Method for non-contact testing of series resistance Rs of solar cell

Abstract

The invention relates to the technical field of battery measurement, and provides a method for testing series resistance Rs of a solar cell in a non-contact mode, and the method comprises the steps: 1, generating preset light intensity based on an excitation light source to irradiate the surface of the solar cell to be tested when the excitation light source meets the excitation requirements of a silicon wafer; 2, configuring a special mask on the surface of the solar cell to be detected; wherein the special mask comprises a shading area formed by at least one shading area and a light receiving area formed by at least one light transmitting area; 3, collecting a PL image of the solar cell to be detected under the special mask through a photoluminescence detection device; 4, adjusting the shielding mode of the special mask or switching the mask, repeating the steps 1-3, and obtaining a plurality of groups of PL images in different shielding states; wherein the shielding state comprises a non-shielding state or a partial shielding state; and 5, according to the brightness change values of the multiple groups of PL images, calculating an equivalent voltage difference and a current difference, and determining a series resistance Rs value of the solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell measurement, and in particular to a method for non-contact testing of the series resistance Rs of a solar cell chip. Background Art

[0002] Existing Rs tests are all contact measurement technologies. Usually, a solar simulator is used as the light source, and a probe or a special fixture is used to contact the positive and negative poles of the solar cell to collect current and voltage to obtain the IV curve. Generally, 2 to 3 light intensities are selected to test the IV of the cell respectively, and then several IV curves are combined to calculate ΔI and ΔV, thereby calculating the RS value of the cell. Under different light intensities, because the test area remains unchanged, the curves are roughly fitted and there is no strong contrast, so the accuracy of the test results is insufficient. Figure 2 shown.

[0003] Existing technology requires the use of probes / test fixtures to contact the positive and negative electrodes of solar cells during measurement. However, with the introduction of various new battery types, solar cell electrodes are becoming increasingly thinner, making precise contact increasingly difficult. This is especially true for full-back contact batteries, which place high demands on fixture positioning accuracy and contact quality. If automation issues arise, contact cannot be guaranteed, resulting in significant errors in test results.

[0004] At the same time, the use of contact methods for measurement will also lead to loss of production capacity (more time-consuming) and wear and tear (contact leads to fragmentation). Summary of the Invention

[0005] The present application proposes a method for contactless testing of the series resistance Rs of a solar cell. The present invention adopts photoluminescence (PL) technology and a special shielding mask to test the RS value of the cell. The "photoluminescence effect" is also called the "fluorescence effect": molecules in the ground state absorb light energy, are excited to an excited state, and then return to the ground state from the unstable excited state and emit photons. When the solar cell to be tested is irradiated with monochromatic light of a specific wavelength, photoluminescence will be generated. These signals can be captured by a camera, and the collected image is called a "PL image". Because the PL signal and voltage V of the solar cell are both related to the separation (Δη) of the quasi-Fermi level, the brightness of the PL image can be directly related to the voltage (V).

[0006] At the same time, if the cell surface is partially blocked, the carriers generated by the photoluminescence of the light-receiving part will flow to the blocked area, resulting in a voltage drop ΔV. At this time, the fluorescence generated by the light-receiving part will be reduced accordingly, and the PL value will be reduced accordingly. Therefore, based on the principle of photoluminescence (PL), the present invention uses different masks to block the sample surface and collects the PL signals of the sample in different states in real time to obtain the ΔI and ΔV of the cell, thereby calculating the RS value of the cell. The specific method is as follows:

[0007] In a first aspect, the present application proposes a method for non-contact testing of the series resistance Rs of a solar cell, comprising:

[0008] Step 1: When the excitation light source meets the silicon wafer excitation requirements, a preset light intensity is generated based on the excitation light source to illuminate the surface of the solar cell to be tested;

[0009] Step 2: placing a special mask on the surface of the solar cell to be tested; wherein the special mask comprises a light-shielding area formed by at least one blocking area and a light-receiving area formed by at least one light-transmitting area;

[0010] Step 3: Use a photoluminescence detection device to collect the PL image of the solar cell to be tested under a special mask;

[0011] Step 4: Adjust the occlusion mode of the custom mask or switch the mask, and repeat steps 1 to 3 to obtain multiple sets of PL images under different occlusion states. The occlusion state includes: unblocked state or partially blocked state. This is equivalent to coordinating the occlusion state with the switching mask and occlusion mode to achieve a coordinated PL image grouping effect. After grouping, PL images with different brightness change values ​​can be directly separated.

