Solar cell, battery assembly, and photovoltaic system

Abstract

The present invention is suitable for the technical field of solar cells, and provides a solar cell, a battery assembly, and a photovoltaic system. The solar cell comprises: a silicon substrate, the surface of which is provided with a P region and an N region; at least one P-type doped polycrystalline silicon layer arranged in the P region and containing a P-type dopant, wherein each P-type doped polycrystalline silicon layer comprises a first portion, a second portion and a third portion which are sequentially arranged in the thickness direction of the P-type doped polycrystalline silicon layer from the silicon substrate to a direction away from the silicon substrate; and at least one N-type doped polycrystalline silicon layer arranged in the N region and containing an N-type dopant, wherein the doping concentration of the P-type dopant of the second portion is greater than the doping concentration of the P-type dopant of the third portion. The solar cell of the present invention can improve the utilization rate of sunlight, and does not affect the passivation effect of the cell, thereby improving the efficiency of the cell.

Description

Solar cell, cell assembly and photovoltaic system

[0001] Cross-reference to Related Applications

[0002] The present disclosure claims priority to the Chinese patent application No. 202411087532.3, filed on August 8, 2024, with the State Intellectual Property Office of China, and entitled “Solar cell, cell assembly and photovoltaic system”, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of solar cells, in particular to a solar cell, a cell assembly and a photovoltaic system. BACKGROUND

[0004] At present, solar cells mainly include bifacial solar cells and back contact solar cells. Among them, the front surface of the back contact solar cell completely avoids the shielding of the metal grid lines compared with the bifacial solar cell, eliminates the optical loss caused by the shielding of the metal grid lines, and can greatly improve the conversion efficiency of the cell.

[0005] In the prior art, the P region of the bifacial solar cell and the back contact solar cell is provided with a P-type doped polysilicon layer, and the N region is provided with an N-type doped polysilicon layer. However, whether it is a bifacial solar cell or a back contact solar cell, the influence of the doping concentration distribution of the P-type dopant of the P-type doped polysilicon layer on the solar cell is usually not considered, and there is a problem that the light transmittance of the P region is low, thereby affecting the cell efficiency.

[0006] DISCLOSURE

[0007] The present disclosure provides a solar cell, which aims to solve the problem that the light transmittance of the P region of the prior art solar cell is low, thereby affecting the cell efficiency.

[0008] The present disclosure is achieved in this way, which provides a solar cell, comprising:

[0009] a silicon substrate, a surface of the silicon substrate is provided with a P region and an N region;

[0010] at least one P-type doped polysilicon layer containing a P-type dopant and arranged in the P region, each P-type doped polysilicon layer comprises a first part, a second part and a third part arranged in turn along the thickness direction thereof and away from the silicon substrate;

[0011] at least one N-type doped polysilicon layer containing an N-type dopant and arranged in the N region;

[0012] The doping concentration of the P-type dopant in the second portion is greater than the doping concentration of the P-type dopant in the third portion.

[0013] In some embodiments, the doping concentration of the P-type dopant in the second portion is greater than the doping concentration of the P-type dopant in the first portion.

[0014] In some embodiments, the doping concentration of the P-type dopant in the third portion is less than the doping concentration of the P-type dopant in the first portion.

[0015] In some embodiments, the doping concentration of the P-type dopant is the sum of the doping concentration of the activated P-type dopant and the doping concentration of the unactivated P-type dopant.

[0016] In some embodiments, the doping concentration of the P-type dopant is the sum of the doping concentration of the activated P-type dopant and the doping concentration of the unactivated P-type dopant.

[0017] In some embodiments, the device further comprises:

[0018] a first passivation layer disposed between the silicon substrate and the first portion of the P-type doped polysilicon layer;

[0019] a second passivation layer disposed between the silicon substrate and the N-type doped polysilicon layer.

[0020] In some embodiments, the device further comprises:

[0021] a third passivation layer disposed on a side of the third portion of the P-type doped polysilicon layer facing away from the silicon substrate;

[0022] a fourth passivation layer disposed on a side of the N-type doped polysilicon layer facing away from the silicon substrate.

[0023] In some embodiments, the first passivation layer contains P-type dopant, and the doping concentration of the P-type dopant in the first passivation layer is greater than the doping concentration of the P-type dopant in the first portion.

[0024] In some embodiments, the third passivation layer contains P-type dopant, and the doping concentration of the P-type dopant in the third passivation layer is greater than the doping concentration of the P-type dopant in the third portion.

