CN114566561A - Heterojunction solar cell and manufacturing method thereof - Google Patents
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- 238000000151 deposition Methods 0.000 claims description 47
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical group [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 39
- 229910052796 boron Inorganic materials 0.000 claims description 39
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- H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
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- H01L31/074—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type comprising a heterojunction with an element of Group IV of the Periodic Table, e.g. ITO/Si, GaAs/Si or CdTe/Si solar cells
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Abstract
The invention provides a heterojunction solar cell and a manufacturing method thereof, wherein the heterojunction solar cell comprises: the silicon substrate is sequentially stacked with a first intrinsic layer and a first doping layer which are arranged on the first surface side of the silicon substrate, and a second intrinsic layer and a second doping layer which are arranged on the second surface side of the silicon substrate and have the doping type opposite to that of the first doping layer; the first intrinsic layer and the second intrinsic layer respectively comprise at least two intrinsic amorphous silicon films which are sequentially stacked, and on each surface side of the silicon substrate, the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate is smaller than that of the intrinsic amorphous silicon film far away from the silicon substrate; based on the design mode of the first intrinsic layer and the second intrinsic layer, the first intrinsic layer and the second intrinsic layer have the optimal passivation effect on the silicon substrate and simultaneously have better conductivity with the corresponding doped layers respectively, so that the comprehensive performance of the heterojunction solar cell is improved.
Description
Technical Field
The invention relates to the field of photovoltaic manufacturing, in particular to a heterojunction solar cell and a manufacturing method thereof.
Background
The heterojunction solar cell is a relatively high-efficiency crystalline silicon solar cell at present, combines the characteristics of a crystalline silicon cell and a silicon-based thin film cell, and has the advantages of short manufacturing process, low process temperature, high conversion efficiency, more generated energy and the like. Fig. 1 is a schematic structural diagram of a heterojunction solar cell in the prior art, which sequentially includes, from top to bottom, a first collector electrode 51 ', a first transparent conductive film layer 41 ', a first doped layer 31 ', a first intrinsic layer 21 ', a silicon substrate 10 ', a second intrinsic layer 22 ', a second doped layer 32 ', a second transparent conductive film layer 42 ', and a second collector electrode 52 '.
The heterojunction solar cell can optimize the passivation at the interface position of the silicon substrate 10 'by inserting an intrinsic layer (comprising a first intrinsic layer 21' and a second intrinsic layer 22 ') between the silicon substrate 10' and a doped amorphous layer (comprising a first doped layer 31 'and a second doped layer 32'), thereby effectively improving the open-circuit voltage and the fill factor and improving the efficiency of the cell. However, in the prior art, the first intrinsic layer 21 'and the second intrinsic layer 22' are usually formed by a single amorphous film, and thus the design method cannot further optimize the conversion efficiency of the heterojunction solar cell.
In view of the above, there is a need to provide an improved solution to the above problems.
Disclosure of Invention
The present invention is designed to solve at least one of the problems of the prior art, and to achieve the above object, the present invention provides a heterojunction solar cell, which is specifically designed as follows.
A heterojunction solar cell, comprising: the semiconductor device comprises a silicon substrate, a first intrinsic layer, a first doping layer, a second intrinsic layer, a second doping layer and a third doping layer, wherein the first intrinsic layer and the first doping layer are sequentially stacked on the first surface side of the silicon substrate, the second intrinsic layer and the second doping layer are sequentially stacked on the second surface side of the silicon substrate, and the doping type of the second doping layer is opposite to that of the first doping layer; the first intrinsic layer and the second intrinsic layer respectively comprise at least two intrinsic amorphous silicon films which are sequentially stacked, and on each surface side of the silicon substrate, the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate is smaller than that of the intrinsic amorphous silicon film far away from the silicon substrate.
Further, the first intrinsic layer comprises three intrinsic amorphous silicon films which are sequentially stacked, and the crystallization rates of the three intrinsic amorphous silicon films are sequentially as follows in the direction from the silicon substrate to the first intrinsic layer: not more than 5%, 10% -20%, 20% -50%.
Further, the second intrinsic layer comprises three intrinsic amorphous silicon films which are sequentially stacked, and the crystallization rates of the three intrinsic amorphous silicon films are sequentially as follows in the direction from the silicon substrate to the second intrinsic layer: not more than 5%, 10% -20%, 20% -50%.
Further, the first intrinsic layer and/or the second intrinsic layer further include an intrinsic amorphous silicon oxide film disposed on an outer surface of the intrinsic amorphous silicon film of the outermost layer.
Further, on each surface side of the silicon substrate, the hydrogen content in the intrinsic amorphous silicon film close to the silicon substrate is larger than the hydrogen content in the intrinsic amorphous silicon film far from the silicon substrate.
Further, at least one of the first doped layer and the second doped layer comprises at least two layers of doped films which are stacked, and in two adjacent doped films, the doped concentration of the doped film far away from the silicon substrate is greater than that of the doped film close to the silicon substrate.
Further, the doped film is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film or a doped microcrystalline silicon oxide film.
Further, the first surface is a light receiving surface, the doped film forming the first doped layer is a phosphorus doped film, the phosphorus doped film comprises a first phosphorus doped film, a second phosphorus doped film and a third phosphorus doped film which are sequentially stacked outside the first intrinsic layer, and the phosphorus doping concentrations in the first phosphorus doped film, the second phosphorus doped film and the third phosphorus doped film are respectively 50-150ppm, 100-300ppm and 200-400 ppm.
Further, the second surface is a backlight surface, the doped film forming the second doped layer is a boron doped film, the boron doped film comprises a first boron doped film, a second boron doped film and a third boron doped film which are sequentially stacked and arranged outside the second intrinsic layer, and the boron doping concentrations in the first boron doped film, the second boron doped film and the third boron doped film are respectively 300ppm, 500ppm and 600ppm respectively.
