Hydrogen-doped indium tin oxide thin film, preparation method therefor, and solar cell containing same

Abstract

Provided in the present application are a hydrogen-doped indium tin oxide thin film, a preparation method therefor, and a solar cell containing same. The hydrogen-doped indium tin oxide thin film has a first X-ray diffraction peak of a (400) crystal plane orientation and a second X-ray diffraction peak of a (222) crystal plane orientation, and the intensity of the first X-ray diffraction peak is greater than the intensity of the second X-ray diffraction peak.

Description

Hydrogen-doped indium tin oxide thin film, method for preparing same, and solar cell comprising same

[0001] This application claims priority to the Chinese patent application No. 202410458381.1, filed on April 16, 2024, and entitled "Hydrogen-doped indium tin oxide thin film, method for preparing same, and solar cell comprising same", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of solar cells, in particular, the present application relates to a hydrogen-doped indium tin oxide thin film, a method for preparing same, and a solar cell comprising same. BACKGROUND

[0003] In the field of solar cell manufacturing, crystalline silicon heterojunction solar cells (HJT cells, Heterojunction Intrinsic Thin Film solar cell) have attracted widespread attention, which are usually referred to as heterojunction cells. The feature of this type of cell is that an intrinsic amorphous silicon layer is added between the emitter and the back high-concentration doped layer and the silicon substrate. HJT cells combine the advantages of single-crystal silicon and amorphous silicon, require lower temperatures during manufacturing, and have good passivation effects. At present, the cumulative production capacity of heterojunction cells is continuously increasing, and it has become an important development direction in the field of high-efficiency crystalline silicon cells.

[0004] In solar cells represented by HJT cells, the TCO thin film transport layer serves as a lateral transport channel for charge carriers. ITO (indium tin oxide, a common TCO thin film material) target material is usually sputtered onto the front and back surfaces of the cell piece by magnetron sputtering technology to form the transport layer. In the process of preparing ITO by water vapor process (H2O process), argon (Ar), oxygen (O2) and water vapor (H2O) are used as working gases to form an ITO thin film on the surface of the cell piece.

[0005] However, there is still room for improvement in the conductive performance of the ITO thin film as a charge carrier transport channel. In addition, during the preparation of the ITO thin film using the H2O process, the vaporized water vapor is directly introduced into the cavity, which can cause the target material to form nodules, thereby reducing the utilization rate of the target material. In addition, the process parameters are highly volatile, which increases the complexity and instability of production. Furthermore, the carrier fixture needs to be cleaned frequently, which prolongs the maintenance cost and production cycle. SUMMARY

[0006] Therefore, the main purpose of the present application is to provide a hydrogen-doped indium tin oxide thin film, a method for preparing same, and a solar cell comprising same, in order to at least partially solve at least one of the above technical problems.

[0007] To achieve the above object, the technical scheme of the present application is as follows:

[0008] According to an embodiment of the present application, a hydrogen-doped indium tin oxide film is provided, having a first X-ray diffraction peak of (400) crystal face orientation and a second X-ray diffraction peak of (222) crystal face orientation, the intensity of the first X-ray diffraction peak being greater than the intensity of the second X-ray diffraction peak.

[0009] According to an embodiment of the present application, in the indium tin oxide film, the grain size of the crystal grains having (400) crystal face orientation or having (222) crystal face orientation is 58-65 nm.

[0010] According to an embodiment of the present application, the lattice spacing of the (400) crystal face is 0.25-0.26 nm, and the lattice spacing of the (222) crystal face is 0.29-0.30 nm.

[0011] According to an embodiment of the present application, the indium tin oxide film further has a third X-ray diffraction peak of (440) crystal face orientation and a fourth X-ray diffraction peak of (622) crystal face orientation, respectively; wherein the intensity of the third X-ray diffraction peak and the fourth X-ray diffraction peak is respectively less than the intensity of the first X-ray diffraction peak.

[0012] According to an embodiment of another aspect of the present application, a preparation method of an indium tin oxide film is provided, comprising: depositing a hydrogen-doped indium tin oxide film on a substrate by using a magnetron sputtering method, wherein the deposition conditions of the magnetron sputtering method include: the working gas includes 94.8%-97.4% argon, 0.6%-2.3% hydrogen and 2%-2.9% oxygen in terms of volume content.

[0013] According to an embodiment of the present application, the deposition conditions further include: the sputtering power of the magnetron sputtering method is 7-14 kw, and the target material used is an indium tin oxide target material.

[0014] According to an embodiment of still another aspect of the present application, a solar cell is provided, comprising: a substrate; a hydrogen-doped indium tin oxide film formed on the substrate; and a metal electrode formed on the indium tin oxide film; wherein the hydrogen-doped indium tin oxide film has a first X-ray diffraction peak of (400) crystal face orientation and a second X-ray diffraction peak of (222) crystal face orientation, the intensity of the first X-ray diffraction peak being greater than the intensity of the second X-ray diffraction peak.

