Preparation method of solar cell and solar cell

Abstract

The invention discloses a preparation method of a solar cell and the solar cell, and relates to the technical field of solar cells. The preparation method of the solar cell comprises the following steps: forming an oxide layer on a first main surface of a silicon substrate; depositing a doping control layer on the oxide layer; performing gettering treatment on the silicon substrate by combining with the doping control layer, and forming a shallow doping layer on one surface, close to the oxide layer, of the silicon substrate; and removing the doping control layer and the oxide layer. According to the embodiment, the doping control layer is arranged, so that the doping concentration of the shallow doping layer can be controlled, the shallow doping layer with relatively low doping concentration is formed, the technological process of preparing the solar cell is simplified, and the cell performance is improved.

Description

Technical Field

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

[0002] The silicon matrix of heterojunction solar cells has high requirements for the minority carrier lifetime, but the metal impurities in the silicon matrix act as deep energy level recombination centers, which will reduce the minority carrier lifetime in the silicon matrix and affect the conversion efficiency of the battery.

[0003] The metal impurity content in the silicon substrate can be reduced by doping treatment. Currently, heterojunction solar cells that have undergone doping treatment have a shallow doping layer and a silicon substrate that has undergone doping treatment. However, the above-mentioned heterojunction solar cell preparation process is complicated, which is not conducive to mass production, and the doping concentration of the shallow doping layer cannot be controlled, resulting in an excessively high doping concentration, which affects the surface passivation of the cell, thereby reducing the performance of the heterojunction solar cell. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a method for preparing a solar cell and a solar cell. A shallow doping layer can be directly obtained through doping treatment, and the doping concentration of the shallow doping layer can be controlled based on the doping control layer, so that a solar cell with excellent performance can be prepared through a simple process flow.

[0005] To achieve the above objectives, in a first aspect, an embodiment of the present invention provides a method for preparing a solar cell, comprising:

[0006] Step 1, forming an oxide layer on a first main surface of a silicon substrate;

[0007] Step 2, depositing a doping control layer on the oxide layer;

[0008] Step 3, combining the doping control layer, performing a doping treatment on the silicon substrate, forming a shallow doping layer on a side of the silicon substrate close to the oxide layer and forming a shallow doping layer between the silicon substrate and the oxide layer;

[0009] Step 4: removing the doping control layer and the oxide layer.

[0010] In a second aspect, a solar cell according to an embodiment of the present invention comprises:

[0011] A shallow doped layer is formed on the first main surface of the silicon substrate, wherein the shallow doped layer is in direct contact with the silicon substrate and is obtained by combining an oxide layer and a doping control layer stacked on the first main surface with a doping treatment.

[0012] An embodiment of the above invention has the following advantages or beneficial effects: by preparing a doping control layer before the doping treatment, under the action of the doping control layer and the oxide layer, a shallow doping layer with a low doping concentration is formed during the doping treatment, so that the shallow doping layer does not affect the surface passivation of the battery and has the function of reducing the surface lateral resistance, further improving the fill factor and battery efficiency of the solar cell, enhancing the battery performance, and at the same time, simplifying the preparation process and reducing the preparation cost of the solar cell.

[0013] The further effects of the above-mentioned non-conventional optional manner will be described below in conjunction with the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0015] Figure 1 is a schematic structural diagram of a semi-finished solar cell product obtained through step 1.6 according to an embodiment of the present invention;

[0016] Figure 2 is a schematic structural diagram of a semi-finished solar cell product obtained through step 1 according to an embodiment of the present invention;

[0017] Figure 3 is a schematic structural diagram of a semi-finished solar cell product obtained through step 2 according to an embodiment of the present invention;

[0018] Figure 4 is a schematic structural diagram of a semi-finished solar cell having a silicon oxide layer or a phosphorus silicon glass layer according to an embodiment of the present invention;

[0019] Figure 5 is a schematic structural diagram of a semi-finished solar cell product obtained through step 4 according to an embodiment of the present invention;

[0020] Figure 6 is a schematic structural diagram of a first solar cell according to an embodiment of the present invention;

[0021] Figure 7 is a schematic structural diagram of a second solar cell according to an embodiment of the present invention.

[0022] Reference numerals:

[0023] 1-silicon substrate; 2-oxide layer; 3-doping control layer; 4-shallow doping layer; 5-silicon oxide layer or phosphosilicate glass layer; 6-first intrinsic silicon-containing film; 7-first doped film; 8-first conductive film; 9-second intrinsic silicon-containing film; 10-second doped film; 11-second conductive film; 12-tunneling oxide layer; 13-first metal electrode; 14-second metal electrode; 15-heavily doped layer. DETAILED DESCRIPTION

[0024] At present, there are mainly two methods for preparing solar cells that have undergone doping treatment and have a shallowly doped layer.

