Selective emitter preparation method, selective emitter battery and preparation process

Abstract

The invention specifically discloses a preparation method of a selective emitter, a selective emitter battery and a preparation process of the selective emitter battery. The preparation method of the selective emitter comprises the following steps: texturing a silicon wafer, oxidizing the textured silicon wafer, and forming an oxide layer on the surface of the silicon wafer; boron diffusion is carried out on the oxidized silicon wafer, and the diffusion temperature is not higher than 900 DEG C; laser doping propulsion is carried out on a metal grid line area on the silicon wafer after boron diffusion, so that a laser area is heavily doped, and a non-laser area is lightly doped; and carrying out oxidation repair and cleaning on the silicon wafer after laser doping. According to the invention, the textured silicon wafer is firstly subjected to oxidation layer generation, then the boron diffusion process is carried out, and finally the laser doping propulsion is carried out, so that the high-temperature propulsion process of boron diffusion is omitted, the process flow is simplified, the production cost is saved, the influence of high temperature on the quality of the silicon substrate is reduced, and the reject ratio of the process is reduced; the problem of insufficient optimization of a non-laser area is effectively solved, and the conversion efficiency of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a selective emitter, a selective emitter cell and a preparation process thereof. Background Art

[0002] Selective emitter (SE) technology is an innovative solar cell manufacturing process that implements high-concentration doping in the area of ​​the silicon wafer that contacts the metal grid lines, while low-concentration doping is used in the remaining areas. In order to achieve high efficiency of solar cells, researchers have designed a variety of cell structures, among which the selective emitter structure is one of the important means to improve efficiency. Selective emitter technology is introduced in the preparation of solar cells. By heavily doping the electrode contact part and lightly doping between the electrodes, the emission area is optimized, the recombination of the diffusion layer is reduced, and the contact resistance between the metal electrode and the silicon wafer is reduced, thereby increasing the output current and voltage of the solar cell and improving the conversion efficiency of the solar cell.

[0003] However, in the actual preparation process of solar cells, especially when using selective emitter technology, existing technical solutions still face many challenges:

[0004] 1. Process complexity and cost issues: The traditional boron diffusion process combined with laser boron doping technology can achieve a certain degree of selective doping, but its three-step deposition plus advancement process is cumbersome, which not only increases the production cycle, but also significantly increases the process cost. In particular, the high oxygen advancement step is not only difficult to control the process, but also leads to high energy consumption and material waste.

[0005] 2. Insufficient optimization of non-laser areas: The existing boron diffusion + laser boron doping technology mainly focuses on the optimization of the laser area, achieving heavy doping through laser doping, but lacks effective optimization methods for the non-laser area. This leads to excessive surface concentration in the non-laser area and serious recombination, which affects the improvement of the overall battery efficiency.

[0006] 3. Damage to the matrix quality: Multiple high-temperature diffusion processes cause certain thermal damage to the silicon matrix material, affecting the crystal structure and electrical properties of the material, thereby limiting the further improvement of the final battery efficiency. In addition, the high-temperature process may also introduce other impurities and defects, further reducing the stability and reliability of the battery.

[0007] Therefore, when realizing the selective emitter structure, the existing solar cell preparation technology has problems such as complex process, high cost, insufficient optimization of non-laser area and damaged substrate quality, which limits the further improvement of cell efficiency. Summary of the invention

[0008] In view of the deficiencies in the prior art, an object of the present invention is to provide a method for preparing a selective emitter, a selective emitter battery and a preparation process thereof.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a selective emitter, the method comprising the following steps:

[0011] (1) texturing the silicon wafer, and oxidizing the texturing silicon wafer to form an oxide layer on the surface of the silicon wafer;

[0012] (2) Boron diffusion is performed on the oxidized silicon wafer, and the diffusion temperature is not higher than 900°C;

[0013] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0014] (4) Oxidation repair and cleaning of laser-doped silicon wafers.

