Solar cell with passivated contact and photovoltaic module

Abstract

A solar cell with a passivated contact, comprising: a silicon substrate having a first region and a third region spaced apart from one another on a rear side thereof, wherein: a dielectric layer, a first doped layer, and a first passivation layer are formed successively in the first region on the rear side of the silicon substrate, the dielectric layer and the first doped layer forming a passivated contact structure in the first region, the first passivation layer is also formed in the third region on the rear side of the silicon substrate, and a second region having a step structure with at least two steps is arranged between the first region and the third region.

Description

Technical FieldThe present invention relates to the field of solar cells and, more particularly, to a passivated contact solar cell and photovoltaic module.BackgroundThe solar cell with passivated contact is a type of solar cell which is based on selective charge carrier transport and has a considerable application potential.The passivated contact structure of the conventional passivated contact solar cell is composed primarily of a dielectric layer and a doped layer (also referred to as a poly layer). However, the doped layer inherently has an extinction capability, which results in increased optical losses in the passivated contact solar cell, which affects the short circuit current and thus the photoelectric conversion efficiency of the passivated contact solar cell. Therefore, it has become a pre-urgent technical problem that needs to be considered to find ways to reduce optical losses in the passivated contact solar cell, increase the short-circuit current, and improve the photoelectric conversion efficiency of the solar cell.Brief Description of the InventionIn order to solve the above-mentioned technical problem, the present invention provides a passivated contact solar cell and a photovoltaic module. The optical losses in the passivated contact solar cell are reduced, so that the short-circuit current and the photoelectric conversion efficiency of the passivated contact solar cell are improved.According to a first aspect, the present invention provides a solar cell having passivated contact with a silicon substrate. The silicon substrate has a first region and a third region spaced apart from each other on its back side. In the first region, a dielectric layer, a first doped layer and a first passivation layer are formed in succession on the rear side of the silicon substrate. The dielectric layer and the first doped layer form a passivated contact structure in the first region. In the third region, the first passivation layer is likewise formed on the rear side of the silicon substrate. A second region is disposed between the first region and the third region. In the second region, a step structure having at least two steps is formed.In some embodiments of the present invention, the step structure includes a first step and a second step. The first stage has a first partial surface and a second partial surface which merge into one another. The second stage has a third sub-surface and a fourth sub-surface which merge into one another.In some embodiments of the present invention, the distance between the first sub-surface and the third sub-surface is H 1, where 0.05 μm≤H 1≤0.2 μm.In some embodiments of the present invention, the distance between the third sub-surface and a first plane is H 2, where 0.5 μm≤H 2≤8 μm. The first plane refers to a portion of a surface of the first passivation layer that faces away from the silicon substrate and is located in the third region.In some embodiments of the present invention, an included angle between the third sub-surface and the fourth sub-surface is α, where α ≥ 90°.In some embodiments of the present invention, the second sub-surface merges with the third sub-surface.In some embodiments of the present invention, the width of the third sub-area W is 1, where 0.01 μm≤W 1≤5 μm.In some embodiments of the present invention, the step structure further comprises a texture structure, wherein the texture structure is recessed relative to the third sub-surface and / or the fourth sub-surface.In some embodiments of the present invention, the texture structure is located on a portion of the silicon substrate corresponding to the third sub-surface and / or the texture structure is located on a portion of the silicon substrate corresponding to the fourth sub-surface and / or the texture structure is located on a portion of the silicon substrate corresponding to a first boundary at which the third sub-surface merges into the fourth sub-surface.In some embodiments of the present invention, the average width of the texture structure is W 2, where 0.5 μm≤W 2≤10 μm.In some embodiments of the present invention, a first electrode is provided in the first region. The first electrode penetrates the first passivation layer to be in contact with the first doped layer.According to a second aspect, the present invention provides a photovoltaic module comprising the solar cell described in the first aspect.Compared to the prior art, the present invention has at least the following advantages:The present invention provides a passivated contact solar cell and a photovoltaic