The invention also provides a manufacturing method of the heterojunction solar cell, which comprises the following steps:
a silicon substrate providing step;
an intrinsic layer forming step of forming a first intrinsic layer and a second intrinsic layer on a first surface side and a second surface side of the silicon substrate, respectively, the first intrinsic layer and the second intrinsic layer forming step each including depositing at least two intrinsic amorphous silicon films in sequence, wherein, on each surface side of the silicon substrate, a temperature of the silicon substrate when a previous intrinsic amorphous silicon film is deposited is lower than a temperature of the silicon substrate when a subsequent intrinsic amorphous silicon film is deposited;
and a doped layer forming step of forming a first doped layer and a second doped layer with opposite doping types on the surfaces of the first intrinsic layer and the second intrinsic layer respectively.
Further, the forming step of the first intrinsic layer comprises the steps of sequentially depositing three layers of intrinsic amorphous silicon films on the first surface side of the silicon substrate through PECVD, and the temperature ranges of the silicon substrate when the three layers of intrinsic amorphous silicon films are deposited are sequentially 200-.
Further, the forming step of the second intrinsic layer comprises the steps of sequentially depositing three layers of intrinsic amorphous silicon films on the second surface side of the silicon substrate through PECVD, and the temperature ranges of the silicon substrate when the three layers of intrinsic amorphous silicon films are deposited are sequentially 200-.
Further, the intrinsic layer forming step further includes depositing an intrinsic amorphous silicon oxide film on the outermost intrinsic amorphous silicon film on at least one surface side of the silicon substrate.
Further, the reaction gas for depositing and forming the intrinsic amorphous silicon film comprises H2 and SiH4, and on each surface side of the silicon substrate, the volume concentration of H2 in the reaction gas when the previous layer of intrinsic amorphous silicon film is deposited is higher than the volume concentration of H2 in the reaction gas when the next layer of intrinsic amorphous silicon film is deposited.
Further, the manufacturing method further comprises the step of introducing pure H2 to the surface of the corresponding intrinsic amorphous silicon film for plasma treatment after each intrinsic amorphous silicon film forming step.
Further, at least one of the first doped layer forming step and the second doped layer forming step includes sequentially forming at least two layers of doped films, and among two adjacent doped films sequentially formed, the doped concentration of the doped film far away from the silicon substrate is greater than that of the doped film close to the silicon substrate.
Further, the first doping layer forming step includes sequentially forming three layers of phosphorus doping films on the surface of the first intrinsic layer, wherein the flow ratio ranges of PH3/SiH4 when the three layers of phosphorus doping films are formed are 50-150ppm, 100-300ppm and 200-400ppm in sequence in the direction away from the silicon substrate.
Further, the second doped layer forming step includes sequentially forming three boron doped films on the surface of the second intrinsic layer, wherein the flow ratio values of B2H6/SiH4 during the formation of the three boron doped films are sequentially 50-150ppm, 100-250ppm and 200-300ppm in the direction away from the silicon substrate.
The invention has the beneficial effects that: in the specific structure of the heterojunction solar cell, because the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate is smaller than that of the intrinsic amorphous silicon film far away from the silicon substrate on each surface side of the silicon substrate, the first intrinsic layer and the second intrinsic layer can have the optimal passivation effect on the silicon substrate and simultaneously have better conductivity with the corresponding doped layers respectively, and further the comprehensive performance of the heterojunction solar cell is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art heterojunction solar cell;
FIG. 2 is a schematic diagram of a first embodiment of a heterojunction solar cell of the invention;
fig. 3 is a schematic diagram of a second embodiment of the heterojunction solar cell of the invention.
In the drawing, 10 is a silicon substrate, 21 is a first intrinsic layer, 211 is a first intrinsic amorphous silicon film, 212 is a second intrinsic amorphous silicon film, 213 is a third intrinsic amorphous silicon film, 31 is a first doped layer, 311 is a first phosphorus doped film, 312 is a second phosphorus doped film, 313 is a third phosphorus doped film, 41 is a first transparent conductive film layer, 51 is a first collector electrode, 22 is a second intrinsic layer, 221 is a fourth intrinsic amorphous silicon film, 222 is a fifth intrinsic amorphous silicon film, 223 is a sixth intrinsic amorphous silicon film, 32 is a second doped layer, 321 is a first boron doped film, 322 is a second boron doped film, 323 is a third boron doped film, 42 is a second transparent conductive film layer, and 52 is a second collector electrode.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Referring to fig. 2, the heterojunction solar cell according to the present invention includes: the silicon substrate 10 includes a first intrinsic layer 21 and a first doped layer 31 sequentially stacked on a first surface side of the silicon substrate 10, and a second intrinsic layer 22 and a second doped layer 32 sequentially stacked on a second surface side of the silicon substrate 10. The doping types of the first doping layer 31 and the second doping layer 32 are opposite, and one of the first doping layer and the second doping layer is doped in an n-type manner, namely doped with phosphorus; the other is p-type doping, i.e. boron doping is used.
More specifically, referring to fig. 2, in the present embodiment, the heterojunction solar cell further includes: the first transparent conductive film layer 41 and the first collector electrode 51 are sequentially stacked outside the first doped layer 31, and the second transparent conductive film layer 42 and the second collector electrode 52 are sequentially stacked outside the second doped layer 32.
For convenience of understanding, in the description of the following embodiments of the present invention, the first surface refers to a surface of the heterojunction solar cell directly receiving sunlight, i.e., a light receiving surface; the second surface refers to the surface of the heterojunction solar cell that is not directly exposed to sunlight, i.e., the backlight surface.
In the present invention, each of the first intrinsic layer 21 and the second intrinsic layer 22 includes at least two intrinsic amorphous silicon films sequentially stacked, and on each surface side of the silicon substrate 10, the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate 10 is smaller than that of the intrinsic amorphous silicon film far from the silicon substrate.
