Solar cell and method of forming the same

Abstract

The embodiment of the present application provides a solar cell and a forming method thereof. The forming method of the solar cell comprises the following steps: providing a substrate; performing boron diffusion treatment on the substrate to form a boron-doped layer and a borosilicate glass layer which are sequentially stacked on the surface of the substrate, and the borosilicate glass layer has interstitial oxygen atoms; the boron diffusion treatment comprises a deposition stage and a pushing stage, the substrate is provided with a boron source and an oxygen source in the deposition stage; the temperature of a reaction chamber in the deposition stage is greater than that in the pushing stage; after the boron diffusion treatment, a passivation stage is performed, a passivation source is provided to the borosilicate glass layer, and the passivation source and the interstitial oxygen atoms react to form an oxygen-containing compound. The embodiment of the present application is beneficial to improving the performance of the solar cell.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of solar cells, and particularly relate to a solar cell and a forming method thereof. BACKGROUND

[0002] With the continuous decrease of fossil energy and the continuous aggravation of environmental pollution, the research and development and popularization and use of new energy have been highly concerned. Among them, as one of the new energy, solar energy has the advantages of abundance and cleanliness, and is most likely to become the dominant new energy. At present, among many kinds of solar cells, crystalline silicon solar cells have become dominant, and improving the conversion efficiency of solar cell pieces is our research focus.

[0003] However, in the preparation process of forming an emitter of a solar cell piece, supersaturated oxygen atoms can generate oxygen precipitates in the substrate, the oxygen precipitates are radially distributed in the substrate, and present concentric ring or spiral oxygen rings, which affect the photoelectric conversion efficiency of the solar cell piece.

[0004] How to reduce the oxygen content in the solar cell piece has become a problem to be solved by those skilled in the art. SUMMARY

[0005] Embodiments of the present application provide a solar cell and a forming method thereof, which are beneficial to solve the problem of excessive oxygen content in the solar cell.

[0006] To solve the above problems, embodiments of the present application provide a forming method of a solar cell, comprising: providing a substrate; performing boron diffusion treatment on the substrate to form a boron-doped layer and a boron-silicon glass layer stacked in sequence on the surface of the substrate, the boron-silicon glass layer having interstitial oxygen atoms; the boron diffusion treatment includes a deposition stage and a pushing stage, the boron source and the oxygen source are provided to the substrate in the deposition stage; the temperature of the reaction chamber in the deposition stage is greater than the temperature of the reaction chamber in the pushing stage; after the boron diffusion treatment, a passivation stage is performed, a passivation source is provided to the boron-silicon glass layer, and the passivation source and the interstitial oxygen atoms react to form an oxygen-containing compound.

[0007] In addition, the passivation source is a gallium source or a molybdenum source, and the oxygen-containing compound formed is gallium oxide or molybdenum oxide.

[0008] In addition, the oxygen source is provided to the substrate in the pushing stage, and the rate of providing the oxygen source in the deposition stage is greater than the rate of providing the oxygen source in the pushing stage.

[0009] In addition, the flow rate of the oxygen source provided in the deposition stage is 200 standard milliliters per minute to 15000 standard milliliters per minute; the flow rate of the oxygen source provided in the pushing stage is 200 standard milliliters per minute to 1000 standard milliliters per minute.

[0010] In addition, the temperature of the reaction chamber in the deposition stage is 980-1200 DEG C, and the temperature of the reaction chamber in the advancing stage is 920-980 DEG C.

[0011] In addition, the substrate is a solar cell piece requiring rework, and the solar cell piece requiring rework has a borosilicate glass layer, and the solar cell piece requiring rework is subjected to a cleaning treatment before the boron diffusion treatment, so as to remove the borosilicate glass layer.

[0012] In addition, the cleaning treatment is performed on the solar cell piece requiring rework by using hydrofluoric acid or nitric acid.

[0013] In addition, the process parameters of the passivation stage include that the flow rate of the gallium source or the molybdenum source is 300-1500 standard milliliter per minute, the pressure of the reaction chamber is -30 Pa, and the temperature of the reaction chamber is 980-1100 DEG C.

[0014] In addition, the temperature of the reaction chamber in the passivation stage is equal to the temperature of the reaction chamber in the advancing stage.

[0015] The embodiment of the present application also provides a solar cell piece, which comprises a substrate having opposite first and second surfaces, wherein the first surface of the substrate has a boron-doped layer and a borosilicate glass layer stacked in sequence, the borosilicate glass layer has an oxygen-containing compound therein, a first passivation layer is located on the surface of the borosilicate glass layer, a first electrode penetrates through the first passivation layer and the borosilicate glass layer and is in contact with the boron-doped layer, the second surface of the substrate has a surface field layer and a second passivation layer stacked in sequence, and a second electrode penetrates through the second passivation layer and is in contact with the surface field layer.