module. The passivated contact solar cell comprises a silicon substrate. The silicon substrate has a first region and a third region spaced apart from each other on a back side thereof. In the first region, a dielectric layer, a first doped layer and a first passivation layer are formed in succession on the rear side of the silicon substrate. The dielectric layer and the first doped layer form a passivated contact structure in the first region. In the third region, the first passivation layer is likewise formed on the rear side of the silicon substrate. A second region is disposed between the first region and the third region. The second region has a step structure with at least two steps. In the present invention, the second region forms a transition region between the first region and the third region. The step structure in the second region is configured to set an angle of incidence of light to facilitate the entry of light into the solar cell, thereby improving the utilization rate of the incident light, reducing optical losses in the solar cell, increasing the short-circuit current of the solar cell, and thus improving the photoelectric conversion efficiency of the solar cell.BRIEF DESCRIPTION OF THE DRAWINGIn order to more clearly describe the technical solutions in the embodiments of the present invention, the accompanying drawings required for describing the embodiments of the present invention will be briefly presented below. It is to be understood that the following drawings illustrate only some embodiments of the present invention and are not to be taken as limiting the scope of the invention. Corresponding other drawings can also be created for a person skilled in the art on the basis of these drawings without any creative efforts. FIG. 1 is a schematic structural view of a solar cell according to an embodiment of the present invention; FIG. 2 is an enlarged partial schematic view of a portion inside a dotted circle in FIG. 1 ; FIG. 3 is a schematic structural view of a step structure according to an embodiment of the present invention; FIG. 4 is a schematic structural view of a step structure according to another embodiment of the present invention; FIG. 5 is a schematic structural view of a step structure according to still another embodiment of the present invention; FIG. 6 is a schematic structural view of a texture structure according to an embodiment of the present invention; FIG. 7 is a schematic structural view of a solar cell according to another embodiment of the present invention; and FIG. 8 is a scanning electron microscope (SEM) photograph of a back surface of a solar cell in Example 1 of the present invention.Description of the Reference Numerals1 Silicon substrate, 2 Dielectric layer, 3 First doped layer, 4 First passivation layer, 5 Step structure, 7 Texture structure, 8 Second doped layer, 9 Second passivation layer, 10 Antireflection layer, 11 First region, 12 Second region, 13 Third region, 51 First step, 52 Second step, 61 First electrode, 62 Second electrode, 101 Back side, 102 Light receiving side, 511 First partial surface, 512 Second partial surface, 521 Third partial surface and 522 Fourth partial surface.DETAILED DESCRIPTION OF THE INVENTIONThe technical solutions in the embodiments of the present invention will be clearly and fully described below in conjunction with the accompanying drawings. It is obvious that the described embodiments represent only a part and not all embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any curative efforts fall within the scope of the present invention.In the present invention, the orientations or positional relationships indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "upper", "lower", "inner", "outer", "vertical", "horizontal", "transverse", and "longitudinal" are based on the orientations or positional relationships illustrated in the accompanying drawings. These terms are used primarily to better describe the present invention and its embodiments, and are not intended to limit the stated devices, elements, or components to particular orientations or to dictate a construction and operation in particular orientations.Moreover, some of the above-mentioned terms may have other meanings besides indicating the orientation or positional relationships. For example, in certain cases, the term "on" may be used to indicate a particular attachment or connection relationship. Those skilled in the art should understand the specific meanings of these terms in the present invention according to specific situations.Moreover, the terms "installed", "arranged", "provided with", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integrated construction; it may be a mechanical connection or an electrical connection; or it may be a direct connection, an indirect connection via an intermediate medium, or a communication between the interior of two devices, elements, or components. Those skilled in the art should understand the specific meanings of the above terms in the present invention according to specific situations.Moreover, the terms "first", "second", etc. are used primarily to distinguish various devices, elements, or components (specific categories and constructions may be the same or different) and are not intended to indicate or imply the relative meaning and amount of