[0012] Step 5: Based on the brightness change values ​​of multiple sets of PL images, calculate the equivalent voltage difference and current difference to determine the series resistance Rs value of the solar cell.

[0013] In combination with the first aspect, the excitation light source is configured to have a wavelength or photon energy sufficient to excite photoluminescence of the cell to be tested;

[0014] Among them, the excitation light source is a laser or LED light source, and the excitation light source includes a cross excitation light source, a single-sided excitation light source and a vertical excitation light source.

[0015] In combination with the first aspect, the special mask includes an unshielded state in which no light is blocked on the solar cell, and a shielded area that is configured to be perpendicular to the fine grid lines on the surface of the solar cell to be tested, forming a partial shading state with alternating light and dark areas; wherein the shape of the shielded area is linear, stripe, grid or dot matrix.

[0016] In combination with the first aspect, the PL detection device includes any one of a camera, a silicon detector, a germanium detector, and an InGaAs detector, and is configured with a lens and a filter to focus the PL signal.

[0017] In combination with the first aspect, the special mask is integrated on an automated turntable, which includes multiple workstations. Each workstation is equipped with a mask of a different version, and the mask is switched by rotation to complete multi-state PL image acquisition; wherein, the automated turntable is configured to have a non-contact Rs test, and the response is started.

[0018] In combination with the first aspect, the different blocking states include no mask at all, blocking by a single mask, and blocking by a combination of multiple masks.

[0019] In combination with the first aspect, the step of calculating the equivalent voltage difference and current difference under different shading states based on the brightness change values ​​of the multiple sets of PL images includes:

[0020] By comparing the brightness distribution of multiple sets of PL images in the shielded state and the unshielded state, the average brightness of the effective light-receiving area and the effective shielded area is extracted;

[0021] According to the average brightness, a brightness-voltage correlation difference model based on the quasi-Fermi level is constructed to determine the current difference of the battery cell in different states.

[0022] In combination with the first aspect, the step of calculating the equivalent voltage difference and current difference under different shading states based on the brightness change values ​​of the multiple sets of PL images further includes:

[0023] By comparing the brightness distribution of PL images in the fully shielded state and the unshielded state, the brightness gradient change at the edge of the light-receiving area is extracted, and a corresponding relationship model between the carrier recombination rate and the photogenerated current is established based on the gradient change.

[0024] Differentiating the brightness attenuation curve at the junction of the light-shielding area and the light-receiving area to generate a voltage drop compensation parameter associated with the lateral potential distribution;

[0025] Performing a spatial convolution operation on the brightness gradient change and the brightness attenuation curve, and dynamically constructing a correlation equation between the open-circuit voltage and the short-circuit current by combining the light intensity attenuation compensation factor and the temperature drift correction coefficient;

[0026] The series resistance influencing factor in the correlation equation is iteratively optimized until the calculated equivalent voltage difference and the measured current difference meet a preset matching threshold, and the final series resistance value is output.

[0027] In combination with the first aspect, the excitation light source is configured as a multi-light source array;

[0028] When the surface of the solar cell to be tested is illuminated by a multi-light source array;

[0029] The multi-light source array is configured with a plurality of combined illumination modes, and each combined illumination mode is configured with a corresponding periodically alternating special mask.

[0030] In combination with the first aspect, the brightness spatial distribution of multiple groups of PL images under different mask states is obtained to form an Rs spatial distribution map of the solar cell;

[0031] According to the Rs spatial distribution map, the difference in local area values ​​is determined, and the local Rs abnormal information is determined;

[0032] According to the local Rs abnormality information, the distribution position and area ratio of the Rs abnormal area are determined, and the defect severity level is output.