[0015] According to an embodiment of the present application, in the indium tin oxide film, the grain size of the crystal grains having (400) crystal face orientation or having (222) crystal face orientation is 58-65 nm.

[0016] According to the embodiments of the present application, the lattice spacing of the (400) crystal plane is 0.25-0.26 nm, and the lattice spacing of the (222) crystal plane is 0.29-0.30 nm.

[0017] According to the embodiments of the present application, the hydrogen-doped indium tin oxide thin film further has a third X-ray diffraction peak of (440) crystal plane orientation and a fourth X-ray diffraction peak of (622) crystal plane orientation; the intensity of the third X-ray diffraction peak and the fourth X-ray diffraction peak is less than the intensity of the first X-ray diffraction peak.

[0018] According to the embodiments of the present application, the substrate comprises a first doped nanocrystalline silicon layer, a first intrinsic amorphous silicon layer, a crystalline silicon substrate, a second intrinsic amorphous silicon layer, and a second doped nanocrystalline silicon layer which are sequentially stacked; the hydrogen-doped indium tin oxide thin film comprises a first indium tin oxide thin film and a second indium tin oxide thin film, the first indium tin oxide thin film is formed on the first doped nanocrystalline silicon layer, and the second indium tin oxide thin film is formed on the second doped nanocrystalline silicon layer; the metal electrode comprises a first metal electrode and a second metal electrode, the first metal electrode is formed on the first indium tin oxide thin film, and the second metal electrode is formed on the second indium tin oxide thin film.

[0019] According to the embodiments of the present application, the thickness of the first indium tin oxide thin film is 65-110 nm, and the thickness of the second indium tin oxide thin film is 65-110 nm.

[0020] According to the embodiments of the present application, the hydrogen-doped indium tin oxide (In2O3:H) thin film prepared by the optimized hydrogen process (H2 process) has specific crystal plane orientations which are different from those of the H2O process. Based on the specific first crystal grains of (400) crystal plane orientation, the In2O3:H thin film of the present application has different characteristics in physical and electrical properties, has fewer defects and good conductivity. The application of the In2O3:H thin film of the present application to solar cells helps to improve the conversion efficiency and other electrical properties of the cells.

[0021] According to the embodiments of the present application, the H2 process adopted by the present application inhibits the target nodule phenomenon which is prone to occur in the H2O process, thereby improving the utilization rate of the target material. Moreover, impurities are not easily generated or introduced, so that the process is relatively stable, the cleaning frequency of the carrier tool of the magnetron sputtering equipment is reduced, the cleaning cycle is prolonged by at least one time, and the continuous production time of the equipment can be increased by at least 30 minutes / day. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative effort based on these drawings.

[0023] Fig. 1 is an X-ray diffraction pattern of a hydrogen-doped indium tin oxide film on a textured cell and a monitor sheet according to an embodiment of the present application;

[0024] Fig. 2 is an X-ray diffraction pattern of a hydrogen-doped and water vapor-doped indium tin oxide film on a monitor sheet according to an embodiment of the present application;

[0025] Fig. 3 is a transmission electron microscope (TEM) image of a hydrogen-doped indium tin oxide film on a textured cell according to an embodiment of the present application;

[0026] Fig. 4 is a high-resolution TEM image of a hydrogen-doped indium tin oxide film on a textured cell according to an embodiment of the present application;

[0027] Fig. 5 is a TEM image of an indium tin oxide film prepared by an H2O process on a monitor sheet according to an embodiment of the present application;

[0028] Fig. 6 is a high-resolution TEM image of an indium tin oxide film prepared by an H2O process on a monitor sheet according to an embodiment of the present application;

[0029] Fig. 7 is a schematic diagram of target nodulation in an H2O process according to an embodiment of the present application;

[0030] Fig. 8 is a schematic diagram of the structure of a heterojunction solar cell according to an embodiment of the present application;

[0031] Fig. 9 is the photovoltaic characteristics of a heterojunction solar cell according to an embodiment of the present application;

[0032] Fig. 10 is the external quantum efficiency and reflectance curve of a heterojunction solar cell according to an embodiment of the present application;

[0033] Fig. 11 is the contact resistance between the front-side indium tin oxide film and the metal electrode of a heterojunction solar cell according to an embodiment of the present application. DETAILED EMBODIMENTS

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the terms "comprises", "comprising", "includes", "including" and the like are specifically intended to be open-ended. Such terms embrace the occurrence of zero instances of the feature that follows the term. As used herein, all terms including technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs unless otherwise defined. It must be noted that as used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The terms "approximately" and "substantially" as used herein refer to the recited characteristic, parameter, or value, and / or anything within an acceptable operational range or manufacturing tolerance, as understood by one of ordinary skill in the art.

[0036] According to an embodiment of the present application, a method for preparing an indium tin oxide film is provided, comprising: depositing a hydrogen-doped indium tin oxide film on a substrate by a magnetron sputtering method, wherein the substrate comprises a polished wafer or a wafer after texturing.

