Passivation contact solar cell and preparation method thereof

Abstract

The invention discloses a passivation contact solar cell and a preparation method thereof. The passivated contact solar cell may include: a silicon substrate; the passivation contact structure is arranged on the first main surface of the silicon substrate; the diffusion regulation and control layer is laminated on one side, deviating from the silicon substrate, of the passivation contact structure; the outer doping layer is laminated on one side, deviating from the silicon substrate, of the diffusion regulation and control layer; the type of a doping element contained in the outer doping layer is consistent with that of a doping element contained in the passivation contact structure; the doping concentration of the outer doping layer is higher than the doping concentration of the passivation contact structure. According to the passivation contact solar cell, the excellent passivation effect and high yield of the passivation contact solar cell can be ensured, and the contact performance of the cell is greatly improved.

Description

Technical Field

[0001] The invention relates to a passivation contact solar cell and a preparation method thereof. Background Art

[0002] The excellent passivation contact effect of the passivation contact solar cell is mainly determined by the stacked tunneling oxide layer and the doped polysilicon layer. Among them, the concentration of the doping element in the doped polysilicon layer will affect the passivation, contact performance and yield of the passivation contact solar cell. Specifically, although the polysilicon layer with a higher doping concentration is conducive to the improvement of passivation and contact performance, the high doping concentration will increase the risk of penetrating the tunneling oxide layer. Based on this, the yield of the passivation contact solar cell is currently mainly guaranteed by sacrificing the contact performance of the passivation contact solar cell. Therefore, the passivation and contact performance of the passivation contact battery have not yet been fully developed, which is the key direction for improving the efficiency of the passivation contact battery. Summary of the invention

[0003] In view of this, the present invention provides a passivated contact solar cell and a preparation method thereof, which can ensure the excellent passivation effect and high yield of the passivated contact solar cell while greatly improving the contact performance of the battery.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a passivated contact solar cell, comprising:

[0006] Silicon substrate;

[0007] A passivation contact structure disposed on the first main surface of the silicon substrate;

[0008] A diffusion control layer stacked on the passivation contact structure and facing away from the silicon substrate;

[0009] An external doping layer stacked on the diffusion regulating layer on a side away from the silicon substrate;

[0010] The type of doping element included in the outer doping layer is consistent with the type of doping element included in the passivation contact structure;

[0011] The doping concentration of the outer doping layer is higher than the doping concentration of the passivation contact structure.

[0012] In a second aspect, an embodiment of the present invention provides a method for preparing a passivated contact solar cell provided in the embodiment of the first aspect, comprising:

[0013] Step 1: forming a passivation contact structure on a first main surface of a silicon substrate;

[0014] Step 2, forming a diffusion control layer and an external doping layer by stacking in sequence on a side of the passivation contact structure away from the silicon substrate;

[0015] Step 3: diffuse the doping elements in the outer doping layer through in-situ annealing and high-temperature diffusion treatment in sequence, so that the doping concentration of the outer doping layer is higher than the doping concentration of the passivation contact structure.

[0016] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0017] The passivated contact solar cell provided by the embodiment of the present invention sequentially stacks a diffusion control layer and an external doping layer on the side of the passivation contact structure on the first main surface of the silicon substrate away from the silicon substrate, and blocks the diffusion of doping elements through the diffusion control layer, so that the doping concentration of the external doping layer can be independently controlled, and the doping concentration of the external doping layer will not affect the doping concentration of the passivation contact structure, so that a stacked structure in which the doping concentration of the external doping layer is higher than the doping concentration of the passivation contact structure can be obtained, so that the passivated contact solar cell can effectively guarantee the excellent passivation effect and high yield of the passivated contact solar cell, and greatly improve the contact performance of the battery.

[0018] In addition, by designing a diffusion control layer to block the diffusion of doping elements and activating the doping elements in the external doping layer, the risk of damage to the passivation contact structure can be avoided, thereby improving the yield rate of the passivation contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional structural diagram of a passivated contact solar cell according to an embodiment of the present invention;

[0020] Figure 2 It is a main process diagram of a first passivated contact solar cell preparation method according to an embodiment of the present invention;

[0021] Figure 3 is a schematic diagram of the main process of a second method for preparing a passivated contact solar cell according to an embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of structural changes corresponding to steps S301 to S311 in the preparation method according to an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of structural changes corresponding to steps S312 to S314 in the preparation method according to an embodiment of the present invention.

[0024] The reference numerals are as follows:

[0025] 10-silicon substrate; 20-passivation contact structure; 21-tunneling oxide layer; 22-internal doping layer; 30-diffusion control layer; 40-external doping layer; 50-first anti-reflection layer; 60-first metal electrode; 70-emitter structure; 80-aluminum oxide layer; 90-second anti-reflection layer; 100-second metal electrode. DETAILED DESCRIPTION

[0026] The tunnel oxide and passivated contact (TOPCon) structure in the existing passivated contact solar cell is mainly composed of a tunnel oxide layer and a phosphorus-doped polysilicon layer formed on the back of the passivated contact solar cell. For the existing passivated contact solar cell, an anti-reflection layer and an electrode in ohmic contact with the phosphorus-doped polysilicon layer are directly formed on the tunnel oxide passivated contact structure composed of the tunnel oxide layer and the phosphorus-doped polysilicon layer. Therefore, the passivation effect and contact performance of the existing passivated contact solar cell are mainly determined by the compactness and thickness of the tunnel oxide layer, and the thickness and doping concentration of the phosphorus-doped polysilicon layer.

[0027] The above existing passivated contact solar cells have a problem: although the phosphorus-doped polysilicon layer (N + Poly-Si) higher concentration (higher concentration is generally not less than 3E 20 atoms / cm 3 The concentration of 3E is more conducive to improving the field passivation effect and contact performance, but it increases the risk of the tunnel oxide layer being penetrated. 20 atoms / cm 3 ), which will reduce the contact performance between it and the metal electrode. At present, although there is a stacking of lightly doped polysilicon layers and heavily doped polysilicon layers in the hope of balancing the contact and passivation issues. However, in the prior art, low pressure The processes represented by the one-step phosphorus diffusion process of Low Pressure Chemical Vapor Deposition (LPCVD) and the in-situ doping and annealing process of Plasma Enhanced Chemical Vapor Deposition (PECVD) have always been unable to achieve a double-layer doped polysilicon layer with a high concentration difference (outer high-concentration doped polysilicon layer / inner low-concentration doped polysilicon layer, N ++ Poly-Si / N + Through research, it was found that the double-layer doped polysilicon layer (N ++ Poly-Si / N +For example, if phosphorus atoms want to penetrate the outermost SiO2 layer into the inner Poly-Si layer, the propulsion temperature needs to be increased, and high flux increases the risk of the tunnel oxide layer being penetrated. Therefore, the process window of this process is narrow, and it is impossible to increase the doping concentration difference between the outer and inner Poly-Si layers. In addition, PECVD preparation of double-layer doped polysilicon layer (N ++ Poly-Si / N + Poly-Si) structure, in order to ensure the uniformity of doping, phosphorus atoms are doped in excess. After high temperature annealing, phosphorus atoms are activated. The solid solubility of phosphorus atoms is directly related to the annealing temperature. Therefore, as long as the annealing is carried out at the same temperature, even if there is a large difference in the amount of PH3 permeation in the inner and outer layers, the final N ++ Poly-Si and N + Poly-Si is only lower than 2E 20 atoms / cm 3 (Among them, aE b atoms / cm 3 =a×10 b atoms / cm 3 ), making it difficult to maximize the benefits of passivation, contact performance improvement, and parasitic absorption losses.

[0028] Furthermore, this patent studies the thickness, doping concentration and other parameters of the phosphorus-doped polysilicon layer in the existing passivated contact solar cells and finds that, from the perspective of the passivation mechanism of the doped polysilicon layer, it is necessary to control the doping concentration in the doped polysilicon layer to 3E 20 atoms / cm 3 ~4E 20 atoms / cm 3 The thickness of the doped polysilicon layer is in the range of 30nm~40nm, which can make the doped polysilicon layer have a better passivation effect, and the higher the concentration, the less effect on the passivation, but the higher the concentration, the better the contact. 20 atoms / cm 3 ~ 4E 20 atoms / cm 3 At a doping concentration of 200 nm and a thickness of 30 nm to 40 nm, the lateral transmission resistance of the doped polysilicon layer is very large and cannot meet the slurry sintering process (>60 nm). The tunneling oxide layer is easily broken, resulting in a low yield or good product rate of the passivated contact solar cell.

[0029] In order to simultaneously improve the passivation effect and contact performance of the doped polysilicon layer and improve the production yield or good product rate of the passivated contact solar cell, an embodiment of the present invention provides a passivated contact solar cell with a new structure.

