Back contact battery, preparation method thereof and photovoltaic system

Abstract

The invention relates to the technical field of back contact, and particularly discloses a back contact cell and a preparation method thereof, 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 present invention relates to the field of back contact technology, and in particular to a back contact battery and a preparation method thereof, and a photovoltaic system. Background Art

[0002] Existing back-contact cells usually have P-type emitters and N-type back surface fields alternately arranged on the backlit side of the silicon wafer. In some back-contact cells, a layer of transparent conductive film is also sputtered on the P-type emitter and the N-type back surface field, and then the PN region spacing area is isolated by laser technology, and then a metal electrode is formed on the anti-reflection layer.

[0003] On the one hand, the transparent conductive film on the existing back-contact battery cannot effectively reduce the reflection of incident light, 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 uses laser technology to achieve isolation of the PN region spacing area. During the laser grooving process, the high energy of the laser can easily lead to phosphorus and boron mutual doping in the PN region spacing area, causing lateral conduction between the P-type emitter and the N-type back surface field, and then causing a short circuit. Summary of the invention

[0005] The purpose of the present invention is to provide a back contact battery and a preparation method thereof, and a photovoltaic system in view of the existing technical status.

[0006] The back contact cell of the present invention can effectively improve light utilization, increase the short-circuit current of the cell, and thus improve the cell 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 present invention adopts the following technical scheme:

[0008] First, the present invention provides a back contact battery, comprising:

[0009] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0010] A first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate;

[0011] A second semiconductor composite layer, at least partially disposed in the second region, comprises a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the first doping layer;

[0012] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0013] The composite TCO layer includes a first TCO layer and a second TCO layer which are sequentially arranged in a 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.

[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 to 5.0 eV, and the work function of the second TCO layer is 3.5 eV to 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 to 5.0 eV, and the work function of the second TCO layer is 4.0 eV to 4.5 eV.

[0021] In some embodiments, the thickness of the first TCO layer is 10 nm to 100 nm, and the thickness of the second TCO layer is 30 nm to 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 tunnel passivation layer is made of silicon oxide, the first doped layer is made of polycrystalline silicon, the second doped layer is made of amorphous silicon or microcrystalline silicon, and the passivation contact layer is made of amorphous silicon or microcrystalline silicon.

[0025] In some embodiments, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0026] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0027] An avoidance hole is provided between the mask layer and the stacked composite section.

[0028] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0029] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0030] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

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

[0032] Secondly, the present invention provides a method for preparing a back contact battery, comprising:

[0033] Providing a silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0034] Depositing a first semiconductor composite layer and a mask layer in sequence on the backlight surface of the silicon substrate, and removing the first semiconductor composite layer and the mask layer outside the first region, wherein the first semiconductor composite layer includes a tunnel passivation layer and a first doping layer arranged in sequence in a direction away from the silicon substrate;

[0035] Depositing a second semiconductor composite layer on the mask layer and the second region, and removing a portion of the mask layer and the second semiconductor composite layer located in the first region to expose a portion of the first doped layer, wherein the second semiconductor composite layer includes a passivation contact layer and a second doped layer sequentially arranged in a direction away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the first doped layer;

[0036] A composite TCO layer is deposited on the second doped layer and the exposed first doped layer, wherein the composite TCO layer comprises a first TCO layer and a second TCO layer sequentially arranged in a direction away from the silicon substrate, and a refractive index of the first TCO layer is greater than a refractive index of the second TCO layer.

[0037] In some embodiments, including:

[0038] Printing ink on the composite TCO layer to form an electrode patterned structure, and then removing the composite TCO layer in the area not covered by the ink by a wet chemical process to form the composite TCO layer with an isolation area;

[0039] A low-temperature paste is printed on the composite TCO layer with the isolation area to form a first electrode and a second electrode, and low-temperature annealing is performed to form an electrode structure, wherein the first electrode is electrically connected to the first doped layer through the composite TCO layer, and the second electrode is electrically connected to the second doped layer through the composite TCO layer.

[0040] In some embodiments, the step of removing the first semiconductor composite layer and the mask layer outside the first region includes:

[0041] The mask layer on the second region is removed by laser etching technology, and the laser etching area is treated by wet chemical process to remove the first semiconductor composite layer and the mask layer outside the first region.

[0042] In some embodiments, the step of removing a portion of the mask layer and the second semiconductor composite layer located in the first region includes:

[0043] A portion of the second semiconductor composite layer located on the first region is removed by laser etching technology to expose a portion of the mask layer, and the laser etching region is treated by a wet chemical process to remove the exposed portion of the mask layer.

[0044] 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.

[0045] 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.

[0046] In some embodiments, the work function of the first TCO layer is greater than the work function of the second TCO layer.

[0047] In some embodiments, the work function of the first TCO layer is 4.0 eV to 5.0 eV, and the work function of the second TCO layer is 3.5 eV to 4.5 eV.

[0048] In some embodiments, the work function of the first TCO layer is 4.4 eV to 5.0 eV, and the work function of the second TCO layer is 4.0 eV to 4.5 eV.

[0049] Furthermore, the present invention provides a photovoltaic system, including the above-mentioned back-contact cell, or, including a back-contact cell prepared by the above-mentioned preparation method.

