Passivation method of half-piece solar cell

Abstract

The invention discloses a half-piece solar cell passivation method, which comprises the following steps that a plurality of half-piece solar cells are placed in a cavity of atomic layer deposition equipment, cutting surfaces of the plurality of half-piece solar cells are exposed, other surfaces are not exposed, and the cutting surfaces of the half-piece solar cells are parallel or in the same plane; the cutting surface is parallel to the direction of airflow arranged in the cavity; the cavity is heated to a preset reaction temperature, an aluminum source and an oxygen source are alternately introduced into the cavity in a pulse mode, an aluminum oxide film is deposited on the cutting faces of the multiple half solar cells so as to achieve passivation, the aluminum source comprises trimethyl aluminum steam, the oxygen source comprises ozone or water vapor, and the airflow inflow direction of the aluminum source and the oxygen source is parallel to the cutting faces; and annealing and cooling the plurality of half-piece solar cells to obtain the passivated half-piece solar cells. According to the method, the passivation uniformity can be improved, the passivation rate is increased, and the passivation duration, raw material consumption and cost are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a passivation method for a half-cell solar cell. Background Art

[0002] The solar cell industry is developing rapidly, and the half-cell technology of photovoltaic modules is becoming increasingly mature. After the whole solar cell is cut in half, on the one hand, the half-cell solar cell reduces the current density and resistance loss, thereby improving the power generation efficiency and reliability of the photovoltaic module; on the other hand, the half-cell solar cell helps to reduce the difficulty of welding and improve production efficiency in the process. However, since the cutting process will cause damage to the cutting edge of the cell, the edge recombination will increase, which will in turn affect the fill factor, opening voltage and efficiency of the cell. Usually, a layer of aluminum oxide film needs to be deposited on the cut surface of the half-cell solar cell as a passivation layer. The aluminum oxide film has good field passivation and chemical passivation properties, which can effectively prevent charge recombination. Such as Figure 1 As shown, a whole solar cell 100 is cut into two half solar cells 101 and a corresponding cut surface a is formed. The cut surface a needs to be passivated.

[0003] Currently, the passivation can be achieved by depositing aluminum oxide thin films using atomic layer deposition (ALD). ALD is a method that deposits materials layer by layer on the substrate surface in the form of alternating pulses of single atomic films. During the atomic layer deposition process, the chemical reaction of the new atomic film is directly related to the previous layer, so that only one layer of atoms is deposited per reaction.

[0004] In the existing half-cell solar cell passivation technology, the air intake method is to intake air perpendicular to the cut surface of the half-cell solar cell. This air intake method will lead to problems such as a large coating area of ​​the aluminum oxide film on the surface of the half-cell solar cell, low gas utilization rate, and uneven coating. Summary of the invention

[0005] In view of this, the present application proposes a passivation method for a half-cell solar cell, which can solve the above existing technical problems. The present application provides the following technical solutions:

[0006] A passivation method for a half-cell solar cell A passivation method for a half-cell solar cell, comprising the following steps: S1: placing a plurality of half-cell solar cells in a cavity of an atomic layer deposition device, wherein the cut surfaces of the plurality of half-cell solar cells are exposed and the other surfaces are not exposed, the cut surfaces of each of the half-cell solar cells are parallel or in the same plane, and the cut surfaces are parallel to the direction of the airflow set in the cavity; S2: heating the cavity to a preset reaction temperature, and alternately introducing an aluminum source and an oxygen source into the cavity in pulses, depositing aluminum oxide films on the cut surfaces of the plurality of half-cell solar cells to achieve passivation, wherein the aluminum source comprises trimethylaluminum vapor, the oxygen source comprises ozone or water vapor, and the airflow inflow directions of the aluminum source and the oxygen source are parallel to the cut surfaces; S3: performing annealing and cooling treatments on the plurality of half-cell solar cells to obtain passivated half-cell solar cells.

[0007] Optionally, the step S1 includes: stacking multiple half-cell solar cells into a group, with the cut surfaces of each group of half-cell solar cells facing the same or opposite directions, and vertically stacking and / or placing multiple groups of half-cell solar cells in parallel in the cavity of the atomic layer deposition equipment, so that the cut surfaces of each half-cell solar cell are parallel or in the same plane; the step S1 also includes: placing a flow uniformity component near the air inlet, wherein the flow uniformity component has multiple mutually parallel airflow channels inside, and the axes of the airflow channels are parallel to the cut surfaces of the multiple half-cell solar cells.

