Light beam induced current measurement system based on galvanometer rapid scanning and solar cell defect detection method

Abstract

The invention discloses a galvanometer rapid scanning light beam induced current measurement system and a solar cell defect detection method, and aims to improve the efficiency and precision of solar cell defect detection. The system adopts a two-dimensional galvanometer scanning technology and combines with an oscilloscope for high-speed data acquisition, so that the surface light current signal of the solar cell is quickly acquired. A galvanometer is controlled to scan a battery at a high speed, a trans-impedance amplifier is used to convert a photocurrent signal into a voltage signal, and an oscilloscope is used to carry out synchronous trigger acquisition, so that a high-resolution photocurrent distribution diagram is obtained. According to the system, the scanning speed is remarkably improved, and the scanning rate is far higher than the detection efficiency of an existing LBIC system; the oscilloscope is used for triggering type multi-frame acquisition, so that the accuracy of data acquisition and time sequence synchronization are ensured, and the signal quality is improved; the method can be applied to the laser damage analysis of the solar cell, and the accurate evaluation of the internal damage of the cell is realized by monitoring the light current change of an irradiation area. The method can be widely applied to the fields of solar cell defect detection and photoelectric property research.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cell defect detection, and particularly relates to a beam induced current measurement system based on galvanometer fast scanning and a solar cell defect detection method. Background Art

[0002] The beam induced current (LBIC) technology is a high-resolution, non-contact non-destructive detection method for solar cells, and has important application value in characterizing the local optoelectronic properties and defect distribution of solar cells. The basic principle of the LBIC technology is to use a focused laser beam as a local light source to perform precise two-dimensional scanning on the surface of a solar cell, measure the photocurrent response of the irradiated area, and finally generate a photocurrent distribution map of the entire measurement area. This method can effectively reveal the optoelectronic conversion characteristics of the material and identify local defects caused by manufacturing processes or operating environments, such as microcracks, metal contamination, and process non-uniformity, etc., thereby providing important experimental basis for the quality control and performance optimization of solar cells.

[0003] Traditional LBIC systems usually adopt a single-point scanning method, and its scanning rate is low, resulting in a serious limitation of the detection efficiency and restricting its large-scale application in industrial production to a certain extent. The currently disclosed LBIC detection systems still have some technical bottlenecks and limitations in the actual application process, which are mainly reflected in: for the detection of defects with different depths, the existing technologies usually rely on multiple lasers with different wavelengths to adapt to the absorption characteristics of the material for light with different wavelengths, and may need to separately configure corresponding laser power supplies for each laser. This method not only increases the volume and cost of the experimental equipment, but also improves the complexity of the system, making the light source management and power control more cumbersome. In addition, after replacing the laser, the entire optical path system needs to be readjusted and precisely calibrated, further affecting the stability and usability of the detection system and restricting its application in high-throughput detection or automated detection scenarios.

[0004] In the existing research, the selection of the beam wavelength is mainly based on the spectral absorption range of the solar cell, usually only considering the basic absorption characteristics of the material, and lacking a systematic optimization strategy and an intelligent wavelength selection scheme. This limitation may lead to insufficient detection sensitivity, unable to fully utilize the potential of light with different wavelengths in revealing defects with different depths, and affecting the accuracy of the measurement results. Especially when detecting micro-defects or composite defects, the selection of the beam wavelength has a particularly significant impact on the measurement resolution and contrast. Therefore, aiming at the limitations of the LBIC technology in light source configuration, scanning speed, and wavelength selection, etc., it is urgent to develop an efficient, accurate, and intelligent LBIC detection system to improve the detection ability and expand its application scope in industrial production and scientific research. Summary of the Invention

[0005] The object of the present invention is to provide a beam-induced current measurement system for galvanometer fast scanning and a solar cell defect detection method in view of the problems existing in the above-mentioned prior art. The proposed system combines an oscilloscope for efficient data acquisition, which can improve the detection speed and accuracy of solar cells and better detect solar cell defects.