Referring to fig. 2, in the present embodiment, the first surface side of the silicon substrate 10 is provided with three intrinsic amorphous silicon films, and specifically, the three intrinsic amorphous silicon films include a first intrinsic amorphous silicon film 211, a second intrinsic amorphous silicon film 212, and a third intrinsic amorphous silicon film 213, which are sequentially stacked and provided on the first surface side of the silicon substrate 10. Wherein the crystallization rate of the first intrinsic amorphous silicon film 211 is smaller than the crystallization rate of the second intrinsic amorphous silicon film 212, and the crystallization rate of the second intrinsic amorphous silicon film 212 is smaller than the crystallization rate of the third intrinsic amorphous silicon film 213.
Further, the second surface side of the silicon substrate 10 is also provided with three intrinsic amorphous silicon films, specifically, the three intrinsic amorphous silicon films include a fourth intrinsic amorphous silicon film 221, a fifth intrinsic amorphous silicon film 222, and a sixth intrinsic amorphous silicon film 223 which are sequentially stacked and provided on the second surface side of the silicon substrate 10. The crystallization rate of the fourth intrinsic amorphous silicon film 221 is smaller than that of the fifth intrinsic amorphous silicon film 222, and the crystallization rate of the fifth intrinsic amorphous silicon film 222 is smaller than that of the sixth intrinsic amorphous silicon film 223.
In the specific structure of the heterojunction solar cell according to the present invention, since the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate 10 is smaller than that of the intrinsic amorphous silicon film far from the silicon substrate 10 on each surface side of the silicon substrate 10, the first intrinsic layer 21 and the second intrinsic layer 22 can have a better conductivity with the corresponding doped layers (i.e. the first intrinsic layer 21 and the first doped layer 31 have a better conductivity, and the second intrinsic layer 22 and the second doped layer 32 have a better conductivity) while having an optimal passivation effect on the silicon substrate 10, so as to improve the comprehensive performance of the heterojunction solar cell.
More specifically, for an intrinsic amorphous silicon film, as the crystallization rate increases, the passivation effect becomes worse and the conductivity becomes better. In the heterojunction solar cell structure, the intrinsic amorphous silicon film closest to the silicon substrate 10 has the largest influence on the passivation effect of the silicon substrate 10, and the intrinsic amorphous silicon film closest to the silicon substrate 10 is set to have the lowest crystallization rate in the invention, so that the optimal passivation of the silicon substrate 10 can be realized; the crystallization rate of the intrinsic amorphous silicon film on the outer side is set to be relatively high, so that the conductivity between the intrinsic amorphous silicon film and other structures on the outer layer can be effectively optimized.
In the embodiment shown in fig. 2, of the three intrinsic amorphous silicon films constituting the first intrinsic layer 21, the crystallization rate of the first intrinsic amorphous silicon film 211 is not more than 5%, the crystallization rate of the second intrinsic amorphous silicon film 212 is 10% -20%, and the crystallization rate of the third intrinsic amorphous silicon film 213 is 20% -50%.
Further, the crystallization rate of the fourth intrinsic amorphous silicon film 221, the crystallization rate of the fifth intrinsic amorphous silicon film 222, and the crystallization rate of the sixth intrinsic amorphous silicon film 223 of the three intrinsic amorphous silicon films constituting the second intrinsic layer 22 are not more than 5%, 10% -20%, and 20% -50%, respectively.
In other embodiments of the present invention, not shown, the first intrinsic layer 21 and/or the second intrinsic layer 22 further comprise an intrinsic amorphous silicon oxide film disposed on an outer surface of the outermost intrinsic amorphous silicon film. The intrinsic amorphous silicon oxide film can improve the field passivation of the heterojunction solar cell, and can improve the light transmittance of the corresponding intrinsic layers (i.e., the first intrinsic layer 21 and the second intrinsic layer 22), so as to further optimize the photoelectric conversion efficiency of the heterojunction solar cell to a certain extent.
Further, in still other preferred embodiments of the present invention, the number of layers of the intrinsic amorphous silicon film in the second intrinsic layer 22 is not more than the number of layers of the intrinsic amorphous silicon film in the first intrinsic layer 21. For the heterojunction solar cell, the first surface side of the heterojunction solar cell is used as the main surface of photo-generated current, the performance requirement on the first intrinsic layer 21 is higher, and the comprehensive performance of the first intrinsic layer 21 can be better optimized by arranging the intrinsic amorphous silicon film with more layers.
Further, in the present invention, the thickness of the first intrinsic layer 21 is less than or equal to the thickness of the second intrinsic layer 22, wherein preferably, the thickness of the first intrinsic layer 21 is less than the thickness of the second intrinsic layer 22. Typically, the thickness of the first intrinsic layer 21 is 4-10nm and the thickness of the second intrinsic layer 22 is 4-20 nm.
For the heterojunction solar cell, the influence of the light absorption effect of the first surface side on the photoelectric conversion efficiency of the cell is far larger than the influence of the light absorption effect of the second surface side on the photoelectric conversion efficiency of the cell, the relatively small thickness of the first intrinsic layer 21 can effectively reduce the loss of sunlight on the first surface side when the sunlight passes through the first intrinsic layer 21, the short-circuit current of the heterojunction solar cell can be improved, and the heterojunction solar cell has better photoelectric conversion efficiency; the second surface side does not need to consider the problem of light absorption too much, and the relatively thick second intrinsic layer 22 can better enhance the passivation effect on the silicon substrate 10.
In the embodiment shown in FIG. 2, the first intrinsic amorphous silicon film 211 has a thickness of 1-2nm, the second intrinsic amorphous silicon film 212 has a thickness of 2-4nm, and the third intrinsic amorphous silicon film 213 has a thickness of 1-2 nm; the thickness of the fourth intrinsic amorphous silicon film 221 is 1-2nm, the thickness of the fifth intrinsic amorphous silicon film 222 is 2-8nm, and the thickness of the sixth intrinsic amorphous silicon film 223 is 1-2 nm.
As a further preference of the present invention, on each surface side of the silicon substrate 10, the hydrogen content in the intrinsic amorphous silicon film close to the silicon substrate 10 is larger than the hydrogen content in the intrinsic amorphous silicon film far from the silicon substrate 10.
