Calibration method of solar cell and application of calibration method in preparation of solar cell

Abstract

The invention discloses a calibration method of a solar cell and application of the calibration method in preparation of the solar cell. The calibration method comprises the following steps: carrying out multiple times of light attenuation treatment on a to-be-calibrated battery piece, and testing electrical performance parameters of the to-be-calibrated battery piece before and after each time of light attenuation treatment until the photoelectric conversion efficiency change of the to-be-calibrated battery piece after continuous three times of light attenuation treatment is less than 0.05%; the first-level standard sheet is adopted to calibrate the to-be-calibrated cell sheet after light attenuation processing, a second-level standard sheet is obtained, and each light attenuation processing independently comprises heating processing and light injection processing and / or electric injection processing. By adopting the method, the to-be-calibrated battery piece with stable efficiency can be obtained in a short time, the manufacturing time of the secondary standard piece can be greatly shortened, the calibration efficiency of the secondary standard piece can be remarkably improved, and the secondary standard piece with good reliability and high detection accuracy can be obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solar cells, and in particular, relates to a method for calibrating solar cells and the use thereof in the preparation of solar cells. BACKGROUND

[0002] A solar cell wafer is a device that converts solar energy into electrical energy and is widely used in solar power generation systems. A standard wafer is a standardized product in the solar cell wafer industry, with certain specifications and standards to ensure product quality and performance. To meet the needs of large-scale power generation, standard wafers of various solar cells need to be calibrated to meet the accuracy and reliability requirements of solar cell standards. Taking HJT (heterojunction) cells as an example, currently, the standard wafers of HJT cells are still made according to the standard wafer production method of PERC cells, i.e., using long-time, high-radiation light to produce standard wafers. However, heterojunctions are currently upgraded from amorphous silicon to microcrystalline silicon, and microcrystalline silicon heterojunction cells themselves have a large dark decay problem. This dark decay is generally considered to be the unstable escape of free H in microcrystalline silicon and TCO film, similar to thin-film cells, which requires a long time to stabilize under normal conditions. Therefore, the standard wafers of heterojunction cells need to reach 300kwh / m 2 , or even 400-500kwh / m 2 to achieve the decay stability of the wafers, and the light usually needs to be performed for 2-3 rounds (one round of light decay still shows decay). The irradiation amount usually takes 300-500h, i.e., the light time usually takes 12.5-20.8 days. This long waiting period of more than ten days is difficult to accept in the fast-paced and rapidly developing modern society, especially for new projects in new factories, without the monitoring of stable standard wafers to guide the efficiency of the production line, the daily loss may be millions of yuan, which is difficult to estimate. SUMMARY

[0003] The present application aims to at least partially solve one of the problems in the related art. To this end, one object of the present application is to provide a method for calibrating solar cells and the use thereof in the preparation of solar cells. The method can obtain stable efficiency of the to-be-calibrated cell wafer in a short time, greatly shorten the production time of the secondary standard wafer, significantly improve the calibration efficiency of the secondary standard wafer, and obtain a secondary standard wafer with good reliability and high detection accuracy.

[0004] In a first aspect of the present application, a method for calibrating solar cells is provided, comprising:

[0005] The to-be-calibrated cell piece is subjected to multiple light decay treatments, and the electrical performance parameters of the to-be-calibrated cell piece before and after each light decay treatment are tested until the photoelectric conversion efficiency changes of the to-be-calibrated cell piece after three consecutive light decay treatments are all less than 0.05%;

[0006] The to-be-calibrated cell piece subjected to the light decay treatment is calibrated by using a primary standard cell piece to obtain a secondary standard cell piece,

[0007] Each of the light decay treatments independently includes a heating treatment, and a light injection treatment and / or an electrical injection treatment.