[0033] The beneficial effects of this application are:

[0034] This application utilizes non-contact photoluminescence (PL) technology combined with mask modulation to achieve contactless Rs testing, addressing the damage and efficiency issues associated with traditional contact testing. A custom mask automatically modulates the distribution of photocurrent on the cell surface, converting the electrical parameter (Rs) into an optical signal (PL brightness variation). Comparing PL images under multiple obstructions improves the accuracy of Rs calculations, overcoming the limitations of a single PL image, which can only provide qualitative analysis.

[0035] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 This is a flow chart of a method for non-contact testing the series resistance Rs of a solar cell according to an embodiment of the present invention;

[0039] Figure 2 A graph showing a measured current-voltage curve in the prior art according to an embodiment of the present invention;

[0040] Figure 3 This is a diagram showing the first component of the technical solution in an embodiment of the present invention;

[0041] Figure 4Schematic diagram of a solar cell to be tested under different masks in an embodiment of the present invention;

[0042] Figure 5 This is a second component diagram of the technical solution in an embodiment of the present invention;

[0043] Figure 6 This is a third component diagram of the technical solution in an embodiment of the present invention;

[0044] Figure 7 Schematic diagram of mask switching of an automated turntable in an embodiment of the present invention;

[0045] Figure 8 Schematic diagram of the defect state of the abnormal area in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0047] This application uses a monochromatic light source with a specific wavelength that meets the excitation conditions as the excitation light source, such as a laser or LED, and uses a camera + lens + filter as a detection device for the PL signal of the battery cell. The excitation light source is then controlled to maintain a light intensity of 1sun, and the PL image of the battery cell is detected without a mask and with different masks. By analyzing the changes in the brightness of the PL image under the same and different mask conditions, the values ​​of ΔV and ΔI are indirectly obtained, thereby calculating the series resistance of the battery cell.

[0048] The detailed process is as follows:

[0049] Example 1:

[0050] like Figure 1 As shown, the present application proposes a method for non-contact testing of the series resistance Rs of a solar cell, comprising:

[0051] Step 1: When the excitation light source meets the silicon wafer excitation requirements, a preset light intensity is generated based on the excitation light source to illuminate the surface of the solar cell to be tested; a monochromatic light source (such as an 808nm laser) is used to excite carrier recombination and luminescence, and a precision light intensity adjustment module, such as an acousto-optic modulator, is used to control the incident photon flux to ensure that the photogenerated carrier concentration matches the preset value. Monochromatic light avoids multi-wavelength interference and improves carrier excitation efficiency. The preset light intensity is standardized to ensure consistency of test conditions and eliminate the influence of ambient light.

[0052] Step 2: Place a custom mask on the surface of the solar cell to be tested. The custom mask comprises at least one light-blocking region (shading area) and at least one light-transmitting region (light-receiving area). The mask's light-blocking region, such as the stripes and grids described in this application, forms a spatially heterogeneous photogenerated current distribution with the light-receiving region. The light-blocking region, lacking an excitation light source, results in a localized voltage drop due to lateral carrier diffusion. The light-receiving region, due to the concentration of photogenerated current, forms a high-carrier concentration region. By varying the light-blocking / light-receiving ratio, the current can be gradient-regulated.

[0053] Step 3: A photoluminescence (PL) image of the solar cell under test is captured using a specially designed mask. The PL imager utilizes a Peltier-cooled CCD, which captures the specific wavelength of luminescence through a narrowband filter. The image acquisition time is controlled within a preset timeframe. The low-temperature CCD suppresses thermal noise, enabling rapid acquisition, ensuring that carrier diffusion does not blur the image.

[0054] Step 4: Adjust the shading pattern of the custom mask or switch the mask, repeating steps 1 to 3 to obtain multiple sets of PL images under different shading conditions; by rotating the mask or replacing different masks, the spatial distribution pattern of the shading area is changed. Multi-angle / multi-scale data fusion reduces resistance calculation errors, and dynamic modulation eliminates the interference of local defects on the overall measurement. This application introduces multiple sets of current gradients by switching the mask, for example: from full shading to partial shading to no shading, to cover different Rs sensitivity ranges.