[0037] Specifically, the method for preparing the indium tin oxide film is a hydrogen-doped indium tin oxide film prepared by a H2 process, comprising: depositing a hydrogen-doped indium tin oxide film on a substrate by a physical vapor deposition (PVD) technique, preferably a magnetron sputtering method, and depositing the hydrogen-doped indium tin oxide film by a magnetron sputtering device.

[0038] According to an embodiment of the present application, the deposition conditions of the magnetron sputtering method include: the working gas comprises 94.8% to 97.4% argon, 0.6% to 2.3% hydrogen and 2% to 2.9% oxygen by volume content, and different gas combinations can affect the growth mode and orientation of the crystal grains during the deposition of the film. Among them, the volume content of hydrogen in the working gas affects the chemical reduction of the indium tin oxide film, which helps to improve the conductivity and transparency of the indium tin oxide film. By adjusting the proportion of these gases, the deposition process of the film can be optimized, the growth mode and orientation of the crystal grains can be controlled, and a film with specific performance can be obtained.

[0039] According to an embodiment of the present application, the water vapor partial pressure in the deposition chamber can be 3×10 -3 to 9×10 -3 Pa, for example, it can be 3.2×10 -3 Pa, 4.5×10 -3 Pa, 5×10 -3 Pa, 6.8×10 -3 Pa, 8×10 -3Pa et al. However, the range of values is not limited to the recited values only, other unrecited values within the range are also applicable. The presence of water vapor affects the adsorption and reaction kinetics on the film surface, thus affecting the film growth process and the final film properties. Appropriate amount of water vapor can help to adjust the film structure and stress state, and adjust the film growth rate and grain orientation. In the process of preparing the film by H2 process, the factors affecting the formation of water vapor partial pressure mainly include: water vapor brought by the carrier plate during circulation, reaction of hydrogen (H2) and oxygen (O2) in the process cavity to generate water (H2O), etc. Among them, different hydrogen content in the working gas will bring changes in water vapor partial pressure. With the change of hydrogen content, the total water vapor partial pressure in the cavity will change regularly. For example, the higher the hydrogen content, the higher the water vapor partial pressure. By adjusting the proportion of working gas and water vapor partial pressure, the film properties can be accurately controlled.

[0040] According to the embodiments of the present application, in the magnetron sputtering process, hydrogen is provided in the form of a mixed gas of argon and hydrogen, for example, the hydrogen concentration can be 2.8wt%, which is convenient for safe transportation. And the water vapor partial pressure in the process cavity of the magnetron sputtering device is monitored by a residual gas analyzer (RGA).

[0041] According to the embodiments of the present application, when preparing the hydrogen-doped indium tin oxide film by H2 process, the process gas can be Ar, O2, mixed gas (Ar+H2); and when preparing the indium tin oxide film by H2O process, the process gas can be Ar, O2, H2O.

[0042] According to the embodiments of the present application, the deposition conditions further include that the sputtering power of the magnetron sputtering method is 7-14kw, for example, it can be 8kw, 9kw, 10kw, 12kw, 13kw, etc., but it is not limited to the recited values, other unrecited values within the range of values are also applicable. The sputtering power affects the deposition rate and film properties of the indium tin oxide film, and further affects the growth rate and orientation of the crystal grains. Higher sputtering power can increase the sputtering rate, but may cause the defects in the film to increase, affecting the film quality. And it is also found that if the sputtering power is too low, it is easy to induce the sputtering target to form a tumor, thereby affecting the quality of the deposited film. Therefore, selecting the sputtering power within the range can effectively control the film deposition process, and balance the relationship between the deposition rate and the film quality.

[0043] According to the embodiments of the present application, the target material used is an indium tin oxide target material. In the magnetron sputtering process, the target material can be, for example, a 991 target material (or VTTO), that is, the target material contains 99% of indium oxide and the remaining 1% of other multi-element substances. Based on the power function matching between the microcrystalline silicon substrate, the 991 target material can provide better sputtering effect, which is helpful to obtain high-quality indium tin oxide film.

[0044] According to the embodiment of the present application, the H2 process is a cleaner process, and impurities are not easily generated or introduced. Therefore, the cleaning cycle of the magnetron sputtering device substrate can be extended by more than one time, the downtime of the device can be reduced, and the production efficiency can be improved. In addition, the target material is not easy to form nodules, and the utilization rate of the target material used in the device can be increased from 70% to more than 80%, and the continuous production time of the device can be increased by more than 30 minutes per day.

[0045] According to the embodiment of the present application, a hydrogen-doped indium tin oxide film is provided, which can reduce the production cost (including initial investment cost and daily operating cost) and effectively improve the photoelectric conversion efficiency of the battery sheet (i.e., improve the ability of the battery to convert light energy into electrical energy) during mass production.

[0046] According to the embodiment of the present application, a hydrogen-doped indium tin oxide film is prepared by an H2 process. The hydrogen-doped indium tin oxide film prepared on a polishing monitoring sheet and the hydrogen-doped indium tin oxide film prepared on a textured battery sheet have common and unique grain orientations.

