CN112466996A - Solar cell and forming method - Google Patents
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- CN112466996A CN112466996A CN202011339973.XA CN202011339973A CN112466996A CN 112466996 A CN112466996 A CN 112466996A CN 202011339973 A CN202011339973 A CN 202011339973A CN 112466996 A CN112466996 A CN 112466996A
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
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Abstract
The embodiment of the invention provides a solar cell and a forming method thereof, wherein the forming method of the solar cell comprises the following steps: providing a substrate, wherein the substrate comprises a tunneling oxide layer; forming a first semiconductor layer, a second semiconductor layer and a third semiconductor layer which are sequentially stacked on the surface of the tunneling oxide layer, wherein the second semiconductor layer contains a first doping element, and the type of the first doping element is N type or P type; performing a first heat treatment adapted to increase a degree of crystallinity of the first semiconductor layer and a degree of crystallinity of the third semiconductor layer; and performing second heat treatment to diffuse the first doping element into the first semiconductor layer and the third semiconductor layer, so that the first semiconductor layer is converted into a first passivation contact layer, the second semiconductor layer is converted into a second passivation contact layer, the third semiconductor layer is converted into a third passivation contact layer, and the temperature of the second heat treatment is higher than that of the first heat treatment. The embodiment of the invention is beneficial to improving the passivation performance of the solar cell.
Description
Technical Field
The embodiment of the invention relates to the field of solar cells, in particular to a solar cell and a forming method thereof.
Background
With the rapid development of the photovoltaic industry and the continuous progress and deepening of the solar Cell technology research, various Passivated contact solar cells with different structures are developed, such as Passivated emitter cells (PERC), Tunnel Oxide Passivated contact cells (TOPCon), Heterojunction with inter-junction solar cells (HIT) and the like, and meanwhile, the requirements on the photoelectric conversion efficiency of the silicon-based solar cells are higher and higher. The tunneling oxide layer passivation contact solar cell can remarkably reduce the recombination of the inside and the surface of the solar cell in a metal contact area, has good contact performance and can greatly improve the efficiency of the solar cell.
However, the crystallinity of the solar cell prepared by the existing method for preparing the solar cell is not high, so that the distribution of doping elements in the solar cell is not uniform, the passivation performance of the solar cell is low, and the conversion efficiency of the cell is further influenced. Therefore, how to improve the passivation performance of the solar cell becomes a technical problem to be solved urgently by those skilled in the art.
Disclosure of Invention
The embodiment of the invention provides a solar cell and a forming method, which are beneficial to solving the problem of low passivation performance of the solar cell.
In order to solve the above problem, an embodiment of the present invention provides a method for forming a solar cell, including: providing a substrate, wherein the substrate comprises a tunneling oxide layer; forming a first semiconductor layer, a second semiconductor layer and a third semiconductor layer which are sequentially stacked on the surface of the tunneling oxide layer, wherein the second semiconductor layer contains a first doping element, and the type of the first doping element is N type or P type; subjecting the first semiconductor layer, the second semiconductor layer and the third semiconductor layer to a first heat treatment adapted to increase a degree of crystallinity of the first semiconductor layer and a degree of crystallinity of the third semiconductor layer; after the first heat treatment, performing a second heat treatment on the first semiconductor layer, the second semiconductor layer and the third semiconductor layer to diffuse the first doping element into the first semiconductor layer and the third semiconductor layer, so that the first semiconductor layer is converted into a first passivation contact layer, the second semiconductor layer is converted into a second passivation contact layer, the third semiconductor layer is converted into a third passivation contact layer, and the temperature of the second heat treatment is higher than that of the first heat treatment.
In addition, before the first heat treatment, the materials of the first semiconductor layer and the third semiconductor layer are both amorphous materials; after the first heat treatment, the materials of the first semiconductor layer and the third semiconductor layer are both polycrystalline materials.
In addition, before the first heat treatment is performed, both the first semiconductor layer and the third semiconductor layer are intrinsic semiconductor layers.
In addition, before the first heat treatment, a second doping element is contained in the third semiconductor layer, the type of the second doping element is the same as that of the first doping element, and the concentration of the second doping element in the third semiconductor layer is smaller than that of the first doping element in the second semiconductor layer.
In addition, before the first heat treatment is performed, the concentration of the first doping element in the second semiconductor layer is in a direct proportional relationship with the thickness of the second semiconductor layer, and the thickness of the first semiconductor layer is in a direct proportional relationship with the concentration of the first doping element in the second semiconductor layer.
