Solar cell and preparation method thereof

Abstract

The invention relates to a solar cell and a preparation method thereof. The solar cell comprises a monocrystalline silicon substrate of a first doping type; the first intrinsic amorphous silicon layer, the first doping material layer of the second doping type, the first transparent conducting layer and the first electrode are sequentially arranged on the first side of the monocrystalline silicon substrate, and the first doping material layer is provided with a third side connected to the first intrinsic amorphous silicon layer and a fourth side connected to the first transparent conducting layer; the second intrinsic amorphous silicon layer, the second doping material layer of the first doping type, the second transparent conductive layer and the second electrode are sequentially arranged on the second side of the monocrystalline silicon substrate. The crystal grain size of the fourth side is small, the crystallinity is high, the effective doping concentration of the fourth side can be improved, the effective doping concentration of the fourth side can be higher, the contact resistance can be reduced, the filling factor can be improved, and the open-circuit voltage loss can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a solar cell and a preparation method thereof. Background Art

[0002] Heterojunction (HJT) cells are solar cells that combine crystalline silicon and amorphous silicon thin film materials. The most advanced technology currently uses a first-type doped single-crystal silicon wafer as a substrate, and deposits a hydrogenated intrinsic amorphous silicon (a-Si:H) film and a first-type doped hydrogenated microcrystalline silicon (mc-Si:H) film on the first side of the cleaned and textured single-crystal silicon wafer in sequence to form a positive surface field; on the second side, an a-Si:H film and a second-type doped mc-Si:H film are deposited in sequence to form a pn heterojunction; then transparent conductive oxide films are deposited on both sides of the doped a-Si:H film; finally, electrodes are prepared on both sides to form a heterojunction cell with a symmetrical structure.

[0003] However, for the second doping type hydrogenated microcrystalline silicon participating in forming the heterojunction, there is a problem of insufficient doping concentration, which leads to high contact resistance and is not conducive to improving the performance of solar cells such as fill factor and open circuit voltage. Summary of the invention

[0004] Based on this, it is necessary to provide a solar cell and a method for preparing the same to solve the problem that the second doping type hydrogenated microcrystalline silicon has insufficient doping concentration, resulting in high contact resistance.

[0005] The first aspect of the present invention is to provide a solar cell, the scheme is as follows:

[0006] A solar cell, comprising:

[0007] a single crystal silicon substrate of a first doping type;

[0008] A first intrinsic amorphous silicon layer, a first doping material layer of a second doping type, a first transparent conductive layer, and a first electrode are sequentially arranged on a first side of the single crystal silicon substrate, the first doping material layer having a third side connected to the first intrinsic amorphous silicon layer and a fourth side connected to the first transparent conductive layer, a grain size of the fourth side being smaller than a grain size of the third side, a crystallinity of the fourth side being greater than a crystallinity of the third side, and a doping concentration of the fourth side being greater than a doping concentration of the third side; and

[0009] A second intrinsic amorphous silicon layer, a second doping material layer of the first doping type, a second transparent conductive layer and a second electrode are sequentially arranged on the second side of the single crystal silicon substrate.

[0010] In one embodiment, the first doping material layer includes a second doping type hydrogenated microcrystalline silicon layer and a second doping type hydrogenated nanocrystalline silicon layer stacked, the hydrogenated microcrystalline silicon layer has the third side, and the hydrogenated nanocrystalline silicon layer has the fourth side.

[0011] In one of the embodiments, the hydrogenated microcrystalline silicon layer has a crystallinity of 20% to 50% and a grain size of 10 nm to 1000 nm.

[0012] The hydrogenated nanocrystalline silicon layer has a crystallinity of 50% to 70% and a grain size of 5nm to 1000nm.

[0013] In one embodiment, the doping concentration of the hydrogenated microcrystalline silicon layer is 1×10 13 ~1×10 21 cm -3 .

[0014] In one embodiment, the doping concentration of the hydrogenated nanocrystalline silicon layer is 1×10 13 ~1×10 22 cm -3 .

[0015] In one embodiment, the thickness of the hydrogenated microcrystalline silicon layer is 10 nm to 30 nm.

[0016] In one of the embodiments, the thickness of the hydrogenated nanocrystalline silicon layer is 8 nm to 30 nm.

[0017] In one embodiment, the material of the second doping material layer is hydrogenated nanocrystalline SiO x , where x is 1~2.

[0018] In one embodiment, the solar cell further comprises a first SiO x layer, wherein x is 1 to 2, the first SiO x A layer is provided between the single crystal silicon substrate and the first intrinsic amorphous silicon layer.

[0019] In one embodiment, the solar cell further comprises a second SiO x layer, wherein x is 1 to 2, the second SiO x A layer is provided between the single crystal silicon substrate and the second intrinsic amorphous silicon layer.

[0020] In one embodiment, the first transparent conductive layer and the second transparent conductive layer are independently selected from one or more of ITO, ICO, AZO, GZO and GAZO.

[0021] In one embodiment, the material of the first transparent conductive layer is MoO x , where x is 2~3.

