Battery piece grading method

Abstract

The invention relates to the technical field of solar cells, in particular to a battery piece grading method. The battery piece grading method comprises the following steps: providing a photovoltaic module made of battery pieces at the same grade as to-be-graded battery pieces; obtaining a forward current of the photovoltaic module; according to the series resistance and the open-circuit voltage of the to-be-graded battery piece and the forward current of the photovoltaic module, the equivalent luminous power of the to-be-graded battery piece is obtained; and grading the to-be-graded battery pieces according to the equivalent luminous power of the to-be-graded battery pieces. According to the grading method of the battery pieces, the EL light and shade consistency of the photovoltaic module formed by the battery pieces which are graded by taking the equivalent luminous power of the battery pieces as the index is greatly improved.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and particularly to a method for grading battery wafers. Background Art

[0002] Tunneling Oxide Passivated Contact (TOPCon) technology is a passivated contact technology. Its key technology is to grow a layer of tunneling silicon oxide (SiO x ) on the surface of the silicon wafer, and prepare a layer of heavily doped polysilicon on the tunneling silicon oxide to achieve a field passivation effect. Thanks to the good passivation performance of TOPCon cells, the production efficiency of its mass-produced cells has currently reached more than 25%; coupled with the compatibility of the production process, the planned production capacity of TOPCon cells is currently increasing rapidly, and it has become the mainstream direction for the expansion of industrial silicon cells.

[0003] Currently, when grading TOPCon cells, in addition to the first-level grading according to the conversion efficiency, the second-level grading can also be carried out according to the open-circuit voltage value to make a more detailed division of the battery wafers; however, the electroluminescence (EL) detection at the photovoltaic module end is related not only to the conversion efficiency and open-circuit voltage, but also to the R s of the battery wafers and the working current. Therefore, the EL brightness difference of the photovoltaic modules composed of the battery wafers graded by the conversion efficiency and open-circuit voltage is relatively large.

[0004] It should be noted that the above content is not necessarily the prior art and does not limit the patent protection scope of this application. Summary of the Invention

[0005] Embodiments of this application provide a method for grading battery wafers to solve or alleviate one or more of the above technical problems.

[0006] Embodiments of this application provide a method for grading battery wafers.

[0007] The method for grading the battery wafers includes the following operations: Provide a photovoltaic module made of battery wafers in the same grade as the battery wafers to be graded; Obtain the forward current of the photovoltaic module; According to the series resistance and open-circuit voltage of the battery wafers to be graded, and the forward current of the photovoltaic module, obtain the equivalent luminous power of the battery wafers to be graded; Grade the battery wafers to be graded according to the equivalent luminous power of the battery wafers to be graded; Wherein, the battery wafers in the same grade as the battery wafers to be graded are the battery wafers in the same grade as the battery wafers to be graded after being graded at the first level or above.

[0008] The grading method of the solar cell in the embodiment of the present application grades the solar cells based on the equivalent luminous power of the solar cells, where the forward current I el is the data at the component end, while the series resistance R s and the open-circuit voltage V oc are the data at the cell end. The present application directly obtains the above parameters and grades the solar cells based on the equivalent luminous power of the solar cells. The grading index is closer to the actual situation in the photovoltaic module. Therefore, for the photovoltaic module composed of the graded solar cells, the EL brightness uniformity has been greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the drawings, unless otherwise specified, the same reference numerals throughout the several views denote 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 accordance with the present application and should not be regarded as limiting the scope of the present application.

[0010] Figure 1 is a flowchart of the solar cell grading method provided by the embodiment of the present application; Figure 2 is the EL test of the photovoltaic module in Embodiment 1, where Figure 2 (a) is the high-brightness grade, Figure 2 (b) is the medium-brightness grade, Figure 2 (c) is the low-brightness grade; Figure 3 is the EL test of the photovoltaic module in Comparative Example 1, where Figure 3 (a) is the high-brightness grade, Figure 3 (b) is the medium-brightness grade, Figure 3 (c) is the low-brightness grade. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Wherever the same or similar reference numerals are used throughout, they denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are exemplary only for explaining the present application and should not be construed as limiting the present application. It should be noted that, without conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0012] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may 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. Thus, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part. And when discussing the second element, component, region, layer, or part, it does not imply that there must be a first element, component, region, layer, or part in the present application.

[0013] In the present application, unless otherwise clearly defined and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0014] It should be noted that the terms "first", "second", etc. in the specification, claims, and above-mentioned drawings of the present application are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0015] In this application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as 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 combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of quantitative intervals such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0016] When TOPCon cells are binned, due to problems such as test fluctuations, electrical performance mismatches, machine tool errors, or uniformity, cells with significantly different electrical performances are often mixed in the same bin. After component welding or encapsulation, there are obvious EL bright and dark areas. Such problems are more obvious in the lower bins after binning by conversion efficiency. Currently, when binning cells, EL gray value binning is also added to distinguish bright and dark in advance; the method of EL binning at the cell end is to uniformly connect a constant power supply to all cells so that the cells emit near-infrared light, while the constant power supply applied at the component end is different from the test at the cell end. After using EL gray value binning, there are still obvious EL bright and dark areas after component welding or encapsulation.