[0047] FIG. 1 is an X-ray diffraction pattern of the hydrogen-doped indium tin oxide film prepared by the H2 process on the textured battery sheet and the monitoring sheet in the embodiment of the present application.

[0048] As shown in FIG. 1, the X-ray diffraction pattern of the hydrogen-doped indium tin oxide film prepared by the H2 process in the embodiment of the present application is shown. The X-ray diffraction peak of the (211) crystal plane orientation specific to the hydrogen-doped indium tin oxide film is observed at 2θ of 21.5°. The X-ray diffraction peak of the (222) crystal plane orientation typical of the indium tin oxide film appears at 2θ of 30.6°, the X-ray diffraction peak of the (400) crystal plane orientation specific to the hydrogen-doped indium tin oxide film is observed at 2θ of 35.5°. The X-ray diffraction peak of the (440) crystal plane orientation specific to the hydrogen-doped indium tin oxide film is observed at 2θ of 51.0°, and the X-ray diffraction peak of the (622) crystal plane orientation specific to the hydrogen-doped indium tin oxide film is observed at 2θ of 61.8°, which presents a polycrystalline structure with a relatively good crystalline state. According to the hydrogen-doped indium tin oxide film prepared on the textured battery sheet of the present application, the first X-ray diffraction peak intensity of the (400) crystal plane measured by the X-ray diffraction method is greater than the second X-ray diffraction peak intensity of the (222) crystal plane. It indicates that the crystallinity of the (400) crystal plane of the hydrogen-doped indium tin oxide film in the present application is stronger than that of the (222) crystal plane.

[0049] According to the embodiments of the present application, the indium tin oxide film further has a third X-ray diffraction peak of (440) crystal face orientation and a fourth X-ray diffraction peak of (622) crystal face orientation, respectively; wherein the intensity of the third X-ray diffraction peak and the fourth X-ray diffraction peak is less than the intensity of the first X-ray diffraction peak, respectively.

[0050] Further, the indium tin oxide film prepared by the H2O process is also taken as a comparative embodiment, and the XRD diffraction test is performed on the indium tin oxide film on the hydrogen-doped monitoring sheet prepared by the H2 process.

[0051] Fig. 2 is an X-ray diffraction diagram of the indium tin oxide film prepared by the H2 process and the H2O process on the monitoring sheet according to the embodiments of the present application.

[0052] As shown in Fig. 2, the X-ray diffraction peaks of the indium tin oxide film prepared by the H2O process and the hydrogen-doped indium tin oxide film prepared by the H2 process at 21.5° and 30.6° correspond to the (211) and (222) crystal face orientations, and the indium tin oxide film prepared by the H2O process further has the X-ray diffraction peaks of (332) and (444) crystal face orientations at 41.8° and 63.7°, wherein the indium tin oxide film prepared by the H2O process does not have the X-ray diffraction peaks of (440) and (622) crystal face orientations.

[0053] In combination with Fig. 2, Gaussian simulation is performed on the (222) crystal face orientation of the hydrogen-doped indium tin oxide film prepared by the H2 process and the (222) crystal face orientation of the indium tin oxide film prepared by the H2O process, the full width at half maximum (FWHM) of the X-ray diffraction peak of the (222) crystal face is obtained, and it is found by calculation that the grain size of the hydrogen-doped indium tin oxide film prepared by the H2 process is 63.7 nm, and the grain size of the indium tin oxide film prepared by the H2O process is 65.2 nm, so it can be known that the grain sizes of the two kinds of indium tin oxide films are basically the same, and there is no great difference. The grain size is calculated by substituting the full width at half maximum (FWHM) of the X-ray diffraction peak corresponding to the 2θ angle into the Scherrer formula, and the grain size of the (400) crystal face orientation is 59-65 nm, for example, it can be 59.5 nm, 60.2 nm, 61.5 nm, 62.3 nm, 64.8 nm, etc.; the grain size of the (222) crystal face orientation is 58-64 nm, for example, it can be 58.2 nm, 59.3 nm, 60.5 nm, 62.7 nm, 63.5 nm, etc. But it is not limited to the listed values, and other values not listed in the range are also applicable.

[0054] Fig. 3 is a transmission electron microscope diagram of the hydrogen-doped indium tin oxide film prepared by the H2 process on the textured cell sheet according to the embodiments of the present application; and Fig. 4 is a high-resolution transmission electron microscope diagram of the hydrogen-doped indium tin oxide film on the textured cell sheet according to the embodiments of the present application.

[0055] As can be seen from Figure 3, the transmission electron microscope cross-sectional view of the hydrogen-doped indium tin oxide film on the textured cell piece prepared by the H2 process shows a uniform non-columnar structure, and the film thickness is 73 nm. The lattice spacing of the regions shown in Figure 4 is 0.253 nm and 0.297 nm, respectively. By comparing the PDF card database, it can be known from the PDF card of the crystal face spacing of indium tin oxide (JCPDS 060416) that the regions shown in the figure correspond to the (400) and (222) crystal faces of the indium oxide (In2O3) phase, which is consistent with the X-ray diffraction data in Figure 1. The lattice spacing of the (400) crystal face is 0.25-0.26 nm, for example, it can be 0.251 nm, 0.252 nm, 0.253 nm, 0.254 nm, 0.255 nm, 0.256 nm, 0.257 nm, 0.258 nm, 0.259 nm or 0.260 nm, and the lattice spacing of the (222) crystal face is 0.29-0.30 nm, for example, it can be 0.291 nm, 0.292 nm, 0.293 nm, 0.294 nm, 0.295 nm, 0.296 nm, 0.297 nm, 0.298 nm, 0.299 nm or 0.290 nm.

