Back contact battery with specific conductive film layer and its preparation and application

Abstract

The present invention belongs to the technical field of back contact batteries, and specifically relates to a back contact battery with a specific conductive film layer, and its preparation and application, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer sequentially arranged from the back of a silicon wafer to the outside, the refractive index of the first transparent conductive film layer is 1.9-2.5, the thickness is 10-30nm, the refractive index of the second transparent conductive film layer is 1.4-1.8, and the oxygen doping amount in the process gas corresponding to the first transparent conductive film layer is controlled to be 0.1%-0.5% by volume flow rate, the oxygen doping amount in the process gas corresponding to the second transparent conductive film layer is controlled to be 2.0%-3.0% by volume flow rate, and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is 1:2-5:3-7. The present invention can effectively increase the reflection of the back of the battery cell to the infrared band, increase the short-circuit current, and thus improve the battery conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of back contact batteries, and in particular relates to a back contact battery with a specific conductive film layer and a preparation and application thereof. Background Art

[0002] In the back-contact battery of the prior art, a first semiconductor layer and a second semiconductor layer are alternately arranged on the back side of a silicon wafer, wherein the first semiconductor layer comprises a tunneling oxide layer and a first doped polysilicon layer, and the second semiconductor layer comprises an intrinsic silicon layer and a second doped silicon layer, and further comprises a front passivation layer and an anti-reflection layer sequentially arranged on the front side of the silicon wafer; and a metal conductive layer (such as Cu) is arranged to cover the entire area of ​​the outer surface and back side of the second semiconductor layer and the second semiconductor layer, thereby replacing a fine grid and saving the amount of silver paste used.

[0003] However, providing a metal conductive layer covering the entire back surface will reduce the reflection of the battery cell in the infrared band, resulting in a decrease in short-circuit current.

[0004] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or known technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defect in the prior art that the metal conductive layer covering the entire back surface of the back-contact battery will reduce the reflection of the battery cell in the infrared band, resulting in a decrease in the short-circuit current. A back-contact battery with a specific conductive film layer and its preparation and application are provided, which can effectively increase the reflection of the back surface of the battery cell to the infrared band and improve the short-circuit current. At the same time, while the first doped polysilicon layer can be thinned to an appropriate thickness, carrier collection can be enhanced, and the short-circuit current and fill factor can be further improved, thereby improving the battery conversion efficiency.

[0006] In order to achieve the above-mentioned purpose, in a first aspect, the present invention provides a back-contact battery with a specific conductive film layer, comprising a silicon wafer, a first semiconductor layer and a second semiconductor layer alternately arranged along the X-axis direction on the back side of the silicon wafer, and a conductive film layer, a metal conductive layer and a main gate electrode that are sequentially arranged outward along the Z-axis direction on the outer surfaces of the first semiconductor layer and the second semiconductor layer, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer sequentially arranged outward from the back side of the silicon wafer, wherein the refractive index of the first transparent conductive film layer is 1.9-2.5 and the thickness is The thickness of the film is 10-30nm, the refractive index of the second transparent conductive film layer is 1.4-1.8, and the first transparent conductive film layer and the second transparent conductive film layer are both introduced with process gas containing argon gas and argon-oxygen mixed gas during sputtering coating preparation, and the oxygen doping amount in the process gas corresponding to the first transparent conductive film layer is controlled to be 0.1%-0.5% by volume flow rate, and the oxygen doping amount in the process gas corresponding to the second transparent conductive film layer is controlled to be 2.0%-3.0% by volume flow rate, and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is 1:2-5:3-7.

[0007] In some preferred embodiments of the present invention, the thickness of the second transparent conductive film layer is 30-100 nm, and / or the thickness of the metal conductive layer is 50-150 nm.

[0008] In some preferred embodiments of the present invention, the transmittance of the first transparent conductive film layer is above 80%, and the resistivity is between 6e-04 Ω·cm and 9e-04 Ω·cm.

[0009] In some preferred embodiments of the present invention, the transmittance of the second transparent conductive film layer is above 90%, and the resistivity is between 3.8e-04 Ω·cm and 4.2e-04 Ω·cm.

[0010] In some preferred embodiments of the present invention, the refractive index ratio of the first transparent conductive film layer to the second transparent conductive film layer is 1.25-1.50:1.

[0011] In some preferred embodiments of the present invention, the materials of the first transparent conductive film layer and the second transparent conductive film layer are independently selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium, and zinc, or from an aluminum- and / or boron-doped zinc oxide-based film, and the material of the metal conductive layer is selected from at least one of copper, aluminum, silver, and nickel-copper alloy.

[0012] In some preferred embodiments of the present invention, the first semiconductor layer includes a tunneling oxide layer and a first doped polysilicon layer, the second semiconductor layer includes an intrinsic silicon layer and a second doped silicon layer, and the first doped polysilicon layer is thinned to 50-100 nm.

[0013] In some preferred embodiments of the present invention, the back contact battery having a specific conductive film layer further comprises:

[0014] A metal anti-oxidation protection layer is arranged on the outer surface of the metal conductive layer in the Z-axis direction, and a conductive stack formed by the metal conductive layer and the metal anti-oxidation protection layer is in ohmic contact with the main gate electrode;

[0015] An insulating layer is arranged on the outer surface of the metal anti-oxidation protection layer in the Z-axis direction. The insulating layer is overall plate-shaped and has a first opening and a second opening alternately arranged along the X-axis direction. The first opening and the second opening are respectively spaced apart along the Y-axis direction. The first opening is arranged on the outer surface of the first semiconductor layer, and the second opening is arranged on the outer surface of the second semiconductor layer. The main gate electrode is located on the outer surface of the insulating layer and makes ohmic contact with the metal anti-oxidation protection layer through the corresponding opening of the insulating layer.