[0008] Optionally, in step S2, the volume flow rate of trimethylaluminum vapor is 24 sccm to 30 sccm; and / or, the pressure of delivering the trimethylaluminum vapor is 20 Torr to 70 Torr, and the duration of a single pulse is 7s to 11s; and / or, the pressure of delivering the ozone or water vapor is 20 Torr to 70 Torr, and the duration of a single pulse is 7s to 11s.

[0009] Optionally, the step S1 includes: placing each group of stacked half-cell solar cells in a wafer carrier boat, and placing multiple wafer carrier boats in the cavity of the atomic layer deposition equipment; and / or, in the step S2, the preset reaction temperature is 150°C to 305°C.

[0010] Optionally, the atomic layer deposition equipment includes an annealing module, the wafer carrier boat includes a quartz boat, and the preset reaction temperature is 275°C to 305°C.

[0011] Optionally, the atomic layer deposition equipment is not provided with an annealing module, the wafer carrier boat comprises an aluminum boat, and the preset reaction temperature is 150°C to 180°C.

[0012] Optionally, the cavity includes a cavity front area, a cavity rear area, and a cavity middle area located between the cavity front area and the cavity rear area, wherein the local reaction temperatures of the cavity front area, the cavity middle area and the cavity rear area are the same, or the local reaction temperatures are different.

[0013] Optionally, when the local reaction temperatures of the front area, the middle area and the rear area of ​​the cavity are different, the temperature difference between the different areas is less than or equal to 20°C.

[0014] Optionally, the wafer boat is a quartz boat, the temperature of the front zone of the cavity is 290°C to 300°C, the temperature of the middle zone of the cavity is 290°C to 300°C, and the temperature of the rear zone of the cavity is 280°C to 290°C.

[0015] Optionally, between step S1 and step S2, it also includes: performing ozone pretreatment or water pretreatment on the multiple half-cell solar cells in the cavity; and / or the thickness of the aluminum oxide film is 30nm to 40nm; and / or the wafer boat is vertically stacked in the cavity, and the number of stacked layers is 2 to 5.

[0016] According to the passivation method of the half-cell solar cell of the embodiment of the present application, only the cut surface is exposed during the deposition process and the cut surface is set parallel to the airflow direction, which can maximize the contact area between the gas flow direction and the cut surface, reduce the situation of blocking the airflow, and help to make the gas density in the cavity uniform, and then help to form a uniform aluminum oxide film. In addition, compared with the vertical airflow, the airflow parallel to the cut surface diffuses to the other surfaces of the half-cell solar cell with less flow, which can reduce the phenomenon of plating around the other surfaces of the half-cell solar cell and improve the utilization rate of raw materials. In addition, there is no need to passivate the entire half-cell solar cell, so the atomic layer deposition reaction of the half-cell solar cell can be completed more concentratedly, the passivation rate is improved, and the passivation time, raw material consumption and cost are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For purposes of illustration and not limitation, the present application will now be described according to its preferred embodiments, particularly with reference to the accompanying drawings, in which:

[0018] Figure 1 Schematic diagram of cutting a whole solar cell into half a solar cell:

[0019] Figure 2 A schematic diagram of a process for passivating a half-cell solar cell according to an embodiment of the present application;

[0020] Figure 3 A schematic diagram of the distribution of a plurality of half-cell solar cells in a chamber of an atomic layer deposition device according to an embodiment of the present application;

[0021] Figure 4 The diagram is a schematic diagram of the distribution of multiple half-cell solar cells in the chamber of an atomic layer deposition device according to the prior art. DETAILED DESCRIPTION

[0022] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0023] A passivation method for a half-cell solar cell according to an embodiment of the present application is as follows: Figure 2 As shown, it mainly includes steps S1 to S3.

[0024] S1: placing a plurality of half-cell solar cells in a cavity of an atomic layer deposition device, wherein the cut surfaces of the plurality of half-cell solar cells are exposed and the other surfaces are not exposed, the cut surfaces of each half-cell solar cell are parallel or in the same plane, and the cut surfaces are parallel to the airflow direction set in the cavity.

[0025] Step S1 may specifically include: stacking a plurality of half-cell solar cells into a group, with the cut surfaces of each group of half-cell solar cells facing the same or opposite directions, and vertically stacking and / or placing the plurality of groups of half-cell solar cells in parallel in the cavity of an atomic layer deposition device, so that the cut surfaces of each half-cell solar cell are parallel or in the same plane. Step S1 may also include: placing each group of stacked half-cell solar cells in a wafer boat, and placing a plurality of wafer boats in the cavity of an atomic layer deposition device. The wafer boat may adopt a box-like shape with only one side open, and the open side is referred to as the opening of the wafer boat. The wafer boat may also adopt other shapes with stronger envelopment, which can better wrap around and cover the non-cut surfaces of the half-cell solar cell.

