Indium-free transparent conductive layer and preparation method thereof, and solar cell and preparation method thereof

Abstract

The invention provides an indium-free transparent conductive layer and a preparation method thereof, and a solar cell and a preparation method thereof. The indium-free transparent conductive layer comprises a first tin oxide thin film, an oxygen-doped metal thin film and a second tin oxide thin film which are sequentially stacked, and the oxygen-tin atomic ratio of the first tin oxide thin film is smaller than that of the second tin oxide thin film. The first tin oxide thin film has relatively high oxygen vacancy, so that the first tin oxide thin film has relatively low contact resistance; the second tin oxide thin film has relatively low oxygen vacancy, so that the second tin oxide thin film has relatively high light transmittance; the oxygen-doped metal film is used as the middle layer, the conductivity of the indium-free transparent conducting layer is improved, light loss is small, light transmittance is high, and therefore the indium-free transparent conducting layer has good conductivity and light transmittance, low contact resistance and good acid and alkali resistance, and the tin material target material can help to reduce the cost of the transparent conducting layer.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to an indium-free transparent conductive layer and a preparation method thereof, a solar cell and a preparation method thereof. Background Art

[0002] Existing solar cells generally use indium tin oxide (ITO) as an anti-reflection film and / or a conductive film layer. ITO has good photoelectric properties and can be used to prepare high-efficiency heterojunction cells, but indium is a rare metal with limited reserves and high prices, which is not conducive to reducing costs.

[0003] At present, the main indium-free materials include aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), fluorine-doped tin oxide (FTO), antimony-doped tin dioxide (ATO), etc. However, compared with indium-based transparent conductive materials, these indium-free materials have one or more disadvantages in light transmittance, electrical conductivity and weather resistance, which in turn limits the application of the above-mentioned indium-free materials in solar cells. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one purpose of the present application is to provide an indium-free transparent conductive layer, which has better conductivity and light transmittance.

[0005] In one aspect of the present application, the present application provides an indium-free transparent conductive layer. According to an embodiment of the present application, the indium-free transparent conductive layer includes a first tin oxide film, an oxygen-doped metal film, and a second tin oxide film stacked in sequence, wherein the oxygen-tin atomic ratio of the first tin oxide film is less than the oxygen-tin atomic ratio of the second tin oxide film. As a result, the first tin oxide film with relatively small oxygen-tin atoms has relatively high oxygen vacancies, which makes it have a lower contact resistance, so the first tin oxide film can help reduce the contact resistance of the indium-free transparent conductive layer; the second tin oxide film with relatively large oxygen-tin atoms has relatively low oxygen vacancies, which makes it have a higher transmittance, so the second tin oxide film helps to improve the transmittance of the indium-free transparent conductive layer; the oxygen-doped metal film as an intermediate layer helps to improve the conductivity of the indium-free transparent conductive layer, and the light loss is small and the transmittance is high. In this way, the indium-free transparent conductive layer of the present application has good conductivity, transmittance, low contact resistance and better acid and alkali resistance, and the use of tin material target as the raw material can help reduce the cost of the transparent conductive layer.

[0006] According to an embodiment of the present application, the oxygen-tin atomic ratio of the first tin oxide film is 1.75-1.90, and / or the oxygen-tin atomic ratio of the second tin oxide film is 1.9-2.0.

[0007] According to an embodiment of the present application, the first tin oxide film also satisfies at least one of the following conditions: the carrier mobility is 20-40cm 2 V -1 s -1 ; Resistivity is 8×10 -4 -2×10 -3 Ω·cm; light transmittance is 75%-85%; thickness is 10~70nm.

[0008] According to an embodiment of the present application, the first tin oxide film contains a first doping element, and the first doping element includes at least one of Ta, Sb, and Al; and / or the second tin oxide film contains a second doping element, and the second doping element includes at least one of Ta, Sb, and Al.

[0009] According to an embodiment of the present application, the second tin oxide film also satisfies at least one of the following conditions: the carrier mobility is 10-30cm 2 V -1 s -1 ; Resistivity 2×10 -3 -3×10 -3 Ω·cm; light transmittance is 75%-85%; thickness is 40~100nm.

[0010] According to an embodiment of the present application, the oxygen-doped metal film satisfies at least one of the following conditions: the oxygen-doped metal film includes at least one of an oxygen-doped copper film, an oxygen-doped gold film or an oxygen-doped silver film; the thickness of the oxygen-doped metal film is 3-10nm; the transmittance of the oxygen-doped metal film is 80%-95%.

[0011] According to an embodiment of the present application, the light transmittance of the indium-free transparent conductive layer is 75%-85%, and / or the resistivity of the indium-free transparent conductive layer is 5×10 -4 -8×10 -4 Ω·cm.

[0012] In another aspect of the present application, the present application provides a method for preparing the aforementioned indium-free transparent conductive layer. According to an embodiment of the present application, the method for preparing the indium-free transparent conductive layer includes: depositing a first tin oxide film, an oxygen-doped metal film and a second tin oxide film on a substrate in sequence, wherein the oxygen vacancies of the first tin oxide film are higher than the oxygen vacancies of the second tin oxide film. Thus, the first tin oxide film with relatively small oxygen tin atoms prepared has relatively high oxygen vacancies, thereby making it have a lower contact resistance, so the first tin oxide film can help reduce the contact resistance of the indium-free transparent conductive layer; the second tin oxide film with relatively large oxygen tin atoms prepared has relatively low oxygen vacancies, thereby making it have a higher light transmittance, so the second tin oxide film helps to improve the light transmittance of the indium-free transparent conductive layer; the prepared oxygen-doped metal film as an intermediate layer helps to improve the conductivity of the indium-free transparent conductive layer, and the light loss is small and the light transmittance is high. In this way, the indium-free transparent conductive layer of the present application has good conductivity, light transmittance, low contact resistance and better acid and alkali resistance, and the tin material can help reduce the cost of the transparent conductive layer.

