A solar cell passivation layer structure and its preparation method and application

Abstract

The present invention provides a solar cell passivation layer structure and a preparation method and application thereof, the preparation method comprising: (1) using one or more of nitrous oxide, ammonia and hydrogen to perform dangling bond chemical activity modification treatment on the substrate surface; depositing an aluminum oxide film layer on the substrate surface, and performing plasma treatment on the aluminum oxide film layer to obtain a modified aluminum oxide film layer; (2) depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer laminated structure; (3) annealing the double-layer laminated structure under a protective atmosphere. The present invention performs plasma treatment on the aluminum oxide film layer, so that the aluminum oxide itself adsorbs more OH bonds and H bonds with stronger binding energy, and deposits an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to enhance the passivation performance of the modified aluminum oxide film layer and the light absorption function of the solar cell, thereby improving the passivation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell passivation layer structure and a preparation method and application thereof. Background Art

[0002] Improving efficiency and reducing costs is an eternal topic in the development of photovoltaics. With the development of solar cell technology, the efficiency limit of Passivated Emitter and Rear Cell (PERC) due to its structure can no longer meet the development needs of photovoltaic technology. Tunnel Oxide Passivating Contacts (TOPCon) solar cells have become a new generation of crystalline silicon solar cell structures to replace mass-produced PERC solar cells due to their excellent structure, theoretical limit efficiency of 29.2%, good production line compatibility, low production cost, high yield and production line stability. However, the serious optical and electrical losses on the back surface of the cell have become a bottleneck restricting the further improvement of cell efficiency, and the development of technology to improve the efficiency of solar cells has been ongoing.

[0003] In order to further improve the efficiency of solar cells, researchers have conducted research and development on the structure of solar cells, mainly including TOPCon solar cells with double-sided passivation tunneling structure and various forms of back contact (x Back Contact, xBC) solar cells. For example, xBC solar cells have the back contact (Back Contact, BC) structure of heterojunction solar cells (HIT) and the BC structure of TOPCon solar cells. However, the development of the above-mentioned cell structures is based on the low-level solar cell production process. The addition of more complex and additional preparation processes will lead to increasing line construction costs, increasing production complexity and control, and there is no substantial progress on the technical level. Instead, it relies on the equipment provided by suppliers to continuously add and subtract.

[0004] A Chinese patent document discloses a HEMT device with a composite passivation layer structure, and its authorization announcement number is CN216719952 U. The patent can effectively suppress the current collapse effect by providing a composite passivation layer structure composed of a first passivation layer and a second passivation layer stacked under the gate field plate. Compared with a single passivation layer of the same thickness, the composite passivation layer structure of the present application makes the parasitic capacitance of the device smaller, effectively improving the performance of the GaN-based high electron mobility transistor (HEMT) device. However, the composite passivation layer structure is not suitable for the above-mentioned general solar cell structure and cannot reduce production costs. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a solar cell passivation layer structure and a preparation method and application thereof, so as to solve the problem that the improvement of the existing solar cell structure depends on the superposition of process equipment, has no substantial technical improvement, and has high production costs.

[0006] To achieve the above-mentioned object and other related objects, the present invention provides a method for preparing a solar cell passivation layer structure, comprising the following steps:

[0007] Step (1): depositing an aluminum oxide film layer on the surface of a substrate, and performing plasma treatment on the aluminum oxide film layer to obtain a modified aluminum oxide film layer;

[0008] Step (2): depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer stacked structure;

[0009] Step (3): annealing the double-layer stacked structure under a protective atmosphere to obtain a solar cell passivation layer structure.

[0010] More preferably, the substrate is a crystalline silicon substrate.

[0011] After the aluminum oxide film layer used in the prior art is deposited on the surface of n-type single crystal silicon, the iVoc that can be achieved is less than 710mV. The present application has found that in addition to the chemical passivation of the crystalline silicon interface, the passivation of aluminum oxide on crystalline silicon mainly depends on the electric field formed by the negative fixed charge it carries to passivate the crystalline silicon surface. That is, the greater the negative fixed charge density, the stronger the field effect passivation formed. The formation of negative fixed charge is related to the OH bond and H bond in aluminum oxide. The more these two chemical bonds there are, the stronger the field effect passivation. Based on this principle, the present application combines the adsorption characteristics of the substance, as well as the ionization and electric field acceleration of the plasma, and creatively performs plasma treatment on the aluminum oxide film layer, so that the aluminum oxide itself adsorbs more OH bonds and H bonds with stronger binding energy, and the iVoc of the obtained modified aluminum oxide film layer is ≥720mV; if applied to a single crystal silicon wafer with a pn junction, its iVoc is ≥735mV, while the iVoc of the conventional aluminum oxide film layer is less than 720mV. The purpose of depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer is to enhance the passivation performance of the modified aluminum oxide film layer and the light absorption function of the solar cell; although the previous plasma treatment causes the modified aluminum oxide film layer to continuously store OH bonds and H bonds, the double-layer stacked structure formed by it and the aluminum oxynitride film layer does not have an excellent passivation effect. The present application adopts an annealing process to move the OH bonds and H bonds in the modified aluminum oxide film layer, thereby activating the fixed charges contained in the aluminum oxide, achieving the purpose of carrying a large amount of negative fixed charges on the aluminum oxide, thereby improving the passivation effect of the passivation layer structure of the solar cell.

[0012] Preferably, in step (1), the plasma treatment of the aluminum oxide film layer comprises: plasma treatment of the aluminum oxide film layer during the deposition of the aluminum oxide film layer and plasma treatment of the aluminum oxide film layer after the deposition of the aluminum oxide film layer is completed.

[0013] The present invention uses two or more alternating plasma treatments during the deposition of the aluminum oxide film layer to allow the aluminum oxide itself to adsorb more OH bonds and H bonds with stronger binding energy.

[0014] Preferably, in step (1), the plasma precursor gas used for plasma treatment is selected from one or more of nitrous oxide, ammonia and hydrogen.

[0015] Preferably, in step (3), the annealing temperature is 300-500° C., and the annealing time is 10-30 min.

[0016] Preferably, the aluminum oxide film layer is deposited by thermal atomic layer deposition.

[0017] Preferably, the aluminum oxynitride film is deposited by plasma-assisted atomic layer deposition or plasma-enhanced chemical vapor deposition. This not only allows the aluminum oxynitride film to have a low and adjustable film refractive index, which is beneficial to the subsequent light absorption of solar cells, but the H in the process is also more beneficial to the subsequent activation of the passivation effect of aluminum oxide through annealing.

[0018] Preferably, the deposition temperature of the aluminum oxide film layer and the aluminum oxynitride film layer is 120-300° C., and low-temperature deposition has low energy consumption.

[0019] Preferably, in step (1), before depositing the aluminum oxide film layer, the step further includes subjecting the substrate surface to chemically active modification of dangling bonds, wherein the substrate surface to chemically active modification of dangling bonds is treated with one or more of nitrous oxide, ammonia and hydrogen.