the devices, elements, or components indicated. Unless otherwise specified, "a plurality" means two or more.The technical solutions of the present invention will be described below in more detail in conjunction with the embodiments and the accompanying drawings.According to a first aspect, the present invention provides a passivated contact solar cell. As shown in FIG. 1, the passivated contact solar cell includes a silicon substrate 1. A back side 101 of the silicon substrate 1 has a first region 11 and a third region 13 which are spaced apart from one another. In the first region 11, a dielectric layer 2, a first doped layer 3 and a first passivation layer 4 are formed in succession on the rear side 101 of the silicon substrate 1. The dielectric layer 2 and the first doped layer 3 form a passivated contact structure in the first region 11. The first passivation layer 4 is likewise formed in the third region 13 on the rear side 101 of the silicon substrate 1. A second region 12 is arranged between the first region 11 and the third region 13. The second region 12 has a step structure 5. At least two steps are provided in the step structure 5. For example, two, three, four or five steps are provided in the step structure 5.In the present invention, the first region 11 shown in FIG. 1 refers to a region on the back surface 101 of the silicon substrate 1 corresponding to an orthogonal projection of a first electrode 61 onto a surface of the silicon substrate 1. The second region 12 refers to a region on the back side 101 of the silicon substrate 1 having the step structure 5. The third region 13 refers to a region on the back side 101 of the silicon substrate 1 that is outside the first region 11 and the second region 12. In the present invention, the step structure 5 in the second region 12 is configured to set an angle of incidence of light to facilitate the entry of light into the solar cell, thereby improving the utilization rate of the incident light, reducing optical losses in the solar cell, increasing the short-circuit current of the solar cell, and thus improving the photoelectric conversion efficiency of the solar cell.In some embodiments, the first passivation layer 4 may also be provided in the second region 12, for example the first passivation layer 4 may cover the entire rear side 101 of the silicon substrate 1. In some embodiments, the shape of the step structure 5 is defined by a back side of the silicon substrate 1 (i.e. a surface of the silicon substrate 1 facing the first passivation layer 4) and a first surface of the first passivation layer 4 facing away from the silicon substrate 1. In some embodiments, the dielectric layer 2 and the first doped layer 3 may be provided in the second region 12. In some alternative embodiments, the dielectric layer 2 and the first doped layer 3 may not be provided in the second region.In an optional embodiment, as shown in FIG. 2, which is an enlarged partial schematic view of a region within a dotted circle in FIG. 1, the step structure 5 includes a first step 51 and a second step 52. The first step 51 has a first partial surface 511 and a second partial surface 512 which merge into one another. The second step 52 has a third partial surface 521 and a fourth partial surface 522, which merge into one another. In the present invention, the step structure 5 has two steps. The first stage 51 serves as a height transition for the second stage 52 The first doped layer 3 is either not provided or is provided only partially below the second stage 52. Under the combined effect of the first stage 51 and the second stage 52, the absorption of the light by the first doped layer 3 is reduced, thereby improving the photon utilization rate of the solar cell and reducing the optical losses in the solar cell. The first sub-surface 511, the second sub-surface 512, the third sub-surface 521 and the fourth sub-surface 522 may each be, for example, a portion of the first surface of the first passivation layer 4.In an optional embodiment, as shown in FIG. 2, the distance between the first sub-surface 511 and the third sub-surface 521 is H 1, where 0.05 μm≤H 1≤0.2 μm. For example, H may be 10,05 μm, 0.1 μm, 0.15 μm, or 0.2 μm. By controlling H 1 within the above-mentioned range, photon absorption can be optimized, and the light absorption effect in the first stage 51 can be improved by adjusting a layer structure and a layer thickness of the first passivation layer 4.In an optional embodiment, as shown in FIG. 2, the distance between the third sub-surface 521 and a first plane is H 2, where 0.5 μm≤H 2≤8 μm. For example, H may be 20,5 μm, 1 μm, 3 μm, 5 μm, or 8 μm. The first plane refers to a portion of the first surface of the first passivation layer 4 located in the third region 13. By controlling H 2 within the above-mentioned range, the passivation performance of the first passivation layer 4 at the second stage 52 can be optimized and the liquid absorption effect at the second stage 52 can be improved.In an optional embodiment, as shown in FIG. 2, the included angle between the third sub-surface 521 and the fourth sub-surface 522 is α, where α≥90°. For example, α may be 90°, 100°, 110°, 120° or 135°. When viewed along a length extension direction of the first electrode 61, the fourth partial surface 522 may