In addition, the temperature of the first heat treatment is 600 to 850 ℃.
In addition, the temperature of the second heat treatment is 850 ℃ to 1050 ℃.
An embodiment of the present invention further provides a solar cell, including: a substrate comprising a tunneling oxide layer; the first passivation contact layer, the second passivation contact layer and the third passivation contact layer are sequentially stacked on the surface of the tunneling oxide layer, the first passivation contact layer, the second passivation contact layer and the third passivation contact layer contain doping elements, and the types of the doping elements are N-type or P-type.
In addition, the thickness of the second passivation contact layer is smaller than that of the third passivation contact layer; the thickness of the second passivation contact layer is less than the thickness of the first passivation contact layer.
In addition, the third passivation contact layer has a higher degree of crystallinity than the second passivation contact layer; the first passivated contact layer is more crystalline than the second passivated contact layer.
Compared with the prior art, the technical scheme provided by the embodiment of the invention has the following advantages:
according to the forming method of the solar cell provided by the embodiment of the invention, the first heat treatment is carried out at a lower temperature to enable the first semiconductor layer and the third semiconductor layer positioned at two sides to improve the crystallization degree, then the second heat treatment is carried out at a higher temperature to enable the first doping element to diffuse to the first semiconductor layer and the third semiconductor layer to form the passivation contact layer, because the temperature of the first heat treatment is not enough to enable the first doping element to diffuse, the first semiconductor layer and the third semiconductor layer have a higher crystallization degree before the first doping element diffuses, the higher the crystallization degree is, the more orderly the atomic arrangement of the semiconductor layers is, and after the subsequent first doping element diffuses, the more uniform the distribution of the first doping element in the formed passivation contact layer is, the better the passivation performance of the solar cell is, and the better the conversion efficiency of the cell is improved.
The third semiconductor layer contains a second doping element, and the concentration of the second doping element in the third semiconductor layer is smaller than that of the first doping element in the second semiconductor layer, so that before the second heat treatment, the third semiconductor layer already contains the doping element, the doping element is not required to be obtained in a first doping element diffusion mode when the third passivation contact layer is formed, and the semiconductor layer of the solar cell, which is required to obtain the doping element through the first doping element diffusion, is reduced.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
Fig. 1 to fig. 4 are schematic structural diagrams illustrating steps of a method for forming a solar cell according to a first embodiment of the present invention;
fig. 5 to 7 are schematic structural diagrams illustrating steps of a method for forming a solar cell according to a second embodiment of the invention;
fig. 8 is a schematic structural diagram of a solar cell according to a third embodiment of the present invention.
Detailed Description
As can be seen from the background, the passivation performance of the solar cell of the prior art is low.
In a general passivation contact structure of a solar cell, an intrinsic polysilicon layer is deposited on the surface of a tunneling oxide layer, and then doping elements are injected or diffused into the intrinsic polysilicon layer to form a passivation contact structure, but the intrinsic polysilicon layer with a higher degree of crystallization is formed first and then the doping elements are injected, so that a large amount of doping elements are easily concentrated on the surface of the passivation contact structure, and a doped dead layer is formed on the surface, so that the passivation performance of the solar cell is reduced, and meanwhile, the crystallization degree of the passivation contact structure is reduced due to the large amount of doped dead layer, so that the contact performance of a metal gate layer of the solar cell and the passivation contact structure is reduced.
Because of the problems of the solar cell, it is naturally easy to think that a doped polycrystalline silicon layer is firstly deposited, and then the doping elements are activated through annealing treatment, so that the doping elements are diffused to form a passivation contact structure, but the activated doping elements are easily diffused to a tunneling oxide layer, and pin-hole-shaped damage is formed on the tunneling oxide layer, so that the passivation performance of the solar cell is reduced, and meanwhile, the crystallization degree of the directly deposited polycrystalline silicon layer with the doping elements is low, so that the subsequent doping elements are not uniformly diffused, and the passivation performance of the solar cell is low.
In order to solve the above problems, embodiments of the present invention provide a method for forming a solar cell, which improves passivation performance of the solar cell, and further improves conversion efficiency of the solar cell.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that in various embodiments of the invention, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.
In this embodiment, the solar cell is a passivated contact cell, and may be specifically a TOPCon cell.
