NL2034509A - Solar cell and photovoltaic module - Google Patents

Abstract

The embodiments of the present application relate to the technical field of solar cells, in particular to a solar cell and a photovoltaic module. and the solar cell includes a substrate 5 having a front surface and a rear surface opposite to the front surface, where the front surface includes a metal pattern region and a non metal pattern region. The solar cell further includes a first tunneling layer and a first doped conductive layer arranged on the metal pattern region of the front surface of the substrate and arranged in sequence in a direction away from the front surface of the substrate, where the first doped conductive layer has a same type of doping lO elements as the sub strate. The solar cell further includes a second tunneling layer and a second doped conductive layer arranged on the rear surface of the substrate and arranged in sequence in a direction away from the rear surface of the substrate, where the second doped conductive layer has different type of doping elements from the first doped conductive layer. The solar cell further includes a diffusion region defined in the metal pattern region of the front surface 15 of the substrate, where a top of the diffusion region is in contact with a bottom surface of the first tunneling layer, and a doping element concentration of the diffusion region is greater than a doping element concentration of the substrate. The embodiments of the present application are conducive to improving the photoelectric conversion performance of the solar cell. 20 (FIG.1) 23

Description

SOLAR CELL AND PHOTOVOLTAIC MODULE

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of solar cells, and in 5S particular to a solar cell and a photovoltaic module.

BACKGROUND

[0002] A solar cell has desirable photoelectric conversion capability. In a tunnel oxide passivated contact (TOPCON) solar cell, a tunneling oxide layer and a doped conductive layer are prepared on one of surfaces of a substrate, which are configured to suppress carrier recombination on the surface of the substrate and enhance the passivation effect on the substrate.

The tunneling oxide layer has a desirable chemical passivation effect, and the doped conductive layer has a desirable field passivation effect. In addition, in order to transmit and collect the photogenerated carriers generated by the solar cell, a front metal electrode is further prepared on the surface of the substrate surface, and the front metal electrode is in electrical contact with the doped conductive layer, enabling the front metal electrode to collect carriers in the doped conductive layer.

[0003] However, at present, the solar cell has a problem of low photoelectric conversion efficiency.

SUMMARY

[0004] Embodiments of the present application provide a solar cell and a photovoltaic module, which are at least beneficial for improving the photoelectric conversion efficiency of the solar cell.

[0005] A solar cell is provided according to the embodiments of the present application, and the solar cell includes a substrate having a front surface and a rear surface opposite to the front surface, where the front surface includes a metal pattern region and a non metal pattern region.

The solar cell further includes a first tunneling layer and a first doped conductive layer arranged on the metal pattern region of the front surface of the substrate and arranged in sequence in a direction away from the front surface of the substrate, where the first doped conductive layer has a same type of doping elements as the substrate. The solar cell further includes a second 1 tunneling layer and a second doped conductive layer arranged on the rear surface of the substrate and arranged in sequence in a direction away from the rear surface of the substrate, where the second doped conductive layer has different type of doping elements from the first doped conductive layer. The solar cell further includes a diffusion region defined in the metal pattern region of the front surface of the substrate; where a top of the diffusion region is in contact with a bottom surface of the first tunneling layer, and a doping element concentration of the diffusion region is greater than a doping element concentration of the substrate.

[0006] In some embodiments, the doping element concentration of the diffusion region gradually decreases in a direction from the first doped conductive layer to the substrate.

[0007] In some embodiments, a doping element concentration of the first doped conductive layer 1s greater than the doping element concentration of the diffusion region.

[0008] In some embodiments, a ratio of the doping element concentration of the diffusion region to the doping element concentration of the substrate is provided between 10 and 1x10”.

[0009] In some embodiments, the doping element concentration of the diffusion region is provided between 110% atom/cm® and 1x10%*!atom/cm?, and the doping element concentration of the substrate is provided between 1x10"atom/cm? and 1x10'7atom/cm?.

[0010] In some embodiments, a ratio of a thickness of the diffusion region to a thickness of the substrate is provided between 2x10 and 1.5%107.

[0011] In some embodiments, a ratio of a thickness of the diffusion region to a thickness of the first doped conductive layer is provided between 0.5 and 8.

[0012] In some embodiments, a depth of the diffusion region is provided between 50 nm and 300 nm.

[0013] In some embodiments, a ratio of a width of the diffusion region to a width of the substrate is provided between 0.01 and 0.15.

[0014] In some embodiments, the width of the diffusion region is provided between 20 um to 200 um.

[0015] In some embodiments, the solar cell further includes a front electrode electrically connected to the first doped conductive layer.

[0016] In some embodiments, the metal pattern region of the front surface of the substrate has a first roughness, the non metal pattern region has a second roughness, and the first roughness is greater than the second roughness.

[0017] In some embodiments, the solar cell further includes a first passivation layer having a first portion and a second portion, where the first portion of the first passivation layer is 2 configured to cover the front surface of the substrate, and the second portion of the first passivation layer is configured to cover a surface of the first doped conductive layer away from the substrate.

[0018] In some embodiments, a surface of the first portion of the first passivation layer away from the substrate is not flush with a surface of the second portion of the first passivation layer away from the substrate.

[0019] In some embodiments, the solar cell further includes a second passivation layer configured to cover a surface of the second doped conductive layer away trom the substrate.

[0020] In some embodiments, the front surface of the substrate has a pyramid structure, and the rear surface of the substrate has a staged protrusion structure; a height of the pyramid structure 1s greater than a height of the staged protrusion structure, and a bottom of the pyramid structure is smaller than a bottom of the staged protrusion structure in size.

[0021] In some embodiments, the substrate is an N-type semiconductor substrate, the first doped conductive layer is an N-type doped conductive layer, and the second doped conductive layer is a P-type doped conductive layer.