[0020] This application modifies the cleanliness of the surface of the crystalline silicon substrate by plasma bombardment, while making it easier for the dangling bonds of silicon atoms and dopant atoms to form chemical passivation with the oxygen element in the aluminum oxide, which is beneficial to the subsequent deposition of the aluminum oxide film layer and enhances the chemical bonding rate between the constituent elements of the aluminum oxide film layer and the crystalline silicon surface. Compared with the existing thermal ALD method of depositing aluminum oxide, this application adopts the above-mentioned technical means to improve the chemical passivation characteristics of the aluminum oxide film layer while cleaning the surface of the crystalline silicon substrate. In addition, the chemically active modification of the dangling bonds on the substrate surface also solves the problem of production cost waste caused by reduced battery efficiency or rework due to the time required between different process steps in the production line (Q-time problem).

[0021] The present invention also provides a solar cell passivation layer structure prepared by the above preparation method.

[0022] Preferably, the solar cell passivation layer structure includes a modified aluminum oxide film layer and an aluminum oxynitride film layer sequentially deposited on the surface of a substrate, wherein the modified aluminum oxide film layer is obtained by subjecting the aluminum oxide film layer to plasma treatment; the thickness of the modified aluminum oxide film layer is 8 to 15 nm, the refractive index range of the aluminum oxynitride film layer is 1.7 to 1.9, and the thickness of the aluminum oxynitride film layer is 2 to 5 nm.

[0023] The present invention also provides an application of the solar cell passivation layer structure in preparing a solar cell.

[0024] The present invention also provides a solar cell comprising the solar cell passivation layer structure.

[0025] Preferably, with the substrate as a reference, the solar cell facing the light-receiving side includes, from the inside to the outside, a first diffusion junction with a conductive polarity opposite to that of the substrate, a first local heavily doped emitter with a conductive polarity opposite to that of the substrate, the above-mentioned solar cell passivation layer structure, a first transparent conductive film layer and a first low-temperature electrode, and the first transparent conductive film layer is in contact with the first local heavily doped emitter; with the substrate as a reference, the solar cell facing the backlight side includes, from the inside to the outside, a first local heavily doped contact area with the same conductive polarity as that of the substrate, the above-mentioned solar cell passivation layer structure, a second transparent conductive film layer and a second low-temperature electrode, and the second transparent conductive film layer is in contact with the first local heavily doped contact area.

[0026] Preferably, the solar cell is a back contact solar cell.

[0027] Preferably, with the substrate as a reference, the solar cell includes the above-mentioned solar cell passivation layer structure and the anti-reflection layer insulation layer in sequence from the inside to the outside on the side facing the light-receiving surface; with the substrate as a reference, the solar cell includes a local second diffusion junction with a conductive polarity opposite to that of the substrate, a second local heavily doped emitter, a second local heavily doped contact region with the same conductive polarity as that of the substrate, the above-mentioned solar cell passivation layer structure and a third transparent conductive film layer in sequence from the inside to the outside on the side facing the backlight surface, and the third transparent conductive film layer is in contact with the second local heavily doped contact region and the second local heavily doped emitter.

[0028] In a solar cell using the solar cell passivation layer structure of the present application, the solar cell passivation layer structure and the transparent conductive film both have the characteristics of conducting, refracting, and absorbing light, and their combination can not only achieve good passivation and transmission effects, but also avoid the poor light absorption properties of the passivation tunneling layer structure represented by materials such as silicon materials. The solar cell passivation layer structure of the present application is prepared in the same equipment, which greatly reduces the basic investment cost of different production equipment and production lines, while reducing the environmental pollution caused by multiple interruptions in the preparation process of solar cells, which is of great benefit to the yield and efficiency of solar cells; the solar cell passivation layer structure of the present application is based on a combination of low-temperature preparation process, shallow junction doping, and low-temperature contact process, which reduces the cost of daily energy consumption of the equipment, and the low energy consumption further extends the service life of the equipment hardware.

[0029] As described above, the solar cell passivation layer structure and the preparation method and application thereof of the present invention have the following beneficial effects:

[0030] (1) By subjecting the aluminum oxide film to plasma treatment, the aluminum oxide itself adsorbs more OH bonds and H bonds with stronger binding energy, and the iVoc of the obtained modified aluminum oxide film is ≥720mV; an aluminum oxynitride film is deposited on the surface of the modified aluminum oxide film to enhance the passivation performance of the modified aluminum oxide film and the light absorption function of the solar cell; the annealing process can move the OH bonds and H bonds in the modified aluminum oxide film, thereby activating the fixed charges contained in the aluminum oxide, and achieving the purpose of carrying a large amount of negative fixed charges on the aluminum oxide;

[0031] (2) In a solar cell using the solar cell passivation layer structure of the present application, the solar cell passivation layer structure and the transparent conductive film both have the characteristics of conducting, refractive and absorbing light. Their combination can not only achieve good passivation and transmission effects, but also avoid the poor light absorption properties of the passivation tunneling layer structure represented by materials such as silicon. The solar cell passivation layer structure of the present application is prepared in the same equipment, and combined with the low-temperature preparation process, shallow junction doping, and low-temperature contact process, it not only reduces the production cost, the low energy consumption prolongs the service life of the equipment hardware, but also reduces the environmental pollution caused by multiple interruptions in the preparation process of the solar cell, which is of great benefit to the yield and efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a schematic diagram of the passivation layer structure of a solar cell prepared in Example 1.

[0033] Figure 2 Shown is a schematic structural diagram of the solar cell prepared in Example 1.

[0034] Figure 3Shown is a schematic structural diagram of the solar cell prepared in Example 2.

[0035] Figure 4 Shown is a schematic structural diagram of the solar cell prepared in Example 3.

[0036] Explanation of the accompanying drawings: substrate 1, modified aluminum oxide film layer 2, aluminum oxynitride film layer 3, first diffusion junction 4, first local heavily doped emitter 5, first transparent conductive film layer 6, first low-temperature electrode 7, first local heavily doped contact area 8, second transparent conductive film layer 9, second low-temperature electrode 10, anti-reflection layer insulating layer 11, second diffusion junction 12, second local heavily doped emitter 13, second local heavily doped contact area 14, third transparent conductive film layer 15. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0038] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0039] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0040] The substrate described in the following embodiments of the present application is made of crystalline silicon.

[0041] In the following embodiments of the present application, the passivation effect test of the solar cell passivation layer structure is performed using a double-sided polished and textured silicon wafer, and the test instrument is a Sintion WCT 120 minority carrier lifetime tester.

[0042] Example 1

[0043] The present application embodiment provides a method for preparing a solar cell passivation layer structure, which is prepared by using a one-plate time-type PE-ALD device, comprising the following steps:

[0044] Step (1): depositing an aluminum oxide film layer on the surface of a substrate, and subjecting the aluminum oxide film layer to plasma treatment to obtain a modified aluminum oxide film layer:

[0045] The crystalline silicon substrate was placed in a reaction furnace of a one-plate time plasma enhanced atomic layer deposition (PE-ALD) device, vacuumed, and plasma precursor gases nitrous oxide and hydrogen were introduced to perform surface dangling bond chemical activity modification on the crystalline silicon substrate, the flow rate of nitrous oxide was controlled to be 2000sccm, the flow rate of hydrogen was controlled to be 4000sccm, the reaction pressure was controlled to be 180Pa, the power supply used was 40kHz, the discharge power was 3000W, the switching ratio was 1 / 10, the process temperature was 120℃, and the processing time was 2min;

[0046] At 120°C, an aluminum oxide film was deposited by thermal atomic layer deposition. The gas sources were TMA and water, the gas flow rate was 2000 sccm, the source pressure was 50 Pa, the nitrogen purge flow rate was 5000 sccm, and the deposited film thickness was 4 nm.