[0006] The technical solution for achieving the object of the present invention is: a beam-induced current measurement system based on galvanometer fast scanning, the system includes a laser light source, a beam expander system, a beam splitter, a power meter, a two-dimensional galvanometer scanning module, an F-theta lens, a lifting platform, a transimpedance amplifier, an oscilloscope and a computer; the laser light source reaches the two-dimensional galvanometer scanning module through the beam expander system and the beam splitter, the power meter is arranged on the reflected light path of the beam splitter, the F-theta lens is arranged on the two-dimensional galvanometer scanning module, the solar cell sample is placed on the lifting platform, the transimpedance amplifier is connected to the solar cell sample, the oscilloscope is connected to the transimpedance amplifier, and the computer is simultaneously connected to the power meter, the two-dimensional galvanometer scanning module and the oscilloscope;

[0007] After the laser emitted by the laser light source passes through the beam expander system, its spot diameter is expanded, and then it is incident on the beam splitter. The reflected light of the beam splitter is measured by the power meter to obtain reference power information, while the transmitted light is focused on the surface of the solar cell sample through the two-dimensional galvanometer scanning module and the F-theta lens to form a focused spot; during this process, the transimpedance amplifier converts the current generated on the surface of the solar cell sample into a voltage in real time and inputs the voltage signal into the oscilloscope. The oscilloscope monitors the photocurrent output of the solar cell sample in real time. At the same time, the computer synchronously collects the measurement data of the power meter and the oscilloscope and controls the two-dimensional galvanometer scanning module to make the laser light source scan different measurement areas of the solar cell sample; after the solar cell sample is scanned, the computer finally generates a photocurrent distribution image of the solar cell sample.

[0008] Further, the laser light source outputs red laser light with a wavelength of 632.8 nm.

[0009] Further, the beam expander system expands the spot diameter to at least more than 5 mm.

[0010] Further, the focused spot is at least less than 50 μm.

[0011] Further, the incident angle of the beam splitter is set to 45°, and its beam splitting ratio is 1:9, that is, the reflected light power accounts for 10% of the total incident light power.

[0012] Further, the system is at least adapted to the case where the defect depth on the surface layer of the solar cell sample is less than 18 μm.

[0013] Furthermore, the system uses a laser marking card to control the high-speed scanning of a two-dimensional galvanometer.

[0014] Furthermore, the two-dimensional galvanometer scanning module includes two mutually perpendicular high-speed two-dimensional galvanometers, which can reflect laser light in the wavelength range of 400nm to 900nm.

[0015] Furthermore, the system synchronously controls the two-dimensional galvanometer scanning and the oscilloscope acquisition to observe the photocurrent characteristics of the sample at a millisecond-level time resolution.

[0016] On the other hand, a method for detecting defects in a solar cell based on the above-mentioned beam-induced current measurement system with rapid galvanometer scanning is provided. The method includes:

[0017] Step 1: Set the scanning conditions through a computer, including the scanning range, scanning step size, and scanning speed, and set the galvanometer scanning path, then proceed to Step 2;

[0018] Step 2: Adjust the lifting platform to accurately position the solar cell sample at the focusing position of the F-theta lens, then proceed to Step 3;

[0019] Step 3: Adjust the beam splitter to control the splitting ratio of the reflected light to the transmitted light to be 1:9; adjust the beam expander system to make the spot diameter incident on the solar cell sample meet the scanning conditions, then proceed to Step 4;

[0020] Step 4: Synchronously control the galvanometer control module to scan through the computer and control the oscilloscope to trigger data acquisition, and collect the voltage signal converted from the photocurrent signal by the transimpedance amplifier;

[0021] Step 5: Perform filtering and noise reduction processing on the collected voltage signal to eliminate power frequency interference;

[0022] Step 6: Process the collected data through a computer to obtain the photocurrent distribution map of the solar cell sample, and detect the defects of the solar cell sample based on the photocurrent distribution.

[0023] Compared with the prior art, the remarkable advantages of the present invention are:

[0024] (1) The system introduces an oscilloscope trigger acquisition mechanism. By setting the trigger voltage, the synchronization and stability of data acquisition are ensured, avoiding signal loss or delay problems that may occur in traditional acquisition methods.