[0022] In some embodiments, materials of the first doped conductive layer and the second doped conductive layer include at least one of silicon carbide, amorphous silicon, microcrystalline silicon, or polycrystalline silicon.

[0023] In some embodiments, the first tunneling layer has different thickness from the second tunneling layer.

[0024] Accordingly, a photovoltaic module is further provided according to the embodiments of the present application, the photovoltaic module includes at least one cell string, where the at least one cell string is formed by connecting multiple solar cells, each of the multiple solar cells being a solar cell according to any one above. The photovoltaic module further includes at least one package layer configured to cover a surface of the at least one cell string and at least one cover plate configured to cover a surface of the at least one package layer away from the at least one cell string.

[0025] The technical solutions provided according to the embodiments of the present application have at least the following advantages.

[0026] In the technical solution of the solar cell provided according to the embodiments of the present application, a first tunneling layer and a first doped conductive layer are formed only in the metal pattern region of the front surface of the substrate, which can reduce the absorption of the first doped conductive layer to incident light irradiated to the front surface. 3

The diffusion region is only provided in the metal pattern region of the substrate, that is, the diffusion region is provided corresponding to the first tunneling layer, and the doping element concentration of the diffusion region is greater than the doping element concentration of the substrate. In this way, the carriers in the substrate can be transported to the doped conductive layer through the diffusion region, thus making the diffusion region act as a carrier transmission channel. In regions outside the metal pattern region, the absence of a diffusion region can prevent serious carrier recombination problems in regions where the first tunneling layer and the first doped conductive layer are not provided. In addition, a second tunneling layer and a second doped conductive layer are arranged on the rear surface, and the doping element concentration of the second doped conductive layer is different from the doping element concentration of the substrate, thereby forming a PN junction with the substrate. That is, the first doped conductive layer on the front surface does not form a PN junction with the substrate, thereby avoiding the problem of serious carrier recombination in the metal pattern region on the front surface caused by the formed PN junction. In addition, a passivation contact structure are formed on both the front surface and the rear surface, which prevents serious carrier recombination problems in the metal pattern region on the front surface, and improves the double-sided ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments are described as examples with reference to the corresponding figures in the accompanying drawings, and the exemplary description does not constitute a limitation to the embodiments. The figures in the accompanying drawings do not constitute a proportion limitation unless otherwise stated.

[0028] FIG. 1 is a schematic structural view of a cross section of a solar cell provided according to an embodiment of the present application;

[0029] FIG. 2 is a schematic structural view of another cross section of the solar cell provided according to an embodiment of the present application;

[0030] FIG. 3 is a schematic structural view of still another cross section of the solar cell provided according to an embodiment of the present application; and

[0031] FIG. 4 is a schematic structural view of a photovoltaic module provided according to another embodiment of the present application. 4

DETAILED DESCRIPTION

[0032] It is known from the background technology that the photoelectric conversion efficiency of the solar cells in the prior art is low.

[0033] Itis found in the analysis that one of the reasons for the low photoelectric conversion efficiency of the solar cell in the prior art is that, currently, a diffusion process is commonly performed on the front surface of the substrate to convert a part of the substrate into an emitter, which has different types of doping elements from the substrate, thereby forming a PN junction with the substrate. However, this structure will lead to excessive carrier recombination in the metal pattern region on the front surface of the substrate, which will affect the open circuit voltage and the conversion efficiency of the solar cell.

[0034] The embodiments of the present application provide a solar cell, in which the first tunneling layer and the first doped conductive layer are formed only in the metal pattern region of the front surface of the substrate, which can reduce the absorption of the first doped conductive layer to incident light irradiated to the front surface. The diffusion region is only provided in the metal pattern region of the substrate. In this way, the carriers in the substrate can be transported to the doped conductive layers through the diffusion region. In regions outside the metal pattern region, the absence of a diffusion region can prevent serious carrier recombination problems in regions where the first tunneling layer and the first doped conductive layer are not provided. In addition, the second tunneling layer and the second doped conductive layer are arranged on the rear surface, and the doping element concentration of the second doped conductive layer is different from the doping element concentration of the substrate, thereby forming a PN junction with the substrate. That is, the first doped conductive layer on the front surface does not form a PN junction with the substrate, thereby avoiding the problem of serious carrier recombination in the metal pattern region on the front surface caused by the formed PN junction.

[0035] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art may appreciate that, in the various embodiments of the present application, numerous technical details are set forth in order to provide the reader with a better understanding of the present application. However, the technical solutions claimed in the present application may be implemented without these technical details and various changes and modifications based on the following embodiments.

[0036] FIG. 1 is a schematic structural view of a cross section of a solar cell provided according to an embodiment of the present application. 5

[0037] Referring to FIG. 1, the solar cell includes a substrate 100 having a front surface and a rear surface opposite to the front surface, where the front surface includes a metal pattern region and a non metal pattern region. The solar cell further includes a first tunneling layer 110 and a first doped conductive layer 120 arranged on the metal pattern region of the front surface of the substrate 100 and arranged in sequence in a direction away from the front surface of the substrate 100. The first doped conductive layer 120 has the same type of doping elements as the substrate 100. The solar cell further includes a second tunneling layer 140 and a second doped conductive layer 150 arranged on the rear surface of the substrate 100 and arranged in sequence in a direction away from the rear surface of the substrate 100, where the second doped conductive layer 150 has different type of doping elements from the first doped conductive layer 120. The solar cell further includes a diffusion region 130 defined in the metal pattern region of the front surface of the substrate 100, where a top of the diffusion region 130 is in contact with a bottom surface of the first tunneling layer 110, and a doping element concentration of the diffusion region 130 is greater than a doping element concentration of the substrate 100.

[0038] On the front surface of the substrate 100, only the first tunneling layer 110 and the first doped conductive layer 120 are formed in the metal pattern region, which can reduce the absorption of the first doped conductive layer 120 to incident light irradiated to the front surface.

