A method for manufacturing a solar cell and a solar cell

Abstract

The present invention discloses a method for manufacturing a solar cell and a solar cell, and relates to the technical field of solar cells, in order to solve the problem that in the process of forming a heavily doped region, a lightly doped region is affected, thereby reducing the performance of the solar cell. The method for manufacturing the solar cell comprises: processing the first surface of a semiconductor substrate to form a doping source layer. The doping source layer is regionally processed by a laser irradiation process, so that the doping elements in the doping source layer diffuse into the semiconductor substrate, so as to form a heavily doped region on one side of the first surface of the semiconductor substrate, and the remaining doping source layer is a lightly doped region. The ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. Within the depth range of 1 micron in the heavily doped region, the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for manufacturing a solar cell and a solar cell. Background Art

[0002] Solar cells are devices that utilize solar energy and directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. In order to improve the efficiency of solar cells, a selective emitter solar cell is usually used. This type of cell is a conventional solar cell surface that evenly arranges a P (phosphorus) atom to form a PN junction of varying depths. The area where the deeper PN junction is located is the deep diffusion area, and the area where the shallower PN junction is located is the shallow diffusion area.

[0003] In the prior art, a mask method is usually used to prepare a selective emitter. In the actual manufacturing process, two diffusions are usually required to form electrode regions and non-electrode regions with different doping concentrations. However, the two diffusions will affect each other. Specifically, in the process of forming the heavily doped region of the electrode region by the second diffusion, the lightly doped region of the non-electrode region will be affected, thereby reducing the performance of the solar cell. Summary of the invention

[0004] The object of the present invention is to provide a method for manufacturing a solar cell and a solar cell, which are used to reduce or avoid the influence on a lightly doped region during the process of forming a heavily doped region, so as to improve the performance of the solar cell.

[0005] In order to achieve the above-mentioned object, in the first aspect, the present invention provides a method for manufacturing a solar cell. The method for manufacturing a solar cell comprises: first, providing a semiconductor substrate, the semiconductor substrate having a first surface and a second surface opposite to each other. Next, the first surface of the semiconductor substrate is processed to form a doping source layer. Next, the doping source layer is regionally processed by a laser irradiation process, so that the doping elements in the doping source layer are diffused into the semiconductor substrate to form a heavily doped region on one side of the first surface of the semiconductor substrate, and the remaining doping source layer is a lightly doped region. Next, the semiconductor substrate, the heavily doped region and the lightly doped region are oxidized to form a selective emitter on the first surface of the semiconductor substrate. Wherein, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1, and less than or equal to 3. Within the depth range of 1 micron in the heavily doped region, the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30%, and less than or equal to 100%.

[0006] Compared with the prior art, in the method for manufacturing a solar cell provided by the present invention, although the doping source layer formed is a whole layer structure, the doping source layer is regionally processed by the laser irradiation process. At this time, only the doping elements in the local area of ​​the doping source layer diffuse into the interior of the semiconductor substrate. The doping elements in the area of ​​the doping source layer that has not been processed by the laser irradiation process do not diffuse into the interior of the semiconductor substrate and remain in the doping source layer. Based on this, the influence on the remaining doping source layer (i.e., the lightly doped area) in the process of forming the heavily doped area is small or has no influence, which improves the performance of the solar cell compared with the prior art. Further, compared with the prior art, there is no second diffusion, so the influence on the lightly doped area is also reduced. Further, since the ratio of the maximum doping concentration of the doping element in the heavily doped area to the maximum doping concentration of the doping element in the lightly doped area is greater than or equal to 1, and less than or equal to 3. Within the depth range of 1 micron in the heavily doped area, the ratio of the doping concentration of the doping element in any heavily doped area to the maximum doping concentration of the doping element in the heavily doped area is greater than or equal to 30%, and less than or equal to 100%. At this time, not only the series resistance is reduced and the fill factor is improved, but also the recombination of carriers is reduced, the photon response of solar cells is improved, the short-circuit current density is increased, and the conversion efficiency of solar cells is effectively improved.

[0007] In one implementation, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 At this point, the series resistance can be further reduced and the fill factor can be increased.

[0008] In one implementation, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3 , and less than or equal to 1.0×10 19 cm -3 At this time, the recombination of carriers can be further reduced, the photon response of solar cells can be improved, and the short-circuit current density can be increased.

[0009] In one implementation, at a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.

[0010] In one implementation, processing the first surface of the semiconductor substrate to form a doping source layer includes: performing a diffusion process on the first surface of the semiconductor substrate to form a doping source layer. The doping source layer includes a first doping layer and a second doping layer, and the second doping layer is formed on the first doping layer. The temperature of the diffusion process is greater than or equal to 750° C. and less than or equal to 1000° C. The time of the diffusion process is greater than 0 min and less than or equal to 120 min, and the doping source used in the diffusion process includes a Group III source.