[0013] According to an embodiment of the present application, the first tin oxide film, the oxygen-doped metal film and the second tin oxide film are formed by magnetron sputtering or plasma reactive coating, and the target material for forming the first tin oxide film and the second tin oxide film is a tin target, and the target material for forming the oxygen-doped metal film is a metal target in the oxygen-doped metal film.

[0014] In another aspect of the present application, the present application provides a solar cell. According to an embodiment of the present application, the solar cell includes: a cell substrate, the cell substrate having a front and a back side arranged opposite to each other; a front electrode, the front electrode is the aforementioned indium-free transparent conductive layer, and is located on the front side of the cell substrate, wherein the first tin oxide film in the indium-free transparent conductive layer is arranged close to the cell substrate; and a back electrode, the back electrode is located on the back side of the cell substrate. As a result, the front electrode of the solar cell has a high light transmittance and conductivity, which helps to improve the cell performance of the solar cell.

[0015] According to an embodiment of the present application, the back battery includes a conductive tin oxide layer.

[0016] According to an embodiment of the present application, the conductive tin oxide layer satisfies at least one of the following conditions: a thickness of 70-140 nm; an oxygen-tin atomic ratio of 1.75-2.00; a carrier mobility of 10-40 cm 2 V -1 s -1 ; The transmittance is 75%-85%; the conductive tin oxide layer contains a third doping element, and the third doping element includes at least one of Ta, Sb, and Al.

[0017] According to an embodiment of the present application, the solar cell is at least one of a crystalline silicon solar cell, a perovskite solar cell, a compound semiconductor solar cell, an organic solar cell or a stacked solar cell.

[0018] In another aspect of the present application, the present application provides a method for preparing the aforementioned solar cell. According to an embodiment of the present application, the method for preparing a solar cell includes: preparing a cell substrate; preparing a front electrode on the front of the cell substrate using the aforementioned method for preparing an indium-free transparent conductive layer; and preparing a back electrode on the back of the cell substrate. Thus, the front electrode of the prepared solar cell has a high light transmittance and conductivity, which helps to improve the cell performance of the solar cell.

[0019] According to an embodiment of the present application, the method for preparing the back electrode includes: forming a conductive tin oxide layer by a plasma reaction plating method, and the target material for forming the conductive tin oxide layer is a tin target.

[0020] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 This is a schematic diagram of the structure of an indium-free transparent conductive layer in one embodiment of the present application;

[0023] Figure 2 is a schematic structural diagram of a solar cell in another embodiment of the present application;

[0024] Figure 3 It is a schematic structural diagram of a solar cell in another embodiment of the present application. DETAILED DESCRIPTION

[0025] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0026] The present application is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present application in any way.

[0027] In one aspect of the present application, the present application provides an indium-free transparent conductive layer. According to an embodiment of the present application, referring to Figure 1 The indium-free transparent conductive layer 10 includes a first tin oxide film 11, an oxygen-doped metal film 12, and a second tin oxide film 13 which are sequentially stacked, wherein the oxygen-tin atomic ratio of the first tin oxide film 11 is less than that of the second tin oxide film 13. Therefore, the first tin oxide film with relatively small oxygen-tin atoms has relatively high oxygen vacancies, thereby making it have a lower contact resistance, so the first tin oxide film 11 can help reduce the contact resistance of the indium-free transparent conductive layer 10; the second tin oxide film with relatively large oxygen-tin atoms has relatively low oxygen vacancies, thereby making it have a higher light transmittance, so the second tin oxide film 13 helps improve the light transmittance of the indium-free transparent conductive layer 10; the oxygen-doped metal film 12, as an intermediate layer, helps improve the conductivity of the indium-free transparent conductive layer 10, and has a small light loss and a high light transmittance. In this way, the indium-free transparent conductive layer 10 of the present application has good conductivity, light transmittance, low contact resistance and better acid and alkali resistance, and the use of tin material target as the raw material can help reduce the cost of the transparent conductive layer.

[0028] Oxygen vacancies refer to the vacancies formed when oxygen atoms (oxygen ions) in the crystal lattice are separated in metal oxides or other oxygen-containing compounds, resulting in oxygen deficiency. The smaller the oxygen-tin atomic ratio, the lower the proportion of oxygen atoms, and the higher the oxygen vacancies; conversely, the larger the oxygen-tin atomic ratio, the higher the proportion of oxygen atoms, and the lower the oxygen vacancies.

[0029] According to some embodiments of the present application, the oxygen-tin atomic ratio (O / Sn) of the first tin oxide film is 1.75 to 1.90, such as 1.75, 1.78, 1.8, 1.82, 1.85, 1.88, and 1.9. According to some embodiments of the present application, the oxygen-tin atomic ratio (O / Sn) of the second tin oxide film is 1.9 to 2.0, such as 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.0, etc. It can be seen that the first tin oxide film has a lower oxygen-tin atomic ratio, that is, it has a relatively high oxygen vacancy, which can help reduce the contact resistance; the second tin oxide film has a higher oxygen-tin atomic ratio, that is, it has a lower oxygen vacancy, which makes it have a higher transmittance, thereby helping to improve the transmittance of the indium-free transparent conductive layer.

[0030] According to some embodiments of the present application, the carrier mobility of the first tin oxide film is 20-40 cm 2 V -1 s -1 , for example, the carrier mobility is 20cm 2 V -1 s-1 、22cm 2 V -1 s -1 、24cm 2 V -1 s -1 、25cm 2 V -1 s -1 、26cm 2 V -1 s -1 、28cm 2 V -1 s -1 、30cm 2 V -1 s -1 、32cm 2 V -1 s -1 、34cm 2 V -1 s -1 、35cm 2 V -1 s -1 、36cm 2 V -1 s -1 、38cm 2 V -1 s -1 、40cm 2 V -1 s -1 As a result, the first tin oxide film has better carrier mobility and better conductivity, which helps to improve the conductivity of the indium-free transparent conductive layer. In some specific embodiments, the carrier mobility of the first tin oxide film is 30-40cm 2 V -1 s -1 .

