solar cell and its production process, photovoltaic module

Abstract

Embodiments of this disclosure relate to the field of solar cells, and in particular to a solar cell and a method for producing it, and a photovoltaic module. The solar cell comprises: an N-type substrate; a P-type emitter provided on a first surface of the N-type substrate and comprising a first part and a second part, an upper surface of the first part having a first pyramidal structure, and at least a portion of at least one inclined surface of the first pyramidal structure being concave or convex with respect to the center of the first pyramidal structure, an upper surface of the second part having a second pyramidal structure, and inclined surfaces of the second pyramidal structure being planes; and a tunnel layer and a doped conducting layer situated on a second surface of the N-type substrate.This disclosure may improve the photoelectric conversion performance of solar cells.

Description

Title of the invention: solar cell and method for producing it, photovoltaic module technical field

[0001] Embodiments of this disclosure relate to the field of solar cells, and in particular a solar cell and a production method for the solar cell, and a photovoltaic module. Background

[0002] Solar cells have good photoelectric conversion capabilities. In solar cells, a diffusion process is necessary on the surface of silicon wafers to produce pn junctions. In existing solar cells, boron diffusion processes are generally carried out on the surface of silicon wafers to form an emitter on the surface of the silicon wafers. On the one hand, the emitter forms a pn junction with the silicon wafer, and on the other hand, the emitter is also electrically connected to a metal electrode, so that the carriers transported in the emitter can be collected by the metal electrode. Therefore, the emitter has a significant influence on the photoelectric conversion performance of solar cells.

[0003] The photoelectric conversion performance of existing solar cells is insufficient. Summary

[0004] Embodiments of the present disclosure provide a solar cell and a method for producing it, and a photovoltaic module, which is at least conducive to improving the photoelectric conversion performance of a solar cell.

[0005] Certain embodiments of this disclosure provide a solar cell comprising: an N-type substrate; a P-type emitter formed on a first surface of the N-type substrate, the P-type emitter comprising a first part and a second part, an upper surface of the first part comprising a first pyramidal structure, and at least a portion of at least one inclined surface of the first pyramidal structure is concave or convex with respect to the center of the first pyramidal structure, an upper surface of the second part comprising a second pyramidal structure, and inclined surfaces of the second pyramidal structure are planes, and in a direction perpendicular to the first surface of the N-type substrate, a junction depth of the first part is greater than a junction depth of the second part; and a layer tunnel and doped conductive layer formed sequentially on a second surface of the N-type substrate in a direction opposite to the N-type substrate.

[0006] In one example, a crystal structure of the first part of the P-type emitter exhibits dislocations.

[0007] In one example, a foil resistance of the first part of the P-type emitter is lower than a foil resistance of the second part of the P-type emitter.

[0008] In one example, the foil resistance of the first part of the P-type emitter varies from 20 ohm / square to 300 ohm / square, and the foil resistance of the second part of the P-type emitter varies from 100 ohm / square to 1000 ohm / square.

[0009] In one example, the height of the first pyramidal structure varies from 0.1 qm to 5 qm, and the sizes of the bottom of the first pyramidal structure vary from 0.1 qm to 5 qm in any dimension.

[0010] In one example, at least a portion of the first pyramidal structure further comprises a first substructure located on the top of the first pyramidal structure, where the first substructure is a sphere or a spheroid.

[0011] In one example, a ratio of the junction depth of the first part to the junction depth of the second part is not less than 2.

[0012] In one example, the junction depth of the first part varies from 2 qm to 10 qm, and the junction depth of the second part varies from 0.1 qm to 3 qm.

[0013] In one example, a doping concentration at the upper surface of the first part of the P-type emitter is greater than or equal to a doping concentration at the upper surface of the second part of the P-type emitter.

[0014] In one example, the doping concentration at the upper surface of the first part of the P-type emitter varies from 1 E18 atoms / cm3 to 5 E20 atoms / cm3.

[0015] In one example, a difference between the doping concentration at the upper surface of the first part and a doping concentration on a lower surface of the first part varies from 1 E16 atoms / cm3 to 5 E20 atoms / cm3.

[0016] In one example, a difference between the doping concentration on the upper surface of the second part and a doping concentration on a lower surface of the second part varies from 1 E16 atoms / cm3 to 1 E20 atoms / cm3.

[0017] In one example, a ratio of the width of the second part to the width of the first part is not less than 60.

[0018] In one example, the solar cell further comprises a first metallic electrode, where the first metallic electrode is provided on the first surface of the N-type substrate, and is electrically connected to the first part of the P-type emitter.

[0019] In one example, the P-type emitter further comprises a transition region located between the first part and the second part, a doping concentration on an upper surface of the transition region is greater than or equal to the doping concentration on the upper surface of the second part, and less than or equal to the doping concentration on the upper surface of the first part.

[0020] Certain embodiments of this disclosure provide a method for producing a solar cell comprising: the provision of an N-type substrate; the formation of a P-type emitter on a first surface of the N-type substrate, wherein the P-type emitter comprises a first part and a second part, an upper surface of the first part comprises a first pyramidal structure, and at least a portion of at least one inclined surface of the first pyramidal structure is concave or convex with respect to the center of the first pyramidal structure, an upper surface of the second part comprises a second pyramidal structure, and inclined surfaces of the second pyramidal structure are planes, and in a direction perpendicular to the first surface of the N-type substrate, a junction depth of the first part is greater than a junction depth of the second part;and the formation of a tunnel layer and a doped conductive layer, where the tunnel layer and the doped conductive layer are located on a second surface of the N-type substrate and are arranged sequentially in a direction opposite to the N-type substrate.

[0021] In one example, the formation of the P-type emitter comprises: the provision of an initial N-type substrate; the deposition of a trivalent doping source on an upper surface of the initial N-type substrate; the treatment, using an external energy source treatment process, of a predefined region of the upper surface of the initial N-type substrate, to diffuse the trivalent doping source treated by the external energy source treatment process into the initial N-type substrate; the performance of a high-temperature treatment on the initial N-type substrate to form the P-type emitter inside the initial N-type substrate, with an upper surface of the P-type emitter being exposed from the initial N-type substrate; the formation of the N-type substrate in a region of the initial N-type substrate excluding the P-type emitter;and the formation of the first part of the P-type emitter in the predefined region of the initial N-type substrate, and the formation of the second part of the P-type emitter in a region of the P-type emitter excluding the predefined region.

[0022] In one example, the deposition of the trivalent doping source on the upper surface of the initial N-type substrate involves the formation of a first thin film layer, wherein the first thin film layer comprises the trivalent doping source, and further comprises at least one of a boron element, an oxygen element, a silicon element, a chlorine element, a nitrogen element, or an element of carbon, a deposition time varies from 20 s to 5000 s, and a temperature varies from 500 °C to 1300 °C; and the carrying out of the high temperature treatment on the initial N-type substrate involves the introduction, for a duration ranging from 500 s to 10000 s and under a temperature ranging from 500 °C to 1500 °C, of ​​oxygen at a first flow rate to form a second thin film layer, a thickness of the second thin film layer being less than a thickness of the first thin film layer.

[0023] In one example, the first flow rate varies from 200 sccm to 80000 sccm.

[0024] In one example, the external energy source processing process includes any one of a laser doping process, a plasma irradiation process, or a directional ion implantation process.

[0025] In one example, the production process further comprises the formation of a first metallic electrode, where the first metallic electrode is electrically connected to the first part of the P-type emitter.

[0026] In one example, a width of the first metallic electrode is less than or equal to a width of the first part of the P-type emitter.

[0027] Certain embodiments of this disclosure provide a photovoltaic module comprising: at least one cell string formed by connecting a plurality of solar cells as described in any one of the above embodiments; at least one encapsulation layer used to cover a surface of at least one cell string; and at least one cover plate used to cover a surface of at least one encapsulation layer oriented opposite to at least one cell string. Brief description of the drawings

[0028] One or more embodiments are illustrated by way of example with reference to the corresponding accompanying drawing(s), and these illustrations given by way of example do not constitute limitations of the embodiments. Unless otherwise indicated, the accompanying drawings do not constitute limitations of scale.

[0029] [Fig-1] Fig. 1 is a structural graphical diagram of a solar cell according to a method of implementation of this disclosure.

[0030] [Fig.2] [Fig.2] is a partial enlarged view of the portion marked by the dotted frame in [Fig.1].

[0031] [Fig.3] The [Fig.3] is a view of a first pyramidal structure using an electron microscope in a solar cell according to an embodiment of the present disclosure.

