Heterojunction solar cell substrate, heterojunction solar cell, photovoltaic module and photovoltaic system

Abstract

The utility model provides a heterojunction solar cell substrate, a heterojunction solar cell, a photovoltaic module and a photovoltaic system, and relates to the technical field of solar cells. The heterojunction solar cell substrate comprises a substrate body, and the substrate body is provided with a front face and a back face which are opposite to each other; the front surface of the substrate comprises a pyramid structure, and the back surface of the substrate comprises an inverted pyramid frustum of which the side surfaces are isosceles trapezoids; and an included angle theta between the long bottom edge of the inverted prismatic table and the bevel edge of the inverted prismatic table is 3-24 degrees. The morphology of the heterojunction solar cell substrate is optimized, the back reflection effect of the substrate can be improved, meanwhile, deposition of a passivation layer is facilitated, and the passivation effect of the solar cell is improved.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and specifically relates to a heterojunction solar cell substrate, a heterojunction solar cell, a photovoltaic module, and a photovoltaic system. Background Art

[0002] Heterojunction solar cells have high photoelectric conversion efficiency, excellent anti-PID (potential-induced degradation) performance and anti-LID (light-induced degradation) performance. In recent years, heterojunction solar cells have become a research hotspot in the field of solar cells. The upper surface and the lower surface of the traditional heterojunction cell substrate are symmetric double-sided textured structures, with a relatively high bifaciality. The pyramid texture on the heterojunction solar cell substrate is beneficial for the cell to capture light. However, there are many defects at the top and bottom of the pyramid, and it is not conducive to the deposition of the passivation layer, which has a certain impact on the passivation effect. Therefore, the asymmetric cell substrate structure with front-side texturing and back-side polishing is becoming a research hotspot in the industry.

[0003] At present, the back-side polishing methods of heterojunction cell substrates are mainly divided into acid polishing and alkali polishing. Among them, acid polishing can completely polish the back side to form a mirror surface, while alkali polishing will leave block-shaped platforms on the back side. The mirror surface is not conducive to the adhesion of metal grid lines. And there are a large number of defects at the edges of the platforms left by alkali polishing, and the carrier recombination is serious, which affects the passivation effect. At the same time, the side surfaces of the platforms naturally formed by alkali polishing are basically based on the (111) crystal plane. Therefore, the bottom angles of the platforms are close to a certain specific value. In this case, a part of the front-side vertically incident light will refract out of the silicon substrate after reaching the back side, resulting in current loss.

[0004] It should be noted that the above content is not necessarily prior art and does not limit the patent protection scope of this application. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of this application is to provide a heterojunction solar cell substrate, a heterojunction solar cell, a photovoltaic module, and a photovoltaic system. The front side of the heterojunction solar cell substrate includes a pyramid structure, and the back side includes an inverted frustum with isosceles trapezoidal sides, which optimizes the morphology of the heterojunction solar cell substrate, can improve the back-side reflection effect of the substrate, and is conducive to the deposition of the passivation layer, thereby improving the passivation effect of the solar cell.

[0006] To achieve the above purpose, this application adopts the following technical solutions:

[0007] A heterojunction solar cell substrate, comprising a substrate, the substrate having opposite front and back sides; the front side of the substrate includes a pyramid structure, and the back side includes an inverted frustum with isosceles trapezoidal sides;

[0008] The included angle θ between the long bottom side of the inverted frustum and the hypotenuse of the inverted frustum is 3° to 24°.

[0009] In some of these embodiments, the bottom surface and the top surface of the frustum are both squares, the side length of the bottom surface is 2 - 40 μm, and the height of the frustum is 0.3 - 1 μm.

[0010] In some of these embodiments, the bottom side length of the pyramid structure is 1.5 - 2.0 μm, and the height of the pyramid is 0.9 - 1.2 μm.

[0011] In some of these embodiments, the bottom angle θ' of the pyramid structure is 54°.

[0012] This application also provides a heterojunction solar cell, including the above-mentioned heterojunction solar cell substrate.

[0013] In some of these embodiments, the heterojunction solar cell includes, in sequence, a first metal electrode, a first TCO layer, a boron-doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, the heterojunction solar cell substrate, a second intrinsic amorphous silicon layer, a phosphorus-doped microcrystalline silicon layer, a second TCO layer, and a second metal electrode.

