A coating process for N-type TOPCon cells

Abstract

The application relates to a N-type TOPCon cell coating process, wherein the cell to be coated is placed in a graphite boat, the graphite boat is sent into a tubular coating reaction process furnace tube through a transmission paddle, the tubular coating reaction process furnace tube is gradually heated, a vacuum state is formed in the tubular coating reaction process furnace tube through a vacuum pump, a vacuum constant temperature environment is formed, the cell is pretreated to form a bottom layer film structure, ammonia and silane are introduced to carry out first deposition, pre-gas and pre-deposition are carried out, ammonia, laughing gas and silane are introduced to carry out second deposition back pressure to complete the process. The uniformity of the prepared coated cell reaches 5%, the conversion efficiency reaches 24.5%, the second deposition coating film layer structure is better, the coating uniformity of the structure is improved, the passivation stability is improved by the action of special gas and nitrogen, the deposition quality of the silicon nitride film layer is improved, and the cell quality is improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell processing technology, specifically to an N-type TOPCon cell coating process. Background Technology

[0002] Crystalline silicon solar cells are electronic devices that convert sunlight into electrical energy, and N-type TOPCon solar cells are among the most popular and efficient crystalline silicon solar cells. With the development of the photovoltaic industry, passivated emitter and PERC (Performance-Reverse Contact) crystalline silicon solar cells are becoming increasingly popular. PECVD (Plasma-Enhanced Chemical Vapor Deposition) is a crucial step in cell surface treatment. In the photovoltaic industry, PECVD uses microwaves or radio frequency to ionize the gas containing the atoms that make up the thin film, creating a localized plasma that deposits a thin film on the cell. This process follows ALD (Alternating Layer Deposition) of double-sided alumina. Currently, the PECVD process for photovoltaic cells commonly uses tubular PECVD for front and back silicon nitride film deposition. After the graphite boat carrier enters the furnace tube, the temperature inside the tubular furnace reaches a set value, and then a vacuum is drawn. Once the vacuum level reaches a set value, the silicon nitride film is deposited. However, current processes suffer from poor alumina film structure and uneven coating, resulting in low silicon nitride film deposition quality, low conversion efficiency, and severely impacting yield. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to overcome the above-mentioned technical problems, the present invention provides an N-type TOPCon battery coating process.

[0004] The technical solution adopted by this invention to solve its technical problem is: an N-type TOPCon battery coating process, comprising the following steps:

[0005] Step 1: Place the passivated battery cells to be coated into a graphite boat;

[0006] Step 2: The graphite boat is fed into the tubular coating reaction furnace tube;

[0007] Step 3: The tubular coating reaction furnace tube is gradually heated, and a vacuum pump is used to evacuate the inside of the coating reaction furnace tube to form a vacuum constant temperature environment.

[0008] Step 4: Pre-treatment of the battery cell to deposit the underlying film structure;

[0009] Step 5: Introduce ammonia and silane for a single deposition;

[0010] Step 6: Pre-aeration and pre-deposition;

[0011] Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition;

[0012] Step 8: Backpressure completes the process.

[0013] In step six, pre-gasification refers to adding a certain amount of nitrogen to maintain pressure in the furnace tube, ensuring reduced fluctuations in the flow rate and pressure of the special gases in the subsequent deposition steps, minimizing high-frequency risks, and ensuring the smooth progress of subsequent process steps. Pre-deposition involves, based on pre-gasification and pressure maintenance, introducing minimum flow rates of silane, ammonia, and nitrous oxide through a flow meter to pre-distribute the special gas field in the furnace tube. Pre-distributing the special gas field in the furnace tube before the secondary deposition action in step seven ensures the uniformity of the film structure.

[0014] In step six, the total time for pre-aeration and pre-deposition is 18–22 s. The total time of step six must be well controlled to ensure that the special gas is distributed on the solar cell before the secondary deposition, but without causing film formation.

[0015] Preferably, the total time for step six is ​​20 seconds, and the amount of nitrogen gas used for pre-ventilation is 2000 sccm.

[0016] Step 1: The passivated and coated solar cells are loaded into a double-boat graphite boat using an automated coating robot. The single boat contains 384 cells, and the double boat contains 768 cells. The double-boat graphite boat is a graphite boat that has completed the saturation process.