[0030] The one structure stacked on another structure involved in the embodiments of the present invention generally means that the one structure is formed after the other structure, and the one structure is located on the main surface of the other structure away from the silicon substrate. It is worth noting that the one structure stacked on the other structure does not specifically mean that the one structure is located above the other structure, and it can also be located below the other structure.

[0031] The type of the doping element involved in the embodiments of the present invention is generally N-type or P-type.

[0032] The doping concentration involved in the embodiments of the present invention generally refers to the concentration of the doping element contained in the doping layer after the doping element is activated.

[0033] It is worth noting that the terms "first", "second", etc. included in the embodiments of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific number or sequence. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, and this is merely a way of distinguishing objects with the same attributes when describing them in the embodiments of the present invention.

[0034] Embodiments of the present invention Figure 1 A schematic cross-sectional structure diagram of a passivation contact solar cell provided by an embodiment of the present invention is shown.

[0035] like Figure 1 As shown, the passivated contact solar cell provided by the embodiment of the present invention may include:

[0036] Silicon substrate 10;

[0037] A passivation contact structure 20 disposed on the first main surface of the silicon substrate 10;

[0038] A diffusion control layer 30 stacked on the side of the passivation contact structure 20 away from the silicon substrate 10;

[0039] An external doping layer 40 stacked on the diffusion control layer 30 on a side away from the silicon substrate 10;

[0040] The type of doping element included in the outer doping layer 40 is consistent with the type of doping element included in the passivation contact structure 20;

[0041] The doping concentration of the outer doping layer 40 is higher than the doping concentration of the passivation contact structure 20 .

[0042] The silicon substrate 10 may be an N-type silicon substrate or a P-type silicon substrate. In a preferred embodiment, the silicon substrate 10 is an N-type silicon substrate.

[0043] In a preferred embodiment, the first main surface of the silicon substrate 10 is the back side of the passivation contact solar cell. More preferably, the first main surface of the silicon substrate 10 is a polished surface to ensure the formation of a uniform passivation contact structure 20, a diffusion control layer 30 and an external doping layer 40.

[0044] The passivated contact solar cell provided by the embodiment of the present invention sequentially stacks a diffusion control layer 30 and an external doping layer 40 on the side of the passivation contact structure 20 on the first main surface of the silicon substrate 10 away from the silicon substrate 10, and blocks the diffusion of doping elements through the diffusion control layer 30, so that the doping concentration of the external doping layer 40 can be independently controlled, and the doping concentration of the external doping layer 40 will not affect the doping concentration of the passivation contact structure 20, thereby obtaining a structure in which the doping concentration of the external doping layer 40 is higher than the doping concentration of the passivation contact structure 20, so that the passivated contact solar cell can effectively guarantee the excellent passivation effect and high yield of the passivated contact solar cell, and greatly improve the contact performance of the battery.

[0045] In addition, by designing the diffusion control layer 30 to block the diffusion of doping elements, the risk of damage to the passivation contact structure 20 can be avoided during the process of activating the doping elements in the external doping layer 40, thereby improving the yield rate of the passivation contact solar cell.

[0046] The specific structure and formation method of each functional layer of the passivation contact solar cell provided by the embodiment of the present invention are described in detail below.

[0047] Among them, the passivation contact structure 20 is laid on the entire first main surface or is arranged at intervals on the first main surface. For the structure in which the passivation contact structure 20 is laid on the entire first main surface, an emitter is arranged on the second main surface of the silicon substrate 10. For the structure in which the passivation contact structure 20 is arranged at intervals on the first main surface, an emitter may also be arranged on the first main surface, wherein the passivation contact structure 20 and the emitter are alternately arranged, and an isolation region is arranged between the passivation contact structure 20 and the emitter, and the isolation region blocks the contact between the passivation contact structure 20 and the emitter. For the structure in which the passivation contact structure 20 and the emitter are alternately arranged on the first main surface of the silicon substrate 10, the emitter can be obtained by the existing preparation method, which will not be repeated here. In a preferred embodiment, in a passivation contact solar cell, the passivation contact structure 20 is laid on the entire first main surface.

[0048] Specifically, Figure 1As shown, the above-mentioned passivation contact structure 20 may include: a tunneling oxide layer 21 and an inner doping layer 22 stacked from the inside to the outside, wherein the doping concentration of the outer doping layer 40 is higher than the doping concentration of the inner doping layer 22. For the structure in which the passivation contact structure 20 includes the tunneling oxide layer 21 and the inner doping layer 22, the doping concentration of the passivation contact structure 20 is substantially the doping concentration of the inner doping layer 22. Since a diffusion control layer 30 is provided between the outer doping layer 40 and the inner doping layer 22, it is convenient to control the concentration difference between the doping concentration of the outer doping layer 40 and the doping concentration of the inner doping layer 22, and the concentration difference can be made to exceed 2E 20 atoms / cm 3 , which can improve the energy level alignment, is beneficial to enhancing the field passivation effect and the passivation effect of the inner doping layer 22, and the passivation effect of the inner doping layer 22 determines the passivation effect of the passivation contact structure 20 and the passivation contact solar cell. Therefore, the passivation effect of the passivation contact structure 20 and the passivation contact solar cell can be effectively improved through the inner doping layer 22.

[0049] Furthermore, the doping concentration of the outer doping layer 40 affects the conductivity and carrier transport selectivity of the outer doping layer 40. The higher the doping concentration of the outer doping layer 40, the lower the square resistance of the outer doping layer 40, the stronger its conductivity, and the higher the electron content, so that the outer doping layer 40 can provide more electrons to the first metal electrode 60 it contacts, thereby reducing its contact resistance and lateral transmission resistance with the first metal electrode 60, and avoiding the risk of the tunneling oxide layer 21 being pierced, effectively improving the current collection capacity of the passivated contact solar cell. In addition, the inner doping layer 22 can ensure the passivation effect of the passivated contact solar cell, and the outer doping layer 40 helps to greatly improve the contact performance of the passivated contact solar cell. Therefore, the inner doping layer 22 cooperates with the outer doping layer 40, so that the passivated contact solar cell can effectively ensure the excellent passivation effect and high yield of the passivated contact solar cell, and greatly improve the contact performance of the battery.

[0050] In addition, by setting the diffusion control layer 30, the doping elements of the outer doping layer 40 can be blocked from entering the passivation contact structure 20, so that the passivation contact structure 20 can enhance the field passivation effect, thereby enhancing the passivation capability. In addition, the doping concentration of the outer doping layer 40 can be enhanced and adjusted, thereby realizing the inner doping layer 22 and the outer doping layer 40 with a high concentration difference, improving the energy level alignment, and the inner doping layer 22 and the outer doping layer 40 with a high concentration difference can reduce the contact resistivity and the lateral transmission resistance, and improve the battery contact performance.

[0051] Furthermore, the diffusion barrier layer 30 can protect the inner doping layer 22 and the tunneling oxide layer 21 from being affected by the doping process of the outer doping layer 40, thereby ensuring the stability of the passivation mechanism and increasing the process window of the passivation contact solar cell.

[0052] Generally speaking, the thickness of the tunnel oxide layer 21 included in the passivation contact structure 20 can be set to 1nm~2nm. For example, the thickness of the tunnel oxide layer 21 can be set to 1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.7nm, 1.8nm, 1.9nm and 2nm, etc. By controlling the thickness of the tunnel oxide layer 21 within the range of 1nm~2nm, it is ensured that the tunnel oxide layer 21 has a relatively good tunneling effect, and can be obtained by using the existing preparation process of the tunnel oxide layer 21. Preferably, the plasma enhanced chemical vapor deposition (PECVD) technology is selected to deposit silicon dioxide to obtain the tunnel oxide layer 21. While ensuring the compactness of the tunnel oxide layer 21, it cooperates with the inner doping layer 21, the diffusion control layer 30 and the outer doping layer 40, which can prevent the tunnel oxide layer 21 from being damaged by the doping elements, and can reduce the recombination loss, improve the transmission capacity of the majority carriers, thereby effectively improving the photoelectric conversion efficiency of the passivation contact solar cell.

[0053] In addition, the inner doping layer 22 included in the passivation contact structure 20 is generally a doped polysilicon layer. The doped polysilicon layer is formed mainly by first forming a doped silicon thin film layer, and then annealing the silicon in the doped silicon thin film layer to form polysilicon, and activating the doping elements therein. The doped polysilicon layer can also be obtained by using an existing preparation process. Preferably, a plasma enhanced chemical vapor deposition (PECVD) technology is selected to deposit and in-situ doping to obtain a doped silicon thin film layer. That is, the inner doping layer 22 can be formed by PECVD deposition of an amorphous silicon layer combined with in-situ doping, and annealing and activation. For the inner doping layer 22, the annealing temperature can be 880°C~900°C. For example, the annealing temperature for the inner doping layer 22 can be controlled to be 880°C, 885°C, 890°C, 893°C, 895°C, 898°C, 900°C, etc. It is worth noting that the annealing process for the inner doping layer 22 can be performed after the doped silicon thin film layer for the inner doping layer 22 is formed and before the diffusion control layer 30 is formed. In addition, the annealing process for the inner doping layer 22 can also be performed after the doped silicon thin film layer for the outer doping layer 40 is initially formed by PECVD deposition of an amorphous silicon layer combined with in-situ doping, that is, the annealing process for the inner doping layer 22, and the doped silicon thin film layer for the outer doping layer 40 and the doped silicon thin film layer for the inner doping layer 22 that are initially formed are annealed simultaneously.