Specifically, as shown in fig. 2 in conjunction, in this embodiment, namely, the hydrogen content in the first intrinsic amorphous silicon film 211 is larger than that in the second intrinsic amorphous silicon film 212, the hydrogen content in the second intrinsic amorphous silicon film 212 is larger than that in the third intrinsic amorphous silicon film 213; the hydrogen content in the fourth intrinsic amorphous silicon film 221 is larger than that in the fifth intrinsic amorphous silicon film 222, and the hydrogen content in the fifth intrinsic amorphous silicon film 222 is larger than that in the sixth intrinsic amorphous silicon film 223.
As described above, the closer the intrinsic amorphous silicon film is to the silicon substrate 10, the more significant the passivation effect on the silicon substrate 10. The first intrinsic amorphous silicon film 211 and the fourth intrinsic amorphous silicon film 221 are directly attached to two surfaces of the silicon substrate 10, and when the first intrinsic amorphous silicon film 211 and the fourth intrinsic amorphous silicon film 221 have relatively highest hydrogen content on respective sides, dangling bonds on the surface of the silicon substrate 10 can be passivated better, so that the passivation effect on the silicon substrate 10 is further optimized.
Further, in the present invention, at least one of the first doped layer 31 and the second doped layer 32 includes at least two doped films stacked one on another, and of the two adjacent doped films, the doped film far from the silicon substrate 10 has a doping concentration greater than that of the doped film near the silicon substrate 10.
Based on the specific structure of the heterojunction solar cell according to the present invention, the doped film of the first doped layer 31 or/and the second doped layer 32 near the silicon substrate 10 has a lower doping concentration, so that the doped atoms can be reduced to the greatest extent to enter the corresponding intrinsic layers (i.e., the first intrinsic layer 21 and the second intrinsic layer 22), and the defect density of the corresponding intrinsic layers can be reduced. The doped film of the first doped layer 31 or/and the second doped layer 32 far from the silicon substrate 10 has a higher doping concentration, which is beneficial to field passivation, and can also reduce the contact resistance between the first doped layer 31 or/and the second doped layer 32 and the corresponding outer layer (in this embodiment, the corresponding outer layer is the first transparent conductive film layer 41 and the second transparent conductive film layer 42).
In the specific implementation process of the invention, the doped film is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film or a doped microcrystalline silicon oxide film. Preferably, the doped film forming the first doped layer 31 includes a doped amorphous silicon film and/or a doped amorphous silicon oxide film, and the doped film forming the second doped layer 32 includes a doped microcrystalline silicon film and/or a doped microcrystalline silicon oxide film.
The light transmittance of the doped amorphous silicon film and the doped amorphous silicon oxide film is respectively stronger than that of the doped microcrystalline silicon film and the doped microcrystalline silicon oxide film, one side of the light receiving surface of the heterojunction solar cell is a main surface of photoproduction current, and the multi-layer doped film positioned on the first doped layer 31 of the light receiving surface is composed of the doped amorphous silicon film and the doped amorphous silicon oxide film, so that the photoproduction current of the light receiving surface of the heterojunction solar cell can be improved; the electrical conductivity of the doped microcrystalline silicon film and the doped microcrystalline silicon oxide film is respectively stronger than that of the doped amorphous silicon film and the doped amorphous silicon oxide film, the multilayer doped film positioned on the second doped layer 32 on the back light surface is formed by the doped microcrystalline silicon film and the doped microcrystalline silicon oxide film, the resistance of the second doped layer 32 can be reduced while the short-circuit current of the heterojunction solar cell is not influenced, and the filling factor of the heterojunction solar cell is optimized.
When the first surface of the silicon substrate 10 is a light receiving surface and the second surface is a backlight surface, it is preferable in the present invention that the average doping concentration of the first doping layer 31 is smaller than the average doping concentration of the second doping layer 32. For the heterojunction solar cell, the first surface side of the heterojunction solar cell is a main surface for generating the photo current, and the first doping layer 31 has relatively low average concentration and can have higher mobility, so that the transmission of the current on the first surface side of the heterojunction solar cell is facilitated; on the second surface side of the heterojunction solar cell, the average doping concentration of the second doping layer 32 is relatively high, so that the resistance of the heterojunction solar cell can be reduced.
In further preferred embodiments of the present invention, the number of layers of doped films in the second doped layer 32 is not greater than the number of layers of doped films in the first doped layer 31. For a heterojunction solar cell, the first surface side of the heterojunction solar cell is used as the main surface of photogenerated current, the performance requirement on the first doping layer 31 is higher, and the comprehensive performance of the first doping layer 31 can be better optimized by arranging doping films with more layers.
Further, the thickness of the first doped layer 31 is less than or equal to the thickness of the second doped layer 32, wherein preferably, the thickness of the first doped layer 31 is less than the thickness of the second doped layer 32. Typically, the thickness of the first doped layer 31 and the second doped layer 32 is in the range of 5-30 nm; preferably, the thickness of the first doped layer 31 is 5-11nm, and the thickness of the second doped layer 32 is 5-13 nm.
For the heterojunction solar cell, the influence of the light absorption effect of the first surface side on the photoelectric conversion efficiency of the cell is far larger than the influence of the light absorption effect of the second surface side on the photoelectric conversion efficiency of the cell, the loss of sunlight on the first surface side when the sunlight passes through the first doping layer 31 can be effectively reduced due to the relatively small thickness of the first doping layer 31, the short-circuit current of the heterojunction solar cell can be improved, and the heterojunction solar cell has better photoelectric conversion efficiency; the second surface side does not need to consider the light absorption problem too much, and the relatively thick second doped layer 32 can have better conductivity, thereby reducing the contact resistance between it and the second transparent conductive film 42.