[0050] The beneficial effects of the present invention are:

[0051] 1) In the present invention, a composite TCO layer is arranged on the backlight surface of the back contact cell, wherein the composite TCO layer includes a first TCO layer and a second TCO layer arranged in sequence in a 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. By increasing the refractive index of the composite TCO layer from the outside to the inside, the refractive index difference between the outer TCO layer (the second TCO layer) and the air can be reduced, which is conducive to more light entering the composite TCO layer. At the same time, when light enters from the outer TCO layer (the second TCO layer), the light is more likely to penetrate The interface enters the first TCO layer with a higher refractive index and enters the battery, reducing reflection losses and being able to regulate the overall spectral absorption characteristics of the composite TCO layer. In addition, the refractive index difference design between the first TCO layer and the second TCO layer enables the composite TCO layer to have a better back reflection effect for the long-wave band (especially in the 900nm to 1200nm band). After the long-wave band passes through the silicon substrate, it is reflected by the composite TCO layer on the backlight surface and then enters the silicon substrate again. The long-wave band light can be reused, and the long-wave band light can be fully utilized to increase the battery short-circuit current. The present invention can effectively improve the light utilization rate, increase the battery short-circuit current, and thus improve the battery conversion efficiency through the mutual coordination of the refractive index between the first TCO layer and the second TCO layer in the composite TCO layer.

[0052] 2) Since the work function of the first TCO layer is greater than that of the second TCO layer, the contact resistance between the composite TCO layer and the doped semiconductor (first doping layer / second doping layer) and the metal electrode can be further reduced, and the resistance loss during the current transmission process inside the battery can be reduced, thereby achieving lower series resistance and higher fill factor, thereby further improving the battery conversion efficiency.

[0053] 3) The present invention introduces a mask layer between the first doping layer and the second doping layer in the first region, which can be used in conjunction with a wet chemical process during the preparation process to prevent high-energy lasers from directly acting on the first doping layer, effectively avoiding the risk of short circuits in the PN region (positive and negative electrodes) inside the battery. Secondly, the present invention uses ink patterning combined with a wet chemical process to effectively avoid the problem of lateral conduction between the P-type emitter and the N-type back surface field that is easily caused by the high energy of the laser during the laser grooving process, thereby avoiding the risk of short circuits in the PN region (positive and negative electrodes) inside the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic structural diagram of the back contact battery of the present invention.

[0055] Figure 2 for Figure 1 A partial enlarged view of .

[0056] Figure 3 It is a structural schematic diagram of the method for preparing a back contact battery of the present invention.

[0057] Figure 4 This is one of the structural schematic diagrams of step 200 in the method for preparing a back contact battery of the present invention.

[0058] Figure 5 This is one of the structural schematic diagrams of step 200 in the method for preparing a back contact battery of the present invention.

[0059] Figure 6 This is one of the structural schematic diagrams of step 200 in the method for preparing a back contact battery of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0061] In the description of the present invention, the terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second", "third", "fourth", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0062] First, see Figure 1 and Figure 2 As shown, the present invention provides a back contact battery, comprising:

[0063] A silicon substrate 1, wherein the backlight surface of the silicon substrate 1 has a plurality of alternately arranged first regions 11 and second regions 12;

[0064] A first semiconductor composite layer 2, disposed in the first region 11, comprising a tunnel passivation layer 21 and a first doping layer 22 sequentially disposed in a direction away from the silicon substrate 1;

[0065] A second semiconductor composite layer 4, at least partially disposed in the second region 12, comprises a passivation contact layer 41 and a second doping layer 42 sequentially disposed in a direction away from the silicon substrate 1, wherein the polarity of the second doping layer 42 is opposite to that of the first doping layer 22;

[0066] The composite TCO layer 5 is provided on at least a portion of the first doping layer 22 and the second doping layer 42 on a side facing away from the silicon substrate 1.

[0067] The composite TCO layer 5 includes a first TCO layer 51 and a second TCO layer 52 which are sequentially arranged in a direction away from the silicon substrate 1 . The refractive index of the first TCO layer 51 is greater than the refractive index of the second TCO layer 52 .

[0068] It is understandable that the silicon substrate 1 has a light-receiving surface and a backlight surface that are arranged relatively, wherein the light-receiving surface generally refers to the side that receives light, and its surface may also be provided with a passivation layer, an anti-reflection layer, etc. commonly used in the art, but not limited thereto. It should be noted that in some embodiments, the backlight surface may also absorb light incident through the backlight surface, thereby generating a photocurrent.

[0069] In the present invention, a composite TCO layer 5 is arranged on the backlight surface of the back contact cell, wherein the composite TCO layer 5 includes a first TCO layer 51 and a second TCO layer 52 which are 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 the refractive index of the second TCO layer 52. By gradually increasing the refractive index of the composite TCO layer 5 from the outside to the inside, the refractive index difference between the outer TCO layer (the second TCO layer 52) and the air can be reduced, which is conducive to more light entering the composite TCO layer 5. At the same time, when light enters from the outer TCO layer (the second TCO layer 52), Light can more easily penetrate the interface and enter the first TCO layer 51 with a higher refractive index, and then enter the battery, thereby reducing reflection losses and regulating the overall spectral absorption characteristics of the composite TCO layer 5. In addition, the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 has a better back reflection effect for the long-wave band (especially in the 900nm to 1200nm band). After the long-wave band passes through the silicon substrate 1, it is reflected by the composite TCO layer 5 on the backlight surface and then enters the silicon substrate 1 again. The long-wave band light can be reused, and the long-wave band light can be fully utilized to increase the battery short-circuit current. Therefore, the present invention can effectively improve the light utilization rate, increase the battery short-circuit current, and thus improve the battery conversion efficiency through the mutual coordination of the refractive indexes between the first TCO layer 51 and the second TCO layer 52 in the composite TCO layer 5.