The second tunneling layer 140 and the second doped conductive layer 150 are arranged on the rear surface, and the doping element concentration of the second doped conductive layer 150 is different from the doping element concentration of the substrate 100, thereby forming a PN junction with the substrate 100. In other words, the first doped conductive layer 120 on the front surface does not form a PN junction with the substrate 100, thereby avoiding the serious problem of carrier recombination in the metal pattern region on the front surface caused by the formed PN junction. Moreover, the second tunneling layer 140 and the second doped conductive layer 150 on the rear surface are configured to cover the rear surface of the substrate 100 as a whole, so that the PN junction formed between the second doped conductive layer 150 and the substrate 100 is bigger, resulting in a larger number of hole electron pairs generated, thus increasing the carrier concentration of carriers in the second doped conductive layer 150 and the substrate 100.

[0039] In addition, the diffusion region 130 is formed only in the metal pattern region of the substrate 100, which is served as a heavily doped region. Carriers in the substrate 100 can be easily transported to the doped conductive layers through the diffusion region 130, that is, the 6 diffusion region 130 is served as a carrier transport channel. It is worth noting that in the embodiments of the present application, the diffusion region 130 is not provided in the non metal pattern region of the substrate 100, so that the carrier concentration on the non metal pattern region of the front surface of the substrate 100 is not excessive, and the problem of serious carrier recombination on the non metal pattern region of the front surface of the substrate 100 is prevented. Moreover, since the diffusion region 130 is only provided in the metal pattern region of the substrate 100, the carriers in the substrate 100 can be centrally transmitted to the diffusion region 130, and then transmitted to the first doped conductive layer 120 via the diffusion region 130, thereby greatly improving the carrier concentration of the first doped conductive layer 120. It is worth noting that the metal pattern region is defined as an electrode region.

[0040] The substrate 100 is configured to receive incident light and generate photogenerated carriers. In some embodiments, the substrate 100 is a silicon substrate, and material of the silicon substrate includes at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon. In other embodiments, the material of the substrate 100 may also be silicon carbide, organic material or multi-component compound. The multi-component compound includes but are not limited to perovskite, gallium arsenide, cadmium telluride, copper indium diselenide, and other materials.

[0041] The front surface and the rear surface of the substrate 100 are configured to receive incoming or reflected light. The first tunneling layer 110 and the first doped conductive layer 120 arranged on the front surface of the substrate 100 are configured to form a passivation contact structure on the front surface of the substrate 100, and the second tunneling layer 140 and the second doped conductive layer 150 on the rear surface of the substrate 100 are configured to form a passivation contact structure on the rear surface of the substrate 100. The passivation contact structures are provided on the front surface and the rear surface of the substrate 100, so that the solar cell is formed into a double-sided tunnel oxide passivated contact (TOPCON) cell. In this way, the passivation contact structures arranged on the front surface and the rear surface of the substrate 100 can play a role in reducing carrier recombination on both the front surface and the rear surface of the substrate 100. Compared to forming a passivation contact structure on only one surface of the substrate 100, the carrier loss of the solar cell is greatly reduced, thereby improving the open circuit voltage and the short circuit current of the solar cell.

[0042] By forming passivation contact structures, the recombination of carriers on the 7 surface of the substrate 100 can be reduced, thereby increasing the open circuit voltage of the solar cell, and improving the photoelectric conversion efficiency of the solar cell.

[0043] The first doped conductive layer 120 and the second doped conductive layer 150 are used to play a field passivation role, which allows minority carriers to escape the interface, thereby reducing minority carrier concentration, making the carrier recombination rate at the interface of the substrate 100 lower, thereby increasing the open circuit voltage, short circuit current, and filling factor of the solar cell, and improving the photoelectric conversion performance of the solar cell.

[0044] In some embodiments, the solar cell further includes a front electrode 160 electrically connected to the first doped conductive layer 120. The PN junction formed on the rear surface of the substrate 100 is used to receive incident light and generate photogenerated carriers. The generated photogenerated carriers are transmitted from the substrate 100 to the first doped conductive layer 120, and then transmitted to the front electrode 160 configured to collect photogenerated carriers. Since the type of doping elements in the first doped conductive layer 120 is the same as the type of doping elements in the substrate 100, the metal contact recombination loss between the front electrode 160 and the first doped conductive layer 120 is reduced, thereby reducing the current carrier contact recombination between the front electrode 160 and the first doped conductive layer 120, and improving the short-circuit current and photoelectric conversion performance of the solar cell. In some embodiments, the front electrode 160 is provided on the metal pattern region of the front surface of the substrate 100.

[0045] In some embodiments, there are doping elements in the substrate 100. The type of doping elements is N-type or P-type. The N-type elements can be group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb) or arsenic (As). The P-type elements can be group

III elements such as boron (B), aluminum (Al), gallium (Ga) or indium (In). For example, in response to the substrate 100 being a P-type substrate, there are P-type doping elements in the substrate 100. Alternatively, in response to the substrate 100 being a N-type substrate, there are N-type doping elements in the substrate 100.

[0046] Specifically, in some embodiments, the substrate 100 is an N-type semiconductor substrate, the first doped conductive layer 120 1s an N-type doped conductive layer, and the second doped conductive layer 150 is a P-type doped conductive layer. The P-type second doped conductive layer 150 forms a PN junction with the N-type substrate 100, thereby forming a rear PN junction. The first doped conductive layer 120 has the same type of doping elements as the substrate 100. Therefore, in response to the front electrode 160 being in electrical 8 contacted with the first doped conductive layer 120 on the front surface of the substrate 100, the metal contact recombination between the first doped conductive layer 120 and the front electrode 160 is reduced, which can reduce the contact recombination of carriers and reduce the current transmission loss.

