A solar cell and a method for preparing the same
By etching the surface of the silicon wafer by laser groove and isotropic corrosion liquid, combined with multiple boron source diffusion, a heavily doped groove expansion zone is formed, which solves the problem of poor boron doping diffusion on the surface of the silicon wafer and improves the electrical performance and conversion efficiency of the silicon battery.
Patent Information
- Application Number
- CN202111550340.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-17
- Publication Date
- 2025-06-10
- Estimated Expiration
- 2041-12-17
AI Technical Summary
The prior art is difficult to effectively diffuse boron atoms when boron is doped on the surface of silicon wafers, resulting in a decrease in the surface concentration of the boron diffusion layer and affecting the formation of the metal/semiconductor ohmic contact structure.
By etching the N-type silicon substrate, a textured surface is formed, and the first boron source diffusion is performed. Then the laser is grooved into the diffusion layer, and the grooved area is etched using isotropic corrosion liquid to form a grooved expansion area, and the boron source slurry is filled into the grooved expansion area for the second boron source diffusion, forming a heavily doped grooved expansion area.
The surface area and transverse width area of the heavily doped region are expanded, the contact resistance is reduced, the conduction loss of carriers at the contact interface is reduced, the short-circuit current and filling factor of the battery are improved, and the electrical performance of silicon batteries is improved.
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Figure CN116266616B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a solar cell wafer and a preparation method thereof. Background Art
[0002] A selective emitter crystalline silicon cell, that is, heavy doping is performed at the contact part between the metal grid line (electrode) and the silicon wafer, and light doping is performed at the position between the electrodes, thereby improving the conversion efficiency.
[0003] Currently, when boron doping is performed on a silicon wafer, since the solubility / segregation coefficient of boron atoms in SiO 2 (borosilicate glass layer, BSG layer) is greater than that in crystalline silicon, when a laser beam is used to heat and drive the borosilicate glass layer, the boron atoms in the borosilicate glass layer cannot be effectively driven into the silicon wafer to form a heavily doped boron diffusion layer. Instead, to a large extent, the boron atoms near the interface between the boron diffusion layer on the silicon wafer surface and the borosilicate glass layer diffuse out into the borosilicate glass layer, reducing the surface concentration of the boron diffusion layer on the silicon wafer surface and / or causing the overall downward shift of the boron diffusion doping concentration curve on the silicon wafer surface. After the boron atom concentration on the silicon wafer surface decreases, it is not conducive to forming a metal / semiconductor ohmic contact structure in this part of the region. Currently, there is a method of grooving the borosilicate glass layer, and then filling boron source paste in the groove and performing secondary laser doping, but the boron diffusion effect of this method is still not good enough. Summary of the Invention
[0004] The purpose of the present invention is to provide a solar cell wafer and a preparation method thereof, which can expand the surface area and the lateral width area of the heavily doped region, expand the cross-sectional area of the carrier diffusion / drift channel, reduce the contact resistance, reduce the conduction loss of carriers at the contact interface, improve the short-circuit current and fill factor of the battery, and improve the electrical performance of the silicon cell.
[0005] To achieve the above object, the following technical solutions are adopted:
[0006] A preparation method of a solar cell wafer, comprising the following steps:
[0007] 1) Etch an N-type silicon substrate to form a textured surface; then perform a first boron source diffusion to form a diffusion layer and a borosilicate glass layer;
[0008] 2) Laser groove or etch the surface of the N-type silicon substrate after the first boron source diffusion to the surface of the diffusion layer or into the diffusion layer or into the N-type silicon substrate to form a grooved area;
[0009] 3) Etch the grooved area with an isotropic etching solution to form a grooved expansion area at the bottom of the grooved area with a bottom cross-sectional area larger than the surface opening cross-sectional area;
[0010] 4) Fill the boron source paste into the grooved extended region, and then perform boron source laser doping or a second boron source diffusion. The boron source diffuses circumferentially into the grooved extended region to form a heavily doped grooved extended region;
[0011] 5) Clean the N-type silicon substrate obtained in step 4), and then prepare a dielectric layer on the diffusion layer. The dielectric layer is a passivation film and / or an antireflection film;
[0012] Print conductive paste corresponding to the heavily doped grooved extended region to prepare electrodes, and form a solar cell after sintering.
