Preparation method of back contact solar cell and back contact solar cell
The tunneled oxide film and silicon nitride passivation film are formed through high-density plasma enhanced chemical vapor deposition technology, which solves the problem of film layer defects in TBC battery preparation and achieves more efficient solar cell performance.
Patent Information
- Application Number
- CN202510112045.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-23
- Publication Date
- 2025-05-09
AI Technical Summary
During the preparation of TBC batteries, the membrane layer may crack or fall off, and the substrate may cause defects such as deformation and microcracks, affecting the battery performance.
The tunneled oxide film and silicon nitride passivation film of the battery are formed through high-density plasma enhanced chemical vapor deposition (HDPCVD) technology. The thickness and structure of the film layer are controlled using specific process conditions such as the flow ratio of oxygen and silane, RF power density, pressure and temperature.
Deposit the film layer at a lower temperature to avoid thermal damage to the substrate by high temperatures, improve the density and stability of the film layer, and thus improve the conversion efficiency and performance of solar cells.
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Figure CN119967937A_ABST
Abstract
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 back-contact solar cell and a back-contact solar cell obtained by the method. Background Art
[0002] TBC cells combine the high short-circuit current of IBC cells with the excellent passivation contact characteristics of TOPCon, thereby achieving higher conversion efficiency. Using TOPCon cell passivation technology for IBC solar cells with no obstruction on the front can improve the passivation effect and open circuit voltage without losing current, thereby achieving higher photoelectric conversion efficiency.
[0003] During the preparation of TBC batteries, the film layer may crack or fall off, and the substrate may produce defects such as deformation and microcracks, which will affect the performance of the TBC battery. Summary of the invention
[0004] In order to overcome the above problems, the present disclosure provides a method for preparing a back-contact solar cell, comprising: forming a tunneling oxide film of the cell by high-density plasma enhanced chemical vapor deposition; forming a silicon nitride passivation film of the cell by high-density plasma enhanced chemical vapor deposition.
[0005] In the preparation method, a tunneling oxide film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: forming a tunneling oxide film on the back of a silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the tunneling oxide film is a SiOx film.
[0006] In the preparation method, the thickness of the tunnel oxide film formed by high-density plasma enhanced chemical vapor deposition is 1-2 nm.
[0007] In the preparation method, the process conditions for forming the tunnel oxide film by high-density plasma enhanced chemical vapor deposition are: using oxygen and silane as process gases, the flow ratio of silane to oxygen is 1:10 to 1:20, and the radio frequency power density is 0.5-20mW / cm 2 , pressure is 0.2-50mbar, temperature is 30-500℃, and time is 1-10min.
[0008] In the preparation method, a silicon nitride passivation film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: forming a silicon nitride passivation film on the front and / or back of a silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is a single-layer film or a multi-layer film.
[0009] In the preparation method, the thickness of the silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition is 50-140 nm, and the refractive index of silicon nitride is 2.00-2.10.
[0010] In the preparation method, the process conditions for forming the silicon nitride passivation film on the front and / or back of the silicon wafer by high-density plasma enhanced chemical vapor deposition are: using silane, nitrogen and ammonia as process gases, the volume ratio of silane to ammonia is 1:3 to 1:10, the volume ratio of nitrogen to silane is 1:1 to 10:1, the temperature is 30-500°C, the time is 10-60min, the pressure is 0.2-50mbar, and the RF power density is 0.5-20mW / cm 2 .
[0011] In the preparation method, before forming the tunneling oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: texturing the silicon wafer; etching and alkali polishing the back of the silicon wafer; forming a polycrystalline silicon film or an amorphous silicon film on the back of the silicon wafer; boron diffusion and annealing the silicon wafer; and patterning the silicon wafer once.
[0012] In the preparation method, after forming the tunneling oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: forming a polycrystalline silicon film or an amorphous silicon film on the back of the silicon wafer; annealing and secondary patterning the silicon wafer; forming a silicon nitride passivation film of the battery by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is formed on the front and back of the silicon wafer by high-density plasma enhanced chemical vapor deposition; and forming electrodes on the front and back of the silicon wafer.