[0047] In other embodiments, the substrate 100 may also be a P-type semiconductor substrate, the first doped conductive layer 120 may also be a P-type doped conductive layer, and the second doped conductive layer 150 may also be an N-type doped conductive layer.

[0048] In some embodiments, the materials of the first doped conductive layer 120 and the second doped conductive layer 150 include at least one of silicon carbide, amorphous silicon, microcrystalline silicon, or polycrystalline silicon.

[0049] The first tunneling layer 110 and the second tunneling layer 140 are configured to achieve interfacial passivation on the front surface and the rear surface of the substrate 100, to achieve chemical passivation. Specifically, by saturating the dangling bonds on the front surface and the rear surface of the substrate 100, the density of interfacial defect states on the front surface and the rear surface of the substrate 100 is reduced, thereby reducing the recombination center on the front surface and the rear surface of the substrate 100.

[0050] Due to the fact that the passivation contact structure on the front surface is only arranged on the metal pattern region of the front surface of the substrate 100, while the passivation contact structure on the rear surface is arranged on the whole rear surface, and a

PN junction is formed on the rear surface of the substrate 100, which makes easy for carrier recombination to occur on the rear surface of the substrate 100. Based on this, in order to adapt to the different settings of the passivation contact structure on the front surface and the rear surface of the substrate 100, in some embodiments, the thickness of the first tunneling layer 110 and the thickness of the second tunneling layer 140 are provided to be different.

Specifically, in some embodiments, the thickness of the first tunneling layer 110 is smaller than the thickness of the second tunneling layer 140. In this way, the second tunneling layer 140 is allowed to have a better chemical passivation effect on the rear surface of the substrate 100.

The dangling bonds on the back of the substrate 100 are further saturated, which reduces the density of interfacial defect states on the rear surface of the substrate 100, thereby improving the problem of carrier recombination on the back of the substrate 100, and improving the filling factor, short circuit current and open circuit voltage.

[0051] In some embodiments, the materials of the first tunneling layer 110 and the second tunneling layer 140 may be dielectric materials, such as any of silicon oxide, magnesium 9 fluoride, silicon oxide, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide.

[0052] The doping element concentration of the diffusion region 130 is greater than the doping element concentration of the substrate 100, which causes the diffusion region 130 to form a heavily doped region. A high-low junction is formed at the heavily doped region of the substrate 100, which creates a barrier effect for carriers, thus not only increasing the rate and quantity of current carriers in the substrate 100 transmitted to the diffusion region 130, but also enabling the first doped conductive layer 120 to effectively collect carriers. Since the diffusion region 130 is only provided on the metal pattern region of the substrate 100, the carrier concentration of the non metal pattern region on the front surface of the substrate 100 is lower, thereby reducing the recombination of carriers on the non metal pattern region of the front surface of the substrate 100, and reducing the recombination of carriers on the whole front surface of the substrate 100.

[0053] In some embodiments, the doping element concentration of the diffusion region 130 gradually decreases along the direction from the first tunneling layer 110 towards the substrate 100. In this way, compared to the constant doping element concentration of the diffusion region 130 in the direction from the first tunneling layer 110 towards the substrate 100, the doping element concentration of the diffusion region 130 is set to gradually decreases, so that the overall concentration of the diffusion region 130 can be smaller, and the doping element concentration of the diffusion region 130 is not excessive compared to the substrate 100, which prevents excessive carrier concentration of the diffusion region 130 from causing excessive carrier concentration of the diffusion region 130 to accumulate on the front surface of the substrate 100, thereby allowing excessive carrier recombination to occur on the front surface of the substrate 100. In addition, the doping element concentration of the diffusion region 130 gradually decreases, which is conducive to the formation of a concentration gradient in the diffusion region 130, thereby accelerating the transport of carriers in the diffusion region 130.

[0054] In some embodiments, the ratio of the doping element concentration of the diffusion region 130 to the doping element concentration of the substrate 100 is provided between 10 and 1x107, such as 10 and 1x10?, Ix10° and 1x10% 1x10* and 1x105, 1x10° and 1x10°, or 1x10° and 1x107. In this range, on the one hand, the difference in the doping element concentration between the diffusion region 130 and the substrate 100 is not excessive, which can prevent the excessive concentration of the diffusion region 130 from causing an excessive number of carriers to be transported from the diffusion region 130 to the front surface of the 10 substrate 100, resulting in a serious problem of carrier recombination on the front surface of the substrate 100 caused by the accumulation of carriers on the front surface of the substrate 100. On the other hand, within this range, the carrier concentration of the diffusion region 130 is larger than the carrier concentration of the substrate 100, which can lead to the formation of high-low junction between the diffusion region 130 and the substrate 100, so as to ensure that the carriers can form potential barriers, thereby improving the transport ability of the carriers.

[0055] Specifically, in some embodiments, the doping element concentration of the diffusion region 130 is provided between 1x10>atom/em’ and 1x10*'atom/cm’, such as 1-10" atom/cm® and 1 10'%atom/cm?, 1+10'atom/cm® and 1+10'7atom/cm?, 1~10"atom/cm’ and 1x10"atom/cm®, 1x10%atom/ecm® and Ix10atom/em’, 1x10Y%atom/cm® and 1x102%atom/cm or 1x10%%atom/cm? and 1x10?atom/cm?. The doping element concentration of the substrate 100 is provided between 1=10atom/em> and 1x10!7atom/cem’, such as

Ix10atom/em> and 1x10%atom/cm®, 1x10%atom/cm® and 1-10'%atom/cm} or 1=10!6atom/cm’ and 1x1077atom/cm}. In response to the doping element concentration of the diffusion region 130 and the doping element concentration of the substrate 100 being within the above ranges, the diffusion region 130 can serve as a better carrier transport channel, thereby enhancing the carrier collection ability.

