Back contact battery and photovoltaic system

Abstract

The utility model relates to the technical field of back contact, and particularly discloses a back contact cell and a photovoltaic system, the back contact cell comprises a silicon substrate, and the backlight surface of the silicon substrate is provided with a plurality of first areas and second areas which are alternately arranged; the first semiconductor composite layer is arranged in the first region and comprises a tunneling passivation layer and a first doping layer which are sequentially arranged in the direction away from the silicon substrate; the second semiconductor composite layer is at least partially arranged in the second area and comprises a passivation contact layer and a second doping layer which are sequentially arranged in the direction away from the silicon substrate, and the polarity of the second doping layer is opposite to that of the first doping layer; the composite TCO layer is arranged in at least partial areas of the sides, back to the silicon substrate, of the first doping layer and the second doping layer, the composite TCO layer comprises a first TCO layer and a second TCO layer which are sequentially arranged in the direction away from the silicon substrate, and the refractive index of the first TCO layer is larger than that of the second TCO layer. And the cell conversion efficiency can be effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to back contact technical field especially relates to a back contact battery, photovoltaic system. BACKGROUND

[0002] The existing back contact battery, usually in the back light surface of silicon wafer alternately sets up P type emitter and N type back field, will sputter a layer of transparent conductive film on P type emitter and N type back field in some back contact batteries, then realizes the isolation of PN interval area through laser technology, forms metal electrode on the antireflection layer again.

[0003] On the one hand, the transparent conductive film on the existing back contact battery can not reduce the reflection of incident light well, and the light is not fully utilized, which affects the conversion efficiency of the battery.

[0004] On the other hand, the existing back contact battery realizes the isolation of PN interval area through laser technology, and the high energy of laser in the process of laser grooving can easily lead to phosphorus boron interdoping in the PN interval area, causing the internal lateral conduction of P type emitter and N type back field, and then causing short circuit. UTILITY MODEL CONTENTS

[0005] The utility model aims at the existing technical situation, and provides a back contact battery and photovoltaic system.

[0006] The back contact battery of the utility model can effectively improve the light utilization rate, improve the battery short circuit current, and further improve the battery conversion efficiency through the mutual cooperation of the first TCO layer and the second TCO layer in the composite TCO layer.

[0007] In order to achieve the above object, the utility model adopts the following technical scheme:

[0008] Firstly, the utility model provides a back contact battery, which comprises:

[0009] The back light surface of the silicon substrate has a plurality of first regions and second regions arranged alternately;

[0010] The first semiconductor composite layer is arranged in the first region and comprises a tunneling passivation layer and a first doped layer arranged in sequence in the direction away from the silicon substrate;

[0011] The second semiconductor composite layer is arranged at least partially in the second region and comprises a passivation contact layer and a second doped layer arranged in sequence in the direction away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the first doped layer;

[0012] The composite TCO layer is arranged in at least part of the region on the side of the first doped layer and the second doped layer away from the silicon substrate,

[0013] The composite TCO layer comprises a first TCO layer and a second TCO layer arranged in sequence in a direction away from the silicon substrate, the refractive index of the first TCO layer being greater than the refractive index of the second TCO layer.

[0014] In some embodiments, the refractive index n1 of the first TCO layer is 1.5 < n1 ≤ 3.0, and the refractive index n2 of the second TCO layer is 1.5 ≤ n2 < 3.0.

[0015] In some embodiments, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.77-0.95.

[0016] In some embodiments, the refractive index n1 of the first TCO layer is 1.9 ≤ n1 ≤ 2.2, and the refractive index n2 of the second TCO layer is 1.7 ≤ n2 ≤ 2.0.

[0017] In some embodiments, the work function of the first TCO layer is greater than the work function of the second TCO layer.

[0018] In some embodiments, the work function of the first TCO layer is 4.0 eV-5.0 eV, and the work function of the second TCO layer is 3.5 eV-4.5 eV.

[0019] In some embodiments, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.8-0.9.

[0020] In some embodiments, the work function of the first TCO layer is 4.4 eV-5.0 eV, and the work function of the second TCO layer is 4.0 eV-4.5 eV.

[0021] In some embodiments, the thickness of the first TCO layer is 10 nm-100 nm, and the thickness of the second TCO layer is 30 nm-150 nm.

[0022] In some embodiments, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0023] In some embodiments, the material of the first TCO layer and / or the second TCO layer is any one of ITO, IWO, and AZO.

[0024] In some embodiments, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon or microcrystalline silicon, and the material of the passivation contact layer is amorphous silicon or microcrystalline silicon.

[0025] In some embodiments, the second semiconductor composite layer comprises a laminated composite segment arranged in the first region,

[0026] The first doped layer is arranged on a side of a mask layer opposite to the silicon substrate, and the laminated composite segment is arranged on a side of the mask layer opposite to the silicon substrate,

[0027] The mask layer and the laminated composite segment are provided with a relief hole,

[0028] The composite TCO layer comprises a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0029] The first composite segment comprises a first sub-segment and a second sub-segment, the first sub-segment is arranged in the relief hole and directly contacts a side of the first doped layer opposite to the silicon substrate, and a first electrode is arranged on a side of the first sub-segment opposite to the silicon substrate, and the second sub-segment is arranged on a side of the second doped extension segment opposite to the silicon substrate,

[0030] A second electrode is arranged on a side of the second composite segment opposite to the silicon substrate.

[0031] In some embodiments, the polarity of the first doped layer is the same as that of the silicon substrate, and the polarity of the second doped layer is opposite to that of the silicon substrate.

[0032] Furthermore, the utility model provides a kind of photovoltaic system, comprising the back contact cell of above.

[0033] The utility model has the advantages of:

[0034] 1) The utility model discloses a composite TCO layer is arranged on the back light surface of back contact battery, wherein, the composite TCO layer includes the first TCO layer and the second TCO layer that are sequentially arranged along the direction away from the silicon substrate, and the refractive index of the first TCO layer is greater than the refractive index of the second TCO layer, through the increasing setting of the refractive index of composite TCO layer from outside to inside, the refractive index difference between the TCO layer (the second TCO layer) of outside and air can be reduced, beneficial to more light shooting into composite TCO layer, simultaneously, when the light is shot from the TCO layer (the second TCO layer) of outside, the light is more easily penetrated interface and enters the first TCO layer of higher refractive index, enters the inside of battery, reduces reflection loss, and can regulate the spectral absorption characteristic of composite TCO layer as a whole, and the refractive index difference design between the first TCO layer and the second TCO layer makes composite TCO layer have better back reflection effect to long wave band (especially in 900nm-1200nm wave band range), after long wave band transmits through the silicon substrate, reflects through the composite TCO layer of back light surface, and is shot into the silicon substrate again, and long wave band light can be repeatedly used, can make full use of long wave band light, improves battery short-circuit current. The utility model discloses the mutual cooperation of the refractive index between the first TCO layer and the second TCO layer in composite TCO layer can effectively improve light utilization, improve battery short-circuit current, and further improve battery conversion efficiency.