[0017] Step 2: The double-boat graphite boat is fed into the tubular coating reaction furnace tube by a transfer paddle. The transfer paddle speed is set to 1000 mm / min by the SiC rod of the coating host, and the boat enters the tubular coating reaction furnace tube.

[0018] Step 3: Set the furnace tube temperature to 400-550℃ and hold for 300 seconds; perform vacuuming and leak detection inside the tubular coating reaction furnace tube. Step 4: Pre-treat the battery cells by depositing the bottom film structure, then introduce ammonia and silane. Step 5: Introduce ammonia and silane for primary deposition, introduce a special gas into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. Step 6: Pre-gas for 20 seconds, then introduce silane, ammonia, and nitrous oxide for pre-deposition. Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition, introduce a special gas into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. Step 8: Maintain vacuum for 85 seconds, then introduce nitrogen for 140 seconds, return to atmospheric pressure, open the furnace door, and complete the process.

[0019] In step five, the first step of the film deposition time is 240s, silane and ammonia are introduced, the discharge power is 20000w, and the pressure is 1550mtorr; the second step of the film deposition time is 250s, silane and ammonia are introduced, the discharge power is 24000w, and the pressure is 1700mtorr; the third step of the film deposition time is 300s, silane and ammonia are introduced, the discharge power is 24000w, and the pressure is 1700mtorr.

[0020] In step seven, the first step of the coating deposition time is 140s, with silane, ammonia, and nitrous oxide introduced, a discharge power of 24000W, and a pressure of 1500mtorr; the second step of the coating deposition time is 135s, with silane, ammonia, and nitrous oxide introduced, a discharge power of 24000W, and a pressure of 1500mtorr; the third step of the coating deposition time is 140s, with silane and ammonia introduced, a discharge power of 24000W, and a pressure of 1450mtorr.

[0021] In step two, the SiC rod is made of silicon carbide, and the propeller inlet tube moves at a constant speed.

[0022] In step three, the vacuum pressure of the tubular coating reaction furnace tube is evacuated to below 50 mtorr, and the leak rate of the furnace tube is controlled to be less than 40 mtorr / min. In step four, the pressure gauge control deviation is below ±5 mtorr, the initial calibration of the flow meter is completed, the flow deviation is ±3 sccm, and the duty cycle off / on values ​​for RF deposition of silane, ammonia, and nitrous oxide are 10~16, 10~14, and 10~14, respectively.

[0023] In step seven, there are no high-frequency or other abnormalities during the process.

[0024] After the graphite boat process in step eight is completed, the wafer needs to be cooled on the host temporary storage stage for 10 minutes before being unloaded. The buffering time is 2 hours.

[0025] The beneficial effects of this invention are that, in an N-type TOPCon battery coating process, a pre-gasification and pre-deposition step is inserted between the multilayer or infinitely gradient silicon nitride antireflection passivation film and the substrate, resulting in a better secondary deposition film structure, improved coating uniformity of the double-boat structure, and enhanced passivation stability by utilizing the effects of special gases and nitrogen to improve the deposition quality of the silicon nitride film and thus improve the quality of the battery cell. Detailed Implementation

[0026] The present invention will now be described in further detail.

[0027] The present invention provides an N-type TOPCon battery coating process, comprising the following steps:

[0028] Step 1: Place the passivated battery cells to be coated into a graphite boat;

[0029] Step 2: The graphite boat is fed into the tubular coating reaction furnace tube;

[0030] Step 3: The tubular coating reaction furnace tube is gradually heated, and a vacuum pump is used to evacuate the inside of the coating reaction furnace tube to form a vacuum constant temperature environment.

[0031] Step 4: Pre-treatment of the battery cell to deposit the underlying film structure;

[0032] Step 5: Introduce ammonia and silane for a single deposition;

[0033] Step 6: Pre-aeration and pre-deposition;

[0034] Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition;

[0035] Step 8: Backpressure completes the process.

[0036] Example 1

[0037] This embodiment provides a PECVD coating process for N-type solar cells, the process including the following steps:

[0038] Step 1: The passivated solar cells to be coated are loaded into a double-boat graphite boat using an automated coating robot. The single boat contains 384 cells, and the double boat contains 768 cells.

[0039] Step 2: Set the paddle speed to 1000 mm / min using the SiC rod of the coating host, and then enter the tubular coating reaction furnace tube.

