A back contact battery with anti-LID effect and its preparation method

Abstract

The present invention belongs to the technical field of back-contact cells, specifically relating to a back-contact cell with resistance to the LID effect and a method for preparing the same. The method comprises: forming a velvet surface on the light-receiving surface of a silicon wafer and a second semiconductor opening region; then sequentially forming a passivation layer and an anti-reflection layer on the light-receiving surface of the silicon wafer, the passivation layer comprising a dense oxide layer and a phosphorus-doped and oxygen-doped amorphous silicon layer formed in sequence; wherein the dense oxide layer is formed by first oxidizing the layer with an ozone flow gradient, followed by a hydrogen plasma treatment; and the phosphorus-doped and oxygen-doped amorphous silicon layer is formed by continuously coating the layer with at least one gradient variation in the gas in the continuous presence of a glow plasma, wherein the at least one gradient variation in the gas causes the phosphorus doping concentration in the phosphorus-doped and oxygen-doped amorphous silicon layer to gradually increase from the inside out. The present invention can enhance the cell's resistance to LID attenuation while effectively improving the overall passivation level and cell efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of back contact batteries, and in particular relates to a back contact battery with an anti-LID effect and a preparation method thereof. Background Art

[0002] At present, the back contact battery manufacturing with relatively low equipment cost adopts the post-texturing process. The photoelectric conversion efficiency (also known as battery efficiency) of existing back contact batteries has been gradually improved. While achieving high conversion efficiency, it is also necessary to consider how to ensure that the battery cells still maintain high conversion efficiency when actually working outdoors. Therefore, in addition to conversion efficiency, reliability has also become a key factor in measuring the quality of crystalline silicon solar cells and modules. LID, or light induced degradation, is one of the indicators for testing the reliability of solar cells. The phenomenon of LID is that when the battery is placed under sunlight for irradiation experiments, the battery's power generation power, short-circuit current, and open-circuit voltage will decay exponentially, and reach a stable state after 12 hours of irradiation. At present, there is a certain LID condition in the back contact battery, and there is an urgent need for a back contact battery that is resistant to the LID effect. However, the conventional film layer in the existing back contact battery generally uses a film layer with different gradient changes in doping elements. The film layer usually adopts PECVD coating method. The process pressure curve in the coating process is as follows Figure 1 As shown, specifically:

[0003] The first gradient corresponds to the film thickness: inlet stable pressure - glow coating - glow end pumping;

[0004] The second gradient corresponds to the film thickness: re-intake stabilization pressure - glow coating - glow end pumping;

[0005] Repeat the above steps for the third gradient corresponding to the film thickness. This prevents the gases between the different gradient film layers from interfering with each other, resulting in better battery efficiency. However, due to the waiting time between each film layer due to the inflating and deflating action, the film surface is susceptible to oxidation due to the high temperature of the special gas inlet. Defects such as weak silicon-silicon bonds or silicon-hydrogen bonds between the different gradient film layers lead to poor film quality and poor LID performance.

[0006] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or public known technology. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defect of the existing back-contact battery in the prior art that it cannot take into account both the battery's anti-LID effect performance and battery efficiency at the same time, and to provide a back-contact battery with an anti-LID effect and a preparation method thereof, which can improve the battery's anti-LID attenuation performance while effectively improving the overall passivation level and battery efficiency.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a back-contact cell with an anti-LID effect, comprising: forming a first semiconductor layer on the backlight surface of a silicon wafer, then etching the first semiconductor layer to form second semiconductor opening regions with spaced distributions; then performing texturing and cleaning to form a textured surface on the light-receiving surface of the silicon wafer and the second semiconductor opening regions; then sequentially forming a passivation layer and an anti-reflection layer on the light-receiving surface of the silicon wafer, the passivation layer comprising a dense oxide layer and a phosphorus-doped and oxygen-doped amorphous silicon layer formed in sequence;

[0009] The formation of the dense oxide layer includes the steps of first oxidizing with an ozone flow gradient increase and then performing a hydrogen plasma treatment;

[0010] The formation of the phosphorus-doped and oxygen-doped amorphous silicon layer includes the steps of continuously coating by introducing at least one gradient change in the gas under the continuous presence of glow plasma, wherein the at least one gradient change in the gas introduced here causes the phosphorus doping concentration in the phosphorus-doped and oxygen-doped amorphous silicon layer to gradually increase from the inside to the outside.

[0011] In some preferred embodiments of the present invention, the thickness of the dense oxide layer is 0.5-2.5 nm, and the thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer is 3-15 nm.

[0012] In some preferred embodiments of the present invention, the thickness ratio of the dense oxide layer to the phosphorus-doped and oxygen-doped amorphous silicon layer is (0.03-0.83):1.

[0013] In some preferred embodiments of the present invention, in the dense oxide layer, ozone flow gradient oxidation is performed by atomic layer deposition, and the oxidation temperature is controlled to be 150-300°C.

[0014] In some preferred embodiments of the present invention, in the dense oxide layer, the hydrogen plasma treatment adopts a tubular PECVD method, and the treatment temperature of the hydrogen plasma treatment is controlled to be 350-600°C.

[0015] In some preferred embodiments of the present invention, the ozone flow rate gradient increase in the formation of the dense oxide layer includes at least three gradient increases: the ozone flow rate F1 of the first gradient is 1000sccm-3000sccm, the ozone flow rate F2 of the second gradient is 3000sccm-5000sccm, and the ozone flow rate F3 of the third gradient is 4000sccm-6000sccm, and F1 <F2<F3。

[0016] In some preferred embodiments of the present invention, the ozone introduction time of the first gradient is 5-10 s, the ozone introduction time of the second gradient is 10-15 s, and the ozone introduction time of the third gradient is 10-15 s.

[0017] In some preferred embodiments of the present invention, the stepwise increase of ozone flow rate gradient in the formation of the dense oxide layer further comprises: purging the chamber and pipelines with nitrogen after oxidation corresponding to each gradient.

[0018] In some preferred embodiments of the present invention, the conditions for hydrogen plasma treatment include:

[0019] The hydrogen flow rate is 5000-15000 sccm, and the processing time is 5-60 s;

[0020] and / or,

[0021] The deposition pressure is 1300-2500 mtorr and the power is 5kw-20kw.

[0022] In some preferred embodiments of the present invention, the phosphorus-doped and oxygen-doped amorphous silicon layer is formed by tubular PECVD, wherein the deposition temperature is controlled to be 350-600° C.; and / or the deposition pressure is controlled to be 1300-2500 mtorr and the power is controlled to be 5 kW-20 kW.