[0035] 2) Since the work function of the first TCO layer is greater than the work function of the second TCO layer, the contact resistance between the composite TCO layer and the doped semiconductor (the first doped layer / the second doped layer) and the metal electrode can be further reduced, the resistance loss in the current transmission process inside the battery can be reduced, thereby realizing lower series resistance and higher fill factor, and further improving the battery conversion efficiency.

[0036] 3) The utility model discloses the mask layer between the first doped layer and the second doped layer in the first area, can cooperate with the wet chemical process in the preparation process, avoids the high energy laser direct action to the first doped layer, effectively avoids the short circuit risk of PN area (positive and negative poles) inside the battery. Secondly, the utility model utilizes the ink patterning to combine the wet chemical process, effectively avoids the problem of P-type emitter and N-type back surface field internal horizontal conduction caused by the high energy of laser in the laser grooving process, avoids the short circuit risk of PN area (positive and negative poles) inside the battery. ACCURACY OF DRAWINGS

[0037] Figure 1 It is the structure diagram of back contact battery of the utility model.

[0038] Figure 2 It is the partial enlarged view of Figure 1 .

[0039] Figure 3The utility model discloses a back contact battery's preparation method's structure schematic drawing.

[0040] Figure 4 The utility model discloses a back contact battery's preparation method's structure schematic drawing of step 200.

[0041] Figure 5 The utility model discloses a back contact battery's preparation method's structure schematic drawing of step 200.

[0042] Figure 6 The utility model discloses a back contact battery's preparation method's structure schematic drawing of step 200. Specific implementation

[0043] In order to make the utility model's purpose, technical scheme and advantage more clearly clear, below combining with the drawing and example, this utility model carries out further detailed explanation. The example of the described example is shown in the drawing, wherein the same or similar label shows the same or similar element or element with the same or similar function. The following example described by referring to the drawing is exemplary, and is only used to explain the utility model, and can not be understood as the limitation of the utility model. In addition, it should be understood that the specific example described here is only used to explain the utility model, and is not used to limit the utility model.

[0044] In the description of the utility model, the term "first", "second", "third", "fourth" and the like are only used for the purpose of description, and can not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", "third", "fourth" and the like can be explicitly or implicitly included one or more of the features. In the description of the utility model, the meaning of "a plurality of" is two or more than two, unless otherwise specifically limited.

[0045] First, referring to Figure 1 And Figure 2 The utility model provides a back contact battery, comprising:

[0046] Silicon substrate 1, the back light surface of silicon substrate 1 has a plurality of first area 11 and second area 12 arranged alternately;

[0047] First semiconductor composite layer 2, be located in first area 11, including the tunneling passivation layer 21 and first doped layer 22 arranged in order along the direction away from silicon substrate 1;

[0048] The second semiconductor composite layer 4, at least partially arranged in the second region 12, comprises a passivation contact layer 41 and a second doped layer 42 arranged in sequence in a direction away from the silicon substrate 1, and the polarity of the second doped layer 42 is opposite to that of the first doped layer 22.

[0049] The composite TCO layer 5 is arranged in at least part of the region on the side of the first doped layer 22 and the second doped layer 42 away from the silicon substrate 1,

[0050] The composite TCO layer 5 comprises a first TCO layer 51 and a second TCO layer 52 arranged in sequence in a direction away from the silicon substrate 1, and the refractive index of the first TCO layer 51 is greater than that of the second TCO layer 52.

[0051] It can be understood that the silicon substrate 1 has a light-receiving surface and a back surface arranged oppositely, wherein the light-receiving surface generally refers to the surface that receives light, and the surface can also be provided with a passivation layer, an anti-reflection layer and the like commonly used in the art, but is not limited thereto. It should be noted that in some embodiments, the back surface can also absorb light rays entering via the back surface, thereby generating a photoelectric current.

[0052] In the utility model, the composite TCO layer 5 is arranged on the back surface of the back contact battery, wherein the composite TCO layer 5 comprises a first TCO layer 51 and a second TCO layer 52 arranged in sequence in a direction away from the silicon substrate 1, and the refractive index of the first TCO layer 51 is greater than that of the second TCO layer 52, by the increasing setting of the refractive index of the composite TCO layer 5 from outside to inside, the refractive index difference between the TCO layer (the second TCO layer 52) on the outside and the air can be reduced, which is beneficial to more light rays entering the composite TCO layer 5, at the same time, when the light rays enter the TCO layer (the second TCO layer 52) on the outside, the light rays can more easily penetrate the interface and enter the first TCO layer 51 with higher refractive index, enter the inside of the battery, reduce the reflection loss, and the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 can control the spectral absorption characteristics of the composite TCO layer 5 as a whole, and the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 has better back reflection effect for long-wave band (especially in the range of 900nm-1200nm wave band), after the long-wave band transmits through the silicon substrate 1, the light rays are reflected by the composite TCO layer 5 on the back surface and then enter the silicon substrate 1, and the long-wave band light rays can be repeatedly used, so that the long-wave band light can be fully utilized, and the battery short-circuit current is improved. Therefore, by the mutual cooperation of the refractive index between the first TCO layer 51 and the second TCO layer 52 in the composite TCO layer 5, the light utilization rate can be effectively improved, the battery short-circuit current is improved, and the battery conversion efficiency is improved.

[0053] In some embodiments, the refractive index n1 of the first TCO layer 51 is 1.5 n1≤3.0, and the refractive index n2 of the second TCO layer 52 is 1.5

[0054] In some embodiments, the refractive index of the first TCO layer 51 and the refractive index of the second TCO layer 52 are not too high or too low, otherwise the light utilization rate will be reduced.

[0055] For example, the refractive index n1 of the first TCO layer 51 is 1.51, 1.55, 1.58, 1.6, 1.62, 1.65, 1.68, 1.70, 1.75, 1.78, 1.8, 1.82, 1.85, 1.88, 1.9, 1.95, 2.0, 2.05, 2.10, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.48, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, or 3.0, but not limited thereto.

[0056] For example, the refractive index n2 of the second TCO layer 52 is 1.5, 1.55, 1.58, 1.6, 1.62, 1.65, 1.68, 1.70, 1.75, 1.78, 1.8, 1.82, 1.85, 1.88, 1.9, 1.95, 2.0, 2.05, 2.10, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.48, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, or 2.99, but not limited thereto.

[0057] In some embodiments, the ratio between the refractive index of the first TCO layer 51 and the refractive index of the second TCO layer 52 is 1:0.77-0.95.

[0058] In some embodiments, the difference between the refractive index of the first TCO layer 51 and the refractive index of the second TCO layer 52 is not too large, otherwise the optical loss will be increased and the effective utilization of light will be reduced.

[0059] For example, the ratio between the refractive index of the first TCO layer 51 and the refractive index of the second TCO layer 52 (i.e. n1 / n2) is 1:0.77, 1:0.8, 1:0.82, 1:0.85, 1:0.88, 1:0.9, 1:0.92, or 1:0.95, but not limited thereto.

