A method and system for testing series resistance of solar cell

Abstract

The present invention discloses a solar cell series resistance test method and system, which is used to solve the problem of limitations in measuring series resistance with electrical contact. The method includes: providing a solar cell, the solar cell having a first surface and a second surface opposite to each other; irradiating the entire area of ​​the first surface with light, and measuring the total photoluminescence intensity value PL corresponding to the entire area oc ; Irradiate at least one partial area of ​​the first surface with the same lighting conditions, and measure at least one local photoluminescence intensity value PL corresponding to each partial area p , when there are at least two partial regions, the partial regions do not overlap; at least one local photoluminescence intensity value PL p The fitting photoluminescence intensity value PL representing the first surface is obtained by fitting; the short-circuit current I of the cell is obtained sc ; According to the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s .

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell testing, and in particular to a method and system for testing series resistance of a solar cell. Background Art

[0002] Solar cell IV tester is an important device in solar cell testing. It measures the current (I) and voltage (V) of solar cells by simulating sunlight (AM1.5G) to obtain the IV characteristic curve of solar cells and other performance parameters that reflect the quality of the cells. The main performance parameters obtained are short-circuit current (I sc )、Open circuit voltage(V oc ), fill factor (FF), photoelectric conversion efficiency (E ta )、series resistance(R s ) and the parallel resistor (R sh ) etc. The series resistance R s It is one of the important parameters of solar cells. Its value will directly affect the output characteristics and conversion efficiency of the battery. It is of great significance to study battery efficiency, optimize battery structure, control process parameters, ensure product quality and improve battery performance.

[0003] At present, get the solar cell series resistance R s The main method is: first, make complete contact with the battery cell electrodes through an electrical contact fixture (such as a probe fixture and a PCB board fixture), use the photovoltaic effect to measure the current and voltage of the battery cell under constant light conditions, and obtain the IV characteristic curve, and then calculate the series resistance R through the IV characteristic curve and Ohm's law R=V / I s However, the electrical contact fixture is not suitable for measuring some solar cells (such as cells without main grid back contact). Summary of the invention

[0004] The object of the present invention is to provide a method and system for testing the series resistance of a solar cell, so as to solve the limitation existing in measuring the series resistance by electrical contact, ensure the test accuracy and reduce the fragmentation rate.

[0005] In a first aspect, the present invention provides a method for testing series resistance of a solar cell, comprising:

[0006] Providing a battery cell, the battery cell having a first surface and a second surface opposite to each other;

[0007] The entire area of ​​the first surface is illuminated and the total photoluminescence intensity value PL corresponding to the entire area is measured. oc ;

[0008] At least one partial area of ​​the first surface is illuminated under the same lighting conditions, and at least one local photoluminescence intensity value PL corresponding to each partial area is measured. p , when there are at least two partial regions, the partial regions do not overlap;

[0009] At least one local photoluminescence intensity value PL p The fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting;

[0010] Get the short-circuit current I of the battery cell sc ;

[0011] According to the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s .

[0012] When the above technical solution is adopted, the entire area and at least a partial area of ​​the first surface of the battery cell are irradiated and lighted respectively, and a non-contact test method is adopted. The principle that the light-generated current generated by the light-receiving area of ​​the battery cell flows to the non-light-receiving area and there is a potential difference between the light-receiving area and the non-light-receiving area is used. The total photoluminescence intensity value, the fitted photoluminescence intensity value and the short-circuit current are measured, and Ohm's law is used to finally calculate the series resistance R of the battery cell. s . Compared with the existing contact fixture for contact measurement of battery cell electrodes, since the test method of series resistance in this application adopts a non-contact test method, there will be no short circuit caused by incorrect connection between the positive and negative poles of the fixture and the battery cell electrodes, and there is no need to use a contact fixture, so it will not be limited by the density of the fine grid of the battery cell, there is no requirement for the accuracy of the contact fixture, and the external resistance will not be too large due to the small number of probes in the contact fixture, affecting the test results. And there is no need to apply elastic pressure to ensure good contact between the probe and the battery cell electrode, which reduces the fragmentation rate of the battery cell and protects the electrode and battery cell structure.

[0013] In some possible implementations, when a partial area of ​​the first surface is illuminated under the same lighting conditions, a local photoluminescence intensity value PL corresponding to the partial area is obtained. p When PL=PL p ; According to the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s include:

[0014] The total photoluminescence intensity PL oc , fitting photoluminescence intensity value PL and short-circuit current Isc Substituting into formula (1), we can calculate the series resistance R of the battery cell. s ;

[0015] Formula (1);

[0016] Among them, V t is the thermal voltage, R s is the series resistance, I sc is the short-circuit current, PL is the fitted photoluminescence intensity value, PL oc is the total photoluminescence intensity value.

[0017] In the case of adopting the above technical solution, when the resistance of each area on the cell is relatively uniform, only a partial area of ​​the first surface of the cell can be irradiated and light can be received to obtain the local photoluminescence intensity value PL of the partial area. p , using formula (1) to calculate the series resistance R of the entire battery cell s Since this method only irradiates a part of the area once, it can quickly measure the series resistance R of the battery cell. s .

[0018] In some possible implementations, when at least two partial regions of the first surface are illuminated under the same lighting conditions, at least two local photoluminescence intensity values ​​PL corresponding to each partial region are obtained. p According to the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s include:

[0019] The total photoluminescence intensity PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Substituting into formula (2), the series resistance R of the battery cell is calculated. s ;

[0020] Formula (2);

[0021] Among them, V t is the thermal voltage, R s is the series resistance, I sc is the short-circuit current, PL is the fitted photoluminescence intensity value, PL oc is the total photoluminescence intensity value.

[0022] When the above technical solution is adopted, at least two partial areas of the first surface of the cell are irradiated with light under the same lighting conditions, and these partial areas do not overlap, and the local photoluminescence intensity value PL corresponding to each partial area is obtained. p When the series resistance R of the entire cell is calculated, formula (2) can be used to calculate s This method is applicable to the case where the resistance of the battery cell is uniform or uneven, and can obtain the series resistance more accurately.

