Solar cell coating method and solar cell

Abstract

The invention provides a solar cell coating method and a solar cell. The method comprises the following steps: depositing a first passivation layer on a backlight side of a silicon substrate; a first temperature curve is adopted to deposit a first anti-reflection layer or a second anti-reflection layer on the light-facing side of the silicon substrate, the first temperature curve is that the temperature is increased to the first temperature and then decreased to the second temperature, the first anti-reflection layer or the second anti-reflection layer on the light-facing side is deposited under the second temperature condition, and a specific temperature difference exists between the first temperature and the second temperature. According to the solar cell coating method disclosed by the invention, the anti-reflection layer is deposited by adopting the first temperature curve, so that the deposition temperatures of the furnace mouth, the furnace middle and the furnace tail are closer, the inter-sheet uniformity of the refractive index of the deposited anti-reflection layer is improved, and the quality of the film layer is improved. And meanwhile, the passivation layer on the back surface has a secondary annealing effect, so that the passivation effect is also improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of solar cell coating, and in particular to a solar cell coating method and a solar cell. Background Art

[0002] The tubular PECVD coating process generally includes loading the vessel, heating, constant temperature, vacuuming, leak detection, pre-deposition, deposition, vacuuming, cleaning, breaking the vacuum, and exiting the vessel. The temperature profiles for heating and constant temperature have a significant impact on the passivation and thickness uniformity of the coating.

[0003] Due to the uneven temperature distribution at different positions of the furnace tube, the refractive index uniformity of the cells during the coating process is poor. Figure 1 As shown, the temperature curves of the front and back films of the current coating process remain stable after the temperature is raised to the set temperature in the heating step, and the passivation effect of the passivation film obtained is also poor. Summary of the Invention

[0004] In view of the above problems, embodiments of the present disclosure provide a solar cell coating method and a solar cell.

[0005] One aspect of the present disclosure provides a solar cell coating method, comprising: depositing a first passivation layer on a backlight side of a silicon substrate; and depositing a first anti-reflection layer or a second anti-reflection layer on a light-facing side of the silicon substrate using a first temperature profile, wherein the first temperature profile comprises first increasing the temperature to a first temperature and then decreasing the temperature to a second temperature, and depositing the first anti-reflection layer or the second anti-reflection layer on the light-facing side under the second temperature condition, wherein the first temperature and the second temperature have a specific temperature difference.

[0006] According to an embodiment of the present disclosure, after depositing a first anti-reflection layer or a second anti-reflection layer on the light-facing side of the silicon substrate using a first temperature curve, the solar cell coating method further includes: depositing a first anti-reflection layer on the first passivation layer on the backlight side using a second temperature curve, the second temperature curve is first heating to a third temperature and then heating to a fourth temperature, and depositing the first anti-reflection layer on the backlight side under the fourth temperature condition, and the third temperature and the fourth temperature have a specific temperature difference.

[0007] According to an embodiment of the present disclosure, the specific temperature difference ranges from 5 to 10°C.

[0008] According to an embodiment of the present disclosure, the fourth temperature is lower than the second temperature, and the temperature difference between the fourth temperature and the second temperature ranges from 20° C. to 100° C.

[0009] According to an embodiment of the present disclosure, before depositing the first anti-reflection layer on the light-facing side of the silicon substrate using the first temperature curve, the solar cell coating method further includes: depositing a first passivation layer on the light-facing side of the silicon substrate; and depositing the first anti-reflection layer on the first passivation layer on the light-facing side.

[0010] According to an embodiment of the present disclosure, before depositing the first passivation layer on the backlight side of the silicon substrate, the solar cell coating method further includes: depositing a second passivation layer on the backlight side of the silicon substrate; depositing a first doped layer on the second passivation layer; and depositing the first passivation layer on the backlight side on the first doped layer. Furthermore, before depositing the first passivation layer on the light-facing side of the silicon substrate, the solar cell coating method further includes: preparing a second doped layer on the light-facing side of the silicon substrate; and depositing the first passivation layer on the light-facing side on the second doped layer.

[0011] According to an embodiment of the present disclosure, before depositing the first passivation layer on the backlight side of the silicon substrate, the solar cell coating method further includes: depositing a second passivation layer on the backlight side of the silicon substrate; depositing first doped layers and third doped layers on the second passivation layer, respectively, with the third doped layers alternating with the first doped layers and having an electrically isolated structure therebetween; and depositing the backlight-side first passivation layer on the first doped layers and the third doped layers.

[0012] According to the embodiments of the present disclosure, by adopting the first temperature profile to deposit the anti-reflection layer, the deposition temperatures at the furnace entrance, furnace center, and furnace tail can be made closer, thereby improving the uniformity of the refractive index of the deposited anti-reflection layer between sheets and enhancing the film quality. Simultaneously, a secondary annealing effect is provided for the backside passivation layer, further enhancing the passivation effect. Thus, the technical issues of poor film uniformity and poor passivation effect are at least partially overcome, thereby achieving the technical effects of improving film quality and enhancing the passivation effect.

[0013] Another aspect of the present disclosure provides a solar cell comprising: a silicon substrate; a first passivation layer disposed on at least one side of the silicon substrate; and a first anti-reflection layer disposed on a side of the first passivation layer away from the silicon substrate. The carbon content of the first anti-reflection layer is less than a specific threshold, and / or the inter-sheet uniformity of the refractive index of the first anti-reflection layer is in a range of 3.5% to 6.5%.

[0014] According to an embodiment of the present disclosure, the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the backlight side of the silicon substrate is greater than the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the light-facing side of the silicon substrate.

[0015] According to an embodiment of the present disclosure, a first passivation layer is provided on the backlight surface of the silicon substrate. A first doped layer and a third doped layer are provided on the side of the first passivation layer away from the silicon substrate. The third doped layer has an opposite polarity to the first doped layer, is alternately provided, and has an electrical isolation structure between them. A first anti-reflection layer is provided on the side of the first doped layer, the third doped layer, and the electrical isolation structure away from the silicon substrate. The thickness of the first anti-reflection layer corresponding to the negatively charged doped layer region is greater than the thickness of the first anti-reflection layer corresponding to the positively charged doped region.

[0016] According to an embodiment of the present disclosure, the specific threshold is 8%.

[0017] According to the embodiments of the present disclosure, the carbon content of the first anti-reflection layer of the solar cell is controlled to be less than a specific threshold and the inter-sheet uniformity of the refractive index is controlled to be in the range of 3.5-6.5%. The low carbon content helps improve the passivation effect, reduce carrier recombination, and increase the short-circuit current density of the battery. At the same time, the improvement of the inter-sheet uniformity of the refractive index of the anti-reflection layer is beneficial to the cell performance of the solar cell, and can improve the color consistency of the solar cell surface and the color matching rate of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1 Schematically shows a temperature curve diagram of the front and back films in a related process according to an embodiment of the present disclosure;

[0020] Figure 2 A flow chart of a solar cell coating method according to an embodiment of the present disclosure is schematically shown;

[0021] Figure 3 Schematically shows a temperature curve diagram of a positive film according to an embodiment of the present disclosure;

[0022] Figure 4 Schematically shows a back film temperature curve diagram according to an embodiment of the present disclosure;

[0023] Figure 5 A diagram schematically shows a comparison between an optimized temperature curve for a positive film according to an embodiment of the present disclosure and a conventional temperature curve;

[0024] Figure 6 A diagram schematically shows a comparison between an optimized temperature curve of a back film according to an embodiment of the present disclosure and a conventional temperature curve;

[0025] Figure 7 Schematically shows an EDS characterization diagram of a sample corresponding to a conventional temperature curve according to an embodiment of the present disclosure;

[0026] Figure 8 Schematically showing an EDS characterization diagram of a sample corresponding to an optimized temperature curve according to an embodiment of the present disclosure;

[0027] Figure 9 Schematically shows a partial structural diagram of a solar cell according to an embodiment of the present disclosure;

[0028] Figure 10 Schematically shows a partial structural diagram of a solar cell according to another embodiment of the present disclosure;

[0029] Figure 11Schematically shows a partial structure diagram of a TOPCON solar cell according to an embodiment of the present disclosure;

[0030] Figure 12 Schematically shows a partial structural diagram of a back-contact solar cell according to an embodiment of the present disclosure;

[0031] Figure 13 The partial structure of a PERC solar cell according to an embodiment of the present disclosure is schematically shown.