[0014] In some of these embodiments, the total thickness of the boron-doped microcrystalline silicon layer, the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, and the phosphorus-doped microcrystalline silicon layer is 20 - 50 nm; and / or

[0015] the thickness of the first TCO layer is 80 - 120 nm; and / or

[0016] the thickness of the second TCO layer is 80 - 120 nm.

[0017] In some of these embodiments, the sheet resistance of the front side of the heterojunction solar cell is 20 - 80 ohm / sq; and / or

[0018] the sheet resistance of the back side of the heterojunction solar cell is 20 - 80 ohm / sq.

[0019] This application also provides a photovoltaic module, which includes a plurality of solar cells connected in series and / or in parallel; wherein, at least one solar cell is the above-mentioned heterojunction solar cell.

[0020] This application also provides a photovoltaic system, including the above-mentioned photovoltaic module.

[0021] In the technical solution of this application, the front side of the heterojunction solar cell substrate includes a pyramid structure, and the back side includes a frustum with an isosceles trapezoid side surface, which optimizes the morphology of the heterojunction solar cell substrate, can improve the back reflection effect of the substrate, and is also conducive to the deposition of the passivation layer, thereby improving the passivation effect of the solar cell. Description of the Drawings

[0022] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0023] Figure 1 It is a schematic structural diagram of a heterojunction solar cell substrate according to an embodiment of the present application.

[0024] Figure 2 It is an intermediate state diagram of a heterojunction solar cell substrate when preparing a heterojunction solar cell substrate according to an embodiment of the present application.

[0025] Figure 3 It is a diagram of the incident light reflection situation of a heterojunction solar cell substrate according to an embodiment of the present application.

[0026] Figure 4 It is a schematic diagram of the change in the incident light angle when the incident light of the present application embodiment sequentially passes through the TCO layer, the doped microcrystalline layer, the intrinsic amorphous layer and then enters the heterojunction solar cell substrate.

[0027] Figure 5 It is a schematic structural diagram of a heterojunction solar cell according to an embodiment of the present application.

[0028] Reference numerals in the figure: 01, the first metal electrode; 02, the first TCO layer; 03, the boron-doped microcrystalline silicon layer; 04, the first intrinsic amorphous silicon layer; 05, the heterojunction solar cell substrate; 06, the second intrinsic amorphous silicon layer; 07, the phosphorus-doped microcrystalline silicon layer; 08, the second TCO layer; 09, the second metal electrode; 1, the substrate; 11, the pyramid structure; 12, the inverted frustum. Detailed Description of the Embodiment

[0029] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements and their relative dimensions may be exaggerated. Among them, the same or similar reference numerals throughout denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as limiting the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0030] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not imply that there must be a first element, component, region, layer, or part in the present disclosure.

[0031] In this application, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] It should be noted that the terms "first", "second", etc. in the specification, claims, and above-mentioned drawings of this application are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0033] In this application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous, and includes the two numerical endpoints of the numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in the numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" is allowed to broadly include quantitative intervals such as percentage intervals, ratio intervals, and ratio value intervals.

[0034] This application provides a heterojunction solar cell substrate, a heterojunction solar cell, a photovoltaic module, and a photovoltaic system. The front surface of the heterojunction solar cell substrate includes a pyramid structure, and the back surface includes an inverted frustum with an isosceles trapezoid side surface, optimizing the morphology of the heterojunction solar cell substrate, capable of enhancing the back reflection effect of the substrate, and at the same time facilitating the deposition of the passivation layer and enhancing the passivation effect of the solar cell.

[0035] An embodiment of this application provides a heterojunction solar cell substrate, including a substrate, where the substrate has opposite front and back surfaces; the front surface of the substrate includes a pyramid structure, and the back surface includes an inverted frustum with an isosceles trapezoid side surface;

[0036] The angle θ between the long bottom side of the inverted frustum and the hypotenuse of the inverted frustum is 3° to 24° (for example, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°).

[0037] In an embodiment of this application, the material of the substrate can be single-crystalline silicon.

[0038] In an embodiment of this application, a pyramid structure is provided on the front surface of the heterojunction solar cell substrate, and an inverted frustum is provided on the back surface; specifically, as Figure 1 shown, the tip of the pyramid on the front surface of the heterojunction solar cell substrate faces upward (i.e., the tip of the pyramid structure is farther from the inverted frustum than the bottom of the pyramid structure); the bottom surface of the inverted frustum on the back surface of the heterojunction solar cell substrate faces upward and the top surface faces downward (it should be noted that the bottom surface area of the frustum is larger than the top surface area; that is, the top surface of the inverted frustum is farther from the pyramid structure than the bottom surface of the inverted frustum). In addition, the angle θ refers to the bottom angle of the frustum, specifically as Figure 1As shown. The frustum can be an inverted quadrangular frustum, an inverted pentagonal frustum, an inverted hexagonal frustum, an inverted heptagonal frustum, or an inverted octagonal frustum.