[0013] According to the above solution, the first boron source diffusion method in step 1) is tube diffusion or chain diffusion, and the second boron source diffusion method in step 4) is tube diffusion or chain diffusion.
[0014] According to the above solution, when grooving or etching into the diffusion layer or the N-type silicon substrate in step 2), the distance from the bottom surface of the grooved region to the surface of the diffusion layer is 0 - 500 nm.
[0015] According to the above solution, the laser spot size during laser grooving in step 2) is 40 - 150 μm.
[0016] According to the above solution, the isotropic etching solution in step 3) is an HF - HNO 3 system, where water or acetic acid is used as a diluent.
[0017] According to the above solution, the mass percentage concentration of the HF solution is 49 ± 1%, and the mass percentage concentration of the HNO 3 solution is 65 - 70%; the molar ratio of HF to HNO 3 is greater than 1:3.
[0018] According to the above solution, an additive is further added to the isotropic etching solution in step 3). The additive is:
[0019] Polyoxyethylene ether series surfactants;
[0020] or a combination of hydrogen peroxide and a surfactant;
[0021] or a combination of a catalyst, a non-ionic surfactant, and a silane coupling agent.
[0022] According to the above solution, the etching temperature when etching the grooved region with the isotropic etching solution in step 3) is 5°C - 35°C.
[0023] According to the above solution, the boron source paste in step 4) protrudes from the grooved extended region or is completely located within the grooved extended region.
[0024] According to the above solution, the size of the laser spot during boron source laser doping in step 4) is 80 - 160 um.
[0025] According to the above solution, the solar cell includes a back contact cell, an IBC cell, a TopcoN cell or an HBC structure cell.
[0026] A solar cell, comprising:
[0027] An N-type silicon substrate;
[0028] A diffusion layer, which is disposed on the N-type silicon substrate;
[0029] A heavily doped groove extended region, which is buried in or penetrates through the diffusion layer, the bottom cross-sectional area of the heavily doped groove extended region is larger than the surface opening cross-sectional area, and the doping concentration of the heavily doped groove extended region is higher than the doping concentration of the non-heavily doped groove extended region within the diffusion layer;
[0030] A dielectric layer, which is disposed on the diffusion layer, and the dielectric layer is a passivation film and / or an antireflection film;
[0031] An electrode, which is filled in the heavily doped groove extended region and extends upward beyond the dielectric layer.
[0032] According to the above solution, the bottom of the heavily doped groove extended region extends into the diffusion layer or the N-type silicon substrate.
[0033] According to the above solution, the bottom surface and / or side surface of the heavily doped groove extended region are in contact with the diffusion layer to form a conduction channel between the heavily doped region and the lightly doped region.
[0034] Compared with the prior art, the beneficial effects of the present invention are:
[0035] The present invention uses an isotropic etching solution system to etch the grooved area of the silicon wafer. Due to the high defect state near the side edge at the bottom of the grooved area, the isotropic etching solution is used to etch the high-defect Si crystal structure in the grooved area to form an etched extended region, and finally a grooved extended region with a bottom cross-sectional area larger than the surface opening cross-sectional area is formed. Since the drilling shape at the bottom of the groove expands the surface area of the heavily doped region (heavily doped groove extended region) and the lateral width region of the heavily doped boron diffusion layer, an adjacent structure layer between the heavily doped region and the surrounding original diffusion layer is formed, which is beneficial to the formation of an effective ohmic contact between the metal paste and the heavily doped region. Therefore, the contact resistance can be reduced, the loss of carriers at the contact interface can be reduced, and then the short-circuit current and fill factor of the battery can be improved, which is beneficial to improving the electrical performance of the silicon battery, and can also improve the conversion efficiency of the silicon battery and reduce the cost. Description of the Drawings
[0036] Figure 1 Schematic diagram of the preparation process of the solar cell wafer in Embodiment 1;
[0037] Figure 2 Schematic diagram of the preparation process of the solar cell wafer in Embodiment 2;
[0038] Figure 3 Schematic diagram of the preparation process of the solar cell wafer in Embodiment 3;
[0039] Figure 4 Schematic diagram of the structure of the solar cell wafer under one embodiment;
[0040] Figure 5 Schematic diagram of the structure of the solar cell wafer under another embodiment;
[0041] Figure 6 Schematic diagram of the structure of the solar cell wafer under another embodiment;
[0042] Wherein, 1 - N-type substrate; 2 - diffusion layer; 3 - heavily doped groove extended region; 4 - dielectric layer; 5 - electrode; 6 - borosilicate glass layer. Detailed implementation manners
[0043] The following embodiments further illustrate the technical solutions of the present invention, but do not limit the protection scope of the present invention.