[0008] According to the embodiments of the present application, by subjecting the to-be-calibrated cell piece to multiple light decay treatments and heating the cell piece in combination with light injection and / or electrical injection during each light decay treatment, higher energy can be repeatedly applied to the to-be-calibrated cell piece, thereby effectively accelerating the initial light-induced decay of the to-be-calibrated cell piece, making the photoelectric conversion efficiency of the to-be-calibrated cell piece quickly stable, so that the to-be-calibrated cell piece with stable efficiency can be obtained in a short time, thereby greatly shortening the production time of the secondary standard cell piece, significantly improving the calibration efficiency of the secondary standard cell piece, and obtaining a secondary standard cell piece with good reliability and high detection accuracy.

[0009] In addition, the calibration method of the solar cell according to the above embodiments of the present application can also have the following additional technical features:

[0010] In some embodiments of the present application, before the light decay treatment, the to-be-calibrated cell piece is subjected to appearance inspection and electroluminescence testing to remove defective to-be-calibrated cell pieces.

[0011] In some embodiments of the present application, the photoelectric conversion efficiency calibration value of the secondary standard cell piece is the average value of the photoelectric conversion efficiencies of all the to-be-calibrated cell pieces after multiple light decay treatments.

[0012] In some embodiments of the present application, the light decay treatment is carried out in a ventilated environment.

[0013] In some embodiments of the present application, the to-be-calibrated cell piece is a heterojunction cell piece, and the multiple light decay treatments include alternately performing the light injection treatment on the front and back surfaces of the to-be-calibrated cell piece.

[0014] In some embodiments of the present application, the heating treatment is performed before or simultaneously with the light injection treatment and / or the electrical injection treatment.

[0015] In some embodiments of the present application, the peak temperature of the light decay treatment is ≤260℃.

[0016] In some embodiments of the present application, the light decay treatment comprises a heating treatment and a light injection treatment in sequence, the temperature of the heating treatment is 160-240 DEG C, and the time is 4-8 min; the power of the light injection treatment is greater than or equal to 50 kW, the time is 1-2 min, and the peak temperature is 200-260 DEG C.

[0017] In some embodiments of the present application, the light decay treatment comprises a heating treatment and an electric injection treatment, the heating treatment and the electric injection treatment are performed in sequence or simultaneously, the temperature of the electric injection treatment is 160-200 DEG C, the current is 5-10 A, and the time is 15-20 min.

[0018] In the second aspect of the present application, the use of the above-mentioned calibration method of the solar cell in the preparation of the solar cell is provided. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flow chart of the calibration method of the solar cell according to an embodiment of the present application.

[0020] Figure 2 is a flow chart of the calibration method of the solar cell according to another embodiment of the present application.

[0021] Figure 3 is a graph of the efficiency change of the solar cell before and after the multiple light decay treatments of the solar cell in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0023] The present application is mainly based on the preparation process of the HJT silicon heterojunction cell secondary standard piece and some technical problems and discoveries faced:

[0024] Currently, the production of heterojunction solar cell secondary standard pieces usually includes the following steps: determining the production machine, selecting a Halm test machine with a stability test GRR value <10, a solar simulator spectrum of AAA level, and no obvious test abnormalities within a preset time as the production machine for the production of secondary standard pieces. The preset time is set to indicate the stability of the test machine, for example, it can be set to one month. The production of secondary standard pieces includes: using a first-level standard piece (a standard piece calibrated by an authoritative third-party certification agency, usually expensive and long cycle) to calibrate the production machine; using the calibrated production machine to test a plurality of to-be-calibrated cell pieces, each to-be-calibrated cell piece is tested at least 3 times or more. Specifically, in the calibration of the production machine using the first-level standard piece, the difference between each electrical performance parameter and the calibration value is required to be within ±0.05%. And before testing the to-be-calibrated cell piece, the to-be-calibrated cell piece needs to be coded according to the coding rules. Data value calibration: check the test raw data, remove abnormal data, and remove cell pieces with an efficiency fluctuation of >0.05% in 3 tests; select the median value of the efficiency test to calibrate the remaining to-be-calibrated cell pieces, and calibrate other electrical performance parameters according to the test value. The above is the calibration process of the solar cell secondary standard piece, and before calibration, it is necessary to ensure that the efficiency of the cell piece itself is stable, and different cell pieces can only be calibrated using the type of cell piece, for example: PERC cells need to be calibrated using PERC cells, and if TOPcon cells are used to calibrate the open voltage and current of the cell, there will be a very large difference in the electrical performance, which will lead to inaccurate cell efficiency testing.