[0025] In some embodiments, the first passivation layer and the third passivation layer both contain P-type dopant, and the doping concentration of the P-type dopant in the third passivation layer is less than the doping concentration of the P-type dopant in the first passivation layer.

[0026] In some embodiments, the thickness of the third passivation layer is greater than the thickness of the first passivation layer.

[0027] In some embodiments, the thickness of the second portion is less than the thickness of the first portion.

[0028] In some embodiments, the thickness of the second portion is less than the thickness of the third portion.

[0029] In some embodiments, the ratio of the doping concentration of the second portion to the doping concentration of the third portion is 1-2, and is not equal to 1.

[0030] In some embodiments, the ratio of the doping concentration of the first portion to the doping concentration of the third portion is 1-1.5, and is not equal to 1.

[0031] In some embodiments, each N-type doped polysilicon layer comprises a fourth portion and a fifth portion arranged in sequence along the thickness direction thereof and from the silicon substrate to the direction away from the silicon substrate, and the doping concentration of the N-type dopant of the fourth portion is less than the doping concentration of the N-type dopant of the fifth portion.

[0032] In some embodiments, the solar cell further comprises:

[0033] The first electrode arranged at the P region is in contact with the third portion of the P-type doped polysilicon layer.

[0034] In some embodiments, the solar cell further comprises:

[0035] The second electrode arranged at the N region is in contact with the fifth portion of the N-type doped polysilicon layer.

[0036] In some embodiments, the thickness of the fourth portion is less than the thickness of the fifth portion.

[0037] In some embodiments, the solar cell is a back contact solar cell, and the P region and the N region are located on the same side of the silicon substrate.

[0038] In some embodiments, the solar cell is a bifacial solar cell, and the P region and the N region are located on opposite sides of the silicon substrate, respectively.

[0039] The disclosure also provides a battery assembly comprising the above solar cell.

[0040] The disclosure also provides a photovoltaic system comprising the above battery assembly.

[0041] The P-type doped polysilicon layer of the solar cell provided by the disclosure comprises a first portion, a second portion and a third portion arranged in sequence along the thickness direction thereof and from the silicon substrate to the direction away from the silicon substrate, and the doping concentration of the P-type dopant of the second portion is greater than the doping concentration of the P-type dopant of the third portion. By reducing the doping concentration of the P-type dopant of the third portion of the outermost region of the P-type doped polysilicon layer, the light transmittance of the P-type doped polysilicon layer can be increased, the light transmittance of the P region is improved, and the thickness of the P-type doped polysilicon layer does not need to be reduced. The utilization rate of sunlight by the solar cell is improved, and the passivation effect of the P-type doped polysilicon layer is not affected, ensuring good sunlight utilization rate and battery passivation effect, and the battery efficiency can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0042] Fig. 1 is a sectional view of a solar cell according to an embodiment of the present disclosure;

[0043] Fig. 2 is a sectional view of another solar cell according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0044] For the purpose of the present disclosure, the technical solutions and advantages are more clearly and specifically described below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and do not limit the present disclosure.

[0045] The P-type doped polysilicon layer of the solar cell provided by the embodiment of the present disclosure comprises a first portion, a second portion and a third portion arranged in sequence along the thickness direction of the P-type doped polysilicon layer and away from the silicon substrate, and the doping concentration of the P-type dopant of the second portion is greater than the doping concentration of the P-type dopant of the third portion. By reducing the doping concentration of the P-type dopant of the third portion of the outermost region of the P-type doped polysilicon layer, the light transmittance of the P-type doped polysilicon layer can be increased, the light transmittance of the P region can be improved, the light transmittance of the P region can be increased, and the thickness of the P-type doped polysilicon layer does not need to be reduced. The utilization rate of solar energy by the solar cell is improved, and the passivation effect of the P-type doped polysilicon layer is not affected, which ensures good utilization rate of solar energy and passivation effect of the cell, and can improve the efficiency of the cell.

[0046] Please refer to Figs. 1 and 2, the embodiment of the present disclosure provides a solar cell, comprising:

[0047] a silicon substrate 1, the surface of the silicon substrate 1 is provided with a P region 11 and an N region 12;

[0048] at least one P-type doped polysilicon layer 2 containing P-type dopant arranged in the P region 11, each P-type doped polysilicon layer 2 comprises a first portion 21, a second portion 22 and a third portion 23 arranged in sequence along the thickness direction of the P-type doped polysilicon layer 2 and away from the silicon substrate 1;

[0049] at least one N-type doped polysilicon layer 3 containing N-type dopant arranged in the N region 12;

[0050] wherein the doping concentration of the P-type dopant of the second portion 22 is greater than the doping concentration of the P-type dopant of the third portion 23.