[0054] Furthermore, the thickness of the inner doping layer 22 is generally set to 30nm~50nm. For example, the thickness of the inner doping layer 22 can be 30nm, 33nm, 35nm, 38nm, 40nm, 45nm, 48nm or 50nm. By controlling the thickness of the inner doping layer 22 within the range of 30nm~50nm, the passivation effect of the inner doping layer 22 can be effectively improved, and the doping elements of the inner doping layer 22 can be prevented from diffusing and destroying the tunneling oxide layer. In addition, the thickness range of the inner doping layer 22 cooperates with the diffusion control layer 30 to prevent the doping elements in the heavily doped outer doping layer 40 from diffusing and destroying the tunneling oxide layer.

[0055] In particular, the doping concentration of the inner doping layer 22 can be set to 3E 20 atoms / cm 3 ~ 4E 20 atoms / cm 3 The doping concentration of the inner doping layer 22 is determined by the amount of in-situ doping during the process of forming the doped silicon film by combining the PECVD deposition of the amorphous silicon layer with in-situ doping. For example, in the case where the doping element of the inner doping layer 22 is an N-type doping element (such as phosphorus), during the in-situ doping process, the doping element comes from the introduced PH3 gas, and the amount of the in-situ doping is the amount of PH3 gas introduced. 20 atoms / cm 3 ~ 4E 20 atoms / cm 3 The phosphorus doping concentration can be obtained by adjusting the amount of PH3 gas introduced. That is to say, in the embodiment of the present invention, the doping elements of the inner doping layer 22 are derived from the doping elements in the doped silicon film formed by the above-mentioned PECVD deposited amorphous silicon layer combined with in-situ doping. The doping elements in the outer doping layer 40 will not diffuse into the inner doping layer 22.

[0056] Furthermore, in order to improve the controllability of the doping concentration of the inner doping layer 22 and ensure that after the doping elements are activated, there is still a relatively large doping concentration difference between the inner doping layer 22 and the outer doping layer 40. The above-mentioned diffusion control layer 30 may contain silicon oxide and / or silicon oxynitride. Preferably, the diffusion control layer 30 is silicon oxide. By selecting silicon oxide to prepare the diffusion control layer 30, no new materials will be introduced in the entire passivated contact solar cell preparation process, which facilitates the process operation and industrialization of the passivated contact solar cell production, and can effectively control the production cost of the passivated contact solar cell.

[0057] Further, in order to ensure the performance of the diffusion control layer 30 and control the production cost of the passivation contact solar cell, the thickness of the diffusion control layer 30 can be set to 2nm~10nm. For example, the thickness of the diffusion control layer 30 can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm. By controlling the thickness of the diffusion control layer 30 within the range of 2nm~10nm, it can be satisfied that the outer doping layer 40 is blocked from spreading to the inner doping layer 22, and during the activation process of the doping elements in the outer doping layer 40, the diffusion control layer 30 can be partially penetrated by the doping elements to produce a pinhole effect, so that during the subsequent metal slurry sintering process, the metal slurry can burn through the outer doping layer 40, but will not affect the tunneling oxide layer 21 in the passivation contact structure 20. Moreover, the thickness control of the diffusion control layer 30 is conducive to the stability of the passivation of the inner doping layer 22, and the subsequent outer doping layer 40 formation process has a relatively large process window, which is convenient for the subsequent preparation of the outer doping layer 40 and the industrialization of the passivation contact solar cell.

[0058] The diffusion control layer 30 can be formed by PECVD. That is to say, the diffusion control layer 30 can be completed in the same PECVD equipment as the tunneling oxide layer 21 and the inner doping layer 22, wherein the gas source used by the diffusion control layer 30 can be the same as the gas source used by the tunneling oxide layer 21, and only the source flux, reaction temperature and other parameters of the gas source need to be adjusted. That is, in the process of forming the tunneling oxide layer 21, the inner doping layer 22 and the diffusion control layer 30, it is only necessary to replace the gas source input into the PECVD equipment and adjust the reaction parameters, without the need to transport the silicon substrate 10, and the process is simple.

[0059] Furthermore, based on the structure of the tunneling oxide layer 21, the internal doping layer 22, and the diffusion control layer 30, the external doping layer 40 is generally also a doped polysilicon layer. Specifically, the external doping layer 40 is generally formed by combining a PECVD deposition process of an amorphous silicon layer, an in-situ doping process, an in-situ annealing process, and a high-temperature diffusion process to form a silicon substrate 10 with a diffusion control layer 30.

[0060] For the external doping layer 40, the corresponding PECVD deposition process of an amorphous silicon layer and the in-situ doping process are specifically implemented as follows: the silicon substrate 10 formed with the diffusion control layer 30 is placed in a PECVD device, a silicon film is deposited on the diffusion control layer 30 by PECVD, and during the deposition of the silicon film, a gas source containing doping elements is introduced, and the silicon film is doped with elements by in-situ doping to form a doped silicon film. The PECVD deposition process of an amorphous silicon layer and the in-situ doping process can be completed in the same PECVD device as the aforementioned tunneling oxide layer 21, the internal doping layer 22 and the diffusion control layer 30. The doping concentration in the doped silicon film initially formed by the PECVD deposition process of an amorphous silicon layer and the in-situ doping process can be controlled according to demand. In a preferred embodiment, in order to facilitate the regulation of the doping concentration in the doped silicon film preliminarily formed by the PECVD deposition of the amorphous silicon layer process and the in-situ doping process, the doping concentration in the preliminarily formed doped silicon film is made consistent with the doping concentration of the doped silicon film corresponding to the internal doping layer 22, that is, the parameters of the preliminarily formed doped silicon film, such as the source flux, the PECVD deposition parameters, etc., are regulated to be consistent with the parameters used to form the doped silicon film corresponding to the internal doping layer 22, thereby simplifying the process regulation of forming the external doping layer 40.

[0061] Further, for the external doping layer 40, the corresponding in-situ annealing process is specifically implemented as follows: after the in-situ doping process, the silicon substrate on which the doped silicon thin film layer corresponding to the external doping layer 40 is formed is subjected to in-situ annealing activation process in the PECVD device, and the in-situ annealing process can be performed simultaneously with the in-situ annealing activation process of the internal doping layer 22, that is, after the doped silicon thin film layer corresponding to the external doping layer 40 is formed, the internal doping layer 22 (i.e., the doped polysilicon layer of the inner layer) is formed by in-situ annealing activation process, and the external doping layer 40 is preliminarily formed. Since the diffusion control layer 30 blocks the diffusion of the doping elements, and the preliminary formation conditions of the doped silicon thin film for the external doping layer 40 are consistent with the formation conditions corresponding to the internal doping layer 22, at this time, the doping concentration of the preliminarily formed external doping layer 40 is substantially consistent with the doping concentration of the internal doping layer 22, and does not reach the actual doping concentration required for the external doping layer 40.

[0062] The high-temperature diffusion treatment process corresponding to the above-mentioned initially formed external doping layer 40 is specifically implemented as follows: after the in-situ annealing treatment process, the silicon substrate with the external doping layer 40 is placed in a high-temperature furnace, the temperature is further increased, and a gas source containing doping elements is introduced thereto, and the doping elements are further deposited and doped on the initially formed external doping layer 40, so that the doping elements are further diffused at high temperature on the initially formed external doping layer 40, the doping concentration of the external doping layer 40 is increased, and the doping concentration of the external doping layer 40 is independently controlled without affecting the doping concentration of the internal doping layer 22.

[0063] Among them, the temperature used in the high-temperature diffusion treatment process is higher than the temperature of the in-situ annealing process. Specifically, the temperature of the annealing process as described above is generally 880°C~900°C, for example, the temperature of the in-situ annealing process can be 880°C, 885°C, 890°C, 893°C, 895°C, 898°C or 900°C. The temperature used in the high-temperature diffusion treatment process is generally 900°C~920°C. For example, the temperature used in the high-temperature diffusion treatment process can be 900°C, 905°C, 910°C, 915°C, 920°C, 910°C, 915°C, 918°C or 920°C. It can be understood that when the temperature of the in-situ annealing process is controlled at 900°C, the temperature used in the high-temperature diffusion treatment process is higher than 900°C. When the temperature of the in-situ annealing process is lower than 900°C, the temperature used in the high-temperature diffusion treatment process can be 900°C or higher than 900°C. By controlling the temperature of the high-temperature diffusion treatment process to be higher than the temperature of the in-situ annealing treatment process, the doping concentration of the external doping layer 40 can be effectively controlled to be increased to a relatively high level, and the doping elements of the external doping layer 40 can be partially diffused through the diffusion control layer 30, so that the diffusion control layer 30 can produce a pinhole effect.