[0044] The present invention provides a method for preparing a solar cell wafer. Referring to Figure 1 , Figure 2 , Figure 3 shown, the specific process includes the following steps:
[0045] (1) An N-type silicon substrate 1 is adopted. The silicon substrate for the solar cell is usually a substrate with a (100) crystal plane. The substrate is etched to form a textured surface, as shown in Figure 1 (a) (the structure of the textured surface is not shown in the figure).
[0046] The first boron source diffusion is performed on the surface of the N-type silicon substrate 1, and the silicon wafer is doped to form a diffusion layer 2 and a borosilicate glass layer 6, as shown in Figure 1 (b). Among them, the process of the first boron source diffusion can be either tube diffusion or chain diffusion.
[0047] (2) Laser grooving is performed on the surface of the N-type silicon substrate 1 after the first boron source diffusion, or etching is performed using a corrosive slurry / solution under the treatment of a mask. Whether it is laser grooving or etching grooving, the groove can be opened to the surface of the diffusion layer 2, or inside the diffusion layer 2, or inside the N-type silicon substrate 1 to form a grooved area.
[0048] When laser grooving or etching to the inside of the diffusion layer 2 or the N-type silicon substrate 1, the distance from the bottom surface of the grooved area to the surface of the diffusion layer 2 is 0 - 500 nm, such as Figure 1 (c), Figure 2 (c) or Figure 3 (c) as shown. Preferably, the distance is 200 - 300 nm. Among them, when using laser grooving, the laser spot size is 40 - 150 μm, preferably, the laser spot size is 60 - 100 μm.
[0049] Among them, when laser grooving, the borosilicate glass layer 6 acts as a mask layer, and its functions are, for example, to prevent POLY from being plated around, as a mask for secondary diffusion, and a mask for polishing. On the one hand, it is convenient to fabricate diffusion layers with different doping concentrations and the subsequent heavily doped layers; on the other hand, it can prevent damage to the substrate during the process of removing the plated-around doped layer and the borosilicate glass layer. The purpose of opening the bottom of the groove into the diffusion layer is to effectively drive the boron atoms in the borosilicate glass layer into the silicon wafer, thereby increasing the boron atom concentration on the surface of the silicon wafer.
[0050] (3) Use an isotropic etching solution to etch the grooved area. Due to the high defect state near the side edge at the bottom of the grooved area, use the isotropic etching solution to etch the high-defect Si crystal structure in the grooved area, and laterally expand at the bottom of the grooved area to form a grooved expansion area with a bottom cross-sectional area larger than the surface opening cross-sectional area, while removing the ablation damage of laser grooving. The grooved expansion area can be completely located in the diffusion layer (such as Figure 1 (d), Figure 2 (d) as shown), or located inside the silicon wafer (such as Figure 3 (d) as shown), depending on the specific process conditions and process situation. After etching, perform cleaning.
[0051] Among them, the reaction rate of the diffusion layer with the isotropic etching solution is greater than the reaction rate of the N-type silicon substrate with the isotropic etching solution, and finally a grooved expansion area with a bottom cross-sectional area larger than the surface opening cross-sectional area is formed.
[0052] Among them, the isotropic etching solution can use the HF-HNO 3 system, adding water or acetic acid as a diluent. Generally, the mass percentage concentration of the HF solution is 49 ± 1%, and the mass percentage concentration of the HNO 3 solution is 65 - 70%. The molar ratio of HF to HNO 3 in the etching solution is greater than 1:3.