[0025] (2) The high-speed two-dimensional galvanometer scanning system is adopted, enabling the light beam to perform fast, continuous, and high-precision scanning on the surface of the solar cell, greatly improving the detection efficiency and ensuring a high spatial resolution.

[0026] (3) In addition, this system combines intelligent signal processing algorithms to denoise, filter, and correct the collected photocurrent signals, effectively improving the measurement accuracy and enhancing the system's ability to detect minor defects in solar cells.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of a beam-induced current measurement system based on galvanometer fast scanning in an embodiment. Detailed Embodiment

[0029] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further elaborates on this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not used to limit this application.

[0030] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, such directional indications are only used to explain the relative positional relationship and movement conditions among components in a specific posture (as shown in the drawings). If this specific posture changes, the directional indications will also change accordingly.

[0031] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, such descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments can be combined with each other, but it must be based on the premise that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0032] In one embodiment, in combination with Figure 1, a beam-induced current measurement system based on galvanometer fast scanning is provided. The system includes a laser light source 1, a beam expander system 2, a beam splitter 3, a power meter 4, a two-dimensional galvanometer scanning module 5, an F-theta lens 6, a lifting platform 8, a transimpedance amplifier 9, an oscilloscope 10, and a computer 11; the laser light source 1 passes through the beam expander system 2 and the beam splitter 3 to reach the two-dimensional galvanometer scanning module 5, the power meter 4 is arranged on the reflected light path of the beam splitter 3, the F-theta lens 6 is arranged on the two-dimensional galvanometer scanning module 5, the solar cell sample 7 is placed on the lifting platform 8, the transimpedance amplifier 9 is connected to the solar cell sample 7, the oscilloscope 10 is connected to the transimpedance amplifier 9, and the computer 11 is simultaneously connected to the power meter 4, the two-dimensional galvanometer scanning module 5, and the oscilloscope 10;

[0033] After the laser emitted by the laser light source 1 passes through the beam expander system 2, its spot diameter is expanded, and then it is incident on the beam splitter 3. The reflected light of the beam splitter 3 is measured by the power meter 4 to obtain reference power information, while the transmitted light is focused on the surface of the solar cell sample 7 through the two-dimensional galvanometer scanning module 5 and the F-theta lens 6 to form a focused spot for precise scanning (after laser irradiation, local photo-generated carriers in the solar cell sample 7 are excited and form a photocurrent inside the cell); during this process, the transimpedance amplifier 9 converts the current generated on the surface of the solar cell sample 7 into a voltage in real time and inputs the voltage signal into the oscilloscope 10. The oscilloscope 10 monitors the photocurrent output of the solar cell sample 7 in real time. At the same time, the computer 11 synchronously collects the measurement data of the power meter 4 and the oscilloscope 10 and controls the two-dimensional galvanometer scanning module 5 to make the laser light source 1 scan different measurement areas of the solar cell sample 7; after the solar cell sample 7 is scanned, the computer 11 finally generates a photocurrent distribution image of the solar cell sample 7 by using an intelligent signal processing algorithm (this image can intuitively display problems such as micro-defects, cracks, and metal contamination inside the solar cell, providing a reliable basis and support for the quality control, defect location, and failure analysis of the solar cell).

[0034] Here, to meet the high-speed scanning requirements, the transimpedance amplifier 9 is specially selected in this system. This amplifier not only has broadband amplification characteristics but also has good anti-noise ability. Especially in the case of high-speed scanning, it can effectively suppress the interference of low-frequency noise, improve the signal quality of the system, and ensure that stable and accurate photocurrent signals can be obtained even in a complex environment. This characteristic enables this system to still efficiently and accurately perform data acquisition and signal processing during high-frequency scanning.

[0035] Here, the oscilloscope 10 adopts the rising edge trigger mode to ensure synchronous acquisition of each line of scanning signals. This design further improves the measurement accuracy and stability, and avoids signal loss or instability that may occur during high-speed scanning.