[0025] HJT silicon heterojunction cells, also known as HIT (Heterojunction with intrinsic thin layer) cells, are characterized by high efficiency and high Voc (open-circuit voltage). These cells typically use N-type silicon wafers as a substrate, and the general manufacturing process includes texturing, CVD, PVD, screen printing, and testing. With rapid technological advancements, the understanding of the high efficiency of heterojunction cells has become increasingly clear. However, such high efficiency requires more accurate standard wafer calibration. Besides primary standard wafers (calibrated by authoritative third-party certification bodies, which are usually expensive and time-consuming), secondary standard wafers are also crucial. Currently, secondary standard wafers are mostly produced using the traditional PERC light-induced degradation method, which is time-consuming, taking 15-30 days. This is labor-intensive and time-consuming, and can significantly extend the adoption time of new patterns or new factories. A large number of secondary standard wafers are needed to properly calibrate the production line efficiency (primary standard wafer factories typically use only one or two wafers; if primary standard wafers are used for calibration daily, the time and cost of recalibrating broken or damaged wafers are even longer and very expensive), ensuring the power output of customers' modules. Different types of solar cells can only be calibrated using that specific type of solar cell. Furthermore, the dark-state degradation problem of heterojunction microcrystalline silicon solar cells remains unresolved, with typical dark-state degradation lasting 3-5 months and a dark-state degradation efficiency exceeding 0.2%.

[0026] To address the current issues of long fabrication time and dark degradation in the production of heterojunction calibration secondary standard sheets, the inventors propose that the stability of the efficiency of the secondary standard sheets can be ensured by first solving the dark degradation problem of heterojunction cells, thereby shortening the fabrication time of the secondary standard sheets, significantly improving the calibration efficiency of the secondary standard sheets, and ensuring the stability of cell production line testing.

[0027] In this invention, before calibrating the battery cell to be calibrated using a primary standard sheet, the battery cell to be calibrated is subjected to multiple high-energy light decay treatments. This can accelerate the initial light-induced decay of the battery cell and make the photoelectric conversion efficiency of the calibrated battery cell quickly stabilize. This not only helps to solve the problem of continuous light decay or dark decay in the current battery cells, but also greatly shortens the production time of the secondary standard sheet.

[0028] In view of this, in the first aspect of this application, a calibration method for solar cells is proposed, with reference to Figure 1 The process includes: subjecting the solar cell to be calibrated to multiple light-induced degradation treatments and testing the electrical performance parameters of the solar cell before and after each light-induced degradation treatment, until the change in photoelectric conversion efficiency of the solar cell after three consecutive light-induced degradation treatments is less than 0.05%; calibrating the solar cell after light-induced degradation treatment using a primary standard sheet to obtain a secondary standard sheet. Each light-induced degradation treatment independently includes heating treatment, light injection treatment, and / or electrical injection treatment.

[0029] It is understood that the heating treatment method may include, but is not limited to, electric heating, radiant heating, and contact heating. When electric heating is used for temperature rise and the light decay treatment includes electro-injection treatment, the heating treatment and electro-injection treatment can be achieved simultaneously by directly adjusting the parameters of the electro-injection treatment. The electrical performance parameters may include photoelectric conversion efficiency, open-circuit voltage, short-circuit current, fill factor, etc.

