Preparation method of silicon-based heterojunction solar cell and solar cell

Abstract

The invention provides a preparation method of a silicon-based heterojunction solar cell. According to the preparation method, an amorphous silicon thin film of the cell is formed through high-density plasma enhanced chemical vapor deposition (HDPCVD or ICPCVD). According to the preparation method disclosed by the invention, the compact and stable amorphous silicon film can be obtained, so that the conversion efficiency of the solar cell is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of crystalline silicon solar cells, and in particular to a method for preparing a silicon-based heterojunction solar cell and a solar cell obtained by the method. Background Art

[0002] Heterojunction is a special PN junction, which is formed by depositing amorphous silicon thin film on crystalline silicon. It is a type of N-type cell. Compared with P-type silicon wafers, N-type silicon wafers have excellent stability and efficiency improvement due to their long minority carrier lifetime and no light-induced degradation. In particular, heterojunction solar cells are more attractive due to their simple process flow, double-sided power generation, and low temperature coefficient.

[0003] In the traditional preparation method of silicon heterojunction cells, plasma chemical vapor deposition (PECVD) is used to form amorphous silicon thin films; however, PECVD has problems such as slow deposition rate and ion damage, which affect the quality of silicon thin films and film stability. Furthermore, the film quality of amorphous silicon thin films has an important influence on the generation, recombination and transmission of battery carriers. Therefore, a new preparation method is needed to improve the film quality of amorphous silicon thin films, thereby improving the performance of solar cells. Summary of the invention

[0004] In order to overcome the above problems, in the first aspect, the present disclosure provides a method for preparing a silicon-based heterojunction solar cell, which forms an amorphous silicon film of the cell by high-density plasma enhanced chemical vapor deposition (HDPCVD or ICPCVD). Through the preparation method described in the present disclosure, a dense and stable amorphous silicon film can be obtained, thereby improving the conversion efficiency of the solar cell.

[0005] In the method for preparing the silicon-based heterojunction solar cell, an amorphous silicon film is formed on the front side of the silicon substrate by high-density plasma enhanced chemical vapor deposition, and the amorphous silicon film includes an i-amorphous silicon film and / or an n-amorphous silicon film.

[0006] In the preparation method of the silicon-based heterojunction solar cell, an amorphous silicon film is formed by high-density plasma enhanced chemical vapor deposition, comprising: using a mixed gas of hydrogen, silane and borane as a process gas to perform high-density plasma enhanced chemical vapor deposition to form the amorphous silicon film, wherein the flow ratio of hydrogen to silane is 1:1.5 to 1:2, the flow ratio of borane to silane is 1:2 to 1:2.5, and the deposition power is 1-300 mW / cm 2 , the deposition pressure is 0.5-10mbar, the deposition temperature is 80℃-300℃, and the deposition time is 5-50min.

[0007] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the i-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-10 nm.

[0008] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the n-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-30 nm.

[0009] The method for preparing the silicon-based heterojunction solar cell further comprises cleaning and texturing the silicon substrate before forming the amorphous silicon film by high-density plasma enhanced chemical vapor deposition.

[0010] The method for preparing a silicon-based heterojunction solar cell, after forming an amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition, further comprises:

[0011] forming an i-amorphous silicon thin film and a p-amorphous silicon thin film on the back side of the silicon substrate;

[0012] forming a transparent conductive film (TCO) on the front and back sides of the silicon substrate; and

[0013] Electrodes are formed on the front and back sides of the silicon substrate.

[0014] In a second aspect, the present disclosure further provides a silicon-based heterojunction solar cell, which includes an amorphous silicon thin film formed by high-density plasma enhanced chemical vapor deposition according to the method for preparing a silicon-based heterojunction solar cell described in the first aspect of the present disclosure.

[0015] In the silicon-based heterojunction solar cell disclosed in the present invention, the amorphous silicon thin film includes an i-amorphous silicon thin film and / or an n-amorphous silicon thin film.