[0022] The second aspect of the present invention is to provide a method for preparing a solar cell, the scheme is as follows:

[0023] A method for preparing a solar cell comprises the following steps:

[0024] providing a single crystal silicon substrate of a first doping type;

[0025] A first intrinsic amorphous silicon layer, a first doping material layer of a second doping type, a first transparent conductive layer, and a first electrode are sequentially formed on a first side of the single crystal silicon substrate, wherein the first doping material layer has a third side connected to the first intrinsic amorphous silicon layer and a fourth side connected to the first transparent conductive layer, a grain size of the fourth side is smaller than a grain size of the third side, a crystallinity of the fourth side is greater than that of the third side, and a doping concentration of the fourth side is greater than that of the third side; and

[0026] A second intrinsic amorphous silicon layer, a second doping material layer of the first doping type, a second transparent conductive layer and a second electrode are sequentially formed on the second side of the single crystal silicon substrate.

[0027] In one embodiment, the process for forming the first doping material layer is CVD, and the process gases used include SiH4, H2 and a doping source of the second doping type, and the flow ratio of H2 to SiH4 when forming the fourth side is higher than the flow ratio of H2 to SiH4 when forming the third side.

[0028] In one embodiment, when forming the fourth side, the flow rate ratio of H2 to SiH4 is 1:200-350.

[0029] When forming the third side, the flow rate ratio of H2 to SiH4 is 1:120-200.

[0030] In one embodiment, the step of forming the first doping material layer includes:

[0031] forming a hydrogenated microcrystalline silicon layer of a second doping type on the first intrinsic amorphous silicon layer, the hydrogenated microcrystalline silicon layer having the third side;

[0032] A hydrogenated nanocrystalline silicon layer is formed on the hydrogenated microcrystalline silicon layer, wherein the hydrogenated nanocrystalline silicon layer has the fourth side.

[0033] In one embodiment, before forming the first intrinsic amorphous silicon layer, the preparation method further includes the following steps:

[0034] A first SiO x Layer, where x is 1~2.

[0035] In one embodiment, the first SiO x The process of the layer is CVD, by introducing CO2, SiO is generated on the first side of the single crystal silicon substrate. x .

[0036] In one embodiment, before forming the second intrinsic amorphous silicon layer, the preparation method further includes the following steps:

[0037] A second SiO x Layer, where x is 1~2.

[0038] Forming the second SiO x The process of the layer is CVD, by introducing CO2, SiO is generated on the second side of the single crystal silicon substrate. x .

[0039] Compared with the conventional technology, the above solar cell and its preparation method have the following beneficial effects:

[0040] The solar cell and its preparation method are provided with a first doping material layer between the first intrinsic amorphous silicon layer and the first transparent conductive layer, the grain size of the first doping material layer connected to the fourth side of the first transparent conductive layer is smaller than the grain size of the first doping material layer connected to the third side of the first intrinsic amorphous silicon layer, and the crystallinity of the fourth side is greater than the crystallinity of the third side. In this way, the lattice adaptability of the intrinsic amorphous silicon on the third side and the inner layer is higher, which is beneficial to reduce the number of dangling bonds at the interface with the intrinsic amorphous silicon layer, is beneficial to passivation, and improves the open circuit voltage. Since the grain size of the fourth side is smaller and the crystallinity is higher, it is beneficial to increase the effective doping concentration of the fourth side, so that the effective doping concentration of the fourth side is higher, which can reduce the contact resistance, improve the fill factor, and reduce the open circuit voltage loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic structural diagram of a solar cell according to an embodiment;

[0042] FIG. 2 is a schematic diagram of a process of manufacturing a solar cell according to an embodiment.

[0043] Description of reference numerals:

[0044] 100, solar cell; 110, single crystal silicon substrate; 110a, first side; 110b, second side; 121, first intrinsic amorphous silicon layer; 122, first doping material layer; 122a, third side; 122b, fourth side; 1221, hydrogenated microcrystalline silicon layer; 1222, hydrogenated nanocrystalline silicon layer; 123, first transparent conductive layer; 124, first electrode; 125, first SiO x layer; 131, a second intrinsic amorphous silicon layer; 132, a second doping material layer; 133, a second transparent conductive layer; 134, a second electrode; 135, a second SiO x layer. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0047] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0049] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] As shown in FIG1 , a solar cell 100 according to an embodiment of the present invention includes a single crystal silicon substrate 110 of a first doping type, a first intrinsic amorphous silicon layer 121, a first doping material layer 122 of a second doping type, a first transparent conductive layer 123, a first electrode 124, a second intrinsic amorphous silicon layer 131, a second doping material layer 132 of a first doping type, a second transparent conductive layer 133 and a second electrode 134.

[0051] The single crystal silicon substrate 110 has a first side 110 a and a second side 110 b which are opposite to each other.

