Passivation contact structure and preparation method thereof, solar cell and photovoltaic module

Abstract

The invention relates to the field of solar cells, and discloses a passivation contact structure and a preparation method thereof, a solar cell and a photovoltaic module, and the passivation contact structure comprises a dielectric layer; the doped polycrystalline silicon layer is doped with an N-type conductive element, the doped polycrystalline silicon layer is arranged on the dielectric layer, the doped polycrystalline silicon layer comprises an oxide of the N-type conductive element, and the oxide of the N-type conductive element is arranged on the doped polycrystalline silicon layer in the direction from the face, away from the dielectric layer, of the doped polycrystalline silicon layer to the face, close to the dielectric layer, of the doped polycrystalline silicon layer. The distribution number of the N-type conductive elements in the doped polycrystalline silicon layer is decreased; wherein in the doped polycrystalline silicon layer which is far away from one side of the dielectric layer, the N-type conductive element has an enrichment region, and the N-type conductive element in the enrichment region comprises an oxide. The passivation contact structure is used in the solar cell, the parasitic absorption degree of the doped polycrystalline silicon layer can be reduced, and the photoelectric conversion efficiency of the solar cell is improved.

Description

[0001] Related cross-references This application is a divisional application of Chinese patent application filed on April 2, 2024, with application number 2024103922758 and title "Passivated contact structure and preparation method thereof, solar cell, photovoltaic module". Technical Field

[0002] This application relates to the field of solar cell technology, and in particular to a passivated contact structure and its preparation method, solar cells, and photovoltaic modules. Background Technology

[0003] Passivated contact solar cells are a type of solar cell based on selective carrier transport, which has high passivation performance and photoelectric conversion efficiency.

[0004] The passivation contact structure of a passivated contact solar cell includes a dielectric layer and a doped polycrystalline silicon layer. Factors such as the presence of semiconductor conductive elements in the doped polycrystalline silicon layer can affect the degree of parasitic absorption in the doped polycrystalline silicon layer, thereby adversely affecting the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0005] This application discloses a passivated contact structure and its preparation method, a solar cell, and a photovoltaic module. The passivated contact structure can effectively reduce the parasitic absorption of the doped polycrystalline silicon layer and improve the photoelectric conversion efficiency of the solar cell.

[0006] In a first aspect, this application discloses a passivated contact structure, the passivated contact structure comprising: Dielectric layer; A doped polycrystalline silicon layer containing an N-type conductive element is disposed on the dielectric layer. The doped polycrystalline silicon layer includes an oxide of the N-type conductive element. From the side of the doped polycrystalline silicon layer away from the dielectric layer to the side of the doped polycrystalline silicon layer close to the dielectric layer, the distribution of the N-type conductive element in the doped polycrystalline silicon layer shows a decreasing distribution. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enriched region of the N-type conductive element, and the N-type conductive element in the enriched region includes the oxide.

[0007] Furthermore, the oxide is a phosphorus oxide compound, wherein the phosphorus in the phosphorus oxide compound is configured not to replace the silicon in the doped polycrystalline silicon layer.

[0008] Furthermore, the doping concentration of the N-type conductive element in the doped polycrystalline silicon layer is 8 × 10⁻⁶. 20 cm -3 ~3×10 22 cm-3 .

[0009] Furthermore, the atomic percentage of the N-type conductive element in the doped polycrystalline silicon layer is 5% to 25%.

[0010] Furthermore, the surface doping concentration of the doped polycrystalline silicon layer is 2×10⁻⁶. 20 cm -2 ~8×10 20 cm -2 The junction depth is 0.05 μm to 0.16 μm, and the sheet resistance is 30 Ω / sq to 90 Ω / sq.

[0011] Furthermore, the precursor of the doped polycrystalline silicon layer is a doped amorphous silicon layer, which is obtained by sequentially fabricating an intrinsic silicon layer and a doped layer on the dielectric layer.

[0012] Secondly, this application discloses a method for preparing the passivated contact structure described in the first aspect, the method comprising the following steps: A silicon substrate is provided, wherein the surface of the silicon substrate is provided with the dielectric layer and the doped amorphous silicon layer doped with the N-type conductive element from the inside out; First, oxygen-containing gas is introduced into the doped amorphous silicon layer, and then an oxygen-containing layer is deposited. Annealing transforms the doped amorphous silicon layer into the doped polycrystalline silicon layer, and the oxygen-containing gas, the oxygen element in the oxygen-containing layer, and the N-type conductive element combine to form the oxide to suppress the diffusion of the N-type conductive element in the doped polycrystalline silicon layer to the dielectric layer side. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enriched region of the N-type conductive element, and the N-type conductive element in the enriched region includes the oxide.

[0013] Furthermore, the amount of oxygen-containing gas introduced is greater than or equal to 1000 sccm.

[0014] Furthermore, the thickness of the oxygen-containing layer is 0.5 nm to 50 nm.

[0015] Furthermore, the oxygen-containing gas includes at least one of N2O and O2; and / or, The oxygen-containing layer is deposited using plasma-enhanced chemical vapor deposition (PECVD), wherein the deposited gas includes SiH4, the oxygen-containing gas, and / or... The dielectric layer is deposited using plasma-enhanced chemical vapor deposition at a temperature of 400°C to 500°C, and the deposited gas includes the oxygen-containing gas and an inert gas.

[0016] Furthermore, the step of depositing the doped amorphous silicon layer includes first depositing a hydrogenated intrinsic silicon layer and then depositing the doped layer, wherein the intrinsic silicon layer has a hydrogen content of 10% to 20% by mass.

[0017] Furthermore, the intrinsic silicon layer is deposited by plasma-enhanced chemical vapor deposition at a deposition temperature of 400°C to 500°C, and the deposited gases include SiH4 and H2. The doped layer is deposited using plasma-enhanced chemical vapor deposition. The deposited gas includes SiH4, a gas containing an N-type conductive element, and H2. The flow rate of the gas containing the N-type conductive element is greater than 400 sccm.

[0018] Furthermore, the junction depth of the doped layer is 0.01 μm to 0.1 μm.

[0019] Furthermore, in the annealing process, the annealing temperature is 900℃~950℃.

[0020] Thirdly, embodiments of this application disclose a solar cell, comprising: a passivated contact structure as described in the first aspect or a passivated contact structure prepared by a method described in the second aspect.

[0021] Fourthly, embodiments of this application disclose a photovoltaic module, including: a passivated contact structure as described in the first aspect or a passivated contact structure prepared by a method described in the second aspect.

[0022] Compared with the prior art, the beneficial effects of this application are as follows: This application provides a passivated contact structure, which includes a dielectric layer and a doped polycrystalline silicon layer doped with N-type conductive elements. The doped polycrystalline silicon layer includes an oxide of N-type conductive elements. This oxide can effectively control the diffusion degree of N-type conductive elements into the dielectric layer and effectively control the content of N-type conductive elements in the activated state, thereby reducing parasitic absorption problems to a greater extent and improving the photoelectric conversion efficiency of solar cells.

[0023] Specifically, the presence of oxides suppresses the diffusion of internal N-type conductive elements towards the dielectric layer. Therefore, under the suppression of oxides, the distribution of N-type conductive elements in the doped polysilicon layer decreases from the side away from the dielectric layer to the side closer to the dielectric layer. This distribution trend can effectively reduce parasitic absorption and other problems caused by the diffusion of N-type conductive elements towards the dielectric layer.

