A crystalline silicon solar cell and a preparation method and application thereof

Abstract

The application provides a crystalline silicon solar cell, a preparation method and application thereof. The crystalline silicon solar cell comprises a substrate, a thin film layer and an electrode which are sequentially arranged. The thin film layer comprises a first thin film area and a second thin film area. The thickness of the first thin film area is greater than that of the second thin film area. The electrode is arranged on the second thin film area and forms a contact with the substrate. By reducing the thickness of the second thin film area which is in contact with the electrode, the contact resistance between the electrode and the substrate is improved, the recombination in the electrode area is reduced, the average open circuit voltage is increased, and the optical performance and the improvement window of the passivation performance of the first thin film area which is not in contact with the electrode are increased. The crystalline silicon solar cell solves the problem that the electrode ablation capacity is incompatible with the thin film composition and thickness, effectively improves the cell efficiency, and the preparation method is compatible with the screen printing high-temperature sintering process, and large-scale mass production at low cost can be realized.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a crystalline silicon solar cell, its preparation method, and its application. Background Technology

[0002] Solar energy, as a sustainable green energy source to replace fossil fuels, has experienced rapid development in recent years. Among existing solar cells, silicon solar cells dominate due to the abundance of silicon in the Earth's crust and its excellent electrical and mechanical properties. In the future development of photovoltaic technology, further improving the photoelectric performance of silicon solar cells, increasing cell conversion efficiency, and reducing solar cell production costs are ongoing goals pursued by the industry.

[0003] To improve the conversion efficiency of crystalline silicon solar cells, one or more thin films are typically deposited on the surface, such as well-known silicon nitride films, alumina / silicon nitride tandem films, and SiO2 / polycrystalline silicon / silicon nitride tandem films. On the front side of the solar cell, a special thin film design can reduce the reflection of incident light and enhance light absorption, thereby generating more charge carriers. Simultaneously, the thin film covering the surface can provide surface passivation, reduce surface recombination, and further improve the conversion efficiency of the solar cell. For example, CN103413838A discloses a crystalline silicon solar cell and its fabrication method. The crystalline silicon solar cell includes a first conductivity type crystalline silicon layer, a second conductivity type crystalline silicon layer, a tunneling dielectric film layer, a metal front electrode, and an anti-reflection film layer arranged sequentially. The tunneling dielectric film layer can both passivate the front side of the first conductivity type crystalline silicon layer and transfer charge carriers, thereby improving the performance of the solar cell. CN102122674A discloses a crystalline silicon solar cell and its fabrication method. The structure of the crystalline silicon solar cell is as follows: the surface of the N+ emitter of the PN+ junction silicon substrate has a first amorphous aluminum oxide layer and an amorphous silicon nitride layer; a silver electrode passes through the amorphous silicon nitride layer and the first amorphous aluminum oxide layer and is connected to the N+ emitter; the surface of the P-type substrate has a composite passivation dielectric layer composed of a silicon oxide layer and a second amorphous aluminum oxide layer; the P-type substrate is in contact with the back electrode; the cell has good passivation effect and anti-reflection performance on the front surface, and the passivation effect of the composite passivation dielectric layer on the back surface is also good.

[0004] In crystalline silicon solar cells, as exemplified by the aforementioned existing technologies, the common method of metallization involves screen printing electrode materials and then ablating the surface film at high temperatures to form ohmic contacts with the substrate. During the ablation of the electrode material, the substrate is simultaneously ablated, creating recombination centers. In solar cells, recombination between the electrode material and the substrate is a key factor limiting the cell's conversion efficiency. Reducing recombination involves lowering the ablation capability of the electrode material. A reduced ablation capability also reduces the ability to ablate the film, preventing the electrode material from forming a good ohmic contact with the substrate and limiting the solar cell's photoelectric conversion efficiency. To balance low ablation capability with good ohmic contact, the film thickness needs to be reduced. However, reducing the thickness affects the passivation, optical performance, and appearance of the film in the non-contact area, thus limiting the window for adjusting the composition and thickness of the solar cell's surface film.