[0023] In some possible implementations, irradiating at least a partial area of ​​the first surface with the same illumination condition includes:

[0024] Using at least one mask plate to successively block different blocked areas of the first surface, so that unblocked areas of the first surface are irradiated and receive light under the same lighting conditions;

[0025] Alternatively, at least one mask plate is used to successively block the light source, so that the light emitted by the light source under the same lighting conditions passes through the hollow pattern of the mask plate and illuminates at least a partial area of ​​the first surface;

[0026] Alternatively, the range of the emitted light from the light source is adjusted successively so that the emitted light is irradiated on at least a partial area on the first surface successively.

[0027] When the above technical solution is adopted, the illumination of partial areas of the first surface of the cell can be achieved in three ways: one is to directly block different blocking areas on the cell by a mask plate, the second is to block the light emitted by the light source by a mask plate so that the light source illuminates different partial areas on the cell, and the third is to directly control the range of the emitted light emitted by the light source itself so that the emitted light illuminates different partial areas on the cell. All three methods can achieve partial illumination of the cell.

[0028] In some possible implementations, at least one partial area of ​​the first surface is illuminated under the same lighting conditions, and at least one local photoluminescence intensity value PL corresponding to each partial area is measured. p ,include:

[0029] The first mask plate is used to block the first blocking area of ​​the first surface, so that the first partial area of ​​the first surface that is not blocked is irradiated and receives light, and a first local photoluminescence intensity value PL corresponding to the first partial area is measured. p1 ;

[0030] The second mask plate is used to block the second blocking area of ​​the first surface, so that the second partial area of ​​the first surface that is not blocked is illuminated under the same lighting conditions, and the second local photoluminescence intensity value PL corresponding to the second partial area is measured.p2 ; Wherein, the first shading area and the second shading area do not overlap, and the ratio of the first shading area to the entire area of ​​the first surface is a, the ratio of the second shading area to the entire area of ​​the first surface is b, and a+b=1;

[0031] At least one local photoluminescence intensity value PL p The fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting, including:

[0032] The first local photoluminescence intensity value PL p1 and the second local photoluminescence intensity value PL p2 By the formula PL = a × PL p1 +b×PL p2 The weighted average value is calculated and fitted to obtain the fitted photoluminescence intensity value PL that characterizes the first surface.

[0033] When the above technical solution is adopted, two shieldings are performed front and back by the first mask plate and the second mask plate, the two shielded areas do not overlap, and the sum of the proportions of the two shielded areas is equal to 1, and the battery cell after the two shieldings is irradiated and received light, and the weighted average of the two local photoluminescence intensity values ​​measured is calculated to obtain a fitted photoluminescence intensity value characterizing the entire battery cell. The fitted photoluminescence intensity value is the average photoluminescence intensity value of the entire battery cell, which improves the accuracy of subsequent calculation of the series resistance.

[0034] In some possible implementations, the absolute value of the difference between a and b is greater than or equal to 0 and less than or equal to 0.2. When the above technical solution is adopted, the first shielding area and the second shielding area are not much different, which ensures the balance of light received by the two partial areas of the battery cell and the uniformity of resistance. In addition, if the proportion of one partial area is too small, the influence of the minority carrier lifetime on the PL test value will increase, thereby reducing R s Therefore, by reducing the size difference between the first shielding area and the second shielding area, the accuracy of the test result of the series resistance can be improved.

[0035] In some possible implementations, the first partial region and the second partial region are both multiple strip regions perpendicular to the length direction of the thin grid of the battery cell, and the first partial region and the second partial region are alternately arranged along the length direction of the thin grid. In this arrangement, the strip regions of the first partial region and the second partial region are perpendicular to the direction of the thin grid, which is convenient for calculation, and the first partial region and the second partial region are alternately arranged along the length direction of the thin grid, which improves the uniformity of the resistance of the first partial region and the second partial region, and the obtained series resistance result is more accurate.

[0036] In some possible implementations, the first mask plate and the second mask plate are different mask plates, and the first mask plate and the second mask plate successively replace each other to cover different blocking areas of the first surface;

[0037] Alternatively, the first mask plate and the second mask plate are the same mask plate, and the first mask plate is moved and switched between two different shielding areas relative to the first surface.

[0038] When the above technical solution is adopted, double shielding of the battery cell is achieved in two ways. When the proportions of the first shielding area and the second shielding area are different, two different mask plates can be used. When the proportions of the first shielding area and the second shielding area are the same, shielding of different areas of the battery cell can be achieved by moving the position of a mask plate.

[0039] In a second aspect, the present invention further provides a solar cell series resistance testing system, comprising:

[0040] A transmission mechanism, used for carrying and transmitting the battery cells;

[0041] A test dark box is located above the transmission mechanism, and the bottom of the test dark box is open;

[0042] A light source is located in the test dark box, and is used to emit light to the battery sheet on the transmission mechanism;

[0043] An imaging component, located in the test dark box, is used to measure the photoluminescence intensity value of the battery sheet;

[0044] The mask plate mechanism is used to carry at least one mask plate and to drive the position of the mask plate between the test dark box and the transmission mechanism to move relative to the battery cell to adjust the shielding area of ​​the mask plate on the battery cell.

[0045] When the above technical solution is adopted, the transmission mechanism transmits the cell to move to the bottom opening of the test dark box, and the mask plate mechanism drives at least one mask plate to move to the position between the test dark box and the transmission mechanism one by one, that is, to the top of the cell, to adjust the shielding area of ​​the mask plate on the cell. During one shielding process, the light source emits light to the cell in the test dark box, so that the unshielded area of ​​the cell is illuminated, and the imaging component measures the illuminated cell to obtain the photoluminescence intensity value of the cell. The solar cell series resistance test system can measure the total photoluminescence intensity value and the local photoluminescence intensity value, which is convenient for the subsequent calculation of the series resistance based on the measured total photoluminescence intensity value and the local photoluminescence intensity value. The solar cell series resistance test system adopts a non-contact measurement method and has the same beneficial effects as the first aspect, which will not be repeated here.