[0025] The first preparation method is to perform impurity gettering treatment on the cleaned silicon substrate, then perform texturing, prepare a mask layer on the first main surface, single-sidedly etch and polish the second main surface, form a mask layer on the second main surface, prepare a shallowly doped layer on the first main surface, and prepare other functional layers on the first main surface and the second main surface to obtain a solar cell.

[0026] The second preparation method is to obtain a solar cell by texturing and doping the cleaned silicon substrate to form a shallow doping layer, single-sided etching and polishing the second main surface, and preparing other functional layers on the first main surface and the second main surface.

[0027] It can be found that the first preparation method has a complicated process flow, a high battery preparation cost, and poor uniformity of the doping concentration of the shallow doped layer; although the second preparation method simplifies the preparation process and can directly form a doping layer by doping, the doping layer is directly obtained by doping treatment, and the doping concentration cannot be controlled, resulting in a high doping concentration, which affects the surface passivation of the battery and further affects the performance of the solar cell.

[0028] The following is a description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0029] It should be pointed out that the embodiments of the present invention and the technical features therein may be combined with each other without conflict.

[0030] The "from inside to outside" involved in the embodiment of the present invention refers to the direction extending from the silicon substrate to the surface of the passivation contact cell.

[0031] The "first", "second", etc. involved in the embodiments of the present invention are used to distinguish different structures or the same structure that is not visible or located at different positions, and are not intended to limit the number, order, etc. of structures or components. For example, the first main surface of the silicon substrate is the main surface of the silicon substrate facing the sunlight, and the second main surface of the silicon substrate is the main surface of the silicon substrate facing away from the sunlight.

[0032] like Figure 1As shown, the method for preparing a solar cell according to an embodiment of the present invention mainly comprises the following steps:

[0033] Step 1, forming an oxide layer 2 on a first main surface of a silicon substrate 1;

[0034] Step 2, depositing a doping control layer 3 on the oxide layer 2;

[0035] Step 3, combining the doping control layer 3, performing a gettering process on the silicon substrate 1, and forming a shallow doping layer 4 on a side of the silicon substrate 1 close to the oxide layer 2;

[0036] Step 4: removing the doping control layer 3 and the oxide layer 2.

[0037] The conductivity type of the silicon substrate 1 can be N-type or P-type. The difference between the N-type silicon substrate and the P-type silicon substrate lies in the different doping elements. The N-type silicon substrate is mainly doped with pentavalent elements, such as phosphorus, etc.; the P-type silicon substrate is mainly doped with trivalent elements, such as boron, etc. Preferably, the N-type silicon substrate is used in the embodiment of the present invention.

[0038] By preparing an oxide layer 2 and a doping control layer 3 on the first main surface of the silicon substrate 1, and then performing a doping treatment, the doping concentration of the shallow doping layer 4 can be controlled. In the process of doping element diffusion treatment, the external doping elements first need to pass through the doping control layer 3 and the oxide layer 2, and then reach the silicon substrate 1, and then diffuse into the silicon substrate 1, so as to form a shallow doping layer 4 on the side of the silicon substrate 1 close to the oxide layer 2. Due to the absorption of doping elements by the doping control layer 3 and the oxide layer 2, compared with the absence of the doping control layer 3, fewer doping elements reach the silicon substrate 1, thereby achieving the effect of controlling the doping concentration of the shallow doping layer 4, so that the doping concentration of the shallow doping layer 4 formed is low, reducing its impact on the passivation performance of the battery. In addition, after the absorption of doping elements by the doping control layer 3 and the oxide layer 2, the concentration of doping elements in the shallow doping layer 4 formed on the surface of the silicon substrate is more uniform. Preferably, phosphorus can be used as the doping element in the doping element diffusion process.

[0039] Furthermore, the doping concentration of the above-mentioned shallow doping layer 4 is negatively correlated with the thickness of the doping control layer 3. Since the doping elements need to pass through the doping control layer 3 and the oxide layer 2 before reaching the silicon substrate 1, the doping concentration of the shallow doping layer 4 can be adjusted by adjusting the thickness of the doping control layer 3. Under the same other process conditions of the doping treatment, when the thickness of the doping control layer 3 is thicker, the fewer doping elements can reach the silicon substrate 1, and the lower the doping concentration of the shallow doping layer 4; when the thickness of the doping control layer 3 is thinner, the more doping elements can reach the silicon substrate 1, and the higher the doping concentration of the shallow doping layer 4.

[0040] Furthermore, the thickness of the doping control layer 3 is 50-300 nm. As an example, the thickness of the doping control layer 3 can be 50 nm, 100 nm, 200 nm or 300 nm. The above-mentioned doping control layer 3 includes at least one of amorphous silicon, microcrystalline silicon, polycrystalline silicon, silicon oxide, and silicon carbide. As an example, the doping control layer 3 can be an amorphous silicon layer or a silicon oxide layer, or a stack of polycrystalline silicon and silicon oxide.