[0005] Therefore, developing a solar cell that combines high battery efficiency, low contact resistivity, and excellent passivation effect is an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a crystalline silicon solar cell, its preparation method, and its application. In the crystalline silicon solar cell, the thickness of the second thin film region in contact with the electrode is less than the thickness of the first thin film region. While ensuring that the first thin film region has excellent passivation effect, optical performance, and appearance, the contact resistivity between the electrode and the substrate is significantly reduced, the recombination in the electrode region is reduced, and the open-circuit voltage and cell efficiency are effectively improved.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a crystalline silicon solar cell, the crystalline silicon solar cell comprising a substrate, a thin film layer and electrodes disposed sequentially therefrom;

[0009] The thin film layer includes a first thin film region and a second thin film region, wherein the thickness of the first thin film region is greater than the thickness of the second thin film region; the electrode is disposed on the second thin film region and forms contact with the substrate.

[0010] A schematic diagram of the structure of the crystalline silicon solar cell is shown below. Figure 1As shown, the solar cell includes a substrate 1, a thin film layer 2, and an electrode 3; wherein the thin film layer 2 includes a first thin film region 21 and a second thin film region 22. This invention optimizes the structure of the solar cell, particularly by designing the thickness of the thin film layer. The thickness of the second thin film region in contact with the electrode is reduced. This improves the high-temperature ablation transmission performance of the electrode material through the thin film while maintaining excellent passivation, optical performance, and appearance in the non-electrode contact first thin film region, thus reducing contact resistance with the substrate. Simultaneously, the thinned second thin film region allows for a reduction in the composition of the ablation film by the electrode material, thereby also reducing its ablation of the substrate and effectively reducing recombination in the electrode region. Furthermore, the window for improving the optical and passivation performance of the non-electrode contact first thin film region is also increased. The crystalline silicon solar cell of this invention effectively solves the problem of incompatibility between electrode ablation capability and thin film composition and thickness, effectively improving cell efficiency.

[0011] In this invention, the thin film layer can be a front thin film layer and the electrode can be a front electrode; the thin film layer can also be a back thin film layer and the electrode can be a back electrode.

[0012] Preferably, the substrate material includes any one or a combination of at least two of monocrystalline silicon, polycrystalline silicon (poly-Si), or amorphous silicon.

[0013] Preferably, the substrate material further includes silicon carbide and / or TCO (transparent conductive film).

[0014] Preferably, the material of the thin film layer includes SiN. x SiO y N x AlO x SiO2, TiO2, SiC z Any one or a combination of at least two of TCO, polycrystalline silicon, or amorphous silicon.

[0015] Wherein, x is independently 0.5 to 2, for example, it can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0016] For example, x is 1.33, SiN x That is, Si3N4; x is 1.5, AlO x That is, Al2O3.

[0017] y is 0.1 to 2, for example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0018] z is 0.5 to 2, for example, it can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0019] For example, the thin film layer is a front thin film layer, including an aluminum oxide layer, a silicon nitride layer and optionally a silicon oxide layer disposed sequentially; the aluminum oxide layer is on the side close to the substrate.

[0020] For example, the thin film layer is a back thin film layer, including a silicon nitride layer; a tunneling oxide layer and a polycrystalline silicon layer are also disposed between the substrate and the back thin film layer.

[0021] Preferably, the material of the electrode includes any one or a combination of at least two of Ag, Al, Ni, Cu or Au.

[0022] Preferably, the thickness of the first thin film region is 10-500 nm, for example, it can be 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0023] In this invention, the thickness of the second thin film region is less than that of the first thin film region. The relatively thinner second thin film region improves the performance and efficiency of the crystalline silicon solar cell while protecting the passivation of the non-electrode metal contact areas. If the second thin film region is completely etched (i.e., its thickness is 0), the passivation performance of the areas outside the metal electrode contact will be affected. Furthermore, from a fabrication process perspective, if laser etching is used to completely etch the second thin film region, damage to the substrate is inevitable, leading to additional efficiency losses. Using paste etching also carries the risk of substrate etching and requires additional cleaning processes. Therefore, this invention, through the design of the thickness of the second thin film region, reduces the contact resistivity between the electrode and the substrate, reduces recombination in the electrode region, improves open-circuit voltage and cell efficiency, and enhances passivation and optical performance, thereby improving the overall performance of the crystalline silicon solar cell.

