Double-sided Poly fingers passivation contact battery

Abstract

The utility model discloses a double-sided Poly fingers passivation contact cell, which relates to the technical field of solar cells, and comprises an N-type silicon substrate with pyramid textured surfaces on the front surface and the back surface, and the front surface and the back surface of the N-type silicon substrate are sequentially provided with a passivation film layer and an antireflection layer from inside to outside; a front metal grid line electrode is arranged on the front face of the N-type silicon substrate, and a tunneling silicon oxide layer with the thickness being 1-2 nm and an N-type doped Poly-Si layer with the film layer thickness being 80-150 nm are arranged on the N + Poly passivation contact high-low junction area pyramid suede. The front and back Poly layers of the N-type silicon substrate are both of Poly finger structures, the Poly area is reduced to the maximum extent, parasitic absorption of the polycrystalline silicon layer to sunlight is reduced, and the current of the cell is remarkably improved; the front metal grid line electrodes and the back metal grid line electrodes are in ohmic contact with the pyramid suede tunneling silicon oxide layer and the Poly layer, and the suede structure is beneficial to reducing contact resistance, reducing Rs and improving FF.

Description

Technical Field

[0001] This utility model relates to the field of solar cell technology, specifically to a double-sided Poly fingers passivated contact cell. Background Technology

[0002] In recent years, the development of renewable energy has been increasing, with solar energy being the most common. Compared with traditional energy sources, solar energy has the advantages of being simple to use, safe, and pollution-free, making it a focus of research in the field of renewable energy. The basic principle of solar cell power generation is the photovoltaic effect. Solar cells are new energy devices that convert sunlight into electrical energy. Bifacial solar cells, which utilize two light-receiving surfaces (front and back), can obtain higher photocurrent density, greatly improving power generation.

[0003] For example, patent CN216120311U proposes an N-type double-sided passivated contact battery structure. In order to further improve the conversion efficiency of the battery, the front surface also adopts a passivated contact structure to solve the problem of metal recombination of the emitter. Patent CN117438496A mentions a double-sided passivated contact battery structure with a Polyfinger structure on the front side, retaining an N+Poly-Si / tunneling SiOx passivated contact structure only at the metal grid line position, and a full-surface P+Poly-Si / tunneling SiOx passivated contact on the polished back side.

[0004] As some of the existing technical solutions in the above patents cause severe parasitic absorption of short-wavelength light due to the doped polycrystalline silicon layer on the front side and the entire back side, the effective absorption of short-wavelength light by the battery is reduced; the contact resistance Rs between the polished structure on the back surface and the metal grid line is high, which has an adverse effect on the FF; and the passivation effect of the P+Poly Si / tunneling SiOx layer is significantly worse than that of alumina. The saturated dark current density J0 of the P+Poly Si / tunneling SiOx layer on the textured surface is about ~13fA / cm2, which is 3 to 4 times that of alumina under the same conditions. In summary, due to the above factors, the overall efficiency of the double-sided passivated contact battery structure does not have a significant advantage. Utility Model Content

[0005] The purpose of this invention is to provide a double-sided Poly fingers passivated contact battery to address the aforementioned shortcomings in the prior art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a double-sided Poly Fingers passivated contact battery, comprising an N-type silicon substrate with a pyramidal textured surface on both the front and back sides. A passivation film and an anti-reflection layer are sequentially disposed on the front and back sides of the N-type silicon substrate from the inside out. The front side of the N-type silicon substrate includes an N+Poly passivated contact high-low junction region and a front non-gateline passivation region. The back side of the N-type silicon substrate includes a P+Poly passivated contact emitter region and a back non-gateline passivation region. A front metal gate electrode is disposed on the front side of the N-type silicon substrate, contacting the N+Poly passivated contact high-low junction region. A tunneling silicon oxide layer with a thickness of 1–2 nm and an N-type doped Poly-Si layer with a thickness of 80–150 nm are disposed on the pyramidal textured surface of the N+Poly passivated contact high-low junction region.

[0007] Preferably, the passivation film thickness on the pyramid textured surface of the N+Poly passivation contact high and low junction regions and the front non-gateline passivation region is 3-10 nm, and the anti-reflection layer thickness is 65-85 nm.

[0008] Preferably, the back side of the N-type silicon substrate is provided with a back metal gate electrode that contacts the P+Poly passivated contact emitter region, and the pyramid textured surface of the P+Poly passivated contact emitter region is provided with a tunneling silicon oxide layer with a thickness of 1-2 nm and a P-type doped Poly-Si layer with a film thickness of 120-250 nm.