[0041] The doping concentration of the shallow doped layer 4 is less than or equal to 1×10 18 atoms / cm 3 In order to prevent the shallow doping layer 4 from affecting the passivation performance of the battery, its doping concentration can be set to be less than or equal to 1×10 18 atoms / cm 3 , while facilitating the collection of photogenerated carriers, it also reduces their impact on the passivation performance of the battery.

[0042] In an optional embodiment, the above step 1 includes: repeatedly and alternately performing acid washing and alkaline washing on the above silicon substrate 1 to form a velvet surface on the first main surface and the second main surface of the above silicon substrate 1; placing the silicon substrate 1 after acid washing and alkaline washing in an ozone environment to form an oxide layer 2 on the above first main surface and the above second main surface.

[0043] The oxide layer 2 may include silicon oxide.

[0044] Specifically, the silicon substrate 1 is repeatedly and alternately subjected to acid washing and alkali washing to form a suede surface on the first main surface and the second main surface of the silicon substrate 1, including the following steps 1.1 to 1.6:

[0045] Step 1.1, pickling the silicon substrate 1 with a mixed solution of hydrogen peroxide and hydrofluoric acid, or pickling the silicon substrate 1 with hydrofluoric acid in an ozone environment, thereby removing impurities on the first main surface and the second main surface of the silicon substrate 1 by pickling, and after pickling, rinsing with deionized water to remove the acidic solution attached to the silicon substrate 1;

[0046] Step 1.2, polishing the silicon substrate 1 with a potassium hydroxide solution, and washing with deionized water to remove the alkaline solution attached to the silicon substrate 1;

[0047] Step 1.3, using a mixed solution of hydrogen peroxide and potassium hydroxide to perform alkaline washing on the silicon substrate 1 to remove impurities on the first main surface and the second main surface of the silicon substrate 1, and using deionized water to wash and remove the alkaline solution attached to the silicon substrate 1;

[0048] Step 1.4, texturing the silicon substrate 1 with a mixed solution containing a texturing additive and potassium hydroxide, so as to preliminarily form a velvet surface on the first main surface and the second main surface of the silicon substrate 1, and washing with deionized water to remove the alkaline solution attached to the silicon substrate 1; wherein the texturing additive can be a chemical additive used to enhance the surface velvet rate, improve the velvet uniformity, and accelerate the texturing speed;

[0049] Step 1.5, using a mixed solution of hydrogen peroxide and potassium hydroxide to alkaline wash the silicon substrate 1 to remove the residual texturing additive dissolved in the alkaline solution after texturing on the first main surface and the second main surface of the silicon substrate 1, and using deionized water to rinse to remove the alkaline solution attached to the silicon substrate 1;

[0050] Step 1.6, using a mixed solution of hydrogen peroxide and hydrofluoric acid to pickle the silicon substrate 1, neutralize the alkaline solution that may remain in step 1.5, and remove the residual texturing additive dissolved in the acidic solution after the first main surface and the second main surface of the silicon substrate 1 are texturized, and use deionized water to rinse and remove the acidic solution attached to the silicon substrate 1, so as to obtain Figure 1 The semi-finished solar cell product shown.

[0051] After the above steps 1.1 to 1.6, the impurities and dirt on the surface of the silicon substrate can be removed, so that the suede surface is less likely to have spots and more uniform. Then, the silicon substrate 1 is placed in an ozone environment to form an oxide layer 2 on the first main surface and the second main surface of the suede surface, and the following is obtained: Figure 2 A semi-finished solar cell product is shown with an oxide layer 2 .

[0052] It is understood that the solutions and processing conditions shown in the above steps 1.1 to 1.6 do not constitute limitations on the embodiments of the present invention. In actual processing, solutions and processing conditions with the same or similar effects may be used. As an example, the potassium hydroxide solution may be replaced with a sodium hydroxide solution or a mixed solution of potassium hydroxide and sodium hydroxide having the same or similar effects.

[0053] Furthermore, the thickness of the oxide layer 2 is 0.5-2.0 nm. As an example, the thickness of the oxide layer 2 can be 0.5 nm, 1.0 nm, 1.5 nm or 2.0 nm.

[0054] The texturing treatment in the prior art usually includes, after obtaining the silicon substrate 1 with the oxide layer 2, using an acid pickling step to remove the oxide layer 2, so as to obtain a silicon substrate 1 with a velvet surface. If the oxide layer 2 is still needed later, it is necessary to re-prepare the oxide layer 2 after the above-mentioned texturing treatment, referring to the first preparation method mentioned above. Compared with the texturing treatment and the preparation of the oxide layer 2 in the prior art, the embodiment of the present invention eliminates the acid pickling step of the last step of the texturing treatment in the prior art. There is no need to remove the oxide layer 2 obtained in the texturing treatment, but the oxide layer 2 obtained in the texturing treatment is retained and directly used as the oxide layer 2 in the subsequent preparation process, thereby simplifying the preparation process, eliminating the need to repeatedly prepare the oxide layer 2, and reducing the cost of solar cell preparation to a certain extent.