[0056] Figure 5 is a transmission electron microscope view of the indium tin oxide film prepared by the H2O process on the monitoring piece in the embodiment of the present application; and Figure 6 is a high-resolution transmission electron microscope view of the indium tin oxide film prepared by the H2O process on the monitoring piece in the embodiment of the present application.

[0057] As can be seen from Figure 5, the indium tin oxide film prepared by the H2O process is similar to the H2 process, and also has a uniform non-columnar crystal structure, and the film thickness is 94.5 nm. The lattice spacing of the regions shown in Figure 5 is 0.213 nm and 0.295 nm, respectively. By comparing the PDF card database, the regions shown in the figure correspond to the (332) and (222) crystal faces of the indium oxide (In2O3) phase, which also verifies the phase analysis result in Figure 1.

[0058] The hydrogen-doped indium tin oxide film on the textured cell piece prepared by the H2 process according to the present application has a thickness of 65-110 nm, for example, it can be 65 nm, 68 nm, 71 nm, 73 nm, 75 nm, 78 nm, 80 nm, 83 nm, 85 nm, 88 nm, 91 nm, 94 nm, 96 nm, 100 nm, 102 nm, 105 nm, 108 nm, 110 nm, etc., and a sheet resistance of 35-50 Ω / sq, for example, it can be 36 Ω / sq, 40 Ω / sq, 43 Ω / sq, 47 Ω / sq, 49 Ω / sq, etc.

[0059] According to embodiments of the present application, the thickness of the indium tin oxide film prepared on the polishing monitor piece by the H2 process is 100-120 nm, for example, 101 nm, 106 nm, 110 nm, 112 nm, 115 nm, 118 nm, 120 nm, etc.; the square resistance is 25-50 Ω / sq, for example, 26 Ω / sq, 30 Ω / sq, 32 Ω / sq, 35 Ω / sq, 40 Ω / sq, 45 Ω / sq, 50 Ω / sq, etc.; the Hall mobility is 65-85 cm2 / v.s, for example, 67 cm2 / v.s, 69 cm2 / v.s, 70 cm2 / v.s, 75 cm2 / v.s, 81 cm2 / v.s, 85 cm2 / v.s, etc.; the carrier concentration is 1.85×1018-2.2×1018cm-3, for example, 1.86×1018cm-3, 1.95×1018cm-3, 2.1×1018cm-3, 2.15×1018cm-3, 2.17×1018cm-3, 2.18×1018cm-3, 2.2×1018cm-3, etc.; and the resistivity is 3×10-5×10-3Ω·cm, for example, 3.2×10-3Ω·cm, 3.5×10-3Ω·cm, 3.8×10-3Ω·cm, 4.2×10-3Ω·cm, 4.8×10-3Ω·cm, etc. But it is not limited to the listed values, other unlisted values within the range are also applicable. The indium tin oxide film can be used in the front or back of the photovoltaic cell with different thicknesses, and has better light transmission and conductivity. 2 2 2 2 2 2 2 20 20 3 20 3 20 3 20 3 20 3 20 3 20 3 20 3 -4 -4 -4 -4 -4 -4 -4

[0060] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​It should be noted that the thickness of the indium tin oxide film can be measured by an ellipsometer, for example. The sheet resistance can be measured by a four-probe method. The Hall mobility, carrier concentration and resistivity can be measured by a Hall effect tester, wherein the measurement of the Hall parameters of the indium tin oxide film can be performed on a transparent glass, i.e., the indium tin oxide film is prepared on a monitoring piece of the transparent glass.

[0061] Table 1 is a performance table of the indium tin oxide films prepared by the H2 process on the monitoring pieces with different hydrogen contents, and Table 2 is a performance table of the indium tin oxide films prepared by the H2O process on the monitoring pieces with different water vapor partial pressures.

[0062] Table 1 is a performance table of the indium tin oxide films prepared by the H2 process on the monitoring pieces with different hydrogen contents

[0063] Table 2 is a performance table of the indium tin oxide films prepared by the H2O process on the monitoring pieces with different water vapor partial pressures

[0064] As can be seen from Table 1, when the hydrogen content in the H2 process is 0.9%, the carrier concentration of the prepared indium tin oxide film is low, indicating that the film has fewer defects, the current is relatively high, and the film has a high mobility and a low sheet resistance, indicating that the conductivity of the indium tin oxide film prepared by the process is good, so that the film can exhibit high conversion efficiency in a battery. In the H2O process, the water vapor partial pressure is controlled by the amount of water introduced by the water vapor generator, and the other parameters remain the same as in the H2 process, for example, the H content corresponding to different water vapor partial pressures is set to 0.9%. As can be known from the analysis of Table 2, when the water vapor partial pressure in the H2O process is 5x10 -3 Pa, the comprehensive performance of the prepared indium tin oxide film is relatively good.