[0030] The reasons for PERC solar cell light-induced degradation include: PERC typically uses P-type silicon wafers, which are doped with boron (B). The B and BO bonds in P-type silicon wafers cause degradation in solar cells under illumination, and changes in cell efficiency affect production line efficiency fluctuations. The main reason for dark degradation in heterojunction microcrystalline silicon solar cells is that a large amount of H2 participates in the reaction during the formation of the microcrystalline silicon film, and the microcrystalline silicon film layer also contains a large amount of H. Some of this H is unstable; after being given some energy, this H will overflow or lose its original passivation effect, resulting in low efficiency. This H will also slowly overflow when the cell is stationary, leading to a persistently low and unstable efficiency. In related fields, illumination is commonly used to stabilize the efficiency of standard cells, but illumination is generally performed at relatively low energies, and the stabilization time for standard cells is still too long. Taking heterojunction microcrystalline silicon solar cells as an example, although illumination can accelerate this process, reducing dark degradation time from 3-5 months to 10-20 days, this time is still too long.

[0031] According to embodiments of the present invention, by heating the solar cell to be calibrated and performing multiple light decay treatments in conjunction with light injection and / or electrical injection, high energy can be applied to the solar cell in each light decay treatment process, and this process can be repeated multiple times. This effectively accelerates the initial light-induced decay of the solar cell to be calibrated, allowing the photoelectric conversion efficiency of the solar cell to stabilize rapidly. Taking a heterojunction microcrystalline silicon solar cell as an example, the detachable hydrogen atoms in the heterojunction cell can redistribute and overflow under energy injection. By heating in conjunction with light injection and / or electrical injection, free hydrogen atoms can be directly overflowed in a short time, achieving stability of the solar cell efficiency. Therefore, a solar cell with stable efficiency can be obtained in a short time, which can greatly shorten the fabrication time of the secondary standard sheet (e.g., the fabrication time of the secondary standard sheet can be controlled to about 10 hours), significantly improving the calibration efficiency of the secondary standard sheet. Furthermore, compared to the existing technology where the secondary standard sheet calibrated using the primary standard sheet still suffers from light decay or dark decay during subsequent use, leading to unstable electrical performance and requiring frequent replacement of the secondary standard sheet or affecting the detection accuracy of the secondary standard cell, the secondary standard sheet obtained by the solar cell calibration method of the above embodiments of the present invention has the advantages of high reliability and high detection accuracy.

[0032] In some specific embodiments of the present invention, reference is made to...Figure 2 It is understood that prior to light decay processing, the calibration process may also include visual inspection and electroluminescence testing (such as EL testing) of the cells to be calibrated, in order to remove defective cells. This allows for the initial screening of cells with defects that could lead to excessive decay (such as black spots, black dots, blackening, scratches, airflow marks, or microcracks), reducing the workload of subsequent light decay processing and improving the calibration efficiency of secondary standard cells.

[0033] In some specific embodiments of the present invention, the photoelectric conversion efficiency range (i.e., photoelectric conversion efficiency range or specific value) of the solar cell to be calibrated can be determined to screen solar cells that meet the light range requirements. Then, the solar cells that meet the range requirements are subjected to appearance inspection and electroluminescence testing. The photoelectric conversion efficiency range of the solar cell to be calibrated can be determined using conventional methods in the art. For example, the photoelectric conversion efficiency range of the solar cell to be calibrated can be determined by the mainstream photoelectric conversion efficiency of the solar cells to be calibrated produced in the entire solar cell production line. For example, it can be the average efficiency or the mean of the normal distribution of the photoelectric conversion efficiency of the solar cells to be calibrated produced in the production line.

[0034] In some specific embodiments of the present invention, the photoelectric conversion efficiency calibration value of the secondary standard sheet can be the average value of the photoelectric conversion efficiency of all the cells to be calibrated after multiple light decay treatments, thereby further improving the reliability and detection accuracy of the secondary standard sheet.