Fig. 1 to fig. 4 are schematic structural diagrams of steps of a solar cell forming method according to a first embodiment of the present invention. A method for forming a solar cell according to a first embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1 and 2, a substrate 100 is provided, the substrate 100 including a tunnel oxide layer 120. The substrate 100 has a double-layer structure including a substrate 110 having an emitter and a tunnel oxide layer 120.
In this embodiment, the substrate 110 having the emitter has a PN junction structure, and if the intrinsic material of the substrate 110 is a P-type single crystal silicon substrate, the emitter is an N-type diffusion layer; if the intrinsic material of the substrate 110 is an N-type single crystal silicon substrate, the emitter thereof is a P-type diffusion layer.
The surface types of the substrate 110 include: suede, polished or etched surfaces, etc.; the material of the substrate 110 may be monocrystalline silicon, polycrystalline silicon, or quasi-monocrystalline silicon, etc.
The substrate 110 is used for receiving sunlight and generating photogenerated carriers, the substrate 110 includes a front surface and a back surface which are oppositely arranged, it is understood that the front surface of the substrate 110 is a surface for receiving sunlight irradiation, the back surface of the substrate 110 is opposite to the front surface and is a backlight surface, and the tunneling oxide layer 120 is arranged on the back surface of the substrate 110.
In this embodiment, the tunneling oxide layer 120 is made of silicon oxide. In other embodiments, the material of the tunnel oxide layer is aluminum oxide.
The tunneling oxide layer 120 may have a thickness of 1nm to 1.5nm (nanometers), and may specifically be 1.1nm, 1.2nm, or 1.3 nm. It is understood that the thickness of the tunnel oxide layer 120 means that the thickness of all regions of the tunnel oxide layer 120 is 1nm to 1.5 nm.
Controlling the thickness of the formed tunnel oxide layer 120 to be between 1nm and 1.5nm can avoid the tunnel oxide layer 120 from being too thick, when the thickness exceeds a certain threshold, the tunnel effect is weakened, the passivation effect is not enhanced continuously, and the thicker the tunnel oxide layer is, the longer the diffusion of the doping elements is needed to match, thereby increasing the cost and reducing the production efficiency.
In one example, the step of forming the tunnel oxide layer 120 may include: forming a first oxide layer on the surface of the substrate 110 by a thermal oxidation method; then, an oxide layer is continuously grown on the first oxide layer by using a wet oxidation method or an ozone oxidation method, so as to form the tunneling oxide layer 120. Firstly, a thermal oxidation method is adopted, and then a wet oxidation method or an ozone oxidation method is adopted to make up a thermal oxidation thin region, so that a uniform tunneling oxide layer 120 is formed, the uniformity of the thickness of the tunneling oxide layer is optimized, the passivation uniformity of the battery is further improved, and finally the conversion efficiency of the battery is improved.
Specifically, the processing temperature of the thermal oxidation method is 550 ℃ to 650 ℃, and specifically may be 580 ℃, 600 ℃, or 630 ℃; the treatment time of the thermal oxidation method is 4min (minutes) to 10min, and specifically, may be 5min, 7min, or 9 min. Optionally, the gas required for the thermal oxidation process comprises oxygen.
In this embodiment, a first semiconductor layer 101, a second semiconductor layer 102, and a third semiconductor layer 103 stacked in sequence are formed on the surface of the tunnel oxide layer 120, the second semiconductor layer 102 contains a first doping element, and the type of the first doping element is N-type or P-type.
Specifically, a first semiconductor layer 101, a second semiconductor layer 102, and a third semiconductor layer 103 are sequentially formed on the surface of the tunnel oxide layer 120 away from the substrate 110.
In other embodiments, a metal gate layer may be further formed on a surface of the third semiconductor layer away from the second semiconductor layer, where the metal gate layer is an electrode of the solar cell.
The first semiconductor layer 101 not only can play a passivation role in the subsequent formation of the first passivation contact layer, but also can prevent the first doping element in the second semiconductor layer 102 from diffusing to the tunneling oxide layer 120 to damage the tunneling oxide layer, thereby reducing the passivation performance of the solar cell. The second semiconductor layer 102 contains a first doping element, and the first doping element forms a second passivation contact layer after diffusion, and the second passivation contact layer realizes selective transmission of majority carriers, so that effective transmission of the majority carriers is ensured, and the solar cell achieves a passivation effect.