[0055] Step 5: Based on the brightness changes from multiple sets of PL images, the voltage and current differences between the illuminated and shaded areas are calculated to determine the series resistance (Rs) of the solar cell. Non-contact measurement avoids probe damage, and a weighted averaging algorithm for multiple data sets provides more accurate results. In practical implementation, PL images rapidly scan the entire cell (in milliseconds), combined with image analysis algorithms, to enable online detection.

[0056] Example 2:

[0057] The excitation light source is configured to have a wavelength or photon energy sufficient to excite the photoluminescence of the cell to be tested;

[0058] The excitation light source is a laser or LED light source, and the excitation light source includes a cross excitation light source, a single-side excitation light source and a vertical excitation light source. Figure 4 , 1, 2, 4 or more excitation light sources can be used; under the irradiation of monochromatic light of a specific wavelength, photoluminescence will be generated to provide measurement parameters.

[0059] Example 3:

[0060] See Figure 7The special mask includes an unshielded state in which no light is blocked on the solar cell, and a shielded area which is configured to be perpendicular to the fine grid lines on the surface of the solar cell to be tested, forming a partially shielded state with alternating light and dark areas; wherein the shielded area is in the shape of a line, stripe, grid or dot matrix.

[0061] The shading area in this application has stripes and grids, which suppress the local photogenerated current through physical shielding, forcing the carriers to diffuse laterally to the adjacent light-receiving area, so that the local Rs difference can be detected; by mechanically translating or replacing the mask, such as full shading → partial shading → no shading, multiple sets of current gradients and multiple shading modes are introduced to reduce local defects and improve measurement accuracy.

[0062] Example 4:

[0063] See Figure 5 and Figure 6 PL detection devices include cameras, silicon detectors, germanium detectors, InGaAs detectors and other detection devices that can collect PL fluorescence signals, and can be configured with lenses to focus PL signals.

[0064] In this application, the function of the PL detection device is to collect photoluminescence signals, the filter transmits the PL signal wavelength, filters out the reflected light of the excitation light source and ambient stray light, and focuses through the lens, so that the collected signal is more accurate.

[0065] Example 5:

[0066] See Figure 3 (Dual excitation light source, camera, lens and filter test combination), Figure 5 (Dual excitation light source, photodetector, lens and filter test combination), Figure 6 (single excitation light source, camera, lens and filter test combination) and Figure 7 (Dual excitation light source, camera, lens and filter test combination, and continuous mask switching under the automated turntable); It can be seen that when the special mask is integrated on the automated turntable, the automated turntable contains multiple workstations, each station is equipped with a mask of a different version, and the mask is switched by rotation to complete multi-state PL image acquisition; Among them, the automated turntable is configured to have a non-contact Rs test, and the response is started.

[0067] In actual implementation, the automated turntable can integrate multiple sets of different geometric parameters, such as mask plates with stripe width W and spacing D, and rotate through a servo motor to achieve millisecond-level rapid switching.

[0068] Example 6:

[0069] See Figure 4 ,Different occlusion states include no mask at all, single mask occlusion, and multiple mask combination occlusion.

[0070] This application realizes the comparison of multiple groups of PL signals by transforming the occlusion state and mask combination. However, in this application, different occlusion states are mainly achieved through automatic switching and automatic measurement by an automated turntable combined with a special mask.

[0071] Example 7:

[0072] The step of calculating the equivalent voltage difference and current difference under different shading states according to the brightness change values ​​of the multiple sets of PL images includes:

[0073] By comparing the brightness distribution of multiple sets of PL images in the shielded state and the unshielded state, the average brightness of the effective light-receiving area and the effective shielded area is extracted;

[0074] According to the average brightness, a brightness-voltage correlation difference model based on the quasi-Fermi level is constructed to determine the current difference of the battery cell in different states.

[0075] In this application, because the PL value and voltage V of a solar cell under an excitation light source are both related to the separation (Δη) of the quasi-Fermi level, the brightness of the PL image can be directly related to the voltage (V), thereby calculating the voltage difference between the effective light-receiving area and the effective light-shielding area. Furthermore, because the current of a solar cell is linearly related to light intensity, the current difference of the cell under different states can be calculated by irradiating the cell with a preset light intensity.