[0035] In some specific embodiments of the present invention, the light decay treatment can be performed in a ventilated environment. When performing light decay treatment on heterojunction solar cells, a ventilated environment is more conducive to the overflow of unstable hydrogen ions in the microcrystalline silicon film, allowing the photoelectric conversion efficiency of the solar cell to be calibrated to stabilize rapidly. As some specific examples, the light decay treatment can be performed in an environment equipped with a ventilation system.

[0036] In some specific embodiments of the present invention, the solar cell to be calibrated can be a heterojunction solar cell, and multiple light decay treatments can include alternating light injection treatments on the front and back sides of the solar cell to be calibrated. Currently, in related fields, when accelerating dark decay of heterojunction solar cells by illumination, usually only one side is illuminated, while the other side does not receive much illumination, as the light is basically absorbed by the window surface. However, heterojunctions are all bifacial cells, and microcrystalline silicon is also bifacial; dark decay occurs not only on the front side but also on the back side. Therefore, current illumination treatments are not only inefficient but also have the aforementioned obvious defects. In the light decay treatment of the present invention, by alternating light injection treatments on the front and back sides of the solar cell to be calibrated, the dark decay process can be further accelerated, allowing the photoelectric conversion efficiency of the solar cell to be calibrated to quickly stabilize.

[0037] In some specific embodiments of the present invention, during the light decay treatment, the heating treatment can be performed sequentially or simultaneously with the light injection treatment and / or electrical injection treatment. It should be noted that the heating treatment method is not particularly limited, and those skilled in the art can flexibly choose according to actual needs. For example, it may include, but is not limited to, electrical heating, radiation heating, contact heating, etc. Furthermore, the calibrated cell under test can be placed in a space environment with a preset temperature for the light injection treatment and / or electrical injection treatment, or the calibrated cell under test can be placed in a heating furnace and heated to a preset temperature before the light injection treatment and / or electrical injection treatment. The heating furnace may include, but is not limited to, a curing furnace.

[0038] In some specific embodiments of the present invention, the peak temperature of the light decay treatment can be ≤260°C. This reduces the risk of damage to the film layer of solar cells (such as heterojunction solar cells) caused by excessively high light decay treatment temperature, thereby reducing the yield of secondary standard wafers and the accuracy of secondary standard wafer testing.

[0039] In some specific embodiments of the present invention, the light decay treatment may include sequential heating treatment and light injection treatment. The heating treatment temperature can be 160℃ to 240℃, for example, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, or 240℃, etc., and the heating treatment time can be 4 min to 8 min, for example, 4 min, 5 min, 6 min, 7 min, or 8 min, etc. Controlling the heating treatment temperature to meet the given range not only allows for the application of higher energy to the solar cell, increasing the overflow of unstable hydrogen states in the microcrystalline silicon film, but also further improves the efficiency of subsequent light injection treatment, further promoting the degradation of the microcrystalline silicon film. The overflow of H in an unstable state rapidly stabilizes the photoelectric conversion efficiency of the solar cell to be calibrated, while also reducing the risk of damage to the solar cell film layer due to excessive temperature. Furthermore, the power of the light injection treatment can be ≥50kW, for example, 50kW, 51kW, 52kW, 55kW, 60kW, or 65kW, and the time can be 1min to 2min, for example, 60s, 70s, 80s, 90s, 100s, 110s, or 120s, with a peak temperature of 200℃ to 260℃. Further placing the heat-treated solar cell in an environment with a power ≥50kW for light irradiation further promotes the rapid stabilization of the photoelectric conversion efficiency. Repeatedly subjecting the solar cell to be calibrated to multiple strong decay treatments under the aforementioned heat treatment and light injection treatment conditions not only significantly shortens the production time of the secondary standard sheet to approximately 10 hours, improving calibration efficiency, but also enhances the reliability and detection accuracy of the obtained secondary standard sheet.

