Solar cell, preparation method thereof, and photovoltaic module

Abstract

The present invention relates to the field of solar cells, and discloses a solar cell, a preparation method thereof, and a photovoltaic module. The solar cell includes: a silicon substrate; a first semiconductor layer and a second semiconductor layer disposed on the silicon substrate, the first semiconductor layer being doped with an N-type conductive element, and the second semiconductor layer being doped with a P-type conductive element; a first electrode, the first electrode being electrically connected to the first semiconductor layer through a plurality of first conductive structures; a second electrode, the second electrode being electrically connected to the second semiconductor layer through a plurality of second conductive structures; wherein, the density of the first conductive structures is greater than the density of the second conductive structures. This solar cell can improve the efficiency of carrier transport, reduce recombination, and reduce scattering.

Description

Technical Field

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

[0002] In a solar cell, the transport ability of carriers between the semiconductor layer and the electrode has an important influence on the photoelectric conversion efficiency of the solar cell. If the resistance encountered by the carriers during transmission to the electrode is large, it will lead to an increased probability of contact between the carriers and defects and impurities in the semiconductor layer, an increased probability of carrier scattering, and more carrier recombination, which limits the further improvement of the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0003] Embodiments of the present invention disclose a solar cell, a preparation method thereof, and a photovoltaic module. The solar cell can improve the carrier transport efficiency, reduce recombination, and reduce scattering, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0004] In a first aspect, embodiments of the present application disclose a solar cell, the solar cell comprising:

[0005] A silicon substrate;

[0006] A first semiconductor layer and a second semiconductor layer disposed on the silicon substrate, the first semiconductor layer being doped with an N-type conductive element, and the second semiconductor layer being doped with a P-type conductive element;

[0007] A first electrode, the first electrode being electrically connected to the first semiconductor layer through a plurality of first conductive structures;

[0008] A second electrode, the second electrode being electrically connected to the second semiconductor layer through a plurality of second conductive structures;

[0009] Wherein, the density of the first conductive structure is greater than the density of the second conductive structure.

[0010] Further, within any 1 mm × 1 mm area of the contact between the first electrode and the first semiconductor layer, the number of the first conductive structures is 1×10 5 to 1×10 6 , and within any 1 mm × 1 mm area of the contact between the second electrode and the second semiconductor layer, the number of the second conductive structures is 5×10 4 to 5×10 5 .

[0011] Further, the projected size of the first conductive structure on the first semiconductor layer is greater than or equal to the projected size of the second conductive structure on the second semiconductor layer. The projected size of any one of the first conductive structures on the first semiconductor layer is 100 nm to 2000 nm, and the projected size of any one of the second conductive structures on the second semiconductor layer is 100 nm to 1000 nm.

[0012] Further, any one of the first conductive structures and any one of the second conductive structures are both in a vein-like shape.

[0013] Further, any one of the first conductive structures includes a plurality of strip-shaped first structures diverging in the direction of the first electrode;

[0014] Any one of the second conductive structures includes a plurality of strip-shaped second structures diverging in the direction of the second electrode.

[0015] Further, any one of the first structures includes a first crystalline main chain and a plurality of first crystalline side chains extending in a growth direction different from that of the first crystalline main chain;

[0016] Any one of the second structures includes a second crystalline main chain and a plurality of second crystalline side chains extending in a growth direction different from that of the second crystalline main chain.

[0017] Further, both the first structure and the second structure are formed by crystallization polymerization of a plurality of conductive particles.

[0018] Further, the elements in the conductive particles include one or a combination of silver element, aluminum element, copper element, and lead element.

[0019] Further, the doping concentration of the N-type conductive element in the first semiconductor layer is 1×10 20 atoms / cm 3 ~1×10 21 atoms / cm 3 ,

[0020] The doping concentration of the P-type conductive element in the second semiconductor layer is 1×10 18 atoms / cm 3 ~1×10 20 atoms / cm 3 。

[0021] Further, the first semiconductor layer and the second semiconductor layer are disposed on the backlight surface of the silicon substrate. The first semiconductor layer and the second semiconductor layer are separated by an isolation region, and the first semiconductor layer and the second semiconductor layer are arranged in an interdigitated pattern.

[0022] Further, the solar cell further includes a first dielectric layer disposed between the first semiconductor layer and the silicon substrate, and a second dielectric layer disposed between the second semiconductor layer and the silicon substrate.

[0023] Further, the silicon substrate is of N type, the second semiconductor layer is disposed on the light-receiving surface of the silicon substrate, the first semiconductor layer is disposed on the backlight surface of the silicon substrate, and a first dielectric layer is further disposed between the first semiconductor layer and the silicon substrate.

[0024] Further, a plurality of the first semiconductor layers are disposed on the backlight surface, any one of the first semiconductor layers is disposed on a partial area of the backlight surface, and adjacent first semiconductor layers are separated by a first separation area; and / or,

[0025] A plurality of the second semiconductor layers are disposed on the light-receiving surface, any one of the second semiconductor layers is disposed on a partial area of the light-receiving surface, and adjacent two second semiconductor layers are separated by a second separation area, wherein a texture structure is disposed on the second separation area.

[0026] In a second aspect, an embodiment of the present application discloses a preparation method of a solar cell as described in the first aspect, and the preparation method includes the following steps:

[0027] Provide the silicon substrate, and the first semiconductor layer and the second semiconductor layer are disposed on the silicon substrate;

[0028] Apply a paste for making the first electrode on the first semiconductor layer, and apply a paste for making the second electrode on the second semiconductor layer;

[0029] Perform heat treatment to form a first conductive precursor at the contact interface between the first electrode and the first semiconductor layer, and form a second conductive precursor at the contact interface between the second electrode and the second semiconductor layer;

[0030] Perform light injection to convert the first conductive precursor into a first conductive structure and convert the second conductive precursor into a second conductive structure, thereby obtaining the solar cell.

[0031] Further, the step of light injection includes:

[0032] A heating stage, heating the first conductive precursor and the second conductive precursor, and a peak temperature of the heating stage is 400°C to 650°C;

[0033] When the temperature in the heating stage drops from the peak temperature to a preset temperature, apply light to the solar cell, a temperature of the light is 50°C to 400°C, and an energy density of the light is 10kW / m 2~100 kW / m 2 ;

[0034] Among them, the preset temperature is 320°C to 360°C.

[0035] Furthermore, the heating stage includes the following processes:

[0036] Heat to the preset temperature;

[0037] After heating from the preset temperature to the peak temperature within a preset time, then cool down to the preset temperature, where the preset time is 10 s to 30 s.

[0038] Furthermore, any one of the first conductive precursors includes a plurality of first crystalline main chains diverging in the direction of the first electrode;

[0039] Any one of the second conductive precursors includes a plurality of second crystalline main chains diverging in the direction of the second electrode.

[0040] Furthermore, in the step of the heat treatment, the heat treatment temperature is 700°C to 900°C.

