Test sample groups, methods, and applications for testing free carrier absorption of polysilicon layers

Abstract

This application provides a set of test samples, methods, and applications for testing the free carrier absorption of polycrystalline silicon layers, belonging to the field of solar cell technology. The method for testing the free carrier absorption of polycrystalline silicon layers includes the following steps: preparing a set of test samples, comprising a test sample and a control sample; measuring the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset wavelength band; integrating A1 and A2 in the preset wavelength band to obtain the current density J1 of the test sample and the current density J2 of the control sample, and then calculating the current density J3 of the polycrystalline silicon layer using Formula 1; Formula 1 is as follows: J3 = J1 - J2. This method can solve the problems of cumbersome sample preparation, low detection accuracy, and inability to quantify absorption in the testing of free carrier absorption of polycrystalline silicon layers.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and more specifically, to test sample sets, methods, and applications for testing the absorption of free carriers in polycrystalline silicon layers. Background Technology

[0002] In the existing technology, the method for testing the absorption of free carriers in polycrystalline silicon layers is usually to use an ellipsometer. However, this measurement method has problems such as cumbersome sample preparation process, low detection accuracy, and inability to quantify the absorption. Summary of the Invention

[0003] The purpose of this application is to provide a set of test samples, methods and applications for testing the absorption of free carriers in polycrystalline silicon layers, which can solve the problems of cumbersome sample preparation process, low detection accuracy and inability to quantify absorption in the process of testing the absorption of free carriers in polycrystalline silicon layers.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide a test sample set for testing the absorption of free carriers in a polycrystalline silicon layer, including a test sample and a control sample. The test sample consists of a control sample and a polycrystalline silicon layer added to the control sample.

[0006] In existing technologies, sample preparation requires that the prepared sample be planar and that a relatively thick oxide layer be grown between the polycrystalline silicon layer and the silicon substrate. In the above-mentioned technical solution, the test sample set includes a test sample and a control sample, and the test sample consists of a control sample and a polycrystalline silicon layer added to the control sample. This sample preparation only requires the presence or absence of a polycrystalline silicon layer. Therefore, using this test sample set to test the free carrier absorption of the polycrystalline silicon layer simplifies the sample preparation process and improves detection efficiency.

[0007] Furthermore, in the prior art, because the sample has a thick silicon layer, the structural difference between the sample and the device under test is large, resulting in deviations in the test structure. In this application, the test sample is only required to have or not have a polycrystalline silicon layer, and the test sample can be configured according to the actual device structure, which can avoid test differences caused by structural differences and thus ensure the detection accuracy.

[0008] Secondly, embodiments of this application provide a method for testing the absorption of free carriers in a polycrystalline silicon layer, comprising the following steps:

[0009] Prepare the test sample set as provided in the first aspect embodiment;

[0010] The optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample were tested in a preset wavelength band.

[0011] Integrate A1 and A2 in the preset wavelength band to obtain the current density J1 of the test sample and the current density J2 of the control sample. Then calculate the current density J3 of the polycrystalline silicon layer using Formula 1.

[0012] Formula 1 is as follows: J3 = J1 - J2.

[0013] In the above technical solution, the optical absorption rate of the test sample group provided in the first aspect embodiment is tested in a preset wavelength band, and then the current absorption density of the test sample group is obtained by integration in the preset wavelength band. Finally, the current density of the polycrystalline silicon layer is obtained, thereby quantifying the absorption of free carriers in the polycrystalline silicon layer through the current density. This test method has the advantages of simple sample preparation and high detection accuracy, as well as the advantage of being able to quantify the absorption of free carriers in the polycrystalline silicon layer.

[0014] In some optional implementations, the step of testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset wavelength band includes:

[0015] The reflectance and transmittance of the test sample and the control sample were tested; then the optical absorptivity of the test sample and the control sample were calculated using Formula 2, expressed as A(λ);

[0016] Formula 2 is as follows: A(λ)=1-R(λ)-T(λ).

[0017] A(λ) is the optical absorptivity at the wavelength of the preset band, R(λ) is the transmittance at the wavelength of the preset band, and T(λ) is the reflectivity at the wavelength of the preset band.

[0018] The above technical solution, which measures the reflectance and transmittance of the test sample and the control sample in a preset band, and then calculates the optical absorptivity of the test sample and the control sample according to the formula A(λ)=1-R(λ)-T(λ), can more accurately reflect the optical absorptivity of the test sample.