[0032] [Fig.4] The [Fig.4] is a view of another first pyramidal structure using an electron microscope in a solar cell according to an embodiment of the present disclosure.

[0033] [Fig. 5] Fig. 5 is a view of a second pyramidal structure using a mi electron microscope in a solar cell according to an embodiment of the present disclosure.

[0034] [Fig.6] Fig.6 is a structural graphical diagram of another solar cell according to a method of implementing this disclosure.

[0035] [Fig.7] Fig.7 is a structural graphical diagram of a photovoltaic module according to an implementation method of this disclosure.

[0036] [Fig.8] The [Fig.8] is a structural graphical diagram corresponding to the operation consisting of providing an initial N-type substrate in a solar cell production process according to an embodiment of the present disclosure.

[0037] [Fig.9] The [Fig.9] is a structural graphical diagram corresponding to the operation consisting of forming a first layer of thin film in the production process according to an embodiment of this disclosure.

[0038] [Fig. 10] The [Fig. 10] is a structural graphical diagram corresponding to the operation of forming a first part of the P-type emitter in the production process according to an embodiment of the present disclosure.

[0039] [Fig. 11] The [Fig. 11] is a structural graphic diagram corresponding to the operation of forming a second layer of thin film in the production process according to an embodiment of the present disclosure.

[0040] [Fig. 12] The [Fig. 12] is a structural graphic diagram corresponding to the operation of forming an anti-reflective layer in the production process according to an embodiment of the present disclosure.

[0041] [Fig. 13] The [Fig. 13] is a structural graphical diagram corresponding to the operation of forming a first metallic electrode in the production process according to an embodiment of the present disclosure.

[0042] [Fig. 14] The [Fig. 14] is a structural graphical diagram corresponding to the operation of forming a tunnel layer and a doped conductive layer in the production process according to an embodiment of the present disclosure. Detailed description

[0043] It is known from the prior art that existing solar cells exhibit insufficient photoelectric conversion performance.

[0044] The analysis revealed that one of the reasons for the insufficient photoelectric conversion performance of existing solar cells is that the emitter is usually electrically connected to a metallic electrode, so that the metallic electrode can collect carriers in the emitter. In order to reduce the contact resistance between the metallic electrode and the emitter, the foil resistance of the emitter must be reduced. Currently, in order to reduce the foil resistance of The emitter's doping concentration is usually increased. However, as the emitter doping concentration increases, the doping element within the emitter becomes too large, making it a strong recombination center and causing increased Auger recombination. Consequently, the emitter's passivation performance deteriorates, which in turn results in insufficient photoelectric conversion performance of the solar cell.

[0045] Embodiments of the present disclosure provide a solar cell having a P-type emitter located on a first surface of an N-type substrate. An upper surface of a first portion of the P-type emitter has a first pyramidal structure, and at least a portion of at least one inclined surface of the first pyramidal structure is concave or convex with respect to the center of the first pyramidal structure. In other words, a crystalline structure of the surface of the first portion of the P-type emitter is an irregular tetrahedral structure, which causes the first portion of the P-type emitter to have a deep energy level inside, thereby reducing the foil resistance of the first portion of the P-type emitter. Thus, the resistance of the first portion of the P-type emitter can be reduced without significantly increasing the doping concentration of the first portion of the P-type emitter.In this way, not only can good passivation performance be maintained in the first part of the P-type emitter, but ohmic contact can also be improved, thus enhancing the photoelectric conversion performance of the solar cell. Furthermore, the second part of the P-type emitter has a shallower junction depth, and the inclined surfaces of the second pyramidal structure on its upper surface are flat, meaning the second part of the P-type emitter is a regular tetrahedral structure. Therefore, no dislocations are formed in the second part of the P-type emitter, resulting in high foil resistance and good passivation performance. In this way, the overall photoelectric conversion efficiency of the solar cell can be improved.

[0046] Embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. Those skilled in the art should understand that, in the embodiments of this disclosure, numerous technical details are provided to aid the reader's understanding of this disclosure. However, even without these technical details and the various modifications and variations based on the following embodiments, the technical solutions claimed in this disclosure can be implemented.

[0047] Figure 1 is a structural graphic diagram of a solar cell according to an embodiment of the present disclosure. Figure 2 is a partial enlarged view of the portion marked by the dashed outline in Figure 1.

[0048] With reference to [Fig.1] and [Fig.2], the solar cell comprises: an N 100 type substrate; a P 10 type emitter formed on a first surface of the N 100 type substrate, the P 10 type emitter comprises a first part 11 and a second part 12, an upper surface of the first part 11 comprises a first pyramidal structure 1, and at least a portion of at least one inclined surface of the first pyramidal structure 1 is concave or convex with respect to the center of the first pyramidal structure 1, an upper surface of the second part 12 comprises a second pyramidal structure 2, and inclined surfaces of the second pyramidal structure 2 are planes, and in a direction perpendicular to the first surface of the N 100 type substrate, a junction depth of the first part 11 is greater than a junction depth of the second part 12;and a tunnel layer 150 and a doped conductive layer 160, the tunnel layer and the doped conductive layer being formed sequentially on a second surface of the N-type substrate 100 in a direction opposite to the N-type substrate. ;

[0049] The N 100 type substrate is used to receive incident light and generate photogenerated carriers. In some embodiments, the N 100 type substrate may be an N 100 type silicon substrate, and the N type silicon substrate material may comprise at least one element of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The N 100 type substrate is an N 100 type semiconductor substrate, that is, the N 100 type substrate is doped with N type doping ions, and the N type doping ions may be any of phosphorus ions, arsenic ions, or antimony ions.

[0050] In some embodiments, the solar cell is a TOPCON oxide passivated contact tunnel cell. The first and second surfaces of the N 100-type substrate are arranged opposite each other, and both surfaces can be used to receive incident or reflected light. In some embodiments, the first surface may be the rear surface of the N 100-type substrate, and the second surface may be the front surface of the N 100-type substrate. In other embodiments, the first surface may be the front surface of the N 100-type substrate, and the second surface may be the rear surface of the N 100-type substrate.

[0051] In certain embodiments, the second surface of the N 100 type substrate can be designed as a pyramidal textured surface, so that the reflectivity of The second surface of the N 100 substrate is exposed to low incident light, therefore the light absorption and utilization rate is high. The first surface of the N 100 substrate can be designed as a non-pyramidal textured surface, such as a stacked step shape, so that the tunnel oxide layer 110 located on the first surface of the N 100 substrate has high density and uniformity, therefore the tunnel oxide layer 110 has a good passivation effect on the first surface of the N 100 substrate. In some embodiments, the first surface can be the back surface of the N 100 substrate, and the second surface can be the front surface of the N 100 substrate. In other embodiments, the first surface can be the front surface of the N 100 substrate, and the second surface can be the back surface of the N 100 substrate.

[0052] With reference to [Fig. 3], the first pyramidal structure 1 comprises a lower surface and three inclined surfaces connected to the lower surface, and the three inclined surfaces are connected to each other to form a tetrahedral structure. At least a portion of at least one inclined surface of the first pyramidal structure 1 is concave or convex with respect to the center of the first pyramidal structure 1, i.e., at least one inclined surface of the first pyramidal structure 1 exhibits an irregular deformation.For example, one of the inclined surfaces of the pyramidal structure 1 may be only concave with respect to the center of the first pyramidal structure 1, or only convex with respect to the center of the first pyramidal structure 1, or a portion of the inclined surface may be concave with respect to the center of the first pyramidal structure 1 and a portion may be convex with respect to the center of the first pyramidal structure 1. In some embodiments, in the first pyramidal structure 1, only one inclined surface exhibits irregular deformation; in some other embodiments, there may be two inclined surfaces exhibiting irregular deformation; again, in some other embodiments, all three inclined surfaces exhibit irregular deformation.Furthermore, in some other embodiments, at least a portion of the lower surface of the first pyramidal structure 1 is concave or convex with respect to the center of the first pyramidal structure 1, i.e., the lower surface of the first pyramidal structure 1 also exhibits an irregular deformation.

[0053] It should be understood that the first pyramidal structure 1 and the second pyramidal structure 2 are here different from the textured structure, and the first pyramidal structure 1 and the second pyramidal structure 2 in the embodiments of the present application refer to the morphologies of the crystal structure of the P 10 type emitter. By modifying the morphology of the crystal structure of the P 10 type transmitter, the performance of the first part 11 of the P 10 type transmitter is modified.