[0024] Meanwhile, this decreasing distribution trend leads to the formation of enriched regions of N-type conductive elements in the doped polysilicon layer on the side away from the dielectric layer, and these enriched regions contain N-type conductive elements in oxides. Therefore, since the N-type conductive elements in the oxides are in an inactive state, the content of activated N-type conductive elements in the enriched regions is effectively controlled, thereby significantly reducing parasitic absorption caused by excessively high levels of activated N-type conductive elements. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the back surface of a solar cell provided in an embodiment of this application; Figure 2 This is a schematic diagram of a structure for depositing an oxygen-containing layer on the back surface of a solar cell, provided in an embodiment of this application. Figure 3 This is a schematic diagram of a structure for depositing a doped amorphous silicon layer on the back surface of a solar cell, provided in an embodiment of this application. Figure 4 This is a schematic diagram of another solar cell back surface deposition structure of intrinsic silicon layer and doped polycrystalline silicon layer provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of the solar cell provided in the embodiments of this application; Figure 6 This is a concentration distribution diagram of silicon, oxygen, and phosphorus elements in the doped polycrystalline silicon layer provided in Embodiment 1 of this application; Figure 7 This is an elemental distribution diagram of phosphorus in the doped polycrystalline silicon layer provided in Embodiment 1 of this application.

[0027] Icons: 1. Silicon substrate; 2. Dielectric layer; 3. Doped polycrystalline silicon layer (doped amorphous silicon layer); 31. Intrinsic silicon layer; 32. Doped layer; 4. Oxygen-containing layer; 5. Second functional layer; 6. Diffusion layer; 7. First passivation layer; 8. First antireflection layer; 9. First electrode; 10. Second electrode. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0030] Furthermore, some of the aforementioned terms, besides indicating direction or positional relationships, may also have other meanings. For example, the term "above" may, in certain circumstances, indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0031] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0032] The technical solutions provided by the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0033] Passivated contact solar cells are formed by creating a thin dielectric layer on the back surface of a silicon wafer and then fabricating a doped polycrystalline silicon layer on top of the dielectric layer. Together, these two elements constitute the core of a passivated contact solar cell.

[0034] In this process, the activated N-type conductive elements in the doped polycrystalline silicon layer diffuse towards the dielectric layer. The higher the degree of diffusion, the more likely it is to exacerbate the parasitic absorption of the solar cell. Furthermore, when the content of activated N-type conductive elements in the doped polycrystalline silicon layer is high, it will also exacerbate the parasitic absorption of the solar cell, which is detrimental to improving the photoelectric conversion efficiency of the solar cell.

[0035] To address the aforementioned issues, this application discloses a passivated contact structure and its preparation method, as well as a solar cell and a photovoltaic module. This passivated contact structure can effectively control the diffusion degree of N-type conductive elements into the dielectric layer and effectively control the content of N-type conductive elements in the activated state, thereby significantly reducing the problem of parasitic absorption.

[0036] The passivated contact structure of this application is a structural component of solar cells. Therefore, in the following description, any part referring to solar cells refers to solar cells including this passivated structure, illustrating the advantages of using the passivated contact structure of this application in solar cells.

[0037] In the first aspect, this application discloses a passivated contact structure, which includes: Dielectric layer; A doped polysilicon layer containing N-type conductive elements is disposed on a dielectric layer. The doped polysilicon layer includes oxides of N-type conductive elements. From the side of the doped polysilicon layer away from the dielectric layer to the side of the doped polysilicon layer close to the dielectric layer, the distribution of N-type conductive elements in the doped polysilicon layer shows a decreasing distribution. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enrichment region of N-type conductive elements, including oxides.

[0038] It is understandable that N-type conductive elements include phosphorus, arsenic, etc. The electrons of these elements are charge carriers and are negatively charged. Among them, when phosphorus is the preferred N-type conductive element, its doping effect on polycrystalline silicon layers is the best.

[0039] This application provides a passivated contact structure in which the doped polysilicon layer includes an oxide of an N-type conductive element. The presence of the oxide suppresses the diffusion of the internal N-type conductive element to the dielectric layer. Therefore, under the suppression of the oxide, the distribution of N-type conductive elements in the doped polysilicon layer decreases from the side away from the dielectric layer to the side closer to the dielectric layer, thereby effectively reducing the problem of parasitic absorption caused by the diffusion of N-type conductive elements to the dielectric layer.

[0040] However, the applicant found that the aforementioned downward distribution trend would cause N-type conductive elements to form an enriched region in the doped polycrystalline silicon layer on the side away from the dielectric layer. If the N-type conductive elements in this enriched region are all in an activated state, it would further aggravate the parasitic absorption in the enriched region, which is not conducive to improving the photoelectric conversion efficiency of solar cells.

[0041] Therefore, this application sets the N-type conductive element in the enrichment region to include an oxide, wherein, since the N-type conductive element in the oxide exists in an inactive state, the content of the active N-type conductive element in the enrichment region is effectively controlled, thereby reducing parasitic absorption caused by excessive content of the active N-type conductive element to a greater extent.

[0042] In other words, the oxide in the passivated contact structure of this application can effectively control the diffusion degree of N-type conductive elements to the dielectric layer side, and can also effectively control the content of activated N-type conductive elements in the enriched region, thereby reducing the problem of parasitic absorption to a high extent.

[0043] Furthermore, the decreasing distribution trend also results in a lower content of N-type conductive elements in the doped polysilicon layer near the dielectric layer. This lower content firstly prevents increased recombination at the interface between the dielectric layer and the doped polysilicon layer, reducing the interfacial recombination rate of charge carriers; secondly, it reduces the entry of high-concentration N-type conductive elements into the dielectric layer, which could adversely affect the pore structure of the dielectric layer and impair charge carrier transport; and finally, it reduces the increased density of unsaturated dangling bonds and exacerbated lattice mismatch caused by excessively high N-type conductive elements at the dielectric layer interface.

[0044] In summary, the distribution region of the N-type conductive element and the presence of oxides in the enriched region of this application can reduce parasitic absorption to a high degree and ensure the interface contact effect between the dielectric layer and the doped polycrystalline silicon layer to a high degree, ensuring the stability of the pore structure of the dielectric layer, thereby more effectively improving the photoelectric conversion efficiency of the solar cell.

[0045] Furthermore, the oxide is a phosphorus oxide compound, and the phosphorus in the phosphorus oxide compound is configured as silicon in the non-substituent-doped polycrystalline silicon layer. Since the phosphorus in the phosphorus oxide compound is configured as silicon in the non-substituent-doped polycrystalline silicon layer, the phosphorus in the phosphorus oxide compound is in an inactive state, which helps to control the content of active phosphorus in the doped polycrystalline silicon layer to a greater extent and effectively improve the problem of parasitic absorption in the doped polycrystalline silicon layer.

[0046] Furthermore, the doping concentration of N-type conductive elements in the doped polycrystalline silicon layer is 8 × 10⁻⁶. 20 cm -3 ~3×10 22 cm -3 By ensuring that the doping concentration of the N-type conductive element is within the aforementioned range, the N-type conductive element can effectively combine with hydrogen, thereby effectively reducing the problem of film explosion in the doped polycrystalline silicon layer caused by "H overflow".

[0047] However, the applicant's research found that the above-mentioned doping concentration leads to a higher degree of diffusion of N-type conductive elements into the dielectric layer, which not only increases parasitic light absorption, but also results in poor interfacial bonding between the dielectric layer and the doped polysilicon layer, leading to damage to the pore structure in the dielectric layer.

[0048] Therefore, by controlling the distribution trend and existence mode of N-type conductive elements, this application can effectively improve the problems caused by severe parasitic absorption, poor bonding between the dielectric layer and the doping interface, and damaged pore structure of the dielectric layer at the above-mentioned doping concentrations, thereby significantly improving the photoelectric conversion efficiency of solar cells. For example, the doping concentration is 8 × 10⁻⁶. 20 cm -3 5×10 21 cm -3 3×10 22 cm -3 wait.

