon, discharge power 5000W, time 10s;
[0122] ④ Secondary N2 injection: Introduce 20,000 sccm nitrogen for 10 seconds to purge CO2 from the cell surface and gaps.
[0123] The above steps were repeated for 400 cycles, and an aluminum oxide film layer with a thickness of 50 nm was grown on the cross section.
[0124] Comparative Example 5
[0125] The conventional half-slice edge passivation process includes the following steps:
[0126] (1) Slicing and loading: Slice the complete battery, stack the cut battery slices uniformly, and load them into the material box with the cut surface facing upward. Put the half-cell battery loaded in the material box into the chamber with the cut surface facing upward. Place the cut surface of the photovoltaic cell half-slice facing upward, and vacuumize, leak test, heat up, and maintain constant temperature. The vacuum degree is 1Pa and the constant temperature is 150℃.
[0127] (2) TMA, N2, H2O, and N2 are introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the cut surface of the photovoltaic cell half slice:
[0128] ① TMA introduction: 1000 sccm of TMA-carrying nitrogen and 0 sccm of dilution nitrogen were introduced for 3 seconds;
[0129] ② Once N2 is introduced: 5000 sccm nitrogen is introduced for 5 seconds to purge the cell surface and gap TMA;
[0130] ③Introduce H2O: introduce 1000 sccm H2O and 0 sccm nitrogen for 3 seconds;
[0131] ④ Secondary N2 injection: Introduce 5000 sccm nitrogen for 5 seconds to purge H2O from the cell surface and gaps.
[0132] The above steps were repeated for 100 cycles, and an aluminum oxide film layer with a thickness of 13 nm was grown on the cross section.
[0133] The solar cell slices processed in Examples 1 to 4 and Comparative Examples 1 to 5 were packaged into modules, and the performance of the solar cell modules was tested. The results are shown in Table 1:
[0134] Table 1 Performance test results of solar cell slice assemblies after treatment in Examples 1 to 4 and Comparative Examples 1 to 5
[0135]
[0136]
[0137] According to the experimental results of Example 1 and Comparative Example 1, combined with the data in Table 1, after the half-cell battery is processed by the process of the present invention, the component power is greatly improved compared with the battery without edge passivation, indicating that the equipment structure of this solution can coat the battery cross-section and passivate it well.
[0138] From Example 2 and Comparative Example 2, combined Figure 3 、 Figure 4 As can be seen from the data in Table 1, by adjusting the distance between the battery section and the lower electrode plate, the width of the edge plating can be controlled, thereby optimizing the effect of the plating on component welding, and the yield can be consistent with that of conventional non-edge passivation.
[0139] From Example 3, Comparative Example 3, Comparative Example 5, combined Figure 5 、 Figure 6 、 Figure 7 As can be seen from the data in Table 1, the CO2 gas used in this solution has low chemical activity and will not react with TMA when not ionized. It can provide an oxygen source during ionization and ensure that no additional wrap-around plating occurs in the non-ionized area. Both O2 ionization and conventional ALD will cause serious wrap-around plating, affecting the component welding yield. In addition, the component power of this solution is higher than that of the conventional solution.
[0140] From Example 4 and Comparative Example 4, combined with the data in Table 1, it can be seen that the power is severely reduced by eliminating the hydrogen ionization component, and the addition of hydrogen ionization during the deposition of aluminum oxide greatly improves the passivation effect of the film layer.
[0141] Combined with all the embodiments, comparative examples and the results obtained. This solution uses a gas with low chemical activity to deposit aluminum oxide under ionization conditions, and uses the fixed motion area characteristics of the plasma to control the aluminum oxide reaction area, ensuring that the battery section is coated with a passivation film without producing an overly wide edge plating. At the same time, hydrogen is added during the deposition of aluminum oxide to increase the hydrogen content in the film layer, thereby improving its passivation effect and thus increasing the power of the battery module after passivation. This solution has a simple equipment structure, and the gases used are all common chemicals in photovoltaic workshops. In addition, the power gain of the module after the process is high and the yield is good, which is conducive to industrial promotion.
[0142] Based on this result, the aluminum oxide deposition solution in this method can also be applied to the ALD process of batteries such as PERC and BC that use aluminum oxide, reducing the occurrence of wrap-around plating and improving its passivation effect.
[0143] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.
Claims
1. A method for limiting the depth of passivation film coating on a photovoltaic cell half-slice by using plasma, characterized in that: The following steps are involved: (1) Add a plasma component to the ALD chamber and set the lower plate of the plasma component into a grid line hollow structure; (2) Place the photovoltaic cell half-slice with the cut surface facing upwards, and place it below the plasma lower plate at a distance of 1 to 10 mm from the back of the plasma lower plate; (3) The ALD chamber is evacuated, leak tested, heated, and kept at a constant temperature. TMA, N2, an oxygen source, N2, H2, and N2 are then introduced in sequence, and this cycle is repeated to deposit an aluminum oxide film on the surface of the cross-section of the photovoltaic cell half slice.
2. The method according to claim 1, characterized in that In step (1), the width of the grid lines in the grid line hollow structure is 1-5 mm, the distance between each grid line is 5-10 mm, and the edges of the grid lines are arc-shaped structures to reduce the generation of tip discharge and make the glow discharge more stable.
3. The method according to claim 1, characterized in that In step (3), after vacuuming, the vacuum degree is 0-10 Pa and the constant temperature is 80-250°C.
4. The method according to claim 1, wherein In step (3), when TMA is introduced, nitrogen gas carrying TMA and diluent nitrogen gas are introduced, the flow rate of the nitrogen gas carrying TMA is 1000-10000 sccm, the time for introducing TMA is 3-20 s, and the flow rate of the diluent nitrogen gas is 0-20000 sccm.
5. The method according to claim 1, wherein In step (3), the flow rate of N2 is 5000-30000 sccm for 5-20 s to purge the TMA in the half-slice section and the gap of the photovoltaic cell.
6. The method according to claim 1, characterized in that In step (3), the oxygen source introduced is CO2, and argon is also introduced when the CO2 is introduced. The flow rate of the CO2 is 1000-10000 sccm, and the flow rate of the argon is 1000-20000 sccm. When the CO2 is introduced, plasma discharge is performed, the discharge power is 3000-9000 W, and the discharge time is 3-20 s.
7. The method according to claim 1, characterized in that In step (3), the nitrogen flow rate of the secondary N2 is 5000-30000 sccm, and the time is 5-20 s to purge the CO2 existing in the cross section and gap of the photovoltaic cell half-slice.
8. The method according to claim 1, characterized in that In step (3), the flow rate of hydrogen when H2 is introduced is 5000-30000 sccm, and plasma discharge is performed when hydrogen is introduced, with a discharge power of 3000-9000 W and a time of 3 to 20 s.
9. The method according to claim 1, characterized in that In step (3), the nitrogen flow rate of N2 is 5000-30000 sccm for three times, and the time is 5-20 seconds to purge the H2 in the half-sliced surface and gap of the photovoltaic cell.
10. The method according to claim 1, characterized in that The number of cycles in step (3) is 100-500 cycles, and the thickness of the aluminum oxide film layer grown on the cross section is 12-65 nm.