[0032] [Description of Reference Numerals]

[0033] 1-silicon substrate; 11-second doped layer; 2-first passivation layer; 3-first anti-reflection layer; 4-second anti-reflection layer; 5-second passivation layer; 6-first doped layer; 7-third doped layer; 8-metal electrode. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0035] It should be noted that in the drawings or descriptions of the specification, similar or identical parts use the same figure numbers. The technical features in the various embodiments exemplified in the specification can be freely combined to form new solutions without conflict. In addition, each claim can be used as an embodiment alone or the technical features in each claim can be combined as a new embodiment. In the drawings, the shape or thickness of the embodiment can be expanded and simplified or conveniently indicated. Furthermore, the elements or implementations not shown or described in the drawings are forms known to ordinary technicians in the relevant technical field. In addition, although this article may provide demonstrations of parameters containing specific values, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint.

[0036] Unless there are technical obstacles or contradictions, the above-mentioned various embodiments of the present disclosure can be freely combined to form additional embodiments, and these additional embodiments are all within the protection scope of the present disclosure.

[0037] Although the present disclosure is described in conjunction with the accompanying drawings, the embodiments disclosed in the drawings are intended to illustrate preferred embodiments of the present disclosure and are not to be construed as limiting the present disclosure. The dimensional ratios in the drawings are merely illustrative and are not to be construed as limiting the present disclosure.

[0038] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined in the claims and their equivalents.

[0039] Figure 2 The flowchart of the solar cell coating method according to the embodiment of the present disclosure is schematically shown. Figure 3 The figure schematically shows a temperature curve of a positive film according to an embodiment of the present disclosure.

[0040] According to the embodiments of the present disclosure, Figure 2 As shown, the present disclosure provides a solar cell coating method, including operations S210 to S220.

[0041] In operation S210 , a first passivation layer 2 is deposited on the backlight side of the silicon substrate 1 .

[0042] In operation S220, a first temperature curve is used to deposit a first anti-reflection layer 3 or a second anti-reflection layer 4 on the light-facing side of the silicon substrate 1. The first temperature curve is to first increase the temperature to a first temperature and then decrease the temperature to a second temperature. The first anti-reflection layer 3 or the second anti-reflection layer 4 on the light-facing side is deposited under the second temperature condition. The first temperature and the second temperature have a specific temperature difference.

[0043] In some embodiments, for example, an N-type single crystal silicon wafer is used as the silicon substrate, and the specific coating steps are as follows:

[0044] First, the single-crystal silicon wafer is cleaned to remove surface impurities and damage. A texturing process then forms a pyramidal structure on the wafer surface to reduce reflectivity. For example, N-type single-crystal silicon wafers can be doped with trace amounts of pentavalent elements such as phosphorus (P) or arsenic (As).

[0045] Next, a thin aluminum oxide film, with a thickness of, for example, 75 nanometers, is deposited on the backlit side (non-illuminated side) of the monocrystalline silicon wafer as the first passivation layer. This step, which can be achieved through methods such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD), aims to reduce minority carrier recombination and improve cell efficiency.

[0046] Next, if Figure 3As shown, a specific first temperature profile is used to deposit the first anti-reflection layer (AR) on the light-facing side (i.e., the illuminated side) of a single-crystal silicon wafer. First, the temperature is raised to a first temperature (e.g., 560°C) and then maintained at this temperature for a period of time to stabilize the environment. Subsequently, the temperature is gradually lowered to a second temperature (e.g., 550°C) according to the first temperature profile. At this second temperature, a 140-nanometer blue anti-reflection film (e.g., silicon nitride) is deposited as the first AR layer. This AR layer is deposited using plasma-enhanced chemical vapor deposition (PECVD) technology, effectively reducing light reflection and improving light absorption. The positive film (the first AR layer on the light-facing side) is heated to a temperature above the set temperature during the heating step, then maintained at the set temperature before the deposition step (coating step). This heating profile significantly optimizes the secondary annealing activation of the aluminum oxide (the first passivation layer), enhancing the passivation effect, increasing the carrier lifetime at the aluminum oxide interface, and increasing the fixed charge density.

[0047] After the anti-reflection layer deposition is completed, the single-crystal silicon wafer is subjected to other necessary processing steps, such as back film deposition, electrode printing, drying, sintering, etc., to finally produce a solar cell.

[0048] For example, P-type single crystal silicon wafers can be used as silicon substrates, and the coating process is slightly different:

[0049] First, cleaning and texturing are also performed to remove surface impurities and defects. The P-type single crystal silicon wafer can be, for example, a single crystal silicon wafer doped with a trace amount of trivalent elements such as boron (B).

[0050] Then, a 100-nanometer-thick aluminum oxide film is deposited on the backlight side as the first passivation layer. The aluminum oxide film not only has an excellent passivation effect but also provides a certain degree of mechanical protection.

[0051] Then, using the same first temperature profile as in the previous embodiment, a second anti-reflection layer made of a different material, such as an 80-nanometer-thick silicon dioxide (SiO2) film, is deposited at a second temperature (e.g., 550°C). This step aims to further optimize the spectral response and improve the photovoltaic conversion efficiency of the cell.

[0052] After the anti-reflection layer deposition is completed, subsequent processes such as back film deposition, electrode production, drying, and sintering are carried out to finally obtain the solar cell product.

[0053] The above two embodiments demonstrate the specific application of "a solar cell coating method". By depositing passivation layers and anti-reflection layers of different materials under different temperature conditions, the photoelectric conversion efficiency and stability of the solar cell are effectively improved.

[0054] It is understood that the silicon substrates in the embodiments of the present disclosure can be either N-type or P-type. In the case of process matching, the present disclosure does not limit the type of silicon substrate.

[0055] It should be noted that the first anti-reflection layer refers to the layer in contact with the first passivation layer (aluminum oxide), while the second anti-reflection layer refers to the layer that is not in contact with the first passivation layer but directly in contact with the second doped layer (obtained by doping a portion of the substrate). The first and second anti-reflection layers can have the same structure and composition. Therefore, the first anti-reflection layer is suitable for solar cells with structures such as TOPCON and back-contact (IBC), while the second anti-reflection layer is suitable for PERC cells.

[0056] Figure 4 The figure schematically shows a back film temperature curve diagram according to an embodiment of the present disclosure.

[0057] According to an embodiment of the present disclosure, after depositing the first anti-reflection layer 3 or the second anti-reflection layer 4 on the light-facing side of the silicon substrate 1 using the first temperature curve, the solar cell coating method further includes operation S310 .

[0058] In operation S310, a first anti-reflection layer 3 is deposited on the first passivation layer 2 on the backlight side using a second temperature curve. The second temperature curve is to first heat the temperature to a third temperature and then heat the temperature to a fourth temperature. The first anti-reflection layer 3 on the backlight side is deposited under the fourth temperature condition. The third temperature and the fourth temperature have a specific temperature difference.

[0059] In some embodiments, based on the above two embodiments, the solar cell coating method is further expanded, especially by adding an anti-reflection layer deposition step on the backlight side to further improve the light absorption efficiency of the cell. The specific implementation steps are as follows:

[0060] Similar to the above embodiment, the silicon substrate (here taking a single crystal silicon wafer as an example) is first cleaned and textured.

[0061] A layer of aluminum oxide film is deposited on the backlight side of the silicon substrate as a first passivation layer with a thickness of 75 nanometers, using the same method as in the above embodiment.

[0062] A first temperature curve (first heating to a first temperature, such as 590°C, and then cooling to a second temperature, such as 585°C) is used to deposit a blue anti-reflection film with a thickness of 140 nm on the light-facing side as a second anti-reflection layer, using the same method as in the above embodiment.

[0063] After the anti-reflection layer on the light side is deposited, the first anti-reflection layer is deposited on the first passivation layer on the backlight side using the second temperature curve. Figure 4 As shown, the second temperature curve is designed to first increase the temperature to the third temperature (such as 510°C) to stabilize the environment and preheat the substrate, and then increase the temperature to the fourth temperature (such as 520°C) to deposit a layer of silicon nitride (SiN xA 100-nanometer-thick thin film serves as the first anti-reflection layer on the backlight side. This step aims to achieve an anti-reflection effect on the backlight side through differential temperature control, while also taking into account compatibility with the first passivation layer. The back film (the first anti-reflection layer on the backlight side) is heated to below the set temperature during the ramp step, reaching the set temperature and maintaining a stable temperature before the deposition step. This ramp profile optimizes the film's electron capture ability, thereby improving conversion efficiency. Using a second temperature profile to deposit the first anti-reflection layer prevents passivation failure caused by hydrogen overflow from the first passivation layer, further improving the passivation effect.

[0064] After completing all the coating steps, the subsequent processes such as electrode production, drying, and sintering are continued to finally produce a solar cell with double-sided anti-reflection effect.

[0065] In the solar cell coating method, not only can an anti-reflection layer be deposited on the light-facing side to improve light absorption, but an anti-reflection layer can also be deposited on the backlight side to further optimize the optical performance of the cell. This temperature rise curve of the front film and the back film, as well as the process sequence of preparing the front film first and then the back film, combined with this matching logic can maximize the performance of ALD-Al2O3 and SiN x Optimization can improve the uniformity of film thickness and enhance the battery conversion efficiency.