[0015] The method for preparing a selective emitter of the present invention is to oxidize the silicon wafer after texturing, and the formed oxide layer can block the diffusion of boron into the silicon substrate. Further, the oxidation temperature in the step (1) is 800-1000°C, and the thickness of the oxide layer is 10-20nm; the oxide layer thickness of 10nm-20nm can just block the diffusion of boron below 900°C, the oxidation temperature required for an oxide layer less than 10nm is too low, and the problem of boron diffusion may occur due to the large temperature difference with the existing temperature, while the oxidation temperature required for an oxide layer greater than 20nm is too high, and in order to match the doping, the temperature of boron diffusion needs to be increased to achieve the effect of just blocking boron doping, which leads to increased costs; and oxidation at a temperature of 800-1000°C can just form an oxide layer of 10nm-20nm, avoiding waste of resources and saving production costs.

[0016] When performing the boron diffusion process, only the deposition diffusion step is performed, and there is no high-temperature advancement step, and the diffusion temperature is not higher than 900°C, which can not only reduce the surface concentration of the non-laser area, reduce the composite, but also reduce the impact of high temperature on the quality of the silicon substrate. At the same time, because there are no three high-temperature advancement steps, it can not only reduce the complexity of the process, but also reduce the production cost. Further, the diffusion temperature in step (2) is 860-900°C; the diffusion temperature is controlled between 860-900°C, which can just match the 10nm-20nm oxide layer, can just block the diffusion of boron, avoid resource waste, and save production costs.

[0017] Furthermore, the diffusion square resistance in step (2) is controlled between 5000 and 10000 Ω / sq. By controlling the diffusion square resistance, it is ensured that the oxide layer plays a role in blocking boron doping. If the diffusion square resistance is less than 5000 Ω / sq, it means that boron has been doped into the silicon substrate and the oxide layer does not play a role in blocking boron doping.

[0018] In the laser doping process of step (3), the non-laser area is lightly doped by blocking the oxide layer, thereby optimizing the laser area and the non-laser area, reducing the recombination of the diffusion layer, and further reducing the contact resistance between the metal electrode and the silicon wafer. Preferably, laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped.

[0019] Furthermore, the surface resistance of the silicon wafer after oxidation repair in step (4) is 250-280Ω / sq.

[0020] Furthermore, the temperature for the oxidation repair in step (4) is 800-1000° C., which saves production costs.

[0021] Furthermore, texturing is performed using N-type crystalline silicon or P-type crystalline silicon as a substrate.

[0022] In a second aspect, the present invention provides a process for preparing a selective emitter battery by using the method for preparing the selective emitter according to the first aspect, wherein the process comprises the following steps:

[0023] (1) Texturing the silicon wafer, and oxidizing the texturing silicon wafer to form an oxide layer on the surface of the silicon wafer;

[0024] (2) Boron diffusion is performed on the oxidized silicon wafer, and the diffusion temperature is not higher than 900°C;

[0025] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0026] (4) Oxidation repair and cleaning of laser-doped silicon wafers;

[0027] (5) removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer in sequence;

[0028] (6) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0029] (7) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0030] (8) Printing metal electrodes on the front and back of the silicon wafer.

[0031] Furthermore, in the step (8), the metal electrode on the front side of the silicon wafer is an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder.

[0032] Furthermore, the front side of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front side Ag paste electrode is processed by light-assisted micro-conduction.

[0033] In a third aspect, the present invention provides a selective emitter cell, wherein the selective emitter cell is prepared by the preparation process described in the second aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention first oxidizes the silicon wafer after texturing to generate an oxide layer to block the diffusion of boron into the silicon substrate, and then performs a boron diffusion process with a diffusion temperature not higher than 900°C, thereby eliminating the high-temperature advancement process of boron diffusion, simplifying the process flow, and reducing the impact of high temperature on the quality of the silicon substrate. Laser doping advancement is then performed to make the laser area heavily doped and the non-laser area lightly doped due to the blocking of the oxide layer, thereby achieving optimization of the laser area and the non-laser area, reducing the recombination of the diffusion layer, thereby reducing the contact resistance between the metal electrode and the silicon wafer, and increasing the output current and voltage of the solar cell, thereby increasing the photoelectric conversion efficiency of the battery.