The third semiconductor layer 103 not only can play a role in passivation when a third passivation contact layer is formed in the subsequent process, but also can prevent excessive first doping elements from diffusing to the surface of the solar cell to form a doping dead layer, so that the contact performance between the solar cell and a metal gate layer is influenced.
The material of the first semiconductor layer 101 and the third semiconductor layer 103 is amorphous material, and the first semiconductor layer 101 and the third semiconductor layer 103 are intrinsic semiconductor layers. Specifically, the material of the first semiconductor layer 101 and the third semiconductor layer 103 may be intrinsic amorphous silicon, which has a better crystallization degree after the first heat treatment compared to doped amorphous silicon, and is beneficial to make the solar cell have a better crystallization degree before the first doping element is diffused.
The process for forming intrinsic amorphous silicon includes: the silane is used as reaction gas to carry out deposition by a chemical vapor deposition method, and the chemical vapor deposition method can be a low-pressure chemical vapor deposition method, a plasma enhanced chemical vapor deposition method, an atmospheric pressure chemical vapor deposition method and the like.
The chemical vapor deposition method comprises the following process conditions: the pressure in the reaction cavity can be 0.1 to 0.5T torr, and specifically can be 0.2 torr, 0.3 torr or 0.4 torr; the reaction temperature is 100-700 ℃, and specifically can be 200 ℃, 400 ℃ or 600 ℃.
The thickness of the first semiconductor 101 and the thickness of the third semiconductor 103 may be 2nm to 2000nm, and specifically may be 100nm, 500nm, or 1500 nm.
In this embodiment, the thickness of the first semiconductor layer 101 is in direct proportion to the concentration of the first doping element in the second semiconductor layer 102, and since the concentration of the first doping element in the second semiconductor layer 102 is high, when the first doping element diffuses into the first semiconductor layer 101, a large amount of the first doping element diffuses into the first semiconductor layer 101, the thickness of the first semiconductor layer 101 needs to be set according to the concentration of the first doping element in the second semiconductor layer 102, so as to prevent fewer dead layers from being doped when the first doping element diffuses into the first semiconductor layer 101, and further prevent the passivation performance of the solar cell from being reduced.
In the present embodiment, by controlling the thickness of the first semiconductor layer 101, the dosage of the first doping element diffused to the tunnel oxide layer is reduced, so as to reduce the damage to the tunnel oxide layer.
The material of the second semiconductor layer 102 may be a doped amorphous silicon layer. The process for forming the doped amorphous silicon layer comprises the following steps: the in-situ deposition is performed by a chemical vapor deposition method, specifically, when the first doping element is a phosphorus element, silane and phosphane can be used as reaction gases, the two reaction gases are introduced into the reaction chamber at a certain volume flow ratio, and the doped amorphous silicon layer with the first doping element is formed by the chemical vapor deposition method.
The thickness of the second semiconductor layer 102 may be 2nm to 2000nm, specifically 100nm, 500nm, or 1500nm, and in this embodiment, the preferred thickness of the second semiconductor layer 102 is 20nm to 300nm, specifically 50nm, 150nm, or 250 nm. It should be noted that the thickness of the second semiconductor layer 102 is smaller than the thickness of the first semiconductor layer 101 and the thickness of the third semiconductor layer 103, because the second semiconductor layer 102 contains the first doping element, the larger the thickness of the first semiconductor layer 101 and the thickness of the third semiconductor layer 103 are, the less the doping dead layer formed by the first doping element diffusing into the first semiconductor layer 101 and the third semiconductor layer 103 after the subsequent second heat treatment.
The type of the first doping element is N type or P type, and the N type may be: 5-valent elements such as phosphorus or arsenic; the P-type may be: indium, boron, and the like.
In this embodiment, the concentration of the first doping element in the second semiconductor layer 102 is in a direct proportional relationship with the thickness of the second semiconductor layer 102, and the higher the concentration of the first doping element in the second semiconductor layer 102 is, the larger the thickness of the second semiconductor layer 102 is, the fewer the doped dead layers in the second semiconductor layer 102 are, so that the crystallization degree of the semiconductor layer is improved by reducing the doped dead layers, and the passivation performance of the solar cell is further improved.
Referring to fig. 3, in the present embodiment, the first semiconductor layer 101, the second semiconductor layer 102, and the third semiconductor layer 103 are subjected to a first heat treatment 107, and the first heat treatment 107 is adapted to improve the crystallinity of the first semiconductor layer 101 and the crystallinity of the third semiconductor layer 103.