[0013] The present disclosure also provides a back-contact solar cell, comprising a tunneling oxide film and a silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition according to the above-mentioned method for preparing a back-contact solar cell.
[0014] According to the preparation method of the back-contact solar cell disclosed in the present invention, the corresponding film layer can be deposited at a relatively low temperature through high-density plasma enhanced chemical vapor deposition. It is friendly to the silicon wafer substrate material and can avoid thermal damage to the substrate caused by high temperature, such as deformation, performance degradation and other problems, and provides stability and density of the membrane structure in the battery. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 is a flow chart of one embodiment of a method for preparing a back-contact solar cell according to the present disclosure.
[0016] Figure 2 is a flow chart of another embodiment of a method for preparing a back-contact solar cell according to the present disclosure.
[0017] Figure 3 FIG. 1 is a structural diagram of one embodiment of a back-contact solar cell according to the present disclosure. DETAILED DESCRIPTION
[0018] 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.
[0019] 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.
[0020] In the absence of conflict, the various embodiments of the present disclosure and the various features therein may be combined with each other.
[0021] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.
[0022] 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.
[0023] 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.
[0024] Among some related technologies, the technical difficulties of TBC batteries are mainly concentrated in the isolation of the back electrode, the uniformity of the polysilicon passivation quality, and the integration with the IBC process route. The technologies used to prepare n-type polysilicon are low-pressure chemical vapor deposition, thermal diffusion, plasma-enhanced chemical vapor deposition, magnetron sputtering deposition, and epitaxial growth. During the high-temperature deposition process, due to the difference in thermal expansion coefficients between the substrate and the film layer, large thermal stress will be generated at the interface. This thermal stress may cause the film layer to crack or fall off, or cause defects such as deformation and microcracks in the substrate.
[0025] The present disclosure aims to provide a method for preparing a TBC cell, aiming to improve the film quality of a passivation film, thereby improving the performance of a solar cell.
[0026] The present disclosure provides a method for preparing a back-contact solar cell. Figure 1 As shown, including:
[0027] S1. Forming a tunnel oxide film of the battery by high-density plasma enhanced chemical vapor deposition (HDPCVD);
[0028] S2. Forming a silicon nitride passivation film for the battery by high-density plasma enhanced chemical vapor deposition.
[0029] In the preparation method, a tunneling oxide film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: forming a tunneling oxide film on the back of a silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the tunneling oxide film is a SiOx film.
[0030] In the preparation method, the thickness of the tunnel oxide film formed by high-density plasma enhanced chemical vapor deposition is 1-2 nm.
[0031] In the preparation method, the process conditions for forming the tunnel oxide film by high-density plasma enhanced chemical vapor deposition are: using oxygen and silane as process gases, the flow ratio of silane to oxygen is 1:10 to 1:20, and the radio frequency power density is 0.5-20mW / cm 2 , pressure is 0.2-50mbar, temperature is 30-500℃, and time is 1-10min.
[0032] In the preparation method, a silicon nitride passivation film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: forming a silicon nitride passivation film on the front and / or back of a silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is a single-layer film or a multi-layer film.
[0033] In the preparation method, the thickness of the silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition is 50-140 nm, and the refractive index of silicon nitride is 2.00-2.10.
[0034] In the preparation method, the process conditions for forming the silicon nitride passivation film on the front and / or back of the silicon wafer by high-density plasma enhanced chemical vapor deposition are: using silane, nitrogen and ammonia as process gases, the volume ratio of silane to ammonia is 1:3 to 1:10, the volume ratio of nitrogen to silane is 1:1 to 10:1, the temperature is 30-500°C, the time is 10-60min, the pressure is 0.2-50mbar, and the RF power density is 0.5-20mW / cm 2 .
