Monocrystalline cell sheet, photovoltaic module, and coating method capable of suppressing occurrence of point-like contamination

Abstract

The application provides a single-crystal cell, a photovoltaic module and a coating method capable of inhibiting the occurrence of point pollution. The method comprises the following steps: placing a cell with an aluminum oxide coating layer in a graphite boat, and placing the graphite boat in a coating cavity of a coating device; performing a first vacuumizing process and a first temperature rising process on the coating cavity, and the pressure of the first temperature rising process is normal pressure; performing a first cleaning process on the cell with the aluminum oxide coating layer by using a first cleaning gas; and coating the cell treated by the first cleaning process. The first vacuumizing process can remove impurity gas in the coating cavity, thereby improving the purity of the coating layer formed in the coating process. The first cleaning process can remove fragments and gas particles in the coating cavity. In the temperature rising process, the gas flow is 0, and the pressure in the furnace is normal pressure, which further reduces the activity of dust and particles in the tube, which is conducive to reducing the occurrence of point pollution and improving the yield and photoelectric conversion efficiency of the cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery piece manufacturing, in particular to a single crystal battery piece, a photovoltaic module and a coating method capable of inhibiting the appearance of point-shaped pollution. BACKGROUND

[0002] The process flow of the laser direct structuring technology (LDSE) of the p-type PERC battery is: alkali texturing, diffusion, laser direct structuring technology (LDSE), etching, oxidation, atomic layer deposition (ALD), front and back PECVD, laser windowing, screen printing, and sintering. Compared with the conventional single crystal process, there are additional LDSE and ALD processes. The PEEC technology refers to forming an aluminum oxide passivation layer on the surface of a solar cell, which can greatly reduce the back electrical recombination, improve the open circuit voltage, short circuit current of the battery, and improve the conversion efficiency. The passivation layer prepared by ALD (atomic deposition) is a dense thin layer with a thickness of about 3-6 nm.

[0003] The function of the PD305 tube machine platform is to coat a silicon nitride layer on the back film of the silicon wafer, which has the functions of passivation and protection of the aluminum oxide passivation layer. However, during the production process of the PD305 machine platform, silicon wafer fragments and dust may be left in the tube. Before coating the silicon nitride layer, the dust and fragments will impact the surface of the passivation layer under the action of the airflow, damaging the passivation layer. The damaged battery piece will exhibit point-shaped pollution (black spots, black spots) under EL after screen printing and sintering, causing the degradation of the battery piece.

[0004] In view of the above problems, it is necessary to provide a coating method capable of inhibiting the appearance of point-shaped pollution. SUMMARY

[0005] The main purpose of the present application is to provide a single crystal battery piece, a photovoltaic module and a coating method capable of inhibiting the appearance of point-shaped pollution, to solve the problem that the existing coating method is easy to cause point-shaped pollution on the single crystal battery piece.

[0006] In order to achieve the above-mentioned purpose, the present application provides a coating method capable of inhibiting the appearance of point-shaped pollution, which comprises the following steps: placing a battery piece containing an aluminum oxide coating layer in a graphite boat, and placing it in a coating cavity of a coating device; performing a first vacuum process and a first temperature rising process on the coating cavity, wherein the pressure of the first temperature rising process is atmospheric pressure; using a first cleaning gas to perform a first cleaning process on the battery piece containing the aluminum oxide coating layer; and coating the battery piece treated by the first cleaning process.

[0007] Further, the pressure of the first vacuum process is lower than 50 mTorr, and the time is 2-6 min; in the first temperature rising process, the gas flow is 0, the target temperature is 300-400℃, and the temperature rising rate is 10-20℃ / min.

[0008] Further, in the first cleaning process, the flow rate of the first cleaning gas is 500-2500sccm, the pressure is 9-11Torr, and the cleaning time is 60-240s.

