TWM669376U - Photoluminescence imaging inspection system for multi-junction solar cells - Google Patents

Abstract

A photoluminescence (PL) imaging detection technology for multi-junction solar cells is disclosed. The technology uses a specific wavelength excitation light source to irradiate the solar cells, causing them to emit photoluminescence. A filter is used to block the excitation light wavelength, allowing the photodetector to capture only the photoluminescence signals emitted by the solar cells. These signals are processed by an image processing module to generate high-resolution images that identify and locate defects within the solar cells. The system and method provided by this disclosure offer high detection sensitivity and accuracy, significantly improving the efficiency of quality control for multi-junction solar cells. It is applicable for real-time quality inspection and defect analysis during the production process of solar cells.

Description

Photoluminescence imaging detection system for multi-junction solar cells

This new patent involves the field of solar cell technology, specifically a photoluminescence (PL) image detection technology for multi-junction solar cells, which aims to improve the detection efficiency and accuracy of solar cells.

Multi-junction solar cells have attracted wide attention due to their efficient photoelectric conversion capabilities, especially in high-demand applications such as satellites and aerospace. However, the complexity of the multi-junction structure makes it easy to produce various defects during the manufacturing process, such as microcracks, dislocations and junction non-uniformity in the crystal structure, which will seriously affect the efficiency and life of the solar cell. Therefore, it is crucial to accurately detect and analyze the internal structure of multi-junction solar cells.

Traditional detection technologies such as electroluminescence (EL) technology mainly rely on applying voltage to stimulate solar cells to emit light, and then judging internal defects by detecting the intensity and distribution of the light. Although EL technology can detect most defects to a certain extent, its detection sensitivity and resolution are limited. Especially in multi-junction structures, EL technology is difficult to effectively distinguish defects between different junction layers. In addition, since EL detection needs to be carried out under the condition of battery operation, such detection method may be affected by the working state of the battery, resulting in unstable detection results.

Another commonly used detection technology is the external quantum efficiency (EQE) test. The EQE test analyzes the performance of the battery by measuring the photoelectric conversion efficiency under different wavelengths of light. However, this method is mainly used for overall performance testing and cannot accurately locate subtle internal defects. In addition, the EQE test requires step-by-step scanning of wavelengths, the detection process is time-consuming, and the sensitivity to subtle defects in multi-junction structures is low.

In order to overcome these limitations, photoluminescence (PL) technology has begun to attract the attention of the industry. PL technology uses a light source to excite solar cells, causing them to emit photoluminescence related to material properties. Since PL technology does not require the application of voltage to the battery, it can avoid the interference of the working state on the detection results. In addition, PL technology has higher sensitivity, especially in detecting tiny defects. However, the existing PL detection system still has shortcomings in detection speed and image processing capabilities, and it is difficult to meet the real-time detection needs of large-scale production lines.

Therefore, the industry urgently needs a PL image detection technology that can perform efficient and high-resolution inspection of multi-junction solar cells. This technology can not only accurately identify and locate internal defects, but also be able to adapt to the online inspection needs of large-scale production lines. This new technology is aimed at these technical challenges and proposes a multi-junction solar cell inspection system and method based on photoexcitation light imaging, aiming to improve the accuracy and efficiency of inspection.

The following is a simplified summary to provide an initial understanding of the present invention. The summary does not necessarily identify the key elements or limit the scope of the present invention, but only serves as an introduction to the following description.

This new patent invention provides a PL image detection system and method for multi-junction solar cells to solve the shortcomings of existing technologies in terms of defect detection sensitivity, resolution and real-time performance. The system includes an excitation light source, a filter, a photodetector and an image processing module. This system can perform high-resolution PL image detection on multi-junction solar cells, effectively improving detection efficiency, and can be widely used in solar cell quality control.