[0054] By way of example, at least one inclined surface in the first pyramidal structure 1 is designed to have an irregular deformation, so that the crystal structure of the first pyramidal structure 1 changes from a regular tetrahedral structure to an irregular tetrahedral structure, which allows the first part 11 of the P-type emitter 10 to have a deep energy level inside, and which reduces the foil resistance of the first part 11 of the P-type emitter 10. In this way, the resistance of the first part 11 of the P-type emitter 10 can be reduced without significantly increasing the doping concentration of the first part 11 of the P-type emitter 10.It must be understood that the regular tetrahedral structure here means that the inclined surfaces and the lower surface of the tetrahedral structure do not exhibit irregular deformation; for example, the inclined surfaces and the lower surface of the tetrahedral structure can be flat.

[0055] Continuing with reference to [Fig. 1] and [Fig. 2], in certain embodiments, the crystal structure of the first part 11 of the P-type emitter exhibits dislocations. In some embodiments, the dislocations are formed by a series of dangling bonds, and thus, when dislocations are present in the crystal structure of the first part 11 of the P-type emitter, dangling bonds are generated accordingly. The dislocations and dangling bonds can form deep energy levels within the first part 11 of the P-type emitter, and the deep energy levels formed reduce the foil resistance of the first part 11 of the P-type emitter.In other words, the foil resistance of the first part 11 of the P-type emitter can be reduced without significantly increasing the doping concentration of the first part 11 of the P-type emitter, so that one can obtain both a low foil resistance of the first part 11 of the P-type emitter and a reduced doping concentration of the first part 11 of the P-type emitter. In this way, not only can the passivation performance of the first part 11 of the P-type emitter be good, but the ohmic contact of the P-type emitter can also be improved.

[0056] It must be understood that the greater the height and size, in any dimension, of the base of the first pyramidal structure 1 in the first part 11 of the P-type emitter 10, the larger the overall size of the first pyramidal structure 1, so that in a unit area, the number of first pyramidal structures 1 in the first part 11 of the P-type emitter 10 is smaller. Since the dislocations in the first part 11 of the P-type emitter 10 are formed by the first pyramidal structures 1, the greater the number of the first The smaller the number of pyramidal structures 1 in the first part 11 of the P-type emitter 10 per unit area, the fewer dislocations are formed, i.e., the lower the dislocation density. Similarly, the smaller the size of the first pyramidal structure 1, the greater the number of first pyramidal structures 1 in the first part 11 of the P-type emitter 10 per unit area, and the greater the dislocation density. Based on this, in some embodiments, the height of the first pyramidal structure 1 is fixed from 0.1 µm to 5 µm, and the sizes of the bottom of the first pyramidal structure 1 in any dimension are fixed from 0.1 µm to 5 µm.Within this range, on the one hand, the dislocation density in the first part 11 of the P-type emitter can be increased, so that the deep energy level formed at the base of the dislocations can be higher, thus leading to a lower foil resistance in the first part 11 of the P-type emitter and improving ohmic contact. On the other hand, within this range, an excessive dislocation density in the first part 11 of the P-type emitter can be avoided, which can prevent the problem of an excessive deep energy level appearing in the first part 11 of the P-type emitter due to an excessive dislocation density, thus forming a strong recombination center in the P-type emitter. In this way, the passivation performance of the first part 11 of the P-type emitter can be improved.

[0057] Referring to [Fig. 4], in certain embodiments, at least a portion of the first pyramidal structure 1 further comprises a first substructure 13 located on top of the first pyramidal structure 1, and the first substructure 13 is a sphere or a spheroid. The first substructure 13 is also one of the irregular deformations of the first pyramidal structure 1. The existence of the first substructure 13 accentuates the degree of deformation of the first pyramidal structure 1, and consequently, larger dislocations can be generated, so that the deep energy level formed is higher, and the foil resistance of the first part 11 of the P-type emitter 10 can be further reduced.

[0058] Referring to [Fig. 1], 2 and 5, the inclined surfaces of the second pyramidal structure 2 on the upper surface of the second part 12 are designed to be flat, i.e., the second pyramidal structure 2 is not irregularly deformed, so that the second pyramidal structure 2 is a regular tetrahedral structure. Thus, dislocations and dangling bonds will not be caused in the second part 12 of the P-type emitter 10, and thus no deep energy level will be formed in the second part 12 of the P-type emitter 10, leading to a relatively high foil resistance of the second part 12 of the P-type emitter 10, and maintaining good passivation performance of The second part 12 of the P-type emitter 10. In this way, the open-circuit voltage and short-circuit current of the solar cell can be relatively high, and the photoelectric conversion performance of the solar cell can be improved. In some other embodiments, the upper surface of the second part 12 of the P-type emitter 10 may be provided to have the second pyramidal structure 2, and at least a portion of at least one inclined surface of the second pyramidal structure 2 is concave or convex with respect to the center of the second pyramidal structure 2. In other words, the upper surface of the entire P-type emitter 10 has an irregular tetrahedral structure, so that the entire P-type emitter 10 exhibits dislocations and dangling bonds, thereby reducing the foil resistance of the entire P-type emitter 10.

[0059] In some embodiments, the foil resistance of the first part 11 of the P-type emitter 10 is lower than the foil resistance of the second part 12 of the P-type emitter 10. In other words, the foil resistance of the first part 11 of the P-type emitter 10 is relatively low, so that a carrier transport velocity in the first part 11 of the P-type emitter 10 can be increased, which promotes the transport of carriers from the first part 11 of the P-type emitter 10 to the metal electrode when an electrical connection is formed between the first part 11 of the P-type emitter 10 and the metal electrode, thus improving a carrier collection velocity by the metal electrode, and improving the photovoltaic performance of the solar cell.By setting the foil resistance of the second part 12 of the P-type emitter 10 to a low value, good passivation performance of the second part 12 of the P-type emitter 10 can be maintained, carrier recombination can be suppressed, and the number of carriers can be increased, thus increasing the open-circuit voltage and short-circuit current of the solar cell. By setting the foil resistance of the first part 11 to be lower than that of the second part 12, ohmic contact can be improved while maintaining good passivation of the P-type emitter 10, thus improving the overall photoelectric conversion performance of the solar cell.

[0060] By way of example, in certain embodiments, the foil resistance of the first part 11 of the P-type emitter 10 may be from 20 ohms / square to 300 ohms / square, for example, may be from 20 ohms / square to 50 ohms / square, from 50 ohms / square to 100 ohms / square, from 100 ohms / square to 150 ohms / square, from 150 ohms / square to 200 ohms / square, from 200 ohms / square to 250 ohms / square, or from 250 ohms / square to 300 ohms / square; the foil resistance of the second part 12 of the P-type emitter 10 may be from 100 ohms / square to 1000 ohms / square, for example, may be of 100 ohm / square-200 ohm / square, of 200 ohm / square-300 ohm / square, of 300 ohm / square-500 ohm / square, of 500 ohm / square~700 ohm / square, of 700 ohm / square~800 ohm / square or of 800 ohm / square-1000 ohm / square. The foil resistance of the first part 11 of the P-type emitter 10 is designed to be in the range of 20 ohms / square-300 ohms / square, so that the foil resistance of the first part 11 is much lower than that of the second part 12, thus an improved ohmic contact of the first part 11 of the P-type emitter can be obtained, which can reduce the contact resistance between the first part 11 of the P-type emitter 10 and the metal electrode when the metal electrode is arranged to be in electrical contact with the first part 11 of the P-type emitter 10, thus improving the efficiency of carrier transport in the first part 11 of the P-type emitter 10 and the second part 12 of the P-type emitter 10.On the other hand, within this range, the foil resistance of the first part 11 of the P-type emitter is not too low, thus preventing it from becoming a strong recombination center. Furthermore, by setting the resistance of the second part 12 of the P-type emitter to between 100 ohms / square and 1000 ohms / square, carrier recombination in the second part 12 can be suppressed, thereby improving the emitter's passivation effect. In this way, the open-circuit voltage, short-circuit current, and photoelectric conversion efficiency of the solar cell can be improved.