[0023] In some preferred embodiments of the present invention, the gases introduced into the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer include silane, a hydrogen mixture carrying phosphine, and laughing gas, the flow rate of silane is 800-2000sccm, the flow rate of the hydrogen mixture carrying phosphine is 50-1000sccm, and the flow rate of laughing gas is 100-2500sccm.

[0024] In some preferred embodiments of the present invention, the flow rates of silane and nitrous oxide are kept constant during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer, and the flow rate of the hydrogen mixture carrying phosphine is changed and increased in a gradient manner by 50-200 sccm; wherein,

[0025] The number of gradient changes is at least 3 times, and / or the flow rate of the hydrogen gas mixture containing phosphine is changed to a corresponding gradient change value every time the deposition thickness is 0.5-2 nm.

[0026] In some preferred embodiments of the present invention, the phosphorus-doped and oxygen-doped amorphous silicon layer has a phosphorus-doped concentration in the range of 1×10 19 cm -3 -9×10 20 cm -3 , the oxygen concentration range is 1×10 18 cm -3 -9×10 19 cm -3 .

[0027] In some preferred embodiments of the present invention, the anti-reflection layer is at least one of silicon nitride, oxygen-doped silicon nitride, and carbon-doped silicon nitride.

[0028] In some preferred embodiments of the present invention, the anti-reflection layer includes carbon-doped silicon nitride, and the formation of carbon-doped silicon nitride includes the steps of continuous coating by introducing at least one gradient change in the gas in the continuous presence of glow plasma, wherein the at least one gradient change in the gas introduced here causes the refractive index of the carbon-doped silicon nitride to gradually decrease from the inside to the outside.

[0029] In some preferred embodiments of the present invention, the carbon doping concentration in carbon-doped silicon nitride is 1×10 19 cm -3 -9×10 21 cm -3 , nitrogen doping concentration is 1×10 19 cm -3 -9×10 21 cm -3 ; and / or, the refractive index of carbon-doped silicon nitride varies in the range of 1.5-2.1.

[0030] In some preferred embodiments of the present invention, carbon-doped silicon nitride is deposited by tubular PECVD, and the deposition conditions include: controlling the deposition temperature to be 350-600° C., the deposition pressure to be 1300-2500 mtorr, and the power to be 5 kW-20 kW.

[0031] In some preferred embodiments of the present invention, the gases introduced into the formation of carbon-doped silicon nitride include silane, ammonia and methane, the flow rate of silane is 800-2000 sccm, the flow rate of ammonia is 6000-15000 sccm, and the flow rate of methane is 20-1000 sccm, preferably 100-1000 sccm.

[0032] In some preferred embodiments of the present invention, the gases introduced into the formation of carbon-doped silicon nitride include silane, ammonia, and methane, during which the flow rate of silane is controlled to remain unchanged, while the flow rates of ammonia and methane are changed in gradients and satisfy the following conditions:

[0033] The flow rates of ammonia and methane were changed every 20-40 nm deposition thickness, with the incremental change range of ammonia flow rate being 1000-2000 sccm and that of methane flow rate being 50-150 sccm.

[0034] and / or,

[0035] The initial flow rate of ammonia is in the range of 6000-8000 sccm, and the initial flow rate of methane is in the range of 0-100 sccm.

[0036] In some preferred embodiments of the present invention, the thickness of the carbon-doped silicon nitride layer is 80-160 nm, and / or the thickness ratio of the carbon-doped silicon nitride layer to the phosphorus-doped and oxygen-doped amorphous silicon layer is (5.3-53.3):1.

[0037] In some preferred embodiments of the present invention, the preparation method further comprises:

[0038] After forming the first semiconductor layer on the backlight side of the silicon wafer, a mask layer is also formed, and then the second semiconductor opening area is formed; and in the final cleaning step of texturing cleaning, it is selected according to demand whether to remove the mask layer outside the second semiconductor opening area on the backlight side of the silicon wafer;

[0039] After forming the anti-reflection layer, cleaning the second semiconductor opening region;

[0040] A second semiconductor layer is then deposited on the back side;

[0041] Performing a second etching operation on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region;

[0042] depositing a conductive film layer on the resulting back surface;

[0043] Performing a third etching opening on a portion of the conductive film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation trench;

[0044] Forming metal electrodes on the outer surfaces of the corresponding conductive film layers in the areas where the first semiconductor opening region and the second semiconductor opening region are located;

[0045] Among them, the first semiconductor layer includes a first passivation layer and a first doped silicon layer arranged in sequence, the second semiconductor layer includes a second passivation layer and a second doped silicon layer arranged in sequence, the first passivation layer and the second passivation layer are each independently a tunneling oxide layer or an intrinsic silicon layer, and the first doped silicon layer and the second doped silicon layer are each independently polycrystalline silicon, amorphous silicon or microcrystalline silicon.

[0046] In a second aspect, the present invention provides a back-contact battery with resistance to LID effect, which is prepared by the preparation method of the back-contact battery with resistance to LID effect described in the first aspect.

[0047] Beneficial effects:

[0048] The present invention adopts the above technical scheme, especially in the post-texturing method, to continuously coat phosphorus-doped and oxygen-doped amorphous silicon layers with gradually increasing phosphorus doping. In this continuous coating method of phosphorus-doped and oxygen-doped amorphous silicon layers, there is no need to evacuate between layers with different gradients, and the glow plasma does not need to be disconnected, so that a natural transition state is formed between film thicknesses corresponding to different gradients. The bond-to-bond bonding between film thicknesses corresponding to different gradients is better, the film layer quality is better, and it has better anti-LID attenuation performance. Combined with the continuous coating method of gradually increasing phosphorus doping, it is beneficial to improve the bond-to-bond bonding in the film layer, which is beneficial to improve The high density of the film layer further improves the battery's resistance to LID attenuation. At the same time, due to continuous coating without stopping, high energy accumulates between film layers with different gradients. The phosphorus atoms doped in the film layer may partially migrate to the bulk silicon (i.e., silicon wafer) as the temperature increases, destroying the interface passivation and generating a higher interface state density. Therefore, the present invention also adopts the steps of first oxidizing with an ozone flow gradient and then performing hydrogen plasma treatment to form a dense oxide layer, effectively blocking the penetration of phosphorus. It can effectively improve the overall passivation level and battery efficiency while maintaining the battery's good resistance to LID attenuation performance. Among them, the ozone flow rate is gradually increased for oxidation, and the ozone flow rate is getting larger and larger, and the degree of oxidation is becoming more and more complete, which is conducive to the formation of a dense film layer. The hydrogen plasma treatment removes the silicon and oxygen dangling bonds with a large number of defects on the surface of the silicon wafer's velvet surface, retaining a dense silicon surface oxide layer, which is conducive to improving the passivation level of subsequent film layers. At the same time, it effectively blocks the infiltration of phosphorus in the phosphorus-doped and oxygen-doped amorphous silicon layer, which can significantly improve the overall passivation level. Without a dense oxide layer, the phosphorus element in the phosphorus-doped and oxygen-doped amorphous silicon layer may migrate to the silicon wafer surface during the deposition process, resulting in severe carrier recombination and a significant decrease in passivation performance. At the same time, the passivation layer process can also effectively passivate the velvet on the back side, effectively reducing the interface defect state density of the velvet surface, thereby synergistically improving the passivation effect on the front and back sides.