[0016] In addition, the oxygen-containing compound is gallium oxide or molybdenum oxide.

[0017] In addition, the content of the oxygen-containing compound on the side of the borosilicate glass layer close to the boron-doped layer is greater than the content of the oxygen-containing compound on the side of the borosilicate glass layer away from the boron-doped layer.

[0018] In addition, the boron-doped layer contains interstitial oxygen atoms, and the depth of the interstitial oxygen atoms in the boron-doped layer is less than or equal to 1.2 microns.

[0019] Compared with the prior art, the technical scheme provided by the embodiment of the present application has the following advantages:

[0020] In the embodiment of the present application, in the boron diffusion process, the temperature of the reaction chamber in the deposition stage is greater than the temperature of the reaction chamber in the advancing stage, and the temperature of the reaction chamber in the advancing stage is smaller, which can appropriately reduce the speed of diffusion of excessive interstitial oxygen atoms to the substrate, and is beneficial to reduce the content of interstitial oxygen atoms on the surface of the solar cell sheet, and further effectively avoid the oxygen from being deposited in the substrate to form an oxygen ring, thereby improving the photoelectric conversion efficiency of the solar cell sheet; and after the boron diffusion process, a passivation stage is performed to provide a passivation source to the boron-silicon glass layer, and the passivation source and the interstitial oxygen atoms react to form an oxygen-containing compound. The passivation source reacts with the interstitial oxygen atoms to reduce the content of the interstitial oxygen atoms, effectively avoids the excessive interstitial oxygen atoms from being deposited in the substrate to form an oxygen ring, and improves the photoelectric conversion efficiency of the solar cell sheet.

[0021] In addition, the rate of providing the oxygen source in the deposition stage is greater than the rate of providing the oxygen source in the advancing stage, and the rate of providing the oxygen source in the advancing stage is smaller, which is beneficial to reduce the content of the interstitial oxygen atoms in the entire reaction chamber, and further beneficial to reduce the oxygen atoms deposited in the substrate, and improve the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0022] One or more embodiments are illustrated by way of example in the figures that form a part of this patent document, these illustrative examples do not limit the embodiments, and elements having the same reference numbers in the figures indicate like elements unless otherwise stated, and the figures in the drawings do not constitute a proportional limitation.

[0023] Figures 1-7 The structure schematic diagram corresponding to each step of the forming method of the solar cell sheet provided by an embodiment of the present application;

[0024] Figure 8 The structure schematic diagram of the solar cell sheet improved by another embodiment of the present application. DETAILED DESCRIPTION

[0025] As known from the background art, the photoelectric conversion efficiency of the solar cell sheet in the prior art needs to be improved.

[0026] A solar cell presents a dark ring under photo luminescence (PL) test or electro luminescence (EL) test, because the intensity of luminescence of the PL test and the EL test is proportional to the density of non-equilibrium minority carriers in the solar cell, and the defects of the solar cell become the recombination center of the minority carriers, the minority carrier density at the defects is small, which leads to the weakening of the fluorescence effect, and thus the dark points, lines or certain areas are shown on the image; after oxygen content analysis of the solar cell, it is found that the oxygen content at the dark ring of the EL test image, that is, the defects of the solar cell, is relatively high, and it can be obtained that the defects of the solar cell are related to the high oxygen content.

[0027] Further analysis shows that, because the solar cell uses a high-temperature diffusion process to form an emitter during boron diffusion, part of the oxygen source provided to the substrate forms a borosilicate glass layer as a reactant, and the remaining excess interstitial oxygen atoms diffuse to the direction of the borosilicate glass layer close to the substrate under high temperature, and generally can diffuse to a depth of 2 microns of the substrate surface; these free-state oxygen atoms precipitate to form oxygen rings in the substrate, which affect the photoelectric conversion efficiency of the solar cell and reduce the product yield.

[0028] To solve the above problems, the present application provides a solar cell forming method, in the boron diffusion process, the temperature of the reaction chamber in the deposition stage is greater than the temperature of the reaction chamber in the pushing stage, and the temperature of the reaction chamber in the pushing stage is smaller, which can appropriately reduce the diffusion speed of the excess interstitial oxygen atoms to the substrate, which is beneficial to reduce the content of the interstitial oxygen atoms on the surface of the solar cell, further effectively avoid the precipitation of the oxygen in the substrate to form oxygen rings, and improve the photoelectric conversion efficiency of the solar cell; and after the boron diffusion process, a passivation stage is performed, a passivation source is provided to the borosilicate glass layer, the passivation source and the interstitial oxygen atoms react to form an oxygen-containing compound, the passivation source reacts with the interstitial oxygen atoms, reduces the content of the interstitial oxygen atoms, effectively avoids the precipitation of the excess interstitial oxygen atoms in the substrate to form oxygen rings, and improves the photoelectric conversion efficiency of the solar cell.