[0051] In the embodiments of the present disclosure, the doping concentration of the P-type dopant is the average value or the peak value of the doping concentration of the P-type dopant, and the doping concentration of the N-type dopant is the average value or the peak value of the doping concentration of the N-type dopant; wherein the peak value is the maximum doping concentration value. When the doping concentration of the P-type dopant or the doping concentration of the N-type dopant is compared, the average value of the doping concentration is compared at the same time or the peak value of the doping concentration is compared at the same time. It can be understood that the doping concentration of the P-type dopant in any region of the second part 22 is greater than the doping concentration of the P-type dopant in any region of the third part 23; or the peak value of the doping concentration of the P-type dopant in any region of the second part 22 is greater than the peak value of the doping concentration of the P-type dopant in any region of the third part 23.

[0052] Please refer to FIG. 1, as an embodiment of the present application, the solar cell is a back contact solar cell, and the P region 11 and the N region 12 are located on the same side of the silicon substrate 1. Among them, the silicon substrate 1 includes a front surface 101 and a back surface 102 opposite to the front surface 101, the front surface 101 of the silicon substrate 1 is the light-receiving surface of the back contact solar cell, the back surface 102 of the silicon substrate 1 is the back surface of the back contact solar cell, and the P region 11 and the N region 12 are both located on the back surface 102 of the silicon substrate 1.

[0053] Among them, the P region 11 and the N region 12 are both multiple, and the multiple P regions 11 and the multiple N regions 12 are sequentially and alternately arranged, and the adjacent P region 11 and the N region 12 are provided with an isolation region 13. The isolation region 13 can be a groove or a gap.

[0054] Please refer to FIG. 2, as another embodiment of the present application, the solar cell is a double-sided solar cell, and the P region 11 and the N region 12 are located on opposite sides of the silicon substrate 1. Among them, the silicon substrate 1 includes a front surface 101 and a back surface 102 opposite to the front surface 101, the front surface 101 of the silicon substrate 1 is the light-receiving surface of the double-sided solar cell, the back surface 102 of the silicon substrate 1 is the back surface of the double-sided solar cell, and the P region 11 and the N region 12 are located on the front surface 101 and the back surface 102 of the silicon substrate 1, respectively.

[0055] Among them, the P region 11 shown in FIG. 2 is located on the front surface 101 of the silicon substrate 1, and the N region 12 is located on the back surface 102 of the silicon substrate 1. Among them, the P region 11 can completely cover the front surface 101 of the silicon substrate 1, or only cover part of the front surface 101 of the silicon substrate 1; the N region 12 can completely cover the back surface 102 of the silicon substrate 1, or only cover part of the back surface 102 of the silicon substrate 1. The P region 11 and the N region 12 can also be multiple. Preferably, the P region 11 covers part of the front surface 101 of the silicon substrate 1, and two adjacent P regions 11 are arranged at a distance from each other; the P region 11 only covers part of the back surface 102 of the silicon substrate 1, and two adjacent N regions 12 are arranged at a distance from each other, which can reduce the light parasitic absorption.

[0056] The dashed lines L1 and L2 in FIGS. 1 and 2 are only used to divide the three regions of the first portion 21, the second portion 22 and the third portion 23 of the P-type doped polysilicon layer 2, and do not actually exist. The dashed line L3 in FIGS. 1 and 2 is only used to divide the two regions of the fourth portion 31 and the fifth portion 32 of the N-type doped polysilicon layer 3, and does not actually exist.

[0057] In the embodiments of the present disclosure, the P-type doped polysilicon layer 2 in the P region 11 can be only one layer, or can be a stacked structure composed of multiple layers. The N-type doped polysilicon layer 3 in the N region 12 can be only one layer, or can be a stacked structure composed of multiple layers.

[0058] In the embodiments of the present disclosure, the P-type doped polysilicon layer 2 of the solar cell includes the first portion 21, the second portion 22 and the third portion 23 arranged along the thickness direction of the P-type doped polysilicon layer 2 and away from the silicon substrate 1, and the doping concentration of the P-type dopant in the second portion 22 is greater than the doping concentration of the P-type dopant in the third portion 23. By reducing the doping concentration of the P-type dopant in the outermost region of the P-type doped polysilicon layer 2, the doping concentration of the P-type dopant in the P-type doped polysilicon layer 2 is non-uniformly distributed, but is in a stepped distribution. The light transmittance of the P-type doped polysilicon layer 2 can be increased, the utilization rate of sunlight by the solar cell can be improved, and the total thickness of the P-type doped polysilicon layer 2 does not need to be reduced. In contrast, in a conventional solar cell, the thickness of the doped polysilicon layer needs to be reduced to increase the light transmittance of the doped polysilicon layer, which reduces the passivation effect. The solar cell of the present disclosure does not affect the passivation effect of the P-type doped polysilicon layer 2, can improve the utilization rate of sunlight by the solar cell, and can maintain good passivation effect, thereby achieving a balance between light transmittance and passivation effect, and improving the efficiency of the solar cell.