[0041] Furthermore, the step of providing the silicon substrate includes:

[0042] Deposit a second dielectric layer and the second semiconductor layer on the backlight surface of the silicon substrate in sequence;

[0043] Perform patterning on the second dielectric layer and the second semiconductor layer located on the backlight surface to expose a part of the backlight surface;

[0044] Deposit a first dielectric layer and the first semiconductor layer on the exposed backlight surface and the second semiconductor layer in sequence;

[0045] Remove the first semiconductor layer and the first dielectric layer located on the second semiconductor layer, and form an isolation region between adjacent second semiconductor layers and the first semiconductor layer.

[0046] Furthermore, the step of providing the silicon substrate includes:

[0047] Deposit the second semiconductor layer on the light-receiving surface of the silicon substrate;

[0048] Deposit a first dielectric layer and the first semiconductor layer on the backlight surface of the silicon substrate in sequence.

[0049] In a third aspect, an embodiment of the present application discloses a photovoltaic module, including: the solar cell as described in the first aspect, or the solar cell prepared by the preparation method as described in the second aspect.

[0050] Compared with the prior art, the beneficial effects of the present application are as follows:

[0051] The present application provides a solar cell, a preparation method thereof, and a photovoltaic module. The solar cell can improve the carrier transport ability, reduce recombination, and reduce scattering, thereby improving the stability and photoelectric conversion efficiency of the solar cell.

[0052] In the above solar cell structure, since the first semiconductor layer is doped with an N-type conductive element and the second semiconductor layer is doped with a P-type conductive element, the diffusion ability of carriers in the first semiconductor layer is higher than that of carriers in the second semiconductor layer. At this time, if the carriers in the first semiconductor layer are difficult to be effectively transmitted to the first electrode, the probability of contact between the carriers in the first semiconductor layer and impurities and defects will increase, resulting in increased scattering and serious recombination of carriers in the first semiconductor layer. Therefore, in order to improve the transmission effectiveness of carriers in the first semiconductor layer, the present application sets the density of the first conductive structure to be higher than that of the second conductive structure, so that the distribution of the first conductive structure is relatively dense, providing multiple paths for the transmission of carriers, reducing the contact resistance, facilitating reducing the transmission resistance between the first semiconductor layer and the first electrode for carriers, thereby improving the carrier mobility, reducing the degree of carrier scattering, and also helping to reduce the recombination of carriers and improve the photoelectric conversion efficiency of the solar cell.

[0053] That is to say, by designing the densities of the first conductive structure and the second conductive structure, the transmission effectiveness of carriers between the first semiconductor layer and the first conductive structure is improved, recombination is reduced, scattering is reduced, and thus the photoelectric conversion efficiency of the solar cell is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0055] Figure 1 is a schematic structural diagram of the first solar cell provided by an embodiment of the present application;

[0056] Figure 2 is provided by an embodiment of the present application Figure 1 an enlarged view of A in;

[0057] Figure 3 is provided by an embodiment of the present application Figure 1 an enlarged view of B in;

[0058] Figure 4It is a schematic structural diagram of the first conductive structure provided by an embodiment of the present application;

[0059] Figure 5 It is a schematic structural diagram of the first structure provided by an embodiment of the present application;

[0060] Figure 6 It is a schematic structural diagram of the second type of solar cell provided by an embodiment of the present application;

[0061] Figure 7 It is a schematic structural diagram of the third type of solar cell provided by an embodiment of the present application;

[0062] Figure 8 It is an electron microscope image of the first conductive precursor provided by an embodiment of the present application;

[0063] Figure 9 It is an electron microscope image of the second conductive structure provided by an embodiment of the present application;

[0064] Figure 10 It is an electron microscope image of the second conductive precursor provided by an embodiment of the present application;

[0065] Figure 11 It is an electron microscope image of the second conductive structure provided by an embodiment of the present application.

[0066] Icons: 1, silicon substrate; 21, first semiconductor layer; 22, second semiconductor layer; 31, first electrode; 32, second electrode; 41, first conductive structure; 411, first structure; 4111, first main crystallization chain; 4112, first crystallization side chain; 42, second conductive structure; 51, first dielectric layer; 52, second dielectric layer; 61, first functional layer; 62, second functional layer; 63, third functional layer; 7, first separation region; 8, second separation region. Detailed implementation manners

[0067] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0068] In the present invention, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0069] Moreover, in addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0070] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "plurality" is two or more.

[0071] The technical solution provided by the present invention will be further described below in conjunction with embodiments and drawings.

[0072] In a solar cell, the concentration of carriers and the carrier transport ability have a very important impact on the performance such as the photoelectric conversion efficiency of the solar cell.

[0073] Since the mobility of electrons is higher than that of holes, under the action of the same electric field, the transport speed of electrons is faster and they can participate in the conduction process more effectively. However, if electrons are difficult to transport to the electrode, the probability of electrons contacting impurities or defects in the semiconductor layer will increase, resulting in an increase in the probability of electron scattering and recombination, and it is difficult to effectively improve the conductivity of the solar cell.

[0074] Based on the above problems, the present application discloses a solar cell, which can improve the carrier mobility, reduce recombination, and thus improve the photoelectric conversion efficiency of the solar cell.

[0075] In the first aspect, as Figures 1 to 3 shown, the embodiment of the present application discloses a solar cell, which includes:

[0076] a silicon substrate 1;

[0077] a first semiconductor layer 21 and a second semiconductor layer 22 disposed on the silicon substrate 1, the first semiconductor layer 21 is doped with an N-type conductive element, and the second semiconductor layer 22 is doped with a P-type conductive element;

[0078] A first electrode 31, the first electrode 31 is electrically connected to the first semiconductor layer 21 through a plurality of first conductive structures 41;

[0079] A second electrode 32, the second electrode 32 is electrically connected to the second semiconductor layer 22 through a plurality of second conductive structures 42;

[0080] Wherein, the density of the first conductive structure 41 is greater than the density of the second conductive structure 42.

[0081] In this application, by setting the density of the first conductive structure 41 to be higher than that of the second conductive structure 42, the distribution density of the first conductive structure 41 is increased, providing multiple transmission channels for the transport of carriers, which helps to reduce the contact resistance, reduce the transport hindrance of carriers between the first semiconductor layer 21 and the first electrode 31, improve the carrier mobility, reduce the scattering of carriers, and also helps to reduce recombination, thereby improving the photoelectric conversion efficiency of the solar cell.

[0082] Moreover, in a solar cell, it is usually set that the doping concentration of the N-type conductive element in the first semiconductor layer is higher than the doping concentration of the P-type conductive element in the second semiconductor layer. Due to the higher doping concentration of the N-type conductive element, the carrier concentration is increased. However, at the same time, if the carriers are difficult to be effectively transported to the electrode, it will increase the probability of carrier scattering and recombination. Therefore, in this application, the density of the first conductive structure is set to be higher than that of the second conductive structure, so that the carriers can be effectively transported to the first electrode through the first conductive structure, reducing carrier recombination and scattering, and improving the photoelectric conversion efficiency of the solar cell.