[0031] According to some embodiments of the present application, the resistivity of the first tin oxide film is 8×10 -4 -2×10 -3 Ω·cm, for example, 8×10 -4 Ω·cm、8.2×10 -4 Ω·cm、8.4×10 -4 Ω·cm、8.6×10 -4 Ω·cm、8.8×10 -4 Ω·cm、9×10 -4 Ω·cm、9.2×10 -4 Ω·cm、9.4×10 -4 Ω·cm、9.6×10 -4 Ω·cm、9.8×10-4 Ω·cm、1×10 -3 Ω·cm、1.2×10 -3 Ω·cm、1.5×10 -3 Ω·cm、1.8×10 -3 Ω·cm、2×10 -3 Therefore, the first tin oxide film has a lower resistivity, which helps to improve the conductivity of the indium-free transparent conductive layer.

[0032] According to some embodiments of the present application, the light transmittance of the first tin oxide film is 75%-85%, such as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc. Therefore, the first tin oxide film has a higher light transmittance, which helps to improve the light transmittance of the indium-free transparent conductive layer.

[0033] According to some embodiments of the present application, the thickness of the first tin oxide film is 10-70 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, etc. The above thickness helps to improve its light transmittance and has good conductivity.

[0034] According to some embodiments of the present application, the first tin oxide film contains a first doping element, and the first doping element includes at least one of Ta, Sb, and Al. Therefore, by doping the first tin oxide film with the above elements, its carrier mobility can be further improved, thereby improving its conductivity.

[0035] According to some embodiments of the present application, the carrier mobility of the second tin oxide film is 10-30cm 2 V -1 s -1 , for example, the carrier mobility is 10cm 2 V -1 s -1 、12cm 2 V -1 s -1 、14cm 2 V -1 s -1 、15cm 2 V -1 s -1 、16cm 2 V -1 s -1 、18cm 2 V -1 s -1 , 20cm 2 V -1s -1 、22cm 2 V -1 s -1 、24cm 2 V -1 s -1 、25cm 2 V -1 s -1 、26cm 2 V -1 s -1 、28cm 2 V -1 s -1 、30cm 2 V -1 s -1 As a result, the second tin oxide film has better carrier mobility and better conductivity, which helps to improve the conductivity of the indium-free transparent conductive layer. In some specific embodiments, the carrier mobility of the second tin oxide film is 10-20cm 2 V -1 s -1 .

[0036] According to some embodiments of the present application, the resistivity of the second tin oxide film is 2×10 -3 -3×10 -3 Ω·cm, for example, 2×10 -3 Ω·cm、2.1×10 -3 Ω·cm、2.2×10 -3 Ω·cm、2.3×10 -3 Ω·cm、2.4×10 -3 Ω·cm、2.5×10 -3 Ω·cm、2.6×10 -3 Ω·cm、2.7×10 -3 Ω·cm、2.8×10 -3 Ω·cm、2.9×10 -3 Ω·cm、3×10 -3 Ω·cm, etc. Therefore, the second tin oxide film has a lower resistivity, which helps to improve the conductivity of the indium-free transparent conductive layer.

[0037] According to some embodiments of the present application, the light transmittance of the second tin oxide film is 75%-85%, such as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc. Thus, the second tin oxide film has a higher light transmittance, which helps to improve the light transmittance of the indium-free transparent conductive layer.

[0038] According to some embodiments of the present application, the thickness of the second tin oxide film is 40-100 nm, such as 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc. The above thickness helps to improve its light transmittance and has good conductivity.

[0039] According to some embodiments of the present application, the second tin oxide film contains a second doping element, and the second doping element includes at least one of Ta, Sb, and Al. Therefore, by doping the second tin oxide film with the above elements, its carrier mobility can be further improved, thereby improving its conductivity. Among them, the above elements can be doped in one of the first tin oxide film and the second tin oxide film, or in the first tin oxide film and the second tin oxide film at the same time, and the doping elements of the two can be the same or different.

[0040] According to some embodiments of the present application, the oxygen-doped metal film includes at least one of an oxygen-doped copper film, an oxygen-doped gold film or an oxygen-doped silver film. As a result, the oxygen-doped metal film of the above material has better conductivity and good light transmittance. Furthermore, in the above oxygen-doped metal film, the doped oxygen combines with at least part (i.e., including part or all) of the metal to form a metal oxide, such as an oxygen-doped copper film, i.e., the film includes copper oxide; such as an oxygen-doped silver film, i.e., the film includes silver oxide; such as the oxygen-doped aluminum film, including aluminum oxide; such as the oxygen-doped gold film including gold oxide. Among them, there is no special requirement for the amount of oxygen doping, and those skilled in the art can flexibly design it according to actual requirements such as its thickness and light transmittance.

[0041] According to some embodiments of the present application, the thickness of the oxygen-doped metal film is 3-10 nm, such as 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc. Therefore, the thinner thickness is conducive to improving its light transmittance, thereby improving the light transmittance of the indium-free transparent conductive layer, and can also well improve the conductivity of the indium-free transparent conductive layer.

[0042] According to some embodiments of the present application, the light transmittance of the oxygen-doped metal film is 80%-95%. For example, it is 80%, 82%, 84%, 85%, 87%, 90%, 91%, 92%, 93%, 94%, 95%, etc. Therefore, the oxygen-doped metal film has a higher light transmittance, which helps to improve the light transmittance of the indium-free transparent conductive layer.

[0043] According to some embodiments of the present application, the light transmittance of the indium-free transparent conductive layer is 75%-85%, such as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc. As a result, the indium-free transparent conductive layer has a high light transmittance. In some specific embodiments, the light transmittance of the indium-free transparent conductive layer is greater than or equal to 80%.