[0049] Furthermore, the atomic percentage of N-type conductive elements in the doped polycrystalline silicon layer is 5% to 25%.

[0050] When the atomic percentage is 5% to 25%, it indicates that the doping content of N-type semiconductor elements in the doped polycrystalline silicon layer is relatively high. This avoids the situation where if the content is too low, the doped polycrystalline silicon layer will have a high degree of film breakage, while if the content is too high, the content of N-type conductive elements will be too high, resulting in an insignificant suppression effect of oxides and affecting parasitic absorption of light. Examples of atomic percentages include 5%, 10%, 20%, and 25%.

[0051] Furthermore, the surface doping concentration of the doped polycrystalline silicon layer is 2 × 10⁻⁶. 20 cm -2 ~8×10 20 cm -2 The junction depth is 0.05μm~0.16μm, and the sheet resistance is 30 Ω / sq~90 Ω / sq.

[0052] It should be noted that the surface doping concentration of the doped polysilicon layer here refers to the surface of the doped polysilicon layer near the oxygen-containing layer.

[0053] The sheet resistance is affected by the junction depth and doping concentration. Junction depth affects the light absorption of the solar cell. When the surface doping concentration, junction depth, and sheet resistance of the doped polycrystalline silicon layer are within the above-mentioned range, the solar cell has higher conductivity and a higher fill factor, resulting in higher photoelectric conversion efficiency. When the doping concentration is higher than this range, Auger recombination is more likely to occur, reducing the open-circuit voltage of the cell. When it is lower than this range, the lateral resistance of the current increases, resulting in higher current loss and affecting the carrier migration effect. When the junction depth is higher than this range, the junction depth is too deep, reducing current collection. When the junction depth is lower than this range, it is more affected by surface contamination, thus affecting the open-circuit voltage of the cell. In addition, the doping concentration of the N-type conductive element in the doped amorphous silicon layer and the degree of diffusion of the N-type conductive element into the doped polycrystalline silicon layer determine the surface doping concentration of the doped polycrystalline silicon layer. Based on providing a high doping concentration, the diffusion suppression effect of oxygen on the N-type semiconductor element is further used to ensure that the surface doping concentration of the doped polycrystalline silicon layer in this application is within the above-mentioned range. For example, the surface doping concentration is 2 × 10⁻⁶. 20 cm -2 4×10 20 cm -2 6×10 20 cm -2 8×10 20 cm -2 Junction depths of 0.05 μm, 0.10 μm, 0.13 μm, 0.16 μm, etc.; sheet resistances of 30 Ω / sq, 40 Ω / sq, 60 Ω / sq, 90 Ω / sq, etc.

[0054] Furthermore, the precursor of the doped polycrystalline silicon layer is a doped amorphous silicon layer, which is then disposed on a dielectric layer to sequentially prepare an intrinsic silicon layer and a doped layer. In this application, when the doped amorphous silicon layer is prepared using a two-step method, the intrinsic silicon layer can act as a barrier layer, increasing the difficulty of N-type conductive elements diffusing into the dielectric layer, effectively reducing surface recombination, and improving the photoelectric conversion efficiency of the solar cell.

[0055] Secondly, embodiments of this application disclose a passivated contact structure, which includes: a dielectric layer; and a doped polysilicon layer doped with an N-type conductive element, the doped polysilicon layer being disposed on the dielectric layer, the doped polysilicon layer comprising an oxide of the N-type conductive element, and the doping concentration of the N-type conductive element in the doped polysilicon layer being 1×10⁻⁶. 20 cm -3 ~3×10 22 cm -3 The distribution of N-type conductive elements in the doped polysilicon layer decreases from the side of the doped polysilicon layer away from the dielectric layer to the side of the doped polysilicon layer closer to the dielectric layer.

[0056] The passivated contact structure disclosed in this application allows for a doping concentration of 1×10⁻⁶ N-type conductive elements in the doped polysilicon layer. 20 cm -3 ~3×10 22 cm -3 At this doping concentration, the N-type conductive element combines with the hydrogen element, thereby effectively reducing the film bursting of the doped polycrystalline silicon layer caused by "H overflow". However, due to the increase in the doping concentration of the N-type conductive element, the N-type conductive element in the doped polycrystalline silicon layer diffuses to the dielectric layer to a greater extent, thereby increasing the parasitic absorption of light and adversely affecting the photoelectric conversion efficiency of the solar cell.

[0057] Therefore, the applicant discovered that since the doped polycrystalline silicon layer of the solar cell in this application includes oxides, the oxides have an inhibitory effect on the diffusion of N-type conductive elements. As a result, the distribution of N-type conductive elements in the doped polycrystalline silicon layer decreases from the side away from the dielectric layer to the side closer to the dielectric layer. This effectively suppresses the diffusion of N-type conductive elements, improves the parasitic absorption of the doped polycrystalline silicon layer, and enhances the photoelectric conversion efficiency of the solar cell.

[0058] It is understood that N-type conductive elements include phosphorus, arsenic, etc. These elements have electrons as charge carriers and are negatively charged. Among them, phosphorus is preferred as the N-type conductive element, resulting in the best doping effect on the polycrystalline silicon layer. For example, the doping concentration is 1×10⁻⁶. 20 cm -3 5×10 21 cm -3 3×10 22 cm -3 wait.

[0059] In summary, this application reduces the degree of film bursting in the doped polycrystalline silicon layer by doping it with a high content of N-type conductive elements. On the other hand, since the N-type conductive elements include oxides in their existence state, they can effectively alleviate the parasitic absorption problem of light caused by high concentration doping. Therefore, this application can simultaneously optimize the film bursting and parasitic absorption problems of the doped polycrystalline silicon layer, thereby improving the photoelectric conversion efficiency of the solar cell.

[0060] Combination Figure 1 It can be seen that, Figure 1 This is a schematic diagram of the back surface of the solar cell provided in the embodiments of this application, showing the direction from the side of the doped polycrystalline silicon layer 3 away from the dielectric layer 2 towards the side of the doped polycrystalline silicon layer 3 closer to the dielectric layer 2 (i.e., Figure 1From bottom to top, the distribution of N-type conductive elements in the doped polysilicon layer 3 shows a decreasing trend. This is because the suppression effect of the oxide creates an enriched region of N-type conductive elements, located on the side of the doped polysilicon layer 3 away from the dielectric layer 2. Since the content of N-type conductive elements in this region is relatively high, the N-type conductive elements on the side of the doped polysilicon layer 3 closer to the dielectric layer show a decreasing trend. This reduces the degree of diffusion of N-type conductive elements into the dielectric layer 2, preventing increased recombination at the interface between the dielectric layer 2 and the doped polysilicon layer 3; it also reduces the adverse effects of high concentrations of N-type conductive elements entering the dielectric layer 2 on its pore structure, affecting carrier transport; and it reduces the increase in unsaturated dangling bond density and exacerbated lattice mismatch caused by excessively high N-type conductive elements at the interface of the dielectric layer 2.

[0061] In addition, analysis Figure 1 As can be seen in the figure, there are phosphorus-rich regions (circled areas in the figure), and the phosphorus content is lower closer to the dielectric layer 2. It can be understood that phosphorus oxides exist in these enriched regions, thereby inhibiting the diffusion of N-type conductive elements to the dielectric layer 2, resulting in an enrichment region of N-type conductive elements in the doped polycrystalline silicon layer 3. The phosphorus element in the phosphorus oxides is in an inactive state and will not substitute for silicon in the doped polycrystalline silicon layer 3. Therefore, the inactive phosphorus will not become an active impurity in the crystalline silicon atomic lattice structure, and thus will not cause parasitic absorption problems, thereby helping to improve the current of the solar cell. Furthermore, phosphorus oxides also passivate dangling bond defects at grain boundaries, improving the photoelectric conversion efficiency of the solar cell.