[0070] 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.

[0071] The refractive index n1 of the first TCO layer 51 and the refractive index n2 of the second TCO layer 52 should not be too high or too low, otherwise the light utilization rate will be reduced.

[0072] Exemplarily, 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 is not limited thereto.

[0073] Exemplarily, 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 is not limited thereto.

[0074] 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.

[0075] The difference between the refractive index of the first TCO layer 51 and the refractive index of the second TCO layer 52 should not be too large, otherwise the optical loss will increase and the effective utilization rate of light will be reduced.

[0076] Exemplarily, the ratio of the refractive index of the first TCO layer 51 to the refractive index of the second TCO layer 52 (ie, 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 is not limited thereto.

[0077] 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.

[0078] 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 enter the battery more easily, effectively reducing reflection loss, and adjusting the overall spectral absorption characteristics of the composite TCO layer 5, which has a better back reflection effect for the long-wave band, can make full use of the long-wave band light, and increase the battery short-circuit current.

[0079] Illustratively, 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.

[0080] Illustratively, 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.

[0081] In some embodiments, a work function of the first TCO layer 51 is less than or equal to a work function of the second TCO layer 52 .

[0082] 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 .

[0083] Since the work function of the first TCO layer 51 is greater than the work function of the second TCO layer 52, the contact resistance between the composite TCO layer 5 and the doped semiconductor (first doping layer 22 / second doping layer 42) and the metal electrode can be further reduced, and the resistance loss during the current transmission process inside the battery can be reduced, thereby achieving lower series resistance and higher fill factor, thereby further improving the battery conversion efficiency.

[0084] In the present invention, by combining the refractive index matching setting between the first TCO layer 51 and the second TCO layer 52 with the work function matching setting, the short-circuit current of the battery can be effectively increased, the series resistance can be reduced, and the fill factor can be increased, thereby effectively improving the battery conversion efficiency.

[0085] 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.

[0086] By adjusting the work function of the first TCO layer 51 and the work function of the second TCO layer 52, it is possible to promote energy band alignment, reduce carrier recombination, and reduce the contact resistance between the composite TCO layer 5 and the doped semiconductor (first doping layer 22 / second doping layer 42) and the metal electrode, thereby reducing the resistance loss during the current transmission process inside the battery, thereby achieving lower series resistance and higher fill factor, and improving the battery conversion efficiency.

[0087] Exemplarily, 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 is not limited thereto.

[0088] Exemplarily, 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 is not limited thereto.

[0089] 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.

[0090] 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. If the difference is too large, it will easily lead to an increase in the contact potential difference at the interface, hinder the transport of carriers, increase non-radiative recombination, and affect the conversion efficiency.

[0091] Exemplarily, the ratio between the work function φ1 of the first TCO layer 51 and the work function φ2 of the second TCO layer 52 (ie, φ1 / φ2) is 1:0.8, 1:0.82, 1:0.85, 1:0.88 or 1:0.9, but is not limited thereto.

[0092] In some embodiments, preferably, the work function of the first TCO layer 51 is 4.4 eV to 5.0 eV, and the work function of the second TCO layer 52 is 4.0 eV to 4.5 eV.

[0093] 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 contact with the doped semiconductor (first doped layer 22 / second doped layer 42) and the metal electrode respectively, further reducing 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, reducing the resistance loss during the current transmission process inside the battery, and the work function of the first TCO layer 51 and the work function of the second TCO layer 52 are more matched, which can reduce the non-radiative recombination of carriers at the interface, thereby achieving a lower series resistance and a higher fill factor.

[0094] Exemplarily, the work function of the first TCO layer 51 is 4.4eV, 4.42eV, 4.45eV, 4.48eV, 4.5eV, 4.52eV, 4.55eV, 4.58eV, 4.6eV, 4.62eV, 4.65eV, 4.68eV, 4.7eV, 4.72eV, 4.75eV, 4.78eV, 4.8eV, 4.82eV, 4.85eV, 4.88eV, 4.9eV, 4.92eV, 4.95eV, 4.98eV or 5.0eV, but is not limited thereto.

[0095] Exemplarily, 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 is not limited thereto.

[0096] 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.

[0097] By adjusting the thickness of the first TCO layer 51 and the second TCO layer 52 , the overall spectral absorption characteristics of the composite TCO layer 5 are regulated, so that it has a better back reflection effect for the long-wave band, further increasing the utilization rate of light by the battery.

[0098] Exemplarily, the thickness of the first TCO layer 51 is 10nm, 15nm, 20nm, 25nm, 28nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, 48nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 88nm, 90nm, 92nm, 95nm, 98nm or 100nm, but is not limited thereto.

[0099] Exemplarily, the thickness of the second TCO layer 52 is 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 128nm, 130nm, 135nm, 138nm, 140nm, 145nm, 148nm or 150nm, but is not limited thereto.

[0100] In some embodiments, the thickness of the first TCO layer 51 is less than the thickness of the second TCO layer 52 .