[0064] For the above-mentioned external doping layer 40, its thickness is generally designed to be 50nm~150nm. For example, the thickness of the external doping layer 40 can be 50nm, 55nm, 58nm, 60nm, 65nm, 70nm, 75nm, 80nm, 90nm, 95nm, 100nm, 110nm, 120nm, 130nm, 140nm or 150nm, etc. By controlling the thickness of the external doping layer 40 within the range of 50nm~150nm, in conjunction with the diffusion control layer 30, the metal slurry can diffuse through the diffusion control layer 30, form an ohmic contact with the internal doping layer 22, and avoid the metal slurry from damaging the tunneling oxide layer 21. Further, by cooperating with the thickness of the external doping layer 40 and the relatively large doping concentration difference between the external doping layer 40 and the internal doping layer 22, the lateral transmission resistance of the internal doping layer 22 can be effectively reduced.

[0065] In particular, the doping concentration of the outer doping layer 40 is generally controlled to be 7E 20 atoms / cm 3 ~ 2E 21 atoms / cm 3 The doping concentration of the outer doping layer 40 is determined by the above-mentioned in-situ doping process and high-temperature diffusion process. For example, the doping concentration of the outer doping layer 40 can be 7E 20 atoms / cm 3 ,8E 20 atoms / cm 3 ,9E 20atoms / cm 3 , 1E 21 atoms / cm 3 or 2E 21 atoms / cm 3 By adjusting the doping concentration of the outer doping layer 40, the 20 atoms / cm 3 ~2E 21 atoms / cm 3 The doping concentration difference between the outer doping layer 40 and the inner doping layer 22 is ensured to be within the range, which can reduce the lateral transmission resistance of the inner doping layer 22 and improve the contact performance. In addition, the high concentration difference can effectively improve the energy level alignment and is conducive to improving the passivation effect.

[0066] In addition, by controlling the doping concentration and thickness of the external doping layer 40, during the process of forming the external doping layer 40, the doping elements in the external doping layer 40 can partially diffuse through the diffusion control layer 30, causing the diffusion control layer 30 to produce a pinhole effect, thereby facilitating the subsequent metal slurry sintering to stably contact the internal doping layer 22, and ensuring that the internal doping layer 22, the diffusion control layer 30 and the external doping layer 40 cooperate with each other, thereby ensuring that the internal doping layer 22 has a high passivation effect, and helping to further reduce the lateral transmission resistance and contact resistivity of the internal doping layer 22.

[0067] For each of the above embodiments, for the inner doping layer 22 and the outer doping layer 40, for the structure where the silicon substrate 10 is an N-type silicon substrate, the doping elements contained in the inner doping layer 22 and the outer doping layer 40 are N-type doping elements such as phosphorus doping elements commonly used in solar cells; for the structure where the silicon substrate 10 is a P-type silicon substrate, the doping elements contained in the inner doping layer 22 and the outer doping layer 40 are P-type doping elements such as boron doping elements commonly used in solar cells. In a preferred embodiment, the silicon substrate 10 is an N-type silicon substrate, and accordingly, the doping elements contained in the inner doping layer 22 and the outer doping layer 40 are N-type doping elements.

[0068] It is worth noting that the above embodiments are only preferred options for the tunnel oxide layer 21. The tunnel oxide layer 21 may also be replaced by an intrinsic polysilicon layer. The intrinsic polysilicon layer may also be formed by the above PECVD deposition.

[0069] Furthermore, if Figure 1 As shown, the above passivated contact solar cell may further include: a first anti-reflection layer 50 stacked on the external doping layer 40 .

[0070] In addition, if Figure 1As shown, the above passivation contact solar cell may further include: a first metal electrode 60 penetrating the first anti-reflection layer 50 , the outer doping layer 40 and the diffusion control layer 30 , wherein the first metal electrode 60 is electrically connected to the inner doping layer 22 .

[0071] The above embodiments mainly relate to the structure of the first main surface of the silicon substrate 10. The first main surface of the silicon substrate 10 can be a light-receiving surface (i.e., the main surface of the silicon substrate 10 facing the sunlight during the use of the passivated contact solar cell) or a backlight surface (i.e., the main surface of the silicon substrate 10 facing away from the sunlight during the use of the passivated contact solar cell). In a preferred embodiment, the first main surface of the silicon substrate 10 is the backlight surface.

[0072] Furthermore, if Figure 1 As shown, with respect to the second main surface of the silicon substrate 10 , the passivated contact solar cell further includes: an emitter structure 70 disposed on the second main surface of the silicon substrate 10 .

[0073] Specifically, the emitter structure 70 may include: a diffusion layer disposed on the second main surface of the silicon substrate 10, wherein the doping type of the diffusion layer is opposite to the doping type of the outer doping layer 40. For example, if the doping type of the outer doping layer 40 is N-type doping, the doping type of the diffusion layer is P-type doping. In addition, for a structure in which the silicon substrate 10 is an N-type silicon substrate, the doping element in the diffusion layer is a P-type doping element; for a structure in which the silicon substrate 10 is a P-type silicon substrate, the doping element contained in the diffusion layer is an N-type doping element.

[0074] In addition, in addition to the diffusion layer, the emitter structure 70 may further include an intrinsic polysilicon layer disposed between the diffusion layer and the silicon substrate 10 .

[0075] Furthermore, if Figure 1 As shown, the second main surface of the silicon substrate 10 may further include: an aluminum oxide layer 80 stacked on the emitter structure 70; a second anti-reflection layer 90 stacked on the aluminum oxide layer 80; and a second metal electrode 100 penetrating the second anti-reflection layer 90 and electrically connected to the diffusion layer.

[0076] It is worth mentioning that Figure 1 The schematic diagram of the cross-sectional structure of the passivation contact solar cell including all the structures of the above-mentioned embodiments is only given as an example. Under the condition of ensuring the structural relationship and coordination between the passivation contact structure 20, the diffusion control layer 30 and the external doping layer 40 given in the embodiment of the present invention, those skilled in the art can add other functional layers or reduce functional layers according to needs, such as reducing the anti-reflection layer, reducing the aluminum oxide layer on the front side, etc. Any passivation contact solar cell realized with the structural relationship and coordination between the passivation contact structure 20, the diffusion control layer 30 and the external doping layer 40 as the design core is within the scope of protection of this patent.

[0077] Furthermore, an embodiment of the present invention provides a method for preparing a passivated contact solar cell. Figure 2 As shown, the method for preparing the passivated contact solar cell may include the following steps:

[0078] Step S201: forming a passivation contact structure 20 on a first main surface of a silicon substrate 10;

[0079] Step S202: forming a diffusion control layer 30 and an external doping layer 40 on the side of the passivation contact structure 20 away from the silicon substrate 10 in sequence;

[0080] Step S203 : diffusing doping elements in the outer doping layer 40 through in-situ annealing and high-temperature diffusion treatment in sequence, so that the doping concentration of the outer doping layer 40 is higher than the doping concentration of the passivation contact structure 20 .

[0081] Specifically, the specific implementation of the above step S201 may include the following steps:

[0082] Step S2011: placing the silicon substrate 10 in a PECVD boat;

[0083] Step S2012: introducing N2O into the PECVD boat at a flow rate of 5000 sccm to 20000 sccm to grow a tunneling oxide layer 21 on the first main surface of the silicon substrate 10;

[0084] For example, in this step, the flow rate can be controlled to be 5000sccm, 6000sccm, 7000sccm, 8000sccm, 10000sccm, 12000sccm, 13000sccm, 15000sccm, 17000sccm, 18000sccm, 19000sccm or 20000sccm, etc., where sccm is standard cubic centimeters per minute. per minute).

[0085] Step S2013: H2, SiH4 and gas A are introduced into the PECVD boat according to the H2 flow rate of 5000sccm~20000sccm, the SiH4 flow rate of 1000sccm~10000sccm and the gas A containing the doping element flow rate of 50sccm~500sccm, and the inner doping layer 22 is grown on the side of the tunneling oxide layer 21 away from the silicon substrate 10, wherein the passivation contact structure 20 includes the tunneling oxide layer 21 and the inner doping layer 22, and A is a gaseous compound containing the doping element required for the outer doping layer 40.

