Hole contact passivation structure, photovoltaic cell and photovoltaic module

Abstract

The embodiment of the invention relates to the technical field of solar cells, in particular to a hole contact passivation structure, a photovoltaic cell and a photovoltaic module. The hole contact passivation structure comprises a graphene oxide layer and a transition metal oxide layer which are stacked, wherein the graphene oxide layer is used for extracting holes. In the embodiment of the invention, the transition metal oxide is used for battery passivation, so that parasitic absorption is reduced, and the optical performance of the battery is improved. And due to the existence of graphene oxide (GO), the GO has a high-electronegativity oxygen functional group, so that the transition metal oxide is in an electroactive state, and the transmission of holes on the transition metal oxide layer is improved. The hole contact passivation structure can improve the efficiency of the photovoltaic cell.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a hole contact passivation structure, a photovoltaic cell and a photovoltaic module. Background Art

[0002] N-type cells mainly include HJT cells (heterojunction cells) and TOPCon cells (tunneling oxide passivation contact cells). Compared with HJT cells, the main improvement of TOPCon cells is the optimization of the back metal contact structure, which reduces photocurrent loss and thus improves conversion efficiency. The theoretical efficiency upper limit is set at 28.2%~28.7%, far exceeding the 24.5% of PERC cells and close to the theoretical limit of 29.43% for all crystalline silicon-based solar cells.

[0003] The passivation contact structure of the TOPCon cell is used to selectively pass electrons, but there is no passivation contact structure for selectively passing holes, resulting in a high recombination rate of carriers at the hole extraction and transport interface.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0005] The embodiments of the present application provide a hole contact passivation structure, a photovoltaic cell and a photovoltaic module to solve or alleviate one or more of the technical problems mentioned above.

[0006] A first aspect of an embodiment of the present application provides a hole contact passivation structure, including: A graphene oxide layer and a transition metal oxide layer are stacked; Wherein, the graphene oxide layer is used for extracting holes.

[0007] In the embodiments of the present application, the use of transition metal oxides for battery passivation is beneficial to reduce parasitic absorption, thereby improving the optical performance of the battery. The presence of graphene oxide (GO), which has highly electronegative oxygen functional groups, will make the transition metal oxides appear electrically active and improve the transmission of holes on the transition metal oxide layer. This hole contact passivation structure can improve the efficiency of photovoltaic cells.

[0008] The second aspect of the embodiment of the present application provides a photovoltaic cell, wherein the photovoltaic cell comprises the hole contact passivation structure as described above, thereby reducing the recombination of carriers at the interface, improving the open circuit voltage and short circuit current, and improving the efficiency of the photovoltaic cell.

[0009] A third aspect of an embodiment of the present application provides a photovoltaic assembly, which includes the photovoltaic cell as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0011] Figure 1 It is a schematic diagram of the structure of a solar cell provided in an embodiment of the present application.

[0012] Description of reference numerals: 1-N type silicon wafer; 2-p + Emitter; 3-graphene oxide layer; 4-transition metal oxide layer; 5-first anti-reflection layer; 6-first electrode; 7-tunneling oxide layer; 8-doped polysilicon layer; 9-second anti-reflection layer; 10-second electrode. DETAILED DESCRIPTION

[0013] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0014] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. When the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0015] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0016] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0017] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0018] The embodiments of the present application provide a hole contact passivation structure, a photovoltaic cell and a photovoltaic module. See below for details.

[0019] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0020] The embodiment of the present application provides a hole contact passivation structure, comprising: a stacked graphene oxide layer 3 and a transition metal oxide layer 4; wherein the graphene oxide layer 3 is used for extracting holes.

[0021] In the embodiment of the present application, a stack of graphene oxide layer 3 and transition metal oxide layer 4 is used as a hole contact passivation structure. Transition metal oxide has the characteristic of low parasitic absorption. Using transition metal oxide for battery passivation is conducive to reducing parasitic absorption, thereby improving the optical performance of the battery. In addition, transition metal oxides have the characteristics of optical transparency, surface passivation and selective passage of holes. The presence of graphene oxide (GO), GO has highly electronegative oxygen functional groups, which will make the transition metal oxide present an electrically active state and improve the transmission of holes on the transition metal oxide layer. The embodiment of the present application solves the problem of high recombination rate of carriers on the hole extraction and transmission interface.

[0022] The work function of transition metal oxides has a wide range, ranging from about 2eV for ZrO2 to about 7eV for V2O5. This wide range of work functions enables transition metal oxides to have good energy level matching with a variety of organic and inorganic materials. By changing the composition, structure or processing conditions (such as temperature, annealing, etc.) of transition metal oxides, their work function can be adjusted to a certain extent. This adjustability makes it possible to optimize device performance.