[0066] According to an embodiment of the present disclosure, the specific temperature difference ranges from 5 to 10° C., for example.

[0067] In some embodiments, the range of specific temperature differences is further clarified, and how to perform the solar cell coating method under specific temperature difference conditions is demonstrated. The following are detailed implementation steps:

[0068] First, high-quality single-crystal silicon wafers are selected as the silicon substrate and subjected to standard cleaning and texturing treatments to ensure that the surface is clean and has a certain light-trapping structure.

[0069] Then, a layer of aluminum oxide film is first deposited on the backlight side of the silicon substrate as a first passivation layer with a thickness of 75 nanometers, using the same method as above.

[0070] The parameters of the first temperature curve are set so that the temperature is first raised to a first temperature of 560° C. to preheat and stabilize the reaction environment.

[0071] After maintaining the first temperature for a period of time to ensure that the system is stable, the temperature is gradually lowered to the second temperature of 555°C according to the set program (the specific temperature difference here is 5°C).

[0072] Under the second temperature condition, a blue anti-reflection film is deposited as the first anti-reflection layer using PECVD technology, with a thickness of 60 to 80 nanometers.

[0073] Next, the backlight side anti-reflection layer is deposited using the second temperature curve, firstly raising the temperature to the third temperature of 450° C. to preheat the substrate and avoid stress caused by sudden temperature changes.

[0074] Then, the temperature is continued to be raised to a fourth temperature of 460° C. (the specific temperature difference here is 10° C.), and a silicon nitride film is deposited under the fourth temperature condition as a first anti-reflection layer on the backlight side with a thickness of 80 nanometers.

[0075] After all coating steps are completed, subsequent processes such as electrode fabrication, drying, and sintering are carried out to ultimately produce a solar cell with bifacial anti-reflection effects. The finished product is then tested for its optoelectronic properties to verify the effectiveness of the coating method.

[0076] During the solar cell coating process, precise control of the temperature curve within a specific temperature range (5-10°C) ensures consistent and stable coating quality. This precise temperature control not only helps optimize the performance of the coating material but also improves the photovoltaic conversion efficiency of the solar cell.

[0077] According to an embodiment of the present disclosure, the fourth temperature is lower than the second temperature, and the temperature difference between the fourth temperature and the second temperature ranges from 20° C. to 100° C.

[0078] In some embodiments, based on the previous embodiments, a new temperature difference range is introduced between the fourth temperature and the second temperature, that is, the fourth temperature is lower than the second temperature, and the temperature difference between the fourth temperature and the second temperature is between 20 and 100°C. This setting may be based on specific material properties and process requirements to further optimize the performance and structure of the coating layer.

[0079] The following are the detailed implementation steps:

[0080] Select suitable single crystal silicon wafers as silicon substrates, and go through standard pre-treatment steps such as cleaning and texturing to ensure a clean surface with good light trapping structure.

[0081] A layer of aluminum oxide film is first deposited on the backlight side as the first passivation layer with a thickness of 4 to 5 nanometers.

[0082] A first temperature curve is set, the temperature is first raised to a first temperature of 570°C, and then cooled to a second temperature of 560°C. At the second temperature, a blue anti-reflection film (silicon nitride) is deposited as a first anti-reflection layer with a thickness of 60 to 80 nanometers.

[0083] Subsequently, the backlight-side anti-reflection layer was deposited using the second temperature profile. The temperature was first raised to the third temperature of 490°C for preheating, and then further increased. However, unlike the previous setting, this time the temperature rise ended at the fourth temperature of 500°C (here the fourth temperature was lower than the second temperature, with a temperature difference of 60°C).

[0084] At the fourth temperature, a 90-nanometer-thick silicon nitride film is deposited as the first anti-reflection layer on the backlight side. Selecting a lower fourth temperature prevents hydrogen overflow from the first passivation layer, which can cause passivation failure and further improve the passivation effect.

[0085] After completing all coating steps, subsequent processes such as electrode production, drying, and sintering are carried out, and the photoelectric performance of the finished solar cells is tested to verify the effectiveness and optimization effect of the coating method.

[0086] This embodiment demonstrates another flexible application of the solar cell coating method by setting the fourth temperature lower than the second temperature, with the temperature difference between the two temperatures within a range of 20-100°C. By adjusting the temperature difference, the growth rate, structure, and performance of the coating layer can be precisely controlled, thereby achieving higher photoelectric conversion efficiency.

[0087] Preferably, the deposition temperature of the first anti-reflection layer or the second anti-reflection layer on the light-facing side is in the range of 520-560°C, and the deposition temperature of the first anti-reflection layer on the backlight side is in the range of 460-520°C.

[0088] Figure 5 A comparison diagram of the positive film optimized temperature curve according to an embodiment of the present disclosure and a conventional temperature curve is schematically shown. Figure 6 A comparison diagram of the optimized temperature curve of the back film according to an embodiment of the present disclosure and a conventional temperature curve is schematically shown.

[0089] In some embodiments, as Figure 5 and Figure 6 As shown, Curve 1 is the conventional temperature curve, Curve 2 is the optimized temperature curve for the front film, and Curve 3 is the optimized temperature curve for the back film. The thickness and refractive index data obtained by depositing the front film using Curves 1 and 2, and the back film using Curves 1 and 3, are shown in Table 1. The unit of film thickness is nm. The electrical performance data of the cells in the experimental group (SY), the control group (BSL), and the control group (ZL) are shown in Table 2.

[0090] Table 1 Film thickness and refractive index data

[0091]

[0092] Table 2 Electrical performance data

[0093]

[0094] The temperature ramping logic of the front film curve 2 and back film curve 3, on the one hand, can achieve a longer secondary annealing activation time and thin film electron capture capability within a limited process time (total coating time remains unchanged), improving the overall passivation effect and the uniformity of film thickness and refractive index between slices. The data in Tables 1 and 2 show that the overall uniformity of film thickness and refractive index between slices has been improved by 1.5-2.5%, and the efficiency has been improved by 0.007-0.02%.

[0095] The refractive index uniformity of the anti-reflection layer can be tested by testing the inter-sheet uniformity of the refractive index of the front or back surface.

[0096] Specifically, you can take any number of points on the cell to test the refractive index of the anti-reflection layer, and then calculate the inter-cell uniformity of the refractive index of the anti-reflection layer based on the measured refractive index. For example, you can take 5 points at the four corners and the center of the cell, or you can select the positions of the four corners of the cell to measure the refractive index of the anti-reflection layer separately. The location of the points should not be too close to the edge (1-2mm from the edge of the cell) to prevent the points from being located in the plating area, the film layer from being too thick, and the test results from being inaccurate. The refractive index can be measured by methods known in the art, for example, by goniometric method, ellipsometry method or spectrophotometry. Take 1-2 cells at the furnace mouth, furnace middle and furnace tail respectively, and obtain the average value of the refractive index measured at five points on each cell as A. The inter-cell uniformity of the refractive index of the anti-reflection layer = (A MAX -A MIN ) / (2*A Average ), where A MAX is the maximum refractive index value, A MIN is the minimum refractive index value, A Average is the average refractive index value.

[0097] It should be noted that when measuring the refractive index of the anti-reflection layer of a solar cell, the refractive index of the anti-reflection layer can be measured at multiple locations on the solar cell to obtain an average value of the refractive index of the anti-reflection layer. The inter-sheet uniformity of the refractive index of the anti-reflection layer can be calculated according to the above calculation formula. The inter-sheet uniformity of the refractive index of the anti-reflection layer obtained by the preparation method of the embodiment of the present disclosure can be controlled within a range of 3.5% to 6.5%.

[0098] Figure 7 The EDS characterization diagram of the sample corresponding to the conventional temperature curve according to the embodiment of the present disclosure is schematically shown. Figure 8 The EDS characterization diagram of the sample corresponding to the optimized temperature curve according to the embodiment of the present disclosure is schematically shown.

[0099] like Figure 7 and Figure 8As shown, EDS (Energy Dispersive Spectroscopy) testing of experimental samples revealed the presence of carbon impurities on the sample surface corresponding to the conventional temperature curve. However, after secondary annealing, the optimized temperature curve eliminated detectable carbon on the sample surface. On the one hand, low carbon content helps improve passivation, reduce carrier recombination, and increase the battery's short-circuit current density. On the other hand, the optimized temperature curve can further reduce energy consumption and production costs. Temperature stability is ensured for the critical glow deposition step, and the ramp rate and curve for the temperature-maintaining step are customized based on the process characteristics of the front and back films, achieving rapid temperature rise and insulation, thereby reducing energy consumption.