In this embodiment, the thermal energy provided by the first thermal treatment 107 is less than the energy required for the first doping element to diffuse from the second semiconductor layer 102 into the third semiconductor layer 103, and the thermal energy provided by the first thermal treatment 107 is less than the energy required for the first doping element to diffuse from the second semiconductor layer 102 into the first semiconductor layer 101.
After the first heat treatment 107 is performed, the material of the first semiconductor layer 101 and the third semiconductor layer 103 are both polycrystalline materials, and may be intrinsic polycrystalline silicon.
The temperature of the first heat treatment 107 is 600 to 850 degrees celsius, and specifically may be 650, 700, or 800 degrees celsius.
The temperature of the first heat treatment 107 may be such that the crystallinity of the first semiconductor layer 101 and the crystallinity of the third semiconductor layer 103 are increased, but the first doping element in the second semiconductor layer 102 is not activated, the first doping element is not diffused, the first semiconductor layer 101 and the third semiconductor layer 103 have a higher crystallinity before the first doping element is diffused, the higher the crystallinity is, the more orderly the atomic arrangement of the semiconductor layers is, and after the subsequent first doping element is diffused, the more uniform the distribution of the first doping element in the formed passivation contact structure is, the better the passivation performance of the solar cell is, thereby increasing the conversion efficiency of the cell.
Referring to fig. 4, after the first heat treatment 107 (refer to fig. 3) is performed, a second heat treatment 108 is performed on the first semiconductor layer 101 (refer to fig. 1), the second semiconductor layer 102 (refer to fig. 1), and the third semiconductor layer 103 (refer to fig. 1) to diffuse the first doping element into the first semiconductor layer 101 and the third semiconductor layer 103, so that the first semiconductor layer 101 is converted into the first passivation contact layer 104, the second semiconductor layer 102 is converted into the second passivation contact layer 105, and the third semiconductor layer 103 is converted into the third passivation contact layer 106.
Specifically, the second heat treatment 108 activates the first doping element in the second semiconductor layer 102, and the first passivation contact layer 104, the second passivation contact layer 105, and the third passivation contact layer 106 formed after diffusion form a passivation contact structure as a whole.
Since the first semiconductor layer 101 and the third semiconductor layer 103 have a higher crystallinity before the first doping element is diffused, the first doping element is distributed more uniformly in the first passivation contact layer 104 and the third passivation contact layer 106, and the first passivation contact layer 104 and the third passivation contact layer 106 have a good passivation effect.
After a portion of the first doping element in the second semiconductor layer 102 diffuses into the first semiconductor layer 101 and the third semiconductor layer 103, the remaining first doping element is less, and meanwhile, due to the second heat treatment 108, the formed second passivation contact layer 105 also has a higher degree of crystallinity, and the second passivation contact structure 105 also has a good passivation effect.
The material of the first passivation contact layer 104, the second passivation contact layer 105 and the third passivation contact layer 106 may be doped polysilicon.
The temperature of the second heat treatment 108 is greater than the temperature of the first heat treatment 107. Since the first heat treatment 107 only needs to increase the crystallinity of the first semiconductor layer 101 and the third semiconductor layer 103, and does not need to activate the first doping element, the temperature is lower, but the second heat treatment 108 needs to activate the first doping element for diffusion, so the temperature of the second heat treatment 108 is higher than that of the first heat treatment 107, and thus the first semiconductor layer 101 and the third semiconductor layer 103 have higher crystallinity before the first doping element is diffused by adopting the stepwise different heating treatment.
In this embodiment, the temperature of the second heat treatment 108 is 850 to 1050 degrees celsius, and specifically may be 900 degrees celsius, 950 degrees celsius, or 1000 degrees celsius.
In the embodiment, through two times of heat treatment with different temperatures, before the first doping element in the second semiconductor layer diffuses, the first semiconductor layer and the third semiconductor layer already have higher crystallization degree, the formed passivation contact structure has higher crystallization degree, the first doping element in the passivation contact structure is also distributed more uniformly, the passivation performance of the solar cell is improved, and the conversion efficiency of the solar cell is further improved.
A second embodiment of the present invention provides a method for forming a solar cell, which is substantially the same as the method for forming a solar cell provided in the first embodiment of the present invention, and mainly differs from the method for forming a solar cell provided in the first embodiment of the present invention in that a third semiconductor layer contains a second doping element.