Specifically, the system of this novel type includes the following core components: (1) Adjustable wavelength excitation light source: This novel type adopts an adjustable wavelength laser as the excitation light source, with a wavelength range of 250 to 1500nm to adapt to the characteristics of different materials and structures in multi-junction solar cells. This adjustable wavelength laser can selectively excite specific junctions, thereby improving the detection sensitivity of internal defects in different junction layers. (2) Precise filtering technology: The system is equipped with multiple layers of filters, which can filter out the wavelength of the excitation light and only allow the optical excitation light of a specific wavelength band to pass through to the optical detector. This design ensures the purity of the captured PL signal, reduces the interference of background noise, and thus improves the detection accuracy. (3) High-sensitivity photodetector: The photodetector in this new model uses a high-sensitivity cooled charge coupled device (CCD), complementary metal oxide semiconductor (CMOS) camera or hyperspectral instrument. These cameras can work in low-light environments and reduce the impact of thermal noise through cooling devices. This configuration allows the system to capture weak PL signals, thereby realizing the detection of tiny defects. (4) Advanced image processing module: This system integrates advanced image processing technology, including image enhancement, edge detection, defect classification and three-dimensional reconstruction algorithms. These technologies can process the captured PL images in a short time, accurately identify and locate various defects inside the solar cell, such as cracks, dislocations, heterogeneous junction discontinuities, etc. The module also supports real-time defect analysis and can automatically report the detection results. (5) Multi-junction recognition capability: This new system has a multi-junction recognition function and can perform independent PL image detection on different junction layers. This function is achieved by adjusting the wavelength of the excitation light during the detection process, so that specific defects in different junction layers can be sensitively detected. (6) Real-time detection and online application: The system is designed to meet the online quality control needs of large-scale production lines. The system's high detection speed and real-time image processing capabilities enable it to be integrated into the automated production line of solar cells for real-time defect detection. This feature greatly improves the efficiency of quality control in the production process and helps to identify and eliminate potential problems in production in a timely manner.

These technical features of this new technology make it far superior to existing PL detection technology in terms of detection accuracy, sensitivity and application range. This system can not only accurately detect tiny defects in multi-junction solar cells, but can also be applied to the production of solar cells of different types and scales, providing strong quality assurance and extending the service life of solar cells.

1: Sample

2: Photoelectric excitation module

21: Light source

211: Detection light

22: Voltage source

3: Detection module

4: Electrode mechanism

41: First electrode

42: Second electrode

43: Sample seat

5: Filter module

6: Excitation light

Figure 1 is a schematic diagram of a preferred embodiment of the multi-junction solar cell photo-induced light image detection system of the present invention.

Figure 2 is a functional block diagram of the preferred embodiment.

Figure 3 is a schematic diagram of another embodiment of the multi-junction solar cell photo-induced light image detection system of the present invention.

Figure 4 shows the results of measuring multi-junction solar cells using the novel multi-junction solar cell photo-excitation imaging detection system.

The above-mentioned and other technical contents, features and effects of the new invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings.

Referring to Figures 1 and 2, the preferred embodiment of the novel material luminescence image detection device is used to detect the excitation light image of a sample 1, and the sample 1 is made of semiconductor material, such as a germanium semiconductor wafer with an epitaxial layer on the surface or other multi-junction materials, but not limited to this. The detection device includes: a photoelectric excitation module 2, a detection module 3, an electrode mechanism 4 and a filter module 5.

The photoelectric excitation module 2 includes a light source 21 and a voltage source 22. The light source 21 can emit a detection light 211 with a wavelength less than the wavelength corresponding to the energy gap of the sample 1. After the detection light 211 irradiates the sample 1, it can excite the material of the sample 1 and make the electrons jump to the excited state and leave holes. The electrons in the excited state return to a more stable low energy level, and at the same time, luminescent recombination is formed to emit light. This phenomenon is called photoluminescence, that is, the excitation light 6 is generated; the voltage source 22 can output a specific voltage to the electrode mechanism 4 to modulate the energy band structure of the sample 1, so that the electron-hole distribution position of the material of the sample 1 after photoexcitation is modulated to affect the luminescent recombination phenomenon. The detection module 3 can be a CCD or CMOS image sensor or a high spectrometer. As shown in FIG1 , the detection module 3 is disposed on one side of the photoelectric excitation module 2 and is used to capture the luminous image of the sample 1 and its spectral information. In combination with the filter module 5, it can be used to determine whether the sample 1 has defects on each interface. Through the characteristics of the image such as brightness uniformity, brightness gradient and gradient morphology, it can be known whether the sample 1 has scratches, hidden marks or material defects on each interface.

The light source 21 can be a laser light source, an LED light source or a light bulb, and the wavelength of the detection light 211 is not limited, as long as the sample 1 can be excited to emit light after being illuminated. Specifically, the wavelength of the detection light 211 can be between 250nm and 1500nm, but is not limited thereto.

The voltage source 22 can be a constant current source, a constant voltage source, an adjustable voltage source, or a voltage source with an ammeter function, as long as the material band structure of the sample 1 can be adjusted after being powered on. Specifically, the voltage range of the voltage source 22 can be between -200V and 200V, but is not limited thereto.