[0061] The junction depth of the first part 11 is greater than that of the second part 12; that is, the junction depth of the first part 11 of the P-type emitter 10 is greater, and the junction depth of the second part 12 of the P-type emitter 10 is less. In other words, the thickness of the first part 11 is relatively large; on the one hand, more doping elements, such as boron, can be found in the first part 11 of the P-type emitter 10, so that the doping concentration of the first part 11 of the P-type emitter 10 is higher, thus further reducing the foil resistance of the first part 11 of the P-type emitter 10, which is conducive to improving ohmic contact.On the other hand, given the significant junction depth of the first part 11 of the P-type emitter 10, an electrical connection can be provided between the metal electrode and the first part 11 of the P-type emitter 10. This avoids the problem of the paste intended for forming the metal electrode penetrating the P-type emitter 10 and coming into direct contact with the initial N-type substrate during paste sintering. Furthermore, the junction depth of the second part 12 is intended to be less significant, i.e., the thickness of the second part 12 of the type emitter . P10 is smaller, so the number of doping elements in the second part 12 is less than in the first part 11; that is, the doping concentration in the second part 12 of the P10 emitter is lower. Consequently, compared to the first part 11 of the P10 emitter, the second part 12 of the P10 emitter has a better passivation effect, which is conducive to reducing carrier recombination and improving the open-circuit voltage and short-circuit current of the solar cell.

[0062] In some embodiments, the ratio of the junction depth of the first part 11 to the junction depth of the second part 12 is not less than 2. Preferably, the ratio of the junction depth of the first part 11 to the junction depth of the second part 12 varies from 2 to 5. By way of example, the ratio may be 2, 2.5, 3, 3.5, 4, 4.5 or 5. The junction depth of the first part 11 is much greater than that of the second part 12, so that the junction depth of the first part 11 of the P-type emitter 10 is greater.In this way, when the metal electrode is electrically connected to the first part 11 of the P-type emitter 10, it can be ensured that the paste will not burn through the first part 11 of the P-type emitter 10 during sintering, thus avoiding the problem of damage to the pn junction due to contact between the metal electrode and the substrate 100, thereby ensuring better photoelectric conversion performance of the solar cell.

[0063] Considering that it is necessary to keep a junction depth of the first part 11 which is not too large in order to avoid too many doping elements in the first part 11 of the P-type emitter 10 forming a strong recombination center, in some embodiments the junction depth of the first part 11 is fixed from 2 qm~ 10 qm, for example, the junction depth can be from 2 qm~3 qm, from 3 qm~4 qm, from 4 qm~5 qm, from 5 qm~6 qm, from 6 qm~7 qm, from 7 qm~8 qm, from 8 qm~9 qm or from 9 qm~10 qm. The junction depth of the second part 12 is fixed from 0.1 μm to 3 μm; for example, the junction depth can be 0.1 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, or 2.5 μm to 3 μm. Within this range, there are fewer doping elements in the second part 12 of the P-type emitter 10, so a better passivation effect can be achieved.

[0064] In certain embodiments, the doping concentration on the upper surface of the first part 11 of the P-type emitter 10 is greater than or equal to the doping concentration on the upper surface of the second part 12 of the P-type emitter 10. By way of example, in certain embodiments, the doping concentration on the upper surface of the first part 11 of the P-type emitter 10 is greater than the doping concentration on the upper surface of the second part 12 of the P-type emitter 10. The doping concentration on the upper surface of the first part 11 of the P-type emitter 10 is relatively high, which is conducive to further reduction of the foil resistance of the first part 11. The doping concentration on the upper surface of the second part 12 of the P-type emitter 10 is relatively low, so the foil resistance of the second part 12 is relatively high, which is conducive to maintaining a good passivation effect of the second part 12 of the P-type emitter 10.

[0065] In some other embodiments, the doping concentration on the upper surface of the first part 11 of the P-type emitter is equal to the doping concentration on the upper surface of the second part 12 of the P-type emitter; that is, the doping concentration on the upper surface of the first part 11 of the P-type emitter is relatively low. The crystalline structure of the surface of the first part 11 of the P-type emitter is an irregular tetrahedral structure that causes dislocations in the first part 11 of the P-type emitter, so that the first part 11 of the P-type emitter exhibits deep energy levels within it. In this way, the foil resistance of the first part 11 of the P-type emitter can be reduced, thus improving the ohmic contact.At the same time, since the doping concentration on the upper surface of the first part 11 of the P-type emitter 10 is relatively low, the passivation effect of the first part 11 of the P-type emitter 10 can remain good. For example, in some embodiments, the doping element in the P-type emitter 10 can be a trivalent P-type doping source, such as boron.

[0066] By way of example, in some embodiments, the doping concentration on the upper surface of the first part 11 of the P-type emitter 10 can be 1E18-5E20 atoms / cm3, for example, can be 1E15-1E16 atoms / cm3, 1E16-1E17 atoms / cm3, 1E17-1E18 atoms / cm3, 1E18-1E19 atoms / cm3 or 1E19-5E20 atoms / cm3. In this range, on the one hand, the doping concentration of the first part 11 formed by the P-type emitter 10 is relatively high, so that the first part 11 of the P-type emitter 10 has a relatively low foil resistance, which can increase the carrier transport efficiency.On the other hand, in this range, the concentration of doping on the upper surface of the first part 11 of the P 10 type emitter will not be too high, i.e., the content of the doping element in the first part 11 of the P 10 type emitter will not be too significant, so as to avoid the problem of the transformation of many doping elements into strong recombination centers due to excessive doping elements in the first part 11 of the P 10 type emitter, leading to poor passivation capacity of the first part 11 of the P 10 type emitter.

[0067] In some embodiments, the concentration on the upper surface of the second part 12 of the P-type emitter can be, for example, 1E18-1E20 atoms / cm3, 1E15-1E16 atoms / cm3, 1E16-1E17 atoms / cm3, 1E17-1E18 atoms / cm3, 1E18-1E19 atoms / cm3, or 1E19-1E20 atoms / cm3. The doping concentration on the upper surface of the second part 12 of the P-type emitter can be fixed at 1E14-9E19 atoms / cm3, so that the doping elements in the second part 12 of the P-type emitter are relatively few. In this way, good passivation performance of the second part 12 of the P-type emitter 10 can be maintained, and the open-circuit voltage and short-circuit current of the formed solar cell can be effectively improved.

[0068] In certain embodiments, in a direction from the upper surface of the P10 emitter to the lower surface of the P10 emitter, the doping concentration inside the first part 11 of the P10 emitter gradually decreases, and the doping concentration inside the second part 12 of the P10 emitter gradually decreases. In other words, each of the first part 11 of the P10 emitter and the second part 12 of the P10 emitter has a downward doping concentration gradient, which favors the transport of carriers in the first part 11 of the P10 emitter and the second part 12 of the P10 emitter from the area of ​​relatively high concentration to the area of ​​relatively low concentration, up to the substrate 100.In this way, the carrier transport speed can be increased and the open-circuit voltage of the solar cell can be improved.

[0069] By way of example, in some embodiments, the difference between the doping concentration on the upper surface of the first part 11 and the doping concentration on the lower surface of the first part 11 is from 1 x 16 atoms / cm³ to 5 x 20 atoms / cm³. In this range, on the one hand, the difference in doping concentration within the first part 11 of the P-type emitter 10 is relatively high, thus facilitating carrier transport. On the other hand, in this range, the overall doping concentration within the first part 11 of the P-type emitter 10 is relatively high, so as to maintain low foil resistance.

[0070] In certain embodiments, the difference between the doping concentration on the upper surface of the second part 12 and the doping concentration on the lower surface of the second part 12 is 1 to 16 atoms / cm³–1 to 20 atoms / cm³. Within this range, the doping concentration inside the second part 12 of the P-type emitter 10 will not be too low, so that normal carrier transport in the second part 12 of the P-type emitter can be ensured. Furthermore, within this range, the overall doping concentration of the second part 12 of the P 10 type emitter can be kept low, which helps to prevent Auger recombination from occurring in the second part 12 of the P 10 type emitter.

[0071] In some embodiments, the ratio of the width of the second part 12 to the width of the first part 11 is not less than 60. For example, the ratio of the width of the second part 12 to the width of the first part 11 can be from 60 to 200; for example, the ratio can be 60, 80, 100, 120, 140, 160, 180, or 200. The width of the second part 12 is designed to be greater than the width of the first part 11; in other words, the second part 12 of the P-type 10 emitter with relatively low foil resistance represents a higher proportion. Since the second part 12 of the P-type 10 emitter has better passivation performance and can suppress carrier recombination, the overall passivation performance of the P-type 10 emitter is are good.Furthermore, since the first part 11 of the P 10 type emitter only needs to be electrically connected to the metal electrode to improve ohmic contact with the metal electrode, a small width can be set for the first part 11 of the P 10 type emitter, so as to improve ohmic contact and maintain relatively good passivation performance of the emitter.