[0083] In summary, in this application, by designing the densities of the first conductive structure 41 and the second conductive structure 42, the influence of the relatively high diffusion rate of carriers in the first semiconductor layer on carrier scattering and recombination is further avoided, promoting the effective transport of carriers to the electrode and improving the performance of the solar cell. That is, with the mutual cooperation of the semiconductor layer and the conductive structure, it helps to improve the contact stability between the semiconductor layer and the electrode, reduce the contact resistance, improve the carrier mobility, reduce recombination, improve the conductivity, and thus improve the photoelectric conversion efficiency of the solar cell.

[0084] Wherein, the type of carriers that the N-type conductive element can provide is electrons, and the N-type conductive element includes at least one of phosphorus and arsenic elements; the type of carriers that the P-type conductive element can provide is holes, and the N-type conductive element includes at least one of boron and gallium elements.

[0085] Further, within any 1 mm × 1 mm area of the contact between the first electrode 31 and the first semiconductor layer 21, the number of the first conductive structures 41 is 1×10 5 pieces to 1×106 pieces, within any 1 mm × 1 mm area of the contact between the second electrode 32 and the second semiconductor layer 22, the number of the second conductive structures 42 is 5 × 10 4 pieces to 5 × 10 5 pieces.

[0086] When the numbers of the first conductive structure 41 and the second conductive structure 42 meet the above ranges, the contact area between the electrode and the semiconductor layer is appropriate at this time, which can effectively reduce the contact resistance and increase the carrier transport. It can not only avoid the situation where the number is small and it is difficult to effectively improve the carrier transport efficiency, but also avoid the problems such as the too large area of the contact region between the semiconductor layer and the electrode, serious damage range and pollution in the contact region when the number is too large, reduce the occurrence of recombination, and thus better optimize the performance of the solar cell.

[0087] Furthermore, referring back to Figure 2 and Figure 3 , the projected size of the first conductive structure 41 on the first semiconductor layer 21 is greater than or equal to the projected size of the second conductive structure 42 on the second semiconductor layer 22. The projected size of any first conductive structure 41 on the first semiconductor layer 21 is 100 nm to 2000 nm, and the projected size of any second conductive structure 42 on the second semiconductor layer 22 is 100 nm to 1000 nm.

[0088] It should be noted that taking the first conductive structure 41 as an example, as Figure 4 shown, the projected size of the first conductive structure 41 refers to the width d between the two farthest points where the first conductive structure 41 diverges and expands outward. Similarly, the projected size of the second conductive structure 42 refers to the width between the two farthest points where the second conductive structure 42 diverges and expands outward.

[0089] Among them, when the projected sizes of the first conductive structure 41 and the second conductive structure 42 are within the above ranges, it can not only ensure that the carriers have good transport ability, but also reduce the damage range of the contact interface between the semiconductor layer and the electrode and reduce the occurrence of contact recombination, and better optimize the contact performance between the semiconductor layer and the electrode. And, since the doping content of the second semiconductor layer 22 is relatively low, preferably, when the projected size of the second conductive structure 42 is smaller than that of the first conductive structure 41, it helps to reduce the defects at the contact interface, further reduce the carrier recombination, and since the projected size of the first conductive structure 41 is larger, it can improve the transport rate of carriers in the first semiconductor layer 21 to a higher degree, reduce the carrier scattering, improve the photoelectric conversion efficiency of the solar cell, and also reduce the consumption of the paste, thereby reducing the use cost of the paste.

[0090] Furthermore, any first conductive structure 41 and any second conductive structure 42 are both in a vein shape.

[0091] In order to further improve the carrier mobility, both the first conductive structure 41 and the second conductive structure 42 of the present application are in the shape of leaf veins. Adopting such a structure not only helps to increase the contact area between any conductive structure and the semiconductor layer, but also provides carrier transport paths in multiple directions. Thus, it not only ensures the uniformity of carrier transport, but also reduces the resistance loss, which helps to improve the photoelectric conversion efficiency of the solar cell. Moreover, it helps to improve the stability of the contact between the electrode and the semiconductor layer, ensuring good contact performance during the welding process and the stability experiments of related batteries or components.

[0092] Furthermore, as Figure 5 shown, any one of the first conductive structures 41 includes a plurality of strip-shaped first structures 411 diverging in the direction of the first electrode 31; any one of the second conductive structures 42 includes a plurality of strip-shaped second structures diverging in the direction of the second electrode 32. The large number of the above-mentioned first structures 411 and second structures is beneficial to ensuring that the first conductive structure 41 and the second conductive structure 42 can provide more carrier transport paths and improving the carrier mobility.

[0093] Moreover, any one of the first structures 411 includes a first crystalline main chain 4111 and a plurality of first crystalline side chains 4112 extending in a growth direction different from that of the first crystalline main chain 4111; any one of the second structures includes a second crystalline main chain and a plurality of second crystalline side chains extending in a growth direction different from that of the second crystalline main chain. Due to the large number of the first crystalline side chains 4112 and the second crystalline side chains, it is beneficial to ensuring that the first conductive structure 41 and the second conductive structure 42 can provide more carrier transport paths, improving the carrier mobility and reducing recombination.

[0094] Specifically, taking the first conductive structure 41 as an example, the first conductive structure 41 includes a plurality of first structures 411, and any one of the first structures 411 is composed of a first crystalline main chain 4111 and a plurality of first crystalline side chains 4112. Therefore, the carriers in the first semiconductor layer 21 can not only be transported along the first crystalline main chain 4111, but also along the first crystalline side chains 4112. Moreover, due to the relatively large number of the first crystalline main chain 4111 and the first crystalline side chains 4112 of the first conductive structure 41, it not only helps to ensure a relatively large contact area between the first electrode 31 and the first semiconductor layer 21, helps to reduce the contact resistance, but also provides multiple transport channels, thus highly improving the carrier mobility to a high degree and ensuring the uniformity of carrier transport and reducing recombination. In addition, due to the structural characteristics of the first conductive structure 41, the binding stability between the first electrode 31 and the first semiconductor layer 21 is high, which helps to improve the stability of subsequent welding of the photovoltaic module and highly improve the performance of the solar cell.

[0095] Furthermore, both the first structure 411 and the second structure are formed by crystallization and polymerization of a number of conductive particles, wherein the elements in the conductive particles include one or a combination of silver, aluminum, copper, and lead.