be a surface perpendicular to the third partial surface 521, or the fourth partial surface 522 may be a surface inclined to the third partial surface 521. By controlling α within the above-mentioned range, the angle of incidence of light at the second stage 52 can be optimized, thereby improving the utilization rate of the incident light.In an optional embodiment, according to FIG. 2, the second sub-surface 512 merges into the third sub-surface 521. Therefore, the first stage 51 and the second stage 52 may be connected, thereby forming the stage structure 5 of the present invention, which is advantageous for reducing the optical loss in the passivated contact solar cell.In an optional embodiment, as shown in FIG. 2, the width of the third sub-surface 521 is W 1, where 0.01 μm≤W 1≤5 μm. For example, W may be 10,01 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. By controlling W 1 within the above-mentioned range, the angle of incidence of light at the third partial surface 521 can be optimized, thereby improving the utilization rate of the incident light.In an optional embodiment, the step structure 5 according to FIG. 2 further comprises a texture structure 7. The texture structure 7 may be provided on a side of the first passivation layer 4 in the vicinity of the silicon substrate 1. For example, the texture structure 7 can be provided on a side of a second surface of the first passivation layer 4 facing the silicon substrate 1. The texture structure 7 is recessed relative to the third sub-surface 521 and / or the fourth sub-surface 522. In the present invention, the texture structure 7 may be a trough-shaped structure that is recessed downward (i.e., recessed away from) relative to the third sub-surface 521 and / or the fourth sub-surface 522. For example, the texture structure 7 may be formed by a downwardly recessed portion of the back surface of the silicon substrate 1. In an example, the texture structure 7 may be a trough in the shape of an inverted pyramid with a top of the inverted pyramid facing away from the third sub-surface 521 and / or the fourth sub-surface 522. A plurality of texture structures 7 can be provided. Among the plurality of texture structures 7, one texture structure 7 may have the shape of an inverted pyramid, or a plurality of texture structures 7 may each have the shape of an inverted pyramid, which is not specifically limited herein. Since the texture structures 7 can improve light absorption by reducing the reflection of the incident light based on the light trapping principle, the light utilization of the passivated contact solar cell can be improved, which is advantageous for improving the photoelectric conversion efficiency.Note that the step structure 5 in the present invention may or may not include the texture structures 7, which is not limited herein.The method of forming the texture structure 7 is not specifically limited here as long as the structure recessed downward relative to the third sub-surface 521 and / or the fourth sub-surface 522 can be formed. For example, the back side 101 of the silicon substrate 1 on which the first doped layer 3 is formed may be subjected to a laser etching treatment and then an alkaline wet etching treatment to form the texture structures 7. Of course, the texture structures 7 may be formed by other methods not specifically limited in the present invention.In an embodiment, according to FIG. 3, the texture structure 7 is arranged on a portion of the silicon substrate 1 that corresponds to the third sub-surface 521, i.e. the texture structure 7 is recessed downward relative to the third sub-surface 521. In a further embodiment, according to FIG. 2, the texture structure 7 is arranged on a portion of the silicon substrate 1 which corresponds to the fourth sub-surface 522, i.e. the texture structure 7 is recessed downward relative to the fourth sub-surface 522. In yet another embodiment, according to FIG. 4, the third sub-surface 521 and the fourth sub-surface 522 merge into one another at a first boundary and the texture structure 7 is arranged on a portion of the silicon substrate 1 that corresponds to the first boundary, i.e. the texture structure 7 is recessed downward relative to the first boundary. In yet another embodiment, as shown in FIG. 5, the texture structures 7 are arranged on a portion of the silicon substrate 1 corresponding to the third sub-surface 521, a portion of the silicon substrate 1 corresponding to the fourth sub-surface 522, and a portion of the silicon substrate 1 corresponding to the first boundary. The step structure 5 of the present invention has the above-mentioned texture structures 7 that can use the light trapping principle to reduce the reflection of light incident on the third sub-surface 521 and / or the fourth sub-surface 522, thereby improving light absorption and increasing the light utilization rate of the passivated contact solar cell.In one embodiment, the average width of the texture structures 7 is W 2, where 0.5 μm≤W 2≤10 μm. For example, W may be 20,5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 10 μm. The width of the texture structure 7 refers to a maximum value of a length of a line connecting any two points on a bottom side of the texture structure. For example, as shown in FIG. 6, when the texture structure 