[0100] To measure carbon content, following the single-variable principle of experimental comparison, the experimental and control samples must be uniformly mixed before the coating process. Then, cells from the same batch are batch-coated for both the experimental and control groups. After coating, the carbon content of the cells, located in the same tube, boat, and position, is measured using an energy dispersive spectrometer.

[0101] It should be noted that Figure 8 The samples in the figure are laboratory samples. The C element can still be detected on the surface of the samples prepared on the actual production line, but the C element content on the surface of the samples corresponding to the conventional temperature curve is much lower.

[0102] According to an embodiment of the present disclosure, before depositing the first anti-reflection layer 3 on the light-facing side of the silicon substrate 1 using the first temperature curve, the solar cell coating method further includes operations S410 to S420.

[0103] In operation S410 , a first passivation layer 2 is deposited on the light-facing side of the silicon substrate 1 .

[0104] In operation S420 , a first anti-reflection layer 3 is deposited on the first passivation layer 2 on the light-facing side.

[0105] In some embodiments, a passivation layer and an anti-reflection layer are deposited on the light-facing side and the backlight side, respectively. The specific implementation steps are as follows:

[0106] High-quality single-crystal silicon wafers are selected as silicon substrates, and standard pre-treatment steps such as cleaning and texturing are carried out to ensure a clean surface with good light-trapping structure.

[0107] A 50-nanometer-thick aluminum oxide film is deposited on the light-facing side of the silicon substrate as the first passivation layer. This step aims to reduce surface defects, slow the recombination rate of photogenerated carriers, and improve the photovoltaic conversion efficiency of the cell.

[0108] The silicon wafer is flipped over and a layer of aluminum oxide film is deposited on the backlight side as the first passivation layer. The thickness is the same as that on the light-facing side or slightly different, for example, 60 nanometers, to adapt to different process requirements.

[0109] On the first passivation layer on the light-facing side, a first anti-reflection layer is deposited using a first temperature profile. The first temperature profile is set to first rise to a first temperature of 580°C, then cool to a second temperature of 572°C (with a specific temperature difference of 8°C). Under the second temperature, a blue anti-reflection film with a thickness of 60 to 110 nanometers is deposited as the first anti-reflection layer.

[0110] Next, a first anti-reflection layer (ARL) is deposited on the first passivation layer on the backlight side using a second temperature profile. This profile is configured to preheat the layer to a third temperature of 510°C, followed by a fourth temperature of 520°C. (Note that the fourth temperature is greater than the third temperature and significantly different from the second temperature on the light-facing side, while also ensuring the temperature difference between the fourth and third temperatures is within the range of 20-100°C, for example, 52°C.) At the fourth temperature, a 100-nanometer-thick silicon nitride film is deposited. The first ARL not only provides mechanical protection but may also enhance cell back reflection or serve as a passivation layer.

[0111] After all coating steps are completed, subsequent processes such as electrode fabrication, drying, and sintering are carried out to ultimately produce a solar cell with excellent performance. The finished product is then tested for its optoelectronic properties to verify the effectiveness of the coating method.

[0112] This example demonstrates the complexity and diversity of solar cell coating methods by depositing a passivation layer and an anti-reflection layer on the light-facing side and backlight side, respectively, and introducing a second temperature profile for the backlight-side anti-reflection coating. Through precise temperature control, the structure and properties of the coating layer can be precisely regulated, thereby optimizing the photovoltaic conversion efficiency of the solar cell. Furthermore, this example emphasizes the interrelationship and importance of each step in the coating process, and how the synergistic effect of multiple steps can improve the overall performance of the solar cell.

[0113] According to an embodiment of the present disclosure, before depositing the first passivation layer 2 on the backlight side of the silicon substrate 1 , the solar cell coating method further includes, for example, operations S510 to S530 .

[0114] In operation S510 , a second passivation layer 5 is deposited on the backlight side of the silicon substrate 1 .

[0115] In operation S520 , a first doping layer 6 is deposited on the second passivation layer 5 .

[0116] In operation S530 , a first passivation layer 2 on the backlight side is deposited on the first doping layer 6 .

[0117] Furthermore, before depositing the first passivation layer 2 on the light-facing side of the silicon substrate 1 , the solar cell coating method further includes, for example, operations S540 to S550 .

[0118] In operation S540 , a second doping layer 11 is formed on the light-facing side of the silicon substrate 1 .

[0119] In operation S550 , a first passivation layer 2 facing the light side is deposited on the second doping layer 11 .

[0120] In some embodiments, the solar cell coating method of the present disclosure is applicable to TOPCON solar cells. In the preparation process of TOPCON solar cells, coating is an important step, especially the deposition of passivation layers and doping layers.

[0121] Select a high-quality N-type silicon substrate as the base of the cell. Clean the silicon substrate to remove surface impurities and contaminants. Chemically treat the silicon substrate, such as wet or dry etching, to create the desired texture and improve light absorption efficiency.

[0122] Using chemical vapor deposition (CVD) technology, specifically plasma-enhanced chemical vapor deposition (PECVD), a layer of high-quality silicon oxide (SiO2) is deposited on the backlight side of the silicon substrate as a second passivation layer. This silicon oxide film can effectively reduce interfacial recombination and improve cell efficiency.

[0123] Using LPCVD (low-pressure chemical vapor deposition) or PECVD technology, a layer of doped polysilicon (such as phosphorus-doped polysilicon) is deposited on the silicon oxide passivation layer as the first doped layer. This doped polysilicon not only serves as a back field but also further reduces recombination losses.

[0124] Using PECVD technology again, a layer of aluminum oxide is deposited on the first doped layer as the first passivation layer on the backlight side to further enhance the passivation effect on the back side.

[0125] For TOPCON cells, the light-facing side can be prepared with a second doped layer through technologies such as front surface field (FSF) or selective emitter (SE) to form a PN junction.

[0126] A layer of aluminum oxide is deposited on the light-facing side of the silicon substrate using ALD technology as the first passivation layer to protect the PN junction and reduce surface recombination.

[0127] A first anti-reflection layer, such as silicon oxide (SiO2) or silicon nitride (SiN), is deposited on the aluminum oxide film on the light-facing side using a specific temperature curve (such as first heating to a first temperature and then cooling to a second temperature). x ) etc. to reduce light reflection and improve light absorption efficiency.

[0128] Similarly, a specific temperature curve (such as first heating to the third temperature and then heating to the fourth temperature) is used to deposit a first anti-reflection layer on the aluminum oxide film on the backlight side to further improve the light absorption efficiency.

[0129] The coating method for TOPCON solar cells is a complex and delicate process involving multiple steps and various technologies. By depositing a passivation layer and a doping layer on the backlight side and the light-facing side of the silicon substrate respectively, the photovoltaic conversion efficiency of the cell can be significantly improved.

[0130] Furthermore, every step in the coating process requires strict control of process parameters such as temperature, pressure, and gas flow rate to ensure coating quality. For example, the gas flow rates for depositing the first anti-reflection layer are 800-1390 sccm for SiH4 and 6960-8000 sccm for NH3, with a pressure of 240 Pa or 1800 mtorr.

[0131] According to an embodiment of the present disclosure, before depositing the first passivation layer 2 on the backlight side of the silicon substrate 1 , the solar cell coating method further includes, for example, operations S610 to S630 .

[0132] In operation S610 , a second passivation layer 2 is deposited on the backlight side of the silicon substrate 1 .

[0133] In operation S620 , a first doping layer 6 and a third doping layer 7 are deposited on the second passivation layer 2 , respectively. The third doping layer 7 and the first doping layer 6 are alternately arranged with an electrical isolation structure therebetween.

[0134] In operation S630 , a first passivation layer 2 on the backlight side is deposited on the first doping layer 6 and the third doping layer 7 .

[0135] In some embodiments, the solar cell coating method of the present disclosure is also applicable to back-contact solar cells.

[0136] A high-quality silicon wafer is chosen as the basis for the cell, which can be either N-type or P-type, depending on the cell design.

[0137] On the backlight side (i.e., non-illuminated side) of the silicon substrate, an ultra-thin second passivation layer, such as aluminum oxide (Al2O3) or silicon nitride (SiN x ) to reduce surface recombination.

[0138] For example, a mask or laser patterning is used to deposit alternately arranged first doping layers and third doping layers on the ultra-thin passivation layer, and an electrical isolation structure is provided between the first doping layer and the third doping layer to achieve isolation between the positive and negative poles of the solar cell.

[0139] A thicker layer of silicon nitride (SiN) is deposited on the first doping layer and the third doping layer. x ) or aluminum oxide (Al2O3) film as the first passivation layer on the backlight side to improve the efficiency and stability of the cell.