[0101] 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 for the long-wave band is increased.

[0102] 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.

[0103] In some embodiments, the silicon substrate 1 is single crystal silicon.

[0104] In some embodiments, the tunnel passivation layer 21 is made of silicon oxide, the first doping layer 22 is made of polysilicon, the second doping layer 42 is made of amorphous silicon or microcrystalline silicon, and the passivation contact layer 41 is made of amorphous silicon or microcrystalline silicon.

[0105] By setting a tunneling passivation layer 21 between the silicon substrate 1 and the first doped layer 22 of polycrystalline silicon, and setting a passivation contact layer 41 between the silicon substrate 1 and the second doped layer 42 of amorphous silicon or microcrystalline silicon, the interface recombination loss is effectively reduced, the open circuit voltage and fill factor of the battery are improved, and the battery conversion efficiency is further improved. Compared with the second doped layer made of polycrystalline silicon, the second doped layer 42 of amorphous silicon or microcrystalline silicon has a better passivation effect on the velvet structure, and has a lower contact resistivity with the composite TCO layer 5, thereby achieving a lower series resistance and a higher fill factor, and further improving the battery conversion efficiency.

[0106] In some embodiments, the light-receiving surface of the silicon substrate 1 is provided with a front passivation layer 71 and a front anti-reflection layer 72 in sequence 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 3nm to 15nm. The material of the front anti-reflection layer 72 is any one of silicon nitride, silicon oxynitride, and silicon oxide, and the thickness is 20nm to 80nm.

[0107] In some embodiments, see Figure 1 and Figure 2 As shown, the second semiconductor composite layer 4 includes a stacked composite segment arranged in the first region 11,

[0108] The first doping layer 22 is disposed on the mask layer 3 at a side facing away from the silicon substrate 1, and the stacked composite section is disposed on the mask layer 3 at a side facing away from the silicon substrate 1.

[0109] An avoidance hole is provided between the mask layer 3 and the stacked composite section.

[0110] The composite TCO layer 5 includes a first composite section disposed in the first region 11 and a second composite section disposed in the second region 12.

[0111] The first composite section includes a first segment 5A and a second segment 5B, wherein the first segment 5A is disposed in the avoidance hole and directly contacts the side of the first doped layer 22 facing away from the silicon substrate 1, and a first electrode 61 is disposed on the side of the first segment 5A facing away from the silicon substrate 1, and the second segment 5B is disposed on the side of the second doped extension section 4B facing away from the silicon substrate 1.

[0112] A second electrode 62 is provided on a side of the second composite section facing away from the silicon substrate 1 .

[0113] The material of the mask layer 3 is any one of PSG and SiNx.

[0114] On the one hand, the mask layer 3 can electrically isolate the first doping layer 22 and the second doping layer 42, and on the other hand, it can cooperate with the wet chemical process during the preparation process to prevent high-energy laser from directly acting on the first doping layer 22, effectively avoiding the risk of short circuit in the PN region (positive and negative electrodes) inside the battery.

[0115] In one embodiment, the polarity of the first doping layer 22 is opposite to the polarity of the silicon substrate 1 , and the polarity of the second doping layer 42 is the same as the polarity of the silicon substrate.

[0116] In another embodiment, preferably, the polarity of the first doping layer 22 is the same as the polarity of the silicon substrate 1, and the polarity of the second doping layer 42 is opposite to the polarity of the silicon substrate, so that the battery conversion efficiency is higher.

[0117] Secondly, see Figures 1 to 3 As shown, the present invention provides a method for preparing a back contact battery, comprising:

[0118] S100. Providing a silicon substrate 1, wherein the backlight surface of the silicon substrate 1 has first regions 11 and second regions 12 arranged alternately;

[0119] S200.See Figures 4 to 6 As shown, a first semiconductor composite layer 2 and a mask layer 3 are sequentially deposited on the backlight surface of the silicon substrate 1, and the first semiconductor composite layer 2 and the mask layer 3 outside the first region 11 are removed, so that only the first semiconductor composite layer 2 and the mask layer 3 are retained in the first region 11, and the first semiconductor composite layer 2 includes a tunnel passivation layer 21 and a first doping layer 22 sequentially arranged in a direction away from the silicon substrate 1;

[0120] S300. Depositing a second semiconductor composite layer 4 on the mask layer 3 and the second region 12, and removing a portion of the mask layer 3 and the second semiconductor composite layer 4 located in the first region 11 to expose a portion of the first doped layer 22, wherein the second semiconductor composite layer 4 includes a passivation contact layer 41 and a second doped layer 42 sequentially arranged 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;

[0121] S400. Depositing a composite TCO layer 5 on the second doped layer 42 and the exposed first doped layer 22, the composite TCO layer 5 comprising a first TCO layer 51 and a second TCO layer 52 sequentially arranged in a direction away from the silicon substrate 1, the refractive index of the first TCO layer 51 being greater than the refractive index of the second TCO layer 52, and the work function of the first TCO layer 51 being greater than the work function of the second TCO layer 52.