[0016] The preparation method of the silicon-based heterojunction solar cell disclosed in the present invention can change the atomic bonding mode in the amorphous silicon film formed by deposition, improve the density and uniformity of the amorphous silicon film, thereby improving the optical properties and electron transmission properties of the amorphous silicon film, and further improve the energy conversion efficiency of the HJT cell.

[0017] The disclosed method for preparing silicon-based heterojunction solar cells can also increase the film deposition rate, optimize the temperature and time of subsequent TCO deposition and metallization processes, and reduce the cost of HJT cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flow chart of a method for preparing a solar cell according to the present invention.

[0019] Figure 2 is a structural diagram of a solar cell according to the present disclosure. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the technical solution of the present disclosure is described in detail below with reference to the accompanying drawings.

[0021] Example embodiments will be described more fully below with reference to the accompanying drawings, but the example embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, the purpose of providing these embodiments is to make the present disclosure thorough and complete and to enable those skilled in the art to fully understand the scope of the present disclosure.

[0022] In the absence of conflict, the various embodiments of the present disclosure and the various features therein may be combined with each other.

[0023] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0024] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It will also be understood that when the terms "comprising" and / or "made of" are used in this specification, the presence of the features, wholes, steps, operations, elements and / or components is specified, but the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof is not excluded.

[0025] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted as having an idealized or overly formal meaning unless explicitly defined as such herein.

[0026] The present invention provides a method for preparing a silicon-based heterojunction solar cell, which forms an amorphous silicon film of the cell by high-density plasma enhanced chemical vapor deposition (HDPCVD or ICPCVD).

[0027] High-density plasma technology (HDPCVD / ICPCVD) can produce high-concentration plasmas, which have higher activity and energy, and can promote effective collisions and chemical reactions between reactive gas molecules, thereby improving deposition rate and film quality. At the same time, the atomic bonding mode can be regulated by process conditions to affect the structure, optical properties and electron transport of the deposited layer. Therefore, through the preparation method disclosed in the present invention, a dense, uniform and stable amorphous silicon film can be obtained in a solar cell, thereby improving the conversion efficiency of the solar cell.

[0028] In the method for preparing the silicon-based heterojunction solar cell, an amorphous silicon film is formed on the front side of the silicon substrate by high-density plasma enhanced chemical vapor deposition, and the amorphous silicon film includes an i-amorphous silicon film and / or an n-amorphous silicon film.

[0029] In the method for preparing the silicon-based heterojunction solar cell, the process conditions for forming the amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition are: using a mixed gas of hydrogen, silane and borane, the flow ratio of hydrogen to silane is 1:1.5 to 1:2, the flow ratio of borane to silane is 1:2 to 1:2.5, and the deposition power is 1 to 300 mW / cm 2 , the deposition pressure is 0.5 to 10 mbar, the deposition temperature is 80°C-300°C, and the deposition time is 5-50 min.

[0030] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the i-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-10 nm.

[0031] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the n-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-30 nm.

[0032] The method for preparing the silicon-based heterojunction solar cell further comprises the step of cleaning and texturing the silicon substrate before forming the amorphous silicon film by high-density plasma enhanced chemical vapor deposition.

[0033] The method for preparing a silicon-based heterojunction solar cell further comprises the following steps after forming an amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition:

[0034] forming an i-amorphous silicon thin film and a p-amorphous silicon thin film on the back side of the silicon substrate;

[0035] forming a TCO layer on the front and back sides of the silicon substrate; and

[0036] Electrodes are formed on the front and back sides of the silicon substrate.

