Bifacial heterojunction solar cells and photovoltaic modules

Abstract

The present invention provides a double-sided heterojunction solar cell and a photovoltaic module. The second doped amorphous layer located on the backlight side of a single-crystal silicon substrate in the double-sided heterojunction solar cell involved in the invention comprises a first doped amorphous silicon film located on the surface of the second intrinsic amorphous layer and a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film located on the surface of the first doped amorphous silicon film. Based on the structure, the light transmittance of the second doped amorphous layer can be improved under the premise of ensuring good contact between the second doped amorphous layer and the second intrinsic amorphous silicon layer, thereby reducing the loss of sunlight when entering the interior of the double-sided heterojunction solar cell from the backlight side, improving the short-circuit current of the double-sided heterojunction solar cell, and further optimizing the photoelectric conversion efficiency of the double-sided heterojunction solar cell while also improving the bifaciality of the double-sided heterojunction solar cell.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic manufacturing, and in particular to a double-sided heterojunction solar cell and a photovoltaic module. Background Art

[0002] Heterojunction solar cells are currently a more efficient crystalline silicon solar cell. They combine the characteristics of crystalline silicon cells and silicon-based thin-film cells, and have the advantages of short manufacturing process, low process temperature, high conversion efficiency and high power generation. Figure 1 The figure shows a schematic diagram of the structure of a double-sided heterojunction solar cell involved in the prior art, which includes, from top to bottom, a first collector 51', a first transparent conductive film layer 41', a first doped amorphous layer 31', a first intrinsic amorphous layer 21', a single crystal silicon substrate 10', a second intrinsic amorphous layer 22', a second doped amorphous layer 32', a second transparent conductive film layer 42', and a second collector 52'.

[0003] The second doped amorphous layer 32' involved in the prior art is usually composed of a doped amorphous silicon film, which has excellent electrical properties and high conductivity, so that the second doped amorphous layer 32' has good contact with the second intrinsic amorphous layer 22'; however, the doped amorphous silicon film has the defect of poor light transmittance, which will, to a certain extent, make it impossible to further improve the bifaciality and efficiency of the double-sided heterojunction solar cell. The prior art has a method of adjusting the optical band gap by adjusting the doping concentration of the second doped amorphous layer 32' in order to increase the light transmittance, but this method is not effective.

[0004] In view of this, it is necessary to provide an improved technical solution to solve the above problems. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To achieve the above-mentioned purpose of the invention, the present invention provides a double-sided heterojunction solar cell, and its specific design is as follows.

[0006] A double-sided heterojunction solar cell comprises: a single-crystal silicon substrate, a first intrinsic amorphous layer, a first doped amorphous layer, a first transparent conductive film layer and a first collector layered in sequence on the light-receiving surface of the single-crystal silicon substrate, a second intrinsic amorphous layer, a second doped amorphous layer with a doping type opposite to that of the first doped amorphous layer, a second transparent conductive film layer and a second collector layered in sequence on the backlight surface of the single-crystal silicon substrate; the second doped amorphous layer comprises a first doped amorphous silicon film located on the surface of the second intrinsic amorphous layer and a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film located on the surface of the first doped amorphous silicon film.

[0007] Further, the thickness of the first doped amorphous silicon film is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

[0008] Further, the thickness of the first doped amorphous silicon film is 1-5 nm, and the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 2-15 nm.

[0009] Furthermore, the carrier concentration in the first doped amorphous silicon film and the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 1E18-1E21 / cm 3 .

[0010] Furthermore, the carrier concentration in the first doped amorphous silicon film is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

[0011] Furthermore, the carrier concentration in the first doped amorphous silicon film is 5E19-5E20 / cm 3 The carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 5E18-5E19 / cm 3 .

[0012] Furthermore, the carrier mobility in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

[0013] Furthermore, the crystallization rate of the first doped amorphous silicon film is 25%-85%.

[0014] Furthermore, the crystallization rate of the first doped amorphous silicon film is 50%-70%.

[0015] Furthermore, the second doped amorphous layer further includes a second doped amorphous silicon film located on a surface of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

[0016] Further, the thickness of the second doped amorphous silicon film is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

[0017] Furthermore, the thickness of the second doped amorphous silicon film is 1-3 nm.

[0018] Furthermore, the carrier concentration in the second doped amorphous silicon film is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

[0019] Furthermore, the carrier concentration in the second doped amorphous silicon film is 1E19-1E21 / cm 3 .