[0065] According to the embodiments of the present application, the H2O process for preparing the indium tin oxide film doped with hydrogen (In2O3:H film) has large fluctuations in the process. Directly introducing water vapor into the water vapor generator during the process in the cavity can cause instability of the preparation process, and the high humidity on the surface of the target material can cause the target material to form nodules, affecting the quality and consistency of the film.

[0066] FIG. 7 is a schematic diagram of nodule formation on a target material in the H2O process according to an embodiment of the present application. As shown in FIG. 7, during sputtering, nodules or clumps can be formed on the surface of the target material, affecting the uniformity of sputtering and the quality of the film. The H2O process has poor stability, which is not conducive to mass production.

[0067] According to an embodiment of the present application, a solar cell is provided, comprising: a substrate; a hydrogen-doped indium tin oxide film formed on the substrate; and a metal electrode formed on the hydrogen-doped indium tin oxide film; wherein the hydrogen-doped indium tin oxide film has a first X-ray diffraction peak of (400) crystal plane orientation and a second X-ray diffraction peak of (222) crystal plane orientation, and the intensity of the first X-ray diffraction peak is greater than the intensity of the second X-ray diffraction peak.

[0068] According to an embodiment of the present application, the hydrogen-doped indium tin oxide film can replace the existing ITO film and can be used to prepare a solar cell comprising a heterojunction cell structure, which can include: a heterojunction cell (HJT), a back contact cell (BC), an HBC cell (HJT-BC) combining HJT and BC technologies, and a TBC cell (Topcan-BC) combining Topcan and BC technologies.

[0069] According to an embodiment of the present application, since the parameters and performance of the indium tin oxide film used in the solar cell are consistent with those of the indium tin oxide film described above, they are not repeated here.

[0070] According to an embodiment of the present application, taking a typical heterojunction solar cell as an example, the substrate can include a first doped nanocrystalline silicon layer, a first intrinsic amorphous silicon layer, a crystalline silicon substrate, a second intrinsic amorphous silicon layer, and a second doped nanocrystalline silicon layer, which are sequentially stacked; the hydrogen-doped indium tin oxide film includes a first indium tin oxide film and a second indium tin oxide film, the first indium tin oxide film is formed on the first doped nanocrystalline silicon layer, and the second indium tin oxide film is formed on the second doped nanocrystalline silicon layer; and the metal electrode includes a first metal electrode and a second metal electrode, the first metal electrode is formed on the first indium tin oxide film, and the second metal electrode is formed on the second indium tin oxide film.

[0071] Figure 8 is a schematic diagram of a structure of a heterojunction solar cell according to an embodiment of the present application. As shown in Figure 8, the heterojunction solar cell includes an n-type silicon substrate (n-Si), the upper surface (light-receiving side surface) of the n-type silicon substrate (n-Si) is a first intrinsic amorphous silicon layer ((i)a-Si:H), the upper surface of the first intrinsic amorphous silicon layer ((i)a-Si:H) is deposited with a zigzag n-doped first doped nanocrystalline silicon layer ((n)nc-Si:H), and the upper surface of the first doped nanocrystalline silicon layer ((n)nc-Si:H) is further deposited with a first indium tin oxide film (ITO) with a relatively thin thickness. The lower surface (backlight side surface) of the n-type silicon substrate (n-Si) is a second intrinsic amorphous silicon layer ((i)a-Si:H), the lower surface of the second intrinsic amorphous silicon layer ((i)a-Si:H) is deposited with a zigzag p-doped second doped nanocrystalline silicon layer ((p)nc-Si:H), and the lower surface of the second doped nanocrystalline silicon layer ((p)nc-Si:H) is deposited with a second indium tin oxide film (ITO) with a relatively thick thickness.

[0072] According to an embodiment of the present application, the first indium tin oxide film is a hydrogen-doped indium tin oxide film with a thickness of 65-110 nm, and the second indium tin oxide film is a hydrogen-doped indium tin oxide film with a thickness of 65-110 nm. By controlling the thickness of the indium tin oxide film within a suitable range, the light transmittance and the electrical conductivity can be balanced.

[0073] According to an embodiment of the present application, the hydrogen-doped indium tin oxide film is used to prepare a high-efficiency crystalline silicon solar heterojunction cell. The manufacturing process of the high-efficiency heterojunction cell includes gettering + cleaning and texturing, plasma-enhanced chemical vapor deposition (PECVD) passivation treatment, physical vapor deposition (PVD) hydrogen-doped indium tin oxide film, and screen printing.