[0024] Preferably, the thickness of the second thin film region is 1 to 500 nm, excluding 500 nm. For example, it can be 2 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0025] Preferably, the thickness difference between the first thin film region and the second thin film region is 2 to 490 nm, for example, it can be 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] Preferably, the width of the second thin film region is greater than or equal to the width of the electrode.

[0027] Preferably, the electrode is in partial or complete contact with the substrate.

[0028] Preferably, a thin film layer B and an electrode B are sequentially disposed on the side of the substrate away from the thin film layer; the electrode B forms contact with the substrate.

[0029] Preferably, the thickness of the thin film layer B is 1 to 500 nm, for example 2 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm or 480 nm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0030] Preferably, the material of the thin film layer B includes SiN. m SiO n N m AlO m SiO2, TiO2, SiC p Any one or a combination of at least two of TCO, polycrystalline silicon, or amorphous silicon.

[0031] Wherein, m is independently 0.5 to 2, for example, it can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0032] For example, m is 1.33, SiN m That is, Si3N4; m is 1.5, AlO m That is, Al2O3.

[0033] n is 0.1 to 2, for example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0034] p is 0.5 to 2, for example, it can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0035] Preferably, the material of electrode B includes any one or a combination of at least two of Ag, Al, Ni, Cu or Au.

[0036] Preferably, the thin film layer B includes a third thin film region and a fourth thin film region, wherein the thickness of the third thin film region is greater than the thickness of the fourth thin film region; the electrode B is disposed on the fourth thin film region and forms contact with the substrate.

[0037] As a preferred embodiment of the present invention, in the crystalline silicon solar cell, the thin film layers on both surfaces of the substrate are thinned, that is, the thickness of the first thin film region is greater than the thickness of the second thin film region, and the thickness of the third thin film region is greater than the thickness of the fourth thin film region; the front electrode and the back electrode are respectively disposed on the second thin film region and the fourth thin film region.

[0038] Preferably, the thickness of the third thin film region is 10-500 nm, for example, it can be 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0039] Preferably, the thickness of the fourth thin film region is 1 to 500 nm, excluding 500 nm. For example, it can be 2 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0040] Preferably, the thickness difference between the third thin film region and the fourth thin film region is 2 to 490 nm, for example, it can be 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm or 480 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] Preferably, the width of the fourth thin film region is greater than or equal to the width of electrode B.

[0042] Preferably, the electrode B is in partial or complete contact with the substrate.

[0043] In a second aspect, the present invention provides a method for preparing a crystalline silicon solar cell as described in the first aspect, the method comprising the following steps: depositing a thin film on the surface of a substrate to obtain a thin film layer; thinning a portion of the thin film layer to form a second thin film region, the unthinned portion being a first thin film region; preparing an electrode on the second thin film region and sintering it to obtain the crystalline silicon solar cell.

[0044] Preferably, the method for depositing the thin film includes: sequentially texturing the substrate, performing boron diffusion, removing the borosilicate glass (BSG) on the back side, and performing secondary texturing on the back side, followed by back side deposition and front side deposition to obtain the thin film layer.

[0045] As a preferred technical solution of the present invention, the morphology, structure and material of the substrate after back-side deposition and front-side deposition may be the same or different; preferably, the morphology and material of the front and back sides of the substrate are different.

[0046] Preferably, the method for secondary texturing on the back side is alkaline etching.

[0047] Preferably, the back-side deposition method includes: sequentially preparing a tunneling oxide layer, a polycrystalline silicon layer, and a silicon nitride layer on the back side after secondary texturing to complete the back-side deposition.

[0048] Preferably, the method for preparing the tunneling oxide layer is thermal oxidation.

[0049] Preferably, the polycrystalline silicon layer is prepared by low-pressure chemical vapor deposition (LPCVD).

[0050] Preferably, the polycrystalline silicon layer is further subjected to an annealing process (e.g., high-temperature annealing) after its preparation.

