Crystalline silicon solar cell ozone gas passivation equipment

Abstract

The invention provides a crystalline silicon solar cell ozone gas passivation device which comprises a control cabinet, an ozone generator is arranged in the control cabinet, oxygen is introduced into the input end of the ozone generator through a first pipeline, the output end of the ozone generator is connected with a passivation tank through a second pipeline, and the second pipeline is communicated with a third pipeline; an ozone concentration detector is arranged on the second pipeline and in front of the passivation tank; the second pipeline is communicated with an annular uniform flow pipe in the passivation tank; and the passivation tank is connected with the heating device through a fourth pipeline, and hot air is introduced into the passivation tank through the heating device, so that a certain temperature is kept in the passivation tank. According to the silicon wafer ozone gas passivation equipment, ozone gas is introduced while the silicon wafer is dried after being cleaned, and an oxide layer grows on the surface of the silicon wafer, so that the production process can be simplified, the uniformity and consistency of the oxide passivation layer on the surface of the silicon wafer can be considered, and the production efficiency is improved. And the oxidizing atmosphere in the passivation tank is controlled in real time through the control cabinet, so that the uniformity of oxide passivation layers of different batches of silicon wafers is ensured.

Description

Technical Field

[0001] This invention relates to the field of solar cell fabrication technology, and in particular to an ozone gas passivation device used in the fabrication process of crystalline silicon solar cells, especially suitable for silicon wafer surface passivation in the fabrication process of high-efficiency TOPcon cells or back contact solar cells (BC cells). Background Technology

[0002] Surface passivation of solar cell silicon wafers refers to the process of forming a protective film or chemically treating the surface of the silicon wafer to reduce surface defects and recombination, thereby improving the conversion efficiency and stability of the cell. Surface passivation technology is crucial for improving the performance of solar cells, significantly enhancing their conversion efficiency; by reducing surface defects and recombination, it can effectively reduce losses during photoelectric conversion, thus improving photoelectric conversion efficiency; furthermore, surface passivation can also enhance the stability and lifespan of the cell.

[0003] Surface contamination on silicon wafers has a significant impact on passivation. Contamination on the wafer surface, such as residual metal ions, can disrupt the interfacial bonding between the oxide layer and the polycrystalline silicon layer. For example, metal impurities such as Fe and Cr tend to exacerbate surface recombination in P-type silicon wafers. Furthermore, contamination can interfere with subsequent doping processes, affecting the uniformity of the doped layer.

[0004] Surface contamination of silicon wafers typically occurs during the cell manufacturing process. After alkaline polishing or RCA cleaning, both the front and back surfaces of the silicon wafer are exposed to the workshop environment, making them susceptible to contamination. Furthermore, the lack of an oxide layer on the back of the silicon wafer makes it prone to natural oxidation with the ambient air, resulting in an uneven, uncontrollable natural oxide layer. The aforementioned natural oxide layer on the silicon surface is a self-inhibiting film that can prevent surface contamination. Therefore, in current solar cell manufacturing processes, a uniform oxide layer is grown on the silicon wafer surface before it is exposed to the non-process environment, achieving a good passivation effect. Currently, there are generally two oxidation methods: wet oxidation and wet oxidation. Wet oxidation involves immersing the silicon wafer in hydrogen peroxide or ozone solution after alkaline polishing or RCA cleaning to form a slightly higher quality wet oxide layer. However, due to the presence of the oxide layer, the dehydration effect is poor after the slow pulling process in the alkaline polishing step, easily resulting in liquid residue entering the passivation tank for drying. As silicon wafers become increasingly thinner, this method easily leads to adjacent wafers sticking together during the drying stage, significantly impacting subsequent processes and product yield. Furthermore, since this wet oxide layer participates in the subsequent battery structure, its growth quality greatly affects the overall battery passivation effect. Additionally, due to the changing activity of the wet oxide reagent throughout the mass production cycle, the actual growth of the wet oxide layer cannot maintain a uniform standard within a single solution change cycle, greatly affecting the stability of the actual production line. The direct consequence is a significant impact on the uniformity of the oxide layer, which directly determines the passivation effect. Uneven oxide layer thickness or local defects can lead to increased carrier recombination rate, reducing open-circuit voltage and conversion efficiency. Another method is dry oxidation, where the silicon wafer is first dried during alkaline polishing or RCA cleaning, and then an oxidizing gas is introduced to grow a dry oxide layer on the wafer surface. Dry oxidation produces oxide layers with high density, good uniformity, and fewer defects. However, dry oxidation also has its own drawbacks. It requires drying the silicon wafer first, and then growing an oxide layer on the silicon wafer in an oxidizing gas atmosphere. The growth rate of the oxide layer is very slow, only one-fifth to one-third of that of wet oxidation.