[0037] According to one embodiment of the present disclosure, referring to Figure 1 , the method for preparing the solar cell comprises the following steps:

[0038] S1, using an N-type silicon wafer as a silicon substrate, cleaning and texturing it;

[0039] S2, forming an i-amorphous silicon thin film and an n-amorphous silicon thin film on the front side of the silicon substrate;

[0040] S3, forming an i-amorphous silicon thin film and a p-amorphous silicon thin film on the back side of the silicon substrate;

[0041] S4, forming a TCO layer on the front and back sides of the silicon substrate; and

[0042] S5. Electrodes are formed on the front and back sides of the silicon substrate.

[0043] According to one embodiment of the present disclosure, in the step S1, a mixed solution of alkali and H2O2 is used to clean the silicon substrate, and a mixed solution of alkali and a texturing additive is used to texturing the silicon wafer. The alkali may be KOH. After cleaning and texturing, the texture size of the surface of the silicon substrate is 0.5 μm to 4.0 μm.

[0044] According to one embodiment of the present disclosure, in the step S2, high-density plasma enhanced chemical vapor deposition is used to form the i-amorphous silicon film and / or the n-amorphous silicon film on the front side of the silicon substrate.

[0045] The process parameters for forming the i-amorphous silicon film on the front side of the silicon substrate by high-density plasma enhanced chemical vapor deposition include: using a mixed gas of hydrogen, silane and borane as the process gas, wherein the flow ratio of hydrogen to silane is 1:1.5 to 1:2, the flow ratio of borane to silane is 1:2 to 1:2.5, and the deposition power is 1 to 300 mW / cm 2 , the deposition pressure is 0.5 to 10 mbar, the deposition temperature is 80°C-300°C, and the deposition time is 5-50 min.

[0046] Specifically, the flow ratio of hydrogen to silane in the mixed gas can be any value between 1:1.5 and 1:2, such as 1:1.6, 1:1.7, 1:1.8 or 1:1.9.

[0047] The flow ratio of borane to silane in the mixed gas may be any value between 1:2 and 1:2.5, such as 1:2.1, 1:2.2, 1:2.3 or 1:2.4.

[0048] The deposition power can be from 1 to 300 mW / cm 2 Any value between 25, 50, 75, 100, 125, 150, 175, 200, 225, 250 or 275 mW / cm 2 wait.

[0049] The deposition pressure may be any value between 0.5 and 10 mbar, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 or 9.5 mbar, etc.

[0050] The deposition temperature may be any value between 80° C. and 300° C., for example, 100, 125, 150, 175, 200, 225, 250 or 275° C., etc.

[0051] The deposition time may be any value between 5 and 50 min, such as 10, 15, 20, 25, 30, 35, 40 or 45 min.

[0052] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the i-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-10 nm, such as 2, 3, 4, 5, 6, 7, 8 or 9 nm.

[0053] In the method for preparing the silicon-based heterojunction solar cell, the thickness of the n-amorphous silicon thin film formed by high-density plasma enhanced chemical vapor deposition is 1-30 nm, such as 5, 10, 15, 20 or 25 nm.

[0054] According to one embodiment of the present disclosure, in the step S3, the i-amorphous silicon film and the p-amorphous silicon film can be formed on the back side of the silicon substrate by any applicable vacuum technology, for example, thermal oxidation, PECVD, low pressure chemical vapor deposition (LPCVD), high temperature diffusion, magnetron sputtering and physical vapor deposition (PVD) technology can be used.

[0055] The thickness of the i-amorphous silicon film is 1-10 nm; the thickness of the p-amorphous silicon film is 1-30 nm.

[0056] According to one embodiment of the present disclosure, in the step S4, the TCO material can be a transparent conductive thin film material such as ITO, IWO, ITiO, IMO, IO and AZO. The TCO layer can be composed of a single layer or a multilayer film. The thickness of the TCO layer is 30-200nm. The TCO layer can be formed by resistive thermal evaporation, electron beam evaporation, magnetron sputtering and plasma deposition.