[0035] In the preparation method, before forming the tunneling oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: texturing the silicon wafer; etching and alkali polishing the back of the silicon wafer; forming a polycrystalline silicon film or an amorphous silicon film on the back of the silicon wafer; boron diffusion and annealing the silicon wafer; and patterning the silicon wafer once.
[0036] In the preparation method, after forming the tunneling oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: forming a polycrystalline silicon film or an amorphous silicon film on the back of the silicon wafer; annealing and secondary patterning the silicon wafer; forming a silicon nitride passivation film of the battery by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is formed on the front and back of the silicon wafer by high-density plasma enhanced chemical vapor deposition; and forming electrodes on the front and back of the silicon wafer.
[0037] The present disclosure also provides a back-contact solar cell, comprising a tunneling oxide film and a silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition according to the above-mentioned method for preparing a back-contact solar cell.
[0038] HDPCVD is able to produce higher plasma density and quality at lower deposition temperatures than conventional PECVD equipment. HDPCVD provides almost independent ion flux and energy control, improving trench or hole filling capabilities. Moreover, another significant advantage of the HDPCVD configuration is that it can be converted to ICP-RIE for plasma etching. In other words, the HDPCVD configuration allows deposition and etching processes to be performed simultaneously in the same reaction chamber, which is very advantageous when the budget or system footprint is limited.
[0039] High-density plasma technology (HDPCVD / ICPCVD) can produce high-concentration plasmas with higher activity and energy, which 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.
[0040] Compared with the traditional chemical vapor deposition method, HDPCVD can deposit a film of the required thickness in a short time, which is conducive to improving production efficiency, reducing production costs, and meeting the needs of large-scale industrial production. The formed film has high density, low defect density and good uniformity. This can enhance the mechanical strength, chemical stability, electrical and optical properties of the film, and can usually be deposited at a relatively low temperature, which is very beneficial to the silicon wafer substrate material, and can avoid the thermal damage caused by high temperature to the substrate, such as deformation, performance degradation and other problems, while also ensuring the stability of the back-end metal connection. By adjusting the process parameters (such as plasma density, power, gas flow, pressure, temperature, etc.), the growth rate, composition, structure and performance of the film can be accurately controlled to meet the needs of different application scenarios and device designs. Therefore, by the preparation method described in the present disclosure, a dense, uniform and stable amorphous silicon film can be obtained in a solar cell, thereby improving the conversion efficiency of the solar cell.
[0041] According to one embodiment of the present disclosure, referring to Figure 2 , the method for preparing the back contact solar cell comprises the following steps:
[0042] S11, texturing the silicon wafer;
[0043] S12, performing etching and alkaline polishing on the back side of the silicon wafer;
[0044] S13, forming a polycrystalline silicon film or an amorphous silicon film on the back side of the silicon wafer;
[0045] S14, performing boron diffusion and annealing on the silicon wafer;
[0046] S15, patterning the silicon wafer once;
[0047] S16, forming a tunnel oxide film on the back side of the silicon wafer by HDPCVD;
[0048] S17, forming a polycrystalline silicon film or an amorphous silicon film on the back side of the silicon wafer;
[0049] S18, annealing and secondary patterning the silicon wafer;
[0050] S19, forming a silicon nitride passivation film on the front and back sides of the silicon wafer by HDPCVD;
[0051] S20, forming electrodes on the front and back sides of the silicon wafer.
[0052] According to an embodiment of the present disclosure, in the step S11, a mixed solution of alkali and a texturing additive is used to texturing the silicon wafer. The alkali may be KOH or NaOH. After cleaning and texturing, the texture size of the silicon wafer surface is 0.3-4.5 μm.
[0053] According to one embodiment of the present disclosure, in the step S12, the concentration of the KOH solution is 1-5 wt %, the reaction temperature is 60-90° C., and the reaction time is 10-30 min.