[0122] In the present invention, a composite TCO layer 5 is arranged on the backlight surface of the back contact cell, wherein the composite TCO layer 5 includes a first TCO layer 51 and a second TCO layer 52 which are 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 the refractive index of the second TCO layer 52. By gradually increasing the refractive index of the composite TCO layer 5 from the outside to the inside, the refractive index difference between the outer TCO layer (the second TCO layer 52) and the air can be reduced, which is conducive to more light entering the composite TCO layer 5. At the same time, when light enters from the outer TCO layer (the second TCO layer 52), Light can more easily penetrate the interface and enter the first TCO layer 51 with a higher refractive index, and then enter the battery, thereby reducing reflection losses and regulating the overall spectral absorption characteristics of the composite TCO layer 5. In addition, the refractive index difference design between the first TCO layer 51 and the second TCO layer 52 has a better back reflection effect for the long-wave band (especially in the 900nm to 1200nm band). After the long-wave band passes through the silicon substrate 1, it is reflected by the composite TCO layer 5 on the backlight surface and then enters the silicon substrate 1 again. The long-wave band light can be reused, and the long-wave band light can be fully utilized to increase the battery short-circuit current. Therefore, the present invention can effectively improve the light utilization rate, increase the battery short-circuit current, and thus improve the battery conversion efficiency through the mutual cooperation of the first TCO layer 51 and the second TCO layer 52 in the composite TCO layer 5.

[0123] Secondly, the present invention introduces a mask layer 3 between the first doping layer 22 and the second doping layer 42 in the first region 11, which can electrically isolate the first doping layer 22 and the second doping layer 42 on the one hand, and on the other hand, can cooperate with the wet chemical process during the preparation process to avoid high-energy laser directly acting on the first doping layer 22, thereby effectively avoiding the risk of short circuit in the PN region (positive and negative electrodes) inside the battery.

[0124] In some embodiments, the preparation method further includes step S500, specifically:

[0125] S510. Printing ink on the composite TCO layer 5 to form an electrode patterned structure, and then removing the composite TCO layer 5 in the area not covered by the ink by a wet chemical process to form the composite TCO layer 5 with an isolation area;

[0126] S520. Print a low-temperature slurry on the composite TCO layer 5 with the isolation area to form a first electrode 61 and a second electrode 62, and perform low-temperature annealing to form an electrode structure, wherein the first electrode 61 is electrically connected to the first doping layer 22 through the composite TCO layer 5, and the second electrode 62 is electrically connected to the second doping layer 42 through the composite TCO layer 5.

[0127] In the present invention, ink patterning combined with wet chemical process is used to effectively avoid the problem of lateral conduction between the P-type emitter and the N-type back surface field easily caused by the high energy of the laser during the laser grooving process, thereby avoiding the risk of short circuit in the PN region (positive and negative electrodes) inside the battery.

[0128] In some embodiments, in step S200, the step of removing the first semiconductor composite layer 2 and the mask layer 3 outside the first region 11 includes:

[0129] S210. Remove the mask layer 3 located on the second region 12 by laser etching technology (see Figure 5 As shown), and the laser etching area is processed by a wet chemical process to remove the first semiconductor composite layer 2 and the mask layer 3 outside the first area 11.

[0130] Laser etching technology is first used to remove the portion of the mask layer 3 located on the second area 12, and then a wet chemical process is used to remove the portion of the first semiconductor composite layer 2 and the mask layer 3 located outside the first area 11. That is, when the first semiconductor composite layer 2 and the mask layer 3 are also deposited on the side walls or the front of the silicon substrate 1, they also need to be removed together, so that only the first semiconductor composite layer 2 and the mask layer 3 located in the first area 11 are retained in the end. The mask layer 3 is combined with the wet chemical process to prevent high-energy laser from directly acting on the first doping layer 22, effectively avoiding the risk of short circuit in the PN area (positive and negative electrodes) inside the battery.

[0131] In some embodiments, step S200 further includes the following steps:

[0132] S220. Using alkaline etching, a velvet structure is formed on the second region 12 of the backlight surface of the silicon substrate 1 and on the light-receiving surface (see Figure 6 shown).

[0133] In some embodiments, after step S220, see Figure 1 As shown, the following steps are also included:

[0134] A front passivation layer 71 and a front anti-reflection layer 72 are sequentially deposited on the light-receiving surface of the silicon substrate 1 .

[0135] In some embodiments, in step S300, the step of removing a portion of the mask layer 3 and the second semiconductor composite layer 4 located in the first region 11 includes:

[0136] S310. Use laser etching technology to remove a portion of the second semiconductor composite layer 4 located on the first area 11 to expose a portion of the mask layer 3, and treat the laser etching area through a wet chemical process to remove the exposed portion of the mask layer 3.

[0137] Thus, by combining the mask layer 3 with the wet chemical process, the high-energy laser is prevented from directly acting on the first doping layer 22, and the risk of short circuit in the PN region (positive and negative electrodes) inside the battery is effectively avoided during the preparation process.

[0138] 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.

[0139] 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.

[0140] In some embodiments, a work function of the first TCO layer 51 is greater than a work function of the second TCO layer 52 .

[0141] 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.

[0142] In some embodiments, the work function of the first TCO layer 51 is 4.4 eV to 5.0 eV, and the work function of the second TCO layer 52 is 4.0 eV to 4.5 eV.

[0143] Furthermore, the present invention also provides a photovoltaic system, comprising the above-mentioned back-contact battery.

[0144] Furthermore, the present invention also provides a photovoltaic system, including a back-contact cell prepared by the above preparation method.