[0057] For example, the process parameters for depositing the front TCO conductive layer using the PECVD process are as follows: the temperature is 10-150°C, a mixed gas of argon, hydrogen and / or oxygen is introduced into the chamber, the volume ratio of argon to hydrogen and / or oxygen is 1-3, the pressure of the chamber is 0.5-2Pa, and vacuum annealing is performed after the deposition is completed. The vacuum annealing treatment temperature is 180-200°C and the annealing time is 5-30min.

[0058] The process parameters for PECVD deposition of the back TCO conductive layer are as follows: the temperature is 20-200°C, a mixed gas of argon, hydrogen and / or oxygen is introduced into the chamber, the volume ratio of argon to hydrogen and / or oxygen is 1-3, the pressure of the chamber is 0.5-2Pa, and vacuum annealing is performed after the deposition is completed. The temperature of the vacuum annealing treatment is 200-220°C, and the annealing time is 5-40min.

[0059] According to one embodiment of the present disclosure, in the step S5, a metal electrode is formed on the TCO layer by screen printing, wherein the front sintering temperature is 150-200°C for 20-30 minutes, and the back sintering temperature is 180-220°C for 20-30 minutes.

[0060] The present disclosure also provides a silicon-based heterojunction solar cell, which includes an amorphous silicon thin film formed by high-density plasma enhanced chemical vapor deposition.

[0061] In the silicon-based heterojunction solar cell disclosed in the present invention, the amorphous silicon thin film includes an i-amorphous silicon thin film and / or an n-amorphous silicon thin film.

[0062] According to one embodiment of the present disclosure, referring to Figure 2 , the battery comprises the following structure:

[0063] N-type silicon wafer; i-amorphous silicon film (i a-Si:H); n-amorphous silicon film (n a-Si:H); p-amorphous silicon film (pa-Si:H); TCO film; N-electrode; P-electrode.

[0064] Compared with the prior art, the preparation method of silicon-based heterojunction solar cells disclosed in the present invention can change the atomic bonding mode in the amorphous silicon film formed by deposition, improve the density and uniformity of the amorphous silicon film, thereby improving the optical properties and electron transmission properties of the amorphous silicon film, and further improve the energy conversion efficiency of the HJT cell.

[0065] The disclosed method for preparing silicon-based heterojunction solar cells can also increase the film deposition rate, optimize the temperature and time of subsequent TCO deposition and metallization processes, and reduce the cost of HJT cells.

[0066] In order to enable those skilled in the art to more clearly understand the technical solutions provided by the embodiments of the present disclosure, the technical solutions provided by the embodiments of the present disclosure are described in detail below through specific examples.

[0067] Example 1

[0068] S1. Select N-type silicon wafer as silicon substrate and clean and texture it. During the texture process, keep it at 95℃ for 420s in a mixed solution with a texture additive concentration of 1wt% and a KOH concentration of 0.05wt%, and the texture size is 1±0.5μm;

[0069] S2. Forming an i-amorphous silicon film and an n-amorphous silicon film on the front side of the silicon substrate by HDPCVD.

[0070] Process parameters for the front i-amorphous silicon film: hydrogen:silane:borane flow ratio of 1:2:1, deposition power of 100mW / cm2 , the deposition pressure is 2 mbar, the deposition temperature is 150°C, and the deposition time is 10 min; the thickness of the formed i-amorphous silicon film is 7 nm.

[0071] Process parameters for the front n-amorphous silicon film: hydrogen:silane:borane flow ratio is 2:3:5, deposition power is 200mW / cm 2 , the deposition pressure is 5 mbar, the deposition temperature is 200°C, and the deposition time is 15 min; the thickness of the formed n-amorphous silicon film is 16 nm.

[0072] S3. Forming an i-amorphous silicon thin film and a p-amorphous silicon thin film on the back side of the silicon substrate by PECVD.