7 is in the form of an inverted pyramid, the width of the texture structure 7 may be a length of a line connecting a point A and a point B on a bottom surface thereof, and the point A and the point B may be any two vertices at the bottom of the texture structure 7. In the present invention, the average width of the texture structures 7 refers to an average value of the widths of 10 texture structures 7 randomly selected from the step structure 5.By controlling W 2 within the above-mentioned range, an angle of incidence of light can be adjusted to improve the utilization rate of the incident light.In an embodiment, as shown in FIG. 1, the first region 11 includes a first electrode 61 penetrating through the first passivation layer 4 to be in contact with the first doped layer 3 and to form an ohmic contact.In an embodiment, a material of the first passivation layer 4 is selected from at least one of alumina, silicon nitride, and silicon oxynitride. The first passivation layer 4 formed of the above-mentioned materials promotes the complete passivation of an interface of the solar cell, thereby improving the performance of the solar cell.In addition, in an embodiment of FIG. 7, on a light receiving side 102 (opposite to the back surface 101) of the passivated contact solar cell of the present invention, a second doped layer 8, a second passivation layer 9, an antireflection layer 10, and a second electrode 62 are further sequentially formed. The light receiving side 102 of the silicon substrate 1 has a textured surface. In the present invention, in order to be able to absorb solar energy more effectively, the light receiving side of the silicon substrate has a textured surface, for example, a pyramidal textured surface. The textured surface can provide a greater surface area for the solar cell while reducing light reflection, diffusion, etc. The method for producing the textured surface is not specifically limited in the present invention as long as the objects of the present invention can be achieved. For example, a conventional magnetron sputtering method may be used.According to a second aspect, the present invention provides a photovoltaic module which comprises the solar cell described according to the first aspect.The present invention also provides a photovoltaic module for converting received light energy into electrical energy and for transmitting the electrical energy to an external load. The photovoltaic module includes: at least one cell string formed by bonding a plurality of the aforementioned solar cells; an encapsulating adhesive sheet covering a surface of the cell string; and a cover plate covering a surface of the encapsulating adhesive sheet facing away from the cell string.A material of the dielectric layer in the present invention may be selected from various dielectric materials, such as at least one material among silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. In particular, the dielectric layer may consist of a silicon oxide layer containing silicon oxide. This is because the silicon oxide film has excellent passivation performance, can minimize recombination loss of minority carriers on a surface of a semiconductor substrate, and is a thin film having excellent durability for the subsequent high temperature process. In order to ensure better passivation of the interface for the substrate, the thickness of the dielectric layer may be in the range from 0.1 nm to 5 nm. For example, the thickness of the dielectric layer may be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc. However, the present invention is not limited thereto, but the thickness of the dielectric layer may have various values. As a potential barrier for electrons and holes, the dielectric layer may be combined with a polycrystalline silicon layer to block the passage of minority charge carriers. The dielectric layer may also serve as a pinhole channel in order to allow charge carriers within the solar cell to move freely. The selective passage for majority carriers is achieved by heavily doped polycrystalline silicon, which is advantageous for reducing the recombination losses of the minority carriers. In addition, the dielectric layer may serve as a diffusion barrier to prevent a dopant in the doped polycrystalline silicon layer from diffusing into the semiconductor substrate.The method for manufacturing the passivated contact solar cell is not specifically limited in the present invention. For example, the passivated contact solar cell may be fabricated by a method comprising:Step A: providing a solar cell output structure including the silicon substrate, wherein the first doped layer and the dielectric layer are formed on a back surface of the silicon substrate, and the second doped layer is formed on the light receiving surface of the silicon substrate;Step B: subjecting the back surface of the silicon substrate to a patterning treatment for forming the first region, the second region, and the third region on the back surface of the silicon substrate;Step C: forming the first passivation layer on the patterned back side of the silicon substrate using a plasma enhanced chemical Gasphasenabscheidungs(PECVD)vorrichtung forming the second passivation layer on a surface of the second doped layer using an atomic layer deposition (ALD) device, and forming the anti-reflective layer on the surface of the second passivation layer using a PECVD device; andStep D: Prepare a first electrode and a second electrode on the back side and the light receiving side of the solar cell output structure, respectively.In step A of the present invention, the silicon substrate may have a first conductivity type. A dopant element in the second doped layer has a second conductivity type. One of the first conductivity type and the second conductivity type is an N type, and the other of the first conductivity type and the second conductivity type is a P type. For example, when the first conductivity type is N-type, the second conductivity type is P-type, and when the first conductivity type is P-type, the second conductivity type is N-type. The silicon substrate may be a textured silicon substrate. The silicon substrate may have a thickness of 100 μm to 200 μm. The present invention is not limited thereto as long as the objects of the present invention can be achieved.In step B of the present invention, in an optional embodiment, the structure including the first region, the second region, and the third region may be formed on the back surface of the silicon substrate by a laser etching process in combination with a wet etching process as described above. The specific process includes: a) sequentially depositing a dielectric layer, a phosphorus-doped amorphous silicon layer, and a silicon oxide mask layer on the back surface of the silicon substrate using a plasma enhanced chemical vapor deposition (PECVD) device at a process temperature controlled between 400° C. and 500° C.; b) converting the amorphous silicon in the phosphorus-doped amorphous silicon layer into polycrystalline silicon and activating phosphorus atoms in the phosphorus-doped amorphous silicon layer by high temperature annealing at 900° C. to 980° C. using a tube-type high temperature device to form the first doped layer, thereby obtaining a semi-finished solar cell; c) scanning a predetermined pattern area (e.g., the third area provided) on the back surface of the semi-finished solar cell by a picosecond green laser having a laser energy density of 150 mJ / cm 2 and 400 mJ / cm 2, to cause a portion of the silicon oxide mask layer in the corresponding area to be peeled or denatured; d) removing the oxide film surrounding a front side and an edge of the solar cell using a chain type RF device, and etching portions of the first doped layer and the dielectric layer in the laser treated region by wet alkaline tank type etching with an alkaline solution at a concentration of 0.5 wt % to 5 wt %, thereby forming the pattern structure including the first region, the second region, and the third region.In another optional embodiment, the above-described structure including the first region, the second region, and the third region may be formed on the back surface of the silicon substrate by a mask method in combination with a wet etching process. The specific process includes:a') sequentially depositing the dielectric layer and the phosphorus doped amorphous silicon layer on the back side of the silicon substrate using a plasma enhanced chemical Gasphasenabscheidungs(PECVD)vorrichtung wherein the process temperature is controlled between 400°C and 500°C;b') converting amorphous silicon in the phosphorus-doped amorphous silicon layer into polycrystalline silicon and activating phosphorus atoms in the phosphorus-doped amorphous silicon layer by high-temperature annealing at 900° C. to 950° C. using a tube-type high-temperature device to form the first doped layer, thereby obtaining a semi-finished solar cell.c') applying an alkali resistant mask slurry to a surface of the semi-finished solar cell by a chain coating method for forming an alkali resistant mask layer, and then laser scanning a predetermined pattern region (e.g., the third provided region) on the back surface of the semi-finished solar cell to cause a portion of the alkali resistant mask layer in the corresponding region to be deformed or denatured to expose the film / layer that is / is otherwise under the portion of the alkali resistant mask layer in the corresponding region;d') RCA cleaning: removing the oxide film surrounding a front side and an edge of the solar cell using a chain type RF device, and etching portions of the first doped layer and the dielectric layer in the exposed region by alkaline wet etching of the tank type with an alkaline solution at a concentration of 0.5 wt % to 2 wt % to form the pattern structure including the first region, the second region, and the third region.In step C of the present invention, the first passivation layer may be formed based on a PECVD process, the second passivation layer may be formed based on an ALD process, and the anti-reflection layer may be formed based on a PECVD process. The first passivation layer may be an aluminum oxide layer having a passivation function; the antireflection layer may be a silicon oxynitride layer having an antireflection function; and in addition, the second passivation layer may be formed on the back surface of the solar cell output structure, which may be a silicon oxynitride layer having a passivation function.The thicknesses of the various functional layers are not particularly limited in the