[0044] According to some embodiments of the present application, the resistivity of the indium-free transparent conductive layer is 5×10 -4 -8×10 -4 Ω·cm, for example, 5×10 -4 Ω·cm、5.5×10 -4 Ω·cm、6×10 -4 Ω·cm、6.5×10 -4 Ω·cm、7×10 -4 Ω·cm、7.5×10 -4 Ω·cm、8×10 -4 Ω·cm, etc. Therefore, the indium-free transparent conductive layer has good conductivity. In some specific embodiments, the carrier mobility of the indium-free transparent conductive layer is less than or equal to 6×10 -4 Ω·cm.

[0045] In another aspect of the present application, the present application provides a method for preparing the aforementioned indium-free transparent conductive layer. According to an embodiment of the present application, the method for preparing the indium-free transparent conductive layer 10 includes: depositing a first tin oxide film 11, an oxygen-doped metal film 12, and a second tin oxide film 13 on a substrate in sequence, wherein the oxygen-tin atomic ratio of the first tin oxide film 11 is less than the oxygen-tin atomic ratio of the second tin oxide film 13. Thus, the first tin oxide film with relatively small oxygen tin atoms has relatively high oxygen vacancies, which makes it have lower contact resistance, so the first tin oxide film can help reduce the contact resistance of the indium-free transparent conductive layer; the second tin oxide film with relatively large oxygen tin atoms has relatively low oxygen vacancies, which makes it have higher transmittance, so the second tin oxide film helps to improve the transmittance of the indium-free transparent conductive layer; the prepared oxygen-doped metal film 12 serves as an intermediate layer, which has small light loss and high transmittance, and helps to improve the conductivity of the indium-free transparent conductive layer 10. In this way, the indium-free transparent conductive layer 10 of the present application has good conductivity, transmittance, low contact resistance and better acid and alkali resistance, and the tin oxide material can help reduce the cost of the transparent conductive layer.

[0046] In some embodiments, the substrate may refer to the battery matrix mentioned below.

[0047] According to some embodiments of the present application, the first tin oxide film, the oxygen-doped metal film and the second tin oxide film are formed by a magnetron sputtering deposition method. The process is mature and stable, and is convenient for determining parameters such as the oxygen-tin atomic ratio of each layer structure.

[0048] According to some embodiments of the present application, a first tin oxide film, an oxygen-doped metal film, and a second tin oxide film are formed by a plasma reactive deposition (RPD) method, and the target material for forming the first tin oxide film and the second tin oxide film is a tin target, and the target material for forming the oxygen-doped metal film is a metal target in the oxygen-doped metal film. In this way, the oxygen vacancies in the first tin oxide film and the second tin oxide film can be regulated by precisely controlling the oxygen content in the deposition environment, so as to regulate the properties such as the transmittance and conductivity of the indium-free transparent conductive layer; moreover, by using a metal target material and adopting an RPD preparation method, compared with direct deposition using metal oxides, the film deposited by the metal target material through RPD has better crystallinity and more excellent photoelectric properties, which is more conducive to improving the properties of the indium-free transparent conductive layer; and the tin target has a lower cost.

[0049] It should be noted that the above-mentioned “target material for forming the oxygen-doped metal film is the metal target material in the oxygen-doped metal film” means that the specific metal material in the metal target material is the same metal type as the metal in the oxygen-doped metal film. For example, for the oxygen-doped silver film, the target material selected during the preparation is a metallic silver target material. For example, for the oxygen-doped copper film, the target material selected during the preparation is a metallic copper target material.

[0050] According to an embodiment of the present application, the deposition environment when depositing the first tin oxide film, the oxygen-doped metal film and the second tin oxide film includes gases such as oxygen, argon, nitrogen and / or hydrogen.

[0051] According to some embodiments of the present application, there are no special requirements for the oxygen flow rate when preparing the first tin oxide film and the second tin oxide film. Those skilled in the art can flexibly design the oxygen flow rate according to the actual situation such as the cavity size of the deposition reaction and the above-mentioned oxygen-tin ratio of the first tin oxide film and the second tin oxide film.

[0052] In some embodiments, when forming a first tin oxide film, an oxygen flow rate is 70-100 sccm, such as 70 sccm, 75 sccm, 80 sccm, 85 sccm, 90 sccm, 95 sccm, 100 sccm, etc., thereby, a first tin oxide film having an oxygen-tin atomic ratio (O / Sn) of 1.75 to 1.90 can be obtained. The prepared first tin oxide film has relatively high oxygen vacancies, which can help reduce contact resistance.

[0053] In some embodiments, when forming the second tin oxide film, the oxygen flow rate is 100-150sccm, for example, 100sccm, 105sccm, 110sccm, 115sccm, 120sccm, 125sccm, 130sccm, 135sccm, 140sccm, 145sccm, 150sccm, etc., thereby, a second tin oxide film with an oxygen-tin atomic ratio (O / Sn) of 1.90 to 2.00 can be obtained. The prepared second tin oxide film has relatively low oxygen vacancies, which makes it have a higher transmittance, thereby helping to improve the transmittance of the indium-free transparent conductive layer.

[0054] According to some embodiments of the present application, when forming an oxygen-doped metal film, there is no special requirement for the specific selection of oxygen flow rate, and those skilled in the art can flexibly select according to actual needs. In some embodiments, when forming a metal oxide film, the oxygen flow rate is greater than 0 and less than or equal to 30 sccm.

[0055] According to an embodiment of the present invention, the method can be used to prepare the indium-free transparent conductive layer described above, wherein the requirements for the prepared first tin oxide film, oxygen-doped metal film and second tin oxide film are the same as those described above and will not be elaborated herein.