[0072] Referring to [Fig. 1], in certain embodiments, the solar cell further comprises: a first metal electrode 140, the first metal electrode is provided on the first surface of the N-type substrate 100 and is electrically connected to the first part 11 of the P-type emitter 10. Since the carriers in the P-type emitter 10 will be transported to the first metal electrode 140 electrically connected to the first part 11 of the P-type emitter 10, and since the foil resistance of the first part 11 of the P-type emitter 10 is low, the contact resistance between the first part 11 of the P-type emitter 10 and the first metal electrode 140 is low, thus increasing the transport rate of the carriers to the first metal electrode 140.Furthermore, since the first part 11 of the P-type emitter 10 has a relatively large junction depth, it is difficult for the first metal electrode 140 formed to penetrate the first part 11 of the P-type emitter 10 during the preparation of the first metal electrode 140. In this way, the structure of the formed pn junction will not be damaged, which is conducive to maintaining the integrity of the solar cell, thus maintaining the good photoelectric conversion performance of the solar cell.

[0073] Referring to [Fig. 6], in certain embodiments, the P-type emitter 10 further comprises a transition region 14 located between the first part 11 and the second part 12, a doping concentration on an upper surface of the transition region 14 is greater than or equal to the doping concentration on the upper surface of the second part 12, and is less than or equal to the doping concentration on the upper surface of the first part 11.For example, in some embodiments, when the doping concentration at the upper surface of the first part 11 is greater than the doping concentration at the upper surface of the second part 12, the doping concentration at the upper surface of the transition region 14 is fixed to be greater than the doping concentration at the upper surface of the second part 12, and lower than the doping concentration at the upper surface of the first part 11, i.e. the doping concentration of the transition region 14 gradually decreases in a direction from the first part 11 to the second part 12.In this way, a larger gradient space can be provided for the concentration of the doping element in the P-type emitter 10, so that a sudden change in the potential energy difference between the first part 11 and the second part 12 can be avoided, thereby reducing the probability of carrier recombination in the transition region 14. Furthermore, the supply of the transition region 14 leads to a gradient tendency of the foil resistance in the transition region 14, thus reducing the transport resistance of the transition region 14 to the carriers, which promotes the transport of carriers from the second part 12 of the P-type emitter 10 to the first part 11 of the P-type emitter 10, and further to the first metal electrode 140. In this way, the carrier transport efficiency can be improved, thereby enhancing the photoelectric conversion efficiency of the solar cell.

[0074] It should be understood that in some other embodiments, the doping concentration at the upper surface of the transition region 14 may be equal to the doping concentration at the upper surface of the first part 11, or be equal to the doping concentration at the upper surface of the second part 12. Also in some other embodiments, the doping concentration at the upper surface of the transition region 14 may be equal to the doping concentration at the upper surface of the first part 11 and to the doping concentration at the upper surface of the second part 12.

[0075] Referring to [Fig. 1], in some embodiments, the solar cell further comprises an antireflective layer 130 located on the upper surface of the first part 11 of the P-type emitter 10 and the upper surface of the second part 12 of the P-type emitter 10. The antireflective layer is used to reduce the reflection of incident light by the substrate. In some embodiments, the antireflective layer may be a silicon nitride layer comprising a material of silicon nitride.

[0076] The tunnel layer 150 is used to perform interface passivation of the second substrate surface. By way of example, in some embodiments, the material of the tunnel layer 150 can be a dielectric material, such as silicon oxide.

[0077] The doped conductive layer 160 is used to form a field passivation. In some embodiments, the material of the doped conductive layer 160 may be doped silicon. By way of example, in some embodiments, the doped conductive layer 160 and the substrate comprise doping elements of the same type of conductivity. The doped silicon may comprise one or more elements from among N-type doped polysilicon, N-type doped microcrystalline silicon, and N-type doped amorphous silicon.

[0078] In some embodiments, the solar cell further comprises a first passivation layer 170 located on the surface of the doped conducting layer 160 away from the substrate. In some embodiments, the material of the first passivation layer 170 may be one or more of the following: silicon dioxide, aluminum oxide, silicon nitride, silicon oxynitride, and silicon oxycarbonitride. By way of example, in some embodiments, the first passivation layer 170 may be a single-layer structure. In other embodiments, the first passivation layer 170 may be a multi-layer structure.

[0079] In some embodiments, the solar cell further comprises a second metallic electrode 180 penetrating the first passivation layer 170 to form an electrical connection with the doped conductive layer 160.

[0080] In the solar cell as described in the embodiments above, at least one inclined surface in the first pyramidal structure 1 is designed to have an irregular deformation, so that the crystalline structure of the first pyramidal structure 1 changes from a regular tetrahedral structure to an irregular tetrahedral structure, which causes the first part 11 of the P-type emitter 10 to have a deep energy level inside, and which reduces the foil resistance of the first part 11 of the P-type emitter 10. In this way, the resistance of the first part 11 of the P-type emitter 10 can be reduced without significantly increasing the doping concentration of the first part 11 of the P-type emitter 10.Furthermore, the inclined surfaces of the second pyramidal structure 2 on the upper surface of the second part 12 are designed to be flat, meaning that the second pyramidal structure 2 is not irregularly deformed, so that the second pyramidal structure 2 is a regular tetrahedral structure. Thus, dislocations and dangling joints will not occur in the second part 12. part 12 of the P-type 10 emitter, and thus no deep energy level will be formed in the second part 12 of the P-type 10 emitter, leading to a relatively high foil resistance of the second part 12 of the P-type 10 emitter, and now good passivation performance of the second part 12 of the P-type 10 emitter. In this way, the open-circuit voltage and short-circuit current of the solar cell can be relatively high, and the photoelectric conversion performance of the solar cell can be improved.

[0081] Embodiments of the present disclosure further provide a photovoltaic module. With reference to [Fig. 7], the photovoltaic module comprises: at least one cell string formed by connecting a plurality of solar cells 101 as described in the above embodiments; at least one encapsulation layer 102 used to cover a surface of at least one cell string; and at least one cover plate 103 used to cover a surface of at least one encapsulation layer 102 oriented opposite to at least one cell string. The solar cells 101 are electrically connected as a single unit or as multiple units to form a plurality of cell strings, and the plurality of cell strings are electrically connected in series and / or in parallel.

[0082] By way of example, in some embodiments, the plurality of cell strings may be electrically connected by conductive strings 104. The encapsulation layer 102 covers the front and rear surfaces of the solar cell 101. By way of example, the encapsulation layer 102 may be an organic encapsulation adhesive film, such as an ethylene-vinyl acetate (EVA) copolymer adhesive film, a polyethylene-octene (POE) coelastomer adhesive film, or a polyethylene terephthalate (PET) adhesive film, and the like. In some embodiments, the cover plate 103 may be a cover plate 103 with a light-transmitting function, such as a glass cover plate, a plastic cover plate, or the like.As an example, the surface of the cover plate 103 facing the encapsulation layer 102 can be a concave / convex surface, thus increasing the utilization rate of incident light.

[0083] Another embodiment of this disclosure further provides a method for producing a solar cell; the solar cell, as described in the above embodiments, can be obtained by implementing the method. The method for producing a semiconductor structure provided by this embodiment of this disclosure will be described in detail below with reference to the accompanying drawings.

[0084] Figures 8 to 14 are structural graphic diagrams corresponding to the operations of the production process for the solar cell provided for by this method of production. reading of this disclosure.

[0085] An N-type substrate is provided.

[0086] The N-type substrate is used to receive incident light and generate photogenerated carriers. In some embodiments, the N-type substrate may be an N-type 100 silicon substrate, and the N-type silicon substrate material may include at least one element of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The N-type substrate is an N-type semiconductor substrate, that is, the N-type substrate is doped with N-type doping ions, and the N-type doping ions may be any of phosphorus ions, arsenic ions, or antimony ions.

[0087] With reference to [Fig.8] to 12, a P-type emitter 10 is formed on a first surface of the N-type substrate, the P-type emitter 10 comprises a first part 11 and a second part 12, an upper surface of the first part 11 comprises a first pyramidal structure 1 (with reference to [Fig.2]), and at least a portion of at least one inclined surface of the first pyramidal structure 1 is concave or convex with respect to the center of the first pyramidal structure 1, an upper surface of the second part 12 comprises a second pyramidal structure 2 (with reference to [Fig.2]), and inclined surfaces of the second pyramidal structure are planes, and in a direction perpendicular to the first surface of the N-type substrate 100, a junction depth of the first part 11 is greater than a junction depth of the second part 12.