[0019] In some optional implementations, the step of integrating A1 and A2 in preset wavelength bands to obtain the current density J1 of the test sample and the current density J2 of the control sample includes:

[0020] Calculate the current density of the test sample and the control sample respectively using Formula 3, in J;

[0021] Formula 3 is as follows:

[0022] q is the charge constant, and I(λ) is the number of photons at the wavelength of the preset band.

[0023] In the above technical solution, the current densities of the test sample and the control sample are obtained by integrating A1 and A2 in preset wavelength bands, respectively, and then... The method of calculating the current density of a polycrystalline silicon layer using the formula can improve the accuracy of the quantization of free carrier absorption in the polycrystalline silicon layer.

[0024] In some alternative implementations, the preset wavelength range is 300–1180 nm.

[0025] In the above technical solution, the preset wavelength range is limited to 300-1180nm. Since there is less test interference in this wavelength range, the accuracy of testing the optical absorption rate of the test sample and the control sample can be improved.

[0026] In some alternative implementations, the preset wavelength range is 900–1180 nm.

[0027] In the above technical solution, the range of the preset wavelength is further limited to 900-1180nm, which can further reduce interference in the testing process and thus further improve the accuracy of testing the optical absorption rate of the test sample and the control sample.

[0028] In some alternative implementations, the optical device is a quantum efficiency tester.

[0029] In the above technical solution, a quantum efficiency tester is used to test the optical absorbance of the test and control samples. Because the equipment operation and detection principle are relatively simple, the requirements for testing technicians are low, making it easy to promote. At the same time, this equipment also has the advantages of high detection efficiency and accuracy.

[0030] Thirdly, embodiments of this application provide an application of the method for testing the free carrier absorption of a polycrystalline silicon layer as provided in the second aspect of the embodiment in testing the free carrier absorption of a polycrystalline silicon layer in a solar cell.

[0031] In the above technical solution, the method for testing the absorption of free carriers in a polycrystalline silicon layer provided in the second aspect embodiment is applied to test the absorption of free carriers in a polycrystalline silicon layer in a solar cell. This method can accurately and efficiently test the absorption of free carriers in a polycrystalline silicon layer in a solar cell and quantify the absorption.

[0032] In some alternative implementations, the test sample includes a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polysilicon layer, and a back film stacked sequentially, while the control sample includes a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially.

[0033] In the above technical solution, the test sample and control sample of the above structure are used for testing, which can more accurately test the absorption of free carriers in the polycrystalline silicon layer of the solar cell.

[0034] In some alternative implementations, the step of testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset band includes testing both the test sample and the control sample from the front.

[0035] In the above technical solution, both the test sample and the control sample are tested from the front, making the test environment more closely resemble the actual application scenario of solar cells, thereby making the test results more accurate. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A process flow diagram of a method for testing free carrier absorption in a polycrystalline silicon layer is provided for embodiments of this application;

[0038] Figure 2 This is a schematic diagram of the structure of a test sample group for testing the absorption of free carriers in a polycrystalline silicon layer, provided in an embodiment of this application.

[0039] Figure 3 The reflectance and transmittance results of a test sample group for testing the absorption of free carriers in a polycrystalline silicon layer are provided in this application embodiment.

[0040] Figure 4 The optical absorptivity results of a test sample group for testing the free carrier absorption of a polycrystalline silicon layer are provided in this application embodiment.

[0041] Figure 5 The reflectance and transmittance results of the test sample and the control sample in the wavelength range of 300 to 1180 nm are provided for the embodiments of this application.

[0042] Figure 6 The reflectance and transmittance results provided for the embodiments of this application are all tested from the reverse side of the test sample and the control sample;

[0043] Figure 7 The optical absorption rate results provided for the embodiments of this application are all from the reverse side of the test sample and the control sample.

[0044] Figure 8 The optical properties of free carrier absorption in a polycrystalline silicon layer, as provided in the embodiments of this application, are tested using an ellipsometer.

[0045] Icons: 100 - Test sample; 110 - Positive film; 120 - P+ doped layer; 130 - N-type silicon wafer; 140 - N+ doped layer; 150 - Back film; 200 - Control sample. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0047] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".

[0048] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0049] The following is a detailed description of the test sample set, method, and application for testing the free carrier absorption of polycrystalline silicon layers according to embodiments of this application.

[0050] In existing technologies, the testing of free carrier absorption in polycrystalline silicon layers mainly utilizes an ellipsometer to measure the extinction coefficient K of the sample, and then follows the formula... The absorption coefficient of the sample is calculated to obtain the optical properties of the test sample.