[0096] In addition, in order to ensure that the solar cell of the present application has good conductivity, the doping concentration of the N-type conductive element in the first semiconductor layer 21 is set to 1×10 20 atoms / cm 3 ~1×10 21 atoms / cm 3 The doping concentration of the P-type conductive element in the second semiconductor layer 22 is 1×10 18 atoms / cm 3 ~1×10 20 atoms / cm 3 When the doping concentration of the conductive element is controlled within the above range, the carrier content and the number of conductive structures are highly matched, thereby effectively improving the conductivity of the solar cell, avoiding the influence of high-concentration doping on carrier transport, improving the mobility of carriers, reducing recombination, and improving the photoelectric conversion efficiency of the solar cell.

[0097] In a first optional implementation, refer to Figure 1 The solar cell is a back contact cell, the first semiconductor layer 21 and the second semiconductor layer 22 are arranged on the backlight side of the silicon substrate 1, the first semiconductor layer 21 and the second semiconductor layer 22 are separated by an isolation region, and the first semiconductor layer 21 and the second semiconductor layer 22 are arranged in an interdigitated manner.

[0098] Among them, for back-contact cells, since the positive and negative electrodes of this type of solar cell are both on the backlight side, there is no metal grid blocking the light-receiving side, which avoids electrode shading losses and reduces recombination on the light-receiving side, thereby improving the photoelectric conversion efficiency of the solar cell.

[0099] In addition, in order to further improve the performance of the solar cell, a passivation contact structure can be set on the back of the solar cell, that is, the solar cell also includes a first dielectric layer 51 arranged between the first semiconductor layer 21 and the silicon substrate 1, and a second dielectric layer 52 arranged between the second semiconductor layer 22 and the silicon substrate 1.

[0100] Since the solar cell includes a dielectric layer and a semiconductor layer, the two together form a passivated contact structure, providing a good interface passivation effect for the backlight surface. Among them, the material of the dielectric layer can include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Preferably, the dielectric layer is a silicon oxide layer formed of silicon oxide, because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of minority carriers on the surface of the silicon substrate, and is a film with excellent durability for subsequent high-temperature processes.

[0101] As a barrier for electrons and holes, the dielectric layer can combine with the semiconductor layer to form a passivated contact structure to prevent minority carriers from passing through; the dielectric layer can also have the function of pinhole channels, enabling the carriers in the solar cell to move freely, generating selective passage for majority carriers through the heavily doped semiconductor layer, which is beneficial to reducing the recombination loss of minority carriers; in addition, the dielectric layer can be used as a diffusion barrier to prevent the conductive elements of the semiconductor layer from diffusing into the silicon substrate. And controlling the thickness of the dielectric layer to be 0.5 nm to 4 nm is beneficial to reducing the transport hindrance of carriers and improving the transport efficiency.

[0102] In addition, setting a first functional layer 61 on the first semiconductor layer 21 and a second functional layer 62 on the second semiconductor layer 22 also helps to improve the performance of the solar cell. The first functional layer 61 is a first passivation layer and / or a first antireflection layer, and the second functional layer 62 is a second passivation layer and / or a second antireflection layer.

[0103] And because the first semiconductor layer 21 and the second semiconductor layer 22 are both located on the backlight surface of the silicon substrate 1, that is, the first functional layer 61 and the second functional layer 62 are both located on the backlight surface of the solar cell. At this time, the first functional layer 61 and the second functional layer 62 are prepared in the same step and are the same type of film layer; in addition, in order to further improve the photoelectric conversion efficiency of the solar cell, a third functional layer 63 is also provided on the light-receiving surface of the silicon substrate 1.

[0104] In the second alternative embodiment, as Figure 6 and Figure 7 shown, the solar cell is a passivated contact cell, the silicon substrate 1 is N-type, the second semiconductor layer 22 is disposed on the light-receiving surface of the silicon substrate 1, the first semiconductor layer 21 is disposed on the backlight surface of the silicon substrate 1, and a first dielectric layer 51 is further provided between the first semiconductor layer 21 and the silicon substrate 1.

[0105] Refer back to Figure 7, in order to further improve the passivation effect of the solar cell and enhance the photoelectric conversion efficiency of the solar cell, the present application is provided with a plurality of first semiconductor layers 21 on the backlight surface. Any one of the first semiconductor layers 21 is disposed on a partial area of the backlight surface, and adjacent first semiconductor layers 21 are separated by a first separation 7 region; and / or, a plurality of second semiconductor layers 22 are provided on the light-receiving surface. Any one of the second semiconductor layers 22 is disposed on a partial area of the light-receiving surface, and adjacent two second semiconductor 22 layers are separated by a second separation region 8, wherein a textured structure is provided on the second separation region 8. When local passivation structures are provided on both the light-receiving surface and the backlight surface, the passivation effect of the light-receiving surface is high at this time, and the influence on the amount of sunlight absorbed is small, while the local passivation structure provided on the backlight surface helps to reduce the production cost, reduce the damage of the contact between the semiconductor layer and the silicon substrate, and improve the photoelectric conversion efficiency of the solar cell.

[0106] In addition, in order to improve the passivation effect of the light-receiving surface, a second dielectric layer 52 can be provided on the light-receiving surface. The second dielectric layer 52 is located between the second semiconductor layer 22 and the silicon substrate 1.

[0107] Moreover, a first functional layer 61 is prepared on the side of the first semiconductor layer 21 away from the silicon substrate 1, and a second functional layer 62 is prepared on the side of the second semiconductor layer 22 away from the silicon substrate 1; the first functional layer 61 is a first passivation layer and / or a first antireflection layer, and the second functional layer 62 is a second passivation layer and / or a second antireflection layer.

[0108] The setting of the passivation layer helps to reduce surface recombination and improve the photoelectric conversion efficiency of the solar cell; the presence of the antireflection layer can reduce the reflection of incident light on the one hand and play a passivation role on the other hand, further improving the photoelectric efficiency of the solar cell. Exemplarily, the first functional layer 61 is a first passivation layer, a first antireflection layer, or a first passivation layer and a first antireflection layer; the second functional layer 62 is a second antireflection layer, a second passivation layer, or a second passivation layer and a second antireflection layer.

[0109] When functional layers are provided on the first semiconductor layer 21 and the second semiconductor layer 22, it helps to improve the photoelectric conversion efficiency of the solar cell. The first electrode 31 needs to pass through the first functional layer 61 and is connected to the first semiconductor layer 21 through the first conductive structure 41. The second electrode 32 needs to pass through the second functional layer 62 and is connected to the second semiconductor layer 22 through the second conductive structure 42. At this time, the second semiconductor layer 22 is located on the light-receiving surface of the solar cell, so the second functional layer 62 is located on the second semiconductor layer 22 and the exposed textured structure, and the first functional layer 61 is located on the first semiconductor layer 21 and the exposed backlight surface.

[0110] Among them, the first functional layer 61 includes at least one of aluminum oxide and silicon oxide, silicon oxynitride, silicon nitride; the second functional layer 62 includes at least one of aluminum oxide and silicon oxide, silicon oxynitride, silicon nitride.