Fig. 5 to fig. 7 are schematic structural diagrams of steps of a solar cell forming method according to a second embodiment of the present invention.
Referring to fig. 5 to 7, in the present embodiment, before the first thermal treatment 207 is performed, the third semiconductor layer 203 contains the second doping element, and the type of the second doping element is the same as the type of the first doping element.
The third semiconductor layer 203 contains the second doping element, so that before the second heat treatment 208, the third semiconductor layer 203 already contains the doping element, the doping element does not need to be obtained by the first doping element diffusion when the third passivation contact layer 206 is formed, and the semiconductor layer of the solar cell which needs to obtain the doping element by the first doping element diffusion is reduced, so that when the second semiconductor layer 202 is formed, the dosage of the first doping element in the second semiconductor layer 202 is reduced, and the risk of forming a doped dead layer in the second semiconductor layer 202 due to excessive first doping element is reduced.
The concentration of the second doping element in the third semiconductor layer 203 is smaller than the concentration of the first doping element in the second semiconductor layer 202. The concentration of the second doping element in the third semiconductor layer 203 is small, and the surface of the formed passivation contact structure is less in doped dead layers, so that the contact performance between the surface of the solar cell and the metal gate layer is improved.
In this embodiment, the concentration of the second doping element in the third semiconductor layer 203 is in direct proportion to the thickness of the third semiconductor layer 203. Since the higher the concentration of the second doping element in the second semiconductor layer 203, the more easily a doped dead layer is generated, the passivation performance of the solar cell is reduced, and the contact performance between the surface of the solar cell and the metal gate layer is reduced, but the doped dead layer can be reduced by correspondingly increasing the thickness of the third semiconductor layer 203.
In the method for forming a solar cell provided in this embodiment, the third semiconductor layer has the second doping element therein, and after the second heat treatment, too much first doping element is not required to diffuse into the third semiconductor layer, so that the dosage of the first doping element in the formed second semiconductor layer is reduced, which is beneficial to reducing a doped dead layer caused by a large amount of the first doping element in the second semiconductor layer.
A third embodiment of the present invention provides a solar cell formed based on the above-mentioned method for forming a solar cell, and the solar cell provided in this embodiment will be described in detail below with reference to the accompanying drawings.
Fig. 8 is a schematic structural diagram of a solar cell according to a third embodiment of the present invention.
Referring to fig. 8, in the present embodiment, the solar cell includes: a substrate 300 including a tunnel oxide layer 320; the first passivation contact layer 304, the second passivation contact layer 305 and the third passivation contact layer 306 are sequentially stacked on the tunnel oxide layer 320, and the first passivation contact layer 304, the second passivation contact layer 305 and the third passivation contact layer 306 contain a doping element, and the type of the doping element is N-type or P-type.
In other embodiments, a metal gate layer may be further formed on a surface of the third passivation contact layer away from the second passivation contact layer, where the metal gate layer is an electrode of the solar cell.
The base 300 has a double-layer structure including a substrate 310 having an emitter and a tunnel oxide layer 320.
The substrate 310 includes a front surface and a back surface opposite to each other, and it is understood that the front surface of the substrate 310 is a surface for receiving solar rays, the back surface of the substrate 310 is opposite to the front surface and is a backlight surface, and the tunnel oxide layer 320 is disposed on the back surface of the substrate 310.
The first passivation contact layer 304, the second passivation contact layer 305, and the third passivation contact layer 306 are made of the same material, and may be doped polysilicon.
The thickness of the second passivation contact layer 305 is less than the thickness of the first passivation contact layer 304. The first passivation contact layer 304 is in contact with the tunnel oxide layer 320, the first passivation contact layer 304 has a larger thickness, and the doping elements diffused to the tunnel oxide layer 320 are less, so that the tunnel oxide layer 320 is not damaged, and the passivation performance of the solar cell is improved.
The first passivation contact layer 304 has a higher degree of crystallinity than the second passivation contact layer 305. Since the first passivation contact layer 304 already has a higher degree of crystallinity before having the doping element in the process of forming the solar cell, the degree of crystallinity of the first passivation contact layer 304 is formed to be higher than that of the second passivation contact layer 305.
