Method for non-contact testing of quantum efficiency EQE and short circuit current ISC of solar cell

Abstract

The application discloses a method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of a solar cell, relates to the technical field of photovoltaic device testing, and aims to solve the problems that the existing quantum efficiency and short-circuit current measurement must contact electrodes, is slow and cannot cover new gateless or process pieces; a non-contact testing method of "multi-wavelength LED excitation + local shielding + carrier lateral diffusion" is provided; the method blocks the excitation light by using a shielding filter, and only transmits the electroluminescence signal of the shielding area; the EL power of each wavelength is extracted through phase-locked amplification and deep learning denoising, the continuous EQE curve is calculated by using the calibrated incident photon flux ratio, and the ISC is obtained by convolution of the AM1.5 spectrum.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and more specifically, to a method for non-contact testing of the quantum efficiency (EQE) and short-circuit current (ISC) of solar cells. Background Technology

[0002] EQE, or External Quantum Efficiency, reflects the percentage of photons of different wavelengths that a solar cell converts into electrons. The higher the EQE, the higher the short-circuit current (ISC) of the solar cell.

[0003] Existing EQE testing methods are all contact-based measurement techniques. Typically, a monochromator generates monochromatic light of known power and shines it onto the solar cell under test; a probe / test fixture collects the current generated by the cell under each monochromatic light. The number of electrons corresponding to this current is then divided by the number of photons corresponding to each monochromatic light, such as... Figure 1 As shown, the quantum efficiency (EQE) curve can be obtained.

[0004] The existing technology has the following shortcomings:

[0005] 1. Testing requires the use of probes / test fixtures to make contact with the positive and negative electrodes of the solar cell. However, with the introduction of various new types of batteries, the electrodes of solar cells are becoming increasingly thinner, making precise contact increasingly difficult, especially for full-back contact batteries, which have very high requirements for the positioning accuracy and contact quality of the fixture. Traditional contact testing methods cannot meet these requirements.

[0006] 2. Testing can only be carried out after the cell electrodes are fully fabricated; the cells in the process phase cannot be tested.

[0007] 3. The testing speed is slow and it cannot be applied to mass production lines; it can only be used in laboratories.

[0008] To address the above problems, this invention proposes a solution. Summary of the Invention

[0009] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for non-contact testing of the quantum efficiency (EQE) and short-circuit current (ISC) of solar cells, thereby addressing the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A non-contact method for testing the quantum efficiency (EQE) and short-circuit current (ISC) of solar cells includes the following steps:

[0012] Step S1: Utilizing multiple center wavelengths λ k The LED array stimulates the solar cell with photoluminescence, and the incident photon flux density φ of each LED is recorded.ph,k ;

[0013] Step S2: A shielding filter is disposed on the surface of the solar cell to form a shielded measurement area;

[0014] Step S3: Photogenerated carriers generated in the unshielded area diffuse laterally within the semiconductor and enter the shielded measurement area. In this area, radiative recombination occurs without external electrode contact, generating an electroluminescent (EL) signal.

[0015] Step S4: Use a light energy capture device placed above the shielding filter to detect the electroluminescence (EL) light energy image of the shielded measurement area at each wavelength;

[0016] Step S5: Based on the average pixel brightness of the EL light energy image and the incident photon flux density of each LED, calculate the external quantum efficiency for each wavelength. Integrate the obtained continuous external quantum efficiency curve with the standard AM1.5 solar spectrum to calculate the short-circuit current density of the solar cell.

[0017] In a preferred embodiment, the method further includes the following steps:

[0018] Select a shielding filter with a specific transmittance, and adjust the position of the shielding filter so that it completely blocks the LED excitation light and allows the electroluminescence signal to pass through;

[0019] Optimize LED light intensity to ensure that the EL light energy signal generated in the shaded area can establish a correct relationship with the incident light photon flux; optimize the size of the shaded area to ensure that the photogenerated carriers generated in the unshaded area can effectively diffuse into the shaded area; perform homogenization processing on multi-wavelength LED light sources to ensure that the light intensity distribution of each wavelength on the surface of the tested cell is uniform.

[0020] The weak electroluminescent signal is captured by a light energy capture device to obtain an EL light energy image;

[0021] The external quantum efficiency value is calculated wavelength by wavelength, and the short-circuit current density is obtained by integration;

[0022] Based on real-time data from the temperature sensor, the final EQE and Isc values ​​of the electroluminescence intensity are corrected for temperature compensation.