[0016] In some preferred embodiments of the present invention, the thickness of the metal anti-oxidation protective layer is 10-30nm, and the material of the metal anti-oxidation protective layer is selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium, and zinc, or selected from an aluminum and / or boron-doped zinc oxide-based film.

[0017] In some preferred embodiments of the present invention, the back-contact cell having a specific conductive film layer further comprises a front passivation layer and an anti-reflection layer sequentially disposed on the front side of the silicon wafer.

[0018] In some preferred embodiments of the present invention, the silicon wafer area where the first semiconductor layer is located is a polishing area, and the silicon wafer area where the second semiconductor layer is located is a texturing area. Isolation grooves arranged at intervals along the X-axis direction are provided on the conductive stack formed by the conductive film layer and the metal conductive layer, and the isolation grooves are arranged across the junction of the texturing area and the polishing area; the two ends of the second semiconductor layer respectively extend outward to cover the back side of the adjacent first semiconductor layer, and a first semiconductor opening area not covering the second semiconductor layer is provided on the back side of the first semiconductor layer, and a second semiconductor opening area is formed between the adjacent first semiconductor layers. The second semiconductor opening area is arranged at intervals from the first semiconductor opening area, and the area between them is an overlapping area; the isolation groove is located in a corresponding area on the outer surface of the overlapping area, and in the overlapping area, a mask layer or no mask layer is provided between the first semiconductor layer and the second semiconductor layer.

[0019] In a second aspect, the present invention provides a method for preparing a back contact battery having a specific conductive film layer, comprising the following steps:

[0020] S1, provide silicon wafers;

[0021] S2, forming a first semiconductor layer and a mask layer on the back side of the silicon wafer in sequence; the first semiconductor layer comprises a tunneling oxide layer and a first doped polysilicon layer, and the first doped polysilicon layer is thinned to 50-100 nm;

[0022] S3, etching an opening on the back surface obtained in S2 to form a second semiconductor opening region;

[0023] S4, performing texturing cleaning, and then selecting whether to perform a step of removing the mask layer outside the second semiconductor opening region on the back side of the silicon wafer through cleaning according to needs;

[0024] S5, depositing a second semiconductor layer on the back side, wherein the second semiconductor layer comprises an intrinsic silicon layer and a second doped silicon layer;

[0025] S6, etching an opening on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region;

[0026] S7, depositing a conductive film layer, a metal conductive layer, and a metal anti-oxidation protective layer in sequence on the back surface obtained in S6 by magnetron sputtering, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer deposited in sequence from the back surface of the silicon wafer outward;

[0027] The deposition conditions of the first transparent conductive film layer include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 1-3kW, the oxygen content of the process gas in terms of volume flow ratio is 0.1%-0.5%, the refractive index is controlled to be 1.9-2.5, and the thickness is 10-30nm;

[0028] The deposition conditions of the second transparent conductive film layer include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 5-7kW, the oxygen content in the process gas is 2.0%-3.0% by volume flow ratio, and the refractive index is controlled to be 1.4-1.8; and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is controlled to be 1:2-5:3-7;

[0029] S8, performing etching on a portion of the conductive film layer and its corresponding film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation groove;

[0030] S9, disposing an insulating layer on the outer surface of the back side, the insulating layer covering the isolation groove, and providing a first opening and a second opening for transmitting the first semiconductor and the second semiconductor respectively on the insulating layer;

[0031] S10, forming a main gate electrode on the back surface obtained in S9, and the main gate electrode makes ohmic contact with the corresponding conductive film layer on the corresponding semiconductor through the corresponding first opening and the second opening of the insulating layer.

[0032] In some preferred embodiments of the present invention, the volume flow ratio of argon to oxygen in the argon-oxygen mixed gas is 7-9:1.

[0033] In some preferred embodiments of the present invention, the flow rate of the argon-oxygen mixed gas is 10-200 sccm, and the flow rate of the argon gas is 500-1000 sccm.

[0034] In some preferred embodiments of the present invention, the method for preparing a back-contact cell having a specific conductive film layer further comprises: in S5, a front passivation layer and an anti-reflection layer are sequentially deposited on the front side of the silicon wafer.

[0035] In a third aspect, the present invention provides a back-contact battery, which is prepared by the method for preparing a back-contact battery with a specific conductive film layer described in the second aspect.

[0036] In a fourth aspect, the present invention provides a photovoltaic module, which includes the back-contact cell with the specific conductive film layer described in the first aspect, or includes the back-contact cell described in the third aspect.

[0037] Beneficial effects:

[0038] The present invention adopts the above technical scheme, especially for the back contact battery structure with a metal conductive layer, and adopts a high-low refractive index lamination method of a first transparent conductive film layer and a second transparent conductive film layer, so as to effectively increase the reflection of the back side of the battery cell to the infrared band and improve the short-circuit current; and because the specific oxygen doping amount in the sputtering coating preparation process of the first transparent conductive film layer and the second transparent conductive film layer can make the corresponding transparent conductive film layer more crystalline, and the oxygen content is sensitive to the transmittance and resistivity of the corresponding transparent conductive film layer, wherein the first transparent conductive film layer with a suitable thinness and a suitable low oxygen doping amount has a high refractive index, suitable transmittance and resistivity, and can be used as a protective layer, and the second transparent conductive film layer with a specific suitable high oxygen doping amount and a suitable thickness ratio has a low refractive index, high transmittance, and low resistivity, which can improve the carrier mobility of the film layer, and the high light transmittance allows as much light as possible to enter the battery emitter, enhances carrier collection, and improves the short-circuit current and fill factor, thereby effectively improving the battery conversion efficiency.