[0055] In an optional embodiment, in step 2, chemical vapor deposition (CVD) can be used to deposit the doping control layer 3. Here, CVD includes low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PCVD), atmospheric pressure chemical vapor deposition (APCVD), etc. After step 2, the following can be obtained: Figure 3 The semi-finished solar cell product shown has a doping control layer 3 and an oxide layer 2 .

[0056] In an optional embodiment, the above step 3 includes: placing the silicon substrate 1 having the doping control layer 3 formed thereon in an atmosphere having doping elements, and forming a shallow doping layer 4 on one side of the silicon substrate 1 close to the above oxide layer 2 through diffusion treatment of the doping elements.

[0057] The process of the impurity treatment includes three processes: pre-cleaning, doping element diffusion treatment and temperature control. First, before the doping element diffusion treatment, the silicon substrate 1 with the doping control layer 3 formed thereon can be pickled to remove impurities on the surface of the doping control layer 3 that may affect the doping element diffusion treatment process. After pickling, deionized water is used to remove the acid solution remaining on the first main surface.

[0058] During the doping element diffusion process, on the first main surface of the silicon substrate 1, the external doping elements first pass through the doping control layer 3, a part of the doping elements are adsorbed by the doping control layer 3, and the other part of the doping elements continue to diffuse into the silicon substrate 1, pass through the oxide layer 2, a part of the doping elements are adsorbed by the oxide layer 2, and the remaining doping elements continue to diffuse into the silicon substrate 1. After diffusing into the silicon substrate 1, a shallow doping layer 4 is formed on the side of the silicon substrate 1 close to the oxide layer 2.

[0059] Further, the temperature of the doping element diffusion treatment is 600-900° C. As an example, the temperature of the doping element diffusion treatment can be 600° C., 700° C., 800° C. or 900° C. By controlling the temperature of the doping element diffusion treatment process, the doping element can be diffused into the silicon substrate 1 at a certain diffusion rate at a suitable temperature.

[0060] After the doping element diffusion process, in order to increase the migration rate of metal impurities in the silicon substrate to the doping control layer 3, the temperature can be adjusted and cooled to 500-700°C. At this temperature, the metal impurities in the silicon substrate can migrate outward to the doping control layer 3 faster, thereby better removing the metal impurities in the silicon substrate. As an example, after entering the variable temperature control process, the temperature can be reduced to 500°C, 600°C, 650°C or 700°C, etc. As an example, the above-mentioned metal impurities include but are not limited to iron, aluminum, calcium, nickel, copper, and chromium.

[0061] In addition, the phosphorus-doped region in the silicon matrix has a greater solubility for metal impurities, so that the silicon matrix can be effectively treated with impurities. The principles of phosphorus-doped region impurity gettering include but are not limited to: Fermi level influence, metal impurities and phosphorus forming metal pairs, metal impurities re-deposition at dislocations, self-interstitial ion implantation to enhance impurity gettering, etc.

[0062] The gettering treatment can improve the quality of the silicon substrate, reduce the content of metal impurities in the substrate, and make the quality consistency of the silicon substrate better, thereby making the battery conversion efficiency higher and the minority carrier concentration higher.

[0063] While the shallow doping layer 4 is being formed, a silicon oxide layer or a phosphorus silicon glass layer 5 is also formed on the surface of the doping control layer 3 away from the silicon substrate 1. Figure 4 shown.

[0064] In addition, at the edge of the second main surface of the silicon substrate 1 and the side of the silicon substrate 1, part of the doping elements diffuse into the silicon substrate 1, so that a lightly doped layer 4 is formed on the side of the silicon substrate 1 close to the oxide layer 2, a silicon oxide layer or a phosphosilicate glass layer 5 is formed on the surface of the oxide layer 2 on the second main surface away from the silicon substrate 1, and a heavily doped layer 15, a silicon oxide layer or a phosphosilicate glass layer 5 are formed on the side of the silicon substrate 1, such as Figure 4 shown.

[0065] By depositing a doping control layer 3 on the first main surface of the silicon substrate 1 and adjusting the diffusion resistance of the doping element by selecting the material of the doping control layer 3, and controlling the doping concentration of the shallow doping layer 4 by the diffusion resistance of the doping element and the thickness of the doping control layer 3, a shallow doping layer 4 with a low doping concentration can be obtained, which is beneficial to the collection of photogenerated carriers and reduces the surface lateral resistance, thereby avoiding the problem of the battery passivation performance being affected by the excessively high doping concentration of the shallow doping layer 4.

[0066] In an optional embodiment, the step 4 includes: performing single-side etching and polishing treatment on the second main surface of the silicon substrate 1 to remove the oxide layer 2 on the second main surface.