[0036] Preferably, in some embodiments, the system synchronously controls the two-dimensional galvanometer scanning and oscilloscope acquisition to observe the photocurrent characteristics of the sample at millisecond-level time resolution.

[0037] Preferably, in some embodiments, the laser light source 1 outputs red laser light with a wavelength of 632.8 nm, providing stable and high-quality laser illumination. The light source is precisely controlled by the two-dimensional galvanometer scanning module 5, enabling the laser beam to scan quickly and uniformly on the surface of the solar cell.

[0038] Preferably, in some embodiments, the beam expander system 2 expands the spot diameter to at least greater than 5 mm.

[0039] Preferably, in some embodiments, the focused spot is at least less than 50 μm.

[0040] Preferably, in some embodiments, the incident angle of the beam splitter 3 is set to 45°, and its splitting ratio is 1:9, that is, the reflected light power accounts for 10% of the total incident light power. This design ensures the uniform distribution of the laser beam and reasonable adjustment of the light intensity, further optimizing the acquisition accuracy of the photocurrent.

[0041] Preferably, in some embodiments, the system is at least adapted to the case where the surface defect depth of the solar cell sample 7 is less than 18 μm.

[0042] Preferably, in some embodiments, the system uses a laser marking card to control the two-dimensional galvanometer for high-speed scanning.

[0043] Preferably, in some embodiments, the two-dimensional galvanometer scanning module 5 includes two mutually perpendicular high-speed two-dimensional galvanometers that can reflect laser light in the wavelength range of 400 nm to 900 nm. And the scanning control of the galvanometer adopts the XY2-100 protocol, which can quickly and accurately position the light beam, thereby ensuring the accurate projection of the laser in a wide scanning area and greatly improving the flexibility and accuracy of the measurement.

[0044] The LBIC measurement system based on galvanometer fast scanning of the present invention has broad application prospects and is particularly suitable for the defect detection of solar cells under various environmental conditions. This system can not only perform laser irradiation damage analysis but also conduct optoelectronic performance tests under high-temperature environments, providing comprehensive support for different test conditions. Compared with traditional LBIC systems, this system significantly improves the efficiency and reliability of solar cell defect detection through the combination of high-speed scanning and high-precision signal acquisition. Especially in the fields of large-scale solar cell production and scientific research, it plays an important role in experimental support. The successful application of this system can provide support for the quality control, performance optimization, and scientific research of solar cells, promoting the development and progress of solar cell technology.

[0045] In one embodiment, a method for detecting defects in a solar cell based on the beam-induced current measurement system based on galvanometer fast scanning is provided. The method includes:

[0046] Step 1, set the scanning conditions through the computer 11, including the scanning range, scanning step size, and scanning speed, and set the galvanometer scanning path, then transfer to Step 2;

[0047] Step 2, adjust the lifting platform 8 to accurately position the solar cell sample 7 at the focusing position of the F-theta lens 6, then transfer to Step 3;

[0048] Step 3, adjust the beam splitter 3 to control the splitting ratio of the reflected light to the transmitted light to be 1:9; adjust the beam expander system 2 to make the spot diameter incident on the solar cell sample 7 meet the scanning conditions, then transfer to Step 4;

[0049] Step 4, synchronously control the galvanometer control module 5 to perform scanning through the computer 11 and control the oscilloscope 10 to trigger data acquisition, and collect the voltage signal converted from the photocurrent signal by the transimpedance amplifier 9;

[0050] Step 5, perform filtering and noise reduction processing on the collected voltage signal to eliminate power frequency interference;

[0051] Step 6, process the collected data through the computer 11 to obtain the photocurrent distribution map of the solar cell sample 7, and detect the defects of the solar cell sample 7 based on the photocurrent distribution.