[0005] Back-contact solar cells (BC cells) are among the most popular high-efficiency solar cells in the photovoltaic industry today. Their most significant feature is their entirely rear-mounted electrode design, with no metal grid lines obstructing the front side. This structure reduces incident light loss by more than 2%, thus improving photoelectric conversion efficiency. To achieve fully rear-mounted electrodes, a special doping process is required to form interdigitated P- and N-regions, with doping precision down to the micrometer level. Compared to another high-efficiency type, TOPCon cells, the uniformity of doping requires even higher precision, reaching ±3μm. Furthermore, in the metal grid line fabrication stage, they abandon the screen printing technology used in TOPCon cells, employing an electroplating copper process. Therefore, their production efficiency is about 30% lower than traditional processes. Additionally, the absence of front-mounted shading in BC cells increases the short-circuit current by more than 1.5mA / cm², but the open-circuit voltage is about 10mV lower than TOPCon, requiring superior passivation technology to compensate.

[0006] Therefore, for back-contact solar cells, during silicon wafer oxidation, it is necessary to ensure both the uniformity of oxide layer growth and production efficiency. On the basis of ensuring the uniformity of oxide layer growth, the production speed of oxide layer should be increased as much as possible. Summary of the Invention

[0007] In response to the application needs of existing technologies, the purpose of this invention is to provide an ozone gas passivation device for crystalline silicon solar cells, which can improve the passivation effect of silicon wafers by obtaining an oxide layer with excellent uniformity while taking into account the growth rate of the oxide layer, thereby improving production efficiency.

[0008] Specifically, to achieve the objectives of this invention, the following technical solution is adopted: An ozone gas passivation device for crystalline silicon solar cells includes a control cabinet housing an ozone generator. Oxygen is introduced into the ozone generator via a first pipe, and its output is connected to a passivation tank via a second pipe and a back pressure valve via a third pipe. The second and third pipes are interconnected. A gas filter, a gas pressure regulating valve, and a pressure sensor are sequentially installed on the first pipe. An ozone concentration detector is installed on the second pipe before the passivation tank. The second pipe is connected to an annular flow equalization pipe within the passivation tank, which has multiple evenly spaced air outlets. The passivation tank is connected to a heating device via a fourth pipe, through which hot air is introduced into the passivation tank to maintain a certain temperature.

[0009] An ozone gas passivation device for crystalline silicon solar cells includes a control cabinet housing an ozone generator. Oxygen is introduced into the ozone generator through a first pipe, and its output is connected to a second pipe and a back pressure valve through a third pipe. The second and third pipes are interconnected. A gas filter, a gas pressure regulating valve, and a pressure sensor are sequentially installed on the first pipe. An ozone concentration detector is installed on the second pipe before the passivation tank. The passivation tank is connected to a heating device through a fourth pipe, which introduces hot air into the tank to maintain a certain temperature. The second and fourth pipes are interconnected, and the ozone output from the ozone generator enters the passivation tank through the fourth pipe.

[0010] Preferably, the ozone concentration detector is connected to the control cabinet, and the ozone output of the ozone generator is adjusted in real time according to the ozone concentration detection results.

[0011] Preferably, the back pressure valve opens to release pressure when the gas pressure is too high, thus ensuring a constant gas pressure.

[0012] Preferably, the heating device is connected to the control cabinet to control the temperature in the passivation tank to a set value.

[0013] Preferably, at the output end of the fourth pipe, an ozone depletor is installed after the back pressure valve to deplete excess ozone before releasing it into the atmosphere.

[0014] Preferably, the ozone generator in the control cabinet is connected to the ozone water tank through a fifth pipe, so as to pass ozone into the ozone water tank to form ozone water with a set concentration that can be used for silicon wafer surface treatment.

[0015] Preferably, a water vapor box is installed on the second pipe before the passivation tank, and water vapor is transported into the passivation tank through the pipe to maintain a certain water vapor atmosphere in the passivation tank.

[0016] Preferably, the water vapor box is connected to the control cabinet, so that the humidity in the passivation tank is within an optimized range, and pure water is automatically replenished to the water vapor box after the water in the water vapor box is consumed to a low level.