[0039] In the embodiments of the present application, the morphology of the heterojunction solar cell substrate is optimized, which can improve the back reflection effect of the substrate, and at the same time is beneficial to the deposition of the passivation layer, improving the passivation effect of the solar cell.

[0040] The heterojunction solar cell substrate provided by the embodiments of the present application can alleviate the problem that the back surface of the acid-etched substrate is not conducive to the attachment of the metal grid lines. Compared with the traditional acid-etched substrate on the back surface, the heterojunction solar cell substrate provided by the embodiments of the present application is more conducive to the attachment of the metal grid lines.

[0041] The heterojunction solar cell substrate provided by the embodiments of the present application can alleviate the problems that a large number of defects exist at the edge of the tower platform on the back surface of the alkali-etched substrate, affecting the passivation effect and the back reflection effect is poor. Compared with the traditional alkali-etched substrate on the back surface, the heterojunction solar cell substrate provided by the embodiments of the present application is more conducive to the deposition of the passivation layer, has a better back reflection effect, and has less current loss.

[0042] In the embodiments of the present application, the calculation and derivation process of the angle θ between the long base side of the frustum and the hypotenuse of the frustum is as follows:

[0043] The main light that can be absorbed by the photovoltaic cell is the primary incident light and the secondary incident light. The secondary incident light is the primary reflected light of the primary incident light on the textured surface of the light-facing surface. Assuming that the light from nature is vertically incident and the bottom angles of the pyramids obtained by texturing are all ideally 54°, the reflection situations of the primary incident light and the secondary incident light are as Figure 3 、 Figure 4 shown, Figure 3 The right light path diagram is the primary incident light, Figure 3The left incident light is the secondary incident light. When light travels from one medium into another, the refraction angle γ can be calculated by the formula n = sinγ / sinβ, where n is the refractive index and β is the incident angle. The refractive indices of the TCO layer, doped microcrystalline layer, and intrinsic amorphous layer on the light-facing side are x, y, and z respectively, and the refractive index of single-crystalline silicon is 3.45. Then the relative refractive index of the TCO layer incident on the doped microcrystalline silicon layer is y / x, the relative refractive index of the doped microcrystalline silicon layer incident on the intrinsic amorphous silicon layer is z / y, and the relative refractive index of the intrinsic amorphous silicon incident on single-crystalline silicon is 3.45 / z. Through the above formula calculation, the incident angle of the incident light passing through the TCO layer, doped microcrystalline layer, and intrinsic amorphous layer and then incident on the single-crystalline silicon substrate has nothing to do with the refractive index and quantity of the intermediate film layers. That is, the angle of the light finally incident on the single-crystalline silicon substrate satisfies sinθ1 / sinθ5 = 3.45, where θ1 = 54°, so θ5 = 13.5°. First, calculate the primary incident light. To make all the light reaching the back of the substrate be reflected, that is, to require that the light that was originally going to transmit through the substrate and refract out be all reflected on the back, that is, to require that the refraction angle β1 ≥ 90°. The exit angle α1 on the back satisfies sinα1 / sinβ1 = 1 / 3.45, that is, α1 ≥ 16.5°. When the incident light reaches the bottom, there will be three situations: reaching the left edge, the right edge, or the bottom plane. It is calculated that the bottom angle should be ≤ 24°. That is, the bottom angle of the frustum should be less than or equal to 24°. The back surface topography also affects the adhesion of the metal grid lines. When the frustum angle is too small, the back surface flatness is higher, the specific surface area decreases, and the adhesion of the metal grid lines will become poor. Therefore, it is required to control the bottom angle of the frustum to be not less than 3°.

[0044] In an alternative embodiment, the bottom and top surfaces of the frustum are both squares. The side length of the bottom surface is 2 - 40 μm (for example, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm), and the height of the frustum is 0.3 - 1 μm (for example, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 cm, 1.0 μm). It should be noted that the side length of the bottom surface here refers to the side length of the square bottom surface of the frustum that is closer to the pyramid structure; since θ is also limited to 3° - 24°, and the height of the frustum (the distance between the two bottom surfaces of the frustum) is 0.3 - 1 μm, the side length of the top surface of the frustum (the side of the frustum away from the pyramid structure) can be calculated; the side length of the bottom surface of the frustum is greater than the side length of the top surface of the frustum.