[0036] (2) The present invention prints and sintered pure Ag paste electrodes on the front side of silicon wafers, and light-assisted micro-conducting is used to process the Ag paste electrodes on the front side, so that the metal diffusion penetration depth is reduced, the composite current density in the metal area is reduced, and the open circuit voltage is increased, thereby improving the reliability of the battery and increasing the conversion efficiency of the battery.

[0037] (3) The selective emission electrode battery prepared based on the preparation method of the selective emission electrode provided by the present invention has excellent conversion efficiency and life. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 A process flow chart of preparing a selective emission electrode provided in Example 1 of the present invention;

[0040] Figure 2 This is a process flow chart for preparing a selective emitter battery provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0042] Example 1

[0043] This embodiment provides a method for preparing a selective emitter. Figure 1 As shown, the preparation method comprises the following steps:

[0044] (1) Texturing an N-type silicon wafer, and oxidizing the texturized N-type silicon wafer at a temperature of 800°C to form a 10nm oxide layer on the surface of the silicon wafer to prevent boron from diffusing into the silicon substrate;

[0045] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 860° C., and the square resistance is 5000 Ω / sq;

[0046] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0047] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 800°C.

[0048] This embodiment also provides a selective emitter battery preparation process, such as Figure 2 As shown, the preparation process comprises the following steps:

[0049] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0050] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0051] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0052] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0053] Example 2

[0054] This embodiment provides a method for preparing a selective emitter, the method comprising the following steps:

[0055] (1) Texturing an N-type silicon wafer, and oxidizing the texturized N-type silicon wafer at a temperature of 900°C to form a 15nm oxide layer on the surface of the silicon wafer to prevent boron from diffusing into the silicon substrate;

[0056] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 860° C., and the sheet resistance is 7500 Ω / sq;

[0057] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0058] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 900°C.

[0059] This embodiment also provides a selective emitter battery preparation process, the preparation process comprising the following steps:

[0060] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0061] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0062] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0063] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0064] Example 3

[0065] This embodiment provides a method for preparing a selective emitter, the method comprising the following steps:

[0066] (1) texturing an N-type silicon wafer, and oxidizing the texturized N-type silicon wafer at a temperature of 1000° C. to form a 20 nm oxide layer on the surface of the silicon wafer;

[0067] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 900° C., and the square resistance is 10000 Ω / sq;

[0068] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0069] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 1000°C.

[0070] This embodiment also provides a selective emitter battery preparation process, the preparation process comprising the following steps:

[0071] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0072] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0073] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0074] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0075] Example 4

[0076] This embodiment provides a method for preparing a selective emitter, the method comprising the following steps:

[0077] (1) Texturing a P-type silicon wafer, and oxidizing the P-type silicon wafer after texturing at a temperature of 800°C to form a 10nm oxide layer on the surface of the silicon wafer to prevent boron from diffusing into the silicon substrate;

[0078] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 860° C., and the square resistance is 5000 Ω / sq;

[0079] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0080] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 800°C.

[0081] This embodiment also provides a selective emitter battery preparation process, the preparation process comprising the following steps:

[0082] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0083] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0084] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0085] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0086] Example 5

[0087] This embodiment provides a method for preparing a selective emitter, the method comprising the following steps:

[0088] (1) texturing an N-type silicon wafer, and oxidizing the texturized N-type silicon wafer at a temperature of 750° C. to form an 8 nm oxide layer on the surface of the silicon wafer;

[0089] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 800° C., and the sheet resistance is 4500 Ω / sq;

[0090] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0091] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 750°C.

[0092] This embodiment also provides a selective emitter battery preparation process, the preparation process comprising the following steps:

[0093] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0094] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0095] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0096] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0097] Example 6

[0098] This embodiment provides a method for preparing a selective emitter, the method comprising the following steps:

[0099] (1) texturing an N-type silicon wafer, and oxidizing the texturized N-type silicon wafer at a temperature of 1050° C. to form a 22 nm oxide layer on the surface of the silicon wafer;

[0100] (2) performing boron diffusion on the oxidized silicon wafer, wherein only a deposition diffusion step is performed without a high temperature advancement step, the boron diffusion temperature is 900° C., and the sheet resistance is 10500 Ω / sq;

[0101] (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped;

[0102] (4) The laser-doped silicon wafer is subjected to oxidation repair and cleaning, and the oxidation repair temperature is 1100°C.