[0056] Since the diffusion region 130 serves as a transmission channel, it is necessary to set a larger depth of the diffusion region 130 so that the overall area of the diffusion region 130 is not too small, to enable the diffusion region 130 to transport more carriers. In addition, considering that the doping element concentration of the diffusion region 130 is greater than the doping element concentration of the substrate 100, the depth of the diffusion region 130 cannot be provided to be excessive. Therefore, it is possible to prevent an overall excessive doping element concentration of the substrate 100 caused by the area ratio of the diffusion region 130 to the substrate 100 being excessive, resulting in, thereby preventing serious carrier recombination problems on the front surface of the substrate 100 caused by carrier accumulation on the front surface of the substrate 100. Based on this, in some embodiments, the ratio of the thickness d1 of the diffusion region 130 to the thickness d2 of the substrate 100 is provided between 2x10 and 1.5x1073, for example, it can be 2x 107% and 510%, 5x10 and 8x10 8x107% and 1x10” or 1x10 and 1.5x10°. In this range, the ratio of the thickness of the diffusion region 130 to the thickness of the substrate 100 is not excessive, thereby preventing the area of the diffusion region 130 in the substrate 100 being excessive due to excessively deep depth of the diffusion region 130, resulting in excessive doping concentration of the 11 substrate 100. On the other hand, within this range, the ratio of the thickness of the diffusion region 130 to the thickness of the substrate 100 is not too small, thereby ensuring that the diffusion region 130 has a desirable carrier transport effect.

[0057] In some embodiments, the depth of the diffusion region 130 1s provided between 50 nm and 300 nm, for example, it can be 50 nm and 100 nm, 100 nm and 150 nm, 150 nm and 200 nm, 200 nm and 250 nm, or 250 nm and 300 nm. In this range, it is possible to ensure that the diffusion region 130 forms a high and low junction with the substrate 100, thereby forming a potential barrier for carriers located in the diffusion region 130, and improving the transport efficiency of carriers. In addition, within this range, the depth of the diffusion region 130 is not too deep, which can prevent the overall doping concentration of the substrate 100 from being too deep due to the excessive depth of the diffusion region 130, resulting in a serious current carrying recombination problem on the front surface of the substrate 100.

[0058] In some embodiments, the ratio of the width L1 of the diffusion region 130 to the width L2 of the substrate 100 is provided between 0.01 and 0.15, such as 0.01 and 0.03, 0.03 and 0.05, 0.05 and 0.08, 0.08 and 0.1, 0.1 and 0.13, or 0.13 and 0.15. It can be understood that the larger the ratio of the width of the diffusion region 130 to the width of the substrate 100, the larger the area occupied by the diffusion region 130 in the substrate 100. Based on this, the ratio of the width of the diffusion region 130 to the width of the substrate 100 is provided within this range, so that the width of the diffusion region 130 is not too large compared to the width of the substrate 100, thereby preventing the problem of excessive carrier recombination on the front surface of the substrate 100 caused by the excessive width of the diffusion region 130.

On the other hand, considering that the diffusion region 130 is arranged in the metal pattern region of the substrate 100, the width of the diffusion region 130 is also affected by the width of the metal pattern region. In response to the width of the metal pattern region being small, the width of the front electrode 160 formed in the metal pattern region is small, and the problem of blocking incident light due to the excessive width of the front electrode 160 can be solved.

Therefore, within this range, the width of the diffusion region 130 and the width of the substrate 100 are not excessive. The width of the diffusion region 130 is matched with the width of the metal pattern region, which ensures that the diffusion region 130 serves as a carrier transport channel while achieving better absorption and utilization of incident light by the substrate 100.

Based on this, specifically, in some embodiments, the width of the diffusion region 130 1s provided between 20 um and 200 um. For example, it can be 20 um and 50 um, 50 um and 80 um, 80 um and 120 um, 120 um and 150 pm or 150 um and 200 um. It is worth noting that the 12 ratio of the width L1 of the diffusion region 130 to the width L2 of the substrate 100 herein refer to the ratio of the width L1 of the diffusion region 130 to the width L2 of the substrate 100 in the same direction.

[0059] In some embodiments, the doping element concentration of the first doped conductive layer 120 is greater than the doping element concentration of the diffusion region 130. The first doped conductive layer 120 is configured to play a field passivation role. The field passivation function is specifically to form an electrostatic field on the front surface of the substrate 100 towards the inside of the substrate 100 by the first doped conductive layer 120, which allows minority carriers to escape the interface, and reduces the concentration of minority carriers, thereby reducing the recombination rate of carriers at the interface of the substrate 100. In response to the doping element concentration of the first doped conductive layer 120 being greater than the doping element concentration of the diffusion region 130, on the one hand, the doping element concentration of the doped layer 120 is higher, and the sheet resistance of the first doped conductive layer 120 is lower, which forms a strong electrostatic field in the first doped conductive layer 120, significantly improves the field passivation effect of the first doped conductive layer 120, and further inhibits the recombination of carriers on the front surface, thereby increasing the carrier concentration, increasing the short circuit current and open circuit voltage, and improving the photoelectric conversion performance of the solar cell. On the other hand, in the direction from the first doped conductive layer 120 towards the substrate 100, a concentration gradient is formed between the first doped conductive layer 120, the diffusion region 130, and the substrate 100, resulting in a Fermi energy level difference between the first doped conductive layer 120 and the diffusion region 130. The energy band bending on the metal pattern region of the front surface of the substrate 100 can effectively block the passage of minority carriers without affecting the transmission of multiple carriers, achieve selective collection of carriers, and further enhance the collection capacity of carriers.