[0067] In step 4, it is necessary to remove the doping control layer 3 and the oxide layer 2 on the first main surface, and the oxide layer 2 on the second main surface. In addition, it is also necessary to remove the silicon oxide layer or phosphorus silicon glass layer 5 on the second main surface and the side surface, the heavily doped layer 15, and the lightly doped layer 4 on the second main surface, and form a polished structure with high reflectivity on the second main surface, so as to obtain Figure 5 The semi-finished solar cell shown in the figure. The high reflectivity polished structure of the second main surface can reflect the absorbed visible light and part of the infrared light, further reducing the damage of sunlight to the solar cell and extending the service life. Specifically, step 4 includes the following steps 4.1 to 4.8:

[0068] Step 4.1, laying a water film on the first main surface of the silicon substrate 1, and single-sidedly etching the second main surface of the silicon substrate 1 with hydrofluoric acid to remove the silicon oxide layer or phosphorus silicon glass layer 5 formed on the second main surface during the gettering process;

[0069] At the same time, the side of the silicon substrate 1 is etched with hydrofluoric acid to remove the silicon oxide layer or phosphorus silicon glass layer 5 formed on the side of the silicon substrate 1 during the impurity treatment process, and the acid solution attached to the silicon substrate 1 is washed away with deionized water;

[0070] Step 4.2, polishing the second main surface of the silicon substrate 1 with a potassium hydroxide solution, removing the lightly doped layer 4 on the second main surface and the heavily doped layer 15 on the side, and washing with deionized water to remove the alkaline solution attached to the silicon substrate 1; at this time, an additive for polishing can be added to the potassium hydroxide solution;

[0071] Step 4.3, using hydrofluoric acid to remove the silicon oxide layer or the phosphosilicate glass layer 5 on the first main surface, and using deionized water to rinse and remove the acidic solution attached to the silicon substrate 1;

[0072] Step 4.4, removing the doping control layer 3 with a potassium hydroxide solution, and removing the alkaline solution attached to the silicon substrate 1 by washing with deionized water;

[0073] Step 4.5, using hydrofluoric acid to remove the oxide layer 2 on the first main surface and the second main surface, and using deionized water to rinse and remove the acidic solution attached to the silicon substrate 1;

[0074] Step 4.6, using a mixed solution of hydrogen peroxide and potassium hydroxide to perform alkaline washing on the silicon substrate 1, and using deionized water to wash away the alkaline solution attached to the silicon substrate 1;

[0075] Step 4.7, pickling the silicon substrate 1 with a mixed solution of hydrogen peroxide and hydrochloric acid to remove metal impurities on the second main surface and dirt dissolved in the acid solution, and washing with deionized water to remove the acid solution attached to the silicon substrate 1;

[0076] Step 4.8, since the hydrogen peroxide in step 4.7 may cause slight oxidation of the second main surface, the silicon substrate 1 is pickled with hydrofluoric acid to remove the oxidized part caused by hydrogen peroxide, and the acidic solution attached to the silicon substrate 1 is washed with deionized water.

[0077] In an optional embodiment, after step 4, the method for preparing a solar cell further includes: forming a first intrinsic silicon-containing film 6, a first doped film 7 and a first conductive film 8 in sequence from the inside to the outside on the above-mentioned shallowly doped layer 4 of the above-mentioned first main surface, that is, forming a first intrinsic silicon-containing film 6, a first doped film 7 and a first conductive film 8 in sequence from the inside to the outside on the surface of the shallowly doped layer 4 away from the silicon substrate 1.

[0078] The first intrinsic silicon-containing film 6 includes but is not limited to a single layer, a multilayer or a stacked layer of one or more silicon-containing films, or a film composed of a mixture of any of silicon, silicon oxide and silicon carbide. The silicon-containing film includes at least one of the films containing silicon, silicon oxide or silicon carbide. It should be noted that the silicon, silicon oxide or silicon carbide in the first intrinsic silicon-containing film 6 refers to microcrystalline, nanocrystalline or amorphous silicon, silicon oxide or silicon carbide.

[0079] The first doped film 7 includes but is not limited to a single layer, multiple layers or stacked layers of one or more doped silicon-containing films, or a film composed of a mixture of any of doped silicon, doped silicon oxide and doped silicon carbide. Among them, the doped silicon-containing film includes at least one of the films containing doped silicon, doped silicon oxide or doped silicon carbide. It should be noted that the doped silicon, doped silicon oxide or doped silicon carbide in the first doped film 7 refers to microcrystalline, nanocrystalline, polycrystalline or amorphous doped silicon, doped silicon oxide or doped silicon carbide.

[0080] The first conductive film 8 is a film composed of a multilayer, stacked layer or mixture of one or more doped metal oxides or doped metal nitrides, wherein the metal oxides in the doped metal oxides include but are not limited to indium oxide, tin oxide, zinc oxide, cadmium oxide, and titanium nitride; the metal nitrides in the doped metal nitrides include but are not limited to titanium nitride; the doping elements of the doped metal oxides or doped metal nitrides include but are not limited to indium, tin, calcium, aluminum, cadmium, zinc, cerium, and fluorine.