[0045] In the embodiments of the present application, since the back surface topography affects the adhesion of the metal gate line, when the ratio of the side length to the height of the bottom surface of the inverted frustum is inappropriate, there will be a problem that the back surface flatness is higher, the specific surface area is reduced, and the adhesion of the metal gate line will become poor; the embodiments of the present application optimize the size of the inverted frustum, which is more conducive to the adhesion of the metal gate line.

[0046] In an alternative embodiment, the bottom side length of the pyramid structure is 1.5 - 2.0 μm (for example, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm), and the tower height is 0.9 - 1.2 μm (for example, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm). Optimizing the size of the pyramid structure is more conducive to the deposition of the passivation layer.

[0047] In an alternative embodiment, the bottom angle θ' of the pyramid structure is 54°. Ideally, the bottom angles of the pyramids obtained by texturing are all 54°. In actual situations, the bottom angles of the pyramid structures will fluctuate around 54°. Controlling the bottom angle of the pyramid closer to 54° and simultaneously controlling the included angle θ within 3° - 24° can further improve the back reflection effect of the heterojunction solar cell substrate.

[0048] The embodiments of the present application can provide a heterojunction solar cell, including a first metal electrode, a first TCO layer, a boron-doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, the heterojunction solar cell substrate, a second intrinsic amorphous silicon layer, a phosphorus-doped microcrystalline silicon layer, a second TCO layer, and a second metal electrode stacked in sequence.

[0049] In the embodiments of the present application, controlling the included angle θ between the long bottom side of the inverted frustum and the hypotenuse of the inverted frustum to be 3° - 24°, and then reasonably controlling the materials of each layer of the heterojunction solar cell can control the refraction conditions of each layer, and ultimately effectively improve the back reflection effect of the heterojunction solar cell, thereby effectively reducing the current loss and improving the efficiency and long-term stability of the battery.

[0050] In the embodiments of the present application, the deposition method of the boron-doped microcrystalline silicon layer can be plasma-enhanced chemical vapor deposition (PECVD); the deposition method of the phosphorus-doped microcrystalline silicon layer can be plasma-enhanced chemical vapor deposition (PECVD); the preparation method of the first TCO layer can be magnetron sputtering coating or reactive ion coating; the preparation method of the second TCO layer can be magnetron sputtering coating or reactive ion coating; the materials for preparing the first TCO layer can be selected from one or more of indium-containing target materials or indium-free target materials such as ICO, ITO, AZO, IWO, and tin oxide; the materials for preparing the second TCO layer can be selected from one or more of indium-containing target materials or indium-free target materials such as ICO, ITO, AZO, IWO, and tin oxide.

[0051] In an alternative embodiment, the total thickness of the boron-doped microcrystalline silicon layer, the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, and the phosphorus-doped microcrystalline silicon layer is 20 to 50 nm (e.g., 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm); and / or

[0052] The thickness of the first TCO layer is 80 to 120 nm (e.g., 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm); and / or

[0053] The thickness of the second TCO layer is 80 to 120 nm (e.g., 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm).

[0054] In the embodiments of the present application, by reasonably controlling the thickness of each layer, on the one hand, the carrier recombination between crystalline silicon and amorphous silicon can be reduced, thereby improving the open-circuit voltage and overall efficiency of the battery; on the other hand, it can enhance the back reflection effect of the heterojunction solar cell, thereby effectively reducing the current loss and improving the efficiency and long-term stability of the battery.

[0055] In an alternative embodiment, the sheet resistance of the front side of the heterojunction solar cell is 20 to 80 ohm / sq (e.g., 20 ohm / sq, 30 ohm / sq, 40 ohm / sq, 50 ohm / sq, 60 ohm / sq, 70 ohm / sq, 80 ohm / sq); and / or

[0056] The sheet resistance of the back side of the heterojunction solar cell is 20 to 80 ohm / sq (e.g., 20 ohm / sq, 30 ohm / sq, 40 ohm / sq, 50 ohm / sq, 60 ohm / sq, 70 ohm / sq, 80 ohm / sq).