[0060] The diffusion region 130 is arranged directly opposite the first doped conductive layer 120, and the carriers collected in the diffusion region 130 are directly transmitted to the first doped conductive layer 120. Since the front electrode 160 in electrical contact with the first doped conductive layer 120 is configured to collect the carriers, it is necessary to ensure that the thickness of the first doped conductive layer 120 is not too small compared to the diffusion region 130, thereby providing more space for forming electrical contact with the front electrode 160. Based on this, in some embodiments, the ratio of the thickness of the diffusion 13 region 130 to the thickness of the first doped conductive layer 120 is provided between 0.5 and 8,suchas0.5and 1, 1 and 2, 2 and 3,3 and 5, 5 and 6.5, or 6.5 and 8. In this range, the thickness of the first doped conductive layer 120 is not too small compared to the thickness of the diffusion region 130, or even larger compared to the thickness of the diffusion region 130.

Therefore, the difference in Fermi energy levels formed between the first doped conductive layer 120 and the diffusion region 130 is large, which enhances the selective collection of carriers by the first doped conductive layer 120. On the other hand, within this range, the thickness of the first doped conductive layer 120 is not too large compared to the thickness of the diffusion region 130, which can prevent stress damage to the substrate 100 due to the excessive thickness of the first doped conductive layer 120, thereby increasing the interface defects of the substrate 100 and causing more recombination centers at the front surface of the substrate 100.

[0061] Referring to FIG. 2, in some embodiments, the front surface of the substrate 100 has a metal pattern region 1 and a non metal pattern region 2. The metal pattern region 1 of the front surface of the substrate 100 has a first roughness, the non metal pattern region 2 of the front surface of the substrate 100 has a second roughness, and the first roughness is greater than the second roughness. The non metal pattern region 2 is an area on the front surface of the substrate 100 other than the metal pattern region 1. The metal pattern region 1 of the front surface of the substrate 100 has bigger roughness, so that the first tunneling layer 110 formed on the metal pattern region 1 of the front surface of the substrate 100 and the first doped conductive layer 120 have the same or similar morphology as the metal pattern region 1 of the front surface of the substrate 100. That is, the roughness of the metal pattern region 1 of the front surface of the substrate 100 is also big, the front electrode 160 located on the metal pattern region 1 of the front surface of the substrate 100 has a bigger contact area with the front surface of the substrate 100, which is beneficial to reducing the contact resistance between the front electrode 160 and the front surface of the substrate 100. In other words, while maintaining the contact resistance between the front electrode 160 and the front surface of the substrate 100 unchanged, it is possible to provide a smaller width of the front electrode 160, thereby reducing the shielding of the front electrode 160 from incident light and improving the absorption ability of the substrate 100 to incident light.

[0062] Due to the absence of the first tunneling layer 110 and the first doped conductive layer 120 in the non metal pattern region 2, the non metal pattern region 2 is not affected by the absorption of incident light by the first doped conductive layer 120. In addition, the non 14 metal pattern region 2 is also not provided with the front electrode 160, which makes the front electrode 160 not shield the incident light in the non metal pattern region 2. In order to increase the absorption and utilization of incident light by the non metal pattern region 2 of the front surface of the substrate 100, the roughness of the non metal pattern region 2 of the front surface of the substrate 100 is set to be smaller, so that the reflectivity of the non metal pattern region 2 of the front surface of the substrate is lower, thereby reducing the reflection of incident light by the non metal pattern region 2 of the front surface of the substrate 100.

[0063] Specifically, in some embodiments, the metal pattern region of the front surface includes a first pyramid structure 11 and a second pyramid structure 12. The bottom of the first pyramid structure 11 is larger than the bottom of the second pyramid structure 12 in size, and the area ratio of the first pyramid structure 11 in the metal pattern region of the front surface of the substrate is referred to as a first ratio. The non metal pattern of the front surface of includes a third pyramid structure and a fourth pyramid structure. The bottom of the third pyramid structure 1s larger than the bottom of the fourth pyramid structure in size, and the area ratio of the third pyramid structure in the metal pattern region of the front surface of the substrate is referred to as a second ratio, and the first ration is larger than the second ratio. In other words, compared to the area ratio of the third pyramid structure in the non metal pattern region of the front surface of the substrate, the area ratio of the first pyramid structure 11 in the metal pattern region of the substrate is larger. In other words, the first pyramid structure 11 with a bigger size accounts for a bigger area ratio of the metal pattern region of the front surface of the substrate, while the third pyramid structure accounts for a smaller area ratio of the non metal pattern region of the front surface of the substrate. Since a bigger pyramid structure will lead to a greater roughness, the roughness of the metal pattern region is greater compared to the roughness of the non metal pattern region.

[0064] By setting the first pyramid structure 11 with a bigger size on the metal pattern region of the front surface of the substrate, and the third pyramid structure accounting for a smaller area ratio of the non metal pattern region of the front surface of the substrate, which not only achieves a greater roughness in the metal pattern region than in the non metal pattern region, but also ensures that both the metal pattern region and the non metal pattern region of the front surface of the substrate have a desirable antireflection effect.

[0065] In some embodiments, the solar cell further includes a first passivation layer 170 having a first portion and a second portion, where a first portion of the first passivation layer 170 is configured to cover the front surface of the substrate 100, and a second portion of the 15 first passivation layer 170 is configured to cover a surface of the first doped conductive layer 120 away from the substrate 100. The first passivation layer 170 can have a good passivation effect on the front surface of the substrate 100, for example, the first passivation layer 170 is configured to perform a desirable chemical passivation on the hanging bonds on the front surface of the substrate 100, to reduce the defect state density on the front surface of the substrate 100, thereby better inhibiting carrier recombination on the front surface of the substrate 100. The first portion of the first passivation layer 170 is in direct contact with the front surface of the substrate 100, so that there is no first tunneling layer 110 and first doped conductive layer 120 between the first portion of the first passivation layer 170 and the substrate 100. Based on this, the parasitic absorption of incident light by the first doped conductive layer 120 can be reduced. Considering that the first tunneling layer 110 and the first doped conductive layer 120 are not provided on the part of front surface of the substrate 100 opposite to the first portion of the first passivation layer 170, the diffusion region 130 is not provided in the part of the substrate 100 opposite to the first portion of the first passivation layer 170, so that the carrier concentration on the front surface of the substrate 100 in contact with the first portion of the first passivation layer 170 is not excessive, and the problem of more carrier recombination on the front surface of the substrate 100 can be prevented.