present invention as long as the objects of the present invention can be achieved. For example, the thickness of the first passivation layer is 70 nm to 120 nm, the thickness of the second passivation layer is 1 nm to 5 nm, and the thickness of the antireflection layer is 60 nm to 100 nm.In step D of the present invention, the first electrode and the second electrode may be formed on the back side and the light receiving side of the solar cell output structure, respectively, by a screen printing method.The methods for controlling H 1 and H 2 are not particularly limited in the present invention. For example, H 1 or H 2 typically increase with the increase in laser power during laser etching treatment and with the increase in etching intensity during wet etching. The etching intensity generally increases with the increase in the etching time, the increase in the etching temperature, or the increase in the alkali solution concentration. Based on this, H 1 or H 2 can be controlled by controlling the laser power, the wet etching process, etc. The methods for controlling W 1 are not particularly limited in the present invention. For example, W 1 typically increases as the etching intensity during wet etching increases. Based thereon, W 1 may be controlled by controlling relevant process parameters of the wet etching. The methods for controlling W 2 are not particularly limited in the present invention. For example, W 2 typically increases as the etching intensity during wet etching increases. Based thereon, W 2 may be controlled by controlling the relevant process parameters of the wet etching.The laser for laser etching is not specifically limited in the present invention as long as the objects of the present invention can be achieved. Parameters of the present invention related to the laser may be as follows: the type of laser is at least one laser among a nanosecond laser, a picosecond laser, and a femtosecond laser; the type of light is an infrared laser, a visible laser, or an ultraviolet laser; the energy density of the laser is 30 mJ / cm 2 to 3000 mJ / cm 2; a wavelength of the laser is 300 nm to 1000 nm; and the shape of the laser beam spot may be circular or square.The alkali solution for wet etching is not specifically limited in the present invention as long as the objects of the present invention can be achieved. For example, the alkali solution may be a NaOH solution or a KOH solution having a concentration of 0.5 wt % to 5 wt %. In addition, the process temperature for alkali etching in the present invention may be in the range of 60° C. to 80° C., with an etching time of 200 s to 1000 s, as long as the textured structure can be formed on the surface of the step structure.ExamplesHereinafter, the passivated contact solar cell and the photovoltaic module in the embodiments of the present invention will be described in detail by way of specific examples.Example 1providing a solar cell output structureA textured solar cell starting structure was provided. The solar cell initial structure comprised a silicon substrate. On a back surface of the silicon substrate, a first doped layer, a dielectric layer and a silicon oxide mask layer were formed, and on its light receiving surface, a second doped layer was formed. The silicon substrate was an N-type silicon wafer having a thickness of 125 μm. A dopant in the first doped layer was the element phosphorus (P) and a dopant in the second doped layer was the element boron (B).Patterning treatmentA picosecond green laser was used to scan a predetermined pattern region designed on a back surface of a semi-finished solar cell to cause the silicon oxide mask layer to be deformed or denatured in the corresponding region. The portions of the first doped layer and the dielectric layer in the corresponding region were removed to form a preliminary step structure. The oxide film surrounding a front side and an edge of the solar cell was removed by a chain type RF device. Thereafter, wet alkaline etching of the tank type was performed to form a pattern structure having a first region, a second region and a third region.Production of a First Passivation LayerA first passivation layer having a thickness of 80 nm was deposited on the back side of the patterned silicon substrate using a PECVD device.Formation of a Second Passivation Layer and an Antireflection LayerA second passivation layer having a thickness of 5 nm was deposited on a surface of the second doped layer facing away from the silicon substrate by an ALD device, and then an antireflection layer having a thickness of 80 nm was deposited on a surface of the second passivation layer by a PECVD device.Production of ElectrodesA first electrode and a second electrode were respectively formed on the back side and the light receiving side of the solar cell base structure by a screen printing method to form a solar cell structure as shown in FIG. 7.Examples 2-6Examples 2 to 6 are substantially the same as Example 1 except that in the patterning treatment, H 1, H 2, W 1 and W 2 shown in Table 1 were controlled by adjusting process parameters such as the laser power and the concentration of the alkali solution for wet etching. Table 1: Relevant process parameters in Examples 1 to 6 Table 1: Relevant process parameters in Examples 1 to 6Example 10,050,50,50,5Example 