[0046] In some possible implementations, the mask mechanism includes:

[0047] Turntable, capable of rotating;

[0048] At least two mask plates are arranged on the turntable at intervals along the circumferential direction of the turntable. The rotation of the turntable drives at least two mask plates to move alternately to the position between the test dark box and the transmission mechanism. Each mask plate forms a different shielding area on the battery cell.

[0049] When the above technical solution is adopted, the rotation of the turntable drives the mask plate thereon to move alternately to the position between the test darkroom and the transmission mechanism, that is, to the top of the battery cell, and different shielding areas are formed on the battery cell through different mask plates. After each irradiation, the turntable rotates to move the next mask plate to the top of the battery cell to complete the mask plate replacement operation. The mask plate mechanism has a simple structure and is easy to operate.

[0050] In some possible implementations, at least two mask plates include a first mask plate and a second mask plate, the hollow areas of the first mask plate and the hollow areas of the second mask plate are both strip areas, the strip areas can be perpendicular to the length direction of the fine grid of the battery cell, and the projections of the hollow areas of the first mask plate and the hollow areas of the second mask plate on the same battery cell are alternately arranged.

[0051] When the above technical solution is adopted, the hollow areas of the first mask plate and the second mask plate are strip areas, and the strip areas are perpendicular to the length direction of the fine grid. When the battery cell is blocked, the fine grid exposed from the hollow areas is complete in the length direction, which is convenient for subsequent calculations. The projections of the hollow areas of the first mask plate and the second mask plate on the same battery cell are arranged alternately, which can make the resistance of the two light-receiving parts of the battery cell uniform, and the series resistance result obtained by test is more accurate.

[0052] In some possible implementations, at least two mask plates further include a third mask plate and a fourth mask plate, the hollow area of ​​the third mask plate is used to expose the entire area of ​​the first surface of the cell, the fourth mask plate does not have a hollow area, and the fourth mask plate is used to block the entire area of ​​the first surface of the cell. In this configuration, when the third mask plate is moved above the cell, the hollow area of ​​the third mask plate is used to allow the entire area of ​​the first surface of the cell to be exposed to light, and the total photoluminescence intensity value is measured. The fourth mask plate is moved above the cell to block the entire area of ​​the first surface of the cell, so as to ensure that the photoluminescence intensity of the cell is reset to zero before being exposed to light, thereby improving the measurement accuracy.

[0053] In some possible implementations, the third mask plate, the first mask plate, the second mask plate, and the fourth mask plate are arranged in sequence along the circumferential direction of the turntable. In this way, according to the test sequence, the turntable rotates in the same direction, and the third mask plate, the first mask plate, the second mask plate, and the fourth mask plate are used in sequence for measurement, thereby avoiding the turntable from rotating back and forth, and improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0055] Figure 1 A schematic diagram of a flow chart of a method for testing series resistance of a solar cell provided by an embodiment of the present invention;

[0056] Figure 2 A schematic diagram of photoluminescence obtained after the entire first surface of a cell is irradiated with light by the test method provided in an embodiment of the present invention;

[0057] Figure 3 A schematic diagram of photoluminescence obtained after irradiating a first part of a first surface of a cell with light by the test method provided in an embodiment of the present invention;

[0058] Figure 4 A schematic diagram of photoluminescence obtained after irradiating the second part of the first surface of the cell with light by the test method provided in an embodiment of the present invention;

[0059] Figure 5 A schematic diagram of the structure of a solar cell series resistance testing system provided by an embodiment of the present invention;

[0060] Figure 6 for Figure 5 A schematic top view of the test system in FIG.

[0061] Figure 7 for Figure 5 A partial side view schematic diagram of the test system in FIG.

[0062] Figure 8 for Figure 5 A schematic structural diagram of a first mask plate of a test system;

[0063] Fig. 9 for Figure 5 A schematic structural diagram of a second mask plate of the test system;

[0064] Fig.10 A data comparison diagram of the series resistance obtained by the test method in the embodiment of the present invention and the series resistance obtained by the existing contact test;

[0065] Fig.11 This is a data comparison diagram of the series resistance obtained by the mask plate test and the series resistance obtained by the grating test in the embodiment of the present invention.

[0066] Figure numerals: 1 is a test dark box, 2 is a transmission mechanism, 3 is a mask plate mechanism, 31 is a turntable, 32 is a mask plate, 321 is a first mask plate, 322 is a second mask plate, 323 is a third mask plate, 324 is a fourth mask plate, 325 is a hollow area, and 4 is a battery cell. DETAILED DESCRIPTION

[0067] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0068] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0069] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0070] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0071] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] The existing solar cell series resistance R s The main method is: first, make complete contact with the battery cell electrodes through an electrical contact fixture (such as a probe fixture and a PCB board fixture), use the photovoltaic effect to measure the current and voltage of the battery cell under constant light conditions, and obtain the IV characteristic curve, and then calculate the series resistance R through the IV characteristic curve and Ohm's law R=V / I s The common laboratory method for obtaining the series resistance R of a solar cell s There are two methods, dual light intensity method (1-Suns and 0.5-Suns) and bright and dark field method (1-Suns and 0-Suns), but all methods are based on electrical contact, using electrical measuring instruments such as ammeters and voltmeters to test actual electrical parameters, and then calculating the series resistance by Ohm's law R=V / I. However, the electrical contact fixture is not suitable for measuring some solar cells (such as non-main grid back contact cells) because of the following problems:

[0073] 1. The PN fine grids on the back of the battery without main grid back contact are distributed in interdigitated patterns. Using too dense probe-type fixtures or PCB-type fixtures may cause the positive and negative electrodes of the fixture to be incorrectly connected to the battery cell electrodes, which can easily cause short circuits. For relatively dense fine grids, the processing accuracy of the contact fixture cannot meet the test requirements.

[0074] 2. If a fixture with fewer probes or a PCB board is used to contact the local electrode, the external resistance will be too large, affecting the test of the fill factor FF and thus the test results.