[0059] In actual application, after the P-type doped polysilicon layer 2 is prepared, an oxidation layer is formed by high-temperature oxidation of the P-type doped polysilicon layer 2. The oxidation layer can be borosilicate glass. The oxidation layer is used to extract part of the P-type dopant in the third portion 23 of the P-type doped polysilicon layer 2, and then the oxidation layer is removed, so that the doping concentration of the P-type dopant in the second portion 22 of the P-type doped polysilicon layer 2 is greater than the doping concentration of the P-type dopant in the third portion 23.

[0060] As an embodiment of the present disclosure, the solar cell further includes:

[0061] The first passivation layer 4 is arranged between the silicon substrate 1 and the first portion 21 of the P-type doped polysilicon layer 2.

[0062] The second passivation layer 5 is arranged between the silicon substrate 1 and the N-type doped polysilicon layer 3.

[0063] In the embodiment, the first passivation layer 4 is located between the P-type doped polysilicon layer 2 and the silicon substrate 1, and the first passivation layer 4 and the P-type doped polysilicon layer 2 form a tunneling passivation contact structure to realize chemical passivation of the P region 11 of the silicon substrate 1 and selective collection of holes, reduce the carrier recombination rate of the side of the silicon substrate 1 where the first passivation layer 4 is formed, and facilitate improvement of the photoelectric conversion efficiency of the solar cell.

[0064] In the embodiment, the second passivation layer 5 and the N-type doped polysilicon layer 3 can form a tunneling passivation contact structure to realize chemical passivation of the N region 12 included in the semiconductor substrate and selective collection of electrons, reduce the carrier recombination rate of the side of the semiconductor substrate where the second passivation layer 5 is formed, and facilitate improvement of the photoelectric conversion efficiency of the solar cell.

[0065] Specifically, the material of the second passivation layer 5 and the material of the first passivation layer 4 can be the same or different. The thickness of the second passivation layer 5 and the thickness of the first passivation layer 4 can be the same or different. In the embodiment of the present disclosure, the material and thickness of the first passivation layer 4 are not specifically limited. For example, the material of the first passivation layer 4 and the second passivation layer 5 can include one or more of silicon oxide, aluminum oxide, titanium oxide, hafnium dioxide, gallium oxide, silicon nitride, silicon carbon nitride, aluminum nitride, titanium nitride, and titanium carbon nitride.

[0066] As one embodiment of the present disclosure, further comprising:

[0067] The third passivation layer 6 is arranged on the side of the third part 23 of the P-type doped polysilicon layer 2 away from the silicon substrate 1.

[0068] The fourth passivation layer 7 is arranged on the side of the N-type doped polysilicon layer 3 away from the silicon substrate 1.

[0069] In the embodiment, the third passivation layer 6 can improve the field passivation effect of the P-type doped polysilicon layer 2, and can block impurities from the outside into the silicon substrate 1, thereby reducing the impurity inward diffusion into the silicon substrate 1 and improving the cell efficiency. The fourth passivation layer 7 can improve the field passivation effect of the N-type doped polysilicon layer 3, and can block impurities from the outside into the silicon substrate 1, thereby reducing the impurity inward diffusion into the silicon substrate 1 and improving the cell efficiency.

[0070] As one embodiment of the present disclosure, the third passivation layer 6 and the fourth passivation layer 7 can be one or a combination of silicon oxide, silicon oxynitride, silicon nitride, and silicon carbide.

[0071] Specifically, the material of the third passivation layer 6 and the material of the fourth passivation layer 7 can be the same or different. The thickness of the third passivation layer 6 and the thickness of the fourth passivation layer 7 can be the same or different.

[0072] As an embodiment of the present disclosure, the doping concentration of the P-type dopant of the second portion 22 is greater than the doping concentration of the P-type dopant of the first portion 21.

[0073] In the embodiment, the average doping concentration of the P-type dopant of the second portion 22 is greater than the average doping concentration of the P-type dopant of the first portion 21; or the peak doping concentration of the P-type dopant of the second portion 22 is greater than the peak doping concentration of the P-type dopant of the first portion 21.