[0017] The embodiment of this application provides a method for binning cells. Based on this, the problem of large differences in EL bright and dark at the component end of the binned cells is solved. See the following for details.

[0018] Next, exemplary embodiments according to this 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 only to the embodiments described herein.

[0019] The embodiment of this application provides a method for binning cells.

[0020] As Figure 1 shown, the method for binning cells may include: S1. Provide a photovoltaic module made of cells in the same bin as the cells to be binned; S2. Obtain the forward current of the photovoltaic module; S3. Obtain the equivalent luminous power of the cells to be binned according to the series resistance and open-circuit voltage of the cells to be binned, and the forward current of the photovoltaic module; Optionally, the equivalent luminous power P0 of the cell to be graded is obtained as follows: The equivalent luminous power P0 of the cell to be graded is obtained according to Equation (1), and Equation (1) is: P0 = I el 2 ×R s +I el ×V oc (1); In Equation (1), I el is the forward current of the photovoltaic module, and R s is the series resistance of the cell to be graded; V oc is the open-circuit voltage of the cell to be graded; S4. Grade the cell to be graded according to the equivalent luminous power of the cell to be graded; Among them, the cells in the same grade as the cell to be graded are the cells that are in the same grade as the cell to be graded after being graded at one level or more than one level.

[0021] In the cell grading method of the embodiment of the present application, grading is performed with the equivalent luminous power of the cell as an index. The forward current I el is data at the module end, while the series resistance R s and the open-circuit voltage V oc are data at the cell end. The present application directly obtains the above parameters and performs grading with the equivalent luminous power of the cell as an index. The grading index is closer to the actual situation in the photovoltaic module. Therefore, for the photovoltaic module composed of graded cells, the EL brightness uniformity has been greatly improved.

[0022] The grading method of the embodiment of the present application can be applicable to grading at multiple levels. The embodiment of the present application does not make any limitations in this regard. In S1 of the embodiment of the present application, the cells in the same grade as the cell to be graded are the cells that are in the same grade as the cell to be graded after being graded at one level or more than one level. Exemplarily, the cells in the same grade as the cell to be graded include: the cells that are in the same grade as the cell to be graded after being graded at the first level by conversion efficiency. Thus, it is applicable to the second-level grading of the first-level graded cells. As other examples, the cells in the same grade as the cell to be graded include the cells that are graded at the first level by conversion efficiency and then graded at the second level by voltage and are in the same grade as the cell to be graded; thus, it is applicable to the third-level grading of the second-level graded cells.

[0023] In S1 of the embodiment of the present application, the grading includes one grading level and multiple grading levels. Thus, the grading method of the embodiment of the present application can be applicable to the grading of specific grading levels and can also perform the grading of multiple grading levels. For example, after the solar cells are graded at the first level according to the conversion efficiency, the solar cells are divided into each efficiency grading level. Among them, those lower than 25.40% are low-efficiency grading levels. Based on the fact that the difference in the EL brightness and darkness of the low-efficiency grading levels is greater, those skilled in the art can selectively adopt the grading method of the embodiment of the present application for the grading of low grading levels. Of course, the grading method of the embodiment of the present application can also be independently adopted for the solar cells of each efficiency grading level for grading.

[0024] In S2 of the embodiment of the present application, obtaining the forward current I of the photovoltaic module el may include: S201. Obtain the maximum operating current I of the photovoltaic module mpp , the I tested for photovoltaic modules made of solar cells of different efficiency grading levels mpp is different, and I el varies with the I of the photovoltaic module mpp changing. Therefore, the embodiment of the present application grades with the equivalent luminous power P0 as an index, which is closer to the actual situation. For the EL detection at the battery end, the forward current I passed into the solar cell el is a unified value, and the magnitude of the forward current passed in cannot be adjusted in real time according to the solar cell. Therefore, the EL test differences of the photovoltaic modules composed of the solar cells graded by EL detection are relatively large.

[0025] Optionally, the photovoltaic module can be subjected to an IV test, and the maximum operating current I can be obtained according to the obtained IV curve mpp .

[0026] Furthermore, the test conditions of the IV curve of the photovoltaic module can be carried out under standard test conditions (STC), and the test is carried out under the spectrum of 25 °C, irradiance of 1000 W / m 2 , and air quality of 1.5 (AM1.5G).

[0027] S202. Calculate the forward current I of the photovoltaic module according to formula (2) el : I el =A × I mpp (2) In formula (2), A is any value in the range of 0.6 to 1.1.