The silicon substrate 10 related in the present invention may specifically be a p-type single crystal silicon substrate, or may be an n-type single crystal silicon substrate; however, in a preferred embodiment of the present invention, the single crystal silicon substrate 10 is an n-type single crystal silicon substrate. When the monocrystalline silicon substrate 10 is an n-type monocrystalline silicon substrate, the first doping layer 31 is doped n-type, that is, doped with phosphorus; the second doped layer 32 is p-type doped, i.e. doped with boron.
In more specific embodiments, as shown in fig. 3, the doping film forming the first doping layer 31 is a phosphorus doping film. Specifically, the phosphorus-doped film includes a first phosphorus-doped film 311, a second phosphorus-doped film 312 and a third phosphorus-doped film 313 stacked in sequence outside the first intrinsic layer 21, wherein the phosphorus-doped concentrations in the first phosphorus-doped film 311, the second phosphorus-doped film 312 and the third phosphorus-doped film 312 are 50-150ppm, 100-300ppm and 200-400ppm, respectively.
Preferably, the thicknesses of the first phosphorus-doped film 311, the second phosphorus-doped film 312, and the third phosphorus-doped film 313 are 2-4nm, and 1-3nm, respectively.
Further, in the embodiment shown in fig. 2, the doped film constituting the second doped layer 32 is a boron doped film, and the boron doped film includes a first boron doped film 321, a second boron doped film 322 and a third boron doped film 323 sequentially stacked and disposed outside the second intrinsic layer 22. Wherein the boron doping concentrations in the first boron doping film 321, the second boron doping film 322 and the third boron doping film 323 are respectively 100-300ppm, 200-500ppm and 400-600 ppm. Since the boron doping concentrations in the first boron-doped film 321, the second boron-doped film 322, and the third boron-doped film 323 are sequentially greater than the phosphorus doping concentrations in the first phosphorus-doped film 311, the second phosphorus-doped film 312, and the third phosphorus-doped film 312, the average doping concentration of the first doped layer 31 can be smaller than the average doping concentration of the second doped layer 32.
Preferably, the thicknesses of the first boron-doped film 321, the second boron-doped film 322, and the third boron-doped film 323 are 2-5nm, and 1-3nm, respectively.
The invention further provides a manufacturing method of the heterojunction solar cell. The method specifically comprises the following steps:
a silicon substrate 10 providing step;
an intrinsic layer forming step of forming a first intrinsic layer 21 and a second intrinsic layer 22 on a first surface side and a second surface side of the silicon substrate 10, respectively, the forming steps of the first intrinsic layer 21 and the second intrinsic layer 22 each including depositing at least two intrinsic amorphous silicon films in sequence, wherein, on each surface side of the silicon substrate 10, a silicon substrate temperature when depositing a previous intrinsic amorphous silicon film is lower than a silicon substrate temperature when depositing a subsequent intrinsic amorphous silicon film;
and a doping layer forming step of forming a first doping layer 31 and a second doping layer 32 having opposite doping types on the surfaces of the first intrinsic layer 21 and the second intrinsic layer 22, respectively.
In the embodiment of the present invention, the first intrinsic layer 21, the first doped layer 31, the second intrinsic layer 22 and the second doped layer 32 are formed by a PECVD process. In the process of forming the first intrinsic layer 21 and the second intrinsic layer 22, the intrinsic amorphous silicon films with different crystallization rates can be manufactured by adjusting the temperature of the silicon substrate 10 during deposition of the intrinsic amorphous silicon films.
In the embodiment of fig. 2 of the present invention, the step of forming the first intrinsic layer 21 includes sequentially depositing three layers of intrinsic amorphous silicon films on the first surface side of the silicon substrate 10 by PECVD, and the temperature ranges of the silicon substrate when depositing the three layers of intrinsic amorphous silicon films are sequentially 200-. Namely, the temperature range for depositing the first intrinsic amorphous silicon film 211 is 200-220 ℃, the temperature range for depositing the second intrinsic amorphous silicon film 212 is 240-260 ℃, and the temperature range for depositing the third intrinsic amorphous silicon film 213 is 280-300 ℃.
Further, the forming step of the second intrinsic layer 22 also includes sequentially depositing three layers of intrinsic amorphous silicon films on the second surface side of the silicon substrate 10 by PECVD, and the temperature ranges of the silicon substrate 10 when depositing the three layers of intrinsic amorphous silicon films are sequentially 200-. Namely, the temperature range for depositing the fourth intrinsic amorphous silicon film 221 is 200-220 ℃, the temperature range for depositing the fifth intrinsic amorphous silicon film 222 is 240-260 ℃, and the temperature range for depositing the sixth intrinsic amorphous silicon film 223 is 280-300 ℃.
Preferably, in some embodiments of the present invention, the intrinsic layer forming step further comprises depositing an intrinsic amorphous silicon oxide film on the outermost intrinsic amorphous silicon film on at least one surface side of the silicon substrate 10.
In other preferred embodiments of the present invention, the reaction gas for depositing the intrinsic amorphous silicon film comprises H2And SiH4H in the reaction gas in depositing the previous intrinsic amorphous silicon film on each surface side of the silicon substrate 102Has a volume concentration higher than that of H in the reaction gas in the deposition of the intrinsic amorphous silicon film2The volume concentration of (c).
In more detail, as shown in fig. 2, in this embodiment, the first intrinsic layer 21 includes a first intrinsic amorphous silicon film 211, a second intrinsic amorphous silicon film 212, and a third intrinsic amorphous silicon film 213 sequentially deposited on the first surface side of the silicon substrate 10 by PECVD, and the second intrinsic layer 22 includes a fourth intrinsic amorphous silicon film 221, a fifth intrinsic amorphous silicon film 222, and a sixth intrinsic amorphous silicon film 223 sequentially deposited on the second surface side of the silicon substrate 10 by PECVD. In specific implementation, the compound is represented by H2And SiH4H is used as a reaction gas, the deposition pressure is 60-300 Pa, and the first intrinsic amorphous silicon film 211 and the fourth intrinsic amorphous silicon film 221 are deposited2Has a volume concentration of 0.5% -2%, and the second intrinsic amorphous silicon film 212 and the fifth intrinsic amorphous silicon film are depositedIntrinsic amorphous silicon film 222H2Has a volume concentration of 0.5% -1%, and is H when the third and sixth intrinsic amorphous silicon films 213 and 223 are deposited2The volume concentration of (A) is 0.1-0.5%.