[0052] The first intrinsic amorphous silicon layer 121, the hydrogenated microcrystalline silicon layer 1221, the hydrogenated nanocrystalline silicon layer 1222, the first transparent conductive layer 123 and the first electrode 124 are sequentially arranged on the first side 110a of the single crystal silicon substrate 110. In other words, the first intrinsic amorphous silicon layer 121 is arranged on the first side 110a of the single crystal silicon substrate 110. The first transparent conductive layer 123 is arranged on the side of the hydrogenated nanocrystalline silicon layer 1222 away from the first doping material layer 122. The first electrode 124 is arranged on the side of the first transparent conductive layer 123 away from the hydrogenated nanocrystalline silicon layer 1222. Among them, the first doping material layer 122 has a third side 122a connected to the first intrinsic amorphous silicon layer 121 and a fourth side 122b connected to the first transparent conductive layer 123, the grain size of the fourth side 122b is smaller than the grain size of the third side 122a, the crystallinity of the fourth side 122b is greater than the crystallinity of the third side 122a, and the doping concentration of the fourth side 122b is greater than the doping concentration of the third side 122a.

[0053] The second intrinsic amorphous silicon layer 131, the second doping material layer 132, the second transparent conductive layer 133 and the second electrode 134 are sequentially arranged on the second side 110b of the single crystal silicon substrate 110. In other words, the second intrinsic amorphous silicon layer 131 is arranged on the second side 110b of the single crystal silicon substrate 110. The second doping material layer 132 is arranged on a side of the second intrinsic amorphous silicon layer 131 away from the single crystal silicon substrate 110. The second transparent conductive layer 133 is arranged on a side of the second doping material layer 132 away from the second intrinsic amorphous silicon layer 131. The second electrode 134 is arranged on a side of the second transparent conductive layer 133 away from the second doping material layer 132.

[0054] The solar cell 100 is provided with a first doping material layer 122 between the first intrinsic amorphous silicon layer 121 and the first transparent conductive layer 123. The grain size of the fourth side 122b of the first doping material layer 122 connected to the first transparent conductive layer 123 is smaller than the grain size of the third side 122a connected to the first intrinsic amorphous silicon layer 121, and the crystallinity of the fourth side 122b is greater than the crystallinity of the third side 122a. In this way, the third side 122a has a higher lattice fit with the intrinsic amorphous silicon of the inner layer, which is beneficial to reduce the number of dangling bonds at the interface with the intrinsic amorphous silicon layer, which is beneficial to passivation and improves the open circuit voltage. Since the grain size of the fourth side 122b is smaller and the crystallinity is higher, it is beneficial to improve the effective doping concentration of the fourth side 122b, so that the effective doping concentration of the fourth side 122b is higher, which can reduce the contact resistance, improve the fill factor, and reduce the open circuit voltage loss.

[0055] In some examples, the solar cell 100 is a heterojunction cell.

[0056] The first doping type is opposite to the second doping type. The first doping type may be N-type doping, such as phosphorus doping, or may be P-type doping, such as boron doping. In one example, the first doping type is N-type doping.

[0057] In some examples, the doping concentration of the single crystal silicon substrate 110 is 1×10 14 ~1×10 20 cm -3 Furthermore, in some of the examples, the doping concentration of the single crystal silicon substrate 110 is 1×10 14 ~1×10 19 cm -3 .

[0058] The first side 110a and the second side 110b of the single crystal silicon substrate 110 can be set to a pyramid texture structure, which can achieve an anti-reflection effect. The pyramid texture structure can be formed by a cleaning and texture making process.

[0059] In some of the examples, the thickness of the single crystal silicon substrate 110 is 100 μm to 120 μm. Further, in some of the examples, the thickness of the single crystal silicon substrate 110 is 105 μm to 115 μm. In some of the examples, the thickness of the single crystal silicon substrate 110 is specifically, for example, 105 μm, 106 μm, 107 μm, 108 μm, 109 μm, 110 μm, 111 μm, 112 μm, 113 μm, 114 μm, 115 μm, 116 μm, 117 μm, 118 μm, etc.

[0060] In some examples, the material of the first intrinsic amorphous silicon layer 121 is hydrogenated intrinsic amorphous silicon (ia-Si:H).

[0061] In some of the examples, the thickness of the first intrinsic amorphous silicon layer 121 is 5 nm to 20 nm. Further, in some of the examples, the thickness of the first intrinsic amorphous silicon layer 121 is 8 nm to 15 nm. In some of the examples, the thickness of the first intrinsic amorphous silicon layer 121 is, for example, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, etc.

[0062] In some examples, the first doping material layer 122 includes a stacked hydrogenated microcrystalline silicon layer 1221 of the second doping type and a hydrogenated nanocrystalline silicon layer 1222 of the second doping type, the hydrogenated microcrystalline silicon layer 1221 having the third side 122a, and the hydrogenated nanocrystalline silicon layer 1222 having the fourth side 122b. In other words, the hydrogenated microcrystalline silicon layer 1221 is disposed on a side of the first intrinsic amorphous silicon layer 121 away from the single crystalline silicon substrate 110. The hydrogenated nanocrystalline silicon layer 1222 is disposed on a side of the hydrogenated microcrystalline silicon layer 1221 away from the first intrinsic amorphous silicon layer 121.