[0009] Preferably, the passivation film thickness on the pyramid textured surface of the P+Poly passivated contact emitter region and the back non-gateline passivation region is 3-10 nm, and the antireflection layer thickness is 75-90 nm.

[0010] In the above technical solution, this utility model provides a double-sided Poly fingers passivated contact battery, which has the following beneficial effects: 1. Both the front and back Poly layers of the N-type silicon substrate are Poly fingers structures, minimizing the Poly area and reducing the parasitic absorption of sunlight by the polycrystalline silicon layer, significantly improving the battery current; both the front and back metal grid electrodes form ohmic contacts with the pyramid-textured tunneling silicon oxide layer and the Poly layer, and the textured structure helps to reduce contact resistance, reduce Rs, and improve FF; 2. In the back Poly fingers structure, about 50% of the P-type doped Poly-Si layer 6 area is retained, and the remaining 50% area is replaced by a passivation film layer 3 with lower J0 and better passivation effect, greatly improving the battery iVoc and the battery turn-on voltage; the battery structure in this utility model specifically improves the shortcomings of existing double-sided passivated contact batteries, improving battery efficiency. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings.

[0012] Figure 1 A schematic diagram of the overall structure provided for an embodiment of this utility model;

[0013] Figure 2 Provided for the embodiments of this utility model Figure 1 Enlarged view of the structure at point A in the middle;

[0014] Figure 3 Provided for the embodiments of this utility model Figure 1 Enlarged view of the structure at point B in the middle.

[0015] Explanation of reference numerals in the attached figures:

[0016] 1. N-type silicon substrate; 2. Antireflection layer; 3. Passivation film layer; 4. Tunneling silicon oxide layer; 5. N-type doped Poly-Si layer; 6. P-type doped Poly-Si layer; 7. Front metal gate electrode; 8. Back metal gate electrode; 100. N+ Poly passivated contact high and low junction region; 200. Front non-gate passivation region; 300. P+ Poly passivated contact emitter region; 400. Back non-gate passivation region. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings.

[0018] Please see Figure 1-3A double-sided Poly Fingers passivated contact battery, the technical solution proposed in this utility model includes an N-type silicon substrate (1) with a pyramidal textured surface on both the front and back sides. A passivation film layer (3) and an anti-reflection layer (2) are sequentially disposed on the front and back sides of the N-type silicon substrate (1) from the inside out. The front side of the N-type silicon substrate (1) includes an N+Poly passivated contact high-low junction region (100) and a front non-gateline passivation region (200). The back side of the N-type silicon substrate (1) includes a P+Poly passivated contact. Emitter region (300) and back non-gate passivation region (400); the N-type silicon substrate (1) has a front metal gate electrode (7) that contacts the N+Poly passivation contact high and low junction region (100), and the pyramid textured surface of the N+Poly passivation contact high and low junction region (100) has a tunneling silicon oxide layer (4) with a thickness of 1-2 nm and an N-type doped Poly-Si layer (5) with a film thickness of 80-150 nm; N+Poly passivation contact On the pyramid-textured surface of the high-low junction region (100), from the inside out, are a tunneling silicon oxide layer (4), an N-type doped Poly-Si layer (5), a passivation film layer (3), and an anti-reflection layer (2). Passivation films (3) are also provided on the front and back sides of the N-type silicon substrate (1), except for the N+Poly passivation contact high-low junction region (100) and the P+Poly passivation contact emitter region (300). An anti-reflection layer is provided on the side of the passivation film layer (3) furthest from the N-type silicon substrate (1). 2) The sheet resistance of the N-type doped Poly-Si layer (5) is 50-150Ω / sq. The passivation film (3) on the front of the N-type silicon substrate (1) is one of AlOx film, SiOx film or SiOxNy film with a thickness of 3-10nm, or it can be a combination of several of them. The antireflection layer (2) on the front of the N-type silicon substrate (1) is a SixNy layer with a refractive index of 1.9-2.05. The N+Poly passivation contact high and low junction region (100) on the front is a Poly fingers structure, which minimizes the Poly area and reduces the parasitic absorption of sunlight by the polycrystalline silicon layer, significantly improving the current of the battery. The tunneling silicon oxide layer (4) at the high and low junction region (100) of the N+Poly passivation contact and the N-type doped Poly-Si layer (5) form an ohmic contact, which is beneficial to reduce the contact resistance of the front metal grid electrode (7), reduce Rs, and improve FF.

[0019] Specifically, the passivation film layer (3) on the pyramid textured surface of the N+Poly passivation contact high and low junction region (100) and the front non-gate passivation region (200) is 3-10 nm thick, and the anti-reflection layer (2) is 65-85 nm thick. The passivation film layer (3) and the anti-reflection layer (2) are arranged from the inside to the outside on the pyramid textured surface of the front non-gate passivation region (200).