[0140] On the light-facing side (i.e., the illuminated side), a layer of aluminum oxide or other suitable first passivation layer is directly deposited to reduce surface recombination and prepare for subsequent anti-reflection layer deposition.

[0141] Using the first temperature curve, the temperature is first raised to the first temperature and then lowered to the second temperature to deposit the first anti-reflection layer on the light-facing side of the first passivation layer. This usually includes one or more layers of materials with different refractive indices, such as silicon oxide (SiO2), silicon nitride (SiN x ) to reduce light reflection and increase light absorption. Controlling the temperature profile is crucial to ensuring the uniformity and quality of the refractive index of the anti-reflection layer between sheets.

[0142] Although the backlight side typically does not directly receive light, in some designs, a first anti-reflection layer can be deposited on the first passivation layer on the backlight side to further improve efficiency. For example, the second temperature profile described above can be used to first increase the temperature to the third temperature and then to the fourth temperature to deposit the first anti-reflection layer on the back side.

[0143] The coating method for back-contact solar cells is a complex and delicate process designed to improve the performance of the cell by optimizing the quality and structure of each layer. In actual applications, the coating process may vary depending on the cell design, material selection and process conditions. The key to back-contact solar cells lies in their unique back contact structure, which allows light to shine from the front of the cell (i.e., the light-facing side) and collects the generated current through an optimized back contact design. Therefore, during the coating process, special attention needs to be paid to the deposition quality and mutual coordination of the passivation layer, doping layer and anti-reflection layer on the backlight side and the light-facing side to ensure the overall performance of the cell is optimized.

[0144] Figure 9 The partial structure of a solar cell according to an embodiment of the present disclosure is schematically shown.

[0145] Another aspect of the present disclosure provides a solar cell, such as Figure 9 As shown, for example, the present invention includes: a silicon substrate 1; a first passivation layer 2 disposed on at least one side of the silicon substrate 1; and a first anti-reflection layer 3 disposed on a side of the first passivation layer 2 away from the silicon substrate. The carbon content of the first anti-reflection layer 3 is less than a specific threshold, and / or the inter-sheet uniformity of the refractive index of the first anti-reflection layer 3 is in the range of 3.5% to 6.5%.

[0146] In some embodiments, high-quality N-type single crystal silicon is used as the substrate, which has a complete lattice structure and few defects, and is conducive to the transmission and collection of carriers.

[0147] A layer of aluminum oxide (Al2O3) is deposited on the backlight side (or light-facing side, depending on the specific design) of the silicon substrate as the first passivation layer. Aluminum oxide is widely used due to its excellent passivation effect and chemical stability. This thin film is precisely controlled in thickness using chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques to reduce recombination centers on the silicon surface and improve the cell's open-circuit voltage and fill factor.

[0148] On the side of the first passivation layer away from the silicon substrate, a layer of silicon nitride (SiN x ) as the first anti-reflection layer. This silicon nitride film is precisely deposited by controlling process parameters (e.g., using the optimized temperature profile, gas flow rate, and pressure described in the method examples) to ensure that the carbon content is below a specific threshold (e.g., less than 8% carbon by mass). This low carbon content helps improve passivation, reduce carrier recombination, and increase the battery's short-circuit current density.

[0149] Furthermore, by optimizing the deposition process to achieve a more uniform temperature distribution within the furnace tube, the inter-sheet uniformity of the refractive index of the first anti-reflection layer can be ensured to be within a range of 3.5% to 6.5%. Specifically, the inter-sheet uniformity of the refractive index of the front first anti-reflection layer is within a range of 3.5% to 5%, and the inter-sheet uniformity of the refractive index of the rear first anti-reflection layer is within a range of 4.5% to 6.5%. This high inter-sheet uniformity is crucial for reducing light scattering and reflection, helping to improve the overall optical performance of the cell. For example, in a related comparative experiment, the inter-sheet uniformity of the refractive index of the front first anti-reflection layer in the experimental group was 4.27%, while that of the control group was 6.57%. The inter-sheet uniformity of the refractive index of the rear first anti-reflection layer in the experimental group was 5.63%, while that of the control group was 7.20%. The battery efficiency of the experimental group increased by 0.007~0.02% compared with the control group, which proves that the coating method is beneficial to improving the uniformity of the anti-reflection layer coating, and ultimately helps to improve the battery efficiency.

[0150] On the light-facing side, an additional passivation layer and an anti-reflection layer may be deposited as needed, and structures such as a PN junction and a metal electrode 8 may be constructed to obtain a complete solar cell.

[0151] It should be noted that the first anti-reflection layer (and the subsequent second anti-reflection layer) can be a single layer or a stack of silicon nitride layers with different refractive indices. The stacked silicon nitride layers can meet the refractive index requirements for incident light at different angles or wavelengths. Using this coating method in a stacked structure can help improve the uniformity of the single silicon nitride layer in the stacked structure, reducing the thickness and refractive index differences between the layers, and improving the uniformity of the overall anti-reflection film.

[0152] The solar cell in this embodiment achieves efficient optical performance and excellent interface quality by precisely controlling the material and process parameters of the silicon substrate, first passivation layer, and first anti-reflection layer. In particular, the first anti-reflection layer effectively improves light transmittance and the cell's short-circuit current density by controlling the inter-sheet uniformity of carbon content and refractive index. This design not only improves the solar cell's conversion efficiency but also ensures its stability during long-term use.

[0153] According to an embodiment of the present disclosure, the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the backlight side of the silicon substrate is greater than the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the light-facing side of the silicon substrate.

[0154] In some embodiments, to further illustrate the structure and characteristics of such a solar cell, the material selection, functions, and design considerations of its related components may be elaborated in detail.

[0155] For example, single-crystal silicon (SSi) is a substrate material with excellent photoelectric conversion efficiency and stability. Due to its more ordered lattice structure, SSi generally offers higher conversion efficiency, but also comes at a relatively high cost. As the core component of solar cells, the silicon substrate absorbs sunlight and generates the photoelectric effect, converting light energy into electricity.

[0156] The material of the first passivation layer can be aluminum oxide (Al2O3), silicon nitride (Si3N4), etc. These materials can effectively reduce the recombination loss on the surface of the silicon substrate and improve the open circuit voltage and conversion efficiency.

[0157] The first passivation layer can be applied to both the backlight side and the light-facing side of the silicon substrate, or only on one side of the silicon substrate, such as the backlight side. The placement of the first passivation layer requires consideration of reducing carrier recombination and compatibility with the first anti-reflection layer. By reducing surface defects and recombination centers, the first passivation layer improves the electrical performance of the battery.

[0158] The material of the first anti-reflection layer can be silicon dioxide (SiO2), silicon nitride (Si3N4) or titanium dioxide (TiO2), etc. These materials can effectively reduce the reflection of light on the surface of the silicon substrate and increase light absorption by precisely controlling their thickness and refractive index.

[0159] The carbon content of the first anti-reflection layer must be below a specific threshold to avoid the introduction of additional recombination centers due to carbon impurities, which could affect cell performance. This requirement can be achieved through precise temperature control and material selection.

[0160] The inter-sheet uniformity of the refractive index of the first anti-reflection layer is controlled within a range of 3.5% to 6.5%, which is crucial for ensuring the consistency and efficiency of solar cells in large-scale production. Furthermore, the inter-sheet uniformity of the refractive index of the anti-reflection layer on the backlight side is greater than that on the light-facing side. The light-facing side of the cell directly receives light, so the anti-reflection layer cannot be too thick, which would affect light transmission. Furthermore, higher reflectivity uniformity ensures the consistency of the solar cell's external color and improves the color matching rate of the solar cell. On the backlight side of the cell, the thickness of the anti-reflection layer can be appropriately increased to reduce the probability of light transmitting from the cell to the backlight side, thereby increasing light absorption. Furthermore, increasing the thickness of the anti-reflection layer on the backlight side can improve the passivation performance of the backlight side. The structural design of this solar cell takes into account the respective functions of the front and back sides of the cell and the need for their mutual coordination to ensure optimal overall cell performance.

[0161] However, in the cell structure produced by the above coating process, the refractive index uniformity of both the anti-reflection layer on the light-facing side and the anti-reflection layer on the backlight side is improved. Improving the refractive index uniformity of the anti-reflection layer can improve the electrical performance of the solar cell.

[0162] This solar cell achieves efficient absorption and conversion of sunlight through a carefully designed silicon substrate, a double-sided passivation layer, and an anti-reflection layer with specific carbon content and refractive index uniformity requirements. The double-sided passivation layer effectively reduces recombination losses on the silicon substrate surface, while the first anti-reflection layer further improves the cell's light absorption efficiency by precisely controlling its material composition and optical properties.

[0163] Figure 10 The figure schematically shows a partial structure of a solar cell according to another embodiment of the present disclosure.