[0066] In some embodiments, the front electrode 160 penetrates the first passivation layer 170 to be in electrical contact with the first doped conductive layer 120.

[0067] In some embodiments, a surface of the first portion of the first passivation layer 170 away from the substrate is not flush with a surface of the second portion of the first passivation layer 170 away from the substrate. Specifically, the surface of the first portion of the first passivation layer 170 away from the substrate can be lower than the surface of the second portion of the first passivation layer 170 away from the substrate, so that the first portion located on the front surface of the substrate 100 is not too thick, which prevents stress damage to the front surface of the substrate 100 due to the large thickness of the first portion, thereby preventing more interfacial defects on the front surface of the substrate 100, and generating more carrier recombination centers.

[0068] In some embodiments, the first passivation layer 170 may be a single layer structure, and in other embodiments, the first passivation layer 170 may also be a multi-layer structure.

In some embodiments, the material of the first passivation layer 170 may be at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

[0069] In some embodiments, the solar cell further includes a second passivation layer 180 16 configured to cover a surface of the second doped conductive layer 150 away from the substrate 100. The second passivation layer 180 1s configured to achieve a desirable passivation effect on the rear surface of the substrate 100, which reduces the density of defect states on the rear surface of the substrate 100, and better inhibits carrier recombination on the rear surface of the substrate 100. In some embodiments, the second passivation layer 180 may be a single layer structure, and in other embodiments, the second passivation layer 180 may also be a multi- layer structure. In some embodiments, the material of the second passivation layer 180 may be at least one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

[0070] In some embodiments, the solar cell further includes a rear electrode 190 arranged on the rear surface of the substrate 100, and the rear electrode 190 penetrates the second passivation layer 180 to be in electrical contact with the second doped conductive layer 150.

[0071] Referring to FIG. 3, in some embodiments, the front surface of the substrate 100 has a pyramid structure 10, and the rear surface of the substrate 100 has a staged protrusion structure 13. The pyramid structure 10 is higher than the staged protrusion structure 13, and the bottom of the pyramid structure 10 is smaller than the bottom of the staged protrusion structure 13. Specifically, the staged protrusion structure 13 is a base portion of a pyramid structure, that is, the remaining structure after removing the tip of the pyramid structure. In other words, the pyramid structure arranged on the front surface of the substrate 100 has bigger degree of convexity than the staged protrusion structure arranged on the rear surface of the substrate 100, so that the roughness of the front surface of the substrate 100 is greater than the roughness of the rear surface of the substrate 100. In some embodiments, due to the large amount of incident light received from the front surface of the substrate 100, in order to enhance the absorption ability of the front surface of the substrate 100 to incident light, the pyramid structure 10 is provided on the front surface of the substrate 100, which has a large specific surface area. Therefore, the diffuse reflection effect of the incident light from the front surface of the substrate 100 can be enhanced, resulting in a greater utilization rate of the incident light from the front surface of the substrate 100. Due to the fact that the rear surface of the substrate 100 receives less incident light, it is possible to provide the staged protrusion structure 13 on the rear surface of the substrate 100, so that the roughness of the rear surface of the substrate 100 is less than the roughness of the front surface of the substrate 100. That is, compared to the front surface of the substrate 100, the rear surface of the substrate 100 has relatively flat morphology, which enables the second tunneling layer 140, the second doped conductive layer 150, and the second passivation layer 180 formed on the rear surface of the substrate 100 to 17 have a flat morphology and can be uniformly formed on the rear surface of the substrate 100, which is conducive to improving the passivation effect of the second tunneling layer 140, the second doped conductive layer 150, and the second passivation layer 180 on the rear surface of the substrate 100, thereby further reducing the density of states of defects on the rear surface.

In this way, it is possible to improve the passivation effect on the substrate 100 while improving the utilization rate of incident light, and overall improve the photoelectric conversion performance of the solar cell.

[0072] Due to the formation of a rear PN junction on the rear surface of the substrate 100, the rear surface of the substrate 100 has a relatively flat morphology, which allows the second tunneling layer 140 to be more closely attached to the rear surface of the substrate 100, and allows the photogenerated carriers generated by the PN junction to be smoothly transmitted to the substrate 100, thereby further improving the carrier transmission efficiency.

[0073] In some embodiments, the pyramid structure 10 include a first pyramid structure 11 arranged on the metal pattern region of the front surface of the substrate, and a second pyramid structure 12 arranged on the non metal pattern region of the front surface of the substrate.

[0074] In the solar cell provided according to the above embodiments, the first tunneling layer 110 and the first doped conductive layer 120 are formed only in the metal pattern region of the front surface of the substrate 100, which can reduce the absorption of the first doped conductive layer 120 to incident light irradiated to the front surface. The diffusion region 130 is only provided in the metal pattern region of the substrate 100. In this way, the carriers in the substrate 100 can be transported to the doped conductive layers through the diffusion region 130. In addition, the second tunneling layer 140 and the second doped conductive layer 150 are arranged on the rear surface, and the doping element concentration of the second doped conductive layer 150 is different from the doping element concentration of the substrate 100, thereby forming a PN junction with the substrate 100. That is, the first doped conductive layer 120 on the front surface does not form a PN junction with the substrate 100, thereby avoiding the problem of serious carrier recombination in the metal pattern region on the front surface caused by the formed PN junction.