[0009] Further, between the first cleaning process and the film coating process, the film coating method capable of inhibiting the occurrence of point-like contamination further comprises: performing a second temperature rising process on the film coating cavity, and then performing a second cleaning process on the battery piece by using a second cleaning gas.

[0010] Further, in the second temperature rising process, the gas flow rate is 0, the pressure is normal pressure, the target temperature is 450-500℃, and the temperature rising time is 10-20min; in the second cleaning process, the second cleaning gas is ammonia and laughing gas, wherein the flow rate of the ammonia is 500-2500sccm, the flow rate of the laughing gas is 500-2500sccm, the pressure in the furnace is returned to 1000-2000mTorr, and the cleaning time is 30-180s.

[0011] Further, the first cleaning gas is selected from one or more of laughing gas, O2, O3, and water vapor.

[0012] Further, the film coating process comprises: performing a third vacuumizing process on the film coating cavity, introducing a special gas into the film coating cavity, and performing silicon nitride film deposition under a predetermined pressure, electron gas flow rate, and radio frequency to form a silicon nitride film layer, wherein the special gas is silane and ammonia.

[0013] Further, in the film coating process, the flow rate of the silane is 0-1000sccm, the flow rate of the ammonia is 500-1000sccm, the pressure is 1200-1700mTorr, the radio frequency power is 3500-4200w, the ratio of the opening time to the closing time of the radio frequency device is 1:7-1:15, and the deposition time is 8-20min.

[0014] Another aspect of the present application also provides a single-crystal battery piece comprising a silicon nitride coating layer formed by using the film coating method capable of inhibiting the occurrence of point-like contamination.

[0015] By using the technical solution of the present application, in the above film coating process, the film coating cavity is first subjected to a first vacuumizing process, which can remove impurity gases present in the film coating cavity, thereby improving the purity of the coating layer formed in the film coating process. After the first vacuumizing process, the first cleaning process is performed, which can remove debris and gas particles present in the film coating cavity, and can also remove impurities on the surface of the silicon piece. This is conducive to greatly reducing the probability of the above-mentioned substances impacting the aluminum oxide layer, reducing the generation of point-like contamination (black spots, black dots), and thereby improving the yield and photoelectric conversion efficiency of the battery piece. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an exemplary embodiment of the application and together with the description, serve to explain the application. In the drawings,

[0017] Figure 1 A film coating process flow provided by Embodiment 1 is shown, which can inhibit the occurrence of point pollution on a battery piece. DETAILED DESCRIPTION

[0018] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0019] As described in the background, the existing film coating method is prone to cause point pollution on a single crystal battery piece. In order to solve the above technical problem, the present application provides a film coating method capable of inhibiting the occurrence of point pollution, which comprises: placing a battery piece with an aluminum oxide coating layer in a graphite boat, and placing it in a film coating cavity of a film coating device; making the film coating cavity undergo a first vacuumizing process and a first temperature rising process, wherein the pressure of the first temperature rising process is normal pressure; using a first cleaning gas to perform a first cleaning process on the battery piece with the aluminum oxide coating layer; and performing film coating on the battery piece treated by the first cleaning process.

[0020] In the above film coating process, the first vacuumizing process is performed on the film coating cavity first, which can remove impurity gases existing in the film coating cavity, thereby improving the purity of the coating layer formed in the film coating process. Meanwhile, the first cleaning process is performed after the first vacuumizing process, which can remove debris and gas particles existing in the film coating cavity, and can also remove impurities on the surface of the silicon piece, which is conducive to greatly reducing the probability of the above-mentioned substances impacting the aluminum oxide layer and reducing the generation of point pollution (black spots, black spots), thereby improving the yield and photoelectric conversion efficiency of the battery piece.

[0021] In a preferred embodiment, the pressure of the first vacuumizing process is lower than 50 mTorr, and the time is 2-6 min; in the first temperature rising process, the gas flow is 0, the target temperature is 300-400℃, and the temperature rising rate is 10-20℃ / min. Limiting the process parameters in the first vacuumizing process and the first temperature rising process to the preferred range of the present application is conducive to further reducing the influence of impurities in the environment on the aluminum oxide layer, thereby further inhibiting the generation of point pollution.