[0020] Furthermore, the first doped amorphous layer includes a third doped amorphous silicon film located on the surface of the first intrinsic amorphous layer and a second doped amorphous silicon oxide film or a second doped amorphous silicon carbide film located on the surface of the third doped amorphous silicon film.

[0021] Further, the thickness of the third doped amorphous silicon film is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

[0022] Further, the thickness of the third doped amorphous silicon film is 1-5 nm, and the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 2-15 nm.

[0023] Furthermore, the carrier concentration in the third doped amorphous silicon film and the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 1E18-1E21 / cm 3 .

[0024] Furthermore, the carrier concentration in the third doped amorphous silicon film is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

[0025] Furthermore, the carrier concentration in the third doped amorphous silicon film is 5E19-5E20 / cm 3 The carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 5E18-5E19 / cm 3 .

[0026] Furthermore, the carrier mobility in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

[0027] Furthermore, a crystallization rate of the third doped amorphous silicon film is lower than a crystallization rate of the first doped amorphous silicon film.

[0028] Furthermore, the crystallization rate of the third doped amorphous silicon film is 20%-70%.

[0029] Furthermore, the crystallization rate of the first doped amorphous silicon film is 45%-65%.

[0030] Furthermore, the first doped amorphous layer further includes a fourth doped amorphous silicon film located on a surface of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

[0031] Further, the thickness of the fourth doped amorphous silicon film is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

[0032] Furthermore, the thickness of the fourth doped amorphous silicon film is 1-3 nm.

[0033] Furthermore, the carrier concentration in the fourth doped amorphous silicon film is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

[0034] Furthermore, the carrier concentration in the fourth doped amorphous silicon film is 1E19-1E21 / cm 3 .

[0035] Furthermore, the sum of the thicknesses of the first intrinsic amorphous layer and the first doped amorphous layer is less than or equal to the sum of the thicknesses of the second intrinsic amorphous layer and the second doped amorphous layer.

[0036] Furthermore, the thickness of the first doped amorphous layer is smaller than the thickness of the second doped amorphous layer.

[0037] The present invention also provides a photovoltaic module, which has the above-mentioned double-sided heterojunction solar cell.

[0038] The beneficial effect of the present invention is that in the double-sided heterojunction solar cell structure provided by the present invention, since the second doped amorphous layer includes a first doped amorphous silicon film located on the surface of the second intrinsic amorphous layer and a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film located on the surface of the first doped amorphous silicon film, the light transmittance of the second doped amorphous layer can be improved under the premise of ensuring that the second doped amorphous layer and the second intrinsic amorphous silicon layer have good contact, thereby reducing the loss of sunlight when entering the interior of the double-sided heterojunction solar cell from the backlight side, improving the short-circuit current of the double-sided heterojunction solar cell, and further optimizing the photoelectric conversion efficiency of the double-sided heterojunction solar cell while also improving the bifaciality of the double-sided heterojunction solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 The figure shows a schematic structural diagram of a double-sided heterojunction solar cell in the prior art;

[0041] Figure 2The figure shows a schematic diagram of the first embodiment of the double-sided heterojunction solar cell of the present invention;

[0042] Figure 3 The figure shows a second structural schematic diagram of a double-sided heterojunction solar cell according to the present invention;

[0043] Figure 4 Shown is a schematic diagram of a third embodiment of a double-sided heterojunction solar cell of the present invention;

[0044] Figure 5 Shown is a schematic diagram of a fourth embodiment of a double-sided heterojunction solar cell of the present invention;

[0045] Figure 6 The figure shows the transmission curves of a 10 nm thick amorphous silicon film, an amorphous silicon oxide film, and an amorphous silicon carbide film.