[0111] In a second aspect, the embodiments of the present application also disclose a method for manufacturing a solar cell, and the manufacturing method includes the following steps:

[0112] Provide a silicon substrate, on which a first semiconductor layer and a second semiconductor layer are provided;

[0113] Apply a paste for making a first electrode on the first semiconductor layer, and apply a paste for making a second electrode on the second semiconductor layer;

[0114] Perform heat treatment to form a first conductive precursor at the contact interface between the first electrode and the first semiconductor layer, and form a second conductive precursor at the contact interface between the second electrode and the second semiconductor layer;

[0115] Perform photo-injection to convert the first conductive precursor into a first conductive structure and the second conductive precursor into a second conductive structure, thereby obtaining a solar cell.

[0116] Among them, the paste can be printed onto the semiconductor layer by means of screen printing.

[0117] It can be understood that the paste includes conductive particles, glass bodies, organic solvents, and binders. Among them, the conductive particles have good electrical conductivity and can form good contact with the semiconductor layer during the heat treatment process to ensure the effective transmission of current. The glass bodies can enable the molten combination of the conductive particles and the semiconductor layer during the heat treatment process and promote the conductive particles to pass through the functional layer and contact the semiconductor layer. The organic solvents and binders change the fluidity of the paste, reduce the printing difficulty, and improve the printing quality.

[0118] In addition, any first conductive precursor includes a plurality of first crystal main chains diverging in the direction of the first electrode, and any second conductive precursor includes a plurality of second crystal main chains diverging in the direction of the second electrode.

[0119] Among them, as Figure 8 shown, during the heat treatment process, the organic solvents and binders in the paste for preparing the first electrode volatilize and are released, leaving behind conductive particles, and some of the conductive particles further crystallize and aggregate. These conductive particles form a first conductive precursor at the contact interface between the first electrode and the first semiconductor layer after crystallization, and the structure of the first conductive precursor presents a plurality of first crystal main chains diverging in the direction of the first electrode. As Figure 9 shown, during the subsequent photo-injection process, some of the conductive particles grow and aggregate along a growth direction different from that on the first crystal main chain under the action of high temperature and strong light catalytic reduction, forming a plurality of slender first crystal side chains, thereby obtaining a first conductive structure in the shape of a leaf vein.

[0120] As Figure 10As shown, during the heat treatment process, the organic solvent and binder in the slurry used to prepare the second electrode volatilize and release, leaving behind conductive microparticles, and some of these conductive microparticles further crystallize and aggregate. After these conductive microparticles crystallize, a second conductive precursor is formed at the contact interface between the second electrode and the second semiconductor layer, and the structure of this second conductive precursor presents several second crystallization main chains diverging towards the second electrode. As Figure 11 shown, during the subsequent photo-injection process, some of the conductive microparticles aggregate and grow along a growth direction different from that of the second crystallization main chain under the action of high temperature and strong light catalytic reduction, forming multiple slender second crystallization side chains, thereby preparing a vein-like second conductive structure.

[0121] That is to say, the step of photo-injection is to make some of the conductive microparticles aggregate and grow on the crystallization main chain, thereby forming crystallization side chains, that is, transforming the first conductive precursor into the first conductive structure and connecting the first electrode and the first semiconductor layer together, transforming the second conductive precursor into the second conductive structure and connecting the second electrode and the second semiconductor layer together. And by using the preparation method of the present application, it is ensured that the density of the obtained second microstructure is lower than that of the first microstructure, which is beneficial to highly improving the carrier transport ability.

[0122] Furthermore, the step of photo-injection includes:

[0123] A heating stage, heating the first conductive precursor and the second conductive precursor, and the peak temperature of the heating stage is 400°C to 650°C;

[0124] When the temperature in the heating stage drops from the peak temperature to a preset temperature, light is applied to the solar cell, the temperature of the light is 50°C to 400°C, and the energy density of the light is 10kW / m 2 ~100kW / m 2 ;

[0125] wherein, the preset temperature is 320°C to 360°C.

[0126] When the parameters of the photo-injection are controlled within the above ranges, it is beneficial to the diffusion and crystallization aggregation of the conductive microparticles, ensuring that the parameters of the formed first conductive structure and second conductive structure are within the scope of the present application, which helps to reduce the contact resistance and improve the carrier transport effect.

[0127] Further, the heating stage includes the following processes: heating to a preset temperature; after heating from the preset temperature to a peak temperature within a preset time and then cooling back to the preset temperature, where the preset time is 10 s to 30 s. Since the vitreous solvent is in a softened state during the heating stage, the conductive particles can be evenly distributed in the vitreous body. When the preset time is controlled within the above range, the conductive particles have sufficient time to move, aggregate, and be reduced to form a conductive structure, thereby ensuring that both the first conductive structure and the second conductive structure obtained meet the scope of this application.

[0128] Further, in the heat treatment step, the heat treatment temperature is 700 °C to 900 °C. When the heat treatment temperature is controlled within the above range, the diffusion and combination of the conductive particles are promoted, which helps to form a conductive precursor and ensures that the structure of the obtained conductive precursor meets the requirements of this application.

[0129] Further, after the step of applying the paste of the first electrode on the first semiconductor layer and before the step of applying the paste of the second electrode on the second semiconductor layer, the preparation method further includes: drying the paste of the first electrode at a temperature of 100 °C to 300 °C; and / or

[0130] After the step of applying the paste of the second electrode on the second semiconductor layer and before the heat treatment step, drying the paste of the second electrode at a temperature of 100 °C to 300 °C.

[0131] Drying the paste before the heat treatment step can cause some organic solvents in the paste to volatilize, reducing the humidity of the paste, thereby avoiding poor stability of the electrode structure caused by rapid volatilization of organic solvents during the heat treatment process, poor stability of the contact area between the electrode and the semiconductor layer, and many defects in the contact area, making it difficult to effectively improve the photoelectric conversion performance of the solar cell.

[0132] In the first alternative embodiment, the step of providing the silicon substrate includes:

[0133] Sequentially depositing a second dielectric layer and a second semiconductor layer on the backlight surface of the silicon substrate;

[0134] Performing patterning on the second dielectric layer and the second semiconductor layer located on the backlight surface to expose a part of the backlight surface;

[0135] Sequentially depositing a first dielectric layer and a first semiconductor layer on the exposed backlight surface and the second semiconductor layer;

[0136] Removing the first semiconductor layer and the first dielectric layer located on the second semiconductor layer and forming an isolation region between the adjacent second semiconductor layer and the first semiconductor layer.

[0137] The preparation processes of the dielectric layer and the semiconductor layer in this application are not limited, as long as the objectives of this application can be achieved.