[0011] In one implementation, the Group III source is a boron source, and the second doping layer is a borosilicate glass layer. The thickness of the borosilicate glass layer is greater than 0 nm and less than or equal to 50 nm. The concentration of the doping element in the first doping layer is greater than or equal to 1.0×10 19 cm -3 , and less than or equal to 5.0×10 20 cm -3 .

[0012] When the above technical solution is adopted, under the combined effect of diffusion treatment and laser irradiation process, not only the concentration of doping elements inside the semiconductor substrate is increased. At the same time, compared with the method of directly doping boron with laser in the prior art, it can reduce or avoid the enrichment of boron atoms in the borosilicate glass layer, or reduce or avoid the enrichment of boron atoms on the surface of the semiconductor substrate to form a dead layer, so as to reduce metal recombination. Furthermore, since the thickness of the borosilicate glass layer is greater than 0nm and less than or equal to 50nm. In the subsequent processing of the solar cell, the borosilicate glass layer can play a protective role, reduce the risk of selective emitter etching, so as to ensure the quality of the solar cell.

[0013] In one implementation, the laser wavelength of the laser irradiation process is greater than or equal to 300 nm and less than or equal to 1500 nm.

[0014] In one implementation, the laser power of the laser irradiation process is greater than or equal to 20 watts and less than or equal to 500 watts.

[0015] In one implementation, a laser processing speed of the laser irradiation process is greater than or equal to 20 m / s and less than or equal to 60 m / s.

[0016] In one implementation, the spot of the laser irradiation process is a rectangular spot, the width of the rectangular spot is greater than or equal to 30 microns and less than or equal to 120 microns, and the ratio of the length of the rectangular spot to the width of the rectangular spot is greater than or equal to 1 and less than or equal to 1.5.

[0017] When the above technical solution is adopted, compared with the square spot with the same width, the rectangular spot can process a larger area in the same time, thereby improving the processing efficiency. At the same time, when the rectangular spot is used to increase the laser engraving speed, the gap between two adjacent rectangular spots can be reduced or avoided, so as to reduce the fault of laser energy, improve the processing efficiency, reduce the square resistance, and increase the production capacity.

[0018] In one implementation, the overlap rate of two adjacent light spots in the light spots of the laser irradiation process is greater than 0% and less than 100%.

[0019] When the above technical solution is adopted, for the area that needs laser irradiation process, the laser energy is accumulated in the area so that the temperature reaches the requirement in a shorter time, reducing the damage of the laser to the suede surface, thereby improving the processing efficiency.

[0020] In a second aspect, the present invention also provides a solar cell. The solar cell includes: a semiconductor substrate having a first surface and a second surface relative to each other. A heavily doped region and a lightly doped region are formed on the first surface of the semiconductor substrate, and the lightly doped region is located on one side of the heavily doped region. The ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. Within a depth range of 1 micron in the heavily doped region, the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.

[0021] Compared with the prior art, in the solar cell provided by the present invention, although the doping source layer formed is a whole layer structure, the doping source layer is regionally processed by the laser irradiation process. At this time, only the doping elements in the local area of ​​the doping source layer diffuse into the semiconductor substrate. The doping elements in the area of ​​the doping source layer that has not been processed by the laser irradiation process do not diffuse into the semiconductor substrate and remain in the doping source layer. Based on this, the influence on the remaining doping source layer (i.e., the lightly doped area) in the process of forming the heavily doped area is small or has no influence, which improves the performance of the solar cell compared with the prior art. Further, compared with the prior art, there is no second diffusion, so the influence on the lightly doped area is also reduced. Further, since the ratio of the maximum doping concentration of the doping element in the heavily doped area to the maximum doping concentration of the doping element in the lightly doped area is greater than or equal to 1, and less than or equal to 3. Within the depth range of 1 micron in the heavily doped area, the ratio of the doping concentration of the doping element in any heavily doped area to the maximum doping concentration of the doping element in the heavily doped area is greater than or equal to 30%, and less than or equal to 100%. At this time, not only the series resistance is reduced and the fill factor is improved, but also the recombination of carriers is reduced, the photon response of solar cells is improved, the short-circuit current density is increased, and the conversion efficiency of solar cells is effectively improved.

[0022] In one implementation, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 At this point, the series resistance can be further reduced and the fill factor can be increased.

[0023] In one implementation, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3 , and less than or equal to 1.0×10 19 cm -3 At this time, the recombination of carriers can be further reduced, the photon response of solar cells can be improved, and the short-circuit current density can be increased.