[0076] Example 8:

[0077] The step of calculating the equivalent voltage difference and current difference under different shading states based on the brightness change values ​​of the multiple sets of PL images further includes:

[0078] By comparing the brightness distribution of PL images in the fully shielded state and the unshielded state, the brightness gradient change at the edge of the light-receiving area is extracted, and a corresponding relationship model between the carrier recombination rate and the photogenerated current is established based on the gradient change.

[0079] Differentiating the brightness attenuation curve at the junction of the light-shielding area and the light-receiving area to generate a voltage drop compensation parameter associated with the lateral potential distribution;

[0080] Performing a spatial convolution operation on the brightness gradient change and the brightness attenuation curve, and dynamically constructing a correlation equation between the open-circuit voltage and the short-circuit current by combining the light intensity attenuation compensation factor and the temperature drift correction coefficient;

[0081] The series resistance influencing factor in the correlation equation is iteratively optimized until the calculated equivalent voltage difference and the measured current difference meet a preset matching threshold, and the final series resistance value is output.

[0082] During implementation, the technical principle for calculating the equivalent voltage difference and current difference based on the brightness change values ​​of multiple sets of PL (photoluminescence) images relies primarily on the positive correlation between photoluminescence intensity and carrier concentration. When the shielded area and the light-receiving area form different carrier distributions due to the dynamic switching of the mask, the brightness difference (ΔL) of the PL image directly reflects the equivalent voltage difference (ΔV) of the quasi-Fermi level splitting. The equivalent voltage difference (ΔV) is determined by the brightness difference (ΔL) of the PL image on the surface of the solar cell. In specific implementations, the equivalent voltage difference is determined by multiplying the Boltzmann constant by the temperature, then dividing by the electron charge, and then multiplying it by the natural logarithm of the ratio of the brightness of the light-receiving area to the brightness of the shielded area. This is the voltage change caused by the difference in carrier distribution between the illuminated area and the non-illuminated area under specific physical conditions (the specific conditions of this solution are energy storage materials such as solar cells), combined with thermodynamic effects. Under the thermodynamic effect, thermal motion causes the carrier distribution to change. The brightness of the light-receiving area and the shielded area determines the value of the logarithmic term. The two work together to determine the potential difference.

[0083] The corresponding model converts optical signals into electrical parameters by exponentially correlating PL brightness with the carrier recombination rate, quantifying the local voltage gradient in the absence of physical contact. The current difference (ΔJ) is calculated based on the difference in lateral current density distribution between the light-shielding and light-receiving regions. The series resistance is derived using Ohm's law (Rs = ΔV / ΔJ) by combining mask geometry with known short-circuit current Isc or independent light intensity calibration data. Geometric parameters include the ratio of stripe width W to spacing D, which regulates current gradient sensitivity.

[0084] Multiple sets of PL images are processed under different shading conditions, such as full shading and partial shading, to introduce redundant data and then statistically average and reduce local defects.

[0085] For example: interference from hidden cracks or edge leakage, while covering sensitive areas of different Rs components;

[0086] Base resistance R0, contact resistance R4 and lateral resistance R3, improve measurement accuracy to ±0.05Ω·cm 2 .

[0087] In addition, the dynamic switching of masks and light intensity control systems, for example, a high shading ratio mask combined with low light intensity expands the detection range, and the rapid analysis of brightness changes makes the single-chip detection time less than 5 seconds, thereby solving the problem that the traditional IV curve method cannot achieve micro-area resolution. The non-contact method prevents the probe from damaging the passivation layer, which is particularly suitable for high-precision online detection of new battery structures such as TOPCon and HJT.

[0088] Example 9:

[0089] The excitation light source is configured as a multi-light source array;

[0090] When the surface of the solar cell to be tested is illuminated by a multi-light source array;

[0091] The multi-light source array is configured with a plurality of combined illumination modes, and each combined illumination mode is configured with a corresponding periodically alternating special mask.