[0051] However, the current testing method has some problems. First, the method can only test the optical properties of free carriers in the polycrystalline silicon layer and cannot quantify their specific impact on battery devices.

[0052] Secondly, the sample prepared using this detection method must be planar, and a thick oxide layer needs to be grown between the polycrystalline silicon layer and the silicon substrate, making the sample preparation process cumbersome and resulting in low testing efficiency. Furthermore, the presence of a thick oxide layer in the prepared sample makes it not entirely consistent with the structure of the actual device, leading to larger errors in the test results and lower reliability. Additionally, the complex structure and working principle of the ellipsometer itself require a high level of technical skill from the testing personnel, hindering its widespread application.

[0053] The inventors discovered that by selecting and optimizing the test samples, test methods, and optical equipment during the testing of free carrier absorption in polycrystalline silicon layers, problems such as cumbersome sample preparation, low detection accuracy, and inability to quantify absorption can be solved.

[0054] In a first aspect, embodiments of this application provide a test sample set for testing the absorption of free carriers in a polycrystalline silicon layer, including a test sample and a control sample. The test sample consists of a control sample and a polycrystalline silicon layer added to the control sample.

[0055] In existing technologies, sample preparation requires that the prepared sample be planar and that a relatively thick oxide layer be grown between the polycrystalline silicon layer and the silicon substrate. In this application, the test sample set includes a test sample and a control sample, and the test sample consists of a control sample and a polycrystalline silicon layer added to the control sample. This sample preparation only requires the presence or absence of a polycrystalline silicon layer. Therefore, using this test sample set to test the free carrier absorption of the polycrystalline silicon layer simplifies the sample preparation process and improves detection efficiency.

[0056] Furthermore, in the prior art, because the sample has a thick silicon layer, the structural difference between the sample and the device under test is large, resulting in deviations in the test structure. In this application, the test sample is only required to have or not have a polycrystalline silicon layer, and the test sample can be configured according to the actual device structure, which can avoid test differences caused by structural differences and thus ensure the detection accuracy.

[0057] Secondly, embodiments of this application provide a method for testing the absorption of free carriers in a polycrystalline silicon layer, see reference. Figure 1 This includes the following steps:

[0058] Prepare the test sample set as provided in the first aspect embodiment;

[0059] The optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample were tested in a preset wavelength band.

[0060] Integrate A1 and A2 in the preset wavelength band to obtain the current density J1 of the test sample and the current density J2 of the control sample. Then calculate the current density J3 of the polycrystalline silicon layer using Formula 1.

[0061] Formula 1 is as follows: J3 = J1 - J2.

[0062] In this application, the optical absorption rate of the test sample group provided in the first aspect embodiment is tested in a preset wavelength band, and then the current absorption density of the test sample group is obtained by integration in the preset wavelength band. Finally, the current density of the polycrystalline silicon layer is obtained, thereby quantifying the absorption of free carriers in the polycrystalline silicon layer through the current density. This testing method has the advantages of simple sample preparation and high detection accuracy, as well as the advantage of being able to quantify the absorption of free carriers in the polycrystalline silicon layer.

[0063] As an example, the steps for testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset wavelength band include:

[0064] The reflectance and transmittance of the test sample and the control sample were tested; then the optical absorptivity of the test sample and the control sample were calculated using Formula 2, expressed as A(λ);

[0065] Formula 2 is as follows: A(λ)=1-R(λ)-T(λ).

[0066] A(λ) is the optical absorptivity at the wavelength of the preset band, R(λ) is the transmittance at the wavelength of the preset band, and T(λ) is the reflectivity at the wavelength of the preset band.

[0067] In this embodiment, the optical absorption rate of the test sample and the control sample is calculated by testing the reflectance and transmittance of the test sample and the control sample in a preset band, and then calculating the optical absorption rate of the test sample and the control sample according to the formula A(λ)=1-R(λ)-T(λ). This method can more accurately reflect the optical absorption rate of the test sample.

[0068] As an example, the steps of integrating A1 and A2 in a preset wavelength band to obtain the current density J1 of the test sample and the current density J2 of the control sample include:

[0069] Calculate the current density of the test sample and the control sample respectively using Formula 3, in J;

[0070] Formula 3 is as follows:

[0071] q is the charge constant, and I(λ) is the number of photons at the wavelength of the preset band.