[0075] 3. In order to ensure the accuracy and repeatability of the test of the main grid-free back contact battery, elastic pressure is applied to the battery cell to ensure good contact between the probe and the battery cell electrode. This greatly increases the fragmentation rate of the battery cell and may also damage the passivation layer or electrode of the battery, thereby affecting the battery performance.

[0076] In view of the above problems, see Figure 1-Figure 4 As shown, an embodiment of the present invention provides a method for testing the series resistance of a solar cell, comprising the following steps:

[0077] Step S100, providing a cell having a first surface and a second surface opposite to each other, at least the first surface of the cell having an electrode, the electrode may be a gate electrode, and the gate electrode may include a main gate electrode and / or a fine gate electrode.

[0078] Step S200, as Figure 2 As shown, the entire area of ​​the first surface is irradiated with light, and the total photoluminescence intensity value PL corresponding to the entire area is measured. oc Among them, a laser light source can be used to emit light to the first surface of the cell, and the entire area of ​​the first surface can be illuminated by some means. Then, a PL (photoluminescence intensity) tester can be used to image and measure the illuminated cell, and the following can be obtained: Figure 2 The open circuit photoluminescence image shown in the figure is used to obtain the total photoluminescence intensity value PL of the cell from the photoluminescence image. oc .

[0079] Step S300, as Figure 3 and Figure 4 As shown, at least one partial area of ​​the first surface is illuminated under the same lighting conditions, and at least one local photoluminescence intensity value PL corresponding to each partial area is measured. p , when there are at least two partial areas, the partial areas do not overlap. The illumination conditions in step S300 are consistent with those in step S200. In step S300, each time the illumination is performed, only a partial area of ​​the first surface of the cell is illuminated, and the remaining area is not illuminated. If the illumination is performed multiple times, the illuminated areas on the cell do not overlap each time the illumination is performed, and each illuminated area corresponds to a local photoluminescence intensity value PL p The operation of obtaining the local photoluminescence intensity value is the same as the operation of obtaining the total photoluminescence intensity value in step S200, and will not be repeated herein.

[0080] Step S400: at least one local photoluminescence intensity value PL p The fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting. That is, all the local photoluminescence intensity values ​​PL obtained in step S300 are p The fitting process obtains a fitting photoluminescence intensity value PL that characterizes the first surface.

[0081] Step S500, obtaining the short-circuit current I of the battery cell sc For example, the battery cell can be tested by IV to obtain the short-circuit current I scThe IV test is a traditional contact measurement, which only needs to measure the short-circuit current, and the measurement accuracy of the short-circuit current is not affected by the probe contact and electrode structure. Therefore, only the short-circuit current in step S500 is measured by the traditional contact measurement, which will not have an adverse effect on the test results of the entire series resistance. Of course, the short-circuit current I of the battery cell can also be obtained by non-contact measurement of the battery cell. sc .

[0082] Step S600: according to the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s .

[0083] When the above technical solution is adopted, the entire area and at least a partial area of ​​the first surface of the battery cell are respectively irradiated with light under the same lighting conditions, and a non-contact test method is adopted. The total photoluminescence intensity value PL is obtained by measuring the principle that the light-receiving area of ​​the battery cell generates a photocurrent that flows to the non-light-receiving area, and there is a potential difference between the light-receiving area and the non-light-receiving area. oc , fitting photoluminescence intensity value PL and short-circuit current I sc , using Ohm's law, the series resistance R of the battery cell is finally calculated s . Compared with the existing contact fixture for contact measurement of battery cell electrodes, since the test method of series resistance in this application adopts a non-contact test method, there will be no short circuit caused by incorrect connection between the positive and negative poles of the fixture and the battery cell electrodes, and there is no need to use a contact fixture, so it will not be limited by the density of the fine grid of the battery cell, there is no requirement for the accuracy of the contact fixture, and the external resistance will not be too large due to the small number of probes in the contact fixture, affecting the test results. And there is no need to apply elastic pressure to ensure good contact between the probe and the battery cell electrode, which reduces the fragmentation rate of the battery cell and protects the electrode and battery cell structure.

[0084] In some embodiments, in step S300, when a partial area of ​​the first surface is illuminated under the same lighting conditions, a local photoluminescence intensity value PL corresponding to the partial area is obtained. p When the at least one local photoluminescence intensity value PL in step S400 is p The fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting, specifically, the local photoluminescence intensity value PL p As the fitted photoluminescence intensity value, PL = PL p In step S600, the total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I scCalculate the series resistance R of the battery cell s A specific step is:

[0085] Step S601: The total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Substituting into formula (1), we can calculate the series resistance R of the battery cell. s ;

[0086] Formula (1);

[0087] Among them, V t is the thermal voltage, R s is the series resistance, I sc is the short-circuit current, PL is the fitted photoluminescence intensity value, PL oc is the total photoluminescence intensity value, V t =KT / q=0.02568, V t is a known number, where K is the Boltzmann constant, T is the thermodynamic temperature of the cell, and q is the electron charge. Both T and q can be measured in advance and are known values. This formula (1) is a modified formula of Ohm's law. After taking the logarithm of the photoluminescence intensity value, the corresponding voltage value can be obtained. When the voltage and short-circuit current are known, the series resistance R can be obtained by calculation. s .

[0088] The above formula (1) is used to calculate the series resistance, which is applicable to the case where the cell is only partially shielded. At this time, it is assumed that the resistance of each area on the cell is relatively uniform. Therefore, only a partial area of ​​the first surface of the cell can be illuminated to obtain the local photoluminescence intensity value PL of the partial area. p , using formula (1) to calculate the series resistance R of the entire battery cell s Since this method only irradiates a part of the area once, it can quickly measure the series resistance R of the battery cell. s , improve the test efficiency of series resistance.