[0138] Optionally, the chemical vapor deposition method is used to prepare the second dielectric layer and the second semiconductor layer on the backlight surface. First, high-purity oxygen is introduced to grow the second dielectric layer at 400°C to 650°C. Subsequently, high-purity SiH4 is introduced to prepare the second amorphous silicon layer at 450°C to 700°C. Finally, BCl3 is introduced at 750°C to 1050°C for boron diffusion, and the second amorphous silicon layer crystallizes and dopes to form the second semiconductor layer.

[0139] The second semiconductor and the second dielectric layer are removed by using laser and wet alkali polishing to expose a part of the backlight surface.

[0140] The chemical vapor deposition method is used to prepare the first dielectric layer and the first semiconductor layer on the backlight surface. High-purity oxygen is introduced to grow the first dielectric layer at 400°C to 650°C. Subsequently, high-purity SiH4 is introduced to prepare the first amorphous silicon layer at 450°C to 700°C. Subsequently, POCl3 is introduced at 700°C to 950°C for phosphorus diffusion, so that the first amorphous silicon layer crystallizes and dopes to form the first semiconductor layer.

[0141] By using the above preparation process, it can not only ensure that the doping concentrations of the conductive elements in the first semiconductor layer and the second semiconductor layer of this application are within the scope of this application, but also make the deposited film layer have high flatness and small interface defects, which helps to reduce recombination.

[0142] Among them, after the first semiconductor and the second semiconductor layer are prepared, the light-receiving surface of the silicon substrate is textured and cleaned. After texturing, a textured surface structure is formed on the entire light-receiving surface. The existence of the textured surface structure helps to reduce the reflection of sunlight and improve the absorption rate of sunlight. And, since the first semiconductor layer and the second semiconductor layer are both located on the backlight surface, that is, the first functional layer on the first semiconductor layer and the second functional layer on the second semiconductor layer are prepared simultaneously. The first functional layer and the second functional layer on the backlight surface of the solar cell belong to the same structure. And, the second electrode passes through the second functional layer and is connected to the second semiconductor layer through the second conductive structure. The first electrode passes through the first functional layer and is connected to the first semiconductor layer through the first conductive structure.

[0143] In the second alternative embodiment, the steps of providing the silicon substrate include:

[0144] The second dielectric layer and the second semiconductor layer are sequentially deposited on the light-receiving surface of the silicon substrate;

[0145] The second dielectric layer and the second semiconductor layer on the light-receiving surface are removed to expose a part of the light-receiving surface;

[0146] The first dielectric layer and the first semiconductor layer are sequentially deposited on the backlight surface of the silicon substrate;

[0147] Remove the first dielectric layer and the first semiconductor layer on the backlight surface to expose a part of the backlight surface.

[0148] After the first semiconductor and the second semiconductor layer are prepared, the light-receiving surface of the silicon substrate is textured and cleaned. After texturing, the obtained structure has a textured surface only on the exposed light-receiving surface. Then, a passivation layer is deposited. The textured surface of the light-receiving surface and the second semiconductor layer are deposited with a second passivation layer, and the first semiconductor layer and the exposed backlight surface have a first passivation layer. Among them, the second electrode passes through the second functional layer and is connected to the second semiconductor layer through a second conductive structure, and the first electrode passes through the first functional layer and is connected to the first semiconductor layer through a first conductive structure.

[0149] In addition, the first functional layer can be prepared by atomic layer deposition and / or plasma-enhanced chemical vapor deposition processes, and the second functional layer is prepared by a plasma-enhanced chemical vapor deposition process. Exemplarily, the first functional layer is prepared by atomic layer deposition; or the first functional layer is prepared by a plasma-enhanced chemical vapor deposition process; or when the first functional layer includes a two-layer structure, at least one layer is prepared by a plasma chemical vapor deposition process, and the other layer can be prepared by atomic layer deposition.

[0150] In addition, in order to ensure the flatness of the first dielectric layer and the second dielectric layer films obtained, before depositing the first dielectric layer and the second dielectric layer, the silicon substrate is polished and cleaned to remove metal ions and damage on the surface of the silicon substrate, which helps to improve the photoelectric conversion efficiency of the solar cell.

[0151] In the third alternative embodiment, the steps of providing the silicon substrate include:

[0152] Deposit a second semiconductor layer on the light-receiving surface of the silicon substrate;

[0153] Deposit a first dielectric layer and a first semiconductor layer on the backlight surface of the silicon substrate in sequence.

[0154] Among them, before the step of depositing the second semiconductor layer, the light-receiving surface of the silicon substrate is textured and cleaned, and the textured surface is on the light-receiving surface after texturing; after the steps of depositing the first dielectric layer and the first semiconductor layer on the backlight surface, a second passivation layer is deposited on the second semiconductor layer on the light-receiving surface, and a first passivation layer is deposited on the first semiconductor layer. Among them, the second electrode passes through the second functional layer and is connected to the second semiconductor layer through a second conductive structure, and the first electrode passes through the first functional layer and is connected to the first semiconductor layer through a first conductive structure.

[0155] The technical solution of the present application will be further explained below in conjunction with more specific embodiments and experimental test results.

[0156] Example 1:

[0157] An embodiment of the present application provides a solar cell. The doping concentration of the N-type conductive element in the first semiconductor layer of the solar cell is 5×10 20 atoms / cm 3 , and the doping concentration of the P-type conductive element in the second semiconductor layer is 5×10 19 atoms / cm 3 . In any 1 mm×1 mm area, the number of the first conductive structures is 5×10 5 . In any 1 mm×1 mm area of the contact between the second electrode and the second semiconductor layer, the number of the second conductive structures is 1×10 5 . The projected size of any first conductive structure on the first semiconductor layer is 1500 nm, and the projected size of any second conductive structure on the second semiconductor layer is 900 nm.

[0158] An embodiment of the present application also provides a method for manufacturing the solar cell:

[0159] The step of providing a silicon substrate includes:

[0160] Polishing: Select an N-type silicon wafer as the substrate, polish the surface of the N-type silicon wafer, remove damage, wire marks, and oil stains, and form a flat and clean silicon substrate;

[0161] The second dielectric layer and the second semiconductor layer: Use plasma chemical vapor deposition to prepare the second dielectric layer and the second semiconductor layer on the backlight surface. First, introduce high-purity oxygen to grow the second dielectric layer at 400°C to 650°C, then introduce high-purity SiH4 to prepare the second amorphous silicon layer at 450°C to 700°C, and finally introduce BCl3 at 750°C to 1050°C for boron diffusion. After the second amorphous silicon layer is crystallized and doped, the second semiconductor layer is formed;

[0162] Use a laser and wet chemical polishing to remove the second semiconductor and the second dielectric layer, exposing a part of the backlight surface;

[0163] The first dielectric layer and the first semiconductor layer: Use chemical vapor deposition to prepare the first dielectric layer and the first semiconductor layer on the backlight surface. Introduce high-purity oxygen to grow the first dielectric layer at 400°C to 650°C, then introduce high-purity SiH4 to prepare the first amorphous silicon layer at 450°C to 700°C, and then introduce POCl3 at 700°C to 950°C for phosphorus diffusion, so that the first amorphous silicon layer is crystallized and doped to form the first semiconductor layer.