[0023] Furthermore, the work function of the transition metal oxide layer 4 is above 4.7 eV. The use of transition metal oxides with high work function (WF) can be used as hole selection contacts. When an undoped material with high WF contacts Si (n-Si or p-Si), electrons will flow from Si to the undoped material with high WF until their Fermi levels are aligned. At this time, p-Si will be generated. + layer, an inverse p + Thus, the field effect passivation surface can be achieved while selectively transporting holes.

[0024] Preferably, the work function of the transition metal oxide layer 4 is 4.7 eV to 7 eV, for example, 4.7 eV, 5 eV, 5.2 eV, 5.5 eV, 6 eV, 6.5 eV, 7 eV, etc. Thus, there are many choices of work functions within this range, and good contact passivation can be achieved. Exemplarily, the transition metal oxide layer 4 includes at least one of molybdenum oxide (MoO3), tungsten oxide (WO3), vanadium oxide (V2O5), and cuprous oxide (Cu2O).

[0025] In some embodiments, in the hole contact passivation structure, the work function of the transition metal oxide layer 4 increases along a first direction; the first direction is along the thickness direction of the graphene oxide layer 3, from the side of the transition metal oxide layer 4 close to the graphene oxide layer 3 to the side away from the graphene oxide layer 3. Therefore, the transition metal oxide layer with increasing work function helps to achieve a better contact passivation effect.

[0026] In some embodiments, in the hole contact passivation structure, the thickness of the graphene oxide layer 3 is less than 5 nm. For example, the thickness of the graphene oxide layer 3 can be 0.8 nm, 1 nm, 1.8 nm, 2.8 nm, 4 nm, 5 nm, etc.

[0027] In some embodiments, in the hole contact passivation structure, the thickness of the transition metal oxide layer 4 is 70 nm to 100 nm. For example, the thickness of the transition metal oxide layer 4 can be 70 nm, 75 nm, 80 nm, 90 nm, 95 nm, 100 nm, etc.

[0028] Preferably, the thickness of the hole selective passivation contact structure is 80nm to 100nm. For example, the thickness of the hole selective passivation contact structure can be 80nm, 90nm, 95nm, 100nm, etc. Thus, while providing contact passivation, the minority carrier lifetime can be increased as much as possible.

[0029] In some embodiments, in the hole contact passivation structure, the graphene oxide layer 3 can be prepared by spin coating graphene oxide, and the transition metal oxide layer 4 can be prepared by thermal evaporation deposition or electron beam deposition.

[0030] In some embodiments, the hole contact passivation structure is used for the front side of an n-type TOPCon cell, the front side of a p-type TOPCon cell, or the back side of an n-type HJT cell, thereby achieving hole contact passivation for different types of cells.

[0031] In some specific embodiments, see Figure 1 The hole contact passivation structure is used for the front side of the n-type TOPCon cell. The TOPCon cell comprises an N-type silicon wafer 1, the front side of the N-type silicon wafer 1 is a textured surface, and the front side of the N-type silicon wafer 1 is prepared by diffusion with p +The emitter 2 has a graphene oxide layer 3, a transition metal oxide layer 4 and a first anti-reflection layer 5 stacked in sequence on the textured surface, and the first electrode 6 is arranged on the outermost side, and one end of the first electrode 6 is in contact with the transition metal oxide layer 4; the graphene oxide layer 3 and the transition metal oxide layer 4 together constitute a hole contact passivation structure. The back of the N-type silicon wafer 1 is stacked with a tunneling oxide layer 7, a doped polysilicon layer 8 and a second anti-reflection layer 9 in sequence, and the outermost side of the back of the N-type silicon wafer 1 is provided with a second electrode 10, and one end of the second electrode 10 is in contact with the doped polysilicon layer 8. Therefore, the front of the TOPCon battery adopts a hole contact passivation structure composed of a graphene oxide layer 3 and a transition metal oxide layer 4, and the back adopts an electron contact passivation structure composed of a tunneling oxide layer 7 and a doped polysilicon layer 8, thereby improving the efficiency of the TOPCon battery.

[0032] The embodiment of the present application also provides a photovoltaic cell, comprising the hole contact passivation structure described in the embodiment of the present application.

[0033] The following will conduct performance tests on the structure or manufacturing method of the TOPCon battery provided in the embodiments of the present application and related comparative examples.