[0086] For example, when the doping element of the inner doping layer 22 is phosphorus, the above A is PH3, and the flow rate of H2 can be 5000sccm, 8000sccm, 10000sccm, 13000sccm, 15000sccm, 17000sccm, 19000sccm or 20000sccm, etc. The flow rate of SiH4 can be 1000sccm, 3000sccm, 5000sccm, 6000sccm, 8000sccm or 10000sccm, etc. The flow rate of PH3 can be 50sccm, 80sccm, 100sccm, 120sccm, 150sccm, 200sccm, 250sccm, 280sccm, 300sccm, 320sccm, 350sccm, 380sccm, 400sccm, 430sccm, 450sccm, 470sccm or 500sccm, etc.

[0087] In the above process, the tunnel oxide layer 21 is formed by PECVD deposition, and the inner doping layer 22 is formed by combining PECVD deposition with in-situ doping. The PECVD deposition parameters used to form the tunnel oxide layer 21 and the inner doping layer 22, such as temperature and equipment operating power, can be adjusted according to demand.

[0088] Furthermore, the specific implementation of the above step S202 may include:

[0089] Step S2021: introducing N2O into the PECVD boat at a flow rate of 10000-50000 sccm to grow a diffusion control layer 30 on the passivation contact structure 20;

[0090] For example, in this step, the flow rate can be controlled to be 5000sccm, 6000sccm, 7000sccm, 8000sccm, 10000sccm, 12000sccm, 13000sccm, 15000sccm, 17000sccm, 18000sccm, 19000sccm, 20000sccm, 21000sccm, 22000sccm, 24000sccm, 25000sccm, 27000sccm, 29000sccm, 30000sccm, 32000sccm, 33000sccm, 35000sccm, 37000sccm, 39000sccm, 40000sccm, 42000sccm, 43000sccm, 45000sccm, 46000sccm, 48000sccm or 50000sccm, etc.

[0091] This step uses the same raw material gas as the step S2011 used to form the tunnel oxide layer 21, which effectively reduces the types of raw materials required for preparing the passivation contact solar cell, thereby effectively controlling the cost.

[0092] Step S2022: H2, SiH4 and gas A are introduced into the PECVD boat according to the H2 flow rate of 5000sccm~20000sccm, the SiH4 flow rate of 1000sccm~10000sccm and the gas A flow rate of 50sccm~500sccm containing the doping element, and an external doping layer 40 is grown on the diffusion control layer 30, wherein A is a gaseous compound containing the doping element required for the external doping layer 40.

[0093] For example, when the doping element of the inner doping layer 22 is phosphorus, the above A is PH3, and the flow rate of H2 can be 5000sccm, 8000sccm, 10000sccm, 13000sccm, 15000sccm, 17000sccm, 19000sccm or 20000sccm, etc. The flow rate of SiH4 can be 1000sccm, 3000sccm, 5000sccm, 6000sccm, 8000sccm or 10000sccm, etc. The flow rate of PH3 can be 50sccm, 80sccm, 100sccm, 120sccm, 150sccm, 200sccm, 250sccm, 280sccm, 300sccm, 320sccm, 350sccm, 380sccm, 400sccm, 430sccm, 450sccm, 470sccm or 500sccm, etc.

[0094] The raw gas and deposition conditions used in step S2022, such as the flow rate, source amount, and deposition parameters of the raw gas, can be independently controlled. In a preferred embodiment, the raw gas and deposition conditions used in step S2022, such as the flow rate, source amount, and deposition parameters of the raw gas, are controlled to be consistent with the parameters of forming the inner doping layer 22 in step S2013, so as to ensure that the high temperature diffusion treatment in the subsequent step S203 accurately controls the doping concentration of the outer doping layer 40 formed in step S2022, and by controlling the various parameters used in step S2022 to be consistent with the parameters of forming the inner doping layer 22 in step S2013, the process operation can be simplified, and the production efficiency and yield rate of the passivated contact solar cell can be effectively improved.

[0095] For each of the above-mentioned preparation method embodiments, further, after the above-mentioned step S202 and before step S203, it also includes: performing in-situ annealing activation treatment on the formed passivation contact structure 20 and the external doping layer 40. Through the in-situ annealing activation treatment, the internal doping layer 22 and the external doping layer 40 of the passivation contact structure 20 form a doped polysilicon layer, and the doping elements therein are activated. During the in-situ annealing activation process, the presence of the diffusion control layer 30 can prevent the doping elements of the external doping layer 40 from entering the internal doping layer 22, and while ensuring the activation of the doping elements, avoid large changes in the doping concentration of the external doping layer 40 and the doping concentration of the internal doping layer 22, so that the purpose of accurately controlling the doping concentration can be achieved when the internal doping layer 22 and the external doping layer 40 are initially formed, thereby improving the controllability of the production process.

[0096] The temperature of the in-situ annealing activation treatment is generally lower than the temperature of the high temperature diffusion treatment in step S203. Specifically, the temperature of the annealing activation treatment is generally 880°C to 900°C. For example, the temperature of the annealing activation treatment can be 880°C, 885°C, 890°C, 893°C, 895°C, 898°C or 900°C.

[0097] More specifically, the temperature of the high temperature diffusion treatment in the above step S203 is 900°C to 920°C. For example, the temperature used in the high temperature diffusion treatment process may be 900°C, 905°C, 910°C, 915°C, 920°C, 910°C, 915°C, 918°C or 920°C. It can be understood that when the temperature of the in-situ annealing process is controlled at 900°C, the temperature used in the high temperature diffusion process is higher than 900°C. When the temperature of the annealing process is lower than 900°C, the temperature used in the high temperature diffusion process may be 900°C or higher than 900°C. By controlling the temperature of the high temperature diffusion process to be higher than the temperature of the annealing process, the doping concentration of the outer doping layer 40 can be effectively controlled to be higher, and the doping element part of the outer doping layer 40 can be diffused through the diffusion control layer 30, so that the diffusion control layer 30 can have a pinhole effect.

[0098] Furthermore, before the above step S201, the following steps may be further included:

[0099] Step 01: placing the silicon substrate 10 in a diffusion furnace, and diffusing doping elements on the second main surface of the silicon substrate 10 to form a diffusion layer;

[0100] Step 02: Remove the silicon glass layer plated on the first main surface and side of the silicon substrate 10 by chemical solution cleaning; for example, use an acid solution to clean the P-type diffusion layer formed on the N-type silicon substrate, and use an alkaline solution to clean the N-type diffusion layer formed on the P-type silicon substrate.

[0101] Step 03: polishing the first main surface of the silicon substrate 10.

[0102] This process is used to prepare an emitter for the second main surface of the silicon substrate 10. The polishing process not only removes the diffusion layer plated on the first main surface and the side of the silicon substrate 10, but also removes the velvet structure of the first main surface of the silicon substrate 10, ensuring that the above-mentioned functional layers such as the tunneling oxide layer 21, the internal doping layer 22, the diffusion control layer 30 and the external doping layer 40 can be uniformly formed on the first main surface of the silicon substrate 10, thereby improving the performance of each functional layer.

[0103] Furthermore, after step S203, the process further includes: wet chemical cleaning the silicon glass layer on the second main surface and the side of the silicon substrate 10. During the high temperature diffusion process in step S203, a silicon glass layer is generated on the second main surface and the side of the silicon substrate, and the silicon glass layer is removed by wet chemical cleaning.

[0104] After wet chemical cleaning of the silicon glass layer on the second main surface and the side surface of the silicon substrate 10, the method further includes: forming an Al2O3 coating film on the diffusion layer.

[0105] After forming the Al2O3 coating film on the diffusion layer, the method further includes: forming an anti-reflection layer on the Al2O3 coating film and the outer doping layer 40 by PEVCD.

[0106] After forming an anti-reflection layer on the Al2O3 coating and the external doping layer 40 by PEVCD, the method further includes: printing metal paste on the anti-reflection layer on the first main surface and the second main surface of the silicon substrate 10 by screen printing, and sintering at high temperature to complete metallization of the metal paste.

[0107] It is worth noting that in the above Figure 2 Based on the steps of the embodiment shown, they can be arbitrarily combined with the steps provided in the following embodiments to obtain a passivation contact solar cell with a passivation contact structure 20, a diffusion control layer 30 and an external doping layer 40 with various structural deformations.

[0108] Combine the following Figure 3 The steps given and Figure 4 and Figure 5 Give corresponding to Figure 3 The structural changes of each step are described in detail to explain the more preferred method for preparing the passivated contact solar cell provided by the embodiment of the present invention. Figure 3 As shown, a more preferred method for preparing the passivated contact solar cell may include the following steps:

[0109] Step S301: placing the silicon substrate 10 with a double velvet structure in a diffusion furnace, and performing diffusion of doping elements on the second main surface of the silicon substrate 10 to form a diffusion layer.

[0110] The amount of raw material gas and deposition parameters used in this step to form the diffusion layer can be directly selected from the amount of raw material gas and deposition parameters used in the existing production process.