[0060] In some embodiments, preferably, the refractive index n1 of the first TCO layer 51 is 1.9≤n1≤2.2, and the refractive index n2 of the second TCO layer 52 is 1.7≤n2≤2.0.

[0061] By adjusting the refractive index n1 of the first TCO layer 51 and the refractive index n2 of the second TCO layer 52, light can more easily enter the battery, effectively reducing reflection loss. It can also adjust the overall spectral absorption characteristics of the composite TCO layer 5, resulting in better back reflection effect in the long wavelength range. This allows for full utilization of long wavelength light and increases the battery's short-circuit current.

[0062] For example, the refractive index n1 of the first TCO layer 51 is 1.9, 1.92, 1.95, 1.98, 2.0, 2.05, 2.08, 2.1, 2.15, 2.18 or 2.2, but is not limited thereto.

[0063] For example, the refractive index n2 of the second TCO layer 52 is 1.7, 1.72, 1.75, 1.8, 1.82, 1.85, 1.9, 1.92, 1.95, 1.98 or 2.0, but is not limited thereto.

[0064] In some embodiments, the work function of the first TCO layer 51 is less than or equal to the work function of the second TCO layer 52.

[0065] In some embodiments, preferably, the work function of the first TCO layer 51 is greater than the work function of the second TCO layer 52.

[0066] Since the work function of the first TCO layer 51 is greater than that of the second TCO layer 52, the contact resistance between the composite TCO layer 5 and the doped semiconductor (first doped layer 22 / second doped layer 42) and the metal electrode can be further reduced, thereby reducing the resistance loss during the current transmission process inside the battery, thus achieving lower series resistance and higher fill factor, and further improving the battery conversion efficiency.

[0067] In this invention, by combining the refractive index setting of the first TCO layer 51 and the second TCO layer 52 with the work function setting, the short-circuit current of the battery can be effectively increased, the series resistance can be reduced, and the fill factor can be improved, thereby effectively improving the battery conversion efficiency.

[0068] In some embodiments, the work function of the first TCO layer 51 is 4.0 eV to 5.0 eV, and the work function of the second TCO layer 52 is 3.5 eV to 4.5 eV.

[0069] By adjusting the work function of the first TCO layer 51 and the work function of the second TCO layer 52, band alignment can be promoted, carrier recombination can be reduced, and the contact resistance between the recombination TCO layer 5 and the doped semiconductor (first doped layer 22 / second doped layer 42) and the metal electrode can be reduced, thereby reducing the resistance loss during the current transmission process inside the battery, thus achieving lower series resistance and higher fill factor, and improving battery conversion efficiency.

[0070] For example, the work function of the first TCO layer 51 is 4.0 eV, 4.05 eV, 4.1 eV, 4.15 eV, 4.2 eV, 4.25 eV, 4.3 eV, 4.35 eV, 4.4 eV, 4.45 eV, 4.5 eV, 4.55 eV, 4.6 eV, 4.65 eV, 4.7 eV, 4.75 eV, 4.8 eV, 4.85 eV, 4.9 eV or 5.0 eV, but not limited thereto.

[0071] For example, the work function of the second TCO layer 52 is 3.5 eV, 3.55 eV, 3.58 eV, 3.4 eV, 3.45 eV, 3.48 eV, 3.5 eV, 3.55 eV, 3.58 eV, 3.6 eV, 3.65 eV, 3.68 eV, 3.7 eV, 3.75 eV, 3.77 eV, 3.8 eV, 3.85 eV, 3.88 eV, 3.9 eV, 3.95 eV, 3.98 eV, 4.0 eV, 4.05 eV, 4.1 eV, 4.15 eV, 4.2 eV, 4.25 eV, 4.3 eV, 4.35 eV, 4.4 eV, 4.45 eV, 4.48 eV or 4.5 eV, but not limited thereto.

[0072] In some embodiments, the ratio between the work function of the first TCO layer 51 and the work function of the second TCO layer 52 is 1:0.8-0.9.

[0073] The difference between the work function of the first TCO layer 51 and the work function of the second TCO layer 52 should not be too large. When the difference is too large, it is easy to cause the contact potential difference at the interface to increase, hinder the transport of carriers, increase the non-radiative recombination, and affect the conversion efficiency.

[0074] For example, the ratio between the work function φ1 of the first TCO layer 51 and the work function φ2 of the second TCO layer 52 (i.e. φ1 / φ2) is 1:0.8, 1:0.82, 1:0.85, 1:0.88 or 1:0.9, but not limited thereto.

[0075] In some embodiments, preferably, the work function of the first TCO layer 51 is 4.4 eV-5.0 eV, and the work function of the second TCO layer 52 is 4.0 eV-4.5 eV.

[0076] By adjusting the work function of the first TCO layer 51 and the work function of the second TCO layer 52, the composite TCO layer 5 can form good contacts with the doped semiconductor (the first doped layer 22 / the second doped layer 42) and the metal electrode respectively, further reduce the contact resistance between the composite TCO layer 5 and the doped semiconductor (the first doped layer 22 / the second doped layer 42) and the metal electrode, reduce the resistance loss in the process of current transmission inside the battery, and the matching degree between the work function of the first TCO layer 51 and the work function of the second TCO layer 52 is higher, which can reduce the non-radiative recombination of carriers at the interface, thereby realizing lower series resistance and higher fill factor.

[0077] For example, the work function of the first TCO layer 51 is 4.4 eV, 4.42 eV, 4.45 eV, 4.48 eV, 4.5 eV, 4.52 eV, 4.55 eV, 4.58 eV, 4.6 eV, 4.62 eV, 4.65 eV, 4.68 eV, 4.7 eV, 4.72 eV, 4.75 eV, 4.78 eV, 4.8 eV, 4.82 eV, 4.85 eV, 4.88 eV, 4.9 eV, 4.92 eV, 4.95 eV, 4.98 eV or 5.0 eV, but not limited thereto.

[0078] For example, the work function of the second TCO layer 52 is 4.0 eV, 4.02 eV, 4.05 eV, 4.08 eV, 4.1 eV, 4.12 eV, 4.15 eV, 4.18 eV, 4.2 eV, 4.22 eV, 4.25 eV, 4.28 eV, 4.3 eV, 4.32 eV, 4.35 eV, 4.38 eV, 4.4 eV, 4.42 eV, 4.45 eV, 4.48 eV or 4.5 eV, but not limited thereto.

[0079] In some embodiments, the thickness of the first TCO layer 51 is 10 nm to 100 nm, and the thickness of the second TCO layer 52 is 30 nm to 150 nm.

[0080] By adjusting the thickness of the first TCO layer 51 and the second TCO layer 52, the spectral absorption characteristics of the composite TCO layer 5 as a whole are regulated, so that it has a better back reflection effect for long-wave band, further increasing the light utilization rate of the battery.

[0081] For example, the thickness of the first TCO layer 51 is 10 nm, 15 nm, 20 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 88 nm, 90 nm, 92 nm, 95 nm, 98 nm or 100 nm, but not limited thereto.

[0082] For example, the thickness of the second TCO layer 52 is 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 128 nm, 130 nm, 135 nm, 138 nm, 140 nm, 145 nm, 148 nm or 150 nm, but not limited thereto.