[0063] The solar cell 100 further sets a hydrogenated nanocrystalline silicon layer 1222 on the hydrogenated microcrystalline silicon layer 1221. Compared with nanocrystalline silicon, the lattice adaptability of microcrystalline silicon and the intrinsic amorphous silicon of the inner layer is higher, and the crystal structure of the nanocrystalline layer grown on the basis of the microcrystalline layer will be better. The hydrogenated microcrystalline silicon layer 1221 is equivalent to forming a buffer layer between the hydrogenated nanocrystalline silicon layer 1222 and the intrinsic amorphous silicon, which is beneficial to reduce the number of dangling bonds at the interface with the intrinsic amorphous silicon layer, which is beneficial to passivation and improve the open circuit voltage. Compared with microcrystalline silicon, nanocrystalline silicon has a higher crystallinity, which is beneficial to improve the effective doping concentration. By setting a hydrogenated nanocrystalline silicon layer 1222 with a higher doping concentration, the contact resistance can be reduced, the fill factor can be improved, and the open circuit voltage loss can be reduced. At the same time, the hydrogenated microcrystalline silicon layer 1221 with a lower doping concentration and the hydrogenated nanocrystalline silicon layer 1222 with a higher doping concentration form a high-low junction, which is beneficial to improve the open circuit voltage.

[0064] In some of the examples, the grain size of the hydrogenated microcrystalline silicon layer 1221 is 10 nm to 1000 nm. Further, in some of the examples, the grain size of the hydrogenated microcrystalline silicon layer 1221 is 10 nm to 800 nm.

[0065] In some of the examples, the hydrogenated microcrystalline silicon layer 1221 has a crystallinity of 20% to 50%. Further, in some of the examples, the crystallinity of the hydrogenated microcrystalline silicon layer 1221 is 30% to 50%.

[0066] Since the hydrogenated microcrystalline silicon layer 1221 is additionally provided, the hydrogenated microcrystalline silicon layer 1221 can be thinned, that is, the thickness of the hydrogenated microcrystalline silicon layer 1221 in the structure of the present invention can be lower than the thickness used in general processes.

[0067] For example, in some of the examples, the thickness of the hydrogenated microcrystalline silicon layer 1221 is 10 nm to 30 nm. Further, in some of the examples, the thickness of the hydrogenated microcrystalline silicon layer 1221 is 10 nm to 20 nm. In some of the examples, the thickness of the hydrogenated microcrystalline silicon layer 1221 is specifically, for example, 15 nm, 15.5 nm, 16 nm, 16.5 nm, 17 nm, 17.5 nm, 18 nm, 18.5 nm, 19 nm, 19.5 nm, 20 nm, 20.5 nm, 21 nm, 21.5 nm, etc.

[0068] In some examples, the doping concentration of the hydrogenated microcrystalline silicon layer 1221 is 1×10 13 ~1×10 21 cm -3 In some examples, the doping concentration of the hydrogenated microcrystalline silicon layer 1221 is 1×10 13 ~1×10 20 cm -3 Furthermore, in some examples, the doping concentration of the hydrogenated microcrystalline silicon layer 1221 is 1×10 15 ~1×10 20 cm -3 .

[0069] Compared with the hydrogenated microcrystalline silicon layer 1221 , the hydrogenated microcrystalline silicon layer 1221 has a smaller grain size and a higher crystallinity, which is beneficial to improving the effective doping concentration.

[0070] In some of the examples, the grain size of the hydrogenated nanocrystalline silicon layer 1222 is 5 nm to 1000 nm. Further, in some of the examples, the grain size of the hydrogenated nanocrystalline silicon layer 1222 is 10 nm to 1000 nm.

[0071] In some examples, the hydrogenated nanocrystalline silicon layer 1222 has a crystallinity of 50% to 70%. Further, in some examples, the hydrogenated nanocrystalline silicon layer 1222 has a crystallinity of 50% to 65%.

[0072] In some of the examples, the thickness of the hydrogenated nanocrystalline silicon layer 1222 is 8 nm to 30 nm. Further, in some of the examples, the thickness of the hydrogenated nanocrystalline silicon layer 1222 is 10 nm to 25 nm. In some of the examples, the thickness of the hydrogenated nanocrystalline silicon layer 1222 is specifically, for example, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, etc.

[0073] In some examples, the doping concentration of hydrogenated nanocrystalline silicon layer 1222 is 1×10 13 ~1×10 22 cm -3 Furthermore, the doping concentration of the hydrogenated nanocrystalline silicon layer 1222 is 1×10 15 ~1×10 22 cm -3 . .

[0074] The material of the first transparent conductive layer 123 may be, but is not limited to, conductive metal oxides, such as one or more of ITO (tin-doped indium oxide), ICO (cerium-doped indium oxide), AZO (aluminum-doped zinc oxide), GZO (gallium-doped zinc oxide), and GAZO (aluminum-gallium co-doped zinc oxide).