[0049] Among them, continuous coating under continuous glow plasma conditions refers to continuous glow deposition between different gradient corresponding film thicknesses in a single chamber, such as Figure 2 As shown, compared to Figure 1 Compared with the conventional process, the present invention does not require evacuation in the middle, the glow plasma does not need to be disconnected, and the glow is not stopped to replace the gas for continuous coating, so that a natural transition state is formed between the film thicknesses corresponding to different gradients. The energy between the layers of different gradients gradually accumulates, the bond bonding force between the film layers of different gradients is better, and the film quality is better. This not only makes the battery have better anti-LID attenuation performance, but also reduces the multiple vacuuming and inflation actions during the coating process, shortens the coating cycle time to a certain extent, and is conducive to improving the utilization rate of the equipment. At the same time, the present invention sets a continuous gradient doping film layer. Because the doping concentration needs to be continuous, the airflow of the doping gas needs to be gradually and continuously increased, so there is no interference problem between different gases.

[0050] In the preferred embodiment of the present invention, the anti-reflection layer adopts continuously coated carbon-doped silicon nitride, which is beneficial to improving the density of the film layer, improving the corrosion resistance and optical properties of the battery, and further improving the battery efficiency in combination with a specific passivation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 This is a coating process curve of a multilayer film deposited by PECVD using conventional technology for passivation layer.

[0053] Figure 2 This is a PECVD deposition coating process curve diagram of the passivation layer phosphorus-doped and oxygen-doped amorphous silicon layer of the present invention.

[0054] Figure 3 It is a structural schematic diagram of a specific embodiment of the back contact battery of the present invention.

[0055] Description of Reference Numerals

[0056] Silicon wafer 1, tunneling silicon oxide layer 2, N-type doped polysilicon layer 3, dense oxide layer 51, phosphorus-doped and oxygen-doped amorphous silicon layer 52, anti-reflection layer 6, intrinsic hydrogenated amorphous silicon layer 7, P-type doped amorphous silicon layer 8, transparent conductive film layer 9, metal electrode 10. DETAILED DESCRIPTION

[0057] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0058] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0059] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein. The terms "optional" and "optional" both mean that a range may or may not be included (or may or may not be present).

[0060] In the present invention, the area close to the silicon wafer is considered as the inside, and the area far from the silicon wafer is considered as the outside.

[0061] In a first aspect, the present invention provides a method for preparing a back-contact battery with resistance to LID effect, comprising: forming a first semiconductor layer on the backlight surface of a silicon wafer, then etching the first semiconductor layer to form a second semiconductor opening area with spaced distributions; then performing texturing and cleaning to form a texturing surface on the light-receiving surface of the silicon wafer and the second semiconductor opening area; then forming a passivation layer and an anti-reflection layer in sequence on the light-receiving surface of the silicon wafer, the passivation layer comprising a dense oxide layer and a phosphorus-doped and oxygen-doped amorphous silicon layer formed in sequence.

[0062] The formation of the dense oxide layer includes the steps of first oxidizing with an ozone flow gradient increase and then performing hydrogen plasma treatment.

[0063] The formation of the phosphorus-doped and oxygen-doped amorphous silicon layer includes the steps of continuously coating by introducing at least one gradient change in the gas under the continuous presence of glow plasma, wherein the at least one gradient change in the gas introduced here causes the phosphorus doping concentration in the phosphorus-doped and oxygen-doped amorphous silicon layer to gradually increase from the inside to the outside.

[0064] In some preferred embodiments of the present invention, the thickness of the dense oxide layer is 0.5-2.5 nm.

[0065] Preferably, the thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer is 3-15 nm, for example, specifically, it can be 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc., and the range between any two point values, and more preferably 3-10 nm.

[0066] In some preferred embodiments of the present invention, the thickness ratio of the dense oxide layer to the phosphorus-doped and oxygen-doped amorphous silicon layer is (0.03-0.83):1, (0.080-0.830):1. Using a dense oxide layer and a phosphorus-doped and oxygen-doped amorphous silicon layer with a suitable thickness ratio is more conducive to improving the passivation effect and preventing elemental phosphorus from penetrating into the bulk silicon.

[0067] In some preferred embodiments of the present invention, in the dense oxide layer, ozone flow gradient increasing oxidation adopts atomic layer deposition. More preferably, the ozone oxidation temperature is controlled at 150-300 °C.

[0068] In some preferred embodiments of the present invention, in the dense oxide layer, hydrogen plasma treatment adopts tube PECVD. More preferably, the treatment temperature of the hydrogen plasma treatment is controlled at 350-600 °C.

[0069] In some preferred embodiments of the present invention, the ozone flow gradient increase in the formation of the dense oxide layer includes at least three gradient increases: the ozone flow F1 in the first gradient is 1000 sccm-3000 sccm, the ozone flow F2 in the second gradient is 3000 sccm-5000 sccm, the ozone flow F3 in the third gradient is 4000 sccm-6000 sccm, and F1 < F2 < F3. In this preferred scheme, the ozone flow increases in a suitable gradient, and the oxidation degree is more and more sufficient, which is more conducive to improving the optimal distribution of the film layer density, thus facilitating the improvement of the uniformity of oxidation at the edge and in the middle of the silicon wafer, and more conducive to the improvement of battery performance.

[0070] In some preferred embodiments of the present invention, the ozone introduction time in the first gradient is 5-10 s, the ozone introduction time in the second gradient is 10-15 s, and the ozone introduction time in the third gradient is 10-15 s. More preferably, the ozone introduction times in the first gradient, the second gradient, and the third gradient gradually increase, which is more conducive to improving the density of oxidation.

[0071] In some preferred embodiments of the present invention, the ozone flow rate gradient increase during the formation of the dense oxidation layer further includes: purging the chamber and pipelines with nitrogen after each corresponding oxidation step, which is more conducive to improving ventilation stability and oxidation density. In a specific embodiment, purging the chamber and pipelines with nitrogen after each corresponding oxidation step includes: purging the chamber and pipelines with nitrogen after a first gradient ozone oxidation step, purging the chamber and pipelines with nitrogen after a second gradient ozone oxidation step, and purging the chamber and pipelines with nitrogen after a third gradient ozone oxidation step.