[0089] In some other embodiments, in step S300, when at least two partial regions of the first surface are illuminated under the same lighting conditions, at least two local photoluminescence intensity values ​​PL corresponding to the partial regions are obtained. p When the total photoluminescence intensity value PL in step S600 is oc , fitting photoluminescence intensity value PL and short-circuit current I sc Calculate the series resistance R of the battery cell s Another specific step is:

[0090] Step S602: The total photoluminescence intensity value PL oc , fitting photoluminescence intensity value PL and short-circuit current I sc Substituting into formula (2), the series resistance R of the battery cell is calculated. s ;

[0091] Formula (2);

[0092] Among them, V t is the thermal voltage, R s is the series resistance, I sc is the short-circuit current, PL is the fitted photoluminescence intensity value, PL oc is the total photoluminescence intensity value, V t =KT / q=0.02568, V t is a known number, where K is the Boltzmann constant, T is the thermodynamic temperature of the cell, and q is the electron charge. Both T and q can be measured in advance and are known values. This formula (2) is a modified formula of Ohm's law. After taking the logarithm of the photoluminescence intensity value, the corresponding voltage value can be obtained. When the voltage and short-circuit current are known, the series resistance R can be obtained by calculation. s .

[0093] The above formula (2) is used to calculate the series resistance, which is applicable to the case where the resistance of the cell is uniform or non-uniform. At least two partial areas of the first surface of the cell are illuminated under the same lighting conditions, and these partial areas do not overlap, and the local photoluminescence intensity value PL corresponding to each partial area is obtained. p When the series resistance R of the entire cell is calculated, formula (2) can be used to calculate s This method can obtain the series resistance more accurately.

[0094] This embodiment provides a specific method of irradiating a partial area of ​​the first surface of the battery cell with light. Specifically, the step of irradiating at least a partial area of ​​the first surface with light under the same lighting conditions in step S300 is:

[0095] Step S310, at least one mask plate is used to successively approach different shielding areas of the first surface so that the unshielded areas of the first surface are irradiated and receive light under the same lighting conditions. That is, the mask plate is close to the first surface of the battery cell to form shielding areas and unshielded areas on the first surface, and the light source is used to illuminate the entire first surface of the battery cell. The light can only be irradiated on the unshielded areas of the battery cell, and the unshielded areas of the battery cell form partial areas that receive light. The hollow areas of different mask plates are different and do not overlap, so the corresponding shielding areas and unshielded areas formed on the battery cell are different and do not overlap, that is, the partial areas that receive light do not overlap. It should be noted that at least one mask plate can be one or more; when there is only one mask plate, the mask plate can only approach and shield a shielding area of ​​the first surface once, or one mask plate can approach and shield different shielding areas on the first surface multiple times. When there are multiple masks, that is, at least two, each mask performs a shielding operation, and these masks can be adjacent to and shield different shielding areas of the first surface multiple times.

[0096] This method directly blocks the solar cell through a mask plate. Since the mask plate is close to the solar cell, the accuracy of the blocking pattern is easy to control. It can be applied to various light, such as parallel light or scattered light, and it is not easy to shine on the solar cell outside the hollow area of ​​the mask plate.

[0097] The data obtained by testing the method of shielding the cell with the mask plate is compared with the data obtained by testing with the existing contact fixture, and the obtained test data is shown in Table 1 below:

[0098] Table 1. Comparison of test data between the method of mask plate shielding the cell and the test method of contact fixture

[0099]

[0100] Plotted from the series resistance data in Table 1 Fig.10 ,like Fig.10 As shown, the correlation coefficient of the series resistance obtained by the two methods is 0.9394, which has a good correlation, indicating that the test results of the mask non-contact test method are more accurate.

[0101] Another embodiment provides another specific method of irradiating a partial area of ​​the first surface of the battery cell. Specifically, the step of irradiating at least a partial area of ​​the first surface under the same lighting conditions in step S300 is:

[0102] Step S320, at least one mask plate is used to successively block the light source, so that the light emitted by the light source under the same lighting conditions passes through the hollow pattern of the mask plate and irradiates at least one partial area of ​​the first surface. That is to say, the light source is directly blocked by the mask plate to adjust the range of the light emitted by the light source, so that the light of the light source passes through the hollow pattern of the mask plate and irradiates on a partial area of ​​the battery sheet. The light source is preferably a planar array laser light source, and the emitted light is parallel light. This method can be referred to as a grating method. It should be noted that at least one mask plate can be one or more; when there is only one mask plate, the mask plate can only block the light source once, so that the light passes through the hollow pattern and irradiates a partial area of ​​the first surface, or a mask plate can be used to block different positions of the light source multiple times, so that the light passes through the hollow pattern and irradiates different partial areas on the first surface. When there are multiple mask plates, that is, at least two, each mask plate blocks the light source once, and these mask plates can be successively blocked by different positions of the light source multiple times, so that the light passes through the hollow pattern and irradiates different partial areas of the first surface.

[0103] The series resistance obtained by the grating method is compared with the series resistance obtained by the method of shielding the battery cell with the mask plate in the embodiment of the present application. Fig.11 As shown, it can be seen that the correlation coefficient of the series resistance obtained by the two methods is 0.98, which has a good correlation, indicating that the results of the mask non-contact test and the grating method non-contact test are both highly accurate.

[0104] In another embodiment, another specific method of irradiating a partial area of ​​the first surface of the battery cell is provided. Specifically, the step of irradiating at least a partial area of ​​the first surface under the same lighting conditions in step S300 is:

[0105] Step S330, by successively adjusting the range of the emitted light of the light source, the emitted light is successively irradiated on at least one partial area on the first surface. In other words, the light receiving area on the cell is not adjusted by the mask plate, but the range of its emitted light is adjusted by the light source itself, such as by line laser scanning, which is equivalent to forming a local shielding effect on the cell, so that a light receiving area and a non-light receiving area are formed on the cell. This method can also be applied to the calculation formula of the series resistance in this application. It should be noted that the range of the emitted light of the light source can be adjusted only once or multiple times.