[0062] Furthermore, the atomic percentage of N-type conductive elements in the doped polycrystalline silicon layer is 5% to 25%. When the atomic percentage is 5% to 25%, it indicates a relatively high doping content of N-type semiconductor elements in the doped polycrystalline silicon layer. This avoids the situation where too low a content would result in a high degree of film breakage in the doped polycrystalline silicon layer, while too high a content would lead to a high concentration of N-type conductive elements, resulting in insufficient suppression of oxides and affecting parasitic light absorption. Examples of atomic percentages include 5%, 10%, 20%, and 25%.

[0063] Furthermore, the surface doping concentration of the doped polycrystalline silicon layer is 2 × 10⁻⁶. 20 cm -2 ~8×10 20 cm -2 The junction depth is 0.05μm~0.16μm, and the sheet resistance is 30 Ω / sq~90 Ω / sq.

[0064] It should be noted that the surface doping concentration of the doped polysilicon layer here refers to the surface of the doped polysilicon layer near the oxygen-containing layer.

[0065] The sheet resistance is affected by the junction depth and doping concentration. Junction depth affects the light absorption of the solar cell. When the surface doping concentration, junction depth, and sheet resistance of the doped polycrystalline silicon layer are within the above-mentioned range, the solar cell has higher conductivity and a higher fill factor, resulting in higher photoelectric conversion efficiency. When the doping concentration is higher than this range, Auger recombination is more likely to occur, reducing the open-circuit voltage of the cell. When it is lower than this range, the lateral resistance of the current increases, resulting in higher current loss and affecting the carrier migration effect. When the junction depth is higher than this range, the junction depth is too deep, reducing current collection. When the junction depth is lower than this range, it is more affected by surface contamination, thus affecting the open-circuit voltage of the cell. In addition, the doping concentration of the N-type conductive element in the doped amorphous silicon layer and the degree of diffusion of the N-type conductive element into the doped polycrystalline silicon layer determine the surface doping concentration of the doped polycrystalline silicon layer. By providing a high doping concentration and further suppressing the diffusion of N-type semiconductor elements by oxygen, the surface doping concentration of the doped polycrystalline silicon layer in this application is kept within the above-mentioned range. For example, the surface doping concentration is 2 × 10⁻⁶. 20 cm -2 4×10 20 cm -2 6×10 20 cm -2 8×10 20 cm -2 Junction depths of 0.05 μm, 0.10 μm, 0.13 μm, 0.16 μm, etc.; sheet resistances of 30 Ω / sq, 40 Ω / sq, 60 Ω / sq, 90 Ω / sq, etc.

[0066] The dielectric layer acts as a barrier for electrons and holes, and can be combined with the doped polysilicon layer to form a passivated contact structure to prevent minority carriers from passing through. The dielectric layer can also act as a pinhole channel, allowing carriers in the solar cell to move freely. The selective passage of majority carriers through the heavily doped polysilicon helps to reduce the recombination loss of minority carriers. In addition, the dielectric layer can be used as a diffusion barrier to prevent the N-type conductive elements in the doped polysilicon layer from diffusing into the semiconductor substrate.

[0067] It is important to note that when the dielectric layer and the doped polysilicon layer combine to form a passivation contact structure, the effectiveness of the passivation contact structure is related to the thickness of both the dielectric and doped polysilicon layers. When the thickness of the dielectric layer is 1 nm to 3 nm and the thickness of the doped polysilicon layer is 100 nm to 120 nm, the solar cell exhibits good passivation contact performance. When the thicknesses of the doped polysilicon layer and the dielectric layer meet these ranges, it helps reduce the likelihood of film bursting. This is because thicker doped polysilicon layers are more prone to film bursting during fabrication. Furthermore, thicker doped polysilicon layers also increase the degree of parasitic absorption. For example, the thickness of the dielectric layer can be 1 nm, 1.4 nm, 1.6 nm, 2 nm, 3 nm, etc.; and the thickness of the doped polysilicon layer can be 100 nm, 110 nm, 120 nm, etc.

[0068] Thirdly, embodiments of this application disclose a method for preparing the passivated contact structure of the first aspect, the method comprising: A silicon substrate is provided, and the surface of the silicon substrate is provided with a dielectric layer and a doped amorphous silicon layer doped with N-type conductive elements from the inside out. First, oxygen-containing gas is introduced into the doped amorphous silicon layer, and then the oxygen-containing layer is deposited. Annealing transforms the doped amorphous silicon layer into a doped polycrystalline silicon layer, and allows oxygen-containing gas and oxygen elements in the oxygen-containing layer to combine with N-type conductive elements to form oxides, thereby inhibiting the diffusion of N-type conductive elements in the doped polycrystalline silicon layer to the dielectric layer side. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enrichment region of N-type conductive elements, including oxides.

[0069] The N-type conductive element in this application exists in an oxide state. This oxide is formed by introducing oxygen-containing gas into a doped amorphous silicon layer, depositing an oxygen-containing layer, and then, during an annealing process, transforming the doped amorphous silicon layer into a doped polycrystalline silicon layer. Simultaneously, the oxygen-containing gas and oxygen elements in the oxygen-containing layer combine with the N-type conductive element. This oxide inhibits the diffusion of the N-type conductive element towards the dielectric layer. In this process, the oxygen-containing gas is injected into the doped amorphous silicon layer before the oxygen-containing layer is formed. Subsequent annealing allows the oxygen in the oxygen-containing gas to further diffuse into the interior of the doped polycrystalline silicon layer, thereby combining with the internal N-type conductive element and inhibiting its diffusion towards the dielectric layer. Furthermore, as annealing progresses, the oxygen in the oxygen-containing layer combines with the N-type conductive element on the surface of the doped polycrystalline silicon layer, thus inhibiting the diffusion of the surface N-type conductive element into the interior of the doped polycrystalline silicon layer. In other words, this method allows oxygen to combine with excess N-type conductive elements in the doped polycrystalline silicon layer, reducing the likelihood of the doped polycrystalline silicon layer bursting. It also effectively reduces the diffusion of N-type conductive elements towards the dielectric layer, decreasing the probability of N-type conductive elements penetrating the dielectric layer and entering the silicon substrate, thus reducing parasitic light absorption and effectively improving the photoelectric conversion efficiency of the solar cell. Furthermore, the oxygen-containing layer can also serve as a protective layer, reducing the corrosion of the doped polycrystalline silicon layer on the back side by the cleaning solution during subsequent cleaning steps.

[0070] This application reduces parasitic light absorption by introducing oxygen-containing gas, which diffuses further into the doped polycrystalline silicon layer during annealing, thereby combining with the phosphorus inside and inhibiting its further inward diffusion. On the other hand, an oxygen-containing layer is deposited, where oxygen combines with phosphorus on the surface of the doped polycrystalline silicon layer during annealing, effectively inhibiting the diffusion of surface phosphorus inward. Therefore, the oxygen-containing gas and oxygen-containing layer design effectively suppresses the tendency of phosphorus to diffuse towards the dielectric layer and reduces the degree of parasitic absorption in the doped polycrystalline silicon layer. Furthermore, although introducing an oxygen source (i.e., the prepared doped amorphous silicon layer includes both phosphorus and oxygen) while depositing the doped amorphous silicon layer without depositing an oxygen-containing layer can improve the parasitic light absorption problem to some extent, the oxygen in this method is randomly distributed in the phosphorus-doped amorphous silicon layer, making it difficult to control the distribution area of ​​the oxygen source in the doped amorphous silicon layer. This results in a low binding rate of oxygen and phosphorus, which adversely affects the inhibition of phosphorus diffusion inward.