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are proposed in order to make the readers better understand the present application. However, the technical solutions claimed by the present application can be realized even without these technical details and various changes and modifications based on the following embodiments.

[0030] Figures 1-7 The solar cell forming method provided by an embodiment of the present application corresponds to a structure schematic diagram of each step.

[0031] Reference Figure 1 The substrate 101 is provided.

[0032] In this embodiment, the solar cell piece can be a double-sided cell piece. The opposite front and back surfaces of the double-sided cell piece, under direct or indirect illumination of sunlight, have internal electron transitions, thereby forming a tiny current, which is then collected by a plurality of sub-grid lines and main grid lines into a larger current and then output externally, realizing conversion of light energy into electrical energy. In other embodiments, the solar cell piece is a single-sided cell piece. The front surface of the solar cell piece is a light-receiving surface, and the back surface is a back light surface.

[0033] The material of the substrate 101 can be a silicon wafer such as monocrystalline silicon, polycrystalline silicon, or single-crystal silicon. The quality of the silicon wafer directly determines the conversion efficiency of the solar cell.

[0034] In this embodiment, the intrinsic material of the substrate 101 is an N-type monocrystalline silicon layer, and the emitter thereof is a P-type diffusion layer. In other embodiments, the intrinsic material of the substrate can also be a P-type monocrystalline silicon layer, and the emitter thereof is an N-type diffusion layer.

[0035] Reference Figure 1 and Figure 2 The substrate 101 is subjected to boron diffusion treatment to form a boron-doped layer 102 and a borosilicate glass layer 103 stacked in sequence on the surface of the substrate 101. The borosilicate glass layer 103 has interstitial oxygen atoms.

[0036] In this embodiment, the boron-doped layer 102 is the emitter of the solar cell piece, the borosilicate glass layer 103 is part of the passivation structure of the solar cell, and the boron-doped layer 102 and the borosilicate glass layer 103 are located on the back surface of the N-type solar cell piece. The boron diffusion treatment will be described in detail below.

[0037] First, the substrate 101 is cleaned and textured: the N-type monocrystalline silicon wafer is subjected to cleaning and texturing treatment. The mechanical damage layer on the surface of the substrate 101 is first removed by cleaning. The thickness of the mechanical damage layer removed from the surface of the substrate 101 is 5-7 microns. Then the substrate 101 is textured to prepare a pyramid textured surface. The height of the prepared pyramid textured surface is 3-4 microns.

[0038] The sampling stage: the cleaned and textured substrate 101 is placed in the furnace tube of the diffusion furnace for boron diffusion treatment. The substrate 101 is placed vertically to the quartz boat of the diffusion furnace, and the substrate insertion process is completed.

[0039] Heating and vacuumizing stage: nitrogen gas is introduced into the reaction chamber of the diffusion furnace at a flow rate of 5000 standard-state cubic centimeter per minute (sccm), and then the reaction chamber is heated and vacuumized to a pressure of -30 Pa (Pascal) in the reaction chamber to form a negative pressure state in the tube.

[0040] Oxidation stage before diffusion: when the temperature rises to 810 degrees Celsius, the nitrogen flow rate is adjusted to 2000 sccm, and an oxygen source is introduced for oxidation before diffusion at a flow rate of 1200 sccm for 600 seconds.

[0041] Boron diffusion treatment: the boron diffusion treatment includes a deposition stage 110 and a pushing stage 120, and the substrate 101 is provided with a boron source and an oxygen source in the deposition stage 110.

[0042] Specifically, the temperature of the reaction chamber is raised to 980-1200 degrees Celsius, and can be 1000 degrees Celsius, 1050 degrees Celsius or 1100 degrees Celsius. After the temperature is stabilized, the deposition stage 110 is performed: a boron source is introduced, which can be BCl3 gas, at a flow rate of 600 sccm for 6-8 minutes. The oxygen source provided in the deposition stage 110 has a flow rate of 200-15000 standard-state cubic centimeter per minute, and can be 2000 sccm, 10000 sccm or 12000 sccm.