[0047] After the aluminum oxide is deposited, the passivation performance of the aluminum oxide film is modified by plasma. The discharge gas is nitrous oxide and ammonia, the gas flow rates are 2000sccm and 4000sccm respectively, the reaction pressure is 180Pa, the power supply is 40kHz, the discharge power is 4000W, the on-off ratio is 1 / 20, the process temperature is 120℃, and the processing time is 2min.

[0048] Then, at 120°C, an aluminum oxide film was deposited again by thermal atomic layer deposition. The gas sources were TMA and water, the ventilation flow rate was 2000 sccm, the source pressure was 50 Pa, the nitrogen purge flow rate was 5000 sccm, and the deposited film thickness was 4 nm.

[0049] Afterwards, the passivation performance of the aluminum oxide film layer was modified again by plasma, the discharge gas was nitrous oxide and ammonia, the gas flow rates were 2000sccm and 4000sccm respectively, the reaction pressure was 180Pa, the power supply was 40kHz, the discharge power was 4000W, the switching ratio was 1 / 20, the process temperature was 120℃, and the processing time was 2min; a modified aluminum oxide film layer with a thickness of 8nm was obtained on the surface of the crystalline silicon substrate;

[0050] Step (2): Depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer stacked structure:

[0051] The aluminum oxynitride film was deposited by plasma-assisted atomic layer deposition at 120°C. The gases used were ammonia, nitrous oxide, and TMA. The deposition gas flow rates were 3000sccm, 2000sccm, and 2000sccm, respectively. The power supply used in the discharge step was 40kHz, the discharge power was 4000W, the switch ratio was 1 / 20, the pressure was 180Pa, the TMA introduction step pressure was 50Pa, and the purge nitrogen flow rate was 5000sccm. The refractive index of the aluminum oxynitride film was 1.7 and the thickness was 2nm.

[0052] Step (3): annealing the double-layer stacked structure in a nitrogen protective atmosphere at a temperature of 300° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 30 min, thereby obtaining a solar cell passivation layer structure.

[0053] like Figure 1 As shown, an embodiment of the present application also provides a solar cell passivation layer structure prepared by the above-mentioned preparation method, comprising a modified aluminum oxide film layer 2 and an aluminum oxide nitride film layer 3 sequentially deposited on the surface of a substrate 1, wherein the modified aluminum oxide film layer is obtained by subjecting the aluminum oxide film layer to plasma treatment; the thickness of the modified aluminum oxide film layer is 8 nm, the refractive index of the aluminum oxide nitride film layer is 1.7, and the thickness of the aluminum oxide nitride film layer is 2 nm.

[0054] The present application also provides a method for preparing a solar cell including the above solar cell passivation layer structure, comprising the following steps:

[0055] (1) The resistivity of 182mm*182mm is 0.5 by chemical solvent -1 Ω·cm, 10,000 pieces of p-type single crystal silicon with a thickness of 130μm were cleaned and textured;

[0056] (2) Place the textured silicon wafer into a boron diffusion furnace and deposit a boron-doped silicon oxide (BSG) film layer on its back surface. The thickness of the BSG film layer is 120 nm.

[0057] (3) The silicon wafer with BSG film deposited on the back is selectively doped with shallow junction by laser, with the highest doping concentration of 5E19 / cm 3 , doping depth is 150nm, heavy doping width is 50μm;

[0058] (4) Chain cleaning removes the BSG film layer on the front and edge, and trough cleaning removes the front expansion layer and edge expansion;

[0059] (5) Place the cleaned surface into a phosphorus diffusion furnace to deposit a phosphorus-doped silicon oxide (PSG) film layer with a thickness of 10 nm, and perform deep junction diffusion with a maximum diffusion depth of 2E20 / cm 3, the junction depth is 50nm;

[0060] (6) Then, the front side of the silicon wafer with the PSG film layer was selectively doped by laser, and the maximum phosphorus concentration in the selectively doped area was 5E20 / cm 3 , the junction depth is 50nm and the selective area width is 50μm;

[0061] (7) Use chain low-concentration HF to remove the PSG film layer on the side edge, and alkali washing to remove the phosphorus expansion on the side edge, and then use trough HF to remove the PSG film layer and BSG film layer on the front and back sides;

[0062] (8) depositing the solar cell passivation layer structure (total thickness 10 nm) on both sides, the film forming method being as described above;

[0063] (9) Double-sided selective laser opening, the position and width of the opening on the back side are the same as those of the heavily doped region described in (3), and the position and width of the opening on the front side are the same as those of the selectively doped region described in (6);

[0064] (10) Using plasma-assisted atomic layer deposition equipment to deposit an indium-doped tin oxide film with a thickness of 80 nm and a square resistance of 40 Ω / sq;

[0065] (11) Printing low-temperature slurry to prepare low-temperature electrodes, the process temperature is 180°C;

[0066] (12) Photoinjection and laser-assisted passivation contacts.

[0067] like Figure 2 As shown, an embodiment of the present application also provides a solar cell with a double-sided textured structure prepared by the above-mentioned preparation method. Taking the substrate 1 as a reference, the solar cell facing the light-receiving side includes, from the inside to the outside, a first diffusion junction 4 with a conductive polarity opposite to that of the substrate, a first local heavily doped emitter 5 with a conductive polarity opposite to that of the substrate, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3, a first transparent conductive film layer 6 and a first low-temperature electrode 7, wherein the first transparent conductive film layer is in contact with the first local heavily doped emitter; taking the substrate 1 as a reference, the solar cell facing the backlight side includes, from the inside to the outside, a first local heavily doped contact area 8 with the same conductive polarity as that of the substrate, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3, a second transparent conductive film layer 9 and a second low-temperature electrode 10, wherein the second transparent conductive film layer is in contact with the first local heavily doped contact area. Among them, the base 1 adopts a p-type crystalline silicon substrate, the first diffused junction 4 is an n-type diffused junction, the first transparent conductive film layer 6 and the second transparent conductive film layer 9 are indium-doped tin oxide film layers, the first local heavily doped emitter 5 is an n-type heavily doped emitter, and the first local heavily doped contact area 8 is a p-type heavily doped contact area.

[0068] Comparative Example 1

[0069] The aluminum oxide film layer of this comparative example is prepared by conventional thermal atomic layer deposition as follows:

[0070] First, the cleaned n-type single crystal silicon surface is pretreated with ozone to clean the residual organic matter on the silicon wafer surface and a thin layer of silicon oxide of about 1nm is deposited on the silicon surface to assist in the chemical passivation of aluminum oxide; then 10nm aluminum oxide is deposited on the silicon oxide surface using water and TMA, and the annealing temperature is 500℃ and the annealing time is more than 30min.