[0092] In the actual implementation of the present invention, the multi-light source array forms a uniform illumination spot, which illuminates the surface of the solar cell, bringing a more uniform PL image and preventing the test result error caused by the uneven light source.

[0093] In a multi-light source array, each sub-light source can be configured with monochromatic light of a different wavelength, forming a multi-wavelength monochromatic light source array. When light of different wavelengths is irradiated on the cell, the fluorescence images excited can reflect the string resistance information at different depths of the cell. PL images under multiple combined irradiation modes can be obtained, and the brightness average of the PL images at different wavelengths can be extracted. Defect anomalies at different depths on the surface, body, or back of the cell can be analyzed. The specific wavelength light source needs to meet the wavelength (or photon energy) conditions for stimulating the PL of the cell to be tested. It can be a single-wavelength LED, a continuous-wavelength LED, a combination of multiple-wavelength LEDs, a single-wavelength laser, a continuous-wavelength light source, or a light source formed by adding a filter to remove a specific wavelength.

[0094] Example 10:

[0095] The step 5 further comprises:

[0096] The spatial distribution of the brightness of multiple sets of PL images under different mask conditions is obtained to construct a spatial Rs distribution map of the solar cell. This map maps all local Rs values ​​to positions on the cell surface. Its function is to expand the traditional single-point Rs test to visualize the Rs distribution across the entire cell. The brightness (grayscale value) of the PL image is positively correlated with the local carrier recombination rate of the cell, which is directly related to the local current density. By analyzing the brightness changes of the PL images under multiple mask conditions, the Rs value of the local area can be determined.

[0097] According to the Rs spatial distribution map, the difference in local area values ​​is determined, and the local Rs abnormal information is determined;

[0098] Local Rs anomaly information is determined by comparing the numerical differences between regions in the Rs spatial distribution map. This is used to prevent potential performance issues in a cell due to local anomalies despite a normal overall Rs value. A normal cell's Rs should have a uniform spatial distribution. If a region's Rs is significantly higher or lower than the average, a local defect exists. Local defects include poor electrode contact, hidden cracks, and material inhomogeneity.

[0099] According to the local Rs abnormal information, the distribution position and area ratio of the Rs abnormal area are determined, and the defect severity level is output, such as Figure 8 As shown in the figure, the bright area is the abnormal position of Rs.

[0100] The defect severity level can provide a quantitative basis for cell sorting and process improvement. By statistically analyzing the distribution location (such as edge, center) and area ratio of abnormal areas, the actual implementation can be combined with industry standards and photovoltaic module EL / PL testing specifications to perform grade classification.

[0101] At the photoelectric conversion level, this application uses a monochromatic light source to excite solar cells, producing a photoluminescence effect of a specific wavelength. When the photon energy is higher than the band gap of the cell material, electron-hole pairs are excited at the PN junction, and their composite luminescence intensity is exponentially related to the carrier concentration. The light-receiving area maintains a high carrier concentration state under continuous illumination, while the light-blocking area forms a carrier concentration gradient due to light blocking. The concentration difference caused by the concentration gradient is converted into brightness contrast in the PL image.

[0102] For spatially resolved measurements, a custom mask creates a controllable carrier transport environment. The mask's geometric structure creates an artificially designed potential distribution field, generating carrier diffusion at the boundary between the light-receiving and light-blocking regions. By using multiple sets of different blocking patterns, multiple localized micro-area circuits are constructed on the battery surface. The carrier transport characteristics of each micro-area can be used to independently characterize the series resistance of the corresponding area, thereby determining the corresponding resistance value.

[0103] At the signal processing level, brightness changes in PL images correspond to voltage distribution information. Because quasi-Fermi level separation corresponds to luminous intensity, the difference in brightness between the illuminated and shaded areas can be characterized as a local voltage difference. Through comparative calibration with standard devices, a quantitative benchmark for brightness-to-voltage conversion is established, converting optical signals into electrical parameters. Dynamic weighted fitting of multiple sets of shading pattern data effectively separates the interference of intrinsic resistance effects and parasitic parameters.