[0074] Specifically, the present application provides an embodiment of a hydrogen-doped indium tin oxide film of a heterojunction cell and an embodiment of a water-doped indium tin oxide film of a heterojunction cell. The surface of a silicon wafer is treated by gettering + cleaning and texturing to improve the electrical properties and surface morphology. Specifically, the size of the silicon wafer is 182x91mm 2A n-type Czochralski (CZ-si) wafer with a thickness of 150 μm is used for the experiment. The surface of the wafer is cleaned by ozone cleaning to remove organic contaminants and other impurities. A phosphorus gettering process is performed at 900 °C for 2 hours to diffuse phosphorus atoms into the surface of the wafer to form an n+ layer and increase the electrical conductivity of the surface. The surface of the wafer is then treated with 5% hydrofluoric acid (HF) solution for 300 seconds to remove the phosphosilicate glass (PSG) and the damage layer on the surface of the wafer caused by mechanical cutting or phosphorus diffusion. A micro-textured structure is formed on the surface of the wafer by a wet etching process to increase light absorption and reduce surface reflection. Finally, a standard cleaning (RCA) process is performed to completely remove organic and inorganic contaminants on the surface of the wafer and ensure that the surface is clean and ready for subsequent process steps.

[0075] According to embodiments of the present application, a plasma enhanced chemical vapor deposition (PECVD) passivation process can be used to improve the electrical properties and stability of the wafer. Specifically, in this process, a commercial PECVD system is used to deposit an intrinsic hydrogenated amorphous silicon layer (a-Si:H) on both the front and back surfaces of the wafer at a frequency of 13.56 MHz and a temperature of 190 °C to form a passivation film to protect the wafer from the external environment. This passivation film can reduce defects and damage on the surface of the wafer and improve the surface flatness and electrical properties of the wafer. After the passivation process, n-doped and p-doped nanocrystalline layers are deposited on the front and back surfaces of the silicon substrate, respectively, by a very high frequency system to change the electrical properties of the silicon substrate.

[0076] According to embodiments of the present application, a physical vapor deposition (PVD) hydrogen-doped indium tin oxide thin film specifically includes: using a magnetron sputtering to deposit a hydrogen-doped indium tin oxide thin film with a thickness of about 70 nm to 80 nm on both the front and back surfaces of the wafer after doping the nanocrystalline layer. Specifically, the H2 process is used for deposition, the 991 target material is selected, and the power is set to 7-14 kW. When the hydrogen-doped indium tin oxide thin film with a thickness of 70 nm to 80 nm is deposited on the front surface, the working gas includes 94.8%-97% argon, 0.7%-2.3% hydrogen, and 2.3%-2.9% oxygen by volume. When the hydrogen-doped indium tin oxide thin film with a thickness of 75 nm to 85 nm is deposited on the back surface, the working gas includes 95.2%-97.4% argon, 0.6%-2.2% hydrogen, and 2%-2.6% oxygen by volume. The water vapor partial pressure formed during the magnetron sputtering deposition process is 3 x 10 -3 Pa to 9 x 10 -3 Pa. The above thickness of the indium tin oxide thin film can be obtained, respectively. The H2O process is used to dope the indium tin oxide thin film. The water vapor partial pressure is controlled by the amount of water vapor introduced by the water vapor generator in the H2O process, and the remaining parameters are consistent with the H2 process.

[0077] According to the embodiment of the present application, taking the silver electrode as an example, the silver paste can be printed on the first and second ITO films of the battery piece by using the screen printing technology, to form the metal grid pattern. Then, the printed battery piece is put into the oven for drying and sintering at 200℃ for 30 minutes, to remove the solvent and organic matter in the silver paste, solidify the silver paste, melt the glass particles in the silver paste and form good contact and adhesion between the silver paste and the ITO film, and form the low-resistance metal conductive path, i.e., the first and second metal electrodes.

[0078] According to the embodiment of the present application, as shown in FIG. 8, the upper surface of the first ITO film is provided with the first metal electrode (Ag), and the lower surface of the second ITO film is provided with the second metal electrode (Ag).

[0079] According to the embodiment of the present application, the heterojunction solar cell prepared above is tested to verify the application performance of the hydrogen-doped ITO film in the finished battery, and the results are shown in FIGS. 9-11.

[0080] FIG. 9 is the photovoltaic characteristic of the heterojunction solar cell in the embodiment of the present application.

[0081] As shown in FIG. 9, the ITO film prepared by the H2 process has a gain of 0.09-0.15% in the conversion efficiency (Eff) of the battery piece compared with the ITO film prepared by the H2O process, mainly in the improvement of 0.18-0.25% in the fill factor (FF). In addition, the short-circuit current (Jsc) of the heterojunction solar cell corresponding to the H2 process is 39.96 mA / cm 2 , and the open-circuit voltage (Voc) is 0.7469 V on average; the short-circuit current (Jsc) of the heterojunction solar cell corresponding to the H2O process is 39.91 mA / cm 2 , and the open-circuit voltage (Voc) is 0.7468 V on average. It can be seen that the ITO film prepared by the H2 process has an advantage in improving the fill factor (FF), thereby bringing a gain in the conversion efficiency (Eff).