[0071] As can be seen from the above analysis, this application reduces the parasitic absorption of light caused by high-concentration phosphorus doping by binding phosphorus with oxygen-containing gas and oxygen in the oxygen-containing layer, thereby simultaneously optimizing the film bursting and parasitic absorption of the doped polycrystalline silicon layer and improving the photoelectric conversion efficiency of the solar cell.

[0072] In this embodiment, the dielectric layer and the doped polysilicon layer can be disposed on the light-receiving surface of the silicon substrate, on the backlight surface of the silicon substrate, or on both sides. The following description uses the example of the dielectric layer and the doped polysilicon layer being disposed on the backlight surface of the silicon substrate for further explanation.

[0073] See Figure 2 , Figure 2 This is a schematic diagram of the structure of the solar cell with an oxygen-containing layer deposited on the back surface provided in the embodiment of this application. On the back surface of the silicon substrate 1, a dielectric layer 2 and a phosphorus-doped amorphous silicon layer 3 are formed sequentially from the inside to the outside. Oxygen-containing gas is introduced into the amorphous silicon layer 3, and then an oxygen-containing layer 4 is deposited. After subsequent annealing, the amorphous silicon layer 3 is transformed into a polycrystalline silicon layer 3. In the figure, the content of phosphorus in the activated state is lower on the side closer to the dielectric layer 2, indicating that the oxygen-containing gas and the oxygen element in the oxygen-containing layer 4 combine with the phosphorus element to inhibit the diffusion of phosphorus element in the polycrystalline silicon layer 3 to the dielectric layer 2.

[0074] To ensure sufficient oxygen to suppress the diffusion of N-type conductive elements within the doped polysilicon layer and effectively address parasitic absorption, the oxygen-containing gas flow rate is greater than or equal to 1000 sccm, preferably within the range of 1000 sccm to 8000 sccm, with an oxygen-containing layer thickness of 0.5 nm to 50 nm. When the oxygen-containing gas flow rate is within this range and the oxygen-containing layer thickness is 0.5 nm to 50 nm, sufficient oxygen is ensured to bind with the N-type conductive elements in the doped polysilicon layer. Furthermore, the advancement of oxygen during subsequent annealing processes reduces excessive phosphorus diffusion within the doped polysilicon layer and, more importantly, reduces phosphorus diffusion from the surface of the doped polysilicon layer inwards. This reduces parasitic absorption in the doped polysilicon layer and the probability of phosphorus penetrating the dielectric layer. It also helps avoid the problems of poor corrosion resistance in the doped polysilicon layer due to excessively high oxygen content, which increases production costs and processing time; and avoids the problem of insufficient oxygen content leading to inadequate binding with N-type semiconductor elements, making it difficult to effectively reduce parasitic absorption. For example, the amount of oxygen-containing gas introduced is 1000 sccm, 5000 sccm, 8000 sccm, 10000 sccm, etc.; the thickness of the oxygen-containing layer is 0.5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc.

[0075] This application can employ deposition methods such as Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Low-Pressure Chemical Vapor Deposition (LPCVD). PECVD is preferred for depositing the dielectric layer, doped amorphous silicon layer, oxygen-containing gas, and oxygen-containing layer. Compared to LPCVD, PECVD offers advantages such as lower plating density, easier plating removal, thinner doped amorphous silicon layer, and higher deposition efficiency. However, the resulting doped polycrystalline silicon layer has a high hydrogen content, which can easily lead to film explosion, affecting the yield and efficiency of solar cells. Therefore, this application increases the doping concentration of N-type conductive elements in the doped polycrystalline silicon layer. By suppressing hydrogen emission through N-type conductive elements, the risk of film explosion caused by hydrogen efflux is reduced.

[0076] Furthermore, the annealing temperature is 900℃~950℃. When the annealing temperature is within this range, it not only transforms the doped amorphous silicon layer into a doped polycrystalline silicon layer, but also allows oxygen elements to further penetrate into the interior of the doped polycrystalline silicon layer and combine with the internal N-type conductive elements. It is worth noting that if the doped polycrystalline silicon layer is prepared using LPCVD, the deposition temperature is 550℃~600℃, which is higher than that of PECVD. Moreover, the annealing process involves not only the transformation of amorphous silicon into a polycrystalline silicon layer, but also the inward diffusion of N-type conductive elements, resulting in an activated state. In contrast, PECVD annealing primarily involves the activation of N-type conductive elements and the transformation of the amorphous silicon layer into a polycrystalline silicon layer. The diffusion of N-type conductive elements in PECVD mainly occurs during the deposition process. Compared to LPCVD, PECVD exhibits a higher uniformity of N-type conductive element distribution in the doped polycrystalline silicon layer.

[0077] Oxygen-containing gas is deposited using PECVD, wherein the deposited oxygen-containing gas includes at least one of N2O and O2. Under the discharge effect of PECVD, the oxygen element enters the interior of the doped amorphous silicon layer. In subsequent annealing processes, the oxygen element can further diffuse inward and combine with the internal N-type conductive elements, reducing the probability of N-type conductive elements penetrating the dielectric layer. In the fabrication process of the oxygen-containing layer, the deposited gas includes SiH4 and oxygen-containing gas, specifically SiH4 and O2, or SiH4, N2O, and O2, or SiH4 and N2O.

[0078] Both the dielectric layer and the doped amorphous silicon layer are deposited under negative pressure at 400℃~500℃. During the deposition of the dielectric layer, the deposited gases include oxygen-containing gases and inert gases. Under the discharge effect of PECVD, these gases are ionized into ions, thereby reacting with the silicon wafer to form the dielectric layer. The deposited gases are N2, N2O, and O2, or N2 and N2O, or N2 and O2, etc.

[0079] In the first alternative implementation, see Figure 3 , Figure 3 This is a schematic diagram of a structure for depositing a doped amorphous silicon layer on the back surface of a solar cell, as provided in this application. The doped polycrystalline silicon layer 3 is formed by directly depositing a doped amorphous silicon layer 3 containing N-type conductive elements, and then annealing it to directly transform the doped amorphous silicon layer 3 into a doped polycrystalline silicon layer 3. In a second optional embodiment, see [link to second optional embodiment]. Figure 4 , Figure 4 This is a schematic diagram of another solar cell back surface deposition structure of intrinsic silicon layer and doped layer provided in this application. The doped polycrystalline silicon layer 3 is prepared by first preparing intrinsic silicon layer 31, then depositing doped layer 32 containing N-type conductive elements, and after annealing, part of the N-type conductive elements in doped layer 32 enters into intrinsic silicon layer 31, so that doped layer 32 and intrinsic silicon layer 31 together form doped polycrystalline silicon layer 3.

[0080] In the second optional embodiment, the intrinsic silicon layer is a hydrogenated intrinsic silicon layer. The deposited gases are SiH4 and H2. Under the discharge action of PECVD, the gases are ionized into an ionic state, thus generating a hydrogenated intrinsic silicon layer. Then, SiH4, PH3 and auxiliary gas H2 are introduced. Under the discharge action of PECVD, a doped polycrystalline silicon layer is generated. After annealing, the amorphous silicon is crystallized. The hydrogenated intrinsic silicon layer and the doped layer are transformed into a doped polycrystalline silicon layer. The mass content of hydrogen in the intrinsic silicon layer is 10% to 20%.

[0081] A two-step method is used to prepare a doped polycrystalline silicon layer. The intrinsic silicon layer acts as a barrier layer, increasing the difficulty of N-type conductive elements diffusing into the dielectric layer, effectively reducing surface recombination, and improving the photoelectric conversion efficiency of the solar cell. Furthermore, since the hydrogen content in the intrinsic silicon layer is within the aforementioned range, it not only reduces the risk of film bursting caused by H escape, but also provides a passivation effect, improving the photoelectric conversion efficiency of the solar cell. This avoids the increased degree of film bursting caused by excessively high H content, and also avoids the poor passivation effect caused by excessively low H content, which would hinder the optimization of the passivation contact structure. For example, the mass content of hydrogen is 10%, 14%, 18%, 20%, etc.