[0017] More preferably, in the passivation equipment, one ozone generator corresponds to one passivation tank, or one ozone generator is connected to multiple passivation tanks through multiple pipes, or multiple ozone generators correspond to multiple passivation tanks.

[0018] The ozone gas passivation equipment for crystalline silicon solar cells of the present invention introduces ozone gas simultaneously with the drying of the silicon wafers after cleaning, growing an oxide layer on the silicon wafer surface. This not only simplifies the production process but also ensures the uniformity and consistency of the oxide passivation layer on the silicon wafer surface, while improving production efficiency. The present invention allows for real-time control of the oxidation atmosphere in the passivation tank via a control cabinet, thereby ensuring the uniformity of the oxide passivation layer across different batches of silicon wafers. Compared to dry oxidation processes, this application offers superior production efficiency and is particularly suitable for the production of BC (carbon dioxide) cells. Attached Figure Description

[0019] The foregoing and other objects, features, and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. Wherein: Figure 1 The diagram shown is a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to an embodiment of the present invention. Figure 2 The diagram shown is a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to another embodiment of the present invention. Figure 3 The diagram shown is a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to another embodiment of the present invention. Figure 4 The diagram shown is a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to another embodiment of the present invention. Detailed Implementation

[0020] To provide a further understanding of the purpose, structure, features, and functions of the present invention, this section will describe in detail specific embodiments of the present invention.

[0021] In the description of this invention, it should be noted that the terms "length", "width", "thickness", "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, and "above," "below," "within," etc. are understood to include the number itself. Where "first" or "second" is used, it is only for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0023] In the description of this invention, unless otherwise explicitly defined, terms such as "set", "install", and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0024] Based on the purpose of this invention and practical application requirements, the structure, working principle, and technical effects of this invention will be described in detail below with reference to the accompanying drawings.

[0025] See Figure 1 The diagram shows a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to an embodiment of the present invention. The passivation device includes a control cabinet 100, which houses an ozone generator 10. Oxygen is introduced into the ozone generator 10 through a first pipe 101, and the output of the ozone generator 10 is connected to a passivation tank 30 through a second pipe 102. A back pressure valve 42 is connected through a third pipe 103, and the second pipe 102 and the third pipe 103 communicate with each other. A gas filter 12, a gas pressure regulating valve 14, and a pressure sensor 16 are sequentially installed on the first pipe 101 to direct the oxygen introduced into the ozone generator 10. The gas is filtered, pressure regulated, and maintained at a certain gas concentration ratio, enabling the ozone generator 10 to effectively convert oxygen into ozone. An ozone concentration detector 18 is installed on the second pipe 102 before the passivation tank 30. The second pipe 102 is connected to the annular flow equalization pipe 32 inside the passivation tank 30. The annular flow equalization pipe 32 has multiple air outlets evenly spaced to ensure uniform distribution of ozone within the passivation tank 30. The passivation tank 30 is connected to the heating device 20 via the fourth pipe 104. Hot air is introduced into the passivation tank 30 through the heating device 20 to maintain a certain temperature inside the passivation tank.

[0026] The ozone gas passivation equipment for crystalline silicon solar cells in the above embodiments of this application cleans the crystalline silicon cells after they have undergone the previous surface texturing process, and then transfers the silicon wafers to the passivation tank 30. At this time, hot air is simultaneously introduced for drying and ozone is introduced to oxidize the silicon wafer surface to form a passivation layer.

[0027] To ensure passivation effectiveness and the uniformity of the oxide layer on the silicon wafer, in addition to using a flow equalization plate to ensure the uniformity of the oxidation atmosphere within the passivation tank, this application installs an ozone concentration detector 18 on the third pipe to control the ozone concentration within the passivation tank, ensuring the oxidation effect on the silicon wafer surface. The ozone concentration detector 18 is connected to the control cabinet 100 and can adjust the ozone output of the ozone generator 10 in real time based on the ozone concentration detection results. A back pressure valve 42 is installed on the fourth pipe. When the gas pressure is too high, the back pressure valve 42 opens to release pressure, ensuring a constant gas pressure. The heating device 20 is also connected to the control cabinet to control the temperature within the passivation tank at a set value. In this way, the silicon wafer within the passivation tank can be kept in a stable state during the surface oxidation process, ensuring the consistency of the oxide layer between different batches even in a batch passivation process.