[0088] In the first pyramidal structure 1 formed, at least a portion of at least one inclined surface is concave or convex with respect to the center of the first pyramidal structure 1; that is, at least one inclined surface of the first pyramidal structure 1 exhibits an irregular deformation, such that the crystal structure of the first pyramidal structure 1 changes from a regular tetrahedral structure to an irregular tetrahedral structure. The irregular tetrahedral structure leads to dislocations and dangling bonds in the emitter, thus modifying the emitter. In particular, the generated dislocations and dangling bonds lead to a deep energy level within the first part 11 of the P-type emitter 10, thereby reducing the foil resistance of the first part 11 of the P-type emitter 10.The first part 11 of the P-type emitter can have a relatively low foil resistance by modifying the structure of the first part 11 of the P-type emitter. In this way, the resistance of the first part 11 of the P-type emitter can be reduced without significantly increasing the doping concentration of the first part 11 of the P-type emitter.

[0089] The inclined surfaces of the second pyramidal structure 2 on the surface su The upper layers of the second part 12 are designed to be planar, meaning that the second pyramidal structure 2 is not irregularly deformed, resulting in a regular tetrahedral structure. Therefore, dislocations and dangling bonds will not occur in the second part 12 of the P-type emitter 10, and thus no deep energy levels will be formed in the second part 12 of the P-type emitter 10. This leads to a relatively high foil resistance in the second part 12 of the P-type emitter 10, and thus good passivation performance in the second part 12 of the P-type emitter 10. In this way, the open-circuit voltage and short-circuit current of the solar cell can be relatively high, and the photoelectric conversion performance of the solar cell can be improved.

[0090] In certain embodiments, a method for forming the P 10 type emitter comprises the following operations.

[0091] Referring to [Fig.8], an initial substrate of type N 20 is provided, and the initial substrate of type N 20 is used as a basis for the formation of the substrate of type N 100 and the emitter of type P 10. Therefore, the materials of the initial substrate of type N 20 and the substrate of type N 100 can be identical.

[0092] In some embodiments, a first surface of the initial N20-type substrate can be designed as a pyramidal textured surface, such that the reflectivity of the first surface of the initial N20-type substrate to incident light is low, and the absorption and utilization rate of light is high. In some embodiments, the initial N20-type substrate is an initial N-type semiconductor substrate, that is, the initial N20-type substrate is doped with N-type doping ions, and the N-type doping ions can be any of phosphorus ions, arsenic ions, or antimony ions.

[0093] The process for forming the P 10 type emitter further comprises, with reference to [Fig.9] and

[10] , the deposition of a trivalent doping source on an upper surface of the initial N 20 type substrate, so as to then diffuse the trivalent doping source into the initial N 20 type substrate to form the P 10 type emitter. In some embodiments, the trivalent doping source may be a boron source, and may for example be boron trichloride or boron tribromide.

[0094] Referring to [Fig. 9], in certain embodiments, the deposition of the trivalent doping source onto the upper surface of the initial N 20 type substrate involves the formation of a first thin film layer 110. This first thin film layer 110 comprises the trivalent doping source and at least one of the following elements: boron, oxygen, silicon, chlorine, nitrogen, or carbon. The deposition time varies from 20 s to 5000 s, and the temperature varies from 500 °C to 1300 °C. By way of example, in certain embodiments In this process, when the trivalent doping source is boron, the main components of the first thin film layer 110 can include silicon dioxide and boron dioxide, and the trivalent doping source can be stored in the first thin film layer 110 in the form of boron dioxide. Since silicon dioxide has high hardness, it can protect the initial N2O-type substrate during the doping process. Furthermore, the first thin film layer 110 also contains small amounts of chlorine, nitrogen, and carbon. These elements provide the first thin film layer 110 with a higher refractive index than existing borosilicate glass.In this way, during the subsequent processing carried out on a predefined region of the first thin film layer 110 using an external energy source processing method, the first thin film layer 110 can absorb more external energy sources, such as the laser, so that more laser can irradiate the interior of the first thin film layer 110. In this way, laser loss can be reduced, and the amount of trivalent doping source diffused into the initial N 20 type substrate can be increased.

[0095] Furthermore, since the thickness of the first thin film layer 110 is relatively small, when a relatively thin first thin film layer 110 contains a relatively large number of trivalent doping sources, the trivalent doping sources aggregate in the first thin film layer 110, thereby increasing the concentration of the trivalent doping source. In this way, when the trivalent doping source is subsequently diffused into the initial N-type substrate 20 by the doping process, the doping process is facilitated, and it is easier to form the first part of the P-type emitter with a relatively high doping concentration, thus reducing the foil resistance of the first part of the P-type emitter.Furthermore, since the thickness of the first thin film layer 110 is relatively small, the trivalent doping source that can be included in the first thin film layer 110 will not be too large, so as to prevent the doping of excessive trivalent doping source elements in the initial N-type substrate 20. In this way, the problem of the transformation of a relatively large number of trivalent doping source elements into strong recombination centers due to an excessive number of trivalent doping source elements contained in the initial N-type substrate is avoided, which leads to a low passivation capacity of the first part 11 formed by the P-type emitter 10.

[0096] In some embodiments, a method for forming the first thin film layer 110 may include depositing a trivalent doping source on the first surface of the initial N-type substrate 20; the trivalent doping source is a substance or a simple compound containing a trivalent element. In some embodiments In this embodiment, when the trivalent doping source is a boron source, the substance or simple compound containing a trivalent element may be boron tribromide or boron trichloride. In some embodiments, boron trichloride may be deposited, as a trivalent doping source, onto the first surface of the initial N2O-type substrate by chemical vapor deposition or spin coating, and the concentration of the trivalent doping source may be 1E18-9E22 atoms / cm3.

[0097] In some embodiments, a method for depositing the trivalent doping source may include: carrying out a boat-feeding process on the initial N 20 type substrate; then raising the temperature to a first predefined temperature, the first predefined temperature being from 500 °C to 900 °C; depositing a trivalent doping source on the first surface of the initial N 20 type substrate; then raising the temperature to a second predefined temperature, the second predefined temperature being higher than the first predefined temperature, for example, the second predefined temperature being from 900 °C to 1300 °C; and carrying out a junction-pushing process in a nitrogen atmosphere, which may improve the density and uniformity of the first thin film layer 110 formed.In some embodiments, during the deposition of the trivalent doping source, a small amount of oxygen may be introduced, for example, 100 sccm to 2000 sccm, which further promotes the formation of a first thin film layer 110 with a relatively high density.

[0098] Referring to [Fig. 10], after the deposition of the trivalent doping source, the predefined region of the upper surface of the initial N 20 type substrate is treated using the external energy source treatment process, and the trivalent doping source treated by the external energy source treatment process is diffused inside the initial N 20 type substrate to form the first part 11 of the P 10 type emitter in the predefined region of the initial N 20 type substrate, and an upper surface of the first part 11 of the P 10 type emitter is exposed from the initial N 20 type substrate. The external energy source treatment process is carried out on the predefined region, so that the trivalent doping source in the predefined region of the first thin film layer 110 is diffused inside the initial N 20 type substrate.Simultaneously, with the external energy source treatment process, the crystal structure of the predefined region of the initial N2O-type substrate is deformed to form the first pyramidal structure 1. It is noteworthy that prior to the external energy source treatment process, the initial N2O-type substrate has a regular tetrahedral structure. After the external energy source treatment process, at least some of the surfaces of the first pyramidal structure 1 become concave. convex with respect to the center of the first pyramidal structure 1, meaning that the first pyramidal structure 1 is transformed from a regular tetrahedral structure to an irregular tetrahedral structure. The first pyramidal structure 1 causes the appearance of dislocations and dangling bonds in the predefined region of the initial N-type substrate 20. After the predefined region of the initial N-type substrate is doped with the trivalent doping source, the upper surface of the first part 11 formed by the P-type emitter 10 exhibits the first pyramidal structure 1. In this way, the first part 11 of the P-type emitter 10 can have a deep energy level, and the foil resistance of the first part 11 of the P-type emitter 10 can be reduced.