[0024] In one implementation, at a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a schematic diagram of a rectangular light spot in an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of a square light spot in the prior art;

[0028] Figure 3 A schematic diagram of a laser line formed by a plurality of rectangular light spots in an embodiment of the present invention;

[0029] Figure 4 4 is a graph showing the relationship between the doping concentration and the doping depth of the doping elements in the heavily doped region and the lightly doped region in an embodiment of the present invention.

[0030] Reference numerals:

[0031] 1-square spot, 2-rectangular spot, 3-laser line. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0035] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] With the rapid development of the global economy, the massive consumption of traditional resources such as oil, coal and natural gas has caused serious ecological damage and the occurrence of extreme climates. Therefore, energy and environmental issues have attracted more and more attention. How to make up for the energy gap and improve the environment has become an issue of sustainable development for mankind. Solar energy is an inexhaustible clean energy source. The use of solar cells for photovoltaic power generation has become the fastest-growing research field in recent years. In order to increase the proportion of photovoltaic power generation, cost reduction and efficiency improvement are the two main lines of photovoltaic manufacturing. The factors affecting the photoelectric conversion efficiency of solar cells are diffusion and metallization. Excessive diffusion concentration is beneficial to screen-printed electrodes and forms good electrode contact with the silicon substrate, but it reduces the absorption efficiency of photons. Higher defect density reduces the short-circuit current and open-circuit voltage of the battery. Although lower diffusion concentration will improve the photon response of the battery and increase the short-circuit current density, it will increase the contact resistance and reduce the fill factor. TOPCon (Tunnel Oxide Passivated Contact solar cell) technology has become one of the most promising new high-efficiency battery technologies due to its high compatibility with the traditional PERC battery production line and its obvious efficiency gain. The TOPCon battery uses boron diffusion to prepare the emitter on the front side, and the superposition of selective emitter (SE) technology is currently one of the main means to reduce front-side recombination and improve battery efficiency.

[0038] In the prior art, laser doping, masking, and boron paste printing and co-diffusion methods are usually used to prepare selective emitters.

[0039] Specifically, for the laser doping method, the laser doping method uses the energy of the laser to push the doping source in the phosphorosilicate glass (PSG) or borosilicate glass (BSG) for a second time to form a heavily doped area. The area that has not been laser treated forms a shallowly doped area. For example, the manufacturing method of the P-type battery laser SE is to use a laser pulse to melt the surface of the silicon wafer, and the phosphorus atoms in the PSG covering the top of the emitter enter the surface of the silicon wafer. After solidification, the doped phosphorus atoms replace the position of the silicon atoms, forming a doping layer with high concentration and high impurity activation rate in the laser melt layer.

[0040] However, when laser doping is used to prepare SE structures, the power and frequency of the laser need to be precisely controlled, and the damage caused is also inevitable. Furthermore, for the direct boron doping of N-type batteries with laser, on the one hand, the solid solubility of boron atoms in BSG is greater than that in silicon, which makes it easier for boron atoms to be enriched in BSG. On the other hand, the doped boron atoms will be enriched on the surface of the silicon wafer due to the mismatch with the silicon lattice, forming a dead layer and causing serious recombination. Therefore, the concentration of direct boron doping by laser is low, which makes it difficult to reduce the contact resistance and metal recombination of heavily doped areas, and is not conducive to increasing the open circuit voltage. At the same time, increasing the laser energy for doping will produce ion sputtering, resulting in epitaxy of the heavily doped area. Excessive energy will form damage and recombination centers on the velvet surface, thereby affecting the battery opening voltage and contact resistance.

[0041] For the mask method, a mask is first prepared, and an electrode window is formed by laser ablation or photolithography. The difference in doping effect of the doping source in the masked and unmasked areas is used to achieve selective doping. For example, in the secondary diffusion: the first boron diffusion (light diffusion) and laser grooving to remove the BSG at the gate line position (heavy diffusion area). In the second heavy diffusion, the light diffusion area is blocked by BSG, thereby achieving local heavy doping to complete the SE structure.

[0042] However, for the two diffusions in the mask method, electrode areas and non-electrode areas with different doping concentrations are formed respectively. The process time is too long, the cost is too high, and the impact on production capacity is great. In addition, multiple high-temperature diffusions will affect the quality of the substrate, resulting in the loss of cell efficiency of the final solar cell. Furthermore, the uniformity of the block resistance in the low-doped area is difficult to control. Moreover, there is an interference effect between the two boron diffusion processes. Specifically, since both are high-temperature processes, the second boron diffusion will affect the light diffusion curve. In addition, this solution has very high requirements for lasers (lossless film opening is required), which increases the equipment cost.