[0028] This is because according to the regulations of the "Technical Specification for Electroluminescence (EL) Detection of Photovoltaic Modules", the forward current I passed into the photovoltaic module in the constant current mode el is its maximum operating current I mppis 0.6 to 1.1. Thus, I can be obtained according to I mpp to obtain I el .

[0029] In S3 of the embodiment of the present application, the series resistance R of the battery cell to be graded s is obtained by: performing an IV test on the battery cell to be graded, and obtaining the series resistance R of each battery cell according to the obtained IV curve s .

[0030] Further, the test conditions for the IV curve of the battery cell to be graded can be: standard test conditions (STC) at 25°C, irradiance of 1000 W / m 2 , and the spectrum of air quality 1.5 (AM1.5G) is tested to obtain a bright-field IV curve; the battery cell to be graded is placed in a completely lightless environment (dark box), and a high-precision current measurement device such as a digital multimeter is used to measure the short-circuit current of the battery cell to be graded. By adjusting the voltage in the test circuit, the current values at different voltages are observed and recorded to obtain the dark current characteristics, that is, a dark-field IV curve is obtained.

[0031] Further, the method for obtaining the series resistance R of the battery cell to be graded from the IV curve s can be, according to the calculation method in the "HALM Solar Cell Test Specification": R s =△V / I sc (3); In formula (3): I sc is the short-circuit current; △V is the difference in voltage corresponding to the negative value of the open-circuit voltage V oc minus I sc on the dark-field forward curve.

[0032] In S3 of the embodiment of the present application, the open-circuit voltage V of the battery cell to be graded oc is obtained by: performing an IV test on the battery cell to be graded, and obtaining the open-circuit voltage V of each battery cell according to the obtained IV curve oc .

[0033] Further, the test conditions for the IV curve of the photovoltaic module can be standard test conditions (STC).

[0034] In S4 of the embodiment of the present application, the grading according to the equivalent luminous power P0 of each battery cell to be graded can include grading at the second level and above, for example, second-level grading, third-level grading, fourth-level grading, etc.

[0035] Further, the grading according to the equivalent luminous power P0 of each cell to be graded includes: obtaining the distribution range of the equivalent luminous power of the cells to be graded according to the equivalent luminous power P0 of each cell to be graded; grading the multiple cells to be graded within the distribution range with each grading change range not exceeding the threshold B; where the threshold B is any value in the range of 0.05W to 0.2W. Exemplarily, first perform a primary grading on each cell to be graded with the conversion efficiency as an index, and grade the conversion efficiency (25.4% - 25.9%) in increments of 0.1%, which can be divided into grade 25.4 (25.4% - 25.5%), grade 25.5 (25.5% - 25.6%), grade 25.6 (25.6% - 25.7%), grade 25.7 (25.7% - 25.8%), grade 25.8 (25.8% - 25.9%); perform a secondary grading on all the cells to be graded in grade 25.4 according to the equivalent luminous power. For example, if the equivalent luminous power of the cells in grade 25.4 is between 13.80W and 13.95W, it can be divided into a low-brightness grade (13.80 - 13.85W), a medium-brightness grade (13.85W - 13.90W), and a high-brightness grade (13.90 - 13.95W) in increments of 0.05W; the other efficiency grades can be divided by referring to the above method.

[0036] It should be noted that for the cell grading method in the embodiments of the present application, the cells include TOPCon cells, PERC cells (passivated emitter and rear local contact cells), HJT cells (heterojunction cells), etc. Thus, it is applicable to the grading of multiple types of cells.

[0037] Next, performance tests will be conducted on the cell grading method provided in the embodiments of the present application and related comparative examples.

[0038]

Example 1

[0039] Step 4: Obtain the series resistance R of the cells to be graded at this gear s and the open-circuit voltage V oc , specifically as follows: Perform IV tests on each cell under STC conditions, and obtain the series resistance R s and the open-circuit voltage V oc of each cell according to the obtained IV curve; Step 5: Obtain the equivalent luminous power P0 of each of the above cells according to formula (1), and formula (1) is: P0 = I el 2 × R s + I el × V oc (1); In formula (1), I el is the forward current of the photovoltaic module; Step 6: Grade according to the conversion efficiency and equivalent luminous power P0 of each cell, and the grading operation is: obtain the equivalent luminous power of the cells at the 25.4 grade. The equivalent luminous power range is 13.80W to 13.95W. Divide the cells at the 25.4 grade into low-bright grade (13.80 - 13.85W), medium-bright grade (13.85W - 13.90W), and high-bright grade (13.90 - 13.95W) according to the threshold B of 0.05W.