[0072] In this embodiment, the current densities of the test sample and the control sample are obtained by integrating A1 and A2 in preset wavelength bands, respectively, and then... The method of calculating the current density of a polycrystalline silicon layer using the formula can improve the accuracy of the quantization of free carrier absorption in the polycrystalline silicon layer.

[0073] The inventors discovered that, considering the accuracy of optical absorption rate testing, a range of preset wavelengths can be selected.

[0074] As an example, the preset wavelength range is 300 to 1180 nm, such as, but not limited to, any one of the wavelengths 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm and 1180 nm or any range between two of them.

[0075] In this embodiment, the preset wavelength range is limited to 300–1180 nm. Since there is less test interference in this wavelength range, the accuracy of testing the optical absorption rate of the test sample and the control sample can be improved.

[0076] Based on this, and considering further improving the accuracy of optical absorption rate testing, the range of preset wavelengths can be adjusted again.

[0077] As an example, the preset wavelength range is 900 to 1180 nm, such as, but not limited to, any one of the wavelengths 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm and 1180 nm or any range between two of them.

[0078] In this embodiment, the range of the preset wavelength is further limited to 900-1180nm, which can further reduce interference during the testing process and thus further improve the accuracy of testing the optical absorption rate of the test sample and the control sample.

[0079] The inventors discovered that, taking into account factors such as the popularization and efficiency of testing methods, the type of optical equipment can be adjusted.

[0080] As an example, the optical device is a quantum efficiency tester.

[0081] In this embodiment, a quantum efficiency tester is used to test the optical absorbance of the test and control samples. Because the equipment operation and detection principle are relatively simple, the requirements for testing technicians are low, making it easy to promote. At the same time, this equipment also has the advantages of high detection efficiency and accuracy.

[0082] Thirdly, embodiments of this application provide an application of the method for testing the free carrier absorption of a polycrystalline silicon layer as provided in the second aspect of the embodiment in testing the free carrier absorption of a polycrystalline silicon layer in a solar cell.

[0083] In this application, the method for testing the absorption of free carriers in a polycrystalline silicon layer provided in the second aspect embodiment is applied to test the absorption of free carriers in a polycrystalline silicon layer in a solar cell. This method can accurately and efficiently test the absorption of free carriers in a polycrystalline silicon layer in a solar cell and can quantify the absorption.

[0084] It should be noted that the specific form of the solar cell is not limited; it can be a conventional N-type bifacial solar cell or a heterojunction cell.

[0085] The inventors discovered that, in order to more accurately test the absorption of free carriers in the polycrystalline silicon layer of a solar cell, the structure of the test sample and the sample itself can be defined.

[0086] As an example, see Figure 2 The test sample 100 includes a positive film 110, a P+ doped layer 120, an N-type silicon wafer 130, an N+ doped polycrystalline silicon layer 140 and a back film 150 stacked sequentially, and the control sample 200 includes a positive film 110, a P+ doped layer 120, an N-type silicon wafer 130 and a back film 150 stacked sequentially.

[0087] In this embodiment, the test sample 100 and control sample 200 with the above structure are used for testing, which can more accurately test the absorption of free carriers in the polycrystalline silicon layer of the solar cell.

[0088] It should be noted that in the steps of testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in the preset band, the testing direction is not specifically limited. The test sample and the control sample can both be tested from the front, or they can be tested from opposite directions, or they can both be tested from the back.

[0089] As an example, the steps for testing the optical absorption rate A1 of the test sample and the optical absorption rate A2 of the control sample in a preset band include: both the test sample and the control sample are tested from the front.

[0090] In this embodiment, both the test sample and the control sample are tested from the front, making the test environment more closely resemble the actual application scenario of solar cells, thereby making the test results more accurate.

[0091] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0092] Example 1

[0093] This embodiment provides a method for testing the absorption of free carriers in a polycrystalline silicon layer, including the following steps:

[0094] Test samples and control samples were prepared. The test sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polycrystalline silicon layer, and a back film stacked sequentially. The control sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially.

[0095] Within the wavelength range of 900–1180 nm, the reflectance and transmittance of the test sample and the control sample were measured from the front using a quantum efficiency tester. The optical absorptivity A1 and A2 of the test sample and the control sample were calculated according to the formula A(λ)=1-R(λ)-T(λ), where A(λ) is the optical absorptivity in the wavelength range of 900–1180 nm, R(λ) is the transmittance in the wavelength range of 900–1180 nm, and T(λ) is the reflectance in the wavelength range of 900–1180 nm.