[0075] The material of the first transparent conductive layer 123 is MoO x , where x is 2 to 3. MoO x The first transparent conductive layer 123 of the composition has a better match with the energy band of nanocrystalline silicon, which can reduce hole transmission loss.

[0076] In some of the examples, the thickness of the first transparent conductive layer 123 is 80nm-150nm. Further, in some of the examples, the thickness of the first transparent conductive layer 123 is 90nm-120nm. In some of the examples, the thickness of the first transparent conductive layer 123 is specifically, for example, 95nm, 96nm, 97nm, 98nm, 99nm, 100nm, 101nm, 102nm, 103nm, 104nm, 105nm, 106nm, 107nm, 108nm, etc.

[0077] The first electrode 124 is made of a conductive material, and the conductive material may be one or more of, but not limited to, silver, copper, tin, aluminum, titanium, and nickel.

[0078] In conventional technology, there is a greater risk of epitaxial growth at the interface between the single crystal silicon substrate 110 and the intrinsic amorphous silicon layer, and the interface passivation is insufficient. To solve this technical problem, as a further improvement of the present invention, as shown in FIG1 , in some examples, the solar cell 100 further includes a first SiO x Layer 125, wherein x is 1 to 2. The first SiO x The layer 125 is disposed between the single crystal silicon substrate 110 and the first intrinsic amorphous silicon layer 121 .

[0079] In the above example, a first SiO x layer 125, can reduce epitaxial growth, and SiO x It can reduce the influence of dangling bonds, improve the interface passivation effect, and increase the open circuit voltage.

[0080] Prepare the first SiO x The method of forming the first intrinsic amorphous silicon layer 125 is, for example, to introduce a small amount of CO2 before forming the first intrinsic amorphous silicon layer 121, so as to react with the single crystal silicon substrate 110 to generate SiO x and CO.

[0081] In some of these examples, the first SiO x The thickness of the layer 125 is 1 nm to 8 nm. Further, in some examples, the first SiO x The thickness of the layer 125 is 2 nm to 5 nm. In some examples, the first SiO x The thickness of layer 125 is specifically, for example, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm, 4 nm, 4.2 nm, 4.4 nm, 4.6 nm, etc.

[0082] In some examples, the material of the second intrinsic amorphous silicon layer 131 is hydrogenated intrinsic amorphous silicon (ia-Si:H).

[0083] In some of the examples, the thickness of the second intrinsic amorphous silicon layer 131 is 5 nm to 15 nm. Further, in some of the examples, the thickness of the second intrinsic amorphous silicon layer 131 is 8 nm to 12 nm. In some of the examples, the thickness of the second intrinsic amorphous silicon layer 131 is specifically, for example, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, etc.

[0084] In the conventional solution, hydrogenated microcrystalline silicon is used as the second doping material layer 132. However, the band gap of hydrogenated microcrystalline silicon is narrow, resulting in serious optical loss. To solve this technical problem, as a further improvement of the present invention, in some examples, the material of the second doping material layer 132 is hydrogenated nanocrystalline SiO x , where x is 1~2. Compared with the traditional hydrogenated microcrystalline silicon, hydrogenated nanocrystalline SiO x The optical band gap is wider and the absorption range of visible light is larger, so the optical response of the solar cell 100 can be effectively improved.

[0085] In other examples, the material of the second doping material layer 132 may also be one or more of hydrogenated microcrystalline silicon, hydrogenated nanocrystalline silicon, and N-type hydrogenated amorphous silicon.

[0086] In some examples, the doping concentration of the second doping material layer 132 is 1×10 14 ~1×10 22 cm -3 Furthermore, in some examples, the doping concentration of the second doping material layer 132 is 1×10 15 ~1×10 22 cm -3 .

[0087] In some of the examples, the thickness of the second doping material layer 132 is 10 nm to 30 nm. Further, in some of the examples, the thickness of the second doping material layer 132 is 15 nm to 25 nm. In some of the examples, the thickness of the second doping material layer 132 is specifically, for example, 15 nm, 15.5 nm, 16 nm, 16.5 nm, 17 nm, 17.5 nm, 18 nm, 18.5 nm, 19 nm, 19.5 nm, 20 nm, 20.5 nm, 21 nm, 21.5 nm, etc.

[0088] The material of the second transparent conductive layer 133 may be, but is not limited to, a conductive metal oxide, for example, one or more of ITO, ICO, AZO, GZO, and GAZO.

[0089] The materials of the first transparent conductive layer 123 and the second transparent conductive layer 133 may be the same or different.

[0090] In some of the examples, the thickness of the second transparent conductive layer 133 is 80 nm to 150 nm. Further, in some of the examples, the thickness of the second transparent conductive layer 133 is 90 nm to 120 nm. In some of the examples, the thickness of the second transparent conductive layer 133 is specifically, for example, 91 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, etc.

[0091] The second electrode 134 is made of a conductive material, and the conductive material may be one or more of, but not limited to, silver, copper, tin, aluminum, titanium, and nickel.