[0164] Texturing cleaning: Use a chain HF equipment to remove the borophosphosilicate glass on the light-receiving surface of the silicon substrate due to boron / phosphorus diffusion. In a tank-type equipment, use sodium hydroxide with a volume ratio of 7:1 and an additive of model TS40, maintain the temperature at 80 °C for 7 minutes, so that a textured structure is formed on the light-receiving surface of the silicon substrate, and the thinning amount of the silicon substrate is controlled within 5 μm.

[0165] On the backlight surface of the silicon substrate, the first functional layer and the second functional layer are prepared by plasma-enhanced chemical vapor deposition.

[0166] Print the paste for making the first electrode on the first functional layer, and dry the paste of the first electrode at 200 °C. Then print the paste for making the second electrode on the second functional layer, and dry the paste of the second electrode at 200 °C.

[0167] Heat treatment: Make the contact interface between the first electrode and the first semiconductor layer form the first conductive precursor, and make the contact interface between the second electrode and the second semiconductor layer form the second conductive precursor. Among them, the heat treatment temperature is 900 °C.

[0168] Light injection: Make the first conductive precursor transform into the first conductive structure, and the second conductive precursor transform into the second conductive structure. And the second electrode passes through the second functional layer and is connected to the second semiconductor layer through the second conductive structure. The first electrode passes through the first functional layer and is connected to the first semiconductor layer through the first conductive structure. The steps of light injection include:

[0169] Heating stage: Heat the first conductive precursor and the second conductive precursor. Specifically, first heat to 350 °C; after heating from 350 °C to 500 °C within 20 s, then cool down to 350 °C;

[0170] When the temperature in the heating stage drops from 500 °C to 350 °C, apply light to the solar cell. The temperature of the light is 200 °C, and the energy density of the light is 100 kW / m 2 .

[0171] Example 2:

[0172] The difference between this example and Example 1 is only that the doping concentration of the N-type conductive element in the first semiconductor layer of the solar cell is 1×10 20 atoms / cm 3 , and the doping concentration of the P-type conductive element in the second semiconductor layer is 9×10 19 atoms / cm 3 .

[0173] Example 3:

[0174] The difference between this embodiment and the first embodiment is only that the projected size of any first conductive structure on the first semiconductor layer is 500 nm, and the projected size of any second conductive structure on the second semiconductor layer is 1000 nm.

[0175] Embodiment 4:

[0176] The difference between this embodiment and the first embodiment is only that the solar cell structure of this embodiment is a passivated contact solar cell. The light-receiving surface of the solar cell is partially provided with a second dielectric layer and a second semiconductor layer, and the backlight surface is partially provided with a first dielectric layer and a first semiconductor layer. For the structural schematic diagram of the manufactured solar cell, see Figure 7 。

[0177] Embodiment 5:

[0178] The difference between this embodiment and the first embodiment is only that the solar cell structure of this embodiment is a passivated contact solar cell. The light-receiving surface of the manufactured solar cell is provided with a second semiconductor layer, and the backlight surface is provided with a first dielectric layer and a first semiconductor layer. For the structural schematic diagram of the manufactured solar cell, see Figure 6 。

[0179] Comparative Example 1:

[0180] The difference between this embodiment and the first embodiment is only that within any 1 mm × 1 mm area, the number of first conductive structures is 5 × 10 4 pieces, and within any 1 mm × 1 mm area where the second electrode is in contact with the second semiconductor layer, the number of second conductive structures is 5 × 10 4 pieces;

[0181] Comparative Example 2:

[0182] The difference between this comparative example and the first embodiment is only that the density of the first conductive structure is less than the density of the second conductive structure.

[0183] Performance Test

[0184] The following relevant tests were conducted on the solar cells prepared in Embodiments 1 to 6 and Comparative Examples 1 to 2:

[0185] For a solar cell provided in this application, a halm test and sorting device was used to conduct performance tests on aspects such as open-circuit voltage, short-circuit current, and fill factor. The halm machine is a device that simulates sunlight, and is equipped with an electronic load, data acquisition and calculation devices, etc., for testing the electrical performance of photovoltaic devices (including solar cells). The silicon wafer of the tested solar cell was controlled to be 182 in size, the calibrated light intensity was 1000 ± 5 W / m 2 , the test temperature was 25°C ± 0.5°C, and the experimental test results are as follows.

[0186] Table 1 Performance test results of solar cells

[0187]

[0188] Analysis of the data of Examples 1 to 3 and Comparative Examples 1 and 2 shows that the performance of the examples is better than that of the comparative examples. This is because the density of the first conductive structure in the examples is greater than that of the second conductive structure, and both are within the scope of this application. Therefore, it helps to improve the diffusion ability of carriers in the first semiconductor layer, thereby helping to reduce the probability of carrier scattering and recombination and improving the photoelectric conversion efficiency of the solar cell.

[0189] Analysis of the data of Examples 1 and 2 shows that the performance of Example 1 is higher than that of Example 2. This is because the doping concentration of the N-type conductive element in Example 1 in the first semiconductor layer is higher, and the doping concentration of the P-type conductive element in the second semiconductor layer is lower. Therefore, the concentration of carriers in the first semiconductor layer is higher. In addition, the matching degree between the carrier concentration in the first semiconductor layer and the density of the first conductive structure is higher, which promotes the improvement of the carrier transmission rate. Thus, it helps to improve the conductivity of the solar cell, reduce the probability of carrier recombination and scattering, and improve the photoelectric conversion efficiency of the solar cell to a higher degree.

[0190] Analysis of the data of Examples 1 and 3 shows that the performance of Example 1 is better than that of Example 3. This is because the projected size of the first conductive structure of Example 1 in the first semiconductor layer is higher than that of Example 3, and the projected size of the second conductive structure in the second semiconductor layer is smaller than that of Example 3. Therefore, the content of carriers that any first conductive structure in Example 1 can transmit is higher, so it can effectively improve the carrier transmission ability in the first semiconductor layer, thereby effectively reducing the probability of carrier scattering and recombination in the first semiconductor layer and improving the performance of the solar cell.

[0191] Analysis of the data of Example 1, Example 4 and Example 5 shows that whether it is a back-contact solar cell or a passivated-contact solar cell (including a solar cell with passivated-contact structures locally provided on both the light-receiving surface and the backlight surface, or a solar cell with a passivated-contact structure only provided on the backlight surface), as long as the density of the first conductive structure is controlled to be greater than that of the second conductive structure, it helps to improve the carrier transmission rate and the performance of the solar cell.