[0051] Preferably, the silicon nitride layer is prepared by plasma-enhanced chemical vapor deposition (PECVD).

[0052] Preferably, the method for front-side deposition includes: sequentially depositing an aluminum oxide layer and a silicon nitride layer on the front side to complete the front-side deposition.

[0053] Preferably, the method for depositing the alumina layer is atomic layer deposition (ALD).

[0054] Preferably, the silicon nitride layer is deposited using plasma-enhanced chemical vapor deposition (PECVD).

[0055] Preferably, the method for depositing the thin film specifically includes: after texturing and boron diffusion processes on the substrate, removing the BSG on the back side on one side, retaining the BSG on the front side as a barrier layer (to protect the PN junction); performing secondary texturing on the back side using alkaline etching, depositing a tunneling oxide layer and a polycrystalline silicon layer on the back side using thermal oxidation and LPCVD, and performing high-temperature annealing; after removing the polycrystalline silicon layer coated around the front side, cleaning to remove the BSG and phosphosilicate glass (PSG) from the silicon wafer surface; depositing an aluminum oxide layer on the front side using ALD; depositing a silicon nitride layer on the front side and a silicon nitride layer on the back side using PECVD to complete the preparation of the thin film layer.

[0056] Preferably, the thinning process includes any one or a combination of at least two of the following: laser ablation, slurry etching, mask reverse etching, or photolithography.

[0057] The thinning process is performed on the thin film layer on the front side of the substrate and / or on the back side of the substrate.

[0058] Preferably, the method for preparing the electrode includes any one or a combination of at least two of screen printing, electroplating, or vapor deposition.

[0059] Preferably, the sintering temperature is 30 to 1000°C, for example, it can be 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, or 950°C, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0060] Thirdly, the present invention provides a photovoltaic module, the photovoltaic module comprising the crystalline silicon solar cell as described in the first aspect.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The crystalline silicon solar cell provided by this invention reduces the thickness of the second thin film region in contact with the electrode. While maintaining excellent passivation, optical performance, and appearance in the first thin film region, it improves the high-temperature ablation transmission performance of the electrode material, reduces the contact resistance between the electrode and the substrate, and lowers the contact resistivity. Simultaneously, the thinned second thin film region allows for a reduction in the composition of the ablation film by the electrode material, decreasing its ablation of the substrate and effectively reducing recombination in the electrode region, thus increasing the average open-circuit voltage of the solar cell. Furthermore, the window for improving the optical and passivation performance of the non-electrode contact first thin film region also increases. This crystalline silicon solar cell effectively solves the problem of incompatibility between electrode ablation capability and thin film composition and thickness, effectively improving cell efficiency. Moreover, its fabrication method is compatible with existing screen printing high-temperature sintering processes, enabling low-cost, large-scale mass production. Attached Figure Description

[0063] Figure 1 A schematic diagram of the structure of a crystalline silicon solar cell provided by the present invention;

[0064] Figure 2 This is a schematic diagram of the structure of the crystalline silicon solar cell provided in Example 1;

[0065] Figure 3 This is a schematic diagram of the structure of the crystalline silicon solar cell provided in Example 2;

[0066] Figure 4 This is a schematic diagram of the structure of the crystalline silicon solar cell provided in Example 3;

[0067] Figure 5 A schematic diagram of the structure of a crystalline silicon solar cell provided for Comparative Example 1;

[0068] Wherein, 1-substrate, 2-thin film layer, 21-first thin film region, 22-second thin film region, 3-electrode, 4-thin film layer B, 41-third thin film region, 42-fourth thin film region, 5-electrode B;

[0069] Figure 6 A comparison diagram of the contact resistivity of crystalline silicon solar cells provided in Example 1 and Comparative Example 1;

[0070] Figure 7 The diagram shows a comparison of the open-circuit voltages of the crystalline silicon solar cells provided in Example 2 and Comparative Example 1. Detailed Implementation

[0071] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0072] Example 1

[0073] A schematic diagram of a crystalline silicon solar cell is shown below. Figure 2 As shown, the substrate includes a substrate 1, a thin film layer 2, and an electrode 3 arranged sequentially. The thin film layer 2 includes a first thin film region 21 and a second thin film region 22. The thickness of the first thin film region 21 is 80 nm, and the thickness of the second thin film region 22 is 30 nm. The electrode 3 (front electrode) is disposed on the second thin film region 21 and forms contact with the substrate 3. On the side of the substrate 3 away from the thin film layer 2, a thin film layer B4 and an electrode B5 are also arranged sequentially. The electrode B5 (back electrode) forms contact with the substrate 3.