20,08220,5Example 30,12330,5Example 40,2550,5Example 50,12331Example 60,12333testing the open circuit voltage, the short circuit current and the fill factor:The current (I) voltage (V) curves of the solar cells in Examples 1 to 6 were tested using an I-V tester (model: MX-MPVC-A20) to obtain the open circuit voltages, the short circuit current densities, and the fill factors of the solar cells.Testing of Photoelectric Conversion Efficiency:The current (I) voltage (V) curves of the solar cells in Examples 1 to 6 were tested using an I-V tester (model: MX-MPVC-A20) to obtain the photoelectric conversion efficiencies (Eta) of the solar cells.Table 2 Performance Data of Examples 1 to 6 Table 2 Performance Data of Examples 1 to 6Open-circuit voltage (V)Short-circuit current density (mA / cm 2)Fill factor (%)Eta (%)Example 10,73649,24685,6626,46Example 20,73649,25185,7626,50Example 30,74119,29686,2426,67Example 40,73819,27885,7126,62Example 50,73849,28085,5526,59Example 60,73819,27685,5726,57From the performance data of Examples 1 to 6 shown in Table 2, it is seen that the solar cell of the present invention has a high open circuit voltage, a high short circuit current density, a high fill factor, and a high photoelectric conversion efficiency. Obviously, the solar cell having the structure according to the present invention has excellent photoelectric conversion performance.FIG. 8 is a SEM image of the back surface of the solar cell according to Example 1 of the present invention. It can be seen from FIG. 8 that the rear side of the solar cell has a first step 51 and a second step 52, wherein the first step 51 has the first partial surface 511 and the second partial surface 512 which merge into one another, while the second step 52 has the third partial surface 521 and the fourth partial surface 522 which merge into one another.The passivated contact solar cell and the photovoltaic module according to the present invention have been described in detail above. Herein, specific examples are used to explain the principle and implementations of the present invention, but the description of the above-mentioned embodiments serves only to facilitate understanding of the technical solution and a gist of the present invention, but those skilled in the art can modify the specific embodiments and application ranges according to the concept of the present invention. In summary, the content of the description should not be understood as a limitation of the present invention.

Claims

A passivated contact solar cell comprising: a silicon substrate having a first region and a third region spaced apart from each other on a rear side thereof, wherein: a dielectric layer, a first doped layer and a first passivation layer are formed in sequence in the first region on the rear side of the silicon substrate, wherein the dielectric layer and the first doped layer form a passivated contact structure in the first region, the first passivation layer is also formed in the third region on the rear side of the silicon substrate, and a second region having a step structure with at least two steps is arranged between the first region and the third region.The solar cell of claim 1, wherein the step structure includes a first step and a second step, wherein the first step includes a first sub-surface and a second sub-surface that merge with each other, and wherein the second step includes a third sub-surface and a fourth sub-surface that merge with each other.The solar cell of claim 2, wherein a distance between the first sub-surface and the third sub-surface is H 1 where 0.05 μm ≤ H 1 ≤ 0.2 μm.The solar cell of claim 2, wherein a distance between the third sub-surface and a first plane is H 2 where 0.5 μm ≤ H 2 ≤ 8 μm, and wherein the first plane refers to a portion of a first surface of the first passivation layer that is opposite the silicon substrate and is located in the third region.The solar cell of claim 2, wherein an included angle between the third sub-surface and the fourth sub-surface is α, where α ≥ 90°.The solar cell of claim 2, wherein the second sub-surface merges into the third sub-surface.The solar cell of claim 2, wherein a width of the third sub-area is W 1 where 0.01 μm ≤ W 1 ≤ 5 μm.The solar cell of claim 2, wherein the step structure further comprises a texture structure that is recessed relative to the third sub-surface or the fourth sub-surface.The solar cell of claim 8, wherein the texture structure is disposed on a portion of the silicon substrate corresponding to the third sub-area, or the texture structure is disposed on a portion of the silicon substrate corresponding to the fourth sub-area, or the texture structure is disposed on a portion of the silicon substrate corresponding to a first boundary at which the third sub-area merges with the fourth sub-area.The solar cell of claim 8, wherein an average width of the texture structure is W 2 where 0.5 μm ≤ W 2 ≤ 10 μm.The solar cell according to any one of claims 1 to 10, wherein a first electrode is provided in the first region, and the first electrode penetrates the first passivation layer to be in contact with the first doped layer.Photovoltaic module comprising the passivated contact solar cell according to any one of claims 1 to 11.

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