[0072] In some preferred embodiments of the present invention, the conditions for hydrogen plasma treatment include: a hydrogen flow rate of 5000-15000 sccm and a treatment time of 5-60 seconds. Using hydrogen plasma treatment under appropriate conditions is more conducive to forming a dense surface state of the oxide layer.

[0073] In some preferred embodiments of the present invention, the conditions for hydrogen plasma treatment include: a deposition pressure of 1300-2500 mtorr and a power of 5 kW-20 kW.

[0074] In some preferred embodiments of the present invention, the phosphorus-doped and oxygen-doped amorphous silicon layer is formed by tubular PECVD, wherein the deposition temperature is preferably controlled to be 350-600°C.

[0075] In some preferred embodiments of the present invention, during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer, the deposition pressure is controlled to be 1300-2500 mtorr and the power is controlled to be 5 kW-20 kW.

[0076] In some preferred embodiments of the present invention, the gases introduced during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer include silane, a hydrogen mixture carrying phosphine, and nitrous oxide. Further preferably, the flow rate of silane is controlled to be 800-2000 sccm, the flow rate of the hydrogen mixture carrying phosphine is controlled to be 50-1000 sccm, and the flow rate of nitrous oxide is controlled to be 100-2500 sccm. The gradient variation can vary within this range.

[0077] During the deposition of the phosphorus-doped and oxygen-doped amorphous silicon layer, at least one of the gases introduced changes in a gradient, which means, for example, that the gases introduced include silane, a hydrogen mixture carrying phosphine, and nitrous oxide. This can be achieved by keeping the flow rates of two of the gases constant and one of the gases changing in a step-by-step manner; or keeping one gas constant and two of the gases changing in a step-by-step manner; or all three gases changing in a step-by-step manner.

[0078] In some preferred embodiments of the present invention, during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer, the flow rates of silane and nitrous oxide are maintained constant, while the flow rate of the hydrogen mixture carrying phosphine is gradually increased. More preferably, the flow rate is increased by 50-200 sccm, which is more conducive to achieving a good passivation effect on the silicon wafer surface.

[0079] Further preferably, the number of gradient changes in the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer is at least 3 times, more preferably 3-5 times, for example, 3 times, 4 times, or 5 times. Using the preferred number of gradient changes to form the phosphorus-doped and oxygen-doped amorphous silicon layer is more conducive to improving the bonding strength of the bonds in the film layer and improving the quality of the film layer.

[0080] Further preferably, during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer, the flow rate of the hydrogen mixed gas with phosphine is set to a corresponding gradient change value every time the deposition thickness is 0.5-2 nm, which is more conducive to ensuring the stability of passivation and improving the anti-LID performance of the film layer.

[0081] In the continuous coating process of the present invention, the doping between the film thicknesses corresponding to different gradients of the same film layer is continuously transitioned. Because the gas flow rate is gradually increased from the flow rate of the previous layer to the set flow rate during the process of changing the doping concentration, the doping in the transition zone is continuously changed. For example, when three gradients of phosphine doping flow rate are set, in the conventional intermittent coating method, the gas flow rate of each layer is fixed at 20 sccm, 40 sccm, and 60 sccm, respectively, and there are gas filling and exhausting actions between different gradients; while in the continuous coating method, the flow rate of each layer is 0-20 The sccm change eventually stabilizes at 20sccm; the 20-40sccm change eventually stabilizes at 40sccm, and the 40-60sccm change eventually stabilizes at 60sccm; the flow rate in the transition zone continuously changes from 0-20sccm, 20-40sccm, and 40-60sccm. There is no need to inflate or pump air between different gradients, and there is no need to restart the glow, so that a natural transition state is formed between the film thicknesses corresponding to different gradients. The bond bonding force between the film thicknesses corresponding to different gradients is better, the film layer quality is better, and it has better anti-LID attenuation performance.

[0082] In some preferred embodiments of the present invention, the phosphorus-doped and oxygen-doped amorphous silicon layer has a phosphorus-doped concentration in the range of 1×10 19 cm -3 -9×10 20 cm -3 , the oxygen concentration range is 1×10 18 cm -3 -9×10 19 cm -3 The use of phosphorus-doped and oxygen-doped amorphous silicon layers with appropriate element doping is more conducive to ensuring passivation while improving the film's anti-LID attenuation performance.

[0083] In some preferred embodiments of the present invention, the anti-reflection layer is at least one of silicon nitride, oxygen-doped silicon nitride, and carbon-doped silicon nitride.

[0084] In some preferred embodiments of the present invention, the antireflection layer comprises carbon-doped silicon nitride. Formation of the carbon-doped silicon nitride includes the steps of continuously depositing the film by introducing at least one gradient in the gas in the continuous presence of a glow plasma. The at least one gradient in the gas causes the refractive index of the carbon-doped silicon nitride to gradually decrease from the inside outward. Continuously depositing the carbon-doped silicon nitride facilitates improved film density and corrosion resistance, balancing both corrosion resistance and optical performance.

[0085] Carbon-doped silicon nitride also adopts a continuous coating method, that is, there is no gas extraction between the corresponding layers of different gradients, and the changes between layers are achieved by controlling the gradient change of at least one of the gases introduced; for example, the gases introduced in the formation of carbon-doped silicon nitride include silane, ammonia and methane. Specifically, the flow rates of two of the gases remain unchanged, and one of the gases changes in steps, or one gas remains unchanged, and two of the gases change in steps, or all three gases change in steps.

[0086] In some preferred embodiments of the present invention, the gases introduced during the formation of carbon-doped silicon nitride include silane, ammonia, and methane, during which the flow rate of silane is kept constant, while the flow rates of ammonia and methane are changed in gradients.

[0087] It is further preferred that the formation of carbon-doped silicon nitride satisfies the following requirements: the flow rates of ammonia and methane change once every 20-40 nm deposition thickness, the incremental change amplitude of the ammonia flow rate is 1000-2000 sccm, and the incremental change amplitude of the methane flow rate is 50-150 sccm, more preferably 50-130 sccm. The incremental change amplitude refers to adding the corresponding incremental change amplitude to the previous gradient flow rate. For example, when the incremental change amplitude of the ammonia flow rate is 1000 sccm, the ammonia flow gradient changes in the order of initial flow rate, initial flow rate + 1000 sccm, and so on according to a gradient change of 1000 sccm. The adoption of this preferred solution is more conducive to ensuring the anti-reflection effect and anti-LID attenuation effect of the film layer.