[0054] According to one embodiment of the present disclosure, in the step S13, a polycrystalline silicon film or an amorphous silicon film may be formed on the back of the silicon wafer by any applicable vacuum technology, such as thermal oxidation, PECVD, low pressure chemical vapor deposition (LPCVD), high temperature diffusion, magnetron sputtering, and physical vapor deposition (PVD) technology.
[0055] According to one embodiment of the present disclosure, the annealing in steps S14 and S18 is to crystallize the silicon wafer using a high-temperature annealing furnace. The annealing method can be rapid thermal annealing and tubular high-temperature annealing. The annealing atmosphere is nitrogen or argon. The annealing temperature is 700-1080°C and the annealing time is 1-120min.
[0056] For example, N is introduced at a temperature of 700-1080°C. 2 , keep annealing for 300s-7200s; among them, N 2 The flow rate can be 2000-80000sccm.
[0057] According to one embodiment of the present disclosure, the functional area is patterned in the step S15 by patterning and etching processes. The patterning process includes screen printing, laser, photolithography technology, etc. The etching process includes wet and dry processes, such as slurry etching, chemical liquid etching, and plasma etching.
[0058] For example, the patterning can be completed by laser etching, with a laser power of 200-1000 W and a laser spot size of 30 μm×30 μm to 300 μm×300 μm.
[0059] In the photolithography process, a photoresist dry film can be used as a mask, infrared light as an exposure light source, NaOH as a developer, and HNO 3 A mixed solution of HF and MgSO4 was used as a wet etching solution, and then acetone was used to remove the residual photoresist.
[0060] According to one embodiment of the present disclosure, in step S16, oxygen and silane are used as process gases, the flow ratio of silane to oxygen is 1:10 to 1:20, and the RF power density is 0.5-20 mW / cm 2 , pressure is 0.2-50 mbar, temperature is 30-500°C, time is 1-10 min. The thickness of the formed tunnel oxide film is 1-2 nm.
[0061] The deposition power can be from 0.5 to 20 mW / cm2 Any value between 1, 1.5, 2, 2.5, 5, 7.5, 10, 12.5, 15, or 17.5 mW / cm 2 wait.
[0062] The deposition pressure may be any value between 0.2 and 50 mbar, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 10, 15, 20, 25, 30, 35, 40 or 45 mbar, etc.
[0063] The deposition temperature may be any value between 30-500° C., for example, 50, 100, 150, 200, 250, 300, 350, 400, 450 or 475° C., etc.
[0064] The deposition time may be any value between 1 and 10 min, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 min, etc.
[0065] According to an embodiment of the present disclosure, in the step S17, LPCVD is used to form an n-amorphous silicon thin film on the back of the silicon wafer. The amorphous silicon thin film can be a single-layer film or a multi-layer film with a thickness of 10-200 nm.
[0066] According to one embodiment of the present disclosure, in the step S18, the patterning method is laser film removal, the laser wavelength is 556nm, the frequency is 3000-54000Hz, and the energy density is 20-100mW / cm 2 .
[0067] According to one embodiment of the present disclosure, in the step S19, silane, nitrogen and ammonia are used as process gases, the volume ratio of silane to ammonia is 1:3 to 1:10, the volume ratio of nitrogen to silane is 1:1 to 10:1, the temperature is 30-500°C, the time is 10-60min, the pressure is 0.2-50mbar, and the RF power density is 0.5-20mW / cm 2 The thickness of the formed silicon nitride passivation film is 50-140 nm, and the refractive index of silicon nitride is 2.00-2.10.
[0068] The deposition power can be from 0.5 to 20 mW / cm 2 Any value between 1, 1.5, 2, 2.5, 5, 7.5, 10, 12.5, 15, or 17.5 mW / cm 2 wait.
[0069] The deposition pressure may be any value between 0.2 and 50 mbar, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 10, 15, 20, 25, 30, 35, 40 or 45 mbar, etc.
[0070] The deposition temperature may be any value between 30-500° C., for example, 50, 100, 150, 200, 250, 300, 350, 400, 450 or 475° C., etc.