In the present invention, since H is contained in the reaction gas during the deposition of the previous intrinsic amorphous silicon film2Has a volume concentration higher than that of H in the reaction gas in the deposition of the intrinsic amorphous silicon film2Can be made such that the hydrogen content in the first intrinsic amorphous silicon film 211 is higher than that in the second intrinsic amorphous silicon film 212, and the hydrogen content in the second intrinsic amorphous silicon film 212 is higher than that in the third intrinsic amorphous silicon oxide film 213. Accordingly, the hydrogen content in the fourth intrinsic amorphous silicon film 221 is also made higher than that in the fifth intrinsic amorphous silicon film 222, and the hydrogen content in the fifth intrinsic amorphous silicon film 222 is made higher than that in the sixth intrinsic amorphous silicon oxide film 223.
In the specific implementation process, the thickness of each intrinsic film can be controlled by controlling the forming time of each intrinsic film.
In addition, in order to save the forming time of the intrinsic layer, in the specific implementation of the implementation structure shown in fig. 2, the first intrinsic amorphous silicon film 211 and the fourth intrinsic amorphous silicon film 221 may be simultaneously deposition-formed, the second intrinsic amorphous silicon film 212 and the fifth intrinsic amorphous silicon film 222 may be simultaneously deposition-formed, and the third intrinsic amorphous silicon film 213 and the sixth intrinsic amorphous silicon film 223 may be simultaneously deposition-formed.
Preferably, the manufacturing method according to the present invention further comprises, after each intrinsic amorphous silicon film forming step, introducing pure H to the surface of the corresponding intrinsic amorphous silicon film2And performing plasma treatment. Specifically, after the first, second, third, fourth, fifth and sixth intrinsic amorphous silicon films 211, 212, 213, 221, 222 and 223 are deposited, pure H is introduced into the respective intrinsic amorphous silicon films2And performing plasma treatment.
In the present invention, by increasing pure H2The plasma treatment can further improve the corresponding intrinsic amorphous silicon filmFurther improves the passivation effect of the first intrinsic layer 21 and the second intrinsic layer 22 on the silicon substrate 10.
It is understood that in some less preferred embodiments of the present invention, pure H may be added only once after the third and sixth intrinsic amorphous silicon films 213 and 223 are formed, respectively2Plasma treatment is performed.
In another embodiment of the present invention, at least one of the steps of forming the first doping layer 31 and the second doping layer 32 includes sequentially forming at least two doping films, and of two adjacent doping films sequentially formed, a doping concentration of a doping film far from the silicon substrate 10 is greater than a doping concentration of a doping film near the silicon substrate.
In the case of the heterojunction solar cell of the embodiment shown in fig. 3, the first doping layer 31 is formed by sequentially forming three phosphorus-doped films on the surface of the first intrinsic layer 21, and forming the three phosphorus-doped films at PH in a direction away from the silicon substrate3/SiH4The flow rate ratio ranges are 50-150ppm, 100-300ppm and 200-400ppm in sequence. The second doping layer 32 forming step includes sequentially forming three boron-doped films on the surface of the second intrinsic layer 22, in a direction away from the silicon substrate, B when the three boron-doped films are formed2H6/SiH4The flow rate ratio ranges are 50-150ppm, 100-250ppm and 200-300ppm in sequence.
More specifically, one specific formation step of the first doping layer 31 is: heating the PECVD coating cavity to 180 ℃, and controlling the pressure to be 30-200 pa; PH is introduced to the surface of the first intrinsic layer 213、SiH4And H2Control of pH3/SiH4The flow rate proportion value is 50-150ppm, and a first phosphorus doped film 311 is formed by deposition; then adjusting the pH3/SiH4The flow rate ratio is 100-300ppm, and a second phosphorus-doped film 312 is deposited; finally adjusting the pH3/SiH4The flow rate ratio is 200-400ppm, and a third phosphorus doped film 313 is deposited. All the doped films in the first doped layer 31 formed by this step are doped amorphous silicon films, and SiH is maintained during the formation of the first doped layer 314The flow rate is not changed, and the flow rate is not changed,by adjusting H2Flow rate to maintain constant chamber pressure.
In still other embodiments of the present invention, when all the doped films of the first doped layer 31 are doped amorphous silicon oxide films, a specific forming step of the first doped layer 31 is: heating the PECVD coating cavity to 180 ℃, and controlling the pressure to be 30-200 pa; PH is introduced to the surface of the first intrinsic layer 213、SiH4、 CO2And H2Control of pH3/SiH4Flow rate ratio of 50-150ppm, CO2/SiH4The flow ratio value is 0.5-2, and a first phosphorus doped film 311 is formed by deposition; then adjusting the pH3/SiH4The flow rate ratio value is 100-300ppm, CO2/SiH4The flow ratio value of 0.5-2, and depositing to form a second phosphorus-doped film 312; finally adjusting the pH3/SiH4The flow rate ratio is 200-400ppm, CO2/SiH4The flow ratio value of (3) is 0.5-2, and the third phosphorus-doped film 313 is deposited. During the formation of the first doped layer 31 by this step, SiH is maintained4The flow is not changed, and H is adjusted2Flow rate to maintain constant chamber pressure.
Accordingly, one specific forming step of the second doping layer 32 is: heating the PECVD coating cavity to 180 ℃, and controlling the pressure to be 30-200 pa; b is introduced to the surface of the second intrinsic layer 222H6、SiH4And H2Control of B2H6/SiH4The flow rate ratio value is 50-150ppm, and a first boron doped film 321 is formed by deposition; then adjust B2H6/SiH4Depositing to form a second boron doped film 322 when the flow ratio value is 100-250 ppm; finally, adjust B2H6/SiH4The flow rate ratio reaches 200-300ppm, and a third boron-doped film 323 is deposited. All the doped films of the second doped layer 32 formed by this step are doped amorphous silicon films, and SiH is maintained during the formation of the second doped layer 324Flow is unchanged by adjusting H2Flow rate to maintain constant chamber pressure.