[0046] In the figure, 10 is a single crystal silicon substrate, 21 is a first intrinsic amorphous layer, 31 is a first doped amorphous layer, 311 is a third doped amorphous silicon film, 312 is a second doped amorphous silicon oxide film or a second doped amorphous silicon carbide film, 313 is a fourth doped amorphous silicon film, 41 is a first transparent conductive film layer, 51 is a first collector, 22 is a second intrinsic amorphous layer, 32 is a second doped amorphous layer, 321 is a first doped amorphous silicon film, 322 is a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film, 323 is a second doped amorphous silicon film, 42 is a second transparent conductive film layer, and 52 is a second collector. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] refer to Figure 2 As shown, the double-sided heterojunction solar cell involved in the present invention includes: a single crystal silicon substrate 10, a first intrinsic amorphous layer 21, a first doped amorphous layer 31, a first transparent conductive film layer 41 and a first collector 51 stacked in sequence on the light-receiving surface of the single crystal silicon substrate 10, and a second intrinsic amorphous layer 22, a second doped amorphous layer 32, a second transparent conductive film layer 42 and a second collector 52 stacked in sequence on the backlight surface of the single crystal silicon substrate 10.

[0049] In the present invention, the light-receiving surface of the monocrystalline silicon substrate 10 involved refers to the surface of the heterojunction solar cell that directly receives sunlight, and the backlight surface refers to the surface of the heterojunction solar cell that does not directly receive sunlight, that is, the surface opposite to the light-receiving surface. The monocrystalline silicon substrate involved can be an N-type silicon substrate or a P-type silicon substrate, wherein an N-type monocrystalline silicon substrate is preferred. The first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 are both intrinsic amorphous silicon. The doping types of the first doped amorphous silicon layer 31 and the second doped amorphous silicon layer 32 are opposite, one of which is N-type doped, that is, phosphorus doped; and the other is P-type doped, that is, boron doped.

[0050] refer to Figure 2 As shown, the second doped amorphous layer 32 involved in the present invention includes a first doped amorphous silicon film 321 located on the surface of the second intrinsic amorphous layer 22 and a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film 322 located on the surface of the first doped amorphous silicon film 321 .

[0051] Doped amorphous silicon oxide and doped amorphous silicon carbide have better light transmittance than doped amorphous silicon. Figure 6 It can be seen that amorphous silicon film completely transmits light above 700nm, but has strong absorption below 700nm, which significantly reduces the transmittance of light below 700nm, making it impossible for light below 700nm to efficiently generate photogenerated carriers, limiting the improvement of the photovoltaic conversion efficiency of the battery. However, compared with amorphous silicon film, amorphous silicon oxide film or amorphous silicon carbide film can significantly improve the transmittance of light below 700nm, thereby significantly increasing the short-circuit current of the battery.

[0052] The second doped amorphous layer 32' in the prior art is usually a single-layer doped amorphous silicon film structure; Figure 2 In the illustrated embodiment, the second doped amorphous layer 32 adopts a double-layer film design, wherein the first doped amorphous silicon film 321 can ensure good contact between the second doped amorphous layer 32 and the second intrinsic amorphous layer 22, and the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is equivalent to replacing part of the doped amorphous silicon in the prior art with doped amorphous silicon oxide or doped amorphous silicon carbide having high transmittance, thereby improving the overall transmittance of the second doped amorphous layer 32 and reducing the loss of sunlight when entering the interior of the double-sided heterojunction solar cell from the backlight side, thereby optimizing the photoelectric conversion efficiency of the double-sided heterojunction solar cell while also improving the bifaciality of the double-sided heterojunction solar cell.

[0053] That is, based on the combination of the first doped amorphous silicon film 321 , the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 , the double-sided heterojunction solar cell provided by the present invention has relatively excellent photoelectric performance.

[0054] exist Figure 2 In the embodiment, the first doped amorphous silicon film 321 is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322; preferably, the first doped amorphous silicon film 321 is generally less than the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322. In this way, while ensuring good contact between the second doped amorphous layer 32 and the second intrinsic amorphous layer 22, the second doped amorphous layer 32 can have good light transmittance to a great extent.

[0055] In a specific implementation process, the thickness of the first doped amorphous silicon film 321 is 1-5 nm, and the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is 2-15 nm.

[0056] In the present invention, the carrier concentration in the first doped amorphous silicon film 321 and the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 are 1E18-1E21 / cm 3 .

[0057] As a preferred embodiment of the present invention, the carrier concentration in the first doped amorphous silicon film 321 is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322. The carrier concentration in the first doped amorphous silicon film 321 is set to be relatively large (i.e., highly doped), so that the second doped amorphous layer 32 has better carrier transport performance at the contact position with the second intrinsic amorphous layer 22; while the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is set to be relatively small, so that the problem of excessive light parasitic absorption due to excessively high doping concentration when light penetrates the second doped amorphous layer 32 can be reduced.