[0040] Step 3: Set the temperature inside the furnace tube to 400–550℃ and hold for 300 seconds; then perform vacuuming and leak detection inside the tubular coating reaction furnace tube. The vacuum pressure inside the tubular coating reaction furnace tube is reduced to below 50 mtorr, and the leak detection rate is controlled to be less than 40 mtorr / min.

[0041] Step four: Pre-treatment of the battery cell to deposit the bottom film structure, followed by the introduction of ammonia and silane. The pressure gauge control deviation is below ±5 mtorr, the initial calibration of the flow meter is completed, and the flow deviation is ±3 sccm. The duty cycle off / on values ​​for RF deposition of silane, ammonia, and nitrous oxide are 10–16, 10–14, and 10–14, respectively.

[0042] Step 5: Introduce ammonia and silane for initial deposition; introduce a special gas into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. Specifically, the first deposition step has a deposition time of 240 seconds, introducing silane and ammonia, with a discharge power of 20000W and a pressure of 1550mtorr; the second deposition step has a deposition time of 250 seconds, introducing silane and ammonia, with a discharge power of 24000W and a pressure of 1700mtorr; and the third deposition step has a deposition time of 300 seconds, introducing silane and ammonia, with a discharge power of 24000W and a pressure of 1700mtorr.

[0043] Step 6: Pre-introduce 2000 sccm of nitrogen to maintain pressure in the furnace tube, and then introduce silane, ammonia and nitrous oxide at the minimum flow rate through a flow meter for pre-deposition to distribute the special gas field of the furnace tube in advance. The total time for this step is 20 seconds.

[0044] Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition; introduce special gases into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. The first deposition step has a deposition time of 140 seconds, introducing silane, ammonia, and nitrous oxide, with a discharge power of 24000W and a pressure of 1500mtorr; the second deposition step has a deposition time of 135 seconds, introducing silane, ammonia, and nitrous oxide, with a discharge power of 24000W and a pressure of 1500mtorr; the third deposition step has a deposition time of 140 seconds, introducing silane and ammonia, with a discharge power of 24000W and a pressure of 1450mtorr.

[0045] Step 8: First, maintain the vacuum for 85 seconds, then introduce nitrogen for 140 seconds, return to normal pressure, open the furnace door, and the process is complete.

[0046] Example 2

[0047] The only difference between Example 2 and Example 1 is that the total time for step six is ​​18 seconds, while the other conditions and parameters are exactly the same as in Example 1.

[0048] Example 3

[0049] The only difference between Example 3 and Example 1 is that the total time for step six is ​​22 seconds, while the other conditions and parameters are exactly the same as in Example 1.

[0050] Comparative Example 1

[0051] The only difference between Comparative Example 1 and Example 1 is that step six is ​​omitted, i.e. there is no pre-aeration or pre-deposition step between the primary and secondary deposition. All other conditions and parameters are exactly the same as in Example 1.

[0052] Comparative Example 2

[0053] The only difference between Comparative Example 2 and Example 1 is step six, where the total time for pre-aeration and pre-deposition is 30 seconds. All other conditions and parameters are exactly the same as in Example 1.

[0054] Comparative Example 3

[0055] The only difference between Comparative Example 3 and Example 1 is step six, where the total time for pre-aeration and pre-deposition is 10 seconds. All other conditions and parameters are exactly the same as in Example 1.

[0056] Table 1 shows the experimental test data of the coating thickness, where Experiments 1 to 5 are the data obtained from 5 experiments in Example 1.

[0057] Table 1

[0058]

[0059]

[0060] As can be seen from Table 1, the uniformity of the coated films prepared in Examples 1-3 is all above 90%, which is generally 3% to 14% higher than that of Comparative Examples 1-3.

[0061] Performance testing: The IV electrical performance parameters of the experimental group were tested using a Halm testing machine. The test results are shown in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] As can be seen from Table 2, the results of the five experiments in Example 1, as well as the results of Examples 2 and 3, are better, with conversion efficiencies greater than those in Comparative Examples 1-3. The cell conversion efficiency of the N-type TOPCon battery dual-boat coating process of the present invention can reach more than 24.5%.