[0192] The above has introduced in detail the solar cell, its manufacturing method, and the photovoltaic module disclosed in the embodiments of this application. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the technical solutions of the embodiments of this application: At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A solar cell, characterized in that, The solar cell includes: a silicon substrate; a first semiconductor layer and a second semiconductor layer disposed on the silicon substrate, the first semiconductor layer being doped with an N-type conductive element, and the second semiconductor layer being doped with a P-type conductive element; a first electrode, the first electrode being electrically connected to the first semiconductor layer through a plurality of first conductive structures; a second electrode, the second electrode being electrically connected to the second semiconductor layer through a plurality of second conductive structures; wherein, the doping concentration of the N-type conductive element in the first semiconductor layer is higher than the doping concentration of the P-type conductive element in the second semiconductor layer, and the density of the first conductive structures is greater than the density of the second conductive structures; the projected size of the first conductive structure on the first semiconductor layer is greater than or equal to the projected size of the second conductive structure on the second semiconductor layer, the projected size of any one of the first conductive structures on the first semiconductor layer is 100 nm to 2000 nm, and the projected size of any one of the second conductive structures on the second semiconductor layer is 100 nm to 1000 nm.

2. The solar cell according to claim 1, wherein In any 1 mm × 1 mm area of the contact between the first electrode and the first semiconductor layer, the number of the first conductive structures is 1 × 10 5 to 1 × 10 6 ; in any 1 mm × 1 mm area of the contact between the second electrode and the second semiconductor layer, the number of the second conductive structures is 5 × 10 4 to 5 × 10 5 .

3. The solar cell according to claim 1, characterized in that, Any one of the first conductive structures and any one of the second conductive structures are both in a vein shape.

4. The solar cell according to claim 3, characterized in that, Any one of the first conductive structures includes a plurality of strip-shaped first structures diverging in the direction of the first electrode; Any one of the second conductive structures includes a plurality of strip-shaped second structures diverging in the direction of the second electrode.

5. The solar cell according to claim 4, characterized in that, Any one of the first structures includes a first crystalline main chain, and a plurality of first crystalline side chains extending in a growth direction different from that of the first crystalline main chain; Any one of the second structures includes a second crystalline main chain, and a plurality of second crystalline side chains extending in a growth direction different from that of the second crystalline main chain.

6. The solar cell according to claim 5, characterized in that, Both the first structure and the second structure are formed by crystallization polymerization of a plurality of conductive particles.

7. The solar cell according to claim 6, wherein The elements in the conductive particles include one or a combination of silver element, aluminum element, copper element, and lead element.

8. The solar cell according to claim 1, wherein, The doping concentration of the N-type conductive element in the first semiconductor layer is 1×10 20 atoms / cm 3 ~1×10 21 atoms / cm 3 , The doping concentration of the P-type conductive element in the second semiconductor layer is 1×10 18 atoms / cm 3 ~1×10 20 atoms / cm 3 .

9. The solar cell according to any one of claims 1 to 8, characterized in that, The first semiconductor layer and the second semiconductor layer are disposed on the backlight surface of the silicon substrate, the first semiconductor layer and the second semiconductor layer are separated by an isolation region, and the first semiconductor layer and the second semiconductor layer are arranged in an interdigitated pattern.

10. The solar cell according to claim 9, characterized in that, The solar cell further includes a first dielectric layer disposed between the first semiconductor layer and the silicon substrate, and a second dielectric layer disposed between the second semiconductor layer and the silicon substrate.

11. The solar cell according to any one of claims 1 to 8, characterized in that, The silicon substrate is of N-type, the second semiconductor layer is disposed on the light-receiving surface of the silicon substrate, the first semiconductor layer is disposed on the backlight surface of the silicon substrate, and a first dielectric layer is further disposed between the first semiconductor layer and the silicon substrate.

12. The solar cell according to claim 11, characterized in that, A plurality of the first semiconductor layers are disposed on the backlight surface, any one of the first semiconductor layers is disposed on a partial region of the backlight surface, and adjacent first semiconductor layers are separated by a first separation region; and / or, a plurality of the second semiconductor layers are disposed on the light-receiving surface, any one of the second semiconductor layers is disposed on a partial region of the light-receiving surface, and adjacent two second semiconductor layers are separated by a second separation region, wherein a matte structure is disposed on the second separation region.

13. A method for preparing a solar cell according to any one of claims 1 to 12, characterized in that, The preparation method includes the following steps: Provide the silicon substrate, on which the first semiconductor layer and the second semiconductor layer are disposed; Apply the paste for fabricating the first electrode on the first semiconductor layer, and apply the paste for fabricating the second electrode on the second semiconductor layer; Perform heat treatment to form a first conductive precursor at the contact interface between the first electrode and the first semiconductor layer, and form a second conductive precursor at the contact interface between the second electrode and the second semiconductor layer; Perform photo-injection to convert the first conductive precursor into a first conductive structure and the second conductive precursor into a second conductive structure, thereby fabricating the solar cell.

14. The preparation method according to claim 13, characterized in that, The step of photo-injection includes: A heating stage, heating the first conductive precursor and the second conductive precursor, and the peak temperature of the heating stage is 400°C to 650°C; When the temperature in the heating stage drops from the peak temperature to a preset temperature, light is applied to the solar cell, the temperature of the light is 50°C to 400°C, and the energy density of the light is 10 kW / m 2 ~100 kW / m 2 ; Wherein, the preset temperature is 320°C to 360°C.

15. The preparation method according to claim 14, characterized in that, The heating stage includes the following processes: Heat to the preset temperature; After heating from the preset temperature to the peak temperature within a preset time and then cooling down to the preset temperature, wherein the preset time is 10s to 30s.

16. The preparation method according to claim 13, characterized in that, Any one of the first conductive precursors includes a plurality of first crystal main chains diverging in the direction of the first electrode; Any one of the second conductive precursors includes a plurality of second crystal main chains diverging in the direction of the second electrode.

17. The preparation method according to claim 13, characterized in that, In the step of heat treatment, the heat treatment temperature is 700°C to 900°C.

18. The preparation method according to claim 13, characterized in that, The step of providing the silicon substrate includes: Deposit a second dielectric layer and the second semiconductor layer on the backlight surface of the silicon substrate in sequence; Perform patterning on the second dielectric layer and the second semiconductor layer located on the backlight surface to expose a part of the backlight surface; Deposit a first dielectric layer and the first semiconductor layer on the exposed backlight surface and the second semiconductor layer in sequence; Remove the first semiconductor layer and the first dielectric layer on the second semiconductor layer, and form an isolation region between adjacent second semiconductor layers and the first semiconductor layer.

19. The preparation method according to claim 13, characterized in that, The step of providing the silicon substrate includes: Deposit the second semiconductor layer on the light-receiving surface of the silicon substrate; Deposit a first dielectric layer and the first semiconductor layer on the backlight surface of the silicon substrate in sequence.

20. A photovoltaic module, characterized in that, Includes: The solar cell according to any one of claims 1 to 12, or the solar cell fabricated by the fabrication method according to any one of claims 13 to 19.

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