[0071] This comparative example prepares TOPCon solar cells according to the preparation process of mass-produced TOPCon solar cell structures, and the main steps are as follows:

[0072] (1) The resistivity of 182mm*182mm is 0.5-1Ω·cm and the thickness is 130 μ 10,000 pieces of n-type single crystal silicon were cleaned and textured;

[0073] (2) Boron diffusion: The silicon wafer after texturing is placed in a boron diffusion furnace, a BSG film layer is deposited on the back surface and a junction is pushed. The thickness of the BSG film layer is 120nm, the diffusion square resistance is 400Ω / sq, and the junction depth is 0.75 μ m;

[0074] (3) Remove the BSG film layer on the edge and back in a chain-like manner, remove the back and side wrapping in a trough-like manner, and perform alkali polishing on the back, with a reflectivity of 40%;

[0075] (4) Depositing a 1-2 nm tunnel oxide layer and a 130 nm phosphorus-doped polysilicon (poly-Si) film layer on the back of the silicon wafer by plasma enhanced chemical vapor deposition, and depositing a 30 nm PSG film layer;

[0076] (5) Anneal the silicon wafer at 920°C for 20 minutes;

[0077] (6) Chain cleaning to remove the edge and front PSG, and then use the slot method to remove the front and side phosphorus-doped poly-Si film layer by wrapping, and then use the slot HF method to remove the front BSG film layer and the back PSG film layer;

[0078] (7) Depositing a 4 nm aluminum oxide film layer on the front of the silicon wafer by thermal atomic layer deposition;

[0079] (8) Using plasma enhanced chemical vapor deposition to deposit an 80nm silicon oxynitride stacked film with a refractive index of 1.95-2.02 on the front of the silicon wafer;

[0080] (9) Using plasma enhanced chemical vapor deposition to deposit 80nm silicon nitride stacked films with a thickness of 1.98-2.05 on the back of the silicon wafer;

[0081] (10) Printing high-temperature slurry on both sides to prepare electrodes;

[0082] (11) Light injection and laser-assisted sintering.

[0083] The passivation effects of the solar cell passivation layer structures of Example 1 and Comparative Example 1 were tested, and the results are shown in Table 1:

[0084] Table 1. Passivation data of solar cell passivation layer structures prepared in Example 1 and Comparative Example 1

[0085] Grouping Number of pieces Wafer Type Passivation layer structure Average silicon wafer resistivity (ohm cm) Average silicon wafer thickness (micrometers) Average iVoc(mV) Example 1 50 n-type Double-sided modified aluminum oxide film + aluminum oxynitride film (total thickness 10nm) 1 130 723 Comparative Example 1 50 n-type Double-sided aluminum oxide film (10nm) 1 130 708

[0086] In Table 1: iVoc is the ideal open circuit voltage, which represents the passivation quality of the solar cell. The larger the value, the better the passivation.

[0087] It can be seen from Table 1 that: under the same thickness condition (10nm), the symmetrical structure film layer is deposited on both sides of the silicon wafer with the same resistivity and conductivity type. The iVoc of the conventional aluminum oxide film passivation layer structure in Comparative Example 1 can only reach 708mV, while the passivation film layer structure of the double-sided modified aluminum oxide film layer and the aluminum oxynitride film layer stacked in the present invention can achieve 723mV.

[0088] The performance of the solar cells of Example 1 and Comparative Example 1 was tested, and the results are shown in Table 2:

[0089] Table 2. Performance data of solar cells prepared in Example 1 and Comparative Example 1

[0090] Grouping Number of pieces Voc (V) Isc (A) FF (%) Eff (%) Example 1 10000 0.745 13.891 84.923 26.620 Comparative Example 1 10000 0.737 13.976 84.801 26.457

[0091] In Table 2: Voc is the open circuit voltage of the solar cell, Isc is the short circuit current of the solar cell, FF is the fill factor of the solar cell, and Eff is the photoelectric conversion efficiency of the solar cell. These four factors represent the important electrical performance parameters of the solar cell for photoelectricity generation.

[0092] Compared with the preparation process of TOPCon solar cells, the above-mentioned solar cell structure preparation process of this embodiment lacks low-pressure chemical vapor deposition (600°C process temperature) or plasma-enhanced chemical vapor deposition (450°C process temperature) used to deposit the tunneling layer and the poly-Si film layer, lacks the traditional ALD (250°C process temperature) equipment, and lacks the plasma-enhanced chemical vapor deposition (500°C process temperature) for depositing silicon nitride on the front and back sides. A total of 4 types of equipment are missing. These four types of equipment are replaced by two laser selective doping equipment (normal temperature), a laser hole opening equipment (normal temperature), a passivation film preparation equipment (which can be coated on both the front and back sides) (up to 400°C), and a plasma-assisted atomic layer deposition equipment (100°C). In terms of the types of equipment, there is a large increase, and the problem of improper dust treatment in the preparation of poly-Si film layers by plasma-enhanced chemical vapor deposition that affects the environment is eliminated.

[0093] It can be seen from Table 2 that the solar cell prepared using the solar cell passivation layer structure of the present application has a high open circuit voltage and a high fill factor, which reflects that the passivation properties of the solar cell passivation layer structure selected in the present invention are not weaker than the passivation effect of the passivation tunneling layer structure in the TOPCon solar cell. The main reason for the low short-circuit current is related to the low utilization rate of the back side reflected light of the back side velvet structure of the present structure.

[0094] Example 2

[0095] The present application embodiment provides a method for preparing a solar cell passivation layer structure, which is prepared by using a one-plate time-type PE-ALD device, comprising the following steps:

[0096] Step (1): depositing an aluminum oxide film layer on the surface of a substrate, and subjecting the aluminum oxide film layer to plasma treatment to obtain a modified aluminum oxide film layer:

[0097] The crystalline silicon substrate is placed in a reaction furnace of a plate-type time-type PE-ALD device, evacuated, and plasma precursor gases nitrous oxide and ammonia are introduced to perform surface dangling bond chemical activity modification treatment on the crystalline silicon substrate, the flow rate of nitrous oxide is controlled to be 2000sccm, the flow rate of ammonia is controlled to be 3000sccm, the reaction pressure is controlled to be 180Pa, the power supply used is 40kHz, the discharge power is 3000W, the switching ratio is 1 / 15, the process temperature is controlled to be 210°C, and the treatment time is controlled to be 2min;

[0098] After the plasma treatment, an aluminum oxide film was deposited by thermal atomic layer deposition at 210°C. The gas sources were TMA and water, the gas flow rate was 2000 sccm, the source pressure was 50 Pa, the nitrogen purge flow rate was 5000 sccm, and the deposited film thickness was 11.5 nm.