[0106] In some embodiments, when a mask is used to partially shield the cell, at least one partial area of ​​the first surface is illuminated under the same lighting conditions in step S300, and at least one local photoluminescence intensity value PL corresponding to each partial area is measured. p, specifically including the following steps:

[0107] Step S311, as Figure 3 and Figure 8 As shown, the first mask plate 321 is used to block the first blocking area of ​​the first surface, so that the first partial area of ​​the first surface that is not blocked is irradiated and receives light, and the first local photoluminescence intensity value PL corresponding to the first partial area is measured. p1 ;

[0108] Step S312, as Figure 4 and Fig. 9 As shown, the second mask plate 322 is used to block the second blocking area of ​​the first surface, so that the second partial area of ​​the first surface that is not blocked is illuminated under the same lighting conditions, and the second local photoluminescence intensity value PL corresponding to the second partial area is measured. p2 ; Wherein, the first shading area and the second shading area do not overlap, and the ratio of the first shading area to the entire area of ​​the first surface is a, the ratio of the second shading area to the entire area of ​​the first surface is b, and a+b=1;

[0109] On this basis, at least one local photoluminescence intensity value PL in step S400 is p The fitting photoluminescence intensity value PL representing the first surface is obtained by fitting. Specifically, step S401 is to convert the first local photoluminescence intensity value PL p1 and the second local photoluminescence intensity value PL p2 By the formula PL = a × PL p1 +b×PL p2 The weighted average value is calculated and fitted to obtain the fitted photoluminescence intensity value PL that characterizes the first surface.

[0110] In the case of the above technical solution, the first mask plate 321 and the second mask plate 322 are used to block the cells twice, the blocked areas do not overlap, and the sum of the proportions of the two blocked areas is equal to 1. The two local photoluminescence intensity values ​​PL are measured by irradiating the cell after the two blocks. p The weighted average value is calculated to obtain the fitted photoluminescence intensity value PL that characterizes the entire cell. The fitted photoluminescence intensity value PL is the average photoluminescence intensity value of the entire cell. Compared with the fitted photoluminescence intensity value PL obtained by only performing a partial shading, the accuracy of the fitted photoluminescence intensity value PL is improved, and the subsequent calculation of the series resistance R is improved. s In other words, when a+b=1, the first partial area and the second partial area are combined to form the entire area of ​​the first surface, and the entire area of ​​the first surface can be tested twice, so that the test results can better reflect the series resistance R of the battery cell. s .

[0111] Furthermore, in this embodiment, the first shielding area can be larger than, equal to, or smaller than the second shielding area, and the absolute value of the difference between a and b is greater than or equal to 0, and less than or equal to 0.2. That is, the size of the first shielding area and the second shielding area is not much different, which ensures the balance of light received by the two partial areas of the battery cell and the uniformity of the resistance of each light-receiving area. In addition, if the proportion of one partial area is too small, the influence of the minority carrier lifetime on the PL test value will increase, thereby reducing the series resistance R s Therefore, by reducing the size difference between the first shielding area and the second shielding area, the accuracy of the test result of the series resistance can be improved.

[0112] For example, the proportion a of the first blocking area is 0.5, and the proportion b of the second blocking area is 0.5; or, the proportion a of the first blocking area is 0.45, and the proportion b of the second blocking area is 0.55; or, the proportion a of the first blocking area is 0.4, and the proportion b of the second blocking area is 0.6, etc. As long as the size of the first blocking area and the second blocking area can be made not much different, the accuracy of the test results of the series resistance can be further improved.

[0113] like Figure 3 and Figure 4 As shown, in some embodiments, the first partial region and the second partial region are both multiple strip regions perpendicular to the length direction of the fine grid of the battery cell, and the first partial region and the second partial region are alternately arranged along the length direction of the fine grid. In this way, the strip regions of the first partial region and the second partial region are perpendicular to the fine grid direction, and there is no need to consider the angle of the non-blocking region relative to the fine grid, which is convenient for calculation. If the angle of the non-blocking region relative to the fine grid needs to be considered, the PL intensity component perpendicular to the length direction of the fine grid needs to be calculated, and the calculation process is relatively complicated. In addition, the first partial region and the second partial region are alternately arranged along the length direction of the fine grid, which improves the uniformity of the resistance of the first partial region and the second partial region, and the obtained series resistance result is more accurate.

[0114] In some embodiments, Figure 8 and Fig. 9 As shown, the first mask plate 321 and the second mask plate 322 are different mask plates, and the first mask plate 321 and the second mask plate 322 successively replace different shielding areas of the first surface. Alternatively, the first mask plate and the second mask plate are the same mask plate, and the first mask plate is moved relative to the first surface to switch between two different shielding areas.

[0115] When the above technical solution is adopted, double shielding of the battery cell is achieved in two ways. When the proportions of the first shielding area and the second shielding area are different or the same, two different mask plates can be used. When the proportions of the first shielding area and the second shielding area are the same, shielding of different areas of the battery cell can be achieved by moving the position of a mask plate.

[0116] Of course, in addition to shielding the cell twice, the cell can also be shielded three, four, five or more times. The light receiving areas formed on the cell each time do not overlap. After multiple shielding, multiple local photoluminescence intensity values ​​PL are obtained. p The weighted average value is calculated to obtain the fitted photoluminescence intensity value PL.

[0117] like Figure 5-Figure 7 As shown, the present invention also provides a solar cell series resistance test system, which can be used to perform the solar cell series resistance test method described in any of the above embodiments, and the test system includes a transmission mechanism 2, a test dark box 1, a light source, an imaging component and a mask plate mechanism 3; wherein the transmission mechanism 2 is used to carry and transmit the battery cell 4; the test dark box 1 is located above the transmission mechanism 2, and the bottom of the test dark box 1 is open, and the area of ​​the bottom opening is greater than or equal to the entire area of ​​the battery cell 4, which is used to align the battery cell 4; the light source is located in the test dark box 1, and the light source is used to emit light to the battery cell 4 on the transmission mechanism 2, so that at least a part of the area of ​​the battery cell 4 is illuminated; the imaging component is located in the test dark box 1, and is used to image the battery cell 4 after being illuminated to obtain a photoluminescence image, as shown Figure 2-Figure 4 As shown, the photoluminescence intensity value of the battery cell is measured; the mask plate mechanism 3 is used to carry at least one mask plate 32, and is used to drive the position of the mask plate 32 between the test darkbox 1 and the transmission mechanism 2 to move relative to the battery cell 4, so as to adjust the shielding area of ​​the mask plate 32 on the battery cell 4.