[0081] In an optional embodiment, after step 4, the method for preparing a solar cell further includes: forming a second intrinsic silicon-containing film 9, a second doped film 10 and a second conductive film 11 in sequence from the inside to the outside on the above-mentioned second main surface to obtain a solar cell; or, forming a tunneling oxide layer 12, a second doped film 10 and a second conductive film 11 in sequence from the inside to the outside on the above-mentioned second main surface to obtain a solar cell.

[0082] The second intrinsic silicon-containing film 9 includes but is not limited to a film composed of a single layer, multiple layers or stacked layers of one or more silicon-containing films, or a film composed of a mixture of any multiple of silicon, silicon oxide and silicon carbide. The silicon-containing film includes at least one of films containing silicon, silicon oxide or silicon carbide. It should be noted that the silicon, silicon oxide or silicon carbide in the second intrinsic silicon-containing film 9 refers to microcrystalline, nanocrystalline or amorphous silicon, silicon oxide or silicon carbide.

[0083] The second doped film 10 includes but is not limited to a single layer, multiple layers or stacked layers of one or more doped silicon-containing films, or a film composed of a mixture of any of doped silicon, doped silicon oxide and doped silicon carbide. Among them, the doped silicon-containing film includes at least one of the films containing doped silicon, doped silicon oxide or doped silicon carbide. It should be noted that the doped silicon, doped silicon oxide or doped silicon carbide in the second doped film 10 refers to microcrystalline, nanocrystalline, polycrystalline or amorphous doped silicon, doped silicon oxide or doped silicon carbide.

[0084] The second conductive film 11 is a film composed of a multilayer, stacked layer or mixture of one or more doped metal oxides or doped metal nitrides, wherein the metal oxides in the doped metal oxides include but are not limited to indium oxide, tin oxide, zinc oxide, cadmium oxide, and titanium nitride; the metal nitrides in the doped metal nitrides include but are not limited to titanium nitride; the doping elements of the doped metal oxides or doped metal nitrides include but are not limited to indium, tin, calcium, aluminum, cadmium, zinc, cerium, and fluorine.

[0085] The tunnel oxide layer 12 may include silicon oxide.

[0086] In an optional embodiment, the method for preparing a solar cell further includes: forming a first metal electrode 13 on the first main surface, forming a second metal electrode 14 on the second main surface, and obtaining Figure 6 or Figure 7 The solar cell shown.

[0087] The first metal electrode 13 is electrically connected to the first conductive film 8 , and the second metal electrode 14 is electrically connected to the second conductive film 11 .

[0088] The method for preparing a solar cell in an embodiment of the present invention prepares a doping control layer before the doping treatment, and under the action of the doping control layer and the oxide layer, a shallow doping layer with a low doping concentration is formed during the doping treatment, so that the shallow doping layer does not affect the surface passivation of the battery and has the function of reducing the surface lateral resistance, further improving the fill factor and battery efficiency of the solar cell and enhancing the battery performance. At the same time, by retaining the oxide layer obtained in the texturing process, there is no need to re-prepare the oxide layer laterally, which simplifies the preparation process and reduces the preparation cost of the solar cell.

[0089] The present invention also provides a solar cell, characterized in that it includes: a shallowly doped layer 4 formed on the first main surface of the above-mentioned silicon substrate 1, wherein the above-mentioned shallowly doped layer 4 is in direct contact with the above-mentioned silicon substrate 1, and the above-mentioned shallowly doped layer 4 is obtained by combining an oxide layer 2 and a doping control layer 3 stacked on the above-mentioned first main surface with doping treatment.

[0090] In an optional embodiment, the solar cell further comprises: a first intrinsic silicon-containing film 6, a first doped film 7 and a first conductive film 8 are sequentially stacked on the first main surface of the silicon substrate 1 from inside to outside.

[0091] In an optional embodiment, if Figure 6 As shown, the solar cell further comprises: a second main surface of the silicon substrate 1 is stacked with a second intrinsic silicon-containing film 9, a second doped film 10 and a second conductive film 11 in sequence from inside to outside.

[0092] In an optional embodiment, if Figure 7 As shown, the solar cell further comprises: a tunnel oxide layer 12, a second doped film 10 and a second conductive film 11 are sequentially stacked from the inside to the outside on the second main surface of the silicon substrate 1.

[0093] In an optional embodiment, when the solar cell includes the first conductive film 8 , the solar cell further includes: a first metal electrode 13 electrically connected to the first conductive film 8 .

[0094] In an optional embodiment, when the solar cell includes the second conductive film 11 , the solar cell further includes: a second metal electrode 14 electrically connected to the second conductive film 11 .

[0095] In an optional embodiment, the doping concentration of the shallowly doped layer 4 is less than or equal to 1×10 18 atoms / cm 3 .