[0074] The method for preparing the crystalline silicon solar cell is as follows:

[0075] (1) Using an n-type single-crystal silicon wafer as a substrate, conventional texturing and boron diffusion processes are performed; then the borosilicate glass (BSG) on the back side is removed on one side, while the BSG on the front side is retained as a barrier layer to protect the PN junction of the battery; the back side is texturized again by alkaline etching, and a tunneling oxide layer plus a polycrystalline silicon (poly-Si) layer is deposited on the back side using thermal oxidation and low-pressure chemical vapor deposition (LPCVD), followed by high-temperature annealing; after removing the poly-Si layer on the front side, the BSG and phosphosilicate glass (PSG) on the silicon wafer surface are cleaned and removed; an aluminum oxide layer with a thickness of 5 nm is deposited on the front side using atomic layer deposition (ALD); a silicon nitride layer with a thickness of 75 nm is deposited on the front side using plasma-enhanced chemical vapor deposition (PECVD), and a silicon nitride layer with a thickness of 75 nm is deposited on the back side to complete the preparation of the thin film layer;

[0076] (2) Thin a portion of the front thin film layer obtained in step (1), and use laser ablation to ablate the front thin film according to the screen printing pattern, reducing the thickness of the front thin film from 80nm (5+75nm) to 30nm (5+25nm) with a width of 80μm to form the second thin film area. The area that is not thinned is the first thin film area.

[0077] (3) Print Ag / Al paste on the second thin film area obtained in step (2), and after screen printing Ag paste on the back thin film layer, heat it to a high temperature of 750°C to burn through the thin film to form an ohmic contact, and obtain the crystalline silicon solar cell.

[0078] Example 2

[0079] A schematic diagram of a crystalline silicon solar cell is shown below. Figure 3As shown, the substrate includes a substrate 1, a thin film layer 2, and an electrode 3 arranged sequentially. The thin film layer 2 includes a first thin film region 21 and a second thin film region 22. The thickness of the first thin film region 21 is 75 nm, and the thickness of the second thin film region 22 is 5 nm. The electrode 3 (back electrode) is disposed on the second thin film region 21 and forms contact with the substrate 3. On the side of the substrate 3 away from the thin film layer 2, a thin film layer B4 and an electrode B5 are also arranged sequentially. The electrode B5 (front electrode) forms contact with the substrate 3.

[0080] The method for preparing the crystalline silicon solar cell is as follows:

[0081] (1) Using an n-type single-crystal silicon wafer as a substrate, conventional texturing and boron diffusion processes are performed; then the BSG on the back side is removed on one side, while the BSG on the front side is retained as a barrier layer to protect the PN junction of the battery; the back side is texturized again by alkaline etching, and a tunnel oxide layer plus a poly-Si layer is deposited on the back side using thermal oxidation and LPCVD, followed by high-temperature annealing; after removing the poly-Si layer around the front side, the BSG and PSG on the silicon wafer surface are cleaned and removed; an aluminum oxide layer with a thickness of 5nm is deposited on the front side using the ALD method; a silicon nitride layer with a thickness of 75nm is deposited on the front side using the PECVD method, and a silicon nitride layer with a thickness of 75nm is deposited on the back side to complete the preparation of the thin film layer;

[0082] (2) Thin a portion of the back film layer obtained in step (1), use screen printing to print etching paste, use the etching paste with etching ability to thin the back film layer from 75nm to 5nm and the width to 80μm, then clean and remove the etching paste to form the second film area, and the area that has not been thinned is the first film area.