[0026] You can refer to Figure 3To understand, multiple half-cell solar cells 101 can be stacked up in the same way with the cut surface a facing the same direction, and then the stacked half-cell solar cells can be placed in the side-wall open box-type wafer boat 200 until it is completely filled. Note that the cut surface a of each half-cell solar cell 101 is in the same direction as the opening of the wafer boat 200. The wafer boat 200 can wrap all other surfaces of the stacked multiple half-cell solar cells and expose the cut surface a. Then, multiple wafer boats 200 are placed in the cavity 300 of the atomic deposition equipment and are symmetrically arranged on both sides of the airflow direction (i.e., the direction of the line from the air inlet A to the air outlet B, which is omitted and not shown). Note that the opening of the wafer boat 200 faces the line of the airflow direction, so as to ensure that the cut surface a of each half-cell solar cell is parallel to the airflow direction. In addition, the wafer boats 200 can also be appropriately stacked vertically in the cavity, and the number of stacked layers can be 2 to 5 layers. Compared with the existing technical solution of "placing the wafer boats in a single layer in the cavity", stacking the wafer boats can increase the wafer capacity of a single cavity, which is more in line with the needs of mass production.

[0027] Optionally, a flow-uniform component 400 may be placed near the air inlet A. The flow-uniform component 400 has a plurality of mutually parallel airflow channels inside, and the axes of these airflow channels are parallel to the cut surfaces of the plurality of half-cell solar cells. The provision of the flow-uniform component enables the gaseous reaction precursor introduced into the cavity to flow evenly and smoothly to the plurality of half-cell solar cells, which helps to improve the uniformity of the passivation film formed on the cut surfaces of the half-cell solar cells of the same batch.

[0028] S2: Raise the temperature of the cavity to a preset reaction temperature, and pulse an aluminum source and an oxygen source into the cavity alternately, and deposit an aluminum oxide film on the cut surfaces of multiple half-cell solar cells to achieve passivation. The aluminum source may include trimethylaluminum vapor, and the oxygen source may include ozone or water vapor. The gas flow direction of the aluminum source and the oxygen source is parallel to the cut surface. The purpose of passivation is to form an aluminum oxide film of a certain thickness. The thickness of the aluminum oxide film may be 30nm to 40nm, for example, 30nm, 32nm, 34nm, 36nm, 38nm or 40nm, etc. A film of this thickness can effectively achieve passivation protection.

[0029] It should be noted that a purge operation may be performed between the pulse input of the aluminum source and the pulse input of the oxygen source. The purge operation refers to the use of an inactive gas (such as nitrogen or an inert gas) to purge and remove excess precursor gas and reaction byproducts in the chamber.

[0030] Taking the reaction of trimethylaluminium (TMA) Al(CH3)3 and water vapor H2O as an example, the specific process of atomic layer deposition passivation is as follows:

[0031] ① Aluminum source injection: The heated trimethylaluminum vapor is injected into the cavity as a metal aluminum source and adsorbed on the cut surface of multiple half-cell solar cells. The trimethylaluminum vapor is in liquid state in the source bottle, and the temperature of the source bottle is 40°C to 45°C. For example, it can be 40°C, 41°C, 42°C, 43°C, 44°C or 45°C, that is, it is in a warm state, which is conducive to low-pressure gasification in the subsequent pipeline to become a gaseous state.

[0032] ②Purge cleaning: Use inert gas to remove excess trimethylaluminum vapor and reaction byproducts from the chamber. The duration of a single purge can be 8s to 12s, such as 8s, 9s, 10s, 11s or 12s.

[0033] ③ Oxygen source injection: Water vapor is injected into the cavity as an oxygen source, and the cut surface of the half-cell solar cell adsorbed by the water vapor and the trimethylaluminum precursor continues to undergo surface chemical reactions.

[0034] ④ Purge cleaning: Use inert gas to remove excess reactants (including water vapor) and residual reaction by-products. The duration of a single purge can be 8s to 12s, such as 8s, 9s, 10s, 11s or 12s.

[0035] The above process can be repeated until the target thickness is reached. Each time the above steps are repeated, a cycle is completed. Each cycle achieves the coating of one layer of aluminum oxide molecules.