[0082] Furthermore, the intrinsic silicon layer prepared in this process has a thickness of 30 nm to 40 nm, and the doped layer has a thickness of 70 nm to 80 nm. When the thicknesses of the intrinsic silicon layer and the doped layer are within these ranges, the resulting doped polycrystalline silicon layer is thicker, which is beneficial for improving the passivation effect of the passivation contact structure. The intrinsic silicon layer thickness within these ranges also ensures a greater diffusion distance for the N-type conductive element, increasing the difficulty of diffusion and thus helping oxygen elements suppress the diffusion of the N-type conductive element and reduce its diffusion into the dielectric layer. Conversely, if the thickness of the intrinsic silicon layer is too low, the diffusion distance of the N-type conductive element into the dielectric layer decreases, increasing its probability of penetrating the dielectric layer. If the thickness is too high, it will affect the passivation contact effect and increase the process cost. If the thickness of the doped layer is too high, the resulting thicker doped polycrystalline silicon layer increases the likelihood of film bursting. If the thickness of the doped layer is too low, the doping content of the N-type conductive element is low, which is not conducive to improving the passivation contact structure. For example, the thickness of the intrinsic silicon layer is 30 nm, 35 nm, 40 nm, etc.; the thickness of the doped layer is 70 nm, 75 nm, 80 nm, etc.

[0083] The junction depth of the doped layer is 0.01 μm to 0.1 μm. Within this range, the doped layer exhibits good current absorption. When the junction depth exceeds this range, the junction becomes too deep, reducing current collection. When the junction depth is below this range, it is more susceptible to contamination on the battery surface, thus affecting the battery's open-circuit voltage. For example, the junction depth of the doped layer is 0.01 μm, 0.04 μm, 0.06 μm, 0.08 μm, 0.1 μm, etc.

[0084] The passivation contact structure is part of the structure of a solar cell. Before the step of preparing the passivation contact structure, the solar cell preparation process includes: texturing a silicon substrate; forming a diffusion layer on the side of the silicon substrate away from the dielectric layer, and the diffusion layer forming a wrap-around coating on the dielectric layer side of the silicon substrate and / or the side edge of the silicon substrate; removing the wrap-around coating and polishing the dielectric layer side of the silicon substrate.

[0085] The purpose of texturing is to remove dirt from the silicon substrate, create a textured surface, and increase its ability to absorb sunlight. The purpose of alkaline polishing is to remove excess coating to prevent leakage and reduce its ability to capture charge carriers. At the same time, it polishes the dielectric layer side of the silicon substrate, so that the subsequently deposited dielectric layer and doped polycrystalline silicon layer have high flatness, which helps to reduce the film bursting phenomenon caused by stress concentration during the deposition process.

[0086] Following the step of fabricating the passivation contact structure, the fabrication process of the solar cell includes: cleaning the silicon substrate to remove the oxygen-containing layer; fabricating a first functional layer on the side of the diffusion layer away from the silicon substrate, and fabricating a second functional layer on the side of the doped polycrystalline silicon layer away from the dielectric layer; the first functional layer is a first passivation layer and / or a first antireflection layer, and the second functional layer is a second passivation layer and / or a second antireflection layer; printing and sintering a first electrode on the first functional layer, so that the first electrode penetrates the first functional layer and makes ohmic contact with the diffusion layer; and printing and sintering a second electrode on the second functional layer, so that the second electrode penetrates the second functional layer and makes ohmic contact with the doped polycrystalline silicon layer.

[0087] It is important to note that during the cleaning process of the silicon substrate, when removing the coating layer formed on the side of the silicon substrate and / or the diffusion layer side during the deposition of the dielectric layer and doped polycrystalline silicon layer, the oxygen-containing layer can act as a protective layer to prevent the passivation contact structure of the silicon substrate from being corroded by the cleaning solution. After removing the coating layer, the oxygen-containing layer is further removed, which facilitates the subsequent deposition of the second functional layer. The passivation layer reduces surface recombination, improving the photoelectric conversion efficiency of the solar cell; the antireflection layer reduces the reflection of incident light and also acts as a passivation layer, further improving the photoelectric efficiency of the solar cell. The printing and sintering of the metal electrodes allows the electrodes and the silicon substrate to form an ohmic contact, increasing the open-circuit voltage and fill factor of the cell, thus improving the photoelectric conversion efficiency. Exemplarily, the first functional layer is a first passivation layer, a first antireflection layer, or a first passivation layer and a first antireflection layer; the second functional layer is a second antireflection layer, a second passivation layer, or a second passivation layer and a second antireflection layer.

[0088] Fourthly, this application provides a solar cell that includes a passivated contact structure as described in the first aspect, or a passivated contact structure prepared by the method described in the second aspect.

[0089] See Figure 5 The solar cell of this application includes a silicon substrate 1. The light-receiving surface of the silicon substrate 1 has a diffusion layer 6, a first passivation layer 7 and a first anti-reflection layer 8 in sequence. The diffusion layer 6 forms a PN junction with the silicon substrate 1. The back-lighting surface of the silicon substrate 1 has a dielectric layer 2, a doped polycrystalline silicon layer 3 and a second passivation layer 5 in sequence. In addition, a first electrode 9 is disposed on the surface of the first anti-reflection layer 8 and a second electrode 10 is disposed on the surface of the second passivation layer 5.

[0090] Fifthly, this application provides a photovoltaic module, which includes a passivated contact structure as described in the first aspect, or a passivated contact structure prepared by the method described in the second aspect.

[0091] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0092] Example 1: This application provides a method for fabricating a solar cell, which includes the following steps: Texturing the silicon substrate: For N-type silicon substrates, texturing is first performed using a 1% alkaline solution, followed by cleaning the silicon substrate with hydrogen peroxide and alkali. The texturized silicon substrate is placed in a boron diffusion furnace, and boron trichloride gas is diffused at 1000℃~1080℃ to form a diffusion layer on the light-receiving surface of the silicon substrate, and the diffusion layer forms a wrap-around coating on the back-light surface and / or the side of the silicon substrate. The boron-containing glass layer on the back surface of the silicon substrate due to boron expansion is removed using a chain-type HF equipment. Then, the winding coating on the back surface and sides of the silicon substrate is removed using a tank-type wet process equipment, and the back surface of the silicon substrate is polished.

[0093] Preparation of passivated contact structures: Using PECVD, under negative pressure and temperature of 450℃, a 1 nm silicon dioxide dielectric layer and a phosphorus-doped amorphous silicon layer are formed sequentially from the inside to the outside on the back surface of a silicon substrate. The doped amorphous silicon layer includes a 40 nm thick hydrogenated intrinsic silicon layer and an 80 nm thick doped layer. Using PECVD, oxygen was first introduced into the doped amorphous silicon layer at a rate of 1000 sccm, and then oxygen was introduced and SiH4 was deposited to form a 10 nm thick oxygen-containing layer. Annealing at 900℃ transforms the intrinsic silicon layer and doped layer into a doped polycrystalline silicon layer. Furthermore, the oxygen-containing gas and oxygen elements in the oxygen-containing layer combine with N-type conductive elements to form oxides, inhibiting the diffusion of N-type conductive elements from the doped polycrystalline silicon layer towards the dielectric layer. The doping concentration of the doped polycrystalline silicon layer is 5 × 10⁻⁶. 21 cm -3 The atomic percentage of phosphorus in the doped polycrystalline silicon layer is 15%. Hydrofluoric acid solution is used to clean the silicon substrate and remove the oxygen-containing layer; A first passivation layer of aluminum oxide and a first antireflection layer of silicon nitride are sequentially prepared from the inside to the outside on the side of the diffusion layer away from the silicon substrate. A second functional layer is prepared on the side of the doped polycrystalline silicon layer away from the dielectric layer. This functional layer is a silicon nitride layer that has both antireflection and passivation functions. A first electrode is printed and sintered on a first antireflection layer, so that the first electrode penetrates the first functional layer and makes ohmic contact with the diffusion layer. A second electrode is printed and sintered on a second functional layer, so that the second electrode penetrates the second functional layer and makes ohmic contact with the doped polycrystalline silicon layer, thus obtaining a solar cell.