[0022] The first cleaning process is beneficial to reduce the probability of point-like contamination on the battery piece. In the first cleaning process, the flow rate, pressure and cleaning time of the first cleaning gas can not be limited, as long as it can reduce the occurrence of point-like contamination compared with the existing method. In a preferred embodiment, in the first cleaning process, the flow rate of the first cleaning gas is 500-2500 sccm, the pressure is 9-11 Torr, and the cleaning time is 60-240 s. The flow rate, pressure and cleaning time of the first cleaning gas in the first cleaning process are included but not limited to the above range, and it is beneficial to further improve the cleaning effect of the first cleaning process by limiting them in the above range.

[0023] In a particular field, the cleanliness of the plated layer in the battery piece is required to be higher, and therefore in order to obtain a battery piece with more excellent cleanliness, in a preferred embodiment, between the first cleaning process and the plating process, the plating method capable of inhibiting the occurrence of point-like contamination further comprises: performing a second temperature rising process on the plating cavity, and then performing a second cleaning treatment on the battery piece by using a second cleaning gas.

[0024] In a preferred embodiment, in the second temperature rising process, the gas flow rate is 0, the pressure is atmospheric pressure, the target temperature is 450-500°C, and the temperature rising time is 10-20 min. In the second cleaning process, no gas is introduced into the furnace in the plating cavity and the vacuum pump is closed, and the atmosphere in the tube is kept static, which is beneficial to minimize the activity of small fragments and dust, thereby further reducing the probability of collision between the above fragments and dust and the passivation layer on the surface of the silicon wafer.

[0025] In a preferred embodiment, in the second cleaning process, the second cleaning gas is ammonia and laughing gas, wherein the flow rate of ammonia is 500-2500 sccm, the flow rate of laughing gas is 500-2500 sccm, the pressure in the furnace is returned to 1000-2000 mTorr, and the cleaning time is 30-180 s. The type, gas flow rate, pressure and cleaning time of the second cleaning process are included but not limited to the above range, and it is beneficial to further improve the cleaning effect of the second cleaning process by limiting them in the above range, thereby further reducing the risk of point-like contamination on the surface of the battery piece.

[0026] The first cleaning gas can be selected from the gases commonly used in the art which do not participate in the plating reaction. Preferably, the first cleaning gas includes but is not limited to one or more of the group consisting of laughing gas, O2, O3 and water vapor.

[0027] The above plating process can be performed by using the process commonly used in the art. For example, in the plating process in the PECVD device, the plating cavity is subjected to a third vacuumizing treatment, a special gas is introduced into the plating cavity, and a silicon nitride film is deposited under a predetermined pressure, electron gas flow rate and radio frequency to form a silicon nitride film layer, wherein the special gas is silane and ammonia.

[0028] In a preferred embodiment, during the coating process, the silane flow rate is 0–1000 sccm, the ammonia flow rate is 500–1000 sccm, the pressure is 1700 mTorr, the RF power is 3500–4200 W, the ratio of the RF device's on-time to off-time is 1:7–1:15, and the deposition time is 8–20 min. During the coating process, the silane and ammonia flow rates, pressures, RF power, RF on / off ratio, and deposition time include, but are not limited to, the above ranges. Limiting these ranges helps improve the smoothness of the silicon nitride coating.

[0029] Another aspect of this application provides a monocrystalline solar cell, including a silicon nitride coating formed using a coating method provided in this application that can suppress the occurrence of point contamination.

[0030] Since the coating method provided in this application can remove debris and gas particles present in the coating cavity, it greatly reduces the probability of these substances impacting the alumina layer, reduces the generation of point contamination (black spots), and thus helps to improve the yield and photoelectric conversion efficiency of the solar cells.