[0083] In some embodiments, the thickness of the first TCO layer 51 is less than the thickness of the second TCO layer 52.

[0084] By adjusting the thickness of the first TCO layer 51 and the second TCO layer 52, the back reflection effect of the composite TCO layer on long-wave band is increased.

[0085] In some embodiments, the material of the first TCO layer 51 and / or the second TCO layer 52 is any one of ITO, IWO and AZO.

[0086] In some embodiments, the silicon substrate 1 is single crystal silicon.

[0087] In some embodiments, the material of the tunneling passivation layer 21 is silicon oxide, the material of the first doped layer 22 is polysilicon, the material of the second doped layer 42 is amorphous silicon or microcrystalline silicon, and the material of the passivation contact layer 41 is amorphous silicon or microcrystalline silicon.

[0088] By arranging the tunneling passivation layer 21 between the silicon substrate 1 and the first doped layer 22 made of polysilicon, and arranging the passivation contact layer 41 between the silicon substrate 1 and the second doped layer 42 made of amorphous silicon or microcrystalline silicon, the interface recombination loss is effectively reduced, the open-circuit voltage and the fill factor of the cell are improved, and the cell conversion efficiency is further improved. Compared with the second doped layer made of polysilicon, the second doped layer 42 made of amorphous silicon or microcrystalline silicon has better passivation effect on the textured structure and lower contact resistivity with the composite TCO layer 5, thereby achieving lower series resistance and higher fill factor and further improving the cell conversion efficiency.

[0089] In some embodiments, the light-receiving surface of the silicon substrate 1 is sequentially provided with a front passivation layer 71 and a front anti-reflection layer 72 in a direction away from the silicon substrate 1, wherein the material of the front passivation layer 71 is amorphous silicon or microcrystalline silicon, and the thickness is 3 nm to 15 nm. The material of the front anti-reflection layer 72 is any one of silicon nitride, silicon oxynitride and silicon oxide, and the thickness is 20 nm to 80 nm.

[0090] In some embodiments, referring to Figure 1 andFigure 2 As shown, the second semiconductor composite layer 4 includes a laminated composite section arranged at the first region 11,

[0091] The first doped layer 22 is arranged at the mask layer 3, and the laminated composite section is arranged at the side of the mask layer 3 away from the silicon substrate 1,

[0092] The mask layer 3 and the laminated composite section are provided with a relief hole,

[0093] The composite TCO layer 5 includes a first composite section arranged in the first region 11 and a second composite section arranged in the second region 12,

[0094] The first composite section includes a first subsection 5A and a second subsection 5B, the first subsection 5A is arranged in the relief hole and directly contacts the side of the first doped layer 22 away from the silicon substrate 1, and the first subsection 5A is provided with a first electrode 61 at the side away from the silicon substrate 1, and the second subsection 5B is arranged at the side of the second doped extension section 4B away from the silicon substrate 1,

[0095] The second composite section is provided with a second electrode 62 at the side away from the silicon substrate 1.

[0096] The mask layer 3 is made of any one of PSG and SiNx.

[0097] The mask layer 3 can electrically isolate the first doped layer 22 and the second doped layer 42, and can cooperate with a wet chemical process in the preparation process to avoid that the high-energy laser directly acts on the first doped layer 22, thereby effectively avoiding the short circuit risk of the PN region (positive and negative electrodes) in the battery.

[0098] In an embodiment, the polarity of the first doped layer 22 is opposite to the polarity of the silicon substrate 1, and the polarity of the second doped layer 42 is the same as the polarity of the silicon substrate.

[0099] In another embodiment, preferably, the polarity of the first doped layer 22 is the same as the polarity of the silicon substrate 1, and the polarity of the second doped layer 42 is opposite to the polarity of the silicon substrate, and the battery conversion efficiency is higher.

[0100] Secondly, referring to Figures 1 to 3 As shown, the utility model provides a preparation method of back contact battery, comprising:

[0101] S100. Provide silicon substrate 1, the back light surface of silicon substrate 1 has first region 11 and second region 12 of alternate arrangement,

[0102] S200. Referring to Figures 4 to 6As shown, a first semiconductor composite layer 2 and a mask layer 3 are sequentially deposited on the back surface of the silicon substrate 1, and the first semiconductor composite layer 2 and the mask layer 3 located outside the first region 11 are removed, so that the first semiconductor composite layer 2 and the mask layer 3 are only reserved in the first region 11, the first semiconductor composite layer 2 comprises a tunneling passivation layer 21 and a first doped layer 22 which are sequentially arranged in the direction away from the silicon substrate 1;

[0103] S300. A second semiconductor composite layer 4 is deposited on the mask layer 3 and the second region 12, and part of the mask layer 3 and the second semiconductor composite layer 4 located in the first region 11 are removed to expose part of the first doped layer 22, the second semiconductor composite layer 4 comprises a passivation contact layer 41 and a second doped layer 42 which are sequentially arranged in the direction away from the silicon substrate 1, and the polarity of the second doped layer 42 is opposite to that of the first doped layer 22;

[0104] S400. A composite TCO layer 5 is deposited on the second doped layer 42 and the exposed first doped layer 22, the composite TCO layer 5 comprises a first TCO layer 51 and a second TCO layer 52 which are sequentially arranged in the direction away from the silicon substrate 1, the refractive index of the first TCO layer 51 is greater than that of the second TCO layer 52, and the work function of the first TCO layer 51 is greater than that of the second TCO layer 52.

[0105] In the utility model, the composite TCO layer 5 is arranged on the back surface of the back contact battery, wherein the composite TCO layer 5 comprises the first TCO layer 51 and the second TCO layer 52 which are sequentially arranged in the direction away from the silicon substrate 1, and the refractive index of the first TCO layer 51 is greater than that of the second TCO layer 52, by the increasing setting of the refractive index of the composite TCO layer 5 from outside to inside, the refractive index difference between the TCO layer (the second TCO layer 52) of outside and air can be reduced, it is favorable for more light to enter the composite TCO layer 5, simultaneously, when the light enters the TCO layer (the second TCO layer 52) of outside, the light more easily penetrates the interface and enters the first TCO layer 51 of higher refractive index, enters the inside of the battery, reduces reflection loss, and the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 can regulate the spectral absorption characteristics of the composite TCO layer 5 as a whole, and the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 has better back reflection effect for long wave band (especially in the 900nm-1200nm wave band range), after the long wave band transmits the silicon substrate 1, is reflected by the composite TCO layer 5 of back surface, and is shot into the silicon substrate 1 again, the long wave band light can be repeatedly used, can fully utilize the light of long wave band, improves battery short-circuit current. Therefore, by the mutual cooperation of the first TCO layer 51 and the second TCO layer 52 in the composite TCO layer 5, the light utilization rate can be effectively improved, the battery short-circuit current is improved, and then the battery conversion efficiency is improved.