[0039] The present invention also cooperates with controlling the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer within an appropriate range, so that the first transparent conductive film layer with a high refractive index can play a sufficient protective role; the second transparent conductive film layer with an appropriate thickness ratio can take into account good battery performance (carrier mobility) and improve Isc and FF; the metal conductive layer with an appropriate thickness ratio can ensure sufficient ohmic contact with the main grid electrode and improve Isc, thereby effectively improving the battery conversion efficiency.

[0040] In the preferred combined passivation structure scheme of the present invention, the specific first transparent conductive film layer and the second transparent conductive film layer cooperate with the combined passivation structure, which can enhance carrier collection while thinning the first doped polysilicon layer to an appropriate thickness, further improve the short-circuit current and fill factor, thereby effectively improving the battery conversion efficiency.

[0041] In the post-texturing preparation method provided by the present invention, the first transparent conductive film layer is deposited to a suitable thickness using a suitable low power (too thin cannot withstand the high-power ion bombardment of the second transparent conductive film layer), so the ion bombardment generated by sputtering is relatively small, so that the first doped polysilicon layer can be made thinner than a conventional back contact battery, and will not cause damage to the thinner polycrystalline layer, thereby enhancing the collection of photogenerated carriers in the PN junction battery, and the first transparent conductive film layer is low-oxygen doped mainly to obtain a high refractive index, suitable transmittance and resistivity. After the first transparent conductive film layer is formed (equivalent to having a protective layer), a higher power and a high oxygen doping amount can be used when depositing the second transparent conductive film layer, so that the second transparent conductive film layer has a low refractive index, a high transmittance and a low resistivity, so as to improve the carrier mobility of the film layer; at the same time, the high-low refractive index transparent conductive film layer stacking method is combined to increase the reflection in the infrared band, improve the short-circuit current, and further effectively improve the battery conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 It is a partial structural schematic diagram of a specific embodiment of a back-contact battery with a specific conductive film layer of the present invention.

[0044] Figure 2 It is a schematic structural diagram of the insulating layer of the present invention.

[0045] Description of Reference Numerals

[0046] 1. Silicon wafer, 2. Tunneling oxide layer, 3. N-type doped polysilicon layer, 4. Intrinsic amorphous silicon layer, 5. P-type doped amorphous silicon layer, 6. First transparent conductive film layer, 7. Second transparent conductive film layer, 8. Metal conductive layer, 9. Front passivation layer, 10. Anti-reflection layer; 102. First opening, 101. Second opening. DETAILED DESCRIPTION

[0047] In the present invention, unless otherwise specified, directional words such as "upper, lower, left, right" are generally understood in conjunction with the directions shown in the drawings and actual applications.

[0048] In addition, the terms "first" and "second" 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. Therefore, the features defined as "first" and "second" 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.

[0049] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0050] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0051] In the present invention, the area close to the silicon wafer is referred to as the inside, and the area far from the silicon wafer is referred to as the outside.

[0052] In a first aspect, the present invention provides a back-contact battery with a specific conductive film layer, comprising a silicon wafer, a first semiconductor layer and a second semiconductor layer alternately arranged along the X-axis direction on the back of the silicon wafer, and a conductive film layer, a metal conductive layer and a main gate electrode in ohmic contact with the metal conductive layer arranged in sequence on the outer surfaces of the first semiconductor layer and the second semiconductor layer in the Z-axis direction, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer arranged in sequence from the back of the silicon wafer to the outside, wherein the refractive index of the first transparent conductive film layer is 1.9-2.5 and the thickness is 10-30 nm, the refractive index of the second transparent conductive film layer is 1.4-1.8, and process gases containing argon gas and argon-oxygen mixed gas are introduced into the first transparent conductive film layer and the second transparent conductive film layer during sputtering coating preparation, and the oxygen doping amount in the process gas corresponding to the first transparent conductive film layer is controlled to be 0.1%-0.5% by volume flow rate, and the oxygen doping amount in the process gas corresponding to the second transparent conductive film layer is controlled to be 2.0%-3.0% by volume flow rate, and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is 1:2-5:3-7.

[0053] In some preferred embodiments of the present invention, the thickness of the second transparent conductive film layer is 30-100 nm. Using a second transparent conductive film layer with a suitable thickness is more conducive to improving the carrier mobility of the film layer, thereby improving the battery efficiency.

[0054] Preferably, the thickness of the metal conductive layer is 50-150 nm. Using a metal conductive layer with a suitable thickness is more conducive to ohmic contact with the main gate electrode.

[0055] In some preferred embodiments of the present invention, the transmittance of the first transparent conductive film layer is above 80%, and the resistivity is between 6e-04 Ω·cm and 9e-04 Ω·cm. Using a first transparent conductive film layer with appropriate transmittance and resistivity is more conducive to improving the refractive index of the film layer.

[0056] Preferably, the transmittance of the second transparent conductive film layer is above 90%, and the resistivity is between 3.8e-04 Ω·cm and 4.2e-04 Ω·cm, preferably between 3.9e-04 Ω·cm and 4.1e-04 Ω·cm. Using a second transparent conductive film layer with appropriate transmittance and resistivity is more conducive to allowing as much light as possible to enter the battery emitter.