[0071] The deposition time may be any value between 10 and 60 min, for example, 15, 20, 25, 30, 35, 40, 45, 50, 55 min, etc.
[0072] According to one embodiment of the present disclosure, in addition to the silicon nitride passivation film, a film layer such as SiOx, AlOx, SiNxOy, MgFx, etc. may be included to form a composite passivation film.
[0073] According to an embodiment of the present disclosure, in the step S20, the metal electrode is formed 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.
[0074] According to one embodiment of the present disclosure, the back contact solar cell includes a tunneling oxide film and a silicon nitride passivation film formed by high density plasma enhanced chemical vapor deposition (HDPCVD).
[0075] According to one embodiment of the present disclosure, referring to Figure 3 The battery comprises a silicon wafer 1, n + Polysilicon layer 2, p + Polysilicon layer 3, aluminum oxide layer 4, silicon nitride film 5, tunnel oxide film 6, N-electrode 7 and P-electrode 8; wherein silicon nitride film 5 and tunnel oxide film 6 are formed by high density plasma enhanced chemical vapor deposition (HDPCVD).
[0076] In order to enable those skilled in the art to more clearly understand the technical solution of the present disclosure, the technical solution of the present disclosure is described in detail below through specific embodiments.
[0077] Example 1
[0078] The silicon wafer was textured using a mixed solution of KOH and a texturing additive. After cleaning and texturing, the texture size of the silicon wafer surface was 1.5 to 3.0 μm. Then, the silicon wafer was alkaline polished using a 5wt% KOH solution at 80°C for 15 minutes.
[0079] Silane gas deposition was used, the deposition temperature was 300°C, the time was 20 minutes, the process pressure was 10 mbar, and the RF power density was 300 mW / cm 2 , forming a polycrystalline silicon film with a thickness of 20nm.
[0080] Boron diffusion and annealing of silicon wafers, N2 2 , N 2 The flow rate can be 20000sccm and maintained for 2200s for annealing.
[0081] The silicon wafer was patterned by laser etching, with a laser power of 500 W and a laser spot size of 100 μm × 100 μm. A photoresist dry film was used as a mask, infrared light was used as an exposure light source, NaOH was used as a developer, and HNO 3 A mixed solution of HF and MgSO4 was used as a wet etching solution, and then acetone was used to remove the residual photoresist.
[0082] A tunnel oxide film is formed on the back of the silicon wafer by HDPCVD. Oxygen and silane are used as process gases. The flow ratio of silane to oxygen is 1:15. The RF power density is 10mW / cm 2 , pressure is 15 mbar, temperature is 300°C, and time is 5 min; the thickness of the formed tunnel oxide film is 1.3 nm.
[0083] Silane gas deposition was used, the deposition temperature was 100°C, the time was 15 minutes, the process pressure was 10 mbar, and the RF power density was 250 mW / cm 2 , forming an amorphous silicon film with a thickness of 50nm.
[0084] The silicon wafer was annealed and patterned again; the annealing atmosphere was nitrogen, the annealing temperature was 850°C, and the annealing time was 60 min; laser stripping was used for patterning, with a laser wavelength of 556 nm, a frequency of 30,000 Hz, and an energy density of 50 mW / cm 2 .
[0085] Silicon nitride passivation film was deposited on the front and back of the silicon wafer by HDPCVD, using silane, nitrogen and ammonia as process gases, with a volume ratio of silane to ammonia of 1:6, a volume ratio of nitrogen to silane of 5:1, a temperature of 200°C, a time of 30 min, a pressure of 20 mbar, and an RF power density of 10 mW / cm 2 ; The thickness of the formed silicon nitride passivation film is 80nm, and the refractive index of silicon nitride is 2.05.
[0086] Electrodes are formed on the front and back of the silicon wafer, and metal electrodes are formed by screen printing. The front side is sintered at a temperature of 150°C for 20 minutes, and the back side is sintered at a temperature of 180°C for 30 minutes.