[0164] According to the embodiments of the present disclosure, Figure 10 As shown, the first passivation layer 2 is respectively arranged on the backlight side and the light-facing side of the silicon substrate 1. The solar cell further includes: a second passivation layer 5, which is arranged on the backlight side of the silicon substrate 1. A first doped layer 6 is arranged on the side of the second passivation layer 5 away from the silicon substrate 1 and is located between the second passivation layer 5 and the first passivation layer 2 on the backlight side.

[0165] In some embodiments, based on the previous embodiments, a solar cell embodiment including a multi-layer structure is further described in detail, especially regarding the configuration of the first passivation layer, the second passivation layer, and the first doping layer.

[0166] High-quality N-type monocrystalline silicon is still used as the substrate of the battery to ensure its excellent electrical performance and crystal quality.

[0167] A layer of aluminum oxide (Al2O3) is deposited on both the backlight side and the light-facing side of the silicon substrate as the first passivation layer. This thin film is formed through a precise deposition process to reduce recombination centers on the silicon surface and improve the photovoltaic conversion efficiency of the cell.

[0168] An additional layer of aluminum oxide (Al2O3) is deposited on the backlight side of the silicon substrate as a second passivation layer. This aluminum oxide film not only provides additional passivation but also acts as a diffusion barrier in subsequent processes, preventing dopant elements from diffusing into the silicon substrate.

[0169] Immediately adjacent to the second passivation layer, on the side facing away from the silicon substrate, a phosphorus-doped N+ layer is deposited as the first doped layer. This doped layer, with its high conductivity, is crucial for current collection in the solar cell. It lies between the second passivation layer and the first passivation layer on the backlight side.

[0170] On top of the first passivation layer on the light-facing side, one or more anti-reflection layers (such as silicon nitride, silicon oxide, etc.) may be deposited to optimize light incidence and reduce reflection.

[0171] Above the first doped layer, there may be other metallization layers or electrode structures for conducting the generated current out of the battery.

[0172] The solar cell in this embodiment employs a more complex layer structure design, specifically the introduction of a second passivation layer and a first doped layer on the backlight side of the silicon substrate. This design not only enhances the cell's passivation effect and improves photoelectric conversion efficiency, but also enables efficient current collection through a precise layered layout. The first and second passivation layers on the backlight side work together to provide dual protection for the silicon substrate, while the first doped layer, as a key component, ensures efficient current transmission. Overall, this design balances the cell's optical, electrical, and reliability performance.

[0173] Figure 11 The partial structure of a TOPCON solar cell according to an embodiment of the present disclosure is schematically shown.

[0174] According to the embodiments of the present disclosure, Figure 11 As shown, the solar cell further includes, for example: a second doping layer 11 , which is located on a different side of the silicon substrate 1 from the first doping layer 6 and is located between the silicon substrate 1 and the first passivation layer 2 on the light-facing side.

[0175] In some embodiments, based on the combination of the aforementioned hierarchical structures, a TOPCON (Tunnel Oxide Passivated Contact) solar cell is specifically described as an example.

[0176] High-quality N-type single crystal silicon is used as the substrate to ensure high purity and low defect density, which is conducive to the transmission of carriers.

[0177] An ultra-thin tunnel oxide layer (Tunnel Oxide) is deposited on the backlit side of the silicon substrate as a second passivation layer. This oxide layer is typically very thin (a few nanometers to tens of nanometers) and is used to prevent impurities from diffusing into the silicon substrate during the subsequent doping process while maintaining a good tunneling effect and promoting carrier transport.

[0178] Immediately adjacent to the second passivation layer, on the side facing away from the silicon substrate, is a phosphorus-doped N+ layer, serving as the first doped layer. This highly conductive doped layer is crucial for current collection in TOPCON solar cells. It lies between the second passivation layer and the first passivation layer on the backlight side.

[0179] On the light-facing side of the silicon substrate, between the silicon substrate and the first passivation layer, a boron-doped P+ layer is deposited as the second doped layer. This doped layer and the first doped layer are located on a different side of the silicon substrate and together form the electrode contact structure of the TOPCON cell. One or more layers of transparent conductive oxide (TCO), such as ITO or FTO, are also applied to the light-facing side of the second doped layer, away from the silicon substrate, to improve light absorption and current collection efficiency.

[0180] A layer of aluminum oxide (Al2O3) or silicon nitride (SiN) is deposited on both the backlight side and the light-facing side of the silicon substrate. x ) as the first passivation layer. These materials have good passivation effects, can effectively reduce the recombination centers on the silicon surface, and improve the open circuit voltage and fill factor of the battery.

[0181] On the first passivation layer on the light-facing side, one or more layers of silicon nitride (SiN x ) as the first anti-reflection layer. This layer is precisely deposited through a controlled deposition process to ensure the carbon content is below a specific threshold (e.g., 8%) and maintain refractive index uniformity between sheets within a range of 3.5% to 5%. This design helps reduce light reflection and scattering, improving light transmittance and the cell's short-circuit current density.

[0182] On top of the first passivation layer on the backlight side, one or more layers of silicon nitride (SiNx) can be deposited as a first anti-reflection layer. This anti-reflection layer is precisely deposited through a controlled deposition process to ensure that the carbon content is below a specific threshold (e.g., 8%) and that the refractive index uniformity between sheets is maintained within a range of 4.5% to 6.5%. This design further reduces light reflection and scattering, improving light transmittance and the cell's short-circuit current density.

[0183] The TOPCON cell may also include metal electrodes, metallized through-holes and other structures for connecting the first doped layer and the second doped layer to an external circuit.

[0184] It should be noted that when the solar cell is a bifacial solar cell, a tunneling oxide layer and a doped polysilicon layer can be set on the back side of the solar cell; or a tunneling oxide layer and a doped polysilicon layer can be set on the entire back side of the solar cell, and a tunneling oxide layer and a doped polysilicon layer can be set in a local area of ​​the front side of the solar cell, such as the position in contact with the electrode.

[0185] The TOPCON solar cell in this embodiment achieves an efficient electrode contact structure and good optical performance by optimizing the configuration of the passivation layer and doping layer on both sides of the silicon substrate. The combination of the second passivation layer (tunneling oxide layer) on the backlight side and the first doping layer effectively improves the carrier transmission efficiency and the current collection capacity of the battery. The optimized design of the first passivation layer and the first anti-reflection layer on the light-facing side and the backlight side reduces light reflection and scattering, improves light utilization and the short-circuit current density of the battery. Overall, this TOPCON solar cell performs well in terms of photoelectric conversion efficiency, stability and reliability, and is an important development direction in the field of solar cells.

[0186] Figure 12 The partial structure of a back-contact solar cell according to an embodiment of the present disclosure is schematically shown.

[0187] According to the embodiments of the present disclosure, Figure 12 As shown, a first passivation layer 2 is provided on the backlight surface of a silicon substrate 1. A first doped layer 6 and a third doped layer 7 are provided on the side of the first passivation layer 2 facing away from the silicon substrate 1. The third doped layer 7 has opposite polarity to the first doped layer 6, and is alternately arranged with an electrical isolation structure between them. Furthermore, a first anti-reflection layer 3 is provided on the side of the first doped layer 6, the third doped layer 7, and the electrical isolation structure facing away from the silicon substrate 1. The thickness of the first anti-reflection layer 3 corresponding to the negatively doped layer region is greater than the thickness of the first anti-reflection layer 3 corresponding to the positively doped region.

[0188] In some embodiments, the structure and features of a back contact solar cell (also referred to as an IBC, i.e., an interdigitated back contact solar cell) are further described as follows:

[0189] High-quality single-crystal silicon or polycrystalline silicon is used as the basic material for photoelectric conversion, and the thickness is adjusted according to design requirements, for example, between 150-200 microns.

[0190] First passivation layer (light-facing side): This layer is made of aluminum oxide (Al2O3) or silicon nitride (SiN x) film, which is used to reduce the recombination loss on the surface of the silicon substrate and increase the open circuit voltage.

[0191] First anti-reflection layer (light-facing side): arranged on the first passivation layer on the light-facing side, the material is, for example, silicon nitride. The carbon content (less than a specific threshold, such as below 8%) and the refractive index uniformity between the sheets (3.5%~5%) are precisely controlled through the above-mentioned first temperature curve to achieve excellent anti-reflection performance and improve the light absorption rate.

[0192] Second passivation layer (backlight side): For example, aluminum oxide may be used, but may have different thicknesses to optimize the passivation effect on the back side. This layer not only reduces recombination losses on the back side, but also provides a good interface for subsequent doping layers.

[0193] The first doped layer (P-type or N-type): located on the backlight side, adjacent to the second passivation layer, formed by ion implantation or diffusion process, serving as a polarity electrode region of the battery.