[0056] In another aspect of the present application, the present application provides a solar cell. According to an embodiment of the present application, referring to Figure 2 The solar cell comprises: a cell substrate 200, the cell substrate 200 having a front side 210 and a back side 220 arranged opposite to each other; a front electrode 100, the front electrode 100 being the aforementioned indium-free transparent conductive layer 10, and being located on the front side 21 of the cell substrate 20, wherein the first tin oxide film 11 in the indium-free transparent conductive layer 10 is arranged close to the cell substrate 20, that is, the second tin oxide film 13 is arranged away from the cell substrate 20; and a back electrode 300, the back electrode 300 being located on the back side 220 of the cell substrate 200. Thus, the front electrode 100 of the solar cell has a high light transmittance and conductivity, which is helpful to improve the cell performance of the solar cell.

[0057] According to some embodiments of the present application, the back battery includes a conductive tin oxide layer. Therefore, it is also prepared using tin materials, which are consistent with the raw materials for preparing the first tin oxide film and the second tin oxide film in the front electrode. During the preparation process, a dual-target RPD can be used to complete the deposition of the front and back transparent conductive layers, reducing the production cost and having good acid and alkali corrosion resistance; and the transparent conductive layers on the front and back are asymmetric structures, and only tin oxide is used on the back, so that it can have a higher mobility and a higher conductivity while meeting the conditions of the back electrode transmittance and low resistivity.

[0058] According to some embodiments of the present application, the thickness of the conductive tin oxide layer is 70-140nm, such as 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, etc. The conductive tin oxide layer of the above thickness has good light transmittance. In some specific embodiments, the thickness of the conductive tin oxide layer is 100-120nm.

[0059] According to some embodiments of the present application, the oxygen-tin atomic ratio (O / Sn) of the conductive tin oxide layer is 1.75-2.00, such as 1.75, 1.8, 1.82, 1.84, 1.85, 1.87, 1.89, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.0, etc. It can be seen that the conductive tin oxide layer has a suitable oxygen-tin atomic ratio, that is, has suitable oxygen vacancies, which can not only help reduce contact resistance and conductivity, but also has high light transmittance.

[0060] According to some embodiments of the present application, the carrier mobility of the conductive tin oxide layer is 10-40 cm 2 V -1 s -1 , for example, the carrier mobility is 10cm 2 V -1 s -1 、12cm 2 V -1 s -1 、14cm 2 V -1 s -1 、15cm 2 V -1 s -1 、16cm 2 V -1 s -1 、18cm 2 V -1 s -1 , 20cm 2 V -1 s -1 、22cm 2 V -1 s -1 、24cm 2 V -1 s -1 、25cm 2 V -1 s -1 、26cm 2 V -1 s -1 、28cm 2 V -1 s-1 、30cm 2 V -1 s -1 、32cm 2 V -1 s -1 、34cm 2 V -1 s -1 、35cm 2 V -1 s -1 、37cm 2 V -1 s -1 、39cm 2 V -1 s -1 、40cm 2 V -1 s -1 As a result, the conductive tin oxide layer has better carrier mobility and better conductivity, which helps to improve the conductivity of the back electrode. In some specific embodiments, the carrier mobility of the conductive tin oxide layer is 30-40cm 2 V -1 s -1 .

[0061] According to some embodiments of the present application, the light transmittance of the conductive tin oxide layer is 75%-85%, such as 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc. As a result, the conductive tin oxide layer has a higher light transmittance, which helps to improve the light transmittance of the back electrode. In some specific embodiments, the light transmittance of the conductive tin oxide layer is 80%-85%.

[0062] According to some embodiments of the present application, the conductive tin oxide layer contains a third doping element, and the third doping element includes at least one of Ta, Sb, and Al. Therefore, by doping the conductive tin oxide layer with the above elements, its carrier mobility can be further improved, thereby improving its conductivity.

[0063] According to the embodiments of the present application, the solar cell is at least one of a crystalline silicon solar cell, a perovskite solar cell, a compound semiconductor solar cell, an organic solar cell or a stacked solar cell, wherein in some embodiments, the crystalline silicon solar cell may be a HJT crystalline silicon cell (heterojunction cell), an IBC crystalline silicon cell (interdigitated back contact cell), etc. That is, the indium-free transparent conductive layer of the present application can be applied to various solar cells, and the asymmetric structure of the front electrode and the back electrode can also be applied to various different solar cells, thereby helping to expand its application field.

[0064] According to the embodiments of the present application, the specific structure of the above-mentioned battery matrix can be selected according to the specific type of solar cell.

[0065] In some embodiments, the solar cell is a heterogeneous crystalline silicon cell. Figure 3 The structure of the cell matrix includes: a silicon substrate 201, a first intrinsic amorphous silicon 202 and a first conductive type amorphous silicon doping layer 203 sequentially arranged on the front side of the silicon substrate 201, and a second intrinsic amorphous silicon 204 and a second conductive type amorphous silicon doping layer 205 sequentially arranged on the back side of the silicon substrate 201. Further, the solar cell also includes a first electrode 206 and a second electrode 207, the first electrode 206 is arranged on the side of the front electrode 100 away from the silicon substrate 201, and the second electrode 207 is arranged on the side of the back electrode 300 away from the silicon substrate 201.

[0066] In some embodiments, the silicon substrate 201 can be an N-type silicon substrate, in which case the first conductive type amorphous silicon doped layer 203 is an N-type amorphous silicon doped layer, and the second conductive type amorphous silicon doped layer 205 is a P-type amorphous silicon doped layer; in other embodiments, the silicon substrate 201 can be a P-type silicon substrate, in which case the first conductive type amorphous silicon doped layer 203 is a P-type amorphous silicon doped layer, and the second conductive type amorphous silicon doped layer 205 is an N-type amorphous silicon doped layer.

[0067] In some embodiments, the materials of the first electrode 206 and the second electrode 207 can be silver, copper, aluminum, tin, etc.

[0068] In another aspect of the present application, the present application provides a method for preparing the aforementioned solar cell. According to an embodiment of the present application, the method for preparing a solar cell includes: preparing a cell substrate 200; preparing a front electrode 100 on the front side 210 of the cell substrate 200 using the aforementioned method for preparing an indium-free transparent conductive layer 10; and preparing a back electrode 300 on the back side 220 of the cell substrate 200. As a result, the front electrode of the solar cell has a high light transmittance and conductivity, which helps to improve the cell performance of the solar cell.