[0092] The materials of the first electrode 124 and the second electrode 134 may be the same or different.

[0093] In conventional technology, there is a greater risk of epitaxial growth at the interface between the single crystal silicon substrate 110 and the intrinsic amorphous silicon layer, and the interface passivation is insufficient. To solve this technical problem, as a further improvement of the present invention, as shown in FIG1 , in some examples, the solar cell 100 further includes a second SiO x Layer 135, wherein x is 1 to 2, the second SiO x The layer 135 is disposed between the single crystal silicon substrate 110 and the second intrinsic amorphous silicon layer 131 .

[0094] In the above example, a second SiO x layer 135, can reduce epitaxial growth, and SiO x It can reduce the influence of dangling bonds, improve the interface passivation effect, and increase the open circuit voltage.

[0095] Preparation of the second SiO x The method of forming the second intrinsic amorphous silicon layer 135 is, for example, to introduce a small amount of CO2 before forming the second intrinsic amorphous silicon layer 131, so as to react with the single crystal silicon substrate 110 to generate SiO x and CO.

[0096] In some of these examples, the second SiO x The thickness of the layer 135 is 1 nm to 8 nm. Further, in some examples, the second SiO x The thickness of the layer 135 is 2 nm to 5 nm. In some examples, the second SiO x Specific examples of the thickness of layer 135 include 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm, 4 nm, 4.2 nm, 4.4 nm, and 4.6 nm.

[0097] Furthermore, the present invention also provides a method for preparing the solar cell 100 of any of the above examples.

[0098] As shown in FIG. 2 , a method for preparing a solar cell 100 according to an embodiment includes the following steps:

[0099] Step S100 , providing a single crystal silicon substrate 110 of a first doping type.

[0100] Step S200, a first intrinsic amorphous silicon layer 121, a second doping type hydrogenated microcrystalline silicon layer 1221, a first transparent conductive layer 123 and a first electrode 124 are sequentially formed on the first side 110a of the single crystal silicon substrate 110, the first doping material layer 122 has a third side 122a connected to the first intrinsic amorphous silicon layer 121 and a fourth side 122b connected to the first transparent conductive layer 123, the grain size of the fourth side 122b is smaller than the grain size of the third side 122a, the crystallinity of the fourth side 122b is greater than the crystallinity of the third side 122a, and the doping concentration of the fourth side 122b is greater than the doping concentration of the third side 122a.

[0101] In step S300 , a second intrinsic amorphous silicon layer 131 , a second doping material layer 132 of the first doping type, a second transparent conductive layer 133 and a second electrode 134 are sequentially formed on the second side 110 b of the single crystal silicon substrate 110 .

[0102] The preparation method of the solar cell 100 is as follows: a first doping material layer 122 is arranged between the first intrinsic amorphous silicon layer 121 and the first transparent conductive layer 123; the grain size of the fourth side 122b of the first doping material layer 122 connected to the first transparent conductive layer 123 is smaller than the grain size of the third side 122a connected to the first intrinsic amorphous silicon layer 121; and the crystallinity of the fourth side 122b is greater than the crystallinity of the third side 122a. In this way, the lattice adaptability of the third side 122a and the intrinsic amorphous silicon of the inner layer is higher, which is beneficial to reduce the number of dangling bonds at the interface with the intrinsic amorphous silicon layer, is beneficial to passivation, and improves the open circuit voltage. Since the grain size of the fourth side 122b is smaller and the crystallinity is higher, it is beneficial to improve the effective doping concentration of the fourth side 122b, so that the effective doping concentration of the fourth side 122b is higher, which can reduce the contact resistance, improve the fill factor, and reduce the open circuit voltage loss.

[0103] In some examples, the process for forming the first doping material layer 122 is CVD, and the process gas used includes SiH4, H2, and a doping source of the second doping type, wherein the P-type doping source is, for example, BH3.

[0104] The ratio of the flow rates of H2 and SiH4 when forming the fourth side 122b is higher than that when forming the third side 122a. For example, when forming the fourth side 122b, the ratio of the flow rates of H2 and SiH4 is 1:200-350. When forming the third side 122a, the ratio of the flow rates of H2 and SiH4 is 1:120-200.

[0105] The hydrogen introduced has a certain corrosive effect on silicon. As the hydrogen dilution ratio (i.e., the ratio of the flow rate of H2 to SiH4) increases, the film deposition rate becomes slower, the formed film becomes denser, and the crystallization rate becomes higher. Increasing the hydrogen dilution ratio is conducive to the formation of nanocrystals. In addition, the introduction of hydrogen can also increase the band gap of the film layer and passivate the dangling bonds.

[0106] The steps of forming the first doping material layer 122 include:

[0107] forming a second doping type hydrogenated microcrystalline silicon layer 1221 on the first intrinsic amorphous silicon layer 121, wherein the hydrogenated microcrystalline silicon layer 1221 has the third side 122a;

[0108] A hydrogenated nanocrystalline silicon layer 1222 is formed on the hydrogenated microcrystalline silicon layer 1221 , and the hydrogenated nanocrystalline silicon layer 1222 has the fourth side 122 b .