[0058] As some preferred embodiments, the carrier concentration in the first doped amorphous silicon film 321 is 5E19-5E20 / cm 3 The carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is 5E18-5E19 / cm 3 .

[0059] In a preferred embodiment of the present invention, since the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 in the second doped amorphous layer 32 is relatively small, the overall carrier transport performance of the second doped amorphous layer 32 is determined by the carrier transport performance of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322. In order to avoid the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 affecting the overall carrier transport performance of the second doped amorphous layer 32, the carrier mobility in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is usually set to be greater than 10 cm 2 V-1 s -1 Preferably, the carrier mobility in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

[0060] To achieve a high doping effect of the first doped amorphous silicon film 321, in a specific implementation process, the first doped amorphous silicon film 321 may be partially crystallized, usually with a crystallization rate of 25%-85%. Preferably, the crystallization rate of the first doped amorphous silicon film 321 is 50%-70%.

[0061] In another embodiment of the present invention, reference Figure 3 As shown, Figure 2 The implemented structures are different. In this embodiment, the second doped amorphous layer 32 includes a second doped amorphous silicon film 323 located on the surface of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322. The second doped amorphous silicon film 323 is provided to optimize the contact between the second doped amorphous layer 32 and the second transparent conductive film layer 42.

[0062] Preferably, the thickness of the second doped amorphous silicon film 323 is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322. In a specific implementation, the thickness of the second doped amorphous silicon film 323 is 1-3 nm.

[0063] To ensure better contact between the second doped amorphous layer 32 and the second transparent conductive film layer 42 , in the present invention, the carrier concentration in the second doped amorphous silicon film 323 is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 .

[0064] The carrier concentration in the second doped amorphous silicon film 323 is 1E19-1E21 / cm 3 ; As a preferred range, the carrier concentration in the second doped amorphous silicon film 323 is 5E19-5E20 / cm 3 .

[0065] refer to Figure 4 As shown, in this embodiment, the first doped amorphous layer 31 involved in the present invention includes a third doped amorphous silicon film 311 located on the surface of the first intrinsic amorphous layer 21 and a second doped amorphous silicon oxide film or a second doped amorphous silicon carbide film 312 located on the surface of the third doped amorphous silicon film 311.

[0066] Compared with doped amorphous silicon, doped amorphous silicon oxide and doped amorphous silicon carbide have better light transmittance. For details, please refer to the above description. The first doped amorphous layer 31' involved in the prior art is also usually a single-layer doped amorphous silicon film structure. Figure 4 In the illustrated embodiment, the first doped amorphous layer 31 adopts a double-layer film design, wherein the third doped amorphous silicon film 311 can ensure good contact between the first doped amorphous layer 31 and the first intrinsic amorphous layer 21, and the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 is equivalent to replacing part of the doped amorphous silicon in the prior art with doped amorphous silicon oxide or doped amorphous silicon carbide having high transmittance, thereby improving the overall transmittance of the first doped amorphous layer 31 and reducing the loss of sunlight when it enters the interior of the double-sided heterojunction solar cell from the light-receiving surface, thereby effectively optimizing the photoelectric conversion efficiency of the double-sided heterojunction solar cell.

[0067] exist Figure 4 In the embodiment, the thickness of the third doped amorphous silicon film 311 is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312; preferably, the third doped amorphous silicon film 311 is generally less than the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312. In this way, while ensuring good contact between the first doped amorphous layer 31 and the first intrinsic amorphous layer 21, the first doped amorphous layer 31 can have good light transmittance to a great extent.

[0068] In a specific implementation process, the thickness of the third doped amorphous silicon film 311 is 1-5 nm, and the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 is 2-15 nm.

[0069] In the present invention, the carrier concentration in the third doped amorphous silicon film 311 and the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 are 1E18-1E21 / cm 3 .

[0070] As a preferred embodiment of the present invention, the carrier concentration in the third doped amorphous silicon film 311 is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312. The carrier concentration in the third doped amorphous silicon film 311 is set to be relatively large (i.e., highly doped), so that the first doped amorphous layer 31 has better carrier transport performance at the contact position with the first intrinsic amorphous layer 21; and the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 is set to be relatively small, so that the problem of excessive light parasitic absorption due to excessively high doping concentration when light penetrates the first doped amorphous layer 31 can be reduced.