[0069] According to some embodiments of the present application, the method for preparing the back electrode includes: forming a conductive tin oxide layer using a tin target material by a magnetron sputtering deposition method. The process is mature and stable, and is convenient for determining parameters such as the oxygen-tin atomic ratio of each layer structure.

[0070] According to some embodiments of the present application, the method for preparing the back electrode includes: forming a conductive tin oxide layer by a plasma reactive deposition (RPD) method, and the target material for forming the conductive tin oxide layer is a tin target. In this way, the oxygen vacancies in the conductive tin oxide layer can be regulated by precisely controlling the oxygen content in the deposition environment, thereby regulating the transmittance and conductivity of the conductive tin oxide layer; and, by using a metal target material and adopting the RPD preparation method, compared with direct deposition using metal oxides, the film deposited by the metal target material through RPD has better crystallinity and better photoelectric properties, which is more conducive to improving the properties of the conductive tin oxide layer; and, the conductive tin oxide layer is also prepared using tin material, which is consistent with the raw materials for preparing the first tin oxide film and the second tin oxide film in the front electrode. In the preparation process, a dual-target RPD can be used to complete the deposition of the front and back transparent conductive layers, reducing the production cost and having good acid and alkali corrosion resistance; and the transparent conductive layers on the front and back are asymmetric structures, and only the tin oxide film is used on the back, so that under the conditions of satisfying the transmittance and low resistivity of the back electrode, it also has a higher mobility, that is, it has a higher conductivity.

[0071] According to the embodiments of the present application, there is no special requirement for the oxygen flow rate when preparing the conductive tin oxide layer. Those skilled in the art can flexibly design the oxygen flow rate according to the actual conditions such as the cavity size of the deposition reaction and the above-mentioned oxygen-tin ratio of the conductive tin oxide layer.

[0072] In some embodiments, when forming a conductive tin oxide layer, the oxygen flow rate is 70-150sccm, for example, 70sccm, 80sccm, 85sccm, 90sccm, 95sccm, 100sccm, 105sccm, 110sccm, 115sccm, 120sccm, 125sccm, 130sccm, 135sccm, 140sccm, 145sccm, 150sccm, etc., thereby, a conductive tin oxide layer with an oxygen-tin atomic ratio (O / Sn) of 1.75 to 2.0 can be obtained. The prepared conductive tin oxide layer has a suitable oxygen-tin atomic ratio, that is, it has suitable oxygen vacancies, which can not only help reduce contact resistance and conductivity, but also has high light transmittance.

[0073] In some embodiments of the present application, the working gas in the deposition environment for depositing the conductive tin oxide layer includes at least one of argon, oxygen and hydrogen.

[0074] According to the embodiments of the present application, the solar cell is at least one of a crystalline silicon solar cell, a perovskite solar cell, a compound semiconductor solar cell, an organic solar cell or a stacked solar cell, wherein in some embodiments, the crystalline silicon solar cell may be a HJT crystalline silicon cell (heterojunction cell), an IBC crystalline silicon cell (interdigitated back contact cell), etc. That is, the indium-free transparent conductive layer of the present application can be applied to various solar cells, and the asymmetric structure of the front electrode and the back electrode can also be applied to various different solar cells, thereby helping to expand its application field.

[0075] According to the embodiments of the present application, the specific preparation method of the above-mentioned battery matrix can be selected according to the specific type and structure of the solar cell.

[0076] In some embodiments, the solar cell is a heterogeneous crystalline silicon cell, and the method for preparing the heterogeneous crystalline silicon cell includes:

[0077] S100: providing a silicon substrate 201 .

[0078] In some embodiments, the silicon substrate may be an N-type silicon substrate.

[0079] In some embodiments, the thickness of the silicon substrate may be 60-100 μm. In some specific embodiments, the thickness of the silicon substrate is 60-80 μm.

[0080] In some embodiments, the resistivity of the silicon substrate is 0.2 Ω·cm to 3 Ω·cm.

[0081] In some embodiments, the surface of the silicon substrate is textured to obtain a silicon substrate having a pyramid-shaped light trapping structure on the surface.

[0082] S200 : forming a first intrinsic amorphous silicon 202 and a second intrinsic amorphous silicon 204 by deposition on the front side and the back side of the silicon substrate 201 , respectively.

[0083] In some embodiments, a PECVD (plasma enhanced chemical vapor deposition system) device may be used to deposit the first intrinsic amorphous silicon 202 and the second intrinsic amorphous silicon 204, and the process gas required for the deposition includes SiH 4 , H 2 , CO 2 and N 2 One or more of O.

[0084] In some embodiments, the thickness of the first intrinsic amorphous silicon 202 and the second intrinsic amorphous silicon 204 are 2 nm to 10 nm, respectively. In some specific embodiments, the thickness of the first intrinsic amorphous silicon 202 and the second intrinsic amorphous silicon 204 are 5 nm to 8 nm, respectively.

[0085] S300 : forming a first conductivity type amorphous silicon doping layer 203 by deposition on a side of the first intrinsic amorphous silicon 202 away from the silicon substrate 201 .

[0086] In some embodiments, the first conductive type amorphous silicon doped layer 203 is an N-type amorphous silicon doped layer. Further, in some embodiments, a PECVD device may be used to deposit the N-type amorphous silicon doped layer, and the process gas required for the deposition includes SiH 4 , H 2 , CO 2 N 2 O and PH 3 One or more of the .

[0087] In some embodiments, the thickness of the first conductive type amorphous silicon doping layer 203 is 2 nm to 10 nm. In some specific embodiments, the thickness of the first conductive type amorphous silicon doping layer 203 is 5 nm to 8 nm.

[0088] S400 : forming a second conductivity type amorphous silicon doping layer 205 by deposition on a side of the second intrinsic amorphous silicon 204 away from the silicon substrate 201 .