[0031] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0032] Example 1

[0033] A coating process that can reduce the proportion of point-like contamination in solar cells during electroluminescence includes the following steps (such as...) Figure 1 As shown):

[0034] 1) The process is carried out in a PECVD apparatus. The solar cells containing the aluminum oxide coating are loaded into a graphite boat, and the graphite boat is placed inside the coating tube (PD305) of the PECVD apparatus.

[0035] 2) Perform the first vacuuming process (target vacuum degree is 50 mTorr, time is 4 min) and the first heating process (target temperature is 350℃, gas flow rate is 0, pressure is atmospheric pressure, heating rate is 15℃ / min) on the above-mentioned coated tube, confirm the vacuum inside the tube and heat up, and do not introduce any gas into the tube during the process.

[0036] 3) Perform a first cleaning process on the battery cells processed in step 2), wherein the flow rate of the first cleaning gas (laughing gas, N2O) is 1500 sccm, the time is 2 min, and the pressure is 10 Torr.

[0037] 4) After the first cleaning process, the coated tube is subjected to a second temperature rising process at normal pressure, and the temperature is kept constant at 480-500°C for 15 min in static state.

[0038] 5) The battery piece treated in step 4) is subjected to a second cleaning process, wherein the second cleaning gas is ammonia and laughing gas, the flow rate of ammonia is 1500 sccm, the flow rate of laughing gas is 1500 sccm, the time is 1 min, and the pressure is 1500 mTorr.

[0039] 6) After the coating cavity is subjected to an evacuation process, the temperature in the coating cavity is kept at 480-500°C, then silane 500 sccm, ammonia 5000 sccm are introduced into the coating cavity, and the pressure is limited to 1700 mTorr, the radio frequency power is 4200 W, the ratio of the opening time and the closing time of the radio frequency power source is 1:8, and the deposition time is 15 min.

[0040] 7) The coating cavity is subjected to furnace cooling, nitrogen filling to release the vacuum in the tube, and the silicon wafer is taken out in sequence, and the coating process is completed.

[0041] Example 2

[0042] The difference from example 1 is that the gas flow rate and cleaning time of the first cleaning process are reduced, specifically, in the first cleaning process, the flow rate of laughing gas is 500 sccm, the time is 1 min, and the pressure in the furnace is 10000 mTorr.

[0043] Example 3

[0044] The difference from example 1 is that the gas flow rate and cleaning time of the first cleaning process and the second cleaning process are increased, specifically, in the first cleaning process, the flow rate of laughing gas is 2500 sccm, the time is 2 min, and the pressure is 10000 mTorr; in the second cleaning process, the flow rate of ammonia is 2500 sccm, the flow rate of laughing gas is 2500 sccm, the time is 3 min, and the pressure is 1500 mTorr.

[0045] Example 4

[0046] The difference from example 1 is that in the first cleaning process, the flow rate of the first cleaning gas is 2500 sccm, the pressure is 10000 mTorr, and the cleaning time is 60 s.

[0047] Example 5

[0048] The difference from example 1 is that in the first cleaning process, the flow rate of the first cleaning gas is 1000 sccm, the pressure is 10000 mTorr, and the cleaning time is 180 s.

[0049] Example 6

[0050] The difference from Example 1 is that in the first cleaning process, the flow rate of the first cleaning gas is 2000 seem, the pressure is 10000 mTorr, and the cleaning time is 180 s.

[0051] Example 7

[0052] The difference from Example 1 is that in the first cleaning process, the flow rate of the first cleaning gas is 3000 seem, the pressure is 10000 mTorr, and the cleaning time is 180 s.

[0053] Example 8

[0054] The difference from Example 1 is that in the second cleaning process, the flow rate of ammonia is 500 seem, the flow rate of laughing gas is 500 seem, and the cleaning time is 120 s.