[0087] Example 2
[0088] A solar cell was prepared in the same manner as in Example 1, except that after a silicon nitride passivation film was deposited on the front and back sides of the silicon wafer by HDPCVD, a magnesium fluoride film (MgFx) with a thickness of 100 nm was deposited on the front silicon nitride passivation film by an ion sputtering apparatus.
[0089] Example 3
[0090] A solar cell is prepared in the same manner as Example 1, except that when a tunneling oxide film is deposited on the front and back sides of the silicon wafer by HDPCVD, the flow ratio of silane to oxygen is 1:20; when a silicon nitride passivation film is deposited on the front and back sides of the silicon wafer by HDPCVD, a silicon oxynitride film layer is superimposed in the middle of the silicon nitride film layer, the silicon oxynitride film layer has a thickness of 30 nm, and the total thickness of the passivation film is 80-100 nm.
[0091] Comparative Example 1
[0092] A solar cell was prepared in the same manner as in Example 1, except that the tunnel oxide film and the front and back silicon nitride films were formed by LPCVD.
[0093] The conditions for forming the tunnel oxide film are: using a mixed gas of oxygen and silane, where O 2 With SiH 4 The volume ratio is 10:1; the deposition temperature is 400°C, the time is 30 minutes; the process pressure is 15mbar, and the RF power density is 350mW / cm 2 The thickness of the tunnel oxide film formed is 1.5 nm.
[0094] The conditions for forming the front and back silicon nitride films are: using a mixed gas of silane, ammonia and nitrogen, with silane (SiH 4 ) and ammonia (NH 3 ) volume ratio is 1:5, nitrogen (N 2 ) and silane (SiH 4 ) volume ratio of 5:1, deposition time of 30min, process pressure of 15mbar, RF power density of 350mW / cm 2 The thickness of the formed silicon nitride film is 80nm.
[0095] Comparative Example 2
[0096] A solar cell was prepared in the same manner as in Example 1, except that the tunnel oxide film and the front and back silicon nitride films were formed by PECVD.
[0097] The conditions for forming the tunnel oxide film are: using a mixed gas of oxygen and silane, where O 2 With SiH 4The volume ratio is 10:1; the deposition temperature is 400°C, the time is 30 minutes; the process pressure is 15mbar, and the RF power density is 350mW / cm 2 The thickness of the tunnel oxide film formed is 1.8 nm.
[0098] The conditions for forming the front and back silicon nitride films are: using a mixed gas of silane, ammonia and nitrogen, with silane (SiH 4 ) and ammonia (NH 3 ) volume ratio of 1:5, nitrogen (N 2 ) and silane (SiH 4 ) volume ratio of 5:1, deposition time of 30min, process pressure of 15mbar, RF power density of 350mW / cm 2 The thickness of the formed silicon nitride film is 80nm.
[0099] The solar cells prepared in the examples and comparative examples were subjected to performance tests, and the performance parameters of the obtained cells are shown in Tables 1-3 below.
[0100] Table 1: Comparison of electrical properties of solar cells of the embodiments of the present disclosure and the comparative examples
[0101] Number of samples Conversion efficiency % Voc(V) Isc(A) FF(%) Yield (%) Example 1 867 25.85 0.7382 13.79 85.004 98.9％ Example 2 812 25.87 0.7383 13.80 85.012 98.5％ Example 3 787 25.86 0.7383 13.80 85.009 98.7％ Comparative Example 1 834 25.83 0.7369 13.78 84.996 96.3％ Comparative Example 2 812 25.79 0.7371 13.76 84.993 96.5％
[0102] Table 2: Comparison of TLM test results of the back side of solar cells prepared in the embodiments of the present disclosure and the comparative examples
[0103] Square resistance average Ω / sq <![CDATA[Contact resistivity mΩcm 2 > Contact resistance Ω Example 1 44.5 0.87 0.63 Example 2 43.7 0.85 0.58 Example 3 45.2 0.93 0.75 Comparative Example 1 46.3 1.03 0.87 Comparative Example 2 47.4 1.24 0.98
[0104] Table 3: Comparison of front TLM test of solar cells prepared in the embodiments of the present disclosure and the comparative examples
[0105] Square resistance average Ω / sq <![CDATA[Contact resistivity mΩcm 2 > Contact resistance Ω Example 1 338.4 1.72 1.09 Example 2 324.8 1.83 1.13 Example 3 342.4 1.63 1.05 Comparative Example 1 336.7 1.50 0.99 Comparative Example 2 337.9 1.54 1.02
[0106] From the data in Table 1, it can be observed that the solar cell prepared by this method has obvious advantages in energy conversion efficiency, which is increased by at least 0.02%, and can significantly improve efficiency and reduce costs. From Table 2, it can be seen that the back contact resistance is effectively reduced, and from Table 3, it can be seen that the front contact resistance is effectively reduced.