[0075] Accordingly, a photovoltaic module is further provided according to another aspect of the embodiments of the present application. Referring to FIG. 4, the photovoltaic module includes: at least one cell string, where the at least one cell string is formed by connecting multiple solar cells 101, each of the multiple solar cells 101 is the solar cell 101 according to any one of above embodiments. The photovoltaic module further includes at least one package 18 layer 102 configured to cover a surface of the at least one cell string, and at least one cover plate 103 configured to cover a surface of the at least one package layer 102 away from the at least one cell string. The solar cell 101 is electrically connected to form multiple cell strings in the form of whole or multiple pieces, and the multiple cell strings are electrically connected in series and/or parallel.

[0076] Specifically, in some embodiments, the multiple cell strings can be electrically connected by a conductive strip 104. The at least one package layer 102 is configured to cover the front surface and the rear surface of the solar cell 101. Specifically, the at least one package layer 102 can be an organic package film such as ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene co-elastomer (POE) film or polyethylene terephthalate (PET) film. In some embodiments, the at least one cover plate 103 may be a glass cover plate, a plastic cover plate and other cover plates with light transmission function. Specifically, the surface of the at least one cover plate 103 towards the at least one package layer 102 may be provided with protrusions and recesses, thus increasing the utilization rate of incident light.

[0077] Although the present application is disclosed above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the concept of the present application. The scope of protection shall be subject to the scope defined by the claims of the present application.

[0078] Those of ordinary skill in the art can understand that the above embodiments are specific examples for realizing the present application, and in actual applications, various changes may be made in form and details without departing from the scope of the present application. Any person skilled in the art can make their own changes and modifications without departing from the scope of the present application. Therefore, the protection scope of the present application should be subject to the scope defined by the claims. 19

Claims (20)

Conclusions A solar cell comprising: a substrate (100) having a front surface and a back surface opposite the front surface, the front surface comprising a metal pattern area and a non-metal pattern area; a first tunnel layer (110) and a first doped conductive layer (120) arranged on the metal pattern area of the front surface of the substrate (100) and arranged successively in a direction away from the front surface of the substrate (100); wherein the first doped conductive layer (120) has the same type of doping elements as the substrate (100); a second tunnel layer (140) and a second doped conductive layer (150) arranged on the rear surface of the substrate (100) and arranged sequentially in a direction away from the rear surface of the substrate (100); wherein the second doped conductive layer (150) has a different type of dopant elements than the first doped conductive layer (120); and a diffusion region (130) defined in the metal pattern region of the front surface of the substrate (100); wherein a top of the diffusion region (130) is in contact with a bottom surface of the first tunnel layer (110), and a dopant concentration of the diffusion region (130) is greater than a dopant concentration of the substrate (100). 2. Solar cell according to claim 1, wherein the dopant element concentration of the diffusion region gradually decreases in a direction from the first doped conductive layer to the substrate. 3. Solar cell according to claim 1 or 2, wherein a dopant element concentration of the first doped conductive layer is greater than a dopant element concentration of the second doped conductive layer. The solar cell of claim 1, wherein a ratio of the dopant element concentration of the diffusion region to the dopant element concentration of the substrate is provided between 10 and 12107. 5. Solar cell according to claim 1 or 4, wherein the dopant concentration of the diffusion region is provided between 1x10:5 atom/em' and 1x10? atom/cm®, and the dopant element concentration of the substrate is provided between 1x10" atom/cm' and 1x 1077 atom/cm'. The solar cell of claim 1, wherein a ratio of the thickness of the diffusion region to the thickness of the substrate is provided between 210% and 1.5x10°. The solar cell of claim 1, wherein a ratio of a thickness of the diffusion region to a thickness of the first doped conductive layer is provided between 0.5 and 8. 8. Solar cell according to claim 6 or 7, wherein a depth of the diffusion region is provided between 50 nm and 300 nm. A solar cell according to claim 1 or 6, wherein a ratio of a width of the diffusion region to a width of the substrate is provided between 0.01 and 0.15. The solar cell according to claim 9, wherein the width of the diffusion region is provided between 20 µm and 200 µm. The solar cell of claim 1, further comprising a front electrode electrically connected to the first doped conductive layer. The solar cell of claim 11, wherein the metal pattern area of the front surface of the substrate has a first roughness and the non-metal pattern area has a second roughness, the first roughness being greater than the second roughness. The solar cell of claim 1 or 12, further comprising a first passivation layer having a first portion and a second portion, the first portion of the first passivation layer being configured to cover the front surface of the substrate, and the second portion of the first passivation layer is configured to cover a surface of the first doped conductive layer away from the substrate. 14. Solar cell according to claim 13, wherein a surface of the first part of the first passivation layer away from the substrate is not flush with a surface of the second part of the first passivation layer away from the substrate. The solar cell of claim 1, further comprising a second passivation layer configured to cover a surface of the second doped conductive layer away from the substrate. The solar cell of claim 1, wherein the front surface of the substrate has a pyramid structure, and the rear surface of the substrate has a stepped protrusion structure; a height of the pyramid structure is greater than a height of the stepped protrusion structure, and a bottom of the pyramid structure is smaller in size than a bottom of the stepped protrusion structure. The solar cell of claim 1, wherein the substrate is an N-type semiconductor substrate, the first doped conductive layer is an N-type doped conductive layer and the second doped conductive layer is a P-type doped conductive layer. 18. Solar cell according to claim 1, wherein materials of the first doped conductive layer and of the second doped conductive layer include at least one of silicon carbide, amorphous silicon. microcrystalline silica or polycrystalline silica. 19. Solar cell according to claim 1, wherein the first tunnel layer has a different thickness than the second tunnel layer. 20. Photovoltaic module, comprising: at least one cell string, wherein the at least one cell string is formed by connecting a plurality of solar cells (101), each of the plurality of solar cells (101) being a solar cell (101) according to any one of claims 1 to 19: at least one packaging layer (102) configured to cover a surface of the at least one cell strand: at least one cover plate (103) configured to cover a surface of the at least one packaging layer (102) away from the at least one cell string.