[0111] After this step, a mask layer may be further covered on the diffusion layer, and in the subsequent step S311 , redundant functional layers such as the silicon glass layer on the second main surface may be removed directly by removing the mask layer.

[0112] Step S302: removing the silicon glass layer plated on the first main surface and the side surface of the silicon substrate 10 by cleaning with a chemical solution.

[0113] Step S303: polishing the first main surface of the silicon substrate 10.

[0114] Step S302 and step S303 can be directly completed through existing processes for preparing solar cells, and will not be described in detail here.

[0115] Step S304: placing the silicon substrate 10 in a PECVD boat.

[0116] Step S305 : introducing N 2 O into the PECVD boat at a flow rate of 5000 sccm to 20000 sccm to grow a tunneling oxide layer 21 on the first main surface of the silicon substrate 10 .

[0117] In this step, the thickness of the tunnel oxide layer 21 can be controlled to be between 1 and 2 nm by the flow rate and the deposition time, and the density of the tunnel oxide layer 21 can be controlled by the flow rate and the deposition time.

[0118] Step S306 : introducing SiH4 , PH3 and H2 into the PECVD boat according to H2 flow rates of 5000 sccm to 20000 sccm, SiH4 flow rates of 1000 sccm to 10000 sccm and PH3 flow rates of 50 sccm to 500 sccm, and growing the inner doping layer 22 on the tunneling oxide layer 21 .

[0119] Step 307 : N 2 O is introduced into the PECVD boat at a flow rate of 10000 sccm to 50000 sccm to grow a diffusion control layer 30 on the passivation contact structure 20 .

[0120] Step 308 : SiH4 , PH3 and H2 are introduced into the PECVD boat according to H2 flow rates of 5000 sccm to 20000 sccm, SiH4 flow rates of 1000 sccm to 10000 sccm and PH3 flow rates of 50 sccm to 500 sccm, to grow an external doping layer 40 on the diffusion control layer 30 .

[0121] Step 309: Performing a simultaneous in-situ annealing activation treatment on the formed inner doping layer 22 and the outer doping layer 40 at a temperature in the range of 880° C. to 900° C.

[0122] Step S310 : In a high temperature furnace, the temperature is raised to a range of 900° C. to 920° C., and doping elements are diffused in the external doping layer 40 by high temperature diffusion treatment, so that the doping concentration of the external doping layer 40 is higher than the doping concentration of the passivation contact structure 20 .

[0123] Step S311 : performing wet chemical cleaning on the second main surface and the side surface of the silicon substrate 10 .

[0124] This step is to remove the silicon glass layer plated onto the second main surface and side surfaces of the silicon substrate 10 in step S310.

[0125] Step S312: forming an Al2O3 coating on the diffusion layer.

[0126] Step S313: forming an anti-reflection layer on the Al2O3 coating film and the outer doping layer 40 by PEVCD.

[0127] Step S314: printing metal paste on the anti-reflection layer on the first main surface and the second main surface of the silicon substrate 10 respectively by screen printing, and sintering at high temperature to complete metallization of the metal paste.

[0128] The above steps S311 to S314 can be completed by using relevant processes in the existing solar cell manufacturing process, and will not be described in detail here.

[0129] The specific process of preparing the passivated contact solar cell according to the embodiment of the present invention and the performance difference between the solar cell prepared in the embodiment and the comparative example are described in detail below with a specific embodiment and a comparative example.

[0130] Example:

[0131] Step S1, texturing an N-type silicon wafer with a resistivity of 1Ω cm and a thickness of 135 μm to form a textured surface.

[0132] Step S2: Load the silicon wafer after texturing in step S1 into a diffusion furnace, introduce a boron source to complete the boron diffusion process, and form a full P + district.

[0133] Step S3: Use 10% HF to clean the BSG (borosilicate glass layer) on the back of the silicon wafer, and polish the back of the silicon wafer to obtain a back side with a tower base of 10 μm in size.

[0134] Step S4: Place the dried silicon wafer in a PECVD boat, introduce 10,000 sccm of N2O, and grow a 1.5 nm thick tunnel oxide layer.

[0135] Step S5, introducing 3000 sccm of SiH4, 200 sccm of PH3 and 10000 sccm of H2 to form a first layer of in-situ doped amorphous silicon.

[0136] Step S6, continue to introduce 15000 sccm of N2O to grow a 5 nm thick SiO2 layer as a diffusion control layer.

[0137] Step S7, introducing 3000 sccm of SiH4, 200 sccm of PH3 and 10000 sccm of H2 to form a second layer of in-situ doped amorphous silicon.

[0138] Step S8, in the annealing tube, firstly raise the temperature to 880° C. to transform the first layer of in-situ doped amorphous silicon and the second layer of in-situ doped amorphous silicon into doped polycrystalline silicon.

[0139] Step S9, in the annealing tube, the temperature is raised to 900°C to deposit and advance the phosphorus source. Since the diffusion control layer has a blocking effect on phosphorus atoms, the phosphorus diffusion process only increases the doping concentration of the second layer of in-situ doped amorphous silicon converted into doped polysilicon, and does not affect the doping concentration of the first layer of in-situ doped polysilicon converted.

[0140] Step S10, wet chemical cleaning is performed on the wrap-around coating on the front and side surfaces of the silicon wafer, the PSG (phosphosilicate glass) layer on the back surface, and the BSG on the front surface.

[0141] Step S11, Al2O3 coating is performed on the front side of the silicon wafer. Trimethylaluminum and water are introduced at 250°C to grow a 6nm thick Al2O3 layer on the front side.

[0142] Step S12: In a plasma enhanced chemical vapor deposition device, silane and ammonia are introduced at 540°C to complete the SiN deposition on both sides. x The thickness of the deposited thin films was 75 nm.

[0143] Step S13, silver paste is printed on the front and back sides of the silicon wafer by screen printing, and metallization is completed after high temperature sintering, wherein the width of the front fine grid line is 15 μm, and the width of the back fine grid line is 20 μm. Finally, after light injection treatment, a passivated contact solar cell with a high concentration difference is obtained.

[0144] Comparative Example 1: The preparation steps of Comparative Example 1 are basically the same as those of the above embodiment, except that Step S6, Step S7 and Step S9 are omitted.

[0145] Comparative Example 2: The preparation steps of Comparative Example 2 are basically the same as those of the above-mentioned embodiment, except that step S6 and step S9 are omitted, and compared with the embodiment, a second layer of in-situ doped amorphous silicon with a higher concentration is formed in step S7.

[0146] The test performances of the passivation structure solar cells prepared in the above embodiment, comparative example 1 and comparative example 2 are shown in Table 1 below.

[0147]

[0148] It can be seen that, by optimizing the N-type doping structure through the solution provided in the embodiment of the present invention, the conversion efficiency (EFF) of the passivated contact solar cell in this embodiment is increased by 0.15%, the open circuit voltage (Voc) is increased by 0.4mV, the short circuit current (Isc) is the same, and the fill factor (FF) is increased by 0.42% compared with Comparative Example 1. Compared with Comparative Example 2, the conversion efficiency (EFF) of the passivated contact solar cell in this embodiment is increased by 0.17%, the open circuit voltage (Voc) is increased by 1mV, the short circuit current (Isc) is increased by 40mA, and the fill factor (FF) is increased by 0.21%. It can be seen that in the embodiment of the present invention, a diffusion control layer 30 and an external doping layer 40 are sequentially stacked on the side of the passivation contact structure 20 away from the silicon substrate 10, wherein the type of doping elements contained in the external doping layer 40 is consistent with the type of doping elements contained in the passivation contact structure 20, and the doping concentration of the external doping layer 40 is higher than the doping concentration of the passivation contact structure 20. The passivation contact structure 20, the diffusion control layer 30 and the high-doping concentration external doping layer 40 cooperate to effectively improve the conversion efficiency, open circuit voltage and fill factor of the passivation contact solar cell.

[0149] Technical Solution 1. A passivated contact solar cell, comprising:

[0150] Silicon substrate 10;

[0151] A passivation contact structure 20 disposed on the first main surface of the silicon substrate 10;

[0152] A diffusion control layer 30 stacked on the passivation contact structure 20 and facing away from the silicon substrate 10;

[0153] An external doping layer 40 stacked on the diffusion regulating layer 30 on a side away from the silicon substrate 10;

[0154] The type of doping element included in the outer doping layer 40 is consistent with the type of doping element included in the passivation contact structure 20;

[0155] The doping concentration of the outer doping layer 40 is higher than the doping concentration of the passivation contact structure 20 .

[0156] Technical Solution 2. A passivated contact solar cell according to Technical Solution 1,

[0157] The passivation contact structure 20 is laid on the entire first main surface;

[0158] or,

[0159] The passivation contact structures 20 are arranged on the first main surface at intervals.