[0066] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A coating process for N-type TOPCon batteries, characterized in that, Includes the following steps: Step 1: Place the passivated battery cells to be coated into a graphite boat; Step 2: The graphite boat is fed into the tubular coating reaction furnace tube; Step 3: The tubular coating reaction furnace tube is gradually heated, and a vacuum pump is used to evacuate the inside of the coating reaction furnace tube to form a vacuum constant temperature environment. Step 4: Pre-treatment of the battery cell to deposit the underlying film structure; Step 5: Introduce ammonia and silane for a single deposition; Step 6: Pre-aeration, pre-deposition. The total time for pre-aeration and pre-deposition is 18-22 seconds, and the nitrogen flow rate for pre-aeration is 2000 sccm. Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition; Step 8: Back pressure completes the process; In step six, the pre-ventilation refers to adding a certain amount of nitrogen to maintain the pressure of the furnace tube, and the pre-deposition refers to, on the basis of pre-ventilation and pressure maintenance, introducing silane, ammonia and nitrous oxide at a minimum flow rate through a flow meter to pre-distribute the special gas field of the furnace tube. In step five, the first step of the film deposition time is 240s, with silane and ammonia gas introduced, a discharge power of 20000W, and a pressure of 1550mtorr; the second step of the film deposition time is 250s, with silane and ammonia gas introduced, a discharge power of 24000W, and a pressure of 1700mtorr; the third step of the film deposition time is 300s, with silane and ammonia gas introduced, a discharge power of 24000W, and a pressure of 1700mtorr. In step seven, the first step of the coating deposition time is 140s, during which silane, ammonia, and nitrous oxide are introduced, with a discharge power of 24000W and a pressure of 1500mtorr; the second step of the coating deposition time is 135s, during which silane, ammonia, and nitrous oxide are introduced, with a discharge power of 24000W and a pressure of 1500mtorr; the third step of the coating deposition time is 140s, during which silane and ammonia are introduced, with a discharge power of 24000W and a pressure of 1450mtorr.

2. The N-type TOPCon battery coating process as described in claim 1, characterized in that, The total time for step six is ​​20 seconds.

3. The N-type TOPCon battery coating process as described in claim 1, characterized in that, Step 1: The passivated and coated solar cells are loaded into a double-boat graphite boat using an automated coating robot. The single boat contains 384 cells, and the double boat contains 768 cells. The double-boat graphite boat is a graphite boat that has completed the saturation process.

4. The N-type TOPCon battery coating process as described in claim 3, characterized in that, Step 2: The double-boat graphite boat is fed into the tubular coating reaction furnace tube by a transfer paddle. The transfer paddle speed is set to 1000 mm / min by the SiC rod of the coating host, and the boat enters the tubular coating reaction furnace tube.

5. The N-type TOPCon battery coating process as described in claim 4, characterized in that, Step 3: Set the furnace tube temperature to 400–550℃ and hold for 300 seconds; perform vacuuming and leak detection inside the tubular coating reaction furnace tube. Step 4: Pre-treat the battery cells by depositing the bottom film structure, introducing ammonia and silane. Step 5: Introduce ammonia and silane for primary deposition, introduce a special gas into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. Step 6: Pre-gas for 20 seconds, then introduce silane, ammonia, and nitrous oxide for pre-deposition. Step 7: Introduce ammonia, nitrous oxide, and silane for secondary deposition, introduce a special gas into the furnace tube while maintaining the furnace tube pressure and flow rate, set the furnace tube pressure, and simultaneously activate the RF power supply's discharge function. Step 8: Maintain vacuum for 85 seconds, then introduce nitrogen for 140 seconds, return to atmospheric pressure, open the furnace door, and complete the process.

6. The N-type TOPCon battery coating process as described in claim 1, characterized in that, In step two, the SiC rod is made of silicon carbide, and the propeller inlet tube moves at a constant speed.

7. The N-type TOPCon battery coating process as described in claim 5, characterized in that, In step three, the vacuum pressure of the tubular coating reaction furnace tube is evacuated to below 50 mtorr, and the leak rate of the furnace tube is controlled to be less than 40 mtorr / min. In step four, the pressure gauge control deviation is below ±5 mtorr, the initial calibration of the flow meter is completed, the flow deviation is ±3 sccm, and the duty cycle off / on values ​​for RF deposition of silane, ammonia, and nitrous oxide are 10~16, 10~14, and 10~14, respectively.

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