[0028] In another preferred embodiment, see Figure 1 At the output end of the fourth pipe 104, an ozone depletion device 40 is installed after the back pressure valve 42. This device can deplete excess ozone before releasing it into the atmosphere, thus preventing the direct emission of ozone gas and meeting environmental protection requirements.

[0029] The ozone gas passivation equipment for crystalline silicon solar cells disclosed in this application eliminates the need to dry the cleaned silicon wafers before surface oxidation. The passivation tank contains a certain amount of moisture, and this humid environment significantly increases the growth rate of the oxide layer on the silicon wafer surface. Compared to dry oxidation in a pure oxygen environment, wet oxidation can increase the rate of SiO2 layer formation by 3-5 times at the same temperature, thus rapidly forming a thicker oxide layer, typically reaching hundreds of nanometers to micrometers. This is because the hydroxyl groups (-OH) in water molecules have higher chemical reactivity in reacting with silicon to form SiO2, as shown in the reaction equation: Si + 2H2O → SiO2 + 2H2↑. Therefore, the process described in this application has fewer steps and better production efficiency compared to dry oxidation, making it more suitable for BC cells, which already have relatively low yields.

[0030] The ozone gas passivation equipment for crystalline silicon solar cells described in the above embodiments is specifically designed for the formation of a passivation layer on the silicon wafer surface through oxidation. In current solar cell manufacturing processes, ozone water is also used for silicon wafer surface treatment during the front-end silicon wafer processing. Therefore, the ozone gas passivation equipment for crystalline silicon solar cells of this application can also be configured to be used simultaneously for both processes. See details below. Figure 2The diagram shows a structural schematic of an ozone gas passivation device for crystalline silicon solar cells according to another embodiment of the present invention. The ozone generator 10 in the control cabinet 100 is connected to an ozone water tank 50 via a fifth pipe 105, allowing ozone to be introduced into the ozone water tank 50 to form ozone water with a set concentration suitable for silicon wafer surface treatment. This saves on equipment investment and reduces equipment costs.

[0031] In another preferred embodiment, see Figure 2 To improve the oxidation efficiency of silicon wafer surfaces within the passivation tank, a water vapor box 24 is installed on the second pipe 102, before the passivation tank 30. Water vapor is supplied to the passivation tank 30 through the pipe, maintaining a certain level of moisture within the passivation tank. The water vapor box 24 is connected to the control cabinet 100. This allows for optimal humidity control within the passivation tank 30. Furthermore, when the water level in the water vapor box 24 drops to a low level, it is automatically replenished with pure water to maintain continuous operation.

[0032] In the above embodiments, to ensure uniform ozone distribution within the passivation tank and guarantee the uniformity of the silicon wafer oxide layer, ozone is transported to various parts of the passivation tank via a flow equalization plate. In another embodiment, to reduce equipment costs, other technical means can also be employed. See [link to documentation]. Figure 3 The diagram shown is a structural schematic of an ozone gas passivation device for a crystalline silicon solar cell according to another embodiment of the present invention. In this embodiment, the third pipe 103 is connected to the fourth pipe 104, that is, the ozone generated by the ozone generator 10 is directly transported to the fourth pipe 104 (hot air pipe). The ozone is distributed to the passivation tank 30 by circulating hot air, which can also ensure that the ozone atmosphere in the passivation tank 30 is uniformly distributed.

[0033] Similarly, the ozone gas passivation equipment for crystalline silicon solar cells in this embodiment can also be configured to be shared with the preceding process, see details below. Figure 4 As shown, the ozone generator 10 in the control cabinet 100 is connected to the ozone water tank 50 via the fifth pipe 105, allowing ozone to be introduced into the ozone water tank 50 to form ozone water with a set concentration suitable for silicon wafer surface treatment. This saves on equipment investment and reduces equipment costs.

[0034] In another preferred embodiment, see Figure 4To improve the oxidation efficiency of silicon wafer surfaces within the passivation tank, a water vapor box 24 is installed on the second pipe 102, before the passivation tank 30. Water vapor is supplied to the passivation tank 30 through the pipe, maintaining a certain level of moisture within the passivation tank. The water vapor box 24 is connected to the control cabinet 100. This allows for optimal humidity control within the passivation tank 30. Furthermore, when the water level in the water vapor box 24 drops to a low level, it is automatically replenished with pure water to maintain continuous operation.