[0020] Specifically, the back side of the N-type silicon substrate (1) is provided with a back metal gate electrode (8) that contacts the P+Poly passivated contact emitter region (300). The pyramid textured surface of the P+Poly passivated contact emitter region (300) is provided with a tunneling silicon oxide layer (4) with a thickness of 1–2 nm and a P-type doped Poly-Si layer (6) with a thickness of 120–250 nm. From the inside out, the pyramid textured surface of the P+Poly passivated contact emitter region (300) consists of a tunneling silicon oxide layer (4), a P-type doped Poly-Si layer (6), and a P-type doped Poly-Si layer (6). The structure consists of a Si layer (6), a passivation film layer (3), and an antireflection layer (2). The doping sheet resistance of the P-type doped Poly-Si layer (6) is 80–200 Ω / sq. The passivation film layer (3) on the back of the N-type silicon substrate (1) is one of AlOx, SiOx, or SiOxNy films with a thickness of 3–10 nm, or a combination of several of them. The antireflection layer (2) on the front of the N-type silicon substrate (1) is a SixNy layer with a refractive index of 2.05–2.15. The P+Poly passivated contact emitter region (300) on the back is Poly The fingers structure minimizes the poly area, reduces parasitic absorption of sunlight by the polycrystalline silicon layer, and significantly improves the current of the battery. The back metal grid electrode (8) forms an ohmic contact with the tunneling silicon oxide layer (4) at the P+Poly passivated contact emitter region (300) and the P-type doped Poly-Si layer (6), which helps to reduce the contact resistance of the front metal grid electrode (7), reduce Rs, and improve FF.

[0021] Specifically, the passivation film (3) on the pyramid textured surface of the P+Poly passivated contact emitter region (300) and the back non-gate passivation region (400) is 3-10 nm thick, and the anti-reflection layer (2) is 75-90 nm thick. The passivation film (3) and the anti-reflection layer (2) are arranged from the inside to the outside on the pyramid textured surface of the back non-gate passivation region (400).

[0022] A method for preparing a double-sided Poly Fingers passivated contact battery, comprising the following steps:

[0023] S1: Texturing and Cleaning: N-type silicon wafers with resistivity of 0.4-2.1 Ω·cm are selected as the substrate. Surface texturing is performed using alkali and texturing additives to remove the damaged layer on the surface of the N-type silicon substrate 1 and reduce the recombination rate of photogenerated carriers. At the same time, a uniform textured surface is formed on the front side of the N-type silicon substrate 1, which can play a light trapping role and improve light absorption. RCA cleaning improves the cleanliness of the surface of the N-type silicon substrate 1.

[0024] S2: Preparation of tunneling, P-type doped Poly-Si layer 6: Tunneling silicon oxide layer 4 and amorphous silicon are deposited on the textured back surface of the battery using LPCVD. The thickness of the ultrathin oxide layer is 1-2 nm, and the thickness of the amorphous silicon layer is 150-250 nm. The textured N-type silicon substrate 1 is inserted into a quartz boat for single-sided boron diffusion. The boron source is BCl3, the deposition temperature is 800-850℃, and the push-bond oxidation temperature is 1020-1050℃. After boron diffusion, the amorphous silicon layer is transformed into P-type doped Poly layer 6 with a sheet resistance of 80-100 Ω / sq and a BSG thickness of 60-80 nm.

[0025] S3: Removal of Borosilicate Glass (BSG) and Secondary Texturing: 1) After diffusion, the N-type silicon substrate 1 is removed using a chain machine under water film protection, with a 28-35% (v / v) HF solution and rollers carrying the liquid. The borosilicate glass is a byproduct of boron diffusion and can be removed with HF solution. 2) After removing the BSG from the back side, a tank machine is used to perform secondary texturing on the front side of the N-type silicon substrate 1 to remove the P-type doped Poly 6 layer of plating. The reaction solution consists of alkali (KOH, NaOH, or organic alkali) and texturing additives, reacting at 80℃ for 360 seconds. No HF is added to the pickling tank, so it does not affect the BSG on the back side.

[0026] S4: Preparation and crystallization of tunneling, N-type doped Poly-Si layer 5: PECVD is used to deposit tunneling silicon oxide layer 4 and doped amorphous silicon on the textured surface of the front side. The thickness of the ultrathin oxide layer is 1-2 nm, the thickness of the phosphorus doped amorphous silicon layer is 80-150 nm, and the sheet resistance of the doped layer is 50-150 Ω / sq. After annealing at 650-850℃, the doped amorphous silicon is crystallized into a doped polycrystalline silicon film.