[0043] For the boron paste printing co-diffusion method, the boron paste is printed on the gate line position, and then nitrogen carries liquid BBr3 for tubular co-diffusion. However, for the boron paste printing co-diffusion, the line width cannot be accurately controlled due to the epitaxy of the boron paste at high temperature, and the residual material at the gate line after high temperature is difficult to clean.

[0044] In order to solve some of the above technical problems, in a first aspect, an embodiment of the present invention provides a method for manufacturing a solar cell.

[0045] The method for manufacturing the solar cell comprises the following steps:

[0046] First, a semiconductor substrate is provided. The semiconductor substrate has a first surface and a second surface opposite to each other.

[0047] In actual application, the semiconductor substrate may be only a semiconductor substrate. Exemplarily, the semiconductor substrate may be a silicon substrate. In terms of conductivity type, the semiconductor substrate may be an intrinsic conductive substrate, an N-type conductive substrate or a P-type conductive substrate. Preferably, the semiconductor substrate is an N-type conductive substrate or a P-type conductive substrate. In terms of structure, the first surface of the semiconductor substrate may be a velvet surface to improve the light trapping effect of the solar cell toward the light surface, thereby improving the utilization rate of light by the solar cell. Of course, the first surface of the semiconductor substrate may also be a plane. As for the second surface of the semiconductor substrate, it may be a polished surface or a velvet surface, which is not specifically limited here. In an embodiment of the present invention, the semiconductor substrate is N-type monocrystalline silicon.

[0048] As a possible implementation manner, the semiconductor substrate is cleaned, and the first surface and the second surface opposite to each other of the semiconductor substrate are textured to form a texture structure.

[0049] Next, the first surface of the semiconductor substrate is processed to form a doping source layer.

[0050] Exemplarily, a first surface of a semiconductor substrate is subjected to diffusion treatment to form a doping source layer. The doping source layer includes a first doping layer and a second doping layer, and the second doping layer is formed on the first doping layer. The temperature of the diffusion treatment is greater than or equal to 750°C and less than or equal to 1000°C. For example, the temperature may be 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C. The time of the diffusion treatment is greater than 0min and less than or equal to 120min. For example, the time of the diffusion treatment may be 1min, 12min, 20min, 35min, 40min, 52min, 60min, 75min, 80min, 85min, 90min, 100min, 115min or 120min. The doping source used in the diffusion treatment includes a group III source. For example, the group III source may be a boron source, a gallium source, an indium source, etc.

[0051] In an optional manner, the above-mentioned Group III source is a boron source, and the second doping layer is a borosilicate glass layer. The thickness of the borosilicate glass layer is greater than 0 nm and less than or equal to 50 nm. For example, the thickness of the borosilicate glass layer can be 1 nm, 5 nm, 10 nm, 15 nm, 21 nm, 25 nm, 30 nm, 35 nm, 42 nm, 48 nm or 50 nm. The concentration of the doping element in the first doping layer is greater than or equal to 1.0×10 19 cm -3 , and less than or equal to 5.0×10 20 cm -3 For example, the concentration of the doping element in the first doping layer may be 1.0×10 19 cm -3, 2.0×10 19 cm -3 4.0×10 19 cm -3 8.0×10 19 cm -3 , 1.0×10 20 cm -3 , 1.5×10 20 cm -3 , 2.0×10 20 cm -3 , 3.0×10 20 cm -3 or 5.0×10 20 cm -3 wait.

[0052] When the above technical solution is adopted, under the combined effect of diffusion treatment and laser irradiation process, not only the concentration of doping elements inside the semiconductor substrate is increased. At the same time, compared with the method of directly doping boron with laser in the prior art, it can reduce or avoid the enrichment of boron atoms in the borosilicate glass layer, or reduce or avoid the enrichment of boron atoms on the surface of the semiconductor substrate to form a dead layer, so as to reduce metal recombination. Furthermore, since the thickness of the borosilicate glass layer is greater than 0nm and less than or equal to 50nm. In the subsequent processing of the solar cell, the borosilicate glass layer can play a protective role, reduce the risk of selective emitter etching, so as to ensure the quality of the solar cell.

[0053] Specifically, in combination with the above description, the chemical bonds of boron and oxygen in the borosilicate glass layer absorb the energy transmitted by the laser and break, becoming boron atoms in a free state. The boron atoms move from the inside of the borosilicate glass layer toward the semiconductor substrate and then enter the inside of the semiconductor substrate. The boron atoms enriched on the surface of the semiconductor substrate (i.e., the boron atoms in the first doping layer) receive the laser energy, and under the action of high temperature, due to the influence of the concentration gradient, the boron atoms gradually diffuse into the inside of the semiconductor substrate.