[0088] It is further preferred that the formation of carbon-doped silicon nitride satisfies the following conditions: the initial flow rate of ammonia is in the range of 6000-8000 sccm, and the initial flow rate of methane is in the range of 0-100 sccm. This preferred solution is more conducive to ensuring the passivation and anti-LID degradation performance of the film layer.

[0089] In some preferred embodiments of the present invention, the carbon doping concentration in carbon-doped silicon nitride is 1×10 19 cm -3 -9×10 21 cm -3, more preferably 1×10 19 cm -3 -4×10 21 cm -3 , the nitrogen doping concentration is 1×10 19 cm -3 -9×10 21 cm -3 .

[0090] Preferably, in the present invention, the refractive index of carbon-doped silicon nitride varies in the range of 1.5-2.1, which is more conducive to the anti-reflection effect of the front film layer.

[0091] In some preferred embodiments of the present invention, carbon-doped silicon nitride is deposited using tubular PECVD. Further preferably, carbon-doped silicon nitride deposition conditions include: controlling the deposition temperature to be 350-600° C., the deposition pressure to be 1300-2500 mtorr, and the power to be 5 kW-20 kW.

[0092] In some preferred embodiments of the present invention, the gases introduced into the formation of carbon-doped silicon nitride include silane, ammonia and methane, the flow rate of silane is 800-2000 sccm, the flow rate of ammonia is 6000-15000 sccm, and the flow rate of methane is 20-1000 sccm, preferably 100-1000 sccm.

[0093] In some preferred embodiments of the present invention, the thickness of carbon-doped silicon nitride is 80-160 nm.

[0094] In the present invention, the thickness ratio of the carbon-doped silicon nitride layer to the phosphorus-doped and oxygen-doped amorphous silicon layer is (5.3-53.3):1, preferably (5.3-11.0):1. The preferred embodiment of the present invention is more conducive to improving the passivation of the film layer while achieving a good anti-reflection effect.

[0095] In some preferred embodiments of the present invention, the preparation method further includes: forming a mask layer after forming the first semiconductor layer on the backlight side of the silicon wafer, and then forming the second semiconductor opening region; and in the final cleaning step of the texturing cleaning, whether to remove the mask layer outside the second semiconductor opening region on the backlight side of the silicon wafer is determined as needed. The type and thickness of the mask layer can refer to the existing technology. Exemplarily, the mask layer is at least one of silicon nitride, silicon oxide, silicon oxynitride, or nitrogen-containing polysilicon, and the mask layer thickness is 50-100 nm.

[0096] The preparation method of the present invention further comprises the step of polishing both sides of the silicon wafer before forming the first semiconductor layer on the backlight side of the silicon wafer.

[0097] In some preferred embodiments of the present invention, the preparation method further comprises: cleaning the second semiconductor opening region after forming the anti-reflection layer, which is more conducive to improving the passivation effect of the second semiconductor layer.

[0098] Further preferably, the method for cleaning the second semiconductor opening region includes using a hydrofluoric acid solution for cleaning, wherein the mass concentration of hydrofluoric acid in the hydrofluoric acid solution is 1%-10%, and the cleaning conditions include: a processing temperature of 20° C.-30° C., and a cleaning time of 30-200 s.

[0099] In some preferred embodiments of the present invention, the preparation method may further include other conventional steps, for example, may include:

[0100] A second semiconductor layer is then deposited on the back side;

[0101] Performing a second etching operation on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region;

[0102] depositing a conductive film layer on the resulting back surface;

[0103] Performing a third etching opening on a portion of the conductive film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation trench;

[0104] Metal electrodes are respectively formed on the outer surfaces of the conductive film layers corresponding to the areas where the first semiconductor opening region and the second semiconductor opening region are located.

[0105] Further preferably, the first semiconductor layer includes a first passivation layer and a first doped silicon layer disposed in sequence, and the second semiconductor layer includes a second passivation layer and a second doped silicon layer disposed in sequence, the first passivation layer and the second passivation layer are each independently a tunneling oxide layer or an intrinsic silicon layer, and the first doped silicon layer and the second doped silicon layer are each independently polycrystalline silicon, amorphous silicon, or microcrystalline silicon. One of the first doped silicon layer and the second doped silicon layer is N-type, and the other is P-type.

[0106] In a preferred embodiment of the present invention, the first semiconductor layer comprises a tunneling oxide layer and a first doped polycrystalline silicon layer, arranged in sequence. The second semiconductor layer comprises an intrinsic silicon layer and a second doped silicon layer, arranged in sequence. The intrinsic silicon layer is preferably an intrinsic amorphous silicon layer (more preferably an intrinsic hydrogenated amorphous silicon layer), and the second doped silicon layer is amorphous silicon or microcrystalline silicon. In this preferred embodiment, the present invention utilizes a combined passivation structure, combined with a front-side structure formed using a specific method, to further enhance cell conversion efficiency.

[0107] The thickness and corresponding doping concentration of the tunnel oxide layer or intrinsic silicon layer, the first doped polysilicon layer, and the second doped silicon layer of the present invention can refer to the range of the prior art and can be used in the present invention. For example, the thickness of the tunnel oxide layer is 1-2nm, the thickness of the intrinsic silicon layer is 5-15nm; the thickness of the second doped silicon layer is 7-45nm, and the effective doping concentration is 2e18cm -3-3e20cm -3 The thickness of the first doped polysilicon layer is 80-150nm, and the effective doping concentration is greater than 5e18cm -3 .

[0108] In a second aspect, the present invention provides a back-contact cell with LID resistance, produced by the method for producing a back-contact cell with LID resistance described in the first aspect. The back-contact cell of the present invention achieves both good LID resistance and excellent passivation, thereby improving cell efficiency.

[0109] The embodiments of the present invention are described in detail below, which are exemplary and only used to explain the present invention, and are not to be construed as limiting the present invention.

[0110] Example 1

[0111] A back contact battery, the structure of which is as follows Figure 3 As shown, it is prepared by the following method:

[0112] S1, silicon wafer 1 (N-type single crystal silicon wafer) double-sided polishing.

[0113] S2. Forming a first semiconductor layer and a mask layer on the back side of the silicon wafer 1:

[0114] The first semiconductor layer includes a tunneling silicon oxide layer 2 and an N-type doped polysilicon layer 3. The mask layer is silicon nitride. The thickness of the tunneling silicon oxide layer 2 is 1.5 nm, the thickness of the N-type doped polysilicon layer 3 is 120 nm, and the effective doping concentration is 9e19 cm -3 , the mask layer thickness is 80nm.