[0082] FIG. 10 is the external quantum efficiency and reflectivity curve of the heterojunction solar cell in the embodiment of the present application; and FIG. 11 is the contact resistance between the ITO film and the metal electrode on the front surface of the heterojunction solar cell in the embodiment of the present application.

[0083] As shown in FIG. 10 in combination with FIG. 9, the hydrogen-doped ITO film prepared by the H2 process has a good response in the wavelength range of 400-600 nm, showing a higher external quantum efficiency and a lower reflectivity, and the corresponding photovoltaic characteristic curve has a short-circuit current (Jsc) of 0.05 mA / cm 2The left and right elevations are improved. Further, as shown in Fig. 11, the H2 process for preparing the indium tin oxide thin film provided in the present application can improve the contact resistance between the silver paste, and the contact resistance of the heterojunction solar cell corresponding to the H2 process for preparing the indium tin oxide thin film is 1.2 mΩ·cm 2 , the contact resistance of the heterojunction solar cell corresponding to the H2O process for preparing the indium tin oxide thin film is 2.0 mΩ·cm 2 . It can be seen that the H2 process for preparing the indium tin oxide thin film can improve the contact resistance between the silver paste, and can improve the efficiency and performance of the solar cell.

[0084] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above-described is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A hydrogen-doped indium tin oxide thin film having a first X-ray diffraction peak of (400) crystal plane orientation and a second X-ray diffraction peak of (222) crystal plane orientation, wherein the first X-ray diffraction peak has a greater intensity than the second X-ray diffraction peak. 2.The indium tin oxide thin film according to claim 1, wherein: the grain size of the grains having the (400) crystal plane orientation or the (222) crystal plane orientation in the indium tin oxide thin film is 58-65 nm; the lattice spacing of the (400) crystal plane is 0.25-0.26 nm, and the lattice spacing of the (222) crystal plane is 0.29-0.30 nm. 4.The indium tin oxide thin film according to any one of claims 1 to 3, wherein: the indium tin oxide thin film further has a third X-ray diffraction peak of (440) crystal plane orientation and a fourth X-ray diffraction peak of (622) crystal plane orientation, respectively; and the third X-ray diffraction peak and the fourth X-ray diffraction peak have intensities less than the intensity of the first X-ray diffraction peak, respectively.

3. The indium tin oxide film of claim 1, wherein, 5.A method for preparing the indium tin oxide thin film according to any one of claims 1 to 4, comprising: depositing a hydrogen-doped indium tin oxide thin film on a substrate by a magnetron sputtering method, wherein the deposition conditions of the magnetron sputtering method comprise: the working gas comprises 94.8-97.4% argon, 0.6-2.3% hydrogen, and 2-2.9% oxygen by volume; and the sputtering power of the magnetron sputtering method is 7-14 kw, and an indium tin oxide target is used. 7.A solar cell, comprising: a substrate; a hydrogen-doped indium tin oxide thin film formed on the substrate; and a metal electrode formed on the indium tin oxide thin film, wherein the hydrogen-doped indium tin oxide thin film has a first X-ray diffraction peak of (400) crystal plane orientation and a second X-ray diffraction peak of (222) crystal plane orientation, and the first X-ray diffraction peak has a greater intensity than the second X-ray diffraction peak. 8.The solar cell according to claim 7, wherein: the grain size of the grains having the (400) crystal plane orientation or the (222) crystal plane orientation in the indium tin oxide thin film is 58-65 nm; the lattice spacing of the (400) crystal plane is 0.25-0.26 nm, and the lattice spacing of the (222) crystal plane is 0.29-0.30 nm. 10.The solar cell according to claim 7, wherein: the indium tin oxide thin film further has a third X-ray diffraction peak of (440) crystal plane orientation and a fourth X-ray diffraction peak of (622) crystal plane orientation, respectively; and the third X-ray diffraction peak and the fourth X-ray diffraction peak have intensities less than the intensity of the first X-ray diffraction peak, respectively. 11.The solar cell according to claim 8, wherein: the substrate comprises a first doped nanocrystalline silicon layer, a first intrinsic amorphous silicon layer, a crystalline silicon substrate, a second intrinsic amorphous silicon layer, and a second doped nanocrystalline silicon layer, which are sequentially stacked. ​ ​ 6. The production method according to claim 5, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. The solar cell of claim 7, wherein, ​ ​ ​ ​ ​ ​ The hydrogen-doped indium tin oxide film comprises a first indium tin oxide film and a second indium tin oxide film, the first indium tin oxide film is formed on the first doped nanocrystalline silicon layer, and the second indium tin oxide film is formed on the second doped nanocrystalline silicon layer. The metal electrode comprises a first metal electrode and a second metal electrode, the first metal electrode is formed on the first indium tin oxide film, and the second metal electrode is formed on the second indium tin oxide film.

12. The solar cell of claim 11, wherein, The thickness of the first indium tin oxide film is 65-110 nm, and the thickness of the second indium tin oxide film is 65-110 nm.

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