[0054] In an optional manner, the above-mentioned diffusion treatment of the first surface of the semiconductor substrate to form a doping source layer can be: placing the semiconductor substrate in a tubular diffusion furnace, diffusing the boron source BCl3 or BBr3 under a nitrogen and oxygen atmosphere, and the temperature of the diffusion treatment is greater than or equal to 750°C and less than or equal to 1000°C. The time of the diffusion treatment is greater than 0min and less than or equal to 120min. At this time, a doping source layer including a first doping layer (i.e., a doping P+ layer) and a second doping layer (i.e., a borosilicate glass layer) is formed. Exemplarily, the temperature of the diffusion treatment can be 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, etc. The time of the diffusion treatment can be 1min, 10min, 65min, 96min or 120min, etc.

[0055] Next, the doping source layer is regionally processed by laser irradiation process to diffuse the doping elements in the doping source layer into the semiconductor substrate to form a heavily doped region on one side of the first surface of the semiconductor substrate, and the remaining doping source layer is a lightly doped region.

[0056] As a possible implementation, the laser wavelength of the laser irradiation process is greater than or equal to 300 nm and less than or equal to 1500 nm. For example, the laser wavelength may be 300 nm, 400 nm, 560 nm, 700 nm, 860 nm, 900 nm, 1000 nm, 1200 nm or 1500 nm, etc. Exemplarily, a continuous laser or a pulsed laser may be selected for processing.

[0057] As a possible implementation, the laser power of the laser irradiation process is greater than or equal to 20 W and less than or equal to 500 W. For example, the laser power may be 20 W, 50 W, 70 W, 90 W, 100 W, 120 W, 130 W, 145 W, or 500 W.

[0058] As a possible implementation, the laser processing speed of the laser irradiation process is greater than or equal to 20 m / s and less than or equal to 60 m / s. For example, the laser processing speed may be 20 m / s, 25 m / s, 30 m / s, 35 m / s, 40 m / s, 45 m / s, 50 m / s, 55 m / s or 60 m / s, etc.

[0059] See also Figure 1 and Figure 2 In actual use, the laser spot after focusing on the surface of the semiconductor substrate is a Gaussian spot or a flat-top spot, and a rectangular spot 2 is formed on the surface of the semiconductor substrate through a shaping mirror. The width W1 of the rectangular spot 2 is greater than or equal to 30 microns and less than or equal to 120 microns. The ratio of the length L1 of the rectangular spot to the width W1 of the rectangular spot is greater than or equal to 1 and less than or equal to 1.5. For example, the width W1 of the rectangular spot can be 30 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns or 120 microns, etc. The ratio can be 1, 1.05, 1.1, 1.2, 1.3, 1.4 or 1.5, etc.

[0060] When the above technical solution is adopted, compared with the square spot 1 of the same width, the rectangular spot 2 processes a larger area in the same time, thereby improving the processing efficiency. At the same time, when the rectangular spot 2 is used to increase the laser engraving speed, the gap between two adjacent rectangular spots 2 can be reduced or avoided to reduce the fault of laser energy, improve processing efficiency, reduce square resistance, and increase production capacity. Furthermore, in the embodiment of the present invention, a rectangular spot is used, and by controlling the energy of a single rectangular spot, it is ensured that the energy of a single rectangular spot will not damage the suede.

[0061] See also Figure 3 As a possible implementation method, the overlap rate of two adjacent light spots in the light spot of the laser irradiation process is greater than 0% and less than 100%; the number of times the light spot is irradiated at the same position is greater than or equal to 1. For example, the overlap rate can be 1%, 5%, 10%, 20%, 30%, 40%, 50%, 52%, 65%, 80% or 90%, etc. The number of irradiations can be 1 time, 2 times, 4 times, etc. At this time, for the area that needs to be processed by the laser irradiation process, the laser energy accumulates in the area so that the temperature reaches the requirement in a shorter time, so that the boron atoms migrate into the semiconductor substrate, thereby improving the processing efficiency. The laser line formed by the above-mentioned light spot is continuous, and the width W2 of the laser line 3 is greater than or equal to 30 microns and less than or equal to 120 microns. For example, the width W2 of the laser line 3 can be 30 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns or 120 microns, etc.

[0062] Next, the semiconductor substrate, the heavily doped region and the lightly doped region are oxidized to form a selective emitter on the first surface of the semiconductor substrate.

[0063] Exemplarily, a tube furnace is used to push and oxidize the semiconductor substrate, the heavily doped region, and the lightly doped region at a high temperature to form a selective emitter on the first side of the semiconductor substrate. The oxidation temperature is greater than or equal to 600°C and less than or equal to 1200°C. For example, the oxidation temperature may be 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C. The oxidation process time is greater than 0min and less than or equal to 240min. For example, the oxidation process time may be 1min, 40min, 80min, 100min, 120min, 140min, 180min, 200min, 220min, or 240min.