[0074] In the embodiment, since the first portion 21 of the P-type doped polysilicon layer 2 is close to the silicon substrate 1, and the second portion 22 of the P-type doped polysilicon layer 2 is farther away from the silicon substrate 1 than the first portion 21, the first portion 21 of the P-type doped polysilicon layer 2 diffuses into the inner extension layer of the silicon substrate 1, so that the doping concentration of the P-type dopant of the first portion 21 can be reduced, and the passivation effect can be improved. In addition, since the P-type dopant of the first portion 21 of the P-type doped polysilicon layer 2 can also partially diffuse into the first passivation layer 4, the doping concentration of the P-type dopant of the second portion 22 can be greater than the doping concentration of the P-type dopant of the first portion 21.

[0075] As an embodiment of the present disclosure, the doping concentration of the P-type dopant of the third portion 23 is less than the doping concentration of the P-type dopant of the first portion 21.

[0076] In the embodiment, the average doping concentration of the P-type dopant of the third portion 23 is less than the average doping concentration of the P-type dopant of the first portion 21; or the peak doping concentration of the P-type dopant of the third portion 23 is less than the peak doping concentration of the P-type dopant of the first portion 21.

[0077] In the embodiment, since the third portion 23 of the P-type doped polysilicon layer 2 is located at the outermost side of the P-type doped polysilicon layer 2, and the first portion 21 of the P-type doped polysilicon layer 2 is close to the silicon substrate 1, the doping concentration of the P-type dopant of the third portion 23 is less than the doping concentration of the P-type dopant of the first portion 21, which can ensure good light transmittance of the P-type doped polysilicon layer 2, maintain good passivation effect, and improve the cell efficiency.

[0078] In the embodiment of the present disclosure, the P-type dopant can be boron or gallium; and the N-type dopant can be phosphorus or arsenic. Preferably, the P-type dopant is boron, and the N-type dopant is phosphorus.

[0079] As an embodiment of the present disclosure, the doping concentration of the P-type dopant is the doping concentration of the activated P-type dopant.

[0080] In the embodiment, the doping concentration of the P-type dopant can be the doping concentration of the activated P-type dopant; similarly, the doping concentration of the N-type dopant can be the doping concentration of the activated N-type dopant, which can be measured by using a spreading resistance profile (SRP) or an electrochemical capacitance-voltage (ECV) method.

[0081] As another embodiment of the present disclosure, the doping concentration of the P-type dopant is the sum of the doping concentration of the activated P-type dopant and the doping concentration of the unactivated P-type dopant.

[0082] In the embodiment, the doping concentration of the P-type dopant can also be the sum of the doping concentration of the activated P-type dopant and the doping concentration of the unactivated P-type dopant; similarly, the doping concentration of the N-type dopant can also be the sum of the doping concentration of the activated N-type dopant and the doping concentration of the unactivated N-type dopant, which can be measured by using a secondary ion mass spectrometry (SIMS) method.

[0083] As an embodiment of the present disclosure, the first passivation layer 4 contains a P-type dopant, and the doping concentration of the P-type dopant in the first passivation layer 4 is greater than the doping concentration of the P-type dopant in the first portion 21.

[0084] In the embodiment, the first passivation layer 4 can contain a P-type dopant such as boron or gallium. Preferably, the first passivation layer 4 and the P-type dopant of the P-type doped polysilicon layer 2 are the same, and both are boron dopants.

[0085] In the embodiment, since the doping concentration of the P-type dopant in the first passivation layer 4 is greater than the doping concentration of the P-type dopant in the first portion 21, the passivation effect of the first passivation layer 4 can be improved, thereby improving the cell efficiency.

[0086] As an embodiment of the present disclosure, the third passivation layer 6 contains a P-type dopant, and the doping concentration of the P-type dopant in the third passivation layer 6 is greater than the doping concentration of the P-type dopant in the third portion 23.

[0087] In the embodiment, the third passivation layer 6 can contain a P-type dopant such as boron or gallium. Preferably, the third passivation layer 6 and the P-type dopant of the P-type doped polysilicon layer 2 are the same, and both are boron dopants.

[0088] In the embodiment, since the doping concentration of the P-type dopant in the third passivation layer 6 is greater than the doping concentration of the P-type dopant in the third portion 23, the passivation effect of the third passivation layer 6 can be improved, thereby improving the cell efficiency.

[0089] As an embodiment of the present disclosure, the first passivation layer 4 and the third passivation layer 6 both contain P-type dopants, and the doping concentration of the P-type dopants of the third passivation layer 6 is less than the doping concentration of the P-type dopants of the first passivation layer 4.