[0115] S3, etching an opening on the back side of the silicon wafer 1 for the first time to form a second semiconductor opening region W2;

[0116] S4, texturing and cleaning the opening areas on the front and back sides of the silicon wafer 1, and during the texturing process on the front side, removing the silicon nitride mask layer on the back side of the silicon wafer through the final cleaning solution;

[0117] S5. Forming a passivation layer and an anti-reflection layer 6 on the front surface of the silicon wafer 1:

[0118] The passivation layer is a combination of a dense oxide layer 51 and a phosphorus-doped and oxygen-doped amorphous silicon layer 52 arranged in sequence;

[0119] The thickness of the dense oxide layer 51 is 1.0 nm, and it is formed by ozone oxidation combined with hydrogen plasma treatment, specifically: the ozone oxidation temperature is 200°C, and the ozone flow rate in the first stage of the ALD equipment is 1500 sccm, the ozone introduction time is 8 seconds, and then nitrogen is used to purge the chamber and pipelines; in the second stage, the ozone flow rate is 4000 sccm, the ozone introduction time is 12 seconds, and then nitrogen is used to purge the chamber and pipelines; in the third stage, the ozone flow rate is 5000 sccm, the ozone introduction time is 15 seconds, and then nitrogen is used to purge the chamber and pipelines.

[0120] After oxidation, hydrogen plasma treatment is performed using a tubular PECVD device at a temperature of 460° C., a hydrogen flow rate of 7000 sccm, a deposition pressure of 1500 mtorr, a power of 10 kW, and a treatment time of 40 s.

[0121] The thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer 52 is 9 nm. During deposition, a tubular PECVD device is used for deposition at a deposition temperature of 460° C., a deposition pressure of 1500 mtorr, and a power of 10 kW. During deposition, the flow rate of silane is 1600 sccm, the flow rate of nitrous oxide is 800 sccm, and the flow rate of the hydrogen mixture carrying phosphine (2% by volume of phosphine mixed with 98% of hydrogen) varies in the range of 50-250 sccm. In the present invention, during the deposition process, the silane and nitrous oxide gases remain unchanged, and the flow rate of phosphine is increased by a fixed gradient of 50 sccm with an amplitude of change every 1 nm of thickness. That is, when depositing a thickness of 0-1 nm, the phosphine flow rate is set to 50 sccm. Because the glow coating is started without waiting for the gas to stabilize, the phosphine flow rate varies in the range of 0-250 sccm. The phosphine flow rate is set to 100 sccm, and the phosphine flow rate is set to 50 sccm until it stabilizes at 50 sccm; when the thickness is 1-2 nm, the phosphine flow rate is set to 100 sccm, and the phosphine flow rate is set to 50-100 sccm until it stabilizes at 100 sccm; when the thickness is 2-3 nm, the phosphine flow rate is set to 150 sccm, and the phosphine flow rate is set to 100-150 sccm until it stabilizes at 150 sccm; when the thickness is 3-4 nm, the phosphine flow rate is set to 200 sccm, and the phosphine flow rate is set to 150-200 sccm until it stabilizes at 200 sccm; when the thickness is 4-5 nm, the phosphine flow rate is set to 250 sccm, and the phosphine flow rate is set to 200-250 sccm until it stabilizes at 250 sccm, and so on until the thickness reaches 9 nm. The phosphorus doping concentration in the phosphorus-doped and oxygen-doped amorphous silicon layer 52 is in the range of 5×10 19 cm -3 -4×10 20 cm -3 , the oxygen doping concentration is 7.9×10 18 cm -3; It is calculated that the thickness ratio of the dense oxide layer 51 and the phosphorus-doped and oxygen-doped amorphous silicon layer 52 is 0.111:1.

[0122] The anti-reflection layer 6 of the present invention is carbon-doped silicon nitride. The carbon-doped silicon nitride is deposited using a PECVD device at a deposition temperature of 460°C, a deposition pressure of 1600 mtorr, and a power of 10 kW. When depositing carbon-doped silicon nitride, the flow rate of silane is 1000 sccm, and the flow rates of ammonia and methane are changed in a gradient. Specifically, the flow rate of silane is kept constant, and the flow rates of ammonia and methane are changed in increments of 30 nm. The initial flow rate of ammonia is 6000 sccm, and the subsequent flow rate is 1500 sccm. The flow rate of the ammonia gas was increased by 6000 sccm, 7500 sccm, and 9000 sccm every 30 nm. The initial flow rate of methane was 50 sccm, and then the flow rate was increased by 100 sccm every 30 nm. The flow rate of methane was increased by 50 sccm, 150 sccm, and 250 sccm, which was divided into three gradient changes. The thickness of the carbon-doped silicon nitride was 90 nm, and the carbon concentration in the carbon-doped silicon nitride ranged from 2.3 × 10 19 cm -3 -1.5×10 21 cm -3 , nitrogen doping concentration ranges from 5.6×10 19 cm -3 -8.9×10 21 cm -3 The refractive index of the carbon-doped silicon nitride decreases gradually from 2.1 to 1.5. Calculation shows that the thickness ratio of the carbon-doped silicon nitride to the phosphorus-doped and oxygen-doped amorphous silicon layer 52 is 10:1.

[0123] S6, cleaning the second semiconductor opening region;

[0124] The second semiconductor open area is cleaned with an HF solution, wherein the HF mass concentration is 2%, the mass percentage of deionized water is the balance, the treatment temperature is 25°C, and the cleaning time is 100s;

[0125] S7, forming a second semiconductor layer on the back side of the silicon wafer 1;

[0126] The second semiconductor layer is a stack of an intrinsic hydrogenated amorphous silicon layer 7 with a thickness of 8 nm and a P-type doped amorphous silicon layer 8; the P-type doped amorphous silicon layer 8 has a thickness of 15 nm and an effective doping concentration of 3e19 cm -3 .

[0127] S8, etching an opening on the back side of the silicon wafer 1 for the second time to form a first semiconductor opening region W1;

[0128] S9, depositing a transparent conductive film layer 9 with a thickness of 60 nm on the back side of the silicon wafer 1;

[0129] S10, etching an opening on the back side of the silicon wafer 1 for the third time to form an isolation trench W3; after etching, the resistance between the first semiconductor and the second semiconductor is greater than 1 kΩ.

[0130] S11 , forming metal electrodes 10 on the outer surfaces of corresponding areas of the first semiconductor opening region W1 and the second semiconductor opening region W2 on the back side of the silicon wafer 1 .