[0099] After the aluminum oxide is deposited, the passivation performance of the aluminum oxide film layer is modified by plasma, the discharge gas is nitrous oxide and hydrogen, the gas flow rates are 2000sccm and 4000sccm respectively, the reaction pressure is 180pa, the power supply is 40kHz, the discharge power is 4000W, the switching ratio is 1 / 10, the process temperature is 210℃, and the processing time is 3min; a modified aluminum oxide film layer is obtained;

[0100] Step (2): Depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer stacked structure:

[0101] Aluminum nitride film was deposited by plasma-assisted atomic layer deposition at 210°C, with a refractive index of 1.8 and a thickness of 3.5 nm. The gases used were ammonia, hydrogen, and TMA, with deposition gas flow rates of 3000 sccm, 4000 sccm, and 2000 sccm, respectively. The power supply used in the discharge step was 40 kHz, the discharge power was 4000 W, the switch ratio was 1 / 15, the pressure was 180 Pa, the TMA introduction step pressure was 50 Pa, and the purge nitrogen flow rate was 5000 sccm.

[0102] Step (3): annealing the laminated film deposited with the modified aluminum oxide film layer and the aluminum oxynitride film layer in a nitrogen atmosphere at an annealing temperature of 400° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 20 min, thereby obtaining a solar cell passivation layer structure.

[0103] An embodiment of the present application also provides a solar cell passivation layer structure prepared by the above-mentioned preparation method, comprising a modified aluminum oxide film layer and an aluminum oxynitride film layer sequentially deposited on the surface of a substrate, wherein the modified aluminum oxide film layer is obtained by subjecting the aluminum oxide film layer to plasma treatment; the thickness of the modified aluminum oxide film layer is 11.5 nm, the refractive index of the aluminum oxynitride film layer is 1.8, and the thickness of the aluminum oxynitride film layer is 3.5 nm.

[0104] The present application also provides a method for preparing a solar cell including the above solar cell passivation layer structure, comprising the following steps:

[0105] (1) The resistivity of 182mm*182mm is 0.5 by chemical solvent -1 Ω·cm, 10,000 pieces of n-type single crystal silicon with a thickness of 130μm were cleaned and textured;

[0106] (2) Place the silicon wafer after texturing into a boron diffusion furnace, deposit a BSG film layer on its front surface, and push the junction. The thickness of the BSG film layer is 120nm, the junction depth is 100nm, and the square resistance is 500Ω / sq;

[0107] (3) The silicon wafer with BSG film deposited on the front side is selectively doped with shallow junction by laser, with the highest doping concentration of 5E19 / cm 3 , doping depth is 150nm, heavy doping width is 50μm;

[0108] (4) Chain cleaning removes the BSG film layer on the back and edge, and trough cleaning removes the back expansion layer and edge expansion, and the back is alkaline polished, with a reflectivity of 40%;

[0109] (5) Place the silicon wafer into a phosphorus diffusion furnace to deposit a PSG film on the alkaline polished surface. The thickness of the PSG film is 10 nm.

[0110] (6) The back of the silicon wafer with PSG deposited on it was then selectively doped with a laser. The maximum phosphorus concentration in the selectively doped area was 5E20 / cm 3 , the junction depth is 50nm and the selective area width is 50μm;

[0111] (7) Use chain low-concentration HF to remove the PSG film layer on the side edge, and alkali washing to remove the phosphorus expansion on the side edge, and then use trough HF to remove the PSG film layer and BSG film layer on the front and back sides;

[0112] (8) depositing the above solar cell passivation layer structure (total thickness 15 nm) on both sides, the film forming method thereof being as described above;

[0113] (9) Double-sided selective laser opening, the position and width of the opening on the back side are the same as those of the heavily doped region described in (3), and the position and width of the opening on the front side are the same as those of the selectively doped region described in (6);

[0114] (10) Using plasma-assisted atomic layer deposition equipment to deposit an indium-doped tin oxide film with a thickness of 80 nm and a square resistance of 45 Ω / sq;

[0115] (11) Printing low-temperature slurry to prepare low-temperature electrodes, the process temperature is 180°C;

[0116] (12) Light injection and laser-assisted passivation contacts.

[0117] like Figure 3As shown, the embodiment of the present application also provides a solar cell made by the above-mentioned preparation method, with a front emitter and a back polished structure. Taking the substrate 1 as a reference, the solar cell facing the light-receiving side includes, from the inside to the outside, a first diffusion junction 4 with a conductive polarity opposite to that of the substrate, a first local heavily doped emitter 5 with a conductive polarity opposite to that of the substrate, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3, a first transparent conductive film layer 6 and a first low-temperature electrode 7, wherein the first transparent conductive film layer is in contact with the first local heavily doped emitter; taking the substrate 1 as a reference, the solar cell facing the backlight side includes, from the inside to the outside, a first local heavily doped contact area 8 with the same conductive polarity as that of the substrate, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3, a second transparent conductive film layer 9 and a second low-temperature electrode 10, wherein the second transparent conductive film layer is in contact with the first local heavily doped contact area. Among them, the substrate 1 adopts an n-type crystalline silicon substrate, the first diffused junction 4 is a p-type diffused junction, the first transparent conductive film layer 6 and the second transparent conductive film layer 9 are indium-doped tin oxide film layers, the first local heavily doped emitter 5 is a p-type heavily doped emitter, and the first local heavily doped contact area 8 is an n-type heavily doped contact area.

[0118] Comparative Example 2

[0119] The aluminum oxide film layer of this comparative example is prepared by conventional thermal atomic layer deposition as follows:

[0120] First, the cleaned p-type single crystal silicon surface is pretreated with ozone to clean the residual organic matter on the silicon wafer surface and a thin layer of silicon oxide of about 1nm is deposited on the silicon surface to assist in the chemical passivation of aluminum oxide; then 15nm aluminum oxide is deposited on the silicon oxide surface using water and TMA, and the annealing temperature is 500℃ and the annealing time is more than 30min.

[0121] This comparative example prepares TOPCon solar cells according to the preparation process of mass-produced TOPCon solar cell structure, and the main steps are as follows:

[0122] (1) The resistivity of 182mm*182mm is 0.5 by chemical solvent -1 Ω·cm, 10,000 pieces of n-type single crystal silicon with a thickness of 130μm were cleaned and textured;

[0123] (2) Boron diffusion: The silicon wafer after texturing is placed in a boron diffusion furnace, a BSG film layer is deposited on the back surface and a junction is pushed. The thickness of the BSG film layer is 120nm, the diffusion square resistance is 400Ω / sq, and the junction depth is 0.75μm;

[0124] (3) Chain removal of the BSG film layer on the edge and back, groove removal of the back and side expansion, and alkaline polishing of the back, with a reflectivity of 40%

[0125] (4) Depositing a 1-2 nm tunneling oxide layer and a 130 nm phosphorus-doped poly-Si film layer on the back of the silicon wafer by plasma enhanced chemical vapor deposition, and depositing a 30 nm thick PSG film layer;

[0126] (5) Anneal the silicon wafer at 920°C for 20 minutes;

[0127] (6) Chain cleaning to remove the edge and front PSG film layer, and then use the slot method to remove the front and side phosphorus-doped poly-Si film layer by wrapping, and then use the slot HF method to remove the front BSG film layer and the back PSG film layer;

[0128] (7) Depositing a 4 nm aluminum oxide film layer on the front of the silicon wafer by thermal atomic layer deposition;

[0129] (8) Using plasma enhanced chemical vapor deposition to deposit an 80nm silicon oxynitride stacked film with a refractive index of 1.95-2.02 on the front of the silicon wafer;

[0130] (9) Using plasma enhanced chemical vapor deposition to deposit 80nm silicon nitride stacked films with a thickness of 1.98-2.05 on the back of the silicon wafer;

[0131] (10) Printing high-temperature slurry on both sides to prepare electrodes;

[0132] (11) Light injection and laser-assisted sintering.