In still other embodiments of the present invention, when all the doped films of the second doped layer 32 are doped amorphous silicon oxideIn the case of a film, one specific formation step of the second doping layer 32 is: heating the PECVD coating cavity to 180 ℃, and controlling the pressure to be 30-200 pa; b is introduced towards the surface of the second intrinsic layer 222H6、SiH4、CO2And H2Control of B2H6/SiH4Flow rate ratio of 50-150ppm, CO2/SiH4The flow ratio value of 0.5-2, and depositing to form a first boron-doped film 321; then adjust B2H6/SiH4The flow rate ratio is 100-250ppm, CO2/SiH4The flow ratio value is 0.5-2, and a second boron-doped film 322 is formed by deposition; finally, adjust B2H6/SiH4The flow rate ratio is 200-300ppm, CO2/SiH4The flow ratio value of 0.5-2, and a third boron-doped film 323 is deposited. During the formation of the second doped layer 32 by this step, SiH is maintained4The flow is not changed, and H is adjusted2Flow rate to maintain constant chamber pressure.
It is understood that in the specific implementation process, the thickness of each doped film can be controlled by controlling the forming time of each doped film.
It can be understood that the method for manufacturing a heterojunction solar cell according to the present invention further comprises:
a transparent conductive film manufacturing step: the first transparent conductive film layer 41 and the second transparent conductive film layer 42 are respectively formed on the surfaces of the first doped layer 31 and the second doped layer 32 by PVD deposition, RPD deposition or magnetron sputtering deposition.
A collector manufacturing step: respectively printing a layer of low-temperature conductive silver paste on the first transparent conductive film layer 41 and the second transparent conductive film layer 42 by a screen printing method, and then sintering at a low temperature of 150-300 ℃ to form good ohmic contact, thereby forming a first collector 51 and a second collector 52.
One specific implementation manner of the first transparent conductive film 41 and the second transparent conductive film 42 is as follows: heating a deposition chamber of the PVD equipment to 190 ℃; placing the silicon substrate 10 with the first doping layer 31 and the second doping layer 32 on a carrier plate and conveying the silicon substrate into a deposition chamber; in the first dopingITO (In) is adopted on the surface of the impurity layer 312O3：SnO297: 3) coating a target to deposit and form a first transparent conductive film layer 41 with the thickness of 70-100 nm; ITO (In) is adopted on the surface of the second doping layer 322O3：SnO2When the ratio is 90: 10) the target is coated to deposit a second transparent conductive film layer 42 of 70-100 nm.
It can be understood that ITO (In)2O3：SnO297: 3) the target refers to In ITO target material2O3With SnO2The mass proportion is 97: 3, ITO (In)2O3：SnO2When the ratio is 90: 10) the target refers to In ITO target material2O3With SnO2The mass proportion is 90: 10. oxide SnO doped in first transparent conductive film layer 412The content of the first transparent conductive film layer 41 is relatively low, so that the light transmission of the first transparent conductive film layer 41 is better, and the light receiving effect of the first surface side of the heterojunction solar cell is facilitated; the second transparent conductive film layer 42 is doped with oxide SnO2The content of (b) is relatively high so that the second transparent conductive film layer 42 has better conductivity, and the contact resistance between the second transparent conductive film layer 42 and the second collector electrode can be optimized.
In addition, in the present invention, one specific embodiment of the step of providing the silicon substrate 10 is: selecting an n-type monocrystalline silicon wafer, preferably selecting an n-type monocrystalline silicon wafer with the resistivity of 0.3-3.3 omega-cm and the thickness of 155-220 mu m; firstly, removing a surface oxide layer by using an HF solution with the volume concentration of 5%, then, using the anisotropic corrosion characteristic of monocrystalline silicon, adopting a KOH or NaOH alcohol-added solution to perform texturing, and forming a shallow pyramid structure on the surface of an n-type monocrystalline silicon wafer by using the anisotropic corrosion of the monocrystalline silicon to obtain the silicon substrate 10. Wherein the temperature of the KOH or NaOH alcohol solution is 85 ℃, the volume concentration of KOH or NaOH is 10%, and the corrosion time is 120-180 s; the cleaned silicon wafer surface has no spots, scratches and water marks, and the cleanness of the silicon wafer surface is high.
It should be understood that although the present description refers to embodiments, not every embodiment contains only a single technical solution, and such description is for clarity only, and those skilled in the art should make the description as a whole, and the technical solutions in the embodiments can also be combined appropriately to form other embodiments understood by those skilled in the art.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.
Claims (18)
1. A heterojunction solar cell, comprising: the semiconductor device comprises a silicon substrate, a first intrinsic layer, a first doping layer, a second intrinsic layer, a second doping layer and a third doping layer, wherein the first intrinsic layer and the first doping layer are sequentially stacked on the first surface side of the silicon substrate, the second intrinsic layer and the second doping layer are sequentially stacked on the second surface side of the silicon substrate, and the doping type of the second doping layer is opposite to that of the first doping layer; the silicon substrate is characterized in that the first intrinsic layer and the second intrinsic layer respectively comprise at least two intrinsic amorphous silicon films which are sequentially stacked, and on each surface side of the silicon substrate, the crystallization rate of the intrinsic amorphous silicon film close to the silicon substrate is smaller than that of the intrinsic amorphous silicon film far away from the silicon substrate.
2. The heterojunction solar cell of claim 1, wherein the first intrinsic layer comprises three intrinsic amorphous silicon films sequentially stacked, and the crystallization rates of the three intrinsic amorphous silicon films are sequentially in a direction from the silicon substrate to the first intrinsic layer: not more than 5%, 10% -20%, 20% -50%.