[0057] In the embodiments of the present application, by reasonably controlling the sheet resistance of the front and back sides of the heterojunction solar cell, it helps to improve the current collection efficiency of the battery and can improve the efficiency and reliability of the battery.

[0058] The following specific embodiments further illustrate the present application in detail, but should not be construed as a limitation to the present application. Without departing from the spirit and essence of the present application, any modification or replacement of the methods, steps or conditions of the present application shall fall within the scope of the present application. Specific Embodiments

[0060] Example 1

[0061] A heterojunction solar cell, as Figure 5 shown, includes a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09, which are stacked in sequence; the heterojunction solar cell substrate 05 (the specific structure is as Figure 1 shown), includes a substrate 1, the material of the substrate 1 is single crystal silicon, and the substrate 1 has opposite front and back sides; the front side of the substrate 1 includes a pyramid structure 11, and the back side includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 14°; the side length of the bottom surface of the inverted frustum 12 is 45 μm, and the height is 1.5 μm; the bottom side length of the pyramid structure 11 is 1.7 μm, and the tower height is 1.0 μm. The sheet resistance of the front side of the heterojunction solar cell is 50 ohm / sq, and the sheet resistance of the back side of the heterojunction solar cell is 50 ohm / sq.

[0062] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 10 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 10 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 10 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 15 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 45 nm;

[0063] The thickness of the first TCO layer 02 is 100 nm; the thickness of the second TCO layer 08 is 100 nm.

[0064] Example 2

[0065] A heterojunction solar cell, comprising a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09, which are stacked in sequence; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single crystal silicon, and the substrate 1 has opposite front and back surfaces; the front surface of the substrate 1 includes a pyramid structure 11, and the back surface includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 3°; the side length of the bottom surface of the inverted frustum 12 is 2 μm, and the height is 0.3 μm; the bottom side length of the pyramid structure 11 is 1.5 μm, and the tower height is 0.9 μm. The sheet resistance of the front surface of the heterojunction solar cell is 20 ohm / sq, and the sheet resistance of the back surface of the heterojunction solar cell is 20 ohm / sq.

[0066] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 5 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 5 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 5 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 5 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 20 nm;

[0067] The thickness of the first TCO layer 02 is 80 nm; the thickness of the second TCO layer 08 is 80 nm.

[0068] Example 3

[0069] A heterojunction solar cell, comprising a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09, which are stacked in sequence; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single crystal silicon, and the substrate 1 has opposite front and back surfaces; the front surface of the substrate 1 includes a pyramid structure 11, and the back surface includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 24°; the side length of the bottom surface of the inverted frustum 12 is 40 μm, and the height is 1 μm; the bottom side length of the pyramid structure 11 is 2.0 μm, and the tower height is 1.2 μm. The sheet resistance of the front surface of the heterojunction solar cell is 80 ohm / sq, and the sheet resistance of the back surface of the heterojunction solar cell is 80 ohm / sq.

[0070] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 10 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 10 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 10 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 20 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 50 nm;

[0071] The thickness of the first TCO layer 02 is 120 nm; the thickness of the second TCO layer 08 is 120 nm.

[0072] Example 4

[0073] A heterojunction solar cell includes, in sequence, a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single-crystalline silicon, and the substrate 1 has opposite front and back sides; the front side of the substrate 1 includes a pyramid structure 11, and the back side includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 14°; the side length of the bottom surface of the inverted frustum 12 is 10 μm, and the height is 0.5 μm; the bottom side length of the pyramid structure 11 is 1.7 μm, and the tower height is 1.0 μm. The sheet resistance of the front side of the heterojunction solar cell is 50 ohm / sq, and the sheet resistance of the back side of the heterojunction solar cell is 50 ohm / sq.

[0074] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 10 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 10 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 10 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 15 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 45 nm;

[0075] The thickness of the first TCO layer 02 is 100 nm; the thickness of the second TCO layer 08 is 100 nm.

[0076] Example 5

[0077] A heterojunction solar cell, comprising a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09, which are stacked in sequence; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single crystal silicon, and the substrate 1 has opposite front and back sides; the front side of the substrate 1 includes a pyramid structure 11, and the back side includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 14°; the side length of the bottom surface of the inverted frustum 12 is 10 μm, and the height is 0.5 μm; the bottom side length of the pyramid structure 11 is 2.2 μm, and the tower height is 1.3 μm. The sheet resistance of the front side of the heterojunction solar cell is 50 ohm / sq, and the sheet resistance of the back side of the heterojunction solar cell is 50 ohm / sq.