[0023] In a preferred embodiment, in step S1, the incident photon flux density φ ph,k Obtained through the following formula:

[0024] Where P opt,k For LED, the measured optical power is inside the integrating sphere, h is Planck's constant, c is the speed of light, and B is the effective irradiation area of ​​the LED on the solar cell after uniform light distribution.

[0025] In a preferred embodiment, in step S1, the multi-wavelength LED light source is subjected to uniform light treatment to ensure that the light intensity distribution of each wavelength on the surface of the battery cell under test is uniform.

[0026] In a preferred embodiment, in step S1, the LED array is arranged symmetrically to ensure uniformity after multiple LEDs are superimposed.

[0027] In a preferred embodiment, in step S2, a shielding filter with a specific transmittance is selected, and the position of the shielding filter is adjusted so that it completely blocks the LED excitation light and allows the electroluminescent signal to pass through.

[0028] In a preferred embodiment, in step S3, the LED light intensity is optimized to ensure that the EL light energy signal generated in the shielded area can establish a correct relationship with the incident light photon flux; the size of the shielded area is optimized to ensure that the photogenerated carriers generated in the unshielded area can effectively diffuse into the shielded area.

[0029] In a preferred embodiment, in step S4, a light energy capturing device placed above a shielding filter is used to detect the electroluminescence (EL) light energy image of the shielded measurement area at each wavelength. The light energy capturing device includes a camera, a lens, and a filter that can shield the LED excitation light at each wavelength, allowing only the EL light energy signal to pass through.

[0030] In a preferred embodiment, temperature compensation correction of electroluminescence intensity based on real-time data from a temperature sensor specifically includes: in step S5, calculating the average pixel brightness of the EL light energy image, combining the incident photon flux density of each LED, calculating the external quantum efficiency of each wavelength, integrating the obtained continuous external quantum efficiency curve with the standard AM1.5 solar spectrum, and calculating the short-circuit current density of the solar cell.

[0031] In a preferred embodiment, in step S5, the temperature of the solar cell is monitored in real time during the test. Based on the real-time data from the temperature sensor and combined with the actual temperature coefficient of the cell, the test results are corrected to obtain the final quantum efficiency (EQE) and short-circuit current (ISC).

[0032] A non-contact quantum efficiency testing apparatus, used for the aforementioned non-contact testing of the quantum efficiency (EQE) and short-circuit current (ISC) of solar cells, comprising:

[0033] Multi-wavelength LED excitation light source modules are used to provide photoluminescence excitation;

[0034] A light-blocking filter is located in a localized area on the surface of the solar cell under test.

[0035] A light-harvesting device is positioned above a shielding filter to detect electroluminescence signals in the shielded area.

[0036] The control unit connects the LED excitation light source module and the light energy capture device. It is used to execute LED light output of different wavelengths and simultaneously perform corresponding EL light energy image capture and real-time temperature reading of the battery cell. It is also used for the calculation of quantum efficiency (EQE) and short-circuit current (ISC) and temperature compensation correction.

[0037] Temperature sensors and temperature control actuators are used to maintain a constant temperature of the solar cells during testing.

[0038] The technical effects and advantages of the non-contact testing method for quantum efficiency (EQE) and short-circuit current (ISC) of solar cells in this invention are as follows:

[0039] This invention combines photoluminescence (PL) and electroluminescence (EL) through a novel mechanism of "multi-wavelength LED excitation + partial shielding + carrier lateral diffusion-induced non-contact EL luminescence," achieving rapid measurement of external quantum efficiency (EQE) and short-circuit current (ISC) without the need for probes, electrodes, or capacitor coupling. Compared to traditional contact monochromator scanning methods, the technical effects and advantages are as follows:

[0040] Fully non-contact: Suitable for battery structures that are sensitive or have not yet formed electrodes, such as ultra-fine grid lines, full back contact, perovskite / stacked cells, eliminating poor contact, indentation damage and fixture adjustment costs.

[0041] Shifting the testing window forward: It can serve as a monitoring node for optoelectronic performance in the middle of the production line, significantly shortening the process feedback loop.