[0036] In step S2, the volume flow rate of trimethylaluminum vapor can be 24sccm to 30sccm. Specifically, for example, it can be 24sccm, 26sccm, 28sccm or 30sccm. The amount of trimethylaluminum vapor introduced has a significant effect on the diffusion rate and diffusion effect of the precursor gas. When the introduction amount is too low, the diffusion rate of the precursor gas will not be significantly improved, and the uniformity of the passivation degree in the cavity and the wafer carrier boat cannot be significantly improved. When the introduction amount is too high, the precursor gas will be blown away, resulting in turbulence and turbulence, which will cause the precursor gas to still be difficult to deposit uniformly throughout the cavity of the atomic layer deposition equipment, so it is still impossible to significantly improve the uniformity of the passivation degree in the cavity and the wafer carrier boat.

[0037] In step S2, the volume flow rate of ozone or water vapor can be set to 10 sccm to 30 sccm, such as 10 sccm, 15 sccm, 20 sccm, 25 sccm or 30 sccm, preferably 20 sccm. The oxygen source has smaller molecules and is easier to diffuse evenly, so its flow rate can be flexibly set.

[0038] In step S2, in order to obtain a good passivation result, the pressure of delivering trimethylaluminum vapor can be 20 Torr to 70 Torr, for example, 20 Torr, 30 Torr, 40 Torr, 50 Torr, 60 Torr or 70 Torr, etc., and the duration of a single pulse can be 7s to 11s, for example, 7s, 8s, 9s, 10s or 11s, etc.; the pressure of delivering ozone or water vapor can be 20 Torr to 70 Torr, for example, 20 Torr, 30 Torr, 40 Torr, 50 Torr, 60 Torr or 70 Torr, etc., and the duration of a single pulse can be 7s to 11s, for example, 7s, 8s, 9s, 10s or 11s, etc.

[0039] In step S2, the preset reaction temperature of the passivation reaction can be 150°C to 305°C, for example, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C or 305°C, etc. Compared with the passivation temperature (usually greater than 310°C) of the prior art, the preset reaction temperature of the present application is lower, which reduces the probability of self-decomposition of trimethylaluminum vapor at high temperature, improves the source utilization rate, and also has the beneficial effects of saving heat energy.

[0040] Atomic layer deposition equipment can use commercially available equipment, which can be divided into two categories according to whether the equipment itself includes an annealing module. For atomic layer deposition equipment that includes an annealing module, a quartz boat can be used as a wafer carrier boat. Since quartz has good heat resistance, the preset reaction temperature can be 275°C to 305°C, such as 275°C, 280°C, 285°C, 290°C, 295°C, 300°C or 305°C. For atomic layer deposition equipment that does not have an annealing module, an aluminum boat can be used as a wafer carrier boat. Since aluminum has medium heat resistance, the preset reaction temperature can be 150°C to 180°C, such as 150°C, 155°C, 160°C, 165°C, 170°C, 175°C or 180°C.

[0041] The chamber of the atomic layer deposition device may include a chamber front region, a chamber rear region, and a chamber middle region located between the chamber front region and the chamber rear region.

[0042] The temperature of the front zone of the cavity can be 290℃ to 300℃, for example, 290℃, 292℃, 294℃, 296℃, 298℃ or 300℃; the temperature of the middle zone of the cavity is 290℃ to 300℃, for example, 290℃, 292℃, 294℃, 296℃, 298℃ or 300℃; the temperature of the rear zone of the cavity is 280℃ to 290℃, for example, 280℃, 282℃, 284℃, 286℃, 288℃ or 290℃.

[0043] The local reaction temperature of each position in the chamber of the atomic layer deposition equipment can be the same, that is, the local reaction temperature of the front area of ​​the chamber, the middle area of ​​the chamber and the rear area of ​​the chamber are the same. When the temperature in the chamber needs to be evenly distributed, the equipment requirements are lower and the overall debugging is easy.

[0044] The local reaction temperatures at various locations in the chamber of the atomic layer deposition equipment may also be different, that is, the local reaction temperatures in the front area of ​​the chamber, the middle area of ​​the chamber, and the rear area of ​​the chamber are different. For example, the local reaction temperatures in the front area of ​​the chamber, the middle area of ​​the chamber, and the rear area of ​​the chamber may be set to gradually increase or decrease. The increase may be a linear increase or decrease, a gradual increase or decrease in a curve, or a segmented gradient increase or decrease. With such a setting, it can also be ensured that the temperature in the chamber is similar, the overall passivation uniformity is less affected by the temperature, and the uniformity at different locations is ensured to be consistent.