[0078] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 10 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 10 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 10 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 15 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 45 nm;

[0079] The thickness of the first TCO layer 02 is 100 nm; the thickness of the second TCO layer 08 is 100 nm.

[0080] Example 6

[0081] A heterojunction solar cell includes, in sequence from bottom to top, a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single-crystalline silicon, and the substrate 1 has an opposite front side and a back side; the front side of the substrate 1 includes a pyramid structure 11, and the back side includes an inverted frustum 12 with an isosceles trapezoid side face; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 14°; the side length of the bottom surface of the inverted frustum 12 is 10 μm, and the height is 0.5 μm; the bottom side length of the pyramid structure 11 is 1.7 μm, and the tower height is 1.0 μm. The sheet resistance of the front side of the heterojunction solar cell is 50 ohm / sq, and the sheet resistance of the back side of the heterojunction solar cell is 50 ohm / sq.

[0082] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 20 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 20 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 20 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 20 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 80 nm;

[0083] The thickness of the first TCO layer 02 is 100 nm; the thickness of the second TCO layer 08 is 100 nm.

[0084] Example 7

[0085] A heterojunction solar cell, comprising a first metal electrode 01, a first TCO layer 02, a boron-doped microcrystalline silicon layer (p-μc s i) 03, a first intrinsic amorphous silicon layer (i-αs i) 04, the heterojunction solar cell substrate 05, a second intrinsic amorphous silicon layer (i-αs i) 06, a phosphorus-doped microcrystalline silicon layer (n-μc s i) 07, a second TCO layer 08, and a second metal electrode 09, which are stacked in sequence; the heterojunction solar cell substrate 05 includes a substrate 1, the material of the substrate 1 is single crystal silicon, and the substrate 1 has opposite front and back sides; the front side of the substrate 1 includes a pyramid structure 11, and the back side includes an inverted frustum 12 with an isosceles trapezoid side; the angle θ between the long bottom side of the inverted frustum 12 and the hypotenuse of the inverted frustum 12 is 14°; the side length of the bottom surface of the inverted frustum 12 is 10 μm, and the height is 0.5 μm; the bottom side length of the pyramid structure 11 is 1.7 μm, and the tower height is 1.0 μm. The sheet resistance of the front side of the heterojunction solar cell is 100 ohm / sq, and the sheet resistance of the back side of the heterojunction solar cell is 100 ohm / sq.

[0086] Among them, the thickness of the boron-doped microcrystalline silicon layer 03 is 10 nm, the thickness of the first intrinsic amorphous silicon layer 04 is 10 nm, the thickness of the second intrinsic amorphous silicon layer 06 is 10 nm, and the thickness of the phosphorus-doped microcrystalline silicon layer 07 is 15 nm; the total thickness of the boron-doped microcrystalline silicon layer 03, the first intrinsic amorphous silicon layer 04, the second intrinsic amorphous silicon layer 06, and the phosphorus-doped microcrystalline silicon layer 07 is 45 nm;

[0087] The thickness of the first TCO layer 02 is 100 nm; the thickness of the second TCO layer 08 is 100 nm.

[0088] Comparative Example 1

[0089] The difference between the heterojunction solar cell in Comparative Example 1 and the heterojunction solar cell in Example 1 is only that the heterojunction solar cell substrates are different; specifically, the heterojunction solar cell substrate in Comparative Example 1 is a conventional single crystal silicon substrate with a symmetric textured surface structure.

[0090] Comparative Example 2

[0091] The difference between the heterojunction solar cell in Comparative Example 2 and the heterojunction solar cell in Example 2 is only that the heterojunction solar cell substrates are different; specifically, the heterojunction solar cell substrate in Comparative Example 2 is a conventional single crystal silicon substrate with a symmetric textured surface structure.

[0092] Comparative Example 3

[0093] The difference between the heterojunction solar cell in Comparative Example 3 and the heterojunction solar cell in Example 3 lies only in that the substrates of the heterojunction solar cells are different; specifically, the substrate of the heterojunction solar cell in Comparative Example 3 is a conventional single-crystalline silicon substrate with a symmetric textured surface structure.

[0094] Comparative Example 4

[0095] The difference between the heterojunction solar cell in Comparative Example 4 and the heterojunction solar cell in Example 4 lies only in that the substrates of the heterojunction solar cells are different; specifically, the substrate of the heterojunction solar cell in Comparative Example 4 is a conventional single-crystalline silicon substrate with a symmetric textured surface structure.