[0042] In summary, the invention overcomes the bottleneck of the difficulty in applying contact-type EQE testing to fine electrodes, early processes, and high-speed production lines, and provides a high-throughput, low-damage, cross-material spectroscopic characterization tool for industrial-scale photovoltaic quality control and the development of new batteries. Attached Figure Description

[0043] Figure 1 The quantum efficiency (EQE) curve obtained by existing technology;

[0044] Figure 2 This is a schematic diagram of the first measurement principle of the non-contact testing device of the present invention;

[0045] Figure 3 This is a schematic diagram of the second measurement principle of the non-contact testing device of the present invention;

[0046] Figure 4 This is a schematic diagram of the third measurement principle of the non-contact testing device of the present invention;

[0047] Figure 5This is a schematic diagram of the fourth measurement principle of the non-contact testing device of the present invention;

[0048] Figure 6 This is a structural diagram of the non-contact testing device module of the present invention;

[0049] Figure 7 This is a timing diagram of the non-contact testing method for quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] See Figures 2 to 6 The present invention provides an embodiment for non-contact testing of the external quantum efficiency (EQE) and short-circuit current (Isc) of solar cells, the apparatus and method comprising the following components and steps.

[0052] Device components: such as Figure 2 As shown, the non-contact testing device includes: multiple LED excitation light source modules, a solar cell under test, a shielding filter, a light energy harvesting device, and a control unit. The multiple LED light sources are arranged around the solar cell under test (at different positions and tilt angles) to provide monochromatic light of different wavelengths as photoluminescence excitation sources. The shielding filter is positioned above a portion of the surface of the solar cell under test to block the incident LED light in that area. The filter employs a custom-designed multilayer film interference structure, allowing only the fluorescence signal generated by the solar cell's photoluminescence (PL / EL) effect to pass through, while completely reflecting or absorbing the LED excitation light (i.e., the filter has a high blocking rate for all LED wavelengths and a high transmittance for the electroluminescence band).

[0053] Preferably, the filter is mounted on a movable or adjustable mechanism to facilitate the correction of its position and angle. A detector is located above the filter, aligned with the shielded area, to collect the luminous signal from that area. The detector can be a high-sensitivity camera (such as a cooled CCD or InGaAs near-infrared camera) with an imaging lens and an additional filter (to shield stray light generated by non-PL / EL effects), or it can be a photodetector directly close to the shielded area (such as a silicon detector, germanium detector, silicon-germanium alloy detector, or InGaAs detector). The control unit is electrically connected to the LED light source and the detector, used to control the sequential lighting and modulation of the LED light source, synchronously collect EL signals, and process the signals to calculate the EQE curve and Isc value. Furthermore, a temperature sensor is also installed on the solar cell to monitor the cell temperature in real time and feed it back to the control unit for subsequent temperature compensation processing.

[0054] Test method steps: The method in this embodiment utilizes the above-described apparatus to perform non-contact EQE testing on solar cells, such as... Figure 7 As shown, the specific steps include:

[0055] Step 1, Filter Calibration: First, select a filter with a specific transmittance and calibrate its positioning. The filter employs a multilayer interference filter structure, such as depositing alternating high / low refractive index dielectric films (e.g., TiO2 / SiO2) on a quartz glass substrate to form a long-pass filter. Its designed cutoff wavelength is approximately the wavelength corresponding to the bandgap of the battery material (e.g., approximately 1100 nm for silicon batteries). This filter should have high reflectivity or absorption (e.g., transmittance <0.1%, equivalent to optical density OD ≥ -5) in the LED emission band below the cutoff wavelength and high transmittance (preferably >90%) in the electroluminescence band above the cutoff wavelength. During installation, fix the filter above the area to be measured and adjust its angle and position to ensure it is directly facing and completely covers the area. Since the cutoff performance of the interference filter is related to the incident angle, the filter should be kept as perpendicular as possible to the surface of the area to be measured, for example, with an incident angle close to 0°, to ensure the expected transmittance characteristics. During calibration, the LED light source is not turned on, and the solar cells do not generate photoluminescence signals. A detector is used to detect the background signal passing through the filter, acquiring an ambient light energy image. This ambient light energy image is then subtracted from the subsequently acquired EL light energy image before calculation, eliminating the influence of environmental factors on the test results. If necessary, a filter (with a center wavelength corresponding to the electroluminescence peak) can be added to the front end of the detector to further improve the signal-to-noise ratio. After optical calibration is completed, the position of the filter relative to the solar cells is recorded, and it is fixed in the calibration position to prepare for formal measurements.

[0056] Specifically, to facilitate subsequent EQE quantization, the input power of each LED needs to be converted into photon flux density. For LED k with wavelength λk, the integrating sphere optical power P is measured. opt,k Then, its photon flux density In the formula, h is Planck's constant, c is the speed of light in a vacuum, and B is the effective irradiation area of ​​the LED on the solar cell after uniform light distribution.