[0133] The passivation effects of the solar cell passivation layer structures of Example 2 and Comparative Example 2 were tested, and the results are shown in Table 3:

[0134] Table 3. Passivation data of solar cell passivation layer structures prepared in Example 2 and Comparative Example 2

[0135] Grouping Number of pieces Wafer Type Passivation layer structure Average silicon wafer resistivity (ohm cm) Average silicon wafer thickness (micrometers) Average iVoc(mV) Example 2 50 p-type Double-sided modified aluminum oxide film + aluminum oxynitride film (total thickness 15nm) 0.5 145 720 Comparative Example 2 50 p-type Double-sided aluminum oxide film (15nm) 0.5 145 704

[0136] In Table 3: iVoc is the ideal open circuit voltage, which represents the passivation quality of the solar cell. The larger the value, the better the passivation.

[0137] It can be seen from Table 3 that: under the same thickness condition (15nm), the symmetrical structure film layer is deposited on both sides of the silicon wafer with the same resistivity and conductivity type. The iVoc of the aluminum oxide film passivation layer structure of Comparative Example 2 can only reach 704mV, while the passivation film layer structure of the double-sided modified aluminum oxide film layer and the aluminum oxynitride film layer stacked in the present invention can achieve 720mV.

[0138] The performance of the solar cells of Example 2 and Comparative Example 2 was tested, and the results are shown in Table 4:

[0139] Table 4. Performance data of solar cells prepared in Example 2 and Comparative Example 2

[0140] Grouping Number of pieces Voc (V) Isc (A) FF (%) Eff (%) Example 2 10000 0.748 14.011 85.053 26.993 Comparative Example 2 10000 0.737 13.976 84.801 26.457

[0141] In Table 4: Voc is the open circuit voltage of the solar cell, Isc is the short circuit current of the solar cell, FF is the fill factor of the solar cell, and Eff is the photoelectric conversion efficiency of the solar cell. These four factors represent the important electrical performance parameters of the solar cell for photoelectricity generation.

[0142] Comparison of the solar cell structures of Example 2 and Comparative Example 2:

[0143] Comparison at the process level: Compared with the preparation process of TOPCon solar cells, the above-described solar cell structure preparation process lacks low-pressure chemical vapor deposition (600°C process temperature) or plasma-enhanced chemical vapor deposition (450°C process temperature) used to deposit tunneling layers and poly-Si film layers, lacks traditional ALD (250°C process temperature) equipment, and lacks plasma-enhanced chemical vapor deposition (500°C process temperature) for depositing silicon nitride on the front and back sides. A total of 4 types of equipment are missing. These four types of equipment are replaced by two laser selective doping equipment (room temperature), a laser hole opening equipment (room temperature), a passivation film preparation equipment (which can coat the front and back sides at the same time) (maximum 400°C), and a plasma-assisted atomic layer deposition equipment (100°C). In terms of the types of equipment, the number of increases is relatively large, but as can be seen from the process temperature, the energy consumption of the equipment is greatly reduced, and the environmental problem of improper dust treatment in the preparation of poly-Si film layers by plasma-enhanced chemical vapor deposition is reduced.

[0144] Comparison of electrical performance parameters: It can be seen from Table 4 that the battery prepared by the battery structure given in this embodiment has a high open circuit voltage, short circuit current, and a high fill factor, which reflects that the passivation properties of the passivation film layer selected in the present invention are not weaker than the passivation effect of the passivation tunneling layer structure in TOPCon.

[0145] Example 3

[0146] The present application embodiment provides a method for preparing a solar cell passivation layer structure, which is prepared by using a one-plate time-type PE-ALD device, comprising the following steps:

[0147] Step (1): depositing an aluminum oxide film layer on the surface of a substrate, and subjecting the aluminum oxide film layer to plasma treatment to obtain a modified aluminum oxide film layer:

[0148] The crystalline silicon substrate was placed in a reaction furnace of a plate-type time-type PE-ALD equipment, vacuumed, and plasma precursor gases hydrogen and ammonia were introduced to perform surface dangling bond chemical activity modification treatment on the crystalline silicon substrate, the flow rate of hydrogen was controlled to be 2000sccm, the flow rate of ammonia was controlled to be 4000sccm, the reaction pressure was controlled to be 220pa, the power supply used was 40kHz, the discharge power was 6000W, the switching ratio was 1 / 15, the process temperature was 300℃, and the treatment time was 2min;

[0149] After the plasma treatment, an aluminum oxide film was deposited by thermal atomic layer deposition at 300°C. The gas sources were TMA and water, the gas flow rate was 2000 sccm, the source pressure was 50 Pa, the nitrogen purge flow rate was 5000 sccm, and the deposited film thickness was 15 nm.

[0150] The passivation performance of the aluminum oxide film layer was modified by plasma. The discharge gas was ammonia and hydrogen, the gas flow rates were 2000sccm and 4000sccm respectively, the reaction pressure was 220pa, the power supply was 40kHz, the discharge power was 4000W, the switch ratio was 1 / 10, the process temperature was 300℃, and the processing time was 3min, thus obtaining a modified aluminum oxide film layer.

[0151] Step (2): Depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer stacked structure:

[0152] A silicon oxynitride film layer was deposited by plasma enhanced chemical vapor deposition at 300°C, with a refractive index of 1.9 and a thickness of 5nm. The gases used were nitrous oxide, silane, and ammonia, with deposition gas flow rates of 3000sccm, 900sccm, and 3000sccm, respectively. The power supply used in the discharge step was 40kHz, the discharge power was 4000W, the switch ratio was 1 / 15, and the pressure was 180Pa.

[0153] Step (3): annealing the laminated film deposited with the modified aluminum oxide film layer and the aluminum oxynitride film layer in a nitrogen atmosphere at an annealing temperature of 500° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 10 min, thereby obtaining a solar cell passivation layer structure.

[0154] An embodiment of the present application also provides a solar cell passivation layer structure prepared by the above-mentioned preparation method, comprising a modified aluminum oxide film layer and an aluminum oxynitride film layer sequentially deposited on the surface of a substrate, wherein the modified aluminum oxide film layer is obtained by subjecting the aluminum oxide film layer to plasma treatment; the thickness of the modified aluminum oxide film layer is 15 nm, the refractive index of the aluminum oxynitride film layer is 1.9, and the thickness of the aluminum oxynitride film layer is 5 nm.