[0096] Comparative Example 5

[0097] The difference between the heterojunction solar cell in Comparative Example 5 and the heterojunction solar cell in Example 5 lies only in that the substrates of the heterojunction solar cells are different; specifically, the substrate of the heterojunction solar cell in Comparative Example 5 is a conventional single-crystalline silicon substrate with a symmetric textured surface structure.

[0098] Comparative Example 6

[0099] The difference between the heterojunction solar cell in Comparative Example 6 and the heterojunction solar cell in Example 6 lies only in that the substrates of the heterojunction solar cells are different; specifically, the substrate of the heterojunction solar cell in Comparative Example 6 is a conventional single-crystalline silicon substrate with a symmetric textured surface structure.

[0100] It should be noted that in the above Examples 1-7, the preparation method of the substrate 05 of the heterojunction solar cell can be as follows: gettering is performed on the roughly polished silicon substrate, specifically, phosphorus diffusion is carried out on the silicon wafer, the phosphorus source is phosphorus oxychloride, the atmosphere is nitrogen and oxygen, the diffusion temperature is 700-950 °C (for example, 700 °C, 800 °C, 950 °C), and the time is 2-4 h (for example, 2 h, 3 h, 4 h). Then, double-sided texturing treatment is carried out. Preferably, the texturing additive is TS53 of Changzhou Shichuang Energy Co., Ltd., the concentration is 0.3%-0.8% (for example, 0.3%, 0.5%, 0.7%, 0.8%), the KOH concentration is 0.6%-2% (for example, 0.6%, 0.8%, 1.6%, 1.8%, 2%), the size of the base of the textured pyramid prepared is 1.5-2 μm, and the height of the pyramid is 0.9-1.2 μm. Next, the light-receiving surface is masked to protect the pyramid texture. Alkaline polishing is carried out on the back. Preferably, the texturing additive used is PS11 of Changzhou Shichuang Energy Co., Ltd., the concentration is 0.3%-3% (for example, 0.3%, 1.5%, 2%, 3%), the KOH concentration is 0.6%-2% (for example, 0.6%, 0.8%, 1.6%, 1.8%, 2%), the size of the base of the polished pyramid prepared is 5-30 μm, and the bottom angle of the pyramid is about 54°, such as Figure 2As shown. After polishing is completed, the mask layer is removed, and the HF concentration is 2%-5% (for example, 2%, 3%, 4%, 5%). Further, the backlight surface is etched. Preferably, the specific method is single-sided etching by a chain machine, and the etching solution is a mixed solution of hydrofluoric acid, nitric acid, and deionized water. The ratio of nitric acid / hydrofluoric acid is 3-8 (for example, 3, 4, 5, 6, 7, 8), the nitric acid concentration is 20%-50% (for example, 20%, 30%, 40%, 50%), and the etching time is 40s-400s (for example, 40s, 100s, 200s, 300s, 400s). As Figure 2 As shown, the shaded part is the etched side (symmetric), and the bottom angle of the frustum is adjusted to 3°-24° by etching. When the bottom angle θ≤24°, the reabsorbed light of the front vertically incident light and the primary reflected light will not refract out of the substrate on the lower surface. The light utilization rate is effectively improved.

[0101] The device performance data of the above embodiments and comparative examples are shown in Table 1 below.

[0102] Table 1

[0103]

[0104]

[0105] It can be seen from the detection results in Table 1 above that the front of the heterojunction solar cell substrate includes a pyramid structure, and the back includes an inverted frustum with an isosceles trapezoid side. The morphology of the heterojunction solar cell substrate is optimized, which can improve the back reflection effect of the substrate, and at the same time is beneficial to the deposition of the passivation layer, improving the passivation effect of the solar cell.

[0106] It can be seen from the Eta (%) (cell efficiency) of the heterojunction solar cells in Embodiment 1 and Embodiments 5-7 above that optimizing the size of the inverted frustum, optimizing the size of the pyramid structure, reasonably controlling the thickness of the boron-doped microcrystalline silicon layer, etc., and reasonably controlling the sheet resistance of the front and back of the heterojunction solar cell can all improve the cell efficiency of the heterojunction solar cell to a certain extent.

[0107] In summary, in the embodiments, the morphology of the heterojunction solar cell substrate is optimized, which can improve the back reflection effect of the substrate, and at the same time is beneficial to the deposition of the passivation layer, improving the passivation effect of the solar cell, and further improving the cell efficiency of the heterojunction solar cell.