[0103] This embodiment also provides a selective emitter battery preparation process, the preparation process comprising the following steps:

[0104] (a) after performing steps (1) to (4), removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and sequentially depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer;

[0105] (b) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer;

[0106] (c) depositing anti-reflection layers on the front and back sides of the silicon wafer;

[0107] (d) Printing metal electrodes on the front and back of the silicon wafer, and then sintering to complete the preparation; the metal electrode on the front of the silicon wafer adopts an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder. The front of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front Ag paste electrode is processed by light-assisted micro-conduction.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that the oxidation process in step (1) is omitted, and the boron diffusion process in step (2) is directly performed. The rest of the preparation methods and parameters are consistent with those in Example 1.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that the boron diffusion process in step (2) includes a deposition diffusion step and a high-temperature advancement step, and the diffusion temperature is 950° C. The rest of the preparation methods and parameters are consistent with Example 1.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that in the step (d), the AgAl slurry electrode is printed and sintered on the front side of the silicon wafer, and the light-assisted micro-conducting treatment of the front AgAl slurry electrode is not used. The rest of the preparation methods and parameters are consistent with Example 1.

[0114] Performance Testing

[0115] The electrical performance of the N-type batteries prepared in Examples 1-6 and Comparative Examples 1-3 was tested.

[0116] The test method is: using an IV tester to measure various parameters of the solar cell, and the results are shown in Table 1.

[0117] Table 1 Test results of battery of embodiment and comparative example

[0118]

[0119] Performance test data conclusion analysis:

[0120] As can be seen from the above table, the present invention eliminates the high-temperature advancement process of boron diffusion, simplifies the process flow, saves production costs, reduces the impact of high temperature on the quality of the silicon substrate, reduces the process defect rate, achieves performance improvement, and effectively solves the problem of insufficient optimization of the non-laser area. In addition, the battery prepared based on the preparation method of the selective emitter provided by the present invention has excellent conversion efficiency and life.

[0121] First, compared with Example 1 in which a 10 nm oxide layer is formed by oxidation at 800°C and boron diffusion is performed at 860°C with a diffusion square resistance of 5000Ω / sq, and Example 5 in which an 8 nm oxide layer is formed by oxidation at 750°C and boron diffusion is performed at 800°C with a diffusion square resistance of 4500Ω / sq, Example 1 can fully diffuse the boron source in the oxide layer, and the laser doping is better than Example 5. After the oxide layer is removed, the doping is more uniform, and the efficiency of the obtained battery is better. In Example 5, the boron diffusion temperature is lower, less boron diffuses into the oxide layer, and the laser doping is better. The doped boron is low, resulting in low battery efficiency; compared with Example 6 in which a 22nm oxide layer is formed by oxidation at 1050°C and boron diffusion is performed at 900°C with a diffusion resistance of 10500Ω / sq, in Example 6, the oxide layer is too thick at high temperature, and diffusion is performed at 900 degrees, which will cause uneven diffusion of the boron source in the oxide layer, and then laser doping will cause uneven boron doping of the silicon substrate, and the surface concentration will be large when the oxide layer is removed, while in Example 1, the boron sources are all in the oxide layer, and the boron doped by laser is uniform, the surface concentration is low, and the recombination is low.

[0122] Secondly, by comparing Example 1 with Comparative Examples 1-3, the boron diffusion process is directly performed in the oxide layer formation process without step (1) in Comparative Example 1, which is similar to the production line process, and the lowered boron diffusion temperature and the lack of front boron advancement will result in a high surface concentration, and a large recombination when the battery is made, which will result in a reduction in various battery indicators of the battery; the boron diffusion process in step (2) in Comparative Example 2 includes a deposition diffusion step and a high-temperature advancement step, and the diffusion temperature is 950°C; resulting in the same as the production line process, if the post-oxidation temperature reaches 1040°C, it is the source for mass production; in step (d) in Comparative Example 3, the AgAl slurry electrode is printed and sintered on the front side of the silicon wafer, and the AgAl slurry electrode on the front side is not processed by light-assisted microconducting. Compared with the Ag slurry on the front side processed by light-assisted microconducting, the AgAl slurry has a high compliance, a low opening voltage, and a low efficiency.