[0057] After completing LED calibration and system correction, the solar cell under test was tested. Electroluminescence (EL) images of its shaded area were acquired according to the formal measurement conditions. The average pixel brightness of the EL images was calculated. Combined with the incident photon flux density of each LED, the external quantum efficiency (EQE) at each wavelength was calculated, thus obtaining the EQE curve. This EQE was then integrated with the standard AM1.5 solar spectrum to calculate the short-circuit current density of the solar cell.

[0058] Step 2, Diffusion Matching: Before the formal measurement, it is necessary to ensure that the photogenerated carriers generated in the unshaded area can effectively diffuse into the shaded area, thereby generating a sufficient electroluminescence signal in that area. To this end, this step optimizes the matching of the shaded area size and the excitation light intensity.

[0059] Step 3, LED homogenization: To ensure the uniformity and comparability of excitation light of different wavelengths on the solar cell, this step involves homogenizing the LED light source. For example... Figure 2 As shown, multiple LED light sources are arranged at appropriate positions and angles around the solar cell, such as symmetrically distributed around the solar cell to provide uniform coverage. There is no significant unevenness in brightness in the effective area of ​​the solar cell, which is important for obtaining an accurate EQE curve.

[0060] Step 4, EL signal extraction. A light-capturing device positioned above a shielding filter is used to detect the electroluminescence (EL) light energy images of the shielded measurement area at each wavelength. The light-capturing device includes a camera, lens, and filter. This filter blocks the LED excitation light at each wavelength, allowing only the EL light energy signal to pass through. This step extracts the extremely weak EL signal, providing a reliable data foundation for accurate EQE calculation.

[0061] Step 5, Multi-wavelength Measurement and Result Calculation: After completing the above preparations and optimizations, non-contact EQE testing of the solar cells is initiated, wavelength by wavelength. The control unit sequentially illuminates the LED light sources of each wavelength band according to a preset order, and performs synchronous data acquisition and processing during illumination at each wavelength. Preferably, the LEDs of each wavelength are illuminated only during their measurement time period, while a light energy capture device synchronously acquires the EL light energy signal of the filter-shielded area, obtains the EL light energy image, and calculates the average pixel brightness of the EL image. Then, the control unit calculates the ratio of this average brightness to the pre-calibrated incident photon flux at that wavelength to obtain the external quantum efficiency (EQE) value (i.e., the percentage of converted electrons out of the incident photons) at that wavelength. Appropriately increasing the types of single-wavelength LEDs can increase the number of non-contact EQE test points, thereby obtaining a more accurate and complete EQE curve. Finally, the corresponding short-circuit current density J can be calculated by weighted integration of the EQE curve with the standard solar spectrum. sc .

[0062] Step 6, Temperature Control Compensation: The luminous efficiency of a solar cell is closely related to its temperature. To ensure the accuracy of the test results, this step eliminates the influence of temperature on the measurement through temperature control and data compensation. The temperature measuring device in the system can read the temperature of the cell under test in real time, thereby compensating and correcting the final ISC.

[0063] In summary, this embodiment achieves a non-contact testing method combining photoluminescence (PL) and localized electroluminescence (EL) by cleverly designing a shielding filter and a multi-wavelength LED light source. Specific measures were taken in various aspects, including system calibration, LED uniform illumination, weak EL signal acquisition, and temperature control compensation, to ensure a stable and reliable testing process and accurate and effective EQE curves and ISC results. The detailed solution provided in this embodiment is practically feasible and can be used to support high-quality patent application drafting and the research and development and manufacturing of solar cell testing equipment.