[0083] (3) Screen print Ag / Al paste on the front side and Ag paste on the second thin film area on the back side. Heat to 750°C to burn through the film to form an ohmic contact, and obtain the crystalline silicon solar cell.

[0084] Example 3

[0085] A schematic diagram of a crystalline silicon solar cell is shown below. Figure 4 As shown, the structure includes a substrate 1, a thin film layer 2, an electrode 3, a thin film layer B4, and an electrode B5 arranged sequentially. The thin film layer 2 includes a first thin film region 21 and a second thin film region 22, with the first thin film region 21 having a thickness of 175 nm and the second thin film region 22 having a thickness of 15 nm. The electrode 3 (front electrode) is disposed on the second thin film region 21 and forms contact with the substrate 1. The thin film layer B4 includes a third thin film region 41 and a fourth thin film region 42, with the third thin film region 41 having a thickness of 100 nm and the fourth thin film region 42 having a thickness of 10 nm. The electrode B5 (back electrode) is disposed on the fourth thin film region 42 and forms contact with the substrate 1.

[0086] The method for preparing the crystalline silicon solar cell is as follows:

[0087] (1) Using an n-type single-crystal silicon wafer as a substrate, conventional texturing and boron diffusion processes are performed; then, the BSG on the back side is removed on one side, while the BSG on the front side is retained as a barrier layer to protect the PN junction of the battery; the back side is texturized again by alkaline etching, and a tunneling oxide layer plus a poly-Si layer is deposited on the back side using LPCVD, followed by high-temperature annealing; after removing the poly-Si layer around the front side, the BSG and PSG on the silicon wafer surface are cleaned and removed; an aluminum oxide layer with a thickness of 5 nm is deposited on the front side using ALD; a silicon nitride layer and a silicon oxide layer with a thickness of 50 nm and a silicon oxide layer with a thickness of 120 nm are deposited on the front side using PECVD; a silicon oxynitride layer with a thickness of 100 nm is deposited on the back side to complete the preparation of the thin film layer;

[0088] (2) Thin a portion of the front thin film layer obtained in step (1), and use laser ablation to ablate the front thin film according to the screen printing pattern, reducing the thickness of the front thin film from 175nm (5+50+120nm) to 15nm (5+10nm) with a width of 80μm to form the second thin film region. The area that is not thinned is the first thin film region.

[0089] (3) Thin a portion of the back film layer obtained in step (1), and use laser ablation to ablate the back film according to the screen printing pattern, reducing the thickness of the back film from 100nm to 10nm and the width to 80μm, forming the fourth film region. The area that was not thinned is the third film region.

[0090] (4) Print Ag / Al paste on the second thin film area on the front side obtained in step (2), and print Ag paste on the second thin film area on the back side obtained in step (3). Heat to 740°C to burn through the film to form an ohmic contact, and obtain the crystalline silicon solar cell.

[0091] Comparative Example 1

[0092] A schematic diagram of a crystalline silicon solar cell is shown below. Figure 5 As shown, the substrate includes a substrate 1, a thin film layer 2, and an electrode 3 arranged sequentially. The thickness of the thin film layer 2 is 80 nm (equal everywhere). On the side of the substrate 3 away from the thin film layer 2, a thin film layer B4 and an electrode B5 are also arranged sequentially. The thickness of the thin film layer B4 is 75 nm.

[0093] The difference between its preparation method and Example 1 is that it does not include step (2), that is, it does not perform thinning treatment. After the thin film layer is prepared in step (1), it directly enters step (3), prints electrode paste, sinters, and obtains crystalline silicon solar cell.

[0094] Performance testing:

[0095] (1) Contact resistivity

[0096] The resistivity of crystalline silicon solar cells was tested according to the transmission line resistance (TLM) method known in the art. A comparison of the contact resistivity of the crystalline silicon solar cells provided in Example 1 and Comparative Example 1 is shown in the figure below. Figure 6 As shown, the front contact resistivity of Comparative Example 1, where the thin film layer was not thinned, was 2.0 mΩ·cm. 2 The front contact resistance of the crystalline silicon solar cell in Example 1 was improved, and the contact resistivity was reduced to 1.0 mΩ·cm. 2 .