[0055] Example 9

[0056] The difference from Example 1 is that in the second cleaning process, the flow rate of ammonia is 2500 seem, the flow rate of laughing gas is 2500 seem, and the cleaning time is 120 s.

[0057] Example 10

[0058] The difference from Example 1 is that in the second cleaning process, the flow rate of ammonia is 1000 seem, the flow rate of laughing gas is 1500 seem, and the cleaning time is 120 s.

[0059] Example 11

[0060] The difference from Example 1 is that in the second cleaning process, the flow rate of ammonia is 3000 seem, the flow rate of laughing gas is 3000 seem, and the cleaning time is 120 s.

[0061] Example 12

[0062] The difference from Example 1 is that in the first vacuuming process, the pressure is 60 mTorr, and the time is 5 min.

[0063] Example 13

[0064] The difference from Example 1 is that in the first temperature increasing process, the target temperature is 450°C.

[0065] Comparative Example 1

[0066] The difference from the example is that the first cleaning process is not performed.

[0067] Comparative Example 2

[0068] The difference from the embodiment is that the first cleaning process and the second cleaning process are not performed.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that the normal pressure static temperature rising is changed to blowing the silicon wafer and the furnace body with 2000 seem nitrogen under a pressure of 1500 mTorr.

[0071] It should be noted that the experimental content: 32000 pieces of front-end process wafer were processed, divided into 16 groups of 2000 pieces each, and a same PD305 coating furnace tube and graphite boat were selected. The method in the embodiment and the comparative example was used for coating.

[0072] After production, the same silk screen printing line was used for production, and the same table electroluminescence tester (EL tester) was used for testing, and the EL point pollution proportions of the 16 groups were counted respectively. The test method was single silicon wafer test, whether it was point pollution was judged according to the EL image, and the dark spots in the middle area with an area of >5mm*5mm and the edge area of >30mm*5mm were mainly point pollution; according to the blackening degree, it was divided into black spots (the black color was lighter, and the color was gray) and black spots (the black color was darker). Under the same equipment, the EL point pollution proportion was counted and shown in Table 1.

[0073] Table 1

[0074] Total proportion of dots Proportion of black dots Proportion of black spots Example 1 0.65％ 0.40％ 0.25％ Example 2 1.30％ 0.63％ 0.67％ Example 3 1.37％ 0.79％ 0.58％ Example 4 1.25％ 0.79％ 0.46％ Example 5 0.99％ 0.56％ 0.43％ Example 6 1.03％ 0.63％ 0.40％ Example 7 2.02％ 1.23％ 0.79％ Example 8 1.15％ 0.79％ 0.36％ Example 9 1.25％ 0.69％ 0.56％ Example 10 0.78％ 0.49％ 0.29％ Example 11 1.99％ 1.16％ 0.83％ Example 12 1.49％ 0.93％ 0.56％ Example 13 1.29％ 0.86％ 0.43％ Comparative Example 1 2.22％ 1.36％ 0.86％ Comparative Example 2 2.11％ 1.19％ 0.92％ Comparative Example 3 2.60％ 2.30％ 0.30％

[0075] As can be seen from Table 1, the point pollution proportion of the embodiments of Examples 1 to 13 is obviously less than that of Comparative Examples 1 to 3, which shows that adding a cleaning process or twice cleaning process can improve the EL point pollution.

[0076] Comparing Examples 1, 2, 5, 8, 10, it can be seen that the cleaning gas flow in the cleaning step is reduced, and the point pollution proportion can be obviously seen to rise.

[0077] Comparing Examples 1, 3, 4, 6, 7, 9 and 11, the cleaning gas flow in the cleaning step is increased, and the point pollution proportion can be obviously seen to increase; at the same time, once it exceeds the preferred range of the application, the point pollution proportion rises obviously, but it still has a good effect of reducing point pollution compared with Comparative Examples 1 to 3.