[0160] Technical Solution 3. According to the passivated contact solar cell of Technical Solution 1, the passivated contact structure 20 comprises: a tunneling oxide layer 21 and an inner doping layer 22 stacked from inside to outside, wherein:

[0161] The doping concentration of the outer doping layer 40 is higher than the doping concentration of the inner doping layer 22 .

[0162] Technical Solution 4. A passivated contact solar cell according to Technical Solution 3,

[0163] The thickness of the tunnel oxide layer 21 is 1 nm to 2 nm;

[0164] and / or,

[0165] The inner doping layer 22 is a doped polysilicon layer;

[0166] and / or,

[0167] The thickness of the inner doping layer 22 is 30nm~50nm;

[0168] and / or,

[0169] The doping concentration of the inner doping layer 22 is 3E 20 atoms / cm 3 ~4E 20 atoms / cm 3 ;

[0170] and / or,

[0171] The internal doping layer 22 is formed by PECVD deposition of an amorphous silicon layer combined with in-situ doping and annealing activation.

[0172] Technical Solution 5. A passivated contact solar cell according to any one of Technical Solutions 1 to 4,

[0173] The diffusion regulating layer 30 comprises silicon oxide and / or silicon oxynitride;

[0174] and / or,

[0175] The thickness of the diffusion control layer 30 is 2nm~10nm;

[0176] and / or,

[0177] The diffusion regulating layer 30 is formed by PECVD;

[0178] and / or,

[0179] The outer doping layer 40 is a doped polysilicon layer;

[0180] and / or,

[0181] The thickness of the outer doping layer 40 is 50nm~150nm;

[0182] and / or,

[0183] The doping concentration of the outer doping layer 40 is 7E 20 atoms / cm 3 -2E 21 atoms / cm 3 .

[0184] Technical Solution 6. A passivated contact solar cell according to any one of Technical Solutions 1 to 4,

[0185] The external doping layer 40 is formed by combining a PECVD amorphous silicon layer deposition process, an in-situ doping process, an in-situ annealing process and a high-temperature diffusion process.

[0186] Technical Solution 7. A passivated contact solar cell according to Technical Solution 6,

[0187] In the process of forming the outer doping layer 40, the high temperature diffusion process is performed after the in-situ annealing process;

[0188] and / or,

[0189] The temperature of the high-temperature diffusion treatment step is higher than the temperature of the annealing treatment step.

[0190] Technical Solution 8. A passivated contact solar cell according to Technical Solution 6 or 7,

[0191] The temperature of the in-situ annealing process is 880°C to 900°C;

[0192] and / or,

[0193] The temperature of the high temperature diffusion treatment process is 900°C to 920°C.

[0194] Technical Solution 9. A passivated contact solar cell according to Technical Solution 6 or 7,

[0195] The doping elements in the outer doping layer 40 partially diffuse through the diffusion regulating layer 30 .

[0196] Technical solution 10. The passivated contact solar cell according to any one of technical solutions 1 to 4 and 7 further comprises: a first anti-reflection layer 50 stacked on the external doping layer 40;

[0197] Preferably, the passivation contact solar cell further comprises: a first metal electrode 60 penetrating the first anti-reflection layer 50, the external doping layer 40 and the diffusion control layer 30, wherein:

[0198] The first metal electrode 60 is electrically connected to the inner doping layer 22 .

[0199] Technical Solution 11. A passivated contact solar cell according to any one of Technical Solutions 1 to 4 and 7,

[0200] In view of the structure that the silicon substrate 10 is an N-type silicon substrate, the doping element contained in the outer doping layer 40 is an N-type doping element;

[0201] In view of the structure that the silicon substrate 10 is a P-type silicon substrate, the doping element contained in the outer doping layer 40 is a P-type doping element.

[0202] Technical Solution 12. The passivated contact solar cell according to any one of Technical Solutions 1 to 4 and 7, further comprising:

[0203] An emitter structure 70 is disposed on the second main surface of the silicon substrate 10 .

[0204] Technical Solution 13. A passivated contact solar cell according to Technical Solution 12,

[0205] The emitter structure 70 comprises: a diffusion layer disposed on the second main surface of the silicon substrate 10, wherein the doping type of the diffusion layer is opposite to the doping type of the outer doping layer 40;

[0206] and / or,

[0207] The passivated contact solar cell further includes: an aluminum oxide layer 80 stacked on the emitter structure 70;

[0208] a second anti-reflection layer 90 stacked on the aluminum oxide layer 80; and

[0209] A second metal electrode 100 penetrates the second anti-reflection layer 90 and is electrically connected to the diffusion layer.

[0210] Technical Solution 14. A passivated contact solar cell according to Technical Solution 13,

[0211] For the structure in which the silicon substrate 10 is an N-type silicon substrate, the doping element in the emitter structure 70 is a P-type doping element;

[0212] When the silicon substrate 10 is a P-type silicon substrate, the doping element contained in the emitter structure 70 is an N-type doping element.

[0213] Technical Solution 15. A passivated contact solar cell according to any one of Technical Solutions 1 to 4, 7, 13 and 14,

[0214] The first main surface of the silicon substrate 10 is the back side of the passivation contact solar cell;

[0215] and / or,

[0216] The first main surface of the silicon substrate 10 is a polished surface.

[0217] Technical Solution 16. The method for preparing a passivated contact solar cell according to any one of Technical Solutions 1 to 15, comprising:

[0218] Step 1: forming a passivation contact structure 20 on a first main surface of a silicon substrate 10;

[0219] Step 2, forming a diffusion control layer 30 and an external doping layer 40 in sequence on the side of the passivation contact structure 20 away from the silicon substrate 10;

[0220] Step 3: diffuse doping elements into the outer doping layer 40 through in-situ annealing and high-temperature diffusion treatment in sequence, so that the doping concentration of the outer doping layer 40 is higher than the doping concentration of the passivation contact structure 20 .

[0221] Technical Solution 17. According to the preparation method described in Technical Solution 16, step 1 comprises:

[0222] Step 11, placing the silicon substrate 10 in a PECVD boat;

[0223] Step 12, introducing N2O into the PECVD boat at a flow rate of 5000 sccm to 20000 sccm, and growing a tunneling oxide layer 21 on the first main surface of the silicon substrate 10;

[0224] Step 13, according to the H2 flow rate of 5000sccm~20000sccm, the SiH4 flow rate of 1000sccm~10000sccm and the gas A containing the doping element flow rate of 50sccm~500sccm, H2, SiH4 and gas A are introduced into the PECVD boat, and an inner doping layer 22 is grown on the tunneling oxide layer 21 on the side away from the silicon substrate 10, wherein the passivation contact structure 20 includes the tunneling oxide layer 21 and the inner doping layer 22, and A is a gaseous compound containing the doping element required for the inner doping layer 22.

[0225] Technical Solution 18. According to the preparation method described in Technical Solution 17, step 2 comprises:

[0226] Step 21, introducing N2O into the PECVD boat at a flow rate of 10000-50000 sccm to grow a diffusion control layer 30 on the passivation contact structure 20;

[0227] Step 22, according to the H2 flow rate of 5000sccm~20000sccm, the SiH4 flow rate of 1000sccm~10000sccm and the gas A flow rate of 50sccm~500sccm containing the doping element, H2, SiH4 and gas A are introduced into the PECVD boat to grow an external doping layer 40 on the diffusion regulation layer 30, wherein A is a gaseous compound containing the doping element required for the external doping layer 40.

[0228] Technical Solution 19. The preparation method according to Technical Solution 17 or 18, after step 2 and before step 3, further comprises:

[0229] Step 2': performing annealing activation treatment on the formed passivation contact structure 20 and the outer doping layer 40.

[0230] Technical Solution 20. According to the preparation method described in Technical Solution 19,

[0231] The temperature of the annealing activation treatment in step 2' is lower than the temperature of the high temperature diffusion treatment in step 3.

[0232] Technical Solution 21. According to the preparation method described in Technical Solution 20,

[0233] The temperature of the annealing activation treatment in step 2' is 880°C to 900°C;

[0234] and / or,

[0235] The temperature of the high temperature diffusion treatment in step 3 is 900°C to 920°C.

[0236] Technical Solution 22. The preparation method according to Technical Solution 20, before step 1, further comprises:

[0237] Step 01, placing the silicon substrate 10 in a diffusion furnace, and diffusing doping elements on the second main surface of the silicon substrate 10 to form a diffusion layer;

[0238] Step 02: removing the silicon glass layer plated on the first main surface and the side surface of the silicon substrate 10 by chemical solution cleaning;

[0239] Step 03: polishing the first main surface of the silicon substrate 10.

[0240] Technical Solution 23. The preparation method according to Technical Solution 22, after step 3, further comprises:

[0241] Step 4: wet chemically clean the silicon glass layer on the second main surface and the side surface of the silicon substrate 10.