[0064] Among them, see Figure 4, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1, and less than or equal to 3. For example, the ratio may be 1, 1.2, 1.5, 1.8, 2, 2.3, 2.5, 2.8 or 3, etc. In the heavily doped region within a depth range of 1 micron, the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30%, and less than or equal to 100%. For example, the ratio may be 30%, 42%, 55%, 67%, 80%, 95% or 100%, etc.

[0065] In the method for manufacturing a solar cell provided by an embodiment of the present invention, although the doping source layer formed is a whole layer structure, the doping source layer is regionally processed by the laser irradiation process. At this time, only the doping elements in the local area of ​​the doping source layer diffuse into the semiconductor substrate. The doping elements in the area of ​​the doping source layer that has not been processed by the laser irradiation process do not diffuse into the semiconductor substrate and remain in the doping source layer. Based on this, the influence on the remaining doping source layer (i.e., the lightly doped area) in the process of forming the heavily doped area is small or has no influence, which improves the performance of the solar cell compared to the prior art. Further, compared to the prior art, there is no second diffusion, so the influence on the lightly doped area is also reduced. Further, since the ratio of the maximum doping concentration of the doping element in the heavily doped area to the maximum doping concentration of the doping element in the lightly doped area is greater than or equal to 1, and less than or equal to 3. Within the depth range of 1 micron in the heavily doped area, the ratio of the doping concentration of the doping element in any heavily doped area to the maximum doping concentration of the doping element in the heavily doped area is greater than or equal to 30%, and less than or equal to 100%. At this time, not only the series resistance is reduced and the fill factor is improved, but also the recombination of carriers is reduced, the photon response of solar cells is improved, the short-circuit current density is increased, and the conversion efficiency of solar cells is effectively improved.

[0066] See also Figure 4 In the embodiment of the present invention, the doping concentration of the doping element in the heavily doped region increases to a peak value and then decreases slowly from the surface of the semiconductor substrate to the inside of the semiconductor substrate. As a possible implementation, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 For example, the doping concentration can be 5×10 18 cm -3 , 6×10 18 cm -3 , 8×10 18 cm -3 ,9×10 18 cm-3 , 1×10 19 cm -3 , 1.2×10 19 cm -3 , 2×10 19 cm -3 , 2.3×10 19 cm -3 or 3×10 19 cm -3 Etc. At this point, the series resistance can be further reduced and the fill factor can be increased.

[0067] See also Figure 4 In the embodiment of the present invention, the doping concentration of the doping element in the lightly doped region increases to a peak value and then decreases slowly from the surface of the semiconductor substrate to the inside of the semiconductor substrate. As a possible implementation, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3 , and less than or equal to 1.0×10 19 cm -3 For example, the doping concentration can be 1.0×10 18 cm -3 , 1.6×10 18 cm -3 , 2.8×10 18 cm -3 , 3.9×10 18 cm -3 , 4.5×10 18 cm -3 , 7.6×10 18 cm -3 , 8.2×10 18 cm -3 , 9.3×10 18 cm -3 or 1.0×10 19 cm -3 Etc. At this time, the recombination of carriers can be further reduced, the photon response of solar cells can be improved, and the short-circuit current density can be increased.

[0068] As can be seen from the above, the doping concentration of the doping element in the heavily doped region and the doping concentration of the doping element in the lightly doped region can be controlled separately, and it is easy to achieve that the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1, and less than or equal to 3. Furthermore, compared with the prior art, the doping concentration and doping amount of the doping element in the heavily doped region are increased, and the doping concentration of the doping element in the lightly doped region is reduced.

[0069] As a possible implementation, see Figure 4 At a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.

[0070] As a possible implementation, the method for manufacturing the solar cell further includes the following steps:

[0071] The second surface (backlight surface) of the semiconductor substrate with the selective emitter is polished by a chain machine and a slot machine to remove the PN junction on the second surface and edge of the semiconductor substrate. As for the specific processing process, the reagents used can refer to the prior art and are not specifically limited here.

[0072] Next, a tunneling layer is formed on the second surface of the semiconductor substrate.

[0073] As for the material and thickness of the tunneling layer, they can be set according to the actual situation and are not specifically limited here. For example, the material of the tunneling layer may include one or more of silicon oxide, aluminum oxide, titanium oxide, hafnium dioxide, gallium oxide, tantalum pentoxide, niobium pentoxide, silicon nitride, silicon carbonitride, aluminum nitride, titanium nitride, and titanium nitride carbide.