[0053] Preferably, in order to moderate the etching rate of the etching solution, additives can be used for groove etching, such as adding:
[0054] A. Polyoxyethylene ether series surfactants
[0055] B, hydrogen peroxide and a small amount of surfactant
[0056] C, catalysts (such as nano - silver particle solution), non - ionic surfactants (such as alkylphenol polyoxyethylene ether, high - carbon fatty alcohol polyoxyethylene ether), silane coupling agents, etc.;
[0057] Preferably, when etching the grooved area with an isotropic etching solution, the etching temperature is 5°C - 35°C.
[0058] Furthermore, (100) silicon crystal planes can be etched at a high rate (about 125 - 140 μ / hour), which is beneficial to controlling the etching rate at the boundary of the boron - doped layer in the grooved area of the silicon wafer and forming a desired undercut shape at the bottom of the groove.
[0059] (4) Align the grooved extended area, and fill the boron - source slurry (such as boron tribromide, TMA - B, or boron - silicon slurry, etc.) into the grooved extended area by printing, spraying, or spin - coating, as shown in Figure 1 (e), Figure 2 (e) or Figure 3 (e). Among them, the boron - source slurry can either protrude from the grooved extended area or be completely located within the grooved extended area (not shown).
[0060] Then, perform boron - source laser doping or second - time boron - source diffusion on the slurry filled in step (4). Since the bottom cross - sectional area of the grooved extended area is large, the amount of dopant boron source that can be effectively utilized is large. Under the action of the laser, the boron source diffuses circumferentially (including the thickness direction) into the grooved extended area, forming a heavily - doped grooved extended area 6. The formed heavily - doped grooved extended area 6 can be completely located within the diffusion layer 2, as shown in Figure 2 (f); or it can be partially located within the diffusion layer 2 and partially within the silicon substrate 1, as shown in Figure 1 (f); or it can be completely located within the silicon substrate but in contact with the diffusion layer 2, as shown in Figure 3 (f). Among them, the process of the second - time boron - source diffusion can be tube diffusion or chain diffusion. When using chain diffusion, the front - and - back processes can achieve an online mode, reducing the loading and unloading operations, and the influence between wafers is very small. The whole wafer is heated more uniformly, greatly ensuring the diffusion uniformity of each wafer. Among them, the size of the laser spot is 80 - 160 μm, preferably 100 - 140 μm.
[0061] Since the undercut shape at the bottom of the grooved extended area (the bottom cross - sectional area is larger than the surface opening cross - sectional area) expands the surface area of the heavily - doped area and the lateral width area of the heavily - doped boron diffusion, a contiguous structural layer of the heavily - doped area (heavily - doped grooved extended area) and the surrounding original diffusion layer is formed (see Figure 1 (f), Figure 2 (f), Figure 3(f)) is conducive to forming an effective ohmic contact between the metal paste layer and the heavily doped region in the heavily doped region circumferentially surrounding the grooved expansion region, expanding the cross-section of the carrier diffusion / drift channel, reducing the contact resistance, and reducing the conduction loss of carriers at the contact interface, thereby increasing the short-circuit current and fill factor of the battery, and being beneficial to improving the electrical performance of the silicon battery.
[0062] (5) After completing the laser doping, the remaining boron source paste and the boron-silicate glass layer 6 are cleaned off, and then a passivation film and / or an antireflection film are prepared on the surface of the diffusion layer 2. The grooved area may or may not be coated. Then, conductive paste is printed corresponding to the grooved position to prepare an electrode corresponding to the heavily doped grooved expansion region 3, and then an electrode is also prepared on the other side of the cell wafer. After sintering, the cell wafer is formed.
[0063] The method for preparing a solar cell wafer proposed by the present invention first makes grooves, and then uses an isotropic etching solution to etch the grooved area. Since the heavily doped region circumferentially surrounding the bottom area of the groove is conducive to forming an effective ohmic contact between the metal paste and the heavily doped region, the contact resistance can be reduced, the loss of carriers at the contact interface can be reduced, thereby increasing the short-circuit current and fill factor of the battery, being beneficial to improving the electrical performance of the silicon battery, and also improving the conversion efficiency of the silicon battery and reducing costs.
[0064] It should be noted that the above preparation method is applicable to both the front side and the back side of the solar cell wafer.