[0043] The pushing stage 120 is performed: the introduction of the boron source is stopped, the nitrogen flow rate is adjusted to 3000 sccm, the temperature of the reaction chamber is lowered to 920-980 degrees Celsius, and can be 940 degrees Celsius, 950 degrees Celsius or 960 degrees Celsius. After the temperature is stabilized, the temperature is kept constant and the pushing stage is performed for 8-12 minutes. The oxygen source provided in the pushing stage 120 has a flow rate of 200-1000 standard-state cubic centimeter per minute, and can be 300 sccm, 500 sccm or 800 sccm. In other embodiments, no oxygen source can be provided in the pushing stage, which is beneficial to reduce the oxygen content in the reaction chamber, and the excess interstitial oxygen atoms after the boron diffusion treatment are less likely to reduce the oxygen content on the surface of the solar cell sheet and improve the photoelectric conversion efficiency of the solar cell sheet.

[0044] Sampling stage: nitrogen gas is introduced to increase the pressure, and the temperature is lowered. After the pressure in the reaction chamber is raised to atmospheric pressure and the temperature is lowered to room temperature, sampling is performed, and the boron diffusion treatment is completed.

[0045] It can be seen from the above that the temperature of the reaction chamber in the deposition stage 110 is greater than the temperature of the reaction chamber in the advancing stage 120; the temperature of the reaction chamber in the advancing stage 120 is smaller, which can appropriately reduce the diffusion speed of the excessive interstitial oxygen atoms to the substrate 101, is conducive to reducing the content of the interstitial oxygen atoms on the surface of the solar cell sheet, further effectively avoids the interstitial oxygen atoms from being deposited in the substrate 101 to form an oxygen ring, and improves the photoelectric conversion efficiency of the solar cell sheet.

[0046] In the embodiment, the oxygen source is provided to the substrate 101 in the advancing stage 120, and the rate at which the oxygen source is provided in the deposition stage 110 is greater than the rate at which the oxygen source is provided in the advancing stage 120. The rate at which the oxygen source is provided in the deposition stage 110 is greater than the rate at which the oxygen source is provided in the advancing stage 120, and the rate at which the oxygen source is provided in the advancing stage 120 is smaller, which is conducive to reducing the content of the interstitial oxygen atoms in the entire reaction chamber, and further conducive to reducing the oxygen atoms deposited in the substrate 101, and improving the photoelectric conversion efficiency of the solar cell.

[0047] Reference Figure 3 After the boron diffusion treatment, the passivation stage 130 is performed to provide a passivation source to the borosilicate glass layer 103 (reference Figure 2 ) to react with the interstitial oxygen atoms to form an oxygen-containing compound.

[0048] The passivation source reacts with the interstitial oxygen atoms to form an oxygen-containing compound, which reacts with the interstitial oxygen atoms to reduce the content of the interstitial oxygen atoms, effectively avoids the excessive interstitial oxygen atoms from being deposited in the substrate 101 to form an oxygen ring, and improves the photoelectric conversion efficiency of the solar cell sheet.

[0049] The oxygen-containing compound and the borosilicate glass layer 103 form a passivation layer 104, which is part of the passivation structure of the subsequently formed solar cell sheet.

[0050] In the embodiment, the boron-doped layer 102 can also have interstitial oxygen atoms on the surface and inside, and the passivation source also reacts with the interstitial oxygen atoms inside or on the surface of the boron-doped layer 102 to form an oxygen-containing compound, so that the content of the interstitial oxygen atoms on the surface of the substrate 101 is smaller, which is conducive to improving the photoelectric conversion efficiency of the solar cell sheet.

[0051] In the embodiment, the passivation source can be a gallium source or a molybdenum source, and the formed oxygen-containing compound is gallium oxide or molybdenum oxide.

[0052] In the embodiment, the process parameters of the passivation stage 130 include: the flow rate of the gallium source or the molybdenum source is 300 standard cubic centimeters per minute to 1500 standard cubic centimeters per minute, and can be 500 sccm, 1000 sccm or 1200 sccm; the pressure of the reaction chamber is -30 Pa; the temperature of the reaction chamber is 980 degrees Celsius to 1100 degrees Celsius, and can be 990 degrees Celsius, 1000 degrees Celsius or 1050 degrees Celsius. When the passivation source is introduced, nitrogen or argon is also introduced into the reaction chamber of the diffusion furnace as a carrier gas, and the flow rate of the nitrogen or argon is 2000 standard cubic centimeters per minute.