[0106] Secondly, the utility model discloses the mask layer 3 between the first doped layer 22 and the second doped layer 42 in the first area 11, one aspect can electrically isolate the first doped layer 22 and the second doped layer 42, the other aspect can cooperate wet chemical process in preparation process, avoid the high energy laser direct effect on the first doped layer 22, effectively avoid the short circuit risk of battery internal PN area (positive and negative pole).

[0107] In some embodiments, the preparation method further comprises step S500, specifically:

[0108] S510. Printing ink on the composite TCO layer 5 to form electrode patterning structure, then removing the composite TCO layer 5 in the area not covered by the ink through wet chemical process to form the composite TCO layer 5 with isolation area.

[0109] S520. Printing low-temperature paste on the composite TCO layer 5 with isolation area to form the first electrode 61 and the second electrode 62, and performing low-temperature annealing to form electrode structure, the first electrode 61 is electrically connected with the first doped layer 22 through the composite TCO layer 5, and the second electrode 62 is electrically connected with the second doped layer 42 through the composite TCO layer 5.

[0110] In the utility model, the ink patterning combined with wet chemical process effectively avoids the problem of horizontal conduction between P-type emitter and N-type back surface field caused by high energy of laser in the laser slotting process, and avoids the short circuit risk of battery internal PN area (positive and negative pole).

[0111] In some embodiments, in step S200, the step of removing the first semiconductor composite layer 2 and the mask layer 3 located outside the first area 11 comprises:

[0112] S210. Removing the mask layer 3 located on the second area 12 by laser etching technology (see Figure 5 ), and removing the first semiconductor composite layer 2 and the mask layer 3 located outside the first area 11 through wet chemical process treatment of laser etching area.

[0113] By first removing the part of the mask layer 3 on the second area 12 by laser etching technology, and then removing the part of the first semiconductor composite layer 2 and the mask layer 3 outside the first area 11 by wet chemical process, that is, when the two side walls or the front surface of the silicon substrate 1 also deposit the first semiconductor composite layer 2 and the mask layer 3, it also needs to be removed together, so that only the first semiconductor composite layer 2 and the mask layer 3 in the first area 11 are finally reserved. By combining the mask layer 3 with the wet chemical process, the high-energy laser is avoided from directly acting on the first doped layer 22, effectively avoiding the short circuit risk of the PN area (positive and negative electrodes) inside the battery.

[0114] In some embodiments, in step S200, the following steps are further included:

[0115] S220. Forming a textured structure on the second area 12 and the light-receiving surface of the silicon substrate 1 by alkaline etching (see FIG. 2B). Figure 6

[0116] In some embodiments, after step S220, referring to FIG. 2C, the following steps are further included: Figure 1

[0117] A front surface passivation layer 71 and a front surface anti-reflection layer 72 are sequentially deposited on the light-receiving surface of the silicon substrate 1.

[0118] In some embodiments, in step S300, the step of removing part of the mask layer 3 and the second semiconductor composite layer 4 in the first area 11 includes:

[0119] S310. Removing part of the second semiconductor composite layer 4 on the first area 11 by laser etching technology to expose part of the mask layer 3, and removing the exposed part of the mask layer 3 by wet chemical process treatment of the laser etching area.

[0120] Thus, by combining the mask layer 3 with the wet chemical process, the high-energy laser is avoided from directly acting on the first doped layer 22, effectively avoiding the short circuit risk of the PN area (positive and negative electrodes) inside the battery during the preparation process.

[0121] In some embodiments, the refractive index n1 of the first TCO layer 51 is 1.5 < n1 ≤ 3.0, and the refractive index n2 of the second TCO layer 52 is 1.5 ≤ n2 < 3.0.

[0122] In some embodiments, the refractive index n1 of the first TCO layer 51 is 1.9 ≤ n1 ≤ 2.2, and the refractive index n2 of the second TCO layer 52 is 1.7 ≤ n2 ≤ 2.0.

[0123] In some embodiments, the work function of the first TCO layer 51 is greater than the work function of the second TCO layer 52.​​

[0124] In some embodiments, the work function of the first TCO layer 51 is 4.0eV-5.0eV, and the work function of the second TCO layer 52 is 3.5eV-4.5eV.

[0125] In some embodiments, the work function of the first TCO layer 51 is 4.4eV-5.0eV, and the work function of the second TCO layer 52 is 4.0eV-4.5eV.

[0126] Further, the utility model provides a photovoltaic system, including the back contact cell of above.

[0127] Further, the utility model provides a photovoltaic system, including the back contact cell prepared by the preparation method.

[0128] The utility model will be further described in connection with the drawings and embodiments:

[0129] Embodiment 1

[0130] The embodiment provides a preparation method of back contact cell, comprising:

[0131] S100. provide silicon substrate, and the back light surface of the silicon substrate has a plurality of first area and second area arranged alternately.

[0132] S200. deposit first semiconductor composite layer and mask layer on the back light surface of the silicon substrate in turn, and remove the first semiconductor composite layer and the mask layer located outside the first area, so that first semiconductor composite layer and mask layer only remain in the part of first area, the first semiconductor composite layer includes the first doped layer and the tunneling passivation layer arranged in turn along the direction away from the silicon substrate, the polarity of the first doped layer is same with the polarity of the silicon substrate, specifically:

[0133] S201. deposit first semiconductor composite layer and mask layer in turn;

[0134] S210. remove the mask layer located on the second area by laser etching technology, and remove the first semiconductor composite layer and the mask layer located outside the first area by wet chemical process treatment laser etching area;

[0135] S220. form the textured structure on the second area of the back light surface of silicon substrate and the light receiving surface by alkali etching.

[0136] S230. deposit front passivation layer and front anti-reflection layer on the light receiving surface of the silicon substrate in turn.

[0137] S300. depositing a second semiconductor composite layer on the mask layer and the second region, and removing part of the mask layer and the second semiconductor composite layer located on the first region to expose part of the first doped layer, the second semiconductor composite layer comprising a passivation contact layer and a second doped layer arranged in sequence away from the silicon substrate, the polarity of the second doped layer being opposite to the polarity of the silicon substrate, in particular:

[0138] S301. depositing a second semiconductor composite layer on the mask layer and the second region;

[0139] S310. removing part of the second semiconductor composite layer located on the first region by laser etching technology to expose part of the mask layer, and removing the exposed part of the mask layer by wet chemical process treatment on the laser etching area.

[0140] S400. depositing a composite TCO layer on the second doped layer and the exposed first doped layer, the composite TCO layer comprising a first TCO layer and a second TCO layer arranged in sequence away from the silicon substrate, the refractive index of the first TCO layer being greater than the refractive index of the second TCO layer.

[0141] S500. metal patterning, in particular:

[0142] S510. printing ink on the composite TCO layer to form an electrode pattern structure, and removing the composite TCO layer in the area not covered by the ink by wet chemical process to form the composite TCO layer with an isolation area;

[0143] S520. printing low-temperature paste on the composite TCO layer with an isolation area to form a first electrode and a second electrode, and performing low-temperature annealing to form an electrode structure, the first electrode being electrically conductive with the first doped layer through the composite TCO layer, and the second electrode being electrically conductive with the second doped layer through the composite TCO layer.