[0078] Comparing Examples 1 and 12, the pressure in the tube does not drop below 50 mTorr in the vacuum process, indicating that the tube contains more gas and dust impurities, and the point pollution proportion is high;

[0079] Comparing Examples 1 and 13, the temperature is set to 450℃, which mainly affects that the temperature rising time before the first cleaning step is longer. The probability of damage of the impurities on the surface of the silicon wafer to the aluminum oxide layer is larger, which leads to the rise of point pollution;

[0080] It should be noted that the terms "first", "second", and the like in the description and in the claims of this application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of practical implementation irrespective of the particular sequential or chronological order of the steps contained therein.

[0081] The preferred embodiments of the application are described above in detail. The application is not limited to the embodiments described above, but can vary and be modified in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the scope of the protection of the application.

Claims

1. A coating method for suppressing the occurrence of point-like contamination, characterized in that, The film coating method capable of inhibiting the occurrence of point-like contamination comprises: placing the battery piece with the aluminum oxide coating into a graphite boat, and placing the graphite boat into a film coating cavity of a film coating device; subjecting the film coating cavity to a first vacuumizing process and a first temperature rising process, wherein the pressure in the first temperature rising process is normal pressure, and the gas flow rate is 0; subjecting the battery piece with the aluminum oxide coating to a first cleaning process using a first cleaning gas selected from one or more of the group consisting of laughing gas, O2, O3 and water vapor; subjecting the battery piece treated by the first cleaning process to a film coating process to form a silicon nitride film layer; the pressure in the first vacuumizing process is lower than 50 mTorr, and the time is 2-6 min; in the first cleaning process, the flow rate of the first cleaning gas is 500-2500 sccm, the pressure is 9-11 Torr, and the cleaning time is 60-240 s.

2. The film coating method capable of inhibiting the occurrence of point-like contamination according to claim 1, wherein in the first temperature rising process, the gas flow rate is 0, the target temperature is 300-400°C, and the temperature rising rate is 10-20°C / min.

3. The film formation method capable of suppressing occurrence of a dot-like stain according to claim 1 or 2, characterized by, between the first cleaning process and the film coating process, the film coating method capable of inhibiting the occurrence of point-like contamination further comprises: subjecting the film coating cavity to a second temperature rising process, and then subjecting the battery piece to a second cleaning process using a second cleaning gas.

4. The film formation method capable of suppressing occurrence of a dot-like stain according to claim 3, characterized by in the second temperature rising process, the gas flow rate is 0, the pressure is normal pressure, the target temperature is 450-500°C, and the temperature rising time is 10-20 min; in the second cleaning process, the second cleaning gas is ammonia and laughing gas, wherein the flow rate of the ammonia is 500-2500 sccm, the flow rate of the laughing gas is 500-2500 sccm, the pressure in the furnace is returned to 1000-2000 mTorr, and the cleaning time is 30-180 s.

5. The film formation method capable of suppressing occurrence of a dot-like stain according to Claim 1, wherein the film coating process comprises: subjecting the film coating cavity to a third vacuumizing process, introducing a special gas into the film coating cavity, and depositing a silicon nitride film layer under a predetermined pressure, electron gas flow rate and radio frequency, wherein the special gas is silane and ammonia.

6. The film formation method capable of suppressing occurrence of a dot-like stain according to claim 5, wherein in the film coating process, the flow rate of the silane is 0-1000 sccm, the flow rate of the ammonia is 500-1000 sccm, the pressure is 1200-1700 mTorr, the radio frequency power is 3500-4200 W, the ratio of the opening time to the closing time of the radio frequency device is 1:7-1:15, and the deposition time is 8-20 min.

7. A single crystal cell comprising a silicon nitride coating, characterized in that, The silicon nitride coating is formed by the film coating method capable of inhibiting the occurrence of point-like contamination according to any one of claims 1 to 6.

8. A photovoltaic module, characterized by The photovoltaic module comprises the single crystal battery piece according to claim 7.

Images