[0065] Among them, the solar cell wafers to which the above preparation method can be applied include back-contact cells, IBC cells, Topcon cells, or HBC-structured cells.
[0066] The present invention also proposes a solar cell wafer. Referring to Figure 4 、 Figure 5 、 Figure 6 shown, it includes:
[0067] An N-type silicon substrate 1; a diffusion layer 2, which is disposed on the N-type silicon substrate 1; a heavily doped grooved expansion region 3, which is buried in or penetrates the diffusion layer 2. The cross-sectional area of the bottom surface of the heavily doped grooved expansion region 3 is larger than the cross-sectional area of the surface opening, and the doping concentration of the heavily doped grooved expansion region 3 is greater than the doping concentration of the non-heavily doped grooved expansion region 3 in the diffusion layer 2; a dielectric layer 4, which is disposed on the diffusion layer 2, and the dielectric layer 4 is a passivation film and / or an antireflection film; an electrode 5, which is filled in the heavily doped groove 3 and extends upward beyond the dielectric layer 2.
[0068] Due to the heavily doped groove extension region with a bottom cross-sectional area larger than the surface opening cross-sectional area in the solar cell of this structure, the heavily doped groove extension region expands the surface area of the heavily doped region and the lateral width region of the heavily doped boron diffusion, which is beneficial to the formation of an effective ohmic contact between the metal paste and the heavily doped region. Therefore, the contact resistance can be reduced, the loss of carriers at the contact interface can be minimized, and further, the short-circuit current and fill factor of the battery can be increased, which is conducive to improving the electrical performance of the silicon battery. It can also improve the conversion efficiency of the silicon battery and reduce costs.
[0069] Preferably, the bottom of the heavily doped groove extension region 3 extends into the diffusion layer 2 or the N-type silicon substrate 1.
[0070] The structure of this solar cell can be various as long as the above effects can be achieved. The difference lies in the position of the heavily doped groove extension region 3. Correspondingly, the electrode fills the heavily doped groove extension region 3 and extends upward beyond the dielectric layer 2 to achieve electrical connection.
[0071] Preferably, the bottom surface and / or side surface of the heavily doped groove extension region 3 are in contact with the diffusion layer 2 to form a conduction channel between the heavily doped region and the lightly doped region.
[0072] When laser doping the boron source paste in the grooved extension region, the boron source can diffuse to the bottom surface and / or side surface, and finally the bottom surface and / or side surface of the heavily doped groove extension region 3 are in contact with the diffusion layer 2.
[0073] The specific structure of the heavily doped groove extension region 3 can be in various forms. For example, when the bottom of the heavily doped groove extension region 3 extends into the diffusion layer 2, as Figure 5 shown, the heavily doped groove extension region 3 is completely located within the diffusion layer 2, and the electrical performance and conversion efficiency of this method are the best. When the bottom of the heavily doped groove extension region 3 extends into the N-type silicon substrate 1, two embodiments can be included: One embodiment is that a part of the heavily doped groove extension region 3 is located within the diffusion layer 2 and a part is located within the N-type silicon substrate 1, as Figure 4 shown; Another embodiment is that the heavily doped groove extension region 3 is completely located within the N-type substrate 1, as Figure 6 shown, and the top of the heavily doped groove extension region 3 is in contact with the diffusion layer 2.
[0074] It should be noted that for those skilled in the art, it is known that there are multiple electrodes in the solar cell, so the number of the heavily doped groove extension regions 3 described in the text is also multiple and is correspondingly connected to the electrodes.
[0075] It should be noted that the heavily doped groove extension region 3 can be located either on the front side or the back side of the solar cell.
[0076] Embodiment 1
[0077] A method for manufacturing a solar cell is as follows, referring to Figure 1 shown:
[0078] 1. Etch the N-type silicon substrate 1 to form a textured surface.
[0079] 2. Perform the first boron source diffusion on the surface of the N-type silicon substrate 1, and form a diffusion layer 2 and a borosilicate glass layer 6. Among them, the thickness of the diffusion layer is 300 nm.
[0080] 3. Directly perform laser grooving on the surface of the N-type silicon substrate after the first boron source diffusion to form a grooved area. The distance from the bottom surface of the grooved area to the surface of the diffusion layer 2 is 250 nm, that is, groove into the diffusion layer 2, see Figure 1 (c); among them, when using laser grooving, the laser spot size is 80 μm.