[0144] Embodiment 2

[0145] The embodiment provides a back contact cell, comprising:

[0146] a silicon substrate, the back surface of the silicon substrate having a plurality of first regions and second regions arranged alternately;

[0147] a first semiconductor composite layer arranged on the first region, comprising a tunneling passivation layer and a first doped layer arranged in sequence away from the silicon substrate, the polarity of the first doped layer being the same as the polarity of the silicon substrate;

[0148] A second semiconductor composite layer is at least partially disposed in the second region and includes, in sequence from the silicon substrate, a passivation contact layer and a second doped layer, the polarity of the second doped layer being opposite to that of the silicon substrate.

[0149] A composite TCO layer is disposed in at least part of the region on the side of the first doped layer and the second doped layer away from the silicon substrate,

[0150] The composite TCO layer includes, in sequence from the silicon substrate, a first TCO layer and a second TCO layer, the refractive index of the first TCO layer being greater than that of the second TCO layer, and the work function of the first TCO layer being greater than that of the second TCO layer.

[0151] In this embodiment, the refractive index n1 of the first TCO layer is 1.6, and the refractive index n2 of the second TCO layer is 1.5.

[0152] In this embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.94.

[0153] In this embodiment, the work function of the first TCO layer is 4eV, and the work function of the second TCO layer is 3.5eV.

[0154] In this embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.88.

[0155] In this embodiment, the thickness of the first TCO layer is 10nm, and the thickness of the second TCO layer is 30nm.

[0156] In this embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0157] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0158] In this embodiment, the silicon substrate is single crystal silicon.

[0159] In this embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0160] In this embodiment, the second semiconductor composite layer includes a laminated composite section disposed in the first region,

[0161] The side of the first doped layer away from the silicon substrate is disposed in a mask layer, and the laminated composite section is disposed on the side of the mask layer away from the silicon substrate,

[0162] The mask layer and the laminated composite section are provided with a relief hole,

[0163] The composite TCO layer includes a first composite section arranged in the first region and a second composite section arranged in the second region.

[0164] The first composite section includes a first sub-section and a second sub-section, the first sub-section is arranged in the relief hole and directly contacts the first doped layer away from the silicon substrate, and the first sub-section is provided with a first electrode away from the silicon substrate, and the second sub-section is arranged away from the silicon substrate on the second doped extension section.

[0165] The second composite section is provided with a second electrode away from the silicon substrate.

[0166] The material of the mask layer is PSG.

[0167] The back contact cell is prepared by the preparation method of Embodiment 1.

[0168] Embodiment 3

[0169] The embodiment provides a back contact cell, which comprises:

[0170] A silicon substrate, the back surface of the silicon substrate has a plurality of first regions and second regions arranged alternately;

[0171] A first semiconductor composite layer is arranged in the first region and comprises a tunneling passivation layer and a first doped layer arranged in sequence away from the silicon substrate, and the polarity of the first doped layer is the same as that of the silicon substrate.

[0172] A second semiconductor composite layer is arranged at least partially in the second region and comprises a passivation contact layer and a second doped layer arranged in sequence away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the silicon substrate.

[0173] A composite TCO layer is arranged on at least part of the side of the first doped layer and the second doped layer away from the silicon substrate.

[0174] The composite TCO layer includes a first TCO layer and a second TCO layer arranged in sequence away from the silicon substrate, the refractive index of the first TCO layer is greater than that of the second TCO layer, and the work function of the first TCO layer is greater than that of the second TCO layer.

[0175] In the embodiment, the refractive index n1 of the first TCO layer is 1.9, and the refractive index n2 of the second TCO layer is 1.7.

[0176] In this embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.89.

[0177] In this embodiment, the work function of the first TCO layer is 5eV, and the work function of the second TCO layer is 4.5eV.

[0178] In this embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.9.

[0179] In this embodiment, the thickness of the first TCO layer is 50nm, and the thickness of the second TCO layer is 120nm.

[0180] In this embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0181] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0182] In this embodiment, the silicon substrate is single crystal silicon.

[0183] In this embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0184] In this embodiment, the second semiconductor composite layer includes a laminated composite segment arranged in the first region,

[0185] The side of the first doped layer away from the silicon substrate is arranged in a mask layer, and the laminated composite segment is arranged on the side of the mask layer away from the silicon substrate,

[0186] The mask layer and the laminated composite segment are provided with a relief hole therebetween,

[0187] The composite TCO layer includes a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0188] The first composite segment includes a first sub-segment and a second sub-segment, the first sub-segment is arranged in the relief hole and directly contacts the side of the first doped layer away from the silicon substrate, and the side of the first sub-segment away from the silicon substrate is provided with a first electrode, and the second sub-segment is arranged on the side of the second doped extension segment away from the silicon substrate,

[0189] The side of the second composite segment away from the silicon substrate is provided with a second electrode.

[0190] The material of the mask layer is PSG.

[0191] The back contact cell is prepared by the preparation method of Embodiment 1.

[0192] Embodiment 4

[0193] The embodiment provides a back contact cell, comprising:

[0194] a silicon substrate, a back surface of the silicon substrate having a plurality of first regions and second regions arranged alternately;

[0195] a first semiconductor composite layer arranged in the first regions, comprising a tunneling passivation layer and a first doped layer arranged in sequence in a direction away from the silicon substrate, the first doped layer having the same polarity as the silicon substrate;

[0196] a second semiconductor composite layer arranged at least partially in the second regions, comprising a passivation contact layer and a second doped layer arranged in sequence in a direction away from the silicon substrate, the second doped layer having a polarity opposite to that of the silicon substrate;

[0197] a composite TCO layer arranged in at least part of regions on a side of the first doped layer and the second doped layer away from the silicon substrate,

[0198] the composite TCO layer comprising a first TCO layer and a second TCO layer arranged in sequence in a direction away from the silicon substrate, the first TCO layer having a refractive index greater than that of the second TCO layer, and the first TCO layer having a work function greater than that of the second TCO layer.

[0199] In the embodiment, the refractive index n1 of the first TCO layer is 1.9, and the refractive index n2 of the second TCO layer is 1.7.

[0200] In the embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.89.

[0201] In the embodiment, the work function of the first TCO layer is 4.5 eV, and the work function of the second TCO layer is 4 eV.

[0202] In the embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.89.

[0203] In the embodiment, the thickness of the first TCO layer is 50 nm, and the thickness of the second TCO layer is 120 nm.

[0204] In the embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0205] In the embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0206] In this embodiment, the silicon substrate is monocrystalline silicon.

[0207] In this embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0208] In this embodiment, the second semiconductor composite layer includes a laminated composite segment arranged in the first region,

[0209] The side of the first doped layer away from the silicon substrate is arranged in a mask layer, and the laminated composite segment is arranged on the side of the mask layer away from the silicon substrate,

[0210] The mask layer and the laminated composite segment are provided with a relief hole therebetween,

[0211] The composite TCO layer includes a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0212] The first composite segment includes a first sub-segment and a second sub-segment, the first sub-segment is arranged in the relief hole and directly contacts the side of the first doped layer away from the silicon substrate, and the side of the first sub-segment away from the silicon substrate is provided with a first electrode, and the second sub-segment is arranged on the side of the second doped extension segment away from the silicon substrate,

[0213] The side of the second composite segment away from the silicon substrate is provided with a second electrode.