[0073] Process parameters for back-side i-amorphous silicon film: hydrogen:silane:borane flow ratio of 1:2:1, deposition power of 130 mW / cm 2 , the deposition pressure is 2 mbar, the deposition temperature is 180°C, and the deposition time is 15 min; the thickness of the formed i-amorphous silicon film is 9 nm.

[0074] Process parameters for back-side p-amorphous silicon film: hydrogen:silane:borane flow ratio of 2:4:3, deposition power of 180 mW / cm 2 , the deposition pressure is 5 mbar, the deposition temperature is 220°C, and the deposition time is 20 min; the thickness of the formed p-amorphous silicon film is 18 nm.

[0075] S4. Forming a TCO film on the front and back sides of the silicon substrate by PECVD.

[0076] The process parameters of the front TCO film are as follows: deposition temperature is 100°C, a mixed gas of argon, hydrogen and oxygen, the volume ratio of argon to hydrogen and oxygen is 1:1, the deposition pressure is 1-2Pa, the vacuum annealing temperature is 180°C, and the annealing time is 10min.

[0077] The process parameters of the back TCO film are as follows: temperature is 120°C, a mixed gas of argon, hydrogen and / or oxygen is introduced into the chamber, the volume ratio of argon to hydrogen and / or oxygen is 1:1, the deposition pressure is 1-2Pa, and vacuum annealing is performed after deposition is completed. The vacuum annealing temperature is 200°C and the annealing time is 12 minutes.

[0078] S5. Electrodes are formed on the front and back sides of the silicon substrate by screen printing.

[0079] Electrodes were formed on the front and back sides of the silicon substrate by screen printing. The sintering temperature of the front side was 150° C. for 20 min, and the sintering temperature of the back side was 180° C. for 30 min.

[0080] The heterojunction solar cell is prepared through the above process.

[0081] Example 2

[0082] A heterojunction cell was prepared in the same manner as in Example 1, except that the process parameters of the front i-amorphous silicon film were as follows: the flow ratio of hydrogen:silane:borane was 1:2:1, and the deposition power was 110 mW / cm 2 , the deposition pressure is 1.8 mbar, the deposition temperature is 140°C, and the deposition time is 12 min; the thickness of the formed i-amorphous silicon film is 8 nm.

[0083] The process parameters for the front n-amorphous silicon film are: hydrogen:silane:borane flow ratio is 2:5:2, and the deposition power is 200mW / cm 2 , the deposition pressure is 5 mbar, the deposition temperature is 200°C, and the deposition time is 15 min; the thickness of the formed n-amorphous silicon film is 15 nm.

[0084] Comparative Example 1

[0085] A heterojunction cell was prepared in the same manner as in Example 1, except that the front i-amorphous silicon film and the n-amorphous silicon film were formed by PECVD.

[0086] The process parameters of the front i-amorphous silicon film are: hydrogen:silane:borane flow ratio is 1:2:1, and the deposition power is 130mW / cm 2 , the deposition pressure is 2 mbar, the deposition temperature is 180°C, and the deposition time is 15 min; the thickness of the formed i-amorphous silicon film is 8 nm.

[0087] The process parameters for the front n-amorphous silicon film are: hydrogen:silane:borane flow ratio of 2:4:3, deposition power of 150mW / cm 2 , the deposition pressure is 6 mbar, the deposition temperature is 200°C, and the deposition time is 18 min; the thickness of the formed n-amorphous silicon film is 19 nm.

[0088] The batteries prepared in the examples and comparative examples were subjected to performance tests, and the electrical performance parameters of the batteries are shown in Table 1 below.

[0089] Table 1: Comparison of electrical properties of solar cells of the embodiments of the present disclosure and the comparative examples

[0090] Number of samples Conversion efficiency % Voc_mV Isc_A FF_% Example 1 20 25.458 752.1 8.71 84.82 Example 2 20 25.447 751.8 8.68 84.80 Comparative Example 1 20 25.268 749.2 8.62 82.69

[0091] As can be seen from Table 1, the solar cells made by this method have obvious advantages in cell performance, with efficiency increased by at least 0.18%, Vov increased by at least 2.6mV, and FF increased by at least 2.11%, which can significantly improve efficiency and reduce costs.