[0145] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0146] Example 1

[0147] This embodiment provides a method for preparing a back contact battery, comprising:

[0148] S100. Provide a silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first regions and second regions that are alternately arranged.

[0149] S200. Depositing a first semiconductor composite layer and a mask layer in sequence on the backlight surface of the silicon substrate, and removing the first semiconductor composite layer and the mask layer outside the first region, so that only the first semiconductor composite layer and the mask layer are retained in the first region, the first semiconductor composite layer includes a tunnel passivation layer and a first doping layer sequentially arranged in a direction away from the silicon substrate, the polarity of the first doping layer is the same as the polarity of the silicon substrate, specifically:

[0150] S201. sequentially depositing a first semiconductor composite layer and a mask layer;

[0151] S210. Using laser etching technology to remove the mask layer located on the second region, and treating the laser etching area by a wet chemical process to remove the first semiconductor composite layer and the mask layer located outside the first region;

[0152] S220. Using alkaline etching, a suede structure is formed on the second area of ​​the backlight surface and the light-receiving surface of the silicon substrate.

[0153] S230. A front passivation layer and a front anti-reflection layer are sequentially deposited on the light-receiving surface of the silicon substrate.

[0154] S300. Depositing a second semiconductor composite layer on the mask layer and the second region, and removing a portion of the mask layer and the second semiconductor composite layer located in the first region to expose a portion of the first doped layer, wherein the second semiconductor composite layer includes a passivation contact layer and a second doped layer sequentially arranged in a direction away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the silicon substrate, specifically:

[0155] S301. Depositing a second semiconductor composite layer on the mask layer and the second region;

[0156] S310. Use laser etching technology to remove a portion of the second semiconductor composite layer located on the first area to expose a portion of the mask layer, and treat the laser etching area through a wet chemical process to remove the exposed portion of the mask layer.

[0157] 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 sequentially arranged 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.

[0158] S500. Metal graphics, specifically:

[0159] S510. Printing ink on the composite TCO layer to form an electrode patterned structure, and then removing the composite TCO layer in the area not covered by the ink by a wet chemical process to form the composite TCO layer with an isolation area;

[0160] S520. Print a low-temperature slurry on the composite TCO layer with the isolation area to form a first electrode and a second electrode, and perform low-temperature annealing to form an electrode structure, wherein the first electrode is electrically connected to the first doped layer through the composite TCO layer, and the second electrode is electrically connected to the second doped layer through the composite TCO layer.

[0161] Example 2

[0162] This embodiment provides a back contact battery, comprising:

[0163] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0164] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0165] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0166] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0167] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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.

[0168] 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.

[0169] 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.

[0170] In this embodiment, the work function of the first TCO layer is 4 eV, and the work function of the second TCO layer is 3.5 eV.

[0171] 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.

[0172] In this embodiment, the thickness of the first TCO layer is 10 nm, and the thickness of the second TCO layer is 30 nm.

[0173] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0174] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0175] In this embodiment, the silicon substrate is single crystal silicon.

[0176] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0177] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0178] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0179] An avoidance hole is provided between the mask layer and the stacked composite section.

[0180] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0181] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0182] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0183] The material of the mask layer is PSG.

[0184] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0185] Example 3

[0186] This embodiment provides a back contact battery, comprising:

[0187] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0188] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0189] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0190] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0191] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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.

[0192] In this 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.

[0193] 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.

[0194] In this embodiment, the work function of the first TCO layer is 5 eV, and the work function of the second TCO layer is 4.5 eV.

[0195] 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.

[0196] In this embodiment, the thickness of the first TCO layer is 50 nm, and the thickness of the second TCO layer is 120 nm.

[0197] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0198] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0199] In this embodiment, the silicon substrate is single crystal silicon.

[0200] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0201] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0202] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0203] An avoidance hole is provided between the mask layer and the stacked composite section.

[0204] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0205] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0206] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0207] The material of the mask layer is PSG.

[0208] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0209] Example 4

[0210] This embodiment provides a back contact battery, comprising:

[0211] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0212] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0213] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0214] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0215] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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.

[0216] In this 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.

[0217] 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.

[0218] In this 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.

[0219] In this embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.89.

[0220] In this embodiment, the thickness of the first TCO layer is 50 nm, and the thickness of the second TCO layer is 120 nm.

[0221] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0222] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0223] In this embodiment, the silicon substrate is single crystal silicon.

[0224] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0225] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0226] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0227] An avoidance hole is provided between the mask layer and the stacked composite section.

[0228] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0229] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0230] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0231] The material of the mask layer is PSG.

[0232] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0233] Example 5

[0234] This embodiment provides a back contact battery, comprising:

[0235] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0236] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0237] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0238] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0239] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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.

[0240] In this 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.

[0241] In this embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.91.

[0242] In this embodiment, the work function of the first TCO layer is 4 eV, and the work function of the second TCO layer is 3.5 eV.

[0243] 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.

[0244] In this embodiment, the thickness of the first TCO layer is 100 nm, and the thickness of the second TCO layer is 150 nm.

[0245] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0246] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0247] In this embodiment, the silicon substrate is single crystal silicon.

[0248] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0249] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0250] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0251] An avoidance hole is provided between the mask layer and the stacked composite section.

[0252] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0253] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0254] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0255] The material of the mask layer is PSG.