[0194] The third doped layer (opposite polarity to the first doped layer) is also located on the backlight side. It is arranged alternately with the first doped layer and has an electrically isolated structure between them, forming a finger-like staggered pattern. This design allows current to flow laterally within the battery while reducing the occupation of the front space and improving the effective use of the illuminated surface.

[0195] The first doped layer and the third doped layer have a certain height difference at the highest point along the thickness direction of the solar cell. Furthermore, after the first anti-reflection layer is deposited, this height difference structure will be maintained. This is to cooperate with the electrical isolation structure to reduce the leakage risk of the two doped layers with opposite polarities. In addition, the coating thickness of the first anti-reflection layer in the negatively charged area will be greater than the coating thickness in the positively charged area. This is because SiN x The film carries a fixed positive charge and has a good passivation effect on the surface of the negatively charged area. Therefore, a thicker anti-reflection layer is needed to passivate this area and improve battery performance.

[0196] It is understood that the first doped layer can be a negatively charged region or a positively charged region. When the first doped layer is a negatively charged region, the third doped layer is a positively charged region. When the first doped layer is a positively charged region, the third doped layer is a negatively charged region.

[0197] First passivation layer (backlight side): This layer is, for example, an aluminum oxide (Al2O3) thin film, which is used to reduce the recombination loss on the surface of the silicon substrate and increase the open circuit voltage.

[0198] First anti-reflection layer (backlight side): arranged on the first passivation layer on the backlight side, the material is, for example, a single layer of silicon nitride, a composite layer of multiple layers of silicon nitride, or a composite layer of silicon oxide (SiO2) and silicon nitride. The carbon content (less than a specific threshold, such as below 8%) and the refractive index uniformity between the sheets (4.5%~6%) are precisely controlled through the above-mentioned second temperature curve to achieve excellent anti-reflection performance and improve light absorption rate.

[0199] Metal contact lines: Through a precise metallization process, thin metal wires (such as silver or aluminum) are deposited on the doped layer on the back side. These wires serve as the battery's electrodes, collecting and conducting current. Because all electrodes are located on the back side, the front side is fully exposed to sunlight without any shielding, thereby improving photoelectric conversion efficiency.

[0200] It should be noted that when the solar cell provided in the embodiment of the present disclosure is a back-contact solar cell, the back-contact solar cell can be a hybrid cell, that is, one of the P region and the N region of the back-contact cell is a passivation contact structure provided by a tunneling oxide layer and a doped polysilicon layer stacked, and the other region is a heterojunction contact structure provided by an intrinsic amorphous silicon layer and a doped amorphous silicon layer stacked; the back-contact solar cell can also be a TBC cell, that is, both the P region and the N region of the back-contact cell are passivation contact structures provided by a tunneling oxide layer and a doped polysilicon layer stacked; the back-contact solar cell can also be an HPBC cell, that is, one of the P region and the N region of the back-contact cell is a passivation contact structure provided by a tunneling oxide layer and a doped polysilicon layer stacked, and the other region is a PERC structure.

[0201] By placing all electrodes on the backlit side of the cell, back-contact solar cells avoid light blocking by the front electrodes, significantly improving photoelectric conversion efficiency. Simultaneously, the use of double-sided passivation layers reduces surface recombination losses, and precise control of the first anti-reflection layer enhances light absorption. Furthermore, the staggered doping layer design not only optimizes the current collection path but also simplifies the cell structure, making the manufacturing process more flexible. These characteristics collectively give back-contact solar cells enormous potential for high-efficiency photovoltaic applications.

[0202] Figure 13 The partial structure of a PERC solar cell according to an embodiment of the present disclosure is schematically shown.

[0203] According to the embodiments of the present disclosure, Figure 13 As shown, the first passivation layer 2 is arranged on the backlight side of the silicon substrate 1, the second doped layer 11 is arranged on the light-facing side of the silicon substrate 1, and the second anti-reflection layer 4 is arranged on the side of the second doped layer 11 away from the silicon substrate 1, the carbon content of the second anti-reflection layer 4 is less than a specific threshold, and the refractive index uniformity of the second anti-reflection layer 4 between sheets is in the range of 3.5~5%.

[0204] In some embodiments, PERC (Passivated Emitter and Rear Cell) technology is a high-efficiency technology widely used in the current solar cell field. It significantly improves the photoelectric conversion efficiency of solar cells by optimizing the front and back surface passivation of the cell and introducing a localized back contact structure. The following is a specific example of a PERC solar cell:

[0205] High-quality N-type or P-type monocrystalline or multicrystalline silicon is used as the base material for the cell. Monocrystalline silicon generally offers higher efficiency due to its higher purity and reduced grain boundary scattering. Depending on the specific design, the thickness of the silicon substrate may be between 150 and 200 microns to achieve the best light absorption and cost-effectiveness ratio.

[0206] Backside passivation materials, such as aluminum oxide (Al2O3), can effectively reduce the surface recombination rate on the backside of the silicon substrate, thereby increasing the open-circuit voltage. The first passivation layer, applied on the backlight side of the silicon substrate, significantly reduces electron recombination on the backside through chemical passivation or field-effect passivation, thereby improving cell efficiency.

[0207] The backside anti-reflection layer, for example, is made of silicon nitride (Si3N4). By adjusting its refractive index and thickness, it can reduce light reflection within a certain wavelength range and increase light absorption in the silicon substrate. The carbon content of this layer is strictly controlled below a specific threshold using the aforementioned second temperature profile to ensure both optical performance and chemical stability. Furthermore, the refractive index uniformity between the layers is controlled between 4.5% and 6.5% to ensure consistent light absorption.

[0208] The light-facing side (front side) of the silicon substrate undergoes phosphorus diffusion or other doping processes to form an N-type or P-type doped layer, which serves as the emitter of the battery. It can enhance the battery's ability to collect photogenerated carriers and form a good ohmic contact with subsequent electrodes.

[0209] The front anti-reflection layer is similar to the back anti-reflection layer, but different optimization parameters may be used to adapt to the characteristics of the front light incidence. The front anti-reflection layer is prepared using the first temperature profile described above, and its carbon content and refractive index uniformity between sheets (3.5% to 5%) can also be controlled to achieve optimal optical performance.

[0210] It can be understood that in the embodiment of the present disclosure, the inter-sheet uniformity of the refractive index of the second anti-reflection layer on the light-facing side is smaller than the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the backlight side, that is, the anti-reflection layer on the light-facing side is more uniform than the anti-reflection layer on the backlight side.

[0211] The PERC solar cell in this example comprises a silicon substrate, a high-efficiency passivation layer on the back, and anti-reflection layers on both sides, effectively improving the cell's light absorption and carrier collection efficiency. Furthermore, combining the first and second temperature profiles described above allows for control of the carbon content and refractive index uniformity of the anti-reflection layer, ensuring stable and consistent cell performance. This structure enables PERC solar cells to achieve an optimal balance between cost-effectiveness and photoelectric conversion efficiency, making them one of the mainstream high-efficiency cell technologies in the current photovoltaic market.

[0212] According to an embodiment of the present disclosure, the first passivation layer is aluminum oxide, and the first anti-reflection layer is silicon nitride.

[0213] In some embodiments, when further describing the specific design of such a solar cell, its structural characteristics, material selection, and possible performance advantages can be further refined. The following is a more detailed example:

[0214] This solar cell can use high-quality n-type or p-type single-crystal silicon as its substrate. Single-crystal silicon, due to its high purity and long-range order, can effectively reduce the recombination of electron-hole pairs and improve photoelectric conversion efficiency. Although polycrystalline silicon is less expensive, single-crystal silicon offers superior performance in certain high-end applications.

[0215] Aluminum oxide is used as the first passivation layer. Its primary function is to reduce dangling bonds and defect states on the silicon substrate surface, thereby significantly reducing the surface recombination rate and improving the open-circuit voltage and fill factor. Aluminum oxide is an ideal passivation material due to its excellent chemical and thermal stability. Methods such as atomic layer deposition (ALD) and chemical vapor deposition (CVD) can be used to precisely control the thickness and uniformity of the aluminum oxide layer to ensure optimal passivation performance.

[0216] In order to maintain the high transmittance and low absorption rate of the silicon nitride anti-reflection layer, its carbon content must be strictly controlled to be less than a specific threshold (such as 8%) to avoid excessive carbon impurities affecting the optical and electrical properties.

[0217] By adopting the above-mentioned first temperature curve and second temperature curve to optimize the deposition process (such as PECVD, i.e., plasma-enhanced chemical vapor deposition), the refractive index uniformity of the silicon nitride layer between sheets can be ensured to be in the range of 3.5% to 6.5%, which helps to reduce the scattering loss of light at the interface and improve the light absorption efficiency.