[0053] In other embodiments, the temperature of the reaction chamber in the passivation stage can also be equal to the temperature of the reaction chamber in the advancing stage. The passivation stage can be a continuation of the advancing stage, and the temperature of the reaction chamber can not be changed, so that the advancing stage continues to form a boron-doped layer with better quality, or the temperature can be used to make the passivation source react with the interstitial oxygen atoms in the borosilicate glass layer to form oxygen-containing compounds, thereby reducing the oxygen atoms on the surface of the solar cell.

[0054] In the embodiment, after the passivation stage 130 is completed, a silicon nitride layer is deposited on the passivation layer 104 using a plasma-enhanced chemical vapor deposition process, and the passivation layer 104 and the silicon nitride layer form a passivation structure of the solar cell. Then, the solar cell is placed in a diffusion furnace, and a phosphorus diffusion process is performed on the front surface of the solar cell to form a phosphorus-diffused N-type front surface field layer. The temperature of the reaction chamber is 790 degrees Celsius to 940 degrees Celsius, and the duration of the phosphorus diffusion process is 30 minutes to 40 minutes. The impurity layer formed by the phosphorus diffusion process is removed by plasma etching or laser scribing, and the phosphorus-silicon impurity glass layer formed on the front surface of the solar cell by the phosphorus diffusion process is removed by a single-sided chemical etching system.

[0055] Then, under the condition that the hydrogen source in the reaction chamber is sufficient, a silicon nitride anti-reflection layer is deposited on the front surface of the substrate 101 using a plasma-enhanced chemical vapor deposition process, and the silicon nitride anti-reflection layer has hydrogen atoms. Then, an annealing process is performed under high temperature and high light. In the annealing process, the temperature of the reaction chamber is 620 degrees Celsius to 680 degrees Celsius, the light intensity is 1.5 kw / m 2 ~ 5 kw / m 2 ( kilowatts per square meter), and the duration of the annealing process is 10 seconds to 30 seconds. The reflectivity of the formed silicon nitride anti-reflection layer is 2.10% to 2.23%.

[0056] The hydrogen atoms in the silicon nitride anti-reflection layer not only enhance the anti-reflection performance of the silicon nitride, but also diffuse to passivate other defects of the solar cell after diffusion.

[0057] Finally, the front and back surfaces of the substrate 101 are printed with silver paste for electrodes by using a screen printing device, and sintering is performed to prepare a N-type silicon solar cell.

[0058] Reference Figure 4 In another example, the substrate 101 is a solar cell requiring rework, and the solar cell requiring rework has a borosilicate glass layer 113. Before boron diffusion treatment is performed, the solar cell requiring rework is subjected to cleaning treatment to remove the borosilicate glass layer 113.

[0059] When the substrate 101 is a solar cell requiring rework, the process steps for forming a new solar cell include: cleaning treatment 140 of the solar cell requiring rework, in which the solar cell requiring rework is cleaned by using hydrofluoric acid or nitric acid to remove the borosilicate glass layer 113 on the surface of the boron doped layer 112 of the solar cell requiring rework.

[0060] In this case, the worker wears gloves to perform the corresponding operation during the transfer / storage of the solar cell requiring rework, so that the sweat / oil of the worker can be effectively prevented from causing secondary pollution or damage to the solar cell requiring rework. Preferably, the gloves worn by the worker during the transfer / storage of the solar cell requiring rework include rubber gloves directly worn on the hands and disposable gloves worn outside the rubber gloves, so that the disposable gloves can be replaced after the transfer / storage of the solar cell requiring rework is completed, and the replacement of the relatively expensive rubber gloves is effectively avoided, further reducing the rework cost.

[0061] After the cleaning treatment 140 etches and removes the borosilicate glass layer 113 from the solar cell requiring rework, the thickness of the solar cell requiring rework is reduced by 2-3 microns, and the mass of the solar cell requiring rework is reduced by 0.2-0.4 grams. In other embodiments, the boron doped layer can also be removed by cleaning.

[0062] Cleaning and texturing the substrate 101: the solar cell requiring rework is subjected to cleaning and texturing treatment, in which the surface mechanical damage layer of the substrate 101 is first removed by cleaning, and then the substrate 101 is textured to prepare a pyramid texture, and the height of the prepared pyramid texture is 3-4 microns.

[0063] Reference Figure 5 and Figure 6 The deposition stage 110 and the advancing stage 120 are sequentially performed to form the borosilicate glass layer 103.

[0064] Reference Figure 7 The passivation stage 130 is performed to form a passivation layer 104 composed of an oxide-containing compound and the borosilicate glass layer 103.