[0256] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0257] Example 6

[0258] This embodiment provides a back contact battery, comprising:

[0259] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0260] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0261] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0262] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0263] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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.

[0264] In this 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.

[0265] In this embodiment, the ratio between the refractive index of the first TCO layer and the refractive index of the second TCO layer is 1:0.93.

[0266] In this embodiment, the work function of the first TCO layer is 5 eV, and the work function of the second TCO layer is 4 eV.

[0267] In this embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:0.8.

[0268] In this embodiment, the thickness of the first TCO layer is 80 nm, and the thickness of the second TCO layer is 100 nm.

[0269] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0270] In this embodiment, the material of the first TCO layer is AZO, and the material of the second TCO layer is ITO.

[0271] In this embodiment, the silicon substrate is single crystal silicon.

[0272] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0273] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0274] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0275] An avoidance hole is provided between the mask layer and the stacked composite section.

[0276] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0277] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0278] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0279] The material of the mask layer is PSG.

[0280] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0281] Example 7

[0282] This embodiment provides a back contact battery, comprising:

[0283] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately;

[0284] a first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the first doping layer is the same as that of the silicon substrate;

[0285] a second semiconductor composite layer, at least partially disposed in the second region, comprising a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the silicon substrate;

[0286] A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate,

[0287] The composite TCO layer includes a first TCO layer and a second TCO layer sequentially arranged 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 second TCO layer is greater than the work function of the first TCO layer.

[0288] In this 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.

[0289] 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.

[0290] In this embodiment, the work function of the first TCO layer is 4 eV, and the work function of the second TCO layer is 4.5 eV.

[0291] In this embodiment, the ratio between the work function of the first TCO layer and the work function of the second TCO layer is 1:1.13.

[0292] In this embodiment, the thickness of the first TCO layer is 50 nm, and the thickness of the second TCO layer is 120 nm.

[0293] In this embodiment, the thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

[0294] In this embodiment, the material of the first TCO layer and the second TCO layer is IWO.

[0295] In this embodiment, the silicon substrate is single crystal silicon.

[0296] In this embodiment, the tunnel passivation layer is made of silicon oxide, the first doped layer is made of polysilicon, the second doped layer is made of amorphous silicon, and the passivation contact layer is made of amorphous silicon.

[0297] In this embodiment, the second semiconductor composite layer includes a stacked composite segment disposed in the first region.

[0298] The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer.

[0299] An avoidance hole is provided between the mask layer and the stacked composite section.

[0300] The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region,

[0301] The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate.

[0302] A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

[0303] The material of the mask layer is PSG.

[0304] Wherein, the above-mentioned back contact battery is prepared by the preparation method of Example 1.

[0305] Comparative Example 1

[0306] The difference between this comparative example and Example 2 is that this comparative example uses a single-layer transparent conductive film to replace the composite TCO layer of Example 2. The single-layer transparent conductive film has a refractive index of 1.5, a work function of 3.5, a thickness of 30 nm, and is made of IWO.

[0307] Comparative Example 2

[0308] The difference between this comparative example and Example 2 is that the refractive index and work function of the first TCO layer in this comparative example are both smaller than those of the second TCO layer. Specifically:

[0309] The refractive index of the first TCO layer is 1.5, and the refractive index of the second TCO layer is 1.6.

[0310] The work function of the first TCO layer is 3.5 eV, and the work function of the second TCO layer is 4 eV.

[0311] The thickness of the first TCO layer is 30 nm, and the thickness of the second TCO layer is 10 nm.

[0312] The material of the first TCO layer and the second TCO layer is IWO.

[0313] The solar cells prepared in Examples 2 to 7 and Comparative Examples 1 to 2 were subjected to performance tests, and the test results are as follows:

[0314]

[0315] By comparing Examples 2 to 7 and Comparative Example 1, it can be seen that compared with the single-layer transparent conductive film, Examples 2 to 7 of the present application using the composite TCO layer have higher short-circuit current density and fill factor, and higher conversion efficiency.

[0316] By comparing Example 4, Example 7 and Comparative Example 2, it can be seen that the setting of the refractive index of the first TCO layer 51 of the present invention being greater than the refractive index of the second TCO layer 52 can effectively improve the conversion efficiency. Combined 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.

[0317] In the description of this specification, the description with reference to the terms "some embodiments", "exemplary", "example", or "for example" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation 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.

[0318] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the field can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A back contact battery, characterized in that: include: A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately; A first semiconductor composite layer, disposed in the first region, comprising a tunnel passivation layer and a first doping layer sequentially disposed in a direction away from the silicon substrate; A second semiconductor composite layer, at least partially disposed in the second region, comprises a passivation contact layer and a second doping layer sequentially disposed in a direction away from the silicon substrate, wherein the polarity of the second doping layer is opposite to that of the first doping layer; A composite TCO layer is provided in at least a portion of the first doped layer and the second doped layer on a side facing away from the silicon substrate, The composite TCO layer includes a first TCO layer and a second TCO layer which are sequentially arranged in a 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.

2. A back contact battery according to claim 1, characterized in that: 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 battery according to claim 2, characterized in that: 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 battery according to claim 2, characterized in that: 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. A back contact battery according to claim 1, characterized in that: The work function of the first TCO layer is greater than the work function of the second TCO layer.