[0155] The present application also provides a method for preparing a solar cell including the above solar cell passivation layer structure, comprising the following steps:

[0156] (1) The resistivity of 182mm*182mm is 1.5 by chemical solvent -2 Ω·cm, 10,000 pieces of n-type single crystal silicon with a thickness of 150 μm were surface polished;

[0157] (2) The polished silicon wafer is placed in a boron diffusion furnace, and a BSG film is deposited on both sides of the wafer. The junction depth is 200nm and the maximum surface doping concentration is 5E18 / cm 3 , BSG thickness is 120nm;

[0158] (3) The back side of the silicon wafer with BSG film layer is selectively doped with shallow junction by laser, and the maximum doping concentration is 5E19 / cm 3 , doping depth is 200nm, heavy doping width is 50μm;

[0159] (4) The BSG film layer in the shallowly doped area on the back side is selectively removed by laser etching, and the laser etching width is 40 μm;

[0160] (5) Trench cleaning to remove the boron-doped layer in the BSG film area by laser selective etching on the back side;

[0161] (6) Place the silicon wafer in a phosphorus diffusion furnace to deposit a PSG film on the back side. The thickness of the PSG film is 25 nm. After the treatment in step 5), only the n-type silicon in the BSG film area is exposed, while the other areas have a 120 nm BSG film as a mask. Therefore, for crystalline silicon, effective PSG deposition and junction pushing are only performed on the exposed areas. The doping concentration here is 5E20 / cm 3 , the junction depth is 50nm;

[0162] (7) The p-type region and the n-type region on the back are laser-segmented at their junctions, with a laser line width of 35 μm.

[0163] (8) After using chain cleaning to remove the boron-phosphorus co-doped silicon oxide layer on the side edges and the front, the B diffusion layer on the front and side edges and the B-doped silicon in the separation area between the p-region and the n-region on the back are removed by trench cleaning, and after texturing, the PSG film layer and the BSG film layer on the back are removed by trench HF;

[0164] (9) depositing the above solar cell passivation layer structure (total thickness 20 nm) on both sides, the film forming method thereof being as described above;

[0165] (10) Selective laser opening of the back side, the position and width of the opening on the back side being the same as the laser processing pattern and position described in (3) and (4);

[0166] (11) Using plasma-assisted atomic layer deposition equipment, an indium-doped tin oxide film is deposited on the back side, with a film thickness of 80 nm and a square resistance of 45 Ω / sq;

[0167] (12) Using laser to perform laser segmentation on the transparent conductive film layer at the junction of the p-type region and the n-type region;

[0168] (13) Using plasma enhanced chemical vapor deposition equipment, a silicon oxide anti-reflection film layer is deposited on the front surface, with a film thickness of 70 nm and a refractive index of 1.72;

[0169] (14) Print low-temperature slurry on the back to prepare low-temperature electrodes at a process temperature of 180°C;

[0170] (15) Photoinjection and laser-assisted passivation contacts.

[0171] like Figure 4 As shown, the embodiment of the present application also provides a back-contact solar cell prepared by the above-mentioned preparation method, taking the substrate 1 as a reference, the solar cell facing the light-receiving side includes, from the inside to the outside, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3 and an anti-reflection layer insulating layer 11; taking the substrate 1 as a reference, the solar cell facing the backlight side includes, from the inside to the outside, a local second diffusion junction 12 with a conductive polarity opposite to that of the substrate, a second local heavily doped emitter 13, a second local heavily doped contact area 14 with the same conductive polarity as the substrate, a modified aluminum oxide film layer 2, an aluminum oxynitride film layer 3 and a third transparent conductive film layer 15, and the third transparent conductive film layer is in contact with the second local heavily doped contact area and the second local heavily doped emitter. Among them, the substrate 1 is an n-type crystalline silicon substrate, the second diffused junction 12 is a p-type diffused junction, the second local heavily doped emitter 13 is a p-type boron-doped heavily doped emitter, the second local heavily doped contact area 14 is an n-type phosphorus-doped heavily doped contact area, the third transparent conductive film layer 15 is an indium-doped tin oxide film layer, and the anti-reflection layer insulating layer 11 is a silicon oxide layer.

[0172] Comparative Example 3

[0173] The aluminum oxide film layer of this comparative example is prepared by conventional thermal atomic layer deposition as follows:

[0174] First, the cleaned n-type single crystal silicon surface is pretreated with ozone to clean the residual organic matter on the silicon wafer surface and a thin layer of silicon oxide of about 1nm is deposited on the silicon surface to assist in the chemical passivation of aluminum oxide; then 20nm aluminum oxide is deposited on the silicon oxide surface using water and TMA, and the annealing temperature is 500℃ and the annealing time is more than 30min.

[0175] This comparative example prepares TBC solar cells according to the preparation process of TOPCon back contact structure (TBC) solar cells currently in mass production, and the main steps are as follows:

[0176] (1) The resistivity of 182mm*182mm is 1.5 by chemical solvent -2 Ω·cm, 10,000 pieces of n-type single crystal silicon with a thickness of 150 μm were surface polished;

[0177] (2) The polished silicon wafer is placed in a boron diffusion furnace, and a BSG film is deposited on both sides of the wafer. The junction depth is 200nm and the maximum surface doping concentration is 5E18 / cm 3 , BSG thickness is 120nm;

[0178] (3) Selectively etch and remove part of the BSG film layer on the back side by laser equipment, with a laser etching width of 500 μm;

[0179] (4) Trench cleaning to remove the boron-doped layer in the BSG film area by laser selective etching on the back side;

[0180] (5) Place the silicon wafer in a plasma enhanced chemical vapor deposition device to prepare a 1-2 nm tunneling oxide layer and a 150 nm phosphorus-doped polysilicon film layer, and then deposit a 30 nm silicon oxide film layer (PSG) on its surface;

[0181] (6) Place the silicon wafer into an annealing furnace to activate and crystallize the deposited phosphorus-doped polysilicon at an annealing temperature of 920°C for 20 minutes;

[0182] (7) The PSG on the surface of the back boron diffusion area is etched by laser, and then the junction area of ​​the p-type area and the n-type area on the back is laser segmented to remove the phosphorus-doped poly-Si film layer and the tunneling layer. The laser scribing width is 35 μm;

[0183] (8) After using chain cleaning to remove the PSG on the side edges and the front side, the poly-Si film layer on the front side, side edges, and the back side boron diffusion area is removed by tank cleaning, and the B-doped silicon layer in the separation area between the p-region and the n-region on the back side is further removed. Then, the BSG film layer on the front side is removed by chain cleaning, and the B diffusion layer on the front side is removed by tank alkaline cleaning, and the front side is textured, and then the PSG film layer and BSG film layer on the back side are removed by tank HF;

[0184] (9) Depositing a 10 nm aluminum oxide film layer on the front and back of the silicon wafer using a thermal atomic layer deposition device;

[0185] (10) Depositing an 80 nm silicon nitride film layer with a refractive index of 2.0-2.05 on the back of the cell using a plasma enhanced chemical vapor deposition device;

[0186] (11) Then, an 80 nm silicon oxynitride layer with a refractive index of 1.95-2.02 is deposited on the front of the cell by plasma enhanced chemical vapor deposition;

[0187] (12) Printing high temperature slurry on the back to prepare electrodes;

[0188] (13) Light injection and laser-assisted sintering.