[0099] In some embodiments, the external energy source processing method comprises any one of a laser doping process, plasma irradiation, or a directional ion implantation process. Taking laser doping as an example, the laser doping process is simple to implement, suitable for large-scale use, and has a high efficiency; thus, the trivalent doping source can be efficiently doped in the initial N2O-type substrate.The first thin film layer 110 can absorb a certain amount of laser energy, which can protect the initial N-type substrate 20 and reduce damage to the initial N-type substrate caused by laser doping, so that the first part 11 formed from the P-type emitter 10 exhibits high integrity, thus achieving good passivation performance of the first part 11 of the P-type emitter 10. In addition, since the concentration of the trivalent doping source in the first thin film layer 110 is high, during laser doping, the trivalent doping source is more easily doped into the initial N-type substrate, so that the junction depth of the first part 11 formed from the P-type emitter 10 is significant.In other words, the large junction depth of the first part 11 formed from the P-type emitter 10 can be achieved using little laser energy, thus the laser energy can be reduced when the junction depth of the first part 11 of the P-type emitter 10 can be ensured to meet expectations, thereby further reducing laser damage to the initial N-type substrate 20.

[0100] Furthermore, after irradiating the predefined region of the initial N 20 type substrate using the laser process, it is easier to transform the crystal structure of the first part 11 of the P 10 type emitter into an irregular tetrahedral structure, so that the density of dislocations formed inside the first part 11 of the P 10 type emitter is relatively high, which is conducive to a further reduction of the foil resistance.

[0101] In certain embodiments, after the formation of the first part 11 of the P-type emitter 10, the process further comprises: performing a cleaning operation on the first surface of the initial N-type substrate 20 to remove the first thin-film layer 110. In this way, the remaining trivalent doping sources in the first thin-film layer 110 and the impurities adsorbed onto the surface of the initial N-type substrate can be removed, which is conducive to leakage prevention. Furthermore, the first thin-film layer 110 contains a large number of trivalent doping sources, and these trivalent doping sources will be converted into unactivated trivalent doping sources, such as unactivated boron, in the subsequent high-temperature process for the formation of the second thin-film layer.The presence of unactivated trivalent doping sources will increase carrier recombination on the surface of the initial N2O-type substrate, thus affecting the photoelectric conversion efficiency of the solar cell. Therefore, removing the first thin-film layer 110 before forming the second thin-film layer can also reduce the content of unactivated trivalent doping sources on the surface of the initial N2O-type substrate after the subsequent formation of the second thin-film layer, thereby reducing carrier recombination on the surface of the initial N2O-type substrate and improving the photoelectric conversion efficiency of the solar cell.As an example, the cleaning operation may involve cleaning the surface of the initial N 20 type substrate with an alkaline solution or an acidic solution, where the alkaline solution may be at least an aqueous solution of KOH or H2O2, and the acidic solution may be at least an aqueous solution of HF or HCl.

[0102] After the formation of the first part 11 of the P-type emitter 10, referring to [Fig. 11] to 12, a high-temperature treatment is carried out on the initial N-type substrate 20 to form the P-type emitter in the initial N-type substrate 20, and the upper surface of the P-type emitter 10 is exposed from the initial N-type substrate 20. By way of example, the N-type substrate 100 is formed in a region of the initial N-type substrate excluding the P-type emitter 10, and the second part 12 of the P-type emitter 10 is formed in a region of the P-type emitter excluding the predefined region. Since the external energy source processing is only carried out on the surface of the predefined region of the initial N 20 type substrate, the trivalent doping sources in the first thin film layer 110 corresponding to the predefined region are diffused inside the initial N 20 type substrate.Thus, the junction depth of the first part 11 formed of the P-type emitter 10 is greater than the junction depth of the second part 12 of the P-type emitter 10, and the metal electrode can be arranged to be in electrical connection with the first part 11 of the P-type emitter 10. From. In this way, it is possible to avoid the problem of the paste intended for the formation of the metal electrode penetrating the P-type emitter 10 and coming into direct contact with the initial N-type substrate 20 during the sintering process. Furthermore, the junction depth of the second part 12 is designed to be shallow; that is, the thickness of the second part 12 of the P-type emitter is small, so the number of doping elements in the second part 12 is less than the number of doping elements in the first part 11, i.e., the doping concentration of the second part 12 of the P-type emitter is lower.Therefore, compared to the first part 11 of the P-type 10 emitter, the second part 12 of the P-type 10 emitter has a better passivation effect, which is conducive to reducing carrier recombination and improving the open-circuit voltage and short-circuit current of the solar cell.

[0103] After the high-temperature treatment on the initial N 20 type substrate, a portion of the trivalent doping sources is doped in the initial N 20 type substrate, so that a portion of the initial N 20 type substrate is transformed into the second part 12 of the P 10 type emitter. In other words, the portion of the initial N 20 type substrate excluding the first part 11 of the P 10 type emitter and the second part 12 of the P 10 type emitter corresponds to the N 100 type substrate.

[0104] Referring to [Fig. 1 1], in certain embodiments, in the operation of carrying out the high-temperature treatment on the initial N 20 type substrate, oxygen at a first flow rate is introduced for a duration ranging from 500 s to 10000 s and under a temperature ranging from 500 °C to 1500 °C, to form a second thin film layer 120, the thickness of the second thin film layer 120 is less than the thickness of the first thin film layer 110. The amount of oxygen introduced in the process of forming the second thin film layer 120 is relatively large, so that the oxygen can react with more trivalent doping sources, thus the thickness of the second thin film layer 120 formed is greater than the thickness of the first thin film layer 110.In this way, on the one hand, when the first thin film layer 110 contains more trivalent doping sources, the trivalent doping sources aggregate within the first thin film layer 110, thus increasing the concentration of trivalent doping sources, which is conducive to laser doping. Furthermore, because the first thin film layer 110 is relatively thin, it is easy for the laser to penetrate the initial N-type substrate 20. On the other hand, the second thin film layer 120 is thicker, which can ensure that the amount of trivalent doping sources absorbed by the second thin film layer 120 in a region excluding the predefined area of ​​the first surface of the initial N-type substrate 20 is relatively large. In this way, the doping concentration at the upper surface of the... first part 11 of the P 10 type emitter and the doping concentration on the upper surface of the second part 12 of the P 10 type emitter can be reduced, and passivation performance can be improved.

[0105] In some embodiments, the first flow rate varies from 200 sccm to 80000 sccm. By way of example, the first flow rate can be from 200 sccm to 1000 sccm, from 1000 sccm to 5000 sccm, from 5000 sccm to 10000 sccm, from 10000 sccm to 20000 sccm, from 20000 sccm to 30000 sccm, from 30000 sccm to 50000 sccm, from 50000 sccm to 70000 sccm, or from 70000 sccm to 80000 sccm. Adjusting the initial flow rate within this range can ensure a high initial flow rate, resulting in a thicker second thin-film layer (120) that can absorb more trivalent doping. This allows for a relatively low doping concentration on the upper surface of the second part (12) of the P-type emitter (10), which promotes high foil resistance in the second part (12) and thus improves the passivation performance of the second part (12).

[0106] Referring to [Fig. 12], in some embodiments, the process further comprises: performing the cleaning operation on the initial N 20 type substrate to remove the second thin film layer 120; forming an antireflective layer 130 on the first surface of the initial N 20 type substrate; the antireflective layer 130 is located on the upper surface of the P 10 type emitter; in some embodiments, the antireflective layer 130 may be a silicon nitride layer comprising a silicon nitride material. In some embodiments, the antireflective layer 130 may be formed by a plasma-enhanced chemical vapor deposition (PECVD) process.

[0107] Referring to [Fig. 13], in certain embodiments, the method further comprises: the formation of a first metal electrode 140, and the first metal electrode 140 is electrically connected to the first part 11 of the P-type emitter 10. The first metal electrode 140 is located on the first surface of the initial N-type substrate 20. Since the foil resistance of the first part 11 of the P-type emitter 10 is low, the first metal electrode 140 is arranged to be electrically connected to the first part 11 of the P-type emitter 10. In this way, the contact resistance between the first metal electrode 140 and the first part 11 of the P-type emitter 10 can be reduced, thereby facilitating the transport of carriers in the first metal electrode 140 penetrating the antireflective layer. The specific principles are as follows.