[0040] As specific examples, when performing light-induced degradation treatment on heterojunction solar cells, in a well-ventilated environment, the cell to be calibrated is first heated with its front (window) facing upwards. The heating temperature is controlled at 160℃~240℃ for 4min~8min, followed by light injection treatment with a power ≥50kW for 1min~2min and a peak temperature of 200℃~260℃, completing the first light-induced degradation treatment. Then, the cell is heated with its back facing upwards, again with the heating temperature controlled at 160℃~240℃ for 4min~8min, followed by light injection treatment with a power ≥50kW for 1min~2min and a peak temperature of 200℃~260℃, completing the second light-induced degradation treatment. This alternating light-induced degradation treatment is repeated multiple times until the photoelectric conversion efficiency change of the cell after three consecutive light-induced degradation treatments is <0.05%. Afterwards, a primary standard cell is used for calibration, completing the fabrication of the secondary standard cell. By employing this modified method, repeated light-degradation treatments of 5-8 times can meet the requirements for secondary standard sheets. Compared to the 10-20 days (average 15 days, 360 hours) required for fabricating standard sheets for heterojunction solar cells using existing methods, this method, which involves multiple light-degradation treatments at higher energies, can shorten the standard sheet fabrication time to 7-12 hours, with an average of approximately 10 hours. This represents a 97.2% reduction in average fabrication time. Consequently, this significantly shortens the fabrication time for secondary standard sheets, substantially improving their calibration efficiency, and resulting in secondary standard sheets with high reliability and accuracy. Furthermore, this modified method allows for the simultaneous light-degradation treatment of multiple solar cells in a flat, layered manner, further enhancing the fabrication efficiency of secondary standard sheets.

[0041] In some specific embodiments of the present invention, the light decay treatment may include heating treatment and electrical injection treatment. The heating treatment and electrical injection treatment can be performed sequentially or simultaneously. For example, the temperature of the cell to be calibrated can be increased by electrical heating, that is, the current and time of electrical injection can be controlled to raise the temperature of the cell to a preset temperature and process it for a certain period of time within the preset temperature range at a preset current, thereby achieving simultaneous heating treatment and electrical injection treatment. The temperature of the electrical injection treatment can be 160℃~200℃, for example, 160℃, 170℃, 180℃, 190℃ or 200℃, etc.; the current can be 5A~10A, for example, 5A, 6A, 7A, 8A, 9A or 10A, etc.; and the time can be 15min~20min, for example, 15min, 16min, 17min, 18min, 19min or 20min, etc. Controlling the electrical injection process to meet given conditions not only allows for the application of higher energy to the solar cell, increasing the overflow of unstable hydrogen ions in the microcrystalline silicon film and rapidly stabilizing the photoelectric conversion efficiency of the cell under calibration, but also reduces the risk of damage to the solar cell film caused by excessively high temperatures due to excessive current or prolonged treatment. Therefore, repeatedly subjecting the cell to calibration for strong degradation under these conditions significantly shortens the fabrication time of the secondary standard sample, reducing it to approximately 10 hours and improving calibration efficiency. Furthermore, it enhances the reliability and accuracy of the resulting secondary standard sample.

[0042] As specific examples, when performing light-induced degradation treatment on heterojunction solar cells, current can be applied to both ends of the cell to be calibrated in a ventilated environment. The temperature of the injection treatment is controlled at 160℃~200℃, the current at 5A~10A, and the time at 15min~20min. This method is applied to both the front and back sides to complete one light-induced degradation treatment. Multiple light-induced degradation treatments are repeated until the photoelectric conversion efficiency change of the cell to be calibrated after three consecutive light-induced degradation treatments is <0.05%. Then, a primary standard cell is used for calibration to complete the fabrication of a secondary standard cell. Using this method, 5~8 light-induced degradation treatments are sufficient to meet the requirements for a secondary standard cell. Compared to the 10~20 days (average time 15 days, 360h) required for fabricating a standard cell using existing methods for heterojunction solar cells, this method, which performs multiple light-induced degradation treatments on the cell at higher energy levels, can shorten the fabrication time to 7~12 hours, with an average time of about 10h. The average fabrication time for standard cells can be reduced by 97.2%. This significantly shortens the production time of secondary standard sheets and greatly improves their calibration efficiency, while also ensuring high reliability and accuracy of the obtained secondary standard sheets. Furthermore, when using this method to perform light decay treatment on heterojunction solar cells, multiple cells can be stacked and treated simultaneously. This not only further improves the production efficiency of secondary standard sheets but also avoids the problem of needing to treat both sides of the solar cell when using light injection.