[0071] As some preferred embodiments, the carrier concentration in the third doped amorphous silicon film 311 is 5E19-5E20 / cm 3 The carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322 is 5E18-5E19 / cm 3.

[0072] In a preferred embodiment of the present invention, since the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 in the first doped amorphous layer 31 is relatively small, the overall carrier transport performance of the first doped amorphous layer 31 is determined by the carrier transport performance of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312. In order to avoid the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 affecting the overall carrier transport performance of the first doped amorphous layer 31, the carrier mobility in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 is generally set to be greater than 10 cm 2 V -1 s -1 Preferably, the carrier mobility in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

[0073] As a preferred embodiment of the present invention, the crystallization rate of the third doped amorphous silicon film 311 is less than that of the first doped amorphous silicon film 321. In the specific implementation process, the higher the crystallization rate, the higher the doping concentration of the corresponding film layer. The setting mode that the crystallization rate of the third doped amorphous silicon film 311 is less than the crystallization rate of the first doped amorphous silicon film 321 can correspondingly make the doping concentration of the third doped amorphous silicon film 311 lower than the doping concentration of the first doped amorphous silicon film 321 to a certain extent, so that the third doped amorphous silicon film 311 located on the light-receiving surface has better light transmission performance, which can ensure that the heterojunction solar cell has a higher photoelectric conversion efficiency as a whole; and the first doped amorphous silicon film 321 located on the backlight surface can reduce the body resistance of the heterojunction solar cell due to the higher doping concentration, thereby improving the filling factor of the heterojunction solar cell.

[0074] In a specific implementation process, the third doped amorphous silicon film 311 is partially crystallized, and the crystallization rate is usually 20%-70%. Preferably, the crystallization rate of the third doped amorphous silicon film 311 is 45%-65%.

[0075] In another embodiment of the present invention, reference Figure 5 As shown, Figure 4 The implemented structures are different. In this embodiment, the first doped amorphous layer 31 includes a fourth doped amorphous silicon film 313 located on the surface of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312. The fourth doped amorphous silicon film 313 is provided to optimize the contact between the first doped amorphous layer 31 and the second transparent conductive film layer 42.

[0076] Preferably, the thickness of the fourth doped amorphous silicon film 313 is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312. In a specific implementation, the thickness of the fourth doped amorphous silicon film 313 is 1-3 nm.

[0077] To ensure better contact between the first doped amorphous layer 31 and the second transparent conductive film layer 42 , in the present invention, the carrier concentration in the fourth doped amorphous silicon film 313 is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312 .

[0078] The carrier concentration in the fourth doped amorphous silicon film 313 is 1E19-1E21 / cm 3 ; As a preferred range, the carrier concentration in the fourth doped amorphous silicon film 313 is 5E19-5E20 / cm 3 .

[0079] In a more specific embodiment of the present invention, the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is less than or equal to the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32. Preferably, the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is less than the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32.

[0080] For a double-sided heterojunction solar cell, the light absorption effect of the light-receiving surface has a much greater influence on the photoelectric conversion efficiency of the cell than the light absorption effect of the backlight surface. Since the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is less than the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32, the loss of sunlight on the light-receiving surface when passing through the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 can be effectively reduced, and the short-circuit current of the double-sided heterojunction solar cell can be increased, so that the double-sided heterojunction solar cell has a better photoelectric conversion efficiency.

[0081] As a further preferred embodiment, the thickness of the first doped amorphous layer 31 is less than or equal to the thickness of the second doped amorphous layer 32 . In some other embodiments of the present invention, the thickness of the first intrinsic amorphous layer 21 is also less than or equal to the thickness of the second intrinsic amorphous layer 22 .

[0082] Furthermore, in the present invention, the thickness of the first transparent conductive film layer 41 is less than or equal to the thickness of the second transparent conductive film layer 42. For the double-sided heterojunction solar cell, since the thickness of the first transparent conductive film layer 41 is relatively small, the loss of sunlight on the light-receiving surface when passing through the first transparent conductive film layer 41 can be effectively reduced, thereby enabling the double-sided heterojunction solar cell to have a better photoelectric conversion efficiency.

[0083] The present invention also provides a photovoltaic module, which has the above-mentioned double-sided heterojunction solar cell.

[0084] The present invention also shows a specific method for manufacturing a double-sided heterojunction solar cell.