[0097] (2) Open circuit voltage

[0098] Using an IV tester, the test was conducted at 25°C and 1000 W / m according to the method in IEC 60904 standard. 2 The open-circuit voltage of crystalline silicon solar cells was tested under light intensity. A comparison graph of the open-circuit voltages of the crystalline silicon solar cells provided in Example 2 and Comparative Example 1 is shown below. Figure 7 As shown, in Example 2, after thinning the thin film in the contact area, the ablation ability of the low-etching paste used on the substrate is weakened, and the recombination rate of the solar cell is reduced. Figure 7 As shown, the average open-circuit voltage of the solar cell increased significantly, from 700mV in Comparative Example 1 to 703mV.

[0099] (3) Battery efficiency

[0100] The IV electrical performance data of the crystalline silicon solar cells provided in Example 3 and Comparative Example 1 were tested using an IV tester according to the method in IEC 60904 standard. The test data are shown in Table 1.

[0101] Table 1

[0102]

[0103] According to the data in Table 1, in the crystalline silicon solar cell provided in Example 3, the second thin film region on the front side and the fourth thin film region on the back side are thinned. The thickness of the first thin film region is greater than that of the second thin film region, and the thickness of the third thin film region is greater than that of the fourth thin film region, which increases the cell current by 10mA; the sintering peak temperature is reduced by 10°C, and a slurry with low ablation performance is used in the preparation, which increases the open circuit voltage of the solar cell by 3mV; the improved contact performance brought about by the thinning reduces the series resistance by 0.1mΩ, increases the fill factor by 0.4%, and ultimately improves the electrical performance (efficiency) of the cell by 0.25%.

[0104] Therefore, compared with Comparative Example 1 which did not undergo thinning treatment, the crystalline silicon solar cell provided by this invention improves the open-circuit voltage and current, and reduces contact resistance through the thickness design of the second thin film region in contact with the electrode, thus significantly improving the cell's electrical performance. Furthermore, since the width of the second thin film region is greater than the width of the metal electrode, completely etching the second thin film region would affect the passivation performance of areas outside the metal contact; the reason for retaining a portion of the thin film is to protect the passivation of this area from being affected. Moreover, complete etching of the second thin film region, if using laser technology, inevitably damages the substrate, leading to additional efficiency losses. Using paste etching methods also carries the risk of substrate etching and requires additional cleaning processes.

[0105] The applicant declares that this invention illustrates the crystalline silicon solar cell, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A crystalline silicon solar cell, characterized in that, The crystalline silicon solar cell includes a substrate, a thin film layer, and electrodes arranged sequentially. The thin film layer includes a first thin film region and a second thin film region, wherein the thickness of the first thin film region is greater than the thickness of the second thin film region; the electrode is disposed on the second thin film region and forms contact with the substrate. On the side of the substrate away from the thin film layer, a thin film layer B and an electrode B are also sequentially disposed; The thin film layer B includes a third thin film region and a fourth thin film region, wherein the thickness of the third thin film region is greater than the thickness of the fourth thin film region; the electrode B is disposed on the fourth thin film region and forms contact with the substrate. The thickness difference between the first thin film region and the second thin film region is 50~490 nm; The thickness difference between the third and fourth thin film regions is 50~490 nm; The method for fabricating the crystalline silicon solar cell includes the following steps: depositing a thin film on the surface of a substrate to obtain a thin film layer; thinning a portion of the thin film layer to form a second thin film region, while the unthinned portion is the first thin film region; An electrode is fabricated on the second thin film region and sintered to form an ohmic contact to obtain the crystalline silicon solar cell. The thin film layer is the back thin film layer of the silicon nitride layer; a tunneling oxide layer and a polycrystalline silicon layer are also disposed between the substrate and the back thin film layer.

2. The crystalline silicon solar cell according to claim 1, characterized in that, The substrate material includes any one or a combination of at least two of monocrystalline silicon, polycrystalline silicon, or amorphous silicon.

3. The crystalline silicon solar cell according to claim 1, characterized in that, The substrate material also includes silicon carbide and / or TCO.