[0108] The incident light reaches the initial N-type substrate 20 through the first part 11 of the P-type emitter 10 and the second part 12 of the P-type emitter 10, and generates a plurality of electron-hole pairs in the initial N-type substrate 20. The plurality of electron-hole pairs in the initial N-type substrate 20 are separated into electrons and holes, respectively, under the action of the photoelectric effect. The separated electrons are transported to the initial N-type substrate 20, and the separated holes are transported to the first part 11 of the P-type emitter 10 and the second part 12 of the P-type emitter 10. The electrons that are transported to the first part 11 of the P-type emitter 10 and the second part 12 of the P-type emitter 10 are collected by the first metal electrode 140 in contact with the first part 11 of the P-type emitter 10, and are transported into the first metal electrode 140 by penetrating the antireflective layer.In other words, the electrons in the first part 11 and the second part 12 are intended to be transported to the first metal electrode 140 in contact with the first part 11 of the P-type emitter 10. Therefore, carrier transport can be greatly improved by improving the contact resistance between the first metal electrode 140 and the first part 11 of the P-type emitter 10.

[0109] In some embodiments, a method for forming the first metal electrode 140 comprises: the impression of a conductive paste on a top surface of the antireflective layer 130 in the predefined region, the conductive material in the conductive paste may be at least one of silver, aluminum, copper, tin, gold, lead or nickel; and the sintering of the conductive paste, for example, the sintering may be carried out under a peak temperature of 750 °C to 850 °C, so as to penetrate the antireflective layer to form the first metal electrode 140.

[0110] In some embodiments, a width of the first metal electrode 140 is less than or equal to the width of the first part 11 of the P-type emitter 10, so that the first metal electrode 140 can be surrounded by the first part 11 of the P-type emitter 10, and the lateral surfaces and the lower surface of the first metal electrode 140 are in contact with the first part 11 of the P-type emitter 10.Compared to the case where part of the lateral surfaces of the first metal electrode 140 is in contact with the second part 12 of the higher foil-resistance P-type emitter, since the foil resistance of the first part 11 of the P-type emitter is lower, the contact resistance between the first metal electrode 140 and the first part 11 of the P-type emitter is lower, which is conducive to a further improvement in carrier transport in the first part 11 of the P-type emitter and the second part 12 of the P-type emitter.

[0111] Referring to [Fig. 14], a tunnel layer 150 and a doped conductive layer 160 are formed, the tunnel layer and the doped conductive layer are located on a second surface of the N-type substrate 100 and are arranged sequentially in a opposite direction to the N 100 type substrate.

[0112] The tunnel layer 150 is used to perform interface passivation of the second surface of the N 100 type substrate. In some embodiments, the tunnel layer 150 can be formed using a deposition process, such as a chemical vapor deposition process. In other embodiments, the tunnel layer 150 can be formed using an in-situ generation process. By way of example, in some embodiments, the material of the tunnel layer 150 can be a dielectric material, such as silicon oxide.

[0113] The doped conductive layer 160 is used to form a field passivation. In some embodiments, the material of the doped conductive layer 160 may be doped silicon. In some embodiments, the doped conductive layer 160 and the N-type substrate 100 have doping elements of the same type of conductivity; the doped silicon may comprise one or more of the following: N-type doped polysilicon, N-type doped microcrystalline silicon, and N-type doped amorphous silicon. In some embodiments, the doped conductive layer 160 may be formed using a deposition process. As an example, intrinsic polysilicon can be deposited on the surface of tunnel layer 150 away from the N-type substrate 100 to form a polysilicon layer, and phosphorus ions can be doped by ion implantation and source diffusion to form an N-type doped polysilicon layer.The N-type doped polysilicon layer serves as a doped conductive layer 160.

[0114] Referring to [Fig. 1], in some embodiments, the process further comprises the formation of a first passivation layer 170 on a surface of the doped conductive layer 160 away from the N-type substrate 100. In some embodiments, the material of the first passivation layer 170 may be one or more of silicon dioxide, aluminum oxide, silicon nitride, silicon oxynitride, and silicon oxycarbonitride. In some embodiments, the first passivation layer 170 may be a single-layer structure. In other embodiments, the first passivation layer 170 may be a multi-layer structure. By way of example, in some embodiments, the first passivation layer 170 may be formed using a PECVD process.

[0115] In some embodiments, the process further comprises the formation of a second metallic electrode 180 penetrating the first passivation layer 170 to form an electrical connection with the doped conductive layer 160. By way of example, the process for forming the second metallic electrode 180 may be the same as the process for forming the first metallic electrode 140, and the material of the first metallic electrode 140 may be the same as the material of the second metallic electrode 180.

[0116] In the process of producing a solar cell as described in the embodiments above, at least one inclined surface of the first pyramidal structure 1 formed exhibits an irregular deformation, such that the crystalline structure of the first pyramidal structure 1 changes from a regular tetrahedral structure to an irregular tetrahedral structure. The irregular tetrahedral structure leads to dislocations and dangling bonds in the emitter, thus modifying the emitter. In particular, the generated dislocations and dangling bonds lead to a deep energy level within the first portion 11 of the P-type emitter 10, thereby reducing the foil resistance of the first portion 11 of the P-type emitter 10. The first portion 11 of the P-type emitter 10 can have a relatively low foil resistance by modifying the structure of the first portion 11 of the P-type emitter 10.In this way, the foil resistance of the first part 11 of the P-type emitter 10 can be reduced without significantly increasing the doping concentration of the first part 11 of the P-type emitter 10, which not only improves ohmic contact, but also helps maintain a good passivation effect of the first part 11 of the P-type emitter, thus improving the overall photoelectric conversion performance of the formed solar cell.

[0117] Although this disclosure is disclosed above with embodiments given by way of example, these are not used to limit the claims. Any person skilled in the art may make certain changes and modifications without departing from the concept of this disclosure. The scope of protection of this disclosure is subject to the scope defined by the claims.

[0118] Persons with ordinary knowledge of the art will understand that the above embodiments are illustrative implementations for carrying out this disclosure. The scope of patent protection for this disclosure is always subject to the limited scope defined by the appended claims.

Claims

Demands

1. Solar cell, characterized in that it comprises: an N-type substrate (100); a P-type emitter (10) formed on a first surface of the N-type substrate (100), wherein the P-type emitter (10) comprises a first part (11) and a second part (12), an upper surface of the first part (11) comprises a first pyramidal structure (1), and at least a portion of at least one inclined surface of the first pyramidal structure (1) is concave or convex with respect to the center of the first pyramidal structure (1), wherein an upper surface of the second part (12) comprises a second pyramidal structure (2), and inclined surfaces of the second pyramidal structure (2) are planes, and wherein, in a direction perpendicular to the first surface of the N-type substrate (100), a junction depth of the first part (11) is greater than a junction depth of the second part (12);and a tunnel layer (150) and a doped conducting layer (160) formed sequentially on a second surface of the N-type substrate (100) in a direction opposite to the N-type substrate (100).;

2. Solar cell according to claim 1, wherein a crystalline structure of the first part of the P-type emitter has dislocations.

3. Solar cell according to claim 1, wherein a sheet resistance of the first part of the P-type emitter is lower than a sheet resistance of the second part of the P-type emitter

4. r. Solar cell according to claim 1, wherein at least a portion of the first pyramidal structure further comprises a first substructure located on top of the first pyramidal structure, wherein the first substructure is a sphere or a spheroid.

5. Solar cell according to claim 1, wherein a ratio of the junction depth of the first part to the junction depth of the second part is not less than 2.

6. Solar cell according to claim 5, wherein a doping concentration at the upper surface of the first part of the P-type emitter is greater than or equal to a doping concentration at the upper surface of the second part of the P-type emitter.

7. Solar cell according to claim 6, wherein the doping concentration at the upper surface of the first part of the P-type emitter varies from 1E18 atoms / cm3 to 5E20 atoms / cm3, a difference between the doping concentration at the upper surface of the first part and a doping concentration on a lower surface of the first part varies from 1E16 atoms / cm3 to 5E20 atoms / cm3, and a difference between the doping concentration at the upper surface of the second part and a doping concentration on a lower surface of the second part varies from 1E16 atoms / cm3 to 1E20 atoms / cm3.

8. Solar cell according to claim 1, wherein a ratio of a width of the second part to a width of the first part is not less than 60.

9. Solar cell according to claim 1, wherein the P-type emitter further comprises a transition region situated between the first part and the second part, wherein a doping concentration on an upper surface of the transition region is greater than or equal to the doping concentration on the upper surface of the second part, and is less than or equal to the doping concentration on the upper surface of the first part.

10. Photovoltaic module, characterized in that it comprises: at least one cell string formed by connecting a plurality of solar cells (101) according to any one of claims 1 to 9; at least one encapsulation layer (102) configured to cover a surface of at least one cell string; and at least one cover plate (103) configured to cover a surface of at least one encapsulation layer oriented opposite to at least one cell string.

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