[0090] In the embodiment, the doping concentration of the P-type dopants of the third passivation layer 6 is lower than the doping concentration of the P-type dopants of the first passivation layer 4, which is beneficial to the light transmission of the third passivation layer 6, increases the light transmission rate of the third passivation layer 6, increases the light transmission amount of the third passivation layer 6, and improves the utilization rate of solar light by the battery, thereby improving the battery efficiency.

[0091] As an embodiment of the present disclosure, the thickness of the third passivation layer 6 is greater than the thickness of the first passivation layer 4.

[0092] In the embodiment, since the doping concentration of the P-type dopants of the third passivation layer 6 is lower than the doping concentration of the P-type dopants of the first passivation layer 4, by reducing the thickness of the first passivation layer 4 with a higher doping concentration of P-type dopants, the good passivation effect of the third passivation layer 6 is ensured, and since the thickness of the first passivation layer 4 is reduced, the light transmission capability of the first passivation layer 4 is not affected, and a good balance between passivation effect and light transmission effect is achieved.

[0093] As an embodiment of the present disclosure, the thickness of the second portion 22 is less than the thickness of the first portion 21.

[0094] In the embodiment, since the doping concentration of the P-type dopants of the second portion 22 is higher than the doping concentration of the first portion 21, by reducing the thickness of the second portion 22, the good light transmission effect of the second portion 22 is ensured, and the thickness of the first portion 21 is thicker than the thickness of the second portion 22, which can ensure the good passivation effect of the first portion 21.

[0095] As an embodiment of the present disclosure, the thickness of the second portion 22 is less than the thickness of the third portion 23.

[0096] In the embodiment, since the doping concentration of the P-type dopants of the second portion 22 is higher than the doping concentration of the third portion 23, by reducing the thickness of the second portion 22, the good light transmission effect of the second portion 22 and the third portion 23 is ensured, and the light transmission capability of the second portion 22 and the third portion 23 is balanced.

[0097] As an embodiment of the present disclosure, the thickness of the first portion 21 is less than the thickness of the third portion 23, which can improve the tunneling passivation effect of the first portion 21. Of course, the thickness of the first portion 21 can also be greater than or equal to the thickness of the third portion 23.

[0098] As one embodiment of the present disclosure, the ratio of the doping concentration of the P-type dopant of the second portion 22 to the doping concentration of the P-type dopant of the third portion 23 is 1-2, and is not equal to 1. It is explained herein that the ratio of the doping concentration of the P-type dopant of the second portion 22 to the doping concentration of the P-type dopant of the third portion 23 can be equal to 2.

[0099] In the present embodiment, the ratio of the doping concentration of the P-type dopant of the second portion 22 to the doping concentration of the P-type dopant of the third portion 23 can be set according to actual conditions. For example, the ratio of the doping concentration of the P-type dopant of the second portion 22 to the doping concentration of the P-type dopant of the third portion 23 can be one of the following: 1.01, 1.05, 1.10, 1.18, 1.25, 1.30, 1.46, 1.52, 1.60, 1.70, 1.81, 1.90, 1.92, 2.

[0100] As one embodiment of the present disclosure, the ratio of the doping concentration of the P-type dopant of the first portion 21 to the doping concentration of the P-type dopant of the third portion 23 is 1-1.5, and is not equal to 1. It is explained herein that the ratio of the doping concentration of the P-type dopant of the first portion 21 to the doping concentration of the P-type dopant of the third portion 23 can be equal to 1.5.

[0101] In the present embodiment, the ratio of the doping concentration of the P-type dopant of the third portion 23 to the doping concentration of the P-type dopant of the first portion 21 can be set according to actual conditions. For example, the ratio of the doping concentration of the P-type dopant of the third portion 23 to the doping concentration of the P-type dopant of the first portion 21 can be one of the following: 1.01, 1.05, 1.10, 1.18, 1.25, 1.30, 1.46, 1.50.

[0102] As one embodiment of the present disclosure, each layer of the N-type doped polysilicon layer 3 includes a fourth portion 31 and a fifth portion 32 arranged in sequence from the silicon substrate 1 to the direction away from the silicon substrate 1 along the thickness direction thereof, and the doping concentration of the N-type dopant of the fourth portion 31 is less than the doping concentration of the N-type dopant of the fifth portion 32.

[0103] In the present embodiment, the average value of the doping concentration of the N-type dopant of the fourth portion 31 is less than the average value of the doping concentration of the N-type dopant of the fifth portion 32, or the peak value of the doping concentration of the N-type dopant of the fourth portion 31 is less than the peak value of the doping concentration of the N-type dopant of the fifth portion 32.