[0242] Technical Solution 24. The preparation method according to Technical Solution 23, after step 4, further comprises:

[0243] Step 5: forming an Al2O3 coating on the diffusion layer.

[0244] Technical Solution 25. The preparation method according to Technical Solution 24, after step 5, further comprises:

[0245] Step 6: Form an anti-reflection layer on the Al2O3 coating and the outer doping layer 40 by PEVCD.

[0246] Technical Solution 26. The preparation method according to Technical Solution 24, after step 6, further comprises:

[0247] Metal paste is printed on the anti-reflection layer on the first main surface and the second main surface of the silicon substrate 10 respectively by screen printing, and sintered at high temperature to complete the metallization of the metal paste.

[0248] The introduction provided in the above steps is only used to help understand the method, structure and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A passivated contact solar cell, characterized in that: include: Silicon substrate (10); A passivation contact structure (20) disposed on a first main surface of the silicon substrate (10); A diffusion control layer (30) stacked on the side of the passivation contact structure (20) facing away from the silicon substrate (10); An external doping layer (40) stacked on the diffusion regulating layer (30) on a side facing away from the silicon substrate (10); The type of doping element contained in the external doping layer (40) is consistent with the type of doping element contained in the passivation contact structure (20); The doping concentration of the external doping layer (40) is higher than the doping concentration of the passivation contact structure (20).

2. The passivated contact solar cell according to claim 1, characterized in that: The passivation contact structure (20) is laid on the entire first main surface; or, The passivation contact structures (20) are arranged at intervals on the first main surface.

3. The passivated contact solar cell according to claim 1, characterized in that: The passivation contact structure (20) comprises: a tunneling oxide layer (21) and an inner doping layer (22) stacked from inside to outside, wherein: The doping concentration of the outer doping layer (40) is higher than the doping concentration of the inner doping layer (22).

4. The passivated contact solar cell according to claim 3, characterized in that: The thickness of the tunnel oxide layer (21) is 1 nm to 2 nm; and / or, The inner doping layer (22) is a doped polysilicon layer; and / or, The thickness of the inner doping layer (22) is 30 nm to 50 nm; and / or, The doping concentration of the inner doping layer (22) is 3E 20 atoms / cm 3 ~4E 20 atoms / cm 3 ; and / or, The internal doping layer (22) is formed by PECVD deposition of an amorphous silicon layer combined with in-situ doping and annealing for activation.

5. The passivated contact solar cell according to any one of claims 1 to 4, characterized in that: The diffusion regulating layer (30) comprises silicon oxide and / or silicon oxynitride; and / or, The diffusion control layer (30) has a thickness of 2 nm to 10 nm; and / or, The diffusion control layer (30) is formed by PECVD; and / or, The external doping layer (40) is a doped polysilicon layer; and / or, The thickness of the external doping layer (40) is 50 nm to 150 nm; and / or, The doping concentration of the outer doping layer (40) is 7E 20 atoms / cm 3 -2E 21 atoms / cm 3 ; Preferably, the external doping layer (40) is formed by combining a PECVD deposition process of an amorphous silicon layer, an in-situ doping process, an in-situ annealing process and a high-temperature diffusion process; Preferably, in the process of forming the external doping layer (40), the high temperature diffusion process is performed after the in-situ annealing process; and / or, The temperature of the high temperature diffusion treatment process is higher than the temperature of the annealing treatment process; Preferably, the temperature of the in-situ annealing process is 880°C to 900°C; and / or, The temperature of the high temperature diffusion treatment process is 900°C to 920°C; Preferably, the doping element in the external doping layer (40) partially diffuses through the diffusion control layer (30).

6. The passivated contact solar cell according to any one of claims 1 to 5, characterized in that: Also includes: a first anti-reflection layer (50) stacked on the external doping layer (40); Preferably, the passivation contact solar cell further comprises: a first metal electrode (60) penetrating the first anti-reflection layer (50), the external doping layer (40) and the diffusion control layer (30), wherein: The first metal electrode (60) is electrically connected to the inner doping layer (22); Preferably, for a structure in which the silicon substrate (10) is an N-type silicon substrate, the doping element contained in the external doping layer (40) is an N-type doping element; In view of the structure in which the silicon substrate (10) is a P-type silicon substrate, the doping element contained in the external doping layer (40) is a P-type doping element; Preferably, it also includes: An emitter structure (70) disposed on the second main surface of the silicon substrate (10); Preferably, the emitter structure (70) comprises: a diffusion layer arranged on the second main surface of the silicon substrate (10), wherein the doping type of the diffusion layer is opposite to the doping type of the outer doping layer (40); and / or, The passivation contact solar cell further comprises: an aluminum oxide layer (80) stacked on the emitter structure (70); a second anti-reflection layer (90) stacked on the aluminum oxide layer (80); and a second metal electrode (100) penetrating the second anti-reflection layer (90) and electrically connected to the diffusion layer; Preferably, for a structure in which the silicon substrate (10) is an N-type silicon substrate, the doping element in the emitter structure (70) is a P-type doping element; In view of the structure in which the silicon substrate (10) is a P-type silicon substrate, the doping element contained in the emitter structure (70) is an N-type doping element; Preferably, the first main surface of the silicon substrate (10) is the back side of the passivation contact solar cell; and / or, The first main surface of the silicon substrate (10) is a polished surface.

7. The method for preparing a passivated contact solar cell according to any one of claims 1 to 6, characterized in that: include: Step 1: forming a passivation contact structure (20) on a first main surface of a silicon substrate (10); Step 2, sequentially stacking a diffusion control layer (30) and an external doping layer (40) on the side of the passivation contact structure (20) facing away from the silicon substrate (10); Step 3: diffusing doping elements in the external doping layer (40) through in-situ annealing and high-temperature diffusion treatment in sequence, so that the doping concentration of the external doping layer (40) is higher than the doping concentration of the passivation contact structure (20).

8. The preparation method according to claim 7, characterized in that: Step 1 includes: Step 11, placing the silicon substrate (10) in a PECVD boat; Step 12: introducing N2O into the PECVD boat at a flow rate of 5000 sccm to 20000 sccm to grow a tunneling oxide layer (21) on the first main surface of the silicon substrate (10); Step 13, introducing H2, SiH4 and gas A into the PECVD boat at a flow rate of 5000sccm to 20000sccm of H2, a flow rate of 1000sccm to 10000sccm of SiH4 and a flow rate of 50sccm to 500sccm of gas A containing doping elements, and growing an inner doping layer (22) on the side of the tunneling oxide layer (21) away from the silicon substrate (10), wherein the passivation contact structure (20) comprises the tunneling oxide layer (21) and the inner doping layer (22), and A is a gaseous compound containing the doping element required for the inner doping layer (22); Preferably, step 2 comprises: Step 21, introducing N2O into the PECVD boat at a flow rate of 10000-50000 sccm to grow a diffusion control layer (30) on the passivation contact structure (20); Step 22, introducing H2, SiH4 and gas A into the PECVD boat at a flow rate of 5000sccm to 20000sccm of H2, a flow rate of 1000sccm to 10000sccm of SiH4 and a flow rate of 50sccm to 500sccm of gas A containing doping elements, and growing an external doping layer (40) on the diffusion control layer (30), wherein A is a gaseous compound containing the doping element required for the external doping layer (40); Preferably, after step 2 and before step 3, the method further comprises: Step 2': performing an annealing activation process on the formed passivation contact structure (20) and the outer doping layer (40).

9. The preparation method according to claim 8, characterized in that: The temperature of the annealing activation treatment in step 2' is lower than the temperature of the high temperature diffusion treatment in step 3; Preferably, the temperature of the annealing activation treatment in step 2' is 880°C to 900°C; and / or, The temperature of the high temperature diffusion treatment in step 3 is 900°C to 920°C; Preferably, before step 1, the method further comprises: Step 01, placing a silicon substrate (10) in a diffusion furnace, and diffusing doping elements on the second main surface of the silicon substrate (10) to form a diffusion layer; Step 02, removing the silicon glass layer plated on the first main surface and side surfaces of the silicon substrate (10) by cleaning with a chemical solution; Step 03: polishing the first main surface of the silicon substrate (10).

10. The preparation method according to claim 9, characterized in that: After step 3, it also includes: Step 4, performing wet chemical cleaning on the second main surface and the silicon glass layer on the side of the silicon substrate (10); Preferably, after step 4, the method further comprises: Step 5, forming an Al2O3 coating on the diffusion layer; Preferably, after step 5, the method further comprises: Step 6: forming an anti-reflection layer on the Al2O3 coating and the outer doping layer (40) by PEVCD; Preferably, after step 6, the method further comprises: Metal paste is printed on the anti-reflection layer on the first main surface and the second main surface of the silicon substrate (10) respectively by screen printing, and sintered at high temperature to complete the metallization of the metal paste.

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