[0057] In some preferred embodiments of the present invention, the refractive index ratio of the first transparent conductive film layer and the second transparent conductive film layer is 1.25-1.50: 1, preferably 1.30-1.50: 1. The use of the first transparent conductive film layer and the second transparent conductive film layer with a suitable refractive index ratio is more conducive to increasing the reflection of the back side of the battery cell to the infrared band and improving the short-circuit current.

[0058] In some preferred embodiments of the present invention, the materials of the first transparent conductive film layer and the second transparent conductive film layer are independently selected from indium oxide-based films doped with at least one of tin, tungsten, titanium, and zinc, or selected from zinc oxide-based films doped with aluminum and / or boron.

[0059] Preferably, the material of the metal conductive layer is selected from at least one of copper, aluminum, silver, and nickel-copper alloy.

[0060] In some preferred embodiments of the present invention, the first semiconductor layer includes a tunneling oxide layer and a first doped polysilicon layer, the second semiconductor layer includes an intrinsic silicon layer and a second doped silicon layer, and the first doped polysilicon layer is thinned to 50-100 nm. In the joint passivation cell structure, the ion bombardment generated by the sputtering coating of the appropriately thin first transparent conductive film layer as a protective layer is small, so that the first doped polysilicon layer can be made thinner than the conventional back contact cell, and will not cause damage to the thinner polycrystalline layer, which is more conducive to enhancing the collection of photogenerated carriers in the PN junction cell.

[0061] In some preferred embodiments of the present invention, the back-contact battery with a specific conductive film layer further includes: a metal anti-oxidation protective layer, which is arranged on the outer surface of the metal conductive layer in the Z-axis direction, and the conductive stack formed by the metal conductive layer and the metal anti-oxidation protective layer is in ohmic contact with the main gate electrode. The metal anti-oxidation protective layer is provided to better ensure the conductivity of the metal conductive layer. The metal conductive layer provided in the present invention has a strong conductivity and fully meets the role of current collection. Adding a metal anti-oxidation protective layer thereon can ensure that the metal conductive layer is not oxidized and thus affects the conductivity, thereby playing the role of a silver paste fine grid, and there is no need to provide a silver paste fine grid.

[0062] In some preferred embodiments of the present invention, the back contact battery with a specific conductive film layer further includes: an insulating layer, which is arranged on the outer surface of the metal anti-oxidation protective layer in the Z-axis direction, and is plate-shaped as a whole and has a first opening and a second opening arranged alternately along the X-axis direction, and the first opening and the second opening are arranged at intervals along the Y-axis direction, respectively, the first opening is arranged on the outer surface of the first semiconductor layer, and the second opening is arranged on the outer surface of the second semiconductor layer, and the main gate electrode is located on the outer surface of the insulating layer and makes ohmic contact with the metal anti-oxidation protective layer through the corresponding opening of the insulating layer. The structure of the insulating layer of the present invention and the connection structure of the main gate electrode and the insulating layer are respectively the same as the insulating layer and its matching structure with the main gate electrode in CN116093176B. The use of the insulating layer with this specific structure, in combination with the specific first transparent conductive film layer, the second transparent conductive film layer, the metal conductive layer and the metal anti-oxidation protective layer of the present invention, is more conducive to ensuring the insulation effect between the first semiconductor region and the second semiconductor region.

[0063] Further preferably, the metal anti-oxidation protection layer has a thickness of 10-30 nm.

[0064] Further preferably, the material of the metal anti-oxidation protection layer is selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium and zinc, or is selected from an aluminum and / or boron-doped zinc oxide-based film.

[0065] In some preferred embodiments of the present invention, the back contact cell with a specific conductive film layer further comprises a front passivation layer and an anti-reflection layer sequentially disposed on the front side of the silicon wafer. The types and thicknesses of the front passivation layer and the anti-reflection layer can be determined by referring to the prior art, and will not be described in detail here.

[0066] In some preferred embodiments of the present invention, the silicon wafer region where the first semiconductor layer is located is a polishing region, and the silicon wafer region where the second semiconductor layer is located is a texturing region. The conductive stack formed by the conductive film layer and the metal conductive layer is provided with isolation grooves spaced along the X-axis direction, and the isolation grooves are arranged across the boundary between the texturing region and the polishing region. The isolation grooves are arranged across the boundary between the texturing region and the polishing region, which is more conducive to reducing the dark current of the battery.

[0067] In some preferred embodiments of the present invention, both ends of the second semiconductor layer extend outward to cover part of the back side of the adjacent first semiconductor layer, and a first semiconductor opening area that does not cover the second semiconductor layer is opened on the back side of the first semiconductor layer, and a second semiconductor opening area is formed between adjacent first semiconductor layers. The second semiconductor opening area is arranged at intervals from the first semiconductor opening area, and the area between them is an overlapping area; the isolation groove is located on the corresponding area on the outer surface of the overlapping area.

[0068] Further preferably, in the overlapping region, a mask layer is disposed between the first semiconductor layer and the second semiconductor layer, or no mask layer is disposed.

[0069] The mask layer may be at least one of silicon nitride, silicon oxide, and silicon oxynitride.

[0070] The widths of the first semiconductor opening region, the second semiconductor opening region, and the isolation groove of the present invention can be determined according to the range of the prior art and actual needs. For example, the width W1 of the second semiconductor opening region can be 300-700 μm, the width W2 of the first semiconductor opening region can be 100-300 μm, and the width WgL of the isolation groove can be 30-200 μm.

[0071] In the present invention, one of the first doped polysilicon layer and the second doped silicon layer is N-type, and the other is P-type.