[0123] The present invention generates a 10-20nm oxide layer on the silicon wafer after texturing to block the diffusion of boron into the silicon substrate; then performs boron diffusion at a temperature not higher than 900°C with only a deposition diffusion step and no high-temperature advancement step, thereby simplifying the process flow, reducing the influence of high temperature on the quality of the silicon substrate, and further reducing the process complexity and cost; then performs laser doping advancement on the metal gate line area of ​​the silicon wafer, so that the laser area is heavily doped, and the non-laser area is lightly doped due to the blocking of the oxide layer, thereby achieving optimization of the laser area and the non-laser area; and oxidation at a temperature of 800-1000°C can It just blocks the diffusion of boron, saving production costs; and by controlling the diffusion resistance between 5000 and 10000Ω / sq, it ensures that the oxide layer plays a role in blocking boron doping. A small diffusion resistance indicates that boron has been doped into the silicon substrate; and by printing and sintering the pure Ag paste electrode on the front side of the silicon wafer and light-assisted micro-conduction processing of the front Ag paste electrode, the metal diffusion penetration depth is reduced, the composite current density in the metal area is reduced, the open circuit voltage is increased, the battery reliability is improved, and the contact resistance between the metal electrode and the p-type doped layer is reduced, thereby improving the battery FF and conversion efficiency.

[0124] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing a selective emitter, characterized in that: The preparation method comprises the following steps: (1) texturing the silicon wafer, and oxidizing the texturing silicon wafer to form an oxide layer on the surface of the silicon wafer; (2) Boron diffusion is performed on the oxidized silicon wafer, and the diffusion temperature is not higher than 900°C; (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped; (4) Oxidation repair and cleaning of laser-doped silicon wafers.

2. The preparation method according to claim 1, characterized in that: The oxidation temperature in step (1) is 800-1000° C., and the thickness of the oxide layer is 10-20 nm.

3. The preparation method according to claim 1, characterized in that: The diffusion temperature in step (2) is 860-900°C.

4. The preparation method according to claim 1, characterized in that: The sheet resistance of the diffusion in step (2) is controlled between 5000 and 10000 Ω / sq.

5. The preparation method according to claim 1, characterized in that: The surface resistance of the silicon wafer after oxidation repair in step (4) is 250-280Ω / sq.

6. The preparation method according to claim 1, characterized in that: The temperature for oxidation repair in step (4) is 800-1000°C.

7. A process for preparing a solar cell based on the method for preparing a selective emitter according to any one of claims 1 to 6, characterized in that: The preparation process comprises the following steps: (1) texturing the silicon wafer, and oxidizing the texturing silicon wafer to form an oxide layer on the surface of the silicon wafer; (2) Boron diffusion is performed on the oxidized silicon wafer, and the diffusion temperature is not higher than 900°C; (3) Laser doping is performed on the metal gate line area on the silicon wafer after boron diffusion, so that the laser area is heavily doped and the non-laser area is lightly doped; (4) Oxidation repair and cleaning of laser-doped silicon wafers; (5) removing the borosilicate glass (BSG) layer on the back of the silicon wafer and performing alkali polishing, and depositing a tunneling oxide layer and an amorphous silicon passivation layer on the back of the silicon wafer in sequence; (6) removing the PSG on the back side of the silicon wafer and the wrap-around and BSG layers on the front side, and depositing an aluminum oxide passivation layer on the front side of the silicon wafer; (7) depositing anti-reflection layers on the front and back sides of the silicon wafer; (8) Printing metal electrodes on the front and back of the silicon wafer.

8. The preparation process according to claim 7, characterized in that: The front metal electrode in step (8) is an Ag paste electrode formed by printing and sintering, and the Ag paste electrode does not contain Al powder.

9. The preparation process according to claim 8, characterized in that: The front side of the silicon wafer is printed with pure Ag paste, dried and sintered, and the front side Ag paste electrode is processed by light-assisted micro-conduction.

10. A selective emitter battery, characterized in that: The selective emitter cell is prepared by the preparation process described in any one of claims 7 to 9.

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