[0218] The refractive index of the silicon nitride layer can be precisely controlled by adjusting its chemical composition (such as Si / N ratio) and thickness to achieve optimal optical matching and anti-reflection effect.

[0219] The solar cell may include a back passivation layer and a possible back surface field (BSF) or back surface field (Passivated Emitter and Rear Cell, PERC) structure disposed on one side of the silicon substrate to further improve performance.

[0220] Fine grid lines printed with silver paste are used as the front electrode, and the back side may adopt an aluminum back surface field (Al-BSF) or an all-aluminum back contact (IBC) design to reduce metal shading losses and improve current collection efficiency.

[0221] The solar cell of this embodiment comprises a silicon substrate, an aluminum oxide passivation layer, and a silicon nitride anti-reflection layer, achieving efficient photoelectric conversion. The aluminum oxide layer effectively reduces the recombination rate on the silicon surface, while the silicon nitride anti-reflection layer achieves excellent optical performance and anti-reflection effects through precise thickness and refractive index control while maintaining a low carbon content. Furthermore, combined with advanced electrode design and possible backside structural optimization, this solar cell exhibits significant advantages in photoelectric conversion efficiency, stability, and cost-effectiveness, making it a key research direction in the current solar photovoltaic field.

[0222] According to an embodiment of the present disclosure, the specific threshold is 8%.

[0223] In some embodiments, the structural characteristics of the solar cell are further refined and illustrated with examples in combination with specific numerical values.

[0224] High-quality n-type or p-type single-crystal silicon is used as the basic material for photoelectric conversion. Due to its high purity and low defect density, single-crystal silicon helps reduce the recombination of electron-hole pairs and improve photoelectric conversion efficiency.

[0225] The first passivation layer is made of aluminum oxide (Al2O3) and is directly disposed on at least one side of the silicon substrate (assuming the backlight side in this example). This can reduce recombination centers on the surface of the silicon substrate and improve the open circuit voltage and fill factor.

[0226] The first anti-reflection layer is made of silicon nitride (Si3N4) and is applied above the first passivation layer. Its carbon content is strictly controlled to a threshold below 8% to ensure optical stability and transmittance. Thickness and composition uniformity across the wafers is controlled within a range of 3.5% to 6.5% to minimize light scattering and improve light absorption efficiency.

[0227] For example, consider an n-type monocrystalline silicon solar cell with an aluminum oxide passivation layer and a silicon nitride anti-reflection layer on the backlight side. The aluminum oxide layer's thickness and uniformity are precisely controlled using atomic layer deposition (ALD) to achieve optimal passivation. The silicon nitride anti-reflection layer is deposited using plasma-enhanced chemical vapor deposition (PECVD). By precisely controlling deposition parameters such as gas flow, temperature (using the first and second temperature profiles described above), and pressure, the carbon content of the silicon nitride layer is maintained below 8%, while ensuring that its thickness and refractive index uniformity remain within specified ranges.

[0228] On the positive light side of the solar cell, there may be another set of passivation layers and anti-reflection layer systems, or directly a doping layer (such as an emitter formed by phosphorus diffusion) and a front electrode structure.

[0229] This solar cell achieves efficient photoelectric conversion by combining a high-quality silicon substrate, an aluminum oxide passivation layer, and a silicon nitride anti-reflection layer. The aluminum oxide passivation layer effectively reduces the recombination rate on the silicon surface, while the silicon nitride anti-reflection layer improves light absorption efficiency by strictly controlling the carbon content and ensuring good refractive index uniformity between sheets. In particular, setting the carbon content threshold of the silicon nitride anti-reflection layer to 8% is a reasonable choice that ensures both optical performance and the feasibility of the preparation process. Overall, this solar cell performs well in terms of photoelectric conversion efficiency, stability, and cost-effectiveness, and is one of the important research directions in the field of solar photovoltaics.

[0230] The details not included in the device embodiment section are similar to those in the method embodiment section. Please refer to the method embodiment section and will not be repeated here.

[0231] It should be understood that the specific order or hierarchy of steps in the disclosed processes is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The accompanying method claims present elements of the various steps in an exemplary order and are not intended to be limited to a specific order or hierarchy.

[0232] It should also be noted that directional terms such as "upper," "lower," "front," "back," "left," and "right" mentioned in the embodiments are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Conventional structures or configurations that may cause confusion in understanding this disclosure will be omitted. Furthermore, the shapes, sizes, and positional relationships of the components in the drawings do not reflect their actual sizes, proportions, or actual positional relationships.

[0233] In the foregoing detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that embodiments of the claimed subject matter require more features than are expressly recited in each claim. On the contrary, as reflected in the appended claims, the disclosure comprises less than all features of any individual disclosed embodiment. The appended claims are therefore hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the disclosure.

[0234] In addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. With respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", as explained in terms of "including" used as a transitional word in the claims. Any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

[0235] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A solar cell coating method, characterized in that: include: Depositing a first passivation layer on the backlit side of the silicon substrate; A first temperature curve is used to deposit a first anti-reflection layer or a second anti-reflection layer on the light-facing side of the silicon substrate. The first temperature curve is to first increase the temperature to a first temperature and then decrease the temperature to a second temperature. The first anti-reflection layer or the second anti-reflection layer on the light-facing side is deposited under the second temperature condition. The first temperature and the second temperature have a specific temperature difference.

2. The solar cell coating method according to claim 1, characterized in that: After depositing the first anti-reflection layer or the second anti-reflection layer on the light-facing side of the silicon substrate using the first temperature curve, the method further includes: A first anti-reflection layer is deposited on the first passivation layer on the backlight side using a second temperature curve, wherein the second temperature curve is first heated to a third temperature and then heated to a fourth temperature, and the first anti-reflection layer on the backlight side is deposited under the fourth temperature condition, and the third temperature and the fourth temperature have a specific temperature difference.

3. The solar cell coating method according to claim 1 or 2, characterized in that: The specific temperature difference ranges from 5 to 10°C.

4. The solar cell coating method according to claim 2, characterized in that: The fourth temperature is lower than the second temperature, and a temperature difference between the fourth temperature and the second temperature is in a range of 20-100° C.

5. The solar cell coating method according to claim 2, characterized in that: Before depositing a first anti-reflection layer on the light-facing side of the silicon substrate using a first temperature curve, the method further includes: Depositing the first passivation layer on the light-facing side of the silicon substrate; and The first anti-reflection layer is deposited on the first passivation layer at the light-facing side.

6. The solar cell coating method according to claim 5, characterized in that: Before depositing the first passivation layer on the backlight side of the silicon substrate, the method further comprises: Depositing a second passivation layer on the backlight side of the silicon substrate; depositing a first doping layer on the second passivation layer; depositing the first passivation layer on the backlight side on the first doped layer; and Before depositing the first passivation layer on the light-facing side of the silicon substrate, the method further comprises: Prepare a second doping layer on the light-facing side of the silicon substrate; The first passivation layer is deposited on the second doped layer facing the light side.

7. The solar cell coating method according to claim 5, characterized in that: Before depositing the first passivation layer on the backlight side of the silicon substrate, the method further comprises: Depositing a second passivation layer on the backlight side of the silicon substrate; Depositing a first doping layer and a third doping layer on the second passivation layer respectively, wherein the third doping layer and the first doping layer are alternately arranged with an electrical isolation structure therebetween; and The first passivation layer on the backlight side is deposited on the first doping layer and the third doping layer.

8. A solar cell, characterized in that: include: Silicon substrate; A first passivation layer disposed on at least one side of the silicon substrate; as well as A first anti-reflection layer disposed on a side of the first passivation layer away from the silicon substrate; The carbon content of the first anti-reflection layer is less than a specific threshold, and / or the inter-sheet uniformity range of the refractive index of the first anti-reflection layer is 3.5-6.5%.

9. The solar cell according to claim 8, characterized in that The inter-sheet uniformity of the refractive index of the first anti-reflection layer on the backlight side of the silicon substrate is greater than the inter-sheet uniformity of the refractive index of the first anti-reflection layer on the light-facing side of the silicon substrate.

10. The solar cell according to claim 8, characterized in that The backlight surface of the silicon substrate is provided with the first passivation layer; A first doping layer and a third doping layer are disposed on a side of the first passivation layer away from the silicon substrate, the third doping layer has opposite polarity to the first doping layer, and are alternately disposed with an electrical isolation structure therebetween; and The first anti-reflection layer is disposed on a side of the first doped layer, the third doped layer, and the electrical isolation structure away from the silicon substrate; The thickness of the first anti-reflection layer corresponding to the negatively charged doped layer region is greater than the thickness of the first anti-reflection layer corresponding to the positively charged doped region.

11. The solar cell according to claim 8, characterized in that The specific threshold is 8%.

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