[0214] The material of the mask layer is PSG.

[0215] The back contact cell is prepared by the preparation method of Embodiment 1.

[0216] Embodiment 5

[0217] The embodiment provides a back contact cell, which comprises:

[0218] A silicon substrate, the back surface of the silicon substrate has a plurality of first regions and second regions arranged alternately;

[0219] A first semiconductor composite layer arranged in the first region, comprising a tunneling passivation layer and a first doped layer arranged in sequence away from the silicon substrate, the polarity of the first doped layer is the same as that of the silicon substrate;

[0220] A second semiconductor composite layer arranged at least partially in the second region, comprising a passivation contact layer and a second doped layer arranged in sequence away from the silicon substrate, the polarity of the second doped layer is opposite to that of the silicon substrate;

[0221] a composite TCO layer disposed on at least a partial region of a side of the first doped layer and the second doped layer away from the silicon substrate,

[0222] The composite TCO layer comprises a first TCO layer and a second TCO layer disposed in sequence in a direction away from the silicon substrate, the refractive index of the first TCO layer is greater than the refractive index of the second TCO layer, and the work function of the first TCO layer is greater than the work function of the second TCO layer.

[0223] In the embodiment, the refractive index n1 of the first TCO layer is 2.2, and the refractive index n2 of the second TCO layer is 2.

[0224] In the embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.91.

[0225] In the embodiment, the work function of the first TCO layer is 4eV, and the work function of the second TCO layer is 3.5eV.

[0226] In the embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.88.

[0227] In the embodiment, the thickness of the first TCO layer is 100nm, and the thickness of the second TCO layer is 150nm.

[0228] In the embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0229] In the embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0230] In the embodiment, the silicon substrate is single crystal silicon.

[0231] In the embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polycrystalline silicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0232] In the embodiment, the second semiconductor composite layer comprises a laminated composite section disposed on the first region,

[0233] The side of the first doped layer away from the silicon substrate is disposed on a mask layer, and the laminated composite section is disposed on a side of the mask layer away from the silicon substrate,

[0234] An avoiding hole is disposed through between the mask layer and the laminated composite section,

[0235] The composite TCO layer comprises a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0236] The first composite segment comprises a first sub-segment and a second sub-segment, the first sub-segment is arranged in the avoidance hole and directly contacts the side of the first doped layer away from the silicon substrate, and the side of the first sub-segment away from the silicon substrate is provided with a first electrode, and the second sub-segment is arranged on the side of the second doped extension segment away from the silicon substrate,

[0237] The side of the second composite segment away from the silicon substrate is provided with a second electrode.

[0238] The mask layer is made of PSG.

[0239] The back contact cell is prepared by the preparation method of Embodiment 1.

[0240] Embodiment 6

[0241] The embodiment provides a back contact cell, comprising:

[0242] A silicon substrate, the back surface of the silicon substrate has a plurality of first regions and second regions arranged alternately;

[0243] A first semiconductor composite layer is arranged in the first region and comprises a tunneling passivation layer and a first doped layer arranged in sequence away from the silicon substrate, and the polarity of the first doped layer is the same as that of the silicon substrate;

[0244] A second semiconductor composite layer is arranged at least partially in the second region and comprises a passivation contact layer and a second doped layer arranged in sequence away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the silicon substrate;

[0245] A composite TCO layer is arranged on at least part of the side of the first doped layer and the second doped layer away from the silicon substrate,

[0246] The composite TCO layer comprises a first TCO layer and a second TCO layer arranged in sequence away from the silicon substrate, the refractive index of the first TCO layer is greater than that of the second TCO layer, and the work function of the first TCO layer is greater than that of the second TCO layer.

[0247] In the embodiment, the refractive index n1 of the first TCO layer is 3, and the refractive index n2 of the second TCO layer is 2.8.

[0248] In the embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.93.

[0249] In the embodiment, the work function of the first TCO layer is 5eV, and the work function of the second TCO layer is 4eV.

[0250] In the embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.8.

[0251] In the embodiment, the thickness of the first TCO layer is 80nm, and the thickness of the second TCO layer is 100nm.

[0252] In the embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0253] In the embodiment, the material of the first TCO layer is AZO, and the material of the second TCO layer is ITO.

[0254] In the embodiment, the silicon substrate is single crystal silicon.

[0255] In the embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0256] In the embodiment, the second semiconductor composite layer includes a laminated composite segment arranged in the first region,

[0257] The side of the first doped layer away from the silicon substrate is arranged in a mask layer, and the laminated composite segment is arranged on the side of the mask layer away from the silicon substrate,

[0258] The mask layer and the laminated composite segment are provided with a relief hole penetrating therebetween,

[0259] The composite TCO layer includes a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0260] The first composite segment includes a first sub-segment and a second sub-segment, the first sub-segment is arranged in the relief hole and directly contacts the side of the first doped layer away from the silicon substrate, and the side of the first sub-segment away from the silicon substrate is provided with a first electrode, and the second sub-segment is arranged on the side of the second doped extension segment away from the silicon substrate,

[0261] The side of the second composite segment away from the silicon substrate is provided with a second electrode.

[0262] The material of the mask layer is PSG.

[0263] The back contact cell is prepared by the preparation method of embodiment 1.

[0264] Embodiment 7

[0265] The embodiment provides a back contact cell, comprising:

[0266] a silicon substrate, a back surface of the silicon substrate having a plurality of first regions and second regions arranged alternately;

[0267] a first semiconductor composite layer arranged in the first regions, comprising a tunneling passivation layer and a first doped layer arranged in sequence in a direction away from the silicon substrate, the first doped layer having the same polarity as the silicon substrate;

[0268] a second semiconductor composite layer arranged at least partially in the second regions, comprising a passivation contact layer and a second doped layer arranged in sequence in a direction away from the silicon substrate, the second doped layer having a polarity opposite to that of the silicon substrate;

[0269] a composite TCO layer arranged in at least some regions on a side of the first doped layer and the second doped layer away from the silicon substrate,

[0270] the composite TCO layer comprises a first TCO layer and a second TCO layer arranged in sequence in a direction away from the silicon substrate, the first TCO layer having a refractive index greater than that of the second TCO layer, and the second TCO layer having a work function greater than that of the first TCO layer.

[0271] In the embodiment, the refractive index n1 of the first TCO layer is 1.9, and the refractive index n2 of the second TCO layer is 1.7.

[0272] In the embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.89.

[0273] In the embodiment, the work function of the first TCO layer is 4eV, and the work function of the second TCO layer is 4.5eV.

[0274] In the embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:1.13.

[0275] In the embodiment, the thickness of the first TCO layer is 50nm, and the thickness of the second TCO layer is 120nm.