[0072] The present invention is further preferred that the thickness and corresponding doping concentration of the tunnel oxide layer or intrinsic silicon layer and the second doped silicon layer, as well as the doping concentration of the first doped polysilicon layer can refer to the range of the prior art, and can be used in the present invention. For example, the thickness of the tunnel oxide layer is 1-2nm, the thickness of the intrinsic silicon layer is 5-15nm; the thickness of the second doped silicon layer is 7-45nm, and the effective doping concentration is 2e18cm -3 -3e20cm -3 The effective doping concentration of the first doped polysilicon layer is greater than 5e18cm -3 .

[0073] In a second aspect, the present invention provides a method for preparing a back contact battery having a specific conductive film layer, comprising the following steps:

[0074] S1, provide silicon wafers;

[0075] S2, forming a first semiconductor layer and a mask layer on the back side of the silicon wafer in sequence; the first semiconductor layer comprises a tunneling oxide layer and a first doped polysilicon layer, and the first doped polysilicon layer is thinned to 50-100 nm;

[0076] S3, etching an opening on the back surface obtained in S2 to form a second semiconductor opening region;

[0077] S4, performing texturing cleaning, and then selecting whether to perform a step of removing the mask layer outside the second semiconductor opening region on the back side of the silicon wafer through cleaning according to needs;

[0078] S5, depositing a second semiconductor layer on the back side, wherein the second semiconductor layer comprises an intrinsic silicon layer and a second doped silicon layer;

[0079] S6, etching an opening on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region;

[0080] S7, depositing a conductive film layer, a metal conductive layer, and a metal anti-oxidation protective layer in sequence on the back surface obtained in S6 by magnetron sputtering, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer deposited in sequence from the back surface of the silicon wafer outward;

[0081] S8, performing etching on a portion of the conductive film layer and its corresponding film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation groove;

[0082] S9, disposing an insulating layer on the outer surface of the back side, the insulating layer covering the isolation groove, and providing a first opening and a second opening for transmitting the first semiconductor and the second semiconductor respectively on the insulating layer;

[0083] S10, forming a main gate electrode on the back surface obtained in S9, and the main gate electrode makes ohmic contact with the corresponding conductive film layer on the corresponding semiconductor through the corresponding first opening and the second opening of the insulating layer.

[0084] In S7, the deposition conditions of the first transparent conductive film layer include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 1-3kW, the oxygen content of the process gas by volume flow rate is 0.1%-0.5%, the refractive index is controlled to be 1.9-2.5, and the thickness is 10-30nm. The deposition conditions of the second transparent conductive film layer of the present invention include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 5-7kW, the oxygen content of the process gas by volume flow rate is 2.0%-3.0%, and the refractive index is controlled to be 1.4-1.8.

[0085] It can be understood that the oxygen doping amount refers to the total proportion of oxygen in the corresponding process gas, including the proportion of oxygen in argon gas and argon-oxygen mixed gas.

[0086] Preferably, the volume flow ratio of argon to oxygen in the argon-oxygen mixed gas is 7-9: 1. Using an argon-oxygen mixed gas with a suitable flow ratio is more conducive to adjusting the amount of oxygen doped required by the process.

[0087] Preferably, the flow rate of the argon-oxygen mixed gas is 10-200 sccm, and the specific flow rate can satisfy the oxygen doping amount required by the corresponding film layer.

[0088] Preferably, the flow rate of argon gas is 500-1000 sccm.

[0089] The thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is controlled to be 1:2-5:3-7. The first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer with a suitable thickness ratio are used to ensure sufficient ohmic contact with the main grid electrode and improve Isc while taking into account good battery performance (carrier mobility) and improving Isc and FF, thereby effectively improving battery conversion efficiency.

[0090] Other conventional steps may also be performed in S2 of the present invention, for example, S2 also includes removing the PSG (phosphosilicate glass) layer after forming the first semiconductor layer, and back-plating the mask layer after backwashing.

[0091] The texturing cleaning in S4 of the present invention can remove the residual mask layer and the first semiconductor layer in the second semiconductor opening area, and simultaneously form a texturing surface on the front side of the silicon wafer and the second semiconductor opening area.

[0092] Other conventional steps may also be performed in S7 of the present invention, for example, S7 also includes first cleaning the silicon wafer, removing the oxide layer in the first semiconductor region (the oxide layer refers to the oxide layer formed when the exposed polycrystalline at the edge of the first semiconductor opening region contacts the air after the first semiconductor opening), and then depositing a conductive film layer and a metal conductive layer in sequence.

[0093] In some preferred embodiments of the present invention, the method for preparing a back-contact cell having a specific conductive film layer further comprises: in S5, a front passivation layer and an anti-reflection layer are sequentially deposited on the front side of the silicon wafer.

[0094] In a third aspect, the present invention provides a back-contact battery, which is prepared by the method for preparing a back-contact battery with a specific conductive film layer described in the second aspect.

[0095] In a fourth aspect, the present invention provides a photovoltaic module, which includes the back-contact cell with the specific conductive film layer described in the first aspect, or includes the back-contact cell described in the third aspect.