The thickness of the second passivation contact layer 305 is less than the thickness of the third passivation contact layer 306. The third passivation contact layer 306 is the surface of the solar cell and needs to be contacted with a metal gate layer subsequently, and the thickness of the third passivation contact layer 306 is large, so that the doped dead layer on the surface of the solar cell is reduced, and the contact performance between the solar cell and the metal gate is improved.
In this embodiment, by controlling the thickness of the third passivation contact layer 306, the dosage of the doping element diffused to the surface of the solar cell can be controlled, so as to better control the concentration of the doping element on the surface of the solar cell and the contact performance between the metal gate layer and the solar cell.
The third passivation contact layer 306 has a higher degree of crystallinity than the second passivation contact layer 305. Since the third passivation contact 306 already has a higher degree of crystallinity before having the doping element during the formation of the solar cell, the third passivation contact 306 is formed with a higher degree of crystallinity than the second passivation contact 305.
The embodiment provides a solar cell, which reduces damage of a doping element to a tunneling oxide layer by controlling the thickness of each layer in the solar cell, and simultaneously improves the contact performance of a metal gate layer and the solar cell, thereby improving the passivation performance of the solar cell.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method of forming a solar cell, comprising:
providing a substrate, wherein the substrate comprises a tunneling oxide layer;
forming a first semiconductor layer, a second semiconductor layer and a third semiconductor layer which are sequentially stacked on the surface of the tunneling oxide layer, wherein the second semiconductor layer contains a first doping element, and the type of the first doping element is N type or P type;
subjecting the first semiconductor layer, the second semiconductor layer and the third semiconductor layer to a first heat treatment adapted to increase a degree of crystallinity of the first semiconductor layer and a degree of crystallinity of the third semiconductor layer;
after the first heat treatment, performing a second heat treatment on the first semiconductor layer, the second semiconductor layer and the third semiconductor layer to diffuse the first doping element into the first semiconductor layer and the third semiconductor layer, so that the first semiconductor layer is converted into a first passivation contact layer, the second semiconductor layer is converted into a second passivation contact layer, the third semiconductor layer is converted into a third passivation contact layer, and the temperature of the second heat treatment is higher than that of the first heat treatment.
2. The method according to claim 1, wherein before the first heat treatment, both the first semiconductor layer and the third semiconductor layer are made of an amorphous material; after the first heat treatment, the materials of the first semiconductor layer and the third semiconductor layer are both polycrystalline materials.
3. The method according to claim 1 or 2, wherein both the first semiconductor layer and the third semiconductor layer are intrinsic semiconductor layers before the first heat treatment.
4. The method according to claim 1 or 2, wherein before the first thermal treatment, a second doping element is contained in the third semiconductor layer, the type of the second doping element is the same as the type of the first doping element, and the concentration of the second doping element in the third semiconductor layer is smaller than the concentration of the first doping element in the second semiconductor layer.
5. The method according to claim 1, wherein a concentration of the first doping element in the second semiconductor layer is in a direct proportional relationship with a thickness of the second semiconductor layer, and a thickness of the first semiconductor layer is in a direct proportional relationship with a concentration of the first doping element in the second semiconductor layer, before the first heat treatment is performed.
6. The method according to claim 1, wherein the temperature of the first heat treatment is 600 to 850 degrees celsius.
7. The method according to claim 1, wherein the temperature of the second heat treatment is 850 to 1050 degrees celsius.
8. A solar cell, comprising:
a substrate comprising a tunneling oxide layer;
the first passivation contact layer, the second passivation contact layer and the third passivation contact layer are sequentially stacked on the surface of the tunneling oxide layer, the first passivation contact layer, the second passivation contact layer and the third passivation contact layer contain doping elements, and the types of the doping elements are N-type or P-type.
9. The solar cell of claim 8, wherein the thickness of the second passivation contact layer is less than the thickness of the third passivation contact layer; the thickness of the second passivation contact layer is less than the thickness of the first passivation contact layer.
10. The solar cell of claim 8, wherein the third passivated contact is more crystalline than the second passivated contact; the first passivated contact layer is more crystalline than the second passivated contact layer.
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| CN117038748A (en) * | 2023-10-08 | 2023-11-10 | 晶科能源(海宁)有限公司 | Solar cell, preparation method thereof and photovoltaic module |
| CN117650196A (en) * | 2023-11-01 | 2024-03-05 | 天合光能股份有限公司 | Passivation contact structure and preparation method thereof, solar cell and preparation method thereof |
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