[0131] Example 2

[0132] The process was carried out in accordance with Example 1, except that the ozone flow rate gradient during the formation of dense oxide layer 51 was increased to two levels, or stages. Specifically, the third stage corresponding to Example 1 was omitted, and only the first and second stages of ozone oxidation were performed. The calculated thickness ratio of dense oxide layer 51 to phosphorus-doped and oxygen-doped amorphous silicon layer 52 was 0.0778:1.

[0133] Example 3

[0134] The same process as in Example 1 was followed, except that the number of gradient changes in the flow rate of the hydrogen mixture carrying phosphine during the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer 52 was different. Specifically, the final gradient change in the flow rate of the hydrogen mixture carrying phosphine in Example 1 was omitted (i.e., the gradient change was continued until the thickness reached 8 nm according to the variation pattern in Example 1, and the gradient change to 9 nm was omitted). At this point, the thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer 52 was 8 nm. The calculated thickness ratio of the carbon-doped silicon nitride to the phosphorus-doped and oxygen-doped amorphous silicon layer 52 was 11.25:1.

[0135] Example 4

[0136] The process was carried out in accordance with Example 1, except that the thickness of the phosphorus- and oxygen-doped amorphous silicon layer 52 was 11 nm. The corresponding process adjustments required to meet this thickness were as follows: the thickness of the first layer in Example 1 was doubled, while the other gradient thicknesses, the number of gradient changes, and the flow rate amplitude remained unchanged. Calculated thickness ratios of the carbon-doped silicon nitride layer to the phosphorus- and oxygen-doped amorphous silicon layer 52 were 8.18:1.

[0137] Example 5

[0138] The same method as in Example 1 was used, except that the flow rates of ammonia and methane in the carbon-doped silicon nitride anti-reflection layer 6 remained constant at 8500 sccm and 200 sccm, respectively, and the refractive index of the carbon-doped silicon nitride remained constant at 2.05. The carbon doping concentration of the carbon-doped silicon nitride was 3.3×10 19 cm -3 , nitrogen doping concentration is 8.2×10 19 cm -3 The thickness is 100 nm. Calculation shows that the thickness ratio of the carbon-doped silicon nitride layer to the phosphorus-doped and oxygen-doped amorphous silicon layer 52 is 11.11:1.

[0139] Example 6

[0140] The same method as in Example 1 was used, except that the methane flow rate during the deposition of the carbon-doped silicon nitride anti-reflection layer 6 was increased by 150 sccm. The initial methane flow rate, the number of changes, and the thickness were the same as those in Example 1. At this time, the refractive index of the carbon-doped silicon nitride varied from 1.75 to 1.98. The carbon doping concentration of the carbon-doped silicon nitride was 2.8×10 20 -5.6×10 21 cm -3 .

[0141] Comparative Example 1

[0142] The process is carried out with reference to Example 1, except that the dense oxide layer 51 is not provided, but the phosphorus-doped and oxygen-doped amorphous silicon layer 52 of Example 1 is directly deposited on the light-receiving surface.

[0143] Comparative Example 2

[0144] The process is carried out with reference to Example 1, except that the ozone flow rate does not increase during the formation of the dense oxide layer 51 , but remains constant at 1000 sccm, and the ozone introduction time remains unchanged.

[0145] Comparative Example 3

[0146] Refer to Example 1, except that the deposition of the phosphorus-doped and oxygen-doped amorphous silicon layer 52 does not adopt a continuous coating method, but adopts a conventional method of intermittent glow with exhaust and intake between different gradients of film thickness: specifically, after each gradient change to the preset value and glow coating to the target thickness, the glow is terminated and exhaust is performed, and then the air is intaken to stabilize the pressure to the preset value corresponding to the next gradient change and glow coating to the target thickness, and this cycle is repeated. The gradient change is the same as that in Example 1.

[0147] Test Case

[0148] The back-contact cells obtained in the above examples and comparative examples were subjected to performance testing, and the results are shown in Table 1. The LID resistance attenuation ratio was tested using a halogen lamp with a light intensity set to 1000 W / m², simulating a standard solar spectrum, for 96 hours. The power attenuation ratio of the cell before and after the cumulative irradiation was evaluated to determine the light decay. The attenuation ratio is calculated as (cell power before cumulative irradiation - cell power after cumulative irradiation) / cell power before cumulative irradiation. The smaller the pre-LID attenuation ratio, the stronger the LID resistance and the higher the cell stability.

[0149] The test method for acid-resistant thickness difference is: the absolute value of the thickness difference before and after the battery with membrane structure is immersed in 5wt% HF solution at room temperature for 120s is called the corrosion resistance thickness difference, which represents the corrosion resistance performance.

[0150] Table 1

[0151]

[0152] It can be seen from the above results that, compared with the comparative example, the embodiment of the present invention can improve the anti-LID attenuation performance of the battery, while effectively improving the overall passivation level and battery efficiency, and the short-circuit current is high, which is beneficial to improving the corrosion resistance and optical performance of the battery.

[0153] Furthermore, according to Example 1 and Examples 2-6, it can be seen that the preferred solution of the present invention is more conducive to improving the anti-LID degradation performance of the battery, while effectively improving the overall passivation level and battery efficiency.

[0154] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a back contact battery with resistance to LID effect, comprising: A first semiconductor layer is formed on the backlight side of the silicon wafer, and then the first semiconductor layer is etched to form second semiconductor opening regions distributed at intervals; Then, texturing cleaning is performed to form a textured surface on the light-receiving surface of the silicon wafer and the second semiconductor opening regions; thereafter, a passivation layer and an antireflection layer are sequentially formed on the light-receiving surface of the silicon wafer. It is characterized in that the passivation layer includes a dense oxide layer and a phosphorus-doped and oxygen-doped amorphous silicon layer formed in sequence; Among them, the formation of the dense oxide layer includes the steps of first performing ozone flow gradient increasing oxidation and then performing hydrogen plasma treatment; in the dense oxide layer, the ozone flow gradient increasing oxidation adopts atomic layer deposition, and the oxidation temperature is controlled at 150 - 300 °C; the hydrogen plasma treatment adopts tube-type PECVD, and the treatment temperature of the hydrogen plasma treatment is controlled at 350 - 600 °C; the ozone flow gradient increasing in the formation of the dense oxide layer includes at least three gradient increases: the ozone flow F1 in the first gradient is 1000 sccm - 3000 sccm, the ozone flow F2 in the second gradient is 3000 sccm - 5000 sccm, the ozone flow F3 in the third gradient is 4000 sccm - 6000 sccm, and F1 < F2 < F3. The ozone introduction time in the first gradient is 5 - 10 s, the ozone introduction time in the second gradient is 10 - 15 s, and the ozone introduction time in the third gradient is 10 - 15 s; The formation of the phosphorus-doped and oxygen-doped amorphous silicon layer includes the step of continuously coating by introducing at least one gradient change in the gas under the continuous existence of glow plasma, where at least one gradient change in the introduced gas makes the phosphorus doping concentration in the phosphorus-doped and oxygen-doped amorphous silicon layer gradually increase from the inside to the outside.

2. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The thickness of the dense oxide layer is 0.5 - 2.5 nm, and the thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer is 3 - 15 nm.

3. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The thickness ratio of the dense oxide layer to the phosphorus-doped and oxygen-doped amorphous silicon layer is (0.03 - 0.83):

1.

4. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The ozone flow gradient increasing in the formation of the dense oxide layer further includes: purging the chamber and pipeline with nitrogen after the corresponding oxidation in each gradient.

5. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The conditions of the hydrogen plasma treatment include: the flow rate of hydrogen is 5000 - 15000 sccm, and the treatment time is 5 - 60 s.

6. The method for preparing a back contact battery with resistance to LID effect according to claim 1 or 5, characterized in that: The conditions of the hydrogen plasma treatment include: the deposition pressure is 1300 - 2500 mtorr, and the power is 5 kw - 20 kw.

7. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The formation of the phosphorus-doped and oxygen-doped amorphous silicon layer adopts tube-type PECVD, where its deposition temperature is controlled at 350 - 600 °C; and / or, the deposition pressure is controlled at 1300 - 2500 mtorr and the power is 5 kw - 20 kw.

8. The method for preparing a back contact battery with resistance to LID effect according to claim 1 or 7, characterized in that: The gases introduced in the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer include silane, a hydrogen mixture carrying phosphine, and nitrous oxide. The flow rate of silane is 800 - 2000 sccm, the flow rate of the hydrogen mixture carrying phosphine is 50 - 1000 sccm, and the flow rate of nitrous oxide is 100 - 2500 sccm.

9. The method for preparing a back contact battery with resistance to LID effect according to claim 8, characterized in that: In the formation of the phosphorus-doped and oxygen-doped amorphous silicon layer, the flow rates of silane and nitrous oxide are controlled to be unchanged, and the flow rate of the hydrogen mixture carrying phosphine changes in a gradient and increases, and the increasing amplitude is 50 - 200 sccm; among them, The number of gradient changes is at least 3 times, and / or the flow rate of the hydrogen gas mixture containing phosphine is changed to a corresponding gradient change value every time the deposition thickness is 0.5-2 nm.

10. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The phosphorus-doped and oxygen-doped amorphous silicon layer has a phosphorus-doped concentration ranging from 1×1019cm-3 to 9×1020cm-3, and an oxygen-doped concentration ranging from 1×1018cm-3 to 9×1019cm-3; And / or, the anti-reflection layer is at least one of silicon nitride, oxygen-doped silicon nitride, and carbon-doped silicon nitride.

11. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The anti-reflection layer includes carbon-doped silicon nitride. The formation of carbon-doped silicon nitride includes the steps of continuously coating by introducing at least one gradient change in the gas in the continuous presence of glow plasma, wherein the at least one gradient change in the gas introduced here makes the refractive index of the carbon-doped silicon nitride gradually decrease from the inside to the outside.

12. The method for preparing a back contact battery with resistance to LID effect according to claim 11, characterized in that: The carbon doping concentration in carbon-doped silicon nitride is 1×1019cm-3-9×1021cm-3, and the nitrogen doping concentration is 1×1019cm-3-9×1021cm-3; And / or, the refractive index of the carbon-doped silicon nitride varies in the range of 1.5-2.

1.

13. The method for preparing a back contact battery with resistance to LID effect according to claim 11, characterized in that: Carbon-doped silicon nitride is deposited using a tubular PECVD method. The deposition conditions include: controlling the deposition temperature to be 350-600°C, the deposition pressure to be 1300-2500 mtorr, and the power to be 5 kW-20 kW. And / or, the gases introduced during the formation of carbon-doped silicon nitride include silane, ammonia and methane, with a flow rate of silane being 800-2000 sccm, a flow rate of ammonia being 6000-15000 sccm, and a flow rate of methane being 20-1000 sccm.

14. The method for preparing a back contact battery with resistance to LID effect according to claim 11 or 13, characterized in that: The gases introduced into the formation of carbon-doped silicon nitride include silane, ammonia, and methane. During this period, the flow rate of silane is controlled to be constant, and the flow rates of ammonia and methane are changed in a gradient manner and meet the following conditions: The flow rates of ammonia and methane were changed every 20-40 nm deposition thickness, with the incremental change range of ammonia flow rate being 1000-2000 sccm and that of methane flow rate being 50-150 sccm. and / or, The initial flow rate of ammonia is in the range of 6000-8000 sccm, and the initial flow rate of methane is in the range of 0-100 sccm.

15. The method for preparing a back contact battery with resistance to LID effect according to claim 11 or 12, characterized in that: The thickness of the carbon-doped silicon nitride layer is 80-160 nm, and / or the ratio of the thickness of the carbon-doped silicon nitride layer to the thickness of the phosphorus-doped and oxygen-doped amorphous silicon layer is (5.3-53.3):

1.

16. The method for preparing a back contact battery with resistance to LID effect according to claim 1, characterized in that: The preparation method further comprises: After forming the first semiconductor layer on the backlight side of the silicon wafer, a mask layer is also formed, and then the second semiconductor opening area is formed; and in the final cleaning step of texturing cleaning, it is selected according to demand whether to remove the mask layer outside the second semiconductor opening area on the backlight side of the silicon wafer; After forming the anti-reflection layer, cleaning the second semiconductor opening region; A second semiconductor layer is then deposited on the back side; Performing a second etching operation on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region; depositing a conductive film layer on the resulting back surface; Performing a third etching opening on a portion of the conductive film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation trench; Forming metal electrodes on the outer surfaces of the corresponding conductive film layers in the areas where the first semiconductor opening region and the second semiconductor opening region are located; Among them, the first semiconductor layer includes a first passivation layer and a first doped silicon layer arranged in sequence, the second semiconductor layer includes a second passivation layer and a second doped silicon layer arranged in sequence, the first passivation layer and the second passivation layer are each independently a tunneling oxide layer or an intrinsic silicon layer, and the first doped silicon layer and the second doped silicon layer are each independently polycrystalline silicon, amorphous silicon or microcrystalline silicon.

17. A back contact battery with resistance to LID effect, characterized in that: The battery is prepared by the method for preparing a back-contact battery with an anti-LID effect according to any one of claims 1 to 16.

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