[0065] Since the solar cell piece needing rework has already been subjected to boron diffusion treatment once before rework, the substrate 101 surface already has a certain amount of interstitial oxygen atoms, and when rework is performed again, the oxygen atom content on the surface of the solar cell piece is high, and a large amount of oxygen atom deposition reduces the photoelectric conversion efficiency of the solar cell piece. In the embodiment, the boron-silicon glass layer 113 formed before is removed during rework, so that the interstitial oxygen atom content of the solar cell piece needing rework is reduced, and then the boron diffusion stage and the passivation stage 130 described above are sequentially performed, so that the oxygen atom on the surface of the solar cell piece after rework is less, and the photoelectric conversion efficiency of the solar cell piece is improved.

[0066] The effect of the solar cell piece formed in the embodiment will be described in detail below in combination with examples.

[0067] Table 1 shows the improvement results of the effect of the formed solar cell piece.

[0068]

[0069] Table 1

[0070] In the example, the solar cell piece formed in the embodiment has an oxygen-containing compound, and another solar cell piece does not have an oxygen-containing compound layer, and the effect is shown in Table 1. The depth of oxygen atoms on the surface of the solar cell piece formed in the embodiment is 0.8 microns to 1.1 microns, and the depth of oxygen atoms on the surface of another solar cell piece is 1.2 microns to 1.8 microns. The oxygen concentration of the solar cell piece formed in the embodiment is 3 to 6 x 10^17 atom / cm 3 , and the oxygen concentration of another solar cell piece is 6 to 12 x 10^17 atom / cm 3 . The proportion of oxygen rings in EL testing of the solar cell piece formed in the embodiment is 0.5%, and the proportion of oxygen rings in EL testing of another solar cell piece is 3.2%.

[0071] It can be obtained that the oxygen content of the solar cell piece formed in the embodiment is less than that of another solar cell piece under each test, and the photoelectric conversion efficiency of the solar cell piece is improved.

[0072] In the boron diffusion process of the embodiment, the temperature of the reaction chamber in the deposition stage 110 is greater than the temperature of the reaction chamber in the advancing stage 120, and the temperature of the reaction chamber in the advancing stage 120 is smaller, which can appropriately reduce the diffusion speed of the excessive interstitial oxygen atoms to the substrate 101, and is beneficial to reduce the content of the interstitial oxygen atoms on the surface of the solar cell sheet, and further effectively avoid the oxygen precipitation in the substrate 101 to form an oxygen ring, and improve the photoelectric conversion efficiency of the solar cell sheet. Moreover, the deposition stage 110 provides the oxygen source at a rate greater than the rate of the advancing stage 120, and the advancing stage 120 provides the oxygen source at a smaller rate, which is beneficial to reduce the content of the interstitial oxygen atoms in the entire reaction chamber, and further beneficial to reduce the oxygen atoms precipitated in the substrate 101, and improve the photoelectric conversion efficiency of the solar cell. Moreover, after the boron diffusion process, the passivation stage 130 is performed to provide a passivation source to the borosilicate glass layer 103, the passivation source and the interstitial oxygen atoms react to form an oxygen-containing compound. The passivation source reacts with the interstitial oxygen atoms to reduce the content of the interstitial oxygen atoms, effectively avoid the excessive interstitial oxygen atoms to precipitate in the substrate 101 to form an oxygen ring, and improve the photoelectric conversion efficiency of the solar cell sheet.

[0073] Another embodiment of the present application provides a solar cell sheet formed by the above-mentioned method for forming a solar cell sheet, which will be described in detail below in combination with the drawings.

[0074] Figure 8 A structure diagram of the solar cell sheet improved by another embodiment of the present application.

[0075] Reference Figure 8 , including: a substrate 201 having opposite first and second surfaces; the first surface of the substrate 201 has a boron-doped layer 202 and a borosilicate glass layer 203 stacked in sequence, and the borosilicate glass layer 203 has an oxygen-containing compound; a first passivation layer 204 located on the surface of the borosilicate glass layer 203; a first electrode 205 penetrating through the first passivation layer 204 and the borosilicate glass layer 203, and contacting the boron-doped layer 202; the second surface of the substrate 201 has a surface field layer 212 and a second passivation layer 214 stacked in sequence; and a second electrode 215 penetrating through the second passivation layer 214 and contacting the surface field layer 212.

[0076] The borosilicate glass layer 203 has an oxygen-containing compound, which combines the interstitial oxygen atoms in the borosilicate glass layer 203 during the formation process, so that the content of the oxygen atoms in the solar cell sheet is reduced, the proportion of the oxygen ring formed by the deposition of the oxygen atoms in the solar cell is reduced, and the photoelectric conversion efficiency of the solar cell sheet is improved.