The electrode mechanism 4 is located below the sample 1 and is used to carry the sample 1. The electrode mechanism 4 includes a sample stand 43, a first electrode 41, and a second electrode 42 as positive and negative electrodes of the voltage source 22. The first electrode 41 and the second electrode 42 are connected to the sample 1. The first electrode 41 and the second electrode 42 can be adjusted to contact the positive and negative electrodes of the sample 1 placed on the sample stand 43 without being limited to the same contact surface to meet the measurement requirements.

The luminescence image can be used to know the luminescence characteristics of different junctions at any detection point on the sample 1. Since the luminescence characteristics are related to the purity, doping concentration, doping type, minority carrier life cycle, junction characteristics, surface recombination rate, built-in electric field and photovoltage characteristics of the sample 1, the luminescence image can be used to obtain the quality of the sample 1 material, minority carrier life cycle distribution, junction characteristics distribution, surface recombination rate distribution, built-in electric field distribution and photovoltage distribution.

When using the present invention, the light source 21, the voltage source 22 or a combination of the light source 2 of the photoelectric excitation module 2 can be selected to excite the sample. The biased PL image of the sample 1 under a specific bias can be measured individually. The biased PL image can reflect the distribution of luminescence characteristics close to different interfaces of the sample; the biased PL image under a specific bias can reflect the carrier distribution under different energy band changes and the distribution of luminescence characteristics at different sample depths.

FIG4 is the result of the multi-junction solar cell photoluminescence image detection system of the present invention measuring the multi-junction solar cell. In this example, an InGaP/GaAs/Ge multi-junction solar cell is taken as an example, and the voltage source 22 provides a voltage of 0V or 3V to the InGaP/GaAs/Ge multi-junction solar cell, and the detection module 3 captures the photoluminescence image (PL Image) of different junctions of the InGaP/GaAs/Ge multi-junction solar cell. As shown in Figure 4, Figure 4(a) is the photoluminescence image of the top junction when the voltage is 0V; 4(b) is the photoluminescence image of the middle junction when the voltage is 0V; 4(c) is the photoluminescence image of the top junction when the voltage is 3V; 4(d) is the photoluminescence image of the middle junction when the voltage is 3V. It can be seen from Figure 4 that the bright and dark spots are epitaxial defects, and the long dark lines are the broken metal lines on the front side of the InGaP/GaAs/Ge multi-junction solar cell.

In summary, the combined application of the light source 21 and the voltage source 22 of the photoelectric excitation module 2 can achieve large-area detection of the sample 1 and the distribution of its luminous characteristics in the vertical and deep directions. On the other hand, the voltage output of the voltage source 22 is automatically program-controlled. When the sample 1 is tested under different conditions, there is no need to manually remove and reinstall the sample 1 and set the measurement parameters. Therefore, the new type is very convenient to use, and the overall detection speed can be improved. Therefore, the new type has the advantages of fast detection speed and high efficiency, and is a very practical and multifunctional detection device.

However, the above is only the preferred embodiment of the present invention, and it cannot be used to limit the scope of implementation of the present invention. In other words, all simple equivalent changes and modifications made according to the scope of the patent application and the content of the description of the present invention are still within the scope of the present patent.

1: Sample

21: Light source

22: Voltage source

3: Detection module

5: Filter module

Claims (5)

A photoexcitation light image detection system for a multi-junction solar cell comprises: a photoexcitation module for irradiating a multi-junction solar cell to excite the multi-junction solar cell to emit a photoexcitation light, the photoexcitation module comprising a light source and a voltage source, the light source is used to provide light irradiation to the multi-junction solar cell, and the voltage source is used to provide a voltage to the multi-junction solar cell; a detection module, arranged on one side of the photoexcitation module, and used to capture the photoexcitation light signal emitted by the multi-junction solar cell; and A filter module is arranged at the front end of the detection module, and is used to filter out the light of the wavelength band of the photoexcitation light of the light source, so that the detection module only receives the photoexcitation light from the multi-junction solar cell. The multi-junction solar cell photo-excitation image detection system as described in claim 1, wherein the light source of the photoelectric excitation module includes a wavelength-adjustable light source with a wavelength range of 250 to 1500 nm. The photoluminescence image detection system of a multi-junction solar cell as described in claim 1, wherein the passband wavelength range of the filter module is adjusted to match different multi-junction solar cells. A photo-induced light imaging detection system for a multi-junction solar cell as described in claim 1, wherein the detection module comprises a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) camera or a hyperspectrometer, and the detection module has a cooling device to reduce the influence of thermal noise on the detection result. The photoexcitation light image detection system of a multi-junction solar cell as described in claim 1, wherein the voltage source of the photoexcitation module is used to provide a bias voltage to the multi-junction solar cell.