[0189] The passivation effects of the solar cell passivation layer structures of Example 3 and Comparative Example 3 were tested, and the results are shown in Table 5:

[0190] Table 5. Passivation data of solar cell passivation layer structures prepared in Example 3 and Comparative Example 3

[0191] Grouping Number of pieces Wafer Type Passivation layer structure Average silicon wafer resistivity (ohm cm) Average silicon wafer thickness (micrometers) Average iVoc(mV) Example 3 50 n-type Double-sided modified aluminum oxide film + aluminum nitride film (total thickness 20nm) 2 150 730 Comparative Example 3 50 n-type Double-sided aluminum oxide film (20nm) 2 150 710

[0192] In Table 5: iVoc is the ideal open circuit voltage, which represents the passivation quality of the solar cell. The larger the value, the better the passivation.

[0193] It can be seen from Table 5 that: under the same thickness condition (20nm), the symmetrical structure film layer is deposited on both sides of the silicon wafer with the same resistivity and conductivity type. The iVoc of the aluminum oxide film passivation layer structure of Comparative Example 3 can only reach 710mV, while the passivation film layer structure of the double-sided modified aluminum oxide film layer and the aluminum oxynitride film layer stacked in the present invention can achieve 730mV.

[0194] The performance of the solar cells of Example 3 and Comparative Example 3 was tested, and the results are shown in Table 6:

[0195] Table 6. Performance data of solar cells prepared in Example 3 and Comparative Example 3

[0196] Grouping Number of pieces Voc (V) Isc (A) FF (%) Eff (%) Example 3 5000 0.749 14.547 83.302 27.492 Comparative Example 3 5000 0.742 14.479 83.247 27.089

[0197] In Table 6: Voc is the open circuit voltage of the solar cell, Isc is the short circuit current of the solar cell, FF is the fill factor of the solar cell, and Eff is the photoelectric conversion efficiency of the solar cell. These four factors represent the important electrical performance parameters of the solar cell for photoelectricity generation.

[0198] Comparison of the solar cell structures of Example 3 and Comparative Example 3:

[0199] Comparison at the process level: Compared with the preparation process of TBC solar cells, the above-described solar cell structure preparation process lacks plasma enhanced chemical vapor deposition (450°C process temperature) for depositing tunneling layers and poly-Si film layers, lacks traditional atomic layer deposition (ALD) (200°C process temperature) equipment, lacks plasma enhanced chemical vapor deposition (500°C process temperature) for depositing silicon nitride on the back, and lacks some wet process machines, a total of 4 types of equipment are missing, and these four types of equipment are replaced by: a passivation film preparation equipment (which can be coated on both the front and back) (up to 400°C), a plasma assisted atomic layer deposition equipment (100°C). First, the wet process is reduced, which can not only save machine investment costs and chemical and power consumption, but also improve the yield rate of solar cells; secondly, the improper dust treatment of plasma enhanced chemical vapor deposition to prepare poly-Si film layers affects the environment.

[0200] Comparison of electrical performance parameters: It can be seen from Table 6 that the battery prepared by the battery structure given in this embodiment has a high open circuit voltage, short circuit current, and a high fill factor, which reflects that the passivation properties of the passivation film layer selected in the present invention are not weaker than the passivation effect of the passivation tunneling layer structure in the TOPCon solar cell.

[0201] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a solar cell passivation layer structure, characterized in that: The following steps are involved: Step (1): using one or more of nitrous oxide, ammonia and hydrogen to modify the substrate surface to chemically activate dangling bonds; An aluminum oxide film layer is deposited on the surface of the substrate after the dangling bond chemical activity modification treatment, and the aluminum oxide film layer is subjected to plasma treatment to obtain a modified aluminum oxide film layer; the plasma treatment of the aluminum oxide film layer is to perform plasma treatment on the aluminum oxide film layer during the process of depositing the aluminum oxide film layer; and the plasma precursor gas used in the plasma treatment is selected from one or more of laughing gas, ammonia and hydrogen; Step (2): depositing an aluminum oxynitride film layer on the surface of the modified aluminum oxide film layer to form a double-layer stacked structure; the refractive index of the aluminum oxynitride film layer is in the range of 1.7 to 1.9; Step (3): annealing the double-layer stacked structure under a protective atmosphere to obtain a solar cell passivation layer structure.

2. The preparation method according to claim 1, characterized in that: In step (3), the annealing temperature is 300-500°C and the annealing time is 10-30 min.

3. The preparation method according to claim 1, characterized in that: The aluminum oxide film layer is deposited by thermal atomic layer deposition; the aluminum oxynitride film layer is deposited by plasma assisted atomic layer deposition or plasma enhanced chemical vapor deposition; the deposition temperature of the aluminum oxide film layer and the aluminum oxynitride film layer is 120-300°C.

4. A solar cell passivation layer structure prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The invention comprises a modified aluminum oxide film layer (2) and an aluminum oxynitride film layer (3) which are sequentially deposited on the surface of a substrate (1), wherein the modified aluminum oxide film layer is obtained by subjecting the aluminum oxide film layer to plasma treatment; the thickness of the modified aluminum oxide film layer is 8 to 15 nm, the refractive index range of the aluminum oxynitride film layer is 1.7 to 1.9, and the thickness of the aluminum oxynitride film layer is 2 to 5 nm.

5. Use of the solar cell passivation layer structure according to claim 4 in preparing a solar cell.

6. A solar cell comprising the solar cell passivation layer structure according to claim 4.

7. The solar cell according to claim 6, characterized in that: Taking the substrate (1) as a reference, the solar cell comprises, from the inside to the outside, a first diffusion junction (4) having a conductive polarity opposite to that of the substrate, a first local heavily doped emitter (5) having a conductive polarity opposite to that of the substrate, the solar cell passivation layer structure, a first transparent conductive film layer (6) and a first low-temperature electrode (7), the first transparent conductive film layer (6) being in contact with the first local heavily doped emitter (5); Taking the substrate (1) as a reference, the solar cell comprises, from the inside to the outside, a first local heavily doped contact region (8) having the same conductive polarity as the substrate, the solar cell passivation layer structure, a second transparent conductive film layer (9) and a second low-temperature electrode (10), the second transparent conductive film layer (9) being in contact with the first local heavily doped contact region (8).

8. The solar cell according to claim 6, characterized in that: the solar cell is a back contact solar cell; with the substrate (1) as a reference, the solar cell comprises, from the inside to the outside, the solar cell passivation layer structure and the anti-reflection layer insulation layer (11) on the side facing the light receiving surface; Taking the substrate (1) as a reference, the solar cell comprises, from the inside to the outside, a local second diffusion junction (12) having a conductive polarity opposite to that of the substrate, a second local heavily doped emitter (13), a second local heavily doped contact region (14) having the same conductive polarity as that of the substrate, the solar cell passivation layer structure, and a third transparent conductive film layer (15), wherein the third transparent conductive film layer (15) comprises two mutually separated parts, one of which is in contact with the second local heavily doped contact region (14), and the other is in contact with the second local heavily doped emitter (13).

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