[0089] In some embodiments, the second conductive type amorphous silicon doped layer 205 is a P-type amorphous silicon doped layer. Further, in some embodiments, a PECVD device may be used to deposit the P-type amorphous silicon doped layer, and the process gas required for the deposition includes SiH 4 , H 2 , CO 2 N 2 O.B 2 H 6 and TMB (trimethylborane, chemical formula C 3 H 9 B) one or more.

[0090] In some embodiments, the thickness of the second conductive type amorphous silicon doping layer 205 is 2 nm to 10 nm. In some specific embodiments, the thickness of the second conductive type amorphous silicon doping layer 205 is 5 nm to 8 nm.

[0091] S500: On the side of the first conductive type amorphous silicon doped layer 203 away from the silicon substrate 201, a first tin oxide film 11, an oxygen-doped metal film 12 and a second tin oxide film 13 are sequentially deposited by magnetron sputtering or RPD (reactive plasma deposition) equipment to obtain an indium-free transparent conductive layer 10.

[0092] S600 : On the side of the second conductive type amorphous silicon doped layer 205 away from the silicon substrate 201 , a conductive tin oxide layer is deposited by magnetron sputtering or RPD (reactive plasma deposition) equipment to obtain a back electrode 300 .

[0093] S700: forming a first electrode 206 on a side of the indium-free transparent conductive layer 10 away from the silicon substrate, and forming a second electrode 207 on a side of the conductive tin oxide layer away from the silicon substrate. The schematic diagram of the structure can be referred to Figure 3 .

[0094] In some embodiments, the first electrode 206 and the second electrode 207 can be formed by screen printing, laser transfer or electroplating. Specifically, the first electrode 206 and the second electrode 207 can be formed by screen printing, laser transfer of low-temperature silver paste / low-temperature copper paste / silver-coated copper paste, or by electroplating one or more metals selected from aluminum, silver, copper, tin, etc.

[0095] Example

[0096] Example 1

[0097] The method for preparing a heterogeneous crystalline silicon cell comprises:

[0098] S100: providing an N-type silicon substrate with a thickness of 80 μm and a resistivity of 1 Ω·cm. performing a texturing process on the surface of the silicon substrate to obtain a silicon substrate with a pyramid-shaped light trapping structure on the surface.

[0099] S200: using PECVD equipment to deposit first intrinsic amorphous silicon and second intrinsic amorphous silicon on the front and back sides of the N-type silicon substrate, respectively. The thickness of the first intrinsic amorphous silicon and the second intrinsic amorphous silicon are 6 nm, respectively.

[0100] S300: using PECVD equipment, depositing an N-type amorphous silicon doping layer on a side of the first intrinsic amorphous silicon away from the N-type silicon substrate 201 , wherein the thickness of the N-type amorphous silicon doping layer is 6 nm.

[0101] S400: using PECVD equipment, depositing a P-type amorphous silicon doping layer on a side of the second intrinsic amorphous silicon away from the N-type silicon substrate, wherein the thickness of the P-type amorphous silicon doping layer is 6 nm.

[0102] S500: Using RPD equipment, a first tin oxide film (oxygen flow rate is 100 sccm), a silver oxide film, and a second tin oxide film (oxygen flow rate is 120 sccm) are sequentially deposited on a side of the N-type amorphous silicon doped layer away from the N-type silicon substrate to obtain an indium-free transparent conductive layer, wherein:

[0103] The oxygen-tin atomic ratio of the first tin oxide film is 1.85, and the carrier mobility is 35.2 cm 2 V -1 s -1 , the resistivity is 9.5×10 -4 Ω·cm, transmittance is 79.3%, thickness is 15nm;

[0104] The thickness of the silver oxide film is 6nm and the transmittance is 90.0%;

[0105] The oxygen-tin atomic ratio of the second tin oxide film is 1.92, and the carrier mobility is 26.4 cm 2 V -1 s -1 , the resistivity is 2.1×10 -3 Ω·cm, transmittance is 83.0%, thickness is 50nm;

[0106] The light transmittance of the indium-free transparent conductive layer is 81.2% and the resistivity is 5×10 -4 Ω·cm.

[0107] S600: Using RPD equipment, a conductive tin oxide layer is deposited on the side of the P-type amorphous silicon doped layer away from the N-type silicon substrate (oxygen flow rate is 90 sccm), where the thickness of the conductive tin oxide layer is 88nm, the oxygen-tin atomic ratio is 1.83, and the carrier mobility is 29.3cm 2 V -1 s -1 , the transmittance is 78.0%.

[0108] S700: By screen printing low-temperature silver paste, a silver electrode is formed on the side of the indium-free transparent conductive layer away from the N-type silicon substrate, and a silver electrode is formed on the side of the conductive tin oxide layer away from the N-type silicon substrate to obtain a heterogeneous crystalline silicon cell.

[0109] Embodiment 2 to Embodiment 4

[0110] The steps for preparing the heterogeneous crystalline silicon cell are basically the same as those in Example 1, except that: the parameters for preparing the indium-free transparent conductive layer, the specific parameter changes can be seen in Table 1, and the parameters not listed in Table 1 indicate that the various embodiments are consistent.

[0111] Comparative Example 1

[0112] The steps for preparing the heterogeneous crystalline silicon cell are basically the same as those in Example 3, except that the oxygen-tin atomic ratio of the first tin oxide film is greater than that of the second tin oxide film, see Table 1 for details.

[0113] Comparative Example 2

[0114] The steps for preparing the heterogeneous crystalline silicon cell are basically the same as those in Example 3, except that when preparing the indium-free transparent conductive layer, no silver oxide film is formed, that is, the indium-free transparent conductive layer only includes the first tin oxide film and the second tin oxide film.