[0045] When the atomic layer deposition equipment adopts the furnace-mouth air intake method, the local reaction temperature of the rear area of ​​the cavity can be controlled to be slightly higher than the local reaction temperature of the front area of ​​the cavity. Specifically, the front area of ​​the cavity is close to the air inlet, so the half-cell solar cell in the front area of ​​the cavity adsorbs slightly more precursor gas, and the rear area of ​​the cavity is close to the air outlet, so the half-cell solar cell in the rear area of ​​the cavity adsorbs slightly less precursor gas. Setting the temperature of the rear area of ​​the cavity slightly higher is essentially to slightly increase the temperature of the position close to the air outlet to increase the reaction rate at the position of the air outlet and compensate for the difference in adsorption degree. When the atomic layer deposition equipment adopts the furnace-tail air intake method, the local reaction temperature of the front area of ​​the cavity can be controlled to be slightly higher than the local reaction temperature of the rear area of ​​the cavity. Specifically, the rear area of ​​the cavity is close to the air inlet, so the half-cell solar cell in the rear area of ​​the cavity adsorbs slightly more precursor gas, and the front area of ​​the cavity is close to the air outlet, so the half-cell solar cell in the front area of ​​the cavity adsorbs slightly less precursor gas. Setting the temperature of the front area of ​​the cavity slightly higher is essentially to slightly increase the temperature of the position close to the air outlet to increase the reaction rate at the position of the air outlet and compensate for the difference in adsorption degree. In this embodiment, the reaction temperature at each location in the cavity is adjusted to control the reaction rate at each location, thereby ensuring that the thickness of the passivation layer deposited at each location in the half-cell solar cell is highly consistent, thereby reducing the differences between the silicon wafers. When the silicon wafers are connected in series to form a solar cell, the overall conversion efficiency of the solar cell is improved.

[0046] When the local reaction temperatures of the front area, the middle area and the rear area of ​​the cavity are different, the temperature difference of different areas is preferably less than or equal to 20°C, otherwise it affects the consistency of the passivation degree of each position in the cavity. For example, the temperature difference can be the temperature difference between the front area and the rear area of ​​the cavity, the temperature difference between the middle area and the rear area of ​​the cavity, the temperature difference between the front area and the middle area of ​​the cavity, etc.; the specific values ​​can be 2°C, 4°C, 6°C, 8°C, 10°C, 12°C, 14°C, 15°C, 16°C, 17°C, 19°C or 20°C, etc.

[0047] Between step S1 and step S2, it may also include: ozone pretreatment or water pretreatment of multiple half-cell solar cells in the cavity, so that a relatively saturated concentration of oxygen atoms can be provided for adsorption by the cut surface of the half-cell solar cell, which is conducive to the subsequent deposition reaction with the aluminum source. The main purposes of ozone pretreatment or water pretreatment include: cleaning the surface of the silicon wafer to prevent chemical reactions that affect the surface of the silicon wafer; removing defects, reducing impurities on the surface and body of the silicon wafer, and eliminating defects such as reflection and refraction, and improving the light absorption and conversion efficiency of the solar cell; improving surface properties, and enhancing the hydrophilicity or hydrophobicity of the silicon wafer surface through pretreatment, and improving the stability and corrosion resistance of the half-cell solar cell in a humid environment. Ozone pretreatment specifically refers to: pulse ozone into the cavity with a carrier gas (such as nitrogen), thereby exposing the half-cell solar cell to an environment containing ozone, and immediately purging with a carrier gas after the ozone is introduced. Water pretreatment specifically refers to: water vapor is pulsed into the cavity along with a carrier gas (such as nitrogen) for 4 seconds, thereby exposing half of the solar cell to an environment containing water vapor. After the water vapor is introduced, it is immediately purged with a carrier gas with a carrier gas purge flow rate of 20L / min and a purge time of 10 seconds.

[0048] S3: performing annealing and cooling treatment on a plurality of half-cell solar cells to obtain passivated half-cell solar cells.

[0049] In the case where the atomic layer deposition equipment includes an annealing module, half of the solar cell can be annealed in the atomic layer deposition equipment, and the annealing temperature is 220°C to 240°C, for example, 220°C, 225°C, 230°C, 235°C or 240°C; the annealing time is 10 min to 15 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0050] In the case where the atomic layer deposition equipment is not equipped with an annealing module, half of the solar cell can be annealed in a separate annealing furnace outside the atomic layer deposition equipment. The annealing temperature is 220°C to 260°C, for example, 220°C, 230°C, 240°C, 250°C or 260°C; the annealing time is 10 min to 15 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0051] The cooling process of half-cell solar cells is usually carried out outside the atomic layer deposition equipment. The half-cell solar cell can be cooled to room temperature (about 25°C) by air cooling or natural cooling. The cooling time is usually 15 to 20 minutes, for example, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes or 20 minutes.