6. A back contact battery according to claim 5, characterized in that: The work function of the first TCO layer is 4.0 eV to 5.0 eV, and the work function of the second TCO layer is 3.5 eV to 4.5 eV.

7. A back contact battery according to claim 6, characterized in that: 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 battery according to claim 6, characterized in that: The work function of the first TCO layer is 4.4 eV to 5.0 eV, and the work function of the second TCO layer is 4.0 eV to 4.5 eV.

9. A back contact battery according to claim 1, characterized in that: The thickness of the first TCO layer is 10 nm to 100 nm, and the thickness of the second TCO layer is 30 nm to 150 nm.

10. A back contact battery according to claim 9, characterized in that: The thickness of the first TCO layer is smaller than the thickness of the second TCO layer.

11. A back contact battery according to claim 1, characterized in that: The material of the first TCO layer and / or the second TCO layer is any one of ITO, IWO and AZO.

12. A back contact battery according to claim 1, characterized in that: The tunnel passivation layer is made of silicon oxide, the first doped layer is made of polycrystalline silicon, the second doped layer is made of amorphous silicon or microcrystalline silicon, and the passivation contact layer is made of amorphous silicon or microcrystalline silicon.

13. A back contact battery according to claim 1, characterized in that: The second semiconductor composite layer includes a stacked composite segment disposed in the first region, The first doped layer is disposed on a side facing away from the silicon substrate on the mask layer, and the stacked composite section is disposed on a side facing away from the silicon substrate on the mask layer. An avoidance hole is provided between the mask layer and the stacked composite section. The composite TCO layer includes a first composite section disposed in the first region and a second composite section disposed in the second region, The first composite section includes a first segment and a second segment, the first segment is arranged in the avoidance hole and directly contacts with a side of the first doped layer facing away from the silicon substrate, and a first electrode is arranged on a side of the first segment facing away from the silicon substrate, and the second segment is arranged on a side of the second doped extension section facing away from the silicon substrate. A second electrode is disposed on a side of the second composite section facing away from the silicon substrate.

14. A back contact battery according to claim 1, characterized in that: The polarity of the first doping layer is the same as that of the silicon substrate, and the polarity of the second doping layer is opposite to that of the silicon substrate.

15. A method for preparing a back contact battery, characterized in that: include: Providing a silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first areas and second areas arranged alternately; Depositing a first semiconductor composite layer and a mask layer in sequence on the backlight surface of the silicon substrate, and removing the first semiconductor composite layer and the mask layer outside the first region, wherein the first semiconductor composite layer includes a tunnel passivation layer and a first doping layer arranged in sequence in a direction away from the silicon substrate; Depositing a second semiconductor composite layer on the mask layer and the second region, and removing a portion of the mask layer and the second semiconductor composite layer located in the first region to expose a portion of the first doped layer, wherein the second semiconductor composite layer includes a passivation contact layer and a second doped layer sequentially arranged in a direction away from the silicon substrate, and the polarity of the second doped layer is opposite to that of the first doped layer; A composite TCO layer is deposited on the second doped layer and the exposed first doped layer, wherein the composite TCO layer comprises a first TCO layer and a second TCO layer sequentially arranged in a direction away from the silicon substrate, and a refractive index of the first TCO layer is greater than a refractive index of the second TCO layer.

16. The method for preparing a back contact battery according to claim 15, characterized in that: include: Printing ink on the composite TCO layer to form an electrode patterned structure, and then removing the composite TCO layer in the area not covered by the ink by a wet chemical process to form the composite TCO layer with an isolation area; A low-temperature paste is printed on the composite TCO layer with the isolation area to form a first electrode and a second electrode, and low-temperature annealing is performed to form an electrode structure, wherein the first electrode is electrically connected to the first doped layer through the composite TCO layer, and the second electrode is electrically connected to the second doped layer through the composite TCO layer.

17. The method for preparing a back contact battery according to claim 15, characterized in that: The step of removing the first semiconductor composite layer and the mask layer outside the first region comprises: The mask layer on the second region is removed by laser etching technology, and the laser etching area is treated by wet chemical process to remove the first semiconductor composite layer and the mask layer outside the first region.

18. The method for preparing a back contact battery according to claim 15, characterized in that: The step of removing a portion of the mask layer and the second semiconductor composite layer located in the first area comprises: A portion of the second semiconductor composite layer located on the first region is removed by laser etching technology to expose a portion of the mask layer, and the laser etching region is treated by a wet chemical process to remove the exposed portion of the mask layer.

19. The method for preparing a back contact battery according to claim 15, characterized in that: 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.

20. The method for preparing a back contact battery according to claim 19, characterized in that: 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.

21. The method for preparing a back contact battery according to claim 15, characterized in that: The work function of the first TCO layer is greater than the work function of the second TCO layer.

22. The method for preparing a back contact battery according to claim 21, characterized in that: The work function of the first TCO layer is 4.0 eV to 5.0 eV, and the work function of the second TCO layer is 3.5 eV to 4.5 eV.

23. The method for preparing a back contact battery according to claim 21, characterized in that: The work function of the first TCO layer is 4.4 eV to 5.0 eV, and the work function of the second TCO layer is 4.0 eV to 4.5 eV.

24. A photovoltaic system, characterized in that: A back-contact battery comprising a back-contact battery according to any one of claims 1 to 14, or a back-contact battery prepared by the preparation method according to any one of claims 15 to 23.

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