[0109] In some examples, the hydrogenated microcrystalline silicon layer 1221 is prepared by a CVD process, more specifically, by a PECVD process, wherein the process gas used includes SiH4, H2, CO2, and a doping source of the second doping type.

[0110] In some examples, the hydrogenated nanocrystalline silicon layer 1222 is prepared by a CVD process, more specifically, a PECVD process, wherein the process gas used includes SiH4, H2, CO2, and a doping source of the second doping type.

[0111] Among them, the P-type doping source is, for example, BH3.

[0112] A small amount of CO2 is introduced, and CO2 plasma treatment can selectively remove the amorphous silicon, which is conducive to the rapid nucleation of nanocrystalline silicon. The flow ratio of CO2 to SiH4 is, for example, 1:1~3.

[0113] Optionally, a small amount of CO2 may be introduced only in the initial stage of preparing the hydrogenated nanocrystalline silicon layer 1222 to better form a seed layer of nanocrystalline silicon. The duration of the initial stage is, for example, 0.1% to 2% of the total duration of preparing the hydrogenated nanocrystalline silicon layer 1222.

[0114] The hydrogen introduced has a certain corrosive effect on silicon. As the hydrogen dilution ratio (i.e., the ratio of the flow rate of H2 to SiH4) increases, the film deposition rate is slower, the film formed is denser, and the crystallization rate is higher. Increasing the hydrogen dilution ratio is conducive to the formation of nanocrystals. The ratio of the flow rate of H2 to SiH4 is, for example, 200-350:1. The use of this high hydrogen dilution ratio is conducive to the formation of nanocrystals. In addition, the introduction of hydrogen can also increase the band gap of the film layer and passivate the dangling bonds.

[0115] In some examples, before forming the first intrinsic amorphous silicon layer 121, the method for preparing the solar cell 100 further includes the following steps:

[0116] A first SiO x Layer 125, wherein x is 1-2.

[0117] Forming the first SiO x The layer 125 is prepared by a CVD process, more specifically, by a PECVD process. By introducing CO2, SiO is generated on the first side 110a of the single crystal silicon substrate 110. x .

[0118] In the above example, a first SiO x layer 125, can reduce epitaxial growth, and SiO x It can reduce the influence of dangling bonds, improve the interface passivation effect, and increase the open circuit voltage.

[0119] In some examples, before forming the second intrinsic amorphous silicon layer 131, the method for preparing the solar cell 100 further includes the following steps:

[0120] A second SiO x Layer 135, wherein x is 1-2.

[0121] Formation of the second SiO x The layer 135 is prepared by a CVD process, more specifically, by a PECVD process. By introducing CO2, SiO is generated on the second side 110b of the single crystal silicon substrate 110. x .

[0122] In the above example, a second SiO x layer 135, can reduce epitaxial growth, and SiO x It can reduce the influence of dangling bonds, improve the interface passivation effect, and increase the open circuit voltage.

[0123] In some examples, the material of the second doping material layer 132 is hydrogenated nanocrystalline SiO x , where x is 1~2. Compared with the traditional hydrogenated microcrystalline silicon, hydrogenated nanocrystalline SiO x The optical band gap is wider and the absorption range of visible light is larger, so the optical response of the solar cell 100 can be effectively improved.

[0124] In some of the examples, the second doping material layer 132 is prepared by a CVD process, more specifically, by a PECVD process. The process gases used include SiH4, H2, CO2, and a doping source of the first doping type. Among them, the doping source of the first doping type is, for example, PH3. A trace amount of CO2 can assist in the nucleation of nanocrystalline silicon, and the flow ratio of CO2 to SiH4 is, for example, 1:1~3. The flow ratio of H2 to SiH4 is, for example, 120~350:1. The use of this high hydrogen dilution ratio is conducive to the formation of nanocrystals.

[0125] It should be understood that, although the various steps in the flowchart shown in FIG. 2 are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless clearly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders or simultaneously, as long as there is no logical contradiction. Moreover, at least a portion of the steps in FIG. 2 may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0126] For example, the first intrinsic amorphous silicon layer 121 and the second intrinsic amorphous silicon layer 131 may be prepared in the same process. For another example, the first transparent conductive layer 123 and the second transparent conductive layer 133 may be prepared in the same process. For another example, the first doping material layer 122 may be prepared first, and then the second doping material layer 132 may be prepared, or the second doping material layer 132 may be prepared first, and then the first doping material layer 122 may be prepared.