[0052] After completing the above steps, subsequent steps such as electrical performance testing, electroluminescent (EL) sorting, and component production can be carried out. Among them, the electrical performance test items can include testing the opening voltage, current, fill factor, light conversion efficiency, yield, etc. of half-cell solar cells. Electroluminescence sorting mainly tests grayscale values, photoelectric conversion efficiency, yield, A-grade rate and other data. Through testing and sorting, the efficiency and quality of the half-cell solar cell after edge passivation can be ensured, thereby improving the battery efficiency and yield, and achieving cost reduction and efficiency improvement. The screened edge passivated half-cell solar cell is used for photovoltaic module manufacturing, and the photovoltaic module process data is collected.

[0053] In summary, according to the passivation method of the half-cell solar cell of the embodiment of the present application, only the cut surface is exposed during the deposition process and the cut surface is set parallel to the airflow direction, which can maximize the contact area between the gas flow direction and the cut surface, reduce the situation of blocking the airflow, and help to make the gas density in the cavity uniform, and then help to form a uniform aluminum oxide film. In addition, compared with the vertical airflow, the airflow parallel to the cut surface diffuses to the other surfaces of the half-cell solar cell with less flow, which can reduce the phenomenon of plating around the other surfaces of the half-cell solar cell and improve the utilization rate of raw materials. In addition, there is no need to passivate the entire half-cell solar cell, so the atomic layer deposition reaction of the half-cell solar cell can be completed more concentratedly, the passivation rate is improved, and the passivation time, raw material consumption and cost are reduced. This technical solution does not require the use of special equipment or additional process steps. It is simple and easy to implement and has good compatibility with current production lines. It can be applied to TOPCon cells (Tunnel Oxide Passivated Contact Cell), PERC cells (Passivated Emitter and Rear Cell), HIT cells (Heterojunction with intrinsic Thinlayer Cell) and SHJ cells (Silicon Heterojunction Solar Cell), with a wide range of applications and good stability.

[0054] In order to enable those skilled in the art to better understand, embodiments are listed below for illustration.

[0055] Example 1

[0056] The sliced ​​half solar cell is Figure 3Loading; then water pretreatment, that is, water vapor enters the cavity with nitrogen pulses, the entry time is 4s, and then immediately purged with carrier gas, the carrier gas purge flow rate is 20L / min, the purge time is 10s; control the temperature of the trimethylaluminum source bottle to 43°C, the volume flow rate of trimethylaluminum vapor to 28sccm, the vapor pressure to 45Torr, and the single pulse entry time is 9s; the volume flow rate of water vapor can be 20sccm, the vapor pressure is 45Torr, and the single pulse entry time is 9s; single nitrogen purge The duration is 9s; the local reaction temperature of the front area of ​​the cavity is controlled to be 295℃, the local reaction temperature of the middle area of ​​the cavity is 290℃, and the local reaction temperature of the rear area of ​​the cavity is 285℃. The cut surface of the half-cell solar cell is subjected to atomic layer deposition passivation, the number of cycles is 180, and the target aluminum oxide passivation film thickness is 32nm; annealing is performed in the cavity of the atomic layer deposition equipment, the annealing temperature is 220℃, and the annealing time is 12min; the passivated half-cell solar cell is taken out and naturally cooled at 25℃ for 15min. The passivation time is recorded as 165min, and the actual aluminum oxide passivation film thickness obtained by sampling and testing is statistically analyzed.

[0057] Example 2

[0058] The sliced ​​half solar cell is Figure 3 Loading is carried out; then water pretreatment is carried out, that is, water vapor enters the cavity with nitrogen pulses for 4 seconds, and then it is immediately purged with a carrier gas, with a carrier gas purge flow rate of 20L / min and a purge time of 10 seconds; the temperature of the trimethylaluminum source bottle is controlled to be 43°C; the volume flow rate of trimethylaluminum vapor is 30sccm, the water vapor pressure is 60Torr, and the single pulse introduction time is 9s; the volume flow rate of water vapor can be 20sccm, the vapor pressure is 45Torr, and the single pulse introduction time is 9s; the single nitrogen purge time is 9s; the local reaction temperature of the front area of ​​the cavity is controlled to be 295°C, the local reaction temperature of the middle area of ​​the cavity is 290°C, and the local reaction temperature of the rear area of ​​the cavity is 285°C. The cut surface of the half-cell solar cell was passivated by atomic layer deposition, with 200 cycles and a target aluminum oxide passivation film thickness of 35nm. Annealing was performed in the chamber of the atomic layer deposition equipment at a temperature of 220°C for 12 minutes. The passivated half-cell solar cell was taken out and naturally cooled at 25°C for 15 minutes. The passivation time was recorded as 188 minutes, and the actual aluminum oxide passivation film thickness obtained by sampling and testing was statistically analyzed.