[0276] In the embodiment, the thickness of the first TCO layer is less than the thickness of the second TCO layer.

[0277] In the embodiment, the materials of the first TCO layer and the second TCO layer are IWO.

[0278] In the embodiment, the silicon substrate is monocrystalline silicon.

[0279] In the embodiment, the material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon, and the material of the passivation contact layer is amorphous silicon.

[0280] In the embodiment, the second semiconductor composite layer includes a laminated composite segment arranged in the first region,

[0281] The side of the first doped layer away from the silicon substrate is arranged in a mask layer, and the laminated composite segment is arranged on the side of the mask layer away from the silicon substrate,

[0282] The mask layer and the laminated composite segment are provided with a relief hole therebetween,

[0283] The composite TCO layer includes a first composite segment arranged in the first region and a second composite segment arranged in the second region,

[0284] The first composite segment includes a first sub-segment and a second sub-segment, the first sub-segment is arranged in the relief hole and directly contacts the side of the first doped layer away from the silicon substrate, and the side of the first sub-segment away from the silicon substrate is provided with a first electrode, and the second sub-segment is arranged on the side of the second doped extension segment away from the silicon substrate,

[0285] The side of the second composite segment away from the silicon substrate is provided with a second electrode.

[0286] The material of the mask layer is PSG.

[0287] The back contact cell is prepared by the preparation method of Embodiment 1.

[0288] Comparative Example 1

[0289] The difference between the present comparative example and Embodiment 2 is that the present comparative example uses a single-layer transparent conductive film to replace the composite TCO layer of Embodiment 2, the refractive index of the single-layer transparent conductive film is 1.5, the work function is 3.5, the thickness is 30 nm, and the material is IWO.

[0290] Comparative Example 2

[0291] The difference between the present comparative example and Embodiment 2 is that the refractive index and work function of the first TCO layer of the present comparative example are both smaller than those of the second TCO layer, specifically:

[0292] The refractive index of the first TCO layer is 1.5, and the refractive index of the second TCO layer is 1.6.

[0293] The work function of the first TCO layer is 3.5 eV, and the work function of the second TCO layer is 4 eV.

[0294] The first TCO layer has a thickness of 30 nm, and the second TCO layer has a thickness of 10 nm.

[0295] The first TCO layer and the second TCO layer are made of IWO.

[0296] The solar cells prepared in Examples 2 to 7 and Comparative Examples 1 to 2 are tested for performance, and the test results are as follows:

[0297]

[0298]

[0299] As can be seen from Comparative Examples 2 to 7 and Comparative Example 1, compared with a single-layer transparent conductive film, the Examples 2 to 7 of the present application using a composite TCO layer have higher short-circuit current density and fill factor, and higher conversion efficiency.

[0300] As can be seen from Comparative Example 4, Example 7 and Comparative Example 2, the setting that the refractive index of the first TCO layer 51 is greater than the refractive index of the second TCO layer 52 can effectively improve the conversion efficiency, and in combination with the setting that the work function of the first TCO layer 51 is greater than the work function of the second TCO layer 52, the conversion efficiency can be further improved.

[0301] In the description of the present specification, the description of the terms "some embodiments", "exemplary", "example", or "for example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0302] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above-mentioned technical content without departing from the technical solution of the present application, and any simple modification, equivalent change and modification of the above-mentioned technical content, which does not depart from the technical solution of the present application, is still within the scope of the present application.

Claims

1. A back contact cell, characterized in that, The application relates to a silicon substrate, which comprises: a back surface of the silicon substrate having a plurality of first regions and second regions arranged alternately; a first semiconductor composite layer arranged in the first regions and comprising a tunneling passivation layer and a first doped layer arranged in sequence in a direction away from the silicon substrate; a second semiconductor composite layer arranged at least partially in the second regions and comprising a passivation contact layer and a second doped layer arranged in sequence in a direction away from the silicon substrate, the polarity of the second doped layer being opposite to that of the first doped layer; a composite TCO layer arranged in at least some regions on the side of the first doped layer and the second doped layer away from the silicon substrate, the composite TCO layer comprising a first TCO layer and a second TCO layer arranged in sequence in a direction away from the silicon substrate, the refractive index of the first TCO layer being greater than that of the second TCO layer.

2. A back contact cell according to claim 1, wherein, The refractive index n1 of the first TCO layer is 1.5 < n1 < 3.0, and the refractive index n2 of the second TCO layer is 1.5 < n2 < 3.

0.

3. A back contact cell according to claim 2, wherein, The ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.77-0.

95.

4. A back contact cell according to claim 2, wherein, The refractive index n1 of the first TCO layer is 1.9 < n1 < 2.2, and the refractive index n2 of the second TCO layer is 1.7 < n2 < 2.

0.

5. The back contact cell of claim 1, wherein, The work function of the first TCO layer is greater than that of the second TCO layer.

6. A back contact cell according to claim 5, wherein, The work function of the first TCO layer is 4.0 eV-5.0 eV, and the work function of the second TCO layer is 3.5 eV-4.5 eV.

7. A back contact cell according to claim 6, wherein, The ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.8-0.

9.

8. A back contact cell according to claim 6, wherein, The work function of the first TCO layer is 4.4 eV-5.0 eV, and the work function of the second TCO layer is 4.0 eV-4.5 eV.

9. The back contact cell of claim 1, wherein, The thickness of the first TCO layer is 10 nm-100 nm, and the thickness of the second TCO layer is 30 nm-150 nm.

10. A back contact cell according to claim 9, wherein, The thickness of the first TCO layer is less than that of the second TCO layer.

11. A back contact cell according to claim 1, wherein, The material of the first TCO layer and / or the second TCO layer is any one of ITO, IWO and AZO.

12. The back contact cell of claim 1, wherein, The material of the tunneling passivation layer is silicon oxide, the material of the first doped layer is polysilicon, the material of the second doped layer is amorphous silicon or microcrystalline silicon, and the material of the passivation contact layer is amorphous silicon or microcrystalline silicon.

13. The back contact cell of claim 1, wherein, The second semiconductor composite layer comprises a laminated composite section arranged in the first regions, the side of the first doped layer away from the silicon substrate is arranged in a mask layer, and the laminated composite section is arranged on the side of the mask layer away from the silicon substrate, an avoiding hole is arranged between the mask layer and the laminated composite section, the composite TCO layer comprises a first composite section arranged in the first regions and a second composite section arranged in the second regions, The first composite section includes a first sub-section and a second sub-section, the first sub-section is arranged in the avoiding hole and directly contacts with the side of the first doped layer away from the silicon substrate, and the side of the first sub-section away from the silicon substrate is provided with a first electrode, and the second sub-section is arranged on the side of the second doped extension section away from the silicon substrate, The side of the second composite section away from the silicon substrate is provided with a second electrode.

14. The back contact cell of claim 1, wherein, The polarity of the first doped layer is the same as that of the silicon substrate, and the polarity of the second doped layer is opposite to that of the silicon substrate.

15. A photovoltaic system characterized by, A back contact cell comprising any one of claims 1 to 14.

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