[0115] Comparative Example 3

[0116] The steps for preparing the heterogeneous crystalline silicon cell are basically the same as those in Example 1, except that the transparent conductive layers on the front and back sides are both ITO transparent conductive layers. The relevant parameters of the ITO transparent conductive layer on the front side and the ITO transparent conductive layer on the back side can be seen in Table 1.

[0117] Comparative Example 4

[0118] The steps for preparing the heterogeneous crystalline silicon cell are basically the same as those in Example 3, except that the transparent conductive layer on the front side is an ITO transparent conductive layer. The relevant parameters of the ITO transparent conductive layer on the front side can be seen in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] By comparing the above-mentioned Examples 1 to 4 with Comparative Examples 3 and 4, the indium-free transparent conductive layer of the present application can be applied to solar cells to obtain better photoelectric conversion efficiency, so it can replace ITO as a transparent conductive layer in solar cells, and compared with the ITO transparent conductive layer used in Comparative Examples 3 and 4, the production cost of the solar cells in Examples 1 to 4 is reduced.

[0123] By comparing the above-mentioned Example 3 with the comparative example 1, the setting requirements for the oxygen-tin ratio in the indium-free transparent conductive layer of the structure of the present application can help to better improve the photoelectric conversion efficiency of the solar cell; by comparing Example 3 with the comparative example 2, it can be seen that the ultra-thin metal doping layer can effectively reduce the resistivity of the transparent conductive layer, thereby improving its conductivity and improving the photoelectric conversion efficiency of the battery.

[0124] 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 technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0125] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0126] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An indium-free transparent conductive layer, characterized in that: The invention comprises a first tin oxide film, an oxygen-doped metal film and a second tin oxide film which are stacked in sequence, wherein the oxygen-tin atomic ratio of the first tin oxide film is smaller than that of the second tin oxide film.

2. The indium-free transparent conductive layer according to claim 1, characterized in that: The oxygen-tin atomic ratio of the first tin oxide film is 1.75-1.90, and / or the oxygen-tin atomic ratio of the second tin oxide film is 1.90-2.

00.

3. The indium-free transparent conductive layer according to claim 1 or 2, characterized in that: The first tin oxide film also satisfies at least one of the following conditions: The carrier mobility is 20-40cm 2 V -1 s -1 ; The resistivity is 8×10 -4 -2×10 -3 Ω·cm; Light transmittance is 75%-85%; The thickness is 10 to 70 nm.

4. The indium-free transparent conductive layer according to any one of claims 1 to 3, characterized in that: The first tin oxide film contains a first doping element, and the first doping element includes at least one of Ta, Sb, and Al; And / or, the second tin oxide film contains a second doping element, and the second doping element includes at least one of Ta, Sb, and Al.

5. The indium-free transparent conductive layer according to any one of claims 1 to 4, characterized in that: The second tin oxide film also satisfies at least one of the following conditions: The carrier mobility is 10-30cm 2 V -1 s -1 ; Resistivity 2×10 -3 -3×10 -3 Ω·cm; Light transmittance is 75%-85%; The thickness is 40 to 100 nm.

6. The indium-free transparent conductive layer according to any one of claims 1 to 5, characterized in that: The oxygen-doped metal film meets at least one of the following conditions: The oxygen-doped metal film includes at least one of an oxygen-doped copper film, an oxygen-doped gold film or an oxygen-doped silver film; The thickness of the oxygen-doped metal film is 3-10 nm; The light transmittance of the oxygen-doped metal film is 80%-95%.

7. The indium-free transparent conductive layer according to any one of claims 1 to 6, characterized in that: The light transmittance of the indium-free transparent conductive layer is 75%-85%, and / or the resistivity of the indium-free transparent conductive layer is 5×10 -4 -8×10 -4 Ω·cm.

8. A method for preparing the indium-free transparent conductive layer according to any one of claims 1 to 7, characterized in that: include: A first tin oxide film, an oxygen-doped metal film and a second tin oxide film are sequentially deposited on a substrate, wherein an oxygen-tin atomic ratio of the first tin oxide film is smaller than an oxygen-tin atomic ratio of the second tin oxide film.

9. The method according to claim 8, characterized in that The first tin oxide film, the oxygen-doped metal film and the second tin oxide film are formed by magnetron sputtering or plasma reaction coating. The target material for forming the first tin oxide film and the second tin oxide film is a tin target, and the target material for forming the oxygen-doped metal film is a metal target in the oxygen-doped metal film.

10. A solar cell, characterized in that: include: A battery substrate, the battery substrate having a front side and a back side arranged opposite to each other; A front electrode, wherein the front electrode is the indium-free transparent conductive layer according to any one of claims 1 to 7 and is located on the front side of the battery substrate, wherein the first tin oxide film in the indium-free transparent conductive layer is arranged close to the battery substrate; A back electrode is located on the back side of the battery substrate.

11. The solar cell according to claim 10, characterized in that The back cell includes a conductive tin oxide layer.

12. The solar cell according to claim 11, characterized in that: The conductive tin oxide layer satisfies at least one of the following conditions: Thickness 70-140nm; The oxygen-tin atomic ratio is 1.75-2.00; The carrier mobility is 10-40cm 2 V -1 s -1 ; Light transmittance is 75%-85%; The conductive tin oxide layer contains a third doping element, and the third doping element includes at least one of Ta, Sb, and Al.

13. The solar cell according to any one of claims 10 to 12, characterized in that: The solar cell is at least one of a crystalline silicon solar cell, a perovskite solar cell, a compound semiconductor solar cell, an organic solar cell or a stacked solar cell.

14. A method for preparing the solar cell according to any one of claims 10 to 13, characterized in that: include: preparing a battery matrix; Prepare a front electrode on the front side of the battery substrate using the method for preparing an indium-free transparent conductive layer according to claim 8 or 9; A back electrode is prepared on the back side of the battery substrate.

15. The method according to claim 14, characterized in that The method for preparing the back electrode comprises: forming a conductive tin oxide layer by a plasma reaction plating method, and the target material for forming the conductive tin oxide layer is a tin target.

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