[0085] S1. Silicon wafer texturing:

[0086] The surface of the N-type crystalline silicon wafer is textured using a KOH solution to form a texture with a size of 2-4 μm, thereby obtaining a single crystal silicon substrate 10; and O3 or H2O2 is used for cleaning.

[0087] S2. Amorphous silicon thin film production:

[0088] The first intrinsic amorphous layer 21 is grown on the light-receiving surface of the single-crystal silicon substrate 10 using SiH4 diluted by atmospheric H2. Then, PH3 (2000ppm), SiH4, and H2 are introduced into one side of the surface of the first intrinsic amorphous layer 21 to form a third doped amorphous silicon film 311; then, PH3 (500ppm), SiH4, H2, and CO2 or CH4 are introduced into the surface to form a second doped amorphous silicon oxide film or a second doped amorphous silicon carbide film 312 on the surface of the third doped amorphous silicon film 311; optionally, PH3 (2000ppm), SiH4, and H2 are continuously introduced into the surface to form a fourth doped amorphous silicon film 313 on the surface of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film 312.

[0089] After the silicon wafer is turned over, SiH4 diluted by H2 atmosphere is used to grow a second intrinsic amorphous layer 22 on the backlight side of the single crystal silicon substrate 10. Then, B2H6 (2000ppm), SiH4, and H2 are introduced into one side of the surface of the second intrinsic amorphous layer 22 to form a first doped amorphous silicon film 321. Subsequently, B2H6 (500ppm), SiH4, H2, and CO2 or CH4 are introduced to form a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film 322 on the surface of the first doped amorphous silicon film 321; optionally, B2H6 (2000ppm), SiH4, and H2 are continued to be introduced to form a second doped amorphous silicon film 323 on the surface of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film 322.

[0090] S3, collector preparation: The two surfaces of the single crystal silicon substrate 10 on which the amorphous silicon thin film is prepared are respectively formed into a first transparent conductive film 41 and a second transparent conductive film 42 by PVD deposition, RPD deposition or magnetron sputtering deposition process. The first transparent conductive film 41 and the second transparent conductive film 42 are usually made of ITO material or other transparent conductive oxide film (TCO) with excellent conductivity. The specific materials of the first transparent conductive film 41 and the second transparent conductive film 42 may be different to a certain extent. In the specific implementation process, one coating condition is: indium oxide doped with 10% mass concentration of tin oxide is used as the target material, the coating pressure is 6mTorr, the coating atmosphere is Ar and O2, the O2 partial pressure is 0.4mTorr, and the temperature is 150°C.

[0091] S4, printing a layer of low-temperature conductive silver paste on the first transparent conductive film 41 and the second transparent conductive film 42 respectively by screen printing, and then sintering them at a low temperature of 150-300° C. to form a good ohmic contact, thereby forming a first collector 51 and a second collector 52.

[0092] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0093] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A double-sided heterojunction solar cell, comprising: A single crystal silicon substrate, a first intrinsic amorphous layer, a first doped amorphous layer, a first transparent conductive film layer and a first collector layer stacked in sequence on the light-receiving surface of the single crystal silicon substrate, and a second intrinsic amorphous layer, a second doped amorphous layer with a doping type opposite to that of the first doped amorphous layer, a second transparent conductive film layer and a second collector layer stacked in sequence on the backlight surface of the single crystal silicon substrate; characterized in that the second doped amorphous layer includes a first doped amorphous silicon film located on the surface of the second intrinsic amorphous layer, a first doped amorphous silicon oxide film or a first doped amorphous silicon carbide film located on the surface of the first doped amorphous silicon film, and a second doped amorphous silicon film located on the surface of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film; the first doped amorphous layer includes a third doped amorphous silicon film located on the surface of the first intrinsic amorphous layer, and the crystallization rate of the third doped amorphous silicon film is less than the crystallization rate of the first doped amorphous silicon film.

2. The double-sided heterojunction solar cell according to claim 1, characterized in that: The thickness of the first doped amorphous silicon film is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

3. The double-sided heterojunction solar cell according to claim 2, characterized in that: The thickness of the first doped amorphous silicon film is 1-5 nm, and the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 2-15 nm.

4. The double-sided heterojunction solar cell according to claim 1, characterized in that: The carrier concentration in the first doped amorphous silicon film and the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 1E18-1E21 / cm 3 .