[0027] S5: Fabrication of front and back poly fingers: Using a green picosecond or ultraviolet picosecond laser, the front side of the N-type silicon substrate 1 is patterned and ablated according to the set pattern, and the PSG mask is ablated. The PSG and N-type doped Poly-Si layer 5 with a width of 60μm to 120μm are retained in the front metal gate electrode area. Using a green picosecond or ultraviolet picosecond laser, the back side of the N-type silicon substrate 1 is patterned and ablated according to the set pattern, and the BSG is ablated. The BSG and P-type doped Poly-Si layer 6 with a width of 300μm to 500μm are retained in the back metal gate electrode area; the area of ​​the back P-type doped Poly-Si layer is retained at 30% to 50%.

[0028] S6: Backside Removal of Plating and Texturing of Non-Laser Areas on Both Sides: 1) Chain etching and acid washing of the back side of the N-type silicon substrate 1, using a 6-15% (v / v) HF solution and roller conveyor to remove the phosphosilicate glass (PSG) from the back side and four sides of the N-type silicon substrate 1. 2) After removing the PSG from the back side, a tank-type machine is used to perform poly removal and secondary texturing on the laser-treated areas on the front and back sides of the N-type silicon substrate 1. The non-laser areas on the front and back sides are protected by PSG and BSG respectively and will not be damaged by the reaction solution. Poly removal of the laser-treated areas generates a pyramidal textured surface structure. The reaction solution is an alkali (KOH or NaOH or organic alkali) and texturing additive reacting at 80℃ for 300-400s. Finally, an HF pickling tank is used to remove BSG and PSG.

[0029] S7: Passivation film preparation: After S6, double-sided AlOx deposition was performed using an ALD machine to passivate the surface. The alumina thickness was 5-10 nm.

[0030] S8: Anti-reflection coating: Silicon nitride layers are deposited on both the front and back sides after S7. The thickness of the silicon nitride film on the front side of the N-type silicon substrate 1 is 60-80nm, and the refractive index is 2.0-2.10. The thickness of the silicon nitride film on the back side of the N-type silicon substrate 1 is 70-90nm, and the refractive index is 2.05-2.15.

[0031] S9: Electrode fabrication: Silver paste is printed on the back of the positive and N-type silicon substrates to prepare electrodes.

[0032] The back-side Polyfins structure retains approximately 50% of the P-type doped Poly-Si layer 6 area, while the remaining 50% is replaced by a passivation film layer 3 with lower J0 and better passivation effect, significantly improving the battery iVoc and opening voltage. This invention addresses the shortcomings of existing double-sided passivated contact batteries, thereby enhancing battery efficiency.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A double-sided polyfins passivated contact battery, comprising an N-type silicon substrate (1) with a pyramidal textured surface on both the front and back sides, characterized in that, The N-type silicon substrate (1) has a passivation film layer (3) and an anti-reflection layer (2) arranged sequentially from the inside to the outside on the front and back sides. The front side of the N-type silicon substrate (1) includes an N+Poly passivated contact high and low junction region (100) and a front non-gate passivation region (200). The back side of the N-type silicon substrate (1) includes a P+Poly passivated contact emitter region (300) and a back non-gate passivation region (400). The N-type silicon substrate (1) has a front metal gate electrode (7) that contacts the N+Poly passivation contact high and low junction region (100). The pyramid textured surface of the N+Poly passivation contact high and low junction region (100) has a tunneling silicon oxide layer (4) with a thickness of 1 to 2 nm and an N-type doped Poly-Si layer (5) with a film thickness of 80 to 150 nm.

2. The double-sided Poly fingers passivated contact battery according to claim 1, characterized in that, The passivation film (3) on the pyramid textured surface of the N+Poly passivation contact high and low junction region (100) and the front non-gateline passivation region (200) has a thickness of 3-10 nm, and the anti-reflection layer (2) has a thickness of 65-85 nm.

3. A double-sided Poly fingers passivated contact battery according to claim 2, characterized in that, The back side of the N-type silicon substrate (1) is provided with a back metal gate electrode (8) that contacts the P+Poly passivated contact emitter region (300). The pyramid textured surface of the P+Poly passivated contact emitter region (300) is provided with a tunneling silicon oxide layer (4) with a thickness of 1-2 nm and a P-type doped Poly-Si layer (6) with a film thickness of 120-250 nm.

4. A double-sided Poly fingers passivated contact battery according to claim 3, characterized in that, The passivation film (3) on the pyramid textured surface of the P+Poly passivated contact emitter region (300) and the back non-gateline passivation region (400) has a thickness of 3-10 nm, and the antireflection layer (2) has a thickness of 75-90 nm.

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