[0043] In a second aspect of this application, the application of the aforementioned solar cell calibration method in the fabrication of solar cells is described. It should be noted that the features and effects described for the aforementioned solar cell calibration method also apply to its application in the fabrication of solar cells, and will not be repeated here. In summary, this method not only improves the reliability and accuracy of secondary standard wafers, thereby ensuring the production efficiency, product quality, and performance of solar cell products, but also helps to improve production efficiency and reduce production costs.

[0044] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0045] Example 1

[0046] Select the photoelectric conversion efficiency range of the heterojunction solar cell to be calibrated, taking an average efficiency of 24.5%. Select a solar cell with a photoelectric conversion efficiency of 24.5%, ensuring that both visual inspection and EL testing are normal. Retest the efficiency of the selected solar cell, then re-pass it through the curing oven (for heat treatment) and light injection, followed by another efficiency test to complete the first strong degradation. During the first strong degradation, the solar cell should be facing upwards during curing and light injection. Then, turn the solar cell to be calibrated so that the back side is facing upwards, re-pass it through the curing oven (for heat treatment) and light injection, and then test the efficiency again to complete the second strong degradation. Repeat this process multiple times until the efficiency of the solar cell is consistently less than 0.05% in three consecutive tests, without a continuous downward trend. After completion, use primary standard sheets to calibrate the efficiency of these secondary standard sheets, thus completing the production of the secondary standard sheets. The curing oven and light injection were performed using a chain-type equipment. The curing oven was heated to 220℃ for 1 minute and had an exhaust system. The light injection power was 52kW for 1 minute, with a peak temperature of 260℃. The Eta electrical performance parameters of the solar cells (including photoelectric conversion efficiency, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF) were tested before and after each degradation step, as detailed in Table 1. The efficiency degradation graph is shown below. Figure 3 As shown.

[0047] Combining Table 1 and Figure 3 It can be seen that, starting from the 5th light decay treatment, the photoelectric conversion efficiency of the solar cell changed by less than 0.05% for three consecutive times, and did not show a continuous downward trend. The degradation of the solar cell basically stabilized, with an overall average efficiency degradation of 0.34%.

[0048] Table 1 Electrical performance parameters of heterojunction solar cells before and after light decay treatment

[0049] Number of times of attenuation Gear Number of tested cell pieces Average photoelectric conversion efficiency / % Voc / V Isc / mA / cm 2 ]] FF / % 0 times 24.5％ 109 24.50 0.7457 8.68 83.45 1 time 24.5％ 109 24.34 0.7457 8.67 83.00 2 times 24.5％ 109 24.26 0.7456 8.67 82.75 3 times 24.5％ 109 24.20 0.7455 8.66 82.67 4 times 24.5％ 109 24.16 0.7454 8.67 82.45 5 times 24.5％ 109 24.15 0.7453 8.66 82.52 6 times 24.5％ 109 24.16 0.7453 8.65 82.41 7 times 24.5％ 109 24.17 0.7454 8.66 82.55

[0050] Example 2

[0051] The photoelectric conversion efficiency range of the heterojunction solar cell to be calibrated was selected, with an average efficiency of 24.5%. Cells with a photoelectric conversion efficiency of 24.5% were selected, and both visual inspection and EL testing were normal. The efficiency of the selected cells was retested, and light decay treatment was performed using electrical injection. Multiple cells were stacked, and current was applied to both ends. The injection temperature was 180℃, the current was 6A, and the time was 16 minutes. This process was repeated multiple times until the efficiency of the cells tested repeatedly showed a change of <0.05% for three consecutive tests, without a continuous downward trend. After completion, the efficiency of these secondary standard cells was calibrated using primary standard cells, thus completing the fabrication of the secondary standard cells. The Eta electrical performance parameters of the cells before and after each decay (including photoelectric conversion efficiency, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF) were tested, as detailed in Table 2.