[0104] In the embodiment, the N-type doped polysilicon layer 3 includes a fourth portion 31 and a fifth portion 32 arranged in sequence from the silicon substrate 1 to the direction away from the silicon substrate 1 along the thickness direction of the N-type doped polysilicon layer 3. Since the fourth portion 31 is close to the silicon substrate 1, the doping concentration of the fourth portion 31 of the N-type doped polysilicon layer 3 is less than the doping concentration of the N-type dopant of the fifth portion 32, and the passivation effect of the N-type doped polysilicon layer 3 can be improved.

[0105] In the embodiment, the second passivation layer 5 is arranged between the fourth portion 31 and the silicon substrate 1, and the fourth passivation layer 7 is arranged on the side of the fifth portion 32 away from the silicon substrate 1.

[0106] As an embodiment of the present disclosure, the doping concentration of the N-type dopant of the fourth portion 31 is less than the doping concentration of the N-type dopant of the fifth portion 32, which facilitates the preparation of the N-type doped polysilicon layer 3.

[0107] As an embodiment of the present disclosure, the semiconductor device further comprises:

[0108] The first electrode 8 arranged on the P region 11 is in contact with the third portion 23 of the P-type doped polysilicon layer 2.

[0109] In the embodiment, the first electrode 8 forms an ohmic contact with the P-type doped polysilicon layer 2. Specifically, the P-type doped polysilicon layer 2 utilizes the first portion 21 and the second portion 22 to achieve the original passivation effect, utilizes the third portion 23 to achieve the current lateral transmission effect and form an ohmic contact with the first electrode 8, and facilitates the balance between the passivation effect and the ohmic contact effect of the P region 11.

[0110] In addition, the thickness of the second portion 22 is set to be less than the thickness of the third portion 23. By thinning the thickness of the second portion 22, the second portion 22 can achieve a good passivation effect, and the thicker the third portion 23, the smaller the lateral transmission resistance. Therefore, by thickening the third portion 23, the third portion 23 can achieve a good current lateral transmission effect, and the third portion 23 can form a good ohmic contact with the first electrode 8, thereby achieving a good passivation effect and an ohmic contact effect of the P region 11.

[0111] As an embodiment of the present disclosure, the semiconductor device further comprises:

[0112] The second electrode 9 arranged on the N region 12 is in contact with the fifth portion 32 of the N-type doped polysilicon layer 3.

[0113] In the embodiment, the N-type doped polysilicon layer 3 utilizes the fourth portion 31 to achieve the original passivation effect, utilizes the fifth portion 32 to achieve the current lateral transmission effect and form an ohmic contact with the second electrode 9, and facilitates the balance between the passivation effect and the ohmic contact effect of the N region 12.

[0114] As one embodiment of the present disclosure, the fourth portion 31 has a thickness smaller than that of the fifth portion 32.

[0115] In the present embodiment, by thinning the fourth portion 31 of the N-type doped polysilicon layer 3, the fourth portion 31 can achieve good passivation effect, and the thicker the fifth portion 32 is, the smaller the lateral transmission resistance is. Therefore, by thickening the fifth portion 32 of the N-type doped polysilicon layer 3, the fifth portion 32 can achieve good current lateral transmission effect, and the fifth portion 32 can form good ohmic contact with the second electrode 9, thereby achieving good passivation effect and ohmic contact effect of the N region 12.

[0116] Embodiment Two

[0117] The present disclosure also provides a battery assembly comprising the solar cell of the above-mentioned embodiment one. It should be noted that the battery assembly has the same or similar beneficial effects as the solar cell, and the related parts between the two can be referred to each other. In order to avoid repetition, it will not be described here.

[0118] Embodiment Three

[0119] The present disclosure also provides a photovoltaic system comprising the battery assembly of the above-mentioned embodiment two. It should be noted that the photovoltaic system has the same or similar beneficial effects as the above-mentioned solar cell, and the related parts between the two can be referred to each other. In order to avoid repetition, it will not be described here.

[0120] The P-type doped polysilicon layer 2 of the solar cell provided by the present disclosure comprises a first portion 21, a second portion 22 and a third portion 23 arranged in turn along the thickness direction of the P-type doped polysilicon layer 2 and away from the silicon substrate 1, and the doping concentration of the P-type dopant of the second portion 22 is greater than that of the third portion 23. By reducing the doping concentration of the P-type dopant of the outermost region of the P-type doped polysilicon layer 2, the light transmittance of the P-type doped polysilicon layer 2 can be increased, the light transmittance of the P region can be increased, and the thickness of the P-type doped polysilicon layer 2 does not need to be reduced, which can improve the utilization rate of solar energy of the solar cell, does not affect the passivation effect of the P-type doped polysilicon layer 2, and can improve the battery efficiency.