[0077] In the embodiment, the material of the substrate 201 can be a silicon wafer such as monocrystalline silicon, polycrystalline silicon or single-crystal silicon-like silicon; the surface type of the substrate 201 includes a textured surface, a polished surface or an etched surface; the intrinsic material of the substrate 201 is an N-type monocrystalline silicon layer, and the emitter thereof is a P-type diffusion layer. In other embodiments, the intrinsic material of the substrate can also be a P-type monocrystalline silicon layer, and the emitter thereof is an N-type diffusion layer.

[0078] In the embodiment, the solar cell wafer can be a bifacial cell wafer including opposite first and second surfaces, the back surface of the bifacial cell wafer is the first surface, and the front surface is the second surface. The first and second surfaces of the bifacial cell wafer are both under direct or indirect irradiation of sunlight, and electron transition occurs inside to form a tiny current, which is then collected by a plurality of sub-grid lines and main grid lines into a larger current and then output externally to realize conversion of light energy into electrical energy. In other embodiments, the solar cell wafer is a single-sided cell wafer, the front surface of the solar cell wafer is a light-receiving surface, and the back surface is a back light surface.

[0079] In the embodiment, the boron-doped layer 202 is an emitter of the solar cell wafer, and the emitter can be formed by a laser doping method; the borosilicate glass layer 203 and the first passivation layer 204 form a first passivation structure, the material of the first passivation layer 204 can be silicon nitride, and the first passivation structure can be formed by a plasma-enhanced chemical vapor deposition process. The first passivation structure passivates defects on the first surface of the substrate 201, which is conducive to improving the open-circuit voltage of the solar cell wafer. In the embodiment, the oxygen-containing compound can be gallium oxide or molybdenum oxide.

[0080] In the embodiment, the content of the oxygen-containing compound on the side of the borosilicate glass layer 203 close to the boron-doped layer 202 is greater than the content of the oxygen-containing compound on the side of the borosilicate glass layer 203 away from the boron-doped layer 202.

[0081] Since the oxygen-containing compound is formed by combining interstitial oxygen atoms in the solar cell, the content of the oxygen-containing compound on the side of the borosilicate glass layer 203 close to the boron-doped layer 202 is greater, which indicates that there are fewer oxygen atoms in the solar cell closer to the substrate 201, the depth of the oxygen atoms doped in the substrate 201 is shallower, and the proportion of the oxygen ring formed in the substrate 201 is smaller, thereby improving the photoelectric conversion efficiency of the solar cell wafer.

[0082] In the embodiment, the boron-doped layer 202 contains interstitial oxygen atoms, and the depth of the interstitial oxygen atoms in the boron-doped layer 202 is less than or equal to 1.2 microns.

[0083] Since excess oxygen atoms will diffuse into the boron-doped layer 202 at high temperature when forming the solar cell, the boron-doped layer 202 has interstitial oxygen atoms, but the boron-silicon glass layer 203 of the present embodiment has oxygen-containing compounds, and the oxygen in the oxygen-containing compounds can also be part of the interstitial oxygen atoms of the boron-doped layer 202. During the formation of the oxygen-containing compounds, the content of free-state oxygen atoms in the boron-doped layer 202 is reduced, so that the depth of the interstitial oxygen atoms in the boron-doped layer 202 is less than or equal to 1.2 microns. The smaller depth of the interstitial oxygen atoms in the boron-doped layer 202 indicates that the content of oxygen atoms is small, which is beneficial to improve the photoelectric conversion efficiency of the solar cell.

[0084] The material of the first electrode 205 is a metal with high conductivity, which can be aluminum metal or silver metal. In the present embodiment, the first electrode 205 is a single-layer structure. In other embodiments, the first electrode can also be a stacked structure having a transparent conductive layer and a metal layer on the transparent conductive layer.

[0085] In the present embodiment, the first electrode 205 can be formed by a screen printing process, a plating process or a deposition process.

[0086] Since the substrate 201 is an N-type substrate in the present embodiment, the surface field layer 212 on the second surface of the substrate 201 has N-type ions with a higher doping concentration than the substrate 201, such as phosphorus ions, arsenic ions, bismuth ions or antimony ions. In other embodiments, when the substrate is a P-type substrate, the surface field layer 212 is doped with P-type ions. The surface field layer 212 can prevent charge-hole pairs from recombining on the surface of the substrate 201 and can enhance the efficiency of the solar cell.

[0087] The material of the second passivation layer 214 can be a transparent insulating material, which can be silicon nitride, hydrogen-containing silicon nitride, silicon oxide or silicon oxynitride. Thus, light can be transmitted through the second passivation layer 214 to the second surface of the substrate 201, thereby enhancing the efficiency of the solar cell.