[0096] The solar cell of the embodiment of the present invention has a shallow doping layer obtained by combining an oxide layer and a doping control layer with a doping treatment, and has a low doping concentration, will not affect the surface passivation of the solar cell, and has the function of reducing the lateral resistance of the cell surface, further improving the fill factor and cell efficiency of the solar cell and enhancing the cell performance.

[0097] In summary, the embodiments of the present invention provide the following technical solutions:

[0098] Technical Solution 1. A method for preparing a solar cell, comprising:

[0099] Step 1, forming an oxide layer 2 on a first main surface of a silicon substrate 1;

[0100] Step 2, depositing a doping control layer 3 on the oxide layer 2;

[0101] Step 3, combining the doping control layer 3, performing a gettering process on the silicon substrate 1, and forming a shallow doping layer 4 on a side of the silicon substrate 1 close to the oxide layer 2;

[0102] Step 4: removing the doping control layer 3 and the oxide layer 2.

[0103] Technical Solution 2. According to the method for preparing a solar cell described in Technical Solution 1, the doping concentration of the shallowly doped layer 4 is negatively correlated with the thickness of the doping control layer 3 .

[0104] Technical Solution 3. According to the method for preparing a solar cell according to Technical Solution 1, step 1 comprises:

[0105] Repeating and alternating acid washing and alkali washing on the silicon substrate 1 to form a suede surface on the first main surface and the second main surface of the silicon substrate 1;

[0106] The silicon substrate after acid washing and alkali washing is placed in an ozone environment to form an oxide layer 2 on the first main surface and the second main surface.

[0107] Technical Solution 4. According to the method for preparing a solar cell according to Technical Solution 3, step 4 comprises:

[0108] The second main surface of the silicon substrate 1 is subjected to single-side etching and polishing to remove the oxide layer 2 on the second main surface.

[0109] Technical Solution 5. The method for preparing a solar cell according to Technical Solution 1,

[0110] The doping concentration of the shallow doped layer 4 is less than or equal to 1×10 18 atoms / cm 3 .

[0111] Technical Solution 6. According to the method for preparing a solar cell according to Technical Solution 1, step 3 comprises:

[0112] The silicon substrate 1 on which the doping control layer 3 is formed is placed in an atmosphere containing doping elements, and a shallow doping layer 4 is formed on a side of the silicon substrate 1 close to the oxide layer 2 through a doping element diffusion process.

[0113] Technical Solution 7. The method for preparing a solar cell according to Technical Solution 6,

[0114] The temperature of the doping element diffusion treatment is 600-900°C.

[0115] Technical Solution 8. The method for preparing a solar cell according to Technical Solution 1,

[0116] The thickness of the doping control layer 3 is 50-300nm;

[0117] and / or,

[0118] The thickness of the oxide layer 2 is 0.5-2.0 nm;

[0119] and / or,

[0120] The doping control layer 3 includes at least one of amorphous silicon, microcrystalline silicon, polycrystalline silicon, silicon oxide, and silicon carbide;

[0121] and / or,

[0122] The doping control layer 3 is prepared by chemical vapor deposition.

[0123] Technical Solution 9. According to the method for preparing a solar cell according to Technical Solution 1, after step 4, the method further comprises:

[0124] A first intrinsic silicon-containing film 6, a first doped film 7 and a first conductive film 8 are sequentially formed on the shallowly doped layer 4 of the first main surface from the inside to the outside.

[0125] Technical Solution 10. The method for preparing a solar cell according to Technical Solution 4, after step 4, further comprising:

[0126] On the second main surface, a second intrinsic silicon-containing film 9, a second doped film 10 and a second conductive film 11 are sequentially formed from inside to outside;

[0127] or,

[0128] A tunneling oxide layer 12, a second doped film 10 and a second conductive film 11 are sequentially formed on the second main surface from inside to outside.

[0129] Technical Solution 11. The method for preparing a solar cell according to Technical Solution 6, further comprising:

[0130] A first metal electrode 13 is formed on the first main surface, and a second metal electrode 14 is formed on the second main surface.

[0131] Technical Solution 12. A solar cell comprising:

[0132] A shallowly doped layer 4 is formed on the first main surface of the silicon substrate 1, wherein the shallowly doped layer 4 is in direct contact with the silicon substrate 1, and the shallowly doped layer 4 is obtained by combining an oxide layer 2 and a doping control layer 3 stacked on the first main surface with a doping treatment.

[0133] Technical Solution 13. The solar cell according to Technical Solution 12 further comprises:

[0134] The first main surface of the silicon substrate 1 is stacked with a first intrinsic silicon-containing film 6, a first doped film 7 and a first conductive film 8 in sequence from the inside to the outside.

[0135] Technical Solution 14. The solar cell according to Technical Solution 12 further comprises:

[0136] The second main surface of the silicon substrate 1 is sequentially stacked with a second intrinsic silicon-containing film 9, a second doped film 10 and a second conductive film 11 from inside to outside;

[0137] or,

[0138] The second main surface of the silicon substrate is sequentially stacked with a tunnel oxide layer 12, a second doped film 10 and a second conductive film 11 from the inside to the outside.