[0059] Example 3

[0060] The sliced ​​half solar cell is Figure 3Loading; then water pretreatment, that is, water vapor enters the cavity with nitrogen pulses, the entry time is 4s, and then immediately purged with carrier gas, the carrier gas purge flow rate is 20L / min, the purge time is 10s; control the temperature of the trimethylaluminum source bottle to 43°C; the volume flow rate of trimethylaluminum vapor is 30sccm, the vapor pressure is 45Torr, and the single pulse entry time is 9s; the volume flow rate of water vapor can be 20sccm, the vapor pressure is 45Torr, and the single pulse entry time is 9s; single nitrogen purge The duration is 9s; the local reaction temperature of the front area of ​​the cavity is controlled to be 295℃, the local reaction temperature of the middle area of ​​the cavity is 290℃, and the local reaction temperature of the rear area of ​​the cavity is 285℃. The cut surface of the half-cell solar cell is subjected to atomic layer deposition passivation, the number of cycles is 230, and the target aluminum oxide passivation film thickness is 38nm; annealing is performed in the cavity of the atomic layer deposition equipment, the annealing temperature is 220℃, and the annealing time is 12min; the passivated half-cell solar cell is taken out and naturally cooled at 25℃ for 15min. The passivation time is recorded as 209min, and the actual aluminum oxide passivation film thickness obtained by sampling and testing is statistically analyzed.

[0061] Comparative Example

[0062] The sliced ​​half solar cell is processed according to the prior art. Figure 4 Loading is performed as shown, such as Figure 4 As shown, the stacked half-cell solar cell 101 is first placed in a wafer carrier boat 200, and then the wafer carrier boat 200 is placed in the cavity 300 of the atomic deposition equipment, wherein the cut surface a of the half-cell solar cell 101 is perpendicular to the direction of the gas flow; water pretreatment is performed, that is, water vapor is introduced into the cavity with a nitrogen pulse for 4 seconds, and then immediately purged with a carrier gas, the carrier gas purge flow rate is 20L / min, and the purge time is 10 seconds; the temperature of the trimethylaluminum source bottle is set to 43°C; the volume flow rate of trimethylaluminum vapor is 30sccm, the vapor pressure is 45Torr, and the single pulse introduction time is 9 seconds; the volume flow rate of water vapor can be 2 0sccm, vapor pressure of 45Torr, single pulse duration of 9s; single nitrogen purge duration of 9s; local reaction temperature of the front area of ​​the cavity is 295℃, local reaction temperature of the middle area of ​​the cavity is 290℃, local reaction temperature of the rear area of ​​the cavity is 285℃, the cut surface of the half-cell solar cell is subjected to atomic layer deposition passivation, the number of cycles is 230, and the target aluminum oxide passivation film thickness is 38nm; annealing is performed in the cavity of the atomic layer deposition equipment, the annealing temperature is 220℃, and the annealing time is 12min; the passivated half-cell solar cell is taken out and naturally cooled at 25℃ for 15min. The passivation time is recorded as 211min, and the actual aluminum oxide passivation film thickness obtained by sampling and testing is statistically analyzed.

[0063] The comparison of the test results of the above three embodiments and the comparative example is shown in Table 1 below. The passivation time refers to the length of time consumed when the coating reaches the target aluminum oxide passivation film thickness. The shorter the value, the better. Intra-chip uniformity refers to: the statistical standard deviation of the aluminum oxide passivation film thickness at multiple sampling points (for example, 5) inside the same half-chip solar cell accounts for the percentage of the statistical mean value. The lower the value, the better the uniformity. Inter-chip uniformity specifically refers to: the statistical standard deviation of the aluminum oxide passivation film thickness of different half-chip solar cells in the same production batch accounts for the percentage of the statistical mean value. The lower the value, the better the uniformity.