[0104] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for non-contact testing of the series resistance Rs of a solar cell, characterized in that: include: Step 1: When the excitation light source meets the silicon wafer excitation requirements, a preset light intensity is generated based on the excitation light source to illuminate the surface of the solar cell to be tested; Step 2: placing a special mask on the surface of the solar cell to be tested; wherein the special mask comprises a light-shielding area formed by at least one blocking area and a light-receiving area formed by at least one light-transmitting area; Step 3: Use a photoluminescence detection device to collect the PL image of the solar cell to be tested under a special mask; Step 4: Adjust the shielding mode of the custom mask or switch the mask, repeat steps 1 to 3, and obtain multiple sets of PL images under different shielding states; the shielding state includes: unshielded state or partially shielded state; Step 5: Based on the brightness change values ​​of multiple sets of PL images, calculate the equivalent voltage difference and current difference to determine the series resistance Rs value of the solar cell.

2. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The excitation light source is configured to have a wavelength or photon energy sufficient to excite the photoluminescence of the cell to be tested; Among them, the excitation light source is a laser or LED light source, and the excitation light source includes a cross excitation light source, a single-sided excitation light source and a vertical excitation light source.

3. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The specially designed mask includes an unshielded state in which no light is blocked on the solar cell, and a shielded area that is configured perpendicular to the fine grid lines on the surface of the solar cell to be tested, forming a partially shielded state with alternating light and dark areas; wherein the shielded area is in the shape of a line, stripe, grid or dot matrix.

4. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, wherein: The PL detection device includes any one of a camera, a silicon detector, a germanium detector, and an InGaAs detector, and is configured with a lens and a filter to focus the PL signal.

5. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The special mask is integrated on an automated turntable, which includes multiple workstations. Each workstation is equipped with a mask of a different version. The mask is switched by rotation to complete multi-state PL image acquisition; wherein, the automated turntable is configured to have a non-contact Rs test, and the response is started.

6. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The different shading states include no mask at all, shading by a single mask, and shading by a combination of multiple masks.

7. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: Calculating the equivalent voltage difference and current difference according to the brightness change values ​​of the multiple sets of PL images includes: By comparing the brightness distribution of multiple sets of PL images in the light-shielded state and the PL images in the unshielded state, the average brightness of the effective light-receiving area and the effective light-shielded area is extracted; According to the average brightness, a brightness-voltage correlation difference model based on the quasi-Fermi level is constructed to determine the current difference of the battery cell in different states.

8. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The calculating of the equivalent voltage difference and current difference according to the brightness change values ​​of the plurality of PL images further includes: By comparing the brightness distribution of PL images in the fully shielded state and the unshielded state, the brightness gradient change at the edge of the light-receiving area is extracted, and a corresponding relationship model between the carrier recombination rate and the photogenerated current is established based on the gradient change. Differentiating the brightness attenuation curve at the junction of the light-shielding area and the light-receiving area to generate a voltage drop compensation parameter associated with the lateral potential distribution; Performing a spatial convolution operation on the brightness gradient change and the brightness attenuation curve, and dynamically constructing a correlation equation between the open-circuit voltage and the short-circuit current by combining the light intensity attenuation compensation factor and the temperature drift correction coefficient; The series resistance influencing factor in the correlation equation is iteratively optimized until the calculated equivalent voltage difference and the measured current difference meet a preset matching threshold, and the final series resistance value is output.

9. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The excitation light source is configured as a multi-light source array; When the surface of the solar cell to be tested is illuminated by a multi-light source array; The multi-light source array is configured with a plurality of combined illumination modes, and each combined illumination mode is configured with a corresponding periodically alternating special mask.

10. The method for non-contact testing of the series resistance Rs of a solar cell according to claim 1, characterized in that: The step 5 further comprises: Obtain the brightness spatial distribution of multiple sets of PL images under different mask states to form the Rs spatial distribution map of the solar cell; According to the Rs spatial distribution map, the difference in local area values ​​is determined, and the local Rs abnormal information is determined; According to the local Rs abnormality information, the distribution position and area ratio of the Rs abnormal area are determined, and the defect severity level is output.

Images