[0092] The contact resistance of the batteries prepared in the examples and comparative examples was tested, and the comparison of the contact resistance of each battery is shown in Table 2 below.

[0093] Table 2: Comparison of contact resistance of solar cells prepared in the embodiments of the present disclosure and the comparative examples

[0094] Number of samples Contact resistance ohm <![CDATA[Contact resistivity mohmcm 2 > Example 1 5 2.75 2.98 Example 2 5 2.84 3.02 Comparative Example 1 5 2.95 3.21

[0095] As can be seen from Table 2, the solar cells made by this method have obvious advantages in front contact, and the contact resistivity is increased by at least 0.19mohmcm2, which can significantly reduce losses and improve efficiency.

[0096] Example embodiments have been disclosed herein, and although specific terms are employed, they are used and should be interpreted only in a general illustrative sense and not for limiting purposes. In some instances, it will be apparent to those skilled in the art that, unless otherwise expressly noted, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments. Therefore, those skilled in the art will appreciate that various changes in form and detail may be made without departing from the scope of the present disclosure as set forth in the appended claims.

Claims

1. A method for preparing a silicon-based heterojunction solar cell, comprising: The amorphous silicon thin film for the battery is formed by high-density plasma enhanced chemical vapor deposition.

2. The preparation method according to claim 1, wherein The preparation method further comprises: An amorphous silicon film is formed on the front side of the silicon substrate by high-density plasma enhanced chemical vapor deposition, wherein the amorphous silicon film includes an i-amorphous silicon film and / or an n-amorphous silicon film.

3. The preparation method according to claim 1, wherein The method comprises: using a mixed gas of hydrogen, silane and borane as a process gas to perform high-density plasma enhanced chemical vapor deposition to form the amorphous silicon film, wherein the flow ratio of hydrogen to silane is 1:1.5 to 1:2, the flow ratio of borane to silane is 1:2 to 1:2.5, and the deposition power is 1-300 mW / cm 2 , the deposition pressure is 0.5-10mbar, the deposition temperature is 80℃-300℃, and the deposition time is 5-50min.

4. The preparation method according to claim 2 or 3, wherein Forming an amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition, further comprising: The i-amorphous silicon film is formed by high-density plasma enhanced chemical vapor deposition with a thickness of 1-10 nm.

5. The preparation method according to claim 2 or 3, wherein: Forming an amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition, further comprising: The thickness of the n-amorphous silicon film formed by high-density plasma enhanced chemical vapor deposition is 1-30 nm.

6. The preparation method according to any one of claims 1 to 3, wherein: Before forming the amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition, the preparation method further comprises: The silicon substrate is cleaned and textured.

7. The preparation method according to any one of claims 1 to 3, wherein: After forming an amorphous silicon thin film by high-density plasma enhanced chemical vapor deposition, the method further comprises: forming an i-amorphous silicon thin film and a p-amorphous silicon thin film on the back side of the silicon substrate; forming a transparent conductive film (TCO) on the front and back sides of the silicon substrate; and Electrodes are formed on the front and back sides of the silicon substrate.

8. A silicon-based heterojunction solar cell, comprising an amorphous silicon thin film formed by high-density plasma enhanced chemical vapor deposition according to the method for preparing a silicon-based heterojunction solar cell according to any one of claims 1 to 7.

9. The silicon-based heterojunction solar cell according to claim 8, wherein: The amorphous silicon film is an i-amorphous silicon film and / or an n-amorphous silicon film.

10. The silicon-based heterojunction solar cell according to claim 9, wherein: The thickness of the i-amorphous silicon film is 1-10 nm, and the thickness of the n-amorphous silicon film is 1-30 nm.

Images