[0108] The embodiments of the present application can provide a heterojunction solar cell, including the above-mentioned heterojunction solar cell substrate.

[0109] The embodiments of the present application can provide a photovoltaic module (not shown), the photovoltaic module includes a plurality of solar cells connected in series and / or in parallel; wherein, at least one solar cell is the above-mentioned heterojunction solar cell.

[0110] Embodiments of the present application may provide a photovoltaic system, including the photovoltaic modules in any of the above embodiments. The advantages possessed by the above photovoltaic modules are also possessed by this photovoltaic system, which will not be elaborated here. The application fields of the above photovoltaic system are extensive, not limited to photovoltaic power stations, such as ground power stations, rooftop power stations, and water surface power stations, but also include various devices and apparatuses that utilize solar energy for power generation, such as user solar power supplies, solar street lamps, solar cars, and solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields that require solar power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a busbar box, and an inverter. The photovoltaic array can be an array combination of multiple photovoltaic modules. For example, multiple photovoltaic modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the busbar box, and the busbar box can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into alternating current required by the commercial power grid and then connected to the commercial power grid to achieve solar power supply.

[0111] It should be noted that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present application. The orientation terms "inner" and "outer" refer to the inside and outside relative to the contour of each component itself. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "on top of other devices or structures" will be positioned as "below other devices or structures" or "beneath other devices or structures" afterwards. Thus, the exemplary term "above..." can include both the orientation of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding explanations are made for the relative spatial descriptions used here.

[0112] It should also be noted that the "one embodiment", "another embodiment", "embodiment", etc. mentioned in the present application refer to the specific features, structures, or characteristics described in connection with that embodiment being included in at least one embodiment generally described in the present application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure, or characteristic in connection with any embodiment, it is intended that the realization of such feature, structure, or characteristic in combination with other embodiments also falls within the scope of the present application.

[0113] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0114] It should also be noted that the above are only the preferred embodiments of the present application, and do not limit the patent protection scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A heterojunction solar cell substrate, characterized in that: The substrate comprises a front side and a back side opposite to each other; the front side of the substrate comprises a pyramid structure, and the back side comprises a chamfered platform with a side surface being an isosceles trapezoid; The angle θ between the long base of the chamfered pyramid and the hypotenuse of the chamfered pyramid is 3° to 24°.

2. The heterojunction solar cell substrate according to claim 1, characterized in that: The bottom surface and the top surface of the chamfered pyramid are both square, the side length of the bottom surface is 2 to 40 μm, and the height of the chamfered pyramid is 0.3 to 1 μm.

3. The heterojunction solar cell substrate according to claim 1, characterized in that: The side length of the base of the pyramid structure is 1.5 to 2.0 μm, and the height of the pyramid structure is 0.9 to 1.2 μm.

4. The heterojunction solar cell substrate according to claim 1, characterized in that: The base angle θ' of the pyramid structure is 54°.

5. A heterojunction solar cell, characterized in that: It comprises the heterojunction solar cell substrate as claimed in any one of claims 1 to 4.

6. The heterojunction solar cell according to claim 5, characterized in that: It comprises a first metal electrode, a first TCO layer, a boron-doped microcrystalline silicon layer, a first intrinsic amorphous silicon layer, the heterojunction solar cell substrate, a second intrinsic amorphous silicon layer, a phosphorus-doped microcrystalline silicon layer, a second TCO layer and a second metal electrode which are stacked in sequence.

7. The heterojunction solar cell according to claim 6, characterized in that: The total thickness of the boron-doped microcrystalline silicon layer, the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer and the phosphorus-doped microcrystalline silicon layer is 20 to 50 nm; and / or The thickness of the first TCO layer is 80-120 nm; and / or The thickness of the second TCO layer is 80-120 nm.

8. The heterojunction solar cell according to claim 6, characterized in that: The square resistance of the front side of the heterojunction solar cell is 20 to 80 ohm / sq; and / or The square resistance of the back side of the heterojunction solar cell is 20-80 ohm / sq.

9. A photovoltaic module, characterized in that: The photovoltaic module comprises a plurality of solar cells connected in series and / or in parallel; wherein at least one solar cell is a heterojunction solar cell as claimed in any one of claims 5 to 8.

10. A photovoltaic system, characterized in that: Comprising the photovoltaic module as claimed in claim 9.

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