[0096] The embodiments of the present invention are described in detail below, which are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0097] Example 1

[0098] A back contact battery, such as Figure 1 As shown, it is prepared by the following preparation method:

[0099] S1, double-sided polishing of silicon wafer 1;

[0100] S2. The first semiconductor layer is deposited on the back of the silicon wafer 1. The first semiconductor layer is a tunneling oxide layer 2 (1 nm thick) and an N-type doped polysilicon layer 3. The thickness of the N-type doped polysilicon layer 3 is 80 nm and the effective doping concentration is 5e19 cm -3 ;

[0101] S3, after removing PSG and backwashing, a mask layer is plated on the back, and the mask layer is silicon nitride;

[0102] S4, etching an opening on the back side of the silicon wafer 1, removing the mask layer and part of the first semiconductor layer, and forming a second semiconductor opening region, wherein the width W1 of the second semiconductor opening region is 500 μm;

[0103] S5, the silicon wafer 1 is textured and cleaned to form a pyramid texture surface on the front side of the silicon wafer 1, and at the same time, the first semiconductor layer in the second semiconductor opening area on the back side of the silicon wafer 1 is removed and then the mask layer is removed to form a silicon wafer 1 with a single-side texture and a single-side polishing structure;

[0104] S6, depositing a front passivation layer 9 and an anti-reflection layer 10 on the front side of the silicon wafer 1, and depositing a second semiconductor layer on the back side, wherein the second semiconductor layer is an intrinsic amorphous silicon layer 4 (with a thickness of 10 nm) and a P-type doped amorphous silicon layer 5 (with a thickness of 15 nm and an effective doping concentration of 5e20 cm -3 );

[0105] S7, performing laser opening on the back side of the silicon wafer 1 to form first semiconductor opening regions alternately arranged with second semiconductor opening regions, and the opening width W2 of the first semiconductor opening regions is 200 μm;

[0106] S8, the silicon wafer 1 is cleaned, and after the oxide layer in the first semiconductor opening area is removed, a first transparent conductive film layer 6, a second transparent conductive film layer 7, a metal conductive layer 8 and a metal anti-oxidation protective layer are sequentially deposited on the back of the silicon wafer 1;

[0107] The first transparent conductive film layer 6, the second transparent conductive film layer 7, the metal conductive layer 8 and the metal anti-oxidation protective layer are all deposited and coated by magnetron sputtering. During the deposition, a process gas containing argon and an argon-oxygen mixture is introduced. The argon flow rate is 700 sccm, and the volume flow ratio of argon and oxygen in the argon-oxygen mixture is 90:10.

[0108] The thickness of the first transparent conductive film layer 6 is 20 nm, the sputtering power is 2 kW, and the flow rate of the argon-oxygen mixed gas is adjusted so that the oxygen content in the process gas (measured as a percentage of volume flow rate, the same applies later) is 0.2%, and the refractive index is controlled to be 2.2, the transmittance is 85%, and the resistivity is 7.2e-04Ω·cm.

[0109] The thickness of the second transparent conductive film layer 7 is 60 nm, the sputtering power is 6 kW, the flow rate of the argon-oxygen mixed gas is adjusted so that the oxygen content in the process gas is 2.5%, the refractive index is controlled to be 1.6, the transmittance is 91%, and the resistivity is 4.0e-04Ω·cm.

[0110] The thickness of the metal conductive layer 8 is 100 nm, and the thickness of the metal anti-oxidation protection layer is 20 nm. According to calculation, the thickness ratio of the first transparent conductive film layer 6, the second transparent conductive film layer 7, and the metal conductive layer 8 is 1:3:5.

[0111] The first transparent conductive film layer 6 and the second transparent conductive film layer 7 are both indium tin oxide thin films ITO, the metal conductive layer 8 is copper, and the metal anti-oxidation protection layer is indium tin oxide thin film ITO.

[0112] S9, etching to form an isolation groove on the overlapping area at the junction between the first semiconductor opening area and the second semiconductor opening area by etching, the isolation groove width WgL is 80 μm, and the isolation groove is formed at the junction of the texturing area and the polishing area;

[0113] S10, printing an insulating ink layer on the back of the silicon wafer 1 to form an insulating layer. Figure 2 As shown, a first opening 102 and a second opening 101 are provided;

[0114] S11, printing silver paste main grid lines on the back of the silicon wafer 1, connecting the conductive film layer on the first semiconductor and the second semiconductor and the stacked layers formed by the metal conductive layer 8 and the metal anti-oxidation protection layer in series through the first opening 102 and the second opening 101 on the insulating layer to form silver paste grid line electrodes.

[0115] Example 2

[0116] The method of Example 1 is referred to, except that the oxygen doping amount of the second transparent conductive film layer is reduced by adjusting the flow rate of the argon-oxygen mixed gas so that the refractive index ratio of the first transparent conductive film layer to the second transparent conductive film layer is 1.25:1. At this time, the refractive index of the second transparent conductive film layer is 1.76, the transmittance is 90%, and the resistivity is 3.8e-04 Ω·cm.

[0117] Example 3

[0118] The method of Example 1 is referred to, except that the oxygen doping amount of the second transparent conductive film layer is increased by adjusting the flow rate of the argon-oxygen mixed gas so that the resistivity of the second transparent conductive film layer is 4.2e-04 Ω·cm. At this time, the transmittance of the second transparent conductive film layer is 92%, the refractive index is 1.46, and the thickness remains unchanged.

[0119] Example 4

[0120] The method of Example 1 is referred to, except that the oxygen doping amount in the deposition of the first transparent conductive film layer is reduced by adjusting the flow rate of the argon-oxygen mixed gas, and the thickness of the first transparent conductive film layer is adjusted so that the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is 1:2:3.3. At this time, the refractive index of the first transparent conductive film layer is 2.0, the transmittance is 83%, and the resistivity is 6.5e-04 Ω·cm.

[0121] Example 5

[0122] The method of Example 1 is referred to, except that the thickness of the metal conductive layer is adjusted so that the thickness ratio of the first transparent conductive film layer to the metal conductive layer is 1:3.