[0096] Within the wavelength range of 900–1180 nm, the optical absorbances A1 and A2 of the test sample and control sample were respectively calculated according to the formula... The current densities J1 and J2 of the test sample and control sample were obtained by integral calculation, where q is the charge constant and I(λ) is the number of photons in the wavelength range of 900 to 1180 nm.

[0097] Then, the current density J3 of the polycrystalline silicon layer is calculated according to the formula J3 = J1 - J2.

[0098] Example 2

[0099] This application provides a method for testing the absorption of free carriers in a polycrystalline silicon layer, which differs from Embodiment 1 only in that:

[0100] The wavelength range was adjusted from 900–1180 nm to 300–1180 nm.

[0101] Example 3

[0102] This application provides a method for testing the absorption of free carriers in a polycrystalline silicon layer, which differs from Embodiment 1 only in that:

[0103] The reflectance and transmittance of the test sample and the control sample were tested from the reverse side using a quantum efficiency tester.

[0104] Comparative Example

[0105] This application provides a method for testing the absorption of free carriers in a polycrystalline silicon layer, including the following steps:

[0106] First, the silicon wafer is polished. Then, a silicon oxide layer with a thickness of 60 nm is grown on the surface of the silicon wafer by high-temperature thermal oxidation. Finally, a doped polycrystalline silicon layer is deposited on the surface of the silicon oxide layer to obtain the sample required for testing.

[0107] Within the wavelength range of 300–1200 nm, the extinction coefficient K of the sample was measured using an ellipsometer, and the result was obtained according to the formula. Calculate the absorption coefficient of the sample.

[0108] Experimental Example 1

[0109] Testing the free carrier absorption of polycrystalline silicon layers

[0110] Test method:

[0111] Test samples and control samples were prepared. The test sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polycrystalline silicon layer, and a back film stacked sequentially. The control sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially. Then, the tests were performed according to the subsequent test steps in Example 1.

[0112] according to Figure 3 and Figure 4 As can be seen, according to the testing method in Example 1, the reflectivity and transmittance of the test sample and the control sample are first measured, and then the optical absorptivity of the two samples is obtained based on the reflectivity and transmittance. Then, the current density of the test sample and the control sample is obtained through an integral formula, and thus the current density of the polycrystalline silicon layer is obtained. This allows for the quantization of the free carrier absorption of the polycrystalline silicon layer, and the quantization value is 0.72 mA / cm². 2 .

[0113] It should be noted that, Figure 3 In the figure, R1 is the transmittance of the test sample at the wavelength of the preset wavelength band, and T1 is the reflectance of the test sample at the wavelength of the preset wavelength band; R2 is the transmittance of the control sample at the wavelength of the preset wavelength band, and T2 is the reflectance of the control sample at the wavelength of the preset wavelength band.

[0114] Experimental Example 2

[0115] Within the wavelength range of 300–1180 nm, the reflectance and transmittance of the test sample and the control sample were measured.

[0116] Test method:

[0117] Test samples and control samples were prepared. The test sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polycrystalline silicon layer, and a back film stacked sequentially. The control sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially. Then, the tests were performed according to the subsequent test steps in Example 2.

[0118] It should be noted that the front film is a stacked film of AlOx and SiNx, with SiNx on the outside of AlOx; the P+ doped layer is a high-concentration boron-doped silicon layer; the N+ doped polycrystalline silicon layer is a phosphorus-doped polycrystalline silicon layer, and the back film is a SiNx thin film.

[0119] according to Figure 5 It can be seen that when testing the reflectance of the test sample and the control sample in the wavelength range of 300-1180nm, there are certain abrupt changes in the reflectance curves of the test sample and the control sample in the wavelength range of 350-450nm. The reason for the abrupt changes may be due to the slight difference in the positive film. Due to the existence of the abrupt changes, there is an error in the free carrier absorption test of the polycrystalline silicon layer in the wavelength range of 300-1180nm, which affects the accuracy of the test results.

[0120] It should be noted that, Figure 5 In the figure, R1 is the transmittance of the test sample at the wavelength of the preset wavelength band, and T1 is the reflectance of the test sample at the wavelength of the preset wavelength band; R2 is the transmittance of the control sample at the wavelength of the preset wavelength band, and T2 is the reflectance of the control sample at the wavelength of the preset wavelength band.

[0121] Experimental Example 3

[0122] The optical absorption rates of the test sample and the control sample were tested from the reverse side.