[0064] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0065] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0066] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0067] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0068] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells, characterized in that; Includes the following steps: Step S1: Photoluminescence excitation of the solar cell is performed using an LED array containing multiple center wavelengths, the incident photon flux density of each LED is recorded, and the multi-wavelength LED light source is homogenized. Step S2: A shielding filter is set on the surface of the solar cell to form a shielded measurement area. The shielding filter is used to block the excitation light of the LED and allow the electroluminescence signal to pass through. The position and angle of the shielding filter are corrected and positioned, and a background signal image is acquired by a detector under the condition that the LED light source is turned off. Step S3: Photogenerated carriers generated in the unshielded area diffuse laterally within the semiconductor and enter the shielded measurement area. In this area, radiative recombination occurs without external electrode contact, generating an electroluminescent (EL) signal. The LED light intensity and the size of the shielded measurement area are optimized to ensure that the photogenerated carriers generated in the unshielded area effectively diffuse into the shielded measurement area. Step S4: Use a light energy capturing device placed above the shielding filter to detect the electroluminescence (EL) light energy image of the shielded measurement area at each wavelength. The light energy capturing device includes a filter structure for shielding the LED excitation light, and the acquired EL light energy image is corrected by comparing it with the background signal image. Step S5: The control unit sequentially lights up LEDs of each wavelength in a preset order, and synchronously acquires EL light energy images of the shielded measurement area during the measurement period corresponding to each wavelength. It calculates the average pixel value brightness of the EL light energy images, and calculates the external quantum efficiency (EQE) of each wavelength by combining the incident photon flux density of the corresponding wavelength LEDs. After obtaining the continuous external quantum efficiency curve, it integrates it with the standard AM1.5 solar spectrum to calculate the short-circuit current density of the solar cell.

2. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that, In step S1, the incident photon flux density is calculated based on the measured optical power of the corresponding wavelength LED in the integrating sphere, the LED wavelength, and the effective irradiation area on the solar cell after the LED is homogenized.

3. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that: In step S1, the multi-wavelength LED light source is homogenized to ensure that the light intensity of each wavelength is uniformly distributed on the surface of the solar cell under test.

4. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 3, characterized in that: In step S1, the LED array is arranged symmetrically so that multiple LED light sources are superimposed to form a uniform coverage on the effective area of ​​the solar cell under test.

5. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that: In step S2, the shielding filter adopts a multilayer film interference structure, which has a high blocking rate for the LED excitation band and a high transmittance for the electroluminescent band, and is installed on a movable or adjustable mechanism for the correction and positioning of the position and angle.

6. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that, In steps S2 and S4, the background signal image is an environmental signal image acquired through the shielding filter when the LED light source is off, and the correction process is to subtract the background signal image from the subsequently acquired EL light energy image before performing the calculation.

7. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that: In step S3, the optimized matching includes optimizing the LED light intensity and optimizing the size of the shielded measurement area to ensure that the EL light energy signal generated in the shielded measurement area corresponds to the incident light photon flux, and to ensure that the photogenerated carriers generated in the unshielded area can effectively diffuse into the shielded measurement area.

8. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 1, characterized in that, In step S4, the light energy capturing device includes a camera, a lens, and a filter. The filter is used to shield the LED excitation light of each wavelength and allow the EL light energy signal to pass through.

9. The method for non-contact testing of quantum efficiency (EQE) and short-circuit current (ISC) of solar cells according to claim 8, characterized in that, In step S5, each wavelength of LED is lit only during its corresponding measurement time period, and the light energy capture device synchronously acquires the EL light energy image of the measurement area blocked by the filter. During the test, the temperature of the solar cell is monitored in real time. Based on the real-time data from the temperature sensor and combined with the actual temperature coefficient of the cell, the test results are corrected for temperature compensation to obtain the quantum efficiency (EQE) and short-circuit current (ISC).

10. A non-contact quantum efficiency testing device, used to implement the non-contact testing method for quantum efficiency (EQE) and short-circuit current (ISC) of solar cells as described in any one of claims 1-9, characterized in that, include: A multi-wavelength LED excitation light source module is used to provide photoluminescence excitation. A shielding filter assembly is located above a local area on the surface of the solar cell under test. It is used to form a shielded measurement area and block the excitation light of the LED while allowing the electroluminescent signal to pass through. The shielding filter assembly includes an adjustment mechanism for position and angle correction. A light energy capturing device is disposed above the shielding filter assembly and is used to detect the electroluminescence signal of the shielded measurement area. The light energy capturing device includes a camera, a lens, and a filter structure for shielding the LED excitation light. The control unit is connected to the multi-wavelength LED excitation light source module, the light energy capture device, the temperature sensor, and the temperature control execution module. It is used to control the LEDs of different wavelengths to output in a preset order and to synchronously acquire EL light energy images during the corresponding measurement period. It is also used to acquire background signal images under LED off conditions and to perform background correction on the EL light energy images. Furthermore, it is used to calculate the quantum efficiency EQE and the short-circuit current ISC and to perform temperature compensation correction. Temperature sensors and temperature control execution modules are used to monitor and maintain the temperature stability of solar cells in real time during testing.

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