[0123] Example 6

[0124] The method of Example 1 is followed, except that the first semiconductor layer is an intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer, the thicknesses of the intrinsic amorphous silicon layer and the N-type doped amorphous silicon layer are 10 nm and 80 nm respectively, and the effective doping concentration of the first doped amorphous silicon layer is 1e19 cm -3 .

[0125] Comparative Example 1

[0126] The method of Example 1 is referred to, except that the N-type doped polysilicon layer has a conventional thickness of 130 nm, and the structure of the conductive film layer is different, specifically a traditional transparent conductive film layer (ITO), the traditional transparent conductive film layer has a refractive index of 1.85, a thickness of 60 nm, a transmittance of 90%, and a resistivity of 3.9e-04 Ω·cm. The magnetron sputtering conditions of the traditional transparent conductive film layer are: the sputtering power is 6.5 kW, the oxygen doping amount is 1.6%, and the sputtering time is 45 s.

[0127] Comparative Example 2

[0128] The method of Example 1 is followed, except that the flow rate of the argon-oxygen mixed gas is adjusted to control the oxygen doping amount during the deposition of the first transparent conductive film layer to 0.7%. The resulting first transparent conductive film layer has a refractive index of 1.8, a thickness of 20 nm, a transmittance of 86%, and a resistivity of 6.5e-04Ω·m.

[0129] Comparative Example 3

[0130] The method of Example 1 is followed, except that the flow rate of the argon-oxygen mixed gas is adjusted to control the oxygen doping amount during the deposition of the second transparent conductive film layer to 1.8%. The resulting second transparent conductive film layer has a refractive index of 1.9, a thickness of 60 nm, a transmittance of 90%, and a resistivity of 3.95e-04Ω·cm.

[0131] Test Case

[0132] The back contact batteries obtained from the above embodiments and comparative examples were subjected to various performance tests on short-circuit current Isc, open-circuit voltage Voc, fill factor FF, and battery conversion efficiency Eta. The results are shown in Table 1. Each performance indicator is the median measured in the same batch of batteries.

[0133] Table 1

[0134]

[0135] It can be seen from the above results that, compared with the comparative example, the embodiment of the present invention can effectively increase the reflection of the infrared band on the back side of the battery cell and improve the short-circuit current. At the same time, it can enhance carrier collection while thinning the first doped polysilicon layer to an appropriate thickness, further improve the short-circuit current and fill factor, and thus improve the battery conversion efficiency.

[0136] Furthermore, according to Example 1 and Examples 2-6, it can be seen that the preferred battery structure scheme of the present invention is more conducive to improving the short-circuit current Isc, open-circuit voltage Voc, fill factor FF, and battery conversion efficiency Et, further improving the overall effect.

[0137] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A back-contact battery with a specific conductive film layer, comprising a silicon wafer, a first semiconductor layer and a second semiconductor layer alternately arranged along the X-axis direction on the back of the silicon wafer, and a conductive film layer, a metal conductive layer and a main gate electrode in ohmic contact with the metal conductive layer sequentially arranged outward along the Z-axis direction on the outer surfaces of the first semiconductor layer and the second semiconductor layer, characterized in that: It also includes a metal anti-oxidation protection layer, which is arranged on the outer surface of the metal conductive layer in the Z-axis direction, and the conductive stack formed by the metal conductive layer and the metal anti-oxidation protection layer is in ohmic contact with the main gate electrode, and the material of the metal anti-oxidation protection layer is selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium, and zinc, or a zinc oxide-based film doped with aluminum and / or boron; and the conductive film layer includes a first transparent conductive film layer and a second transparent conductive film layer which are sequentially arranged from the back side of the silicon wafer to the outside, the refractive index of the first transparent conductive film layer is 1.9-2.5, the thickness is 10-30nm, and the refractive index of the second ... The refractive index is 1.4-1.8, and process gases containing argon gas and argon-oxygen mixed gas are introduced into the first transparent conductive film layer and the second transparent conductive film layer during sputtering coating preparation, and the amount of oxygen doped in the process gas corresponding to the first transparent conductive film layer is controlled to be 0.1%-0.5% by volume flow rate, and the amount of oxygen doped in the process gas corresponding to the second transparent conductive film layer is controlled to be 2.0%-3.0% by volume flow rate, and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is 1:2-5:3-7, the transmittance of the first transparent conductive film layer is above 80%, and the resistivity is between 6e-04 Ω·cm and 9e-04Ω·cm; the transmittance of the second transparent conductive film layer is above 90%, and the resistivity is between 3.8e-04 Ω·cm and 4.2e-04Ω·cm.

2. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The thickness of the second transparent conductive film layer is 30-100 nm, and / or the thickness of the metal conductive layer is 50-150 nm.

3. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The refractive index ratio of the first transparent conductive film layer and the second transparent conductive film layer is 1.25-1.50:

1.

4. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The materials of the first transparent conductive film layer and the second transparent conductive film layer are independently selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium, and zinc, or from a zinc oxide-based film doped with aluminum and / or boron, and the material of the metal conductive layer is selected from at least one of copper, aluminum, silver, and nickel-copper alloy.

5. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The first semiconductor layer includes a tunneling oxide layer and a first doped polysilicon layer, the second semiconductor layer includes an intrinsic amorphous silicon layer and a second doped amorphous silicon layer, and the first doped polysilicon layer is thinned to 50-100 nm.

6. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The back contact battery with a specific conductive film layer also includes: An insulating layer is arranged on the outer surface of the metal anti-oxidation protection layer in the Z-axis direction. The insulating layer is overall plate-shaped and has a first opening and a second opening alternately arranged along the X-axis direction. The first opening and the second opening are respectively spaced apart along the Y-axis direction. The first opening is arranged on the outer surface of the first semiconductor layer, and the second opening is arranged on the outer surface of the second semiconductor layer. The main gate electrode is located on the outer surface of the insulating layer and makes ohmic contact with the metal anti-oxidation protection layer through the corresponding opening of the insulating layer.

7. The back contact battery with a specific conductive film layer according to claim 1 or 6, characterized in that: The thickness of the metal anti-oxidation protection layer is 10-30 nm.

8. The back contact battery with a specific conductive film layer according to claim 1, characterized in that: The back contact cell with a specific conductive film layer also includes a front passivation layer and an anti-reflection layer sequentially arranged on the front side of the silicon wafer; and / or, The silicon wafer area where the first semiconductor layer is located is the polishing area, and the silicon wafer area where the second semiconductor layer is located is the texturing area. Isolation grooves arranged at intervals along the X-axis direction are opened on the conductive stack formed by the conductive film layer and the metal conductive layer, and the isolation grooves are arranged across the junction of the texturing area and the polishing area; the two ends of the second semiconductor layer respectively extend outward to the outside of the back side of the portion covering the adjacent first semiconductor layer, and a first semiconductor opening area not covering the second semiconductor layer is opened on the back side of the first semiconductor layer, and a second semiconductor opening area is formed between the adjacent first semiconductor layers. The second semiconductor opening area is arranged at intervals from the first semiconductor opening area, and the area between them is the overlapping area; the isolation groove is located in the corresponding area on the outer surface of the overlapping area, and in the overlapping area, a mask layer is set between the first semiconductor layer and the second semiconductor layer, or no mask layer is set.

9. A method for preparing a back contact battery having a specific conductive film layer, characterized in that: The steps include: S1, provide silicon wafers; S2, forming a first semiconductor layer and a mask layer on the back side of the silicon wafer in sequence; the first semiconductor layer comprises a tunneling oxide layer and a first doped polysilicon layer, and the first doped polysilicon layer is thinned to 50-100 nm; S3, etching an opening on the back surface obtained in S2 to form a second semiconductor opening region; S4, performing texturing cleaning, and then selecting whether to perform a step of removing the mask layer outside the second semiconductor opening region on the back side of the silicon wafer through cleaning according to needs; S5, depositing a second semiconductor layer on the back side, wherein the second semiconductor layer comprises an intrinsic amorphous silicon layer and a second doped amorphous silicon layer; S6, etching an opening on a portion of the second semiconductor layer on the back side of the silicon wafer to form a first semiconductor opening region spaced apart from the second semiconductor opening region; S7, depositing a conductive film layer, a metal conductive layer, and a metal anti-oxidation protective layer in sequence on the back surface obtained in S6 by magnetron sputtering, wherein the conductive film layer comprises a first transparent conductive film layer and a second transparent conductive film layer deposited in sequence from the back surface of the silicon wafer outward; the material of the metal anti-oxidation protective layer is selected from an indium oxide-based film doped with at least one of tin, tungsten, titanium, and zinc, or is selected from an aluminum- and / or boron-doped zinc oxide-based film; The deposition conditions of the first transparent conductive film layer include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 1-3kW, the oxygen content of the process gas in terms of volume flow ratio is 0.1%-0.5%, the refractive index is controlled to be 1.9-2.5, and the thickness is 10-30nm; The deposition conditions of the second transparent conductive film layer include: the process gas introduced includes argon gas and argon-oxygen mixed gas, the sputtering power is 5-7kW, the oxygen content in the process gas is 2.0%-3.0% by volume flow ratio, and the refractive index is controlled to be 1.4-1.8; and the thickness ratio of the first transparent conductive film layer, the second transparent conductive film layer, and the metal conductive layer is controlled to be 1:2-5:3-7; The transmittance of the first transparent conductive film layer is higher than 80%, and the resistivity is between 6e-04 Ω·cm and 9e-04 Ω·cm; the transmittance of the second transparent conductive film layer is higher than 90%, and the resistivity is between 3.8e-04 Ω·cm and 4.2e-04 Ω·cm; S8, performing etching on a portion of the conductive film layer and its corresponding film layer located between the first semiconductor opening region and the second semiconductor opening region to form an isolation groove; S9, disposing an insulating layer on the outer surface of the back side, the insulating layer covering the isolation groove, and providing a first opening and a second opening for transmitting the first semiconductor and the second semiconductor respectively on the insulating layer; S10, forming a main gate electrode on the back surface obtained in S9, and the main gate electrode makes ohmic contact with the corresponding conductive film layer on the corresponding semiconductor through the corresponding first opening and the second opening of the insulating layer.

10. The method for preparing a back contact battery having a specific conductive film layer according to claim 9, characterized in that: The volume flow ratio of argon gas to oxygen in the argon-oxygen mixture is 7-9:1, the flow rate of the argon-oxygen mixture is 10-200 sccm, and the flow rate of argon gas is 500-1000 sccm; and / or, The method for preparing a back-contact battery with a specific conductive film layer further includes: in S5, a front passivation layer and an anti-reflection layer are sequentially deposited on the front side of the silicon wafer.

11. A back contact battery, characterized in that: The battery is prepared by the method for preparing a back-contact battery with a specific conductive film layer as claimed in claim 9 or 10.

12. A photovoltaic module, characterized in that: It comprises the back contact battery having a specific conductive film layer as claimed in any one of claims 1 to 8, or comprises the back contact battery as claimed in claim 11.

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