[0118] When the test system is working, the transmission mechanism 2 transmits the cell 4 to the bottom opening of the test dark box 1 and then stops transmission. The mask mechanism 3 drives at least one mask 32 to move to the position between the test dark box 1 and the transmission mechanism 2, that is, to the top of the cell 4 carried by the transmission mechanism 2, so as to adjust the shielding area of ​​the mask 32 on the cell 4. In each shielding process, the light source emits light to the cell 4 in the test dark box 1, so that the unshielded area of ​​the cell 4 is illuminated, and the imaging component images the illuminated cell 4 to obtain the following image: Figure 3 and Figure 4 The photoluminescence diagram shown is taken, and the photoluminescence intensity value of the cell 4 is measured.

[0119] The solar cell series resistance test system can measure the total photoluminescence intensity value and the local photoluminescence intensity value in a non-contact manner, which is convenient for subsequent calculation of the series resistance according to the measured total photoluminescence intensity value and the local photoluminescence intensity value. The solar cell series resistance test system adopts a non-contact measurement method and has the same beneficial effects as the first aspect, which will not be repeated here.

[0120] like Figure 5-Figure 7 As shown, further, in some embodiments, the mask plate mechanism 3 includes a turntable 31 and at least two mask plates 32; wherein, the turntable 31 can rotate, specifically, it can be driven by a rotating motor or other power components to drive the turntable 31 to rotate; at least two mask plates 32 are arranged on the turntable 31 at intervals along the circumferential direction of the turntable 31, and the rotation of the turntable 31 drives at least two mask plates 32 to move alternately to the position between the test darkroom 1 and the transmission mechanism 2, and these mask plates 32 have different hollow areas, and each mask plate 32 forms a different shielding area on the battery cell 4, that is, the formed local light-receiving areas are different, and the local light-receiving areas do not overlap.

[0121] When the mask plate mechanism is working, the turntable 31 rotates to drive the mask plate 32 thereon to move alternately to the position between the test darkroom 1 and the transmission mechanism 2, that is, to the position directly above the battery cell 4, and different shielding areas are formed on the battery cell 4 by different mask plates 32. After each irradiation, the turntable 31 rotates to move the next mask plate 32 above the battery cell 4, completing the replacement operation of the mask plate 32. The mask plate mechanism 3 has a simple structure and is easy to operate.

[0122] like Figure 6-Figure 9 As shown, exemplarily, at least two mask plates 32 include a first mask plate 321 and a second mask plate 322, and the hollow areas 325 of the first mask plate 321 and the hollow areas 325 of the second mask plate 322 are both strip areas, which can be perpendicular to the fine grid length direction of the battery cell 4 when the mask plate 32 is rotated above the battery cell 4, and the projections of the hollow areas 325 of the first mask plate 321 and the hollow areas 325 of the second mask plate 322 on the same battery cell 4 are alternately arranged.

[0123] When the above technical solution is adopted, the hollow areas 325 of the first mask plate 321 and the second mask plate 322 are strip areas, which are perpendicular to the length direction of the fine grid. When the cell 4 is blocked, only the blocking ratio needs to be considered, and the angle of the hollow area 325 relative to the fine grid does not need to be considered, which is convenient for subsequent calculations. If the angle of the hollow area 325 relative to the fine grid needs to be considered, the PL intensity component perpendicular to the length direction of the fine grid needs to be calculated, and the calculation process is relatively complicated. In addition, the projections of the hollow areas 325 of the first mask plate 321 and the hollow areas 325 of the second mask plate 322 on the same cell 4 are alternately arranged, which can make the resistance of the light-receiving parts of the cell 4 twice uniform, and the series resistance result obtained by the test is more accurate.

[0124] Of course, in addition to partially shielding the cell 4 by the first mask plate 321 and the second mask plate 322, the cell 4 can also be partially shielded by three, four, five or more mask plates 32, and the multiple mask plates 32 are arranged along the circumferential direction of the turntable 31, as long as the space allows, and the mask plates 32 do not interfere with each other when moving to the shielding position. The hollow areas 325 on the multiple mask plates 32 are all different.

[0125] like Figure 6 As shown, further, at least two mask plates 32 further include a third mask plate 323 and a fourth mask plate 324, the hollow area of ​​the third mask plate 323 is used to expose the entire area of ​​the first surface of the battery cell 4, the fourth mask plate 324 does not have a hollow area, and the fourth mask plate 324 is used to cover the entire area of ​​the first surface of the battery cell 4. In this way, when the third mask plate 323 moves above the battery cell 4, the hollow area of ​​the third mask plate 323 is used to make the entire area of ​​the first surface of the battery cell 4 receive light, and the total photoluminescence intensity value PL is measured. oc The fourth mask plate 324 is moved above the cell to cover the entire area of ​​the first surface of the cell 4, so as to ensure that the photoluminescence intensity of the cell 4 is reset to zero before being exposed to light, thereby avoiding the superposition of the number of photons when being exposed to light next time and improving the measurement accuracy.

[0126] Of course, the third mask plate 323 may not be provided. When the entire area of ​​the first surface of the battery cell 4 needs to be irradiated and exposed to light, the first mask plate 321 and the second mask plate 322 may be removed, and the mask plate 32 is not provided above the battery cell 4. When the bottom opening of the test dark box 1 is relatively large, and the distance between the actual power generation area on the battery cell 4 and the edge of the battery cell 4 is relatively large, the third mask plate 323 may be provided to better shield the invalid area of ​​the battery cell through the hollow area thereon, thereby achieving a better light exposure test. Of course, the fourth mask plate 324 may not be provided. After each exposure, the light source may be turned off and left to rest for a suitable period of time so that the battery cell 4 can be restored to its initial state without being exposed to light in the test dark box 1. The fourth mask plate 324 may save the resting time and the operation of turning off the light source, thereby improving the test efficiency.