4. The crystalline silicon solar cell according to claim 1, characterized in that, The electrode material includes any one or a combination of at least two of Ag, Al, Ni, Cu, or Au.

5. The crystalline silicon solar cell according to claim 1, characterized in that, The thickness of the first thin film region is 10~500 nm.

6. The crystalline silicon solar cell according to claim 1, characterized in that, The thickness of the second thin film region is 1~500 nm, excluding 500 nm.

7. The crystalline silicon solar cell according to claim 1, characterized in that, The width of the second thin film region is greater than or equal to the width of the electrode.

8. The crystalline silicon solar cell according to claim 1, characterized in that, The electrode is in partial or complete contact with the substrate.

9. The crystalline silicon solar cell according to claim 1, characterized in that, The thickness of the thin film layer B is 1~500nm.

10. The crystalline silicon solar cell according to claim 1, characterized in that, The material of the thin film layer B includes SiN. m SiO n N m AlO m SiO2, TiO2, SiC p The TCO, polycrystalline silicon, or amorphous silicon, or any one or a combination of at least two of them; wherein m is 0.5 to 2, n is 0.1 to 2, and p is 0.5 to 2.

11. The crystalline silicon solar cell according to claim 1, characterized in that, The material of electrode B includes any one or a combination of at least two of Ag, Al, Ni, Cu, or Au.

12. The crystalline silicon solar cell according to claim 1, characterized in that, The thickness of the third thin film region is 10~500 nm.

13. The crystalline silicon solar cell according to claim 1, characterized in that, The thickness of the fourth thin film region is 1~500 nm, excluding 500 nm.

14. The crystalline silicon solar cell according to claim 1, characterized in that, The width of the fourth thin film region is greater than or equal to the width of electrode B.

15. The crystalline silicon solar cell according to claim 1, characterized in that, The electrode B is in partial or complete contact with the substrate.

16. The crystalline silicon solar cell according to claim 1, characterized in that, The method for depositing the thin film includes: sequentially texturing the substrate, performing boron diffusion, removing the borosilicate glass on the back side, and performing secondary texturing on the back side, followed by back side deposition and front side deposition to obtain the thin film layer.

17. The crystalline silicon solar cell according to claim 16, characterized in that, The method for secondary texturing on the back side is alkaline etching.

18. The crystalline silicon solar cell according to claim 16, characterized in that, The method for back-side deposition includes: sequentially preparing a tunneling oxide layer, a polycrystalline silicon layer, and a silicon nitride layer on the back side after secondary texturing to complete the back-side deposition.

19. The crystalline silicon solar cell according to claim 18, characterized in that, The method for preparing the tunneling oxide layer is thermal oxidation.

20. The crystalline silicon solar cell according to claim 18, characterized in that, The polycrystalline silicon layer is prepared by low-pressure chemical vapor deposition.

21. The crystalline silicon solar cell according to claim 18, characterized in that, The silicon nitride layer is prepared by plasma-enhanced chemical vapor deposition.

22. The crystalline silicon solar cell according to claim 16, characterized in that, The method for front-side deposition includes: sequentially depositing an aluminum oxide layer and a silicon nitride layer on the front side to complete the front-side deposition.

23. The crystalline silicon solar cell according to claim 22, characterized in that, The method for depositing the alumina layer is atomic layer deposition.

24. The crystalline silicon solar cell according to claim 18, characterized in that, The silicon nitride layer was deposited using plasma-enhanced chemical vapor deposition.

25. The crystalline silicon solar cell according to claim 1, characterized in that, The thinning process includes any one or a combination of at least two of the following: laser ablation, slurry etching, mask reverse etching, or photolithography.

26. The crystalline silicon solar cell according to claim 1, characterized in that, The method for preparing the electrode includes any one or a combination of at least two of screen printing, electroplating, or vapor deposition.

27. The crystalline silicon solar cell according to claim 1, characterized in that, The sintering temperature is 30~1000℃.

28. A photovoltaic module, characterized in that, The photovoltaic module includes a crystalline silicon solar cell as described in any one of claims 1 to 27.

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