[0052] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A beam-induced current measurement system based on rapid scanning of a galvanometer, characterized in that: The system comprises a laser light source (1), a beam expansion system (2), a spectroscope (3), a power meter (4), a two-dimensional galvanometer scanning module (5), an F-theta lens (6), a lifting platform (8), a transimpedance amplifier (9), an oscilloscope (10) and a computer (11); the laser light source (1) reaches the two-dimensional galvanometer scanning module (5) via the beam expansion system (2) and the spectroscope (3); the power meter (4) is arranged on the reflection light path of the spectroscope (3); the two-dimensional galvanometer scanning module (5) is provided with an F-theta lens (6); the solar cell sample (7) is placed on the lifting platform (8); the transimpedance amplifier (9) is connected to the solar cell sample (7); the oscilloscope (10) is connected to the transimpedance amplifier (9); and the computer (11) is simultaneously connected to the power meter (4), the two-dimensional galvanometer scanning module (5) and the oscilloscope (10); After the laser light emitted by the laser light source (1) passes through the beam expansion system (2), its spot diameter is expanded and then incident on the spectroscope (3). The reflected light of the spectroscope (3) is measured by the power meter (4) to obtain reference power information, while the transmitted light is focused onto the surface of the solar cell sample (7) via the two-dimensional galvanometer scanning module (5) and the F-theta lens (6) to form a focused spot. During this process, the transimpedance amplifier (9) converts the current generated on the surface of the solar cell sample (7) into voltage in real time, and inputs the voltage signal into the oscilloscope (10). The oscilloscope (10) monitors the photocurrent output of the solar cell sample (7) in real time. At the same time, the computer (11) synchronously collects the measurement data of the power meter (4) and the oscilloscope (10), and controls the two-dimensional galvanometer scanning module (5) to enable the laser light source (1) to scan different measurement areas of the solar cell sample (7). After the scanning of the solar cell sample (7) is completed, the computer (11) finally generates a photocurrent distribution image of the solar cell sample (7).

2. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1 is characterized in that: The laser light source (1) outputs red laser light with a wavelength of 632.8 nm.

3. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1 is characterized in that: The beam expansion system (2) expands the spot diameter to at least be greater than 5 mm.

4. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1 is characterized in that: The focused light spot is at least smaller than 50 μm.

5. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1, characterized in that: The incident angle of the beam splitter (3) is set to 45°, and its splitting ratio is 1:9, that is, the reflected light power accounts for 10% of the total incident light power.

6. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1 is characterized in that: The system is at least suitable for the case where the depth of surface defects of the solar cell sample (7) is less than 18 μm.

7. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1 is characterized in that: The system uses a laser marking card to control a two-dimensional galvanometer for high-speed scanning.

8. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1, characterized in that: The two-dimensional galvanometer scanning module (5) comprises two mutually perpendicular high-speed two-dimensional galvanometers, and can reflect laser light within a wavelength range of 400 nm to 900 nm.

9. The beam-induced current measurement system based on galvanometer rapid scanning according to claim 1, characterized in that: The system synchronously controls two-dimensional galvanometer scanning and oscilloscope acquisition to observe the photocurrent characteristics of the sample at millisecond time resolution.

10. A method for detecting defects in solar cells based on the system according to any one of claims 1 to 9, characterized in that: The method comprises: Step 1, setting scanning conditions including scanning range, scanning step length and scanning speed through a computer (11), and setting a scanning path of a galvanometer, and then proceeding to step 2; Step 2, adjusting the lifting platform (8) so that the solar cell sample (7) is accurately located at the focus position of the F-theta lens (6), and then proceeding to step 3; Step 3, adjust the beam splitter (3) to control the splitting ratio of reflected light to transmitted light to be 1:9; adjust the beam expansion system (2) to make the spot diameter incident on the solar cell sample (7) meet the scanning conditions, and proceed to step 4; Step 4, synchronously controlling the galvanometer control module (5) to scan and control the oscilloscope (10) to trigger data acquisition through the computer (11), and collecting the voltage signal converted by the transimpedance amplifier (9) from the photocurrent signal; Step 5, filtering and noise reduction processing is performed on the collected voltage signal to eliminate power frequency interference; Step 6, processing the collected data by a computer (11) to obtain a photocurrent distribution diagram of the solar cell sample (7), and detecting defects of the solar cell sample (7) based on the photocurrent distribution.

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