[0127] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A solar cell, characterized in that: include: a single crystal silicon substrate of a first doping type; A first intrinsic amorphous silicon layer, a first doping material layer of a second doping type, a first transparent conductive layer and a first electrode are sequentially arranged on a first side of the single crystal silicon substrate, the first doping material layer has a third side connected to the first intrinsic amorphous silicon layer and a fourth side connected to the first transparent conductive layer, a grain size of the fourth side is smaller than a grain size of the third side, a crystallinity of the fourth side is greater than a crystallinity of the third side, and a doping concentration of the fourth side is greater than a doping concentration of the third side; as well as A second intrinsic amorphous silicon layer, a second doping material layer of the first doping type, a second transparent conductive layer and a second electrode are sequentially arranged on the second side of the single crystal silicon substrate.

2. The solar cell according to claim 1, wherein: The first doping material layer includes a second doping type hydrogenated microcrystalline silicon layer and a second doping type hydrogenated nanocrystalline silicon layer which are stacked, the hydrogenated microcrystalline silicon layer has the third side, and the hydrogenated nanocrystalline silicon layer has the fourth side.

3. The solar cell according to claim 2, characterized in that The hydrogenated microcrystalline silicon layer has a crystallinity of 20% to 50% and a grain size of 10 nm to 1000 nm; and / or The hydrogenated nanocrystalline silicon layer has a crystallinity of 50% to 70% and a grain size of 5nm to 1000nm.

4. The solar cell according to claim 2, wherein: The doping concentration of the hydrogenated microcrystalline silicon layer is 1×10 13 ~1×10 21 cm -3 ; and / or The doping concentration of the hydrogenated nanocrystalline silicon layer is 1×10 13 ~1×10 22 cm -3 .

5. The solar cell according to claim 2, characterized in that: The thickness of the hydrogenated microcrystalline silicon layer is 10 nm to 30 nm; and / or The thickness of the hydrogenated nanocrystalline silicon layer is 8nm-30nm.

6. The solar cell according to any one of claims 1 to 5, characterized in that The material of the second doping material layer is hydrogenated nanocrystalline SiO x , where x is 1~2.

7. The solar cell according to any one of claims 1 to 5, characterized in that The solar cell further comprises a first SiO x layer, wherein x is 1 to 2, the first SiO x A layer is provided between the single crystal silicon substrate and the first intrinsic amorphous silicon layer.

8. The solar cell according to any one of claims 1 to 5, characterized in that The solar cell further comprises a second SiO x layer, wherein x is 1 to 2, the second SiO x A layer is provided between the single crystal silicon substrate and the second intrinsic amorphous silicon layer.

9. The solar cell according to any one of claims 1 to 5, characterized in that The first transparent conductive layer and the second transparent conductive layer are independently selected from one or more of ITO, ICO, AZO, GZO and GAZO.

10. The solar cell according to claim 9, characterized in that The material of the first transparent conductive layer is MoO x , where x is 2~3.

11. A method for preparing a solar cell, characterized in that: The following steps are involved: providing a single crystal silicon substrate of a first doping type; A first intrinsic amorphous silicon layer, a first doping material layer of a second doping type, a first transparent conductive layer, and a first electrode are sequentially formed on a first side of the single crystal silicon substrate, wherein the first doping material layer has a third side connected to the first intrinsic amorphous silicon layer and a fourth side connected to the first transparent conductive layer, a grain size of the fourth side is smaller than a grain size of the third side, a crystallinity of the fourth side is greater than that of the third side, and a doping concentration of the fourth side is greater than that of the third side; and A second intrinsic amorphous silicon layer, a second doping material layer of the first doping type, a second transparent conductive layer and a second electrode are sequentially formed on the second side of the single crystal silicon substrate.

12. The preparation method according to claim 11, characterized in that: The process for forming the first doping material layer is CVD, and the process gases used include SiH4, H2 and a doping source of the second doping type. The flow ratio of H2 to SiH4 when forming the fourth side is higher than the flow ratio of H2 to SiH4 when forming the third side.

13. The preparation method according to claim 12, characterized in that: When forming the fourth side, the flow rate ratio of H2 to SiH4 is 1:200-350; and / or When forming the third side, the flow rate ratio of H2 to SiH4 is 1:120-200.

14. The preparation method according to any one of claims 11 to 13, characterized in that: The step of forming the first doping material layer comprises: forming a hydrogenated microcrystalline silicon layer of a second doping type on the first intrinsic amorphous silicon layer, the hydrogenated microcrystalline silicon layer having the third side; A hydrogenated nanocrystalline silicon layer is formed on the hydrogenated microcrystalline silicon layer, wherein the hydrogenated nanocrystalline silicon layer has the fourth side.

15. The preparation method according to any one of claims 11 to 13, characterized in that: Before forming the first intrinsic amorphous silicon layer, the preparation method further comprises the following steps: A first SiO x Layer, where x is 1 to 2; and / or Before forming the second intrinsic amorphous silicon layer, the preparation method further comprises the following steps: A second SiO x Layer, where x is 1~2.

16. The preparation method according to claim 15, characterized in that: Forming the first SiO x The process of the layer is CVD, by introducing CO2, SiO is generated on the first side of the single crystal silicon substrate. x ; and / or Forming the second SiO x The process of the layer is CVD, by introducing CO2, SiO is generated on the second side of the single crystal silicon substrate. x .

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