[0081] 4. Etch the grooved area with an isotropic etching solution, and the bottom of the grooved area expands laterally to form a grooved expansion area located in the diffusion layer 2, see Figure 1 (d). After the cross-sectional area of the bottom surface of the grooved area is larger than the cross-sectional area of the surface opening, perform cleaning after etching. Among them, the isotropic etching solution is an HF-HNO 3 system, with water as a diluent; the mass percentage concentration of the HF solution is 49%, and the mass percentage concentration of HNO 3 is 69%; the molar ratio of HF to HNO 3 is greater than 1:3, and additives such as a combination of hydrogen peroxide and a surfactant are also added to the isotropic etching solution. Among them, the etching temperature for etching the grooved area is 20 °C.
[0082] 5. Align the grooved expansion area, and fill the grooved expansion area with boron source slurry (doping source) by printing, spraying, or spin coating, so that the formed doping source protrudes from the grooved expansion area, see Figure 1 (e).
[0083] 6. Perform laser doping on the filled slurry. Under the action of the laser, the boron source diffuses circumferentially into the grooved expansion area to form a heavily doped grooved expansion area 3, a part of which is located in the diffusion layer 2 and a part is located in the N-type silicon substrate 1, see Figure 1 (f). Among them, the size of the laser spot during laser doping is 120 um.
[0084] 7. After completing the laser doping, wash off the remaining boron source slurry.
[0085] 8. Prepare a passivation film and / or an antireflection film on the surface of the diffusion layer 2.
[0086] 9. Then perform conductive slurry printing corresponding to the grooving position to prepare an electrode corresponding to the heavily doped grooved expansion area 3, and then also prepare an electrode on the other side of the battery chip. After sintering, a battery chip is formed.
[0087] Example 2
[0088] The difference between this embodiment and Embodiment 1 lies in the different depths of the heavy doping. Refer to Figure 2 (f).
[0089] Specifically, in Step 3, the distance from the bottom surface of the grooved area to the surface of the diffusion layer 2 is 50 nm, which is relatively closer to the diffusion layer 2. Therefore, the heavily doped groove extended area 3 formed in Step 6 is completely located within the diffusion layer 2 and does not contact the N-type silicon substrate 1. See Figure 2 (f).
[0090] Embodiment 3
[0091] The differences between this embodiment and Embodiment 1 are the different depths of the grooved area and the different depths of the heavy doping. Refer to Figure 3 .
[0092] Specifically, in Step 2, the thickness of the diffusion layer is 400 nm.
[0093] In Step 3, the distance from the bottom surface of the grooved area to the surface of the diffusion layer 2 is 500 nm, that is, the bottom surface of the grooved area is located within the N-type silicon substrate 1. See Figure 3 (c).
[0094] In Step 4, an isotropic etching solution is used to etch the grooved area, and the bottom of the grooved area expands laterally to form a grooved extended area located within the N-type silicon substrate 1. See Figure 3 (d)
[0095] The heavily doped groove extended area 3 formed in Step 6 is completely located within the N-type silicon substrate 1. See Figure 3 (f).
[0096] Embodiment 4
[0097] The differences between this embodiment and Embodiment 1 are that when laser grooving in Step 3, the laser spot size is 40 μm; when laser doping in Step 6, the laser spot size is 80 μm.
[0098] Embodiment 5
[0099] The differences between this embodiment and Embodiment 1 are that when laser grooving in Step 3, the laser spot size is 140 μm; when laser doping in Step 6, the laser spot size is 160 μm.