[0127] Furthermore, in this embodiment, if Figure 6 As shown, the third mask plate 323, the first mask plate 321, the second mask plate 322 and the fourth mask plate 324 are arranged in sequence along the circumferential direction of the turntable 31. In this way, according to the test sequence, the turntable 31 rotates in the same direction, and the third mask plate 323, the first mask plate 321, the second mask plate 322 and the fourth mask plate 324 are used in sequence for measurement, so that the turntable 31 is prevented from rotating back and forth, and the test efficiency can be improved.

[0128] Of course, the mask plate mechanism 3 adopts Figure 5-Figure 7 In addition to the turntable method for switching the mask plate 32, a linear drive structure can also be used, that is, multiple mask plates are arranged along the same straight line, and the linear drive mechanism drives the mask plates to move linearly to the top of the battery cell to block. Alternatively, only one mask plate is included, and the position of the mask plate relative to the battery cell is driven by the linear drive mechanism to adjust different blocking areas on the battery cell. As long as the adjustment of different blocking areas on the battery cell can be achieved, it is not limited to the structural forms listed in this embodiment.

[0129] It should be noted that the transmission mechanism 2 may be a conveyor belt or a transmission roller, and a positioning component may also be provided on the transmission mechanism 2 for positioning the battery cell 4 under the test dark box 1 when the battery cell 4 moves to the bottom of the test dark box 1 .

[0130] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0131] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for testing the series resistance of a solar cell, characterized in that: include: Providing a battery cell, the battery cell having a first surface and a second surface opposite to each other; The entire area of ​​the first surface is illuminated and receives light, and a total photoluminescence intensity value PL corresponding to the entire area is measured. oc ; At least one partial area of ​​the first surface is illuminated under the same lighting conditions, and at least one local photoluminescence intensity value PL corresponding to each of the partial areas is measured. p , when there are at least two partial regions, the partial regions do not overlap; The at least one local photoluminescence intensity value PL p Fitting to obtain a fitted photoluminescence intensity value PL characterizing the first surface; Obtain the short-circuit current I of the battery cell sc ; According to the total photoluminescence intensity value PL oc , the fitted photoluminescence intensity value PL and the short-circuit current I sc The series resistance R of the battery cell is calculated s ; When a partial area of ​​the first surface is illuminated under the same lighting conditions, a local photoluminescence intensity value PL corresponding to the partial area is obtained. p When PL=PL p ; According to the total photoluminescence intensity value PL oc , the fitted photoluminescence intensity value PL and the short-circuit current I sc The series resistance R of the battery cell is calculated s include: The total photoluminescence intensity value PL oc , the fitted photoluminescence intensity value PL and the short-circuit current I sc Substituting into formula (1), the series resistance R of the battery cell is calculated. s ; Formula (1): Alternatively, when at least two partial regions of the first surface are illuminated under the same lighting conditions, at least two local photoluminescence intensity values ​​PL corresponding to each partial region are obtained. p When the total photoluminescence intensity value PL oc , the fitted photoluminescence intensity value PL and the short-circuit current I sc The series resistance R of the battery cell is calculated s include: The total photoluminescence intensity value PL oc , the fitted photoluminescence intensity value PL and the short-circuit current I sc Substituting into formula (2), the series resistance R of the battery cell is calculated. s ; Formula (2): Among them, V t is the thermal voltage, R s is the series resistance, I sc is the short-circuit current, PL is the fitted photoluminescence intensity value, PL oc is the total photoluminescence intensity value.

2. The method for testing the series resistance of a solar cell according to claim 1, characterized in that: The step of irradiating at least a partial area of ​​the first surface with light under the same lighting conditions comprises: Using at least one mask plate to successively block different blocked areas of the first surface, so that unblocked areas of the first surface are irradiated with light under the same lighting conditions; Alternatively, at least one mask plate is used to successively block the light source, so that the light emitted by the light source under the same lighting conditions passes through the hollow pattern of the mask plate and illuminates at least one of the partial areas of the first surface; Alternatively, the range of the emitted light of the light source is adjusted successively so that the emitted light is irradiated on at least one of the partial areas on the first surface successively.

3. The method for testing the series resistance of a solar cell according to claim 1, characterized in that: The at least one partial area of ​​the first surface is illuminated under the same lighting conditions, and at least one local photoluminescence intensity value PL corresponding to each of the partial areas is measured. p ,include: A first mask plate is used to block a first blocking area of ​​the first surface so that a first partial area of ​​the first surface that is not blocked is irradiated and receives light, and a first local photoluminescence intensity value PL corresponding to the first partial area is measured. p1 ; The second mask plate is used to block the second blocking area of ​​the first surface, so that the second partial area of ​​the first surface that is not blocked is irradiated and receives light, and a second local photoluminescence intensity value PL corresponding to the second partial area is measured. p2 ; Wherein, the first shading area and the second shading area do not overlap, and the ratio of the first shading area to the entire area of ​​the first surface is a, the ratio of the second shading area to the entire area of ​​the first surface is b, and a+b=1; The at least one local photoluminescence intensity value PL p The fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting, including: The first local photoluminescence intensity value PL p1 and the second local photoluminescence intensity value PL p2 By the formula PL = a × PL p1 +b×PL p2 A weighted average value is calculated, and a fitting photoluminescence intensity value PL characterizing the first surface is obtained by fitting.

4. The method for testing the series resistance of a solar cell according to claim 3, characterized in that: The absolute value of the difference between a and b is greater than or equal to 0 and less than or equal to 0.

2.

5. The method for testing the series resistance of a solar cell according to claim 3, characterized in that: The first partial region and the second partial region are both a plurality of strip regions perpendicular to the length direction of the fine grid of the battery cell, and the first partial region and the second partial region are alternately arranged along the length direction of the fine grid.

6. The method for testing series resistance of a solar cell according to claim 3, characterized in that: The first mask plate and the second mask plate are different mask plates, and the first mask plate and the second mask plate successively replace each other to cover different blocking areas of the first surface; Alternatively, the first mask plate and the second mask plate are the same mask plate, and the first mask plate is moved and switched between two different shielding areas relative to the first surface.

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