[0094] Performance Test 1: See Figure 6 , Figure 6This diagram shows the concentration distribution of silicon, oxygen, and phosphorus in the doped polycrystalline silicon layer of this application. A high concentration of oxygen has been observed in the doped polycrystalline silicon layer. This oxygen reacts with excess phosphorus to form phosphorus oxides. The phosphorus in these phosphorus oxides is in an inactive state, thereby improving the problem of parasitic absorption. At the same time, due to the binding of oxygen, the inward diffusion of phosphorus into the dielectric layer is restricted, reducing the probability of phosphorus penetrating the dielectric layer and improving the photoelectric conversion efficiency of the solar cell.

[0095] See Figure 7 , Figure 7 This is an elemental distribution diagram of phosphorus in the polycrystalline silicon layer after annealing. In the diagram, there are enriched regions of phosphorus in the polycrystalline silicon layer. The existence of these enriched regions is mainly due to the inhibitory effect of oxygen-containing gas on phosphorus inside the polycrystalline silicon layer and the inhibitory effect of the oxygen-containing layer on phosphorus on the surface of the polycrystalline silicon layer. This causes the phosphorus in the polycrystalline silicon layer to decrease towards the dielectric layer, reducing the probability of it penetrating the dielectric layer. Moreover, the phosphorus in this enriched region is non-activated phosphorus, which does not produce parasitic absorption and will not have an adverse effect on the current of the solar cell.

[0096] Example 2 The only difference between this embodiment and Embodiment 1 is that the doping concentration of the N-type conductive element in the doped polycrystalline silicon layer is 1×10⁻⁶. 20 cm -3 .

[0097] Example 3 The only difference between this embodiment and Embodiment 1 is that the doping concentration of the N-type conductive element in the doped polycrystalline silicon layer is 3 × 10⁻⁶. 22 cm -3 .

[0098] Example 4 The only difference between this embodiment and Embodiment 1 is that the thickness of the oxygen-containing layer is 5 nm.

[0099] Example 5 The only difference between this embodiment and Embodiment 1 is that the thickness of the oxygen-containing layer is 30 nm.

[0100] Example 6 The only difference between this embodiment and Embodiment 1 is that the thickness of the oxygen-containing layer is 70 nm.

[0101] Example 7 The only difference between this embodiment and Embodiment 1 is that the amount of oxygen-containing gas introduced is 300 sccm.

[0102] Example 8 The only difference between this embodiment and Embodiment 1 is that the amount of oxygen-containing gas introduced is 2500 sccm.

[0103] Example 9 The only difference between this embodiment and Embodiment 1 is that the thickness of the intrinsic silicon layer is 25 nm.

[0104] Example 10 The only difference between this embodiment and Embodiment 1 is that the thickness of the intrinsic silicon layer is 50 nm.

[0105] Example 11 The only difference between this embodiment and Embodiment 1 is that the doped polysilicon layer is deposited using LPCVD, and the thickness of the doped polysilicon layer is 100 nm.

[0106] Example 12 The only difference between this embodiment and Embodiment 1 is that in the process of preparing the doped polycrystalline silicon layer, there is no need to deposit an intrinsic silicon layer; instead, a doped amorphous silicon layer with a thickness of 120 nm is directly deposited.

[0107] Comparative Example 1 The difference between this comparative example and Example 1 is that oxygen-containing gas is not introduced into the phosphorus-doped amorphous silicon layer, nor is an oxygen-containing layer deposited.

[0108] Comparative Example 2 The difference between this comparative example and Example 1 is that oxygen-containing gas is not introduced into the phosphorus-doped amorphous silicon layer, but an oxygen-containing layer is directly deposited on the surface of the phosphorus-doped polycrystalline silicon layer.

[0109] Comparative Example 3 The difference between this comparative example and Example 1 is that only oxygen-containing gas is introduced into the phosphorus-doped amorphous silicon layer, but no oxygen-containing layer is deposited.

[0110] Comparative Example 4 The difference between this comparative example and Example 1 is that the doping concentration of the N-type conductive element in the doped amorphous silicon layer is 5 × 10⁻⁶. 19 cm -3 .

[0111] Comparative Example 5 The difference between this comparative example and Example 1 is that the doping concentration of the N-type conductive element in the doped amorphous silicon layer is 1×10⁻⁶. 23 cm -3 .

[0112] Performance Test 2: Surface doping concentration: measured using the electrochemical capacitance-voltage profiler (ECV).

[0113] Junction depth: The junction depth is determined by observing the depth corresponding to the concentration inflection point using an electrochemical capacitance-voltage profiler (ECV).

[0114] Sheet resistance: Sheet resistance is tested using a four-probe sheet resistance tester.

[0115] Table 1 Performance test results of doped polysilicon layers

[0116] Analysis of the surface doping concentration, junction depth, and sheet resistance values ​​of the embodiments and comparative examples shows that the above-mentioned characterization parameters of the embodiments are all within the scope of this application, while the above-mentioned parameters in the comparative examples are not within the scope of this application. Therefore, the solar cells prepared in the embodiments have a higher degree of light absorption, higher conductivity, and higher fill factor, which helps to improve the photoelectric conversion efficiency of the solar cells.

[0117] Performance Test 3: The solar cells prepared in Examples 1 to 12 and Comparative Examples 1 to 5 were subjected to the following related tests: This application describes the performance testing of a solar cell using a Halm testing and sorting device, including tests for open-circuit voltage, short-circuit current, and fill factor. The Halm device simulates sunlight and is equipped with electronic loads, data acquisition and calculation equipment to test the electrical performance of photovoltaic devices (including solar cells). The silicon wafer of the solar cell used in the test was 182mm in size, and the calibrated light intensity was 1000±5 W / m². The experimental test results are as follows.

[0118] Table 2 Performance test results of solar cells

[0119] Analysis of the data from Examples 1 to 12 and Comparative Examples 1 to 3 shows that the photoelectric conversion efficiency of the examples is better than that of the comparative examples. This is because in the preparation process of the doped polycrystalline silicon layer in the examples, oxygen-containing gas is first introduced and then the oxygen-containing layer is deposited. Therefore, under the action of annealing, the oxygen element in the oxygen-containing gas diffuses into the interior of the doped polycrystalline silicon layer and combines with the phosphorus element, inhibiting the inward diffusion of the phosphorus element inside. Meanwhile, the oxygen element in the oxygen-containing layer combines with the phosphorus element on the surface of the doped polycrystalline silicon layer, inhibiting the diffusion of the surface phosphorus element into the interior of the doped polycrystalline silicon layer. As a result, the phosphorus element in the doped polycrystalline silicon layer shows a decreasing trend, reducing the parasitic absorption of the doped polycrystalline silicon layer and improving the photoelectric conversion efficiency of the solar cell.