Claims
1. A method for preparing a solar cell chip, characterized in that, it comprises the following steps: 1) Etch the N-type silicon substrate to form a textured surface; then perform the first boron source diffusion to form a diffusion layer and a borosilicate glass layer; 2) Laser grooving or etching the surface of the N-type silicon substrate after the first boron source diffusion to the surface of the diffusion layer or within the diffusion layer or within the N-type silicon substrate to form a grooved area; 3) Etch the grooved area with an isotropic etching solution, and laterally expand at the bottom of the grooved area to form a grooved expanded area with a bottom cross-sectional area larger than the surface opening cross-sectional area; 4) Fill the boron source paste into the grooved expanded area, and then perform boron source laser doping or the second boron source diffusion. The boron source diffuses circumferentially into the grooved expanded area to form a heavily doped grooved expanded area; 5) Clean the N-type silicon substrate obtained in step 4), and then prepare a dielectric layer on the diffusion layer. The dielectric layer is a passivation film and / or an antireflection film; Print a conductive paste corresponding to the heavily doped grooved expanded area to prepare an electrode, and form a solar cell chip after sintering.
2. The method for preparing a solar cell chip according to claim 1, characterized in that, the first boron source diffusion method in step 1) is tube diffusion or chain diffusion, and the second boron source diffusion method in step 4) is tube diffusion or chain diffusion.
3. The method for preparing a solar cell chip according to claim 1, characterized in that, when grooving or etching to within the diffusion layer or within the N-type silicon substrate in step 2), the distance from the bottom surface of the grooved area to the surface of the diffusion layer is 0 - 500 nm.
4. The method for preparing a solar cell chip according to claim 1, characterized in that, when laser grooving in step 2), the laser spot size is 40 - 150 μm.
5. The method for preparing a solar cell chip according to claim 1, characterized in that, The isotropic etching solution in step 3) is HF-HNO 3 system, where water or acetic acid is used as a diluent.
6. The method for preparing a solar cell chip according to claim 5, characterized in that, The mass percentage concentration of the HF solution is 49 ± 1%, and the mass percentage concentration of the HNO 3 solution is 65 - 70%; the molar ratio of HF to HNO 3 is greater than 1:
3.
7. The method for preparing a solar cell chip according to claim 5, characterized in that, an additive is further added to the isotropic etching solution in step 3), and the additive is: a polyoxyethylene ether series surfactant; or a combination of hydrogen peroxide and a surfactant; or a combination of a catalyst, a nonionic surfactant, and a silane coupling agent.
8. The method for preparing a solar cell chip according to claim 1, characterized in that, when etching the grooved area with an isotropic etching solution in step 3), the etching temperature is 5°C - 35°C.
9. The method for preparing a solar cell chip according to claim 1, characterized in that, the boron source paste in step 4) protrudes from the grooved expanded area or is completely located within the grooved expanded area.
10. The method for preparing a solar cell chip according to claim 1, characterized in that, when performing boron source laser doping in step 4), the size of the laser spot is 80 - 160 um.
11. The method for preparing a solar cell chip according to any one of claims 1 to 10, characterized in that, the solar cell chip includes a back contact cell, an IBC cell, a Topcon cell, or an HBC structure cell.
12. A solar cell chip, characterized in that, it includes: an N-type silicon substrate; a diffusion layer, which is arranged on the N-type silicon substrate; a heavily doped groove extended region, which is prepared in the following way: laser grooving or etching the surface of the N-type silicon substrate after the first boron source diffusion to the surface of the diffusion layer or inside the diffusion layer or inside the N-type silicon substrate to form a grooved region; etching the grooved region with an isotropic etching solution to laterally expand at the bottom of the grooved region to form a grooved extended region with a bottom cross-sectional area larger than the surface opening cross-sectional area; filling boron source paste into the grooved extended region, and then performing boron source laser doping or the second boron source diffusion, and the boron source diffuses circumferentially to the grooved extended region to form a heavily doped groove extended region buried in or penetrating through the diffusion layer; the doping concentration of the heavily doped groove extended region is greater than the doping concentration of the non-heavily doped groove extended region in the diffusion layer; a dielectric layer, which is arranged on the diffusion layer, and the dielectric layer is a passivation film and / or an antireflection film; an electrode, which is filled in the heavily doped groove extended region and extends upward beyond the dielectric layer.
13. The solar cell chip according to claim 12, characterized in that, the bottom of the heavily doped groove extended region extends into the diffusion layer or the N-type silicon substrate.
14. The solar cell chip according to claim 12, characterized in that, the bottom surface and / or side surface of the heavily doped groove extended region are in contact with the diffusion layer to form a conduction channel between the heavily doped region and the lightly doped region.
Citation Information
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