[0052] As can be seen from Table 2, starting from the third light decay treatment, the photoelectric conversion efficiency of the solar cell changed by less than 0.05% for three consecutive treatments, and did not show a continuous downward trend. The degradation of the solar cell basically stabilized, and the overall efficiency decreased by an average of 0.30% before stabilizing.

[0053] Table 2 Electrical performance parameters of heterojunction solar cells before and after light decay treatment

[0054] Number of times of attenuation Gear Number of tested cell pieces Average photoelectric conversion efficiency / % Voc / V Isc / mA / cm 2 ]] FF / % 0 times 24.5％ 77 24.50 0.7463 8.69 83.30 1 time 24.5％ 77 24.40 0.7461 8.68 83.07 2 times 24.5％ 76 24.35 0.7464 8.70 82.70 3 times 24.5％ 76 24.30 0.7463 8.69 82.60 4 times 24.5％ 76 24.30 0.7468 8.70 82.45 5 times 24.5％ 76 24.31 0.7464 8.70 82.58 6 times 24.5％ 76 24.31 0.7454 8.71 82.57

[0055] In summary, the calibration method described in the above embodiments of the present invention can significantly shorten the production time of secondary standard films and improve calibration efficiency.

[0056] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0057] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A calibration method for solar cells, characterized in that, include: The solar cell to be calibrated was subjected to multiple light decay treatments, and the electrical performance parameters of the solar cell to be calibrated were tested before and after each light decay treatment, until the change in photoelectric conversion efficiency of the solar cell to be calibrated after three consecutive light decay treatments was <0.05%. The primary standard sheet is used to calibrate the solar cells to be calibrated after light decay treatment, resulting in a secondary standard sheet. Each optical decay process independently includes a heating process, an optical injection process, and / or an electrical injection process.

2. The method according to claim 1, characterized in that, The process before performing the light decay treatment also includes: The cells to be calibrated are subjected to visual inspection and electroluminescence testing in order to remove defective cells.

3. The method according to claim 1, characterized in that, The photoelectric conversion efficiency calibration value of the secondary standard sheet is the average value of the photoelectric conversion efficiency of all the cells to be calibrated after multiple light decay treatments.

4. The method according to claim 1, characterized in that, The light decay treatment is performed in a well-ventilated environment.

5. The method according to claim 1, characterized in that, The solar cell to be calibrated is a heterojunction solar cell, and the multiple light decay processes include: alternately performing the light injection process on the front and back sides of the solar cell to be calibrated.

6. The method according to any one of claims 1 to 5, characterized in that, The heating treatment is performed sequentially or simultaneously with the photoinjection treatment and / or the electroinjection treatment.

7. The method according to any one of claims 1 to 5, characterized in that, The peak temperature of the light decay treatment is ≤260℃.

8. The method according to any one of claims 1 to 5, characterized in that, The optical decay treatment includes a heating treatment and an optical injection treatment performed sequentially. The heating treatment is performed at a temperature of 160℃ to 240℃ for a time of 4 min to 8 min. The optical injection treatment is performed at a power of ≥50kW for a time of 1 min to 2 min, with a peak temperature of 200℃ to 260℃.

9. The method according to any one of claims 1 to 5, characterized in that, The optical decay treatment includes heating treatment and electrical injection treatment, which are performed sequentially or simultaneously. The temperature of the electrical injection treatment is 160℃~200℃, the current is 5A~10A, and the time is 15min~20min.

10. Use of the method according to any one of claims 1 to 9 in the preparation of solar cells.

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