[0120] Analysis of the data from Examples 1 to 3 and Comparative Examples 4 and 5 shows that the photoelectric conversion efficiency of Examples 1 to 3 is better than that of Comparative Example 4. This is because the doping concentration of the polycrystalline silicon layer in Examples 1 to 3 is higher, which helps to solve the problem of polycrystalline silicon layer film bursting, thereby improving the performance of solar cells. The data of Examples 1 to 3 are better than that of Comparative Example 5. This is because the doping concentration of Examples 1 to 3 is lower, so the content of phosphorus element expansion is lower, which improves the photoparasitic absorption problem of the polycrystalline silicon layer and improves the performance of solar cells.

[0121] Analysis of the data from Examples 1, 4 to 6 shows that the data from Examples 1, 4 to 5 are better than that from Example 6. This is because the deposition thickness of the oxygen-containing layer in Examples 1, 4 and 5 is within the preferred range of this application, thereby avoiding excessive oxygen content in the doped polycrystalline silicon layer due to excessive oxygen layer thickness, which would result in poor stability of the doped polycrystalline silicon layer and affect the performance of the solar cell.

[0122] Analysis of the data from Examples 1, 7, and 8 shows that the data from Examples 1 and 8 are superior to those from Example 7. This is because the amount of oxygen-containing gas introduced in Examples 1 and 8 is within the preferred range of this application. While effectively suppressing the downward expansion of phosphorus elements inside the doped polycrystalline silicon layer, it also solves the problem of photoparasitic absorption in the doped polycrystalline silicon layer and improves the quality of passivation contacts, thereby improving the photoelectric conversion efficiency of the solar cell.

[0123] Analysis of the data from Examples 1, 9, and 10 shows that the data from Example 1 is better than that from Example 9. This is because the intrinsic silicon layer in Example 1 is thicker, which can effectively block the inward diffusion of phosphorus elements, thereby improving the photoparasitic absorption problem and increasing the photoelectric conversion efficiency of the solar cell. The data from Example 1 is better than that from Example 10 because the intrinsic silicon layer in Example 1 is thinner, which helps to improve the passivation effect of the passivation contact structure, thereby increasing the photoelectric conversion efficiency of the solar cell.

[0124] Analysis of the data from Example 1 and Example 11 shows that the data from Example 1 is superior to that from Example 11. This is because Example 1 uses the PECVD deposition method to prepare solar cells. PECVD is an in-situ doping preparation method. Specifically, it involves ionizing silane and phosphine through plasma discharge at a low doping temperature to form an in-situ phosphorus-doped amorphous silicon layer. By introducing oxygen-containing gas and depositing the oxygen-containing layer, the tendency of phosphorus to expand inward when the doped amorphous silicon layer transforms into a doped polycrystalline silicon layer is further reduced, thereby increasing the short-circuit current density and optimizing the photoelectric conversion efficiency of the solar cell. Moreover, this method has higher deposition efficiency.

[0125] Analysis of the data from Example 1 and Example 12 shows that the data from Example 1 is better than that from Example 12. This is because the preparation process of the doped polycrystalline silicon layer in Example 1 involves first preparing intrinsic silicon and then depositing the doped layer. The intrinsic silicon layer can act as a barrier layer, which increases the difficulty of phosphorus diffusion to the dielectric layer, reduces surface recombination, and improves the photoelectric conversion efficiency of the solar cell.

[0126] The passivated contact structure and its preparation method, solar cell, and photovoltaic module disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A passivated contact structure, characterized in that, The passivated contact structure includes: Dielectric layer; A doped polycrystalline silicon layer containing an N-type conductive element is disposed on the dielectric layer. The doped polycrystalline silicon layer includes an oxide of the N-type conductive element. From the side of the doped polycrystalline silicon layer away from the dielectric layer to the side of the doped polycrystalline silicon layer close to the dielectric layer, the distribution quantity of the N-type conductive element in the doped polycrystalline silicon layer shows a decreasing distribution. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enriched region of the N-type conductive element, and the N-type conductive element in the enriched region includes the oxide.

2. The passivated contact structure according to claim 1, characterized in that, The oxide is a phosphorus oxide compound, wherein the phosphorus in the phosphorus oxide compound is configured not to replace the silicon in the doped polycrystalline silicon layer.

3. The passivated contact structure according to claim 1, characterized in that, The doping concentration of the N-type conductive element in the doped polycrystalline silicon layer is 8 × 10⁻⁶. 20 cm -3 ~3×10 22 cm -3 .

4. The passivated contact structure according to claim 1, characterized in that, The atomic percentage of the N-type conductive element in the doped polycrystalline silicon layer is 5% to 25%.

5. The passivated contact structure according to any one of claims 1 to 4, characterized in that, The surface doping concentration of the doped polycrystalline silicon layer is 2×10⁻⁶. 20 cm -2 ~8×10 20 cm -2 The junction depth is 0.05 μm to 0.16 μm, and the sheet resistance is 30 Ω / sq to 90 Ω / sq.

6. The passivated contact structure according to claim 1, characterized in that, The precursor of the doped polycrystalline silicon layer is a doped amorphous silicon layer, which is obtained by sequentially fabricating an intrinsic silicon layer and a doped layer on the dielectric layer.

7. A method for preparing a passivated contact structure as described in any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: A silicon substrate is provided, wherein the surface of the silicon substrate is provided with the dielectric layer and the doped amorphous silicon layer doped with the N-type conductive element from the inside out; First, oxygen-containing gas is introduced into the doped amorphous silicon layer, and then an oxygen-containing layer is deposited. Annealing transforms the doped amorphous silicon layer into the doped polycrystalline silicon layer, and the oxygen-containing gas, the oxygen element in the oxygen-containing layer, and the N-type conductive element combine to form the oxide to suppress the diffusion of the N-type conductive element in the doped polycrystalline silicon layer to the dielectric layer side. In the doped polycrystalline silicon layer on the side away from the dielectric layer, there is an enriched region of the N-type conductive element, and the N-type conductive element in the enriched region includes the oxide.

8. The preparation method according to claim 7, characterized in that, The amount of oxygen-containing gas introduced is greater than or equal to 1000 sccm.

9. The preparation method according to claim 7, characterized in that, The oxygen-containing gas includes at least one of N2O and O2; and / or, The oxygen-containing layer is deposited using plasma-enhanced chemical vapor deposition (PECVD), wherein the deposited gas includes SiH4, the oxygen-containing gas, and / or... The dielectric layer is deposited using plasma-enhanced chemical vapor deposition at a temperature of 400°C to 500°C, and the deposited gas includes the oxygen-containing gas and an inert gas.

10. The preparation method according to claim 7, characterized in that, The step of depositing the doped amorphous silicon layer includes first depositing a hydrogenated intrinsic silicon layer and then depositing a doped layer, wherein the intrinsic silicon layer has a hydrogen content of 10% to 20% by mass.

11. The preparation method according to claim 10, characterized in that, The intrinsic silicon layer was deposited using plasma-enhanced chemical vapor deposition at a temperature of 400°C to 500°C, and the deposited gases included SiH4 and H2. The doped layer is deposited using plasma-enhanced chemical vapor deposition. The deposited gas includes SiH4, a gas containing an N-type conductive element, and H2. The flow rate of the gas containing the N-type conductive element is greater than 400 sccm.

12. The preparation method according to claim 11, characterized in that, The junction depth of the doped layer is 0.01 μm to 0.1 μm.

13. The preparation method according to claim 7, characterized in that, In the annealing process, the annealing temperature is 900℃~950℃.

14. A solar cell, characterized in that, include: The passivated contact structure as described in any one of claims 1 to 6, or the passivated contact structure prepared by the preparation method as described in any one of claims 7 to 13.

15. A photovoltaic module, characterized in that, include: The passivated contact structure as described in any one of claims 1 to 6, or the passivated contact structure prepared by the preparation method as described in any one of claims 7 to 13.

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