[0034] [Example 1] The specific preparation process of TOPCon battery is as follows: Step 1: The N-type silicon wafer 1 uses an N-type middle ring silicon wafer with a thickness of 140 μm and a two-dimensional size of 210 mm×182 mm, and cleans and polishes the back side of the N-type silicon wafer 1; Step 2: a 1 nm thick silicon oxide film is prepared on the back side of the N-type silicon wafer 1 as a tunneling oxide layer 7, and 90 nm thick polysilicon is grown on the tunneling oxide layer 7 to obtain a polysilicon layer; Step 3: doping phosphorus element on the back side to form a doped polysilicon layer 8 on the polysilicon layer, and then removing the phosphorus silicon glass; Step 4: preparing a 5 nm thick aluminum oxide layer and a 35 nm thick silicon nitride layer 5 on the doped polysilicon layer 8 as a second anti-reflection layer 9; Step 5: Printing silver paste and metallizing to obtain the second electrode 10; wherein the silver paste is purchased from the RX2835 model silver paste of Guangzhou Ruxing Technology Co., Ltd.; Step 6: Cleaning and texturing the front side of the N-type silicon wafer 1; Step 7: doping with boron element to form an emitter 2 with a thickness of 240 nm on the front side; Step 8: Spin-coating graphene oxide on the side of the emitter 2 away from the N-type silicon wafer 1 to obtain a graphene oxide layer 3 with a thickness of 1 nm; Step 9: Deposit MoO with a thickness of 70 nm using electron beam deposition x layer; Step 10: preparing an aluminum oxide layer with a thickness of 5 nm and a silicon nitride layer with a thickness of 35 nm as the second anti-reflection layer 5; Step 11: Use silver paste to print the first electrode 6 and perform metallization; wherein the silver paste is purchased from Guangzhou Ruxing Technology Co., Ltd. as RX2835 model silver paste.

[0035] The other operations of Examples 2 to 11 and Comparative Example 1 are the same as those of Example 1, and the differences are detailed in Table 1.

[0036] Table 1

[0037] The TOPCon cells of Examples 1 to 12 were subjected to IV tests. The IV test conditions were a light irradiance of 1000 W / m 2 , temperature is 25℃±10℃, relative humidity: ≤85%. The test results are shown in Table 2.

[0038] Table 2:

[0039] It can be seen from Table 2 above that the open circuit voltage and conversion efficiency of Examples 1 to 11 are better than those of Comparative Example 1, because the stacked graphene oxide layer 3 and transition metal oxide layer 4 as a passivation contact structure have a better passivation effect than a single transition metal oxide layer 4 as a passivation contact structure. Furthermore, the open circuit voltage and conversion efficiency of Examples 11 to 12 are improved compared to Example 2, because the use of the graphene oxide layer 3 and the transition metal oxide layer with increasing work function as a passivation contact structure further optimizes the passivation effect.

[0040] The embodiment of the present application may also provide a photovoltaic assembly (not shown), wherein the photovoltaic assembly includes the photovoltaic cell described above. The photovoltaic cell may be connected in series and / or in parallel with one or more other solar cells in a preset manner. Among them, a plurality of cells may form a battery string, and adjacent batteries may be connected together by string welding.

[0041] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The orientation words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0042] It should also be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0043] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0044] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A hole contact passivation structure, characterized in that: include: A graphene oxide layer (3) and a transition metal oxide layer (4) arranged in a stacked manner; The graphene oxide layer (3) is used for extracting holes.

2. The hole contact passivation structure according to claim 1, characterized in that: The work function of the transition metal oxide layer (4) is above 4.7 eV.

3. The hole contact passivation structure according to claim 2, characterized in that: The work function of the transition metal oxide layer (4) is 4.7 eV to 7 eV.

4. The hole contact passivation structure according to claim 2, characterized in that: The work function of the transition metal oxide layer (4) increases along a first direction; The first direction is along the thickness direction of the graphene oxide layer (3), from a side of the transition metal oxide layer (4) close to the graphene oxide layer (3) to a side away from the graphene oxide layer (3).

5. The hole contact passivation structure according to claim 1, characterized in that: The thickness of the graphene oxide layer (3) is less than 5 nm; The thickness of the transition metal oxide layer (4) is 70 nm to 100 nm.

6. The hole contact passivation structure according to claim 5, characterized in that: The thickness of the hole selective passivation contact structure is 80nm-100nm.

7. The hole contact passivation structure according to claim 1, characterized in that: The transition metal oxide layer (4) comprises at least one of molybdenum oxide, tungsten oxide, vanadium oxide and cuprous oxide.

8. The hole contact passivation structure according to any one of claims 1 to 7, characterized in that: The hole contact passivation structure is used for the front side of an n-type TOPCon cell, the front side of a p-type TOPCon cell or the back side of an n-type HJT cell.

9. A photovoltaic cell, characterized in that: The invention comprises the hole contact passivation structure as described in any one of claims 1 to 8.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises the photovoltaic cell according to claim 9.

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