5. The double-sided heterojunction solar cell according to claim 4, characterized in that: The carrier concentration in the first doped amorphous silicon film is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

6. The double-sided heterojunction solar cell according to claim 5, characterized in that: The carrier concentration in the first doped amorphous silicon film is 5E19-5E20 / cm 3 The carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is 5E18-5E19 / cm 3 .

7. The double-sided heterojunction solar cell according to claim 5, characterized in that: The carrier mobility in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

8. The double-sided heterojunction solar cell according to claim 1, characterized in that: The crystallization rate of the first doped amorphous silicon film is 25%-85%.

9. The double-sided heterojunction solar cell according to claim 8, characterized in that: The crystallization rate of the first doped amorphous silicon film is 50%-70%.

10. The double-sided heterojunction solar cell according to claim 1, characterized in that: The thickness of the second doped amorphous silicon film is less than or equal to the thickness of the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

11. The double-sided heterojunction solar cell according to claim 10, characterized in that: The thickness of the second doped amorphous silicon film is 1-3 nm.

12. The double-sided heterojunction solar cell according to claim 1, characterized in that: The carrier concentration in the second doped amorphous silicon film is greater than the carrier concentration in the first doped amorphous silicon oxide film or the first doped amorphous silicon carbide film.

13. The double-sided heterojunction solar cell according to claim 12, characterized in that: The carrier concentration in the second doped amorphous silicon film is 1E19-1E21 / cm 3 .

14. The double-sided heterojunction solar cell according to any one of claims 1 to 13, characterized in that: The first doped amorphous layer further includes a second doped amorphous silicon oxide film or a second doped amorphous silicon carbide film located on the surface of the third doped amorphous silicon film.

15. The double-sided heterojunction solar cell according to claim 14, characterized in that: The thickness of the third doped amorphous silicon film is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

16. The double-sided heterojunction solar cell according to claim 15, characterized in that: The thickness of the third doped amorphous silicon film is 1-5 nm, and the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 2-15 nm.

17. The double-sided heterojunction solar cell according to claim 16, characterized in that: The carrier concentration in the third doped amorphous silicon film and the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 1E18-1E21 / cm 3 .

18. The double-sided heterojunction solar cell according to claim 17, characterized in that: The carrier concentration in the third doped amorphous silicon film is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

19. The double-sided heterojunction solar cell according to claim 18, characterized in that: The carrier concentration in the third doped amorphous silicon film is 5E19-5E20 / cm 3 The carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is 5E18-5E19 / cm 3 .

20. The double-sided heterojunction solar cell according to claim 18, characterized in that: The carrier mobility in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film is not less than 40 cm 2 V -1 s -1 .

21. The double-sided heterojunction solar cell according to claim 1, characterized in that: The crystallization rate of the third doped amorphous silicon film is 20%-70%.

22. The double-sided heterojunction solar cell according to claim 21, characterized in that: The crystallization rate of the third doped amorphous silicon film is 45%-65%.

23. The double-sided heterojunction solar cell according to claim 14, characterized in that: The first doped amorphous layer further includes a fourth doped amorphous silicon film located on a surface of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

24. The double-sided heterojunction solar cell according to claim 23, characterized in that: The thickness of the fourth doped amorphous silicon film is less than or equal to the thickness of the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

25. The double-sided heterojunction solar cell according to claim 24, characterized in that: The thickness of the fourth doped amorphous silicon film is 1-3 nm.

26. The double-sided heterojunction solar cell according to claim 23, characterized in that: The carrier concentration in the fourth doped amorphous silicon film is greater than the carrier concentration in the second doped amorphous silicon oxide film or the second doped amorphous silicon carbide film.

27. The double-sided heterojunction solar cell according to claim 26, characterized in that: The carrier concentration in the fourth doped amorphous silicon film is 1E19-1E21 / cm 3 .

28. The double-sided heterojunction solar cell according to any one of claims 1 to 13, characterized in that: The sum of the thicknesses of the first intrinsic amorphous layer and the first doped amorphous layer is less than or equal to the sum of the thicknesses of the second intrinsic amorphous layer and the second doped amorphous layer.

29. The double-sided heterojunction solar cell according to any one of claims 1 to 13, characterized in that: The thickness of the first doped amorphous layer is smaller than the thickness of the second doped amorphous layer.

30. A photovoltaic module, characterized in that: A double-sided heterojunction solar cell as described in any one of claims 1 to 29.

Images