[0088] The material of the second electrode 215 is a metal with high conductivity, which can be aluminum metal or silver metal. In the present embodiment, the second electrode 215 is a single-layer structure. In other embodiments, the second electrode can also be a stacked structure having a transparent conductive layer and a metal layer on the transparent conductive layer.

[0089] In the present embodiment, the second electrode 215 can be formed by a screen printing process, a plating process or a deposition process.

[0090] The solar cell provided by the embodiment contains an oxygen-containing compound in the borosilicate glass layer 203, the oxygen-containing compound combines with the interstitial oxygen atoms in the borosilicate glass layer 203 in the forming process, so that the content of oxygen atoms in the solar cell piece is reduced, the proportion of oxygen rings formed by the deposition of oxygen atoms in the solar cell is reduced, and the photoelectric conversion efficiency of the solar cell piece is improved.

[0091] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for realizing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make respective changes and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A method for forming a solar cell, characterized in that, include: Provide a base; The substrate is subjected to boron diffusion treatment to form a boron-doped layer and a borosilicate glass layer stacked sequentially on the surface of the substrate, wherein the borosilicate glass layer contains interstitial oxygen atoms; The boron diffusion process includes a deposition stage and a propulsion stage, wherein a boron source and an oxygen source are provided to the substrate in the deposition stage, and the oxygen source is provided to the substrate in the propulsion stage, wherein the rate at which the oxygen source is provided in the deposition stage is greater than the rate at which the oxygen source is provided in the propulsion stage. The temperature of the reaction chamber during the deposition stage is higher than the temperature of the reaction chamber during the propulsion stage. After the boron diffusion treatment, a passivation stage is performed, in which a passivation source is provided to the borosilicate glass layer. The passivation source reacts with the interstitial oxygen atoms to form an oxygen-containing compound. The passivation source is a gallium source or a molybdenum source, and the formed oxygen-containing compound is gallium oxide or molybdenum oxide.

2. The method for forming a solar cell according to claim 1, characterized in that, The oxygen source is supplied at a flow rate of 200 standard milliliters per minute to 15,000 standard milliliters per minute during the deposition stage; The oxygen source is supplied at a flow rate of 200 standard milliliters per minute to 1000 standard milliliters per minute during the propulsion phase.

3. The method for forming a solar cell according to claim 1, characterized in that, The temperature of the reaction chamber during the deposition stage is 980°C to 1200°C; the temperature of the reaction chamber during the propulsion stage is 920°C to 980°C.

4. The method for forming a solar cell according to claim 1, characterized in that, The substrate is a solar cell that needs to be reworked. The solar cell that needs to be reworked has a borosilicate glass layer. Before the boron diffusion treatment, the solar cell that needs to be reworked is cleaned to remove the borosilicate glass layer.

5. The method for forming a solar cell according to claim 4, characterized in that, The solar cells requiring rework are cleaned using hydrofluoric acid or nitric acid.

6. The method for forming a solar cell according to claim 1, characterized in that, The process parameters for the passivation stage include: the flow rate of the gallium source or the molybdenum source is 300 standard milliliters per minute to 1500 standard milliliters per minute; the pressure of the reaction chamber is -30 Pascals; and the temperature of the reaction chamber is 980 degrees Celsius to 1100 degrees Celsius.

7. The method for forming a solar cell according to claim 1, characterized in that, The temperature of the reaction chamber during the passivation phase is equal to the temperature of the reaction chamber during the propulsion phase.

8. A solar cell, characterized in that, The solar cell is formed by the method for forming a solar cell according to any one of claims 1 to 7, the solar cell comprising: A substrate having opposing first and second surfaces; The first surface of the substrate has a boron-doped layer and a borosilicate glass layer stacked sequentially, wherein the borosilicate glass layer contains an oxygen-containing compound, which is gallium oxide or molybdenum oxide; A first passivation layer is located on the surface of the borosilicate glass layer; The first electrode penetrates the first passivation layer and the borosilicate glass layer, and is in contact with the boron-doped layer; The second surface of the substrate has a surface field layer and a second passivation layer stacked sequentially; The second electrode penetrates the second passivation layer and is in contact with the surface field layer.

9. The solar cell according to claim 8, characterized in that, The content of oxygen-containing compounds on the side of the borosilicate glass layer closer to the boron-doped layer is greater than the content of oxygen-containing compounds on the side of the borosilicate glass layer farther from the boron-doped layer.

10. The solar cell according to claim 8, characterized in that, The boron-doped layer contains interstitial oxygen atoms, and the depth of the interstitial oxygen atoms in the boron-doped layer is less than or equal to 1.2 micrometers.

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