[0040]

Comparative Example 1

[0041]

Test Example

[0042] Compare Figure 2 and Figure 3 , the EL of the photovoltaic module in Comparative Example 1 has obvious uneven light and dark compared with the EL of the photovoltaic module in Example 1. This is mainly because the EL at the cell end uses the same forward current for all cell pieces. When testing the EL at the module end, there are differences in the normalized current for modules made of cells in different gears. Therefore, the EL gray level at the cell end cannot fully correspond to its EL performance at the module end, resulting in a certain degree of EL light and dark still appearing after gray level grading. In Example 1, for modules made of cells in different gears, I mpp is pre-tested and introduced into the calculation of the equivalent luminous power, which can effectively reduce the phenomenon of inconsistent EL light and dark in the module.

[0043] It should be noted that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing this application and simplifying the description, rather than indicating or implying 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 to this application. The orientation terms "inner and outer" refer to the inside and outside of the contour of each component itself. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "on top of other devices or structures" will be positioned as "below other devices or structures" or "beneath other devices or structures" afterwards. Thus, the exemplary term "above..." can include both the orientation of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding explanations are made for the relative spatial descriptions used here.

[0044] It should also be noted that the "one embodiment", "another embodiment", "embodiment", etc. mentioned in this application refer to the specific features, structures or characteristics described in connection with this embodiment being included in at least one embodiment described in the general description of 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 connection with any one embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also falls within the scope of this application.

[0045] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0046] It should also be noted that the above are only the preferred embodiments of this application, and do not limit the scope of patent protection of this application. Any equivalent structure or equivalent process transformation made using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall similarly be included in the scope of patent protection of this application.

Claims

1. A battery cell grading method, characterized in that: The following operations are included: Providing a photovoltaic module made of cells in the same grade as the cells to be graded; Obtaining the forward current of the photovoltaic module; Obtaining the equivalent luminous power of the cell to be binned according to the series resistance and open circuit voltage of the cell to be binned and the forward current of the photovoltaic module; Classifying the battery cells to be classified according to the equivalent luminous power of the battery cells to be classified; The battery cell that is in the same gear as the battery cell to be binned is a battery cell that is in the same gear as the battery cell to be binned after being binned by one level or more.

2. The battery cell binning method according to claim 1, characterized in that: The obtaining of the equivalent luminous power of the cell to be binned comprises: The equivalent luminous power P0 of the cell to be binned is obtained according to formula (1), which is: P0=I el 2 ×R s +I el ×V oc ; In formula (1): I el is the forward current of the photovoltaic module; R s is the series resistance of the battery cell to be classified; V oc is the open circuit voltage of the battery cell to be classified.

3. The battery cell grading method according to claim 2, characterized in that: The obtaining of the forward current of the photovoltaic module comprises: Get the maximum operating current I of the photovoltaic module mpp ; According to formula (2), the forward current I of the photovoltaic module is calculated el : I el =A×I mpp (2) In formula (2), A is any value between 0.6 and 1.

1.

4. The battery cell binning method according to claim 3, characterized in that: Get the maximum operating current I of the photovoltaic module mpp include: The photovoltaic module is subjected to an IV test, and the maximum operating current I is obtained according to the obtained IV curve. mpp .

5. The battery cell binning method according to claim 2, characterized in that: The series resistance R of the battery cell to be classified s Ways to obtain include: The battery cell to be classified is subjected to an IV test, and the series resistance R of the battery cell to be classified is obtained according to the obtained IV curve. s ; and / or The open circuit voltage V of the battery cell to be classified oc Ways to obtain include: The battery cell to be classified is subjected to an IV test, and the open circuit voltage V of the battery cell to be classified is obtained according to the obtained IV curve. oc .

6. The battery cell binning method according to claim 4 or 5, characterized in that: The IV tests were conducted independently at 25°C and 1000 W / m 2 , and tested under the spectrum of AM1.5G.

7. The battery cell binning method according to claim 1, characterized in that: The battery cells in the same gear as the battery cells to be graded include: A cell that is in the same grade as the cell to be graded after primary graded by conversion efficiency; or The battery cells that are in the same grade as the battery cells to be graded after the first grade classification is performed using conversion efficiency and the second grade classification is performed using voltage.

8. The battery cell binning method according to claim 1, characterized in that: The battery cells to be binned are binned according to the equivalent luminous power of the battery cells to be binned, including binning at level two and above.

9. The battery cell binning method according to claim 1, characterized in that: The battery cells to be binned are binned according to the equivalent luminous powers of the battery cells to be binned, including: According to the equivalent luminous power of each of the cells to be binned, obtaining the equivalent luminous power distribution intervals of the plurality of cells to be binned; The plurality of cells to be binned in the equivalent luminous power distribution range are binned with each bin variation interval not exceeding a threshold value B; The threshold value B is any value between 0.05W and 0.2W.

10. The battery cell binning method according to claim 1, characterized in that: The battery cell includes a TOPCon battery cell, a PERC battery cell or a HJT battery cell.

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