[0035] In the above embodiments of the present invention, one ozone generator corresponding to one passivation tank is used as an example for illustration. In actual use, depending on the size of the ozone generator and the specifications of the passivation tank, one ozone generator can be connected to multiple passivation tanks through multiple pipes, or multiple ozone generators can be used to correspond to multiple passivation tanks. This application does not make specific limitations in this regard.

[0036] This invention provides an ozone gas passivation device for silicon wafers used in crystalline silicon solar cells. Ozone gas is introduced simultaneously with the drying process after silicon wafer cleaning to grow an oxide layer on the wafer surface. This not only simplifies the production process but also ensures the uniformity and consistency of the oxide passivation layer on the silicon wafer surface, while improving production efficiency. Compared to existing wet oxidation processes that completely immerse the silicon wafer in a liquid environment, this device can monitor the humidity in the passivation tank in real time and control the water vapor box to ensure process consistency. Furthermore, unlike existing wet oxidation processes where the activity of the wet reagent changes throughout the production cycle, leading to inconsistent growth of the oxide layer within a single solution change cycle and affecting oxide layer uniformity, this invention allows for real-time control of the oxidation atmosphere in the passivation tank via a control cabinet, thus ensuring the uniformity of the oxide passivation layer across different batches of silicon wafers. Compared to dry oxidation processes, this invention offers superior production efficiency and is particularly suitable for BC battery production applications.

[0037] This invention is not limited to the embodiments described. Those skilled in the art can make some modifications or changes without departing from the spirit and scope of this invention. Therefore, the scope of protection of this invention is defined by the claims.

Claims

1. An ozone gas passivation device for crystalline silicon solar cells, characterized in that, The passivation equipment includes a control cabinet containing an ozone generator. Oxygen is introduced into the ozone generator through a first pipe, and its output is connected to the passivation tank through a second pipe and a back pressure valve through a third pipe. The second and third pipes are interconnected. A gas filter, a gas pressure regulating valve, and a pressure sensor are sequentially installed on the first pipe. An ozone concentration detector is installed on the second pipe before the passivation tank. The second pipe is connected to an annular flow equalization pipe inside the passivation tank, which has multiple evenly spaced air outlets. The passivation tank is connected to a heating device through a fourth pipe, through which hot air is introduced into the passivation tank to maintain a certain temperature.

2. An ozone gas passivation device for crystalline silicon solar cells, characterized in that, The passivation equipment includes a control cabinet containing an ozone generator. Oxygen is introduced into the ozone generator through a first pipe, and its output is connected to a second pipe and a back pressure valve through a third pipe. The second and third pipes are interconnected. A gas filter, a gas pressure regulating valve, and a pressure sensor are sequentially installed on the first pipe. An ozone concentration detector is installed on the second pipe before the passivation tank. The passivation tank is connected to a heating device through a fourth pipe, which introduces hot air into the tank to maintain a certain temperature. The second and fourth pipes are interconnected, and the ozone output from the ozone generator enters the passivation tank through the fourth pipe.

3. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, The ozone concentration detector is connected to the control cabinet and adjusts the ozone output of the ozone generator in real time based on the ozone concentration detection results.

4. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, The back pressure valve opens to release pressure when the gas pressure is too high, thus ensuring a constant gas pressure.

5. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, The heating device is connected to the control cabinet to control the temperature in the passivation tank to a set value.

6. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, At the output end of the fourth pipe, an ozone depletor is installed after the back pressure valve to deplete excess ozone before releasing it into the atmosphere.

7. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, The ozone generator in the control cabinet is connected to the ozone water tank through the fifth pipe, and ozone is introduced into the ozone water tank to form ozone water with a set concentration that can be used for silicon wafer surface treatment.

8. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, A water vapor box is installed on the second pipe before the passivation tank. Water vapor is supplied to the passivation tank through the pipe to maintain a certain water vapor atmosphere in the passivation tank.

9. The ozone gas passivation device for crystalline silicon solar cells as described in claim 9, characterized in that, The water vapor box is connected to the control cabinet, which keeps the humidity in the passivation tank within an optimized range, and automatically replenishes pure water to the water vapor box after the water level in the water vapor box is depleted to a low level.

10. The ozone gas passivation device for crystalline silicon solar cells as described in claim 1 or 2, characterized in that, In the passivation equipment, one ozone generator corresponds to one passivation tank, or one ozone generator is connected to multiple passivation tanks through multiple pipes, or multiple ozone generators correspond to multiple passivation tanks.

Images