[0123] Test method:

[0124] Test samples and control samples were prepared. The test sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polycrystalline silicon layer, and a back film stacked sequentially. The control sample consisted of a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially. Then, the tests were performed according to the subsequent test steps in Example 3.

[0125] It should be noted that the front film is a stacked film of AlOx and SiNx, with SiNx on the outside of AlOx; the P+ doped layer is a high-concentration boron-doped silicon layer; the N+ doped polycrystalline silicon layer is a phosphorus-doped polycrystalline silicon layer, and the back film is a SiNx thin film.

[0126] according to Figure 6 and Figure 7 It is known that when testing the reflectance and transmittance of the test sample and control sample from the reverse side within the wavelength range of 900–1180 nm, the optical absorptivity of the test sample and control sample can also be measured. However, since the incident light direction of solar cells in actual outdoor operation is from the front of the cell, testing from the reverse side does not conform to the actual application of the cell, thus affecting the accuracy of the test results.

[0127] It should be noted that, Figure 6 In the figure, R1 is the transmittance of the test sample at the wavelength of the preset wavelength band, and T1 is the reflectance of the test sample at the wavelength of the preset wavelength band; R2 is the transmittance of the control sample at the wavelength of the preset wavelength band, and T2 is the reflectance of the control sample at the wavelength of the preset wavelength band.

[0128] Test Example 4

[0129] Ellipsometry for measuring free carrier absorption in polycrystalline silicon layers

[0130] Test method:

[0131] Perform the test according to the test procedure in Comparative Example 1.

[0132] according to Figure 8 It can be seen that, according to the test method in Comparative Example 1, that is, using an ellipsometer for testing, only the absorption coefficient α of free carriers in the polycrystalline silicon layer can be obtained, but the absorption cannot be quantified.

[0133] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for testing the absorption of free carriers in a polycrystalline silicon layer, characterized in that, Includes the following steps: Prepare a test sample group, the test sample group comprising: a test sample and a control sample, the test sample being composed of the control sample and a polycrystalline silicon layer added to the control sample; The optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample were tested in a preset wavelength band. A1 and A2 are integrated in the preset band to obtain the current density J1 of the test sample and the current density J2 of the control sample. Then, the current density J3 of the polycrystalline silicon layer is calculated using Formula 1. Formula 1 is as follows: .

2. The method for testing free carrier absorption in a polycrystalline silicon layer according to claim 1, characterized in that, The step of testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset wavelength band includes: The reflectance and transmittance of the test sample and the control sample are tested; then the optical absorptivity of the test sample and the control sample is calculated using Formula 2, expressed as A(λ); Formula 2 is as follows: A(λ) is the optical absorptivity at the wavelength of the preset band, R(λ) is the transmittance at the wavelength of the preset band, and T(λ) is the reflectivity at the wavelength of the preset band.

3. The method for testing free carrier absorption in a polycrystalline silicon layer according to claim 1, characterized in that, The step of integrating A1 and A2 in the preset wavelength band to obtain the current density J1 of the test sample and the current density J2 of the control sample includes: Calculate the current density of the test sample and the control sample respectively using Formula 3, in J; Formula 3 is as follows: q is the charge constant, and I(λ) is the number of photons at the wavelength of the preset band.

4. The method for testing free carrier absorption in a polycrystalline silicon layer according to any one of claims 1 to 3, characterized in that, The preset wavelength range is 300~1180nm.

5. The method for testing free carrier absorption in a polycrystalline silicon layer according to claim 4, characterized in that, The preset wavelength range is 900~1180nm.

6. The method for testing free carrier absorption in a polycrystalline silicon layer according to any one of claims 1 to 3, characterized in that, The optical device used to test optical absorption rate is a quantum efficiency meter.

7. The application of the method for testing the free carrier absorption of a polycrystalline silicon layer as described in any one of claims 1 to 6 in testing the free carrier absorption of a polycrystalline silicon layer in a solar cell.

8. The application according to claim 7, characterized in that, The test sample includes a positive film, a P+ doped layer, an N-type silicon wafer, an N+ doped polycrystalline silicon layer, and a back film stacked sequentially. The control sample includes a positive film, a P+ doped layer, an N-type silicon wafer, and a back film stacked sequentially.

9. The application according to claim 7, characterized in that, The step of testing the optical absorptivity A1 of the test sample and the optical absorptivity A2 of the control sample in a preset wavelength band includes: Both the test sample and the control sample were tested from the front.

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