[0074] Next, a doped polysilicon layer is formed on the tunneling layer.

[0075] The doped polysilicon layer may be a phosphorus-doped polysilicon layer, and may also be doped with other substances, which is not specifically limited here.

[0076] The chemical passivation of the tunneling layer and the field passivation of the doped polysilicon layer can significantly reduce the degree of recombination on the surface of the semiconductor substrate. At the same time, the tunneling layer can also ensure the effective tunneling of the majority carriers, and the doped polysilicon layer can significantly improve the conductivity of the photogenerated carriers, thereby improving the open circuit voltage and fill factor of the tunneling oxide layer passivated contact cell.

[0077] Next, a chain machine and a slot machine are used to remove the polysilicon and borosilicate glass layers on the first side (light-receiving side) of the semiconductor substrate, as well as the phosphorus-expanded glass layer on the second side of the semiconductor substrate. As for the specific treatment process, the reagents used, etc. can refer to the existing technology and are not specifically limited here.

[0078] Next, a passivation layer is formed on the first surface of the semiconductor substrate.

[0079] As for the material and thickness of the passivation layer, they can be set according to the actual situation and are not specifically limited here. For example, the material of the passivation layer may include one or more of silicon nitride, hydrogenated silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, zinc oxide, and hafnium dioxide.

[0080] Next, an anti-reflection layer is formed on the passivation layer.

[0081] As for the material and thickness of the anti-reflection layer, they can be set according to the actual situation and are not specifically limited here. For example, the material of the anti-reflection layer can include one or more of silicon nitride, hydrogenated silicon nitride, silicon oxide, silicon oxynitride, and aluminum oxide.

[0082] Next, electrodes are prepared on the first surface and the second surface of the semiconductor substrate by a printing device.

[0083] Wherein, on the first surface of the semiconductor substrate, the electrodes are connected to the heavily doped region, and the area between the electrodes is a lightly doped region.

[0084] In summary, the method for manufacturing a solar cell provided by an embodiment of the present invention is used to obtain a heavily doped region and a lightly doped region, and the process is simple, the equipment investment is low, and the cost is reduced compared to the prior art, the process time is saved, and the production capacity is improved. Further, the present invention only involves a diffusion process once, which reduces the impact on the quality of the semiconductor substrate compared to the multiple high-temperature diffusions in the prior art, and improves the battery efficiency of the solar cell finally formed compared to the prior art. Further, since the present invention does not need to use a laser to open the film, there is no need to have excessively high requirements for the laser. In addition, the present invention does not need to print boron paste, so there is no problem that the line width cannot be accurately controlled due to the epitaxy of the boron paste, and the residual material at the grid line after the high temperature is difficult to clean.

[0085] In a second aspect, an embodiment of the present invention further provides a solar cell. Figure 4 , the solar cell comprises: a semiconductor substrate having a first surface and a second surface opposite to each other. A heavily doped region and a lightly doped region are formed on the first surface of the semiconductor substrate, and the lightly doped region is located on one side of the heavily doped region. Wherein, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1, and less than or equal to 3. For example, the ratio may be 1, 1.2, 1.5, 1.8, 2, 2.3, 2.5, 2.8 or 3, etc. Within a depth range of 1 micron in the heavily doped region, the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30%, and less than or equal to 100%. For example, the ratio may be 30%, 42%, 55%, 67%, 80%, 95% or 100%, etc.

[0086] In the solar cell provided by the embodiment of the present invention, although the doping source layer formed is a whole layer structure, the doping source layer is regionally processed by the laser irradiation process. At this time, only the doping elements in the local area of ​​the doping source layer diffuse into the semiconductor substrate. The doping elements in the area of ​​the doping source layer that has not been processed by the laser irradiation process do not diffuse into the semiconductor substrate and remain in the doping source layer. Based on this, the influence on the remaining doping source layer (i.e., the lightly doped area) in the process of forming the heavily doped area is small or has no influence, which improves the performance of the solar cell compared with the prior art. Further, compared with the prior art, there is no second diffusion, so the influence on the lightly doped area is also reduced. Further, since the ratio of the maximum doping concentration of the doping element in the heavily doped area to the maximum doping concentration of the doping element in the lightly doped area is greater than or equal to 1, and less than or equal to 3. Within the depth range of 1 micron in the heavily doped area, the ratio of the doping concentration of the doping element in any heavily doped area to the maximum doping concentration of the doping element in the heavily doped area is greater than or equal to 30%, and less than or equal to 100%. At this time, not only the series resistance is reduced and the fill factor is improved, but also the recombination of carriers is reduced, the photon response of solar cells is improved, the short-circuit current density is increased, and the conversion efficiency of solar cells is effectively improved.