[0121] The above are only the preferred embodiments of the present disclosure, and are not used to limit the present disclosure. Any modification, equivalent replacement and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A solar cell, comprising: a silicon substrate, a surface of the silicon substrate being provided with a P region and an N region; at least one P-type doped polysilicon layer provided in the P region and containing a P-type dopant, each of the P-type doped polysilicon layers comprising, along a thickness direction thereof and in sequence from the silicon substrate to a direction away from the silicon substrate, a first portion, a second portion and a third portion; at least one N-type doped polysilicon layer provided in the N region and containing an N-type dopant; wherein a doping concentration of the P-type dopant in the second portion is greater than a doping concentration of the P-type dopant in the third portion. The doping concentration of the P-type dopant in the second portion is greater than a doping concentration of the P-type dopant in the first portion. The doping concentration of the P-type dopant in the third portion is less than the doping concentration of the P-type dopant in the first portion. The doping concentration of the P-type dopant is a sum of a doping concentration of activated P-type dopant and a doping concentration of unactivated P-type dopant. Further comprising: a first passivation layer provided between the silicon substrate and the first portion of the P-type doped polysilicon layer; and a second passivation layer provided between the silicon substrate and the N-type doped polysilicon layer.

2. The solar cell of claim 1, wherein, Further comprising: a third passivation layer provided on a side of the third portion of the P-type doped polysilicon layer away from the silicon substrate; and a fourth passivation layer provided on a side of the N-type doped polysilicon layer away from the silicon substrate.

3. The solar cell of claim 1, wherein, The first passivation layer contains P-type dopant, and a doping concentration of the P-type dopant in the first passivation layer is greater than the doping concentration of the P-type dopant in the first portion.

4. The solar cell of claim 1, wherein, The third passivation layer contains P-type dopant, and a doping concentration of the P-type dopant in the third passivation layer is greater than the doping concentration of the P-type dopant in the third portion.

5. The solar cell of claim 1, wherein, The third passivation layer contains P-type dopant, and a doping concentration of the P-type dopant in the third passivation layer is greater than the doping concentration of the P-type dopant in the third portion.

6. The solar cell of claim 1, wherein, The third passivation layer has a thickness greater than a thickness of the first passivation layer. The second portion has a thickness less than a thickness of the first portion. The second portion has a thickness less than a thickness of the third portion.

7. The solar cell of claim 6, wherein, A ratio of the doping concentration of the second portion to the doping concentration of the third portion is 1-2 and not equal to 1. A ratio of the doping concentration of the first portion to the doping concentration of the third portion is 1-1.5 and not equal to 1. Each of the N-type doped polysilicon layers comprises, along a thickness direction thereof and in sequence from the silicon substrate to a direction away from the silicon substrate, a fourth portion and a fifth portion, and a doping concentration of N-type dopant in the fourth portion is less than a doping concentration of N-type dopant in the fifth portion.

8. The solar cell of claim 6, wherein, Further comprising: a first electrode provided in the P region and in contact with the third portion of the P-type doped polysilicon layer.

9. The solar cell of claim 7, wherein, Further comprising: a second electrode provided in the N region and in contact with the fifth portion of the N-type doped polysilicon layer.

10. The solar cell of claim 7, wherein, The fourth portion has a thickness less than a thickness of the fifth portion.

11. The solar cell of claim 7, wherein, The solar cell is a back contact solar cell, and the P region and the N region are located on a same side of the silicon substrate.

12. The solar cell of claim 1, wherein, ​ 13. The solar cell of claim 1, wherein, ​ 14. The solar cell of claim 1, wherein, ​ 15. The solar cell of claim 3, wherein, ​ 16. The solar cell of claim 1, wherein, ​ 17. The solar cell of claim 1, wherein, ​ ​ 18. The solar cell of claim 16, wherein, ​ ​ 19. The solar cell of claim 18, wherein, ​ 20. The solar cell of claim 1, wherein, ​ 21. The solar cell of claim 1, wherein, The solar cell is a bifacial solar cell, and the P region and the N region are respectively located on opposite sides of the silicon substrate.

22. A battery assembly comprising the solar cell according to any one of claims 1 to 21.

23. A photovoltaic system comprising the battery assembly according to claim 22.

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