[0107] 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 back contact solar cell, comprising: Forming the battery's tunnel oxide film by high-density plasma enhanced chemical vapor deposition; The silicon nitride passivation film of the battery is formed by high-density plasma enhanced chemical vapor deposition.
2. The preparation method according to claim 1, wherein The tunnel oxide film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: A tunnel oxide film is formed on the back side of the silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the tunnel oxide film is a SiOx film.
3. The preparation method according to claim 2, wherein The thickness of the tunnel oxide film formed by high-density plasma enhanced chemical vapor deposition is 1-2 nm.
4. The preparation method according to claim 2, wherein The process conditions for forming the tunnel oxide film by high-density plasma enhanced chemical vapor deposition are: using oxygen and silane as process gases, the flow ratio of silane to oxygen is 1:10 to 1:20, and the RF power density is 0.5-20mW / cm 2 , pressure is 0.2-50mbar, temperature is 30-500℃, and time is 1-10min.
5. The preparation method according to any one of claims 1 to 4, wherein: The silicon nitride passivation film of the battery is formed by high-density plasma enhanced chemical vapor deposition, including: A silicon nitride passivation film is formed on the front and / or back side of the silicon wafer by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is a single-layer film or a multi-layer film.
6. The preparation method according to claim 5, wherein: The thickness of the silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition is 50-140 nm, and the refractive index of silicon nitride is 2.00-2.
10.
7. The preparation method according to claim 5, wherein: The process conditions for forming a silicon nitride passivation film on the front and / or back of a silicon wafer by high-density plasma enhanced chemical vapor deposition are as follows: silane, nitrogen and ammonia are used as process gases, the volume ratio of silane to ammonia is 1:3 to 1:10, the volume ratio of nitrogen to silane is 1:1 to 10:1, the temperature is 30-500°C, the time is 10-60min, the pressure is 0.2-50mbar, and the radio frequency power density is 0.5-20mW / cm 2 .
8. The preparation method according to any one of claims 1 to 4, wherein: Before forming the tunnel oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: Texturing of silicon wafers; Etch and alkali polish the back of the silicon wafer; forming a polycrystalline silicon film or an amorphous silicon film on the back side of the silicon wafer; Boron diffusion and annealing of silicon wafers; The silicon wafer is patterned once.
9. The preparation method according to claim 8, wherein: After forming the tunnel oxide film of the battery by high-density plasma enhanced chemical vapor deposition, it also includes: forming a polycrystalline silicon film or an amorphous silicon film on the back side of the silicon wafer; Annealing and re-patterning the silicon wafer; Forming a silicon nitride passivation film of the battery by high-density plasma enhanced chemical vapor deposition, wherein the silicon nitride passivation film is formed on the front and back sides of the silicon wafer by high-density plasma enhanced chemical vapor deposition; Electrodes are formed on the front and back sides of the silicon wafer.
10. A back-contact solar cell, comprising a tunneling oxide film and a silicon nitride passivation film formed by high-density plasma enhanced chemical vapor deposition according to the method for preparing a back-contact solar cell according to any one of claims 1 to 9.