[0087] As a possible implementation method, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 For example, the doping concentration can be 5×10 18 cm -3 , 6×10 18 cm -3 , 8×10 18 cm -3 ,9×10 18 cm -3 , 10×10 18 cm -3 , 1.2×10 19 cm -3 , 2×10 19 cm -3 , 2.3×10 19 cm -3 or 3×10 19 cm -3 Etc. At this point, the series resistance can be further reduced and the fill factor can be increased.

[0088] As a possible implementation method, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3, and less than or equal to 1.0×10 19 cm -3 For example, the doping concentration can be 1.0×10 18 cm -3 , 1.6×10 18 cm -3 , 2.8×10 18 cm -3 , 3.9×10 18 cm -3 , 4.5×10 18 cm -3 , 7.6×10 18 cm -3 , 8.2×10 18 cm -3 , 9.3×10 18 cm -3 or 1.0×10 19 cm -3 Etc. At this time, the recombination of carriers can be further reduced, the photon response of solar cells can be improved, and the short-circuit current density can be increased.

[0089] As a possible implementation method, at a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.

[0090] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0091] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for manufacturing a solar cell, characterized in that: include: Providing a semiconductor substrate; The semiconductor substrate has a first surface and a second surface opposite to each other; Processing the first surface of the semiconductor substrate to form a doping source layer; Performing regional processing on the doping source layer by laser irradiation process, so that the doping elements in the doping source layer diffuse into the semiconductor substrate, so as to form a heavily doped region on one side of the first surface of the semiconductor substrate; The remaining doping source layer is a lightly doped region; Performing oxidation treatment on the semiconductor substrate, the heavily doped region and the lightly doped region to form a selective emitter on the first surface of the semiconductor substrate; Wherein, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3; Within a depth range of 1 micron in the heavily doped region, a ratio of a doping concentration of a doping element in any of the heavily doped regions to a maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.

2. The method for manufacturing a solar cell according to claim 1, characterized in that: The doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 .

3. The method for manufacturing a solar cell according to claim 1 or 2, characterized in that: The doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3 , and less than or equal to 1.0×10 19 cm -3 .

4. The method for manufacturing a solar cell according to claim 1 or 2, characterized in that: At a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.

5. The method for manufacturing a solar cell according to claim 1, characterized in that: Processing the first surface of the semiconductor substrate to form a doping source layer includes: Performing diffusion treatment on the first surface of the semiconductor substrate to form a doping source layer; The doping source layer includes a first doping layer and a second doping layer; the second doping layer is formed on the first doping layer; The temperature of the diffusion treatment is greater than or equal to 750° C. and less than or equal to 1000° C.; the time of the diffusion treatment is greater than 0 min and less than or equal to 120 min; and the doping source used in the diffusion treatment includes a Group III source.

6. The method for manufacturing a solar cell according to claim 5, characterized in that: The group III source is a boron source; the second doping layer is a borosilicate glass layer; The thickness of the borosilicate glass layer is greater than 0 nm and less than or equal to 50 nm; the concentration of the doping element in the first doping layer is greater than or equal to 1.0×10 19 cm -3 , and less than or equal to 5.0×10 20 cm -3 .

7. The method for manufacturing a solar cell according to claim 1, characterized in that: The laser wavelength of the laser irradiation process is greater than or equal to 300 nm and less than or equal to 1500 nm; The laser power of the laser irradiation process is greater than or equal to 20 watts and less than or equal to 500 watts; The laser processing speed of the laser irradiation process is greater than or equal to 20 m / s and less than or equal to 60 m / s; The light spot of the laser irradiation process is a rectangular light spot; the width of the rectangular light spot is greater than or equal to 30 microns and less than or equal to 120 microns; the ratio of the length of the rectangular light spot to the width of the rectangular light spot is greater than or equal to 1 and less than or equal to 1.5; The overlap rate of two adjacent light spots in the light spots of the laser irradiation process is greater than 0% and less than 100%.

8. A solar cell, characterized in that: include: A semiconductor substrate having a first surface and a second surface opposite to each other; A heavily doped region and a lightly doped region are formed on the first surface of the semiconductor substrate, wherein the lightly doped region is located on one side of the heavily doped region; Wherein, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3; Within a depth range of 1 micron in the heavily doped region, a ratio of a doping concentration of a doping element in any of the heavily doped regions to a maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.

9. The solar cell according to claim 8, characterized in that The doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 , and less than or equal to 3×10 19 cm -3 .

10. The solar cell according to claim 8 or 9, characterized in that: The doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0×10 18 cm -3 , and less than or equal to 1.0×10 19 cm -3 .

11. The solar cell according to claim 8 or 9, characterized in that: At a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.

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