[0064] Table 1 Comparison of test results of the embodiment and the comparative example

[0065] Example 1 Example 2 Example 3 Comparative Example Passivation time 165min 188min 209min 211min In-chip uniformity 5.34％ 4.84％ 6.57％ 7.63％ Inter-chip uniformity 7.25％ 6.16％ 8.04％ 9.57％

[0066] Compared with the existing passivation half-cell solar cell process, the passivation time in the method provided in the embodiment of the present application is shortened, and both the intra-cell uniformity and the inter-cell uniformity are reduced, that is, the intra-cell uniformity and the inter-cell uniformity are improved. Compared with the comparative example, the intra-cell uniformity of Example 3 is optimized from 7.63% to 6.57%, and the inter-cell uniformity is optimized from 9.57% to 8.04%.

[0067] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A passivation method for a half-cell solar cell, comprising the following steps: S1: placing a plurality of half-cell solar cells in a chamber of an atomic layer deposition device, wherein: The cut surfaces of the plurality of half-cell solar cells are exposed, and the other surfaces are not exposed, the cut surfaces of each half-cell solar cell are parallel or in the same plane, and the cut surfaces are parallel to the airflow direction set in the cavity; S2: heating the chamber to a preset reaction temperature, and alternately introducing an aluminum source and an oxygen source into the chamber in pulses, depositing an aluminum oxide film on the cut surfaces of a plurality of half-cell solar cells to achieve passivation, wherein the aluminum source comprises trimethylaluminum vapor, the oxygen source comprises ozone or water vapor, and the gas flow directions of the aluminum source and the oxygen source are parallel to the cut surfaces; S3: performing annealing and cooling treatment on the plurality of half-cell solar cells to obtain passivated half-cell solar cells.

2. The passivation method for a half-cell solar cell according to claim 1, characterized in that: The step S1 comprises: stacking a plurality of the half-cell solar cells into a group, wherein the cut surfaces of each group of the half-cell solar cells face the same direction or face each other, and vertically stacking and / or placing the plurality of groups of the half-cell solar cells in parallel in the chamber of the atomic layer deposition device, so that the cut surfaces of each half-cell solar cell are parallel or in the same plane; The step S1 further includes: placing a flow-uniform component near the air inlet, wherein the flow-uniform component has a plurality of mutually parallel airflow channels inside, and the axes of the airflow channels are parallel to the cut surfaces of the plurality of half-cell solar cells.

3. The passivation method for a half-cell solar cell according to claim 1, characterized in that: In step S2, the volume flow rate of trimethylaluminum vapor is 24 sccm to 30 sccm; and / or, the pressure of delivering the trimethylaluminum vapor is 20 Torr to 70 Torr, and the duration of a single pulse is 7s to 11s; and / or, the pressure of delivering the ozone or water vapor is 20 Torr to 70 Torr, and the duration of a single pulse is 7s to 11s.

4. The passivation method for a half-cell solar cell according to claim 2, characterized in that: The step S1 comprises: placing each group of stacked half-cell solar cells in a wafer carrier boat, and placing a plurality of wafer carrier boats in the cavity of the atomic layer deposition device; and / or, in the step S2, the preset reaction temperature is 150°C to 305°C.

5. The passivation method for a half-cell solar cell according to claim 4, characterized in that: The atomic layer deposition equipment includes an annealing module, the wafer carrier boat includes a quartz boat, and the preset reaction temperature is 275° C. to 305° C.

6. The passivation method for a half-cell solar cell according to claim 4, characterized in that: The atomic layer deposition equipment is not provided with an annealing module, the wafer carrier boat comprises an aluminum boat, and the preset reaction temperature is 150° C. to 180° C.

7. The passivation method for a half-cell solar cell according to claim 4, characterized in that: The cavity includes a cavity front area, a cavity rear area, and a cavity middle area located between the cavity front area and the cavity rear area, wherein the local reaction temperatures of the cavity front area, the cavity middle area and the cavity rear area are the same, or the local reaction temperatures are different.

8. The passivation method for a half-cell solar cell according to claim 7, characterized in that: When the local reaction temperatures of the front area, the middle area and the rear area of ​​the cavity are different, the temperature difference between the different areas is less than or equal to 20°C.

9. The passivation method for a half-cell solar cell according to claim 8, characterized in that: The wafer boat is a quartz boat, the temperature of the front area of ​​the cavity is 290°C to 300°C, the temperature of the middle area of ​​the cavity is 290°C to 300°C, and the temperature of the rear area of ​​the cavity is 280°C to 290°C.

10. The passivation method for a half-cell solar cell according to claim 1, characterized in that: Between step S1 and step S2, the method further includes: performing ozone pretreatment or water pretreatment on the plurality of half-cell solar cells in the cavity; And / or, the thickness of the aluminum oxide film is 30 nm to 40 nm; And / or, the wafer boats are stacked vertically in the cavity, with the number of stacking layers being 2 to 5.

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