3. The heterojunction solar cell of claim 1, wherein the second intrinsic layer comprises three intrinsic amorphous silicon films stacked in sequence, and the crystallization rates of the three intrinsic amorphous silicon films are sequentially in a direction from the silicon substrate to the second intrinsic layer: not more than 5%, 10% -20%, 20% -50%.
4. The heterojunction solar cell of any of claims 1 to 3, wherein said first intrinsic layer and/or said second intrinsic layer further comprises an intrinsic amorphous silicon oxide film disposed on an outer surface of said intrinsic amorphous silicon film of the outermost layer.
5. The heterojunction solar cell of any of claims 1 to 3, wherein on each surface side of said silicon substrate, the hydrogen content in the intrinsic amorphous silicon film closer to said silicon substrate is greater than the hydrogen content in the intrinsic amorphous silicon film farther from said silicon substrate.
6. The heterojunction solar cell of claim 1, wherein at least one of the first doped layer and the second doped layer comprises at least two doped films stacked one on another, and a doping concentration of a doped film far from the silicon substrate is greater than a doping concentration of a doped film near the silicon substrate in two adjacent doped films.
7. The heterojunction solar cell of claim 6, wherein the doped film is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film, or a doped microcrystalline silicon oxide film.
8. The heterojunction solar cell of claim 6 or 7, wherein the first surface is a light-receiving surface, the doped film constituting the first doped layer is a phosphorus-doped film, the phosphorus-doped film comprises a first phosphorus-doped film, a second phosphorus-doped film and a third phosphorus-doped film sequentially stacked and disposed outside the first intrinsic layer, and the phosphorus-doped concentrations in the first phosphorus-doped film, the second phosphorus-doped film and the third phosphorus-doped film are 50-150ppm, 100-300ppm and 200-400ppm, respectively.
9. The heterojunction solar cell of claim 6 or 7, wherein the second surface is a backlight surface, the doped film constituting the second doped layer is a boron doped film, the boron doped film comprises a first boron doped film, a second boron doped film and a third boron doped film sequentially stacked and arranged outside the second intrinsic layer, and the boron doping concentrations in the first boron doped film, the second boron doped film and the third boron doped film are respectively 100-300ppm, 200-500ppm and 400-600 ppm.
10. A method for manufacturing a heterojunction solar cell is characterized by comprising the following steps:
a silicon substrate providing step;
an intrinsic layer forming step of forming a first intrinsic layer and a second intrinsic layer on a first surface side and a second surface side of the silicon substrate, respectively, the first intrinsic layer and the second intrinsic layer forming step each including depositing at least two intrinsic amorphous silicon films in sequence, wherein, on each surface side of the silicon substrate, a temperature of the silicon substrate when a previous intrinsic amorphous silicon film is deposited is lower than a temperature of the silicon substrate when a subsequent intrinsic amorphous silicon film is deposited;
and a doped layer forming step of forming a first doped layer and a second doped layer with opposite doping types on the surfaces of the first intrinsic layer and the second intrinsic layer respectively.
11. The method as claimed in claim 10, wherein the step of forming the first intrinsic layer comprises sequentially depositing three intrinsic amorphous silicon films on the first surface side of the silicon substrate by PECVD, and the temperature ranges of the silicon substrate when depositing the three intrinsic amorphous silicon films are sequentially 200-220 ℃, 240-260 ℃ and 280-300 ℃.
12. The method as claimed in claim 10, wherein the step of forming the second intrinsic layer comprises sequentially depositing three intrinsic amorphous silicon films on the second surface side of the silicon substrate by PECVD, and the temperature ranges of the silicon substrate when depositing the three intrinsic amorphous silicon films are sequentially 200-220 ℃, 240-260 ℃ and 280-300 ℃.
13. The method of claim 10, wherein the intrinsic layer forming step further comprises depositing an intrinsic amorphous silicon oxide film on the outermost intrinsic amorphous silicon film on at least one surface side of the silicon substrate.
14. The method of any of claims 10-13, wherein the reaction gas for depositing the intrinsic amorphous silicon film comprises H2And SiH4H in the reaction gas in depositing the previous intrinsic amorphous silicon film on each surface side of the silicon substrate2Has a volume concentration higher than that of H in the reaction gas in the deposition of the intrinsic amorphous silicon film2The volume concentration of (c).
15. The method of any one of claims 10-13, further comprising passing pure H toward the surface of the corresponding intrinsic amorphous silicon film after each intrinsic amorphous silicon film formation step2And performing plasma treatment.
16. The method according to claim 10, wherein at least one of the first doped layer forming step and the second doped layer forming step comprises sequentially forming at least two doped films, and the doped film far away from the silicon substrate has a doping concentration greater than that of the doped film near the silicon substrate in two adjacent doped films sequentially formed.
17. The method according to claim 16, wherein the first doping layer forming step comprises sequentially forming three phosphorus-doped films on the surface of the first intrinsic layer, and forming three phosphorus-doped films at PH in a direction away from the silicon substrate3/SiH4The flow rate ratio ranges are 50-150ppm, 100-300ppm and 200-400ppm in sequence.
18. The method of claim 16 or 17The manufacturing method of the heterojunction solar cell is characterized in that the second doping layer forming step comprises the steps of sequentially forming three boron doping films on the surface of the second intrinsic layer, and forming B when the three boron doping films are formed in the direction far away from the silicon substrate2H6/SiH4The flow rate ratio ranges are 50-150ppm, 100-250ppm and 200-300ppm in sequence.
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| 戴松元: "薄膜太阳电池关键科学和技术", 31 January 2013, 上海：上海科学技术出版社, pages: 58 - 59 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024198703A1 (en) * | 2023-03-29 | 2024-10-03 | 晶澳（扬州）太阳能科技有限公司 | Solar cell and manufacturing method therefor |
| CN116646429A (en) * | 2023-05-30 | 2023-08-25 | 眉山琏升光伏科技有限公司 | Carbon dioxide gradient layering doping passivation amorphous silicon method and solar cell |
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