[0139] Technical Solution 15. The solar cell according to Technical Solution 13 or 14,

[0140] The doping concentration of the shallow doped layer 4 is less than or equal to 1×10 18 atoms / cm 3 ;

[0141] and / or,

[0142] When the solar cell includes the first conductive film 8, the solar cell further includes: a first metal electrode 13 electrically connected to the first conductive film 8;

[0143] and / or,

[0144] When the solar cell includes the second conductive film 11 , the solar cell further includes: a second metal electrode 14 electrically connected to the second conductive film 11 .

[0145] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a solar cell, characterized in that: include: Step 1: forming an oxide layer (2) on a first main surface of a silicon substrate (1); Step 2: depositing a doping control layer (3) on the oxide layer (2); Step 3: performing a gettering treatment on the silicon substrate (1) in combination with the doping control layer (3), and forming a shallow doping layer (4) on a side of the silicon substrate (1) close to the oxide layer (2); Step 4: removing the doping control layer (3) and the oxide layer (2).

2. The method for preparing a solar cell according to claim 1, characterized in that: The doping concentration of the shallow doping layer (4) is negatively correlated with the thickness of the doping control layer (3).

3. The method for preparing a solar cell according to claim 1, characterized in that: The step 1 comprises: Repeating and alternating acid washing and alkali washing on the silicon substrate (1) to form a velvet surface on the first main surface and the second main surface of the silicon substrate (1); The acid-washed and alkali-washed silicon substrate is placed in an ozone environment to form an oxide layer (2) on the first main surface and the second main surface.

4. The method for preparing a solar cell according to claim 3, characterized in that: The step 4 comprises: The second main surface of the silicon substrate (1) is subjected to single-side etching and polishing to remove the oxide layer (2) on the second main surface.

5. The method for preparing a solar cell according to claim 1, characterized in that: The doping concentration of the shallow doping layer (4) is less than or equal to 1×10 18 atoms / cm 3 .

6. The method for preparing a solar cell according to claim 1, characterized in that: The step 3 comprises: Placing the silicon substrate (1) having the doping control layer (3) formed thereon in an atmosphere containing doping elements, and performing a doping element diffusion process to form a shallow doping layer (4) on a side of the silicon substrate (1) close to the oxide layer (2); Preferably, the temperature of the doping element diffusion treatment is 600-900° C.; Preferably, the method further comprises: A first metal electrode (13) is formed on the first main surface, and a second metal electrode (14) is formed on the second main surface.

7. The method for preparing a solar cell according to claim 1, characterized in that: The thickness of the doping control layer (3) is 50-300 nm; and / or, The thickness of the oxide layer (2) is 0.5-2.0 nm; and / or, The doping control layer (3) comprises at least one of amorphous silicon, microcrystalline silicon, polycrystalline silicon, silicon oxide, and silicon carbide; and / or, The doping control layer (3) is prepared by chemical vapor deposition; Preferably, after step 4, the method further comprises: A first intrinsic silicon-containing film (6), a first doped film (7) and a first conductive film (8) are sequentially formed on the shallowly doped layer (4) on the first main surface from the inside to the outside; Preferably, after step 4, the method further comprises: Forming a second intrinsic silicon-containing film (9), a second doped film (10) and a second conductive film (11) in sequence from the inside to the outside on the second main surface; or, A tunneling oxide layer (12), a second doped film (10) and a second conductive film (11) are sequentially formed on the second main surface from the inside to the outside.

8. A solar cell, characterized in that: include: A shallow doped layer (4) is formed on the first main surface of the silicon substrate (1), wherein the shallow doped layer (4) is in direct contact with the silicon substrate (1), and the shallow doped layer (4) is obtained by combining an oxide layer (2) and a doping control layer (3) stacked on the first main surface with a doping treatment.

9. The solar cell according to claim 8, characterized in that Also includes: The first main surface of the silicon substrate (1) is stacked with a first intrinsic silicon-containing film (6), a first doped film (7) and a first conductive film (8) in sequence from the inside to the outside.

10. The solar cell according to claim 8, characterized in that Also includes: The second main surface of the silicon substrate (1) is stacked with a second intrinsic silicon-containing film (9), a second doped film (10) and a second conductive film (11) in sequence from the inside to the outside; or, The second main surface of the silicon substrate is sequentially stacked with a tunneling oxide layer (12), a second doped film (10) and a second conductive film (11) from the inside to the outside; Preferably, The doping concentration of the shallow doping layer (4) is less than or equal to 1×10 18 atoms / cm 3 ; and / or, When the solar cell includes a first conductive film (8), the solar cell further includes: a first metal electrode (13) electrically connected to the first conductive film (8); and / or, When the solar cell comprises a second conductive film (11), the solar cell further comprises: a second metal electrode (14) electrically connected to the second conductive film (11).

Images